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

[vsnet-grb-info 38731] Fermi GBM Sub-Threshold Detection of GRB 250610B
by GCN Circulars 11 Jun '25

11 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40692 SUBJECT: Fermi GBM Sub-Threshold Detection of GRB 250610B DATE: 25/06/11 19:54:51 GMT FROM: rhamburg(a)usra.edu R. Hamburg (USRA) reports on behalf of the Fermi-GBM Team: The SVOM/ECLAIRs and SVOM/GRM instruments detected GRB 250610B on 2025-06-10T16:32:58 (GCN 40671). There was no Fermi-GBM onboard trigger around this event time. An automated, blind search for gamma-ray bursts below the onboard triggering threshold in Fermi-GBM identified no candidates. The GBM Targeted Search [1], the most sensitive, coherent search for GRB-like signals in GBM data, identified a transient starting approximately 31 seconds after the SVOM/ECLAIRs trigger time, most significantly on the 16.384 s timescale and with a false alarm rate of 9.7e-5 Hz. Using the standard search protocol, the Targeted Search localization was found to be spatially consistent with the SVOM/ECLAIRs location. Additionally, the GBM Targeted Search transient was found with the highest significance using a "soft" spectrum (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7) for a GRB. This is roughly consistent with the soft spectrum found by Wang et al. 2025 (GCN 40682). [1] Goldstein et al. 2019 arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/40692. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38730] GRB 250610B: Swift/UVOT Detection
by GCN Circulars 11 Jun '25

11 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40691 SUBJECT: GRB 250610B: Swift/UVOT Detection DATE: 25/06/11 15:39:28 GMT FROM: Alice Breeveld at MSSL-UCL <a.breeveld(a)ucl.ac.uk> A.A. Breeveld (UCL-MSSL) and M.A. Williams (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250610B 2 ks after the SVOM trigger (Saccardi et al., GCN Circ. 40671). The optical source at the position of XRT source 1 (Evans et al., GCN Circ. 40679) seen by Schneider et al., (GCN Circ. 40676), Gompertz et al., (GCN Circ. 40677), Li et al., (GCN Circ. 40678), Bochenek et al., (GCN Circ. 40684) and Qiu et al. (GCN Circ. 40685) was also detected in the UVOT U-band filter and shows signs of fading. 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 u 2939 4660 1694 20.20 ± 0.15 u 8634 8923 285 20.50 ± 0.36 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.0104 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/40691. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38729] EP250610A: Swift/UVOT Upper limits
by GCN Circulars 11 Jun '25

11 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40690 SUBJECT: EP250610A: Swift/UVOT Upper limits DATE: 25/06/11 14:39:47 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of EP250610A 3 ks after the EP trigger (Zhang et al., GCN Circ. 40660). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 40662) is seen in the initial UVOT exposures. Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag u 3087 9399 2103 >21.44 u 35617 41300 1846 >21.33 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/40690. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38728] GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
by GCN Circulars 11 Jun '25

11 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40689 SUBJECT: GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations DATE: 25/06/11 13:50:37 GMT FROM: Benjamin Schneider at MIT <bschn(a)mit.edu> Benjamin Schneider (LAM), Diego López-Cámara (UNAM), Rosa L. Becerra (U Roma), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Antonio de Ugarte Postigo (LAM), A. Saccardi (CEA), and J. Rodriguez (CEA): We imaged the field of the SVOM GRB 250610B (Saccardi et al., GCN Circ. 40671) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-06-11 04:35 to 06:40 UTC (from 12.0 to 14.1 hours after the trigger) and obtained 32 minutes of exposure in each of the g, r and i filters. The data were reduced and coadded with the COLIBRÍ pipeline and analysed 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 Schneider et al., GCN Circ. 40676; Gompertz et al., GCN Circ. 40677; Li et al., GCN Circ. 40678; Bochenek et al., GCN Circ. 40684, and Qiu et al., GCN Circ. 40685 at preliminary magnitudes of: g = 21.83 +/- 0.14 r = 21.56 +/- 0.10 i = 21.49 +/- 0.09 Our detections are consistent with the shallow decay reported by the SVOM/VT team (Qiu et al., GCN Circ. 40685) and imply a temporal decay index of ~0.6. Further observations are planned. 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/40689. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38727] EP250610a: TNG NIR upper limit
by GCN Circulars 11 Jun '25

11 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40688 SUBJECT: EP250610a: TNG NIR upper limit DATE: 25/06/11 11:56:27 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio(a)inaf.it> R. Brivio, P. D'Avanzo, M. Ferro, S. Campana (INAF-OAB), L. Izzo (INAF - OACn), D. B. Malesani (DAWN/NBI & Radboud Univ.), R. Salvaterra (INAF-IASF Milan), A. Melandri (INAF-OAR), V. Lorenzi (INAF-TNG) report on behalf of the CIBO collaboration: We observed the field of EP250610a detected by EP/WXT (Zhang et al., GCN 40660) with the Italian 3.6m TNG telescope, located in Canary Islands (Spain), equipped with the near-infrared camera NICS in imaging mode. A series of images were obtained with the J filter on 2025-06-11 at a mid-time of about 18.1 hours after the burst. No clear afterglow candidate is detected within the XRT position (source 1, Evans et al., GCN 40662) down to a 3-sigma limiting magnitude of J ~ 22 (Vega; calibrated against the 2MASS catalogue). View this GCN Circular online at https://gcn.nasa.gov/circulars/40688. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38726] GRB 250610B: REM optical/NIR observations
by GCN Circulars 11 Jun '25

11 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40687 SUBJECT: GRB 250610B: REM optical/NIR observations DATE: 25/06/11 11:49:21 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio(a)inaf.it> 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 250610B detected by SVOM/ECLAIRs (Saccardi et al., GCN 40671) 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, and H bands, started on 2025 June 10 at 22:45:52 UT (i.e. 6.2 hr after the burst), and lasted for about 1 hour. From preliminary inspection, we do not detect any possible counterpart at the position of the optical afterglow (Schneider et al., GCN 40676; Gompertz et al., GCN 40677; Li et al., GCN 40678; Bochenek et al., GCN 40684; Qiu et al., GCN 40685) down to the following 3sigma limits: r > 19.6 (AB; calibrated against the Pan-STARRS catalogue), at a mid-time of 6.7 hr after the trigger; H > 15.6 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 6.2 hr after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/40687. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38725] EP250610a: Liverpool Telescope optical upper limits
by GCN Circulars 11 Jun '25

11 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40686 SUBJECT: EP250610a: Liverpool Telescope optical upper limits DATE: 25/06/11 10:13:31 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris, P. T. O’Brien and R. L. C. Starling (U of Leicester) report: We observed the field of the X-ray transient EP250610a (Zhang et al., GCN 40660; Lian et al., GCN 40669) with the 2m Liverpool Telescope using the IO:O instrument. We obtained 6x150s exposures in each of the SDSS r’ and SDSS g’ filters starting at 2025-05-11 00:16:50 UT, approximately 19.9 hours after the X-ray detection. We performed image subtraction on the stacked images using reference images from Pan-STARRS and also compared the stacked and reference images manually. In agreement with Schneider et al. (GCN 40661), Brivio et al. (GCN 40665), Yao et al. (GCN 40666) and Lipunov et al. (GCN 40673), we identify no new sources within the positional uncertainty of the X-ray source identified by Evans et al. (GCN 40662) and Lian et al. (GCN 40669). At the position of the X-ray source, we derive 3-sigma upper limits of r’ > 22.1 and g’ > 22.1 with photometry calibrated to Pan-STARRS and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40686. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38724] GRB 250610B: SVOM/VT optical shallow decay
by GCN Circulars 11 Jun '25

11 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40685 SUBJECT: GRB 250610B: SVOM/VT optical shallow decay DATE: 25/06/11 09:54:28 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> Y. L. Qiu, H. L. Li, L. P. Xin, C. Wu, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, Y. N. Ma, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), A. Saccardi, J. Rodriguez, N. Dagoneau (CEA), C. Van Hove (IJCLab) report on behalf of the SVOM mission team. SVOM/VT made a second ToO observation for GRB250610B (Saccardi et al., GCN 40671; Wang et al., GCN 40682; Wang et al, GCN 40683). The observation was performed in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With more data, the brightness of the counterpart (Schneider et al., GCN 40676; Gompertz et al., GCN 40677; Li et al., GCN 40678; Bochenek et al., GCN 40684) was fading by about 0.6+/-0.1 mag in both band within 9 hours. The latest brightness is derived as follows: Mid-time after the burst | exposure time| band | mag (AB) | mag err -------------------------|--------------|------|----------|-------- 9.53 hour | 14*70 sec | VT_B | 21.3 ｜ 0.1 9.50 hour | 12*70 sec | VT_R | 21.1 ｜ 0.1 Our photometry was not corrected for Galactic extinction. We noticed that there is a faint blue source at the position of the counterpart in Legency Survey DR10 with g=23.0 mag and r=22.75 mag. Considering the possible host galaxy's brightness and blue color，the photometry at later phase might be contaminated by the host galaxy's light, particularly in the VT_B band. With the slow decaying behavior of X-ray emission (Evans et al., GCN 40679; Liang et al., GCN 40681) and optical at early phase, it is not an ordinary GRB event. More multiband follow-up and spectrum observations are encouraged. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/40685. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38723] GRB 250610B: additional Liverpool Telescope optical observations
by GCN Circulars 11 Jun '25

11 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40684 SUBJECT: GRB 250610B: additional Liverpool Telescope optical observations DATE: 25/06/11 08:39:42 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 GRB 250610B (Saccardi et al., GCN 40671) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 4x100s exposures in the SDSS r’ and i’ filters starting at 2025-06-10 23:34:02 UT, approximately 7.0 hours after the trigger. We report detections in stacked images in both filters at the position of the reported optical counterpart (Schneider et al., GCN 40676). The obtained magnitudes are r = 21.21 ± 0.11 and i = 21.14 ± 0.13, in line with previous optical observations (Schneider et al., GCN 40676; Gompertz et al., GCN 40677; Li et al., GCN 40678). The photometry was calibrated using nearby PanSTARRS secondary standards and was not corrected for extinction. MJD (mid) T_mid-T_0 Filter Mag. (AB) 60836.98618 7.12 h r 21.21 ± 0.11 60836.99384 7.30 h i 21.14 ± 0.13 View this GCN Circular online at https://gcn.nasa.gov/circulars/40684. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38722] GRB 250610B: SVOM/GRM analysis
by GCN Circulars 11 Jun '25

11 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40683 SUBJECT: GRB 250610B: SVOM/GRM analysis DATE: 25/06/11 06:39:58 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: A. Saccardi, J. Rodriguez, N. Dagoneau (CEA) Report on behalf of the SVOM team: SVOM/GRM detected the burst GRB 250610B at 2025-06-10T16:32:58 UTC (T0), which is also detected by SVOM/ECLAIRs (A. Saccardi et al., GCN #40671) and Fermi/GBM (Yun Wang et al., GCN #40682) With the event-by-event data downloaded through the X-band ground station, we conducted the standard analysis pipeline of GRB 250610B. The GRM light curve shows that this burst consists of a single pulse with a T90 of 94 +/-14 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250610B.png With the localization of ECLAIRs (RA=200.1831, DEC=31.1028), the time-averaged spectrum from T0-10 to T0+80 s is best fitted by a Blackbody function. The temperature, parameterized as kT, is 13 +/- 1 keV. The event fluence (10-1000 keV) in this time interval is (2.3 +/- 0.2)E-06 erg/cm^2. The time-averaged spectrum can also be fitted by a power law function with an exponential high-energy cutoff adequately. The power law index is -1.2 +/- 0.5 and the cutoff energy, parameterized as Epeak, is 66 +15/-12 keV. The event fluence (10-1000 keV) in this time interval is (2.2 +/- 0.3)E-06 erg/cm^2. Thus GRB 250610B is consistent with Type II GRBs in the 'Amati' relation diagram, as shown at: https://www.bursthub.cn//admin/static/grb250610B_amati.png We note that the calibration of SVOM/GRM is undergoing thus these results are preliminary. Refined analysis will be reported later. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Chen-Wei Wang (IHEP) (cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/40683. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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