TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3080 SUBJECT: Swift 107873: P60 Optical Observations DATE: 05/03/09 12:29:15 GMT FROM: S. Bradley Cenko at Caltech S. Bradley Cenko and Derek B. Fox report on behalf of the Caltech-NRAO-Carnegie GRB Colloboration: We have imaged the field of Swift trigger 107873 with the automated Palomar 60-inch telescope. Observations began 5 minutes after receiving the alert, and we have obtained 3 x 120 second exposures in each of the Kron R and I and Gunn z filters. A visual comparison with DSS archive images reveals no new sources in any filter to the DSS limit. Further observations are planned. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3081 SUBJECT: GRB 050309 : Lulin R-band observation DATE: 05/03/09 12:47:01 GMT FROM: Kuiyun Huang at IANCU GRB 050309 : Lulin R-band observation H.Hsieh, R.Mann (IfAUH) K.Y. Huang, W.H. Ip (NCU), Y. Urata, T. Tamagawa (RIKEN), Y. Qiu (BAO), Y.Q. Lou(THCA) on behalf of the East Asian collaboration report: We observed the SWIFT/BAT error region for GRB 050309 (trigger no. 107873) using Lulin 1-m telescope at Taiwan. We imaged a single R-band 300 sec exposure at 11.14 UT (~ 25 mins after the burst ). Compare with DSS-II image, no new object was found. The limiting magnitude is about 19 mag ( S/N=3 , with USNOB1.0 catalogue). This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3082 SUBJECT: Swift-BAT trigger 107873 (GRB050309): possible X-ray counterparts DATE: 05/03/09 23:09:32 GMT FROM: Scott Barthelmy at NASA/GSFC S. Barthelmy (GSFC), D.Burrows (PSU), L. Barbier (GSFC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (GSFC/UMD), J. Kennea (PSU), H. Krimm (GSFC/USRA), D. Malesani (SISSA), C. Markwardt (GSFC/UMD), A. Moretti (INAF-OAB), K. Page (U. Leicester), D. Palmer (LANL), A. Parsons (GSFC), P. Romano (INAF-OAB), T. Sakamoto (GSFC), G. Sato (ISAS), M. Suzuki (Saitama), J. Tueller (GSFC) on behalf of the Swift-BAT/-XRT teams: Further analysis of Swift data on BAT trigger #107873 has led to an ambiguous situation regarding the reality of this marginal BAT trigger. The Swift-BAT triggered (#107873) at 10:43:21 UT. The trigger occurred on the rising edge of the SAA. Ground analysis has confirmed the very low image-domain detection significance of this trigger. A visual inspection of the mask-tagged light curve also shows very marginal emission. As a result, a retraction GCN Notice was issued earlier today. We are now ammending that Notice. The BAT position was within the Swift Earth limb constraint at the time of the burst, so Swift did not execute a prompt automated slew. The spacecraft executed a delayed slew to the BAT location at about 11:33 UT and XRT observations began at 11:35:54 UT. Two orbits of data were collected by the XRT, for a total of 4157s of exposure. Preliminary analysis indicates that there are four X-ray sources in the XRT field of view, two of which fall inside the BAT error circle. These are: Source #1: RA(J2000) = 12 10 29.1, Dec(J2000) = +77 37 04.8. This is a very weak source (about 0.006 cps). It appears to be roughly constant in intensity, but the source is so faint that we cannot determine with confidence whether or not it is varying in flux. Source #2: RA(J2000) = 12 09 37.2, Dec(J2000) = +77 35 56.5. This source is brighter (about 0.01 cps) and may be fading. Again, we cannot be certain with the data currently in hand. The other two sources are a bright star and a very faint object well outside the BAT error circle. The estimated uncertainty in the XRT positions is 6 arcseconds radius. A 20 ks Target of Opportunity observation has been initiated to provide a second set of data beginning at about 19:45 UT. This should help us determine the likelihood that either XRT source is related to the BAT trigger. In light of these XRT observations, the BAT team cannot rule out the possibility that this trigger represents a threshold-level GRB. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3083 SUBJECT: GRB050309: Early optical limit from P60 DATE: 05/03/10 06:49:44 GMT FROM: Derek Fox at CIT Derek B. Fox and S. Bradley Cenko report on behalf of the Caltech-NRAO-Carnegie GRB collaboration: "Examination of a coadded R-band image from our P60 observations for the BAT localization region of GRB050309 (Barthelmy et al, GCN 3082), taken at a mean epoch of 10:55 UT (12 minutes after the burst), confirms our earlier report (Cenko & Fox, GCN 3080) of the absence of new optical sources to the limit of the Digitized Sky Survey and our own observations. We estimate this limit to be R < 20.5 mag as calibrated against the USNO B-1.0 catalog magnitudes of bright stars in the region. This limit applies to XRT source #2 (GCN 3082), where no emission is seen. The position of XRT source #1 is 6-arcsec (twice the FWHM in our images) from a bright star and USNO B-1.0 catalog object having R=12.98 mag. No extension of the catalog star is apparent in our images." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3085 SUBJECT: GRB 050309, Early optical limits from RAPTOR DATE: 05/03/11 00:57:16 GMT FROM: Przemyslaw R. Wozniak at LANL P.R. Wozniak, S. Evans, W.T. Vestrand, R. White, J. Wren (LANL) on behalf of the RAPTOR team. The RAPTOR A telescope responded to Swift-BAT trigger 107873 and began optical imaging of the burst location in 6.7 seconds from the time of receiving the alert (2.3 min. after GRB time). Photometry at the locations of the two X-ray candidate counterparts to GRB 050309 reported by Barthelmy et al. (GCN 3082) shows no optical emission in a series of 10 second exposures, each with the limiting magnitude R=15.0. A stack of the first 10 images with the mean time of observation 4.2 min. after the GRB time had a magnitude limit of R=16.1. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3087 SUBJECT: Swift-BAT trigger 107873: No Swift XRT counterpart DATE: 05/03/11 18:34:58 GMT FROM: David Burrows at PSU/Swift D. Malesani, A. Moretti, P. Romano, G. Tagliaferri, S. Campana, G. Chincarini (INAF-OAB), V. La Parola, T. Mineo (INAF-IASF/Palermo), A. P. Beardmore, O. Godet (U. Leicester), M. Capalbi, M. Perri (ASDC), J. A. Kennea, D. Grupe, D. N. Burrows (PSU), S. Barthelmy, L. Barbier, N. Gehrels (GSFC), J. Cummings (GSFC/NRC) report on behalf of the Swift XRT and BAT teams: The Swift X-ray Telescope (XRT) re-observed the field of BAT trigger 107873 (also referred to as GRB050309; Barthelmy et al., GCN 3082), starting on 2005 Mar 9 at 19:46:51 UT. Observations ended on 2005 Mar 10 at 9:10:40 UT, with a net exposure time of 15.7 ks distributed over 9 orbits. (The first observation, reported in GCN 3082, was for 4ks). We report here the analysis of the second epoch data for the two possible X-ray sources discussed in GCN 3082 (Barthelmy et al.). Source #1 is confirmed to be a real object, and its flux increased since our previous observation by a factor of ~2. Its refined coordinates are: RA(J2000) = 12:10:31.1, Dec(J2000) = +77:37:04.4. This object coincides to within 1.4 arcsec with a USNO star with R~13.5, B~15.4. Its X-ray spectrum is very soft, well described by a power law with photon index Gamma = 3.2 +- 0.3. The properties of this object are consistent with those of a Galactic coronal source. With the additional data, it is now apparent that source #2 is an instrumental artifact. Therefore, given the absence of any X-ray counterpart, and the low significance of the BAT detection, we conclude that this BAT trigger is unlikely to be a real GRB event. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3090 SUBJECT: GRB050309: CONCAM pre-trigger and trigger coincident optical DATE: 05/03/12 20:21:38 GMT FROM: Robert Nemiroff at Michigan Tech. V. Tilvi, L. Shamir, W. Pereira, D. Cordell, V. Muzzin, M. Merlo & R. Nemiroff (Michigan Tech) report on behalf of the greater Night Sky Live Collaboration The NightSkyLive.net CONCAM2 operating on Mauna Kea has recorded fisheye images including the location of GRB050309, being sensitive to the GRB location starting about 28 minutes before Swift trigger. No bright optical transient was found consistent with the GRB location on any frame. A 170-second exposure including the GRB region was in progress during the trigger time and prompt optical emission can be limited as being more faint than unfiltered optical CCD magnitude 3.8. The MK CONCAM image at the time of trigger is here: http://nightskylive.net/mk/mk050309/mk050309ut104239a.jpg A table of observation times and approximate limiting magnitudes follows: Date From (UT) To (UT) m_limit Remarks 2005-03-09 10:15:03 10:17:53 2.5 28 minutes before trigger 2005-03-09 10:19:00 10:21:50 2.8 Before trigger 2005-03-09 10:22:56 10:24:46 3.0 Before trigger 2005-03-09 10:26:53 10:28:43 3.1 Before trigger 2005-03-09 10:30:47 10:32:37 3.2 Before trigger 2005-03-09 10:38:41 10:40:31 3.5 Before trigger 2005-03-09 10:42:39 10:44:29 3.8 During! Swift trigger: 10:43:21 UT 2005-03-09 10:46:34 10:48:24 4.0 After trigger 2005-03-09 10:50:32 10:52:22 4.0 After trigger 2005-03-09 10:54:29 10:56:19 4.0 After trigger