GCN Circular 9253
Subject
GRB090424: R-band detection (37.5 hrs post-burst), jet break?
Date
2009-04-26T11:30:29Z (16 years ago)
From
Myungshin Im at Seoul Nat U <mim@astro.snu.ac.kr>
M. Im, W. Park, Y. Jeon, I. Lee (CEOU/Seoul National Univ),
Y.-B. Jeon (KASI) and Y. Urata (NCU) on behalf of EAFON team.
We continued the follow-up observation of GRB090424 (Cannizzo et al.
GCN 9223) in BVR using the 1.0m telescope at Mt. Lemmon (Arizona, US)
operated by the Korea Astronomy Space Science Institute.
The R-band imaging started at 2009 April 26, 03:11:23 UT.
The mid-point of the R-band obseravation is April 26,
03:39:43 UT (37.45 hrs after the burst).
From a stacked image of 13 frames (3 min exp. each),
the afterglow is visible at R=20.96 +- 0.17 mag, suggesting
a significant fading occurred since last night (Im et al. GCN 9248),
more than the expected amount of fading with the power-law index
of 0.71 reported earlier (Urata et al. GCN 9247). This suggests that
jet break might have occured. The afterglow is also visible in
B- and V-bands.
The photometry was calibrated against USNO-B1 stars in the vicinity.
We thank the LOAO operator, J. Yoon for his assistance for this
observation.