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GCN Circular 10137

Subject
GRB 091029: Observations from Stardome Observatory
Date
2009-11-05T08:44:38Z (15 years ago)
From
Antonio Deugarte at IAA-CSIC <deugarte@iaa.es>
G. W. Christie (Stardome Obs., New Zealand),
S. Dong (IAS, Princeton), A. de Ugarte
Postigo (INAF-OAB, Italy) and T. Natusch
(Stardome Obs., New Zealand) report:

We observed the field of GRB 091029 (Swift
trigger 372210, Grupe et al. GCN 10097) with
the Stardome 0.4m telescope located in
Auckland (New Zealand) starting at 07:55UT,
3.90 hours after BAT trigger. We used a SG530
filter that transmits wavelengths above 5300
Angstroms and a SBIG ST-L-6303E CCD (KAF-6303E
detector).

A nearly continuous series of 300s images was
taken until 16:30UT under mostly clear
conditions (seeing: 1.6-2.5"). These were
co-added making 15 stacks of 6 images (1800s
exposure each).

The fading afterglow (Filgas et al., GCN 10098;
LaCluyze et al., GCN 10099; de Ugarte Postigo
et al., GCN 10104; Marshall et al. GCN 10108)
was clearly detected in all images over the
observing period, yielding the following psf
photometry(DOPHOT):

UT (mid)    delT      R1      Err (statistical)
29.32713    3.901    19.34    0.09
29.34906    4.428    19.32    0.08
29.37120    4.959    19.43    0.08
29.39311    5.485    19.46    0.08
29.41503    6.011    19.67    0.08
29.43360    6.456    19.57    0.08
29.45862    7.057    19.73    0.08
29.50946    8.277    19.93    0.12
29.53164    8.809    19.94    0.09
29.56044    9.501    20.16    0.09
29.59390   10.304    20.21    0.11
29.61620   10.839    20.21    0.13
29.63853   11.375    20.36    0.16
29.66081   11.910    20.41    0.17

where delT is the mid-exposure time in hours
since trigger. Photometric calibration was
done against USNOB1 0340-0030262 RA (J2000.0):
04h 00m 38.61s,  DEC( J2000.0): -55d 55' 37.3"
assuming R1=16.40.

The mean power-law index over this interval
was -0.94 (+/-0.05). Astrometry of the images
gave the afterglow position (UCAC2) as:

RA (J2000.0) = 04h 00m 42.62s
DEC (J2000.0) = -55d 57' 20.2"

with an uncertainty of 0.18"

This position is in agreement with Marshall et
al. (GCN 10108) and Grupe et al. (GCN 10097).
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