Contributed Talk - Splinter Relativistic

Friday, 25 September 2020, 11:00   (virtual room J)

NICER and Swift monitoring of a new black hole X-ray binary

H. Stiele, A. Kong
National Tsing Hua University

The X-ray Timing Instrument of the Neutron star Interior Composition Explorer (NICER) allows investigating short-term variability of compact objects in the soft (0.2-12 keV) X-ray band. We analysed publicly available NICER and Swift monitoring data of the bright, recently detected black hole X-ray binary MAXI J1820+070. The monitoring capabilities of NICER did not only allow us to investigate the main outburst, but also to study the source evolution after the end of the outburst, resulting in the detection of (several) reflares or mini-outbursts. We computed the fundamental diagrams commonly used to study black hole transients and present our findings on outburst evolution, quasi-periodic oscillations and state transitions. MAXI J1820+070 showed in many observations type-C quasi-periodic oscillations with a characteristic frequencies below 1 Hz. This finding suggests that the source stayed in a state of low effective accretion for large parts of its outburst. In addition, we present the results of our study of covariance spectra and of multi-waveband studies based on Swift/UVOT data, and discuss implications on the accretion geometry.