Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 3416

GRB 050509b: Keck/Chandra Cross-Correlation
2005-05-12T08:48:39Z (19 years ago)
Josh Bloom at Harvard/CFA <>
J. S. Bloom, R. J. Foley, D. Pooley, A. V. Filippenko, R. Chornock (UCB),
C. Blake (Harvard), J. X. Prochaska (UCSC), J. Hennawi (UCB), M. Gladders
(Carnegie), B. Koester (U Michigan) and H. W. Chen (MIT) report:

We observed the field of GRB 050509b (#3383,#3385) with Keck I (+LRIS)
with g' and R filters.  Starting at 20050511.25 UT, we took 5 dithered
images in each band for a total of 1660 and 1620 sec exposures in g and R,
respectively. At the location of the two reported Chandra sources we find
no significantly-detected flux in either band, however there are
indications of an R counterpart (at the few sigma level) to Chandra#8.
Moreover, these images do reveal a number of sources in the XRT fainter
than reported deep imaging with the VLT (3410) and Keck II (3401), which
we label J1-J4:

   J1 12:36:13.56 +28:59:03.4
   J2       13.44        04.7
   J3       13.41     58:56.3
   J4       13.47     59:06.2

(J2000; estimated errors of 0.3 arcsec in each direction).

We note that S5, which is less than 2 arcsec from the Chandra source #5,
appears bluer than neighboring S3 and S2.

The finding chart can be found at:
Looking for U.S. government information and services? Visit