open access publication

Article, 2024

AGN STORM 2. V. Anomalous Behavior of the C iv Light Curve of Mrk 817* * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with program GO-16196.

The Astrophysical Journal, ISSN 0004-637X, 1538-4357, Volume 963, 2, Page 123, 10.3847/1538-4357/ad1be4

Contributors

Homayouni, Yasaman (Corresponding author) [1] [2] Kriss, Gerard A 0000-0002-2180-8266 [2] De Rosa, Gisella 0000-0003-3242-7052 [2] Plesha, Rachel J 0000-0002-2509-3878 [2] Cackett, Edward M 0000-0002-8294-9281 [3] Goad, Michael R. [4] Korista, Kirk T 0000-0003-0944-1008 [5] Horne, Keith [6] Fischer, Travis Cody 0000-0002-3365-8875 [2] Waters, Tim 0000-0002-5205-9472 [7] Barth, Aaron J 0000-0002-3026-0562 [8] Kara, Erin A [9] Landt, Hermine [10] Arav, Nahum 0000-0003-2991-4618 [11] Boizelle, Benjamin D 0000-0001-6301-570X [12] Bentz, Misty C 0000-0002-2816-5398 [13] Brotherton, Michael S 0000-0002-1207-0909 [14] Chelouche, Doron 0000-0002-4830-7787 [15] Bontà, Elena Dalla 0000-0001-9931-8681 [16] [17] Dehghanian, Maryam [18] Du, Pu 0000-0002-5830-3544 [19] Ferland, Gary J 0000-0003-4503-6333 [18] Fian, Carina 0000-0002-2306-9372 [15] [20] Gelbord, Jonathan M 0000-0001-9092-8619 [21] Grier, Catherine J 0000-0001-9920-6057 [22] Hall, Patrick B. [23] Hu, Chen [19] Ilić, Dragana 0000-0002-1134-4015 [24] [25] Joner, Michael D. [12] Kaastra, Jelle S 0000-0001-5540-2822 [26] [27] Kaspi, Shai 0000-0002-9925-534X [20] Kovačević, Andjelka B 0000-0001-5139-1978 [25] Kynoch, Daniel 0000-0001-8638-3687 [28] [29] Li, Yan-Rong [19] Mehdipour, Missagh 0000-0002-4992-4664 [2] Miller, Jake A [3] Mitchell, Jake A J 0000-0002-5493-1420 [10] Montano, John W 0000-0001-5639-5484 [8] Netzer, Hagai 0000-0002-6766-0260 [20] Neustadt, J. M. M. [30] Partington, Ethan R 0000-0003-1183-1574 [3] Popović, Luka Č 0000-0003-2398-7664 [25] [31] Proga, Daniel 0000-0002-6336-5125 [7] Storchi-Bergmann, Thaisa 0000-0003-1772-0023 [32] Sanmartim, David [33] Siebert, Matthew R. [34] Treu, Tommaso L 0000-0002-8460-0390 [35] [36] Vestergaard, Marianne 0000-0001-9191-9837 [37] [38] Wang, Jian-Min [19] [39] [40] Ward, Martin J 0000-0003-1810-0889 [10] Zaidouni, Fatima [9] Zu, Ying 0000-0001-6966-6925 [41]

Affiliations

  1. [1] Pennsylvania State University
    2. [NORA names: United States; America, North; OECD];
  2. [2] Space Telescope Science Institute
    3. [NORA names: United States; America, North; OECD];
  3. [3] Wayne State University
    4. [NORA names: United States; America, North; OECD];
  4. [4] University of Leicester
    5. [NORA names: United Kingdom; Europe, Non-EU; OECD];
  5. [5] Western Michigan University
    6. [NORA names: United States; America, North; OECD];

Abstract

An intensive reverberation mapping campaign of the Seyfert 1 galaxy Mrk 817 using the Cosmic Origins Spectrograph on the Hubble Space Telescope revealed significant variations in the response of broad UV emission lines to fluctuations in the continuum emission. The response of the prominent UV emission lines changes over an ∼60 day duration, resulting in distinctly different time lags in the various segments of the light curve over the 14 month observing campaign. One-dimensional echo-mapping models fit these variations if a slowly varying background is included for each emission line. These variations are more evident in the C iv light curve, which is the line least affected by intrinsic absorption in Mrk 817 and least blended with neighboring emission lines. We identify five temporal windows with a distinct emission-line response, and measure their corresponding time delays, which range from 2 to 13 days. These temporal windows are plausibly linked to changes in the UV and X-ray obscuration occurring during these same intervals. The shortest time lags occur during periods with diminishing obscuration, whereas the longest lags occur during periods with rising obscuration. We propose that the obscuring outflow shields the broad UV lines from the ionizing continuum. The resulting change in the spectral energy distribution of the ionizing continuum, as seen by clouds at a range of distances from the nucleus, is responsible for the changes in the line response.

Keywords

Cosmic, Cosmic Origins Spectrograph, Hubble, Hubble Space Telescope, Mrk, NAS5, NASA, NASA/ESA, NASA/ESA Hubble Space Telescope, Science Institute, Seyfert, Seyfert 1 galaxy Mrk, Space Telescope, Space Telescope Science Institute, UV, UV emission lines, UV lines, X-ray, X-ray obscuration, absorption, association, behavior, campaign, changes, cloud, continuum, continuum emission, curves, days, days duration, delay, distance, distribution, duration, emission, emission lines, emission-line response, energy distribution, fluctuations, institutions, interval, intrinsic absorption, ionizing continuum, lag, light curves, line response, lines, long lag, mapping campaign, model, month observing campaign, months, nucleus, obscuration, observational campaign, observations, outflow, period, research, response, reverberation mapping campaign, segments, short time lag, space, spectral energy distribution, spectrograph, telescope, temporal window, time, time delay, time lag, variation, window

Funders

  • National Natural Science Foundation of China
  • Heising-Simons Foundation
  • National Aeronautics and Space Administration
  • Chinese Academy of Sciences
  • Natural Sciences and Engineering Research Council
  • Alexander von Humboldt Foundation
  • David and Lucile Packard Foundation
  • Directorate for Mathematical & Physical Sciences
  • Science and Technology Facilities Council
  • Gordon and Betty Moore Foundation

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