EUROPEAN SPACE AGENCY

AGN STORM 2. VIII. Investigating the Narrow Absorption Lines in Mrk 817 Using HST-COS Observations

DOI: 10.3847/1538-4357/ad5ff4 Bibcode: 2024ApJ...972..141D

Kaspi, Shai; Filippenko, Alexei V.; Barth, Aaron J.; Horne, Keith; Kriss, Gerard A.; Mehdipour, Missagh; Storchi-Bergmann, Thaisa; Kochanek, Christopher S.; Goad, Michael R.; Ferland, Gary J.; Joner, Michael D.; De Rosa, Gisella; Vestergaard, Marianne; Gelbord, Jonathan; Korista, Kirk T.; Lewin, Collin; Cackett, Edward M.; Arav, Nahum; Bentz, Misty C.; Brotherton, Michael S.; Siebert, Matthew R.; Landt, Hermine; Wang, Jian-Min; Rogantini, Daniele; Dalla Bontà, Elena; Dehghanian, Maryam; Fian, Carina; Homayouni, Yasaman; Ilić, Dragana; Kovačević, Andjelka B.; Zaidouni, Fatima; Kosec, Peter; Boizelle, Benjamin D.; Byun, Doyee; Popović, Luka Č.; Proga, Daniel; Zu, Ying; Kara, Erin A.; Partington, Ethan R.; Walker, Gwen; Sharma, Mayank; Waters, Timothy.

United States, Italy, United Kingdom, Spain, Serbia, Germany, Israel, Brazil, Denmark, China

Abstract

We observed the Seyfert 1 galaxy Mrk 817 during an intensive multiwavelength reverberation mapping campaign for 16 months. Here, we examine the behavior of narrow UV absorption lines seen in the Hubble Space Telescope/Cosmic Origins Spectrograph spectra, both during the campaign and in other epochs extending over 14 yr. We conclude that, while the narrow absorption outflow system (at ‑3750 km s‑1 with FWHM = 177 km s‑1) responds to the variations of the UV continuum as modified by the X-ray obscurer, its total column density (log N H = 19.5 ‑0.13+0.61 cm‑2) did not change across all epochs. The adjusted ionization parameter (scaled with respect to the variations in the hydrogen-ionizing continuum flux) is log U H = ‑1.0 ‑0.3+0.1 . The outflow is located at a distance smaller than 38 pc from the central source, which implies a hydrogen density of n H > 3000 cm‑3. The absorption outflow system only covers the continuum emission source and not the broad emission line region, which suggests that its transverse size is small (< 1016 cm), with potential cloud geometries ranging from spherical to elongated along the line of sight. * 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, and archival data from programs 11505, 11524, and 17105.

2024 • The Astrophysical Journal
eHST 1
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