The Soft State of the Black Hole Transient Source MAXI J1820+070: Emission from the Edge of the Plunge Region?

Abstract

The Galactic black hole X-ray binary MAXI J1820+070 had a bright outburst in 2018 when it became the second brightest X-ray source in the Sky. It was too bright for X-ray CCD instruments such as XMM-Newton and Chandra, but was well observed by photon-counting instruments such as NICER and NuSTAR. We report here on the discovery of an excess emission component during the soft state. It is best modelled with a blackbody spectrum in addition to the regular disk emission, modelled either as diskbb or kerrbb. Its temperature varies from about 0.9 to 1.1 keV which is about 30 to 80 per cent higher than the inner disc temperature of diskbb. Its flux varies between 4 and 12 percent of the disc flux. Simulations of magnetised accretion discs have predicted the possibility of excess emission associated with a non-zero torque at the Innermost Stable Circular Orbit (ISCO) about the black hole, which from other NuSTAR studies lies at about 5 gravitational radii or about 60 km (for a black hole mass is 8 M). In this case the emitting region at the ISCO has a width varying between 1.3 and 4.6 km and would encompass the start of the plunge region where matter begins to fall freely into the black hole.

8 pages, 10 figures, accepted for publication in MNRAS

References in corpus (5)

• The corona contracts in a black-hole transient
• Three-Dimensional Simulations of Magnetized Thin Accretion Disks around Black Holes: Stress in the Plunging Region
• X-ray reflection in accreting stellar-mass black hole systems
• X-ray and Optical Monitoring of State Transitions in MAXI J1820+070
• The thickness of a weakly-magnetized accretion flow inside the last stable orbit of a Kerr black hole

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• The NICER "Reverberation Machine": A Systematic Study of Time Lags in Black Hole X-Ray Binaries
• Re-estimating the Spin Parameter of the Black Hole in Cygnus X-1
• A New Spin on an Old Black Hole: NuSTAR Spectroscopy of EXO 1846-031
• A variable corona during the transition from type-C to type-B quasi-periodic oscillations in the black hole X-ray binary MAXI J1820+070
• Physical origin of the nonphysical spin evolution of MAXI J1820+070
• A spectral study of the black hole X-ray binary MAXI J1820+070 with AstroSat and NuSTAR
• A spectrally stratified hot accretion flow in the hard state of MAXI J1820+070
• A timing-based estimate of the spin of the black hole in MAXI J1820+070
• The current state of disk wind observations in BHLMXBs through X-ray absorption lines in the iron band
• Observations of the Disk/Jet Coupling of MAXI J1820+070 During its Descent to Quiescence
• The Evolution of Rapid Optical/X-ray Timing Correlations in the Initial Hard State of MAXI J1820+070
• Dips and eclipses in the X-ray binary Swift J1858.6-0814 observed with NICER
• Accretion within the innermost stable circular orbit: analytical thermodynamic solutions in the adiabatic limit
• The origin of optical emission lines in the soft state of X-ray binary outbursts: the case of MAXI J1820+070
• Accretion Scenario of MAXI J1820+070 during 2018 Outbursts with Multi-mission Observations
• Impact of the reflection model on the estimate of the properties of accreting black holes
• The Donor of the Black-Hole X-Ray Binary MAXI J1820+070
• Dynamics of spinning particles in Reissner-Nordström black hole exterior
• MAXI J1820+070 with NuSTAR II. Flaring during the hard to soft state transition with a long soft lag
• A multi-wavelength study of the hard and soft states of MAXI J1820+070 during its 2018 outburst
• Gamma-ray observations of MAXI J1820+070 during the 2018 outburst
• The bright black hole X-ray binary 4U 1543--47 during 2021 outburst: a thick accretion disk inflated by high luminosity
• NICER and Swift/XRT monitoring of the 2023 outburst of Swift J1727.7-1613
• The plunging region of a thin accretion disc around a Schwarzschild black hole
• A rapid black hole spin or emission from the plunging region?
• Evidence for a dynamic corona in the short-term time lags of black hole X-ray binary MAXI J1820+070
• Revisiting the galactic X-ray binary MAXI J1631-479: Implications for high inclination and a massive black hole
• The inner structure and thermodynamics of a thin accretion disc
• Intermittent QPO properties of MAXI J1820+070 revealed by Insight-HXMT
• Accretion disc winds in X-ray binaries
• Generally Applicable Formalism for Modeling the Observable Signatures of Inflows, Outflows, and Moving Coronal Plasma Close to Kerr Black Holes
• The population of NuSTAR Black Hole X-ray Binaries
• Testing theories of accretion and gravity with super-extremal Kerr discs
• Tracking optical variability and outflows across the accretion states of the black hole transient MAXI J1820+070
• Accretion Geometry of Black Hole X-ray Binaries: Insights from X-ray Observations
• Spectral and Timing Analysis of NuSTAR and Swift/XRT Observations of the X-Ray Transient MAXI J0637-430
• Tracking the evolution of the accretion flow in MAXI J1820+070 during its hard state with the JED-SAD model
• Multiwavelength study of 1eRASS J085039.9-421151 with eROSITA NuSTAR and X-shooter
• The complex spectral behavior of the newly discovered neutron star X-ray binary Swift J1858.6-0814