TY - JOUR

T1 - AGN STORM 2. VI. Mapping Temperature Fluctuations in the Accretion Disk of Mrk 817

AU - Neustadt, Jack M.M.

AU - Kochanek, Christopher S.

AU - Montano, John

AU - Gelbord, Jonathan

AU - Barth, Aaron J.

AU - De Rosa, Gisella

AU - Kriss, Gerard A.

AU - Cackett, Edward M.

AU - Horne, Keith

AU - Kara, Erin A.

AU - Landt, Hermine

AU - Netzer, Hagai

AU - Arav, Nahum

AU - Bentz, Misty C.

AU - Dalla Bontà, Elena

AU - Dehghanian, Maryam

AU - Du, Pu

AU - Edelson, Rick

AU - Ferland, Gary J.

AU - Fian, Carina

AU - Fischer, Travis

AU - Goad, Michael R.

AU - González Buitrago, Diego H.

AU - Gorjian, Varoujan

AU - Grier, Catherine J.

AU - Hall, Patrick B.

AU - Homayouni, Y.

AU - Hu, Chen

AU - Ilić, Dragana

AU - Joner, Michael D.

AU - Kaastra, Jelle

AU - Kaspi, Shai

AU - Korista, Kirk T.

AU - Kovačević, Andjelka B.

AU - Lewin, Collin

AU - Li, Yan Rong

AU - McHardy, Ian M.

AU - Mehdipour, Missagh

AU - Miller, Jake A.

AU - Panagiotou, Christos

AU - Partington, Ethan

AU - Plesha, Rachel

AU - Pogge, Richard W.

AU - Popović, Luka

AU - Proga, Daniel

AU - Storchi-Bergmann, Thaisa

AU - Sanmartim, David

AU - Siebert, Matthew R.

AU - Signorini, Matilde

AU - Vestergaard, Marianne

AU - Zaidouni, Fatima

AU - Zu, Ying

N1 - Publisher Copyright: © 2024. The Author(s). Published by the American Astronomical Society.

PY - 2024

Y1 - 2024

N2 - We fit the UV/optical lightcurves of the Seyfert 1 galaxy Mrk 817 to produce maps of the accretion disk temperature fluctuations δ T resolved in time and radius. The δ T maps are dominated by coherent radial structures that move slowly (v ≪ c) inward and outward, which conflicts with the idea that disk variability is driven only by reverberation. Instead, these slow-moving temperature fluctuations are likely due to variability intrinsic to the disk. We test how modifying the input lightcurves by smoothing and subtracting them changes the resulting δ T maps and find that most of the temperature fluctuations exist over relatively long timescales (hundreds of days). We show how detrending active galactic nucleus (AGN) lightcurves can be used to separate the flux variations driven by the slow-moving temperature fluctuations from those driven by reverberation. We also simulate contamination of the continuum emission from the disk by continuum emission from the broad-line region (BLR), which is expected to have spectral features localized in wavelength, such as the Balmer break contaminating the U band. We find that a disk with a smooth temperature profile cannot produce a signal localized in wavelength and that any BLR contamination should appear as residuals in our model lightcurves. Given the observed residuals, we estimate that only ∼20% of the variable flux in the U and u lightcurves can be due to BLR contamination. Finally, we discus how these maps not only describe the data but can make predictions about other aspects of AGN variability.

AB - We fit the UV/optical lightcurves of the Seyfert 1 galaxy Mrk 817 to produce maps of the accretion disk temperature fluctuations δ T resolved in time and radius. The δ T maps are dominated by coherent radial structures that move slowly (v ≪ c) inward and outward, which conflicts with the idea that disk variability is driven only by reverberation. Instead, these slow-moving temperature fluctuations are likely due to variability intrinsic to the disk. We test how modifying the input lightcurves by smoothing and subtracting them changes the resulting δ T maps and find that most of the temperature fluctuations exist over relatively long timescales (hundreds of days). We show how detrending active galactic nucleus (AGN) lightcurves can be used to separate the flux variations driven by the slow-moving temperature fluctuations from those driven by reverberation. We also simulate contamination of the continuum emission from the disk by continuum emission from the broad-line region (BLR), which is expected to have spectral features localized in wavelength, such as the Balmer break contaminating the U band. We find that a disk with a smooth temperature profile cannot produce a signal localized in wavelength and that any BLR contamination should appear as residuals in our model lightcurves. Given the observed residuals, we estimate that only ∼20% of the variable flux in the U and u lightcurves can be due to BLR contamination. Finally, we discus how these maps not only describe the data but can make predictions about other aspects of AGN variability.

U2 - 10.3847/1538-4357/ad1386

DO - 10.3847/1538-4357/ad1386

M3 - Journal article

AN - SCOPUS:85183963378

VL - 961

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 2

M1 - 219

ER -