{
  "submitter": "Jean-Luc Atteia at Lab d Astrophys.,OMP,Toulouse  <atteia@ast.obs-mip.fr>",
  "version": 2,
  "subject": "Search for SN light in XRF 040912 with MEGACAM",
  "editedBy": "Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov>",
  "body": "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:\n\nWe 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.\n\nTwo 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). \n\nWe looked for a possible SN emission for the 22 X-ray sources detected with Chandra \n(Butler et al., GCN Circ=2716).  The observation results follow:        \n\n\tFirst exposure (T)            Second exposure (T+15min)\n------  ---------------------------   --------------------------\nCXO      Distance to      i-band      Distance to      i-band \nsource   X-ray position   mag         X-ray position   mag  \n        (\")                          (\")                  \n------  ---------------------------   -------------------------- \n#1 *    1.5            20.60           -               - \n#2      1.6            22.25           1.5             22.26 \n#3      1.4            20.17           1.5             20.20 \n#4       -             -               -               - \n#5      1.4            21.21           1.5             21.00 \n#6      1.5            18.96           1.3             18.99 \n#7      1.0            21.82           1.1             21.61 \n#8      1.8            23.02           1.3             23.09 \n#9      -              -               -               - \n#10     3.2            20.74           2.1             20.66 \n#11     1.0            21.68           0.9             22.44 \n#12     -              -               -               - \n#13 *   -              -               0.5             22.21 \n#14     1.2            21.84           1.6             21.39 \n#15     1.6            22.79           -               - \n#16     -              -               -               - \n#17     -              -               -               - \n#18     0.7            21.35           0.6             20.86 \n#19     -              -               -               -      \n#20     -              -               -               -             \n#21     -              -               -               -      \n#22     -              -               -               -     -------------------------------------------------------------------- \n* Source was at the CCD line separation and was missed in one image\n--------------------------------------------------------------------\n\nWe did not consider sources at distances greater than 2.5\" from the \nX-ray source position. \nOur conclusions from these observations are:\n\n1- 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.\n\n2- 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. \n\nWe 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.  \nThis 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). \nFurther observations of source #6 are welcome.\n\nA comparison of the two CFHT images that show the nearest objects to the\nChandra sources detected in the i' band, can be found at\nhttp://www.cfht.hawaii.edu/~grb/XRF040912.html",
  "eventId": "XRF 040912",
  "createdOn": 1097594288000,
  "circularId": 2797,
  "email": "atteia@ast.obs-mip.fr",
  "editedOn": 1777053029518,
  "bibcode": "2004GCN..2797....1S"
}