<p>One thing that seems to be clear is that HgMn stars have only an extremely weak net longitudinal magnetic field component, if any. <a href="http://www.ast.obs-mip.fr/users/donati/pub/weak.pdf" rel="nofollow">Shorlin et al. (2002)</a> did an early survey of HgMn, Am, and Ap stars, and detected no longitudinal magnetic fields in the former, with a median 1$\sigma$ uncertainty of 39 Gauss. <a href="http://journals.cambridge.org/download.php?file=%2FIAU%2FIAU6_S272%2FS1743921311010349a.pdf&amp;code=d09eb28ac837ffb701f7ea49a2a202a6" rel="nofollow">Makaganiuk et al. (2010)</a> also found $B_z$ values of 0 in the stars they surveyed, with a higher precision - a 1$\sigma$ uncertainty of 0.81-10 Gauss, varying between stars. Other studies also yielded precisions of less than a few Gauss for some stars (see mentions by <a href="https://uu.diva-portal.org/smash/get/diva2:450464/FULLTEXT01.pdf" rel="nofollow">Makaguniak (2011)</a>).</p>

<p>Some reports have found longitudinal values in the 10s to 100s of Gauss, but as <a href="http://www.astro.uu.se/~oleg/papers/moscow13.pdf" rel="nofollow">Kochukhov</a> notes, subsequent inveistigations have failed to confirm these findings, which have had extremely high uncertainties. One example is <a href="http://arxiv.org/abs/1208.2910" rel="nofollow">Hubrig et al. (2012)</a>, the paper you cite, which claimed to have found weak longitudinal and quadratic fields in several stars, including HD 65949. <a href="http://www.diva-portal.org/smash/get/diva2:644466/FULLTEXT01.pdf" rel="nofollow">Kochukhov et al. (2013)</a> then found no longitudinal fields on the star, to within a few Gauss, and <a href="http://arxiv.org/abs/1309.2158?context=astro-ph.SR" rel="nofollow">Bagnulo et al. (2013)</a> attributed to 2012 findings to instrument error, leading to flawed data.</p>

<p>Non-longitudinal magnetic fields have not been observed in much detail (small-scale longitudinal fields have not yet been ruled out, either, by large-scale global ones appear to be nonexistent), and complicated ones could still exist. Kochukhov et al. (2013) do say that they have ruled out large so-called tangled magnetic fields, but small-scaled ones are still possible, according to <a href="http://www.ta3.sk/caosp/Eedition/FullTexts/vol27no3/pp296-303.pdf" rel="nofollow">Hubrig</a>.</p>

<p>One thing worth noting is that the vast majority of these studies, including the one you referenced, which has been disputed, are focused on B-type HgMn stars, in part because fewer A-type HgMn stars have been discovered.</p>

CC BY-SA 3.0
2016-04-09T20:30:41.057Z
2016-04-09T20:30:41.057Z
HDE 226868
<p>Do <a href="https://en.wikipedia.org/wiki/Mercury-manganese_star">HgMn</a> (peculiar A type) stars really possess global magnetic fields? See, for example, <a href="http://arxiv.org/abs/1208.2910">this paper</a> by Hubrig et al. from 2012.</p>

CC BY-SA 3.0
2015-08-17T16:13:43.670Z
As this is an area of debate in the scientific community, could someone who knows about it summarise both sides of the debate? @HDE226868, I don't think we're ever sure, but someone with a background in this area would know how to find the relevant papers and explain the results in laymans terms.
FJC
CC BY-SA 3.0
2014-11-30T02:41:36.157Z
[A related meta discussion](http://meta.astronomy.stackexchange.com/questions/271/what-in-the-world-do-we-do-with-this-question). The issue here is that the answer to this is a "We're not sure", but I'm reluctant to post an answer built around that.
HDE 226868
CC BY-SA 3.0
2014-03-13T10:39:21.007Z
'Do they possess magnetic fields'... Not 'are they possess magnetic fields'. Why do you ask? Is there something about the paper that is a problem for you? Is there a reason why you would find it surprising to have it claimed that HgMn stars have a magnetic field, al beit a weak one?
Jeremy
CC BY-SA 3.0
2014-08-13T17:42:53.010Z
My interpretation of the question (and of course correct me if I'm wrong) was that @user2579566 was asking if the magnetic fields exist on these stars, due to the ongoing debate in the scientific community. Is that the case, or am I off-track?
HDE 226868
CC BY-SA 3.0
2014-08-14T10:35:09.983Z
Yes, you are right @HDE226868
user2579566
CC BY-SA 3.0
2014-11-24T01:54:05.417Z
So, what does the paper say about?
Py-ser
<star><magnetic-field>
Magnetic fields of peculiar HgMn A type stars
user2579566
# Magnetic fields of peculiar HgMn A type stars

(Asked by: username_0 on 2014-01-14)

Do [HgMn](https://en.wikipedia.org/wiki/Mercury-manganese_star) (peculiar A type) stars really possess global magnetic fields? See, for example, [this paper](http://arxiv.org/abs/1208.2910) by Hubrig et al. from 2012.

**Tags:** star, magnetic-field
> **Comments:**
> **username_3**: 'Do they possess magnetic fields'... Not 'are they possess magnetic fields'. Why do you ask? Is there something about the paper that is a problem for you? Is there a reason why you would find it surprising to have it claimed that HgMn stars have a magnetic field, al beit a weak one?  
> **username_2**: My interpretation of the question (and of course correct me if I'm wrong) was that @user2579566 was asking if the magnetic fields exist on these stars, due to the ongoing debate in the scientific community. Is that the case, or am I off-track?  
> **username_0**: Yes, you are right @HDE226868  
> **username_4**: So, what does the paper say about?  
> **username_2**: [A related meta discussion](http://meta.astronomy.stackexchange.com/questions/271/what-in-the-world-do-we-do-with-this-question). The issue here is that the answer to this is a "We're not sure", but I'm reluctant to post an answer built around that.  
> **username_1**: As this is an area of debate in the scientific community, could someone who knows about it summarise both sides of the debate? @HDE226868, I don't think we're ever sure, but someone with a background in this area would know how to find the relevant papers and explain the results in laymans terms.  

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## 1 answers

### Answer by username_2 on 2016-04-09. Score: 4

One thing that seems to be clear is that HgMn stars have only an extremely weak net longitudinal magnetic field component, if any. [Shorlin et al. (2002)](http://www.ast.obs-mip.fr/users/donati/pub/weak.pdf) did an early survey of HgMn, Am, and Ap stars, and detected no longitudinal magnetic fields in the former, with a median 1$\sigma$ uncertainty of 39 Gauss. [Makaganiuk et al. (2010)](http://journals.cambridge.org/download.php?file=%2FIAU%2FIAU6_S272%2FS1743921311010349a.pdf&code=d09eb28ac837ffb701f7ea49a2a202a6) also found $B\_z$ values of 0 in the stars they surveyed, with a higher precision - a 1$\sigma$ uncertainty of 0.81-10 Gauss, varying between stars. Other studies also yielded precisions of less than a few Gauss for some stars (see mentions by [Makaguniak (2011)](https://uu.diva-portal.org/smash/get/diva2:450464/FULLTEXT01.pdf)).

Some reports have found longitudinal values in the 10s to 100s of Gauss, but as [Kochukhov](http://www.astro.uu.se/~oleg/papers/moscow13.pdf) notes, subsequent inveistigations have failed to confirm these findings, which have had extremely high uncertainties. One example is [Hubrig et al. (2012)](http://arxiv.org/abs/1208.2910), the paper you cite, which claimed to have found weak longitudinal and quadratic fields in several stars, including HD 65949. [Kochukhov et al. (2013)](http://www.diva-portal.org/smash/get/diva2:644466/FULLTEXT01.pdf) then found no longitudinal fields on the star, to within a few Gauss, and [Bagnulo et al. (2013)](http://arxiv.org/abs/1309.2158?context=astro-ph.SR) attributed to 2012 findings to instrument error, leading to flawed data.

Non-longitudinal magnetic fields have not been observed in much detail (small-scale longitudinal fields have not yet been ruled out, either, by large-scale global ones appear to be nonexistent), and complicated ones could still exist. Kochukhov et al. (2013) do say that they have ruled out large so-called tangled magnetic fields, but small-scaled ones are still possible, according to [Hubrig](http://www.ta3.sk/caosp/Eedition/FullTexts/vol27no3/pp296-303.pdf).

One thing worth noting is that the vast majority of these studies, including the one you referenced, which has been disputed, are focused on B-type HgMn stars, in part because fewer A-type HgMn stars have been discovered.


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