SURVEY OF CARBON MONOXIDE OUTFLOWS ASSOCIATED WITH MOLECULAR HYDROGEN EMISSION FEATURES IN THE NORTHERN ORION A MOLECULAR CLOUD
Park Geum-Sook;Choi Min-Ho 31
Near-IR $H_2$ emission features in the northern region of the Orion A giant molecular cloud were observed in the $CO\;J\;=\;1\;{\rightarrow}\;0$ line in search of CO outflows. Out of the 30 sources surveyed, CO line wings were detected toward 28 positions, suggesting a strong correlation between $H_2$ jets and CO outflows. Blueshifted wings were detected toward 26 positions while redshifted wings were detected toward 15 positions, which suggests that there is a bias in the source selection. The bias is more severe in OMC 3 than in OMC 2. Since the protostars in OMC 3 are younger and more deeply embedded, the bias may be caused by the difference of extinction between blueshifted and redshifted outflows. Some physical parameters of the outflows were derived from the line profiles.
A PHOTOMETRIC STUDY OF THE CONTACT BINARY XZ LEONIS
Lee Jae-Woo;Lee Chung-Uk;Kim Chun-Hwey;Kang Young-Woon 41
We present the results of new multi-color CCD photometry for the contact binary XZ Leo, together with reasonable explanations for the period and light variations. Six new times of minimum light have been determined. A period study with all available timings confirms Qian's (2001) finding that the O-C residuals have varied secularly according to $dP/dt\;=\;+8.20{\times}10^{-8}\;d\;yr^{-l}$. This trend could be interpreted as a conservative mass transfer from the less massive cool secondary to the more massive hot primary in the system with a mass flow rate of about $5.37{\times}10^{-8}\;M_{\odot}\;yr^{-l}$. By simultaneous analysis of our light curves and the previously published radial-velocity data, a consistent set of light and velocity parameters for XZ Leo is obtained. The small differences between the observed and theoretical light curves are modelled by a blue third light and by a hot spot near the neck of the primary component. Our period study does not support the tertiary light but the hot region which may be formed by gas streams from the cool secondary. The solution indicates that XZ Leo is a deep contact binary with the values of q=0.343, $i=78^{\circ}.8$, ${\Delta}(T_1-T_2)=126\;K$, and f=33.6 %, differing much from those of Niarchos et al. (1994). Absolute parameters of XZ Leo are determined as follows: $M_1=1.84\;M_{\odot},\;M_2=0.63\;M_{\odot},\;R_1=1.75\;R_{\odot},\;R_2=1.10\;R_{\odot},\;L_1=7.19\;L_{\odot},\;and\;L_2=2.66\;L_{\odot}$.
DEVELOPMENT OF SEMI-VLBI SYSTEM AND OBSERVATION OF SUN AT 21 cm
Park Yong-Sun;Kang Hyun-Woo;Kim Hyo-Uk;Kang Heui-Jeong;Jee Myeong-Keun;Lee Sul-Gi;Ahn Jung-Hyun;Kim Jin-Su;Shin Young-Soo;Kang Song-Hun 51
We report the development of a semi-VLBI observation system operating at 21 cm and present the measurement of visibility function toward the sun using this system. The system consists of two 2.3 meter antennas with a maximum separation of 35 meter, a conventional high speed data acquisition system, and a set of programs for software correlation. Since two local oscillators of receiver modules are independent, data had to be fringe-fitted to yield the visibility amplitude. It is found that the visibility amplitude decreases and then bounces back as baseline increases. We confirm that solar disk with brighter limb best explains the measured visibility amplitude.