//////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2701 SUBJECT: GRB040912 (= H3557): A Long GRB or XRF Localized by HETE DATE: 04/09/12 23:14:09 GMT FROM: George Ricker at MIT GRB040912 (= H3557): A Long GRB or XRF Localized by HETE N. Butler, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley, on behalf of the HETE Science Team; T. Donaghy, E. Fenimore, M. Galassi, C. Graziani, M. Matsuoka, Y. Nakagawa, T. Sakamoto, R. Sato, Y. Shirasaki, M. Suzuki, T. Tamagawa, Y. Urata, T. Yamazaki, Y. Yamamoto, and A. Yoshida, on behalf of the HETE WXM Team; G. Crew, J. Doty, A. Dullighan, G. Prigozhin, R. Vanderspek, J. Villasenor, J. G. Jernigan, A. Levine, G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and HETE Optical-SXC Teams; C. Barraud, M. Boer, J-F Olive, J-P Dezalay, and K. Hurley, on behalf of the HETE FREGATE Team; report: At 14:12:17 UT (13260 SOD) on 12 September 2004, the Fregate and WXM instruments on HETE detected GRB040912 (= H3557), an unusual, long X-ray rich GRB or XRF. The burst has been localized to a circle of 7' radius centered on RA = 23h 56m 54s, Dec = -1d 00' 02" (J2000) The burst duration is ~20 seconds in the 7-30 keV band, but the 2-10 keV emission extends for ~150s. Preliminary analyses of the first 40 seconds of burst data show the burst to have Epeak of 58 keV, a 2-30 keV fluence of 7e-7 erg/cms and a 30-400 keV fluence of 4e-7 erg/cm2. While this analysis shows the burst to be an X-ray rich GRB, we expect the ratio of 2-30/30-400 keV fluence to increase once the analysis of the entire burst is complete, at which time H3557 may be re-classified as an XRF. We anticipate providing additional spectral information from this unusual event in a subsequent GCN Circular. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2703 SUBJECT: Optical observations of field of GRB040912 DATE: 04/09/13 00:40:23 GMT FROM: AAVSO GRB Network at AAVSO B. Monard (Bronberg Obs.) reports on behalf of the AAVSO International GRB network: Observations of the HETE error circle for GRB040912 (Butler et al., GCN 2701; HETE trigger 3557) were made with the Bronberg 0.30m telescope + unfiltered CCD. Fifty-five 28-second exposures with UT midpoint of 040912.813 (5.3hrs after the burst) were stacked, with a limiting magnitude of 20.2CR (based on USNO-A red magnitudes). The field was centered at the revised ground analysis coordinates, with a field of view of 20arcmin(E/W) x 13arcmin(N/S), covering all but the extreme north and south limits of the error circle. No new object is seen down to approximately CR=19.5 when comparing against a DSS2-red image. The AAVSO International GRB network is greatful for a generous grant from the Curry Foundation and to NASA for the financial support for the High Energy Workshops for Amateur Astronomers. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2705 SUBJECT: GRB040912 : Kiso Optical follow-up observation DATE: 04/09/13 07:52:51 GMT FROM: Yuji Urata at RIKEN K. Ogura(Kokugakuin Univ.), S. Nishiura (Tokyo Gakugei Univ.) M. Isogai(Tokyo Univ.) and Y. Urata(RIKEN) report: " We have imaged the entire HETE-2 error circle (Butler et al., GCN 2701) using Kiso 1.05 m Schmidt telescope with 2kx2k CCD camera starting at 2004 Sep 12.668 UTC. We obtained 3 x 300 sec R-band images. Each R-band image gives limiting magnitude of R~20 mag. using R magnitudes of near USNO_A2.0 stars as photometric references. We found a source around "23:57:10 -00:56:42" (R~19.4 mag.) which is not in DSS II images. But, comparing our second image with our third one, it seem to move about 4 arcsec in 5 minute. It may be minor planet. Because of our network trouble we cannot access "MINOR PLANET CHECKER" page now." This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2707 SUBJECT: Optical observations of GRB/XRF 040912 = HETE 3557 DATE: 04/09/13 14:35:54 GMT FROM: Jens Hjorth at U.Copenhagen M. I. Andersen (AIP), M. Weidinger (U. Aarhus), J. Hjorth, J. P. U. Fynbo, B. L. Jensen (U. Copenhagen) report: "Using the ALFOSC at the 2.56-m Nordic Optical Telescope, La Palma, we have obtained 2 x 2 mosaic CCD images covering the HETE-2 error circle of GRB/XRF 040912 (Butler et al., GCNC 2701) on two epochs. Each pointing consists of 3 x 300 sec in the R band. Comparison of the two epochs (Sep 12.92-12.97 and Sep 13.19-13.24 2004 UT) through visual inspection and difference imaging does not reveal any sources exhibiting significant variability between the two epochs. The 3-sigma variability limit is R ~ 23.4." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2708 SUBJECT: GRB 040912, BVRI observations DATE: 04/09/13 14:52:02 GMT FROM: Sylvio Klose at TLS Tautenburg S. Klose, U. Laux, Thueringer Landessternwarte Tautenburg, J. Greiner, MPE Garching, report: The error circle of GRB 040912 (HETE trigger 3557; Butler et al., GCN 2701) was imaged in BVRI with the Tautenburg Schmidt telescope equipped with the prime focus CCD camera (field of view ~40'x 40'). Observations started Sep 12, 19:34 UT, about 5 hours after the burst, and lasted for altogether 6 hours. During the observing run the sky conditions were good. Based on the USNO SA2.0 catalogue (Monet et al. 1996), we estimate a limiting magnitude of R = 22.5 for the combined R-band image. The combined I-band image goes about 2 mag deeper than the DSS2 infrared image, while the combined B-band image is about 1 mag less deep than the DSS1. In addition to the reported non-detections in the R-band (Pimbblet & Price, GCN 2702; Monard, GCN 2703; Ogura et al., GCN 2705; Andersen et al., GCN 2707) we can state that there is no I-band candidate down to the DSS2 infrared plate limit. There is also no evidence for any point source in R and I potentially superimposed one of the two brightest galaxies in the field. There is no potential afterglow candidate in the B-band. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2709 SUBJECT: GRB/XRF040912,optical observations DATE: 04/09/14 10:54:44 GMT FROM: Shouta Maeno at U.of Miyazaki S.maeno,E.Sonoda,Y.Matsuo, M.Yamauchi (University of Miyazaki) We have observed the HETE-2 error circle of GRB/XRF040912(HETE trigger 3557)with the unfiltered CCD camera on the 30-cm telescope at University of Miyazaki. Observed field of view is 43 arcmin centerd on (23h 57m 04s -00d 59' 12" ). After co-adding a set of 8 images of 30 sec exposures, we have compared our images with the USNO A2.0 catalog. Preliminary analysis shows there is no new source brighter than 16.0mag. in our observed field at Sep 13, 12:09:30 UT. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2710 SUBJECT: GRB 040912: Optical Observations DATE: 04/09/15 04:36:26 GMT FROM: James Rhoads at STScI Armin Rest (CTIO), James Rhoads (STScI), and Peter Weilbacher (Durham) report on behalf of a larger collaboration: We have observed the field of GRB 040912 using the 4m Blanco telescope and CCD Mosaic-2 camera at CTIO. We obtained two epochs during the first night following the burst, at UT September 13.033 and 13.205. Each epoch consisted of four R band exposures of 300 seconds, for a total of 20 minutes' integration per epoch. Conditions were photometric but seeing was mediocre, at 1.35" in the first epoch and 1.01" in the second epoch. Preliminary image subtraction analysis reveals no compelling afterglow candidates. Our search is sensitive to a change in flux density of 1.9 microJansky, which corresponds to the complete disappearance of an object with magnitude R=23.0 //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2711 SUBJECT: GRB040912 (= H3557): Chandra Observations Scheduled DATE: 04/09/15 18:35:44 GMT FROM: George Ricker at MIT GRB040912 (= H3557): Chandra Observations Scheduled G. Ricker, P. Ford, N. Butler, R. Vanderspek (MIT), and D. Lamb (U. Chicago), on behalf of a Chandra GRB ToO Team, write: Chandra target-of-opportunity observations of the entire HETE WXM error circle for GRB040912 (= H3557: Butler et al, GCN 2701) have been approved and scheduled, subject to possible high background radiation constraints. The first epoch observation will commence near 22h UT on 15 September, with a second epoch observation ~1 week later. As noted by Butler et al (GCN 2701), although GRB040912 exhibits the spectral characteristics of an XRF, its temporal characteristics are quite unusual. The scheduling of contemporaneous observations at other wavelengths, especially deep initial and second epoch optical and IR observations, is strongly encouraged. We are grateful to Harvey Tananbaum and Andrea Prestwich for approving this DDT observation. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2716 SUBJECT: GRB040912(=H3557): Observations with the Chandra X-ray Observatory DATE: 04/09/16 18:21:46 GMT FROM: Roland Vanderspek at MIT GRB040912(=H3557): Observations with the Chandra X-ray Observatory N. Butler, P. Ford, G. Ricker, R. Vanderspek, J. Villasenor, P. Csatorday (MIT); D. Lamb (U. Chicago); and J.G. Jernigan (UCB), on behalf of a Chandra GRB ToO Team, write: On 15 September 2004, the Chandra Observatory targeted the field of GRB040912, an X-ray flash localized by the HETE satellite (=H3557; Butler et al, GCN 2701). The 20 ksec observation spanned the interval 21:57 UT on 15 September to 3:48 UT on 16 September, 3.32 - 3.57 days after the burst. The WXM error circle from Butler et al. was completely contained within the field-of-view of the Chandra ACIS-I array. Within the WXM error region, we detect 22 sources with more than 6 source counts in the 0.5-8 keV band: # Chandra Name RA DEC Cts HR 1 CXOU J235631.0-005946 23 56 30.96 -0 59 46.1 55 -0.5 2 CXOU J235700.0-010009 23 56 59.96 -1 0 9.7 40 -0.3 3 CXOU J235712.2-005942 23 57 12.17 -0 59 42.1 33 -0.3 4 CXOU J235642.9-005520 23 56 42.91 -0 55 20.4 32 -0.7 5 CXOU J235645.7-005655 23 56 46.71 -0 56 54.9 32 -0.3 6 CXOU J235707.6-005713 23 57 7.57 -0 57 12.6 31 0.8 7 CXOU J235716.4-010109 23 57 16.37 -1 1 8.7 27 -0.2 8 CXOU J235639.1-005556 23 56 39.10 -0 55 55.8 20 0.9 9 CXOU J235651.2-005513 23 56 51.17 -0 55 12.5 17 -0.3 10 CXOU J235636.7-005431 23 56 36.74 -0 54 31.2 15 -0.6 11 CXOU J235711.1-005637 23 57 11.12 -0 56 37.1 12 -0.2 12 CXOU J235637.3-010160 23 56 37.26 -1 1 59.9 12 -0.6 13 CXOU J235656.4-005839 23 56 56.42 -0 58 39.2 11 -0.1 14 CXOU J235700.1-005713 23 57 0.09 -0 57 12.6 11 -1.0 15 CXOU J235659.8-005903 23 56 59.83 -0 59 2.8 10 -0.6 16 CXOU J235649.1-010344 23 56 49.07 -1 3 44.2 9 0.4 17 CXOU J235700.4-010018 23 57 0.36 -1 0 17.6 9 -0.7 18 CXOU J235646.4_005621 23 56 46.45 -0 56 21.4 8 1.1 19 CXOU J235647.0-010045 23 56 46.97 -1 0 45.1 8 0.0 20 CXOU J235648.8-010319 23 56 48.81 -1 3 18.6 8 -1.0 21 CXOU J235704.0-005859 23 57 4.03 -0 58 58.8 8 -0.2 22 CXOU J235707.2-010420 23 57 7.18 -1 4 19.6 7 0.4 We estimate a position uncertainty of 1.0" for the Chandra sources. Astrometry was performed using five stars from the USNO-A2 catalog. The column labeled HR in the table above refers to the hardness ratio ( Cts_2-8keV - Cts_0.5-2keV )/ Cts_0.5-8 keV. This quantity is typically in the range -0.5 to -0.1 for GRBs at high Galactic latitude and attenuated by the Galactic absorption only. An image of the Chandra data, with the detected sources overlaid, can be found at http://space.mit.edu/HETE/Bursts/GRB040912. We gratefully acknowledge the timely assistance of the observatory staff at the Chandra Science Center in arranging for the acquisition and preliminary processing of these data. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2720 SUBJECT: XRF040912, BVRcIc field calibration DATE: 04/09/17 17:09:35 GMT FROM: Arne A. Henden at USNO/USRA A. Henden (USRA/USNO) reports on behalf of the USNO GRB team: We have acquired BVRcIc all-sky photometry for a 11x11 arcmin field centered on the HETE coordinates for GRB/XRF040912 (trigger 3557; Butler et al. GCN 2701) with the USNOFS 1.0-m telescope on one photometric night. Stars brighter than V=13.5 are saturated and should be used with care. We have placed the photometric data on our anonymous ftp site: ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/xrf040912.dat The astrometry in this file is based on linear plate solutions with respect to UCAC2. The external errors are less than 100mas. The estimated external photometric error is about 0.03mag and will be improved with additional calibration nights if an afterglow is discovered. As always, you should check the dates on the .dat file prior to final publication to get the latest photometry. There is a README file on the ftp directory to give you information about the procedures used to calibrate these fields. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2723 SUBJECT: XRF 040912 (=H3557): Spectral and Temporal Properties DATE: 04/09/17 20:17:03 GMT FROM: Don Lamb at U.Chicago XRF 040912 (=H3557): Spectral and Temporal Properties J-F Olive, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley, on behalf of the HETE Science Team; T. Donaghy, E. Fenimore, M. Galassi, C. Graziani, M. Matsuoka, Y. Nakagawa, T. Sakamoto, R. Sato, Y. Shirasaki, M. Suzuki, T. Tamagawa, Y. Urata, T. Yamazaki, Y. Yamamoto, and A. Yoshida, on behalf of the HETE WXM Team; N. Butler, G. Crew, J. Doty, A. Dullighan, G. Prigozhin, R. Vanderspek, J. Villasenor, J. G. Jernigan, A. Levine, G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and HETE Optical-SXC Teams; C. Barraud, M. Boer, J-P Dezalay, and K. Hurley, on behalf of the HETE FREGATE Team; report: The burst-average photon number spectrum of GRB 040912 is best fit by a power-law times exponential (PLE) model with a photon index alpha = 1.75 +0.28/-0.30 and a peak energy E_peak = 14.5 +/-14.5 keV. The fluence of the burst is (8.3 +1.4/-1.3 ) x 10-7 erg cm-2 in the 2-30 keV energy band and (3.3 +2.9/-1.7) x 10-7 erg cm-2 in the 30-400 keV energy band. The ratio of the fluences in the two energy bands is 2.5, clearly making this burst an X-Ray Flash. The T50 and T90 durations of XRF 040912 are 80 +/-5 sec and 127 +/-13 sec in the 6-40 keV energy band, and 81 +/-5 sec and 122 +/-7 sec in the 6-80 keV energy band, respectively. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2724 SUBJECT: XRF 040912, identification of CXO sources DATE: 04/09/17 21:55:13 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia J. Gorosabel (IAC-CSIC Granada), J. Cepa (IAC Tenerife), A. de Ugarte Postigo (IAA-CSIC), D. Martínez-Delgado (MPIfA Heidelberg), V. Casanova, S. Guziy, M. Jelínek (IAA-CSIC, Granada), J. M. Castro Cerón (San Fernando), H. Castaneda (IAC Tenerife), D. Zucker, E. F. Bell (AIP Potsdam) and A. J. Castro-Tirado (IAA-CSIC) report: "We have acquired optical images covering the entire error box of the XRF 040912 detected by HETE-2 (Ricker et al. GCN Circ. 2701) starting on 12 Sep 21:27 UT (i.e. 7.25 hr after the event). The observations were performed with the 4.2m WHT (+PFC) at La Palma (16'x 16' FOV). The observing log follows: ----------------------------------- Date 2004 UT Exp.Time (s) Filter ----------------------------------- 12 Sep 21:27:56 1455 B 12 Sep 21:53:45 900 V 13 Sep 04:26:41 900 V 13 Sep 21:07:58 1200 V 16 Sep 01:49:11 300 I 16 Sep 01:58:17 300 I 16 Sep 02:05:06 300 I 16 Sep 02:11:17 300 I 16 Sep 02:18:16 300 I 16 Sep 02:31:05 180 V 16 Sep 02:35:14 1200 V ---------------------------------- Additional images (I-band, 720-s) were also taken at the 1.5m telescope at IAA Sierra Nevada Observatory on 13 Sep (03:00 UT). Internal comparison between the three V-band frames did not reveal any optical variable source in the entire HETE-2 error box. For the 22 X-rays sources detected by the Chandra X-ray Observatory (Butler et al., GCN Circ 2716) we detect the following optical counterparts in the co-added V-band image (3 sigma limiting magnitude = 25.1): ------------------------------------- CXO V-band Distance to source magnitude X-ray position (") ------------------------------------- #1 21.6 2.0 #2 24.0 2.0 #3 21.1 2.0 #4 24.0 2.0 #5 21.9 1.4 #6 21.0 1.7 #7 22.9 1.7 #8 23.9 1.4 #9 23.9 1.8 #10 21.1 1.6 #11 23.0 1.4 #12 24.2 1.9 #13 23.6 0.5 #14* 23.9 0.9 22.7 1.8 #15 23.9 2.1 #16** >25.1 - #17 24.5 2.0 #18 23.3 0.1 #19 >25.1 - #20 >25.1 - #21 >25.1 - #22 >25.1 - -------------------------------------- * Two possible counterparts * V = 22.1 optical source at 3".5 -------------------------------------- Optical magnitudes are based on the calibration provided by A. Henden (GCN Circ. 2720)." This message can be quoted. [GCN OPS NOTE (21sep04): The affiliation for D. Martinez-Delgado from "AIP Potsdam" to "MPIfA Heidelberg".] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2728 SUBJECT: GRB040912(=H3557): Candidate Optical Afterglow DATE: 04/09/20 17:09:10 GMT FROM: Nat Butler at MIT/CSR GRB040912(=H3557): Candidate Optical Afterglow N. Butler, G. Ricker, R. Vanderspek, J. Villasenor, P. Csatorday, P. Schechter, S. Burles (MIT); S. Malhotra (STSCI), and D. Osip (LCO), on behalf of a larger collaboration report: We observed the HETE WXM error region from Butler et al. (GCN 2701) in two epochs with the 27'x27' FOV IMACS camera on the Magellan 6.5m Baade Telescope at Las Campanas Observatory. Epoch1 consisted of 3x180s exposures in R band, with a mean observing time of Sep 13.15716 UT (t_burst + 13.57 hours). Epoch2 consisted of 2x300s exposures in R band, with a mean observing time of Sep 14.20236 UT (t_burst + 38.65 hours). The 3-sigma limiting magnitudes are R=25.3 and R=25.6 for Epoch1 and Epoch2, respectively. We calibrate our astrometry and photometry against the USNO stars of Henden et al. (GCN 2720). We detect sources within 1" of the Chandra positions for 8 of the 22 Chandra sources reported in Butler et al. (GCN 2716): CX0# R-magE1 R-magE2 1 . . 2 23.95+/-0.07 24.10+/-0.07 3 . . 4 24.29+/-0.01 24.02+/-0.08 5 . . 6 . . 7 22.55+/-0.04 22.53+/-0.04 8 . . 9 . 24.4+/-0.1 10 . . 11 . . 12 25.00+/-0.13 24.67+/-0.09 13 22.25+/-0.04 23.27+/-0.05 14 . . 15 . . 16 . . 17 . . 18 22.38+/-0.04 22.31+/-0.03 19 . . 20 . . 21 25.12+/-0.14 24.56+/-0.10 22 . . Of the optical sources we detect, the source corresponding to CXO#13 has declined in brightness the most (by 1.02 pm 0.09 mag), and we tentatively suggest this source to be the optical afterglow of GRB040912. The flux decay between our 2 epochs corresponds to a fade with temporal index alpha=-0.9+/-0.1. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2731 SUBJECT: GRB040912(=H3557): Chandra Candidate X-ray Afterglow DATE: 04/09/22 14:23:36 GMT FROM: Nat Butler at MIT/CSR GRB040912(=H3557): Chandra Candidate X-ray Afterglow P. Ford, N. Butler, G. Ricker, R. Vanderspek, J. Villasenor, P. Csatorday (MIT); D. Lamb (U. Chicago); and J.G. Jernigan (UCB), on behalf of a Chandra GRB ToO Team, write: On 21 September 2004, the Chandra Observatory targeted the field of GRB040912, an X-ray flash localized by the HETE satellite (=H3557; Butler et al., GCN 2701; Olive et al., GCN 2723). This was a 20 ksec followup observation to the observation beginning on 15 September reported by Butler et al. (GCN 2716). It spanned the interval 10:56 UT to to 17:01 UT on September 21, 8.86-9.12 days after the burst. The WXM error circle from Butler et al. (GCN 2701) was completely contained within the field-of-view of the Chandra ACIS-I array. At the location of the 22 X-ray sources reported in our Epoch 1 (E1) observation (GCN 2716), we find: # Chandra Name Cts_E2 Null_Prob 1 CXOU J235631.0-005946 55 53 0.421 2 CXOU J235700.0-010009 35 40 0.703 3 CXOU J235712.2-005942 39 37 0.404 4 CXOU J235642.9-005520 36 15 0.003 5 CXOU J235645.7-005655 30 20 0.068 6 CXOU J235707.6-005713 30 21 0.108 7 CXOU J235716.4-010109 33 41 0.791 8 CXOU J235639.1-005556 19 30 0.921 9 CXOU J235651.2-005513 15 13 0.359 10 CXOU J235636.7-005431 18 27 0.874 11 CXOU J235711.1-005637 15 8 0.090 12 CXOU J235637.3-010160 7 9 0.675 13 CXOU J235656.4-005839 10 8 0.325 14 CXOU J235700.1-005713 13 19 0.848 15 CXOU J235659.8-005903 12 9 0.259 16 CXOU J235649.1-010344 10 3 0.047 17 CXOU J235700.4-010018 16 7 0.042 18 CXOU J235646.4_005621 3 3 0.386 19 CXOU J235647.0-010045 16 7 0.042 20 CXOU J235648.8-010319 10 7 0.297 21 CXOU J235704.0-005859 3 1 0.213 22 CXOU J235707.2-010420 12 3 0.032 In this table, "" refers to the number of counts detected in E1, scaled to the exposure in E2. The number of counts detected in E2 for each source is reported in the column labeled "Cts_E2," and the probability that the source remained constant given the E1 and E2 detected count rates is presented under "Null_Prob." We note that source #13 has not faded between our two epochs, and this strongly dis-favors the candidate OT of Butler et al. (GCN 2728). Several sources appear to have faded at or beyond the 2-sigma significance level (#'s 4,17,19,and 22). However, given the 22 trials conducted to find the candidate X-ray afterglow, only source #4 exhibits a statistically significant decline in brightness (3-sigma single trial, ~2-sigma in 22 trials). The decrease in count rate from source #4 between E1 and E2 implies a temporal decay index of alpha=-0.9+/-0.3. We determine a refined position for this source of: RA= 23h 56m 42.96s, Dec= -0d 55' 19.8" (J2000), with an uncertainty of 1". A faint (R~24) optical source, spatially coincident with this position, was reported by Butler et al. (GCN 2728). However, this source did not appear to decrease in flux between t_burst + 13.57 hours and t_burst + 38.65 hours. We gratefully acknowledge the timely assistance of the observatory staff at the Chandra Science Center in arranging for the acquisition and preliminary processing of these data. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2733 SUBJECT: XRF 040912: Radio Observations DATE: 04/09/23 15:59:42 GMT FROM: Alicia Soderberg at Caltech A. M. Soderberg (Caltech) and D. A. Frail (NRAO) report on behalf of a larger collaboration: "On 2004 Sept. 23.24 UT we carried out follow-up observations with the VLA at 8.46 GHz toward two positions centered on the X-ray afterglow candidates (GCN 2716; GCN 2731) of XRF 040912 (GCN 2723). Within a circle of 1-arcsec radius there are no radio sources toward either X-ray candidate to a 3-sigma limit of 120 microJy. No further observations are planned." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2797 SUBJECT: Search for SN light in XRF 040912 with MEGACAM DATE: 04/10/12 15:18:08 GMT FROM: Jean-Luc Atteia at Lab d Astrophys.,OMP,Toulouse 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: We 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. Two 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). We looked for a possible SN emission for the 22 X-ray sources detected with Chandra (Butler et al., GCN Circ=2716). The observation results follow: First exposure (T) Second exposure (T+15min) ------ --------------------------- -------------------------- CXO Distance to i-band Distance to i-band source X-ray position mag X-ray position mag (") (") ------ --------------------------- -------------------------- #1 * 1.5 20.60 - - #2 1.6 22.25 1.5 22.26 #3 1.4 20.17 1.5 20.20 #4 - - - - #5 1.4 21.21 1.5 21.00 #6 1.5 18.96 1.3 18.99 #7 1.0 21.82 1.1 21.61 #8 1.8 23.02 1.3 23.09 #9 - - - - #10 3.2 20.74 2.1 20.66 #11 1.0 21.68 0.9 22.44 #12 - - - - #13 * - - 0.5 22.21 #14 1.2 21.84 1.6 21.39 #15 1.6 22.79 - - #16 - - - - #17 - - - - #18 0.7 21.35 0.6 20.86 #19 - - - - #20 - - - - #21 - - - - #22 - - - - -------------------------------------------------------------------- * Source was at the CCD line separation and was missed in one image -------------------------------------------------------------------- We did not consider sources at distances greater than 2.5" from the X-ray source position. Our conclusions from these observations are: 1- 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. 2- 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. We 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. This 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). Further observations of source #6 are welcome. A comparison of the two CFHT images that show the nearest objects to the Chandra sources detected in the i' band, can be found at http://www.cfht.hawaii.edu/~grb/XRF040912.html [GCN OPS (12oct04): Carridge returns provided.]