GRB250424A

This page lists all entries on GRB250424A in GRBweb

Summary Swift GCN 40224 GCN 40225 GCN 40226 GCN 40227 GCN 40229 GCN 40230 GCN 40231 GCN 40232 GCN 40233 GCN 40240 GCN 40241 GCN 40243 GCN 40244 GCN 40249 GCN 40250 GCN 40251 GCN 40255 GCN 40263 GCN 40298

Summary table
Variable Value Source
T0 6:52:13.431 UTC GCN_circulars,Konus-Wind Det
ra 217.5000° Swift
decl -35.0252° Swift
pos_error 8.15e-05° Swift
redshift 0.3100
GBM_located False
mjd 60789.2862665625 GCN_circulars,Konus-Wind Det
Swift table
GRB_name GRB250424A
t_trigger 6:52:28.510 UTC
ra 217.5000°
decl -35.0252°
pos_error 8.15e-05°
redshift 0.3100
GCN 40224 table
GRB_name GRB250424A
GCN_number 40224
Detection_method Swift Det
t_trigger 6:52:28.510 UTC
ra 217.5130°
decl -35.0220°
Circular_text TITLE: GCN CIRCULAR NUMBER: 40224 SUBJECT: GRB 250424A: Swift detection of a burst with an optical counterpart DATE: 25/04/24 07:12:30 GMT FROM: K.L. Page at U Leicester S. B. Cenko (GSFC), V. D'Elia (SSDC & INAF-OAR), J. J. DeLaunay (PSU), R. Gupta (NASA GSFC), A. Melandri (INAF-OAR), K. L. Page (U Leicester) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 06:52:28.51 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250424A (trigger=1306404). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 217.513, -35.022 which is RA(J2000) = 14h 30m 03s Dec(J2000) = -35d 01' 19" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 30 sec. The peak count rate was ~25000 counts/sec (15-350 keV), at ~15 sec before the trigger. The XRT began observing the field at 06:56:39.3 UT, 250.9 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 217.50010, -35.02493 which is equivalent to: RA(J2000) = 14h 30m 00.03s Dec(J2000) = -35d 01' 29.7" with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 39 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 does not constrain the column density. UVOT took a finding chart exposure of 150 seconds with the White filter starting 254 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 14:29:60.00 = 217.49998 DEC(J2000) = -35:01:30.6 = -35.02518 with a 90%-confidence error radius of about 0.63 arc sec. This position is 1 arc sec. from the center of the XRT error circle. The estimated magnitude is 18.80 with a 1-sigma error of about 0.15. No correction has been made for the expected extinction corresponding to E(B-V) of 0.064. Burst Advocate for this burst is S. B. Cenko (brad.cenko AT nasa.gov). 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 40225 table
GRB_name GRB250424A
GCN_number 40225
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40225 SUBJECT: GRB 250424A: REM optical/NIR afterglow detection DATE: 25/04/24 08:19:08 GMT FROM: Riccardo Brivio at INAF-OAB R. Brivio (INAF-OAB), A. Melandri (INAF-OAR), M. Ferro, P. D'Avanzo, S. Covino, G. Tagliaferri, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of GRB 250424A detected by Swift/BAT (Cenko et al., GCN 40224) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, and K bands, started on 2025 April 24 at 06:54:31 UT (i.e. 123 s after the burst). From preliminary photometry, we detect the optical/NIR counterpart (Francile et al., 40222) at the Swift/UVOT position (Cenko et al., GCN 40224) with the following magnitudes: r = 17.7 +/- 0.1 (AB; calibrated against the SkyMappercatalogue), at a mid-time of 205 s after the trigger, H = 14.5 +/- 0.2 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 164 s after the trigger.
GCN 40226 table
GRB_name GRB250424A
GCN_number 40226
Detection_method Swift-BAT Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 40226 SUBJECT: GRB 250424A: DDOTI Afterglow Detection DATE: 25/04/24 08:30:40 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma Rosa L. Becerra (U Roma), Sahil Atri (U Roma), Alan M. Watson (UNAM), Eleonora Troja (U Roma), Camila Angulo Valdez (UNAM), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM) and Margarita Pereyra (UNAM) report: We observed the field of the GRB 250424A detected by Swift/BAT (Cenko et al., GCN Circ. 40136) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) on the night of 2025-04-24 UTC from 07:23 UTC to 7:45 UTC (from T+30.6 h to T+53.5 min after the trigger) and obtained a total exposure of 20 minutes. Comparing our observations to the USNO-B1 and Pan-STARRS PS1 DR2 catalogues, we detect a source consistent with the UVOT position (Cenko et al., GCN Circ. 40136) and the previous optical detections (Francile et al., GCN Circ. 40222, Brivio et al., GCN Circ. 40225), with an AB magnitude of: w = 19.4 +/- 0.1 Further observations and analysis are ongoing. This value is not corrected for the Galactic extinction. We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir.
GCN 40227 table
GRB_name GRB250424A
GCN_number 40227
Detection_method Swift-UVOT Det
ra 217.4999°
decl -35.0252°
Circular_text TITLE: GCN CIRCULAR NUMBER: 40227 SUBJECT: GRB 250424A: likely host galaxy DATE: 25/04/24 08:54:58 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia (ULL), and A. López-Oramas (IAC and ULL) We report on the likely host galaxy of the Swift/BAT GRB 250424A (Cenko et al., GCN circ. 40224), with Swift/XRT and Swift/UVOT detections (Cenko et al., GCN circ. 40224) and detections in the optical by Global MASTER-net (Francile et al. GCN circ. 40222) and DDOTI (Becerra et al., GCN circ. 40226) and in the optical and near-IR by REM (Brivio et al., GCN circ. 40225). A catalogued Legacy Surveys DR10 (LS DR10) galaxy (RA, Dec = 217.4999, -35.0252) is visible at the position of the optical and near-IR counterpart of GRB 250424A, with magnitudes in the LS DR10 catalog of g=22.60, r=21.98, i=22.05, and z=21.70. This galaxy is located at about 0.3" from the Swift/UVOT position and 0.2" from the Global MASTER-net position. We propose that this galaxy is the host of GRB 250424A.
GCN 40229 table
GRB_name GRB250424A
GCN_number 40229
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40229 SUBJECT: GRB 250424A: BlackGEM optical afterglow detection DATE: 25/04/24 09:43:29 GMT FROM: Simon de Wet at University of Cape Town S. de Wet (DTU), P.J. Groot (Radboud/UCT/SAAO) and P.M. Vreeswijk (Radboud) report on behalf of the BlackGEM consortium: The BlackGEM Unit Telescope 4 (BG4) located at ESO La Silla, Chile, responded automatically to the Swift trigger on GRB 250424A (Cenko et al., GCN 40224) and obtained a repeating series of 60 s exposures in the q,u,g,r,i,z bands. The first exposure started 264 s after the trigger time at 06:56:53 UT on 2025 April 24. A total of 26 exposures were obtained. We detect the optical afterglow with the following AB magnitudes: q = 18.30 +/- 0.03 at 06:57:24 UT u = 19.33 +/- 0.18 at 06:58:47 UT g = 18.98 +/- 0.05 at 07:01:32 UT r = 18.58 +/- 0.04 at 07:04:17 UT i = 18.26 +/- 0.04 at 07:07:02 UT z = 18.22 +/- 0.10 at 07:09:46 UT BlackGEM is an array of wide-field telescopes designed, built and operated by a consortium consisting of Radboud University, the Netherlands Research School for Astronomy NOVA, KU Leuven, the University of Manchester, Tel Aviv University, the Weizmann Institute, the Hebrew University of Jerusalem, the University of Potsdam, Texas Tech University, the University of California at Davis, the Danish Technical University and the Armagh Observatory and Planetarium.
GCN 40230 table
GRB_name GRB250424A
GCN_number 40230
Detection_method Swift-BAT Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 40230 SUBJECT: GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart DATE: 25/04/24 10:48:17 GMT FROM: J.-G. Ducoin at CPPM Jean-Grégoire Ducoin (CPPM), Benjamin Schneider (LAM), Ramandeep Gill (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA/IJCLAB), Jean-Luc Atteia (IRAP), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM) and Antonio de Ugarte Postigo (LAM) report: We imaged the field of Swift/BAT GRB 250424A (Cenko et al., GCN Circ. 40224) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We started observing at 2025-04-24T08:39:07 UTC (1.78h after the trigger). The data were coadded with the COLIBRÍ pipeline and analyzed in STDWeb/STDPipe (Karpov 2025), with photometric calibration against SkyMapper DR4. Our photometry is in the AB system and is not corrected for Galactic extinction. In our first 780 seconds of exposure, At the position of the optical counterpart (Francile et al. GCN Circ. 40222; Cenko et al. GCN Circ. 40224; Brivio et al. GCN Circ. 40225; Becerra et al. GCN Circ. 40226; Saccardi et al. GCN Circ. 40228; de Wet et al. GCN Circ. 40229), we detect a source with i = 18.93 +/- 0.05 Further observations and analysis are ongoing. We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir.
GCN 40231 table
GRB_name GRB250424A
GCN_number 40231
Detection_method AstroSat CZTI
Circular_text TITLE: GCN CIRCULAR NUMBER: 40231 SUBJECT: GRB 250424A: AstroSat CZTI detection of a bright long burst DATE: 25/04/24 11:37:06 GMT FROM: Gaurav Waratkar at IIT Bombay Harsha K. H. (IUCAA), M. Tembhurnikar (IUCAA), G. Waratkar (IITB), 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 ML pipeline (Abraham et al., 2021, MNRAS, 504, 3084) and the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a bright long-duration GRB 250424A which was also detected by Swift/BAT (Cenko et. al., GCN Circ. 40224), and Calet/CGBM (Trigger No. 1429512582). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-04-24 06:52:13.50 UTC. The measured peak count rate associated with the burst is 332.3 (+35.7 -27.5) counts/s above the background in the combined data of two quadrants (out of four), with a total of 2298 (+184 -190) counts. The local mean background count rate was 157.4 (+2.7 -3.0) counts/s. Using cumulative rates, we measure a T90 of 9.2 (+1.5 -1.0) s. In the preliminary analysis, we find 665 Compton events associated with this event. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-04-24 06:52:12.48 UTC. The measured peak count rate associated with the burst is 1364 (+88, -94) counts/s above the background in the combined data of all quadrants, with a total of 8511 (+491, -536) counts. The local mean background count rate was 1507 (+7, -8) counts/s. We measure a T90 of 14 (+1, -3) 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 40232 table
GRB_name GRB250424A
GCN_number 40232
Detection_method Swift-XRT Det
ra 217.4992°
decl -35.0250°
Circular_text TITLE: GCN CIRCULAR NUMBER: 40232 SUBJECT: GRB 250424A: Enhanced Swift-XRT position DATE: 25/04/24 12:21:10 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 3429 s of XRT Photon Counting mode data and 5 UVOT images for GRB 250424A, 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 = 217.49920, -35.02504 which is equivalent to: RA (J2000): 14h 29m 59.81s Dec (J2000): -35d 01' 30.2" 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 40233 table
GRB_name GRB250424A
GCN_number 40233
Detection_method Swift-XRT Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 40233 SUBJECT: GRB 250424A: Swift-XRT refined Analysis DATE: 25/04/24 13:59:17 GMT FROM: Phil Evans at U of Leicester C. Salvaggio (INAF-OAB), M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU), M. A. Williams (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.9 ks of XRT data for GRB 250424A, from 259 s to 18.9 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=0.20 (+0.12, -0.13). At T+2382 s the decay steepens to an alpha of 0.53 (+0.16, -0.11) before breaking again at T+17.4 ks to a final decay with index alpha=4.5 (+3.5, -2.8). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.05 (+/-0.11). The best-fitting absorption column is 1.04 (+0.11, -0.10) x 10^22 cm^-2, in excess of the Galactic value of 6.4 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 4.9 x 10^-11 (9.6 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.04 (+0.11, -0.10) x 10^22 cm^-2 Galactic foreground: 6.4 x 10^20 cm^-2 Excess significance: 15.7 sigma Photon index: 2.05 (+/-0.11) If the light curve continues to decay with a power-law decay index of 4.5, the count rate at T+24 hours will be 5.3 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.6 x 10^-14 (5.1 x 10^-14) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01306404. This circular is an official product of the Swift-XRT team.
GCN 40240 table
GRB_name GRB250424A
GCN_number 40240
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40240 SUBJECT: GRB 250424A: Kilonova-Catcher optical afterglow detection DATE: 25/04/24 18:25:31 GMT FROM: Damien Turpin at CEA-Saclay D. Turpin (CEA-Saclay/Irfu), R. Hellot, P. Jaquiery, M. Freeberg (KNC), C. Andrade(UMN), S. Antier (OCA), M. Coughlin (UMN),S. Karpov (FZU), I. Tosta e Melo (UniCT-DFA), P. Hello (IJCLAB), P-A Duverne (APC), T. Pradier (Unistra/IPHC), N. Guessoum (AUS), M. Pillas (ULiege) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 250424A (Cenko et al., GCN 40224) detected by Swift/BAT with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the iT30 telescope at the Siding Spring Observatory, a Celestron C14 telescope at Beverly Begg Observatory (New Zealand) and a CDK17 telescope located at AITP San Pedro Chile Observatory starting from TGRB+1.3hr. In our stacked frames, subtracted from the Legacy Survey DR10 template image, we detect the optical afterglow at the position reported by Swift/UVOT (Cenko et al., GCN 40224), REM (Brivio et al., GCN 40225), DDOTI (Becerra et al., GCN 40226), VLT/X-Shooter (Saccardi et al., GCN 40228), BlackGEM (de Wet et al., GCN 40229)and COLIBRI (Ducoin et al., GCN 40230). We report some of our detections in the table below: +---------------+-----------+-----------+----------------+------------+ | Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument | +===============+===========+===========+================+============+ | 1.3 | 1 x 300s | r (AB) | 19.34 +/- 0.09 | CDK17-AITP | | 4.0 | 20 x 120s | r (AB) | 19.74 +/- 0.07 | C14-BBO | | 6.8 | 17 x 180s | Rc (Vega) | 19.95 +/- 0.09 | iT30 | +---------------+-----------+-----------+----------------+------------+ All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained in Johnson Cousin filters were calibrated using the Gaia DR3 Synphot catalog while the sloan images were calibrated using the SkyMapper DR4 catalog. We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/).
GCN 40241 table
GRB_name GRB250424A
GCN_number 40241
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40241 SUBJECT: GRB 250424A: Skynet Optical Observations DATE: 25/04/24 20:17:01 GMT FROM: Dylan Dutton at UNC Chapel Hill Dylan Dutton, Daniel Reichart, Joshua Haislip, Vladimir Kouprianov, and Donovan Schlekat report on behalf of the Skynet Robotic Telescope Network at the University of North Carolina at Chapel Hill. We observed the field of GRB 250424A detected by Swift (Cenko, GCN 40224) with one of Skynet's PROMPT telescopes located at the Cerro Tololo Inter-American Observatory. We detect the optical afterglow (Francile et al., GCN 40222; Cenko et al., GCN 40224; Brivio et al., GCN 40225; Becerra et al., GCN 40226; Saccardi et al., GCN 40228; de Wet et al., GCN 40229; Ducoin et al., GCN 40230; and D. Turpin et al., GCN 40240) in the B, V, and R bands and report the initial photometry below. Exposure lengths were calculated using our automated exposure length scaling model. Tmid - T0 (s)| Telescope | Filter | Exposure (s) | Mag | Mag Error ------------------------------------------------------------------ 1224 | PROMPT-5 | B | 264 | 19.610 | 0.054 1467 | PROMPT-5 | V | 216 | 19.253 | 0.065 1649 | PROMPT-5 | R | 144 | 18.500 | 0.051 Our images have been calibrated using stars from the APASS catalog. Magnitudes were not corrected for dust extinction.
GCN 40243 table
GRB_name GRB250424A
GCN_number 40243
Detection_method Konus-Wind Det
t_trigger 6:52:13.431 UTC
redshift 0.3100
Circular_text TITLE: GCN CIRCULAR NUMBER: 40243 SUBJECT: Konus-Wind detection of GRB 250424A DATE: 25/04/24 22:12:37 GMT FROM: Anna Ridnaia at Ioffe Institute A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB GRB 250424A (Swift-BAT detection: Cenko et al., GCN 40224; AstroSat CZTI detection: Harsha et al., GCN 40231) triggered Konus-Wind at T0=24733.431 s UT (06:52:13.431). The burst light curve shows a single pulse which starts at ~T0-17.9 s and has a total duration of ~40.5 s. The emission is seen up to ~2 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250424_T24733/ As observed by Konus-Wind, the burst had a fluence of 5.83(-0.16,+0.16)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+4.192 s, of 8.88(-0.94,+0.95)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+21.760 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.30(-0.06,+0.06), the high energy photon index beta = -2.87(-0.15,+0.11), the peak energy Ep = 104(-3,+3) keV (chi2 = 94/82 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+5.376 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.09(-0.06,+0.07), the high energy photon index beta = -2.91(-0.15,+0.12), the peak energy Ep = 129(-4,+5) keV (chi2 = 72/66 dof). Assuming the redshift z=0.310 (Saccardi et al., GCN 40228) and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the following rest-frame parameters: the isotropic energy release E_iso is 1.49(-0.04,+0.04)x10^52 erg, the peak luminosity L_iso is 2.97(-0.31,+0.32)x10^51 erg/s, the rest-frame peak energy of the time-averaged spectrum Ep,i,z is 137(-4,+4) keV and the spectrum near the maximum count rate Ep,p,z is 169(-5,+7) keV. With the obtained estimates, GRB 250424A is inside 68% prediction bands for both 'Amati' and 'Yonetoku' relations derived for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB250424_T24733/GRB250424A_rest_frame.pdf All the quoted errors are at the 68% confidence level. All the quoted values are preliminary.
GCN 40244 table
GRB_name GRB250424A
GCN_number 40244
Detection_method Swift-UVOT Det
ra 217.5000°
decl -35.0252°
Circular_text TITLE: GCN CIRCULAR NUMBER: 40244 SUBJECT: GRB 250424A: Swift/UVOT Detection DATE: 25/04/24 23:09:21 GMT FROM: Mike Siegel at PSU/Swift MOC M.H. Siegel (PSU) and S. B. Cenko (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250424A 254 s after the BAT trigger (Cenko et al., GCN Circ. 40224). A source consistent with the XRT position (Evans et al., GCN Circ. 40232) and the optical transient (Francile et al., GCN Circ. 40222, Brivio et al., GCN Circ. 40225; Becerra et al., GCN Circ. 40226; de Wet et al., GCN Circ. 40229; Ducoin et al., GCN Circ. 40230; Turpin et al., GCN Circ. 40240; Dutton et al., GCN Circ. 40241) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 14:29:60.00 = 217.49998 (deg.) Dec (J2000) = -35:01:30.6 = -35.02518 (deg.) with an estimated uncertainty of 0.47 arc sec. (radius, 90% confidence). 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 254 404 147 18.96 +/- 0.07 v 411 1918 175 >18.7 b 509 1844 136 19.97 +/- 0.26 u 485 1647 136 19.15 +/- 0.20 w1 460 1795 156 19.44 +/- 0.31 m2 436 1598 97 >18.4 w2 559 1894 156 >19.9 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.064 in the direction of the burst (Schlegel et al. 1998).
GCN 40249 table
GRB_name GRB250424A
GCN_number 40249
Detection_method Swift-BAT Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 40249 SUBJECT: GRB 250424A: EIRSAT-1 GMOD Detection DATE: 25/04/25 20:36:05 GMT FROM: Caimin McKenna at University College Dublin C. McKenna, P. McDermott, D. Murphy, C. de Barra, A. Ulyanov, G. Finneran, G. Corcoran, L. Cotter, A. Empey, J. Fisher, F. Gibson Kiely, J. Thompson, D. McKeown, A. Martin-Carrillo, L. Hanlon, S. McBreen, on behalf of the EIRSAT-1 team: EIRSAT-1 reports the detection of the long gamma-ray burst GRB 250424A by the Gamma-ray Module (GMOD) instrument, which was also detected by Swift-BAT (GCN [40224](https://gcn.nasa.gov/circulars/40224)), Calet/CGBM (Trigger No. 1429512582), AstroSat CZTI (GCN [40231](https://gcn.nasa.gov/circulars/40231)), and Konus-Wind (GCN [40243](https://gcn.nasa.gov/circulars/40243)). The GMOD detection was made starting at 2025-04-24 06:52:12.6 UTC. The GMOD light curve for GRB 250424A, with 1.2s binning, shows a long, smooth, single pulse, consistent with other observations. The spacecraft location at time of detection was 23.407 S, 123.088 W and an altitude of 402.9 km. The light curve for this event as measured by GMOD can be found here: https://grb.eirsat1.ie/250424A/250424A_LC_onboard_preliminary.png EIRSAT-1 is Ireland’s first satellite (Doyle et al. Proceedings of the 4th SSEA, 2022). It is a 2U CubeSat and carries onboard a number of experiments including the Gamma-Ray Module (GMOD), a novel, compact, gamma-ray detector (Murphy et al, Experimental Astronomy, 53, 961–990, 2022). GMOD consists of a 25 mm × 25 mm × 40 mm Cerium Bromide scintillator coupled to SiPMs and is designed to detect gamma-ray bursts in the ~ 60 keV - 1.5 MeV range. EIRSAT-1 was developed in University College Dublin with support from ESA’s Fly Your Satellite! programme and was launched on 1st December 2023.
GCN 40250 table
GRB_name GRB250424A
GCN_number 40250
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40250 SUBJECT: GRB 250424A: WINTER J-band detection DATE: 25/04/25 20:51:47 GMT FROM: Benjamin Schneider at MIT Benjamin Schneider (LAM), Geoffrey Mo (MIT), Tomas Ahumada (Caltech), Viraj Karambelkar (Caltech), Danielle Frostig (CfA), Robert Stein (UMD), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the GRB 250424A (Cenko et al., GCN 40224; Harsha et al., GCN 40231; Ridnaia et al., GCN 40243) in the near-infrared with the Palomar 1-m telescope, equipped with the 1-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024). Observations started on 2025-04-24 at 07:33:24 UT (40.92 min after the Swift trigger) and consisted of 15 exposures of 120 s in the J-band. In the stacked image, we detect the optical counterpart reported by Cenko et al., GCN 40224; Brivio et al., GCN 40225; Becerra et al., GCN 40226; Saccardi et al., GCN 40228; de Wet et al., GCN 40229; Ducoin et al., GCN 40230; Turpin et al., GCN 40240, Dutton et al., GCN 40241; Siegel et al., GCN 40244. The preliminary AB magnitude derived for that source is: J = 18.1 +/- 0.2 The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565). The photometric calibration was performed using nearby stars from the 2MASS catalog and the magnitude is not corrected for Galactic extinction. 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 Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research.
GCN 40251 table
GRB_name GRB250424A
GCN_number 40251
Detection_method Swift Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 40251 SUBJECT: GRB 250424A: PRIME near-infrared detection DATE: 25/04/26 00:30:37 GMT FROM: O. Guiffreda at UMD M. Elkabir (U Rome), O. Guiffreda (UMD), J. Durbak (UMD), N. Passaleva (U Rome), E. Troja (U Rome), A. S. Kutyrev (NASA/GSFC), S. B. Cenko (NASA/GSFC) Following the Swift BAT detection (GCN 40224), we observed the transient field in J and H filters with PRIME ~12 hours after the initial Swift detection. At the position of the optical counterpart reported by Swift UVOT (GCN 40244), we detect an uncatalogued source in both J and H band. Using nearby VISTA Hemispherical Survey (VHS) for preliminary calibration we derive the following magnitudes and limits, not corrected for Galactic extinction: |Filter | Mag(AB) | |-------|---------------| |J | 18.8 +/- 0.06 | |H | 19.2 +/- 0.05 | PRIME is a 1.8m telescope with 1.56 square degree FOV (0.5 arcsec/pixel) located in Sutherland, South Africa at the South African Astronomical Observatory (SAAO) (Kutyrev et al. 2023, Yama et al. 2023, Durbak et al. 2024). We thank the Osaka University observers at PRIME and the staff at SAAO for their support with these observations.
GCN 40255 table
GRB_name GRB250424A
GCN_number 40255
Detection_method Swift-BAT Det
ra 217.5280°
decl -35.0250°
Circular_text TITLE: GCN CIRCULAR NUMBER: 40255 SUBJECT: GRB 250424A: Swift-BAT refined analysis DATE: 25/04/26 22:48:38 GMT FROM: Rahul Gupta at NASA GSFC C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), 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 250424A (trigger #1306404) (Cenko, et al., GCN Circ. 40224). The BAT ground-calculated position is RA, Dec = 217.528, -35.025 deg which is RA(J2000) = 14h 30m 06.7s Dec(J2000) = -35d 01' 30.6" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 39%. The mask-weighted BAT light curve of the burst (began during a slew) shows a faint precursor emission followed by a bright main pulse. T90 (15-350 keV) is 19.03 +- 1.06 sec (estimated error including systematics), with the T90 starting at T0-20.76 sec due to the slew-delayed T0. The time-averaged spectrum from T-38.75 to T+262.67 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.54 +- 0.13, and Epeak of 106.5 +- 33.7 keV (chi squared 47.05 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 3.2 +- 0.1 x 10^-05 erg/cm2 and the 1-sec peak flux measured from T-15.38 sec in the 15-150 keV band is 47.0 +- 1.3 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.79 +- 0.03 (chi squared 58.54 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/1306404
GCN 40263 table
GRB_name GRB250424A
GCN_number 40263
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40263 SUBJECT: GRB 250424A: LCO optical observation DATE: 25/04/27 13:05:34 GMT FROM: ankur ghosh at CAPP, University of Johannesburg Ankur Ghosh, Soebur Razzaque (CAPP, University of Johannesburg), Alexander Moskvitin, Yulia Sotnikova (SAO RAS), Naveen Dukiya (ARIES), Rahul Gupta (NASA GSFC) on behalf of a larger collaboration. We observed the field of the GRB 250424A triggered by Swift (Cenko et al., GCN 40224), AstroSat CZTI (Harsha et al., GCN 40231), Konus-Wind (Ridnaia et al., GCN 40243) and EIRSAT-1 GMOD (McKenna et al., GCN 40249)in B, V, r filters of the 1-meter Sinistro at the Las Cumbres Observatory Global Telescope (LCOGT) node located at Cerro Tololo Interamerican Observatory, Chille. The 1-m Sinistro telescope is equipped with a 4K x 4K CCD (FOV: 26 x 26 arcmin, scale: 0.39 arcsec/pixel). Observations began on , starting from 2025-04-24, 17.8 hours after the GRB trigger. Observation for later epochs are still going on. We clearly detect the optical transient (OT) reported by GCNs (Francile et al., GCN 40222; Cenko et al., GCN 40224; Brivio et al., GCN 40225; Becerra et al., GCN 40226; Saccardi et al., GCN 40228; de Wet et al., GCN 40229; Ducoin et al., GCN 40230; and D. Turpin et al., GCN 40240, Dutton et al., GCN Circ. 40241, Siegel et al., GCN 40244) in our B, V, r band images. ------------------------------------------------------------------------------------------------------ |Date| Start JD |t-T0 (hours)| |Exp (sec)| |Filter| |Magnitude| ------------------------------------------------------------------------------------------------------ 2025-04-25 2460790.52730 17.78 1 x 900 V V = 21.31+/- 0.08 2025-04-25 2460790.78105 23.87 1 x 900 B B = 22.07+/- 0.08 2025-04-25 2460790.79155 24.12 1 x 900 r r = 21.04 +/- 0.05 ------------------------------------------------------------------------------------------------------ The field was calibrated against nearby APASS stars, with magnitudes converted using Lupton (2005) equations, and has not been corrected for Galactic extinction.
GCN 40298 table
GRB_name GRB250424A
GCN_number 40298
Detection_method CALET
Circular_text TITLE: GCN CIRCULAR NUMBER: 40298 SUBJECT: GRB 250424A: CALET Gamma-Ray Burst Monitor detection DATE: 25/05/01 03:19:12 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University GRB 250424A: CALET Gamma-Ray Burst Monitor detection S. Nakahira (JAXA), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The long GRB 250424A (Swift detection: Cenko et al., GCN Circ. 40224; Swift-BAT refined analysis: Markwardt et al., GCN Circ. 40255; AstroSat CZTI detection: Harsha et al., GCN Circ. 40231; Konus-Wind detection: Ridnaia et al., GCN Circ. 40243; EIRSAT-1 GMOD Detection: McKenna et al., GCN Circ. 40249; SVOM/GRM observation: Jin-Peng et al., GCN Circ. 40252) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 06:52:04.323 UTC on 24 April 2025 (https://cgbm.calet.jp/cgbm_trigger/flight/1429512582/index.html). The burst signal was seen by all CGBM detectors. The burst light curve shows a single pulse that starts at T+2.5 sec, peaks at T+8.4 sec, and ends at T+27.5 sec. The T90 and T50 durations measured by the SGM data are 13.5 +/- 0.8 sec and 4.6 +/- 0.2 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1429512582/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at Waseda University.