AGN STORM 2. V. Anomalous Behavior of the C iv Light Curve of Mrk 817

0584408 - ASÚ 2025 RIV GB eng J - Journal Article
Homayouni, Y. - Kriss, G. A. - De Rosa, G. - Kynoch, Daniel … Total 52 authors
AGN STORM 2. V. Anomalous Behavior of the C iv Light Curve of Mrk 817.
Astrophysical Journal. Roč. 963, č. 2 (2024), č. článku 123. ISSN 0004-637X. E-ISSN 1538-4357
Institutional support: RVO:67985815
Keywords : broad-line region * active galactic nuclei * H-beta emission
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 4.9, year: 2022
Method of publishing: Open access

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 similar to 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.
Permanent Link: https://hdl.handle.net/11104/0353231