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Space Telescope and Optical Reverberation Mapping Project 2: the variable X-ray obscurer in Mrk 817

Presentation #104.03 in the session “AGN STORM 2: initial results from this large, multi-wavelength reverberation mapping campaign on Mrk 817”.

Published onApr 01, 2022
Space Telescope and Optical Reverberation Mapping Project 2: the variable X-ray obscurer in Mrk 817

The Seyfert 1 galaxy Mrk 817 was targeted by the AGN STORM 2 collaboration for a year-long multiwavelength, coordinated reverberation mapping campaign including HST, Swift, XMM and NICER. Early observations with NICER and XMM reveal a soft X-ray state 10x fainter than historical observations, consistent with the presence of a new dust-free, ionized obscurer. Analysis of NICER spectra shows that X-ray variability is largely driven by changes in the column density of the obscurer alongside continuum brightness. While the X-ray flux generally remains in a faint state, there is one large flare during which Mrk 817 returns to its historical brightness. Correlation between the density of the X-ray absorber and the width of UV broad absorption lines suggests that both the X-ray and UV continuum are affected by the same obscurer, consistent with a clumpy disk wind launched from the inner broad line region. In this talk, we will discuss the individual contributions of the continuum and the obscurer towards daily X-ray variability in the AGN.


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