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Simultaneous observations of SiO v=1 and v=2, J=1-0 masers toward WX Pisces with the KVN+VERA
윤영주,조세형,김재헌,윤동환,조치영,Yun, Youngjoo,Cho, Se-Hyung,Imai, Hiroshi,Kim, Jaeheon,Yoon, Dong-Hwan,Cho, Chi-Young 한국천문학회 2012 天文學會報 Vol.37 No.2
We present the results of simultaneous observations of SiO v=1 and 2, J=1-0 maser lines which were carried out with the combined network of the KVN and VERA in 2012 April. The observations were performed toward a long period OH/IR star, WX Psc in order to test the technical and scientific feasibilities of the KVN+VERA combination. The resultant (u, v) coverage of the KVN+VERA combined array enhances the image quality. We confirmed that the distribution and intensity of individual maser spots using the combined network are more reliable compared with the images using the KVN or VERA only. This observation also provides a chance to find a high sensitivity and imaging quality which are comparable to those of VLBA. In addition, the simultaneous observations of two SiO v=1 and 2, J=1-0 maser lines enable us to trace the detail physical environments close to the central star due to different high excitation conditions between two lines at a time.
Simultaneous observations of SiO and $H_2O$ masers toward AGB and post-AGB stars
윤동환,조세형,김재헌,조치영,윤영주,박용선,Yoon, Dong-Hwan,Cho, Se-Hyung,Kim, Jaeheon,Cho, Chi-Young,Yun, Youngjoo,Park, Yong-Sun 한국천문학회 2012 天文學會報 Vol.37 No.2
We performed simultaneous observations of SiO v=1, 2, $^{29}SiO$ v=0, J=1-0 and $H_2O$ $6_{16}-5_{23}$ maser lines toward 132 AGB and 183 post-AGB stars in order to investigate how evolutionary characteristics from AGB to post-AGB stars appear in these two maser emissions. The observations were carried out from 2011 February to 2012 March using the Korean VLBI Network 21-m radio telescopes. We have detected SiO and/or $H_2O$ maser emission from 29 sources out of 183 post-AGB stars including 19 new detections. Of 132 AGB stars which are mainly selected based on the IRAS Point Source Catalog, we detected SiO and/or $H_2O$ maser emission from 38 stars including 18 newly detected sources. An evolutionary characteristic from AGB to post-AGB stars is discussed in IRAS two-color diagram. It is found that SiO v=2, J=1-0 maser emission without SiO v=1 maser detections was detected from 8 sources among 21 SiO detected post-AGB stars and the intensity of SiO v=2, J=1-0 maser tends to be much stronger than that of SiO v=1. We also found that for the post-AGB stars the maser detection rate of blue group sources (which have higher outflow velocities than red group) are higher than that of red group. Especially, only $H_2O$ maser emission was detected from 7 sources among 94 red group sources without SiO maser detections.
Simultaneous observations of SiO and $H_2O$ masers toward OH/IR stars
조치영,조세형,김재헌,윤동환,윤영주,김성은,Cho, Chi-Young,Cho, Se-Hyung,Kim, Jaeheon,Yoon, Dong-Hwan,Yun, Youngjoo,Ki, Sungeun 한국천문학회 2012 天文學會報 Vol.37 No.2
We performed simultaneous observations of SiO v=1, 2, $^{29}SiO$ v=0, J=1-0 and $H_2O$ $6_{16}-5_{23}$ maser lines toward 252 OH/IR stars using the Korean VLBI Network 21m telescopes. The observations were carried out from 2011 November to 2012 July for studying SiO and $H_2O$ maser properties associated with the evolutionary stages of OH/IR stars. Both $H_2O$ and SiO masers were detected from 49 sources, one-side maser of SiO and $H_2O$ was detected from 109 and 11 sources, respectively. Mutual relations between SiO and $H_2O$ maser properties are investigated based on statistical analyses. We also investigate these maser properties in the IRAS two-color diagram related with stellar evolutionary sequence.