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

[vsnet-grb-info 36934] GRB 250114A: Swift detection of a burst with an optical counterpart
by GCN Circulars 14 Jan '25

14 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38927 SUBJECT: GRB 250114A: Swift detection of a burst with an optical counterpart DATE: 25/01/14 07:50:30 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> N. J. Klingler (GSFC/UMBC/CRESSTII), R. Brivio (INAF-OAB), J. J. DeLaunay (PSU), K. L. Page (U Leicester), C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), M. H. Siegel (PSU) and A. Tohuvavohu (Caltech) report on behalf of the Neil Gehrels Swift Observatory Team: At 07:33:19 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250114A (trigger=1281241). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 166.590, -15.143 which is RA(J2000) = 11h 06m 22s Dec(J2000) = -15d 08' 34" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 50 sec. The peak count rate was ~875 counts/sec (15-350 keV), at ~3 sec after the trigger. The XRT began observing the field at 07:35:27.7 UT, 128.3 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 166.57673, -15.11138 which is equivalent to: RA(J2000) = 11h 06m 18.42s Dec(J2000) = -15d 06' 41.0" with an uncertainty of 3.6 arcseconds (radius, 90% containment). This location is 122 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (5.06 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.9 (+3.65/-3.04) x 10^21 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 4.84e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 136 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 11:06:18.43 = 166.57679 DEC(J2000) = -15:06:41.7 = -15.11159 with a 90%-confidence error radius of about 0.74 arc sec. This position is 3.2 arc sec. from the center of the XRT error circle. The estimated magnitude is 20.35 with a 1-sigma error of about 0.20. No correction has been made for the expected extinction corresponding to E(B-V) of 0.056. Burst Advocate for this burst is N. J. Klingler (noelklin AT umbc.edu). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/38927. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36933] GRB 250101A: Terskol Zeiss-2000 optical observations
by GCN Circulars 14 Jan '25

14 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38926 SUBJECT: GRB 250101A: Terskol Zeiss-2000 optical observations DATE: 25/01/14 06:25:40 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> E. Mazaeva (IKI), N. Pankov (HSE, IKI), A. Pozanenko (IKI), N. Kapitanov (INASAN), A. Moskvitin (SAO RAS) report on behalf of the IKI-GRB-FuN collaboration: We performed optical observations of the field of GRB 250101A (Page et. al, GCN 38752; Li et. al, GCN 38753; Mohan et. al, GCN 38754; Zhu et. al, GCN 38755; Budnev et. al, GCN 38756; Wu et. al, GCN 38758; Zhu et. al, GCN 38759; Goad et. al, GCN 38761; Moskvitin et. al, GCN 38762; Odeh et. al, GCN 38763; Hu et. al, GCN 38764; Moskvitin et. al, GCN 38765; D'Avino et. al, GCN 38768; Escudero-Coca et. al, GCN 38769; Leonini et. al, GCN 38771; Dichiara et. al, GCN 38773; Zhang et. al, GCN 38774; Siegel, GCN 38775; Li et. al, GCN 38776; Komesh et. al, GCN 38777; Ghosh et. al, GCN 38779; Moskvitin et al., GCN 38780; Krimm et. al, GCN 38782; Komesh et. al, GCN 38790; Méndez-Lapido et. al, GCN 38810; Gupta et. al, GCN 38818; Ferro et. al, GCN 38831; Lin et. al, GCN 38837; Pankov et. al., GCN 38869; Pankov et. al, GCN 38890) in the R filter with the 2-meter Zeiss-2000 telescope of the Terskol observatory starting on 2025-01-01 17:27 UT, i.e. ~4.8 hours since trigger. The preliminary photometry of the optical afterglow is as follows: Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) (mid, days) (s) 2025-01-01 17:27:31 0.19926 38*120 R 20.11 0.04 22.4 2025-01-01 21:37:20 0.35498 30*60 R 19.40 0.05 21.5 2025-01-02 14:57:45 1.07870 57*30 R 22.13 0.33 22.1 2025-01-02 21:44:44 1.35811 39*30 R 21.93 0.28 22.1 2025-01-03 18:02:09 2.22881 90*60 R n/d n/d 22.7 The photometry is based on nearby stars from the PS1 catalog (Lupton 2005 transformations). No correction has been made for the Galactic extinction. The obtained results confirm the re-brightening visible in other observations (Moskvitin et. al, GCN 38765; Pankov et. al, GCN 38890). View this GCN Circular online at https://gcn.nasa.gov/circulars/38926. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36932] EP250108a / AT 2025kg: SAO RAS optical observations
by GCN Circulars 13 Jan '25

13 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38925 SUBJECT: EP250108a / AT 2025kg: SAO RAS optical observations DATE: 25/01/13 21:42:08 GMT FROM: Moskvitin Alexander at SAO RAS <mosk(a)sao.ru> A. S. Moskvitin and O. I. Spiridonova (SAO RAS), report on behalf of the GRB follow-up team. We observed the field of X-ray transient EP250108a detected by EP-WXT (Li et al. GCN 38861) with the SAO RAS 1-m telescope Zeiss-1000 on January 11, 17:34:02--18:47:16 UT (t_mid - T0 = 3.2362 days). We obtained 8 x 300 sec images in Rc band. The OT (Eyles-Ferris, GCN 38878; Zhu et al., GCN 38885; Malesani et al., GCN 38902; Kumar et al., GCN 38907; Zhu et al., GCN 38908, Levan et al., GCN 38909; Izzo, GCN 38912; Zou et al., GCN 38914) is marginally detected in our stacked image with the brightness of R = 20.56 +/- 0.27 (calibrated anainst nearby USNO-B1 stars and not corrected for the MW extinction). View this GCN Circular online at https://gcn.nasa.gov/circulars/38925. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36931] EP241021a: SMA radio observation
by GCN Circulars 13 Jan '25

13 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38924 SUBJECT: EP241021a: SMA radio observation DATE: 25/01/13 15:44:13 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> Amar Aryan (Graduate Institute of Astronomy, National Central University, Taiwan),Giorgos Michailidis (Aristotle University of Thessaloniki, Greece), Sourya Ranjan Das (Indian Institute of Space Science and Technology, India), Bhushan Kayastha (University of Chinese Academy of Sciences, China), Garrett K. Keating (Center for Astrophysics | Harvard & Smithsonian, Cambridge, USA), and Joshua Bennett Lovell (Center for Astrophysics | Harvard & Smithsonian, Cambridge, USA) report: We observed the field of the fast X-ray Transient EP 241021a (Hu et al. GCN 37834) with the Submillimeter Array (SMA) under program 2024B-S052 (PI: G. Keating) starting on 2024 Dec 25 at 03:13:33 UTC (64.92 days after the EP trigger) for 8.63 hours. Our observations were performed in “dual receiver mode”. We use "Uranus" as flux calibrator, "3c84" as bandpass calibrator and "0224+069" as gain calibrator. We did not find statistically significant emission at the position of the optical counterpart discovered by Fu et al. (GCN 37840, 37842), and the corresponding radio counterpart reported by Ricci et al. (GCN 37949), Carotenuto et al. (GCN 38014) and Schroeder et al. (GCN 38640). Thus, we estimate a 3-sigma upper limit of ~ 0.8 mJy at 235 GHz. We thank the the organizers of 2025 Submillimeter Array Interferometry School and the SMA observing staffs for scheduling and executing these observations. The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. We recognize that Maunakea is a culturally important site for the indigenous Hawaiian people; we are privileged to study the cosmos from its summit. View this GCN Circular online at https://gcn.nasa.gov/circulars/38924. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36930] GRB 250113A: SVOM/GRM observation of a long burst
by GCN Circulars 13 Jan '25

13 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38923 SUBJECT: GRB 250113A: SVOM/GRM observation of a long burst DATE: 25/01/13 14:04:20 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) report on behalf of the SVOM team: During the commissioning phase, SVOM/GRM was triggered in-flight by a long burst GRB 250113A (SVOM trigger reference: sb25011303) at 2025-01-13T06:24:36.900 UTC (T0). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multi-pulses with a T90 of 42 +2/-3 s. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250113A.png The SVOM/GRM on-ground localization of this burst is (J2000): RA: 321.4 deg DEC: -21.6 deg Error: 2.7 deg (1sigma, statistical only) We caution that the calibration of SVOM/GRM is undergoing and this localization is subject to systematic errors. In addition, the position of this burst, as determined by GRM, is located at about 159 degrees from the SVOM optical axis. However, we note that this GRM location is broadly consistent with the non-detection of ECLAIRs. 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/38923. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36929] GRB 250107A: VZLUSAT-2 detection
by GCN Circulars 13 Jan '25

13 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38922 SUBJECT: GRB 250107A: VZLUSAT-2 detection DATE: 25/01/13 12:05:33 GMT FROM: Andras Pal at Konkoly Observatory <apal(a)szofi.net> A. Pal (Konkoly Observatory), M. Dafcikova, J. Ripa, N. Werner (Masaryk U.), M. Ohno (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), K. Torigoe (Hiroshima U.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU) -- the VZLUSAT-2/GRB payload collaboration. The long-duration GRB 250107A (Fermi/GBM detection: GCN 38836; Swift/BAT-GUANO detection: GCN 38840; INTEGRAL/SPI-ACS peak detection at 2025-01-07 ~05:02:35 UTC) was detected by the GRB detector on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/). The data acquisition was performed by the GRB detector unit no. 1. The detection was confirmed at the peak time 2025-01-07 05:02:34 UTC. The T90 duration is 21 s and the significance during T90 reaches 9 sigma. The light curve obtained by VZLUSAT-2 is available here: https://vzlusat2.konkoly.hu/static/share/GRB250107A_GCN_VZLUSAT2.pdf All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/ The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral. View this GCN Circular online at https://gcn.nasa.gov/circulars/38922. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36928] EP250109b: optical upper limits with the Liverpool Telescope
by GCN Circulars 13 Jan '25

13 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38921 SUBJECT: EP250109b: optical upper limits with the Liverpool Telescope DATE: 25/01/13 12:00:00 GMT FROM: Amit Kumar at Royal Holloway - UoL/ U of Warwick, UK <amitkundu515(a)gmail.com> A. Kumar (RHUL), N. C. Sun (UCAS), J. R. Maund (RHUL), W. X. Li, Y. N. Wang (NAOC), and K. Wiersema (Herts) report: We observed the field of EP-WXT-detected transient EP250109b (Cheng et al., ATel #16974) using the IO:O imager on the 2m Liverpool Telescope. Observations were carried out between 2025-01-10 UT 23:39:42 and 2025-01-11 UT 01:02:34, corresponding to ~1.65 and ~1.71 days post-trigger, respectively, in the g, r, and z bands. In each band, 3×600s exposures were obtained. However, the g- and z-band frames were affected by trailing and are unsuitable for analysis. In the stacked r-band image (at ~1.67 days post-trigger), no new, uncatalogued source was detected within the EP-FXT localization uncertainty region (Cheng et al., ATel #16974), down to a limiting magnitude of r > 21.8 (AB). This circular may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/38921. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36927] GRB 250109A / EP250109a: GRBAlpha detection
by GCN Circulars 13 Jan '25

13 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38920 SUBJECT: GRB 250109A / EP250109a: GRBAlpha detection DATE: 25/01/13 11:54:38 GMT FROM: Andras Pal at Konkoly Observatory <apal(a)szofi.net> A. Pal (Konkoly Observatory), M. Dafcikova, J. Ripa, M. Kolar, N. Werner (Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), N. Husarikova, F. Munz , M. Topinka, M. Duriskova, L. Szakszonova, J.-P. Breuer, F. Hroch (Masaryk U.), T. Urbanec, M. Kasal, A. Povalac (Brno U. of Technology), J. Hudec, J. Kapus, M. Frajt (Spacemanic s.r.o), R. Laszlo, M. Koleda (Needronix s.r.o), M. Smelko, P. Hanak, P. Lipovsky (Technical U. of Kosice), G. Galgoczi (Wigner Research Center/Eotvos U.), Y. Uchida, H. Poon, H. Matake (Hiroshima U.), N. Uchida (ISAS/JAXA), T. Bozoki (Eotvos U.), G. Dalya (Eotvos U.), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), G. Friss (Eotvos U.), Y. Fukazawa, K. Hirose (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), K. Kapas (Eotvos U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), J. Takatsy (Eotvos U.), K. Torigoe (Hiroshima U.), N. Kogiso, M. Yoneyama (Osaka Metropolitan U.), M. Moritaki (U. Tokyo), T. Kano (U. Michigan) -- the GRBAlpha collaboration. The long-duration GRB 250107D (EP/WXT detection: GCN 38864; Fermi/GBM detection: GCN 38873; Swift/BAT-GUANO detection: GCN 38900) was observed by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; https://ui.adsabs.harvard.edu/abs/2023A%26A...677A..40P/abstract). The detection was confirmed at the peak time 2025-01-09 06:17:11.3 UTC. The T90 duration measured by GRBAlpha is 0.5 s and the overall significance during T90 reaches 6.6 sigma in the ~120-400 keV band. The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB250109A_GCN.pdf All GRBAlpha detections are listed at: https://monoceros.physics.muni.cz/hea/GRBAlpha/ GRBAlpha, launched on 2021 March 22, is a demonstration mission for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). The detector of GRBAlpha consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~50 keV to ~1000 keV. To increase the duty cycle and the downlink rate, the upgrade of the on-board data acquisition software stack is in progress. The ground segment is also supported by the radio amateur community and it takes advantage of the SatNOGS network for increased data downlink volume. View this GCN Circular online at https://gcn.nasa.gov/circulars/38920. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36926] GRB 250107D: GRBAlpha detection
by GCN Circulars 13 Jan '25

13 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38919 SUBJECT: GRB 250107D: GRBAlpha detection DATE: 25/01/13 11:53:21 GMT FROM: Andras Pal at Konkoly Observatory <apal(a)szofi.net> A. Pal (Konkoly Observatory), M. Dafcikova, J. Ripa, M. Kolar, N. Werner (Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), N. Husarikova, F. Munz , M. Topinka, M. Duriskova, L. Szakszonova, J.-P. Breuer, F. Hroch (Masaryk U.), T. Urbanec, M. Kasal, A. Povalac (Brno U. of Technology), J. Hudec, J. Kapus, M. Frajt (Spacemanic s.r.o), R. Laszlo, M. Koleda (Needronix s.r.o), M. Smelko, P. Hanak, P. Lipovsky (Technical U. of Kosice), G. Galgoczi (Wigner Research Center/Eotvos U.), Y. Uchida, H. Poon, H. Matake (Hiroshima U.), N. Uchida (ISAS/JAXA), T. Bozoki (Eotvos U.), G. Dalya (Eotvos U.), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), G. Friss (Eotvos U.), Y. Fukazawa, K. Hirose (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), K. Kapas (Eotvos U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), J. Takatsy (Eotvos U.), K. Torigoe (Hiroshima U.), N. Kogiso, M. Yoneyama (Osaka Metropolitan U.), M. Moritaki (U. Tokyo), T. Kano (U. Michigan) -- the GRBAlpha collaboration. The long-duration GRB 250107D (IPN Triangulation: GCN 38880; Konus/Wind detection: GCN 38881; CALET/CGBM detection: GCN 38897; INTEGRAL/SPI-ACS peak detection at 2025-01-07 ~05:23:36 UTC) was observed by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; https://ui.adsabs.harvard.edu/abs/2023A%26A...677A..40P/abstract). The detection was confirmed at the peak time 2025-01-07 05:23:36.7 UTC. The T90 duration measured by GRBAlpha is 0.5 s and the overall significance during T90 reaches 6.6 sigma in the ~120-400 keV band. The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB250107D_GCN.pdf All GRBAlpha detections are listed at: https://monoceros.physics.muni.cz/hea/GRBAlpha/ GRBAlpha, launched on 2021 March 22, is a demonstration mission for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). The detector of GRBAlpha consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~50 keV to ~1000 keV. To increase the duty cycle and the downlink rate, the upgrade of the on-board data acquisition software stack is in progress. The ground segment is also supported by the radio amateur community and it takes advantage of the SatNOGS network for increased data downlink volume. View this GCN Circular online at https://gcn.nasa.gov/circulars/38919. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36925] GRB 250106A: Swift-XRT afterglow detection
by GCN Circulars 13 Jan '25

13 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38918 SUBJECT: GRB 250106A: Swift-XRT afterglow detection DATE: 25/01/13 10:26:18 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne (U. Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , M. A. Williams (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has conducted further observations of the field of the SVOM/ECLAIRs-detected burst GRB 250106A. The observations now extend from T0+20.2 ks to T0+579.8 ks and have a total exposure time of 7.9 ks. Of the sources previously reported, "Source 1" is fading with >3-sigma significance, and is therefore likely the GRB afterglow. Using 2981 s of PC mode data and 3 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 = 117.23873, +63.81242 which is equivalent to: RA (J2000): 07h 48m 57.29s Dec(J2000): +63d 48' 44.7" with an uncertainty of 3.0 arcsec (radius, 90% confidence). This position is 3.4 arcmin from the SVOM/ECLAIRs position. The source is fading with alpha >0.6. A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.4 (+0.8, -0.7). The best-fitting absorption column is 3.7 (+3.4, -2.4) x 10^21 cm^-2, in excess of the Galactic value of 4.5 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 3.1 x 10^-11 (6.2 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.7 (+3.4, -2.4) x 10^21 cm^-2 Galactic foreground: 4.5 x 10^20 cm^-2 Excess significance: 2.2 sigma Photon index: 2.4 (+0.8, -0.7) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00021753. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021753. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/38918. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36924] Fermi trigger No 758442826: Global MASTER-Net observations report
by GCN Circulars 13 Jan '25

13 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38917 SUBJECT: Fermi trigger No 758442826: Global MASTER-Net observations report DATE: 25/01/13 07:16:53 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB250113.27 (trigger No 758442826,07h 04m 33.60s , -27d 46m 12.0s, R=6.15) errorbox 86 sec after notice time and 112 sec after trigger time at 2025-01-13 06:35:33 UT, with upper limit up to 19.0 mag. The observations began at zenith distance = 28 deg. The sun altitude is -31.0 deg. The galactic latitude b = -9 deg., longitude l = 240 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2741637 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 122 | 2025-01-13 06:35:33 | MASTER-OAFA | (07h 22m 47.71s , -30d 20m 23.7s) | C | 20 | 17.1 | 123 | 2025-01-13 06:35:34 | MASTER-OAFA | (07h 12m 10.44s , -30d 42m 28.8s) | C | 20 | 18.5 | 157 | 2025-01-13 06:36:13 | MASTER-OAFA | (07h 22m 47.78s , -30d 20m 22.3s) | C | 10 | 16.8 | 167 | 2025-01-13 06:36:13 | MASTER-OAFA | (07h 12m 10.49s , -30d 42m 28.2s) | C | 30 | 18.7 | 198 | 2025-01-13 06:36:49 | MASTER-OAFA | (07h 22m 47.77s , -30d 20m 21.5s) | C | 20 | 17.1 | 208 | 2025-01-13 06:36:49 | MASTER-OAFA | (07h 12m 10.51s , -30d 42m 27.8s) | C | 40 | 18.8 | 248 | 2025-01-13 06:37:35 | MASTER-OAFA | (07h 22m 47.82s , -30d 20m 20.3s) | C | 30 | 17.3 | 259 | 2025-01-13 06:37:35 | MASTER-OAFA | (07h 12m 10.55s , -30d 42m 27.3s) | C | 50 | 18.9 | 309 | 2025-01-13 06:38:30 | MASTER-OAFA | (07h 22m 47.86s , -30d 20m 19.2s) | C | 40 | 17.4 | 319 | 2025-01-13 06:38:31 | MASTER-OAFA | (07h 12m 10.60s , -30d 42m 26.6s) | C | 60 | 19.0 | 381 | 2025-01-13 06:39:37 | MASTER-OAFA | (07h 22m 47.91s , -30d 20m 18.3s) | C | 50 | 17.5 | 391 | 2025-01-13 06:39:37 | MASTER-OAFA | (07h 12m 10.66s , -30d 42m 26.1s) | C | 70 | 19.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/38917. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36923] EP250111a: KAIT optical observations
by GCN Circulars 12 Jan '25

12 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38916 SUBJECT: EP250111a: KAIT optical observations DATE: 25/01/12 05:08:43 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of EP250111a (Zhao et al., GCN 38905) starting at 02:53:32 UT on 2025-01-11, ~1.55 hr after the trigger. A set of clear (roughly R) band images were obtained. We marginally detect the optical afterglow (Fu et al., GCN 38906; Pankov et al., GCN 38913) in the 11x60s coadd image and measure its brightness to be 20.5 +/- 0.3 (Vega) at a mid time of ~2.70 hr after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/38916. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36922] GRB 250109A / EP250109a: Mephisto optical upper limits
by GCN Circulars 12 Jan '25

12 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38915 SUBJECT: GRB 250109A / EP250109a: Mephisto optical upper limits DATE: 25/01/12 04:25:54 GMT FROM: Chenxu Liu at Mephisto Team <cxliu(a)ynu.edu.cn> Xingzhu Zou, Chenxu Liu, Guowang Du, Brajesh Kumar, Tao Wang, Edoardo Lagioia, Yuan Fang, Xinlei Chen, Yu Pan (all SWIFAR, YNU), Xuhui Han, Pinpin Zhang, Liping Xin, Chao Wu (all NAOC), Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team: The Mephisto team observed the field of the GRB 250109A / EP250109a (EP Team , GCN 38864, GCN 38889; Fermi GBM team, GCN 38873, GCN 38887; the Swift XRT team, GCN 38867, GCN 38899; James DeLaunay et al., GCN 38900; A. Moskvitin et al. GCN 38901; the SVOM team, GCN 38904) with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. Simultaneous uvgriz band photometric observations were conducted starting from 12:27:02 2025-01-09 UT (6.15 hr after the EP-WXT trigger) under fair observational conditions. Several frames with different exposure time were taken. No new uncatalogued optical sources were detected within the EP-WXT error circle in our stacked images of uvgriz bands. The preliminary photometry and 3 sigma upper limits are below. Start_Time(UT) | Band | Exp(s) | LimMag (AB) --------------------|------|--------|------------ 2025-01-09T12:27:02 | u | 180*2 | >20.02 2025-01-09T12:34:13 | v | 180*2 | >20.15 2025-01-09T12:27:03 | g | 50*6 | >20.64 2025-01-09T12:34:14 | r | 50*6 | >20.73 2025-01-09T12:27:02 | i | 79*4 | >20.14 2025-01-09T12:34:14 | z | 79*4 | >19.19 ------------------------------------------------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m 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/38915. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36921] EP250108a: Mephisto detection
by GCN Circulars 12 Jan '25

12 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38914 SUBJECT: EP250108a: Mephisto detection DATE: 25/01/12 03:05:54 GMT FROM: Chenxu Liu at Mephisto Team <cxliu(a)ynu.edu.cn> Xingzhu Zou, Chenxu Liu, Brajesh Kumar, Xinlei Chen, Guowang Du, Tao Wang, Edoardo Lagioia, Yuan Fang, Yu Pan (all SWIFAR, YNU), Xuhui Han, Pinpin Zhang, Liping Xin, Chao Wu (all NAOC), Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team: The X-ray transient EP250108a detected by EP-WXT (Li et al. GCN 38861) was confirmed with an optical counterpart by Eyles-Ferris (GCN 38878); Zhu et al., (GCN 38885); Malesani et al., (GCN 38902); Kumar et al., (GCN 38907) and L. Izzo (GCN 38861). The VLT/X-shooter spectroscopic analysis by Zhu et al. (GCN 38908) confirms the source redshift z = 0.176 and classified the transient as LFBOT (dubbed “the kangaroo”). We observed the field of EP250108a with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. Simultaneous uvgriz band photometric observations were conducted on 2025-01-09 and 2025-01-10 (0.97 day and 2.06 days after the EP-WXT trigger) under fair observational conditions. Here, we report the preliminary analysis of our images taken on 2025-01-09. An optical counterpart is clearly detected (>5σ) at the transient location identified by Eyles-Ferris (GCN 38878) in the stacked images of uvgr bands. The preliminary u-, v-, g-, r- bands PSF photometry and the 3 sigma i-, z-bands upper limits are listed below. Further analysis is in progress and multi-band observations are planned in the upcoming nights. Start_Time(UT) | Band | Exp | Mag/LimMag (AB) | Significance ------------------------|------|----------|------------------|-------------- 2025-01-09T11:45:52 | u | 180s*2 | 19.89 ± 0.23 | 6.4σ 2025-01-09T11:53:04 | v | 180s*2 | 20.02 ± 0.19 | 6.6σ 2025-01-09T11:45:53 | g | 50s*6 | 20.05 ± 0.14 | 7.8σ 2025-01-09T11:53:04 | r | 50s*6 | 20.45 ± 0.17 | 5.7σ 2025-01-09T11:45:53 | i | 79s*4 | >20.66 | < 3σ 2025-01-09T11:53:04 | z | 79s*4 | >19.92 | < 3σ ---------------------------------------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m 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/38914. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36920] EP250111a: Mondy optical observation
by GCN Circulars 11 Jan '25

11 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38913 SUBJECT: EP250111a: Mondy optical observation DATE: 25/01/11 23:14:49 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex(a)gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP) report on behalf of the IKI GRB FuN collaboration: We performed optical observations of the field of EP250111a (Zhao et. al, GCN 38905; Kennea et. al, GCN 38910) in the R filter with the 1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy). The observations started on 2025-01-11 11:57 UT, i.e. ~0.46 days since trigger. We detect the optical source proposed by Fu et. al, GCN 38906 as an optical transient of EP250111a. Preliminary photometry of the source is the following: Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) (mid, days) (s) 2025-01-11 11:57:42 0.46301 51*70 R 21.20 0.15 21.4 View this GCN Circular online at https://gcn.nasa.gov/circulars/38913. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36919] EP250108a / AT 2025kg: LCO optical observations
by GCN Circulars 11 Jan '25

11 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38912 SUBJECT: EP250108a / AT 2025kg: LCO optical observations DATE: 25/01/11 22:31:07 GMT FROM: luca.izzo(a)inaf.it L. Izzo (INAF-OACn and DARK/NBI) reports: We observed the field of EP250108A (Li et al., GCN #38861) / AT 2025kg (the "kangaroo"; Zhu et al., GCN #38908) with the Sinistro instrument mounted on the 1-m telescope of the LCO network, located at the Sutherland Observatory, South Africa. Observations started on 2025 January 11 at 20:59 UT (3.35 days after the EP trigger). We obtained a series of 3x300 s images in the SDSS-G and SDSS-r filters. At the location of AT 2025kg (Eyles-Ferris, GCN #38878; Zhu et al., GCN #38885; Malesani et al., GCN #38902; Kumar et al., GCN #38907; Levan et al., GCN #38909) we detect the source in both stacked images. We measure preliminary magnitudes of g = 20.49 +/- 0.10 mag, and r = 20.61 +/- 0.11 mag (AB), calibrated against nearby stars from the Pan-STARRS catalog. This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 101004719. We also acknowledge the use of the ECSnoopy package by E. Cappellaro. View this GCN Circular online at https://gcn.nasa.gov/circulars/38912. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36918] EP250111a: Global MASTER-Net observations report
by GCN Circulars 11 Jan '25

11 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38911 SUBJECT: EP250111a: Global MASTER-Net observations report DATE: 25/01/11 16:27:37 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP250111a ( EP Team et al., GCN 38905) errorbox 22034 sec after notice time and 48770 sec after trigger time at 2025-01-11 14:53:34 UT, with upper limit up to 17.1 mag. Observations started at twilight. The observations began at zenith distance = 50 deg. The sun altitude is -10.3 deg. The galactic latitude b = 20 deg., longitude l = 158 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2740256 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 48800 | 2025-01-11 14:53:34 | MASTER-Kislovodsk | (06h 27m 26.49s , +56d 59m 55.8s) | C | 60 | 16.7 | 48845 | 2025-01-11 14:53:34 | MASTER-Kislovodsk | (06h 27m 26.49s , +56d 59m 55.8s) | C | 150 | 17.1 | Coadd 48880 | 2025-01-11 14:54:54 | MASTER-Kislovodsk | (06h 27m 31.58s , +57d 00m 09.6s) | C | 60 | 16.7 | 48945 | 2025-01-11 14:56:13 | MASTER-Kislovodsk | (06h 27m 29.58s , +57d 01m 53.7s) | C | 30 | 16.4 | 48994 | 2025-01-11 14:57:03 | MASTER-Kislovodsk | (06h 27m 30.55s , +57d 00m 00.6s) | C | 30 | 16.4 | 49059 | 2025-01-11 14:57:52 | MASTER-Kislovodsk | (06h 27m 34.60s , +57d 01m 58.6s) | C | 60 | 16.7 | 49139 | 2025-01-11 14:59:12 | MASTER-Kislovodsk | (06h 27m 27.57s , +57d 01m 01.9s) | C | 60 | 16.7 | 49218 | 2025-01-11 15:00:32 | MASTER-Kislovodsk | (06h 27m 27.53s , +57d 02m 04.4s) | C | 60 | 16.7 | 49299 | 2025-01-11 15:01:52 | MASTER-Kislovodsk | (06h 27m 32.46s , +57d 01m 06.5s) | C | 60 | 16.8 | 49378 | 2025-01-11 15:03:12 | MASTER-Kislovodsk | (06h 27m 26.35s , +57d 00m 09.3s) | C | 60 | 16.8 | 49458 | 2025-01-11 15:04:31 | MASTER-Kislovodsk | (06h 27m 32.25s , +57d 00m 29.7s) | C | 60 | 16.8 | 49537 | 2025-01-11 15:05:51 | MASTER-Kislovodsk | (06h 27m 30.17s , +57d 02m 06.8s) | C | 60 | 16.8 | 49617 | 2025-01-11 15:07:11 | MASTER-Kislovodsk | (06h 27m 29.07s , +57d 00m 33.5s) | C | 60 | 16.8 | 49697 | 2025-01-11 15:08:30 | MASTER-Kislovodsk | (06h 27m 32.95s , +57d 01m 50.4s) | C | 60 | 16.8 | 49777 | 2025-01-11 15:09:51 | MASTER-Kislovodsk | (06h 27m 25.83s , +57d 01m 23.6s) | C | 60 | 16.8 | 49887 | 2025-01-11 15:11:10 | MASTER-Kislovodsk | (06h 27m 25.75s , +57d 02m 27.6s) | C | 120 | 16.9 | 50027 | 2025-01-11 15:13:30 | MASTER-Kislovodsk | (06h 27m 33.48s , +57d 01m 32.6s) | C | 120 | 17.0 | 50166 | 2025-01-11 15:15:50 | MASTER-Kislovodsk | (06h 27m 25.14s , +57d 00m 38.8s) | C | 120 | 16.9 | 50306 | 2025-01-11 15:18:10 | MASTER-Kislovodsk | (06h 27m 29.80s , +57d 00m 54.7s) | C | 120 | 16.9 | 50446 | 2025-01-11 15:20:29 | MASTER-Kislovodsk | (06h 27m 28.56s , +57d 02m 34.7s) | C | 120 | 17.0 | 50586 | 2025-01-11 15:22:50 | MASTER-Kislovodsk | (06h 27m 28.31s , +57d 01m 22.1s) | C | 120 | 17.0 | 50726 | 2025-01-11 15:25:09 | MASTER-Kislovodsk | (06h 27m 30.15s , +57d 02m 55.1s) | C | 120 | 17.0 | 50866 | 2025-01-11 15:27:29 | MASTER-Kislovodsk | (06h 27m 23.97s , +57d 02m 04.2s) | C | 120 | 16.9 | 51006 | 2025-01-11 15:29:49 | MASTER-Kislovodsk | (06h 27m 23.64s , +57d 03m 10.2s) | C | 120 | 16.9 | 51145 | 2025-01-11 15:32:09 | MASTER-Kislovodsk | (06h 27m 30.20s , +57d 02m 15.1s) | C | 120 | 16.9 | 51285 | 2025-01-11 15:34:29 | MASTER-Kislovodsk | (06h 27m 22.93s , +57d 01m 20.6s) | C | 120 | 16.9 | 51425 | 2025-01-11 15:36:49 | MASTER-Kislovodsk | (06h 27m 29.84s , +57d 01m 53.1s) | C | 120 | 16.8 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/38911. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36917] EP250111a: Swift/XRT detection and fading
by GCN Circulars 11 Jan '25

11 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38910 SUBJECT: EP250111a: Swift/XRT detection and fading DATE: 25/01/11 14:46:54 GMT FROM: Jamie Kennea at Penn State <jak51(a)psu.edu> J. A. Kennea (PSU), P. A. Evans and K. L. Page (Leicester) on behalf of the Swift/XRT report: At 04:08UT on January 9th, 2025 Swift began a 1.7ks target-of-opportunity observation of the Einstein Probe discovered transient EP250111a (GCN #38905), approximately 2.8 hours after the EP trigger. XRT detects a previously uncatalogued point source at the following coordinates: RA/Dec(J2000) = 97.17996, +56.8970, which is equivalent to: RA(J2000) = 06h 28m 43.19s Dec(J2000) = +56° 53′ 49.1″ with an estimated uncertainty of 5.8 arc-seconds radius (90% confidence). This position lies 5 arc-seconds from the reported localization by the EP FXT reported in GCN #38905. This position lies 5.6 arc-seconds from the reported NOT optical candidate (GCN #38906). The X-ray flux of this source is 3.9(+1.4/-1.1) x 10^-13 erg/s/cm^2 (0.3-10 keV), approximately an order of magnitude fainter than the FXT flux. View this GCN Circular online at https://gcn.nasa.gov/circulars/38910. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36916] EP250108a / AT 2025kg: Swift UVOT detections
by GCN Circulars 11 Jan '25

11 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38909 SUBJECT: EP250108a / AT 2025kg: Swift UVOT detections DATE: 25/01/11 13:01:52 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> A.J. Levan (Radboud), L. Cotter (UCD), D. B. Malesani (DAWN/NBI & Radboud), A. Martin-Carrillo (UCD), P.G. Jonker (Radboud) report on behalf of a larger collaboration. The location of EP250108a (Lin et al., GCN 38861; Eyles-Ferris, GCN 38878) was observed with the Neil Gehrels Swift Observatory on 10 Jan 2025, starting at 15:17 UT, that is 2.12 days since the onset of the outburst. At the location of the optical counterpart AT 2025kg (the “kangaroo”; Eyles-Ferris, GCN 38878; Zhu et al., GCN 38885; Malesani et al., GCN 38902; Kumar et al., GCN 38907) we clearly identify the source in both the UVW1 and UVW2 filters, with preliminary AB magnitudes of UVW1 = 20.6 +/- 0.2 and UVW2 = 21.4 +/- 0.2. These detections confirm the blue shape of the spectral energy distribution, as also indicated by Zhu et al. (GCNs 38885, 38908) and Malesani et al. (GCN 38902), but also indicate that it does not continue to rise strongly through the UV region. At a redshift of z = 0.176 (Zhu et al., GCN 38908) our measurement corresponds to an absolute AB magnitude of M_UVW1 = -18.9. At 3 days post discovery (likely somewhat later post-onset) AT 2018cow had M_UVW1 = -20.6 AB (Perley et al. 2019, doi:10.1093/mnras/sty3420), suggesting that, in the UV, AT 2025kg is somewhat fainter than AT 2018cow. At the position of AT 2025kg, no significant X-ray emission is detected by XRT, down to a 3-sigma upper limit of 3.8*10^-3 c s^-1, computed using the online tool at the University of Leicester (https://www.swift.ac.uk/user_objects/). We thank the Swift team for the very rapid scheduling of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/38909. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36915] EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
by GCN Circulars 11 Jan '25

11 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38908 SUBJECT: EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification DATE: 25/01/11 12:14:29 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> Z.P. Zhu (NAOC), G. Corcoran (UCD), A. J. Levan (Radboud), L. Izzo (INAF/OACn), R. Eyles-Ferris (Leicester), J. P. U. Fynbo (DAWN/NBI), G. Leloudas (DTU Space), D. B. Malesani (DAWN/NBI and Radboud), A. Saccardi (CEA/Irfu), A. L. Thakur (INAF/IAPS), D. Xu (NAOC), B. P. Gompertz (U. Birmingham), P. G. Jonker (Radboud), report on behalf of the Stargate collaboration. We observed the optical counterpart AT 2025kg (Eyles-Ferris, GCN 38878; Zhu et al., GCN 38885; Malesani et al., GCN 38902; Kumar et al., GCN 38907) of the transient EP250108a (Li et al., GCN 38861) using the ESO VLT UT3 (Melipal) equipped with the X-shooter instrument. Our spectra cover the wavelength range 3000-21000 AA, and consist of 4 exposures by 600 s each. The observation mid time was 2025 Jan 11.08 UT (2.56 days after the EP trigger). Bright, blue continuum is detected over the UVB and VIS arms. Emission lines from Halpha, [O II] 3727/29, and faint [O III] 5007 are visible at a common redshift z = 0.176. At the same redshift, we also detect (narrow) absorption from Ca II H and K. This is thus the likely redshift of EP250108a. In the UV, there is a broad absorption feature, at an observed wavelength of ~3600 AA and with a FWHM of ~15,000 km s^-1. This feature is not identified at the moment. The spectral shape (mostly featureless) and luminosity are overall similar to the early AT 2018cow (e.g., Prentice et al., doi:10.3847/2041-8213/aadd90), both being hot blackbodies. The luminosity (absolute g-band magnitude ~ -20) and blue color robustly put this object in the region of luminous FBOTs (e.g. Ho et al., doi:10.3847/1538-4357/acc533). We tentatively suggest that AT 2025kg belongs to this class of objects, and humorously dub it "the kangaroo". At this redshift, the X-ray peak flux (Li et al., GCN 38861) corresponds to a luminosity of ~1.3*10^46 erg s^-1. We thank excellent support from the observing staff in Paranal, in particular Francesca Lucertini, Rodrigo Palominos, and Linda Schmidtobreick. View this GCN Circular online at https://gcn.nasa.gov/circulars/38908. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36914] EP250108a: optical follow-up observations with the Liverpool Telescope
by GCN Circulars 11 Jan '25

11 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38907 SUBJECT: EP250108a: optical follow-up observations with the Liverpool Telescope DATE: 25/01/11 11:54:00 GMT FROM: Amit Kumar at Royal Holloway - UoL/ U of Warwick, UK <amitkundu515(a)gmail.com> A. Kumar, J. R. Maund (RHUL), N. C. Sun (UCAS), W. X. Li, Y. N. Wang (NAOC), and K. Wiersema (Herts) report: We conducted optical follow-up observations of the possible optical counterpart (Eyles-Ferris, GCN 38878; Zhu et al., GCN 38885; Malesani et al., GCN 38902) of the EP-detected X-ray transient EP250108a (Li et al., GCNs 38861 and 38888) using the IO:O imager at the 2m Liverpool Telescope. Multi-band observations were performed starting on 2025-01-09 UT 22:06:09.685 and 2025-01-10 UT 19:41:48.380 (nearly 1.4 and 2.3 days post-trigger, respectively). Based on our preliminary analysis: In the stacked g-band image observed at ~1.4 days post-trigger, we detected the optical counterpart of EP250108a at a position consistent with the optical counterpart identified by Eyles-Ferris, GCN 38878. Based on our preliminary PSF photometry, the magnitude of the counterpart in the stacked g-band image is 20.2 ± 0.1 (AB); consistent with the magnitudes reported by Zhu et al., GCN 38885. The counterpart exhibits clear signs of brightening (as suggested by Zhu et al., GCN 38885), and we recommend continued follow-up observations. The quoted magnitudes are not corrected for the Galactic extinction in the direction of the EP-transient. Further analysis and observations are planned. This circular may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/38907. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36913] EP250111a: NOT likely optical counterpart
by GCN Circulars 11 Jan '25

11 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38906 SUBJECT: EP250111a: NOT likely optical counterpart DATE: 25/01/11 09:42:34 GMT FROM: Dong Xu at NAOC/CAS <dxu(a)nao.cas.cn> S.Y. Fu, J. An, S.Q. Jiang, X. Liu, Z.P. Zhu, D. Xu (NAOC), J.P.U. Fynbo (DAWN/NBI), A. H. de la Fuente, S. G. Sorensen (NOT) report on behalf of a large collaboration: We observed the field of EP250111a detected by Einstein Probe (EP, Zhao et al., GCN 38905), using the ALFOSC instrument mounted on the Nordic Optical Telescope (NOT). Observations started at 02:58:45.5 UT on 2025-01-11, i.e. 1.63 hr after the trigger, and 9 x100 s frames were obtained in the SDSS-r band. An uncatalogued source is detected in the stacked frame within the EP/FXT error circle (EP, Zhao et al., GCN 38905) and localized at coordinates R.A. (J2000) = 06:28:43.29 Dec. (J2000) = +56:53:54.76 with an uncertainty of ~ 0.5 arcsec. The source has r ~ 20.7 mag, calibrated with Pan-STARRS DR1 and not corrected for Galactic extinction. There was no known NEO object at the above position by checking MPC. We thus conclude the source is very likely the optical counterpart of EP250111a. Further observations are encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/38906. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36912] EP250111a: a new X-ray transient detected by Einstein Probe
by GCN Circulars 11 Jan '25

11 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38905 SUBJECT: EP250111a: a new X-ray transient detected by Einstein Probe DATE: 25/01/11 08:44:14 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> T. Zhao (NAO, CAS), X. L. Chen (YNU), Q. C. Shui (IHEP, CAS), Kaushik Chatterjee (YNU), T. Y. Lian and C. C. Jin (NAO, CAS) report on behalf of the Einstein Probe team We report on the detection of an X-ray transient designated EP250111a by the Einstein Probe (EP) mission, which triggered the on-board processing unit at 2025-01-11T01:20:44 (UTC) (trigger ID: 01709130131). The transient event started at 2025-01-11T01:20:24 (UTC) and lasted for 83s before the observation was interrupted by the autonomous follow-up observation. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic equivalent hydrogen column density of 1.11 x 10^21 cm^-2 and a photon index of 1.01 (-0.52/+0.54). The derived average observed 0.5-4 keV flux is 1.39 (-0.40/+0.53) x 10^(-9) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. An autonomous observation was performed by the Follow-up X-ray Telescope (FXT) about four minutes later. An uncatalogued source was detected at R.A. = 97.1809, DEC = 56.8983 (J2000) with an uncertainty of about 20 arcsec (radius, 90% C.L. statistical and systematic). The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic equivalent hydrogen column density of 1.11 x 10^21 cm^-2 and a photon index of 2.42 (-0.14/+0.15). The derived average observed 0.5-10 keV flux is 3.43 (-0.33/+0.36) x 10^(-12) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. More information on this source will be updated when the full telemetry data is received. Further follow-up observations are encouraged to identify the nature of this X-ray transient. 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/38905. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36911] EP250109a/GRB 250109A:SVOM/VT optical counterpart
by GCN Circulars 11 Jan '25

11 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38904 SUBJECT: EP250109a/GRB 250109A:SVOM/VT optical counterpart DATE: 25/01/11 02:50:01 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> SVOM/VT commissioning team: Y. L. Qiu, H. L. Li, L. P. Xin, C. Wu, X. H. Han, J. Wang, W. J. Xie, H. B. Cai, Y. Xu, Y. J. Xiao, P. P. Zhang, J. S. Deng, L. Lan, X. M. Lu, R. S. Zhang, Z. H. Yao (NAOC), J. Zhang, L. J. Dan, G. Y. Zou, C. J. Wang, Y. F. Du, C. Huang (XIOPM) SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Olivier Godet (IRAP), Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Shao-Lin Xiong (IHEP), Bing Zhang (UNLV) report on behalf of the SVOM team: The further analysis of the candidate(Qiu et al., GCN 38872) for the first ToO observation EP250109a / GRB 250109A(Li et al., GCN 38864; Fermi GBM team, GCN 38873, DeLaunay et al., GCN 38900) showed that it was fading for about 0.5 mag from 4.13 hours to 9.65 hours. The SVOM/VT conducted the second ToO follow-up observations for the transient in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously, from 31.27 hours to 38.79 hours after the burst. The candidate was still clearly detected in VT_R stacked image with VT_R=23.2+/-0.2 in AB magnitude at the mid time of 35.2 hours post the burst, with a total exposure time of 102*100 seconds. Given the continuous fading of about 0.9 mag during VT_R total observations, as well as the optical detection of Zeiss-2000 (Moskvitin et al., GCN 38901) and the XRT detection (Kennea et al., GCN 38899), it is confirmed that this source is the optical afterglow of the burst. 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/38904. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36910] GRB 250101B: Fermi GBM Observation
by GCN Circulars 11 Jan '25

11 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38903 SUBJECT: GRB 250101B: Fermi GBM Observation DATE: 25/01/11 01:26:07 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA), S. Bala (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 23:14:12.65 UT on 01 January 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250101B (trigger 757466057/250101968). which was also detected by SVOM/GRM (Zhang et al. 2025, GCN 38793). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 70.87, Dec = -3.25 (J2000 degrees, equivalent to J2000 4h 43m, -3d 15'), with a statistical uncertainty of 3.29 degrees. (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a mixture of two Gaussians, one with a radius of 1.8 degrees (52% contribution) and one with a radius of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]). The angle from the Fermi LAT boresight is 49 degrees. The GBM light curve consists of a single emission episode with two distinct peaks with a duration (T90) of about 4.5 s (50-300 keV). The time-averaged spectrum from T0-1.0 to T0+5.1 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.34 +/- 0.09 and the cutoff energy, parameterized as Epeak, is 146 +/- 7 keV. The event fluence (10-1000 keV) in this time interval is (2.418 +/- 0.8)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.77 s in the 10-1000 keV band is 5 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/38903. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36909] EP250108a: further NOT optical observations
by GCN Circulars 11 Jan '25

11 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38902 SUBJECT: EP250108a: further NOT optical observations DATE: 25/01/11 00:43:54 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> D. B. Malesani (DAWN/NBI and Radboud), A. J. Levan (Radboud and Warwick), A. van Hoof (Radboud), P. G. Jonker (Radboud), D. Xu (NAOC), report on behalf of a larger collaboration: We observed the possible optical counterpart (Eyles-Ferris, GCN 38878; Zhu et al., GCN 38885) of the Einstein Probe transient EP250108a (Li et al., GCN 38861), using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were carried out in the griz filters and began on Jan 10.88 UT (2.36 days after the trigger). Conditions were not ideal, with a nearby full Moon and mediocre seeing (1.7-2"). The counterpart is detected in all filters, and shows a remarkably blue SED. Comparison of the new data with those taken on the night of Jan 9 (Zhu et al., GCN 38885) shows moderate or no change in brightness in the g band, and a fading in the redder filters. The spectral slope can be roughly fitted with a power-law F_nu propto nu^2, consistent with a hot black-body. The bright, blue optical spectral shape and the lack of X-ray emission (Li et al., GCN 38888) of this transient are very unusual among GRB and FXT afterglows, as already noted by Zhu et al. (GCN 38885). If associated with EP250108a, the transient is revealing an uncommon emission component, or could be due to a different progenitor. We acknowledge expert support from the NOT observing staff. View this GCN Circular online at https://gcn.nasa.gov/circulars/38902. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36908] GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38901 SUBJECT: GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations DATE: 25/01/10 22:51:16 GMT FROM: Moskvitin Alexander at SAO RAS <mosk(a)sao.ru> A. Moskvitin, O. Spiridonova (SAO), A. Pozanenko (IKI), N. Kapitanov (INASAN), N. Pankov (IKI, HSE) report on behalf of larger GRB follow-up GRB IKI FuN collaboration. We observed the field of the GRB 250109A / EP250109a (Li et al., GCN 38864; Fermi GBM team, GCN 38873) with two telescopes, 2-m Zeiss-2000 of Terskol observatory and 1-m Zeiss-1000 of SAO RAS on January 9. We obtained 100 x 60 sec. images R band on Jan. 09, 19:36:42--21:28:07 UT with 2-m telescope and 11 x 300 sec. images in Rc band on Jan. 09, 21:12:33--22:23:56 UT with 1-m telescope. In the stacked image of Zeiss-2000 observation we marginally detect the afterglow candidate (Qiu et al., GCN 38872) within XRT error circle (Kennea et al., GCN 38899). Photometry of the staked images is the following: Date UT start t-T0, h(mid) Filter Exp.,s OT, err, UL(3sigma) Telescope 25-01-09 19:36:42 14.254 R 100 x 60 22.5 0.4 22.4 Zeiss-2000 25-01-09 21:12:33 15.518 Rc 11 x 300 n/d n/d 22.2 Zeiss-1000 The photometry is based on nearby stars of the PS1 catalog (Lupton 2005 transformations) and not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/38901. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36907] GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38900 SUBJECT: GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst DATE: 25/01/10 21:06:43 GMT FROM: Jimmy DeLaunay at Penn State <delauj2(a)gmail.com> James DeLaunay (PSU), Samuele Ronchini (PSU), Aaron Tohuvavohu (Caltech), Gayathri Raman (PSU), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC) report: Swift/BAT did not localize GRB 250109A onboard (T0: 2025-01-09T06:17:08.60 UTC, Fermi trig 758096233) The Fermi notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground. The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 12.1 in a 16.384 s analysis time bin, starting at T0 - 8.192 s. Using the NITRATES analysis, parameter estimation was performed to obtain the localization of this burst in the form of a HEALPIX Multi-Order Coverage (MOC) skymap. This localization accounts for both statistical and systematic errors. More details in the creation and calibration of these maps will soon be published (DeLaunay et al. 2025. in prep) The 90% credible area is 0.06 deg2 and the 50% credible area is ~0.01 deg2. The integrated probability inside the coded field of view is 98%. 55% of the NITRATES localization probability is contained within a 0.1 deg radius circle around the maximum probability position. The majority of the remaining probability is contained within similarly sized peaks of probability across the BAT coded field of view. The maximum probability position of the NITRATES skymap is, RA, Dec = 88.806, -12.458 deg which is RA(J2000) = 05h 55m 13.4s Dec(J2000) = -12d 27′ 28.8″ The NITRATES skymap is consistent with the Fermi localization reported in the final position notice (GCN 38873). It is also consistent with the position of the X-ray transient EP250109a (GCN 38864, GCN 38889), with the position lying on the 0.28 credible region contour. The spatial and temporal coincidence of GRB 250109A and EP250109a make it very likely that they originate from the same cosmic event. A plot of the probability skymap can be viewed here: [skymap_plot](https://guano.swift.psu.edu/trigger_report?id=758096263/#:~:te… The probability skymap file can be downloaded from the link here [skymap_fits_file](https://guano.swift.psu.edu/files/758096263/0_n_PROBMAP) Instructions on how to read and manipulate this map can be found here: https://guano.swift.psu.edu/documentation More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=758096263 GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/ View this GCN Circular online at https://gcn.nasa.gov/circulars/38900. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36906] GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38899 SUBJECT: GRB 250109A / EP250109a: Swift detection of the X-ray afterglow DATE: 25/01/10 20:57:21 GMT FROM: Jamie Kennea at Penn State <jak51(a)psu.edu> J. A. Kennea (PSU), P. A. Evans and K. L. Page (Leicester) report on behalf of the Swift/XRT team: Swift/XRT performed a further 3.1ks of exposure on GRB 250109A (GCN #38887) AKA EP250109a (GCN #38864), following on from a rapid 1ks observation which did not detect the counterpart (GCN #38867). Combining the two datasets, we detect one point source inside the EP WXT error circle, at the following position: RA/Dec(J2000) = 88.80698, -12.4958, which is equivalent to: RA(J2000) = 05h 55m 13.67s, Dec(J2000) = -12° 29′ 44.8″, with an estimated uncertainty of 5.8 arc-seconds radius (90% containment). This position lies 6 arc-seconds from the EP FXT position, and 1.1 arc-seconds from the SVOM-VT reported optical position (GCN #38872). Given the localization coincidence, this source is likely to be the afterglow of GRB 250109A. The combined XRT flux from this afterglow is 9(+5,-4) x 10^-14 erg/s/cm^2 (0.3-10 keV). View this GCN Circular online at https://gcn.nasa.gov/circulars/38899. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36905] GRB 250108A: Swift/XRT afterglow fading
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38898 SUBJECT: GRB 250108A: Swift/XRT afterglow fading DATE: 25/01/10 17:28:08 GMT FROM: Tullia Sbarrato at INAF-OAB <tullia.sbarrato(a)inaf.it> Tullia Sbarrato (INAF-OAB) & Noel Klinger (GSFC/UMBC/CRESSTII) report on behalf of the Swift-XRT team: Swift-XRT has performed further follow-up observations of the SVOM/ECLAIRs GRB 250108A (Zheng et al., GCN 38845), collecting 6.6 ks of Photon Counting (PC) mode data between T0+16.1 ks and T0+192.1 ks. The X-ray source detected in the first 2.7 ks of data reported as “Source 1” and presented as possible GRB afterglow candidate (Ambrosi et al., GCN 38853) has faded more than 2 sigma in the latest observation, and it is thus confirmed as the X-ray afterglow of the burst. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00021755. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/38898. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36904] GRB 250107D: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38897 SUBJECT: GRB 250107D: CALET Gamma-Ray Burst Monitor detection DATE: 25/01/10 17:22:49 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> T. Sakamoto, A. Yoshida, 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), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The short GRB 250107D (IPN triangulation: Kozyrev et al., GCN Circ. 38880; Konus-Wind detection: Frederiks et al., GCN Circ. 38881) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 05:23:36.72 UTC on 7 January 2025 (https://cgbm.calet.jp/cgbm_trigger/flight/1420262534/index.html). The burst signal was seen by only the SGM detector. Because of a problem with the ground alert processing script, the GCN notice was not distributed automatically for this event. The burst light curve shows a single pulse that starts at T+0.17 sec, peaks at T+0.25 sec, and ends at T+0.32 sec. The T90 and T50 durations measured by the SGM data are 0.13 +/- 0.03 sec and 0.08 +/- 0.02 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1420262534/ 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/38897. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36903] GRB 250107C: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38896 SUBJECT: GRB 250107C: CALET Gamma-Ray Burst Monitor detection DATE: 25/01/10 16:51:07 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> 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), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The long GRB 250107C (SVOM/GRM observation: SVOM/GRM team, GCN Circ. 38870; IPN triangulation: Svinkin et al., GCN Circ. 38879; Konus-Wind detection: Frederiks et al., GCN Circ. 38895) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 18:52:15.99 UTC on 7 January 2025 (https://cgbm.calet.jp/cgbm_trigger/flight/1420311052/index.html). The burst signal was seen by only the SGM detector. Because of a problem with the ground alert processing script, the GCN notice was not distributed automatically for this event. The burst light curve shows a double-peaked structure that starts at T-0.2 sec, peaks at T+0.7 sec, and ends at T+3.0 sec. The T90 and T50 durations measured by the SGM data are 2.6 +/- 0.2 sec and 1.6 +/- 0.1 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1420311052/ 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/38896. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36902] Konus-Wind detection of GRB 250107C
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38895 SUBJECT: Konus-Wind detection of GRB 250107C DATE: 25/01/10 15:59:26 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long GRB 250107C (SVOM/GRM observation: Xue et al., GCN 38870; IPN triangulation: Svinkin et al., GCN 38879) triggered Konus-Wind (KW) at T0=67934.719 s UT (18:52:14.719). The burst consists of two overlapping peaks and had the total duration of ~4 s. The emission is seen up to ~10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250107_T67934/ As observed by Konus-Wind, the burst had a fluence of (3.02 ± 0.13)x10^-5 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 0.960 s, of (2.23 ± 0.15)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+10.752 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 = -0.41 (-0.06,+0.06), the high energy photon index beta = -3.03 (-0.28,+0.18), the peak energy Ep = 254 (-10,+11) keV, chi2 = 78/79 dof. The spectrum near the peak count rate (measured from T0+0.768 s to T0+1.024 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 = -0.01 (-0.13,+0.15), the high energy photon index beta = -3.09 (-0.49,+0.29), the peak energy Ep = 286 (-22,+21) keV, chi2 = 30/38 dof. All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/38895. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36901] LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38894 SUBJECT: LIGO/Virgo/KAGRA S250109bi: Updated Sky localization DATE: 25/01/10 14:58:34 GMT FROM: alexandresebastien.goettel(a)LIGO.org The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1) and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S250109bi (GCN Circular 38863). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250109bi For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 2819 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 2255 +/- 734 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. (2023) arXiv:2307.13380 View this GCN Circular online at https://gcn.nasa.gov/circulars/38894. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36900] LIGO/Virgo/KAGRA S250109f: Updated Sky localization
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38893 SUBJECT: LIGO/Virgo/KAGRA S250109f: Updated Sky localization DATE: 25/01/10 14:55:16 GMT FROM: alexandresebastien.goettel(a)LIGO.org The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S250109f (GCN Circular 38860). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250109f For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 243 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 3200 +/- 948 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. (2023) arXiv:2307.13380 View this GCN Circular online at https://gcn.nasa.gov/circulars/38893. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36899] LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38892 SUBJECT: LIGO/Virgo/KAGRA S250108eo: Updated Sky localization DATE: 25/01/10 14:50:11 GMT FROM: alexandresebastien.goettel(a)LIGO.org The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S250108eo (GCN Circular 38851). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250108eo For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 795 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 4306 +/- 1349 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. (2023) arXiv:2307.13380 View this GCN Circular online at https://gcn.nasa.gov/circulars/38892. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36898] EP-WXT trigger EP250108a：Xinglong optical follow-up observations
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38891 SUBJECT: EP-WXT trigger EP250108a：Xinglong optical follow-up observations DATE: 25/01/10 14:14:46 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Report on behalf of the Xinglong collaboration: Junjie-Jin(NAOC), Haiyang-Mu(NAOC), Jinlei-Zhang(NAOC), Shengsheng-Zhang(NAOC), Pengliang-Du(NAOC), JianFeng-Tian(NAOC), Zhou-Fan(NAOC), Hong-Wu(NAOC), Jie-Zheng (NAOC) We observed the field of the X-ray transient, EP 250108a by the the Tsinghua-NAOC 0.8-m telescope (TNT) located at Xinglong, Hebei, China. A total of 300 s g-band exposures were taken , with a median observation time of 2025-01-09 T11:51:01, approximately 23.5 hours after the EP trigger. No optical counterpart was detected, with a 5-sigma limiting magnitude of 21.85, calibrated with Pan-STARRS sources in the field. View this GCN Circular online at https://gcn.nasa.gov/circulars/38891. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36897] GRB 250101A: CMO RC-500 optical observations
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38890 SUBJECT: GRB 250101A: CMO RC-500 optical observations DATE: 25/01/10 12:36:46 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI RAS), A. Pozanenko (IKI RAS), A. Tarasenkov (INASAN), A. Moskvitin (SAO RAS) report on behalf of a larger collaboration: We performed optical observations of the field of GRB 250101A (Page et. al, GCN 38752; Li et. al, GCN 38753; Mohan et. al, GCN 38754; Zhu et. al, GCN 38755; Budnev et. al, GCN 38756; Wu et. al, GCN 38758; Zhu et. al, GCN 38759; Goad et. al, GCN 38761; Moskvitin et. al, GCN 38762; Odeh et. al, GCN 38763; Hu et. al, GCN 38764; Moskvitin et. al, GCN 38765; D'Avino et. al, GCN 38768; Escudero-Coca et. al, GCN 38769; Leonini et. al, GCN 38771; Dichiara et. al, GCN 38773; Zhang et. al, GCN 38774; Siegel, GCN 38775; Li et. al, GCN 38776; Komesh et. al, GCN 38777; Ghosh et. al, GCN 38779; Moskvitin et al., GCN 38780; Krimm et. al, GCN 38782; Komesh et. al, GCN 38790; Méndez-Lapido et. al, GCN 38810; Gupta et. al, GCN 38818; Ferro et. al, GCN 38831; Lin et. al, GCN 38837; Pankov et. al., GCN 38869) in the R filter with the 0.5-meter RC-500 telescope located at the Caucasus Mountain Observatory (CMO). The observations began on 2025-01-01 14:40:56 UT, i.e. ~1.28 hours since trigger. The preliminary light curve of the optical afterglow is available at http://grb.rssi.ru/GRB250101A/GRB250101A_RC50_KGO.png. After a typical power-law decay, the afterglow light curve demonstrates a re-brightening occurring at ~5 hr since burst, initially reported by Moskvitin et. al, GCN 38765. View this GCN Circular online at https://gcn.nasa.gov/circulars/38890. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36896] EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38889 SUBJECT: EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation DATE: 25/01/10 09:43:01 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.-Z. Li (YNAO, CAS), X.-L. Chen (YNU), K. Chatterjee (YNU), Y.-L. Hua (PMO, CAS), H. Sun and Y. Liu (NAO, CAS) report on behalf of the Einstein Probe team: Since 2025-01-09 06:17:58 (UTC, T0), EP250109a (Li et al., GCN 38864) has been detectable with high significance using the WXT onboard the EP, peaking about 60 seconds post-trigger. The observed peak flux in the 0.5–4 keV range is about 2.5 x 10^-9 erg/s/cm^2. The flux then rapidly decayed to background levels within 200 seconds post-trigger. The average 0.5-4 keV WXT spectrum can be fitted with an absorbed power law with a photon index of 2.9 +/- 1.0 (with a fixed Galactic equivalent hydrogen column density of 3.04 x 10^21 cm^-2). The derived lower limit of the intrinsic column density is 5.0 (-0.3, +0.4) x 10^21 cm^-2 when the redshift is fixed at 0. The derived average unabsorbed 0.5-4 keV flux is 2.5 (-1.2, +4.6) x 10^-9 erg/s/cm^2. In addition to the follow-up observation, we conducted a follow-up observation of EP241217a using the FXT onboard the EP. The observation began at 2025-01-09T08:06:40 (UTC, 1.8 hours post-trigger), with an exposure time of approximately 4.2 ks. The average 0.5–4 keV FXT spectrum can be modeled with an absorbed power law, featuring a photon index of 1.9 (-0.7, +1.9) and a fixed Galactic equivalent hydrogen column density of 3.04 x 10^21 cm^-2). The derived lower limit of the intrinsic column density is about 3 x 10^20 cm^-2 when the redshift is fixed at 0. The estimated average unabsorbed 0.5–4 keV flux is about 4.9 (-1.2, +2.0) x 10^13 erg/s/cm^2. The detection of EP-WXT/FXT (GCN 38864) and Fermi-GBM (GCN 38873 and GCN 38887), combined with the non-detection by Swift-XRT (GCN 38867), indicates that the flux of this transient has decreased very rapidly. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard 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/38889. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36895] EP250108a: EP-FXT follow-up observation
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38888 SUBJECT: EP250108a: EP-FXT follow-up observation DATE: 25/01/10 07:45:32 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.-Z. Li (YNAO, CAS), X.-L. Chen (YNU), K. Chatterjee (YNU), Y.-L. Hua (PMO) and Y. Liu (NAOC) report on behalf of the Einstein Probe team: We performed a follow-up observation of EP250108a using the FXT onboard the EP. The observation began at 2025-01-09T10:42:46 (UTC, about 22.2 hours post-trigger), with an exposure time of about 6 ks. No new uncatalogued X-ray sources were detected within the EP-WXT error circle (GCN 38861). The 5-sigma upper limit flux is about 3 x 10^-14 erg/s/cm^2 in the 0.5–10 keV range. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard 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/38888. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36894] GRB 250109A: Fermi GBM Observation
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38887 SUBJECT: GRB 250109A: Fermi GBM Observation DATE: 25/01/10 06:40:17 GMT FROM: Utkarsh Pathak at IIT Bombay <utkarshpathak.07(a)gmail.com> U. Pathak (IITB) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 06:17:08.60 UT on 09 January 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250109A (trigger 758096233/250109262). which was also detected by EP-WXT and EP-FXT (Li et al. 2025, GCN 38864). The Fermi GBM on-ground location is consistent with the EP-FXT position. A possible optical counterpart was also detected by SVOM/VT (Qiu et al. 2025, GCN 38872). The angle from the Fermi LAT boresight is 72 degrees. The GBM light curve consists of multiple weak spikes from a single emission episode with a duration (T90) of about 15 s (50-300 keV). The time-averaged spectrum from T0-8.2 to T0+9.2 s is best fit by a power law function. The power law index is -1.57 +/- 0.05. The event fluence (10-1000 keV) in this time interval is (1.9 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+2.9 s in the 10-1000 keV band is 1.3 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/38887. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36893] The EP-WXT trigger 01709130111 is likely a flaring star
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38886 SUBJECT: The EP-WXT trigger 01709130111 is likely a flaring star DATE: 25/01/10 05:17:40 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.-Z. Li (YNAO, CAS), X.-L. Chen, K. Chatterjee (YNU) and H. Q. Cheng, Z. X. Ling (NAOC, CAS) report on behalf of the Einstein Probe team: The EP-WXT trigger (ID 01709130111) on 2025-01-10 04:52:13 (UTC) is likely a stellar flare associated with a Low-mass Star RX J0429.3-3124. The estimated flux of the flare is around 1.6 x 10^-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 5.5 x 10^30 erg/s. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard 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/38886. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36892] EP250108a: NOT optical observations
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38885 SUBJECT: EP250108a: NOT optical observations DATE: 25/01/10 04:55:01 GMT FROM: Dong Xu at NAOC/CAS <dxu(a)nao.cas.cn> Z.P. Zhu, X. Liu, S.Y. Fu, S.Q. Jiang, J. An, D. Xu (NAOC) report on behalf of large collaboration: We observed the field of EP250108a (Li et al., GCN 38861) using the Nordic Optical Telescope (NOT) equipped with ALFOSC. The observations were carried out in the g-/r-/i-/z- bands, starting at 22:16:55 UT on 2025-01-09, i.e., 1.4 days after the EP/WXT trigger. The previously reported likely optical counterpart by LT (Eyles-Ferris et al., GCN 38878) is clearly detected in NOT individual images, and it has brightened from g = 20.79 +/- 0.05 at ~1.31 days post-trigger to g = 20.05 +/- 0.03 at ~ 1.44 days post-trigger. The SED from g-/r-/i-/z- bands is opposite to the typical GRB optical afterglow, i.e., non-thermal power-law decay. Instead, it appears as quasi-thermal. The quick brightening and the quasi-thermal SED make this source unlikely a conventional GRB afterglow. It would be more consistent with early behaviors of Fast Blue Optical Transients (FBOT) or novel Fast X-ray Transients by EP, if it is indeed associated with EP250108a. In addition, we performed image subtraction on the stacked NOT g-/r- band images using Legacy Survey images as templates, and only the LT source is credible in the differencing images, down to limiting magnitudes of g > 22.7 and r > 23.2. We acknowledge the excellent support from the NOT staff, in particular Samuel Grund Sorensen. View this GCN Circular online at https://gcn.nasa.gov/circulars/38885. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36891] EP-WXT trigger EP250109a：Xinglong optical follow-up observations
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38884 SUBJECT: EP-WXT trigger EP250109a：Xinglong optical follow-up observations DATE: 25/01/10 04:52:16 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Report on behalf of the Xinglong collaboration: Junjie-Jin(NAOC), Haiyang-Mu(NAOC), Feng-Xiao(NAOC), Pengliang-Du(NAOC), Ying-Wu(NAOC), Zhou-Fan(NAOC), Hong-Wu(NAOC), Jie-Zheng (NAOC) We observed the field of the X-ray transient, EP 250109a by the Xinglong 2.16-m telescope located at Xinglong, Hebei, China. A total of 6 x 600 s N-band exposures were taken , with a median observation time of 2025-01-09 T13:06:56, approximately 6.5 hours after the EP trigger. No optical counterpart was detected, with a 5-sigma limiting magnitude of 22.48, calibrated with Pan-STARRS sources in the field. View this GCN Circular online at https://gcn.nasa.gov/circulars/38884. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36890] GRB 250109a: GMG Optical Upper Limit
by GCN Circulars 10 Jan '25

10 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38883 SUBJECT: GRB 250109a: GMG Optical Upper Limit DATE: 25/01/10 03:05:29 GMT FROM: wangbaiting(a)ynao.ac.cn B.-T. Wang, R.-Z. Li, F.-F. Song, J. Mao, X.-L. Zhang and J.-M. Bai (YNAO, CAS) report: We observed the field of EP250109a (EP team, GCN 38864; Kennea et. al, GCN 38867; Kumar et. al, GCN 38868; Lipunov et. al, GCN 38871; Fermi GBM team, GCN 38873）with the GMG-2.4m telescope at the Lijiang Observatory. The observation began at 2025-01-09T13:30:50 (UT), about 7.2 hours after the trigger. No new uncataloged optical counterpart was detected within the EP/FXT error circle (GCN 38864). The preliminary photometry is as follows: ----------------------------------------------------------------------------- UT EXP(s) filter mag ----------------------------------------------------------------------------- 2025-01-09T13:30:50 1800 sdss-z >23.0 ----------------------------------------------------------------------------- The magnitudes were calibrated using nearby stars of Pan-STARRS DR1 field and without corrections for Galactic extinction. We acknowledge the staff at the Lijiang Observatory for conducting the observation. View this GCN Circular online at https://gcn.nasa.gov/circulars/38883. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36889] EP250109a: Swift/UVOT non-detection
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38882 SUBJECT: EP250109a: Swift/UVOT non-detection DATE: 25/01/09 23:46:29 GMT FROM: Sam Shilling at Lancaster University <shilling.sam(a)gmail.com> S. P. R. Shilling (Lancaster U.), S. R. Oates (Lancaster U.), A. A. Breeveld (UCL-MSSL) and N. P. M. Kuin (UCL-MSSL) report on behalf of the Swift UVOT team: Swift/UVOT observed the field of EP250109a (Li et al., GCN 38864) for 938 seconds in the U-band starting at 09:22:16 UT, 3 hours after the detection by Einstein Probe WXT. No optical afterglow is detected within a 5" radius of the EP FXT position (Li et al., GCN 38864) to a preliminary 3-sigma U-band upper limit of >20.6, calculated using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373). The non-detection reported here is consistent with the non-detections reported in other optical observations using the GOTO (Kumar et al., GCN 38868), MASTER (Lipunov et al., GCN 38871), and the SVOM/VT in one of the two filters (Qiu et al., GCN 38872). View this GCN Circular online at https://gcn.nasa.gov/circulars/38882. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36888] Konus-Wind detection of GRB 250107D (short/hard)
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38881 SUBJECT: Konus-Wind detection of GRB 250107D (short/hard) DATE: 25/01/09 22:08:34 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The short GRB 250107D (IPN triangulation: Kozyrev et al., GCN 38880) triggered Konus-Wind (KW) at T0=19411.897 s UT (05:23:31.897). The burst light curve shows a single, multi-peaked emission pulse which starts at ~T0-0.112 s and has a duration of ~0.208 s. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250107_T19411/ As observed by Konus-Wind, the burst had the total fluence of 2.06(-0.34,+0.62)x10^-6 erg/cm^2 and a 16-ms peak energy flux, measured from T0-0.064 s, of 1.99(-0.32,+0.59)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). Since a major part of the burst emission was detected before the trigger time, the time-averaged spectral analysis was performed using the KW 3-channel light curve data. Modeling the 3-channel time-integrated spectrum (measured from T0-0.112 s to T0+0.096 s) by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) yields alpha = -0.40 (-0.32, + 0.41) and Ep = 897(-203,+453) keV. All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/38881. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36887] IPN triangulation of GRB 250107D (short/hard)
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38880 SUBJECT: IPN triangulation of GRB 250107D (short/hard) DATE: 25/01/09 22:06:45 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the HEND/Mars Odyssey team, D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, E. Burns on behalf of the IPN, E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu on behalf of the Swift-BAT team, and W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report: The short-duration GRB 250107D was detected by Konus-Wind, INTEGRAL (SPI-ACS), Swift (BAT), and Mars-Odyssey(HEND), at about 19406 s UT (05:23:26). The burst was outside the coded field of view of the BAT. We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 259.300 (17h 17m 12s) -29.710 (-29d 42' 37") Corners: 259.267 (17h 17m 04s) -28.346 (-28d 20' 46") 259.147 (17h 16m 35s) -30.541 (-30d 32' 29") 259.382 (17h 17m 32s) -30.988 (-30d 59' 15") 259.469 (17h 17m 52s) -28.855 (-28d 51' 18") --------------------------------------------- The error box area is 1635 sq. arcmin, and its maximum dimension is 2.6 deg (the minimum one is 12.6 arcmin). The Sun distance was 27 deg. This localization may be improved. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB250107_T19411/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/38880. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36886] IPN triangulation of GRB 250107C
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38879 SUBJECT: IPN triangulation of GRB 250107C DATE: 25/01/09 22:04:46 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, Y. Zhang, C. Wang, S. Xiong, J. Wei, and B. Cordier on behalf of the SVOM-GRM team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM team, S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu on behalf of the Swift-BAT team, report: The long-duration GRB 250107C (SVOM-GRM and GECAM-B detections: Xue et al., GCN 38870) was detected by Konus-Wind, SVOM (GRM), and GECAM-B at about 67936 s UT (18:52:16). We have triangulated it to a preliminary, 3 sigma error box whose area is 22.6 sq. deg, and its maximum dimension is 22.8 deg (the minimum one is 1.0 deg). The Sun distance was 73 deg. This localization may be improved. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB250107_T67934/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/38879. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36885] EP250108a: Liverpool Telescope likely optical counterpart
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38878 SUBJECT: EP250108a: Liverpool Telescope likely optical counterpart DATE: 25/01/09 21:42:48 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. Eyles-Ferris (U of Leicester) reports: We observed the field of the X-ray transient EP250108a (Li et al., GCN 38861) using the IO:O on the 2m Liverpool Telescope. We obtained 6x200s exposures in the SDSS g’ filter starting at 2025-01-09 19:59:08 UT, approximately 31.5 hours after the trigger. We performed image subtraction on the stacked image using a reference Pan-STARRS image and identify a source of g’ = 20.79+/-0.05 with photometry calibrated to Pan-STARRS and not corrected for Galactic extinction. The source is located at RA, Dec = 55.61823, -22.50587 deg, which is equivalent to: RA (J2000) : 03:42:28.38 Dec (J2000): -22:30:21.1 This source is within the error region of the Einstein Probe detection and is the only source within it in the subtracted image. It is also visible in the individual frames. There is a catalogued DES DR1/2 source with a measured g’ band magnitude of 23.3 and a photometric redshift of 0.882+/-0.379 consistent with our measured position. We suggest this is the host galaxy. Further observations are planned. View this GCN Circular online at https://gcn.nasa.gov/circulars/38878. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36884] GRB 250108B: Gemini-North likely redshift z = 2.197
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38877 SUBJECT: GRB 250108B: Gemini-North likely redshift z = 2.197 DATE: 25/01/09 17:37:07 GMT FROM: Jillian Rastinejad at Northwestern Univ. <jillianrastinejad2024(a)u.northwestern.edu> Daniele B. Malesani (DAWN/ NBI and Radboud), Jillian C. Rastinejad (Northwestern), Andrew J. Levan (Radboud), Wen-fai Fong, Charlie Kilpatrick (Northwestern), Gavin P. Lamb (LJMU), and Nial R. Tanvir (Leicester) report on behalf of a larger collaboration: Following the detection of the optical afterglow (Rastinejad et al., GCN 38855) of GRB 250108B (Klinger et al., GCN 38847), we obtained optical spectroscopy using the Gemini Multi-Object Spectrograph (GMOS-N) mounted on Gemini-North, under Program GN-2024B-Q-107 (P.I. Rastinejad). The mean time of the observation was 15:12 UT on 2025 Jan 8 (4.81 hr post-burst). The total exposure time was 4x400 s using the R400 grating, which covers the wavelength range 4650-9450 AA. Given the faintness of the target (r ~ 23.4; Rastinejad et al., GCN 38855), only a weak trace is detected, with most of the signal apparent at the red end of the spectrum. A few absorption features are weakly detected. A possible redshift solution, based on the detection of Mg I 2852, Mg II 2796,2803, Fe II 2600, and Fe II 2586, yields z = 2.197, which we suggest to be the redshift of GRB 250108B. The slit was aligned in order to cover also the nearby galaxy (Rastinejad et al., GCN 38855) at coordinates RA = 13:25:18.72, Dec = +25:37:12.7, with photometric redshift z = 0.2-0.3, resulting in a bright trace. We detect Halpha, [N II], and [S II] at z = 0.302, consistent with the Legacy Survey photometric redshift of z = 0.29 +/- 0.04 (Zhou et al., 2021). Our observations indicate that this object is unlikely to be physically connected to the GRB. We thank Jen Miller, Leila Alamos, Brian Lemaux and additional Gemini staff for excellent support in the rapid planning and execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/38877. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36883] GRB 250108B: Swift-BAT refined analysis
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38876 SUBJECT: GRB 250108B: Swift-BAT refined analysis DATE: 25/01/09 16:42:39 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta(a)nasa.gov> S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC), R. Gupta (GSFC), N. J. Klingler (GSFC/UMBC/CRESSTII), H. A. Krimm (NSF), 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+792 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250108B (trigger #1280056) (Klinger et al., GCN Circ. 38847). The BAT ground-calculated position is RA, Dec = 201.312, 25.622 deg which is RA(J2000) = 13h 25m 14.8s Dec(J2000) = +25d 37' 19.4" with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 89%. The mask-weighted light curve exhibits multi-peaked structures, including evidence of precursor emission prior to the main burst. T90 (15-350 keV) is 229.66 +- 43.30 sec (estimated error including systematics). The time-averaged spectrum from T-63.14 to T+218.21 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.63 +- 0.19. The fluence in the 15-150 keV band is 1.7 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+1.56 sec in the 15-150 keV band is 0.6 +- 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/1280056 View this GCN Circular online at https://gcn.nasa.gov/circulars/38876. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36882] GRB 250108B: 1.3m DFOT upper limit
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38875 SUBJECT: GRB 250108B: 1.3m DFOT upper limit DATE: 25/01/09 16:23:09 GMT FROM: Amit Kumar Ror at ARIES <mitturor77894(a)gmail.com> Amit K. Ror, Anshika Gupta, RKS Yadav, Shashi B. Pandey, Kuntal Mishra (ARIES) report: We observed the field of GRB 250108B detected by Swift (Swift Observatory Team, Klingler et al. 2025, GCN 38847) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2025-01-08 at 21:58:57 UT, i.e., ~ 0.48 days after the Swift-BAT trigger. We have taken multiple frames with an exposure time of 300s in the R filter. We stacked the images after the alignment. We could not detect the optical emission reported by Rastinejad et al. (2025, GCN 38855) in our stacked image within the error box enhanced Swift-XRT position (Osborne et al. 2025, GCN 38848). We obtain the following 3-sigma upper limit in the stacked image: Date Start_UT T_start-T0 (days) Filter Exp time (s) Magnitude ========================================================= 2025-01-08 21:58:57 ~ 0.48 R 300s*12 >21.8 The non-detection of the burst is consistent with the upper limits reported by Breeveld et al. 2025, GCN 38850 and Lipunov et al. 2025, GCN 38858. The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalogue. This circular may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/38875. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36881] GRB 250108B: REM optical/NIR upper limits
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38874 SUBJECT: GRB 250108B: REM optical/NIR upper limits DATE: 25/01/09 16:12:35 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 250108B detected by Swift (Klingler et al., GCN 38847) 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 January 09 at 07:02:48 UT (i.e. 21.07 hours after the Swift trigger), and lasting for about 1 hour. Within the XRT-enhanced position (Osborne et al., GCN 38848), from preliminary photometry we do not detect any optical or NIR counterpart consistent with the candidate optical afterglow (Rastinejad et al., GCN 38855), down to the following 3sigma magnitude upper limits: r > 20.1 (AB; calibrated against the PanSTARRS catalogue) at a mid-time of t - t0 = 21.2 hr after the trigger, H > 17.0 (Vega; calibrated against the 2MASS catalogue) at a mid-time of t - t0 = 21.1 hr after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/38874. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36880] GRB 250109A /EP250109a: Fermi GBM Final Localization
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38873 SUBJECT: GRB 250109A /EP250109a: Fermi GBM Final Localization DATE: 25/01/09 16:02:55 GMT FROM: Utkarsh Pathak at IIT Bombay <utkarshpathak.07(a)gmail.com> The Fermi GBM team reports the detection of a likely LONG GRB At 06:17:08.60 UT on 9 January 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250109A (trigger 758096233/250109262). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 84.43, Dec = 2.26 (J2000 degrees, equivalent to J2000 05h 37m, 02d 15'), with a statistical uncertainty of 13.52 degrees. This event is associated with EP250109a (Li et al. 2025, GCN 38864). The angle from the Fermi LAT boresight is 69.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250109262/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250109262/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250109262/… View this GCN Circular online at https://gcn.nasa.gov/circulars/38873. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36879] EP250109a: SVOM/VT optical candidate
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38872 SUBJECT: EP250109a: SVOM/VT optical candidate DATE: 25/01/09 13:56:18 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> SVOM/VT commissioning team: Y. L. Qiu, H. L. Li, H. Sun, L. P. Xin, C. Wu, X. H. Han, J. Wang, W. J. Xie, H. B. Cai, Y. Xu, Y. J. Xiao, P. P. Zhang, J. S. Deng, L. Lan, X. M. Lu, R. S. Zhang, Z. H. Yao (NAOC), J. Zhang, L. J. Dan, G. Y. Zou, C. J. Wang, Y. F. Du, C. Huang (XIOPM) SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Olivier Godet (IRAP), Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Shao-Lin Xiong (IHEP), Bing Zhang (UNLV) report on behalf of the SVOM team: The SVOM/VT conducted a ToO follow-up observations of EP250109a triggered by EP-WXT(Li et al., GCN 38864) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously, from 4.13 hours to 4.80 hours after the burst. An uncatalogued source was detected within the errorbox of FXT (Li et al.,GCN 38864) in VT_R stacked image, compared to the Pan-STARRS catalog. This source is the only one source within the error box. The brightness of the source was estimated to be VT_R=22.34+/-0.15 in AB magnitude at the mid time of 4.47 hours post the burst, with a total exposure time of 38*100 seconds. The source was not detected in VT_B stacked image down to a 3 sigma upper limit of 23.6 mag with a total exposure time of 21*100 sec. The source is located at RA, Dec = 88.80672, -12.49599 deg, which is equivalent to: RA (J2000) : 05:55:13.61 Dec (J2000): -12:29:45.6 with an uncertainty of 0.5 arcsec. We are waiting for more data to confirm the fading of the source. 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/38872. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36878] EP250109a: Global MASTER-Net observations report
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38871 SUBJECT: EP250109a: Global MASTER-Net observations report DATE: 25/01/09 13:10:18 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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 (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the EP250109a ( EP Team et al., GCN 38864) errorbox 10841 sec after notice time and 22040 sec after trigger time at 2025-01-09 12:25:18 UT, with upper limit up to 16.2 mag. The observations began at zenith distance = 77 deg. The sun altitude is -28.1 deg. The galactic latitude b = -18 deg., longitude l = 218 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2739026 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 22049 | 2025-01-09 12:25:18 | MASTER-Tunka | (05h 55m 17.63s , -12d 32m 20.4s) | C | 15 | 15.5 | 22083 | 2025-01-09 12:25:53 | MASTER-Tunka | (05h 55m 17.99s , -12d 31m 16.2s) | C | 15 | 15.4 | 22112 | 2025-01-09 12:26:21 | MASTER-Tunka | (05h 55m 24.27s , -12d 32m 15.0s) | C | 15 | 15.4 | 22139 | 2025-01-09 12:26:48 | MASTER-Tunka | (05h 55m 19.06s , -12d 33m 13.7s) | C | 15 | 14.9 | 22165 | 2025-01-09 12:27:15 | MASTER-Tunka | (05h 55m 24.58s , -12d 32m 56.1s) | C | 15 | 14.9 | 22191 | 2025-01-09 12:27:41 | MASTER-Tunka | (05h 55m 21.14s , -12d 31m 40.0s) | C | 15 | 14.8 | 22503 | 2025-01-09 12:32:57 | MASTER-Tunka | (05h 55m 20.91s , -12d 32m 45.4s) | C | 5 | 15.5 | 22522 | 2025-01-09 12:33:16 | MASTER-Tunka | (05h 55m 24.47s , -12d 31m 13.3s) | C | 5 | 15.4 | 22540 | 2025-01-09 12:33:33 | MASTER-Tunka | (05h 55m 17.12s , -12d 31m 49.4s) | C | 8 | 15.3 | 22560 | 2025-01-09 12:33:53 | MASTER-Tunka | (05h 55m 18.59s , -12d 30m 47.9s) | C | 8 | 15.3 | 22582 | 2025-01-09 12:34:16 | MASTER-Tunka | (05h 55m 23.95s , -12d 31m 47.5s) | C | 8 | 15.2 | 22604 | 2025-01-09 12:34:37 | MASTER-Tunka | (05h 55m 18.35s , -12d 32m 43.7s) | C | 8 | 15.2 | 22626 | 2025-01-09 12:35:00 | MASTER-Tunka | (05h 55m 23.61s , -12d 32m 10.6s) | C | 8 | 15.3 | 22648 | 2025-01-09 12:35:21 | MASTER-Tunka | (05h 55m 20.84s , -12d 31m 08.9s) | C | 8 | 14.8 | 22671 | 2025-01-09 12:35:43 | MASTER-Tunka | (05h 55m 20.86s , -12d 32m 22.5s) | C | 10 | 14.6 | 22694 | 2025-01-09 12:36:07 | MASTER-Tunka | (05h 55m 23.91s , -12d 31m 03.4s) | C | 10 | 14.3 | 22718 | 2025-01-09 12:36:30 | MASTER-Tunka | (05h 55m 18.05s , -12d 31m 34.6s) | C | 10 | 14.6 | 22741 | 2025-01-09 12:36:55 | MASTER-Tunka | (05h 55m 18.67s , -12d 30m 33.0s) | C | 5 | 14.6 | 22774 | 2025-01-09 12:37:28 | MASTER-Tunka | (05h 55m 23.56s , -12d 31m 31.8s) | C | 5 | 14.9 | 22794 | 2025-01-09 12:37:48 | MASTER-Tunka | (05h 55m 17.70s , -12d 32m 31.2s) | C | 5 | 15.0 | 22814 | 2025-01-09 12:38:07 | MASTER-Tunka | (05h 55m 24.18s , -12d 32m 28.8s) | C | 10 | 15.3 | 24449 | 2025-01-09 13:05:18 | MASTER-Tunka | (05h 55m 20.96s , -12d 29m 25.1s) | C | 15 | 16.2 | 24477 | 2025-01-09 13:05:46 | MASTER-Tunka | (05h 55m 20.83s , -12d 30m 45.1s) | C | 15 | 15.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/38871. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36877] GRB 250107C: SVOM/GRM observation
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38870 SUBJECT: GRB 250107C: SVOM/GRM observation DATE: 25/01/09 13:01:24 GMT FROM: Kai <wcxuemail(a)gmail.com> SVOM/GRM team: Wang-Chen Xue, Chen-Wei Wang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) report on behalf of the SVOM team: During the commissioning phase, SVOM/GRM was triggered in-flight by a long burst GRB 250107C (SVOM trigger reference: sb25010702) at 2025-01-07T18:52:16.300 UTC (T0), which was also detected by GECAM-B. With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple pulses with a duration of about 4 s. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250107C.png 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: Wang-Chen Xue (IHEP)(xuewc(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/38870. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36876] GRB 250101A: Terskol K-800 optical observations
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38869 SUBJECT: GRB 250101A: Terskol K-800 optical observations DATE: 25/01/09 12:38:39 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI RAS), A. Pozanenko (IKI RAS), V. Agletdinov (KIAM), A. Moskvitin (SAO RAS) report on behalf of a larger collaboration: We performed optical observations of the field of GRB 250101A (Page et. al, GCN 38752; Li et. al, GCN 38753; Mohan et. al, GCN 38754; Zhu et. al, GCN 38755; Budnev et. al, GCN 38756; Wu et. al, GCN 38758; Zhu et. al, GCN 38759; Goad et. al, GCN 38761; Moskvitin et. al, GCN 38762; Odeh et. al, GCN 38763; Hu et. al, GCN 38764; Moskvitin et. al, GCN 38765; D'Avino et. al, GCN 38768; Escudero-Coca et. al, GCN 38769; Leonini et. al, GCN 38771; Dichiara et. al, GCN 38773; Zhang et. al, GCN 38774; Siegel, GCN 38775; Li et. al, GCN 38776; Komesh et. al, GCN 38777; Ghosh et. al, GCN 38779; Moskvitin et al., GCN 38780; Krimm et. al, GCN 38782; Komesh et. al, GCN 38790; Méndez-Lapido et. al, GCN 38810; Gupta et. al, GCN 38818; Ferro et. al, GCN 38831; Lin et. al, GCN 38837) in the clear light with the 0.8-meter K-800 telescope of the Terskol observatory of INASAN. The observations began on 2025-01-01 18:09:54 UT, i.e. ~0.2 days since trigger. The preliminary photometry of the optical afterglow in the combined image of 160*30 sec is as follows: Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) (mid, days) (s) 2025-01-01 18:09:54 0.22713 160*30 Clear 20.03 0.18 21.5 The photometry is based on nearby stars of PS1 catalog (Lupton transformations) and not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/38869. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36875] EP250109a: GOTO optical upper limits
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38868 SUBJECT: EP250109a: GOTO optical upper limits DATE: 25/01/09 12:35:49 GMT FROM: Amit Kundu at Royal Holloway - UoL/ U of Warwick, UK <amitkundu515(a)gmail.com> A. Kumar, D. O'Neill, G. Ramsay, B. P. Gompertz, R. Starling, M. Kennedy, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Palle and D. Pollacco report on behalf of the GOTO collaboration: We report on observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to EP-WXT detected EP250109a (Li et al., GCN 38864); also observed by the Swift-XRT (Kennea et al., GCN 38867). Targeted observations were performed using the GOTO-South at 11:42:03 UT on 2025-01-09 (5.401 hours post-trigger). The stacked image is composed of 3x90s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations of the same pointings. No new optical source within the EP-FXT localisation region (Li et al., GCN 38864) is identified to a 3-sigma limiting magnitude of L > 17.8. The shallower upper limit is attributed to the unfavourable weather conditions at the Siding Spring Observatory (SSO). 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). View this GCN Circular online at https://gcn.nasa.gov/circulars/38868. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36874] EP250109a: Swift/XRT non-detection
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38867 SUBJECT: EP250109a: Swift/XRT non-detection DATE: 25/01/09 12:12:58 GMT FROM: Jamie Kennea at Penn State <jak51(a)psu.edu> J. A. Kennea (PSU) and P. A. Evans (Leicester) on behalf of the Swift XRT Team report: On 09:19:41UT Swift XRT began a 950s exposure of the field containing the recently reported transient EP250109a (GCN #38864), 3 hours after detection by Einstein Probe WXT. Examination of the XRT data does not reveal any new X-ray sources, with an upper limit on count rate of 0.01 c/s at the EP FXT position. For a typical GRB-like spectrum this equates to an upper limit on flux of 3 x 10^-13 erg/s/cm^2 (0.3-10 keV). Although GCN #38864 does not report flux, the Swift/XRT non-detection suggests that this transient has rapidly faded. View this GCN Circular online at https://gcn.nasa.gov/circulars/38867. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36873] GRB 250108A: Swift/UVOT Upper Limits
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38866 SUBJECT: GRB 250108A: Swift/UVOT Upper Limits DATE: 25/01/09 10:33:26 GMT FROM: Alice Breeveld at MSSL-UCL <a.breeveld(a)ucl.ac.uk> A. A. Breeveld (UCL-MSSL) and N. J. Klingler (GSFC/UMBC/CRESSTII) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of SVOM/ECLAIRs-detected burst GRB 250108A 102468 s after the SVOM trigger (Zheng et al., GCN Circ. 38845). No optical afterglow consistent with either the Swift-XRT proposed X-ray counterpart (Ambrosi et al., GCN Circ. 38853) or the VT optical afterglow candidate (Qiu et al., GCN Circ. 38852), is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag w1 102468 109462 2632 >20.9 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.012 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/38866. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36872] EP250108a: Global MASTER-Net observations report
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38865 SUBJECT: EP250108a: Global MASTER-Net observations report DATE: 25/01/09 09:45:53 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP250108a ( EP Team et al., GCN 38861) errorbox 731 sec after notice time and 66442 sec after trigger time at 2025-01-09 06:57:50 UT, with upper limit up to 17.9 mag. The observations began at zenith distance = 78 deg. The sun altitude is -27.7 deg. The galactic latitude b = -51 deg., longitude l = 216 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2738908 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 66472 | 2025-01-09 06:57:50 | MASTER-OAFA | (03h 42m 49.01s , -22d 23m 39.2s) | C | 60 | 17.9 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/38865. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36871] EP250109a: EP-WXT detection of an X-ray transient
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38864 SUBJECT: EP250109a: EP-WXT detection of an X-ray transient DATE: 25/01/09 09:20:17 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.-Z. Li (YNAO, CAS), X.-L. Chen (YNU), K. Chatterjee (YNU), Y.-L. Hua (PMO, CAS), H. Sun and Y. Liu (NAO, CAS) report on behalf of the Einstein Probe team: We report on the detection of an X-ray transient detected by EP-WXT, which triggered the on-board processing unit at 2025-01-09 06:17:58 (UTC) (trigger ID: 01709130082). The source position is R.A. = 88.806 deg, DEC = -12.500 deg (J2000) with an uncertainty of about 3 arcmin (radius, 90% C.L. statistical and systematic). A follow-up observation on the X-ray transient was performed by the EP-FXT, which detected an uncatalogued X-ray source at R.A. = 88.8055 deg, DEC = -12.4966 deg (J2000) with an uncertainty of about 20 arcsec (radius, 90% C.L. statistical and systematic), consistent with the position of the WXT transient within the uncertainties. More information will be updated when the telemetry data is received. Further observations are encouraged to explore the origin of the transient. 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/38864. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36870] LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38863 SUBJECT: LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate DATE: 25/01/09 08:29:17 GMT FROM: davis(a)lpccaen.in2p3.fr The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250109bi during real-time processing of data from LIGO Hanford Observatory (H1) and Virgo Observatory (V1) at 2025-01-09 07:45:52.379 UTC (GPS time: 1420443970.379). The candidate was found by the GstLAL [1] analysis pipeline. S250109bi is an event of interest because its false alarm rate, as estimated by the online analysis, is 2e-08 Hz, or about one in 1 year, 6 months. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250109bi After parameter estimation by RapidPE-RIFT [2], the classification of the GW signal, in order of descending probability, is BBH (98%), Terrestrial (2%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [3] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [3] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [4], distributed via GCN notice about 28 seconds after the candidate event time. * bayestar.multiorder.fits,2, an initial localization generated by BAYESTAR [4], distributed via GCN notice about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,2. For the bayestar.multiorder.fits,2 sky map, the 90% credible region is 8841 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1246 +/- 386 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625 [2] Rose et al. (2022) arXiv:2201.05263 and Pankow et al. PRD 92, 023002 (2015) doi:10.1103/PhysRevD.92.023002 [3] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [4] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/38863. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36869] GRB 250108A: NOT optical upper limit
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38862 SUBJECT: GRB 250108A: NOT optical upper limit DATE: 25/01/09 07:58:40 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> S. De Wet (DTU Space), D. B. Malesani (DAWN/NBI and Radboud), L. Izzo (INAF/OACn and DARK/NBI), D. Xu (NAOC), S. Grund Sorensen (NOT and Aarhus), N. Pyykkinen (NOT and Turku) report on behalf of a larger collaboration: We observed the field of the SVOM GRB 250108A (Zheng et al., GRB 38845) using the Nordic Optical Telescope (NOT) equipped with ALFOSC. The observations were carried out in the z band, with a mid time 2025 Jan 9.14 UT (22.72 hr after the GRB), and for a total exposure time of 2000 s. In the stack of our images, we do not detect any source at either the position of the VT optical afterglow candidate (Qiu et al., GCN 38852), nor within the Swift/XRT localization region of the proposed X-ray counterpart (Ambrosi et al., GCN 38853). The limiting magnitude is approximately z > 22.1 (AB), calibrated against nearby stars from the Pan-STARRS catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/38862. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36868] EP250108a: EP-WXT detection of an X-ray transient
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38861 SUBJECT: EP250108a: EP-WXT detection of an X-ray transient DATE: 25/01/09 06:41:37 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.-Z. Li (YNAO, CAS), X.-L. Chen (YNU), K. Chatterjee (YNU), Y.-L. Hua (PMO) and Y. Liu (NAOC) report on behalf of the Einstein Probe team: We report on the detection of an X-ray transient, designated EP250108a, by the Wide-field X-ray Telescope (WXT, trigger ID: 06800000356) on board the Einstein Probe (EP) mission. The transient event was detected at 2025-01-08T12:30:28.34 (UTC). The WXT position of the source is R.A. = 55.623 deg, DEC = -22.509 deg (J2000) with an uncertainty of 2.2 arcmin in radius (90% C.L. statistical and systematic). The transient event lasts for about 2500 seconds. The peak flux in the 0.5-4 keV is around 1.4 x 10^-10 erg/s/cm^2. The average 0.5-4 keV spectrum can be fitted with an absorbed power law with a photon index of 1.35 +/- 0.40 (with a Galactic column density fixed at 1.6 x 10^20 cm^-2). The derived average unabsorbed 0.5-4 keV flux is 4.2 (+1.2/-0.9) x 10^-11 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. A follow-up observation with the Follow-up X-ray Telescope (FXT) on board EP has been scheduled. Further observations are encouraged to explore the origin of the transient. 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). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES. View this GCN Circular online at https://gcn.nasa.gov/circulars/38861. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36867] LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38860 SUBJECT: LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate DATE: 25/01/09 01:52:52 GMT FROM: 陳正敏 <cjhengmin(a)gmail.com> S250109f_circular The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250109f during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-01-09 01:05:41.482 UTC (GPS time: 1420419959.482). The candidate was found by the CWB [1], cWB BBH [2], GstLAL [3], MBTA [4], and PyCBC Live [5] analysis pipelines. S250109f is an event of interest because its false alarm rate, as estimated by the online analysis, is 2.9e-12 Hz, or about one in 1e4 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250109f After parameter estimation by RapidPE-RIFT [6], the classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [7] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [7] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [8], distributed via GCN notice about 25 seconds after the candidate event time. * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [8], distributed via GCN notice about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,1. For the bayestar.multiorder.fits,1 sky map, the 90% credible region is 614 deg2. Marginalized over the whole sky, the posteriori luminosity distance estimate is 3259 +/- 876 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 [2] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [3] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625 [4] Aubin et al. CQG 38, 095004 (2021) doi:10.1088/1361-6382/abe913 [5] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [6] Rose et al. (2022) arXiv:2201.05263 and Pankow et al. PRD 92, 023002 (2015) doi:10.1103/PhysRevD.92.023002 [7] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [8] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/38860. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36866] GRB 250108B: Swift-XRT refined Analysis
by GCN Circulars 09 Jan '25

09 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38859 SUBJECT: GRB 250108B: Swift-XRT refined Analysis DATE: 25/01/09 01:41:47 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> M. Capalbi (INAF-IASFPA), D.N. Burrows (PSU), M. A. Williams (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 8.5 ks of XRT data for GRB 250108B, from 97 s to 33.7 ks after the BAT trigger. The data comprise 608 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+5.5 ks) can be modelled with a power-law decay with a decay index of alpha=0.35 (+/-0.13). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.37 (+/-0.04). The best-fitting absorption column is 1.47 (+/-0.09) x 10^21 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 2.07 (+0.17, -0.16) and a best-fitting absorption column of 1.3 (+0.5, -0.4) x 10^21 cm^-2. 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: 1.3 (+0.5, -0.4) x 10^21 cm^-2 Galactic foreground: 1.2 x 10^20 cm^-2 Excess significance: 4.8 sigma Photon index: 2.07 (+0.17, -0.16) If the light curve continues to decay with a power-law decay index of 0.35, the count rate at T+24 hours will be 0.045 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.5 x 10^-12 (2.0 x 10^-12) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01280056. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/38859. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36865] Swift GRB 250108B: Global MASTER-Net observations report
by GCN Circulars 08 Jan '25

08 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38858 SUBJECT: Swift GRB 250108B: Global MASTER-Net observations report DATE: 25/01/08 21:47:28 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 250108B ( N. J. Klingler et al., GCN 38847) errorbox 35528 sec after notice time and 35573 sec after trigger time at 2025-01-08 20:16:00 UT, with upper limit up to 17.8 mag. The observations began at zenith distance = 84 deg. The sun altitude is -65.6 deg. The galactic latitude b = 82 deg., longitude l = 23 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2737810 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 35664 | MASTER-Kislovodsk | C | 180 | 16.7 | 35664 | MASTER-Kislovodsk | C | 180 | 16.7 | 35864 | MASTER-Kislovodsk | C | 180 | 16.7 | 35864 | MASTER-Kislovodsk | C | 180 | 16.7 | 36908 | MASTER-Kislovodsk | C | 180 | 17.5 | 36908 | MASTER-Kislovodsk | C | 180 | 17.5 | 38307 | MASTER-Kislovodsk | C | 180 | 17.6 | 38307 | MASTER-Kislovodsk | C | 180 | 17.6 | 38757 | MASTER-Kislovodsk | C | 120 | 17.6 | 38757 | MASTER-Kislovodsk | C | 120 | 17.6 | 39177 | MASTER-Kislovodsk | C | 120 | 17.5 | 39177 | MASTER-Kislovodsk | C | 120 | 17.5 | 39547 | MASTER-Kislovodsk | C | 180 | 17.8 | 39547 | MASTER-Kislovodsk | C | 180 | 17.8 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/38858. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36864] Fermi Gamma-ray Burst Monitor trigger 758061038/250108855 is not a GRB
by GCN Circulars 08 Jan '25

08 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38857 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 758061038/250108855 is not a GRB DATE: 25/01/08 21:33:43 GMT FROM: atrigg2(a)lsu.edu A. C. Trigg (LSU) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 758061038/250108855 at 20:30:33.28 UT on 08 January 2025 is not due to a GRB. This trigger is likely due to local particles. This trigger is not associated with LIGO/Virgo/KAGRA S250108ha (GCN 38856)" View this GCN Circular online at https://gcn.nasa.gov/circulars/38857. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36863] LIGO/Virgo/KAGRA S250108ha: Retraction of GW compact binary merger candidate
by GCN Circulars 08 Jan '25

08 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38856 SUBJECT: LIGO/Virgo/KAGRA S250108ha: Retraction of GW compact binary merger candidate DATE: 25/01/08 21:26:41 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 S250108ha, initially reported because of a coincidence with Fermi/GBM trigger 758061038/250108855, is no longer considered to be a candidate of interest. That Fermi trigger is no longer classified as a GRB. Without this, the GW candidate’s significance is below our alert threshold. View this GCN Circular online at https://gcn.nasa.gov/circulars/38856. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36862] GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
by GCN Circulars 08 Jan '25

08 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38855 SUBJECT: GRB 250108B: Gemini-North Candidate Optical Afterglow Detection DATE: 25/01/08 16:51:54 GMT FROM: Jillian Rastinejad at Northwestern Univ. <jillianrastinejad2024(a)u.northwestern.edu> Jillian Rastinejad (Northwestern), Andrew J. Levan (Radboud), Wen-fai Fong, Charlie Kilpatrick (Northwestern), Daniele B. Malesani (DAWN/ NBI and Radboud), Nial R. Tanvir (U. Leicester), Gavin P Lamb (LJMU), Benjamin P. Gompertz (U. Birmingham) and Brian D. Metzger (Columbia/CCA) report on behalf of a larger collaboration: We observed the location of the X-ray afterglow of GRB 250108B (Klinger et al., GCN 38847; Osborne et al., GCN 38848) with the Gemini Multi-Object Spectrograph (GMOS-N) mounted on Gemini-North under Program GN-2024B-Q-107. We obtained 15x120-s imaging in r-band at a mid-time of 2025-01-08 12:42:45.8 UT (2.33 hours post-burst), at a median airmass of 1.7 and seeing < 1.2''. We clearly detect a faint source not present in archival Legacy Survey DR10 r-band imaging but within the XRT localization at a position of RA (J2000) = 13:25:18.50 Dec (J2000) = 25:36:55.82 with an uncertainty of 0.7''. We suggest that this is the afterglow of GRB 250108B. We note that the candidate afterglow is 16.8'' offset from a bright galaxy (r = 19.5 AB mag). This galaxy has a Legacy Survey DR9 photometric redshift of z = 0.29 +/- 0.04 (Zhou et al., 2021) and an SDSS photometric redshift of z = 0.22 +/- 0.04 (Alam et al., 2015), corresponding to projected separations of 74 kpc and 60 kpc from the transient, respectively. We determine a probability of chance coincidence between this galaxy and the candidate afterglow of Pcc = 0.13 (Bloom et al., 2002). With present data we cannot rule out the presence of a faint, underlying host at the position of the transient. Calibrated to SDSS, we measure a preliminary brightness for the optical source of r = 23.4 +/- 0.1 AB mag, not corrected for Galactic extinction. At a redshift of z = 0.29, this corresponds to an optical luminosity of 2.1 x 10^42 erg/s. Further observations are planned to monitor the variability of the source. We thank Jen Miller, Leila Alamos, Brian Lemaux and additional Gemini staff for excellent support in the rapid planning and execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/38855. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36861] GRB 250103A: 1.6m Mephisto optical observations
by GCN Circulars 08 Jan '25

08 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38854 SUBJECT: GRB 250103A: 1.6m Mephisto optical observations DATE: 25/01/08 16:27:20 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Guowang Du, Jinghua Zhang, Yangwei Zhang, Brajesh Kumar, Xufeng Zhu, Fanchuan Kong, Chenxi Shang, Yuan Fang, Xinlei Chen, Xingzhu Zou, Yu Pan, Yuanpei Yang (all SWIFAR, YNU), Xuhui Han, Pinpin Zhang, Liping Xin, Chao Wu (all NAOC), Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team: The field of GRB 250103A (sb25010301) detected by SVOM/ECLAIRs (Wang et al. GCN 38786) was observed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. Simultaneous uvgriz band photometric observations were conducted starting from 11:35:51 2025-01-03 UT (~1.65 hr after the SVOM/ECLAIRs trigger) and several frames with different exposure times were taken. There is detection of the optical candidate (Li et al., GCN 38795; Qiu et al., GCN 38802; Xu et al., GCN 38808; Leonini et al., GCN 38811) in our r and i band single frames but not in the stacked images of uvgz bands. The preliminary photometry and 3 sigma upper limits are below: Start_Time(UT) | Band | Exp(s) | Mag/LimMag (AB) ---------------------------|--------|---------------- 2025-01-03T11:35:52 | u | 180*2 | >21.89 2025-01-03T11:43:02 | v | 180*2 | >22.28 2025-01-03T11:35:52 | g | 50*6 | >22.15 2025-01-03T11:43:03 | r | 50*1 | 20.91(+/-0.35) 2025-01-03T11:35:51 | i | 79*1 | 19.72(+/-0.32) 2025-01-03T11:43:02 | z | 79*4 | >20.46 ------------------------------------------------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m 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/38854. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36860] GRB 250108A: Swift-XRT afterglow detection
by GCN Circulars 08 Jan '25

08 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38853 SUBJECT: GRB 250108A: Swift-XRT afterglow detection DATE: 25/01/08 16:18:44 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-IASFPA), J.A. Kennea (PSU), D.N. Burrows (PSU), M. A. Williams (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), M. Perri (SSDC & INAF-OAR) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected burst GRB 250108A. We searched for X-ray sources in 2.7 ks of Photon Counting (PC) mode data. The total exposure at the position of the afterglow (see below) is 3.2 ks, obtained between T0+16.1 ks and T0+34.4 ks. An uncatalogued X-ray source is detected within the estimated 3-sigma SVOM/MXTs error region (98 arcsec) and is above the LSXPS 3-sigma upper limit at this position, and is therefore likely the GRB afterglow. Using 2670 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 = 207.92093, +26.21642 which is equivalent to: RA (J2000): 13h 51m 41.02s Dec(J2000): +26d 12' 59.1" with an uncertainty of 4.1 arcsec (radius, 90% confidence). This position is 73 arcsec from the SVOM/MXTs position. The source has a mean count rate of 1.7e-02 ct/sec; we cannot determine at the present time whether it is fading. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00021755. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021755. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/38853. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36859] GRB 250108A:SVOM/VT optical candidate
by GCN Circulars 08 Jan '25

08 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38852 SUBJECT: GRB 250108A:SVOM/VT optical candidate DATE: 25/01/08 16:14:39 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> SVOM/VT commissioning team: Y. L. Qiu, H. L. Li (NAOC), W. K. Zheng (UCB), Z. Q. Wang (GXU), X. H. Han, L. P. Xin, C. Wu, J. Wang, W. J. Xie, H. B. Cai, Y. Xu, Y. J. Xiao, P. P. Zhang, J. S. Deng, L. Lan, X. M. Lu, R. S. Zhang, Z. H. Yao (NAOC), J. Zhang, L. J. Dan, G. Y. Zou, C. J. Wang, Y. F. Du, C. Huang (XIOPM) SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Olivier Godet (IRAP), Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Shao-Lin Xiong (IHEP), Bing Zhang (UNLV) report on behalf of the SVOM team: The SVOM/VT conducted follow-up observations of the GRB 250108A (Zheng et al., GCN 38845) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. With the X band downlinked data, an uncatalogued optical source was detected within the errorbox of MXT (Zheng et al., GCN 38845) in VT_R stacked image, compared to the DESI catalog. It is the only new source within the error box down to the 3 sigma limit of about 22.7 mag. The brightness of the source was estimated to be 22.1+/-0.2 mag in AB magnitude in VT_R image at the mid time of 1.516 hours post the burst, with a total exposure time of 8*100 seconds. The source can not be detected in VT_R 19*100 sec stacked image with a 3 sigma limit of 23.0 mag at the middle time of 3.978 hours. The source is located at RA, Dec = 207.89654, 26.23741, which is equivalent to: RA (J2000) : 13:51:35.17 Dec (J2000): +26:14:14.68 with an uncertainty of 0.5 arcsec. Additionally, no any new sources were detected within the errorbox of XRT #1 source (Phil Evans et al., GCN 38846). We proposed that this source is the candidate for the gamma-ray burst. More deep follow-ups are encouraged to confirm the nature of the source. 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/38852. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36858] LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
by GCN Circulars 08 Jan '25

08 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38851 SUBJECT: LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate DATE: 25/01/08 16:01:16 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: We identified the compact binary merger candidate S250108eo during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-01-08 15:22:21.704 UTC (GPS time: 1420384959.704). The candidate was found by the CWB [1], cWB BBH [2], GstLAL [3], MBTA [4], and PyCBC Live [5] analysis pipelines. S250108eo is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.8e-11 Hz, or about one in 1e3 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250108eo After parameter estimation by RapidPE-RIFT [6], the classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [7] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [7] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [8], distributed via GCN notice about 32 seconds after the candidate event time. * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [8], distributed via GCN notice about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,1. For the bayestar.multiorder.fits,1 sky map, the 90% credible region is 938 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 2826 +/- 750 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 [2] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [3] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625 [4] Aubin et al. CQG 38, 095004 (2021) doi:10.1088/1361-6382/abe913 [5] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [6] Rose et al. (2022) arXiv:2201.05263 and Pankow et al. PRD 92, 023002 (2015) doi:10.1103/PhysRevD.92.023002 [7] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [8] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/38851. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36857] GRB 250108B: Swift/UVOT Upper Limits
by GCN Circulars 08 Jan '25

08 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38850 SUBJECT: GRB 250108B: Swift/UVOT Upper Limits DATE: 25/01/08 14:32:24 GMT FROM: Alice Breeveld at MSSL-UCL <a.breeveld(a)ucl.ac.uk> A. A. Breeveld (UCL-MSSL) and N. J. Klingler (GSFC/UMBC/CRESSTII) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250108B 117 s after the BAT trigger (Klingler et al., GCN Circ. 38847). No optical afterglow consistent with the enhanced XRT position (Osborne et al., GCN Circ. 38848) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 117 267 147 >20.7 white 117 980 247 >21.2 u_FC 275 525 246 >20.2 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.012 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/38850. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36856] GRB 250103A: Swift-XRT afterglow detection
by GCN Circulars 08 Jan '25

08 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38849 SUBJECT: GRB 250103A: Swift-XRT afterglow detection DATE: 25/01/08 13:48:01 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU), M. A. Williams (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has conducted further observations of the field of the SVOM/ECLAIRs-detected burst GRB 250103A. The observations now extend from T0+24.3 ks to T0+432.8 ks and have a total exposure time of 5.5 ks. The source previously reported, "Source 1", is fading with >3-sigma significance, and is therefore likely the GRB afterglow. Using 1509 s of PC mode data and 3 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 = 22.06415, -5.05179 which is equivalent to: RA (J2000): 01h 28m 15.40s Dec(J2000): 05d 03' 06.4" with an uncertainty of 2.5 arcsec (radius, 90% confidence). This position is 2.9 arcmin from the SVOM/ECLAIRs position. The light curve can be modelled with a power-law decay with a decay index of alpha=0.82 (+0.24, -0.18). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.14 (+0.31, -0.28). The best-fitting absorption column is 1.4 (+0.9, -0.7) x 10^21 cm^-2, in excess of the Galactic value of 4.5 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 3.2 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 (+0.9, -0.7) x 10^21 cm^-2 Galactic foreground: 4.5 x 10^20 cm^-2 Excess significance: 2.3 sigma Photon index: 2.14 (+0.31, -0.28) The results of the XRT-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/ToO_GRBs/00021752/Source1.php. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021752. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/38849. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36855] GRB 250108B: Enhanced Swift-XRT position
by GCN Circulars 08 Jan '25

08 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38848 SUBJECT: GRB 250108B: Enhanced Swift-XRT position DATE: 25/01/08 12:44:36 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 558 s of XRT Photon Counting mode data and 1 UVOT images for GRB 250108B, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 201.32654, +25.61519 which is equivalent to: RA (J2000): 13h 25m 18.37s Dec (J2000): +25d 36' 54.7" with an uncertainty of 2.2 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/38848. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36854] GRB 250108B: Swift detection of a burst
by GCN Circulars 08 Jan '25

08 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38847 SUBJECT: GRB 250108B: Swift detection of a burst DATE: 25/01/08 10:45:05 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> N. J. Klingler (GSFC/UMBC/CRESSTII), R. Brivio (INAF-OAB), J. J. DeLaunay (PSU), R. Gupta (NASA GSFC), K. L. Page (U Leicester), C. Salvaggio (INAF-OAB) and T. Sbarrato (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team: At 10:23:06 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250108B (trigger=1280056). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 201.297, +25.613 which is RA(J2000) = 13h 25m 11s Dec(J2000) = +25d 36' 46" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 30s sec. The peak count rate was ~1210 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 10:24:54.0 UT, 107.8 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source with an enhanced position: RA, Dec 201.32686, 25.61541 which is equivalent to: RA(J2000) = 13h 25m 18.45s Dec(J2000) = +25d 36' 55.5" with an uncertainty of 2.0 arcseconds (radius, 90% containment). This location is 97 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.16 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.6 (+2.37/-2.05) x 10^21 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 9.22e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 250 seconds with the U filter starting 274 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.2 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18.0 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.012. Burst Advocate for this burst is N. J. Klingler (noelklin AT umbc.edu). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/38847. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36853] GRB 250108A: Swift ToO observations
by GCN Circulars 08 Jan '25

08 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38846 SUBJECT: GRB 250108A: Swift ToO observations DATE: 25/01/08 09:04:41 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the SVOM/ECLAIRs GRB 250108A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021755 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 SVOM/ECLAIRs 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/38846. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36852] GRB 250108A: SVOM detection of a soft long burst
by GCN Circulars 08 Jan '25

08 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38845 SUBJECT: GRB 250108A: SVOM detection of a soft long burst DATE: 25/01/08 05:57:19 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> W. Zheng (UCB), Z-Q. Wang (GXU), W.-J. XIE (NAOC, CAS), D.-H. ZHAO (NAOC, CAS), S. Guillot (IRAP), D. Götz (CEA), H. Goto (CEA), C-W. Wang (IHEP) report on behalf of the SVOM team. The SVOM/ECLAIRs telescope triggered and located the long duration GRB 250108A (sb25010802) starting at 2025-01-08T04:37:01.513 UTC (Tb). The following trigger information was received on the ground with low-latency by the SVOM VHF Alert Network. The burst was detected by both the on-board Count-Rate Trigger (CRT) and Image Trigger (IMT) and 9 alerts were received. The best detection is obtained by IMT with a signal-to-noise ratio of 10.2 in the 5-8 keV energy band over a time window of 40.96 s starting at Tb. The light curve in ECLAIRs with a preliminary T90 duration is about 40 s. The localization of the best Alert is RA, Dec = 207.946, 26.204 (J2000). The uncertainty on this position is 7.79 arcminutes at 90% C.L. which includes 2 arcminutes of systematic uncertainty in quadrature. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250108A.png SVOM performed an automatic slew and MXT started observing the ECLAIRs error box at 04:40:49 UTC, i.e. 228 s after Tb. An uncatalogued X-ray source has been found by the on board software at R.A., Dec. = 207.906, 26.232 (J2000) (13:51:38, +26:13:56, J2000) with an uncertainty of 60 arc sec (90% C.L., including systematics). This source is located at 2.7 arc minutes from the ECLAIRs position. VT results will be reported later. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. The SVOM point of contact for this burst is: Weikang Zheng ( weikang(a)berkeley.edu) View this GCN Circular online at https://gcn.nasa.gov/circulars/38845. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36851] GRB 250107A: Fermi GBM Observation
by GCN Circulars 08 Jan '25

08 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38844 SUBJECT: GRB 250107A: Fermi GBM Observation DATE: 25/01/08 01:46:08 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA), A. Myers (NPP/GSFC) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 05:02:30.29 UT on 07 January 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250107A (trigger 757918955/250107210). which was also detected by Swift/BAT-GUANO (DeLaunay et al. 2025, GCN 38840). The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position. The angle from the Fermi LAT boresight is 21 degrees. The GBM light curve consists of a single emission episode with multiple peaks with a duration (T90) of about 53 s (50-300 keV). The time-averaged spectrum from T0-2.8 to T0+35.1 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.22 +/- 0.06 and the cutoff energy, parameterized as Epeak, is 390 +/- 80 keV. The event fluence (10-1000 keV) in this time interval is (7.8 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+6.85 s in the 10-1000 keV band is 3.6 +/- 0.24 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/38844. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36850] GCN Announcement: GCN at AAS 245, Legacy Circulars Address Retirement
by GCN Announcements 07 Jan '25

07 Jan '25

The GCN Team is pleased to announce: Visit GCN at the NASA Booth at the 245th AAS Meeting If you are at the 245th AAS meeting in National Harbor, MD on January 12-16, 2025, be sure to stop by the GCN table at the NASA booth in the exhibit hall to: - play with our Raspberry Pi Kafka demo(https://github.com/nasa-gcn/gcn-raspberry-pi-demo) - sign up for GCN, if you aren't already subscribed - collect an all new official GCN patch - talk with the GCN developers about your feature requests and issues. Retirement of Legacy Email Submission Address We retired the legacy email address (gcncirc(a)capella2.gsfc.nasa.gov) for GCN Circular submission on December 31, 2024. Please utilize one of the other Circular submission methods: - Email circulars(a)gcn.nasa.gov - Submit via the web form(https://gcn.nasa.gov/circulars/new), which also offers enhanced features with Markdown capability to add tables, links, and formatting. 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…

1 0

[vsnet-grb-info 36849] GRB 241228B: Fermi-LAT detection
by GCN Circulars 07 Jan '25

07 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38843 SUBJECT: GRB 241228B: Fermi-LAT detection DATE: 25/01/07 18:46:55 GMT FROM: N. Di Lalla at Stanford University <niccolo.dilalla(a)stanford.edu> N. Di Lalla (Stanford University), A. Holzmann Airasca (UniTrento and INFN Bari), T. Khalil (Johannesburg Univ), S. Lopez (CNRS / IN2P3), D. Depalo (Politecnico and INFN Bari), C.C. Cheung (Naval Research Lab), C. Bartolini (UniTrento and INFN Bari) report on behalf of the Fermi-LAT Collaboration: On December 28, 2024, Fermi-LAT detected high-energy emission from GRB 241228B, which was also detected by Fermi-GBM (trigger 757051990/241228176, GCN 38714), Swift-XRT (GCN 38713), Swift/BAT-GUANO (GCN 38700), GOTO24jmz (GCN 38684), TRT (GCN 38687), LCOGT (GCN 38692), GROWTH-India Telescope (GCN 38694), VLT/X-shooter (GCN 38704), LCO (GCN 38702), D50 (GCN 38715), SAO RAS (GCN 38733), 1.6m Mephisto (GCN 38739), 1.3m DFOT (GCN 38816). The best LAT on-ground location is found to be: RA, Dec = 127.8, 6.9 (J2000) with an error radius of 0.1 deg (90 % containment, statistical error only).This was 56 deg from the LAT boresight at the time of the GBM trigger (T0 = 04:13:05.39 UT). The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the GBM emission with high significance. The photon flux above 100 MeV in the time interval 0 - 520 s after the GBM trigger is (1.2 +/- 0.3) E-5 ph/cm2/s. The estimated photon index above 100 MeV is 2.0 +/- 0.2. The highest-energy photon is a 16 GeV event which is observed about 31 seconds after the GBM trigger. The Fermi-LAT point of contact for this burst is Francesco Longo (francesco.longo(a)ts.infn.it <mailto:francesco.longo@ts.infn.it>). The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/38843. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36848] Fermi GRB 250107B: Global MASTER-Net observations report
by GCN Circulars 07 Jan '25

07 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38842 SUBJECT: Fermi GRB 250107B: Global MASTER-Net observations report DATE: 25/01/07 16:33:51 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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 (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 250107B ( Fermi GBM team, GCN 38839) errorbox 14186 sec after notice time and 14221 sec after trigger time at 2025-01-07 15:31:05 UT, with upper limit up to 19.3 mag. The observations began at zenith distance = 12 deg. The sun altitude is -55.2 deg. The galactic latitude b = 28 deg., longitude l = 157 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2736509 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 14251 | 2025-01-07 15:31:05 | MASTER-Tunka | (04h 13m 49.68s , +54d 32m 00.7s) | C | 60 | 19.1 | 14311 | 2025-01-07 15:31:05 | MASTER-Tunka | (04h 13m 49.68s , +54d 32m 00.8s) | C | 180 | 19.1 | Coadd 14483 | 2025-01-07 15:34:57 | MASTER-Tunka | (04h 27m 33.78s , +54d 31m 30.6s) | C | 60 | 19.3 | 14543 | 2025-01-07 15:34:57 | MASTER-Tunka | (04h 27m 33.77s , +54d 31m 30.6s) | C | 180 | 19.3 | Coadd 14557 | 2025-01-07 15:36:11 | MASTER-Tunka | (03h 58m 53.28s , +56d 25m 31.5s) | C | 60 | 18.8 | 14617 | 2025-01-07 15:36:11 | MASTER-Tunka | (03h 58m 53.29s , +56d 25m 31.6s) | C | 180 | 18.8 | Coadd 14719 | 2025-01-07 15:38:53 | MASTER-Tunka | (04h 13m 21.56s , +56d 24m 57.2s) | C | 60 | 19.0 | 14953 | 2025-01-07 15:42:46 | MASTER-Tunka | (04h 13m 49.60s , +54d 32m 46.9s) | C | 60 | 19.0 | 15109 | 2025-01-07 15:45:23 | MASTER-Tunka | (04h 27m 30.11s , +54d 32m 56.0s) | C | 60 | 19.1 | 15183 | 2025-01-07 15:46:37 | MASTER-Tunka | (03h 58m 51.42s , +56d 25m 51.6s) | C | 60 | 18.6 | 15803 | 2025-01-07 15:56:57 | MASTER-Tunka | (04h 13m 16.36s , +56d 26m 13.9s) | C | 60 | 17.8 | 16036 | 2025-01-07 16:00:50 | MASTER-Tunka | (04h 13m 42.42s , +54d 32m 55.6s) | C | 60 | 17.5 | 16206 | 2025-01-07 16:03:40 | MASTER-Tunka | (04h 27m 32.57s , +54d 33m 24.4s) | C | 60 | 17.0 | 16282 | 2025-01-07 16:04:56 | MASTER-Tunka | (03h 58m 39.55s , +56d 26m 20.1s) | C | 60 | 16.6 | 16530 | 2025-01-07 16:09:04 | MASTER-Tunka | (04h 13m 12.79s , +56d 26m 02.5s) | C | 60 | 17.4 | 16874 | 2025-01-07 16:14:47 | MASTER-Tunka | (04h 15m 44.55s , +52d 38m 47.2s) | C | 60 | 17.8 | 17283 | 2025-01-07 16:21:36 | MASTER-Tunka | (04h 01m 08.58s , +54d 33m 43.0s) | C | 60 | 18.4 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/38842. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36847] GRB 250107A: Swift ToO observations
by GCN Circulars 07 Jan '25

07 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38841 SUBJECT: GRB 250107A: Swift ToO observations DATE: 25/01/07 15:53:44 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the Swift/BAT GRB 250107A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021754 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 Swift/BAT 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/38841. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36846] GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
by GCN Circulars 07 Jan '25

07 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38840 SUBJECT: GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst DATE: 25/01/07 14:50:34 GMT FROM: Jimmy DeLaunay at Penn State <delauj2(a)gmail.com> James DeLaunay (PSU), Aaron Tohuvavohu (Caltech), Samuele Ronchini (PSU), Gayathri Raman (PSU), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC) report: Swift/BAT did not localize GRB 250107A onboard (T0: 2025-01-07T05:02:30.29 UTC, Fermi Trig 757918955). The Fermi notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground. The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), detects the burst in a 16.384 s analysis time bin starting at T0 - 0.0 s with a sqrt(TS) of 21.8. An arcminute localization is found with DeltaLLHOut of 19.3 and a DeltaLLHPeak of 10.5. See Section 9.1 and Figures 10 and 17 in the NITRATES paper for brief descriptions and interpretations of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut. The BAT position is RA, Dec = 302.52, 45.564 deg which is RA(J2000) = 20h 10m 04.80s Dec(J2000) = 45d 33' 50.4″ with an estimated uncertainty of 4 arcmin radius. XRT and UVOT follow-up has been requested. Results of follow-up observations will be reported in future circulars. GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/ View this GCN Circular online at https://gcn.nasa.gov/circulars/38840. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36845] GRB 250107B: Fermi GBM Final Real-time Localization
by GCN Circulars 07 Jan '25

07 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38839 SUBJECT: GRB 250107B: Fermi GBM Final Real-time Localization DATE: 25/01/07 11:44:24 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely SHORT GRB At 11:34:04 UT on 7 Jan 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250107B (trigger 757942449.293284 / 250107482). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 110.8, Dec = 59.6 (J2000 degrees, equivalent to J2000 07h 23m, 59d 36'), with a statistical uncertainty of 25.9 degrees. The angle from the Fermi LAT boresight is 69.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250107482/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250107482/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250107482/… View this GCN Circular online at https://gcn.nasa.gov/circulars/38839. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36844] GRB 250106A: SVOM/VT 2nd optical deep observation
by GCN Circulars 07 Jan '25

07 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38838 SUBJECT: GRB 250106A: SVOM/VT 2nd optical deep observation DATE: 25/01/07 09:31:41 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> SVOM/VT commissioning team: Y. L. Qiu, H. L. Li, C. Wu, D. H. Zhao, L. P. Xin, X. H. Han, J. Wang, W. J. Xie, H. B. Cai, Y. Xu, Y. J. Xiao, P. P. Zhang, J. S. Deng, L. Lan, X. M. Lu, R. S. Zhang, Z. H. Yao (NAOC), J. Zhang, L. J. Dan, G. Y. Zou, C. J. Wang, Y. F. Du, C. Huang (XIOPM) SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Olivier Godet (IRAP), Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Shao-Lin Xiong (IHEP), Bing Zhang (UNLV) report on behalf of the SVOM team: The SVOM/VT conducted TOO observations of GRB 250106A (Zhao et al., GCN 38826) at 8.88 hr after the trigger. The observations were carried out in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. The candidate reported by Qiu et al. (GCN 38829) were detected in both of stacked images of VT_B and VT_R. The brightness are, channel (t-T0)_mid(hr) exptime mag(AB) VT_B 13.25 149x100s 23.5 +/-0.2 VT_R 13.26 142x100s 22.4 +/-0.1 No definite fading was found compared to brightness reported (Qiu et al., GCN 38829). This observation is consistent with the result (Izzo et al. GCN 38834). Thus, this source is not a good candidate for the burst. A new source with a low S/N with a magnitude of VT_R~24.0 mag was tentatively detected near the errorbox of XRT source #1 (Osborne et al. GCN 38830), with a distance of 4.0 arcseconds from the XRT source #1. Its position is RA=117.2372, DEC=63.8132 deg, which is equivalent to: RA (J2000) : 07:48:56.93 Dec (J2000): +63:48:47.5 with an uncertainty of 0.5 arcsec. 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/38838. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36843] GRB 250101A: J band upper limit by SYSU 80cm telescope
by GCN Circulars 07 Jan '25

07 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38837 SUBJECT: GRB 250101A: J band upper limit by SYSU 80cm telescope DATE: 25/01/07 06:20:55 GMT FROM: Jiaqi Lin <islinjiaqi(a)gmail.com> Jia-Qi Lin, Jin-Ji Li, Zhong-Nan Dong, Si-Yuan Zhu, Wei-Sen Huang, Pu Lin, Hao-Nan Yang, Yan Yu, Hao-Ran Zhang, Pak-Hin Thomas Tam, Bin Ma (Sun Yat-sen University) report on behalf of the SYSU 80cm telescope team: We observed the field of GRB 250101A (Page et al., GCN 38752), using the Sun Yat-sen University 80cm telescope, with 158 × 20 s exposures in J band. Our observations began at 2025-1-1 15:18:18 UTC, 1.92 hours after the BAT trigger. We did not detect any counterpart in the stacked images at the position of the optical afterglow (Li et al., GCN 38753; Mohan et al., GCN 38754; Zhu et al., GCN 38755; Budnev et al., GCN 38756; Wu et al., GCN 38758; Odeh et al., GCN Circular 38763), down to a 5-sigma depth of J ~ 18.0 Vega magnitudes. View this GCN Circular online at https://gcn.nasa.gov/circulars/38837. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36842] GRB 250107A: Fermi GBM Final Real-time Localization
by GCN Circulars 07 Jan '25

07 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38836 SUBJECT: GRB 250107A: Fermi GBM Final Real-time Localization DATE: 25/01/07 05:12:57 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 05:02:30 UT on 7 Jan 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250107A (trigger 757918955.285842 / 250107210). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 309.4, Dec = 45.3 (J2000 degrees, equivalent to J2000 20h 37m, 45d 17'), with a statistical uncertainty of 3.5 degrees. The angle from the Fermi LAT boresight is 23.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250107210/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250107210/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250107210/… View this GCN Circular online at https://gcn.nasa.gov/circulars/38836. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36841] EPWXT01709129925: Xinglong optical observations
by GCN Circulars 07 Jan '25

07 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38835 SUBJECT: EPWXT01709129925: Xinglong optical observations DATE: 25/01/07 03:27:21 GMT FROM: Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong(a)nao.cas.cn> Yu-Zhang(NAOC), Jianfeng-Tian(NAOC), Ying-Wu(NAOC), Pengliang-Du(NAOC), Junjie-Jin(NAOC), Haiyang-Mu(NAOC), Yuguang-Sun(NAOC), Zheng-Jie (NAOC), Zhou-Fan(NAOC), Hong-Wu(NAOC) report on behalf of a large collaboration: In response to the detection of the likely flaring star 1RXS J060224.9-163451 by EP/WXT, an automatic trigger initiated follow-up observations using the 0.8-m telescope at Xinglong Observatory, Hebei, China. We obtained one 300-second exposure in both the g-band and r-band filters, with a median time of 2025-01-06T13:07:42, i.e., 16.2 hr after the EP trigger (ID 01709129925). For this target, we measured magnitudes of g ~ 12.82 mag and r ~ 11.48 mag, calibrated with the Pan-STARRS g-band and r-band field. View this GCN Circular online at https://gcn.nasa.gov/circulars/38835. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36840] GRB 250106A: NOT optical observations
by GCN Circulars 07 Jan '25

07 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38834 SUBJECT: GRB 250106A: NOT optical observations DATE: 25/01/07 01:47:52 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> L. Izzo (INAF/OACn and DARK/NBI), D. B. Malesani (DAWN/NBI and Radboud Univ.), D. Xu (NAOC), Z.P. Zhu (NAOC), X. Liu (NAOC), T. Pursimo (NOT), report on behalf of a larger collaboration: We observed the field of GRB 250106A (Zhao et al., GCN 38826) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera, using the SDSS z filter. The instrument was rotated in order to include XRT sources #1 and #2 (Osborne et al., GCN 38830), as well as the candidate SVOM/VT optical afterglow (which is consistent with the position of XRT source #2; Qiu et al., GCN 38829). The observation mid time was 2025 Jan 6.982 UT (10.13 hr after the SVOM trigger), and the exposure time was 2000 s. No source is detected within the localization circle of XRT source #1, down to a limiting magnitude z > 23.3 (AB). Two sources are detected within the localization circle of XRT source #2. Source A (coincident with the SVOM/VT optical candidate): RA = 07:49:29.04 Dec = +63:42:29.4 mag z = 22.23 +- 0.10 AB Source B: RA = 07:49:27.99 Dec = +63:42:31.5 mag z = 19.90 +- 0.02 AB At the locations of both sources, objects are visible in the Legacy Survey, for which we measure AB magnitudes z = 22.24 +- 0.11 and z = 19.84 +- 0.02 for sources A and B, respectively. Our measured values are thus fully consistent with those in the archival images. Source B is also detected by Gaia, which provides a QSO classification. This opens the question whether object B could be responsible for the X-ray emission detected by Swift/XRT. Source A could be the host galaxy of GRB 250106A, though we note that its archival r-band magnitude (r = 23) is only marginally fainter than the SVOM/VT magnitude (R = 22.5 +- 0.3 mag; Qiu et al., GCN 38829). We encourage further observations with both SVOM/VT and Swift/XRT in order to establish variability of both the optical and X-ray sources. View this GCN Circular online at https://gcn.nasa.gov/circulars/38834. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36839] GRB 210506A NOT GCN draft
by GCN Circulars 07 Jan '25

07 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38834 SUBJECT: GRB 210506A NOT GCN draft DATE: 25/01/07 01:47:52 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> Hi. I doubt anyone is online, but here's the GCN draft for the NOT observations, which I'll submit soon. TLTR: no obvious candidate, one possible host galaxy, but I would hold spectroscopy until variability is confirmed by VT or XRT. d ============================== GRB 250106A: NOT optical observations L. Izzo (INAF/OACn and DARK/NBI), D. B. Malesani (DAWN/NBI and Radboud Univ.), D. Xu (NAOC), Z.P. Zhu (NAOC), X. Liu (NAOC), T. Pursimo (NOT), report on behalf of a larger collaboration: We observed the field of GRB 250106A (Zhao et al., GCN 38826) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera, using the SDSS z filter. The instrument was rotated in order to include XRT sources #1 and #2 (Osborne et al., GCN 38830), as well as the candidate SVOM/VT optical afterglow (which is consistent with the position of XRT source #2; Qiu et al., GCN 38829). The observation mid time was 2025 Jan 6.982 UT (10.13 hr after the SVOM trigger), and the exposure time was 2000 s. No source is detected within the localization circle of XRT source #1, down to a limiting magnitude z > 23.3 (AB). Two sources are detected within the localization circle of XRT source #2. Source A (coincident with the SVOM/VT optical candidate): RA = 07:49:29.04 Dec = +63:42:29.4 mag z = 22.23 +- 0.10 AB Source B: RA = 07:49:27.99 Dec = +63:42:31.5 mag z = 19.90 +- 0.02 AB At the locations of both sources, objects are visible in the Legacy Survey, for which we measure AB magnitudes z = 22.24 +- 0.11 and z = 19.84 +- 0.02 for sources A and B, respectively. Our measured values are thus fully consistent with those in the archival images. Source B is also detected by Gaia, which provides a QSO classification. This opens the question whether object B could be responsible for the X-ray emission detected by Swift/XRT. Source A could be the host galaxy of GRB 250106A, though we note that its archival r-band magnitude (r = 23) is only marginally fainter than the SVOM/VT magnitude (R = 22.5 +- 0.3 mag; Qiu et al., GCN 38829). We encourage further observations with both SVOM/VT and Swift/XRT in order to establish variability of both the optical and X-ray sources. View this GCN Circular online at https://gcn.nasa.gov/circulars/38834. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36838] LIGO/Virgo/KAGRA S250104v: Updated Sky localization
by GCN Circulars 06 Jan '25

06 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38833 SUBJECT: LIGO/Virgo/KAGRA S250104v: Updated Sky localization DATE: 25/01/06 21:54:46 GMT FROM: Sylvia Biscoveanu at Northwestern CIERA <sylvia.biscoveanu(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S250104v (GCN Circular 38812). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250104v For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 1514 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 4932 +/- 1471 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. (2023) arXiv:2307.13380 View this GCN Circular online at https://gcn.nasa.gov/circulars/38833. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36837] GRB 250103B: REM optical/NIR upper limits
by GCN Circulars 06 Jan '25

06 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38832 SUBJECT: GRB 250103B: REM optical/NIR upper limits DATE: 25/01/06 15:59:56 GMT FROM: Matteo Ferro at INAF-OAB <matteo.ferro(a)inaf.it> M. Ferro, R. Brivio, P. D’Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of GRB 250103B detected by Swift (Eyles-Ferris et al., GCN 38796), also detected by SVOM (Bouchet et al., GCN 38797) 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 January 04 at 00:47:49 UT (i.e. 9.1 hours after the Swift trigger), and lasting for about 1 hour. From preliminary photometry we do not detect any optical or NIR counterpart at the optical afterglow position (Qiu et al., GCN 38813; Habeeb et al., GCN 38820; Turpin et al., GCN 38822) down to the following 3sigma magnitude upper limits: r > 20.4 (AB; calibrated against the SkyMapper catalogue) at a mid-time of t - t0 = 9.5 hr after the trigger, H > 17.3 (Vega; calibrated against the 2MASS catalogue) at a mid-time of t - t0 = 9.4 hr after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/38832. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36836] GRB 250101A: REM optical/NIR counterpart detection
by GCN Circulars 06 Jan '25

06 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38831 SUBJECT: GRB 250101A: REM optical/NIR counterpart detection DATE: 25/01/06 15:58:24 GMT FROM: Matteo Ferro at INAF-OAB <matteo.ferro(a)inaf.it> M. Ferro, R.Brivio, P. D’Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of GRB 250101A, detected by Swift (Page et al., GCN 38752) 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 January 02 at 00:47:33 UT (i.e. 11.4 hours after the Swift trigger), and lasting for about 1 hour. From preliminary photometry we detect the counterpart in the optical and NIR images at the position of the optical afterglow (e.g., Page et al., GCN 38752; Li et al., GCN 38753; Mohan et al., GCN 38754; Zhu et al., GCN 38755; Wu et al., GCN 38758), in agreement with the rebrightening reported by Moskvitin et al., GCN 38765, with the following magnitudes: r = 19.3 +- 0.1 (AB; calibrated against the PanSTARRS catalogue) at a mid-time of t - t0 = 11.9 hr after the trigger, H = 17.2 +- 0.2 (Vega; calibrated against the 2MASS catalogue) at a mid-time of t - t0 = 11.9 hr after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/38831. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 36835] GRB 250106A: Swift-XRT observations
by GCN Circulars 06 Jan '25

06 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38830 SUBJECT: GRB 250106A: Swift-XRT observations DATE: 25/01/06 14:45:52 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne (U. Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , M. A. Williams (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected burst GRB 250106A (Zhao et al., GCN Circ. 38826), collecting 2.9 ks of Photon Counting (PC) mode data between T0+19.9 ks and T0+27.1 ks. Four uncatalogued X-ray sources have been detected, however none of them is above the RASS limit or shows definitive signs of fading. However, Source 2 was reported by Qiu et al. (GCN Circ. 38829) to be consistent with the position of a SVOM/VT optical candiate. Details of the Swift-XRT sources are given below: Source 1: RA (J2000.0): 117.2387 = 07:48:57.28 Dec (J2000.0): +63.8123 = +63:48:44.3 Error: 3.0 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: 0.0209 +/- 0.0032 ct s^-1 Distance: 205 arcsec from SVOM/ECLAIRs position. Flux: (5.99 +/- 0.91)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 2: RA (J2000.0): 117.3686 = 07:49:28.47 Dec (J2000.0): +63.7079 = +63:42:28.6 Error: 5.9 arcsec (radius, 90% conf.) Count-rate: (5.7 [+2.1, -1.7])e-3 ct s^-1 Distance: 411 arcsec from SVOM/ECLAIRs position. Flux: (4.1 [+1.5, -1.2])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 3: RA (J2000.0): 116.9049 = 07:47:37.18 Dec (J2000.0): +63.9115 = +63:54:41.5 Error: 6.5 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: (4.5 [+1.9, -1.5])e-3 ct s^-1 Distance: 642 arcsec from SVOM/ECLAIRs position. Flux: (3.1 [+1.3, -1.0])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 4: RA (J2000.0): 117.2096 = 07:48:50.31 Dec (J2000.0): +63.8218 = +63:49:18.4 Error: 7.1 arcsec (radius, 90% conf.) Count-rate: (2.4 [+1.4, -1.0])e-3 ct s^-1 Distance: 207 arcsec from SVOM/ECLAIRs position. Flux: (7.3 [+4.2, -3.1])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV) The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00021753. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/38830. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0