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GCN Circular 14594

GRB 130505B: Swift Candidate Afterglow
2013-05-06T23:15:51Z (11 years ago)
Frank Marshall at GSFC <>
D. Kocevski (NASA/GSFC/ORAU), F. E. Marshall (NASA/GSFC), 
M. De Pasquale (MSSL-UCL), P. D'Avanzo (INAF-OAB), 
and A. Melandri (INAF-OAB) report on behalf of the Swift team:

The Swift began tiling observations of the field of GRB 130505B
16 hours after the MAXI trigger (Serino et al., GCN Circ. 14586).
A bright source not in the DSS is seen in the UVOT observation
at a preliminary position of 
   RA(J2000)  =    09:17:22.18 = 139.34124
   DEC(J2000) =   +01:42:03.1  =  +1.70085
with a 90%-confidence error radius of about 0.6 arc sec.
It is not possible to determine whether the source is varying
with the currently available data.

The position is consistent with that of SDSS J091721.89+014203.2,
but more than 5 magnitudes brighter in the u band.
The SDSS source could be the host galaxy for the burst,
or could indicate that the MAXI source is a galactic transient.

The preliminary detection using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the exposure is:

Filter         T_start(s)   T_stop(s)      Exp(s)        Mag
u                58617        59042         425        18.0 +/- 0.1

The magnitude is not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.024 in the direction of the burst
(Schlegel et al. 1998).

We have also analysed 426 s of Swift-XRT data from 58.6 ks 
to 59.0 ks after the MAXI trigger. The data are all in 
Photon Counting (PC) mode. A preliminary
analysis reveals the presence of a source at the following position 
RA, Dec = 139.34180, +1.70215 which is equivalent to:

RA (J2000): 09 17 22.03
Dec(J2000): +01 42 07.7

with an uncertainty of 4.5 arcsec (radius, 90% confidence). 
This position is consistent with the UVOT one. The observed count rate 
is (3.0 +/- 1.0) x 10^-2 cts/s.  Given the low significance of 
the detection, at the present stage, it is not possible to determine 
whether the source is variable.

Automated analysis of the XRT data can be found online at

Details of the XRT automated analysis methods are detailed in 
Evans et al. (2007, A&A, 469, 379; and 2009, MNRAS, 397, 1177).

Additional observations with Swift are scheduled. Observations
with other observatories of this interesting object are encouraged.
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