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 (HEASARC).
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 makes 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.
| Catalog | Name | Reported RA | Reported DEC | Reported Obj-Type | Reported Redshift | Host Name | Host Redshift | Remarks | TNS RA | TNS DEC | TNS Obj-Type | TNS Redshift |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| TNS | 2020xnd [ZTF20acigmel] | 22:20:02.030 | -02:50:25.30 | SN | 0.2442 | 22:20:02.030 | -02:50:25.30 | |||||
| TNS | 2018cow [ZTF18abcfcoo] | 16:16:00.220 | +22:16:04.91 | SN Ic-BL | 0.0141 | 16:16:00.220 | +22:16:04.91 | SN Ic-BL | 0.014 | |||
| Other | 04:58:34.398 | -08:18:04.34 | SN | 0.034 |
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