GCN Circular 10625
Subject
GRB 100418A: Swift/UVOT Observations
Event
Date
2010-04-19T21:54:40Z (16 years ago)
From
Mike Siegel at PSU/Swift MOC <siegel@astro.psu.edu>
M. H. Siegel (PSU) and F. Marshall (NASA/GSFC) report on behalf
of the Swift/UVOT team.
The Swift/UVOT began settled observations of the field of GRB
100418A 87s after the BAT trigger (Marshall et al., GCN Circ. 10612).
Data summed from the first and second orbits reveals the source
reported by Marshall et al. The source shows no fading between
the first and second orbits within the photometric uncertainties.
The photometry is consistent with a constant source with a white
magnitude of 20.48+-0.13. This likely represents the GRB host
galaxy reported by Malesani (GCN Circ. 10621) and not the
afterglow reported by Filgas et al. (GCN Circ. 10617), Updike
et al. (GCN Circ. 10619) and Antonelli et al. (GCN Circ. 10620).
The UVOT position of the source is:
RA(J2000.0) = 17:05:26.96 = 256.36278 (deg)
Dec(J2000.0) = +11:27:41.9 = +11.46167 (deg)
with a 90% confidence interval of 0."67.
The 3-sigma upper limits for the finding chart (fc) and
summed exposures from the first and second orbits are reported
below:
FILTER T_start(s) T_stop Exposure Mag/3UL
========================================================
white fc 87 237 147 20.62+-0.29
white 89 1548 390 20.58+-0.20
white 6143 6343 196 20.32+-0.20
v 628 6754 491 >19.90
b 554 6138 294 20.61+-.44
u 299 7348 697 20.47+-0.41
uvw1 678 7164 491 20.47+-0.42
uvm2 653 6959 491 20.09+-0.32
uvw2 604 6548 308 20.73+-0.54
=======================================================
The above magnitudes are not corrected for the Galactic extinction
corresponding to a reddening of E_{B-V} = 0.07 (Schlegel et al.,
1998, ApJS, 500, 525). The photometry is on the UVOT photometric
system described in Poole et al. (2008, MNRAS, 383, 627).