LBA observations for project V589 semester 2022APRS

High-mass gamma-ray binaries are very rare objects, with less than 10 known. The contain an O or B star and a compact object, usually a neutron star. Observations with the Fermi gamma-ray satellite recently identified a new binary system, 4FGL J1405.1?6119, with its binary nature confirmed with X-ray and ATCA observations. VLBI studies of the known gamma-ray binaries have been illuminating, detecting radio jets in case of one binary, and helping determine the distance to another. Our pilot study observation in March 2020 revealed the source is detectable (and potentially shows an interesting E-W elongation) and has established \r\n the most suitable of the potential phase reference calibrator sources trialled. We propose here for four more epochs, spread over a year, to measure the proper motion and parallax of the system.

大质量γ射线双星（High-mass gamma-ray binaries）是极为罕见的天体，目前已发现的此类系统不足10个。此类系统包含一颗O型或B型恒星与一颗致密天体（compact object），通常为中子星（neutron star）。借助费米γ射线空间望远镜（Fermi Gamma-ray Satellite）的观测数据，研究人员近期新发现了一个双星系统4FGL J1405.1?6119，其双星性质已通过X射线与ATCA观测得到证实。针对已知γ射线双星开展的甚长基线干涉测量（Very Long Baseline Interferometry, VLBI）研究已颇具成果：在一个双星系统中探测到了射电喷流（radio jets），并助力确定了另一系统的距离。我们在2020年3月开展的先导观测研究显示，该源可被探测到（且可能呈现出有趣的东西向伸长结构），并确定了所有候选相位参考校准源中经测试后最适宜的一个。我们在此提出申请，计划在为期一年的周期内安排4个额外的观测历元，以测量该系统的自行（proper motion）与视差（parallax）。