Formation of a Possible Black-hole Ultracompact X-ray Binary with the Shortest Orbital Period

Xing-Peng Yang, Kun Xu, Zhi-Fu Gao +2

In the bulge of M31, the Chandra observations discovered a possible black hole (BH) ultracompact X-ray binary (UCXB) Seq.1 with an orbital period of 7.7 minutes and a maximum X-ray…