Chandra detection of X-ray emission at the location of FBOT AT2020xnd
ATel #14154; David Matthews (Northwestern), Raffaella Margutti (Northwestern), Daniel Brethauer (Northwestern), Joe Bright (Northwestern), Deanne Coppejans (Northwestern), Kate D. Alexander (Northwestern), Tanmoy Laskar (Bath), Lindsay DeMarchi (Northwestern), Wynn Jacobson-Galan (Northwestern), Giulia Migliori (INAF/IRA), Adriano Baldeschi (Northwestern), Michael C. Stroh (Northwestern), Katie Auchettl (University of Melbourne/UCSC)
on 5 Nov 2020; 23:14 UT
Credential Certification: Raffaella Margutti (rafmargutti@gmail.com)
Subjects: X-ray, Supernovae, Tidal Disruption Event
Referred to by ATel #: 14156
We report observations of the Fast Blue Optical Transient (FBOT) AT2020xnd (ATel #14105, AstroNote #2020-199) with the Chandra X-ray Observatory (CXO). We observed AT2020xnd on November 4th, 2020 (t=21-27 days since explosion) with the ACIS instrument for a total exposure of 20 ks (OBS ID: 23547, Proposal 22500192 PI: D. Matthews).
We detect significant X-ray emission from the location of AT2020xnd, and we infer an absorbed flux of ~3.5E-14 erg/s/cm^2 (0.3-10 keV) for a power law spectral model with a photon index of 1.3 (+0.5, -0.4) 1 sigma c.l. The Galactic neutral hydrogen column density along the line of sight of the transient is 5.12E+20 cm^-2 (Kalberla+ 2005).
At a redshift of z=0.2442 (d~1.24 Gpc) this corresponds to a luminosity of ~6.4E+42 erg/s (0.3-10 keV), which is comparable to the luminosity of AT2018cow at similar times (Margutti+ 2019, Sandoval+ 2019). We emphasize that this would make AT2020xnd the highest-z detection of a FBOT in X-rays, the second FBOT with X-rays detected at such an early epoch, and the third FBOT ever detected in X-rays, alongside AT2018cow and CSS161010 (Coppejans+ 2020). Further observations are planned.
We thank the entire CXO team for carrying out these observations.
