//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 33592 SUBJECT: GRB 230409B: Swift detection of a burst DATE: 23/04/09 05:21:45 GMT FROM: Kim Page at U.of Leicester A. P. Beardmore (U Leicester), C. Gronwall (PSU), A. Y. Lien (U Tampa), K. L. Page (U Leicester), T. Sakamoto (AGU), M. H. Siegel (PSU) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 04:56:57 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 230409B (trigger=1163401). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 329.530, +52.854 which is RA(J2000) = 21h 58m 07s Dec(J2000) = +52d 51' 15" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The immediately available BAT light curve starts at ~ a few seconds after the BAT trigger time. The light curve shows a small hump from ~50 to 100 s, however, further ground data will be required to determine whether the hump is due to background fluctuation. The XRT began observing the field at 04:58:38.0 UT, 101.2 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 329.51486, 52.83228 which is equivalent to: RA(J2000) = 21h 58m 03.57s Dec(J2000) = +52d 49' 56.2" with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 84 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. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 7.56 x 10^21 cm^-2 (Willingale et al. 2013). UVOT took a finding chart exposure of 150 seconds with the White filter starting 386 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 none of the XRT error circle. 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 large, but uncertain, extinction expected. Burst Advocate for this burst is A. P. Beardmore (apb AT star.le.ac.uk). 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: 33594 SUBJECT: GRB 230409B: Enhanced Swift-XRT position DATE: 23/04/09 11:34:35 GMT FROM: Phil Evans at U of Leicester P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 1709 s of XRT Photon Counting mode data and 2 UVOT images for GRB 230409B, 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 = 329.51474, +52.83212 which is equivalent to: RA (J2000): 21h 58m 3.54s Dec (J2000): +52d 49' 55.6" with an uncertainty of 2.2 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: 33595 SUBJECT: GRB 230409B: Swift/UVOT Detection DATE: 23/04/09 14:26:27 GMT FROM: Paul Kuin at MSSL GRB 230409B: Swift/UVOT Detection N. Paul Kuin (UCL/MSSL) and A. P. Beardmore (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 230409B 386 s after the BAT trigger (Beardmore et al., GCN Circ. 33592). A weak fading source consistent with the XRT position (Beardmore et al. GCN Circ. 33592) is detected in the initial UVOT exposures at position RA=329.5158, Dec=52.8321 deg. Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 386 536 147 19.35 +/- 0.20 v 542 1931 156 >18.1 b 642 2029 156 >19.4 u 616 2004 156 >19.0 w1 592 1980 156 >18.8 m2 567 1955 156 >19.2 w2 692 1906 136 >20.0 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 1.226 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 33596 SUBJECT: Swift GRB 230409B: Global MASTER-Net observations report DATE: 23/04/09 16:58:40 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, E.Gorbovskoy, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, G.Antipov, D.Zimnukhov, V.Senik, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D.Cheryasov, Ya.Kechin (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev (Irkutsk State University, API), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational State University) MASTER-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 230409B ( A. P. Beardmore et al., GCN 33592) errorbox 42781 sec after notice time and 42806 sec after trigger time at 2023-04-09 16:50:23 UT, with upper limit up to 15.5 mag. Observations started at twilight. The observations began at zenith distance = 83 deg. The sun altitude is -12.2 deg. The galactic latitude b = -2 deg., longitude l = 99 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2209455 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 42897 | MASTER-Kislovodsk | C | 180 | 15.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 33598 SUBJECT: GRB 230409B: Swift-BAT refined analysis DATE: 23/04/09 17:50:01 GMT FROM: Amy Lien at GSFC D. M. Palmer (LANL), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), 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) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 230409B (trigger #1163401) (Beardmore et al., GCN Circ. 33592). The BAT ground-calculated position is RA, Dec = 329.516, 52.832 deg which is RA(J2000) = 21h 58m 03.8s Dec(J2000) = +52d 49' 55.1" with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 32%. The mask-weighted light curve shows a single-pulse structure that starts at ~T-1 s, peaks at ~T+1 s, and ends at ~T+12 s. The hump at ~50 s to 100 s mentioned in the previous circular (Beardmore et al., GCN Circ. 33592) is due to background fluctuation and is not part of the burst. T90 (15-350 keV) is 9.79 +- 2.59 sec (estimated error including systematics). The time-averaged spectrum from T-0.58 to T+11.78 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.86 +- 0.19. The fluence in the 15-150 keV band is 9.9 +- 1.2 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.43 sec in the 15-150 keV band is 3.7 +- 0.5 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/1163401/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 33599 SUBJECT: GRB 230409B: Swift-XRT refined Analysis DATE: 23/04/09 21:57:51 GMT FROM: Phil Evans at U of Leicester P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , D.N. Burrows (PSU), J. D. Gropp (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and A.P. Beardmore report on behalf of the Swift-XRT team: We have analysed 6.6 ks of XRT data for GRB 230409B (Beardmore et al. GCN Circ. 33592), from 338 s to 52.1 ks after the BAT trigger. The data comprise 19 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 33594). The light curve can be modelled with a power-law decay with a decay index of alpha=0.87 (+0.04, -0.03). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.97 (+0.22, -0.21). The best-fitting absorption column is 1.23 (+0.27, -0.24) x 10^22 cm^-2, in excess of the Galactic value of 7.6 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 5.2 x 10^-11 (9.9 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.23 (+0.27, -0.24) x 10^22 cm^-2 Galactic foreground: 7.6 x 10^21 cm^-2 Excess significance: 3.3 sigma Photon index: 1.97 (+0.22, -0.21) If the light curve continues to decay with a power-law decay index of 0.87, the count rate at T+24 hours will be 0.020 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x 10^-12 (2.0 x 10^-12) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01163401. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 33607 SUBJECT: GRB 230409B: OHP/T193 optical upper limit DATE: 23/04/12 13:30:17 GMT FROM: Benjamin Schneider at MIT C. Adami (LAM), B. Schneider (MIT), S. Basa (LAM), E. Le Floc'h, D. Turpin, D. Götz (CEA Paris-Saclay), S. D. Vergani (GEPI, Obs. de Paris), report on behalf of a larger collaboration: We observed the field of GRB 230409B (Beardmore et al., GCN 33592) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. Four exposures were obtained in the i-band (2x300s + 2x600s) from 2023 10 April 03:03:03 UT to 2023 10 April 03:44:17 UT (mid time ~22.3h after trigger). In the combined frame, we do not detect any source at the position reported by Evans et al., GCN 33594 and Kuin et al., GCN 33595 down to the following 3-sigma limit: i > 20.6 mag (AB) The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitude is not corrected for Galactic extinction. We acknowledge the excellent support from Observatoire de Haute-Provence, in particular Jean-Pierre Troncin. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 33608 SUBJECT: GRB 230409B: Mondy optical upper limit DATE: 23/04/12 23:21:33 GMT FROM: Alexei Pozanenko at IKI, Moscow S. Belkin (IKI), E. Klunko (ISTP), A. Pozanenko (IKI), N. Pankov (HSE) report on behalf of GRB IKI FuN: We observed the field of Swift GRB 230409B (Beardmore et al., GCN 33592) with AZT-33IK telescope of Mondy observatory in R-filter on 2023-04-09 starting (UT) 14:52:05. We do not detect the optical counterpart (Kuin et al., GCN 33595) within the enhanced Swift/XRT error box (Evans et al., GCN 33594). Preliminary photometry of a stacked image is following Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) (mid, days) (s) 2023-04-09 14:52:05 0.42231 26*60 R n/d n/d 20.5 The photometry is based on nearby USNO-B1.0 stars. USNO-B1.0 RA DEC R2 21:58:01.9195200 +52:49:21.982800 15.15 21:58:13.7054400 +52:48:57.002400 15.56 21:57:54.5028000 +52:50:57.080400 15.95 The upper limit does not contradict result reported by Adami et al. (GCN 33607). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 33627 SUBJECT: GRB 230409B: 3.6m DOT near-infrared detection, afterglow confirmation DATE: 23/04/15 08:39:33 GMT FROM: Rahul Gupta at ARIES, India Rahul Gupta, Amit K. Ror, S. B. Pandey, A. Aryan, K. Misra (ARIES), A. J. Castro-Tirado (IAA-CSIC), D. Bhattacharya (Ashoka University/IUCAA), and V. Bhalerao (IITB) report on behalf of a larger collaboration: GRB 230409B was detected by the Swift Burst Alert Telescope (BAT) at 04:56:57 UT on 9th April 2023 (Beardmore et al., GCN 33592). The prompt emission mask-weighted BAT light curve consists of a single-peaked structure with a T90 duration of 9.79 +- 2.59 sec in 15-350 keV energy range (Palmer et al., GCN 33598). We compare the reported value of BAT fluence and peak photon flux for this GRB (Palmer et al., GCN 33598) with all the BAT-detected GRBs sample; this burst is positioned at the middle-near top of this distribution. We also determine the peak energy of the burst using BAT energy fluence and peak energy correlation. We calculated the peak energy of the burst is 61.49 (+23.39, -16.96) KeV; the softer value of peak energy is consistent with those of long GRBs (Type II). The Swift XRT detected an X-ray afterglow ~ 101.2 sec after the BAT trigger (Beardmore et al., GCN 33592). The XRT count-rate light curve could be best described with a broken power-law model with temporal indices of 0.62 (+0.12, -0.12) and 1.15 (+0.19, -0.18) before and after break time (~4600-sec post-BAT detection), respectively. As no redshift has been reported for this source, we modeled the late time time-averaged XRT spectrum (T0 + 18528 to 113195 sec) considering redshift = 2, roughly average redshift value for long GRBs (Type II). The spectrum could be modeled using an absorption power-law with the following spectral parameters: NH_host= 4.85 (-4.85,+8.76) X 10^{22} cm^{-2} and \beta_x= 0.73 (-0.36,+0.40). Considering the adiabatic deceleration without energy injection, closure relations indicate that the late time X-ray afterglow could be best described with \nu_m < \nu < \nu_c spectral regime for ISM medium for the electron energy index p ~ 2.46. The Swift UVOT detected a weak fading source within the XRT error circle (Kuin et al., GCN 33595). We performed the follow-up observations of this fading optical source using the TANSPEC mounted at the axial port of the 3.6m Devasthal Optical Telescope (DOT) of ARIES Nainital at multiple epochs in J filter (near-infrared). We report the preliminary brightness of the afterglow to be J = 20.1 +/- 0.3 mag ~ 0.75 days after the BAT trigger. We obtained the limiting mag of 20.5 mag ~ 2.7 days post-burst at successive epochs. Our observations confirm this fading source to be the afterglow of GRB 230409B. The magnitude values reported are calibrated against 2MASS nearby stars. This circular may be cited. 3.6m Devasthal Optical Telescope (DOT) is the recently commissioned facility in the Northern Himalayan region of India (long:79 41 04E, lat:29 21 40N, alt:2540m) owned and operated by the Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital ( https://www.aries.res.in). Authors of this GCN circular thankfully acknowledge consistent support from the staff members to run and maintain the 3.6m DOT. We also thank Director ARIES for approving the DDT slot for the ToO observations.