Observations of the disk/jet coupling of MAXI J1820+070 during its descent to quiescence
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 ac...
| Main Authors: | , , , , , , , , , , |
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| Format: | Journal Article |
| Language: | English |
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IOP Publishing Ltd
2021
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| Subjects: | |
| Online Access: | http://purl.org/au-research/grants/arc/FT140101082 http://hdl.handle.net/20.500.11937/91527 |
| _version_ | 1848765538894872576 |
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| author | Shaw, A.W. Plotkin, Richard Miller-Jones, James Homan, J. Gallo, E. Russell, D.M. Tomsick, J.A. Kaaret, P. Corbel, S. Espinasse, M. Bright, J. |
| author_facet | Shaw, A.W. Plotkin, Richard Miller-Jones, James Homan, J. Gallo, E. Russell, D.M. Tomsick, J.A. Kaaret, P. Corbel, S. Espinasse, M. Bright, J. |
| author_sort | Shaw, A.W. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | 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. |
| first_indexed | 2025-11-14T11:36:51Z |
| format | Journal Article |
| id | curtin-20.500.11937-91527 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| language | English |
| last_indexed | 2025-11-14T11:36:51Z |
| publishDate | 2021 |
| publisher | IOP Publishing Ltd |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-915272024-04-11T03:45:45Z Observations of the disk/jet coupling of MAXI J1820+070 during its descent to quiescence Shaw, A.W. Plotkin, Richard Miller-Jones, James Homan, J. Gallo, E. Russell, D.M. Tomsick, J.A. Kaaret, P. Corbel, S. Espinasse, M. Bright, J. Science & Technology Physical Sciences Astronomy & Astrophysics Black holes Accretion Low-mass x-ray binary stars X-ray transient sources X-RAY BINARIES HARD-STATE SYNCHROTRON EMISSION FLUX CORRELATION ACCRETION FLOWS LOW/HARD-STATE XTE J1550-564 COMPACT JET RADIO OUTBURST astro-ph.HE astro-ph.HE 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. 2021 Journal Article http://hdl.handle.net/20.500.11937/91527 10.3847/1538-4357/abd1de English http://purl.org/au-research/grants/arc/FT140101082 IOP Publishing Ltd fulltext |
| spellingShingle | Science & Technology Physical Sciences Astronomy & Astrophysics Black holes Accretion Low-mass x-ray binary stars X-ray transient sources X-RAY BINARIES HARD-STATE SYNCHROTRON EMISSION FLUX CORRELATION ACCRETION FLOWS LOW/HARD-STATE XTE J1550-564 COMPACT JET RADIO OUTBURST astro-ph.HE astro-ph.HE Shaw, A.W. Plotkin, Richard Miller-Jones, James 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 |
| title | Observations of the disk/jet coupling of MAXI J1820+070 during its descent to quiescence |
| title_full | Observations of the disk/jet coupling of MAXI J1820+070 during its descent to quiescence |
| title_fullStr | Observations of the disk/jet coupling of MAXI J1820+070 during its descent to quiescence |
| title_full_unstemmed | Observations of the disk/jet coupling of MAXI J1820+070 during its descent to quiescence |
| title_short | Observations of the disk/jet coupling of MAXI J1820+070 during its descent to quiescence |
| title_sort | observations of the disk/jet coupling of maxi j1820+070 during its descent to quiescence |
| topic | Science & Technology Physical Sciences Astronomy & Astrophysics Black holes Accretion Low-mass x-ray binary stars X-ray transient sources X-RAY BINARIES HARD-STATE SYNCHROTRON EMISSION FLUX CORRELATION ACCRETION FLOWS LOW/HARD-STATE XTE J1550-564 COMPACT JET RADIO OUTBURST astro-ph.HE astro-ph.HE |
| url | http://purl.org/au-research/grants/arc/FT140101082 http://hdl.handle.net/20.500.11937/91527 |