NUMBER:  2403
SUBJECT: XRF030723 : Detection of the likely host galaxy
DATE:    03/09/25 15:13:29 GMT

"We have observed the field of XRF 030723 (=HETE trigger 2777, GCN 2320) with the FORS1 optical camera on the ESO VLT on September 24. In a deep (about 1 hr) R-band image with a mean seeing of 0.68 arcsec we detect a very faint, extended source at the position of the optical afterglow (GCN 2323). The galaxy has a position angle of about 90 degrees EofN. We interpret this as the likely host galaxy of XRF 030723. The magnitude of the galaxy is about R=26.8+/-0.4. An image of the galaxy can be seen at http://www.astro.ku.dk/~brian_j/xrf/xrf030723

We acknowledge excellent support from the Paranal staff, in particular Poshak Gandhi."

NUMBER:  2345
SUBJECT: XRF 030723 : Detection of a rebrightening in the optical afterglow
DATE:    03/08/06 18:38:00 GMT

J. U. Fynbo (U. Aarhus), J. Hjorth (U. Copenhagen), J. Gorosabel (IAA-CSIC/STScI), B. L. Jensen (U. Copenhagen), M. I. Andersen (AIP), R. A. M. J. Wijers (U. Amsterdam), C. Kouveliotou (NASA), on behalf of GRACE, report:

"We have monitored the afterglow of XRF 030723 (Prigozhin et al. GCN #2313; Fox et al. GCN #2323; Butler et al. GCN #2328) with the ESO VLT. Between Aug 3.2 UT and Aug 6.3 2003 UT the optical afterglow brightened by 1.0 mag to R ~ 24.3. If this is due to the emergence of a supernova it would strengthen the link between GRBs and XRFs. It would also indicate a fast rise for the supernova and a relatively low redshift for XRF 030723, z < 1, consistent with the earlier spectroscopic constraints (Fynbo et al. GCN #2327). Alternatively, we may be seeing a rebrightening due to late energy injection (refreshed shock). Continued spectroscopic and photometric monitoring is planned.
Images are posted at http://www.astro.ku.dk/~brian_j/grb/grb030723

We thank the Paranal Observatory staff for efficiently conducting the reported service-mode observations."

NUMBER:  2321
SUBJECT: XRF 030723 : optical observations
DATE:    03/07/25 16:20:25 GMT

B. L. Jensen (U. Copenhagen), J. Gorosabel (IAA-CSIC/STScI), J. Hjorth, C. Vinter (U. Copenhagen), J. U. Fynbo (ESO), P. M. Vreeswijk (ESO Chile) report:

"R-band exposures covering the 2' radius HETE-2 SXC error circle of XRF 030723 (Prigozhin et al., GCN #2313) were obtained at the Danish 1.5-m telescope (ESO La Silla) on July 24.3 and July 25.3 2003 UT. In the combined images, reaching limiting magnitudes of R ~ 24, no counterpart to the first ROTSE-III source (Smith & Quimby, GCN #2318) is apparent. At RA(J2000.0) = 21 49 24.54, Dec (J2000.0) = -27 40 35.0, 2.1" from the reported location of the second ROTSE-III source, an object with R = 23.2 +- 0.3 is detected (photometry based on the calibration provided by Henden (GCN #2317)). The object is unresolved in 1.3" seeing and appears to be constant in brightness between the two epochs. Images are posted at http://www.astro.ku.dk/~brian_j/grb/grb030723 "