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

[vsnet-grb-info 38086] EP250404a: LAST detection of optical counterpart
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40063 SUBJECT: EP250404a: LAST detection of optical counterpart DATE: 25/04/04 18:17:33 GMT FROM: Ruslan Konno at Weizmann Institute of Science <ruslan.konno(a)desy.de> R. Konno (WIS), S. Garrappa (WIS), E. A. Zimmerman (WIS), A. Horowicz (WIS), E. O. Ofek (WIS), S. Ben-Ami (WIS), D. Polishook (WIS), O. Yaron (WIS), P. Chen (WIS), A. Krassilchtchikov (WIS), Y. M. Shani (WIS), E. Segre (WIS), A. Gal-Yam (WIS), S. Spitzer (WIS), and K. Rybicki (WIS) on behalf of the LAST Collaboration We report observations of the X-ray transient EP250404a (Hu et al., GCN 40051), detected by Einstein Probe, with the Large Array Survey Telescope (LAST; Ofek et al. 2023 PASP 135, 5001; Ben-Ami et al. 2023 PASP 135, 5002). We observe the field of EP250404a using 4 parallel telescopes, each with a FoV of 7.4 deg^2 and no filter (clear - similar to the GAIA Bp band) over several epochs. In each epoch, we coadd 20 images with each of 20s exposure, and the limiting magnitude of a single coadd is around 20.5 (AB mag). We clearly detect the optical counterpart reported by Jiang et al. (GCN 40052), Perez-Garcia et al. (GCN 40053), and Du et al. (GCN 40058). The earliest detection with a 20x20s exposure image is confirmed at 2025-04-04 17:01:04 UTC (T-T0=2.68h) at an AB magnitude of 19.31 +/- 0.07. LAST is scheduled to continue observations of the source, and additional analysis will follow. LAST is a survey telescope array of the Weizmann Astrophysical Observatory (https://www.weizmann.ac.il/wao/) View this GCN Circular online at https://gcn.nasa.gov/circulars/40063. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38085] GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40062 SUBJECT: GRB 250402A: Swift/BAT-GUANO localization skymap of a burst DATE: 25/04/04 18:11:36 GMT FROM: Jimmy DeLaunay at Penn State <delauj2(a)gmail.com> James DeLaunay (PSU), Samuele Ronchini (PSU), Aaron Tohuvavohu (Caltech), Gayathri Raman (PSU), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC) report: Swift/BAT did not localize GRB 250402A onboard (T0: 2025-04-02T23:08:01.467 UTC, SVOM trig sb25040203, Fermi trig 765328094) The Fermi and SVOM notices, 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). 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. The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 8.2 in a 4.096 s analysis time bin, starting at T0 + 7.168 s. Using the NITRATES analysis, parameter estimation was performed to obtain the localization of this burst in the form of a HEALPIX Multi-Order Coverage (MOC) skymap. This localization accounts for both statistical and systematic errors. More details in the creation and calibration of these maps will soon be published (DeLaunay et al. 2025. in prep) The 90% credible area is 5,905 deg2 and the 50% credible area is 1,632 deg2. The integrated probability inside the coded field of view is 1%. The NITRATES skymap is consistent with the SVOM/ECLAIRS position (GCN 40014), and the afterglow position (SVOM/VT GCN 40015, SVOM/MXT GCN 40019, LCO GCN 40020, SVOM/COLIBRI GCN 40023, Swift/XRT GCN 40027, EP/FXT GCN 40040, Mondy GCN 40049) A plot of the probability skymap can be viewed here: [skymap_plot](https://guano.swift.psu.edu/trigger_report?id=765328116/#:~:te… The probability skymap file can be downloaded from the link here [skymap_fits_file](https://guano.swift.psu.edu/files/765328116/0_n_PROBMAP) Instructions on how to read and manipulate this map can be found here: https://guano.swift.psu.edu/documentation More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=765328116 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/40062. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38084] EP250404a: Xinglong-2.16m spectroscopic redshift
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40061 SUBJECT: EP250404a: Xinglong-2.16m spectroscopic redshift DATE: 25/04/04 18:05:48 GMT FROM: Dong Xu at NAOC/CAS <dxu(a)nao.cas.cn> Z.P. Zhu, J. An, X. Liu, S.Q. Jiang, J.J. Jin, Z. Fan, D. Xu (NAOC), S.Y. Fu (HUST), report on behalf of a large collaboration: We carried out spectroscopy of the optical counterpart (e.g., Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058) of EP250404a (Hu et al., GCN 40051), likely the identical event to GRB 250404A (GBM team, GCN 40050), using the 2.16-m telescope equipped with the BFOSC instrument, located at Xinglong, Hebei, China. Our spectra cover the wavelength range 3800 - 9000 AA, and consist of 2 exposures of 1800 s each. The continuum is throughout the spectrum. From the detection of a broad Lya absorption feature at ~ 4400 AA and relatively weak absorption features, which interpreted as being due to Si IV and Al III, we infer a common redshift of z = 2.63. We conclude this is the likely redshift of the event. An intervening system is also detected with absorption features, interpreted as being due to Mg II and Fe II, we inferred its redshift of z = 1.88. We acknowledge the expert support from the Xinglong-2.16m staff, in particular Junjun Jia and Jie Zheng. View this GCN Circular online at https://gcn.nasa.gov/circulars/40061. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38083] GRB 250403A: Fermi GBM observations
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40060 SUBJECT: GRB 250403A: Fermi GBM observations DATE: 25/04/04 16:31:50 GMT FROM: Peter Veres at University of Alabama in Huntsville <veresp(a)gmail.com> P. Veres (UAH), M. Godwin (UAH), C. Meegan (UAH) and E. Bissaldi (Politecnico and INFN Bari) report on behalf of the Fermi GBM Team: "At 15:15:22.83 UT on 03 April 2025, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 250403A (trigger 765386127 / 250403636). This GRB was also detected by the SVOM (Julakanti et al. 2025, GCN 40026). The Fermi GBM Final Real-time Localization (GCN 40025) is consistent with the SVOM position. The angle from the Fermi LAT boresight at the GBM trigger time is 59 degrees. The GBM light curve consists of multiple pulses with a duration (T90) of about 16.4 s (50-300 keV). The time-averaged spectrum from T0-4.1 s to T0+14.3 s is best fit by a simple power law function with index -1.65 +/- 0.02. The event fluence (10-1000 keV) in this time interval is (6.7 +/- 0.2)E-6 erg/cm^2. The 1-sec peak photon flux measured starting from T0+3.3 s in the 10-1000 keV band is 4.2 +/- 0.2 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/40060. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38082] GRB 250327B: VIRT Optical Upper Limit
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40059 SUBJECT: GRB 250327B: VIRT Optical Upper Limit DATE: 25/04/04 16:21:28 GMT FROM: Priya Gokuldass at ERAU <gokuldap(a)my.erau.edu> K. Smith (UVI), P. Gokuldass (ERAU), N. Orange (OrangeWave Innovative Science, LLC), B. Gendre (UVI), D. Morris (NASA), T. Lombardi (Eckerd College), F. George (ERAU), D. Smith (UVI), C. Watson (UVI) report: We observed the field of GRB 250327B (Bouchet et al., GCN 39888) detected by SVOM/ECLAIRs with the 0.5m Virgin Island Robotic Telescope (VIRT) at the University of the Virgin Islands' Etelman Observatory on 2025-03-28 starting at 06:52:58.6 (T-mid ~ T0 + 10.5 hrs). We performed a series of exposures in an R filter with a total exposure of 2560s. The weather conditions were partly cloudy during the hours of observation with an average airmass of 1.6. We do not detect any source at the position reported by SAO/RAS (Moskvitin et al., GCN 39889). This non-detection is consistent with reported detections (Moskvitin et al., GCN 39889; Pankov et al., GCN 39906; Xin et al., GCN 39890; O’Neill et al., GCN 39891;Malesani et al., GCN 39893; Lian et al, GCN 39894; Shrestha et al., GCN 39896; Kumar et al., GCN 39904; Pérez-Fournon et al., GCN 39912; Ducoin et al., GCN 39897; Ducoin et. al., GCN 39930; Perley et al., GCN 39902; Dennefeld et al., GCN 39905; Tarasenkov et al., GCN 39913; Broens et. al., GCN 40006 and Siegel et. al., GCN 40009) and upper limits (Mo et. al., GCN 39914 and della Vecchia et. al., GCN 39969). We report the following 3-sigma upper limit: T_mid ||Exposure ||Filter ||Limit T+ 10.5 hrs || 2560 s || R || > 20.8 The limit is estimated from comparison to nearby USNO B1 stars and is not corrected for Galactic extinction. We acknowledge financial support from NASA EPSCoR award 80NNSC22M0063, NSF PAARE award 2319415, and NASA EPSCoR award 80NSSC24M0112. This message can be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40059. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38081] EP250404a: Mephisto multi-band optical detection
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40058 SUBJECT: EP250404a: Mephisto multi-band optical detection DATE: 25/04/04 16:19:08 GMT FROM: Chenxu Liu at Mephisto Team <cxliu(a)ynu.edu.cn> Guowang Du, Ziwei Li, Chenxu Liu, Dezi Liu, Yaosong Yu, Chenxi Shang, Jinghua Zhang, Yuan Fang, Xufeng Zhu, Tao Wang, Xinlei Chen, Xingzhu Zou, Yu Pan, Brajesh Kumar, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team: We performed simultaneous multi-band photometric observations of EP250404a (EP-WXT ID: 01709133918) detected by EP (Hu et al., GCN 40051) and by Fermi/GBM (Fermi team, GCN 40050) with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at the Lijiang Observatory. The observations were initiated at 14:32:03UTC2025-04-04 (i.e., 723s after the EP/WXT trigger) and are still ongoing at the time of this report. Multiple frames were obtained in uvgriz- bands. The optical counterpart is clearly detected in all bands. The photometry of the initial frames is listed below: UT start |Band | Exp | Mag (AB) --------------------|-----|-------|----------|-------------------------- 2025/4/4 14:32:03 | u | 180s | 18.65+/-0.08 2025/4/4 14:32:04 | i | 79s | 14.60+/-0.01 2025/4/4 14:32:05 | g | 50s | 15.72+/-0.01 2025/4/4 14:39:20 | v | 180s | 16.91+/-0.02 2025/4/4 14:39:21 | z | 79s | 14.03+/-0.01 2025/4/4 14:39:22 | r | 50s | 14.83+/-0.01 Our results echo the detection from Nanshan/HMT (Jiang et al., GCN 40052) and BOOTES-4/MET (I. Perez-Garcia et al., GCN 40053). ---------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The on-site telescope assemblage and commissioning were carried out in September 2022. The first light in all three channels was achieved on 2023 December 21. ---------------------------------------------------------- View this GCN Circular online at https://gcn.nasa.gov/circulars/40058. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38080] GRB 250331C Swift-BAT refined analysis
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40057 SUBJECT: GRB 250331C Swift-BAT refined analysis DATE: 25/04/04 16:17:44 GMT FROM: Mike Moss at NASA GSFC <mikejmoss3(a)gmail.com> A. Y. Lien (U Tampa), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250331C (trigger #1299967) (Cenko, et al., GCN Circ. 39959). The BAT ground-calculated position is RA, Dec = 80.963, 33.068 deg which is RA(J2000) = 05h 23m 51.0s Dec(J2000) = +33d 04' 03.4" with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows a dim pulse of emission with some possible complex structure. The T90 (15-350 keV) is 70.10 +- 11.70 sec (estimated error including systematics). The time-averaged spectrum from T-12.59 to T+66.67 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.88 +- 0.23. The fluence in the 15-150 keV band is 6.6 +- 1.0 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T-3.19 sec in the 15-150 keV band is 0.3 +- 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/1299967 View this GCN Circular online at https://gcn.nasa.gov/circulars/40057. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38079] GRB 250331B Swift-BAT refined analysis
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40056 SUBJECT: GRB 250331B Swift-BAT refined analysis DATE: 25/04/04 16:16:25 GMT FROM: Mike Moss at NASA GSFC <mikejmoss3(a)gmail.com> S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), 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+842 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250331B (trigger #1299965) (Cenko, et al., GCN Circ. 39958). The BAT ground-calculated position is RA, Dec = 71.377, 43.794 deg which is RA(J2000) = 04h 45m 30.4s Dec(J2000) = +43d 47' 39.1" with an uncertainty of 2.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 55%. The mask-weighted light curve displays a single dim pulse. The T90 (15-350 keV) is 3.95 +- 0.77 sec (estimated error including systematics). The time-averaged spectrum from T-0.72 to T+3.76 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.61 +- 0.38. The fluence in the 15-150 keV band is 1.5 +- 0.3 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+1.28 sec in the 15-150 keV band is 0.9 +- 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/1299965 View this GCN Circular online at https://gcn.nasa.gov/circulars/40056. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38078] GRB 250331B Swift-BAT refined analysis
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40056 SUBJECT: GRB 250331B Swift-BAT refined analysis DATE: 25/04/04 16:16:25 GMT FROM: Mike Moss at NASA GSFC <mikejmoss3(a)gmail.com> S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), 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+842 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250331B (trigger #1299965) (Cenko, et al., GCN Circ. 39958). The BAT ground-calculated position is RA, Dec = 71.377, 43.794 deg which is RA(J2000) = 04h 45m 30.4s Dec(J2000) = +43d 47' 39.1" with an uncertainty of 2.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 55%. The mask-weighted light curve displays a single dim pulse. The T90 (15-350 keV) is 3.95 +- 0.77 sec (estimated error including systematics). The time-averaged spectrum from T-0.72 to T+3.76 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.61 +- 0.38. The fluence in the 15-150 keV band is 1.5 +- 0.3 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+1.28 sec in the 15-150 keV band is 0.9 +- 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/1299965 View this GCN Circular online at https://gcn.nasa.gov/circulars/40056. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38077] GRB 250403A: Swift/UVOT Detection
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40048 SUBJECT: GRB 250403A: Swift/UVOT Detection DATE: 25/04/04 13:28:59 GMT FROM: Sam Shilling at Lancaster University <shilling.sam(a)gmail.com> S. P. R. Shilling (Lancaster U.), S. R. Oates (Lancaster U.) and S. Dichiara (PSU) report on behalf of the Swift UVOT team: Swift/UVOT observed the field of GRB 250403A detected by Fermi GBM (Fermi team, GCN Circ. 40025) and SVOM/ECLAIRs (Julakanti et al., GCN Circ. 40026), starting at 17:22:59 UT on 24/04/03, ~2.1 hours after the initial detections. An optical afterglow is initially detected in the U-band consistent with the position of the uncatalogued X-ray source detected by Swift/XRT (Dichiara et al., GCN Circ. 40037) and the optical afterglow detected by various facilities (Starling et al., GCN Circ. 40028; Wu et al., GCN Circ. 40029; Du et al., GCN Circ. 40031; Li et al., GCN Circ. 40032; Ghosh et al., GCN Circ. 40039; Jiang et al., GCN Circ. 40041; Pérez-Fournon et al., GCN Circ. 40043; Xin et al., GCN Circ. 40045). At 00:02:02 UT on 25/04/04, ~6.7 hours later, the optical afterglow is no longer detected. The preliminary detection and 3-sigma upper limits calculated using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial and subsequent exposures are: Filter T_start(h) Exp(s) Mag u 2.1 396 19.2 +/- 0.2 u 8.8 492 >20.3 b 8.8 386 >20.5 v 9.0 130 >19.0 w1 12.1 164 >19.3 m2 12.0 245 >19.7 w2 8.9 246 >19.8 The magnitudes given are calculated using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) and are not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40048. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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