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GCN Circular 3129

Subject
GRB 050319: Swift-UVOT detection of the afterglow
Date
2005-03-21T00:38:06Z (19 years ago)
From
Martin Still at NASA/GSFC Swift SSC <Martin.Still@gsfc.nasa.gov>
P. Boyd (GSFC/UMBC), S. T.  Holland, M. Still (GSFC/USRA), W. Landsman
(GSFC), S. Hunsberger (PSU), A.  Breeveld (MSSL), P. Roming (PSU), K. 
Mason, P. Schady (MSSL), M.  Ivanushkina (PSU), T. Poole (MSSL), C. 
Gronwall (PSU) A. Blustin (MSSL), P. Brown (PSU), S. Rosen, K. McGowan 
(MSSL), S. Koch (PSU), M. Carter, H. Huckle, M. De Pasquale (MSSL), P. 
Broos (PSU), T. Kennedy, P. Smith, B. Hancock (MSSL), H. Krimm 
(GSFC/USRA), J. Nousek (PSU), N. Gehrels (GSFC), on behalf of the Swift 
UVOT team.

The Swift Ultra-Violet/Optical Telescope (UVOT) began
settled observations of the field of GRB 050319 (Krimm
et al; GCN 3117Not found
 
 
) at 09:32:48 UT, 90 after the BAT
trigger. A comparison of the 100s finding chart (with
mid-exposure 140s after the trigger) against the
Digitized Sky Survey reveals a new source inside the BAT
and XRT error circles at:

RA = 10h 16m 47.76(3)s Dec = +43d 32m 54.9(5)s J2000

and consistent with the ROTSE-IIIb position reported by
Rykoff et al. (GCN 3116Not found
 
 
) The V band magnitude is V =
17.5(1).

The UVOT obtained a series of images of this burst with
a variety of integration times. Mid-exposure times,
Delta-T, with respect to the BAT trigger at 09:31:18 UT
are measured in seconds. Observations with the V and B
filters are listed below:

Delta-T	 Exposure(s)  Filter   Mag
   140      100         V      17.5    (Finding Chart)
   380       80         B      18.8
   600       80         V      18.4
  1030      100         B      18.9
  1250      100         V      19.2
  5400      900         B      20.9
  7080      700         V      20.2
 17000      900         B      21.2
 18700      700         V      20.6

No signal was detected in the U band in a total exposure
time of 90s centered approximately 600s after the
trigger with an upper limit of U = 19.

We caution that the absolute magnitude scale is based on
ground calibration and will require confirmation in
flight.