重力探测器B的VLBI。VII。飞马座IM射电结构的演化
VLBI for Gravity Probe B. VII. The Evolution of the Radio Structure of IM Pegasi
摘要：
我们目前的测量总的无线电通量密度，以及甚长基线干涉（VLBI）图像的恒星，飞马座IM，这是作为指导星的美国宇航局/斯坦福大学的相对论任务重力探测器B。我们获得了1997年1月至2005年7月期间在8.4 GHz（波长= 3.6 cm）的35次观测的通量密度和图像。这些观测是精确地相位参考几个河外参考源，我们提出的图像在一个以恒星为中心的框架，对齐的恒星的位置，从我们的拟合其轨道运动，视差和自行。IM Peg的通量密度和形态都是可变的。对于大多数会话，发射区域具有单峰结构，但25%的时间，我们观察到双峰（有时可能是三峰）结构。平均而言，发射区被拉长了1.4 ± 0.4质量（半高宽），平均拉长方向接近轨道法线的天空投影。发射区的平均长度近似等于主星的直径。没有显着的相关性与轨道相位被发现无论是流量密度或伸长的方向，并没有偏好任何特定的经度上的恒星所示的发射区。
英文摘要：
We present measurements of the total radio flux density as well as very-long-baseline interferometry (VLBI) images of the star, IM Pegasi, which was used as the guide star for the NASA/Stanford relativity mission Gravity Probe B. We obtained flux densities and images from 35 sessions of observations at 8.4 GHz (wavelength = 3.6 cm) between 1997 January and 2005 July. The observations were accurately phase-referenced to several extragalactic reference sources, and we present the images in a star-centered frame, aligned by the position of the star as derived from our fits to its orbital motion, parallax, and proper motion. Both the flux density and the morphology of IM Peg are variable. For most sessions, the emission region has a single-peaked structure, but 25% of the time, we observed a two-peaked (and on one occasion perhaps a three-peaked) structure. On average, the emission region is elongated by 1.4 +- 0.4 mas (FWHM), with the average direction of elongation being close to that of the sky projection of the orbit normal. The average length of the emission region is approximately equal to the diameter of the primary star. No significant correlation with the orbital phase is found for either the flux density or the direction of elongation, and no preference for any particular longitude on the star is shown by the emission region.
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