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

[vsnet-grb-info 38046] GRB 250403A: Fermi GBM Final Real-time Localization
by GCN Circulars 03 Apr '25

03 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40025 SUBJECT: GRB 250403A: Fermi GBM Final Real-time Localization DATE: 25/04/03 15:26:06 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 15:15:22 UT on 3 Apr 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250403A (trigger 765386127.830438 / 250403636). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 204.2, Dec = -25.4 (J2000 degrees, equivalent to J2000 13h 36m, -25d 23'), with a statistical uncertainty of 5.1 degrees. The angle from the Fermi LAT boresight is 56.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250403636/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250403636/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250403636/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40025. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38045] GRB 250225B: VLT host galaxy redshift z = 0.950
by GCN Circulars 03 Apr '25

03 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40024 SUBJECT: GRB 250225B: VLT host galaxy redshift z = 0.950 DATE: 25/04/03 14:50:19 GMT FROM: Andrea Saccardi at CEA/Irfu <andrea.saccardi(a)cea.fr> A. Saccardi (CEA/Irfu), G. Corcoran (UCD), B. Schneider (LAM), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), A. J. Levan (Radboud and Warwick) report on behalf of the Stargate collaboration: We observed with the ESO VLT UT3 (Melipal) the object visible in the Legacy Survey underlying the position of the optical/NIR afterglow (Schneider et al., GCN 39494; Yang et al., GCN 39495, 39521; Rayson et al., GCN 39535; Yang et al., GCN 39544) of GRB 250225B (Williams et al., GCN 39473; Zhang et al., GCN 39493; Ridnaia et al., GCN 39498; Godwin et al., GCN 39502; Thakur et al., GCN 39517; Finneran et al., GCN 39541; Liu et al., GCN 39830). Due to its spatial coincidence, this is the likely GRB host galaxy. We obtained two spectra of 1000 s each with the X-shooter instrument, starting at 07:08:05 UT on 2025 April 3, i.e. about 36.5 days after the Swift trigger. The observations were obtained under good conditions, with a measured seeing of 0.5". Emission lines are detected in the visible and near-infrared arms, which we identify as H-alpha, [O III] 5007 and the [O II] 3726,3729 doublet at a common redshift of z = 0.950. This value is consistent with the photometric solution z_phot = 1.12 +/- 0.18 from the Legacy Survey (Zhou et al. 2021, doi:10.1093/mnras/staa3764). The absolute magnitude of the galaxy is M_B ~ -21, which is at the bright end of the distribution of long-duration (collapsar) GRB hosts. Our redshift measurement rules out an association between the object in the Legacy Survey and ESO 340-26 at z = 0.018. Considering the low chance association probability (Schneider et al., GCN 39494; Yang et al., GCN 39495), we consider this to be the likely redshift of GRB 250225B. We acknowledge the excellent support from the ESO staff in Paranal, in particular Matias Jones, Rob van Holstein, and Rodrigo Palominos. View this GCN Circular online at https://gcn.nasa.gov/circulars/40024. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38044] GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
by GCN Circulars 03 Apr '25

03 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40023 SUBJECT: GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart DATE: 25/04/03 10:48:39 GMT FROM: Francesco Magnani at Aix-Marseille Université, CPPM/CNRS <francesco.magnani.work(a)gmail.com> Francesco Magnani (CPPM), Camila Angulo (UNAM), Damien Dornic (CPPM), Jean-Luc Atteia (IRAP), Stéphane Basa (UAR Pytheas), Alan M. Watson (UNAM), William H. Lee (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU) , Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), , Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), and X. Chen (YNU) report: We imaged the field of the SVOM/ECLAIRs GRB 250402A (sb25040203, Chen et al. GCN 40014) with the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed from 2025-04-03 04:37 to 06:49 UTC (between 5.49 and 7.69 hours after the trigger) and obtained 43 minutes of exposure in the i filter. The data were coadded with the COLIBRÍ pipeline and analyzed in STDWeb/STDPipe (Karpov 2025), with photometric calibration against Pan-STARRS DR1. Our photometry is in the AB system and is not corrected for Galactic extinction. At the position of the previously reported optical afterglow (Xin et al., GCN 40015; Pérez-Fournon et al. GCN 40020; Schneider et al. GCN 40022), we detect a source with a magnitude of i = 21.22 +/- 0.11 Further observations are ongoing. We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/40023. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38043] GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
by GCN Circulars 03 Apr '25

03 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40022 SUBJECT: GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823 DATE: 25/04/03 09:52:28 GMT FROM: luca.izzo(a)inaf.it B. Schneider (LAM), A. Saccardi (CEA/Irfu), A. de Ugarte Postigo (LAM), L. Izzo (INAF-OACn and DARK/NBI), D. B. Malesani (DAWN/NBI and Radboud), N. R. Tanvir (U. Leicester), A. Martin-Carrillo (UCD) report on behalf of the Stargate collaboration: We observed the afterglow of the SVOM/ECLAIRs GRB 250402A (Chen et al., GCN 40014; Xin et al., GCN 40015, Maggi et al., GCN 40019; Pérez-Fournon et al., GCN 40020) using the ESO/VLT UT1 (Antu) equipped with the FORS2 spectrograph. Observations started on April 3 at 05:54:45 UT (6.78 hr after the SVOM trigger). Four exposures of 600 s were obtained. From a 60 s acquisition image obtained on April 3 at 05:43:17 UT (6.59 hr after the SVOM trigger), we measure r ~ 21.1 +/- 0.2 (AB). From a preliminary reduction of the 300V spectrum, a trough due to Lya absorption is visible at 4645 AA. From the detection of multiple absorption features, which we interpret as due to Si II, O I, C II, Si IV, Si II*, C IV, Fe II, and Al II, we infer a redshift of z = 2.823. Additionally, we note the presence of an intervening absorber at z = 1.409 with multiple Fe II absorption lines. We acknowledge excellent support from the ESO observing staff in Paranal. View this GCN Circular online at https://gcn.nasa.gov/circulars/40022. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38042] GRB 250402A: REM optical/NIR upper limits
by GCN Circulars 03 Apr '25

03 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40021 SUBJECT: GRB 250402A: REM optical/NIR upper limits DATE: 25/04/03 09:46:37 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 the SVOM/ECLAIRs GRB 250402A (Chen et al., GCN 40014) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, and K bands, started on 2025 April 03 at 00:50:28 UT (i.e. 1.7 hr after the burst), and lasted for about 2 hours. From preliminary inspection, we do not find any counterpart at the position of the reported optical afterglow candidate (Xin et al., GCN. 40015; Pérez-Fournon et al., GCN 40020) down to the following 3sigma limits: r > 20.3 (AB; calibrated against the Pan-STARRS catalogue), at a mid-time of 2.8 hours after the trigger, H > 16.1 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 2.2 hours after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/40021. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38041] GRB 250402A: LCO optical counterpart detection
by GCN Circulars 03 Apr '25

03 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40020 SUBJECT: GRB 250402A: LCO optical counterpart detection DATE: 25/04/03 09:09:55 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia (ULL), and A. López-Oramas (IAC and ULL) We report Las Cumbres Observatory Global Telescope network (LCOGT) observations of the SVOM GRB 250402A (Chen et al., GCN circ. 40014; Maggi et al., GCN circ. 40019). We observed the field of GRB 250402A with the three LCOGT 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at Cerro Tololo Inter-American Observatory (Chile) in the SDSS r, g, and i filters, starting at 2025-04-03 02:58:50 UTC, about 3.85 hours after the SVOM trigger. An uncatalogued source is clearly detected in the three filters at the position of the optical counterpart detected by SVOM/VT (Xin et al., GCN circ. 40015). We measure the following magnitudes, calibrated against Pan-STARRS DR2 stars and not corrected for Galactic extinction: Date | UT start | mag | error | filter | exposure time (sec) --------------------------------------------------------------------- 2025-04-03 02:58:50 21.01 0.14 r 300 2025-04-03 03:15:44 21.91 0.17 g 300 2025-04-03 03:21:06 20.80 0.13 i 300 This work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT observing programme IAC2025A-009, SGLF). View this GCN Circular online at https://gcn.nasa.gov/circulars/40020. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38040] GRB 250402A: LCO optical counterpart detection
by GCN Circulars 03 Apr '25

03 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40020 SUBJECT: GRB 250402A: LCO optical counterpart detection DATE: 25/04/03 09:09:55 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia (ULL), and A. López-Oramas (IAC and ULL) We report Las Cumbres Observatory Global Telescope network (LCOGT) observations of the SVOM GRB 250402A (Chen et al., GCN circ. 40014; Maggi et al., GCN circ. 40019). We observed the field of GRB 250402A with the three LCOGT 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at Cerro Tololo Inter-American Observatory (Chile) in the SDSS r, g, and i filters, starting at 2025-04-03 02:58:50 UTC, about 3.85 hours after the SVOM trigger. An uncatalogued source is clearly detected in the three filters at the position of the optical counterpart detected by SVOM/VT (Xin et al., GCN circ. 40015). We measure the following magnitudes, calibrated against Pan-STARRS DR2 stars and not corrected for Galactic extinction: Date | UT start | mag | error | filter | exposure time (sec) --------------------------------------------------------------------- 2025-04-03 02:58:50 21.01 0.14 r 300 2025-04-03 03:15:44 21.91 0.17 g 300 2025-04-03 03:21:06 20.80 0.13 i 300 This work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT observing programme IAC2025A-009, SGLF). View this GCN Circular online at https://gcn.nasa.gov/circulars/40020. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38039] GRB 250402A: refined SVOM/MXT data analysis
by GCN Circulars 03 Apr '25

03 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40019 SUBJECT: GRB 250402A: refined SVOM/MXT data analysis DATE: 25/04/03 07:20:33 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> P. Maggi (ObAS), D. Götz (CEA), H. Goto (Kanazawa University/CEA), M. Moita (CEA), C. Plasse (CEA), F. Robinet (IJCLab), C. Van Hove (IJCLab) report of behalf of the SVOM/MXT Team: GRB 250402A (Chen et al. GCN 40014) was observed by SVOM/MXT after an automatic SVOM slew starting at T0 = 2025-04-02T23:10:59.278 (183s after trigger time Tb). MXT observed for 4.3 ks effective exposure. Using the full X band dataset, we find a rapidly fading uncatalogued source with a light curve temporal index of -0.75+/-0.02. At times T0>500s the source is no longer detected and hence we restricted the analysis to the first 500s of data. Its position is RA=213.4051, Dec=-5.94374 RA (J2000) = 14h13m37s Dec (J2000) = -05d56m37s with a statistical 90% C.L. radius of 38". The position is 51" away from, but consistent with, the one reported for the SVOM/VT afterglow candidate (Xin et al. GCN 40015) when including a 35" systematic uncertainty. The X-ray spectrum (t<T0+500s) can be fit by an absorbed power law model with a photon index of 3.2 (-0.8, +1.3) and an NH value of 0.21 (-0.1, +0.2) x 1e22 /cm2 (90% C.L. uncertainties). The absorbed X-ray flux in the 0.3-10 keV range is 8.4e-11 (+/-0.5e-11) erg/cm2/s. Follow-up observations at other wavelengths are encouraged. 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. MXT was developed jointly by CEA, CNES, University of Leicester, IJCLab and MPE. The SVOM point of contact for this burst is: X. Chen: xlchen(a)stu.ynu.edu.cn View this GCN Circular online at https://gcn.nasa.gov/circulars/40019. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38038] The EP-WXT trigger 01709133862 is a flaring star
by GCN Circulars 03 Apr '25

03 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40018 SUBJECT: The EP-WXT trigger 01709133862 is a flaring star DATE: 25/04/03 07:02:53 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.-Z. Li (YNAO, CAS), H. Q. Cheng (NAO, CAS), Q. C. Zhao, Z. H. Yang (IHEP, CAS), Y. Liu (NAO, CAS) report on behalf of the Einstein Probe team: The EP-WXT triggered event 01709133862 at the time of 2025-04-02 17:38:19, which is a stellar flare associated with the Rotating Variable star ASAS J145837-3915.1. The estimated flux of the flare is around 1.0 x 10^-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 1.6 x 10^32 erg/s. 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/40018. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38037] EP250402a: Einstein Probe detected of a fast X-ray transient
by GCN Circulars 03 Apr '25

03 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40017 SUBJECT: EP250402a: Einstein Probe detected of a fast X-ray transient DATE: 25/04/03 06:33:31 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.-Z. Li (YNAO, CAS), H. Q. Cheng (NAO, CAS), Q. C. Zhao, Z. H. Yang (IHEP, CAS), Y. Liu (NAO, CAS) report on behalf of the Einstein Probe team: We report on the detection of a fast X-ray transient EP250402a (trigger ID: 01709133860) at 2025-04-02T12:29:06.850 (UTC) by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The position of the source is R.A., DEC. = 172.168, -47.290 deg (J2000) with an uncertainty of 2.5 arcmin (radius, 90% C.L. statistical and systematic). The transient event lasted for about 80 seconds, with a peak 0.5-4 keV flux of 5.7 x 10^-9 erg/s/cm^2. The 0.5-4.0 keV spectrum can be fitted with an absorbed powerlaw model, with the column density nH fixed at the Galactic value of 1.43 x 10^21 cm^-2 and a photon index of 1.3 (+0.7/-0.7). The unabsorbed 0.5-4.0 keV flux is 1.2 (+0.6, -0.4) x10^-9 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Follow-up observations by EP-FXT are prepared. 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/40017. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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