//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6137 SUBJECT: GRB 070224: Swift detection of a burst DATE: 07/02/24 20:48:09 GMT FROM: Scott Barthelmy at NASA/GSFC J. L. Racusin (PSU), L. M. Barbier (NASA/GSFC), S. D. Barthelmy (GSFC), M. M. Chester (PSU), G. Cusumano (INAF-IASFPA), D. Grupe (PSU), J. A. Kennea (PSU), D. M. Palmer (LANL), R. L. C. Starling (U Leicester) and L. Vetere (PSU) report on behalf of the Swift Team: At 20:27:58 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 070224 (trigger=261880). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 178.990, -13.340 which is RA(J2000) = 11h 55m 58s Dec(J2000) = -13d 20' 23" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single peak with a duration of about 25 sec. The peak count rate was ~500 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 20:30:21 UT, 143 seconds after the BAT trigger. XRT found a bright, fading, uncatalogued X-ray source located at RA, Dec 179.0257, -13.3294 which is RA(J2000) = 11h 56m 06.2s Dec(J2000) = -13d 19' 46.0" with an uncertainty of 4.2 arcseconds (radius, 90% containment). This location is 131 arcseconds from the BAT on-board position, within the BAT error circle. The initial flux in the 2.5s image was 3.1e-10 erg/cm2/s (0.2-10 keV). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 153 seconds after the BAT trigger, and a finding chart of nominal 400 seconds with the V filter starting 259 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The 3-sigma upper limit in White at the XRT position is 19.3 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. No correction has been made for the expected extinction corresponding to E(B-V) of 0.06. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6138 SUBJECT: GRB 070224: MASTER observations DATE: 07/02/24 21:03:48 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, D.Kuvshinov, N.Tyurina, A.Belinski, E.Gorbovskoy, A.Krylov,N.Shatskiy ,G.Borisov, A.Sankovich, G.Antipov, V.Vladimirov P.Gritsyk Sternberg Astronomical Institute, Moscow Union 'Optic' MASTER robotic system (http://observ.pereplet.ru) responded to GRB070224.9 (GRB_TIME is 2007-02-24 20:27:58.21). The first image was at 2007-02-24 20:30:04 UT, 51s after notice arrivel time and 00:02:05.79 after the GRB time The unfiltered image is calibrated relative to USNO A2.0 (0.8 R + 0.2 B). The robot not find OT-candidate in error box brighter then 16.2 (s/n=10). The JPG-image will be available at http://observ.pereplet.ru/images/GRB070224.9/img/i12.jpg The reduction is continuing. This message can be cited. Mailto: lipunov@sai.msu.ru //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6139 SUBJECT: GRB 070224: MASTER-VWF-Kislovodsk observations DATE: 07/02/24 21:43:27 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, N.Shatskiy, E.Gorbovskoy, A.Belinski, D.Kuvshinov, N.Tyurina, P.Gritsyk Sternberg Astronomical Institute, Moscow Union 'Optic' A. Tlatov, I.Golubov Kislovodsk Solar Station of the Pulkovo observatory MASTER Very Wide Field Camera located at Kislovodsk Solar Station (http://observ.pereplet.ru, D=70 mm, 420 square degrees, 11 Mpixel's CCD) has moved to the Swift-BAT trigger 261880 and it has taken a series of 5s exposures starting 2 s after notice arrivel time at 20:29:38.285 UT under good weather condition and waxing moon. We note that the GBR position (J. L. Racusin et al. GCN Circ No. 6137) was at 4 degrees outside of the our field of view. We note that the VWF camera continuously takes frames during the night. These unfiltered images are calibrated relative to USNO A2.0 (R). There is no OT was found inside Swift error box. T-Tgrb Mean Time Limit Coadd? 29s 29.5s 11.0 no 29s 59 s 12.0 12 The message can be cited. mailto: lipunov@sai.msu.ru //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6140 SUBJECT: GRB 070224: MASTER-Net refind analysis DATE: 07/02/24 22:53:17 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, D.Kuvshinov, A.Belinski, E.Gorbovskoy, A.Krylov, N.Shatskiy, N.Tyurina,G.Borisov, A.Sankovich, V.Vladimirov, V.Vibornov, A.Kuznetsov Sternberg Astronomical Institute, Moscow Union 'Optic' A. Tlatov, I.Golubov Kislovodsk Solar Station of the Pulkovo observatory MASTER Very Wide Field Camera located at Kislovodsk Solar Station (http://observ.pereplet.ru, D=70 mm, 420 square degrees, 11 Mpixel's CCD) has moved to the Swift-BAT trigger 261880 and it has taken a series of 5s exposures starting 2 s after notice arrivel time at 20:29:38.285 UT under good weather condition and waxing moon. We note that the GBR position (J. L. Racusin et al. GCN Circ No. 6137) was at 4 degrees outside of the our field of view. We note that the VWF camera continuously takes frames during the night. These unfiltered images are calibrated relative to USNO A2.0 (R). The robot not find OT-candidate. T-Tgrb Mean Time Limit Coadd? Exp 100s 100.5s 11.0 no 5s 100s 130 s 12.0 yes 12x5s 100s 222 s 13.3 yes 47x5s MASTER robotic system (D=355mm, http://observ.pereplet.ru, Moscow) responded to GRB070224 (GRB_TIME is 2007-02-24 20:27:58.21). The first image was at 2007-02-24 20:30:04 UT, 51s after notice arrivel time and 00:02:05.79 after the GRB time at large zenit distance. The unfiltered image is calibrated relative to USNO A2.0 (0.8 R + 0.2 B). The robot not find OT-candidate. T-Tgrb Mean Time Limit Coadd? Exp 125s 140s 16.2 no 30s 125s 924s 18.0 yes 31x30s This message can be cited. Mailto: lipunov@sai.msu.ru //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6141 SUBJECT: GRB 070224, Swift-BAT refined analysis DATE: 07/02/25 00:34:25 GMT FROM: Scott Barthelmy at NASA/GSFC J. Tueller (GSFC), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), J. L. Racusin (PSU), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU) on behalf of the Swift-BAT team: Using the data set from T-239 to T+482 sec from the recent telemetry downlink, we report further analysis of BAT GRB 070224 (trigger #261880) (Racusin, et al., GCN Circ. 6137). The BAT ground-calculated position is RA, Dec = 178.987, -13.356 deg which is RA(J2000) = 11h 55m 57.0s Dec(J2000) = -13d 21' 20.1" with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted lightcurve shows two overlapping peaks starting at ~T-20 sec and decaying back to background at ~T+50 sec. T90 (15-350 keV) is 34 +- 1 sec (estimated error including systematics). The time-averaged spectrum from T-13.8 to T+24.3 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.42 +- 0.30. The fluence in the 15-150 keV band is 3.1 +- 0.5 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-13.76 sec in the 15-150 keV band is 0.3 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6142 SUBJECT: GRB 070224: optical afterglow candidate DATE: 07/02/25 05:02:38 GMT FROM: Christina Thoene at Niels Bohr Institute,DARK Cosmo Ctr Christina C. Thoene (DARK), D. Alexander Kann (TLS Tautenburg) and Thomas Augusteijn (NOT) report: We observed the field of GRB 070224 (GCN 6137) with NOT and StanCAM in R and I filters starting 4.35h after the burst. In 3x300s stacked images, we detect a faint object in both R and I close to the XRT error circle at RA = 11:56:06.68 Dec = -13:19:47.6 (J2000) with conservative errors of 1". This is about 5 arcseconds from the refined XRT error circle center (GCN 6143). We propose this object to be the optical afterglow of GRB 070224. At the moment, we cannot confirm if the object is fading or not. Further observations are planned. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6143 SUBJECT: GRB070224: Swift-XRT Refined Analysis DATE: 07/02/25 05:11:37 GMT FROM: Judith Racusin at PSU J. Racusin, J. Kennea, D. Morris, C. Pagani, L. Vetere (PSU) report on behalf of the Swift-XRT team: We have analysed the first 3 orbits of Swift-XRT data available for GRB 070224 (Racusin et al., GCN 6137), consisting of 45 s of Windowed Timing (WT) mode data, and ~1.7 ks of Photon Counting (PC) mode data. The refined XRT position from the PC data is RA,Dec= 179.02684, -13.3304 which is: RA(J2000) = 11h 56m 06.44s Dec(J2000) = -13d 19' 49.5" with an uncertainty of 3.8 arcsec (90% containment). This is 5.0 arcseconds from the initial position reported in GCN 6137, and 134 arcseconds from the BAT refined position (Tueller et al., GCN 6141). The preliminary 0.3-10.0 keV lightcurve shows a steep fading behavior in the first orbit with a decay index of 3.1 +/- 0.2. The data in the subsequent orbits provides only an upper limit. It is not currently possible to determine if there has been a break to a flatter decay. The WT spectrum is fit by an absorbed power-law with a photon index of 2.8 +/- 0.6. The absorption is at a level of 6.0e20 cm^-2, consistent with Galactic absorption along the line of sight (4.1e20 cm^-2). The average 0.3-10 keV unabsorbed flux of the WT spectrum is 2.1e-10 ergs cm^-2 s^-1. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6144 SUBJECT: GRB 070224: SARA upper limit DATE: 07/02/25 07:49:49 GMT FROM: Adria C. Updike at Clemson U A. C. Updike, H. A. Eid, D. H. Hartmann (Clemson University), T. H. Robertson, T. M. Jordan (Ball State University), and D. A. Kann (TLS) report on behalf of the Clemson GRB Follow-Up Team: The .9m SARA telescope began imaging the field of GRB 070224 approximately 9 hours after the Swift Trigger 261880 at 20:29:12 UT. Our observations were comprised of 180-second exposures in the R band. After stacking 2 hours worth of exposures, we do not detect any new sources down to a limiting magnitude of R ~ 21.4 +/- 0.4 mag (based on calibration to 10 field sources from USNO B1.0 R2 band). The Clemson University GRB Response Site may be found at: http://people.clemson.edu/~kgarime/burst/index.php The SARA Homepage can be found at: http://saraobservatory.org This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6145 SUBJECT: GRB070224: Gemini Imaging Observations DATE: 07/02/25 07:55:51 GMT FROM: Hsiao-Wen Chen at U Chicago H.-W. Chen (U Chicago), K. Glazebrook (Swinburne University), and J. S. Bloom (UC Berkeley) report on behalf of a larger collaboration: "We obtained 2x900 sec dithered exposures of the field around GRB070224 (Racusin et al., GCN 6137), using GMOS and an i' filter on the Gemini south telescope. The observations started at Feb 25.102 UT, ~ 6 hours after the initial Swift trigger. We continued the observations with 2x900 sec dithered exposures in the z'-band, starting at Feb 25.125 UT. Within the refined XRT position (Racusin et al., GCN 6143), we detect a compact source at RA(J2000)=11:56:06.6 and Dec(J2000)=-13:19:48.9 (+/- 350 mas relative to USNO B1.0) that shows no apparent changes in the brightness between two exposures of 15 min apart. We note the presence of extremely faint (~2 sigma) source at RA(J2000)=11:56:06.5 and Dec(J2000)=-13:19:49.9 in the first i'-band exposure. Further analysis is underway." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6146 SUBJECT: GRB 070224: MDM Observations DATE: 07/02/25 08:03:48 GMT FROM: Nestor Mirabal at Columbia U N. Mirabal, K. Stanonik, N. Zimmerman, S. Alayyoubi, & J. P. Halpern (Columbia U.) report on behalf of the MDM Observatory GRB follow-up team: "We observed the field of GRB 070224 (Racusin et al., GCNs 6137, 6143) in I-band with the MDM 1.3m telescope. The object reported by Thoene et al. (GCN 6142) is present in our images, with a preliminary magnitude I~22.1 +/- 0.2 on Feb. 25.287." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6147 SUBJECT: GRB 070224: WHT K-band imaging DATE: 07/02/25 11:08:53 GMT FROM: Nial Tanvir at IofA U.Cambridge E. Rol, N.R. Tanvir, R. Starling (U. Leicester) and P. Groot (U. Nijmegen) report on behalf of a larger collaboration: We observed the field of GRB 070224 with the WHT/LIRIS instrument in poor seeing, beginning at Feb 24 23:06 UT. Our 6 minute K-band image reached a 3-sigma limit of K~19.2 (based on calibration via four 2MASS stars in the field). A later observation in better seeing, beginning at Feb 25 04:44 UT, reached a limiting magnitude of K~19.7. In both images within the XRT error circle (GCN 6143) we see a source at the position of the candidate reported by Thoene et al. (GCN 6142), with a magnitude that is consistent with K~19.2 in both cases, although some fading can't be ruled out. In the second image we also see (close to the limit) another source with (2000) coordinates approximately: 11 56 06.26 -13 19 50.0 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6148 SUBJECT: GRB070224: Magellan Imaging Observations DATE: 07/02/26 02:43:41 GMT FROM: Hsiao-Wen Chen at U Chicago H.-W. Chen (U Chicago), K. Glazebrook (Swinburne University), and J. S. Bloom (UC Berkeley) report on behalf of a larger collaboration: "We continued imaging observations of the field around GRB 070224 (Racusin et al., GCN 6137), using MagIC on the Magellan Clay telescope. The observations consisted of 5x300 sec dithered exposures in the i' band and 6x600 sec dithered exposures in the z' band, starting at Feb 25.180 UT, ~ 8 hours after the initial Swift trigger. The images were taken under photometric conditions with a mean seeing of 0.5" in i' and 0.6" in z'. Object photometry was calibrated using a Sloan Digital Sky Survey photometric standard observed after the GRB field. Combining the images obtained using GMOS and MagIC, we measure photometry of the compact source at RA(J2000)=11:56:06.6 and Dec(J2000)=-13:19:48.9 (Chen, Glazebrook, & Bloom, GCN 6145; see also Thoene et al. GCN 6142, Mirabal et al. GCN 6146, Rol et al. GCN 6147) as the following: Filter AB UT(mid) Camera i' 22.60 +/- 0.10 25.107 GMOS z' 22.40 +/- 0.20 25.135 GMOS i' 22.54 +/- 0.05 25.188 MagIC z' 22.56 +/- 0.05 25.221 MagIC We therefore conclude that this is not a variable source. The source at RA(J2000)=11:56:06.5 and Dec(J2000)=-13:19:49.9 that appeared at low level in the first GMOS i'-band image (Chen, Glazebrook, & Bloom GCN 6145) remains absent in the MagIC images." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6151 SUBJECT: GRB070224: Swift-XRT Astrometrically Corrected Position DATE: 07/02/26 19:22:30 GMT FROM: Judith Racusin at PSU J. Racusin (PSU), M. Goad (U. Leicester), D.N. Burrows (PSU), O. Godet (U. Leicester), R. Starling (U. Leicester) report on behalf of the Swift XRT team: Based on an accurate mapping between the XRT and UVOT detector coordinate systems, we have used the simultaneous UVOT V-band images to astrometrically correct (relative to stellar catalogues, e.g. USNO-B1) the XRT world coordinate system, and thereby refine the XRT position. We obtain a new XRT position at RA,Dec=179.02792,-13.3304 which is: RA(J2000): 11h 56m 06.7s Dec(J2000): -13d 19' 49.6" with an uncertainty of 2.6 arcseconds (90% containment). This is 3.8 arcseconds from the refined XRT position (Racusin et al., GCN 6143), and 2.0 arcseconds from the optical candidate first identified by Thoene et al. (GCN 6142). This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6152 SUBJECT: GRB 070224: Swift/UVOT Upper Limits DATE: 07/02/26 20:25:11 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC S. T. Holland (CRESST/GSFC/USRA), F. E. Marshall (NASA/GSFC), M. M. Chester (PSU) and J. L. Racusin (PSU) report on the behalf of the Swift/UVOT team: The Swift/UVOT observed the field of GRB 070224 starting 132 s after the BAT trigger (Racusin et al. 2007, GCN Circ. 6137). We do not find any source, in any of the UVOT observations, inside the astrometrically corrected XRT error circle (Racusin et al., 2007 GCN Circ. 6151). The 3-sigma upper limits for detecting a source anywhere inside the XRT error circle in the finding chart images, and the co-added exposures are: Filter T_start T_stop Exp(s) Mag (3-sigma upper limit) ------------------------------------------------------------- White Finding 156 254 96 20.4 V Finding 259 659 393 20.1 V 259 1367 806 20.5 B 737 747 10 18.6 U 713 733 19 18.7 UVW1 689 5512 132 20.0 UVM2 665 833 39 18.3 UVW2 766 785 19 18.2 White 154 962 206 20.9 V 35,712 126,303 1553 20.9 B 7159 128,636 1987 22.0 U 6954 93,932 1952 21.7 UVW1 6750 145,987 4321 22.2 UVM2 12,574 143,883 4621 22.4 UVW2 29,833 122,852 4358 22.6 ------------------------------------------------------------- The values quoted above are not corrected for the expected Galactic extinction corresponding to a reddening of E_{B-V} = 0.06 mag towards the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6154 SUBJECT: GRB 070224: Optical afterglow confirmation DATE: 07/02/27 19:12:04 GMT FROM: Alexander Kann at TLS Tautenburg Christina C. Thoene (Dark/NBI), D. Alexander Kann (TLS Tautenburg), Thomas Augusteijn (NOT) and Celine Reyle-Laffont (Observatoire de Besancon) report: We observed the OT candidate (Thoene et al., GCN 6142) of GRB 070224 (Racusin et al., GCN 6137) again on Feb. 27 (2.27 days after the burst) with NOT and StanCam in R. The proposed candidate (Thoene et al., GCN 6142, see also Chen et al., GCN 6145, Mirabal et al., GCN 6146, Rol et al., GCN 6147 and Chen et al., GCN 6148) is clearly fading between our three epochs. We get the following magnitudes: t after burst   exptime   R mag: 0.20 d            900s        22.1 +- 0.2 0.39 d            1800s       22.5 +- 0.2 2.27 d            2400s       24.1 +- 0.3 based on two nearby USNO-B1.0 stars. We therefore conclude that this object is the afterglow of GRB 070224. It thus may have had an early plateau phase (Rol et al., GCN 6147, Chen et al., GCN 6148). Improved astrometry gives a refined position of the afterglow at (J2000): RA = 11:56:06.65 Dec = -13:19:48.8 with an error of 0.5 arcsec. This is 1.1 arcsec from the center of the revised XRT error circle (Racusin et al., GCN Report 36.1) and 0.8 arcsec from the center of Nat Butler's error circle (v2.5) (http://astro.berkeley.edu/~nat/swift/xrt_pos.html). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6164 SUBJECT: VLA observation of GRB 070224 DATE: 07/03/01 16:40:05 GMT FROM: Poonam Chandra at U Virginia/NRAO Poonam Chandra (NRAO/UVA) and Dale A. Frail (NRAO) report on behalf of the Caltech-NRAO-Carnegie GRB Collaboration: "We used the Very Large Array to observe the field of view toward GRB 070224 (GCN 6137) at a frequency of 8.46 GHz on 2007 February 28 at 9.99 UT. The GRB is undetected and the peak radio flux at the SWIFT-XRT position (GCN 6143) is -83 uJy ± 47 uJy. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc."