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AGN STORM 2. IV. Swift X-Ray and Ultraviolet/Optical Monitoring of Mrk 817

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posted on 2024-01-31, 20:32 authored by EM Cackett, J Gelbord, AJ Barth, G De Rosa, R Edelson, MR Goad, Y Homayouni, K Horne, EA Kara, GA Kriss, KT Korista, H Landt, R Plesha, N Arav, MC Bentz, BD Boizelle, E Dalla Bontà, M Dehghanian, F Donnan, P Du, GJ Ferland, C Fian, AV Filippenko, DH González Buitrago, CJ Grier, PB Hall, C Hu, D Ilić, J Kaastra, S Kaspi, CS Kochanek, AB Kovačević, D Kynoch, YR Li, JN McLane, M Mehdipour, JA Miller, J Montano, H Netzer, C Panagiotou, E Partington, L Č. Popović, D Proga, D Rogantini, D Sanmartim, MR Siebert, T Storchi-Bergmann, M Vestergaard, JM Wang, T Waters, F Zaidouni

The AGN STORM 2 campaign is a large, multiwavelength reverberation mapping project designed to trace out the structure of Mrk 817 from the inner accretion disk to the broad emission line region and out to the dusty torus. As part of this campaign, Swift performed daily monitoring of Mrk 817 for approximately 15 months, obtaining observations in X-rays and six UV/optical filters. The X-ray monitoring shows that Mrk 817 was in a significantly fainter state than in previous observations, with only a brief flare where it reached prior flux levels. The X-ray spectrum is heavily obscured. The UV/optical light curves show significant variability throughout the campaign and are well correlated with one another, but uncorrelated with the X-rays. Combining the Swift UV/optical light curves with Hubble Space Telescope UV continuum light curves, we measure interband continuum lags, τ(λ), that increase with increasing wavelength roughly following τ(λ) ∝ λ 4/3, the dependence expected for a geometrically thin, optically thick, centrally illuminated disk. Modeling of the light curves reveals a period at the beginning of the campaign where the response of the continuum is suppressed compared to later in the light curve—the light curves are not simple shifted and scaled versions of each other. The interval of suppressed response corresponds to a period of high UV line and X-ray absorption, and reduced emission line variability amplitudes. We suggest that this indicates a significant contribution to the continuum from the broad-line region gas that sees an absorbed ionizing continuum.

Funding

AGN Reverberation Mapping of Gas Flows in Mrk 817 with Swift and Hubble

National Aeronautics and Space Administration

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NAS5-26555

AST-1907290

Extended Monitoring of the Dramatically-Varying AGN Mrk 817

National Aeronautics and Space Administration

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AST-2307385

AST-2009230

Daphne Jackson Fellowship

University of Belgrade—Faculty of Mathematics (contract 451-03-68/2022-14/200104)

Astronomical Observatory Belgrade (contract 451-03-68/2022-14/200002)

Chinese Academy of Sciences President's International Fellowship Initiative (PIFI)

DFF 8021-00130

Supermassive black hole in the center of an active galaxy

National Natural Science Foundation of China

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12273041

History

Citation

Edward M. Cackett et al 2023 ApJ 958 195 DOI 10.3847/1538-4357/acfdac

Author affiliation

School of Physics and Astronomy, University of Leicester

Version

  • VoR (Version of Record)

Published in

Astrophysical Journal

Volume

958

Issue

2

Pagination

195 - 195

Publisher

American Astronomical Society

issn

0004-637X

eissn

1538-4357

Acceptance date

2023-09-25

Copyright date

2023

Available date

2024-01-31

Language

en

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