Highlights from NICER's coverage of the black hole transient MAXI J1820+070

Jeroen Homan, Ronald Remillard, James F. Steiner, Joseph Neilsen, Keith Gendreau, Zaven Arzoumanian, Andrew Fabian, Erin Kara, Diego Altamirano, Phil Uttley, Abigail Stevens, Sara Motta, Rob Fender, James Miller-Jones, Joe Bright, David A. Williams

Research output: Contribution to conferenceAbstract


MAXI J1820+070 is a relatively nearby (3 kpc) black hole transient that showed an exceptionally bright outburst in 2018 that lasted for more than 250 days. This outburst was observed in great detail by NICER, with more than 700 individual pointings covering nearly six orders of magnitude in flux. The NICER data set of MAXI J1820+070 is one of the richest data sets for any black hole transient. Here we briefly present two of the main highlights from our ongoing analysis. The first result concerns the presence of a warm absorber during the fast rising phase of the outburst. From semi-regular dips in the light curve we infer that this absorbing structure is located at a few thousand gravitational radii from the black hole and has a large vertical extent. We suggest that its origin may be related to the disk not being able to handle the sudden increase in accretion rate. The second result concerns a rapid (few days) state transition near the peak of the outburst. Unprecedented monitoring with NICER enabled us to follow the evolution of the source in near real-time during this transition. Combined with high-quality coverage of a radio flare that occurred around the time of the transition, the NICER data allowed to address the question of whether or not a relatively rare type of low-frequency QPO is connected to the launch of transient radio jets in black hole X-ray binaries....
Original languageEnglish
Publication statusPublished - Mar 2019


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