GRB240421B

This page lists all entries on GRB240421B in GRBweb

Summary Fermi GBM IPN Swift GCN 36208 GCN 36213 GCN 36214 GCN 36215 GCN 36216 GCN 36217 GCN 36218 GCN 36219 GCN 36220 GCN 36221 GCN 36223 GCN 36269 GCN 36291

Summary table
Variable Value Source
GRB_name_Fermi GRB240421405
T0 9:42:41.910 UTC GCN_circulars,Fermi GBM Det
ra 299.7009° Swift
decl 14.8597° Swift
pos_error 2.59e-04° Swift
T90 12.288 s Fermi_GBM
T90_error 0.362 s Fermi_GBM
T90_start 9:42:44.217 UTC Fermi_GBM
fluence 1.26e-05 erg/cm² Fermi_GBM
fluence_error 1.70e-08 erg/cm² Fermi_GBM
T100 14.595 s
GBM_located False
mjd 60421.40465173611 GCN_circulars,Fermi GBM Det
Fermi GBM table
GRB_name_Fermi GRB240421405
trigger_name bn240421405
ra 299.6858°
decl -14.8789°
pos_error 4.42e+00°
datum 2024-04-21
t_trigger 9:42:41.913 UTC
T90 12.288 s
T90_error 0.362 s
T90_start 9:42:44.217 UTC
fluence 1.26e-05 erg/cm²
fluence_error 1.70e-08 erg/cm²
flux_1024 3.19e+01 erg/cm²/s
flux_1024_error 4.53e-01 erg/cm²/s
flux_1024_time 1.21e+01 erg/cm²/s
flux_64 4.75e+01 erg/cm²/s
flux_64_error 2.02e+00 erg/cm²/s
IPN table
GRB_name GRB240421B
ra 299.6875°
decl -14.8833°
pos_error 5.00e-02°
Swift table
GRB_name GRB240421B
t_trigger 9:42:54 UTC
ra 299.7009°
decl 14.8597°
pos_error 2.59e-04°
GCN 36208 table
GRB_name GRB240421B
GCN_number 36208
Detection_method Swift Det
t_trigger 9:42:54 UTC
ra 299.6860°
decl -14.8790°
Circular_text TITLE: GCN CIRCULAR NUMBER: 36208 SUBJECT: GRB 240421B: Swift detection of a burst DATE: 24/04/21 10:02:18 GMT FROM: Simone Dichiara at Pennsylvania State University M. A. Williams (PSU), J. J. DeLaunay (PSU), S. Dichiara (PSU), J.D. Gropp (PSU) and T. Sakamoto (AGU) report on behalf of the Neil Gehrels Swift Observatory Team: At 09:42:54 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 240421B (trigger=1223470). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 299.686, -14.879 which is RA(J2000) = 19h 58m 45s Dec(J2000) = -14d 52' 42" 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 20 sec. The peak count rate was ~9000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 09:45:00.4 UT, 126.3 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 299.70011, -14.86012 which is equivalent to: RA(J2000) = 19h 58m 48.03s Dec(J2000) = -14d 51' 36.4" with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 83 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 in excess of the Galactic value (1.24 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 3.8 (+2.62/-2.25) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 129 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 100% 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 0.183. 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/)
GCN 36213 table
GRB_name GRB240421B
GCN_number 36213
Detection_method Swift-XRT Det
ra 299.7009°
decl -14.8596°
Circular_text TITLE: GCN CIRCULAR NUMBER: 36213 SUBJECT: GRB 240421B: Enhanced Swift-XRT position DATE: 24/04/21 18:31:11 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 1017 s of XRT Photon Counting mode data and 1 UVOT images for GRB 240421B, 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 = 299.70085, -14.85962 which is equivalent to: RA (J2000): 19h 58m 48.20s Dec (J2000): -14d 51' 34.6" with an uncertainty of 2.1 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.
GCN 36214 table
GRB_name GRB240421B
GCN_number 36214
Detection_method Swift-UVOT Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 36214 SUBJECT: GRB 240421B: Swift/UVOT Upper Limits DATE: 24/04/21 19:04:49 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL) and M. Williams (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 240421B 130s after the BAT trigger (Williams et al., GCN Circ. 36208). No optical afterglow consistent with the XRT position Beardmore et al. (GCN Circ. 36213) 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 130 279 148 >20.6 u_FC 343 592 246 >20.2 white 130 1708 218 >20.9 v 672 1764 78 >18.4 b 598 1854 84 >19.8 u 343 1827 339 >20.2 w1 721 1813 78 >19.4 w2 648 1568 78 >18.8 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.182 in the direction of the burst (Schlegel et al. 1998).
GCN 36215 table
GRB_name GRB240421B
GCN_number 36215
Detection_method Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 36215 SUBJECT: GRB 240421B: J-band upper limits from WINTER DATE: 24/04/21 19:08:39 GMT FROM: Viraj Karambelkar at Indian Inst of Tech,Bombay Viraj Karambelkar (Caltech), Geoffrey Mo (MIT), Robert Stein (Caltech), Danielle Frostig (MIT), Tomas Ahumada (Caltech), Nathan Lourie (MIT), Robert Simcoe (MIT), Mansi Kasliwal (Caltech) We observed the field of the long GRB 240421B (GCN 36208, 36213, 36214) in the near-IR J-band with the WINTER camera on the Palomar 40-inch telescope. Our observations started at UTC 2024-04-19T11:16:00 (~1.5 hours since trigger) and lasted for an hour. The images were processed through the WINTER data reduction pipeline implemented using mirar (https://zenodo.org/records/10888437), with image subtraction performed relative to reference images built from the VISTA Hemisphere Survey (McMahon et al. 2013). We do not detect any source at the location of the X-ray counterpart (reported in GCN 36213) to a limit of m_J = 19.5 mag (AB, not corrected for Galactic extinction). No other new sources are found within the 3 arcmin localization of the GRB. WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucille Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research
GCN 36216 table
GRB_name GRB240421B
GCN_number 36216
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 36216 SUBJECT: GRB240421B: BOOTES-5/JGT optical upper limit DATE: 24/04/21 21:10:58 GMT FROM: Youdong HU at INAF-OAB E. Fernandez-Garcia, I. Perez-Garcia, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy, S.-Y. Wu and A. J. Castro-Tirado (IAA-CSIC, Granada), Y.-D. Hu (INAF-OAB), P. J. Meintjes and H. J. van Heerden (UFS, South Africa), A. Martin-Carrillo and L. Hanlon (UCD, Ireland) and C. J. Perez del Pulgar (UMA, Malaga), on behalf of a larger collaboration, report: Following the detection of GRB 240421B by Swift (Williams et al. GCNC 36208), the BOOTES-5/JGT 0.6m robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) automatically observed the GRB location starting on April. 21, 09:43:44 UT (~ 50 s after trigger). No new optical source is detected on the co-added images (20 x 1 s, clear-filter) within the enhanced Swift/XRT error box (Beardmore et al. GCNC 36213) down to 18.4 mag. which is consistent with both reports from UVOT (Kuin et al., GCNC 36214) and WINTER (Karambelkar et al. GCNC 36215). We thank the staff at Observatorio Astronomico Nacional in San Pedro Martir for their excellent support.
GCN 36217 table
GRB_name GRB240421B
GCN_number 36217
Detection_method Swift-XRT Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 36217 SUBJECT: GRB 240421B: Swift-XRT refined Analysis DATE: 24/04/21 22:50:00 GMT FROM: Phil Evans at U of Leicester J.P. Osborne (U. Leicester), B. Sbarufatti (INAF-OAB), C. Salvaggio (INAF-OAB), M. Ferro (INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.6 ks of XRT data for GRB 240421B, from 110 s to 36.0 ks after the BAT trigger. The data comprise 42 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The light curve can be modelled with an initial power-law decay with an index of alpha=0.50 (+/-0.07), followed by a break at T+2500 s to an alpha of 1.20 (+/-0.10). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.87 (+/-0.13). The best-fitting absorption column is 6.5 (+1.0, -0.9) x 10^21 cm^-2, in excess of the Galactic value of 1.2 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 4.6 x 10^-11 (7.3 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 6.5 (+1.0, -0.9) x 10^21 cm^-2 Galactic foreground: 1.2 x 10^21 cm^-2 Excess significance: 9.6 sigma Photon index: 1.87 (+/-0.13) 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 0.023 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x 10^-12 (1.7 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/01223470. This circular is an official product of the Swift-XRT team.
GCN 36218 table
GRB_name GRB240421B
GCN_number 36218
Detection_method Fermi GBM Det
t_trigger 9:42:41.910 UTC
Circular_text TITLE: GCN CIRCULAR NUMBER: 36218 SUBJECT: GRB 240421B: Fermi GBM Observation DATE: 24/04/21 23:05:42 GMT FROM: Cori Fletcher at USRA C. Fletcher (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 09:42:41.91 UT on 21 April 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240421B (trigger 735385366/240421405). which was also detected by Swift BAT (M. A. Williams et al. 2024, GCN 36208). The Fermi GBM on-ground location is consistent with the Swift BAT position. The angle from the Fermi LAT boresight is 29 degrees. The GBM light curve consists of multiple peaks with a duration (T90) of about 12.3 s (50-300 keV). The time-averaged spectrum from T0+0.003 to T0+18.4 s is best fit by a Band function with Epeak = 141 +/- 8 keV, alpha = -0.91 +/- 0.04, and beta = -2.31 +/- 0.09. The event fluence (10-1000 keV) in this time interval is (1.28 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+12 s in the 10-1000 keV band is 31.9 +/- 0.5 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN 36219 table
GRB_name GRB240421B
GCN_number 36219
Detection_method Swift Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 36219 SUBJECT: Swift GRB 240421B: Global MASTER-Net observations report DATE: 24/04/22 00:24:46 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik, D. Vlasenko, G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij (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. Gress, N.M. Budnev, O.Ershova (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), V. Yurkov, A. Gabovich (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 240421B ( M. A. Williams et al., GCN 36208) errorbox 52346 sec after notice time and 52368 sec after trigger time at 2024-04-22 00:15:42 UT, with upper limit up to 16.5 mag. The observations began at zenith distance = 70 deg. The sun altitude is -20.3 deg. The galactic latitude b = -22 deg., longitude l = 27 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2430219 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 52459 | MASTER-Kislovodsk | C | 180 | 15.8 | 52459 | MASTER-Kislovodsk | C | 180 | 16.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.
GCN 36220 table
GRB_name GRB240421B
GCN_number 36220
Detection_method Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 36220 SUBJECT: Fermi GRB 240421B: Global MASTER-Net observations report DATE: 24/04/22 02:15:40 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik, D. Vlasenko, G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij (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. Gress, N.M. Budnev, O.Ershova (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), V. Yurkov, A. Gabovich (Blagoveschensk Educational State University) MASTER-Tavrida robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 240421B ( C. Fletcher (USRA) and C. Meegan (UAH) report on behalf of et al., GCN 36218) errorbox 19358 sec after notice time and 56607 sec after trigger time at 2024-04-22 01:26:08 UT, with upper limit up to 17.1 mag. Observations started at twilight. The observations began at zenith distance = 67 deg. The sun altitude is -14.1 deg. The galactic latitude b = -22 deg., longitude l = 22 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2430649 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 56637 | 2024-04-22 01:26:08 | MASTER-Tavrida | (19h 37m 21.45s , -18d 16m 09.9s) | C | 60 | 16.4 | 56785 | 2024-04-22 01:28:36 | MASTER-Tavrida | (19h 53m 26.05s , -18d 16m 57.8s) | C | 60 | 14.1 | 56858 | 2024-04-22 01:29:50 | MASTER-Tavrida | (19h 49m 21.85s , -22d 05m 18.0s) | C | 60 | 14.2 | 57563 | 2024-04-22 01:41:35 | MASTER-Tavrida | (19h 50m 44.40s , -20d 11m 20.7s) | C | 60 | 15.8 | 57636 | 2024-04-22 01:42:47 | MASTER-Tavrida | (19h 59m 17.11s , -20d 10m 02.0s) | C | 60 | 16.6 | 57709 | 2024-04-22 01:44:00 | MASTER-Tavrida | (19h 37m 21.08s , -18d 16m 19.0s) | C | 60 | 17.1 | 57782 | 2024-04-22 01:45:13 | MASTER-Tavrida | (19h 45m 45.17s , -18d 15m 26.6s) | C | 60 | 17.0 | 57926 | 2024-04-22 01:47:38 | MASTER-Tavrida | (19h 43m 02.18s , -20d 11m 33.0s) | C | 60 | 16.8 | 57999 | 2024-04-22 01:48:50 | MASTER-Tavrida | (19h 53m 25.96s , -18d 17m 25.9s) | C | 60 | 16.7 | 58144 | 2024-04-22 01:51:16 | MASTER-Tavrida | (19h 49m 20.84s , -22d 05m 40.1s) | C | 60 | 14.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.
GCN 36221 table
GRB_name GRB240421B
GCN_number 36221
Detection_method Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 36221 SUBJECT: GRB240421B: Zadko Observations DATE: 24/04/22 02:30:22 GMT FROM: Bruce Gendre at UWA B. Gendre, E. Moore, F. Panther, D. Coward, J. A. Moore (OzGrav-UWA), and A. Klotz (IRAP-CNRS-OMP), report: We imaged the field of GRB 240421B detected by SWIFT (trigger 1223470) with the Zadko robotic telescope (D=100cm) located at the observatory - Gingin, Australia. The observations started 7.97h after the GRB trigger. The elevation of the field increased from 25 degrees above horizon and weather conditions were good. The date of trigger : t0 = 2024-04-21T09:42:54.050 The first image is 60.0s exposure in tracking mode: t0+28754.8s to t0+28814.8s : R > 16.2 We co-added a series of exposures: t0+28754.8s to t0+29599.3s : R > 17.7 Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction. N.B. Galactic coordinates are lon= 26.7039 lat=-21.4736 and the galactic extinction in R band is 0.7 magnitudes estimated from D. Schlegel et al. 1998ApJ...500..525S. This message may be cited.
GCN 36223 table
GRB_name GRB240421B
GCN_number 36223
Detection_method AstroSat CZTI
Circular_text TITLE: GCN CIRCULAR NUMBER: 36223 SUBJECT: GRB 240421B: AstroSat CZTI detection DATE: 24/04/22 04:47:37 GMT FROM: Gaurav Waratkar at IIT Bombay G. Waratkar (IITB), J. Joshi (IUCAA), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 240421B which was also detected by Swift-BAT (Williams et al., GCN Circ. 36208) and Fermi-GBM (Fletcher et al., GCN Circ. 36218). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2024-04-21 09:42:54.5 UTC. The measured peak count rate associated with the burst is 368 (+44, -52) counts/s above the background in the combined data of all quadrants, with a total of 843 (+148, -223) counts. The local mean background count rate was 474 (+5, -4) counts/s. Using cumulative rates, we measure a T90 of 6.3 (+3.2, -2.7) s. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2024-04-21 09:42:53.8 UTC. The measured peak count rate is 745 (+82, -87) counts/s above the background in the combined Veto data of all quadrants, with a total of 1802 (+268, -278) counts. The local mean background count rate was 1740 (+7, -8) counts/s. We measure a T90 of 5.6 (+1.6, -1.7) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb
GCN 36269 table
GRB_name GRB240421B
GCN_number 36269
Detection_method Fermi GBM Det
t_trigger 9:42:53.511 UTC
Circular_text TITLE: GCN CIRCULAR NUMBER: 36269 SUBJECT: GRB 240421B: GRBAlpha detection DATE: 24/04/24 03:33:17 GMT FROM: Marianna Dafčíková at Masaryk University <500025@mail.muni.cz> M. Dafcikova, J. Ripa, M. Kolar (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), N. Husarikova, F. Munz , M. Topinka, M. Duriskova, L. Szakszonova, J.-P. Breuer, F. Hroch (Masaryk U.), T. Urbanec, M. Kasal, A. Povalac (Brno U. of Technology), J. Hudec, J. Kapus, M. Frajt (Spacemanic s.r.o), R. Laszlo, M. Koleda (Needronix s.r.o), M. Smelko, P. Hanak, P. Lipovsky (Technical U. of Kosice), G. Galgoczi (Wigner Research Center/Eotvos U.), Y. Uchida, H. Poon, H. Matake (Hiroshima U.), N. Uchida (ISAS/JAXA), T. Bozoki (Eotvos U.), G. Dalya (Eotvos U.), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), G. Friss (Eotvos U.), Y. Fukazawa, K. Hirose (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), K. Kapas (Eotvos U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), J. Takatsy (Eotvos U.), K. Torigoe (Hiroshima U.), N. Kogiso, M. Yoneyama (Osaka Metropolitan U.), M. Moritaki (U. Tokyo), T. Kano (U. Michigan) -- the GRBAlpha collaboration. The long-duration GRB 240421B (Swift/BAT detection: GCN 36208; Fermi/GBM detection: GCN 36218; AstroSat detection: GCN 36223; Konus/Wind detection trigger at 2024-04-21 09:42:53.511 UT; INTEGRAL/SPI-ACS peak detection at 2024-04-21 ~09:42:54 UT) was observed by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; https://ui.adsabs.harvard.edu/abs/2023A%26A...677A..40P/abstract). The detection was confirmed at the peak time 2024-04-21 09:42:53.5 UTC. The T90 duration measured by GRBAlpha is 5.0 s and the overall significance during T90 reaches 11 sigma. The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB240421B_GCN.pdf All GRBAlpha detections are listed at: https://monoceros.physics.muni.cz/hea/GRBAlpha/ GRBAlpha, launched on 2021 March 22, is a demonstration mission for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). The detector of GRBAlpha consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~50 keV to ~1000 keV. To increase the duty cycle and the downlink rate, the upgrade of the on-board data acquisition software stack is in progress. The ground segment is also supported by the radio amateur community and it takes advantage of the SatNOGS network for increased data downlink volume.
GCN 36291 table
GRB_name GRB240421B
GCN_number 36291
Detection_method Swift-BAT Det
ra 299.6850°
decl -14.8780°
Circular_text TITLE: GCN CIRCULAR NUMBER: 36291 SUBJECT: GRB 240421B: Swift-BAT refined analysis DATE: 24/04/24 21:46:59 GMT FROM: Sibasish Laha at GSFC S. D. Barthelmy (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC),A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 240421B (trigger #1223470) (Williams, et al., GCN Circ. 36208). The BAT ground-calculated position is RA, Dec = 299.685, -14.878 deg which is RA(J2000) = 19h 58m 48.03s Dec(J2000) = -14d 51' 36.4" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 4%. The BAT light curve shows a complex structure with a duration of ~ 40 sec. T90 (15-350 keV) is 24.00 +- 9.22 sec (estimated error including systematics). The time-averaged spectrum from T-30.4 to T+7.6 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.63 +- 0.52, and Epeak of 81.3 +- 22.3 keV (chi squared 50.17 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 6.4 +- 0.5 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T-0.36 sec in the 15-150 keV band is 14.1 +- 1.6 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.55 +- 0.10 (chi squared 61.45 for 57 d.o.f.). All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1223470