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

[vsnet-grb-info 41104] GRB 251205A: Liverpool Telescope further optical follow-up observations
by GCN Circulars 07 Dec '25

07 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43024 SUBJECT: GRB 251205A: Liverpool Telescope further optical follow-up observations DATE: 25/12/07 16:36:22 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek, D. A. Perley (LJMU), report: We observed the field of GRB 251205A (Lanava et al., GCN 43005) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 4x100s exposures the SDSS i and r filters starting at 2025-12-07 04:57:54 UT, approximately 29.3 hours after trigger. Some exposures were affected by telescope wobble or poor seeing and had to be discarded before stacking. We report detections in both filters, at the position first reported by Lanava et al., GCN 43005: MJD (mid) T_mid-T_0 Filter Mag. (AB) 61016.21035 29.4 h i 19.57 ± 0.06 61016.21529 29.5 h r 19.72 ± 0.07 The photometry is consistent with measurements by Lanava et al. GCN 43005; Lipunov et al. GCN 43006; de Ugarte Postigo et al. GCN 43008; Malesani et al. GCN 43009; O’Neill et al., GCN 43010; Mandarakas et al. GCN 43011; Pankov et al., GCN 43012; Bochenek and Perley, GCN 43015; Klingler et al., GCN 43016; Patil et al., GCN 43019; and Pérez-Fournon et al., GCN 43020. The photometry was obtained using nearby PanSTARRS secondary standards and was not corrected for extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43024. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41103] SVOM GRB251206.86: Global MASTER-Net observations report
by GCN Circulars 07 Dec '25

07 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43023 SUBJECT: SVOM GRB251206.86: Global MASTER-Net observations report DATE: 25/12/07 12:28:31 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the SVOM GRB251206.86 (trigger No 1765053354,20h 01m 18.62s , -04d 30m 48.6s, R=1) errorbox 53447 sec after notice time and 53742 sec after trigger time at 2025-12-07 11:31:36 UT, with upper limit up to 17.8 mag. The observations began at zenith distance = 71 deg. The sun altitude is -22.6 deg. The galactic latitude b = -18 deg., longitude l = 37 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3062682 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 53773 | 2025-12-07 11:31:36 | MASTER-Tunka | (20h 01m 24.73s , -04d 19m 35.9s) | C | 60 | 17.8 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43023. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41102] EP-WXT trigger 01709249380: confirmation of a stellar flare by BOOTES-5
by GCN Circulars 07 Dec '25

07 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43022 SUBJECT: EP-WXT trigger 01709249380: confirmation of a stellar flare by BOOTES-5 DATE: 25/12/07 10:30:51 GMT FROM: I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg(a)iaa.es> I. Perez-Garcia, E. J. Fernandez-Garcia, M. D. Caballero-Garcia, S.-Y. Wu, R. Sanchez-Ramirez, S. Guziy and A. J. Castro-Tirado (IAA-CSIC, Granada), I. M. Carrasco (SMA), M. Gritsevich (Univ. of Helsinki), C. Perez del Pulgar (Univ. of Malaga), Y.-D. Hu (GXU), S. Jeong (ADD, Daejeon), G. Garcia-Segura and D. Hiriart (IA-UNAM, Ensenada), D. R. Xiong (Yunnan Observatories of CAS, Kunming), and W. H. Lee (UNAM, Mexico DF), on behalf of a larger collaboration, report: Following the detection of trigger 01709249380 by EP-WXT (Li et al. GCN 43021), the 0.6m robotic telescopes BOOTES-5/JGU robotic telescope at San Pedro Martir Observatory (Mexico) responded to the alert on Dec 07, 9:25 UT (i.e. 6 min after the detection). Within the reported EP-FXT error circle we find the star 2MASS J05100460-0428037 decreasing 0.3 mag in brightness (g filter) and 0.15 mag (r filter) during a 50 min time interval, confirming the EP X-ray trigger due to a stellar flare. We would like to thank the staff at San Pedro Martir Observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/43022. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41101] The EP-WXT trigger 01709249380 is likely a flaring star
by GCN Circulars 07 Dec '25

07 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43021 SUBJECT: The EP-WXT trigger 01709249380 is likely a flaring star DATE: 25/12/07 09:58:15 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.-Z. Li (YNAO, CAS), K. R. Ni (CCNU), Y. J. Yi (BNU) , X. X. Sun and C. C. Jin (NAO,CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709249380 at the time of 2025-12-07T09:19:14, is likely a stellar flare associated with 2MASS J05100460-0428037 (T Tauri Star). The estimated flux of the flare is around 8e-11erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 6.5e31 erg/s erg/s. 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/43021. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41100] GRB 251205A: ZTF and ATLAS optical afterglow detections
by GCN Circulars 07 Dec '25

07 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43020 SUBJECT: GRB 251205A: ZTF and ATLAS optical afterglow detections DATE: 25/12/07 09:28:50 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> I. Pérez-Fournon (IAC and ULL), J. Basurto Merino, P.G. Berdayes, A. Caballero-Almagro, A. Cerón, M. Contreras, F. Díaz-Segado, T. Ferrer-Laviña, B. Gandolfi, V. Ghiraldo, J. Hernández Fung, L. Juliá-Maroto, E. Lekaroz-Urriza, M. Manzano García, E. Mejía-Martínez, J. Prieto Polo, M. Pulido-Torres, M. Quintana-Ansaldo, A. Schenone-Zanuzzi, A. Selezneva, T. Tundidor Rodríguez, E. Urquijo-Rodríguez (all ULL) and M. Abdul-Masih (IAC and ULL). We report on ZTF and ATLAS detections of the optical afterglow of the Swift GRB 251205A (Lanava et al., GCN Circ. 43005; Beardmore et al., GCN Circ. 43007; Dichiara et al., GCN Circ. 43017; and Krimm et al., GCN Circ. 43018) at a spectroscopic redshift of z = 1.100 (de Ugarte Postigo et al., GCN Circ. 43008). Both ZTF and ATLAS detected the optical afterglow of GRB 251205A during standard observations of these time-domain surveys. ZTF first detected this transient (ZTF25acgbeof) on 2025-12-06 at 12:16:12 UT at a ZTF g-band magnitude of g-ZTF = 19.168 +/- 0.169. It was reported to the Transient Name Server by Rehemtulla et al. (AT 2025afws, TNS Astronomical Transient Report No. 279483). Using the ATLAS forced-photometry server (Shingles et al. 2021, Transient Name Server AstroNote 2021-7), we find three ATLAS detections, as reported in the following table of ZTF and ATLAS photometry: MJD mag (AB) error survey filter 61015.511250 19.168 0.169 ZTF g 61015.543854 18.788 0.105 ZTF r 61015.625035 19.062 0.279 ATLAS orange 61015.628805 19.225 0.321 ATLAS orange 61015.646040 18.889 0.229 ATLAS orange These ZTF and ATLAS detections are consistent with other reported UV and optical detections: Lanava et al. (GCN Circ. 43005), Lipunov et al. (GCN Circ. 43006), de Ugarte Postigo et al. (GCN Circ. 43008), Malesani et al. (GCN Circ. 43009), O'Neill et al. (GCN Circ. 43010), Mandarakas et al. (GCN Circ. 43011), Pankov et al. (GCN Circ. 43012), Bochenek and Perley (GCN Circ. 43015), Klingler et al. (GCN Circ. 43016), and Patil et al. (GCN Circ. 43019). The ZTF coordinates of ZTF25acgbeof / AT 2025afws are RA (J2000) = 13:21:05.324, Dec (J2000) = 29:55:43.64, consistent within the errors with the optical and X-ray positions of the GRB 251205A afterglow reported by Lanava et al. (GCN Circ. 43005), Lipunov et al. (GCN Circ. 43006), Beardmore et al. (GCN Circ. 43007), de Ugarte Postigo et al. (GCN Circ. 43008), and Klingler et al. (GCN Circ. 43016). This work made use of the Astro-COLIBRI platform (P. Reichherzer et al. 2021, ApJS, 256, 5). View this GCN Circular online at https://gcn.nasa.gov/circulars/43020. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41099] GRB 251205A: GROWTH-India Telescope optical observations
by GCN Circulars 07 Dec '25

07 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43019 SUBJECT: GRB 251205A: GROWTH-India Telescope optical observations DATE: 25/12/07 08:44:48 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> S. Patil, A.P. Saikia, V. Swain, V. Vijaykumar, T. Mohan, V. Bhalerao (IITB), G.C. Anupama, S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of Swift GRB 251205A (Lanava et al., GCN Circ. 43005), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2025-12-05T23:46:13 UT, i.e., 6.43 minutes after the Swift BAT trigger. We obtained multiple exposures in r' filter. We detected the optical afterglow in our stacked image of r' filter at position reported by Swift UVOT (Lanava et al., GCN Circ. 43005). The photometry results are as follow: | MJD (mid) | Filter | t-t0 (in minutes) |Total Exposure Time (sec) | Magnitude (AB) | | ------------- | ------ |-----| ------------------ | -------------- | | 61014.99251157 | r' | 9.43 | 360 | 16.84 +/- 0.06 | | 61015.00966435 | r' | 34.13 | 360 | 17.02 +/- 0.06 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. Our magnitude is consistent with other optical observations (Lipunov et al., GCN 43004, de Ugarte Postigo et al., GCN 43008, Malesani et al. GCN 43009, O'Neill et al. 43010, Mandarakas et al. GCN 43011, Pankov et al. 43012, Bochenek et al. 43015, Klingler et al. 43016, ). The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. View this GCN Circular online at https://gcn.nasa.gov/circulars/43019. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41098] GRB 251205A: Swift-BAT refined analysis
by GCN Circulars 07 Dec '25

07 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43018 SUBJECT: GRB 251205A: Swift-BAT refined analysis DATE: 25/12/07 04:06:20 GMT FROM: Amy <yarleen(a)gmail.com> H. A. Krimm (NSF), S. D. Barthelmy (GSFC), R. Gupta (GSFC), S. Laha (GSFC/UMBC), S. Lanava (PSU), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 251205A (trigger #1420873) (Lanava et al., GCN Circ. 43005). The BAT ground-calculated position is RA, Dec = 200.260, 29.906 deg which is RA(J2000) = 13h 21m 02.5s Dec(J2000) = +29d 54' 21.2" with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 45%. The mask-weighted light curve shows a weak pulse that starts at ~T0 and peaks at ~T+9 s. The main pulse ends at ~T+40s, followed by a weak tail emission that lasts till ~T+140 s. T90 (15-350 keV) is 128.00 +- 65.97 sec (estimated error including systematics). The time-averaged spectrum from T+0.94 to T+144.94 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.67 +- 0.27. The fluence in the 15-150 keV band is 1.1 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+8.44 sec in the 15-150 keV band is 0.5 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1420873 View this GCN Circular online at https://gcn.nasa.gov/circulars/43018. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41097] GRB 251205A: Swift-XRT refined Analysis
by GCN Circulars 07 Dec '25

07 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43017 SUBJECT: GRB 251205A: Swift-XRT refined Analysis DATE: 25/12/07 03:50:01 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), C. Salvaggio (INAF-OAB), M. Ferro (INAF-OAB), R. Brivio (INAF-OAB) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.3 ks of XRT data for GRB 251205A, from 129 s to 94.1 ks after the trigger. The data comprise 352 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The late-time light curve (from T0+9.7 ks) can be modelled with a power-law decay with a decay index of alpha=0.77 (+0.12, -0.11). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.14 (+/-0.06). The best-fitting absorption column is 5.6 (+1.3, -1.2) x 10^20 cm^-2, in excess of the Galactic value of 1.2 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.95 (+0.16, -0.15) and a best-fitting absorption column of 3.8 (+3.5, -2.6) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.4 x 10^-11 (3.7 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.8 (+3.5, -2.6) x 10^20 cm^-2 Galactic foreground: 1.2 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.95 (+0.16, -0.15) The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01420873. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43017. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41096] GRB 251205A: Swift/UVOT Detection
by GCN Circulars 06 Dec '25

06 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43016 SUBJECT: GRB 251205A: Swift/UVOT Detection DATE: 25/12/06 18:47:19 GMT FROM: N. Klingler at NASA-GSFC/UMBC/CRESST II <noelklingler(a)gmail.com> N. Klingler (NASA-GSFC / UMBC / CRESST II) and Sophia Lanava (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251205A 149 s after the BAT trigger (Lanava et al., GCN Circ. 43005). A source consistent with the XRT position (RA, Dec = 13h 21m 05.26s, +29d 55' 44.2"; Beardmore et al., GCN Circ. 43007) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 13:21:05.34 = 200.27223 (deg.) Dec (J2000) = +29:55:44.0 = 29.92890 (deg.) with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence). Preliminary detections 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) Mag white 148.9 298.7 17.61 +/- 0.06 white 586.8 606.5 16.96 +/- 0.09 white 759.1 869.1 16.89 +/- 0.08 white 16513.5 17308.6 17.77 +/- 0.05 b 562.4 582.2 17.32 +/- 0.17 b 734.9 754.7 17.29 +/- 0.18 b 15601.3 16508.4 18.18 +/- 0.05 u 306.8 556.6 16.65 +/- 0.06 u 710.3 730.0 16.57 +/- 0.16 u 22323.1 22838.7 17.51 +/- 0.06 v 636.4 656.2 17.10 +/- 0.27 v 808.6 828.4 16.92 +/- 0.24 v 10660.9 11393.6 18.45 +/- 0.10 uvw1 685.8 705.5 16.18 +/- 0.18 uvw1 21416.9 22316.6 17.83 +/- 0.07 uvw2 9754.6 10654.4 18.44 +/- 0.10 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.014 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/43016. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41095] GRB 251205A: Liverpool Telescope optical follow-up observations
by GCN Circulars 06 Dec '25

06 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43015 SUBJECT: GRB 251205A: Liverpool Telescope optical follow-up observations DATE: 25/12/06 18:26:59 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek, D. A. Perley (LJMU), report: We observed the field of GRB 251205A (Lanava et al., GCN 43005) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 4x100s exposures the SDSS i and r filters starting at 2025-12-06 05:37:14 UT, approximately 5.95 hours after trigger. Some exposures were affected by telescope movement and had to be discarded. We report detections in both filters, at the position first reported by Lanava et al. GCN 43005: MJD (mid) T_mid-T_0 Filter Mag. (AB) 61015.23465 5.97 h i 17.93 ± 0.05 61015.24283 6.16 h r 18.06 ± 0.03 The photometry is consistent with measurements by Lanava et al. GCN43005; Lipunov et al. GCN 43006; de Ugarte Postigo et al. GCN 43008; Malesani et al. GCN 43009; O’Neill et al., GCN 43010; Mandarakas et al. GCN 43011 and Pankov et al., GCN 43012. The photometry was obtained using nearby PanSTARRS secondary standards and was not corrected for extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43015. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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