A dataset provided by the European Space Agency

Name 074401
Title THE ORIGIN OF OPTICAL VARIABILITY IN AGN: XMM AND GROUND OBSERVATIONS OF NGC4395
URL

http://nxsa.esac.esa.int/nxsa-sl/servlet/data-action-aio?obsno=0744010101
http://nxsa.esac.esa.int/nxsa-sl/servlet/data-action-aio?obsno=0744010201

DOI 10.5270/esa-2ilgu1y
Author Prof Ian McHardy
Description The underlying driver behind the optical variability of AGN, and its link to the X-ray variability, is currently in dispute. Are the optical variations dominated by reprocessing of X-ray photons (ie the optical lags), or by inwardly propagating accretion rate fluctuations which alter the intrinsic thermal emission from the disc (ie the optical leads)? Current observations favour optical lags there are no unambiguous examples. In NGC4395, a well known highly variable X-ray AGN, we have previously found a tentative 400s UV lag, a timescale well suited to observations with XMM. Here, with a combination of XMM and ground-based observations we aim to measure the lag accurately and hence show whether optical variability in AGN is driven by disc variations or by X-ray reprocessing.
Publication The origin of UV-optical variability in AGN and test of disc models: XMM-Newton and ground-based observations of NGC 4395 . McHardy, I. M., Connolly, S. D., et all. . AN . 337-500 . 2016 . 2016AN....337..500M ,
X-ray variability of Seyfert 1.8-1.9 galaxies . Hernandez-Garcia, L., Masegosa, J., et all. . A&A . 602-65 . 2017 . 2017A&A...602A..65H ,
The Nature of the Broadband X-Ray Variability in the Dwarf Seyfert Galaxy NGC 4395 . Kammoun, E. S., Nardini, E., et all. . ApJ . 886-145 . 2019 . 2019ApJ...886..145K ,
EUCLIA. II. On the Puzzling Large UV to X-Ray Lags in Seyfert Galaxies . Cai, Zhen-Yi, Wang, Jun-Xian, . ApJ . 892-63 . 2020 . 2020ApJ...892...63C ,
A Hard Look at Local, Optically Selected, Obscured Seyfert Galaxies . Kammoun, E. S., Miller, J. M., et all. . ApJ . 901-161 . 2020 . 2020ApJ...901..161K ,
Instrument EMOS1, EMOS2, EPN, OM, RGS1, RGS2
Temporal Coverage 2014-12-28T10:07:16Z/2014-12-31T00:41:44Z
Version 17.56_20190403_1200
Mission Description The European Space Agency's (ESA) X-ray Multi-Mirror Mission (XMM-Newton) was launched by an Ariane 504 on December 10th 1999. XMM-Newton is ESA's second cornerstone of the Horizon 2000 Science Programme. It carries 3 high throughput X-ray telescopes with an unprecedented effective area, and an optical monitor, the first flown on a X-ray observatory. The large collecting area and ability to make long uninterrupted exposures provide highly sensitive observations.
Since Earth's atmosphere blocks out all X-rays, only a telescope in space can detect and study celestial X-ray sources. The XMM-Newton mission is helping scientists to solve a number of cosmic mysteries, ranging from the enigmatic black holes to the origins of the Universe itself. Observing time on XMM-Newton is being made available to the scientific community, applying for observational periods on a competitive basis.
Creator Contact https://www.cosmos.esa.int/web/xmm-newton/xmm-newton-helpdesk
Date Published 2016-01-19T23:00:00Z
Publisher And Registrant European Space Agency
Credit Guidelines European Space Agency, 2016-01-19T23:00:00Z, 074401, 17.56_20190403_1200. https://doi.org/10.5270/esa-2ilgu1y