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

[vsnet-grb-info 40154] GRB 251002A: Swift-XRT afterglow detection
by GCN Circulars 03 Oct '25

03 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42084 SUBJECT: GRB 251002A: Swift-XRT afterglow detection DATE: 25/10/03 10:06:49 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.A. Kennea (PSU), D.N. Burrows (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA), S. Lanava (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of GRB 251002A. We searched for X-ray sources in 1.5 ks of Photon Counting (PC) mode data. The total exposure at the position of the afterglow (see below) is 1.5 ks, obtained between T0+3.6 ks and T0+9.2 ks. Three uncatalogued X-ray sources are detected within the estimated 3-sigma SVOM/ECLAIRs error region (392 arcsec), of which one ("Source 1") is above the RASS 3-sigma upper limit at this position, and is therefore likely the GRB afterglow. Using 1503 s of PC mode data and 2 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 13.90813, -5.56678 which is equivalent to: RA (J2000): 00h 55m 37.95s Dec(J2000): -05d 34' 00.4" with an uncertainty of 2.6 arcsec (radius, 90% confidence). This position is consistent with the optical candidate (Palmerio et al. GCN 42061) and the EP-FXT X-ray candidate (Sun et al. GCN 24075). The light curve can be modelled with a power-law decay with a decay index of alpha=1.27 (+0.28, -0.25). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.62 (+0.20, -0.18). The best-fitting absorption column is 8.3 (+6.5, -2.8) x 10^20 cm^-2, consistent with the Galactic value of 5.5 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 4.2 x 10^-11 (4.7 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 8.3 (+6.5, -2.8) x 10^20 cm^-2 Galactic foreground: 5.5 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.62 (+0.20, -0.18) If the light curve continues to decay with a power-law decay index of 1.27, the count rate at T+24 hours will be 0.014 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.9 x 10^-13 (6.5 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/03000125. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/SVOM/SVOM_FIELD00039. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42084. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40153] GRB 251001B: AbAO optical upper limit
by GCN Circulars 03 Oct '25

03 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42083 SUBJECT: GRB 251001B: AbAO optical upper limit DATE: 25/10/03 09:51:25 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), R. Ya. Inasaridze (AbAO) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of GRB 251001B detected by Fermi/GBM (The Fermi GBM team et. al, GCN 42038), and Swift/BAT (Beardmore et. al, GCN 42039) with the AS-32 0.7m telescope of the Abastumani Observatory (AbAO). The R-filter observations began on 2025-10-01 22:37 UT, i.e. ~0.35 days since trigger and consisted of 55x30 s exposures. The optical source at z = 2.162 (Sanchez-Ramirez et. al, GCN 42053) found by GOTO (Gompertz et. al, GCN 42040) and also observed by (An et. al, GCN 42041; Strausbaugh & Cucchiara, GCN 42043; O'Neill et. al, GCN 42046; de Ugarte Postigo et. al, GCN 42050; Ma et. al, GCN 42051; Sanchez-Ramirez et. al, GCN 42053; Schneider et. al, GCN 42054; Breeveld et. al, GCN 42055) is not detected in the co-add image of 51x30 s. Preliminary photometry and observation details are presented below: Date UT start t-T0 Exp. Filter OT Err. UL (mid, days) (s) (3sigma) 2025-10-01 22:37:48 0.35641 51x30 R n/d n/d 19.9 The photometry was calibrated using nearby stars from USNO-B1.0 (R2 magnitudes) and not corrected for the Galactic extinction. Ref. stars USNO-B1.0 RA Dec R2 42.63445 -23.02161 14.13 42.77496 -23.05166 13.47 View this GCN Circular online at https://gcn.nasa.gov/circulars/42083. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40152] GRB 251002A: Kilonova-Catcher optical afterglow detection
by GCN Circulars 03 Oct '25

03 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42082 SUBJECT: GRB 251002A: Kilonova-Catcher optical afterglow detection DATE: 25/10/03 09:49:33 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> S. Leonini, M. Freeberg (KNC), D. Turpin (CEA-Saclay/Irfu), C. Andrade(UMN), S. Antier (OCA/IJCLab), M. Coughlin (UMN),S. Karpov (FZU), P. Hello (IJCLAB), M. Pillas (IAP) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 251002A detected by SVOM/ECLAIRs and GRM (Saccardi et al., GCN 42060) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the TEC160FL and iT72 telescopes operated by M. Freeberg and with the automated and remoted 0.53m Ritchey-Chretien telescope at Montarrenti Observatory (Siena, Italy, IAU code C88) operated by S. Leonini. Our observations started at TGRB+1.2hr. In our stacked frames, subtracted from the PanSTARRS DR2 template image, we detect the optical counterpart reported by SVOM/VT (Palmerio et al., GCN 42061), LCO-1m (Turpin et al., GCN 42062), FRAM-ORM (Jelinek et al., GCN 42063), LCO-40cm (Perez-Fournon et al., GCN 42064), SAO RAS (Moskvitin et al., GCN 42065), BOOTES-6 (Perez-Garcia et al., GCN 42066), MASTER (Lipunov et al., GCN 42067), VLT/Xshooter (Saccardi et al., GCN 42076), OHP/T193 (Mandrakas et al., GCN 42077), SYSU (Cao et al., GCN 42078), SVOM/COLIBRI (FM-GFT) (Schneider et al., GCN 42080) and AbAO (Pankov et al., GCN 42081). We report part of our follow-up results in the table below: +---------------+-----------+-----------+----------------------+-------------+ | Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument | +===============+===========+===========+======================+=============+ | 2.28 | 60 x 40s | Rc (Vega) | 19.08 +/- 0.22 | Montarrenti | | 5.10 | 18 x 180s | Rc (Vega) | 19.86 +/- 0.09 | iT72 | | 8.54 | 20 x 180s | r (AB) | 20.42 (5 sigma U.L.) | TEC160FL | +---------------+-----------+-----------+----------------------+-------------+ All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the sloan filters were calibrated using the PanSTARRS DR1 catalog. Images obtained with the Johnson-cousins 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/42082. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40151] GRB 251002A: AbAO optical observations
by GCN Circulars 03 Oct '25

03 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42081 SUBJECT: GRB 251002A: AbAO optical observations DATE: 25/10/03 08:39:52 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), R. Ya. Inasaridze (AbAO) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of GRB 251002A detected by SVOM (Saccardi et. al, GCN 42060) in the R-filter with the AS-32 0.7m telescope of the Abastumani Observatory (AbAO). The observations began on 2025-10-02 21:46 UT, i.e. ~0.09 days since trigger and consisted of 87x60 s exposures. The optical source found by SVOM (Palmerio et. al, GCN 42061) at z = 2.178 (Saccardi et. al, GCN 42076) and also observed by (Turpin et. al, GCN 42062; Jelinek et. al, GCN 42063; Juliá-Maroto et. al, GCN 42064; Moskvitin et. al, GCN 42065; Perez-Garcia et. al, GCN 42066; Saccardi et. al, GCN 42076; Mandarakas et. al, GCN 42077; Cao et. al, GCN 42078) is clearly visible in the co-add image of 87x60 s. Preliminary photometry and observation details are presented below: Date UT start t-T0 Exp. Filter OT Err. UL (mid,days) (s) (3sigma) 2025-10-02 21:46:03 0.09351 87*60 R 19.48 0.16 21.7 The photometry was calibrated using reference stars from (Moskvitin et. al, GCN 42065) and not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42081. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40150] GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
by GCN Circulars 03 Oct '25

03 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42080 SUBJECT: GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations DATE: 25/10/03 08:37:03 GMT FROM: Benjamin Schneider at MIT <bschn(a)mit.edu> Benjamin Schneider (LAM), Enrique Moreno Méndez (UNAM), Camila Angulo (UNAM), Ny Avo Rakotondrainibe (LAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Antonio de Ugarte Postigo (LAM), Andrea Saccardi (CEA/Irfu), and Diego Gotz (CEA/Irfu): We imaged the field of the SVOM GRB 251002A (Saccardi et al., GCN Circ. 42060) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-10-03 03:33:53 to 05:48:35 UTC (from 7.32 to 9.56 hr after the trigger) and obtained 16 minutes of exposure in the g, r, i, z and y filters. The data were reduced and coadded with the COLIBRÍ pipeline and analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We detected the optical counterpart reported by Palmerio et al., GCN Circ. 42061, Turpin et al., GCN Circ. 42062; Jelinek et al., GCN Circ. 42063; Juliá-Maroto et al. GCN Circ. 42064; Moskvitin et al. GCN Circ. 42065; Perez-Garcia et al. GCN Circ. 42066; Senik et al., GCN Circ. 42067; Saccardi et al., GCN Circ. 42076; Mandarakas et al., GCN Circ. 42077; Cao et al, GCN 42078 at preliminary magnitudes of: g = 20.96 +/- 0.09 (mid-time 8.41 hr) r = 20.82 +/- 0.07 (mid-time 8.44 hr) i = 20.64 +/- 0.07 (mid-time 8.46 hr) z = 20.76 +/- 0.15 (mid-time 8.42 hr) y = 20.30 +/- 0.22 (mid-time 7.84 hr) Further observations and analysis are ongoing in g, r, i, z and y filters. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/42080. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40149] GRB 251001C: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 03 Oct '25

03 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42079 SUBJECT: GRB 251001C: CALET Gamma-Ray Burst Monitor detection DATE: 25/10/03 08:15:26 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> P. S. Marrocchesi (U of Siena), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (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), and the CALET collaboration: The GRB 251001C (Glowbug gamma-ray detection: Cheung et al., GCN Circ. 42049) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 15:07:25.84 UTC on 1 October 2025 (https://cgbm.calet.jp/cgbm_trigger/flight/1443366004/index.html). The burst signal was seen by only the SGM detector. The burst light curve shows a single pulse that starts at T+0.2 sec, peaks at T+1.0 sec, and ends at T+2.4 sec. The T90 and T50 durations measured by the SGM data are 2.0 +/- 0.1 sec and 0.7 +/- 0.2 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1443366004/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/42079. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40148] GRB 251002A: J band observations by SYSU 80cm infrared telescope
by GCN Circulars 03 Oct '25

03 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42078 SUBJECT: GRB 251002A: J band observations by SYSU 80cm infrared telescope DATE: 25/10/03 07:45:53 GMT FROM: caodle(a)mail2.sysu.edu.cn Dou-Le Cao, Jia-Qi Lin, Chen Chun, Zhong-Nan Dong, Wei-Sen Huang, Jin-Ji Li, Pu Lin, Yan Yu, Hao-Nan Yang, Hao-Ran Zhang, P H Thomas Tam, Rong-Feng Shen, Bin Ma (Sun Yat-sen University) report on behalf of the SYSU 80cm infrared telescope team: We observed the field of GRB251002A detected by SVOM/ECLAIRs (A. Saccardi et al., GCN 42060), using the Sun Yat-sen University 80cm infrared telescope with 20s exposures in J band. The calculated position is R.A. = 13.9082 deg, DEC = -5.5671 deg J2000, from SVOM/VT observation. Our observations began at 2025-10-2 20:55:00 UTC, 0.62 hours after the SVOM trigger. We detected an infrared counterpart at the position of the optical afterglow (J. T. Palmerio et al., GCN 42061; D. Turpin et al., GCN 42062; Martin Jelinek et al., GCN 42063; L. Juliá-Maroto et al., GCN 42064; A. S. Moskvitin et al., GCN 42065; I. Perez-Garcia et al., GCN 42066; V.Senik et al., GCN 42067) in the stacked images. The preliminary photometric magnitudes in J band are below: Start Time (UTC) |Band | Exp | Mag (Vega) ------------------------|-------|---------|------------------ 2025/10/2 20:55:00 | J | 300s | 17.03+/-0.24 2025/10/2 21:00:00 | J | 300s | 17.19+/-0.14 2025/10/2 21:05:00 | J | 300s | 17.64+/-0.20 2025/10/2 21:10:00 | J | 300s | 17.44+/-0.15 2025/10/2 21:15:00 | J | 300s | 17.74+/-0.19 2025/10/2 21:20:00 | J | 900s | 17.65+/-0.16 2025/10/2 21:35:00 | J | 2100s | 18.27+/-0.15 The photometric calibration was performed using nearby stars from the 2MASS catalog and the magnitudes are not corrected for Galactic extinction. The SYSU 80cm infrared telescope is operated and managed by the Department of Astronomy, Sun Yat-sen University. View this GCN Circular online at https://gcn.nasa.gov/circulars/42078. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40147] GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
by GCN Circulars 03 Oct '25

03 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42077 SUBJECT: GRB 251002A: OHP/T193 MISTRAL optical afterglow detection DATE: 25/10/03 07:34:37 GMT FROM: Christophe Adami at LAM <christophe.adami(a)lam.fr> N. Mandarakas (LAM), C. Adami (LAM/Pytheas/AMU), N.A. Rakotondrainibe (LAM), B. Schneider (LAM), E. Le Floc'h (CEA/Irfu), S.D. Vergani (LUX-Paris Obs.) report on behalf of a larger collaboration: We observed the field of the SVOM/ECLARIs GRB 251002 (Saccardi et al., GCN 42060) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained three exposures of 240s (for a total of 12 min) in the r-band starting at 22:05:40 UT on 2025-10-02 (observations mid-time at T-To=2h20min), under modest weather conditions. In the stacked images, we detect the optical counterpart reported and followed by Palmerio et al. (GCN 42061), Turpin et al. (GCN 42062), Jelinek et al. (GCN 42063), Julia-Maroto et al. (GCN 42064), Moskvitin et al. (GCN 42065), Perez-Garcia et al. (GCN 42066), Senik et al. (GCN 42067), Sun et al. (GCN 42075), and Saccardi et al. (GCN 42076) The preliminary magnitude derived for that source is: r’ = 19.39 +/- 0.07 mag (AB) The detection limit (3 sigma) is r=21.10 +/- 0.15 The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitudes are not corrected for Galactic extinction. We used the STDWeb/STDPipe tools (Karpov 2025). We acknowledge the excellent support from the Observatoire de Haute-Provence and in particular Yoann Degot-Longhi. View this GCN Circular online at https://gcn.nasa.gov/circulars/42077. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40146] GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
by GCN Circulars 03 Oct '25

03 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42076 SUBJECT: GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178 DATE: 25/10/03 06:54:12 GMT FROM: Andrea Saccardi at CEA/Irfu <andrea.saccardi(a)cea.fr> A. Saccardi (CEA/Irfu), N. Habeeb (U. Leicester), A. de Ugarte Postigo (LAM), B. Schneider (LAM), A. Martin-Carrillo (UCD), D. B. Malesani (DAWN/NBI and Radboud), S. D. Vergani (LUX-Paris Obs.), B. C. Rayson (Leicester), N. R. Tanvir (U. Leicester) report on behalf of the Stargate collaboration: We observed the optical counterpart (Palmerio et al., GCN 40061; Turpin et al., GCN 40062; Jelinek et al., GCN 40063; Juliá-Maroto et al. GCN 42064; Moskvitin et al. GCN 42065; Perez-Garcia et al. GCN 42066) of the SVOM/ECLAIRs GRB 251002A (Saccardi et al., GCN 42060) using the ESO/VLT UT3 (Melipal) equipped with the X-shooter spectrograph. From the 3x30 s acquisition image at 2025-10-03 04:55:20 UT (8.67 hr post-trigger), the optical afterglow is well detected with a magnitude of r = 20.74 +/- 0.12 (AB) calibrated against PanSTARRS nearby stars and not corrected for Galactic extinction. Our spectra cover the wavelength range 3000-21000 AA and consist of 4 exposures of 600 s each. Observations started on 2025 October 3 at 05:04:11 UT (8.82 hr after the burst). In a preliminary reduction of the spectra, we clearly detect a continuum over the entire wavelength range. From the detection of multiple absorption features, including Lya, S II, Si II, Si II*, O I, O I*, C II, C II*, Si IV, C IV, Fe II, Al II, Zn II, Cr II, Ni II*, Fe II*, Mg II, and Mg I we infer a redshift of z = 2.178. We acknowledge the prompt response and excellent support of the ESO observing staff in Paranal, in particular Aaron Labdon, Jonathan Smoker and Rodrigo Palominos. The analysis of this spectrum was carried out with the help of the zHunter tool (https://doi.org/10.5281/zenodo.15189495). View this GCN Circular online at https://gcn.nasa.gov/circulars/42076. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40145] GRB 251002A: EP-FXT counterpart detection
by GCN Circulars 03 Oct '25

03 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42075 SUBJECT: GRB 251002A: EP-FXT counterpart detection DATE: 25/10/03 06:02:41 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> X. X. Sun(NAO,CAS), Y.Q. Zhao(USTC,PRIC), Y. L. Wang (NAO, CAS; ICE, CSIC-IEEC)，and Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of the SVOM/ECLAIRs-detected burst GRB 251002A (SVOM/sb25100211, Saccardi et al. GCN 42060) at 2025-10-02T20:52:13Z (UTC), 2239 seconds after the SVOM/ECLAIRs trigger, with an exposure time of 2918s. One uncatalogued source is detected within the ECLAIRs error circle, and the source is spatially consistent with the counterpart reported in optical bands (Palmerio et al. GCN 42061, Turpin et al. GCN 42062, Jelinek et al. GCN 42063, Juliá-Maroto et al. GCN 42064, Moskvitin et al. GCN 42065，Perez-Garcia et al. GCN 42066, Senik et al. GCN 42067). Preliminary analysis on this source are automatically conducted, and details are listed as follows. Source 1: EPF_J005537.9-053402 RA(J2000): 13.9078 Dec (J2000): -5.5669 Flux: 1.295e-11 erg/s/cm2 (observed, 0.5-10 kev) Flux_err: 7.6399e-13 erg/s/cm2 (1 sigma) The position uncertainty of the source is about 10 arcsec in radius (90% C.L. statistical and systematic). Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/42075. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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