GCN Circular 4749
Subject
GRB 050826: Optical Afterglow and Host Galaxy
Date
2006-02-12T01:53:14Z (19 years ago)
From
Jules Halpern at Columbia U. <jules@astro.columbia.edu>
J. P. Halpern (Columbia U.) and N. Mirabal (U. Michigan) report
on behalf of the MDM Observatory GRB follow-up team:
"Follow-up observations summarized here support our original
suggestion in GCN 3891 of an optical afterglow for the Swift
GRB 050826 (GCN 3884, 3888), and indicate the presence of a
relatively bright host galaxy for this long burst.
First, the Swift XRT position of the afterglow, which was
originally determined to lie 8" from the optical candidate
with an 90% uncertainty radius of 6" (GCN 3889, 3891), was
subsequently refined (as were all XRT positions). In the
revised catalog of Moretti et al. (astro-ph/0511604), the
XRT position falls only 3.1" from the optical position,
consistent with the improved 3.4" X-ray uncertainty.
---------------------------------------------------
R.A. (2000) Dec. (2000) +/- (")
---------------------------------------------------
Swift XRT 05 51 01.49 -02 38 38.6 3.4
MDM 1.3m OT 05 51 01.58 -02 38 35.8 0.5
MDM 2.4m host 05 51 01.59 -02 38 36.2 0.5
---------------------------------------------------
Second, image subtraction among observations obtained on three
consecutive nights on the MDM 1.3m reveals a point-like OT on
the first night only, and shows that the light is dominated by
the host galaxy on the second and third nights. The OT is offset
~0.4" to the north of the brightest part of the galaxy.
------------------------------------------------------
MDM 1.3m
------------------------------------------------------
Date(UT) Time(UT) t-t0(hours) Diff OT R(mag)
------------------------------------------------------
Aug. 26 10:42-11:57 4.40- 5.65 22.23 +/- 0.15
Aug. 27 10:43-11:58 28.42-29.67 > 22.8
Aug. 28 11:03-11:57 52.75-53.65
------------------------------------------------------
MDM 2.4m Host R(mag)
------------------------------------------------------
Dec. 25 21.67 +/- 0.05
------------------------------------------------------
Third, using the MDM 2.4m, RETROCAM imager, and SDSS r' filter
on 2005 Dec. 25, a bright core and irregular extension of the
presumed host galaxy are clearly resolved in seeing of 1".
The host magnitude listed above is measured in a 1.8" radius.
Optical magnitudes were calibrated with Landolt standard stars,
and positions were derived with respect to the USNO B1.0 catalog.
The MDM images are posted at
http://www.astro.columbia.edu/~jules/grb/050826/
Spectroscopy and deeper imaging are needed to measure the redshift
and star-forming properties of the presumed host galaxy.
This message may be cited."