GRB240225B

This page lists all entries on GRB240225B in GRBweb

Summary IPN GCN 35796 GCN 35797 GCN 35798 GCN 35805 GCN 35810 GCN 35811 GCN 35812 GCN 35819 GCN 35820 GCN 35824 GCN 35826 GCN 35828 GCN 35829 GCN 35830 GCN 35832 GCN 35835 GCN 35836 GCN 35839 GCN 35848

Summary table
Variable Value Source
T0 20:12:07.251 UTC GCN_circulars,Konus-Wind Det
ra 128.4542° IPN
decl 27.4833° IPN
pos_error 1.33e-01° IPN
redshift 0.9460 GCN_circulars,Konus-Wind Det
GBM_located False
mjd 60365.841750590276 GCN_circulars,Konus-Wind Det
IPN table
GRB_name GRB240225B
ra 128.4542°
decl 27.4833°
pos_error 1.33e-01°
redshift 0.9460
GCN 35796 table
GRB_name GRB240225B
GCN_number 35796
Detection_method MAXI Det
t_trigger 20:15:46 UTC
ra 128.4580°
decl 27.4870°
Circular_text TITLE: GCN CIRCULAR NUMBER: 35796 SUBJECT: GRB 240225B: MAXI/GSC detection DATE: 24/02/26 03:37:58 GMT FROM: Yuta Kawakubo at Louisiana State University M. Nakajima, H. Negoro (Nihon U.), Y. Kawakubo (LSU), K. Kobayashi, M. Tanaka, Y. Soejima, Y. Kudo (Nihon U.), T. Mihara, T. Kawamuro, S. Yamada, S. Wang, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, H. Hiramatsu, H. Nishikawa, A. Yoshida (AGU), Y. Tsuboi, S. Urabe, S. Nawa, N. Nemoto, E.Goto (Chuo U.), M. Shidatsu (Ehime U.), I. Takahashi, M. Niwano, S. Sato, N. Higuchi, Y. Yatsu (Tokyo Tech), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, T. Kurihara (JAXA), Y. Ueda, K. Setoguchi, T. Yoshitake, Y. Nakatani, Y. Okada (Kyoto U.), M. Yamauchi, Y. Hagiwara, Y. Umeki, Y. Otsuki (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (NAOC), W. Iwakiri (Chiba U.) report on behalf of the MAXI team: The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 20:15:46 UT on February 25, 2024. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (128.458 deg, 27.487 deg) = (08 33 49, +27 29 13) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.13 deg and 0.11 deg, respectively. The roll angle of long axis from the north direction is 67.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 874 +- 86 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (R.A., Dec) = (127.906, 26.756) deg = (08 31 37, +26 45 21) (J2000) (R.A., Dec) = (128.157, 26.654) deg = (08 32 37, +26 39 14) (J2000) (R.A., Dec) = (128.895, 28.075) deg = (08 35 34, +28 04 29) (J2000) (R.A., Dec) = (128.642, 28.179) deg = (08 34 34, +28 10 44) (J2000) There was no significant excess flux in the previous transit at 18:43 UT and in the next transit at 21:48 UT with an upper limit of 20 mCrab for each.
GCN 35797 table
GRB_name GRB240225B
GCN_number 35797
Detection_method Swift Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 35797 SUBJECT: GRB 240225B: Tiled Swift observations DATE: 24/02/26 04:13:59 GMT FROM: Phil Evans at U of Leicester P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a series of observations, tiled on the sky, of the MAXI GRB 240225B. Automated analysis of the XRT data will be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00124 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. The probability of finding serendipitous sources, unrelated to the MAXI event is high: any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team.
GCN 35798 table
GRB_name GRB240225B
GCN_number 35798
Detection_method AstroSat CZTI
Circular_text TITLE: GCN CIRCULAR NUMBER: 35798 SUBJECT: GRB 240225B: AstroSat CZTI detection DATE: 24/02/26 09:04:31 GMT FROM: Gaurav Waratkar at IIT Bombay J. Joshi (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 CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 240225B which was also detected by MAXI/GSC (M. Nakajima et al., GCN Circ. 35796). Inspection of INTEGRAL/SPI-ACS data also showed the detection of the burst. We note that the INTEGRAL/SPI-ACS detection time is consistent with our time which is about 3 min offset from the time reported in the MAXI/GSC detection (GCN 35796). 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 2024-02-25 20:12:08.50 UTC. The measured peak count rate associated with the burst is 185 (+40, -22) counts/s above the background in the combined data of all quadrants, with a total of 1617 (+331, -224) counts. The local mean background count rate was 346 (+1, -5) counts/s. Using cumulative rates, we measure a T90 of 19 (+10, -5) s. The source 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 2024-02-25 20:12:01.80 UTC. The measured peak count rate associated with the burst is 570 (+72, -69) counts/s above the background in the combined data of all quadrants, with a total of 5119 (+490, -666) counts. The local mean background count rate was 1539 (+7, -6) counts/s. We measure a T90 of 23 (+3, -4) 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 35805 table
GRB_name GRB240225B
GCN_number 35805
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 35805 SUBJECT: GRB 240225B: GOTO detection of a candidate optical afterglow DATE: 24/02/26 20:45:40 GMT FROM: Ben Gompertz at U of Birmingham B. P. Gompertz, R. L. C. Starling, M. Kennedy, G. Ramsay, D. B. Malesani, B. Godson, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, A. Kumar, D. O'Neill, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Pall'e and D. Pollacco report on behalf of the GOTO collaboration: We report on observations of the MAXI-discovered GRB 240225B (Nakajima et al, GCN 35796) with the Gravitational-wave Optical Transient Observer (GOTO, Steeghs et al. 2022). GOTO-North serendipitously tiled the MAXI localisation at 21:45:51 UT on 2024-02-25, 1.5 hours after trigger. The observation consisted of 4x45 s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using recent survey observations of the same pointings. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogues. Human vetting was carried out in real time on any candidates that passed the above checks. We identify a new optical source (GOTO24tz/AT2024dgu) with a magnitude of L = 17.12 +/- 0.04 at RA 08:33:26.67, Dec +27:04:32.71 (J2000). The optical source is close to the probable X-ray afterglow identified in tiled Swift observations (Evans, GCN 35797), offset by 7.2”, whilst formally outside the 4.4” 90% confidence contour of the X-ray localisation. This source was not present in the previous GOTO epoch, taken one day prior at 22:05:36 UT on 2024-02-24, to a limiting magnitude of L > 18.7. Given the tight pre-burst limit and close proximity with a new X-ray source, we propose this as a strong candidate afterglow of GRB 240225B. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC).
GCN 35810 table
GRB_name GRB240225B
GCN_number 35810
Detection_method Swift-XRT Other
ra 128.3629°
decl 27.0746°
Circular_text TITLE: GCN CIRCULAR NUMBER: 35810 SUBJECT: GRB 240225B: Swift-XRT observations DATE: 24/02/26 22:22:37 GMT FROM: Phil Evans at U of Leicester A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and P.A. Evans (U. Leicester) and A. A. Breeveld (UCL-MSSL) reports on behalf of the Swift-XRT and the Swift-UVOT team: Swift-XRT has performed follow-up observations of the MAXI-detected burst GRB 240225B in a series of observations tiled on the sky. The total exposure time is 1.8 ks, distributed over 7 tiles; the maximum exposure at a single sky location was 693 s. The data were collected between T0+29.1 ks and T0+30.9 ks, and are entirely in Photon Counting (PC) mode. Two uncatalogued X-ray sources are detected, of which one ("Source 1") is above the RASS 3-sigma upper limit at this position. The position of this source is RA, Dec=128.3629, +27.0746 which is equivalent to: RA (J2000): 08:33:27.11 Dec(J2000): +27:04:28.5 with an uncertainty of 4.4 arcsec (radius, 90% confidence). This position is 25.3 arcmin from the MAXI position. At the present time the light curve of Source 1 shows no signs of fading and we can not confirm this source as the GRB afterglow. The results of the full analysis of the tiled XRT observations are available at https://www.swift.ac.uk/xrt_products/TILED_GRB00124. Source 1 was out of the field of view for UVOT so we can't say anything about optical properties. This circular is an official product of the Swift team.
GCN 35811 table
GRB_name GRB240225B
GCN_number 35811
Detection_method CALET
Circular_text TITLE: GCN CIRCULAR NUMBER: 35811 SUBJECT: GRB 240225B: CALET Gamma-Ray Burst Monitor detection DATE: 24/02/26 22:35:56 GMT FROM: Yuta Kawakubo at Louisiana State University Y. Kawakubo (LSU), A. Yoshida, T. Sakamoto, S. Sugita (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), 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 240225B (MAXI/GSC detection: Nakajima et al., GCN Circ. 35796; AstroSat CZTI detection: Joshi et al., 35798) was detected in the ground analysis of the CALET Gamma-ray Burst Monitor (CGBM) data around 20:12:08.50 on 25 February 2024 (referenced to the AstroSat detection: GCN Circ. 35798) (http://cgbm.calet.jp/cgbm_trigger/flight/1392926875/index.html). The main episode that AstroSat CZTI detected was seen by all CGBM detectors. Also, a hint of emission that MAXI/GSC detected was seen in the HXM data around T+230 s. The burst light curve of the main episode shows a multi-peaked structure that starts at T-7.6 sec, and ends at T+31.1 sec. The T90 and T50 durations measured by the SGM data are 33.0 +/- 0.9 sec and 17.1 +/- 1.3 sec (40-1000 keV), respectively. The ground-processed light curve is available at http://cgbm.calet.jp/cgbm_trigger/ground/1392926875/index.html The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at Waseda University.
GCN 35812 table
GRB_name GRB240225B
GCN_number 35812
Detection_method Optical
ra 128.3617°
decl 27.0758°
Circular_text TITLE: GCN CIRCULAR NUMBER: 35812 SUBJECT: GRB 240225B: Nanshan/HMT optical afterglow detection DATE: 24/02/26 23:18:55 GMT FROM: Dong Xu at NAOC/CAS X. Liu,, J. An, S.Y. Fu, S.Q. Jiang, Z.P. Zhu, T.H. Lu, D. Xu (NAOC), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report: We observed the field of GRB 240225B detected by MAXI (Nakajima et al., GCN 35796) and AstroSat (Joshi et al., GCN 35798) using the HMT-0.5m telescope with big FOV (~1 deg^2) located at Nanshan, Xinjiang, China. Photometry was carried out twice in the same night without any filter.. A slowly decaying uncatalogued optical transient is detected at coordinates R.A. = 08:33:26.80 (J2000) Dec. = +27:04:32.77 (J2000) with an uncertainty of radius ~ 0.3 arcsec, with r ~ 18.9 +/- 0.1 mag (AB) at a median time of 18.90 hr post-burst, calibrated with the nearby PanSTAR field. This OT is positionally at the border of the error circle of Swift/XRT "Source 1" (D'Ai et al., GCN 35810), and is also consistent with and thus confirming the GOTO candidate (Gompertz et al., GCN 35805). We thus think the OT is the optical afterglow of GRB 240225B.
GCN 35819 table
GRB_name GRB240225B
GCN_number 35819
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 35819 SUBJECT: GRB 240225B: NOT optical observations DATE: 24/02/27 12:24:03 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University D. B. Malesani (DAWN/NBI and Radboud Univ.), B. P. Gompertz (Birmingham), Z.-P. Zhu, D. Xu (NAOC), L. Izzo (INAF/OACN and DARK/NBI), on behalf of a larger collaboration, and R. Forsberg (Lund), S. Bijavara Seshashayana (Malmo univ.), report: We observed the optical afterglow (Gompertz et al., GCN 35805; D'Ai et al., GCN 35810) of GRB 240225B (Nakajima et al., GCN 35796; Joshi et al., GCN 35798; Kawakubo et al., GCN 35811). We used the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations started on 2024 Feb 26.934 UT (1.09 days after the MAXI trigger time). In a single 300-s exposure in the r band, we measure r = 19.53 +- 0.03 (AB), calibrated against nearby Pan-STARRS stars. This confirms the decay of the GOTO candidate noted by Liu et al. (GCN 35812). Assuming an unbroken power law decay (F propto t^-alpha) between their observation and ours, the inferred decay slope is alpha = 1.8 +- 0.3, suggesting a faster decay then indicated in Liu et al. (GCN 35812).
GCN 35820 table
GRB_name GRB240225B
GCN_number 35820
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 35820 SUBJECT: GRB 240225B: Liverpool Telescope optical afterglow observations DATE: 24/02/27 16:49:48 GMT FROM: Jacob Wise at Liverpool John Moores University J. Wise, A. Bochenek, D. A. Perley (LJMU) report: We report observations the optical afterglow GOTO24tz/AT2024dgu (Gompertz et al, GCN 35805; D'Ai et al, GCN 35810; Xu, D., GCN 35812; Malesani et al, GCN 35819) associated with GRB 240225B (Nakajima et al, GCN 35796; Joshi et al, GCN 35798; Kawakubo et al, GCN 35811) using the IO:O optical camera on the 2-meter Liverpool Telescope. Observations commenced at 2024-02-27 00:20:06.433 UTC, approximately 28.1 hours after the burst. 2x75s exposures were taken using the SDSS g, r, i, and z filters, with Pan-STARRS foreground stars used for calibration. Conditions were generally favourable throughout. The transient was well detected in all 4 filters, with magnitudes listed in the following table. Times since burst for each filter were calculated using the strongest peak found with the AstroSat CsI anticoincidence (Veto) detector as reference (Joshi et al, GCN 35798). MJD Time since burst (hours) Filter Mag. (AB) 60367.01396 28.135 g 19.97 ± 0.12 60367.01624 28.189 r 19.51 ± 0.15 60367.01848 28.243 i 19.44 ± 0.10 60367.02073 28.297 z 19.28 ± 0.14 Magnitudes are not corrected for foreground extinction.
GCN 35824 table
GRB_name GRB240225B
GCN_number 35824
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 35824 SUBJECT: GRB 240225B: Liverpool Telescope afterglow observations DATE: 24/02/28 00:26:44 GMT FROM: Ben Gompertz at U of Birmingham B. P. Gompertz (U. Birmingham), D. B. Malesani (DAWN/NBI and Radboud Univ.) report: We observed the position of the optical afterglow (Gompertz et al., GCN 35805; Liu et al., GCN 35812; Malesani et al., GCN 35819; Wise et al., GCN 35820) of GRB 240225B (Nakajima et al., GCN 35796; Joshi et al., GCN 35798; Kawakubo et al., GCN 35811) with the IO:O camera on the 2m robotic Liverpool Telescope (LT). Observations began at 21:37:18 on 2024-02-27, 2.06 days after trigger, and consisted of 15x120 s exposures in the SDSS r filter. We detect the afterglow with an AB magnitude of r = 20.04 +/- 0.05, calibrated against nearby SDSS stars and not corrected for foreground extinction. Between this epoch and the initial detection by GOTO (Gompertz et al., GCN 35805), the afterglow is well described by a power-law decay with an index of 0.8, which is consistent with the magnitudes reported by NOT (Malesani et al., GCN 35819) and LT (Wise et al., GCN 35820), though under-predicts those reported by Nanshan/HMT (Liu et al., GCN 35812), potentially suggestive of flaring behaviour at the time of their observation. The steepening in the light curve noted in GCN 35819 may be thus due to local variability, rather than a break in the power-law evolution. We note the presence of a faint underlying source at the afterglow position in Legacy Survey archival imaging, which may be the host galaxy of GRB 240225B.
GCN 35826 table
GRB_name GRB240225B
GCN_number 35826
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 35826 SUBJECT: GRB 240225B: Mondy afterglow observations DATE: 24/02/28 07:44:44 GMT FROM: Alexei Pozanenko at IKI, Moscow N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP), S. Belkin (IKI, HSE) report on behalf of IKI-GRB-FuN: We observed the field of GRB 240225B (Nakajima et al., GCN 35796; Evans, GCN 35797, Joshi et al., GCN 35798; D'Ai et al., GCN 35810; Kawakubo et al., GCN 35811) with AZT-33IK telescope of Sayan observatory (Mondy) equipped with CMOS-photometer ANDOR NEO. We took 60x120 sec frames in the R-filter starting on 2024-02-26 (UT) 12:30:03. The optical afterglow (Gompertz et al., GCN 35805; Liu et al., GCN 35812; Malesani et al., GCN 35819; Wise et al., GCN 35820; Gompertz & Malesani, GCN 35824) is well detected in the stacked frame with a total exposure of 59x120 sec. Photometry of the optical afterglow is following: Date UT-start t-T0 Exp Filter OT Err UL FWHM (UT) (mid.) (nxT) (3sigma) (arcsec) 2024-02-27 13:01:23 1.71919 59x120 R 19.16 0.09 22.8 2.1 The magnitudes were calibrated using nearby USNO-B1.0 stars (R2 magnitudes).
GCN 35828 table
GRB_name GRB240225B
GCN_number 35828
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 35828 SUBJECT: GRB 240225B: SAO RAS optical observations DATE: 24/02/28 22:16:52 GMT FROM: Moskvitin Alexander at SAO RAS A. S. Moskvitin, O. I. Spiridonova (SAO RAS) report on behalf of the GRB follow-up team. We observed the field of GRB 240225B (Nakajima et al., GCN 35796; Evans, GCN 35797; Joshi et al., GCN 35798; D'Ai et al., GCN 35810; Kawakubo et al., GCN 35811) with the SAO RAS 1m telescope Zeiss-1000 equipped with CCD-photometer. We obtained 8 x 300 sec frames in the Rc band on Feb. 28, 18:20:36--19:11:22 UT (t_mid - T0 = 2.9307 days). The OT (Gompertz et al., GCN 35805; Liu et al., GCN 35812; Malesani et al., GCN 35819; Wise et al., GCN 35820; Gompertz & Malesani, GCN 35824; Pankov et al., GCN 35826) is clearly detected in our stacked frame with the brightness of R = 20.51 +/- 0.02. The photometry is based on nearby SDSS stars (magnitudes converted with Lupton 2005 equations).
GCN 35829 table
GRB_name GRB240225B
GCN_number 35829
Detection_method Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 35829 SUBJECT: GRB 240225B: WINTER near-IR observations and upper limits DATE: 24/02/29 01:10:22 GMT FROM: Geoffrey Mo at MIT Geoffrey Mo (MIT), Viraj Karambelkar (Caltech), Danielle Frostig (MIT), Robert Stein (Caltech), Nathan Lourie (MIT), Tomas Ahumada (Caltech), Robert Simcoe (MIT), Mansi Kasliwal (Caltech) report: We observed the field of GRB 240225B (Nakajima et al., GCN 35796; Evans, GCN 35797; Joshi et al., GCN 35798; D'Ai et al., GCN 35810; Kawakubo et al., GCN 35811) using the Palomar 1-m telescope equipped with the 1-square degree infrared WINTER camera (Lourie et al., 2020) in the Y and J bands. Observations began at 2024-02-28T05:55:09 UTC (~2.4 days after the GRB) and consisted of 8 x 120 s exposures in each filter. The images were processed using the WINTER data reduction pipeline (https://github.com/winter-telescope/mirar), with J-band image subtraction performed against reference images from the UKIRT Hemisphere Survey (Dye et al., 2017). We do not detect the GOTO-discovered counterpart (Gompertz et al., GCN 35805; Liu et al., GCN 35812; Malesani et al., GCN 35819; Wise et al., GCN 35820; Gompertz & Malesani, GCN 35824; Pankov et al., GCN 35826; Moskvitin et al., GCN 35828), setting the following upper limits (AB): Y = 18.3 mag and J = 18.8 mag.
GCN 35830 table
GRB_name GRB240225B
GCN_number 35830
Detection_method Swift Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 35830 SUBJECT: GRB 240225B: 3.6m DOT observation DATE: 24/02/29 06:15:59 GMT FROM: Amit Kumar Ror at ARIES Amit K. Ror, Shashi B. Pandey, Rahul Gupta, and Amar Aryan, Shivangi Pandey (ARIES) report: We observed the field of GRB 240225B detected by MAXI (Nakajima et al. 2024, GCN 35796), Swift (Evans 2024, GCN 35797), and AstroSat (Joshi et al. 2024, GCN 35798) using the 3.6m Devasthal Optical Telescope of ARIES Nainital. The observations were started on 2024-02-28 at 01:04:01.085 UT, i.e., 2.2 days after the MAXI trigger. We have taken multiple frames with a 60-second exposure time in the r, i, and z filters. We detected the OT at the position of the GOTO afterglow candidate reported by Gompertz et al. (2024, GCN 35805) in each observed image in the i and z bands and the stacked image of the r band, indicating a redder nature. The preliminary magnitude measurements are as follows: Date Start_UT T_start-T0 (days) Filter Exp time (s) Limiting magnitude ========================================================= 2024-02-28 01:04:01.085 2.2 i 60s 19.96 +/- 0.04 Our i-band observation, combined with the observation of Wise et al. (2024, GCN 35820), yielded a decay index of ~ 0.8 in the i-band. The magnitude quoted is not corrected for the host and Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the Pan-STARRS catalog. Our detection is consistent with Gompertz et al. 2024, GCN 35805; Liu et al. 2024, GCN 35812; Malesani et al. 2024, GCN 35819; Wise et al. 2024, GCN 35820; Gompertz et al. 2024, GCN 35824; Pankov et al. 2024, GCN 35826; Moskvitin et al. 2024, GCN 35828; and Geoffrey et al. 2024, GCN 35829. This circular may be cited. 3.6m Devasthal Optical Telescope (DOT) is a 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.
GCN 35832 table
GRB_name GRB240225B
GCN_number 35832
Detection_method Optical
redshift 0.9230
Circular_text TITLE: GCN CIRCULAR NUMBER: 35832 SUBJECT: GRB 240225B: VLT/X-shooter redshift DATE: 24/02/29 10:36:12 GMT FROM: Andrea Rossi at INAF B. Schneider (MIT), G. Pugliese (API), A. Rossi (INAF/OAS), J. Palmerio (GEPI/Obs. de Paris & IAP), D. B. Malesani (DAWN/NBI and Radboud Univ.), Z. Zhu (NAOC), D. Xu (NAOC), B. P. Gompertz (Birmingham), A. Saccardi (GEPI/Obs. de Paris) report on behalf of the Stargate collaboration: We observed the field of the MAXI/GSC GRB 240225B (Nakajima et al., GCN 35796; see also Joshi et al. 2024, GCN 35798; Kawakubo et al., GCN 35811) using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. Our spectra cover the wavelength range 3000-21000 AA, and consist of 4 exposures of 1200 s each. The observation mid-time is 02:29:56 UT on 2024 Feb 29 (~3.3 days after the MAXI trigger). In grz images taken with the acquisition camera on Feb 29 01:37:53 UT, we clearly detect the optical afterglow (Gompertz et al., GCN 35805; Liu et al., GCN 35812; Malesani et al., GCN 35819; Wise et al., GCN 35820; Gompertz et al., GCN 35824; Pankov et al., GCN 35826; Moskvitin et al., GCN 35828; Mo et al., GCN 35829; Ror et al., GCN 35830; Sasada et al., GCN 35831), for which we measure a preliminary AB magnitude r ~ 21 (the absolute calibration is uncertain due to the low number of Pan-STARRS calibrators in our small FoV). In a preliminary reduction of the spectra, we clearly detect a continuum over the entire wavelength range. From detection of multiple absorption features, which we interpret as being due to Fe II, Mg II, AlIII, Ca II, and Fe II*, we infer a common redshift of z = 0.946. We conclude this is the redshift of the burst. We also detect emission lines ([O II] and [O III] doublets, and H_alpha) at a consistent redshift, which we interpret as being due to the GRB host galaxy. As noted by Gompertz & Malesani (GCN 35824), the host galaxy is also detected in the Legacy Survey with r ~ 24.2 and a photometric redshift z ~ 0.9, which is consistent with the value we measured. We acknowledge expert support from the ESO staff in Paranal, in particular Francesca Lucertini, Israel Blanchard and Thomas Rivinius.
GCN 35835 table
GRB_name GRB240225B
GCN_number 35835
Detection_method Konus-Wind Det
t_trigger 20:12:07.251 UTC
redshift 0.9460
Circular_text TITLE: GCN CIRCULAR NUMBER: 35835 SUBJECT: Konus-Wind detection of GRB 240225B (long) DATE: 24/02/29 14:46:36 GMT FROM: Dmitry Frederiks at Ioffe Institute D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: GRB 240225B (MAXI/GCS detection: Nakajima et al., GCN 35796; AstroSat CZTI detection: Joshi al., GCN 35798) triggered Konus-Wind (KW) at T0=72727.251 s UT (20:12:07.251), i.e., ~3.5 min before the MAXI trigger. The burst light curve shows a multi-peaked emission pulse, which starts at ~T0 - 2 s, peaks around ~T0 + 6 s, and has a total duration of ~35 s. The emission is seen up to ~3 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB240225_T72727/ As observed by Konus-Wind, the burst had a fluence of (2.16 ± 0.35)x10^-5 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 6.144 s, of (2.87 ± 0.41)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). A time-averaged spectrum (measured from T0 to T0+41.216 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -1.37 (-0.14,+0.15), the high energy photon index beta = -2.74 (-7.26,+0.43), the peak energy Ep = 270 (-43,+64) keV, chi2 = 107/97 dof. A spectrum near the peak count rate (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.85 (-0.110,+0.10), the high energy photon index beta = -2.43 (-0.55,+0.24), the peak energy Ep = 287 (-47,+59) keV, chi2 = 75/79 dof. Assuming the redshift z=0.946 (Schneider et al., GCN 35832) 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 burst isotropic energy release E_iso to (5.38 ± 0.95)x10^52 erg, the isotropic peak luminosity L_iso to (1.87 ± 0.27)x10^52 erg/s, the rest-frame peak energy of the time-integrated spectrum Ep,i,z to ~525 keV, and the rest-frame peak energy at the peak of the emission Ep,p,z to ~558 keV. With the obtained estimates, GRB 240225B 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/GRB240225_T72727/GRB240225B_rest_frame.pdf All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary.
GCN 35836 table
GRB_name GRB240225B
GCN_number 35836
Detection_method Swift Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 35836 SUBJECT: GRB 240225B: Swift ToO observations DATE: 24/02/29 15:26:30 GMT FROM: Phil Evans at U of Leicester P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the MAXI GRB 240225B. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021682 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the MAXI event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team.
GCN 35839 table
GRB_name GRB240225B
GCN_number 35839
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 35839 SUBJECT: GRB 240225B: further SAO RAS optical observations DATE: 24/02/29 18:48:28 GMT FROM: Moskvitin Alexander at SAO RAS A. S. Moskvitin, O. I. Spiridonova (SAO RAS) report on behalf of the GRB follow-up team. We observed the field of GRB 240225B (Nakajima et al., GCN 35796; Evans, GCN 35797; Joshi et al., GCN 35798; D'Ai et al., GCN 35810; Kawakubo et al., GCN 35811; Frederiks et al., GCN 35835) with the SAO RAS 1m telescope Zeiss-1000 equipped with CCD-photometer. We obtained 8 x 300 sec frames in the Rc band on Feb. 29, 17:11:52--18:03:46 UT (t_mid - T0 = 3.8903 days). The OT (Gompertz et al., GCN 35805; Liu et al., GCN 35812; Malesani et al., GCN 35819; Wise et al., GCN 35820; Gompertz & Malesani, GCN 35824; Pankov et al., GCN 35826; Ror et al., GCN 35830; Sasada et al., GCN 35831; Schneider et al., GCN 35832) is clearly detected in our stacked frame with the brightness of R = 21.11 +/- 0.04. The photometry is based on nearby SDSS stars (magnitudes converted with Lupton 2005 equations).
GCN 35848 table
GRB_name GRB240225B
GCN_number 35848
Detection_method CALET
Circular_text TITLE: GCN CIRCULAR NUMBER: 35848 SUBJECT: GRB 240225B: Glowbug gamma-ray detection DATE: 24/03/03 04:22:32 GMT FROM: C.C. Cheung at Naval Research Lab C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2], operating on the International Space Station, reports the detection of GRB 240225B, which was also detected by MAXI/GSC (GCN 35796), AstroSat/CZTI (GCN 35798), CALET (GCN 35811), and Konus/Wind (GCN 35835). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2024-02-25 20:11:58.416 with a duration of 38.9 s and a total significance of ~89 sigma. The light curve comprises a multi-peaked structure with two primary peaks at ~T0+3s and ~T0+8s, and a fainter peak at ~T0+34s. Using a standard power-law function with an exponential high-energy cutoff [3] to model the emission in two defined intervals from T0 to T0+22.5s and T0+22.5s to +38.9s resulted respectively in photon indices dN/dE~E^x of x=0.6 and x=0.7, and cutoff energies ("Epeak") of 324 keV and 262 keV. The respective modeled 10-10000 keV fluences are 9.7e-06 erg/cm^2 and 2.0e-06 erg/cm^2. The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS. The detector comprises 12 large-area (15 cm x 15 cm) CsI:Tl panels covering the surface of a half cube, and two hexagonal (5-cm diameter, 10-cm length) CLLB scintillators, giving it a large field of view (instantaneous FoV ~2/3 sky) over a wide energy band of 50 keV to >2 MeV. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Goldstein, A. et al. 2020, ApJ 895, 40, arXiv :1909.03006 Distribution Statement A: Approved for public release. Distribution is unlimited.