A. Melandri (INAF-OAB), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), L.M.
McCauley (PSU), S.L. Gibson (U. Leicester), J.P. Osborne (U.
Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC) and P.A. Evans (U.
Leicester) report on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the INTEGRAL-detected
burst GRB 160221A (Mereghetti et al. GCN Circ. 19046), collecting 1.3
ks of Photon Counting (PC) mode data between T0+21.3 ks and T0+25.8 ks.
One uncatalogued X-ray source has been detected inside or close to the
INTEGRAL error region, it is below the RASS limit and shows no
definitive signs of fading. Therefore, at the present time we cannot
confirm this as the afterglow. Details of this source are given below:
RA (J2000.0): 232.0897 = 15:28:21.54
Dec (J2000.0): -28.4552 = -28:27:18.7
Error: 4.5 arcsec (radius, 90% conf.)
Count-rate: 0.0151 +/- 0.0040 ct s^-1
Flux: (5.6 +/- 1.5)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)
Another uncatalogued was also detected, however this was too far from
the GRB position to be the afterglow.
The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
This circular is an official product of the Swift-XRT team.