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GCN Circular 8938

Subject
GRB 090305: Swift/UVOT Upper Limits
Date
2009-03-06T12:49:24Z (15 years ago)
From
Stephen Holland at USRA/NASA/GSFC/SSC <sholland@milkyway.gsfc.nasa.gov>
S. T. Holland (CRESST/GSFC/USRA) and A. P. Beardmore (U Leicester)
report on the behalf of the Swift UVOT team:

     The Swift/UVOT observed the field of GRB 090305 starting 78 s
after the BAT trigger (Beardmore, et al. 2009, GCN Circ. 8932).
Settled exposures started at T+96 s.  We do not find any new source,
relative to the DSS, USNO-B1.0, or 2MASS, or any variable source at
the position of the GMOS-S afterglow (Cenko, et al. 2009, GCN
Circ. 8933).  Preliminary 3-sigma upper limits for detecting a source
in the white finding chart, and the co-added images, using a 2.5
arcsecond radius circular aperture, are

Filter   T_start   T_stop   Exp(s)     Mag
------------------------------------------
white        96      198      100   >20.6

v        3503   11,765     1034   >20.6
b        4323   15,980     1278   >21.8
u        4118     5755      393   >20.6
uvw1       3913     5550      393   >20.6
uvm2       3708     5345      393   >20.3
uvw2       4734   17,549     1723   >21.6
white      4528   16,892     1982   >22.7
------------------------------------------

The quoted upper limits have not been corrected for the expected
Galactic extinction along the line of sight corresponding to a
reddening of E_{B-V} = 0.21 mag (Schlegel, et al., 1998, ApJS, 500,
525).  All photometry is on the UVOT photometry system described in
Poole et al. (2008, MNRAS, 383, 627).

    The GMOS-S afterglow is located in the wings of the B = 13.72
mag USNO-B1.0 star 0584-0391760.  UVOT photometry at this location is
contaminated by this star.
Please update my e-mail address in your Address Book to <Stephen.T.Holland@nasa.gov 
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