TITLE: GCN CIRCULAR NUMBER: 6716 SUBJECT: GRB070805 XRT and UVOT afterglow candidate DATE: 07/08/07 22:04:03 GMT FROM: Valentina La Parola at INAF-IASPA V. La Parola, P. Schady, F.E. Marshall, S. T. Holland and A. M. Parsons, E. Troja, J. Kennea report on behalf of the Swift team We have analysed the XRT and UVOT observations of GRB070805 (Parsons et al., GCN 6708). The XRT observed the BAT position twice, with 2.3 and 7.7 ksec exposure times. We find a faint source (estimated unabsorbed flux: 3.4e-13 erg/s/cm2) within the BAT error circle, at RA= 16 20 02.8 (245.01175) Dec= -59 57 34.8 (-59.959657) (4 arcsec error radius, 90% confidence) that is 82 arcsec from the BAT position (Stamatikos et al, GCN 6711) This source does not show any sign of decay, its count rate being consistent between the two observations. The source is too faint to allow for any detailed spectral or temporal analysis. A second, fainter source is detected only in the second observation, at RA= 16 20 16.8 (245.069937) Dec= -59 57 12.7 (-59.95352) (4.7 arcsec error radius, 90% confidence) The estimated unabsorbed flux is 1.13e-13 erg/s/cm2. At present, neither of these sources can be confidently associated with the GRB afterglow. On further inspection of the UVOT observations, an uncatalogued source is detected at the position of the first XRT source. This source was initially unidentified (GCN Circ. 6712) due to the density of the field and size of the BAT error circle. The source is detected in the white band filter at more than 3 sigma with an estimated magnitude of 20.1+/-0.2, and is marginally detected in the V, B and U filters. The refined UVOT coordinates of this source are RA = 16 20 03.11 (245.0131) Dec = -59 57 34.9 (-59.9597) with an uncertainty of 0.7 arcseconds. There is little evidence for variability in the limited data currently available. Observations are ongoing. I.A.S.F. INAF Mailing System Outgoing mail is certified Virus Free. Checked by McAfee anti-virus system