//////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2551 SUBJECT: GRB 040323: a long GRB detected with INTEGRAL DATE: 04/03/23 14:15:09 GMT FROM: Sandro Mereghetti at IASF/CNR S. Mereghetti, D.Gotz (IASF-Milano), M. Beck, J. Borkowski on behalf of the IBAS Localization Team, S. Shaw and N. Mowlavi on behalf of the INTEGRAL Science Data Centre and the INTEGRAL Science Working Team report: A 20 s long GRB has been detected with the INTEGRAL Burst Alert System (IBAS) on March 23 at 13:02:59 UT. The GRB has been detected with IBIS/ISGRI in the 15-300 keV band. The refined coordinates (J2000) are: R.A. 13h 53m 52.7s Dec. -52deg 21' 10'' with an uncertainty of 2 arcmin. The preliminary peak flux in the 20-200 keV range is about 1.7 photons/cmsq/s (2.2 x 10^-7 erg/cmsq/s) (1 s integration time). This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2553 SUBJECT: GRB 040323, a dark GRB ? DATE: 04/03/23 22:25:10 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia GRB 040323, a dark GRB ? ---------------------------------------- A. J. Castro-Tirado, J. Gorosabel and A. de Ugarte (Instituto de Astrofísica de Andalucía, IAA-CSIC, Granada), P. Tristram (MJO, Canterbury Univ.), Ph. Yock (Auckland Univ.), M. Jelínek (Astronomical Observatory, Ondrejov), M.D. Pérez- Ramírez (Univ. de Jaén) and J. M. Castro Cerón (STScI, Baltimore) communicate: "We have observed the field of the GRB 040323 detected by INTEGRAL (GCN Circ. 2551, Mereghetti et al.) on 23 Mar 2004 (15:24 UT) with the 0.6-m telescope at Canterbury's Univ. Mt. John Observatory. Imagery was obtained in the I- and B-band (300-s exposure time each). No optical variable source is detected within the 2' radius error box provided by IBIS/IGRIS when comparing to the DSS-2. Even if there is considerable absorption towards this location (Av = 1.1), the fact that no afterglow is detected 2.33 hr after the event in the MJO images down to the DSS-2-Infrared limiting magnitude might be indicative of a dark GRB. We therefore encourage further deep, near-infrared imaging at larger telescopes." This message is quotable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2555 SUBJECT: GRB040323: NIR Observations and Variable Object DATE: 04/03/26 23:39:48 GMT FROM: Derek Fox at CIT A. Gal-Yam, D. Fox, and E. Berger (Caltech), with P. Wyatt (OCIW) report on behalf of a larger collaboration: We have observed the INTEGRAL localization of GRB040323 (Mereghetti et al., GCN 1551) using the PANIC NIR camera on the Baade 6.5-m telescope at Las Campanas Observatory. The PANIC field of view covers the central ~50% of the INTEGRAL error circle (Mereghetti et al. 2004; GCN 2551). Two epochs of J-band (1.25 micron) and one epoch of K-band (2.16 micron) imaging have been obtained on the nights of March 24 (J and K) and March 25 (J only) UT. PSF-matched image subtraction of the two J-band epochs reveals a bright point-like source at RA 13:53:53.20, Dec -52:20:31.3 (J2000; uncertainty ~0.3 arcsec), which decays by ~0.3 mag from the first epoch (March 24.35 UT; 0.81 days post-burst) to the second epoch (March 25.37 UT; 1.83 days post-burst), with approximate magnitude J=18.0 at the second (later) epoch. Referenced to the time of the burst, this corresponds to a power-law decay with index alpha~-0.34. A faint source is present at the position of this variable J-band object on the red DSS plates. We are therefore uncertain whether this fading source is related to GRB040323 or is an unrelated variable star or AGN. Continued monitoring of the field is advocated.