February 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 37426] GRB 250221A: Swift-XRT refined Analysis
by GCN Circulars 22 Feb '25

22 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39414 SUBJECT: GRB 250221A: Swift-XRT refined Analysis DATE: 25/02/22 00:09:17 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> C. Salvaggio (INAF-OAB), M. Ferro (INAF-OAB), M. A. Williams (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), R. Brivio (INAF-OAB) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 7.0 ks of XRT data for GRB 250221A, from 107 s to 66.9 ks after the BAT trigger. The data comprise 9 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a power-law decay with a decay index of alpha=1.06 (+/-0.06). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.09 (+0.24, -0.23). The best-fitting absorption column is 1.4 (+0.7, -0.6) x 10^21 cm^-2, in excess of the Galactic value of 3.7 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.3 x 10^-11 (4.4 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.4 (+0.7, -0.6) x 10^21 cm^-2 Galactic foreground: 3.7 x 10^20 cm^-2 Excess significance: 2.7 sigma Photon index: 2.09 (+0.24, -0.23) If the light curve continues to decay with a power-law decay index of 1.06, the count rate at T+24 hours will be 2.5 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.4 x 10^-14 (1.1 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01290305. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39414. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37425] GRB 250221A: NOT optical observations
by GCN Circulars 22 Feb '25

22 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39413 SUBJECT: GRB 250221A: NOT optical observations DATE: 25/02/22 00:06:03 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> L. Cotter (UCD), D. B. Malesani (DAWN/NBI and Radboud Univ.), J. Palmerio (CEA/Irfu), A. de Ugarte Postigo (LAM), A. Martin-Carrillo (UCD), report on behalf of a larger collaboration: We observed the optical afterglow (Francile et al., GCN 39395; Watson et al., GCN 39397; Melandri et al., GCN 39406; Shilling et al., GCN 39409; Guo et al., GCN 39412) of the Swift GRB 250221A (Caputo et al., GCN 39396), using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were carried out in the griz filters. The afterglow is well detected in all filters. In a single r-band observation with mid-time 2025 Feb 21.86 UT (17.07 hr after the trigger), we measure for the afterglow r = 22.0 +- 0.15 AB, calibrated against nearby Pan-STARRS objects. Our measurement is affected by the presence of a nearby object about 1" to the NW, visible in the Legacy Survey (Watson et al., GCN 39397). More accurate photometry can be attained via template subtraction. The nearby object has a photometric redshift z = 0.34 +- 0.08 (Zhou et al. 2021, doi:10.1093/mnras/staa3764). The relationship between this object and the GRB is unclear at the moment. We thank Alan Watson (UNAM) for providing us with accurate coordinates of the afterglow. We also thank the observers at the NOT for securing our data, in particular Linda Lombardo, Annika Schichtel, Clara Peter, Diego Mederos Leber, Svenja Heil, and Nina Caviziel (all Goethe University Frankfurt). View this GCN Circular online at https://gcn.nasa.gov/circulars/39413. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37424] GRB 250221A: 1.6m Mephisto optical detection
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39412 SUBJECT: GRB 250221A: 1.6m Mephisto optical detection DATE: 25/02/21 18:35:37 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Helong Guo, Guowang Du, Xinlei Chen, Xiaotong Chen, Yiheng Xie, Brajesh Kumar, Yuan Fang, Xingzhu Zou, Yu Pan (all SWIFAR, YNU), Xuhui Han, Pinpin Zhang, Liping Xin, Chao Wu (all NAOC), Yuanpei Yang, Jinghua Zhang, Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of Mephisto Team: Simultaneous multi-band photometric observations of the Swift GRB 250221A (Caputo et al., GCN 39396; Beardmore et al., GCN 39404) was performed with 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. The observations were started from 11:55:52 2025-02-21 UT (~8.35 hr after the trigger) and several frames with different exposure time were obtained in uvgr bands. The afterglow candidate (Watson et al., GCN 39397; Melandri et al., GCN 39406; Shilling et al., GCN 39409) is clearly detected in the stacked images of g and r band but not in u and v bands. The preliminary magnitudes and 3-sigma upper limits are below: Start_Time(UT) Filter Exp(sec) Mag/LimMag(AB) 2025-02-21T11:55:53 u 120*4, 300*3 >22.20 2025-02-21T12:05:54 v 120*3, 300*3 >22.61 2025-02-21T11:55:52 g 120*4, 300*3 21.57 +/- 0.26 2025-02-21T12:05:54 r 120*3, 300*3 20.87 +/- 0.13 ---------------------------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The on-site telescope assemblage and commissioning were carried out in September 2022. The first light in all three channels was achieved on 2023 December 21. ---------------------------------------------------------------------------- View this GCN Circular online at https://gcn.nasa.gov/circulars/39412. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37423] LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39411 SUBJECT: LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate DATE: 25/02/21 18:19:53 GMT FROM: Isaac McMahon at University of Zurich <isaac.mcmahon(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: The trigger S250221gb is no longer considered to be a candidate of interest: there was a transient noise glitch in the LIGO Hanford detector. View this GCN Circular online at https://gcn.nasa.gov/circulars/39411. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37422] GRB 250221A: AKO Optical Upper Limit
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39410 SUBJECT: GRB 250221A: AKO Optical Upper Limit DATE: 25/02/21 16:45:15 GMT FROM: Mohammad Odeh at Al Khatim Observatory M44 <mshodeh(a)gmail.com> Mohammad Odeh (Al-Khatim Observatory, AKO, operated by the International Astronomical Center in Abu Dhabi, UAE), and Shaikha Alshamsi, Nuha Manal Pattani, and Nidhal Guessoum (American University of Sharjah, UAE), report: We observed the field of GRB 240221A (Swift BAT and XRT team, Caputo et al. GCN 39396, Beardmore et al., GCN 39404; Shilling et al., GCN 39409; COLIBRÍ/DDRAGO, Watson et al. GCN 39397; REM, Melandri et al. GCN 39406) with our 0.36m f/7.7 robotic telescope. The observation was performed on 21 February 2025 at 15:53: 37 UTC (mid-time), 12.32 hours after the trigger. We obtained 11x180s images using Ic filter at the position given by Swift/XRT: RA (J2000): 03h 57m 51.09s Dec (J2000): -15d 08' 00.6" We did not detect an afterglow candidate at the above position down to a magnitude of Ic = 19.7 for the stacked images. The magnitude was estimated using the Atlas catalogue as a reference. The magnitude is not corrected for galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39410. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37421] GCN Announcement: New SVOM Notices, Planned Retirement of VOEvent Brokers
by GCN Announcements 21 Feb '25

21 Feb '25

The GCN Team is pleased to announce new features on https://gcn.nasa.gov. SVOM VOEvent Notices Available Over Kafka The SVOM Team and the GCN team are pleased to announce the availability of SVOM notice types via the new GCN in VOEvent format. These notices can be streamed via Kafka. They are not available via GCN Classic. The SVOM Team plans to add JSON format notices at a later date. SVOM Mission Summary: The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a French-Chinese mission, result of a collaboration between the two national space agencies, China National Space Administration (CNSA) and Centre national d'études spatiales (CNES). SVOM mission is dedicated to the study of the most powerful transient phenomena, with a particular emphasis on gamma-ray bursts (GRBs). The SVOM spacecraft carries four multi-wavelength instruments: ECLAIRs, Gamma Ray burst Monitor (GRM), Microchannel X-ray Telescope (MXT) and Visual Telescope (VT). Notice topics: new SVOM notices provide GRB detection and follow-up observation details. Each of the four instruments has its own dedicated topic to stream notices with their related information, see table below: - gcn.notices.svom.voevent.grm - gcn.notices.svom.voevent.eclairs - gcn.notices.svom.voevent.mxt - gcn.notices.svom.voevent.vt A more extensive description of the information provided in these new notices is available at https://gcn.nasa.gov/missions/svom. Planned Retirement of GCN Classic VOEvent Brokers The result of the November 2024 user survey of those utilizing the GCN VOEvent Brokers to receive VOEvent-format Notices with the VOEvent Transport Protocol is overwhelmingly in favor of retiring the brokers and users migrating to receive VOEvent Notices over Kafka. This service is already available for all GCN Classic Notice types with self-subscription via the Start Streaming Notices Guide. The GCN Classic VOEvent brokers will be retired shortly after the conclusion of the O4 gravitational wave network observing run, currently scheduled for October 7, 2025. We recommend the following actions for users currently utilizing VOEvent via GCN Classic. - Sign up to receive VOEvent format Notices via Kafka or email - Let the GCN Team know when you're ready to unsubscribe from receiving them via the GCN Classic brokers. All GCN Classic VOEvent subscribers will be unsubscribed after the end of O4 and the brokers will be taken offline. For more details on this new feature and an archive of GCN news and announcements, see https://gcn.nasa.gov/news. For questions, issues, or bug reports, please contact us via: - Contact form: https://gcn.nasa.gov/contact - GitHub issue tracker: https://github.com/nasa-gcn/gcn.nasa.gov/issues --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37420] GRB 250221A: Swift/UVOT Detection
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39409 SUBJECT: GRB 250221A: Swift/UVOT Detection DATE: 25/02/21 15:27:39 GMT FROM: Sam Shilling at Lancaster University <shilling.sam(a)gmail.com> S.P.R. Shilling (Lancaster U.), A.A. Breeveld (UCL-MSSL) and R. Caputo (NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250221A 107 s after the BAT trigger (Caputo et al., GCN Circ. 39396). A source consistent with the enhanced XRT position (Beardmore et al., GCN Circ. 39404) is detected in the initial UVOT exposures and appears to be fading. An optical candidate in this field is also detected by Watson et al., (GCN Circ. 39397) and by Melandri et al., (GCN Circ. 39406). 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 127 277 147 17.52 +/- 0.04 white 620 639 19 18.41 +/- 0.17 v 107 118 10 17.10 +/- 0.32 v 4484 4683 197 >18.8 b 595 615 19 >18.7 u 340 590 245 17.78 +/- 0.07 w1 4894 5041 144 >19.0 m2 4689 4889 197 >18.6 w2 4279 4479 197 >18.7 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.332 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/39409. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37419] EP250220a: Liverpool Telescope upper limits
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39408 SUBJECT: EP250220a: Liverpool Telescope upper limits DATE: 25/02/21 14:53:53 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek and D. A. Perley (LJMU) report: We observed the field of the fast X-ray transient EP250220a (Wang et al., GCN 39387) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 6x90s exposures in the SDSS r’ and i’ filters starting at 2025-02-20 21:40:49.049 UT, approximately 19.5 hours after the trigger. The images were stacked and the background was subtracted relative to Pan-STARRS-1, as well as Legacy Sky Survey reference imaging using PSF matching with the help of PSFEx. We do not detect any new object at the EP/WXT error region of the transient: the 3-sigma limiting magnitudes on the stacked images are r > 21.7 mag and i > 21.8 mag, in line with Zhang et al. (GCN 39393), Fan et al. (GCN 39400), Eyles-Ferris et al. (GCN 394001) and Guo et al. (GCN 394002). However, we note that there is a bright, saturated star inside the error region, impacting our observations as well as the reference fields. View this GCN Circular online at https://gcn.nasa.gov/circulars/39408. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37418] GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39407 SUBJECT: GRB 250219A: GRANDMA/Kilonova-Catcher upper limits DATE: 25/02/21 14:08:21 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> D. Turpin (CEA-Saclay/Irfu), D. Marchais (KNC), 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) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 250219A (Daigne et al., GCN 39376) detected by SVOM/ECLAIRs with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the T-CAT 0.4m telescope at Crous des Gats Observatory (Cintegabelle, France) and the 0.43m CDK telescope at Alnitak Observatory (Spain) starting from TGRB + 5.8hr. In our stacked frames, we do not detect any optical afterglow at the position reported by Swift/XRT (Kennea et al., GCN 39379), SVOM/VT (Xin et al., GCN 39380) and COLIBRÍ (Magnani et al., GCN 39382). We obtain the following 5-sigma (Vega) upper limits: +---------------+-----------+--------+---------+-----------+ | Tmid-TGRB (hr)| Exp (s) | Filter | Mag U.L.| Instrument| +===============+===========+========+=========+===========+ | 6.6 | 119 x 32s | Rc | 20.7 | T-CAT | | 6.6 | 119 x 32s | V | 21.3 | T-CAT | | 6.8 | 10 x 180s | Rc | 20.9 | 0.43m CDK | | 8.5 | 102 x 32s | Rc | 20.8 | T-CAT | | 8.5 | 102 x 32s | V | 21.4 | T-CAT | +---------------+-----------+--------+---------+-----------+ 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. 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/). View this GCN Circular online at https://gcn.nasa.gov/circulars/39407. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37417] GRB 250221A: REM optical/NIR afterglow detection
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39406 SUBJECT: GRB 250221A: REM optical/NIR afterglow detection DATE: 25/02/21 13:50:48 GMT FROM: Andrea Melandri at INAF-OAR <andrea.melandri(a)inaf.it> A. Melandri (INAF-OAR), R. Brivio, M. Ferro, P. D’Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of GRB 250221A detected by Swift (Caputo et al., GCN 39396; Beardmore et al., GCN 39404) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, K bands, starting on 2025 February 21 at 03:35:39 UT (i.e. ~60 s after the Swift trigger), and lasting for about 2 hours. From preliminary photometry we detect the counterpart in the optical and NIR images at the position of the optical afterglow (Watson et al., GCN 39397) with the following early-time magnitudes: r = 16.5 +/- 0.2 (AB; calibrated against the Pan-STARRS catalogue) at a mid-time of t - t0 = 70 s after the trigger. H = 14.8 +/- 0.3 (Vega; calibrated against the 2MASS catalogue) at a mid-time t - t0 = 87 s after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/39406. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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