Kavli Affiliate: Erin Kara
| First 5 Authors: Megan Masterson, Kishalay De, Christos Panagiotou, Erin Kara, Wenbin Lu
| Summary:
Mid-infrared (MIR) emission from tidal disruption events (TDEs) is a powerful
probe of the circumnuclear environment around dormant supermassive black holes.
This emission arises from the reprocessing of intrinsic emission into thermal
MIR emission by circumnuclear dust. While the majority of optical- and
X-ray-selected TDEs show only weak dust echoes consistent with primarily
unobscured sight lines, there have been growing efforts aimed at finding TDEs
in obscured environments using MIR selection methods. In this work, we present
the first JWST observations of 4 MIR-selected TDEs with JWST Mid-Infrared
Instrument (MIRI) Medium-Resolution Spectrometer (MRS). Two of these sources
show flares in other wavelength bands (one in optical, one in X-ray), while the
other two are MIR-only transients. None of these TDEs showed pre-outburst
nuclear activity, but all of the MIRI/MRS observations reveal emission lines
associated with highly ionized gas in the nucleus, implying ionization from TDE
accretion. Additionally, all four sources show silicate emission features
around 10 and 18 $mu$m that are much stronger than the features seen in active
galactic nuclei (AGN). We suggest that the emitting dust is optically thin to
its own emission and show that the MIR spectrum is consistent with emission
from optically thin dust in the nucleus. All four sources show an excess at
short wavelengths ($lambda < 8, mu$m), which could arise from a late-time
plateau in the intrinsic flare, akin to what is seen in late-time UV
observations of unobscured TDEs, although self-consistent dust modeling is
required to fully assess the strength of this late-time plateau.
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