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

[vsnet-grb-info 39080] LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
by GCN Circulars 08 Jul '25

08 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41029 SUBJECT: LIGO/Virgo/KAGRA S250701bp: Updated Sky localization DATE: 25/07/08 15:05:19 GMT FROM: lucy.thomas(a)ligo.org The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Livingston Observatory (L1) data around the time of the compact binary merger (CBC) candidate S250701bp (GCN Circular 40879). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN and SCiMMA notices, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250701bp For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 26503 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 939 +/- 300 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. PRD 108, 123040 (2023) doi:10.1103/PhysRevD.108.123040 View this GCN Circular online at https://gcn.nasa.gov/circulars/41029. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39079] GRB 250708A: Fermi GBM Final Real-time Localization
by GCN Circulars 08 Jul '25

08 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41028 SUBJECT: GRB 250708A: Fermi GBM Final Real-time Localization DATE: 25/07/08 15:02:38 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 14:52:02 UT on 8 Jul 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250708A (trigger 773679127.950166 / 250708619). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 255.1, Dec = 13.0 (J2000 degrees, equivalent to J2000 17h 00m, 13d 00'), with a statistical uncertainty of 5.0 degrees. The angle from the Fermi LAT boresight is 83.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250708619/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250708619/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250708619/… View this GCN Circular online at https://gcn.nasa.gov/circulars/41028. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39078] GRB 250706B/C: Konus-Wind analysis of the prompt emission
by GCN Circulars 08 Jul '25

08 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41027 SUBJECT: GRB 250706B/C: Konus-Wind analysis of the prompt emission DATE: 25/07/08 13:55:05 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: We report on a further analysis of the KW detection of the very bright, long-duration GRB 250706C (Frederiks et al., GCN 41013), which common origin with the SVOM/ECLAIRs GRB 250706B (Palmerio et al., GCN 40989) was confirmed from the FERMI/LAT observation (Longo et al., GCN 41019). GRB 250706C triggered Konus-Wind (KW) at T0=60322.626 s UT (16:45:22.626), ~1200 s before the SVOM/ECLAIRs trigger on GRB 250706B. The burst light curve shows a very bright, multi-peaked emission pulse with the duration of ~50 s (20-1500 keV). This pulse is followed by a weaker, smoothly decaying emission tail, visible up to the end of the KW triggered data record (~T0+250 s). The emission in the main pulse is seen up to ~15 MeV. The KW light curve is available at http://www.ioffe.ru/LEA/GRBs/GRB250706_T60322/ As observed by Konus-Wind, the burst had the total fluence of (5.12 ± 0.06)x10^-4 erg/cm^2 and a 16-ms peak energy flux, measured from T0 + 36.800 s, of (4.16 ± 0.22)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+51.968 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 = -1.00 (-0.01,+0.01), the high energy photon index beta = -3.65 (-0.44,+0.23), the peak energy Ep = 850(-15,+15) keV, chi2 = 125/96 dof. The spectrum near the peak count rate (measured from T0+36.608 s to T0+37.120 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 = -1.10 (-0.04,+0.04), the high energy photon index beta = -2.91 (-0.60,+0.30), the peak energy Ep = 1005(-91,+104) keV, chi2 = 69/58 dof. The spectrum of the decaying tail (measured from T0+51.968 s to T0+232.192) is best fit by a simple power law (PL) function with the PL photon index of (-2.0 ± 0.06), chi2 = 92/99 dof. Assuming the redshift z=0.942 (Palmerio et al., GCN 41022) and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the burst isotropic energy release E_iso to (1.26 ± 0.02)x10^54 erg, the isotropic peak luminosity L_iso to (2.00 ± 0.11)x10^53 erg/s, and the rest-frame peak spectral energy Epi,z to 1650(-30,+30) keV. With the obtained estimates, GRB 250706B/C is consistent with 68% prediction bands of both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB250706_T60322/GRB250706BC_rest_frame.pdf 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/41027. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39077] GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
by GCN Circulars 08 Jul '25

08 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41026 SUBJECT: GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C DATE: 25/07/08 13:38:21 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> J. T. Palmerio, D. Adrien (CEA), M. G. Bernardini (INAF-OAB, LUPM), M. Brunet, J.-L. Atteia, O. Godet (IRAP), P. Maggi (ObAS), L. P. Xin (NAOC), D. B. Malesani (DAWN/NBI and Radboud), C. W. Wang (IHEP), A. Saccardi, D. Götz (CEA), F. Cangemi (APC) report on behalf of the SVOM mission team: Following the detection of GRB 250706C reported by Konus-Wind (Frederiks et al., GCN 41013) and Fermi/LAT (Longo et al., GCN 41019), we discuss below the interpretation of GRB 250706B detected by SVOM (Palmerio et al., GCN 4989) as the hard X-ray afterglow of GRB 250706C. At the Konus-Wind trigger time (Frederiks et al., GCN 41013), the position of GRB 250706B was occulted by the Earth for SVOM/ECLAIRs. The SVOM/ECLAIRs trigger for GRB 250706B occurred 21 min after the Konus-Wind trigger, right after the source was no longer occulted by the Earth. SVOM/ECLAIRs shows a featureless and long-lasting (~1000 s) emission in the 4-50 keV energy band. The time-averaged spectrum after the slew (from 134 s to 1000 s after the ECLAIRs trigger time, GCN 4989) in the energy range 5-120 keV is best fitted by a power law model with index 2.01 +/- 0.11 (68% c.l. errors). With this model, the total 4-120 keV fluence is 2.6e-6 erg/cm^2. There is no significant signal in the SVOM/GRM VHF data. Taking the Konus-Wind detection time as T0 (16:45:22 UT), the SVOM/VT lightcurve appears as a single, unbroken power-law with index ~1.2. Assuming the same power-law decay held continuously before the VT observations, extrapolating the optical light curve to T0 + 1 min yields a magnitude of roughly 10 in VT_R. We encourage all-sky monitors to check for any emission at this location around the Konus-Wind trigger time. Extrapolating the SVOM/MXT lightcurve to T0 + 1 min yields a 0.3-10 keV flux of 6.5x10^-8 erg/cm^2/s, assuming the same power-law decay held continuously before the MXT observations reported by Maggi et al. (GCN 41009). We encourage further follow-up of this burst. The Space-based multi-band astronomical 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. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The SVOM point of contact for this burst is Jesse Palmerio: palmerio(a)cea.fr Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/41026. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39076] GRB 250704B: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 08 Jul '25

08 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41025 SUBJECT: GRB 250704B: CALET Gamma-Ray Burst Monitor detection DATE: 25/07/08 13:15:29 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> Y. Shimizu (Kanagawa U), 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), 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 250704B (SVOM/GRM observation: Wang et al., GCN 40940; Konus-Wind detection: Frederiks et al., GCN 40972; Insight-HXMT detection: Wang et al., GCN 40978) associated with the EP X-ray transient EP250704a (Einstein Probe detection: Li et al., GCN 40941; refined analysis of the EP-WXT and FXT follow-up observations: Li et al., GCN 40956) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 08:16:26.88 UTC on 4 July 2025 and the GCN/CALET Notice was distributed near real-time (https://cgbm.calet.jp/cgbm_trigger/flight/1435651911/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+0.21 sec, peaks at T+0.37 sec, and ends at T+0.51 sec. The T90 and T50 durations measured by the SGM data are 0.28 +/- 0.03 sec and 0.23 +/- 0.04 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1435651911/ 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/41025. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39075] GRB 250704B / EP250704a: Mondy and AbAO optical observations
by GCN Circulars 08 Jul '25

08 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41024 SUBJECT: GRB 250704B / EP250704a: Mondy and AbAO optical observations DATE: 25/07/08 12:26:15 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex(a)gmail.com> A. Volnova (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), R. Ya. Inasaridze (AbAO), N. Pankov (HSE) report on behalf of GRB IKI FuN: We observed the field of the EP250704a (Li et al., GCN 40941) also detected by SVOM (GRB 250704B; Wang et al., GCN 40940) with AZT-33IK telescope of Mondy observatory in R-filter on 2025-07-05 and with AS-32 telescope of Abastumani observatory on 2025-07-05. The optical afterglow (Li et al., GCNs 40941; Schneider et al., GCN 40942; Malesani et al., GCN 40945; Brivio et al., GCN 40947; Evans et al., GCN 40951; Perez-Garcia et al., GCN 4957; Gillanders et al., GCN 40958; Xin et al., GCN 40960; Mohan et al., GCN 40962; Moskvin et al., GCN 40963; Liu et al., GCN 40965; An et al., GCN 40966; Yang et al., GCN 4970; Martin-Carillo et al., GCN 40971; Frederiks et al., GCN 40972,Malte Busmann et al., GCN 40974, Li et al., GCN40975, Li et al., GCN 40986; An et al., GCN 40993; Wang et al., GCN 40999). We detect the afterglow on 2025-07-05. Preliminary photometry of a stacked image is the following Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) Tel. (mid, days) (s) 2025-07-05|16:34:49| 1.36693| 30*120 |R|21.06 |0.05| 22.9 |AZT-33IK 2005-07-06|19:39:17| 2.51241| 52*60 |R|n/d |- | 21.2 |AS-32 The photometry is based on nearby reference stars from PS1 (Lupton transformations) RA Dec R_Lupton 20:03:37.87 +12:01:59.6 17.385 20:03:26.50 +12:02:18.5 17.436 20:03:24.72 +11:59:09.1 16.41 View this GCN Circular online at https://gcn.nasa.gov/circulars/41024. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39074] GRB 250702F: radio detection with the VLA
by GCN Circulars 08 Jul '25

08 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41023 SUBJECT: GRB 250702F: radio detection with the VLA DATE: 25/07/08 12:10:37 GMT FROM: Stefano Giarratana at INAF-OAB <s.giarratana(a)ira.inaf.it> S. Giarratana (INAF-OAB), M. Giroletti (INAF-IRA), G. Ghirlanda (INAF-OAB), N. Di Lalla (Stanford Univ.), N. Omodei (Stanford Univ.), O. S. Salafia (INAF-OAB), L. Nava (INAF-OAB) At 02:54:00 UT on 2025 July 6 (T_mid = 3.27 days post-burst) the Karl G. Jansky VLA observed the field of GRB 250702F (Fermi GBM team, GCN 40892; Klingler et al., GCN 40894; Frederiks et al., GCN 40948) in three bands, with central frequencies of 6, 10 and 15 GHz. The standard 3C286 was used as bandpass and flux density calibrator, while J1415+1320 was used as phase calibrator. From a preliminary analysis, an unresolved radio source is detected at a position (J2000): RA: 14:11:44.641 +- 0.004 Dec: +16:44:54.68 +- 0.06 consistent with the X-ray (Goad et al., GCN 40902; Liang et al., GCN 40967) and optical (Klingler et al., GCN 40894; Jelinek et al., GCN 40895; Kumar et al., GCN 40896; Lipunov et al., GCN 40899; Martin-Carrillo et al., GCN 40900; de Ugarte Postigo et al., GCN 40901; Angulo et al., GCN 40907; Becerra et al., GCN 40911; Brivio et al., GCN 40913; An et al., GCN 40916; Dutton et al., GCN 40921; Odeh et al., GCN 40925; Moretti et al., GCN 40926; Siegel et al., GCN 40933; Ma et al., GCN 40936; Vinko et al., GCN 40939; Mohan et al., GCN 40946; Ciabattari et al., GCN 40968; Broens et al., GCN 40969; Calapai et al., GCN 40973; Antier et al., GCN 41011) position of the transient. The preliminary analysis yields the following results: ================================================================ T_mid Freq Peak r.m.s. Beam PA [days] [GHz] [uJy/b] [uJy/b] [arcsec^2] [deg] ================================================================ 3.27 6 158 7 3.31x3.03 22 3.27 10 127 6 2.09x1.95 31 3.27 15 141 7 1.39x1.26 1 ================================================================ We would like to thank the staff of the VLA for approving, executing, and processing the observations. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. These observations were carried out as part of project SF171028, approved in the framework of the Fermi - NRAO joint program agreement. View this GCN Circular online at https://gcn.nasa.gov/circulars/41023. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39073] GRB 250706B/C: VLT/X-shooter redshift z = 0.942
by GCN Circulars 08 Jul '25

08 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41022 SUBJECT: GRB 250706B/C: VLT/X-shooter redshift z = 0.942 DATE: 25/07/08 12:04:56 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> J. T. Palmerio (CEA/Irfu), B. Schneider (LAM), A. Saccardi (CEA/Irfu), M. Garnichey (LUX-Paris Obs.), G. Corcoran (UCD), V. D'Elia (ASI/SSDC), M. De Pasquale (Univ. Messina), L. Izzo (INAF/OACn and DARK/NBI), D. B. Malesani (DAWN/NBI and Radboud), P. O'Brien (Leicester), N. R. Tanvir (Univ. Leicester), S. D. Vergani (LUX-Paris Obs.) report on behalf of the Stargate collaboration: We observed the optical afterglow (Zhu et al., GCN 40991) of the SVOM GRB 250706B (Palmerio et al., GCN 40989), an extension of GRB 250706C detected by Konus-Wind and Fermi/LAT (Frederiks et al., GCN 41013; Longo et al., GCN 41019), using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. Our spectra cover the wavelength range 3000-25000 AA, and consist of 2 exposures of 600 s each. The observation mid time was 2025 Jul 8.40 UT (1.70 days after the Konus-Wind trigger). In a 30 s image taken with the acquisition camera on Jul 8.39 UT (1.69 days after the Konus-Wind trigger), the optical afterglow is clearly detected, and we measure a magnitude r = 20.37 +- 0.02 AB (calibrated against a single star from the SkyMapper catalog). In a preliminary reduction of the spectra, continuum is visible over the entire covered wavelength range. From the detection a multitude of absorption lines, which we interpret as due to Al II, Ni II, Si II, Si II*, Al III, Cr II, Zn II, Ni II*, Fe II, Fe I, Mn II, Mg II, Mg I, Ca II, Ca I, we infer a redshift of z = 0.942. We also detect two emission lines which we identify as the [O III] 4959,5007 doublet at the same redshift. The detection of fine-structure lines, as well as of nebular emission, allows us to securely identify z = 0.942 as the redshift of GRB 250706B/C. We acknowledge excellent support from the ESO observing staff in Paranal, in particular Diego Parraguez. The analysis of this spectrum was carried out with the help of the zHunter tool (https://doi.org/10.5281/zenodo.15189495) View this GCN Circular online at https://gcn.nasa.gov/circulars/41022. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39072] GRB 250706B/C: VLT/X-shooter redshift z = 0.942
by GCN Circulars 08 Jul '25

08 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41022 SUBJECT: GRB 250706B/C: VLT/X-shooter redshift z = 0.942 DATE: 25/07/08 12:04:56 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> J. T. Palmerio (CEA/Irfu), B. Schneider (LAM), A. Saccardi (CEA/Irfu), M. Garnichey (LUX-Paris Obs.), G. Corcoran (UCD), V. D'Elia (ASI/SSDC), M. De Pasquale (Univ. Messina), L. Izzo (INAF/OACn and DARK/NBI), D. B. Malesani (DAWN/NBI and Radboud), P. O'Brien (Leicester), N. R. Tanvir (Univ. Leicester), S. D. Vergani (LUX-Paris Obs.) report on behalf of the Stargate collaboration: We observed the optical afterglow (Zhu et al., GCN 40991) of the SVOM GRB 250706B (Palmerio et al., GCN 40989), an extension of GRB 250706C detected by Konus-Wind and Fermi/LAT (Frederiks et al., GCN 41013; Longo et al., GCN 41019), using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. Our spectra cover the wavelength range 3000-25000 AA, and consist of 2 exposures of 600 s each. The observation mid time was 2025 Jul 8.40 UT (1.70 days after the Konus-Wind trigger). In a 30 s image taken with the acquisition camera on Jul 8.39 UT (1.69 days after the Konus-Wind trigger), the optical afterglow is clearly detected, and we measure a magnitude r = 20.37 +- 0.02 AB (calibrated against a single star from the SkyMapper catalog). In a preliminary reduction of the spectra, continuum is visible over the entire covered wavelength range. From the detection a multitude of absorption lines, which we interpret as due to Al II, Ni II, Si II, Si II*, Al III, Cr II, Zn II, Ni II*, Fe II, Fe I, Mn II, Mg II, Mg I, Ca II, Ca I, we infer a redshift of z = 0.942. We also detect two emission lines which we identify as the [O III] 4959,5007 doublet at the same redshift. The detection of fine-structure lines, as well as of nebular emission, allows us to securely identify z = 0.942 as the redshift of GRB 250706B/C. We acknowledge excellent support from the ESO observing staff in Paranal, in particular Diego Parraguez. The analysis of this spectrum was carried out with the help of the zHunter tool (https://doi.org/10.5281/zenodo.15189495) View this GCN Circular online at https://gcn.nasa.gov/circulars/41022. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39071] IceCube-250706A: EP-FXT follow-up observations
by GCN Circulars 08 Jul '25

08 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41021 SUBJECT: IceCube-250706A: EP-FXT follow-up observations DATE: 25/07/08 09:58:11 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Q. Y. Wu, Y. Liu (NAO, CAS), G. Giulia, A. L. Thakur (INAF-IAPS) on behalf of the Einstein Probe (EP) team: EP-FXT performed two follow-up observations of the IceCube-250706A (GCN 40994) (goldtrack) event. The first follow-up observation (obs1) started from 2025-07-06T13:56:24, about 40 minutes after the neutrino trigger, with an exposure time of 5.9 ks. The second one (obs2) started from 2025-07-06T21:01:14, about 8 hours after the trigger, with an exposure time of 4.1 ks. With the 1 deg x 1 deg FoV, EP-FXT covered most part of the 90% C.L. error region of the neutrino event. Within the neutrino localization error region, only one source exhibited significant variability compared with historical fluxes or historical upper limits. The details are listed below: Source: EPF_J174217.4+392257 RA (J2000): 265.5726 Dec (J2000): 39.3826 Position error in radius: 10 arcsec (90% C.L.) Flux in obs1: 1 x 10^-12 erg/s/cm2 (0.5-10 keV) Flux in obs2: not detected, with an upper limit around 5 x 10^-14 erg/s/cm2 (0.5-10 keV) A BY Dra variable star, ZTF J174217.39+392252.1, is 5 arcsec away from EPF_J174217.4+392257. Thus, the significant variability is likely due to the flare of this star with the X-ray luminosity of 6 x 10^30 erg/s. No other source exhibited significant variability between the two observations. 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/41021. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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