Parkes observations for project P1131 semester 2021OCTS_07

Fast Radio Bursts (FRBs) are extragalactic radio transients with the duration time in the range of several microseconds to tens of milliseconds. The origin of them is still unclear. Ultraluminous X-ray Sources (ULXs) are objects that mostly discovered in external galaxies which host black holes or neutron stars, with isotropic luminosities exceeding the usual Eddington value for stellar-mass black holes. The host galaxies of ULXs, and their spatial offsets within their hosts, show broad similarities to those of FRB. Periodicity of days to years of some repeated FRBs could be attributed to the companion effect of ULXs. Moreover, pulsing ULXs (PULXs) which hots neutron stars may be the manifestation of accreting magnetars. Therefore, we propose targeted FRB searches of known PULXs, which have not yet been carried out by other telescopes according to published literature to date. Our observations will play an important role in investigating the FRB progenitors. If FRBs were detected in our selected ULXs, then puzzle of FRBs' origin would be directly resolved. If no FRB is detected, we can still constrain some ULX-related models statistically, e.g. the upper limit of the burst rate, the period of duty cycle, etc. Our observations can also be used to hunt for radio pulsars in PULXs.

快速射电暴（Fast Radio Bursts，FRBs）是一类河外射电暂现源，持续时长介于数微秒至数十毫秒之间，其起源至今尚未明确。超亮X射线源（Ultraluminous X-ray Sources，ULXs）是一类主要在河外星系中发现的天体，这类星系的宿主天体为黑洞或中子星，其各向同性能度远超恒星级黑洞的标准爱丁顿极限。超亮X射线源的宿主星系，以及其在宿主星系内的空间偏移特征，与快速射电暴的对应属性存在广泛相似性。部分重复快速射电暴所呈现的数日至数年周期特性，可归因于超亮X射线源的伴星效应。此外，宿主为中子星的脉冲型超亮X射线源（pulsing ULXs，PULXs），可能是吸积磁星的观测表现形式。基于上述关联，我们提出对已知脉冲型超亮X射线源开展针对性的快速射电暴搜寻工作，而截至目前已发表的研究文献显示，其他望远镜尚未开展此类观测项目。本次观测将在探究快速射电暴的起源前身天体方面发挥关键作用：若在我们选定的超亮X射线源中探测到快速射电暴，将可直接破解快速射电暴的起源之谜；若未探测到快速射电暴，我们仍可通过统计分析约束多款与超亮X射线源相关的理论模型，例如暴发率上限、占空比周期等。此外，本次观测还可用于搜寻脉冲型超亮X射线源中的射电脉冲星。