GCN Circular 6462
Subject
GRB 070518, deep LBT photometry
Date
2007-05-25T21:45:51Z (17 years ago)
From
Peter Garnavich at U of Notre Dame <pgarnavi@nd.edu>
P. Garnavich (Notre Dame), N. Bouche, P. Buschkamp (MPE),
O. Kuhn (LBTO/UAz), X. Fan, (U Ariz), X. Dai, J. Prieto,
K. Z. Stanek (Ohio State), J. Hill (LBTO/UAz), J. Bechtold,
J. Kern (U Ariz), R. M. Wagner (LBTO/OSU), J. Rhoads (Ariz State)
report:
The Large Binocular Telescope (LBT) imaged the position of the GRB 070518
afterglow (Guidorzi et al, GCN 6415; Xin et al. GCN 6416) with the
LBC-blue CCD camera (http//lbc.mporzio.astro.it) and 8.4-m SX mirror on
three epochs beginning 2007 May 19.32 (UT) (17.2 hours after the burst).
A fading source is clearly detected at the position of the afterglow
at all three epochs. Assuming the USNO-B.1 star at 16:56:47.39
+55:17:45.8 (J2000) has an R2=19.12 mag, we estimate the total brightness
of the source (shown in the table below) using a 1.3" radius aperture.
UT Date Age (hr) Exposures Seeing R2 mag Error
-----------------------------------------------------------
May 19.32 17.2 5x200s 0.75" 23.03 0.05
May 20.31 41.0 5x200s 1.0" 23.36 0.05
May 22.21 86.4 15x200s 1.1" 23.56 0.05
The slow fading implies significant contribution from a host
galaxy, and in good seeing the source appears elongated to the
southwest.
Combining observations from Price et al. (GCN 6443), Covino et al.
(GCN 6426) and Jelinek et al. (GCN 6418, corrected to USNO-B.1 catalog)
with the LBT estimates shows that a single power-law decline with index
0.95+/-0.05 added to a host galaxy of R=23.8+/-0.1 mag fits all the
observations spanning 10 minutes to 100 hours after the burst.
The May 19 LBT image can be found at:
http://www.nd.edu/~pgarnavi/grb070518/grb070518_LBT.jpg
The LBT is an international collaboration among institutions in the
United States, Italy and Germany. The LBT Corporation partners are:
* The University of Arizona on behalf of the Arizona university system
* Istituto Nazionale di Astrofisica, Italy
* LBT Beteiligungsgesellschaft, Germany, representing the Max Planck
Society, the Astrophysical Institute Potsdam, and Heidelberg University
* The Ohio State University
* The Research Corporation, on behalf of The University of Notre Dame,
University of Minnesota and University of Virginia
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