GCN Circular 2797
Subject
Search for SN light in XRF 040912 with MEGACAM
Date
2004-10-12T15:18:08Z (20 years ago)
From
Jean-Luc Atteia at Lab d Astrophys.,OMP,Toulouse <atteia@ast.obs-mip.fr>
G. Stratta (OMP), F. Malacrino (OMP), M. Boer (OHP), A. Klotz (OMP), J-L Atteia (OMP), P. Martin (CFHT), C. Veillet (CFHT), J-C Cuillandre (CFHT) and Lisa Wells (CFHT) communicate:
We observed the HETE WXM error region of XRF 040912 (Butler et al. GCN 2701) with the wide-field imager MegaCam (36 2048 x 4612 pixel CCDs, 1 square degree FOV), mounted on the 3.6-m CFH Telescope.
Two exposures with integration time of 860s each, in the i' band have been performed consecutively starting on October 5.4197 UT (T_grb+22.8 days).
We looked for a possible SN emission for the 22 X-ray sources detected with Chandra
(Butler et al., GCN Circ=2716). The observation results follow:
First exposure (T) Second exposure (T+15min)
------ --------------------------- --------------------------
CXO Distance to i-band Distance to i-band
source X-ray position mag X-ray position mag
(") (")
------ --------------------------- --------------------------
#1 * 1.5 20.60 - -
#2 1.6 22.25 1.5 22.26
#3 1.4 20.17 1.5 20.20
#4 - - - -
#5 1.4 21.21 1.5 21.00
#6 1.5 18.96 1.3 18.99
#7 1.0 21.82 1.1 21.61
#8 1.8 23.02 1.3 23.09
#9 - - - -
#10 3.2 20.74 2.1 20.66
#11 1.0 21.68 0.9 22.44
#12 - - - -
#13 * - - 0.5 22.21
#14 1.2 21.84 1.6 21.39
#15 1.6 22.79 - -
#16 - - - -
#17 - - - -
#18 0.7 21.35 0.6 20.86
#19 - - - -
#20 - - - -
#21 - - - -
#22 - - - - --------------------------------------------------------------------
* Source was at the CCD line separation and was missed in one image
--------------------------------------------------------------------
We did not consider sources at distances greater than 2.5" from the
X-ray source position.
Our conclusions from these observations are:
1- If source #4 is the afterglow of XRF 040912 (as suggested in GCN 2731), we do not observed any SN emission down to i=23.2+/0.2 mag at 22.8 days after the burst event.
2- Source #13, which has been considered as the tentative afterglow of XRF 040912 (GCN 2728) does not appear to vary from the second Magellan observation.
We note that source #6 is coincident with an underlying galaxy with i'=19 mag, it has a decaying behavior in X-rays (Butler et al. GCN=2716) and shows the highest V-i' color index (V-i'=2.05, V magnitude reported by Gorosabel et al., GCN 2724), requiring a very red galaxy, or a rebrightning.
This resemble the case of XRF 040701 (Barraud et al. GCN 2620) for which the potentially associated Chandra source (Fox et al. GCN 2626) was coincident with a z=0.2146 emission-line galaxy (Kelson et al. GCN 2631) with lower limit R~17.9 mag that possibly prevented the observation of a delayed SN emission, assuming a SN fainter than SN 1998bw and more similar to SN2002ap or SN1994I (Pian et al. GCN 2638).
Further observations of source #6 are welcome.
A comparison of the two CFHT images that show the nearest objects to the
Chandra sources detected in the i' band, can be found at
http://www.cfht.hawaii.edu/~grb/XRF040912.html