//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8842 SUBJECT: GRB 090123: Swift detection of a burst DATE: 09/01/23 08:10:31 GMT FROM: Dirk Grupe at PSU/Swift-XRT D. Grupe (PSU), P. A. Evans (U Leicester), C. Gronwall (PSU), C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC), J. L. Racusin (PSU), M. Stamatikos (NASA/ORAU) and L. Vetere (PSU) report on behalf of the Swift Team: At 07:51:56 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 090123 (trigger=340895). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 6.775, -23.514 which is RA(J2000) = 00h 27m 06s Dec(J2000) = -23d 30' 49" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 30 sec, beginning at about T-10 sec. The peak count rate was ~1000 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 07:53:36.2 UT, 99.9 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 6.7863, -23.5007 which is equivalent to: RA(J2000) = 00h 27m 08.71s Dec(J2000) = -23d 30' 02.5" with an uncertainty of 5.1 arcseconds (radius, 90% containment). This location is 60 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. UVOT took a finding chart exposure of 150 seconds with the White filter starting 107 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 00:27:08.74 = 6.78641 DEC(J2000) = -23:30:03.9 = -23.50108 with a 90%-confidence error radius of about 0.75 arc sec. This position is 1.4 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.71 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02. Burst Advocate for this burst is D. Grupe (grupe AT astro.psu.edu). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8843 SUBJECT: GRB090123: Enhanced Swift-XRT position DATE: 09/01/23 12:50:55 GMT FROM: Phil Evans at U of Leicester J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 1885 s of XRT Photon Counting mode data and 1 UVOT images for GRB090123, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 6.78599, -23.50156 which is equivalent to: RA (J2000): 00h 27m 8.64s Dec (J2000): -23d 30' 05.6" with an uncertainty of 1.7 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401 http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an extension of this method. This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8844 SUBJECT: GRB 090123: Swift-BAT refined analysis DATE: 09/01/23 15:28:59 GMT FROM: Scott Barthelmy at NASA/GSFC T. N. Ukwatta (GWU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), D. Grupe (PSU), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from recent telemetry downlinks, we report further analysis of BAT GRB 090123 (trigger #340895) (Grupe, et al., GCN Circ. 8842). The BAT ground-calculated position is RA, Dec = 6.794, -23.503 deg, which is RA(J2000) = 00h 27m 10.5s Dec(J2000) = -23d 30' 12.6" with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 36%. The mask-weighted light curve shows multiple overlapping peaks starting at ~T-48 sec, with the max peak at ~T+3 sec, and ending at ~T+120 sec. T90 (15-350 keV) is 131 +- 23 sec (estimated error including systematics). The time-averaged spectrum from T-49.6 to T+117.9 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.74 +- 0.12. The fluence in the 15-150 keV band is 2.9 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+0.08 sec in the 15-150 keV band is 1.7 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/340895/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8846 SUBJECT: GRB 090123: Swift/UVOT Observations DATE: 09/01/23 17:29:12 GMT FROM: Frank Marshall at GSFC F.E. Marshall (NASA/GSFC) and D. Grupe (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT observed the field of GRB 090123 starting 107 s after the BAT trigger (Grupe et al., GCN Circ. 8842). We detect the optical afterglow (Grupe et al.) in the white, v, b, u, uvw1, uvm2, and uvw2 filters at the position: RA(J2000) = 00:27:08.73 = 6.78639 DEC(J2000) = -23:30:04.1 = -23.50113 with an estimated uncertainty of 0.5 arc sec. (radius, 90% confidence). There is a broad peak in the light curve ~600 sec. after the trigger. The 3.4-sigma detection in the uvw2 filter indicates that the redshift is less than ~1.4. The magnitudes in the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) in the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white (FC) 107 257 147 17.8 +/- 0.1 v 649 669 20 15.4 +/- 0.1 b 575 595 20 15.8 +/- 0.1 u 320 570 250 16.4 +/- 0.1 uvw1 698 718 20 17.3 +/- 0.23 uvm2 1251 8112 294 19.6 +/- 0.25 uvw2 1547 7843 413 20.5 +/- 0.29 The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8847 SUBJECT: GRB 090123: Swift XRT refined analysis DATE: 09/01/23 19:21:36 GMT FROM: Dirk Grupe at PSU/Swift-XRT D. Grupe (PSU) reports on behalf of the Swift-XRT team: We have analyzed 7.7 ks of XRT data for GRB090123 (Grupe et al. GCN Circ. 8842), beginning 106 s after the BAT trigger. The data comprise 334 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN. Circ 8843). The light curve can be modeled with an initial power-law decay with an index of alpha=1.78 (+0.06, -0.08), followed by a break at T+1530 (+720,-220) s to an alpha of 1.20 (+0.08, -0.10). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.65+/-0.05 with an absorption column fixed to the Galactic value of 1.79 x 1020 cm-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 1.81+/-0.08 and an absorption column density also consistent with the Galactic value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.2 x 10-11 (4.5 x 10-11) erg cm-2 count-1. If the light curve continues to decay with a power-law decay index of 1.20, the count rate at T+24 hours will be 0.0031 counts/s, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.3 x 10-13 (1.4 x 10-13) erg cm-2 s-1. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8849 SUBJECT: GRB 090123: GROND detection DATE: 09/01/24 11:09:19 GMT FROM: Jochen Greiner at MPI A. Rossi (Tautenburg Obs.) and J. Greiner (MPE Garching) report on behalf of the GROND team: GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile) imaged the field of GRB 090123 (Swift trigger 340895, Grupe et al. 2009, GCN #8842) simultaneously in g'r'i'z'JHK. Observation started on 2009-01-24 at 01:22 UTC, about 17 hours after the burst. The total exposure time was 25 minutes, the average seeing 1.3 at airmass 2.5. We detect the afterglow at the position reported by SWIFT UVOT (Marshall et al 2009, GCN #8846) in g'r'i'z', but not in JHK. We estimate the following observed magnitudes and upper limits (all in AB system): g' = 22.77 +- 0.05 r' = 22.45 +- 0.05 i' = 21.95 +- 0.08 z' = 22.09 +- 0.12 J > 21.5 H > 21.0 K > 20.5 calibrated against GROND zeropoints and 2MASS field stars.