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

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journal contribution
posted on 2023-08-09, 08:22 authored by 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 Hernandez Santisteban, Chen Hu, Jelle Kaastra, Hermine Landt, Yan-Rong Li, Jake A Miller, John Montano, Ethan Partington, Jesus Aceituno, Jin-Ming Bai, Dongwei Bao, Misty C Bentz, Thomas G Brink, Doron Chelouche, Yong-Jie Chen, Elena Dalla Bonta, Maryam Dehghanian, Pu Du, Rick Edelson, Gary J Ferland, Laura Ferrarese, Carina Fian, Alexei V Filippenko, Travis Fischer, Michael R Goad, Diego H Gonzalez Buitrago, Varoujan Gorjian, Catherine J Grier, Wei-Jian Guo, Patrick B Hall, Y Homayouni, Keith Horne, Dragana Ilic, Bo-Wei Jiang, Michael D Joner, Shai Kaspi, Christopher S Kochanek, Kirk T Korista, Daniel Kynoch, Sha-Sha Li, Jun-Rong Liu, Ian M Mc Hardy, Jacob N McLane, Jake AJ Mitchell, Hagai Netzer, Kianna A Olson, Richard W Pogge, Luka C Popovic, 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
We present the first results from the ongoing, intensive, multi-wavelength monitoring program of the luminous Seyfert 1 galaxy Mrk 817. While this AGN 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 recovers in the next 42 days of the campaign, as Mrk 817 enters a less obscured state. The short CIV and Ly alpha lags suggest that the accretion disk extends beyond the UV broad line region.


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School of Physics & Astronomy, University of Leicester


  • AM (Accepted Manuscript)

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