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dc.contributor.authorShaw, A.W.
dc.contributor.authorPlotkin, Richard
dc.contributor.authorMiller-Jones, James
dc.contributor.authorHoman, J.
dc.contributor.authorGallo, E.
dc.contributor.authorRussell, D.M.
dc.contributor.authorTomsick, J.A.
dc.contributor.authorKaaret, P.
dc.contributor.authorCorbel, S.
dc.contributor.authorEspinasse, M.
dc.contributor.authorBright, J.
dc.date.accessioned2023-04-18T14:48:56Z
dc.date.available2023-04-18T14:48:56Z
dc.date.issued2021
dc.identifier.citationShaw, A.W. and Plotkin, R.M. and Miller-Jones, J.C.A. and Homan, J. and Gallo, E. and Russell, D.M. and Tomsick, J.A. et al. 2021. Observations of the disk/jet coupling of MAXI J1820+070 during its descent to quiescence. Astrophysical Journal. 907 (1): ARTN 34.
dc.identifier.urihttp://hdl.handle.net/20.500.11937/91527
dc.identifier.doi10.3847/1538-4357/abd1de
dc.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 LX ∼ 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 LX ≈ 1034 erg s−1 (≈10−5 LEdd). 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 (LR)-X-ray luminosity correlation of the form LR ∝ LX0.52±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 LX. Comparing the radio/X-ray spectral evolution(s) with the LR-LX 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.

dc.languageEnglish
dc.publisherIOP Publishing Ltd
dc.subjectScience & Technology
dc.subjectPhysical Sciences
dc.subjectAstronomy & Astrophysics
dc.subjectBlack holes
dc.subjectAccretion
dc.subjectLow-mass x-ray binary stars
dc.subjectX-ray transient sources
dc.subjectX-RAY BINARIES
dc.subjectHARD-STATE
dc.subjectSYNCHROTRON EMISSION
dc.subjectFLUX CORRELATION
dc.subjectACCRETION FLOWS
dc.subjectLOW/HARD-STATE
dc.subjectXTE J1550-564
dc.subjectCOMPACT JET
dc.subjectRADIO
dc.subjectOUTBURST
dc.subjectastro-ph.HE
dc.subjectastro-ph.HE
dc.titleObservations of the disk/jet coupling of MAXI J1820+070 during its descent to quiescence
dc.typeJournal Article
dcterms.source.volume907
dcterms.source.number1
dcterms.source.issn0004-637X
dcterms.source.titleAstrophysical Journal
dc.date.updated2023-04-18T14:48:53Z
curtin.departmentSchool of Elec Eng, Comp and Math Sci (EECMS)
curtin.accessStatusOpen access
curtin.facultyFaculty of Science and Engineering
curtin.contributor.orcidMiller-Jones, James [0000-0003-3124-2814]
curtin.contributor.researcheridMiller-Jones, James [B-2411-2013]
curtin.identifier.article-numberARTN 34
dcterms.source.eissn1538-4357
curtin.contributor.scopusauthoridMiller-Jones, James [10044231400]
curtin.contributor.scopusauthoridPlotkin, Richard [13205184900]
curtin.repositoryagreementV3


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