Multiwavelength Observations of the Black Hole X-ray Binary MAXI J1820$+$070 in the Rebrightening Phase

Abstract

We report the results of quasi-simultaneous multiwavelength (near-infrared, optical, UV, and X-ray) observations of the Galactic X-ray black hole binary MAXI J1820+070 performed in 2019 May 10-13, $\sim 60$ days after the onset of the first rebrightening phase. It showed a much larger optical-to-X-ray luminosity ratio ($\sim 8$) than in the initial outburst epoch. The primary components of the spectral energy distribution (SED) can be best interpreted by radiatively inefficient accretion flow (RIAF) spectrum showing a luminosity peak in the optical band. By comparison with theoretical calculations, we estimate the mass accretion rate to be $\dot{M}/(8L_{\mathrm{Edd}}/c^2)\sim 10^{-3}$, where $c$ is the light speed and $L_{\mathrm{Edd}}$ is the Eddington luminosity. In addition to the RIAF emission, a blue power-law component is detected in the optical-UV SED, which is most likely synchrotron radiation from the jet. The optical spectrum taken at the Seimei telescope shows a weak and narrow H$\alpha$ emission line, whose emitting region is constrained to be $\gtrsim 2\times 10^4$ times the gravitational radius. We suggest that the entire disk structure cannot be described by a single RIAF solution but cooler material responsible for the H$\alpha$ emission must exist at the outermost region.

11 pages, 5 figures, Published in PASJ in 2022

References in corpus (14)

• Modelling the behaviour of accretion flows in X-ray binaries
• X-ray irradiation in XTE J1817-330 and the inner radius of the truncated disc in the hard state
• Reprocessing of X-rays in the outer accretion disc of the black hole binary XTE J1817--330
• An extremely powerful long-lived superluminal ejection from the black hole MAXI J1820+070
• Discovery of oscillations above 200 keV in a black hole X-ray binary with Insight-HXMT
• A radio parallax to the black hole X-ray binary MAXI J1820+070
• The binary mass ratio in the black hole transient MAXI J1820+070
• Opening angles, Lorentz factors and confinement of X-ray binary jets
• Insight-HXMT observations of jet-like corona in a black hole X-ray binary MAXI J1820+070
• X-ray and Optical Monitoring of State Transitions in MAXI J1820+070
• Near-infrared emission lines trace the state-independent accretion disc wind of the black hole transient MAXI J1820+070
• A Black Hole X-ray Binary at $\sim$100 Hz: Multiwavelength Timing of MAXI J1820+070 with HiPERCAM and NICER
• Black hole spin-orbit misalignment in the X-ray binary MAXI J1820+070
• Observations of the Disk/Jet Coupling of MAXI J1820+070 During its Descent to Quiescence

Cited by in corpus (3)

• 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
• Evolution of Accretion Disk Structure of the Black Hole X-ray Binary MAXI J1820$+$070 during the Rebrightening Phase
• Ultraviolet spectroscopy of the black hole X-ray binary MAXI J1820+070 across a state transition