Astrometry of AGB Variables with VERA : Annual Parallax and the Orbit of SY Sculptoris in the Galaxy
Astrometry of AGB Variables with VERA : Annual Parallax and the Orbit of SY Sculptoris in the Galaxy
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DOI：
10.1093/pasj/63.1.63
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发表时间：
2011-02
影响因子：
2.3
通讯作者：
Daisuke Nyu;A. Nakagawa;M. Matsui;H. Imai;Y. Sofue;T. Omodaká;T. Kurayama;R. Kamohara;T. Hirota;M. Honma;K. Shibata;H. Kobayashi;K. Iwadate;T. Miyaji
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文献类型：
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作者：
Daisuke Nyu;A. Nakagawa;M. Matsui;H. Imai;Y. Sofue;T. Omodaká;T. Kurayama;R. Kamohara;T. Hirota;M. Honma;K. Shibata;H. Kobayashi;K. Iwadate;T. Miyaji
报道了2006年10月至2008年10月利用VLBI射电天体测量探测（VERA）对Mira变星雕塑星SY（SY Scl）的H2O脉泽天体测量观测结果。我们确定SY Scl的年视差为0.75 stec 0.03 mas，对应的距离为1.33 stec 0.05 kpc。SY Scl位于银道面以南1.3千秒差距，以63 stec 2k m·s-1的速度从银道面向南移动。从目前的位置和运动，我们计算了SY Scl的轨道的最后1 Gyr的基础上的银河系引力位的参数化模型。SY Scl的轨道是银河系厚盘星的一员。减去脉泽的平均绝对自行，我们导出了SY Scl中H_2O脉泽的内部运动。脉泽的运动学与单一平面内的运动是一致的。发现SY Scl周围的脉泽分布在70 Au ~ 80 Au的区域内，相当于恒星光球直径5 Au的15倍。根据对SY Scl的距离和视星等的测量，我们得到SY Scl的绝对星等为MK = 8.07 tec0.08 mag，这与由银河系Mira周期光度关系（2008，MNRAS，386，313）推导出的8.09 tec0.07 mag的值基本一致。
We report on the results of astrometric observations of H2O masers toward a Mira variable, SY Sculptoris (SY Scl), with the VLBI Exploration of Radio Astrometry (VERA) from 2006 October to 2008 October. We determined that SY Scl’s annual parallax is 0.75 ˙ 0.03 mas, corresponding to a distance of 1.33 ˙ 0.05 kpc. SY Scl is 1.3 kpc south of the Galactic plane and moves approximately south from the plane with a velocity of 63 ˙ 2k m s � 1 with respect to the LSR. From the present position and motion, we calculated SY Scl’s orbit for the last 1 Gyr based on a parametrized model of the Galactic gravitational potential. SY Scl has an orbit as a member of the Galactic thick disk stars. Subtracting the averaged absolute proper motions of masers, we derived an internal motion of H2O masers in SY Scl. The kinematics of the masers is consistent with motion in a single plane. The masers around SY Scl were found to be distributed in an area of 70 AU � 80 AU, corresponding to 15 times as large as the stellar photosphere diameter of 5 AU. Based on the measured distance and apparent magnitude of SY Scl, we find the absolute magnitude of SY Scl to be MK = � 8.07 ˙ 0.08 mag. This is approximately consistent with the value of � 8.09˙0.07 mag, which was derived from the Galactic Mira period–luminosity relation (2008, MNRAS, 386, 313).