AGN STORM 2. I. First results: A Change in the Weather of Mrk 817

December 2021 • 2021ApJ...922..151K

Authors • Kara, Erin • Mehdipour, Missagh • Kriss, Gerard A. • Cackett, Edward M. • Arav, Nahum • Barth, Aaron J. • Byun, Doyee • Brotherton, Michael S. • De Rosa, Gisella • Gelbord, Jonathan • Hernández Santisteban, Juan V. • Hu, Chen • Kaastra, Jelle • Landt, Hermine • Li, Yan-Rong • Miller, Jake A. • Montano, John • Partington, Ethan • Aceituno, Jesús • Bai, Jin-Ming • Bao, Dongwei • Bentz, Misty C. • Brink, Thomas G. • Chelouche, Doron • Chen, Yong-Jie • Colmenero, Encarni Romero • Bontà, Elena Dalla • Dehghanian, Maryam • Du, Pu • Edelson, Rick • Ferland, Gary J. • Ferrarese, Laura • Fian, Carina • Filippenko, Alexei V. • Fischer, Travis • Goad, Michael R. • González Buitrago, Diego H. • Gorjian, Varoujan • Grier, Catherine J. • Guo, Wei-Jian • Hall, Patrick B. • Ho, Luis C. • Homayouni, Y. • Horne, Keith • Ilić, Dragana • Jiang, Bo-Wei • Joner, Michael D. • Kaspi, Shai • Kochanek, Christopher S. • Korista, Kirk T. • Kynoch, Daniel • Li, Sha-Sha • Liu, Jun-Rong • McHardy, Ian M. • McLane, Jacob N. • Mitchell, Jake A. J. • Netzer, Hagai • Olson, Kianna A. • Pogge, Richard W. • Popović, Luka C̆. • Proga, Daniel • Storchi-Bergmann, Thaisa • Strasburger, Erika • Treu, Tommaso • Vestergaard, Marianne • Wang, Jian-Min • Ward, Martin J. • Waters, Tim • Williams, Peter R. • Yang, Sen • Yao, Zhu-Heng • Zastrocky, Theodora E. • Zhai, Shuo • Zu, Ying

Abstract • We present the first results from the ongoing, intensive, multiwavelength monitoring program of the luminous Seyfert 1 galaxy Mrk 817. While this active galactic nucleus was, in part, selected for its historically unobscured nature, we discovered that the X-ray spectrum is highly absorbed, and there are new blueshifted, broad, and narrow UV absorption lines, which suggest that a dust-free, ionized obscurer located at the inner broad-line region partially covers the central source. Despite the obscuration, we measure UV and optical continuum reverberation lags consistent with a centrally illuminated Shakura─Sunyaev thin accretion disk, and measure reverberation lags associated with the optical broad-line region, as expected. However, in the first 55 days of the campaign, when the obscuration was becoming most extreme, we observe a de-coupling of the UV continuum and the UV broad emission-line variability. The correlation recovered in the next 42 days of the campaign, as Mrk 817 entered a less obscured state. The short C IV and Lyα lags suggest that the accretion disk extends beyond the UV broad-line region.

Links

• PREPRINT http://arxiv.org/abs/2105.05840
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2021ApJ...922..151K
• ELECTR https://doi.org/10.3847/1538-4357/ac2159
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