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Flares in the Changing Look AGN Mrk 590. II: Deep X-ray observations reveal a Comptonizing inner accretion flow

Flares in the Changing Look AGN Mrk 590. II: Deep X-ray observations reveal a Comptonizing inner accretion flow
Flares in the Changing Look AGN Mrk 590. II: Deep X-ray observations reveal a Comptonizing inner accretion flow
Mrk 590 is a Changing Look AGN currently in an unusual repeat X-ray and UV flaring state. Here, we report on deep X-ray observations with XMM-Newton, NuSTAR, and NICER, obtained at a range of X-ray flux levels. We detect a prominent soft excess below 2 keV; its flux is tightly correlated with that of both the X-ray and UV continuum, and it persists at the lowest flux levels captured. Our Bayesian model comparison strongly favors inverse Comptonization as the origin of this soft excess, instead of blurred reflection. We find only weak reflection features, with R~0.4 assuming Compton-thick reflection. Most of this reprocessing occurs at least $\sim$800 gravitational radii (roughly three light-days) from the continuum source. Relativistically broadened emission is weak or absent, suggesting the lack of a standard `thin disk' at small radii. We confirm that the predicted broad-band emission due to Comptonization is roughly consistent with the observed UV--optical photometry. This implies an optically thick, warm ($kT_e\sim0.3$ keV) scattering region that extends to at least $\sim10^3$ gravitational radii, reprocessing any UV thermal emission. The lack of a standard `thin disk' may also explain the puzzling $\sim3$-day X-ray to UV delay previously measured for Mrk 590. Overall, we find that the X-ray spectral changes in Mrk 590 are minimal, despite substantial luminosity changes. Other well-studied changing look AGN display more dramatic spectral evolution, e.g., disappearing continuum or soft excess. This suggests that a diversity of physical mechanisms in the inner accretion flow may produce a UV--optical changing-look event.
astro-ph.GA, astro-ph.HE, galaxies: Seyfert, galaxies: active, accretion, accretion discs
1365-2966
501-541
Lawther, Daniel
801e4d22-4330-436a-a2c5-c3fe471f5094
Vestergaard, Marianne
3d2377bc-0c0a-4198-9439-e7e9ac344b4e
Raimundo, Sandra
e409d9d3-17e8-4049-ad29-43ada60b24e2
Fan, Xiaohui
8923f74c-3cc4-4769-b9c9-280c63feabb1
Koay, Jun Yi
d5153ec3-724b-4396-bdc8-6021b79dd477
Lawther, Daniel
801e4d22-4330-436a-a2c5-c3fe471f5094
Vestergaard, Marianne
3d2377bc-0c0a-4198-9439-e7e9ac344b4e
Raimundo, Sandra
e409d9d3-17e8-4049-ad29-43ada60b24e2
Fan, Xiaohui
8923f74c-3cc4-4769-b9c9-280c63feabb1
Koay, Jun Yi
d5153ec3-724b-4396-bdc8-6021b79dd477

Lawther, Daniel, Vestergaard, Marianne, Raimundo, Sandra, Fan, Xiaohui and Koay, Jun Yi (2025) Flares in the Changing Look AGN Mrk 590. II: Deep X-ray observations reveal a Comptonizing inner accretion flow. Monthly Notices of the Royal Astronomical Society, 539 (1), 501-541. (doi:10.1093/mnras/staf424).

Record type: Article

Abstract

Mrk 590 is a Changing Look AGN currently in an unusual repeat X-ray and UV flaring state. Here, we report on deep X-ray observations with XMM-Newton, NuSTAR, and NICER, obtained at a range of X-ray flux levels. We detect a prominent soft excess below 2 keV; its flux is tightly correlated with that of both the X-ray and UV continuum, and it persists at the lowest flux levels captured. Our Bayesian model comparison strongly favors inverse Comptonization as the origin of this soft excess, instead of blurred reflection. We find only weak reflection features, with R~0.4 assuming Compton-thick reflection. Most of this reprocessing occurs at least $\sim$800 gravitational radii (roughly three light-days) from the continuum source. Relativistically broadened emission is weak or absent, suggesting the lack of a standard `thin disk' at small radii. We confirm that the predicted broad-band emission due to Comptonization is roughly consistent with the observed UV--optical photometry. This implies an optically thick, warm ($kT_e\sim0.3$ keV) scattering region that extends to at least $\sim10^3$ gravitational radii, reprocessing any UV thermal emission. The lack of a standard `thin disk' may also explain the puzzling $\sim3$-day X-ray to UV delay previously measured for Mrk 590. Overall, we find that the X-ray spectral changes in Mrk 590 are minimal, despite substantial luminosity changes. Other well-studied changing look AGN display more dramatic spectral evolution, e.g., disappearing continuum or soft excess. This suggests that a diversity of physical mechanisms in the inner accretion flow may produce a UV--optical changing-look event.

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2503.08959v1 - Author's Original
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More information

Accepted/In Press date: 11 March 2025
e-pub ahead of print date: 13 March 2025
Published date: May 2025
Additional Information: Accepted for publication in MNRAS. 47 pages, 41 figures
Keywords: astro-ph.GA, astro-ph.HE, galaxies: Seyfert, galaxies: active, accretion, accretion discs

Identifiers

Local EPrints ID: 501427
URI: http://eprints.soton.ac.uk/id/eprint/501427
ISSN: 1365-2966
PURE UUID: b8f50349-492f-489c-a80c-0f6bfa51c8eb
ORCID for Sandra Raimundo: ORCID iD orcid.org/0000-0002-6248-398X

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Date deposited: 30 May 2025 16:58
Last modified: 03 Sep 2025 02:01

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Contributors

Author: Daniel Lawther
Author: Marianne Vestergaard
Author: Sandra Raimundo ORCID iD
Author: Xiaohui Fan
Author: Jun Yi Koay

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