Kavli Affiliate: Erin A. Kara
| First 5 Authors: Hermine Landt, Hermine Landt, , ,
| Summary:
The AGN Space Telescope and Optical Reverberation Mapping 2 (STORM 2)
campaign targeted Mrk 817 with intensive multi-wavelength monitoring and found
its soft X-ray emission to be strongly absorbed. We present results from 157
near-IR spectra with an average cadence of a few days. Whereas the hot dust
reverberation signal as tracked by the continuum flux does not have a clear
response, we recover a dust reverberation radius of $sim 90$ light-days from
the blackbody dust temperature light-curve. This radius is consistent with
previous photometric reverberation mapping results when Mrk 817 was in an
unobscured state. The heating/cooling process we observe indicates that the
inner limit of the dusty torus is set by a process other than sublimation,
rendering it a luminosity-invariant `dusty wall’ of a carbonaceous composition.
Assuming thermal equilibrium for dust optically thick to the incident
radiation, we derive a luminosity of $sim 6 times 10^44$ erg s$^-1$ for
the source heating it. This luminosity is similar to that of the obscured
spectral energy distribution, assuming a disk with an Eddington accretion rate
of $dotm sim 0.2$. Alternatively, the dust is illuminated by an unobscured
lower luminosity disk with $dotm sim 0.1$, which permits the UV/optical
continuum lags in the high-obscuration state to be dominated by diffuse
emission from the broad-line region. Finally, we find hot dust extended on
scales $> 140-350$ pc, associated with the rotating disk of ionised gas we
observe in spatially-resolved [SIII] $lambda 9531$ images. Its likely origin
is in the compact bulge of the barred spiral host galaxy, where it is heated by
a nuclear starburst.
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