Kavli Affiliate: Erin A. Kara
| First 5 Authors: Jack M. M. Neustadt, Christopher S. Kochanek, John Montano, Jonathan Gelbord, Aaron J. Barth
| Summary:
We fit the UV/optical lightcurves of the Seyfert 1 galaxy Mrk 817 to produce
maps of the accretion disk temperature fluctuations $delta T$ resolved in time
and radius. The $delta T$ maps are dominated by coherent radial structures
that move slowly ($v ll c$) inwards and outwards, which conflicts with the
idea that disk variability is driven only by reverberation. Instead, these
slow-moving temperature fluctuations are likely due to variability intrinsic to
the disk. We test how modifying the input lightcurves by smoothing and
subtracting them changes the resulting $delta T$ maps and find that most of
the temperature fluctuations exist over relatively long timescales ($sim$100s
of days). We show how detrending AGN lightcurves can be used to separate the
flux variations driven by the slow-moving temperature fluctuations from those
driven by reverberation. We also simulate contamination of the continuum
emission from the disk by continuum emission from the broad line region (BLR),
which is expected to have spectral features localized in wavelength, such as
the Balmer break contaminating the $U$ band. We find that a disk with a smooth
temperature profile cannot produce a signal localized in wavelength and that
any BLR contamination should appear as residuals in our model lightcurves.
Given the observed residuals, we estimate that only $sim$20% of the variable
flux in the $U$ and $u$ lightcurves can be due to BLR contamination. Finally,
we discus how these maps not only describe the data, but can make predictions
about other aspects of AGN variability.
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