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

[vsnet-grb-info 38106] GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40083 SUBJECT: GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection DATE: 25/04/05 22:56:51 GMT FROM: leavittob(a)gmail.com E. Pavoni, L. Moretti (Leavitt Observatory, Italy) Members of: GRB/UAI - Gamma Ray Burst Section of Unione Astrofili Italiani ATA - Associazione Tuscolana di Astronomia In a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy), K. Kalinowski (Aarhus University, Department of Physics and Astronomy), report: We observed the field of EP250404a detected by Einstein Probe (Hu et al., GCN 40051), which is temporally and spatially consistent with GRB 250404A (Fermi team, GCN 40050), with our RC telescope (D=250 mm, F/D=8) of Leavitt Observatory, Manciano, Italy. Median moon illumination of 47% was present. The observations started approximately 5.1 hours after the trigger time, stacking a series of R-Cousins filtered exposures, for a total integration time of approximately 88 minutes. All images were processed using the astropy package (Astropy Collaboration et al., 2022ApJ...935..167A). We detected the optical counterpart (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al. GCN 40063; Odeh et al., GCN 40064; Lipunov et al., GCN 40066; He et al., GCN 40069; Perez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al., GCN 40073; Taguchi et al., GCN 40074; Ruocco, GCN 40076; Martin-Carrillo et al., GCN 40080) in the stacked image at the following coordinates +/- 2 arcsec: R.A. (J2000) = 08:20:14:59 Dec. (J2000) = +35:31:41:75 with the following photometry: Date UT at mid-exposure: 2025-04-04 20:24:18 UTC Mag (R Cousins) 19.47 Error +/- 0.2 Magnitudes were estimated with the Pan-STARRS cat. and converted using Lupton (2005) equations. No corrected for galactic dust extinction. The message may be cited. Reference: https://leavittobservatory.altervista.org View this GCN Circular online at https://gcn.nasa.gov/circulars/40083. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38105] GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40082 SUBJECT: GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations. DATE: 25/04/05 22:22:30 GMT FROM: Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, Messina, Italy <giovannicalapai(a)tiscali.it> Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. Report: We observed the field of GRB 250402A (SVOM burst-id sb25040203, Chen et al., GCN 40014) with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3. The observations were started at 2025-04-02 23:57 UT (approximately 49 min after burst) stacking a set of unfiltered CCD image. The observations were carried out with clear skies and fair visibility conditions. The OT was detected at the following position (+/- 0.3 arcsec): RA (J2000.0) 14h 13m 38.17s Decl. (J2000.0) -05° 55' 48.8" Photometry was obtained using nearby PanSTARRS stars as follows: Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Err. 2025-04-03 01:39:02 UT 2.52 180x60s CR 21.6 +/- 0.4 Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied. Our observations are consistent with other already reported L.P. Xin et al. (GCN 40015), Pérez-Fournon et al. (GCN 40020), Brivio et al. (GCN 40021), Schneider et al. (GCN 40022), Magnani et al. (GCN 40023), Komesh et al. (GCN 40033), Shilling et al. (GCN 40047), Mazaeva et al. (GCN 40049). The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40082. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38104] EP250402a: Optical upper limit with PD 1.3m observations
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40081 SUBJECT: EP250402a: Optical upper limit with PD 1.3m observations DATE: 25/04/05 17:05:25 GMT FROM: Jonathan Quirola at Radboud University <jaquirola1990(a)gmail.com> Jonathan Quirola-Vásquez (Radboud), Peter G. Jonker (Radboud), Franz Bauer (PUC), Antonio Martin-Carrillo (UCD), Andrew J. Levan (Radboud), Daniele B. Malesani (DAWN/ NBI and Radboud), Javi Sánchez-Sierras (Radboud), Agnes van Hoof (Radboud), Jennifer Chacon (PUC), Joyce van Dalen (Radboud) report on behalf of a larger collaboration: We obtained photometric observations of the field of the fast X-ray transient EP250402a discovered by Einstein Probe (Li et al., GCN 40017, GCN 40038) using the Planaetry Defense 1.3m telescope localized in Cerro Tololo Inter-American Observatory, Chile. We obtained 30 images of 120 s each in the r-band filter beginning at 2025-04-03 07:06:41 UT and with a middle time at T0+0.797 days after the EP trigger. Within the EP-FXT error circle, we detect no plausible optical counterpart down to a 3sigma limit of r > 21.8 AB mag, calibrated against SkyMapper nearby reference stars We acknowledge the excellent support from the PD 1.3m staff, in particular Tyler Linder. View this GCN Circular online at https://gcn.nasa.gov/circulars/40081. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38103] GRB 250404A / EP250404a: NOT optical observations
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40080 SUBJECT: GRB 250404A / EP250404a: NOT optical observations DATE: 25/04/05 15:27:15 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie> A. Martin-Carrillo (UCD), B. Schneider (LAM), A. de Ugarte Postigo (LAM), D. B. Malesani (DAWN/NBI and Radboud Univ.), J. An (NAOC), D. Xu (NAOC), G. Corcoran (UCD), Dimple (U. Birmingham), M. A. Diaz Teodori (NOT and Turku Univ.), report on behalf of a larger collaboration: We observed the field of EP250404a (Hu et al., GCN 40051), likely associated with GRB 250404A detected by Fermi/GBM (Fermi GBM team, GCN 40050; Mukherjee & Meegan, GCN 40067) using the ALFOSC camera mounted on the Nordic Optical Telescope (NOT). We obtained exposures in the SDSS-r (3x180 s) and SDSS-z (2x180 s) bands, starting at 22:09:17 UT on 2025-04-04 (7.82 hr after the EP trigger). The optical counterpart reported by Jiang et al. (GCN. 40052), Perez-Garcia et al. (GCN 40053), Du et al. (GCN 40058), Zhu et al. (GCN 40061), Konno et al. (GCN 40063), Odeh et al. (GCN 40064), He et al. (GCN 40069), Pérez-Fournon et al. (GCN 40071), Jelinek et al. (GCN 40072), Rakotondrainibe et al. (GCN 40073), Taguchi et al. (GCN 40074), Ruocco et al. (GCN 40076) is well detected in the stacked images, with the following preliminary magnitudes: r = 20.43 +/- 0.05 (7.90 hr after trigger); z = 19.79 +/- 0.06 (8.04 hr after trigger). The photometric calibration was performed using nearby stars from the Pan-STARRS catalog and the magnitudes are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40080. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38102] GRB 250331D: Swift-XRT afterglow detection
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40079 SUBJECT: GRB 250331D: Swift-XRT afterglow detection DATE: 25/04/05 12:24:26 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has conducted further observations of the field of the Swift/BAT-detected burst GRB 250331D. The observations now extend from T0+45.3 ks to T0+406.9 ks and have a total exposure time of 8.6 ks. Of the sources previously reported, "Source 2" is fading with >3-sigma significance, and is therefore likely the GRB afterglow. Using 3064 s of PC mode data and 2 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 48.65718, +62.28326 which is equivalent to: RA (J2000): 03h 14m 37.72s Dec(J2000): +62d 16' 59.8" with an uncertainty of 3.5 arcsec (radius, 90% confidence). This position is 3.9 arcmin from the Swift/BAT position. There is evidence that the source may be fading, however we cannot constrain the decay at the current time. The results of the XRT-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/ToO_GRBs/00021825/Source2.php. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021825. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40079. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38101] GRB 250404B: AstroSat CZTI detection of a short burst
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40078 SUBJECT: GRB 250404B: AstroSat CZTI detection of a short burst DATE: 25/04/05 10:39:48 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> S. Salunke (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a short duration GRB 250404B. The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-04-04 18:36:09.15 UTC. The measured peak count rate associated with the burst is 720 (+181, -101) counts/s above the background in the combined data of three quadrants (out of four), with a total of 375 (+52, -54) counts. The local mean background count rate was 292 (+10, -13) counts/s. Using cumulative rates, we measure a T90 of 0.79 (+0.04, -0.05) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaked at 2025-04-04 18:36:08.40 UTC. The measured peak count rate associated with the burst is 665 (+73, -81) counts/s above the background in the combined data of all quadrants, with a total of 635 (+154, -167) counts. The local mean background count rate was 1266 (+14, -15) counts/s. Due to the intrinsic 1 s binning of veto data, we cannot reliably estimate a T90 from it. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/40078. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38100] GRB 250403A: AstroSat CZTI detection
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40077 SUBJECT: GRB 250403A: AstroSat CZTI detection DATE: 25/04/05 10:38:20 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> M. Tembhurnikar (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long duration GRB 250403A which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 40025) and SVOM/ECLAIRs (Y. Julakanti et. al. GCN Circ. 40026). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-04-03 15:15:26.00 UTC. The measured peak count rate associated with the burst is 80 (+18, -23) counts/s above the background in the combined data of three quadrants (out of four), with a total of 343 (+110, -184) counts. The local mean background count rate was 225 (+3, -2) counts/s. Using cumulative rates, we measure a T90 of 9.1 (+1.3, -5.5) s. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/40077. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38099] EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40076 SUBJECT: EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart DATE: 25/04/05 10:05:39 GMT FROM: Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy - MPC Code C82 <osservatorionastroverde(a)gmail.com> Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy in a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy) and K. Kalinowski (Aarhus University, Department of Physics and Astronomy) report: Following the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission triggered EP-WXT (ID: 01709133918) (GCN Circular 40051 J. W. Hu (NAO, CAS), Q. C. Liu (THU), B. B. Zhang (BNU), Y. L. Hua (PMO, CAS), Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team), I pointed at the coordinates RA(J2000)= 08:20:14.59 : Dec(J2000)= +35:31:42.3 and started observations with telescope of Nastro Verde Observatory - Sorrento (Naples), Italy. Member of: AAVSO - American Association of Variable Star Observers. GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. Clear sky but moon presence at about 20 degrees from the target. The observations started at 20:36 UT of 2025/04/04, after about 6 hours after the GRB trigger, with clear sky, with principal telescope SC 0.35 f/10 with focal reduced + CCD Sbig ST10 XME I took 22 unfiltered images of 120 sec . Start End Rlim 20:36:23 UT 21:22:15 UT 20.5 All images, calibrated with masterdark and masterflat have been measured with Thycho Tracker software We have detected a faint source at the enhanced position reported by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission AT following position RA (J2000.0) 08 20 15.95 Dec (J2000.0) +35 31 48.3 with the following photometry and astrometry: EP250404a 08 20 15.95 +35 31 48.3 19.0 C82 Magnitudes were estimated with the ATLAS cat. and are not corrected for galactic dust extinction. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40076. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38098] EP250404a: REM optical/NIR observations
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40075 SUBJECT: EP250404a: REM optical/NIR observations DATE: 25/04/05 09:32:41 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 EP250404a (Hu et al., GCN 40051), likely associated with GRB 250404A detected by Fermi/GBM (Fermi GBM team, GCN 40050) 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 04 at 23:26:12 UT (i.e. 9.1 hr after the burst), and lasted for about 1 hour. From preliminary inspection, we do not detect any counterpart at the position of the optical afterglow (Jiang et al., GCN. 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al., GCN 40063; Odeh et al., GCN 40064; He et al., GCN 40069; Pérez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al., GCN 40073; Taguchi et al., GCN 40074) down to the following 3sigma limits: r > 19.7 (AB; calibrated against the Pan-STARRS catalogue), at a mid-time of 9.6 hours after the trigger; H > 16.3 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 9.5 hours after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/40075. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38097] EP250404a: Seimei/TriCCS optical counterpart detection
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40074 SUBJECT: EP250404a: Seimei/TriCCS optical counterpart detection DATE: 25/04/05 09:09:53 GMT FROM: Kenta Taguchi <kentagch(a)kusastro.kyoto-u.ac.jp> Kenta Taguchi, Keiichi Maeda (Kyoto U.), Masaomi Tanaka (Tohoku U.) report on behalf of a larger collaboration: We observed the field of EP250404a detected by Einstein Probe (Hu et al., GCN 40051) using the Tricolor CMOS Camera and Spectrograph (TriCCS) on the 3.8-m Seimei telescope. Observations started at 15:27:48 UT on 2025-04-04 (MJD = 60769.64). We detected a counterpart at a position consistent with the source detected by Jiang et al. (GCN 40052, also reported by Perez-Garcia et al. GCN 40053, Du et al. GCN 40058, Konno et al. GCN 40063, Odeh et al. GCN 40064, He et al. GCN 40069, Pérez-Fournon et al. GCN 40071, Jelinek et al. GCN 40072, Rakotondrainibe et al. GCN 40073). Preliminary analysis gives the following magnitudes of the source: g = 18.20 +- 0.05 r = 17.46 +- 0.04 i = 17.10 +- 0.03 View this GCN Circular online at https://gcn.nasa.gov/circulars/40074. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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