GCN Circular 17405

B. Sbarufatti (INAF-OAB/PSU), F. E. Marshall (NASA/GSFC), A. Maselli 
(INAF-IASFPA), A. Melandri (INAF-OAB),	V. Mangano (PSU), M.C. Stroh
(PSU), D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), C. Pagani (U. Leicester) and P.A. Evans (U. Leicester)
report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 150202B (Axelsson et al. GCN Circ. 17385
Not found
 
 
)
in a series of observations tiled on the sky. The total exposure time
is 4.2 ks, distributed over 2 tiles; the maximum exposure at a single
sky location was 4.7 ks. The data were collected between T0+95.4 ks and
T0+107.3 ks, and are entirely in Photon Counting (PC) mode. 

Four uncatalogued X-ray sources have been detected, however none of
them is above the RASS limit or shows definitive signs of fading.
Therefore, at the present time we cannot identify which, if any, is the
afterglow. Details of these sources are given below:

Source 1:
  RA (J2000.0):  86.9565  =  05:47:49.57
  Dec (J2000.0): +58.8301  =  +58:49:48.2
  Error: 4.1 arcsec (radius, 90% conf.)
  Count-rate: 0.0183 +/- 0.0030 ct s^-1
  Flux: (6.1 +/- 1.0)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 2:
  RA (J2000.0):  86.5922  =  05:46:22.14
  Dec (J2000.0): +58.9223  =  +58:55:20.5
  Error: 5.7 arcsec (radius, 90% conf.)
  Count-rate: (5.9 +/- 1.9) -3 ct s^-1
  Flux: (3.2 +/- 1.0)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 3:
  RA (J2000.0):  86.7927  =  05:47:10.25
  Dec (J2000.0): +58.7852  =  +58:47:06.8
  Error: 6.4 arcsec (radius, 90% conf.)
  Count-rate: (4.0 +/- 1.7) -3 ct s^-1
  Flux: (1.60 +/- 0.67)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 4:
  RA (J2000.0):  86.8219  =  05:47:17.25
  Dec (J2000.0): +58.9746  =  +58:58:28.7
  Error: 5.5 arcsec (radius, 90% conf.)
  Count-rate: (3.03 +/- 0.99) -3 ct s^-1
  Flux: (6.5 +/- 2.1)e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Sources 3 and 4 are positionally coincident with stars from the USNO B1
catalogue.

The results of the XRT-team automatic analysis of the tiled XRT
observations, including a position-specific upper limit calculator, are
available at http://www.swift.ac.uk/xrt_products/TILED_GRB00039.

The UVOT observation covers sources 1 and 3 in the UVW1 filter. There
is nothing at the position of source 1; source 3 is bright as expected
from the catalogued source.

This circular is an official product of the Swift-XRT team.