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

[vsnet-grb-info 37047] GRB 250126A: MAXI/GSC detection
by GCN Circulars 26 Jan '25

26 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39038 SUBJECT: GRB 250126A: MAXI/GSC detection DATE: 25/01/26 12:11:19 GMT FROM: Hitoshi Negoro at Nihon University/MAXI team <negoro.hitoshi(a)nihon-u.ac.jp> Y. Okada (Kyoto U.), H. Negoro (Nihon U.), Y. Kawakubo (AGU), M. Nakajima, Y. Kudo, H. Shibui, K. Takagi, H. Takahashi, K. Tatano, H. Nishio (Nihon U.), T. Mihara, S. Yamada, S. Wang, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, H. Hiramatsu, H. Nishikawa, Y. Kondo, S. Sasao, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima (Chuo U.), M. Shidatsu, Y. Niida (Ehime U.), I. Takahashi, M. Niwano, N. Higuchi, Y. Yatsu (Tokyo Tech), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara (Kyoto U.), M. Yamauchi, Y. Otsuki, T. Hasegawa, M. Nishio (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.), report on behalf of the MAXI team: The MAXI/GSC nova alert system triggered on a bright uncatalogued X-ray transient source, probably GRB 250126A (GCN Circ. 39035, 39036), at 05:01:45 UT on January 26, 2025. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (337.621 deg, -14.383 deg) = (22 30 29, -14 22 58) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.32 deg and 0.23 deg, respectively. The roll angle of the long axis from the north direction is 50.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 148 +- 29 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (R.A., Dec) = (337.049, -14.721) deg = (22 28 11, -14 43 15) (J2000) (R.A., Dec) = (337.415, -14.977) deg = (22 29 39, -14 58 37) (J2000) (R.A., Dec) = (338.598, -13.378) deg = (22 34 23, -13 22 40) (J2000) (R.A., Dec) = (338.233, -13.124) deg = (22 32 55, -13 07 26) (J2000) There was no significant excess flux in the previous transit at 03:29 UT and in the next transit at 06:34 UT with an upper limit of 20 mCrab for each. View this GCN Circular online at https://gcn.nasa.gov/circulars/39038. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37046] EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
by GCN Circulars 26 Jan '25

26 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39037 SUBJECT: EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection DATE: 25/01/26 08:05:59 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.-Z. Li, J. Mao (YNAO, CAS), H. Sun, Y. Liu (NAO, CAS) and B. Zhang (UNLV) report on behalf of the Einstein Probe team: We re-analysed the WXT spectrum extracted from T0 to T0 + 2200 seconds (Li et al., GCN 38861). The average 0.5-4 keV WXT spectrum can be fitted by an absorbed power law model with a photon index of 3.03 (-1.52, +2.23) (with a fixed Galactic equivalent hydrogen column density of 1.6 x 10^20 cm^-2). The derived upper limit of the intrinsic column density is nH < 1.18 x 10^22 cm^-2 when the redshift is fixed at 0.176 (Zhu et al., GCN 38908). The derived average unabsorbed 0.5-4 keV flux is 6.38 (-3.00, +22.52) x 10^-11 erg/s/cm^2. Note that the presence of large uncertainties in the spectral parameters. Due to a mistake in spectrum extraction, an incorrect photon index of ~ 1.4 was reported in our preliminary GCN circular (Li et al., GCN 38861). We apologize for any confusion this may have caused. View this GCN Circular online at https://gcn.nasa.gov/circulars/39037. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37045] GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
by GCN Circulars 26 Jan '25

26 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39036 SUBJECT: GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208) DATE: 25/01/26 08:00:56 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 759560335 at 04:58:50 on 26 Jan. 2025 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 334.6 deg Decl.(2000.0) = -15.8 deg The 1 sigma statistical error radius is 2.0 deg. We estimate an additional systematic error of 1 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB250126208/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB250126208/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB250126208/json View this GCN Circular online at https://gcn.nasa.gov/circulars/39036. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37044] GRB 250126A: Fermi GBM Final Real-time Localization
by GCN Circulars 26 Jan '25

26 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39035 SUBJECT: GRB 250126A: Fermi GBM Final Real-time Localization DATE: 25/01/26 05:09:08 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 04:58:50 UT on 26 Jan 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250126A (trigger 759560335.992228 / 250126208). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 337.4, Dec = -11.6 (J2000 degrees, equivalent to J2000 22h 29m, -11d 35'), with a statistical uncertainty of 2.2 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/bn250126208/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250126208/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250126208/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39035. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37043] GECAM-A detection of a bright burst from SGR 1E1841-045
by GCN Circulars 26 Jan '25

26 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39034 SUBJECT: GECAM-A detection of a bright burst from SGR 1E1841-045 DATE: 25/01/26 02:47:44 GMT FROM: zhangjinpeng(a)ihep.ac.cn Jin-Peng Zhang (IHEP), Shao-Lin Xiong (IHEP), Peng Zhang (IHEP), Yan-Qiu Zhang (IHEP), Chao Zheng (IHEP), Chen-Wei Wang (IHEP) report on behalf of the GECAM team: GECAM-A detected a bright burst from SGR 1E1841-045 at 2025-01-23T08:47:19.600 UTC (denoted as T0), which was also detected by Konus-Wind (GCN 39024), Fermi/GBM (GBM trigger 759314844), and SVOM/GRM. The location is consistent with SGR 1E1841-045 by IPN triangulation (GCN 39022). According to the GECAM-A light curves in about 15-70 keV, this burst mainly consists of a single pulse with a duration of about 0.2 s. The GECAM light curve could be found here: https://www.bursthub.cn//admin/static/gasgr_250123_084719.png Please note that all GECAM results here are preliminary. The refined analysis will be reported later. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time), which was funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/39034. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37042] GRB 250118A: Fermi GBM Observation
by GCN Circulars 25 Jan '25

25 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39033 SUBJECT: GRB 250118A: Fermi GBM Observation DATE: 25/01/25 20:29:13 GMT FROM: Peter Veres at University of Alabama in Huntsville <veresp(a)gmail.com> P. Veres (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 18:31:11.97 UT on 18 January 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250118A (trigger 758917876/250118772). which was also detected by Swift-BAT/GUANO (Ronchini et al. 2025, GCN 39004). The Fermi GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 14 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 0.3 s (50-300 keV). The time-averaged spectrum from T0-0.13 to T0+0.06 s is best fit by a simple power law function with index -1.18 +/- 0.06. The event fluence (10-1000 keV) in this time interval is (4.1 +/- 0.4)E-07 erg/cm^2. The 64-ms peak photon flux measured starting from T0-0.064 s in the 10-1000 keV band is 7.4 +/- 0.9 ph/s/cm^2. A power law function with an exponential high-energy cutoff gives an acceptable fit to the spectrum. The power law index is -0.73 +/- 0.22 and the cutoff energy, parameterized as Epeak, is 1100 +/- 500 keV. 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/39033. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37041] EP250125a: Optical upper limit with Kinder observations
by GCN Circulars 25 Jan '25

25 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39032 SUBJECT: EP250125a: Optical upper limit with Kinder observations DATE: 25/01/25 18:40:30 GMT FROM: Janet Chen at National Central University <janetstars(a)gmail.com> A. Aryan, T.-W. Chen, Y.-H. Lee, W.-J. Hou, C.-S. Lin (all NCU), A. K. H. Kong (NTHU), S. J. Smartt (Oxford/QUB), J. Gillanders (Oxford), A. Sankar.K, Y. J. Yang, M.-H. Lee, H.-Y. Miao, Y.-C. Pan, C.-C. Ngeow, C.-H. Lai, H.-Y. Hsiao, H.-C. Lin, J.-K. Guo (all NCU), S. Yang, Z. N. Wang, L. L. Fan, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the fast X-ray transient EP250125a (Wu et al., GCN 39028) using the 1m LOT at the Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al., 2024 arXiv:2406.09270). The first LOT epoch of observations started at 16:39 UTC on 25th Januaryr 2025 (MJD 60700.694), 14.04 hr after the EP-WXT trigger. We utilized the astroalign (Beroiz et al., 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al., 2022, ApJ, 935, 167) packages to align and stack the individual frames. In the stacked frame, we did not detect the optical counterpart candidate suggested by Levan et al., (GCN 39027) and Ferro et al., (GCN39031). Considering the decay rate by two above-mentioned optical detections, probably, the optical counterpart candidate faded beyond the detection limit in our observations. We utilized the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform PSF photometry on our stacked frame. The details of the observations and measured 3-sigma upper limit (in the AB system) are as follows: ---------------------------------------------------------------------------------------------------Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass LOT | r | 60700.694 | 14.04 | 300 * 6 | >22.5 | 1".47 | 1.83 The presented magnitudes were calibrated using the field stars from the Pan-STARRS1 catalog (Chambers et al., 2016 arXiv:1612.05560) and were not corrected for the expected Galactic foreground extinction corresponding to a reddening of A_r = 0.112 mag in the direction of the transient (Schlafly & Finkbeiner 2011). View this GCN Circular online at https://gcn.nasa.gov/circulars/39032. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37040] EP250125a: REM optical counterpart detection
by GCN Circulars 25 Jan '25

25 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39031 SUBJECT: EP250125a: REM optical counterpart detection DATE: 25/01/25 16:51:30 GMT FROM: Matteo Ferro at INAF-OAB <matteo.ferro(a)inaf.it> M. Ferro, P. D’Avanzo, R. Brivio, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of the X-ray transient EP250125a, detected by Einstein Probe (Wu et al., GCN 39028) and Swift/XRT (Kennea et al., GCN 39029) 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 25 at 02:44:32 UT (i.e. 493 seconds after the EP trigger), and lasting for about 3 hours. From preliminary photometry we detect the counterpart in the optical images at the position reported by Levan et al. (GCN 39027), with the following magnitudes: r = 19.3 +- 0.3 (AB; calibrated against the Pan-STARRS catalogue) at a mid-time of t - t0 = 765 s after the trigger, H > 15.8 (Vega; calibrated against the 2MASS catalogue) at a mid-time of t - t0 = 641 s after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/39031. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37039] GRB 250119C: Fermi GBM Observation
by GCN Circulars 25 Jan '25

25 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39030 SUBJECT: GRB 250119C: Fermi GBM Observation DATE: 25/01/25 14:45:44 GMT FROM: Jacob Smith at Fermi-GBM Team <jrs0118(a)uah.edu> Jacob Smith (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: At 22:41:06.30 UT on 19 January 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250119C (trigger 759019271/250119945). which was also detected by Swift/BAT-GUANO (Ronchini, S. et al. 2025, GCN 39008). The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position. The angle from the Fermi LAT boresight is 66 degrees. The GBM light curve consists of a single short emission episode with a duration (T90) of about 1 s (50-300 keV). The time-averaged spectrum from T0-0.2 to T0+0.2 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.63 +/- 0.2 and the cutoff energy, parameterized as Epeak, is 1120 +/- 420 keV. The event fluence (10-1000 keV) in this time interval is (5.4 +/- 0.4)E-07 erg/cm^2. The 64-ms peak photon flux measured starting from T0-0.064 s in the 10-1000 keV band is 4.9 +/- 0.7 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/39030. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37038] EP250125a: Swift/XRT detection of a fading counterpart
by GCN Circulars 25 Jan '25

25 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39029 SUBJECT: EP250125a: Swift/XRT detection of a fading counterpart DATE: 25/01/25 14:04:22 GMT FROM: Jamie Kennea at Penn State <jak51(a)psu.edu> J. A. Kennea (PSU), K. L. Page, P. A. Evans (Leicester) and B. Sbarufatti (INAF) report on behalf of the Swift XRT Team. At 03:26UT Swift performed a series of Target-of-Opportunity observations of the Einstein Probe transient EP250125a (GCN #39028), approximately 49 minutes after the EP trigger. In the XRT data we detect a bright X-ray source at the following coordinates: RA/Dec(J2000) = 175.36337, -21.71347 RA (J2000): 11h 41m 27.21s, Dec (J2000): -21d 42' 48.5", with an estimated error radius of 3.8 arc-seconds (90% confidence). This lies 2.1 arc-seconds from the reported EP FXT position of the transient, and 3.9 arc-seconds from the proposed optical afterglow of the source (GCN #39029). We note that the source is fading with a 3-sigma significance. The peak flux seen by XRT is 4.3 (±1.0) ×10^-12 erg cm^-1 s^-1 (0.3-10 keV), dropping to a flux of 4.8 (±1.1) x 10^-13 erg cm^-1 s^-1 (0.3-10 keV) at a second observation taken at T0+8.9 hours. View this GCN Circular online at https://gcn.nasa.gov/circulars/39029. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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