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GCN Circular 8773

Subject
GRB 090102: P60 Imaging and P200 Spectroscopy
Date
2009-01-03T01:55:08Z (15 years ago)
From
S. Bradley Cenko at Caltech <cenko@srl.caltech.edu>
S. B. Cenko (UC Berkeley), A. Rau and M. Salvato (Caltech) report on
behalf of a larger collaboration:

We have imaged the field of GRB090102 (Mangano et al., GCN 8762) with the
automated Palomar 60-inch telescope beginning at 03:46 on 2 Jan 2008 UT (~
50 min after the burst).  Observations were taken in the R, i', and g'
filters and continued throughout the night until sunrise roughly 10 hours
later.

The optical afterglow (Klotz et al., GCN 8761, Covino et al., GCN 8763) is
well detected in all three filters.  All three bands exhibit a relatively
smooth power-law decay with index ~ 0.9, consistent with the value
reported by Afonso et al. (GCN 8771).  We report here the following subset
of our R-band observations:

Tmid (s)   Texp (s)   Mag    Err
--------------------------------------
3190.2     120.0      19.75  0.13
5266.2     120.0      20.02  0.06
7704.3     120.0      20.41  0.07
9973.9     120.0      20.56  0.07
11911.5    120.0      20.78  0.08
14068.6    120.0      21.01  0.09
16144.7    120.0      21.09  0.09
18522.6    600.0      21.23  0.06
20631.5    600.0      21.42  0.06
22756.7    600.0      21.58  0.07
24832.6    600.0      21.86  0.08
27994.7   1200.0      21.72  0.05
32188.5   1200.0      22.02  0.06
36411.3   1200.0      21.93  0.11

Photometric calibration was performed relative to the SDSS DR7, with
photometric transformations from Jordi, Grebel, & Ammons (A&A, 460, 2006).

In addition, we have obtained a single 1800 s spectrum of the afterglow
with the Double Beam Spectrograph mounted on the Palomar 200" Hale
telescope at a mean epoch of Jan 2.22.  The spectrograph was configured to
provide wavelength coverage from the atmospheric cutoff to ~ 8000 A.  We
confirm the results of de Ugarte Postigo (GCN 8766), finding a single
strong absorption system at z = 1.546.  Given the lack of strong
Ly-alpha absorption, we place a slightly stricter limit on the host
redshift of z < 1.9.
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