//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 33206 SUBJECT: GRB 230123A: Swift detection of a burst DATE: 23/01/23 10:36:16 GMT FROM: Kim Page at U.of Leicester M. A. Williams (PSU), R. A. J. Eyles-Ferris (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), A. Y. Lien (U Tampa) and K. L. Page (U Leicester) report on behalf of the Neil Gehrels Swift Observatory Team: At 10:19:44 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 230123A (trigger=1150429). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 40.937, -65.676 which is RA(J2000) = 02h 43m 45s Dec(J2000) = -65d 40' 33" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 10 sec. The peak count rate was ~800 counts/sec (15-350 keV), at ~1 sec after the trigger. The immediately available BAT light curve does not include data from ~T+8 s to ~T+100 s. There might be additional burst emission in that time interval. The XRT began observing the field at 10:21:13.6 UT, 88.8 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 40.85977, -65.68672 which is equivalent to: RA(J2000) = 02h 43m 26.34s Dec(J2000) = -65d 41' 12.2" with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 120 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (2.95 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 1.3 (+1.44/-1.26) x 10^22 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 92 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 12% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.022. Burst Advocate for this burst is M. A. Williams (mjw6837 AT 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/) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 33208 SUBJECT: GRB 230123A: Zadko observatory - Gingin optical observations DATE: 23/01/23 14:31:21 GMT FROM: Bruce Gendre at UVI B. Gendre (UWA/OzGrav), G. Stratta (INAF/Goethe University Frankfurt), E. Moore (UWA/OzGrav), F. Panther (UWA/OzGrav), D. Coward (UWA/OzGrav), J. A. Moore (OzGrav-UWA), A. Klotz (IRAP-CNRS-OMP), and P. Thierry (AGORA) report: We imaged the field of GRB 230123A detected by SWIFT (trigger 1150429, GCN 33206, Williams et al. 2023) with the Zadko robotic telescope (D=100cm) located at the Zadko observatory - Gingin, Australia. The observations started 2.56h after the GRB trigger (t0+9213.4s). The elevation of the field decreased from 51 degrees above horizon and weather conditions were good. We observed the field for one hour, and have not detected any afterglow down to magnitude 18.7 in individual images. On a stack of 6 images, we reached an upper limit of R = 19.0 with no detection of the afterglow. Further observations are planned. Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction. N.B. Galactic coordinates are lon=286.2098 lat=-47.6419 and the galactic extinction in R band is 0.0 magnitudes estimated from D. Schlegel et al. 1998ApJ...500..525S. This message may be cited. ====================================================================== //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 33209 SUBJECT: GRB 230123A: Enhanced Swift-XRT position DATE: 23/01/23 16:43:36 GMT FROM: Phil Evans at U of Leicester A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 1184 s of XRT Photon Counting mode data and 2 UVOT images for GRB 230123A, 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 = 40.85842, -65.68648 which is equivalent to: RA (J2000): 02h 43m 26.02s Dec (J2000): -65d 41' 11.3" with an uncertainty of 4.1 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) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 33210 SUBJECT: GRB 230123A: Swift-XRT refined Analysis DATE: 23/01/23 17:57:03 GMT FROM: Phil Evans at U of Leicester S. Dichiara (PSU), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), T. Sbarrato (INAF-OAB), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto) and M.A. Williams report on behalf of the Swift-XRT team: We have analysed 6.4 ks of XRT data for GRB 230123A (Williams et al. GCN Circ. 33206), from 73 s to 18.4 ks after the BAT trigger. The data comprise 8 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN Circ. 33209). The light curve can be modelled with a power-law decay with a decay index of alpha=0.68 (+0.08, -0.07). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.1 (+0.4, -0.3). The best-fitting absorption column is 1.4 (+1.0, -0.8) x 10^21 cm^-2, in excess of the Galactic value of 3.0 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.2 x 10^-11 (4.3 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.4 (+1.0, -0.8) x 10^21 cm^-2 Galactic foreground: 3.0 x 10^20 cm^-2 Excess significance: 2.2 sigma Photon index: 2.1 (+0.4, -0.3) If the light curve continues to decay with a power-law decay index of 0.68, the count rate at T+24 hours will be 3.4 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x 10^-13 (1.4 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01150429. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 33211 SUBJECT: GRB 230123A: Swift/UVOT Upper Limits DATE: 23/01/23 19:25:47 GMT FROM: Alexander Belles at PSU/Swift A. Belles (PSU) and M. Williams (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 230123A 93 s after the BAT trigger (Williams et al., GCN Circ. 33206). No optical afterglow consistent with the XRT position (Beardmore et al. GCN Circ. 33209) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 93 243 147 >20.6 u_FC 305 555 246 >20.6 white 93 1704 412 >21.0 v 637 1754 136 >19.4 b 562 1679 117 >20.0 u 305 1825 359 >20.5 w1 686 1804 117 >20.8 m2 1412 1605 39 >18.7 w2 612 1209 78 >20.1 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.022 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 33214 SUBJECT: GRB 230123A: Swift-BAT refined analysis DATE: 23/01/24 05:08:44 GMT FROM: Amy Lien at GSFC D. M. Palmer (LANL), S. D. Barthelmy (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), T. Parsotan (GSFC/UMBC), T. Sakamoto (AGU), M. Stamatikos (OSU), M. A. Williams (PSU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 230123A (trigger #1150429) (Williams et al., GCN Circ. 33206). The BAT ground-calculated position is RA, Dec = 40.905, -65.661 deg which is RA(J2000) = 02h 43m 37.3s Dec(J2000) = -65d 39' 39.9" with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 88%. The mask-weighted light curve shows a single-peaked structure that starts at ~T-2 s, peaks at ~T+1, and ends at ~T+6 s. T90 (15-350 keV) is 5.37 +- 1.03 sec (estimated error including systematics). The time-averaged spectrum from T-1.25 to T+4.75 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.06 +- 0.24. The fluence in the 15-150 keV band is 2.7 +- 0.4 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.12 sec in the 15-150 keV band is 1.1 +- 0.2 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/1150429/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 33217 SUBJECT: GRB 230123A: LCOGT Optical Upper Limits DATE: 23/01/24 17:19:20 GMT FROM: Robert Strausbaugh at University of Minnesota R. Strausbaugh (University of Minnesota), A. Cucchiara (NASA) report on behalf of a larger collaboration: We observed the GRB 230123A (Williams et al., GCN 33206) field with the LCOGT 1-meter Sinistro instrument at the Cerro Tololo Interamerican Observatory, Chile site, on January 24, from 02:06 to 02:38 UT (corresponding to 15.78 to 16.32 hours from the GRB trigger time) with the Bessel R and I filters. We performed a series of 3x300s exposures in each band. We do not detect a source in either band within the XRT enhanced error region (Beardmore et al., GCN 33209), consistent with other optical upper limits (Gendre et al., GCN 33208; Belles et al., 33211). The following upper limits are calculated using the USNO-B1.0 catalog as reference: R > 20.8 I > 20.1 These magnitudes are not corrected for galactic extinction.