GCN Circular 17726

Subject

GRB150418A: Swift/UVOT did not detect a new source

Event

Date

2015-04-21T23:05:38Z (11 years ago)

From

Paul Kuin at MSSL <npkuin@gmail.com>

N.P.M. Kuin (UCL/MSSL) reports on behalf of the Swift UVOT team:

Swift UVOT observations were made concurrently with the XRT observations
reported by  Sbarufatti et al. (GCN Circ. 17722Loading...
 
  and 17725Loading...
 
 ) of
GRB 150418A which was discovered by MAXI (Serino et al., GCN Circ.
No. 17719). At the location of the possible X-ray source detections
named source 1 and source 2 no new source was detected in the
u-band, with the following limits:

Source 1: u > 22.9 at 72.2 ks since the MAXI trigger at
    2015-04-18T00:52:08UT for an exposure time of 3.9ks
Source 2: u > 21.17 at t = 19ks since the MAXI trigger,
    for an exposure time of 322s.

However, we note that source 1 is at a distance of 4.6 arcsec of
a known nearby source in GSC2.3 (designated S5FU004949). That
source was detected with a magnitude u=20.38 +/- 0.15.

No correction was made for the galactic reddening
of E(B-V) = 0.043 and 0.373 respectively (Schlafly & Finkbeiner
2011 (ApJ 737, 103) ) at the locations of the sources 1 and 2.