The underlying driver behind the optical variability of AGN, and its link to theX-ray variability, is currently in dispute. Are the optical variations dominatedby reprocessing of X-ray photons (ie the optical lags), or by inwardlypropagating accretion rate fluctuations which alter the intrinsic thermalemission from the disc (ie the optical leads)? Current observations favouroptical lags there are no unambiguous examples. In NGC4395, a well known highlyvariable X-ray AGN, we have previously found a tentative 400s UV lag, atimescale well suited to observations with XMM. Here, with a combination of XMMand ground-based observations we aim to measure the lag accurately and henceshow whether optical variability in AGN is driven by disc variations or by X-ray reprocessing.
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 Agencys (ESA) X-ray Multi-Mirror Mission (XMM-Newton) was launched by an Ariane 504 on December 10th 1999. XMM-Newton is ESAs 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 Earths 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.
European Space Agency, Prof Ian McHardy, 2016, 'THE ORIGIN OF OPTICAL VARIABILITY IN AGN: XMM AND GROUND OBSERVATIONS OF NGC4395', 17.56_20190403_1200, European Space Agency, https://doi.org/10.5270/esa-2ilgu1y
