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

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

Research output: Contribution to journalArticlepeer-review

61 Scopus citations


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.

Original languageEnglish
Article number151
JournalAstrophysical Journal
Issue number2
StatePublished - Dec 1 2021

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ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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