X-ray Observations of Two Very Faint X-ray Transients (VFXTs) during their outbursts
Abstract
We will present results obtained from a detailed study of two VFXTs, namely; MAXI J1957+032 (J1957) and Swift J1357.2-0933 (J1357). J1957 showed four short outbursts since its discovery in 2015. The nature of the compact object is not clear. We found that the identification depends on the distance to J1957. If the source is <2 kpc, then J1957 might be a black hole system, for distances between 4-8 kpc our results suggest that the source harbors neutron star and if the distances are larger than 8 kpc it is difficult to infer strong constraint on the nature of the accretor.J1357 is the only confirmed black hole VFXT. A toroidal structure in the inner region of the disk has been postulated similar to the obscuring tori seen around AGN. On April 20, 2017, it went into outburst for the second time. Spectral fitting performed using data of Swift-XRT and NuSTAR showed no signatures of cut-off, or any reflection from the disc or the putative torus.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E.298B