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

[vsnet-grb-info 37037] EP250125a: a new X-ray transient detected by Einstein Probe
by GCN Circulars 25 Jan '25

25 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39028 SUBJECT: EP250125a: a new X-ray transient detected by Einstein Probe DATE: 25/01/25 10:27:35 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Q.-Y. Wu (NAOC, CAS), J. Yang (NJU), X.-Y. Zhou (PRIC) and C.-C. Jin (NAOC, CAS) report on behalf of the Einstein Probe team: We report on the detection of an X-ray transient, designated EP250125a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, which triggered the on-board processing unit at 2025-01-25T02:37:31 (UTC) (trigger ID: 01709130802). The transient event started at 2025-01-25T02:36:19 (UTC) and lasted for 74 s before the observation was interrupted by the autonomous follow-up observation. The WXT position of the source is R.A. = 175.364 deg, DEC = -21.708 deg (J2000) with an uncertainty of 2.3 arcmin in radius (90% C.L. statistical and systematic). 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 4.15 x 10^20 cm^-2 and a photon index of 0.8 (-0.5/+0.5). The derived average unabsorbed 0.5-4 keV flux is 1.8 (-0.5/+0.7) 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 two minutes later. An uncatalogued source was detected at R.A. = 175.3639, DEC = -21.7138 (J2000) with an uncertainty of about 20 arcsec (radius, 90% C.L. statistical and systematic), which is consistent with the optical conterpart reported by Levan et al., GCN 39027. 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 4.15 x 10^20 cm^-2 and a photon index of 2.0 (-0.1/+0.1). The derived average unabsorbed 0.5-10 keV flux is 5.4 (-0.6/+0.6) 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/39028. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37036] EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
by GCN Circulars 25 Jan '25

25 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39027 SUBJECT: EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89 DATE: 25/01/25 09:26:10 GMT FROM: Andrew Levan at Radboud University <a.levan(a)astro.ru.nl> A. J. Levan (Radboud Univ. and Warwick Univ.), J. A. Quirola-Vasquez (Radboud Univ.), F. E. Bauer (PUC), D. B. Malesani (DAWN/NBI and Radboud Univ.), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud Univ.) report on behalf of a larger collaboration. We observed the field of the EP transient 01709130802 (EP250125a, trigger time: 2025-01-25 02:37:31.749 UT) using the Gemini South telescope equipped with the GMOS-S camera and spectrograph. A set of images in the r and z bands were secured, starting on 2025 25.294 UT (4.43 hr after the trigger). A point-like object not present in the archival Pan-STARRS images of the field is detected in both filters at coordinates (J2000), well within the 3 arcmin-radius WXT error circle: RA = 11:41:27.39 Dec = -21:42:51.5 For this object, we measure an AB magnitude r = 21.60 +- 0.03, calibrated against nearby objects from the Pan-STARRS catalog. We suggest this object is the optical counterpart of EP250125a. A spectrum of the source was taken with the B480 grism, starting at 08:39 UT. In the first 600 s exposure, the source is well detected across the spectral range from 4300 to 8200 AA (preliminary wavelength calibration). A strong absorption trough is visible at ~4730 AA, which we interpret as a DLA. From the detection of several narrow absorption features, including those from Si II, C II, Si IV, Al II, and Fe II we determine z = 2.89, which we suggest to be the redshift of EP250125a. We thank the Gemini staff, in particular Karleyne Silva, for masterfully executing the requested observations View this GCN Circular online at https://gcn.nasa.gov/circulars/39027. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37035] The EP-WXT trigger 01709130758 is a false trigger
by GCN Circulars 25 Jan '25

25 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39026 SUBJECT: The EP-WXT trigger 01709130758 is a false trigger DATE: 25/01/25 04:54:26 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Q.-Y. Wu (NAOC, CAS), J. Yang (NJU), X.-Y. Zhou (PRIC) and C.-C. Jin (NAOC, CAS) report on behalf of the Einstein Probe team: The EP-WXT trigger (ID 01709130758) on 2025-01-24T20:52:02.899 (UTC) is a false trigger, likely caused by the nearby known extended bright source 3C 84, and does not correspond to a real transient. 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/39026. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37034] The EP-WXT trigger 01709130758 is a false trigger
by GCN Circulars 25 Jan '25

25 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39025 SUBJECT: The EP-WXT trigger 01709130758 is a false trigger DATE: 25/01/25 04:50:44 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> The EP-WXT trigger (ID 01709130758) on 2025-01-24T20:52:02.899 (UTC) is a false trigger, likely caused by the nearby known extended bright source 3C 84, and does not correspond to a real transient. 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/39025. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37033] Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
by GCN Circulars 24 Jan '25

24 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39024 SUBJECT: Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23 DATE: 25/01/24 17:52:25 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A.Ridnaia, D. Frederiks, A.Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: A bright burst from SGR 1E1841-045 (IPN triangulation: Svinkin et al., GCN 39022) triggered Konus-Wind at T0=31634.552 s UT (08:47:14.552) on 2025 January 23. The burst light curve shows a bright pulse, which starts at ~T0-100 ms and has a total duration of ~172 ms. The emission is seen up to ~200 keV. The Konus-Wind light curve of this burst is available at http://www.ioffe.ru/LEA/SGRs/250123_T31634/ As observed by Konus-Wind, the burst had a fluence of 2.30(-0.07,+0.07)x10^-6 erg/cm2, and a 16-ms peak flux, measured from T0-0.054 s, of 2.02(-0.14,+0.14)x10^-5 erg/cm2/s (both in the 20 - 500 keV energy range). The spectrum of the burst (measured from T0-0.112 to T0+0.080 s) is best fit in the 20 - 500 keV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha ~ -0.46 and Ep ~ 30 keV. All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/39024. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37032] GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
by GCN Circulars 24 Jan '25

24 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39023 SUBJECT: GRB 250121A: Swift/BAT-GUANO localization skymap of a burst DATE: 25/01/24 17:29:42 GMT FROM: Samuele Ronchini at PSU <sjs8171(a)psu.edu> Samuele Ronchini (PSU), James DeLaunay (PSU), Aaron Tohuvavohu (Caltech), Gayathri Raman (PSU), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC) report: Swift/BAT did not localize GRB 250121A onboard (T0: 2025-01-21T23:36:05.78 UTC, Fermi GBM GCN 39006 and 39018, Fermi LAT GCN 39010, INTEGRAL GCN 39011, CALET GCN 39021) 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 38.1 in a 2.048 s analysis time bin, starting at T0 - 0.0001 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 153 deg2 and the 50% credible area is 46 deg2. The integrated probability inside the coded field of view is <1%. The NITRATES skymap is consistent with the Fermi-GBM and Fermi-LAT localizations. The joint NITRATES+GBM localization has a 90% credible area of 68 deg2 and a 50% credible area of 17 deg2 A plot of the probability skymap can be viewed here: [skymap_plot](https://guano.swift.psu.edu/trigger_report?id=759195400/#:~:te… The probability skymap file can be downloaded from the link here [skymap_fits_file](https://guano.swift.psu.edu/files/759195400/0_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=759195400 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/39023. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37031] IPN triangulation of a bright burst from SGR 1E1841-045
by GCN Circulars 24 Jan '25

24 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39022 SUBJECT: IPN triangulation of a bright burst from SGR 1E1841-045 DATE: 25/01/24 16:18:56 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, A. Ridnaia, D. Frederiks, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM team, Y. Zhang, C. Wang, S. Xiong, J. Wei, and B. Cordier on behalf of the SVOM-GRM team, report: A very bright, short-duration, soft burst was detected by Konus-Wind, Fermi (GBM trigger 759314844), and SVOM (GRM) at about 31640 s UT (08:47:20) on January 23. We have triangulated it to the following annuli: --------------------------------------------------- annulus R.A. Dec. R dR (3sigma) (deg) (deg) (deg) (deg) --------------------------------------------------- Konus-GBM 285.928 -20.729 16.594 0.148 Konus-GRM 285.926 -20.738 16.277 0.567 --------------------------------------------------- Among known SGRs, only the position of SGR 1E1841-045 is inside the annuli. Given the positional coincidence of this burst with SGR 1E1841-045, its time history, and softness of its spectrum (as observed by Konus-Wind), we conclude this burst is likely originated from SGR 1E1841-045. A triangulation map is posted at http://www.ioffe.ru/LEA/SGRs/250123_T31634/IPN/ The time history and spectrum will be given in forthcoming GCN circulars. View this GCN Circular online at https://gcn.nasa.gov/circulars/39022. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37030] GRB 250121A: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 24 Jan '25

24 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39021 SUBJECT: GRB 250121A: CALET Gamma-Ray Burst Monitor detection DATE: 25/01/24 14:43:22 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 long GRB 250121A (Fermi GBM Final Real-time Localization: Fermi GBM team, GCN Circ. 39006; Fermi-LAT detection: Holzmann Airasca et al., GCN Circ. 39010; INTEGRAL/SPI-ACS detection: Barria et al., GCN Circ. 39011; Fermi GBM Observation: Godwin et al., GCN Circ. 39018; ) was detected in the ground analysis of the CALET Gamma-ray Burst Monitor (CGBM) data around 23:36:05.78 on 21 January 2025 (referenced to the Fermi-GBM Observation: GCN Circ. 39018). (https://cgbm.calet.jp/cgbm_trigger/flight/1421537655/index.html) The burst signal was seen by only the SGM detector. The burst light curve shows a double-peaked structure that starts at T+0.1 sec, peaks at T+0.7 sec, and ends at T+5.4 sec. The T90 and T50 durations measured by the SGM data are 4.7 +/- 0.2 sec and 2.6 +/- 0.4 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1421537655/ 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/39021. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37029] EP250108a: AbAO, CMO and Terskol optical upper limits
by GCN Circulars 24 Jan '25

24 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39020 SUBJECT: EP250108a: AbAO, CMO and Terskol optical upper limits DATE: 25/01/24 06:26:37 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), A. Tarasenkov (INASAN), R. Ya. Inasaridze (AbAO), I. Sokolov (INASAN) report on behalf of the IKI-GRB-FuN collaboration: We performed optical observations of the field of EP250108a (Li et. al, GCN 38861; V.Lipunov et. al, GCN 38865; Eyles-Ferris, GCN 38878; Zhu et. al, GCN 38885; Li et. al, GCN 38888; et. al, GCN 38891; 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; Moskvitin et. al, GCN 38925; Zhu et. al, GCN 38937; Carotenuto et. al, GCN 38958; Schroeder et. al, GCN 38970; Song et. al, GCN 38972; Eyles-Ferris et. al, GCN 38983; Xu et. al, GCN 38984; Levan et. al, GCN 38987; An et. al, GCN 38998; Ror et. al, GCN 39002) in the R filter with AS-32 of the Abastumani Observatory (AbAO), Zeiss-2000 and RC-500 telescopes of the Terskol (INASAN) Observatory, and RC-500 telescope of the Caucasian Mountain Observatory (CMO). The observations started on 2025-01-11 at 15:03 UT, i.e. ~3.11 days since trigger. We do not detect the optical counterpart in the stacked images. The preliminary photometry is as follows: Date UT start t-T0 Exp. Filter UL(3sigma) Site (mid, days) (s) 2025-01-11 15:03:26 3.19199 247*60 R 19.6 CMO/RC-500 2025-01-11 16:06:14 3.17622 76*60 R 19.8 AbAO/AS-32 2025-01-11 16:25:13 3.19184 166*30 R 20.6 Terskol/Zeiss-2000 2025-01-20 15:16:48 12.27071 100*120 R 19.8 CMO/RC-500 2025-01-21 15:39:53 13.15306 31*120 R 18.2 Terskol/RC-500 The photometry has been calibrated using nearby stars from the USNO-B1.0 catalog (R2 magnitudes). No correction has been made for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39020. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37028] Konus-Wind detection of GRB 250118B
by GCN Circulars 23 Jan '25

23 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39019 SUBJECT: Konus-Wind detection of GRB 250118B DATE: 25/01/23 20:34:26 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 250118B (IPN triangulation: Kozyrev et al., GCN 39017) triggered Konus-Wind at T0=13107.725 s UT (03:38:27.725). The burst light curve shows a multipeaked structure, which starts at ~T0-5.8 s and has a total duration of ~9.4 s. We note a weaker and softer pulse seen in the same KW detector before the main pulse, from ~T0-58.8 s to ~T0-55.9 s. Since this pulse was detected by KW only, its relation to GRB 250118B cannot be currently confirmed. The emission is seen up to ~2 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250118_T13107/ As observed by Konus-Wind, the burst had a fluence of 3.49(-0.35,+1.30)x10^-6 erg/cm^2 and a 64-ms peak flux, measured from T0-0.244 s, of 2.97(-0.60,+1.22)x10^-6 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 spectral analysis was performed using the KW 3-channel light curve data. Modelling the KW 3-channel time-integrated spectrum (measured from T0-5.837 s to T0+3.552 s) by a power law with exponential cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep), yields alpha = -1.55(-0.14,+0.18) and Ep = 287(-95,+256) 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/39019. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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