Shaw, A. W.;
Plotkin, R. M.;
Miller-Jones, J. C. A.;
Homan, J.;
Gallo, E.;
Russell, D. M.;
Tomsick, J. A.;
Kaaret, P.;
Corbel, S.;
Espinasse, M.;
Bright, J.
Observations of the Disk/Jet Coupling of MAXI J1820+070 during Its Descent to Quiescence
You can manage bookmarks using lists, please log in to your user account for this.
Media type:
E-Article
Title:
Observations of the Disk/Jet Coupling of MAXI J1820+070 during Its Descent to Quiescence
Contributor:
Shaw, A. W.;
Plotkin, R. M.;
Miller-Jones, J. C. A.;
Homan, J.;
Gallo, E.;
Russell, D. M.;
Tomsick, J. A.;
Kaaret, P.;
Corbel, S.;
Espinasse, M.;
Bright, J.
Published:
American Astronomical Society, 2021
Published in:
The Astrophysical Journal, 907 (2021) 1, Seite 34
Language:
Not determined
DOI:
10.3847/1538-4357/abd1de
ISSN:
0004-637X;
1538-4357
Origination:
Footnote:
Description:
Abstract Black hole X-ray binaries in the quiescent state (Eddington ratios typically ≲10−5) display softer X-ray spectra (photon indices Γ ∼ 2) compared to higher-luminosity black hole X-ray binaries in the hard state (Γ ∼ 1.7). However, the cause of this softening and its implications for the underlying accretion flow are still uncertain. Here, we present quasi-simultaneous X-ray and radio spectral monitoring of the black hole X-ray binary MAXI J1820+070 during the decay of its 2018 outburst and of a subsequent reflare in 2019, providing an opportunity to monitor a black hole X-ray binary as it actively transitions into quiescence. We probe 1–10 keV X-ray luminosities as low as L X ∼ 4 × 1032 erg s−1, equivalent to Eddington fractions of ∼4 × 10−7. During its decay toward quiescence, the X-ray spectrum of MAXI J1820+070 softens from Γ ∼ 1.7 to Γ ∼ 2, with the softening taking ∼30 days and completing at L X ≈ 1034 erg s−1 (≈10−5 L Edd). While the X-ray spectrum softens, the radio spectrum generally remains flat or inverted throughout the decay. We also find that MAXI J1820+070 follows a radio (L R)–X-ray luminosity correlation of the form L R ∝ L X 0.52±0.07, making it the fourth black hole system to follow the so-called “standard track” unbroken over several (in this case, four) decades in L X. Comparing the radio/X-ray spectral evolution(s) with the L R–L X plane, we find that the X-ray softening is consistent with X-rays produced by Comptonization processes in a radiatively inefficient accretion flow. We generally disfavor X-ray emission originating solely from within the jet, with the possible exception of X-rays produced via synchrotron self-Compton processes.