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Swift Observations of the TDE ASASSN-15oi

ATel #7945; I. Arcavi (UCSB/LCOGT), S. B. Cenko (GSFC), A. Horesh (WIS), S. Valenti, D. A. Howell (UCSB/LCOGT) and L. Yan (IPAC)
on 24 Aug 2015; 04:52 UT
Credential Certification: Iair Arcavi (iarcavi@lcogt.net)

Subjects: Ultra-Violet, X-ray, Transient

We reduced the first epoch of ToO observations of the tidal disruption event ASASSN-15oi (ATels #7910, #7936, #7937) taken by Swift. A UVOT image in the UVW2 filter was obtained. We find a source at a magnitude of 14.97 (with a 1-sigma uncertainty of 0.07 magnitudes) at the position of ASASSN-15oi. This source may contain contamination from the host galaxy in addition to emission from the TDE. From the XRT data we find a 3-sigma upper limit on the count rate of 1.6e-2 cps. Assuming a power-law spectrum with a (photon) index of 2, this corresponds to a flux limit of ~7e-13 erg cm^-2 s^-1 (0.3 -10.0 keV). At the distance of ASASSN-15oi, assuming a redshift of 0.02, this translates to an upper luminosity limit of ~1.6e41 erg/s. We thank the Swift team for scheduling and obtaining these observations. Additional Swift UVOT and XRT observations have been requested.