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GCN Circular 2638

XRF040701: Optical Observations at ESO
2004-08-09T18:15:33Z (20 years ago)
Elena Pian at IASF,CNR,Bologna <>
E.  Pian, J.  Fynbo , U. G. Joergensen, A. Levan, N.  Masetti, E. Palazzi,
F. Patat, E. Rol, J. Hjorth, B. Lindgren Jensen, P. Mazzali, C.
Kouveliotou, K. Nomoto, E. Cappellaro, on behalf of a larger
collaboration, report:

The field of source CXOU J204816.1-401108 (Fox et al.  GCN 2626), detected
in the error box of XRF040701 (Barraud et al., GCN 2620), was imaged with
the ESO Danish 1.5m telescope at La Silla on 2004 Jul
03,15,16,17,19,23,24, Aug 4,5, and with the VLT and FORS1 on 2004 Jul
23.16, 23.33, 30.35 UT in the R band. The VLT imaging of Jul 23 was done
under excellent seeing conditions (0.6").

Both R-band photometry and PSF-matched image subtraction of the galaxy at z
= 0.2146 underlying CXOU J204816.1-401108 (Kelson et al.  GCN 2627)  rule
out flux variations larger than a few hundredths of a magnitude.

Considering that we determine a lower limit of R~17.9 for the galaxy
brightness, an event similar to supernova 1998bw would produce an observed
variation of about 6% from explosion to maximum light. Therefore, our data
appear marginally to exclude a supernova similar to 1998bw (see also
Berger et al.  GCN 2631), but not a weaker one, like SN2002ap or SN1994I.

A 2hr VLT+FORS1+300V spectrum of the galaxy taken on Jul 23 does not
reveal conspicuous supernova features. The 2 galaxies located at ~4" West
and ~6" South of the galaxy underlying CXOU J204816.1-401108 have
redshifts 0.215 and 0.17, respectively.

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