Kavli Affiliate: Erin Kara
| First 5 Authors: Megan Masterson, Kishalay De, Christos Panagiotou, Erin Kara, Iair Arcavi
| Summary:
Most tidal disruption events (TDEs) are currently found in time-domain
optical and soft X-ray surveys, both of which are prone to significant
obscuration. The infrared (IR), however, is a powerful probe of dust-enshrouded
environments, and hence, we recently performed a systematic search of NEOWISE
mid-IR data for nearby, obscured TDEs within roughly 200 Mpc. We identified 18
TDE candidates in galactic nuclei, using difference imaging to uncover nuclear
variability amongst significant host galaxy emission. These candidates were
selected based on the following IR light curve properties: (1)
$L_mathrm{W2}gtrsim10^{42}$ erg s$^{-1}$ at peak, (2) fast rise, followed by
a slow, monotonic decline, (3) no significant prior variability, and (4) no
evidence for AGN activity in WISE colors. The majority of these sources showed
no variable optical counterpart, suggesting that optical surveys indeed miss
numerous obscured TDEs. Using narrow line ionization levels and variability
arguments, we identified 6 sources as possible underlying AGN, yielding a total
of 12 TDEs in our gold sample. This gold sample yields a lower limit on the
IR-selected TDE rate of $2.0pm0.3times10^{-5}$ galaxy$^{-1}$ year$^{-1}$
($1.3pm0.2times10^{-7}$ Mpc$^{-3}$ year$^{-1}$), which is comparable to
optical and X-ray TDE rates. The IR-selected TDE host galaxies do not show a
green valley overdensity nor a preference for quiescent, Balmer strong
galaxies, which are both overrepresented in optical and X-ray TDE samples. This
IR-selected sample represents a new population of dusty TDEs that have
historically been missed by optical and X-ray surveys and helps alleviate
tensions between observed and theoretical TDE rates and the so-called missing
energy problem.
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