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

[vsnet-grb-info 36787] EP250101a: Xinglong optical upper limit
by GCN Circulars 02 Jan '25

02 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38785 SUBJECT: EP250101a: Xinglong optical upper limit DATE: 25/01/03 03:28:53 GMT FROM: Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong(a)nao.cas.cn> Yu-Zhang(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: Following the detection of EP250101a by EP-WXT (Y. F. Liang et al., GCN 38778), we observed the field of EP250101a using the 80cm telescope at Xinglong Observatory, NAOC. We obtained 11x400s clear-band frames with a median time of 2025-01-03T01:08:55 i.e., 43 hr after the EP trigger. No uncatalogued optical transient is detected in the stacked images within the 3.2 arcmin EP/WXT error circle (Y. F. Liang et al., GCN 38778), down to 5-sigma limiting magnitudes of clear ~ 20.1, calibrated with Pan-STARRS sources in the field. Also, there is no apparent brightening for the catalogued sources within the error circle. View this GCN Circular online at https://gcn.nasa.gov/circulars/38785. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 36786] GRB 250102A: Fermi GBM Final Real-time Localization
by GCN Circulars 02 Jan '25

02 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38784 SUBJECT: GRB 250102A: Fermi GBM Final Real-time Localization DATE: 25/01/02 22:48:43 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 22:38:05 UT on 2 Jan 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250102A (trigger 757550290.223546 / 250102943). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 340.8, Dec = 42.3 (J2000 degrees, equivalent to J2000 22h 43m, 42d 17'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 2.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250102943/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250102943/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250102943/… View this GCN Circular online at https://gcn.nasa.gov/circulars/38784. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 36785] LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
by GCN Circulars 02 Jan '25

02 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38783 SUBJECT: LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO DATE: 25/01/02 22:22:30 GMT FROM: Maia Williams at PSU <mjw6837(a)psu.edu> Maia Williams (PSU), Samuele Ronchini (PSU), Gayathri Raman (PSU), James DeLaunay (PSU), Tyler Parsotan (NASA GSFC), Jamie A. Kennea (PSU), Aaron Tohuvavohu (Caltech) report: Swift/BAT was observing 75.9% of the GW localization probability ([Bilby.multiorder.fits](https://gracedb.ligo.org/api/superevents/S241230bd/f…) at merger time. A fraction 32.05% of the GW localization posterior is contained inside the BAT coded FoV. The LVK 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](https://iopscience.iop.org/article/10.3847/1538-4357/aba94f)) 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. Using the NITRATES analysis ([DeLaunay + Tohuvavohu 2022, ApJ, 941, 169](https://iopscience.iop.org/article/10.3847/1538-4357/ac9d38)) we searched for emission on 8 timescales from 0.128s to 16.384s in the interval [-20,+20] seconds around the merger time. We find no evidence for a signal, and derive the following upper limits. We quote the 5-sigma flux upper limits in the 15-350 keV band, weighted over the GW localization, for four spectral templates (soft, normal, and hard GRB-like templates described in [arXiv:1612.02395], and spectral shape from GRB170817A [arXiv:1710.05446]) and for four time bins. In units of 10^-7 erg/s/cm^2: |time_bin (s) |soft |normal|hard |GRB170817 |-|-|-|-|-| |0.256 |10.80 |7.25 |6.44 |8.08 |1.024 |5.50 |3.69 |3.28 |4.11 |4.096 |2.96 |1.99 |1.77 |2.21 |16.384 |1.84 |1.24 |1.10 |1.38 The upper limits as function of sky position are plotted here, alongside the GW localization: https://zenodo.org/records/14589498 The solid and dashed lines indicate the 90% and 50% GW contour levels, respectively. The corresponding fits file is also included. 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/38783. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 36784] GRB 250101A: Swift-BAT refined analysis
by GCN Circulars 02 Jan '25

02 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38782 SUBJECT: GRB 250101A: Swift-BAT refined analysis DATE: 25/01/02 21:38:42 GMT FROM: Amy <yarleen(a)gmail.com> H. A. Krimm (NSF), S. D. Barthelmy (GSFC), R. Gupta (GSFC), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), K. L. Page (U Leicester), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+800 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250101A (trigger #1278305) (Page et al., GCN Circ. 38752). The BAT ground-calculated position is RA, Dec = 37.057, 19.181 deg which is RA(J2000) = 02h 28m 13.7s Dec(J2000) = +19d 10' 50.5" with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 47%. The mask-weighted light curve shows a weak pulse that starts at ~T0, peaks at ~T+1 s, and ends at ~T+35 s. T90 (15-350 keV) is 34.19 +- 7.71 sec (estimated error including systematics). The time-averaged spectrum from T-0.22 to T+36.50 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.12 +- 0.24. The fluence in the 15-150 keV band is 6.3 +- 1.0 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+0.95 sec in the 15-150 keV band is 0.8 +- 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/1278305/ View this GCN Circular online at https://gcn.nasa.gov/circulars/38782. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 36783] IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 02 Jan '25

02 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38781 SUBJECT: IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/01/02 19:41:35 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 2025-01-02 13:48:01.92 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_Bronze alert stream. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 4.2015 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/140314_61338661.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 2025-01-02 Time: 13:48:01.92 UT RA: 262.79 (+1.32, -1.09 deg 90% PSF containment) J2000 Dec: 6.69 (+0.97, -0.84 deg 90% PSF containment) J2000 We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. There are two Fermi 4FGL-DR4 or 3FHL catalog source in the 90% uncertainty region: 4FGL J1731.6+0630 at RA: 262.92 deg, Dec: 6.50 deg J2000 (0.23 deg away from the best-fit event position), and 4FGL J1727.2+0644 at RA: 261.81 deg, Dec: 6.74 deg J2000 (0.97 deg away from the best-fit event position). The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/38781. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 36782] GRB 250101A: further SAO RAS optical observations
by GCN Circulars 02 Jan '25

02 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38780 SUBJECT: GRB 250101A: further SAO RAS optical observations DATE: 25/01/02 18:41:47 GMT FROM: Moskvitin Alexander at SAO RAS <mosk(a)sao.ru> A. S. Moskvitin and O. I. Spiridonova, Yu. V. Sotnikova (SAO RAS), A. Ghosh, S. Razzaque (CAPP, University of Johannesburg) and A. S. Pozanenko (IKI RAS) report on behalf of the GRB follow-up team. We observed the field of Swift GRB 250101A (Page et al., GCN 38752) with the 1-m telescope of SAO RAS, Zeiss-1000 + CCD-photometer on January 2, 15:20:13--18:06:55 UT (t_mid - T0 = 1.1394 days). We obtained 19 x 300 sec. images in Rc band. The OT (Page et al., GCN 38752; Li et al., GCN 38753, GCN 38776; Mohan et al., GCN 38754; Zhu et al., GCN 38755, GCN 38759; Budnev et al., GCN 38756; Wu et al., GCN 38758; Moskvitin et al., GCN 38762, GCN 38765; Odeh and Guessoum, GCN 38763; Hu et al., GCN 38764; D'Avino and Izzo, GCN 38768; Escudero-Coca et al., GCN 38769; Leonini et al., GCN 38771; Zhang et al., GCN 38774; Siegel and Page, GCN 38775; Komesh et al., GCN 38777; Ghosh et al., GCN 38779) is clearly detected in our stacked image with the brightness of R = 21.86 +/- 0.06, calibrated against nearby PS1 stars (magnitudes were converted with the Lupton 2005 equations) and not corrected for the MW extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/38780. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 36781] GRB 250101A: LCO optical counterpart detection
by GCN Circulars 02 Jan '25

02 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38779 SUBJECT: GRB 250101A: LCO optical counterpart detection DATE: 25/01/02 16:56:31 GMT FROM: ankur ghosh at CAPP, University of Johannesburg <ghosh.ankur1994(a)gmail.com> Ankur Ghosh, Soebur Razzaque (CAPP, University of Johannesburg), Rahul Gupta (NASA GSFC), Alexander Moskvitin, Yulia Sotnikova (SAO RAS), Naveen Dukiya (ARIES) on behalf of a larger collaboration. We observed the field of the GRB 250101A triggered by Swift (Page et. al., GCN 38752) in B, V filter of the 1-meter Sinistro telescope at the Las Cumbres Observatory Global Telescope (LCOGT) node located at McDonald Observatory. The 1-m Sinistro telescope is equipped with a 4K x 4K CCD (FOV: 26 x 26 arcmin, scale: 0.39 arcsec/pixel). Observations began on January 02, 2025, starting from 14.48 hours after the GRB trigger. We clearly detect the optical transient (OT) reported by GCNs (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; Moskvitin et al., GCN 38762; Odeh et al., GCN 38763, Hu et al., GCN 38764; D'Avino et al., GCN 38768; Escudero-Coca et al., GCN 38769, Coca et al., Zhang wt al., GCN 38774, Komesh et al., GCN 38777) in our B, V band image. |Date| |UTstart| |t-T0 (hours)| |Exp (sec)| |Filter| |Magnitude| --------------------------------------------------------------------------------------------------- 2025-01-02 03:51:30.528 14.48 1 x 900 V V = 20.61 +/- 0.04 2025-01-02 06:19:33.312 16.95 2 x 1200 B B = 21.82 +/- 0.03 The field was calibrated against nearby APASS stars, with magnitudes converted using Lupton (2005) equations, and has not been corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/38779. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 36780] EP241231b and EP250101a: EP-WXT detection of two X-ray transients
by GCN Circulars 02 Jan '25

02 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38778 SUBJECT: EP241231b and EP250101a: EP-WXT detection of two X-ray transients DATE: 25/01/02 14:53:21 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. F. Liang (PMO, CAS), A. Li (BNU), H. L. Peng (NNU), W. F. Wen(SATU), W. D. Zhang (NAOC, CAS) on behalf of the Einstein Probe team: We report on the detection of two X-ray transients designated EP241231b and EP250101a, respectively, by the Einstein Probe (EP) mission. EP241231b was detected by EP-WXT at 2024-12-31T19:27:29 (UTC). The WXT position is R.A.= 100.064 deg, DEC= 16.171 deg (J2000) with an uncertainty of about 2.6 arcmin (radius, 90% C.L. statistical and systematic), corresponding to Galactic l, b = 197.255 deg, 4.893 deg. The absorbed average flux in 0.5-4 keV is 1.5(+1.1/-0.5) x 10^(-10) erg/s/cm^2 with column density fixed at the Galactic value 4.1 x 10^21 cm^-2 and a photon index of 2.1(+1.1/-0.9). EP250101a was detected by EP-WXT at 2025-01-01T05:52:21 (UTC). The WXT position is R.A.=85.575 deg, DEC=0.352 deg (J2000) with an uncertainty of about 3.2 arcmin (radius, 90% C.L. statistical and systematic), corresponding to Galactic l, b = 204.535 deg, -15.167 deg. A flare with a duration of around 2,500 seconds is visible in the WXT lightcurve. The peak flux of the X-ray is ~ 1.7 x 10^(-10) erg/s/cm^2 in the 0.5-4 keV band. The average 0.5-4 keV spectrum can be fitted with an absorbed power law with a photon index of 1.5(+1.6/-1.1) (with column density fixed at the Galactic value 3.3 x 10^21 cm^-2). The derived average unabsorbed 0.5-4 keV flux is 4.4(+2.3/-1.7) x 10^(-11) erg/s/cm^2. The quoted uncertainties are at the 90% confidence level for the above parameters. No previously known bright X-ray sources are found within the error circle around the source positions of either EP241231b or EP250101a. Following the WXT detections, we performed two follow-up observations, one for each transient, with the Follow-up X-ray Telescope (FXT) on board EP. Further follow-up observations are encouraged to identify the nature of these X-ray transients. 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/38778. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 36779] GRB 250101A NUTTelA-TAO / BSTI Early Measurements
by GCN Circulars 02 Jan '25

02 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38777 SUBJECT: GRB 250101A NUTTelA-TAO / BSTI Early Measurements DATE: 25/01/02 12:04:47 GMT FROM: Toktarkhan Komesh at Nazarbayev University <toktarkhan.komesh(a)nu.edu.kz> T. Komesh (NU), Z. Abdullayev (NU), Z. Maksut (NU), B. Grossan (UCB, NU), D. Berdikhan (NU), M. Krugov (FAI) and E. Abdikamalov (NU) report on behalf of the Energetic Cosmos Laboratory: The Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) pointed at GRB 250101A on receipt of an automated GCN / BAT position alert, observing in Sloan g' and r' bands, with the Burst Simultaneous Three-Channel Imager (BSTI; Grossan, Kumar & Smoot 2019, JHEA, 32, 14). We started observations at 13:24:00 UT on 2025-01-01, 70 s after the BAT trigger. Observations were made in partly cloudy conditions. A new and changing source consistent with the XRT position (M.R. Goad et al., GCN 38761) was detected. Note that these observations provide essentially full-time coverage, simultaneous in two bands. We report the following photometric values for the optical transient: tc-t0(s) g'(mag) err r'(mag) err exposure_time (s) -------------------------------------------------------------- 100.1 18.7 0.1 18.2 0.1 57 166.0 17.6 0.1 17.2 0.1 15 181.0 17.5 0.1 17.0 0.1 15 196.0 17.1 0.1 16.9 0.1 15 211.0 17.3 0.1 16.9 0.1 15 226.0 17.4 0.1 16.8 0.1 15 241.0 17.3 0.1 16.7 0.1 15 256.0 17.3 0.1 16.8 0.1 15 271.0 17.4 0.1 16.9 0.1 15 286.0 17.4 0.1 16.9 0.1 15 301.0 17.5 0.2 17.0 0.1 15 316.0 17.7 0.2 17.0 0.1 15 331.0 17.5 0.1 17.0 0.1 15 346.0 17.7 0.1 17.1 0.1 15 361.0 17.6 0.1 17.1 0.1 15 376.0 17.6 0.1 17.0 0.1 15 391.0 18.0 0.1 16.9 0.1 15 406.0 17.6 0.2 17.4 0.1 15 421.0 17.8 0.1 17.2 0.1 15 436.0 17.5 0.1 17.4 0.1 15 451.0 18.1 0.2 17.4 0.1 15 466.0 17.8 0.2 17.3 0.1 15 481.0 17.8 0.1 17.3 0.1 15 496.0 17.7 0.2 17.4 0.1 15 511.0 17.9 0.1 17.4 0.1 15 526.0 17.7 0.1 17.5 0.1 15 541.0 18.3 0.2 17.5 0.1 15 556.0 17.9 0.2 17.3 0.1 15 571.0 18.0 0.1 17.3 0.1 15 586.0 17.7 0.2 17.4 0.1 15 601.0 18.2 0.2 17.8 0.1 15 616.0 17.9 0.1 17.7 0.2 15 631.0 17.9 0.1 17.2 0.1 15 653.5 18.1 0.1 17.6 0.1 30 683.5 18.1 0.1 17.5 0.1 30 713.5 18.1 0.1 17.5 0.1 30 743.5 18.0 0.1 17.5 0.1 30 864.3 18.2 0.0 17.5 0.0 60 924.3 18.2 0.1 17.7 0.1 60 984.3 18.2 0.1 17.7 0.0 60 1044.3 18.3 0.1 17.8 0.0 60 1104.3 18.4 0.1 17.8 0.1 60 1164.3 18.3 0.1 17.8 0.0 60 1224.3 18.5 0.1 17.8 0.0 60 1284.3 18.5 0.1 17.9 0.1 60 1344.3 18.6 0.1 17.8 0.1 60 1404.3 18.4 0.1 18.0 0.1 60 1464.3 18.4 0.1 18.1 0.1 60 1524.3 18.6 0.1 18.1 0.1 60 1584.3 18.7 0.1 18.2 0.1 60 1644.3 18.7 0.1 18.3 0.1 60 1704.3 18.7 0.1 18.2 0.1 60 1764.3 18.7 0.1 18.2 0.1 60 1824.3 18.8 0.1 18.4 0.1 60 1884.3 18.8 0.1 18.4 0.1 60 1944.3 19.0 0.1 18.3 0.1 60 2004.3 18.8 0.1 18.4 0.1 60 2064.3 18.9 0.1 18.3 0.1 60 2124.3 18.8 0.1 18.3 0.1 60 2184.3 19.0 0.1 18.5 0.1 60 2244.3 19.0 0.1 18.5 0.1 60 2304.3 18.9 0.1 18.5 0.1 60 2364.3 19.2 0.1 18.4 0.1 60 2424.3 19.0 0.1 18.4 0.1 60 2484.3 19.0 0.1 18.6 0.1 60 2544.3 19.1 0.1 18.6 0.1 60 2604.3 19.0 0.1 18.8 0.1 60 2664.3 19.1 0.1 18.8 0.1 60 2724.3 18.9 0.1 18.8 0.1 60 2784.3 19.2 0.1 18.9 0.1 60 2844.3 19.2 0.1 18.8 0.1 60 2904.3 19.4 0.1 18.6 0.1 60 2964.3 19.2 0.1 18.9 0.1 60 3024.3 19.2 0.1 18.7 0.1 60 3084.3 19.2 0.1 18.7 0.1 60 3144.4 19.3 0.2 18.9 0.1 60 3204.4 19.2 0.1 19.1 0.2 60 3294.4 19.4 0.1 18.9 0.1 120 3414.4 19.4 0.1 18.7 0.1 120 3534.4 19.4 0.1 19.0 0.1 120 3654.4 19.4 0.2 19.0 0.1 120 3774.4 19.4 0.2 19.0 0.2 120 4166.8 19.7 0.1 18.9 0.1 360 4526.8 19.8 0.2 19.2 0.1 360 tc-t0 = trigger time minus image center time. Calibration was done with 5 bright Pan-STARRS catalog stars on our images. A light curve of the optical transient is presented in Figure 1: https://ecl.nu.edu.kz/research/observations/gamma-ray-bursts/grb250101a Our results are in agreement with those reported in previously published circulars (Li et al., GCN 38753; Mohan et al., GCN 38754; Wu et al., GCN 38758; Escudero-Coca et al., GCN 38769; Zhang et al., 38744). We caution the reader that these are preliminary results, without color or other corrections, and will likely change in small measure. Please also note that times are approximate. ---------------------------------- NU = Nazarbayev University, Astana, Kazakhstan UCB = University of California, Berkeley, USA FAI = Fesenkov Astrophysical Institute, Kazakhstan This research has been funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP26103591). The NUTTelA-TAO Team acknowledges the support of the staff of the Assy-Turgen Astrophysical Observatory, Almaty, Kazakhstan, and the Fesenkov Astrophysical Institute, Almaty, Kazkhstan. View this GCN Circular online at https://gcn.nasa.gov/circulars/38777. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 36778] GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
by GCN Circulars 02 Jan '25

02 Jan '25

TITLE: GCN CIRCULAR NUMBER: 38776 SUBJECT: GRB 250101A: GMG spectroscopic redshift at z ~ 2.481 DATE: 25/01/02 10:05:57 GMT FROM: Rui-Zhi Li at Yunnan Observatories, CAS <liruizhi(a)ynao.ac.cn> R.-Z. Li, B.-T. Wang, F.-F. Song, J. Mao, S.-S. Li, H. Lin and J.-M. Bai (YNAO, CAS) report: We observed the optical counterpart 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; Moskvitin and Spiridonova, GCN 38762; Odeh and Guessoum, GCN 38763; Hu et al., GCN 38764; Moskvitin et al., GCN 38765; D’Avino and Izzo, GCN 38768; Escudero-Coca et al., GCN 38769; Leonini et al., GCN 38771). The observation was conducted using the GMG-2.4m telescope with Grism #14, which provides a wavelength coverage of 3600–7460 AA. A single 1800s spectrum was obtained, with exposure beginning at 14:24:54.5 UT on 2025-01-01, about 1.03 hours after the Swift trigger. The Ly-alpha absorption feature at ~ 4250 AA is evident. Despite the low signal-to-noise ratio of the spectrum, we identified multiple metal absorption lines: Si II at 1303 AA, C II at 1335 AA, Si IV at 1394 AA, Si IV at 1403 AA, C IV at 1549 AA, Al II at 1671 AA, Al III at 1855 AA, and Al III at 1863 AA. These metal absorption features consistently indicate a redshift of z ~ 2.481, which is consistent with the Xinglong-2.16m result (Zhu et al., GCN 38759). We acknowledge the staff at the Lijiang Observatory for conducting the observation. View this GCN Circular online at https://gcn.nasa.gov/circulars/38776. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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