TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3567
SUBJECT: GRB 050525a: ARC 3.5-meter Optical and NIR Observations
DATE:    05/07/06 19:00:54 GMT
FROM:    Don Lamb at U.Chicago  <lamb@oddjob.uchicago.edu>

GRB 050525a: ARC 3.5-meter Optical and NIR Observations

J. Flasher (Colorado), F. Hearty (Colorado), G. Stringfellow
(Colorado), J. Walawender (Colorado), D. Q. Lamb (Chicago), D. G. York
(Chicago), G. Wallerstein (Washington), V. Woolf (Washington), S.
Anderson (Washington), J. Dembicky (APO), J. Barentine (APO), R.
McMillan (APO), and B. Ketzeback (APO) report on behalf of the ARC GRB
team of the FUN GRB collaboration:

We observed the afterglow (Rykoff et al., GCN Circular No. 3465;
Malesani et al., GCN Circular No. 3469) of GRB 050525a, a burst
localized by Swift/BAT (Band et al., GCN Circular No. 3466; Markwardt
et al., GCN Circular No. 3467), on the night of May 24th, using SPIcam
and NIC-FPS on the ARC 3.5-meter telescope at Apache Point
Observatory.  The observation began at 08.33 UT on 25 May 2005 (8.28
hours after the burst) and ended at 11.07 UT on 25 May 2005 (11.02
hours after the burst).  The observation consisted of two 300-second
exposures each in r, i, and z; and a series of 60-, 60-, 10-, and
10-second exposures in Z, J, H, and Ks, respectively.  We have
constructed stacked images of the GRB field, corresponding to 10-minute
integrations in r, i, z, and Z; and 20-minute integrations in J, H, and
Ks.  We detect the afterglow in all seven filters, and measure J = 18.3
± 0.1 at 09:50 UT (the mid-point time of the J-band observation),
calibrated relative to the 2MASS stars in the field.

NIC-FPS is currently in its commissioning phase.

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