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Remembering the fallen
Local services marking Anzac Day this year include special recognition of the Battle of Bullecourt at the Breakfast Point War Memorial.
Of the many First World War battles those at Bullecourt in northern France were amongst the most horrific. Four experienced Australian divisions of I ANZAC Corps were part of the British 5th Army under Sir Hubert Gough. The general wanted to attack at Bullecourt to support an important offensive by the adjoining British 3rd Army to the north and the French Army further to the south. However poor planning resulted in heavy losses. The first attack launched at Bullecourt on 11 April 1917 was a disaster. Despite this a further attack across the same ground was ordered for 3 May. The Australians broke into and took part of the Hindenburg Line but no important strategic advantage was ever gained. In the two battles the AIF lost 10,000 men.
The Breakfast Point War Memorial lists the names of eight local men who died at Bullecourt.
The photograph shows the unveiling of the Australian Gas Light Company (AGL) war memorial by Sir Dudley de Chair, Governor of NSW in 1926. It has since been replaced by the Breakfast Point memorial.
Posted in Breakfast Point, Mortlake
Tags: AGL, AGL War Memorial, Australian Gas Light Company, Breakfast Point, Breakfast Point War Memorial, Canada bay Connections, City of Canada Bay, First World War, Mortlake, World War I
Greetings from afar
During the First World War the Australian Comforts Fund co-ordinated the distribution of small gifts to soldiers to make their life a little more pleasant.
It was formed in August 1916 and co-ordinated the efforts made by various existing State based patriotic funds. In the field, its activities were overseen by commissioners who held honorary rank as officers. Local Drummoyne Alderman, Mayor and politician, Thomas Henley was one such commissioner who visited Egypt, France and Britain in his work for the Australian Comforts Fund. His own son, Lieutenant Harold Leslie Henley was killed in action on 15 August 1916 in France.
This postcard was distributed to soldiers by the Australian Comforts Fund at Christmas 1916. It was sent by Private Henry George Jeffery to his family in Five Dock. Harry was killed in action on 4 October 1917 in Belgium.
The postcard artwork is by Laurie Tayler (Lawrence B. Tayler), an Australian artist and cartoonist of the period. The gentle humour of the postcard ('People have been very kind to me in London') belies the horror of the First World War experience.
Posted in Drummoyne, Five Dock, More than just a name
Tags: Canada bay Connections, Christmas, Christmas cards, City of Canada Bay, First World War, More than just a name, postcards, World War I
Remembrances of war
Throughout the City of Canada Bay there are many memorials, large and small, dedicated to the memory of local men and women who served our country in war.
Local Studies is custodian of two memorials to those who served in the First World War, the Drummoyne War Service Record, which records those who served from the Drummoyne area and the Lysaght Bros Roll of Honour, which records the names of workers from the Lysaght factory at Chiswick who served .
The beautiful memorial, above, pays tribute to nine soldiers from the Five Dock Methodist Church (now Five Dock Uniting Church) who did not return from the First World War. Undoubtedly it was crafted with love and compassion.
Images of some of the war memorials in the City of Canada Bay can be seen on flickr.
Posted in Canada Bay, Chiswick, Drummoyne, Five Dock, More than just a name
Tags: Canada bay Connections, City of Canada Bay, Drummoyne War Service Record, First World War, Five Dock Methodist Church, Five Dock Uniting Church, Lysaght Bros, Lysaght's, More than just a name, war memorials, World War I
An album of memories
A small display in the Local Studies area at Concord Library provides a glimpse into the story of two brothers who served in the First World War.
Margaret Jeffery lovingly collected the letters and postcards sent by her sons during the First World War in an album. One hundred years later they provide a very special glimpse into the lives of the soldiers and the conditions they experienced. Private Henry (Harry) Jeffery was killed in action in Belgium on the 4 October 1917, aged 19 years. His brother, Private Robert (Bob) Jeffery was only 15 years 8 months when he enlisted. He served in the Middle East until the Army found out he was underage and sent him back to Australia.
The photograph of soldiers, above, includes Harry Jeffery (second from the left, marked with a cross). The photograph may have been taken during training in Britain. The hut in the background would appear to be an army mess or kitchen, judging by the pots and utensils in the picture.
The Jeffery Album was generously donated to Local Studies by Christine Tracy, a descendant of the brothers, in 2014.
Posted in Five Dock, More than just a name
Tags: Canada bay Connections, City of Canada Bay, First World War, Five Dock, More than just a name, World War I
While brothers from the same family often enlisted in the First World War, it was uncommon to see four brothers do so. At Drummoyne the Erickson brothers, Albert Victor, Roy Robert, Bertie Theodore and George Peter all enlisted to serve.
Educated at Drummoyne Public School, the Erickson brothers were keen sportsmen. All four swam with the Drummoyne Amateur Swimming Club, with Bertie (known as 'Bert') and George also playing in the Drummoyne Water Polo team. Albert's other enthusiasm was Australian Rules Football, playing first for Drummoyne he then captained the Western Central team. Bert was also a rower with the Balmain Rowing Club.
Albert Victor Erickson, enlisted in August 1915 and served with the 3 Battalion, later transferring to the 45 Battalion. Roy Robert Erickson enlisted in July 1915 and served with the 18 Battalion. Tragically, Albert and Roy were killed in action within a day of one another in the Battle of Pozieres in France. Roy died on 5 August 1916, aged 19 years while Albert died on 6 August 1916, aged 23 years.
The photograph of the memorial plaques commemorating Albert Victor and Roy Robert was kindly donated to 'Canada Bay Connections' earlier this year by Ian Vinall.
Posted in Drummoyne, More than just a name
Tags: Canada bay Connections, City of Canada Bay, Drummoyne, First World War, World War I
In 1915 Private Robert (Bob) Jeffery sent this simple card from Cairo to his family in Five Dock. It was printed on lightweight paper in Cairo and distributed to soldiers by the Australian Comforts Fund. At home it was lovingly preserved by his mother Margaret Jeffery in an album of postcards and letters sent by her two sons and nephew while serving in the First World War.
Bob was only 15 at the time of his enlistment. On Christmas day 1915 he wrote to his family,'I hope you all enjoyed your Xmas dinner, because I did, I had some roast turkey, boiled cabbage & roast potatoes, also some pudding and the day before yesterday most of us got our Xmas gifts from the Australian Comforts Fund. I got a billy can full of tobacco, cigarettes, cigars and matches, chocolate…writing paper, a plum pudding and a little square box with a dozen postcards… I don't think I'll go short of smokes for a while.'
After serving in the Middle East, Bob, like the message on the card, returned to his family in Australia.
Tags: Canada bay Connections, Christmas, Christmas cards, City of Canada Bay, First World War, Five Dock, More than just a name, World War I
Restoring their names
Erected in 1921, the Concord War Memorial has been the focal point for Anzac Day services for over ninety years.
Some 600 men and women from the Concord area enlisted to serve in the First World War, a remarkable number considering the population at the time is estimated to have been less than 11, 000.
At present conservation work is being carried out on the marble tablets so the names will be legible once again. Thus the original intention of the memorial 'to perpetuate the memory of our nurses, sailors and soldiers who enlisted in the Great War 1914-1919' will be fulfilled.
The work will be completed by Remembrance Day, 11 November 2015.
Posted in Concord, More than just a name
Tags: Canada bay Connections, City of Canada Bay, Concord, First World War, More than just a name, World War I
Rhodes art work remembers local soldiers
A new art work by Olev Muska at McIlwaine Park commemorates the service of local soldiers during the First World War.
Olev (left) has drawn on images from the Local Studies photographic collection, Canada Bay Connections and the Australian War Memorial to create a fascinating work. Against the background photograph of the unveiling of the Rhodes Honour Roll in 1919 can be seen images of Walter Brooks, the Seabrook brothers and a Field Post Office card sent by Harry Jeffery to his mother before going into battle.
The art work ensures that those who served in the First World War are remembered as 'More than just a name'.
Posted in More than just a name, Rhodes
Tags: Canada bay Connections, City of Canada Bay, First World War, More than just a name, Rhodes, World War I
A camera on Gallipoli
The Australian War Memorial's digital exhibition 'A camera on Gallipoli', featuring First World War photographs taken by Sir Charles Ryan, can now be viewed at Concord Library.
In 1914, at the age of 61, Sir Charles Ryan was appointed consulting surgeon to the AIF, embarking from Melbourne in October to the Middle East, then on to Gallipoli.
'A camera on Gallipoli' showcases a series of 39 candid photographs. The Director of the Australian War Memorial, Dr Brendan Nelson, says 'Charles Ryan's photographs capture the reality behind the 1915 Gallipoli campaign, depicting a unique and often harsh view of our soldiers' experiences'.
Charles Ryan led a remarkable life. He served as a doctor with the Turkish army in 1877–78, treated Ned Kelly at Glenrowan, was a leading Melbourne surgeon and gave long service as a senior military officer.
The digital exhibition is a centenary initiative supported by the Concord RSL to commemorate the centenary of the First World War. It can be viewed at Concord Library until Sunday, 3 August 2015.
Posted in More than just a name
Tags: Canada bay Connections, City of Canada Bay, First World War, Gallipoli, More than just a name, World War I
St Bede's Baseball Club, 1914
While baseball was first played in Australia in the nineteenth century, it was the visit of the American Fleet in 1908 that particularly boosted interest in the game. In that year baseball first began to be played in NSW schools.
By 1914 St Bede's (Anglican Church), Drummoyne had a well organised baseball team. Players in the photograph, above, were back row: A. Norman (Pitcher), H. Kay (1st Base), L. Kay (Catcher), Honorary Treasurer E. Gordon (Centre Field); second row: F. Hall (3rd Base), A. E. Kelshaw (Short Stop), Captain A. Mackenzie (2nd Base), Vice Captain and Honorary Secretary E. Stutchbury (Right Field); front row: E. Boon (Left Field), A Parsons (Centre Field).
It appears that at least six of the young men enlisted in the First World War. Brothers Harold Brooks Kay and Leslie Frank Kay, Ernest Gordon, Frederick Poole Hall, Albert Edward Kelshaw and Eric William Stutchbury. Ernest Gordon was killed in action in 1917 but the others all returned to Australia after the war ended. Eric Stutchbury became a Major in the 55 Battalion and was highly decorated, being awarded a Military Cross with Bar.
The photograph of St Bede's Baseball Club was recently donated to Local Studies by Major Stutchbury's son, Kevin.
Tags: Baseball, Canada bay Connections, City of Canada Bay, Drummoyne, First World War, More than just a name, St Bede's Anglican Church Drummoyne, World War I


Just a placeholder note. I'm converting the previous blog, "The Ochosi Chronicles," to a new page, "RodDavisWriter.com" in order to expand the scope of postings and information. Basically it will become my own website and I hope be easier to find under this name. I can't use "RodDavis" per se because it's already being used. If you go there, sorry, it ain't me.
I'll be redesigning the page soon as well and it will look more like the web pages of other authors.


text:
Our WWI History
Membership/Shop
THE STEPSHORT HERALD,
return to film page
ABOUT REMEMBERING FOLKESTONE
Coming up to the centenary anniversary of the outbreak of the First World War, the so-called Great War, Beeping Bush have worked with Folkestone cultural heritage organisation, Step Short, to produce an interactive 3-D film resource to reach and educate all ages about the First World War.
INTERACTIVE DOCUMENTARY FILM CONCEPT
With funding support from Screen South Digital Inventions Programme, digital-media arts filmmakers, Beeping Bush have transformed the standard approach of documentary filmmaking - to deliver a seminal 3D interactive film model of heritage information distribution, centred around the role of Folkestone, Kent, during WW1.
left: Anaglyph (red/cyan) of a Parade through Folkestone Town Centre. One of the many 2D archive photos transformed into stereographic 3D for the documentary.
Attracting new audiences through both a lean back passive approach and a fully explorative interaction, this ground-breaking stereographic 3D heritage documentary presents archive material in an immersive and informed way. It enhances and compliments the work of Step Short to showcase Folkestone's WWI heritage and culture, linking the past with the present and vice versa.
During the dark days of the Great War, millions of men boarded ships that would take them to the trenches of France and Belgium and an uncertain future. Those ships left from Folkestone on the short
journey to Boulogne and the horror of war in the trenches. Not all the passengers were soldiers, but most were fighting men – and estimates suggest that while ten million left for the Western Front, two million fewer return journeys were made. For many, the sights and sounds of Folkestone harbour would be the last they saw of home.
We hope that this project will influence the way future true stories are told, bringing documentary filmmaking into a really exciting new format.
Twin Town
Site by Created | © Step Short 2010

redpajama_set_name: RedPajamaCommonCrawl


text:
Enrique Carreras (6 January 1925 – 29 August 1995) was a Peruvian-born Argentine film director, screenwriter and film producer, and was one of the most prolific film directors in the history of the Cinema of Argentina.

Born in Lima, Peru, Carreras directed nearly 100 films in his 40-year career between 1951 and 1991. His 1964 film The Escaped was seen at the 14th Berlin International Film Festival. His 1977 film Crazy Women was entered into the 10th Moscow International Film Festival. He died in Buenos Aires in 1995.

Filmography

 El mucamo de la niña (1951)
 Las zapatillas coloradas (1952)
 ¡Qué noche de casamiento! (1953)
 Suegra último modelo (1953)
 Los tres mosquiteros (1953)
 La tía de Carlitos (1953)
 La mano que aprieta (1953)
 Siete gritos en el mar (1954)
 Somos todos inquilinos (1954)
 Romeo y Julita (1954)
 Mi marido hoy duerme en casa (1955)
 Escuela de sirenas... y tiburones (1955)
 El fantasma de la opereta (1955)
 La cigüeña dijo ¡Sí! (1955)
 Ritmo, amor y picardía (1955)
 Luces de candilejas (1956)
 Música, alegría y amor (1956)
 Pecadora (1956)
 De noche también se duerme (1956)
 De Londres llegó un tutor (1958)
 El ángel de España (1958)
 El primer beso (1958)
 Angustias de un secreto (1959)
 Nubes de humo (1959)
 Obras maestras del terror (1960)
 Canción de arrabal (1961)
 Punto y banca o Patricia mía (1961)
 Tres alcobas (1962)
 El noveno mandamiento (1962)
 Los viciosos (1962)
 Hombres y mujeres de blanco (1962)
 Cuarenta años de novios (1963)
 El sexto sentido (1963)
 La mujer de tu prójimo (1963)
 La industria del matrimonio (1964)
 Ritmo nuevo, vieja ola (1964)
 Un viaje al más allá (1964)
 Los evadidos (1964)
 El Club del Clan (1964)
 Los hipócritas (1965)
 Fiebre de primavera (1965)
 Del brazo y por la calle (1966)
 De profesión sospechosos (1966)
 Mi primera novia (1966)
 El andador (1967)
 Ya tiene comisario el pueblo (1967)
 ¡Esto es alegría! (1967)
 ¿Quiere casarse conmigo? (1967)
 Operación San Antonio (1968)
 Matrimonio a la argentina (1968)
 Un muchacho como yo (1968)
 ¡Viva la vida! (1969)
 Corazón contento (1969)
 Los muchachos de antes no usaban gomina (1969)
 Amalio Reyes, un hombre (1970)
 Los muchachos de mi barrio (1970)
 Muchacho que vas cantando (1971)
 Aquellos años locos (1971)
 El veraneo de los Campanelli (1971)
 La valija (1971)
 Vamos a soñar con el amor (1971)
 La familia hippie (1971)
 Había una vez un circo (1972)
 El picnic de los Campanelli (1972)
 La sonrisa de mamá (1972)
 Hoy le toca a mi mujer (1973)
 Los padrinos (1973)
 Me gusta esa chica (1973)
 Yo tengo fe (1974)
 No hay que aflojarle a la vida (1975)
 Las procesadas (1975)
 La super, super aventura (1975)
 Los chicos crecen (1976)
 Así es la vida (1977)
 Las locas (1977)
 La mamá de la novia (1978)
 Los drogadictos (1979)
 Frutilla (1980)
 Sucedió en el fantástico Circo Tihany (1981)
 Ritmo, amor y primavera (1981)
 Los fierecillos indomables (1982)
 Los extraterrestres (1983)
 Los fierecillos se divierten (1983)
 Sálvese quien pueda (1984)
 Los reyes del sablazo (1984)
 Las barras bravas (1985)
 Mingo y Aníbal contra los fantasmas (1985)
 Miráme la palomita (1985)
 Mingo y Aníbal en la mansión embrujada (1986)
 Rambito y Rambón, primera misión (1986)
 Los colimbas se divierten (1986)
 Galería del terror (1987)
 Los colimbas al ataque (1987)
 El profesor punk (1988)
 Atracción peculiar (1988)
 Delito de corrupción (1991)

Productor
 Bólidos de acero (1950)
 La niña de fuego (1952)
 El protegido (1956)

References

External links

1925 births
1995 deaths
Argentine film directors
Argentine film producers
Male screenwriters
Peruvian film directors
Peruvian film producers
Peruvian screenwriters
People from Lima
Peruvian emigrants to Argentina
Burials at La Chacarita Cemetery
20th-century Argentine screenwriters
20th-century Argentine male writers

redpajama_set_name: RedPajamaWikipedia


Candidates are require to read all the instructions and fill in carefully when doing the online registration. These would avoid any unnecessary penalty impose on any corrections if require.
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Otherwise, you will NOT be allowed to sit for the test. Only the followings will be accepted.


Skin CarpeNoctem33 was added 08.04.2019, skin has a size of 64x64 pixels. This skin using 1 players. Below is a list of players who use this skin.
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text:
Rajasthan high court extends stay on collecting school fee till October 20
Home » City Reports » Rajasthan high court extends stay on collecting school fee till October 20
Rajasthan high court. Image credit: Post staff
Jaipur: A double bench of the Rajasthan high court on Wednesday extended the stay on collecting school fee by schools till October 20. The Rajasthan high court has directed the government to take a decision in this regard.
The double bench of Chief Justice Indrajeet Mohanty and Justice SK Sharma had on October 1 stayed a single bench's order which allowed private schools to collect tuition fee during the COVID-19 situation even as the schools were closed. The double bench issued a stay on the single bench's order till October 9. The double bench on Wednesday extended the stay till October 20.
The court on Wednesday said that the state government has certain powers when the Epidemic Diseases Act is in effect. The Rajasthan government has the authority to determine school fees to be charged by the private schools. The court asked the government to submit an affidavit by October 19.
The Rajasthan high court's single bench had on September 7 allowed private schools to collect 70% of the tuition fee from parents in three instalments. The orders in this regard were issued on petition filed by various school organizations including Society of Catholic Education Institutions in Rajasthan and Progressive School Association. The non-payment could allow schools to prevent a child from attending online classes, but they were not allowed to rusticate the child from school.
The double bench then stayed the order. The ball is now in the Rajasthan government's court.
First published: October 14, 2020


Bennington's North Shore 24-inch Towel Bar brings the polished look of stainless with its glossy satin nickel finish. Measuring at a standard 24 inches, the North Shore Towel Bar fits well in most bathrooms. This towel bar is a classic addition to any bathroom and comes in a set to complete the look. Mounting hardware and instructions are included for easy installation.
Towel Bar: 2-3/8" mounting base diameter, extends 3-3/4" from wall when installed, post center to post center measures 23-5/8", bar diameter is 5/8"
Looks sleek and contemporary.The towel bar looks nice and matched the cabinet hardware that was already installed in our bathroom.


On Wednesday, a storm is moving out of Kansas and hitting every state along its path to Ohio, where it should arrive by Friday afternoon. In case that isn't clear, the rain isn't over for Missouri, southern Illinois, Indiana, Michigan, Ohio, and Kentucky quite yet, Dale Mohler of Accuweather says.
MDA Weather Services is predicting that 2 to 5 inches of rain will fall as the storm crosses over the southern and eastern Midwest.
"In the east, once the storm leaves on Friday, I don't see any big storms coming there anytime soon," says Mohler who says cooler temperatures will plague the eastern Corn Belt once the storms pass through.
For the remaining northwestern Midwest states, don't expect rain but don't expect seasonal warm temperatures quite yet, either. In the west, temperatures will be in the 50s and 60s as opposed to the 70s, which are often seen at this point in May.
On Wednesday, the game will change for states starting with Minnesota. Thursday and Friday will host a bigger storm bringing .5 to 1 inch of rainfall to the western Midwest before it makes its way east across the Belt.
After that larger system passes, temperatures should warm up a bit by the weekend bringing temperatures in the 60s to the northern states and in the 70s to the southern Corn Belt states.
What's next for your soggy and chilly fields? Find out here.
Looking toward the end of May, Mohler thinks states west of the Mississippi will have near or slightly below-normal rainfall while the states in the eastern Corn Belt could experience normal to slightly higher-than-normal rainfall amounts.
"I would say the pattern would favor near- or above-normal temperatures and near-normal rainfall for the last week of May," Mohler says.
By the end of the month, temperatures should be about 1 to 3°F. above normal in the west and normal in the eastern Corn Belt.
Summer is inching closer every day and for 2017, that means slightly above-normal temperatures and most likely normal rainfall, according to Mohler.
"If what we're saying is accurate, it should be a good year in the east and yields could be a little off in the west," Mohler says. States west of the Mississippi might experience some dryness due to higher temperatures and a better chance of dryness.
Pollination, Mohler believes, could be a week early in a few spots and maybe normal or a week later than usual in the eastern Corn Belt.


text:
Research and Tech
QC 101
Submit a post +
Citynews
By Matt Swayne
U.S. House Bill Would Authorize $100 Million to Build Out Robust Quantum Infrastructure
House legislation aims to promote the quantum internet, a network of quantum communication and computational devices. (Pixabay)
The House of Representatives passed legislation to advance the Energy Department's initiative infrastructure for a quantum network, according to a story in NexGov.
The Quantum Network Infrastructure Act would authorize $100 million to Energy's Office of Science for 2021 through 2025 to form and maintain the effort. The bill was introduced by co-chairs of the National Labs Caucus Reps. Lee Zeldin, R-N.Y., and Bill Foster, D-Ill.
NextGov reports that if passed, the bill would amend the National Quantum Initiative Act that President Trump signed in 2018 to establish "research, development, and demonstration program to accelerate innovation in quantum network infrastructure."
In a statement, Zeldin said that creating an expansive quantum network would allow quantum computers to communicate faster, more reliably and more securely across longer distances. However, the establishment of a large quantum network relies on the quantum network infrastructure needed to support it. This bipartisan legislation establishes a national research and development program for the advancement of this quantum network infrastructure, accelerating the widespread implementation of quantum technology.
"Quantum technology enables us to store significantly more information, faster, more securely and more efficiently, improving our lives and nation with everything from healthcare to national security to the financial sector," said Zeldin."Thanks to investments in our nation's best and brightest scientists, we're now closer than ever to a large scale implementation of this technology, and we're not slowing down now! This bipartisan legislation continues to invest in the implementation of this revolutionary technology, including right here at Brookhaven National Lab."
Brookhaven National Lab in Upton, New York, and Stony Brook University in Stony Brook, New York are leading in the field of quantum computing and have established an 80 mile quantum network testbed.
In addition to this legislation, last month, Brookhaven National Lab was awarded $115 million in federal funding for the establishment of a new quantum information science (QIS) research institute, which will focus on a range of key QIS research topics, including quantum networking, sensing, computing, and materials manufacturing.
The bill was referred to the House Committee on Science, Space, and Technology on the day it was introduced.
Matt Swayne is a contributor at The Quantum Daily. He focuses on breaking news about quantum discoveries and quantum computing. Matt enjoys working on -- and with -- startups and is currently working on a media studies master's degree, specializing in science communication.
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text:
Deutsche Bank Cancels $9 Million Expansion at North Carolina Location Because of HB2
By Adam Polaski •	April 12, 2016 • 10:44 am
The fallout continues over North Carolina's hasty passage of House Bill 2, which knocks down municipalities' ability to enact local ordinances protecting LGBT North Carolinians from discrimination and then codifies anti-transgender policies into state law. This morning Deutsche Bank canceled plans to invest $9 million in an expansion in Cary, North Carolina.
In September 2015, the bank announced its plans to expand its operations in Cary, North Carolina, adding 250 new jobs. This morning, the bank walked back those plans, citing HB2 and saying it was uncomfortable adding these new jobs in a state that discriminates.
Deutsche Bank Co-Chief Executive Officer John Cryan said today:
"We take our commitment to building inclusive work environments seriously. We're proud of our operations and employees in Cary and regret that as a result of this legislation we are unwilling to include North Carolina in our US expansion plans for now. We very much hope that we can re-visit our plans to grow this location in the near future."
In September, Governor Pat McCrory – who signed the anti-LGBT HB2 into law less than 12 hours after its introduction – proudly heralded the bank's plans to expand in Cary. Just seven months later, his actions, and the actions of the North Carolina General Assembly, ultimately are to blame for the loss of this economic development.
Deutsche Bank's announcement comes a week after similar canceled plans from Paypal, which withdrew plans to open a new global operations center in Charlotte.
With more and more businesses finding House Bill 2 incompatible with their business plans and future in North Carolina, one thing is clear: The North Carolina General Assembly must take action this year to begin to repair the damage it has already done, and repeal HB2.
Take a look at more of the businesses that have condemned HB2 here.
FILED UNDER: Business Support, North Carolina


TYPHOON MANGKHUT, which will be locally named Ompong once it enters the Philippine Area of Responsibility (PAR), has intensified as it moves westward towards the northern part of the country. In its Sept. 11 update, weather bureau PAGASA said Ompong is expected to be within PAR by Wednesday afternoon and remain until Saturday. "The typhoon is threatening Northern Luzon and may traverse the Cagayan-Batanes area this Saturday. Tropical Cyclone Warning Signal (TCWS) # 1 may be raised as early as tomorrow evening (12 Sept.). The typhoon may strengthen the Southwest Monsoon bringing scattered light to moderate rains and thunderstorms over the Zamboanga Peninsula, Western Visayas and Palawan starting Thursday," PAGASA said. National Disaster Risk Reduction and Management Council Spokesperson Edgar L. Posadas, in a press conference yesterday, said preparations by government agencies are underway for the potential impact of the typhoon.


text:
\section{Introduction} \label{intro}

T Tauri stars (TTS) are by definition variable stars, named after their
prototype T Tau. Variability in this class of objects is ubiquitous and
has inspired a long history of study \citep[e.g.,][]{joy45, joy49,
rydgren76}. The majority of more recent studies have focused on their
optical and near-infrared (NIR) emission. \citet{carpenter01} found
significant variability of TTS in Orion A based on near-IR JHK
2MASS photometry.  The typical timescale of variation in these TTS was
on the order of days and could be explained by cool spots, hot spots,
extinction, and$/$or changes in the mass accretion rate onto the star.
Work by \citet{eiroa02} further supported these results.  For many TTS
in that study the optical and JHK photometry varied simultaneously,
supporting that in most objects variability is due to star spots and
variable extinction.  However, for several of the objects in that sample
there is no correlation between the optical and NIR.  This points to
structural changes in the disk, which begin to dominate the SED in the
K-band, on the order of days.

With the arrival of the {\it Spitzer Space Telescope} \citep{werner04},
more detailed studies probing the mid-IR have been possible,
particularly with the Infrared Spectrograph \citep[IRS;][]{houck04}
which provides simultaneous wavelength coverage between
$\sim$5 and 38~{$\mu$m}. Variations in the shape and size of the
10~{$\mu$m} silicate emission feature has been seen in DG Tau, XZ Tau,
\citep{bary09} and LRLL 31 \citep{muzerolle09}.  In the case of EX Lupi,
transient changes in the dust composition of the disk have been detected with
multi-epoch spectra of the silicate emission feature \citep{abraham09}.

Flux changes in the IRS spectra of disks have also been observed.
\citet{muzerolle09} found substantial variability in LRLL 31, located in
IC 348, on timescales down to days. The flux of this object oscillated
around a pivot point at 8.5~{$\mu$m} -- as the emission decreased at
wavelengths shortwards of the pivot point, the emission increased at
longer wavelengths and vice versa. The star spots proposed to explain
variability at shorter wavelengths could change the irradiation heating, but
this would cause an overall increase or decrease of the flux, not an
anti-correlation between the flux centered at the pivot point.
\citet{muzerolle09} proposed that the observed ``seesaw'' variability
was due to dynamical changes in the disk itself. In particular, changes
in the height of the inner disk edge or wall located at the dust
destruction radius (which emits primarily in the NIR) could lead to
variable shadowing of the outer disk material (which emits at longer
wavelengths). Indeed, the overall characteristics of the flux changes
observed can be explained by models of a disk with an inner warp
that leads the scale height of the inner disk to change with time
\citep{flaherty10}.

It is important to note that the above-mentioned object, LRLL 13, is
surrounded by a transitional disk. Transitional disks have nearly
photospheric near-IR (1--5~{$\mu$m}) and mid-IR (5--20~{$\mu$m})
emission below the median excess of Class II objects, coupled with
substantial emission above the stellar photosphere at wavelengths beyond
$\sim$20~{$\mu$m} \citep{strom89}.  This dip in the infrared flux has
been attributed to a central ``hole'' in the dust distribution of the
disk. This has been inferred from detailed modeling of some of these
transitional objects \citep{calvet02,calvet05,espaillat07a,espaillat08b}
and confirmed with sub-millimeter and millimeter interferometric imaging
\citep{hughes07,hughes09,andrews09}.

Motivated by the variability observed in the transitional disk of LRLL~13,
we conducted a {\it Spitzer} IRS variability study of transitional
disks and pre-transitional disks. Pre-transitional disks have
significant near-infrared excesses relative to their stellar
photospheres, similar to the median spectral energy distribution of
disks in Taurus \citep{dalessio99}, while also exhibiting the
characteristics seen in transitional disks (i.e. deficits of
mid-infrared flux  and substantial excesses beyond $\sim$20~{$\mu$m}).
This indicates a gapped disk structure where the inner disk is separated
from the outer disk. Sub-millimeter and millimeter interferometric
imaging \citep[Andrews et al, in prep;][]{andrews09, pietu06} has confirmed the location of the wall of the
outer disk inferred from SED modeling for a few pre-transitional disks
(e.g. LkCa~15, UX~Tau~A, Rox 44).  The near-IR
emission of these objects is due to dust in an optically thick inner disk, a result
obtained by using the ``veiling"
\citep{hartigan89} of near-infrared spectra
\citep{espaillat08a, espaillat10}.

Here we perform detailed modeling of the broad-band spectral energy
distributions of the 14 transitional and pre-transitional
disks in our sample at different epochs.  We take
into account the effect of shadowing by the inner disk on the outer disk
by employing the irradiated accretion disk models of \citet{dalessio06}
with the modifications to include shadowing presented in
\citet{espaillat10}. Our work adds to the number of detailed modeling
efforts of disk variability in the literature which have found some
success in reproducing the observations by varying the height of the
inner disk wall \citep{juhasz07, sitko08}. \citet{juhasz07}'s study of
the UX Ori-type star SV Sep came to the conclusion that the variability
in the optical and near-IR emission could be explained by changing the
height of the inner disk edge, but they were unable to simultaneously
fit the variability from the IR out to 100~{$\mu$m} using a
self-shadowed disk. \citet{sitko08} reported the variability of two
Herbig Ae stars between 1-5~{$\mu$m}, the region dominated by the inner disk
wall, and could explain this change by varying the height of the inner
disk edge.  However, this work did not have data at longer wavelengths
and so could not test if these models fit the emission from the outer
disk.

The advantage of our study over previous works is the quality of
the data and the simultaneous wavelength coverage (5-38~{$\mu$m})
provided by {\it Spitzer} IRS. Thus we are able to present the largest
and most detailed modeling study of variability in disks around TTS to
date.  We find that we can explain the variability of most of the
pre-transitional disks in the sample by
changing the height of the inner disk wall and thus the extent of its
shadow on the outer disk, thereby affecting the resulting emission from
the outer disk.  We also find that the objects in the sample with the
largest amounts of crystalline silicates in their disks exhibit variability on the
shortest timescales observed in this study.

\section{Sample Selection} \label{sample}

Our sample of 14 objects was chosen to include bright transitional and
pre-transitional disks in Taurus and Chamaeleon, two nearby 1--2 Myr old
star--forming regions with low extinction that were well covered by a
{\it Spitzer} guaranteed-time observing (GTO) program \citep[Manoj et
al., submitted;][]{furlan06, kim09}. For each of our 14 objects we obtained
a pair of general observer (GO) observations taken within 1 week of each
other.  When combined with the GTO data, these observations give us
baselines of $\sim$3--4 yr and $\sim$1 wk.

We included the well-studied and previously modeled transitional disks
CS~Cha, DM~Tau, and GM~Aur \citep{espaillat07a,calvet05} and the
pre-transitional disks LkCa~15 and UX~Tau~A \citep{espaillat07b}. We
also included other transitional and pre-transitional disks in
Chamaeleon (T25, T35, T56, SZ~Cha) which had been identified by
\citet{kim09}.  Four objects in our sample were chosen based on analysis
conducted in \citet{furlan09}.  In that work, we compared the observed
equivalent width of the 10~{$\mu$m} silicate emission feature and the
SED slope between 13 and 31~{$\mu$m} against a grid of disk models.
RY~Tau, IP~Tau, CR~Cha, and WW~Cha were four of the many objects that
fell outside of range of EW(10~{$\mu$m}) and n$_{13-31}$ covered by the
full disk model grid.  One explanation proposed by \citet{furlan09} and
\citet{espaillat09} to explain these outliers was that these disks are
actually pre-transitional disks with smaller gaps than had been
previously observed.  Therefore, we included these objects in the sample
based on their potential for being pre-transitional disks. ISO~52 is the
only object in our sample which could be explained by the full disk
model grid presented in \citet{furlan09}.  However, we chose to include
this object in our variability study because qualitatively its GTO IRS
spectrum resembled what would be expected from a pre-transitional disk
with a small gap \citep[see Figure 12 in][]{espaillat10}.
Except for CS~Cha, the objects in our
sample are thought to be single stars and so the holes and gaps in our
objects indicate the likely presence of planets
\citep[see discussion in][]{espaillat08a,espaillat10}.\footnote{Even in the case of the spectroscopic
binary of CS~Cha, the 38~AU hole is too large to be cleared out by the
binary system alone.  A binary system with a circular orbit can clear a
hole twice the size of the semi-major axis; a binary with an
eccentricity of 0.8 can clear out a region 3.5 times the semi-major axis
\citep{artymowicz94,pichardo05,aguilar08}. Since the separation of the
binary in CS~Cha is $\sim$4~AU \citep{guenther07}, the binary should
clear only a region up to 14~AU.}

\section{Data Reduction} \label{redux}

\subsection{Observations}

Here we present three {\it Spitzer} IRS spectra for each of our targets
(Table~\ref{tab:log}). The first spectra were obtained
through IRS GTO in Program 2 (PI: Houck) and have been previously
presented elsewhere \citep[Manoj et al., submitted;][]{furlan06,furlan09,
kim09}.  The last two spectra for each target were obtained in GO
Program 50403 (PI: Calvet).  For consistency, we have re-reduced the GTO
data in the same way we reduce the GO data (see {\S}~\ref{datredux}).
We note that we also searched the {\it Spitzer} archive for all other IRS observations
of objects in our sample.  We reduced those data as we did
our GTO and GO data and comment further on these additional spectra in
the Appendix.

All of the GO observations were performed in staring mode using the
low-resolution modules (Short-Low (SL) and Long-Low (LL)) of IRS, spanning
wavelengths from 5--14~{$\mu$m} and 14-38~{$\mu$m}, respectively,
with a resolution $\lambda/\delta\lambda\sim$90. The Chamaeleon GTO
spectra were obtained in staring mode as well while the Taurus GTO
spectra were obtained in mapping mode with 2$\times$3 step maps (2
parallel and 3 perpendicular to the slit) on the target. Most of the GTO
spectra use the SLLL configuration.  The exceptions are RY~Tau, CR~Cha,
and WW~Cha which were taken with the SL module and the high-resolution
modules Short-High (SH) and Long-High (LH), which cover 10--19~{$\mu$m}
and 19--37~{$\mu$m}, with $\lambda/\delta\lambda\sim$600.
We note that in the case of DM~Tau, two GTO spectra were obtained in
Program 2 and are listed in Table~\ref{tab:log} as GTO1 and GTO2.
Throughout this paper, we only show the GTO2 spectrum since it was taken
in staring mode, as were our GO observations.  In addition, the SL
spectrum has a higher SNR in the GTO2 observation due to a longer
integration time. We note that the GTO1 spectrum is equivalent to the
GTO2 spectrum (i.e. flux, shape) within the uncertainties of the
observations.

\subsection{Extraction and Calibration of Spectra} \label{datredux}

Details on the observational techniques and general data reduction
steps, including bad pixel identification, sky subtraction, and flux
calibration, can be found in \citet{furlan06} and  \citet{watson09}.
Here we provide a brief summary. Each object was observed twice along
the slit, at a third of the slit length from the top and bottom edges of
the slit. Basic calibrated data (BCD) with pipeline version S18.7 for
both the GTO and GO observations were obtained from the {\it Spitzer}
Science Center.  With the BCDs, we extracted and calibrated the spectra
using the SMART package \citep{higdon04}. Bad and rogue pixels were
corrected by interpolating from neighboring pixels. For the
low-resolution spectra, the data were sky subtracted using the sky
emission in the off-target nods except in the cases of CS~Cha GO1, IP
Tau GO 1, and LkCa~15 GO 2 where the off-target orders were used in
order to minimize over-subtraction of H~I from the sky background at
$\sim$20~{$\mu$m}. For the GTO SH and LH modules, no background subtraction
was performed and so the emission of these targets could be slightly
overestimated, particularly in LH since the slit is larger. However, the
targets are much brighter than the background, and so the emission from
the disks should clearly dominate in the mid-IR. After sky subtraction,
the low-resolution spectra were extracted from the 2D spectral images
using a tapered column which varies with the width of the IRS
point-spread function.  For the SH and LH modules, a full slit
extraction was performed. To flux calibrate the observations we used
spectra of $\alpha$ Lac (A1 V) for the low-resolution modules and $\xi$
Dra (K2III) for the high resolution modules.  We performed a nod-by-nod
division of the target spectra and the $\alpha$ Lac or $\xi$ Dra spectra
and then multiplied the result by a template spectrum \citep{cohen03}.
The final spectrum was produced by averaging the calibrated spectra from
the two nods. For the 2$\times$3 maps, only the central map positions
were used for the final spectrum. The high-resolution data were rebinned
to same sampling as the low-resolution data. Our spectrophotometric
accuracy is 2--5$\%$ estimated from half the difference between the
nodded observations. We note that there are artifacts in the T25 GO1,
ISO~52 GO1, T56 GO1, and CR~Cha GTO spectra at $\sim$9~{$\mu$m},
$\sim$7~{$\mu$m}, $\sim$15~{$\mu$m}, and $>$35~{$\mu$m},
respectively.  These spikes are due to additional bad pixels not
captured by the bad pixel and rogue masks used in our data reduction.
For clarity, we manually mask these artifacts from the spectra. The
final spectra used in this study are shown in
Figures~\ref{figirsptd1},~\ref{figirsptd2},~and~\ref{figirstd}.

\subsection{Uncertainties due to Mispointing} \label{mispoint}

Apparent variability could also be the effect of mispointings, which
would cause loss in flux especially in SL, which is the module with the
narrowest slit width. PCRS peak-up, which we used for our GO
observations, yields a pointing accuracy of 0.4$^\prime$$^\prime$
(1-sigma radial rms); this is just slightly less than the accuracy for
blind pointing (0.5$^\prime$$^\prime$; however, note that earlier in the
mission the blind pointing of Spitzer was only accurate to
$<$1$^\prime$$^\prime$). According to a detailed study in
\citet{swain08}, a 0.4$^\prime$$^\prime$ pointing offset in SL1 causes a
drop in flux of about 7$\%$, with a slight (1-2$\%$) dependence on
wavelength. Therefore, if we observe a flux variation $\geq$10$\%$ that
fluctuates with wavelength more than on the few percent level, we can
most likely exclude mispointing as the cause of the variability.

The GTO observations did not use peak-ups.  However, the GTO data of our Chamaeleon
objects were taken later in the mission, when the blind pointing of {\it Spitzer}
was improved.
The objects in our sample that could be affected by some mispointing are
the Taurus GTO observations, taken in 2004 February. They were obtained
with blind pointing in mapping mode; the spectra presented here are
extracted from the central map positions. For IP Tau, DM Tau GTO1, and LkCa
15, the SL and LL spectra match at 14~{$\mu$m}, which argues against
mispointing; since the SL and LL slits are perpendicular to each other,
mispointings should affect one module more than the other, resulting in
an offset. There were small (5$\%$) offsets between SL and LL for DM Tau GTO2, GM Aur
and UX Tau A, with SL lower than LL, suggesting small mispointings. RY
Tau likely suffered from larger mispointing, since SH is lower than SL
and LH by 20-30$\%$ (the mispointing relative to SL is more difficult to
determine, given that part of SL1 in the GO spectra is saturated); also,
compared to the GO data, the SL spectrum appears low. Overall, the GTO
spectrum of RY Tau is quite uncertain, but the other GTO observations
should have a pointing accuracy of 0.5$^\prime$$^\prime$ or better. In
order to account for the mispointing discussed here we scale the SL spectra
upward so that the SL and LL spectra match.
We note that the high-resolution
modules SH and LH are much less affected by small mispointings,
since the slits are wider than for the low-resolution modules.

We note that none of the other GTO or GO observations were mispointed.
Aside from those observations discussed above, there is no mismatch between SL and LL, so we can be confident that
the observations are well pointed and that therefore both the SL and LL
slits contain the full flux of the object.
As an additional check, we find that the sources are located
within $\sim$1$^\prime$$^\prime$ of each other
in the SL and LL slits amongst the GTO, GO1, and GO2 observations, further evidence
that these sources were well-centered in the slit.
We note that at $\sim$14{$\mu$m} the SL module ends and the LL module
begins.  Given that several of our objects have large holes and gaps, the emission of
the outer wall begins to dominate at 15--20{$\mu$m}, coinciding with
where SL ends and LL starts.

We also overlaid the IRS slit positions for each AOR on 2MASS K-band
images to check for anomalous behavior.  In WW~Cha GO1 and GO2 both of
the modules were mispointed due to an error in the coordinates (the
declination was off by $\sim$1$^\prime$$^\prime$). Judging from the overlay,  the LL
module was more off-target than the SL module and the mispointing
is more along the spatial direction of the SL slit, but it is difficult to
tell how much flux was lost. We note that in the GO observations of
SZ~Cha, two faint objects entered the SL and LL slits at
5.3$^\prime$$^\prime$ and 12.5$^\prime$$^\prime$ from the target.  However, it is known
that these two objects are not members of Cha I and are likely very
faint at mid-IR wavelengths \citep{luhman07}.  Therefore, SZ~Cha dominates the emission
in the GO spectra. In the GTO observations of ISO~52 a faint object is
present in the LL slit 8.5$^\prime$$^\prime$ from the target.  Due to the different orientation of the IRS
slit positions in the GO observations, this object is not present in the
LL slit in this epoch. However, this object is much fainter than ISO~52,
with a magnitude of about 14 in the 3.6 and 4.5~{$\mu$m} IRAC bands (K.
Luhman, 2010, private communication), and so we can conclude that ISO~52
dominates the emission seen in its GTO spectrum.

\section{Analysis} \label{sec:ana}

\subsection{Flux Variability} \label{sec:var}

It is evident from the IRS spectra of our pre-transitional
(Figures~\ref{figirsptd1} and~\ref{figirsptd2}) and transitional objects
(Figure~\ref{figirstd}) that there is some variability in their fluxes.
Here we quantitatively discern if there is true variability in the
sample and then qualitatively discuss the overall behavior of the
variability that is present.

Figures~\ref{figptd1err}--\ref{fignovar2} illustrate the change in
flux seen in an object in our sample between different epochs.
The differences in flux between the GTO and GO1 spectra are
shown in Figures~\ref{figptd1err}--\ref{figtderr}.  (Note: the same
analysis for UX~Tau~A and T35 is plotted in Figure~\ref{fig1wkerr}).
The difference in flux ($\delta$F$_{\lambda}$) is plotted in terms of the
percentage difference in emission between the GTO and GO1 data relative
to the GTO data. The error bars in the figures correspond to the
uncertainties in the observations. Except for the cases of
DM~Tau and T25 (where $\delta$F$_{\lambda}\sim$0), we observe
significant variability outside of the observational uncertainties in
each of the targets between the GTO and GO1 observations, which were
taken more than a year apart. We performed the same analysis comparing
the GO1 and GO2 spectra, which were taken about one week apart, and we
only see variability on these timescales in four objects:  UX~Tau~A
(Figure~\ref{figptd1err}), ISO~52, T56 (Figure~\ref{fig1wkerr}), T35
(Figure~\ref{figptd1err}).  In Figures~\ref{fignovar1} and~\ref{fignovar2} we show that the
rest of the objects in our sample do not vary significantly between the GO1 and GO2 epochs.

In many of the pre-transitional targets, the flux clearly oscillates
around a pivot wavelength (Figure~\ref{figptd1err}).  As the short
wavelength emission decreases, the emission at longer wavelengths
increases and as the short wavelength emission increases, the emission
at longer wavelengths decreases. The spectra of LkCa~15 can be taken as
representative of this group of objects.  In Figure~\ref{figptd1err} the
flux of its GO1 spectrum is $\sim$10$\%$ lower than the GTO spectrum at
wavelengths $<$8~{$\mu$m}.  The fluxes of the two spectra are the same
around $\sim$10~{$\mu$m}, but the GO1 spectrum is higher beyond that
point. In the other objects mentioned above, the overall behavior is
similar while the pivot wavelength and magnitude of the flux change can
vary from object to object. UX~Tau~A does not display this seesaw
behavior between the GTO and GO1 spectra (Figure~\ref{fig1wkerr}), but
it does between the GO1 and GO2 spectra (Figure~\ref{figptd1err}).  We
point out that while the RY~Tau GTO and WW~Cha GO observations were
mispointed, that should have resulted in an decrease of flux at all
wavelengths relative to the GO and GTO observations, respectively.
However, we see flux losses at some wavelengths while flux gains at
others, indicating that there is true variability
in these objects, but we cannot accurately constrain the difference in
the flux or the pivot wavelength due to the mispointing.

Whether or not this seesaw behavior is present in the other
pre-transitional objects in the sample is unclear
(Figure~\ref{figptd2err}). The GO1 spectrum of CR~Cha has less emission
than the GTO spectrum shortwards of $\sim$6~{$\mu$m}, but substantially
more at longer wavelengths.  Due to the artifacts in the GTO spectrum
$>$35~{$\mu$m} discussed in {\S}~\ref{redux}, we cannot confidently
tell whether or not the GTO and GO spectra agree at these wavelengths.
In IP~Tau the flux at $\lambda$ $<$7{$\mu$m} is about the same, but it
is lower for the GO1 spectrum at longer wavelengths. For T56, the
emission in the GO1 spectrum is higher than the GTO spectrum beyond
$\sim$20~{$\mu$m}.  It appears that the flux in the GO1 spectrum is
lower at $<$20~{$\mu$m}, but the SNR is too poor $<$7~{$\mu$m} to tell
if this holds at the shortest wavelengths. In T35, when comparing the
GO1 and GO2 spectra, the flux is the same $<$7~{$\mu$m}, but the GO2
spectrum has less emission beyond that.  Again, the spread in
uncertainties is large in T35 because of the poorer SNR.

The behavior observed in the transitional disks is displayed in
Figure~\ref{figtderr}. GM~Aur has the seesaw behavior seen in LkCa~15,
where the pivot is at $\lambda$$\sim$18~{$\mu$m}. In CS~Cha, only the
flux of the 10~{$\mu$m} silicate emission feature changes substantially
between the GTO and GO1 spectra. DM~Tau and T25 have no discernible
variability.

The four objects in our sample which vary on 1~wk timescales display behavior
that could be classified as seesaw-like as already described above, but
they also exhibit additional behavior (Figure~\ref{fig1wkerr}).
UX~Tau~A's GO1 spectrum is weaker at all wavelengths relative to the GTO
spectrum, indicating that the emission of this object has decreased with
time. The spread in uncertainties is large in ISO~52, T56, and T35 because of
poor SNR; however, it appears that the ISO~52 and T56 spectra diverge beyond
$\sim$20~{$\mu$m} between the GO1 and GO2 spectra and that the T35
spectra diverge shortwards of $\sim$10~{$\mu$m} between the GTO and GO1
spectra.

\subsection{Disk Model} \label{sec:mod}

Using disk models, we attempt to reproduce the SED variability observed
in Figures~\ref{figirsptd1}--\ref{figirstd}. The models used here are
those of \citet{dalessio98,dalessio99,dalessio01,dalessio05,dalessio06}. We refer the reader to
those papers for details of the model and to \citet{espaillat10} for a
summary of how we fit the SEDs of pre-transitional and transitional
disks in particular.

A full disk model has an irradiated accretion disk with a
sharp transition at the dust sublimation radius.
We model this transition
as a frontally illuminated wall which
dominates the near-IR
emission. Pre-transitional disks have a gap in the
disk.  They have an inner disk separated from an outer disk by the gap.
The optically thick inner disk also has a sharp transition at the dust sublimation
radius, as seen in full disks, which we model as an inner wall.
 In the subsequent modeling analysis, we do not include the
contribution to the SED from the inner disk behind this wall since
previous work has shown that the inner wall dominates the emission at
these shorter wavelengths. There is another wall located where the outer
disk is inwardly truncated (i.e. the outer edge of the gap) and this
outer wall dominates the SED emission from $\sim$20--30~{$\mu$m}.
Behind this wall, there is an outer disk which dominates the emission
beyond $\sim$40~{$\mu$m}. Since transitional disks have holes in their
disks, they do not have the inner wall seen in pre-transitional disks.
When modeling transitional disks, we include the outer wall and outer
disk described above. In both pre-transitional and transitional disks,
the gap or hole sometimes contains a small amount of optically thin dust
which dominates the contribution to the 10~{$\mu$m} silicate emission
feature. We calculate the emission from this optically thin dust region
following \citet{calvet02}. We note that in the case of the
pre-transitional disks, the inner optically thick disk will cast a
shadow on the outer disk and here we include the effect of this
shadowing on the outer wall following \citet{espaillat10}.
In short, since the star is a finite source, there is both a penumbra and umbra on the outer wall.
In the umbra, the wall is not illuminated and in the penumbra, the wall is partially illuminated.  Above
the penumbra, the wall is fully illuminated.
Refer to the Appendix of \citet{espaillat10} for more details.

\subsubsection{Stellar Properties}

Table~\ref{tab:stellar} lists stellar properties for our sample which
are relevant for the disk model.
We note that the stellar properties of our objects are based on optical and near-infrared
data which are not contemporaneous with the IRS spectra analyzed in this work.
If the star's properties change over time this can
result in uncertainties in the input stellar parameters and hence the disk properties derived here.

Spectral types for our objects are from
the literature and the temperature for the spectral type listed in
Table~\ref{tab:stellar} was taken from \citet{kh95}. The stellar
properties for our sample (L$_{*}$, M$_{*}$, R$_{*}$) are from the HR
diagram and \citet{siess00} tracks. When U-band photometry was
available, the mass accretion rates were derived in this work using
U-band data and the relation in \citet{gullbring98}. Extinction
corrections were made by matching V- , R- , I-band, and 2MASS photometry
to photospheric colors from \citet{kh95}.  The spectra were dereddened
with the \citet{mathis90} dereddenning law. The distance adopted for
Taurus is 140~pc \citep{bertout99} and for Chamaeleon this is 160~pc
\citep{whittet97}.

\subsubsection{Disk Properties}

Table~\ref{tab:disk} lists the disk properties of our sample.  When
parameters are specific to only one epoch, this distinction is made in
the table (see table footnote). We assume that the inclination of the
disk is 60 degrees, unless a measurement could be found in the
literature. $T_{wall}$ is the temperature at the surface of the
optically thin wall atmosphere. The temperature of the inner wall
(T$_{wall}^i$) is typically held fixed at 1400~K (except in the cases of
UX~Tau~A and T35 which will be addressed in the Appendix). The
temperature of the outer wall (T$_{wall}^o$) is varied to fit the SED
best.  The radius of the wall ($R_{wall}$) is derived using $T_{wall}$
following Equation 2 in \citet{espaillat10}. The heights of the walls
(z$_{wall}$) and the maximum grain sizes (a$_{max}$) are adjusted to fit
the SED. The parameters of the outer disk are also varied to fit the
SED. These include the viscosity parameter ($\alpha$) and the settling
parameter ($\epsilon$; i.e. the dust-to-gas mass ratio in the upper disk
layers relative to the standard dust-to-gas mass ratio).  M$_{disk}$ is
calculated according to Equation 38 in \citet{dalessio98} and it is
proportional to ${\hbox{$\dot M$}}/{\alpha}$. We adopt an outer disk radius of
300~AU for all of our disks.

\subsubsection{Dust Opacities} \label{sec:moddustopa}

As discussed in \citet{espaillat10}, the opacity of the disk has
important consequences on the resulting SED.  The opacity is affected by the
sizes of the dust grains and the composition of the
dust used. The grain size distribution used in the models follows the
form $a^{-3.5}$ where $a$ varies between $a_{min}$ and $a_{max}$
\citep{mathis77}.
We assume the grains are spherical and note that while
irregularly shaped grains may have different opacities from spherical grains \citep{min07}, it is outside the scope of this work to constrain the shape of the dust
grains.
Throughout the disk,  $a_{min}$ is held fixed at
0.005~{$\mu$m}. In the walls, $a_{max}$ is varied to achieve the best
fit to the SED.
We try maximum grain sizes between 0.25~{$\mu$m} and 10~{$\mu$m}.  The
wall emission is primarily optically thick, but also has an optically
thin component from the wall atmosphere which contributes to the
silicate emission features. Smaller grain sizes lead to a strong, narrow
10~{$\mu$m} silicate emission feature while larger grain sizes produce
wider and less prominent emission features \citep[see Figure 3 in][]{espaillat07a}. In the outer disk, there are two dust grain size
distributions in order to simulate dust growth and settling
\citep[see][for more details]{dalessio06}. In the upper disk layers,
$a_{max}$=0.25~{$\mu$m} and in the disk midplane the maximum grain size
is 1~mm \citep{dalessio06}. For the dust composition of the inner wall
we follow \citet{dalessio05} and \citet{espaillat10} in adopting
silicates with a dust-to-gas mass ratio (${\zeta}_{sil}$) of 0.0034.   We note that only silicates
exist at the high temperatures at which the inner wall is located.
There are other types of dust such
as metallic iron that can exist at high temperatures  \citep{pollack94}.
However, here we adopt a dust composition consistent with the one proposed by \citet{pollack94}
for accretion disks.

We perform a more detailed dust composition fit for the silicates in the
outer wall and disk than done in our previous works.  The motivation is
that for a variability study trying to trace small changes in the flux,
it is important to isolate the continuum emission of the disk.  By
fitting the silicate dust features seen in the IRS spectrum as closely
as possible, one can then more clearly see the effect of changing the
disk continuum. Here we adopt a dust-to-gas mass ratio (${\zeta}_{sil}$)
of 0.0034 for the silicates in the outer wall and disk and explore
silicate dust mixtures incorporating olivines, pyroxenes, forsterite,
enstatite, and silica. (We note that throughout this work we are
referring to amorphous material of olivine or pyroxene stoichiometry
when using the terms ``olivine'' and ``pyroxene.'') We list the derived mass
fractions in Table~\ref{tab:silwall}.

The optical constants used for
olivines and pyroxenes come from \citet{dorschner95}.  We calculate the
opacities assuming segregated spheres and Mie theory for the adopted dust grain
size distribution.
For an explanation of how the forsterite opacity was computed, see the discussion
by \citet{poteet10}.

We also calculated the opacity for enstatite.  We adopt optical constants for
enstatite from \citet{huffman71} and  \citet{egan77},
crystalline bronzite at 300K from  \citet{henning97}, the three
crystalline axes of orthoenstatite from  \citet{jaeger98}, and crystalline
hypersthene from \citet[][Sample 1S]{jaeger94} for the 0.1--0.5, 0.533--1.105,
6.7--8.4, 8.7--98, and 98--8000~{$\mu$m} wavelength regimes, respectively.  The
optical constants from \citet{jaeger94} were modified to match the values
from \citet{jaeger98} as was done for forsterite as described by \citet{poteet10}.  Beyond 585~{$\mu$m},
the real part of the index of refraction, $n$, was chosen to be a constant value equal to
the value of $n$ at 585~{$\mu$m} obtained by modifying the \citet{jaeger94} $n$
values, and the
imaginary part of the index of refraction, $k$, was determined by scaling a 1$/{\lambda}$ curve to the value of $k$, at
585~{$\mu$m} from the modified \citet{jaeger94} values.  The absorption
opacity was then computed from these optical constants by CDE theory \citep{bohren83}.
The scattering opacity is assumed to be zero.

Finally, we compute the opacity for silica.  We adopt optical constants from the
following sources for silica.  Between 0.05 to 0.15~{$\mu$m}, alpha quartz from
\citet{palik85} is used.  From 3-8~{$\mu$m}, $k$ comes from $k_{abs}$ for amorphous
silica from \citet{palik85}.  For $k$ between 0.15 and 3~{$\mu$m}, $k$ is interpolated
between its values at 0.15 and 3~{$\mu$m}.  From 0.15 to 5.5~{$\mu$m}, $n$ comes
from \citet{palik85} for alpha quartz.  Between 8 and 30~{$\mu$m}, the $n$ and $k$
values for beta quartz at 975~K from \citet{gervais75} are used.  From
50-333~{$\mu$m}, both $n$ and $k$ are from \citet{loewenstein73} for alpha quartz
at room temperature.  The value of $n$ at 333~{$\mu$m} was kept constant to 8000~{$\mu$m}.  For $k$, a 1$/{\lambda}$ curve fit to the value of $k$ at 333~{$\mu$m} was used.
To compute the absorption opacity, we employed CDE at all wavelengths except 8 to 40~{$\mu$m}. Between
8 to 40~{$\mu$m} the absorption opacity was for annealed silica from \citet{fabian01}.
The scattering opacity at all wavelengths is assumed to be zero.

In addition to silicates, for
each of the disks, we add organics and troilite to the dust mixture
following \citet{espaillat10} with ${\zeta}_{org}$ = 0.001 and
${\zeta}_{troi}$ = 0.000768 and sublimation temperatures of $T_{org}$ =
425~K and $T_{troi}$ = 680~K. We include water ice as well with a
sublimation temperature of 110~K.  Unless otherwise noted, we use
${\zeta}_{ice}$ = 0.00056. Optical constants for organics, troilite, and water
ice are adopted from \citet{pollack94}, \citet{begemann94}, and
\citet{warren84}. In objects where we include optically thin dust within
the hole or gap, the silicate dust composition is listed in
Table~\ref{tab:silthin}.  The abundances of silicates, organics, and
troilite in the optically thin dust region are given in the subsequent
sections.  We do not include ice in the optically thin region since the
temperatures here are high enough for it to have sublimated.

\subsection{SED Modeling} \label{sec:modsed}

Here we provide an overview of our modeling results.
In the Appendix, we describe in detail the modeling conducted in this
study for each individual object.

\subsubsection{Disk Structure}

We can explain most of the seesaw variability observed in the pre-transitional disks
by changing the height of the inner disk wall. (We note that other possible explanations
including changes in the stellar and disk properties have not been explored here.)
In the pre-transitional disks of LkCa~15,
SZ~Cha, and UX~Tau~A we can reproduce the
seesaw variability by changing the height of the inner
disk wall by $\sim$22$\%$, 33$\%$, and 17$\%$ respectively (Figure~\ref{figlkca15}).
When the inner wall is taller, the emission at the shorter wavelengths where the wall
dominates the emission is higher; there is also a larger shadow on the outer wall and hence the
emission seen from the outer wall is less and the IRS spectrum is lower.   Correspondingly, when the inner wall is lower there is less near-IR emission and the shadow on the outer wall is smaller and so we see more emission from the outer wall longwards of 20~{$\mu$m}.  The
10~{$\mu$m} silicate emission in LkCa~15 and SZ~Cha does not change. This emission is
dominated by small dust in the optically thin region.  UX~Tau~A does not have
a discernible 10~{$\mu$m} silicate emission feature.

Because of uncertainties
introduced to the observations by mispointing, we do not attempt to reproduce the
variability seen in RY~Tau (Figure~\ref{figrytau}).
However, we can fit the SED of RY Tau with an 18~AU gap which contains some
optically thin dust.  In the case of WW~Cha (Figure~\ref{figwwcha}), due to the fact that the GO
observations were significantly mispointed and that we do not have a mass accretion rate estimate, we do not attempt to model its disk here.

We also do not have a mass accretion rate for ISO~52 (Figure~\ref{figiso52}).  However, these observations
were well pointed and for the purposes of reproducing
the general trend seen in the variability, we assume a typical value (see the Appendix for more details).
In this object, we need to increase the height
of the inner wall by $\sim$400$\%$ between the GTO and GO epochs
to explain the observed variability.   Assuming that
our assertion that the inner wall height is varying is correct, this is by far the largest
change in wall height seen in the sample.

CR~Cha has a substantial change in slope at $\sim$6~{$\mu$m} (Figure~\ref{figchx3}), from which
one could
infer that there is either a substantial change in the temperature of the wall or a change in the nature of the emission from
optically thick to optically thin.  We find that
CR~Cha is best explained with a pre-transitional disk model in the GTO
observations and either a pre-transitional or transitional disk model in the GO observations.
See the Appendix for more details and {\S}~\ref{crchadis} for a discussion.

In the pre-transitional disks of IP~Tau, T56, and T35, we can reasonably reproduce the
emission within the uncertainties of the observations by varying the height of the inner
disk wall by 17$\%$, 50$\%$,
and 20$\%$, respectively (Figure~\ref{figiptau}).
In addition to varying the height of the inner
wall, we also had to change the amount of dust in the optically thin
regions of IP~Tau and T56 in order to reproduce the variability in the
10~{$\mu$m} silicate emission feature.

We also modeled the transitional disks in the sample (Figures~\ref{figgmaur}
and~\ref{figdmtau}).  GM~Aur displays seesaw behavior. To fit it we vary the amount of
optically thin dust in the hole and have to change the height of the
outer wall as well.  In CS~Cha, only
the 10~{$\mu$m} silicate emission changes between epochs and to fit
this variability we alter the amount of dust in the optically thin
region. In DM~Tau and T25 there is no variability and there
is no evidence for significant amounts of dust in their holes.

There is some variability in the pre-transitional disks which we cannot
explain by changing the height of the inner disk wall.
The GO2 spectrum of T35 has a change in slope at $\sim$7~{$\mu$m} which we
could not explain with the disk models presented here.  We have no
obvious explanation for this but speculate it could be related to the
high temperature derived for the inner disk wall (1800~K).
In UX~Tau~A, the overall emission from the disk
has decreased with time (i.e. the GO spectra have less emission than the
GTO spectra).
While we do not try to fit this decrease with models,  it
can possibly be attributed to a decrease in the luminosity  at the bands where the disk absorbs
stellar radiation, most likely due to star spots \citep{skrutskie96}, or
an overall decrease in the accretion luminosity of the disk, most likely from a change in
the mass accretion rate by a factor of about 3.
We also analyzed an additional SHLH spectrum from the {\it Spitzer} archive (see Appendix for more details).  This spectrum has substantially lower emission at ${\lambda}>$13~{$\mu$m} (Figure~\ref{uxshlh}).
We can fit the SHLH spectrum using an inner wall
with a temperature of 1800~K.  This hotter inner wall is closer to the star and leads to a larger shadow on the outer wall.
Given that we do not have simultaneous data at shorter wavelengths, we
cannot test if this wall fits the SED at ${\lambda}<$10~{$\mu$m} at the time the SHLH spectrum was taken.

\subsubsection{Dust Composition}

As a result of trying to reproduce the variability observed in our
sample, in this study we also performed fitting of the silicate
emission features visible in the IRS spectra, deriving the mass fraction
of amorphous and crystalline silicates in the outer wall and the
optically thin regions (Tables~\ref{tab:silwall} and~\ref{tab:silthin}).
(We refer the reader to Figure 1 of \citet{watson09} for the positions
of the strongest features of crystalline silicates visible in IRS spectra.)
We do not attempt a detailed ${\chi}^{2}$ fitting since it would be too computationally
expensive to do so with our disk code.  Thus, the derived mass fractions in
Tables~\ref{tab:silwall} and~\ref{tab:silthin} should be taken as
representative of a dust composition that can reasonably explain the
observed SED.
We refer the reader to \citet{sargent09} for
a review of the typical degeneracies of dust fitting.  In short, large grains of amorphous olivine and amorphous pyroxene composition are the most degenerate, in the sense that one of these components
could be replaced by the other and a similar fit would be found.  Enstatite and forsterite are
also somewhat degenerate at cooler temperatures.  Another caveat, which was noted earlier,
is that the shapes of the grains in the disk are not well known.
We leave it to future work to further constrain the mass fractions of silicates in these disks.

For the inner wall of our objects, the silicate composition consisted
solely of amorphous olivines.  However, since the inner wall does not
produce significant 10~{$\mu$m} silicate emission in the objects in
this study, we have no way to distinguish between pyroxene and olivine
silicates in the inner wall.  Also, while we included crystalline
silicates in the disk behind the outer wall, it is the outer wall that
dominates the emission at the longer IRS wavelengths.  Because of these
previous two points, here we only discuss the composition of silicates
in the optically thin dust region and the outer wall.

Most of the absorption and emission of the outer walls in our sample are dominated by amorphous
silicates (Table~\ref{tab:silwall}).  The exception is T35 which is dominated by crystalline
silicates ($\sim$60$\%$). The optically thin region also tends to be dominated by
amorphous silicates with typically $\sim$10$\%$ or less of crystalline
silicates.  This is not the case in T56 which contains $\sim$25$\%$
crystalline silicates. Of the three crystalline silicates studied in
this work, we are more likely to see forsterite rather than
enstatite and silica in the optically thin region (Table~\ref{tab:silthin}). Comparing the
optically thin region and outer wall in objects that have both, it
appears that silica is more likely to be present in the outer wall.
Relative to the optically thin region, we find more crystalline
silicates in the outer walls of T56, SZ~Cha, and LkCa~15 and less for
CS~Cha and GM~Aur. The amount of crystalline silicates in CR~Cha and
IP~Tau is the same between both regions. RY~Tau has no evidence for
significant amounts of crystalline
silicates in its disk.

The results from the dust fitting performed in this work are in
reasonably good agreement with the detailed dust fitting conducted by
\citet{sargent09} which used a two-temperature model.  The objects that
the two samples have in common are DM~Tau, GM~Aur, IP~Tau, and LkCa~15.
 Both works find that these four disks are dominated by amorphous
silicates and that there are relatively few crystalline silicates
present.  Furthermore, olivine silicates dominate the inner parts of the
disk that contribute to the 10~{$\mu$m} emission.

\section{Discussion} \label{sec:discuss}

\subsection{Linking Infrared Variability to Disk Structure}

Understanding the underlying causes of the variability observed in this
sample depends upon the physical locations in the disk from which the
changes in flux arise.  Given that the sample was chosen to include
pre-transitional and transitional disks, the nature of these objects
will necessarily play a key role in this. The disk structures of
LkCa~15, UX~Tau~A, GM~Aur, and RY~Tau have been independently confirmed.
LkCa~15, UX~Tau~A, and GM~Aur have been imaged with millimeter
interferometers and large cavities in their disks have been observed
\citep[Andrews et al, in prep;][]{pietu06,hughes09}. Near-infrared
spectra have confirmed that the inner disks of LkCa~15 and UX~Tau~A are
optically thick while the inner disk of GM~Aur is optically thin
\citep{espaillat10}. Millimeter interferometric imaging of RY~Tau by
\citet{isella10} detects two spatially resolved peaks, an indicator of a
disk hole, whose separation translates to a cavity that is consistent
with the 18~AU gap inferred from the SED modeling in this work. For the
other objects in the sample, the disk structure is inferred solely from
SED modeling. Millimeter interferometry and near-IR data are needed to
confirm that there are cavities in these disks and to probe if the inner
disk is optically thick. However,  the IRS spectra of SZ~Cha, WW~Cha,
and T56 are reminiscent of LkCa~15, suggesting that they are gapped
disks as well.  Likewise, T35 resembles UX~Tau~A.  CS~Cha, DM~Tau, and
T25 have large deficits of flux which are strong indicators of inner
disk holes, as seen in GM~Aur.

It follows that one can roughly divide the disk into two regions --
inner (inner wall and$/$or optically thin dust region) and outer (outer
wall and outer disk). Interestingly, the only disks that do not display
variability in our sample are the transitional disks DM~Tau and T25
whose inner regions do not contain substantial amounts of small dust.
DM~Tau's inner hole is relatively devoid of small
dust and T25's inner region  contains only 10$^{-13}$~{\hbox{M$_{\odot}$}}.  In
contrast, the transitional disks of GM~Aur and CS~Cha have about ten times more small dust within
their optically thin inner cavities than the transitional disks of DM~Tau and T25. We can infer that there is not
enough material in the inner regions of DM~Tau and T25 to lead to
significant variability.  Objects in the sample that have a notable
amount of material in their inner region do vary.

\subsubsection{Inner Wall}

We attempted to understand the variability seen in our sample by fitting the
SED with disk models.
In the pre-transitional disks
of LkCa~15, SZ~Cha, UX Tau~A, IP~Tau, T56, and T35 we can reasonably
reproduce the emission between 5--38~{$\mu$m} within the uncertainties by varying the height of
the inner disk wall by 22$\%$, 33$\%$, 17$\%$, 17$\%$, 50$\%$,
and 20$\%$, respectively (Figures~\ref{figlkca15} and~\ref{figiptau}). When
the inner wall is taller, the emission at the shorter wavelengths is
higher since the inner wall dominates the emission at 2--8~{$\mu$m}.
The taller inner wall casts a larger shadow on the outer disk wall and
we see less emission at the wavelengths beyond 20~{$\mu$m} where the
outer wall dominates.  When the inner wall is shorter, the reverse
occurs. ISO~52 is an extreme case.  Its inner wall height has to change by
400$\%$ to explain the observed variability (Figure~\ref{figiso52}).

We did not attempt to fit the variability seen in the pre-transitional
disks of RY~Tau and WW~Cha due to complications introduced by
mispointing and insufficient data. However, these disks exhibit
seesaw-like variability
(Figures~\ref{figrytau} and~\ref{figwwcha}). Taking the
modeling described above into consideration, one can surmise that the
variability in these disks is also due to an inner wall which varies in
height.
While the variations in the SED for many objects in the sample can be reproduced by changes in the
height of the inner wall, we note that other explanations that have not been considered here
may possibly result in similar SED behaviors.  We leave exploration of this to future work.

\subsubsection{Optically Thin Dust Region}  \label{disoptthin}

In the pre-transitional disks of IP~Tau and T56 the 10~{$\mu$m}
silicate emission changes (Figure~\ref{figiptau}).  This feature is
dominated by sub-micron sized grains in the optically thin dust region
located within the disk gap.  We can reproduce the change in this
emission by adjusting the amount of small dust in this region.
Alternatively, given that the spatial distribution of this dust is
largely unknown, it is possible that part of the optically thin dust
region is in the shadow of the inner wall and so in some cases the
amount of dust we see in this region varies as the height of the inner
wall changes. In LkCa~15 and SZ~Cha, the 10~{$\mu$m} silicate emission
does not change. This indicates that the optically thin dust is
vertically distributed in such a way that it is not shadowed by the inner wall.
This could suggest that there is more dust in the gap that we do not
detect. Therefore, the values for the amount of dust in the gaps of
pre-transitional disks should be taken as a lower limit.  Alternatively,
this optically thin dust could be heated indirectly.
In order to explain the presence of the 10~{$\mu$m} silicate emission
feature in self-shadowed Herbig Ae$/$Be stars,
\citet{dullemond04} proposed that light reaches the shadowed
regions after being scattered off of the upper parts of the inner wall.
In addition, they suggest that the thermal emission from the wall
may also irradiate the shadowed region.  Similar mechanisms may
be at work in the optically thin regions of pre-transitional disks.

Of the four transitional disks in the sample, two exhibit variability:
CS~Cha and GM~Aur (Figure~\ref{figgmaur}). In CS~Cha, only the
10~{$\mu$m} silicate emission changes between epochs. We can explain
this by varying the amount of optically thin dust located within the
central cavity.  On the other hand, the dust in CS~Cha could be
spatially distributed in such a way as to cause the observed
variability. For example, CS~Cha is a spectroscopic binary and, while we
do not see the type of variability expected for a circumbinary disk
\citep{nagel10},  the optically thin dust in the hole of CS~Cha could be
unevenly distributed in such a way that the alignment of the binary
system at the time when the GO data was taken illuminates more of the
dust. High-resolution near-infrared interferometry of this object would
be ideal to test this.

To fit the variability of GM~Aur, we not only change the amount of
optically thin dust in the hole, we have to change the height of the
outer wall as well. \citet{espaillat10} demonstrated that GM~Aur's
near-infrared excess continuum between 1--5~{$\mu$m} could be
reproduced by emission from sub-micron-sized optically thin dust.  These
variability data suggest that there is some optically thick structure
in the inner disk
perhaps composed of large grains
and$/$or limited in spatial extent
which does not contribute
substantially to the emission between 1--5~{$\mu$m} and leads to
shadowing of the outer disk.  Alternatively,  it could be that while the
dust in the hole is vertically optically thin, it becomes horizontally
optically thick at some radius and shadows the outer disk
\citep{mulders10}.  This scenario implies that the vertical extent of
the optically thin dust region changes to produce a shadow commensurate with the variable emission
at the longer wavelengths.
Then again, the fact that we have to change the height of the outer wall of GM Aur to fit its variability may not be linked
to shadowing of the outer wall by inner disk material, but by changes in the outer wall itself.  For example, our models assume the outer wall is axisymmetric, but changes in the visible area of the wall could lead
to different emission from the outer wall.  We note however that the orbital timescales at the outer wall are much
longer than the timescales probed in this work.
The case of GM~Aur needs to be explored further.

\subsubsection{The Unique Case of CR Cha} \label{crchadis}

CR~Cha displays a considerable change in slope at 6~{$\mu$m}
(Figure~\ref{figchx3}). In the other objects in this sample, the
emission at this wavelength is typically dominated by either an
optically thick inner wall or an optically thin dust region. This could
suggest that the inner disk alternates from being dominated by
optically thick material in the GTO epoch to being dominated by
optically thin dust at the time that the GO observations were taken
3~yrs later.  Alternatively, the change in slope at 6~{$\mu$m} could
also be due to a substantial decrease in the temperature of the inner
wall.
Accordingly, we reproduced the variability observed in
CR~Cha by fitting it with a pre-transitional disk model in the GTO epoch
and both a transitional and pre-transitional disk model in the GO epoch.

In the case where we fit the GO spectra with a transitional disk model, it follows that once the
optically thick inner wall disappears, we see all of the optically thin
dust within the disk hole.  Hence there is substantially more
10~{$\mu$m} emission in the GO observations which we reproduce by
increasing the amount of dust in the optically thin region.
We note that the height of the outer wall in the GO epoch, where we assume
that there is no shadowing, is less than the height of the wall in the GTO epoch
when there is an optically thick inner wall shadowing part of the outer wall.
Given that we take the shadowed portion of the outer wall into account in the case where the inner disk is optically
thick, this decrease in wall height in the case where the inner disk is optically thin
may imply that a portion of the outer wall is still shadowed.
As in the case of GM Aur discussed in {\S}~\ref{disoptthin}, this suggests
that either there is an optically thick structure in the inner disk that we cannot detect or that the vertically optically thin dust is radially optically thick.
It is expected that the optically thick inner disk in pre-transitional
disks will disappear at some point via accretion onto the star and$/$or
a lack of resupply of dust and gas from the outer disk, leaving behind a
transitional disk.   However, the viscous timescale at these radii
is on the order of 10$^{4}$~yrs making it improbable that we are detecting
this transition.

Alternatively, in the case where we fit the GO spectra with a pre-transitional disk model, we have to
decrease the temperature of the wall from 1400~K (in the GTO fit) to 800~K.  This corresponds
to a change in radius from 0.2~AU to 1~AU.  This may not be a viable model, since it is not clear
what process could make the dust grains sublimate above 800~K.  In any event, the amount of optically thin dust in the gap
remains about the same as seen in the GTO epoch.

Near-IR spectra at shorter wavelengths are necessary to decipher whether or not
the inner disk of CR~Cha is optically thick or optically thin.  Multi-epoch spectra would
be useful in constraining if the nature of the inner disk changes with time.
Millimeter confirmation of the hole in CR~Cha with
{\it ALMA} is necessary to decipher if there is indeed a cavity in this
disk.

\subsection{Physical Mechanisms Behind Variable Disk Structures}

\subsubsection{Variable Accretion}

A higher mass accretion rate will lead to a higher surface density in
the disk and so the height of the wall (defined as the point where the
optical depth to the stellar radiation reaches $\sim$1) will increase
\citep{muzerolle04}. In the cases of LkCa~15, SZ~Cha, UX Tau~A, IP~Tau,
T56, and T35  the change in the near-IR emission could be explained if
the mass accretion rate varies by factors of $\sim$3--10 relative to the
mass accretion rate used in this work. Studies have shown
that mass accretion rates onto the star are indeed variable. In the
transitional disk of TW Hya, accretion rates of 5$\times 10^{-10}$
M$_{\sun}$ yr$^{-1}$ (Muzerolle et al. 2000), 2$\times 10^{-9}$
M$_{\sun}$ yr$^{-1}$ (Herczeg et al. 2004), and 3.5$\times 10^{-9}$
M$_{\sun}$ yr$^{-1}$ (Ingleby \& Calvet, submitted) have been measured.
Alencar \& Batalha (2002) found that TW Hya's mass accretion rate varied
between 10$^{-9}$ -- 10$^{-8}$ M$_{\sun}$ yr$^{-1}$ over a one year
period and that smaller variations were seen even on periods of days.
While these accretion rates have been measured onto the star (i.e. the accretion columns),
the orbital timescales at the dust sublimation radius ($\sim$1~week) are within the timescales of
infrared variability seen. Hence the changes in the mass accretion rate in the inner disk necessary to change the
wall height are plausible.

However, if the mass accretion rate increases, the radius of the dust
sublimation radius will increase as well given that
$R_{wall}\propto(L_* + L_{acc})^{0.5}$ and $L_{acc}$ $\sim GM_*\hbox{$\dot M$}/R_*$ \citep{dalessio05}.
The change in the radius is much larger than the change in the wall height.
For a wall with a relatively similar height and a larger radius, the
shadow on the outer wall \citep[see Equations A4 and A5 in the appendix of][]{espaillat10} will not
be large enough to diminish the flux at the longer wavelengths to
the levels observed.  Therefore, a change in mass accretion rate alone
cannot explain the observed SEDs in the pre-transitional disks in our
sample, indicating that the variability in these disks is due to a
change in the wall height while keeping the radius of the wall fixed.

Earlier we noted that to fit the variability in the transitional disks
of  GM~Aur and CS~Cha and the pre-transitional disks of IP~Tau and T56,
we altered the amount of dust in the optically thin region.  It has been
proposed that this small dust exists in the holes of some objects due to
dust traveling with gas from the outer disk and into the inner disk
after being filtered at the outer wall \citep{rice06}.    In this
scenario, changes in the amount of dust in the optically thin region
could be due to variable mass accretion rates.

The reason behind the variability of accretion is not understood.
\citet{turner10} proposed that changes in the disk magnetic flux coupled
with changes in the X-ray luminosity can lead to substantial changes in
the mass accretion rates of typical TTS disks.  However, this applies to
accretion flows onto the star.  For the inner disk,  accretion variability
could be linked to the formation mechanism behind cavities in
disks, namely planets. One can speculate that changes in
mass accretion rate could be due to planetary companions which alter the
accretion flow in the inner disk regions, eventually getting onto the star. \citet{lubow06} and \citet{zhu10} demonstrate that planets will affect the mass accretion rate
into the inner disk.
It is possible that this could occur on the timescales seen here given that the 1--3 yr variability observed in our sample corresponds to orbital timescales of 1--2 AU, plausible
radii for planets to be located.

\subsubsection{Disk Warps} \label{diskwarps}

The changes seen in the inner disk could be due to warps. To explain the
variability seen in the transitional disk of LRLL 13,
\citet{muzerolle09} proposed that the variability was due to dynamical
changes in the inner disk, particularly in the form of disk warps.
\citet{flaherty10} showed that the seesaw-like variability observed
could be explained by models of a disk with an inner warp which
leads the height of  the inner disk to change with time. Such warps
could be due to the presence of multiple planets in the disk. While a
disk would damp the eccentricity of a single planet, multiple planets
would be able to maintain eccentric orbits which would induce
modulations that would effect the inner disk edge \citep{dangelo06},
leading to the change in the height of the inner wall needed to
reproduce the observations of pre-transitional disks.

Warps caused by planets could account for the timescales of the flux
changes seen in our sample. Variability on timescales of 1--3 yr
corresponds to orbital timescales of 1--2 AU and 1 wk timescales
correspond to 0.07~AU. Radii of 1--2~AU are plausible locations for
planetary companions.  A radius of 0.07~AU is comparable to the dust
destruction radius.   Many ``hot Jupiters'' are known to exist at radii
$<$0.1~AU \citep{marcy05}, comparable to or within the magnetospheric
radius of their host stars and well within the dust sublimation radius,
most likely reaching their current positions via migration
\citep{rice08}.

\subsection{The Composition of Silicate Dust in the Disk}

The formation of crystalline silicates requires high temperatures
\citep{fabian01}. One proposed mechanism for the formation of
crystalline silicates is accretion heating in the innermost disk,
close to the dust sublimation radius \citep[e.g.][]{gail01}. However, in
our objects crystalline silicates can be seen in the outer wall, which
is located at radii much further than the dust sublimation radius. In
several other studies, it is also found that crystalline silicates are
in the outer regions of the disk \citep{bouwman08,watson09,sargent09,olofsson09,olofsson10}.
This suggests that large-scale radial mixing is necessary to transport
the crystalline silicates that form near the dust destruction radius out
to larger radii in the disk  \citep[e.g.][]{boss04, gail04, keller04, ciesla07},
but this must occur before the hole or gap forms.  Alternatively,
crystalline silicates can form in the inner disk due to heating from shocks
in the disk created by planets \citep{desch05, boss05, bouwman08}.
In this case, the crystalline silicates would still need to be transported to
the outer disk.
Changes in the accretion rate or stellar luminosity could possibly lead to
the formation of crystalline silicates in the surface layers of the disk as proposed in the
case of EX Lupi  \citep{abraham09}.
Or as noted
by \citet{espaillat07b}, local processing may be due to collisions of
larger bodies that produce small grains heated to temperatures high
enough to create crystals.

One interesting by-product of this study is the possibility to explore
how or if the silicate composition is linked to the variability seen in
the sample. Indeed, we find that the four disks with 1~wk
variability contain the highest amounts of
crystalline silicates in the sample.   In UX~Tau~A, ISO~52, T35, and
T56, the outer wall is composed of $\sim$19$\%$, 20$\%$, 60$\%$, and 18$\%$
crystalline silicates, respectively.  (The next highest fraction is
$\sim$13$\%$, found in SZ~Cha.)  The optically thin regions of ISO~52 and T56 are
$\sim$20$\%$ and $\sim$25$\%$
crystalline silicates, respectively, higher than any other disks in the sample by a factor of at least 2.
In larger studies of samples
focusing on low-mass stars, there is very little correlation between the crystalline silicate mass fraction and any
stellar or disk property aside from the positive correlations with other crystalline silicate abundances
and the amount of dust settling in the disk \citep{sargent09,watson09}.

The trend between crystalline mass fraction and short timescale variability
points to a link behind the underlying cause of the silicate composition
of the disk and the seesaw behavior observed. We propose that this link
is planets.  Planets can instigate warps, shocks, and collisions in the
disk which can lead to both changes in the height of the inner disk wall
and a higher abundance of crystalline silicates.
Planets can also lead to recurring changes in the disk.
In T56 and T35, the variability observed at $\lambda >$ 20~{$\mu$m} appears
to oscillate between a maximum and minimum flux.  For T56, the flux at these wavelengths
is at a minimum in the GTO epoch, it increases in the GO1 epoch, and in the GO2 epoch it
decreases back to the same flux observed in the GTO epoch.
In T35, the GTO and GO1 spectra are both at the maximum and the GO2 spectrum
is lower.
Such changes point to a periodic origin, such as a planetary orbit.
Since planets are
likely present in most of the disks in this sample, it would seem that
these four disks with high amounts of crystalline silicates either have more planets or that the presence of hot
Jupiters (see {\S}~\ref{diskwarps}) is significant.

\section{Summary \& Conclusions} \label{sed:sum}

In this work we see various types of variability on 3-4 year timescales
and in some cases we see variability on 1 week timescales. The dominant
type of variability observed can be classified as seesaw-like behavior,
whereby the emission at shorter wavelengths varies inversely with the
emission at longer wavelengths.

We attempted to understand the origin of the variability in pre-transitional
and transitional disks by modeling the overall
SEDs at different epochs.
For many of the pre-transitional disks
we find that the variability can be explained by changing the height of
the inner disk wall and hence the shadow on the outer disk.  Typically, the
height of the wall varies by $\sim$20$\%$.   We also
perform SED model fitting for the transitional disks GM~Aur and CS~Cha.
To fit the variability of GM~Aur, we vary the amount of
optically thin dust in the hole and the height of the
outer wall.  In CS~Cha, only
the 10~{$\mu$m} silicate emission changes between epochs and so we only alter the amount of dust in the optically thin region.
The transitional disks DM~Tau and T25 are the
only two disks in the sample which display no variability.  These disks' inner regions do not contain discernible amounts of dust.

We propose that planets are responsible for the changes observed in
our sample.
Overall, it seems that most of the variability seen is due to material
in the inner disk casting a shadow on the outer disk.  The height of the
inner wall can vary due to disk warps caused by planets in the
disk. We can also link the silicate dust
compositions found in this work to the presence of planets.
We find that crystalline silicates are
common in the outer disks of our objects, too far from the central star
to be explained by most crystallization mechanisms.  In addition, the four disks in
our sample which have the highest crystalline silicate mass fractions
vary on 1~wk timescales.  In two of these four disks, we see periodic changes
in the infrared emission.
Planets can cause shocks and collisions which can heat the dust to
high enough temperatures to crystallize the dust.  Planets
can also lead to short timescale and periodic variability.
Follow-up variability studies conducted with the {\it James Webb Space Telescope} will
give us the simultaneous, multi-wavelength data needed to
test if the variability observed in our sample is periodic as well as the sensitivity to
significantly expand the sample size.

 \acknowledgments{
 We thank the referee for a constructive and thorough report.
 We thank Lee Hartmann for providing comments on the manuscript
and Steve Lubow for useful discussions.
C.~E.~was supported by the National Science Foundation under Award No. 0901947.
 E.F. was supported by NASA through the Spitzer Space Telescope
Fellowship Program, through a contract issued by JPL/Caltech
under a contract with NASA.
P.~D.~acknowledges a grant from PAPIIT-DGAPA UNAM.
 E.~N. acknowledges a postdoctoral grant from CONACyT.
N.~C.~acknowledges support from NASA Origins Grant NNX08AH94G.
}

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