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

[vsnet-grb-info 38651] GRB 250603A: Swift-XRT position and confirmation of GRB nature
by GCN Circulars 03 Jun '25

03 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40615 SUBJECT: GRB 250603A: Swift-XRT position and confirmation of GRB nature DATE: 25/06/03 05:40:03 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> K.L. Page and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: The XRT began observing the field of GRB 250603A (GCN Circ. 40613) at 01:12:04.7 UT, 101.7 seconds after the BAT trigger. Using promptly-collected data (although downlinked after a delay), we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 129.93750, -39.29289 which is equivalent to: RA(J2000) = 08h 39m 45.00s Dec(J2000) = -39d 17' 34.4" with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 104 arcseconds from the BAT onboard position, within the BAT error circle. Given the nature of the fading X-ray light-curve, we confirm this trigger as GRB 250603A, and not a new Galactic transient. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40615. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38650] Swift GRB250603.05: Global MASTER-Net observations report
by GCN Circulars 03 Jun '25

03 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40614 SUBJECT: Swift GRB250603.05: Global MASTER-Net observations report DATE: 25/06/03 02:48:43 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB250603.05 (trigger No 1320335,08h 39m 40.32s , -39d 16m 04.8s, R=0.05) errorbox 19 sec after notice time and 41 sec after trigger time at 2025-06-03 01:11:04 UT, with upper limit up to 19.2 mag. The observations began at zenith distance = 57 deg. The sun altitude is -44.5 deg. The galactic latitude b = 2 deg., longitude l = 260 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2890204 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 46 | MASTER-OAFA | C | 10 | 17.9 | 62 | MASTER-OAFA | C | 10 | 17.9 | 78 | MASTER-OAFA | C | 10 | 17.9 | 99 | MASTER-OAFA | C | 20 | 18.3 | 126 | MASTER-OAFA | C | 20 | 18.3 | 157 | MASTER-OAFA | C | 30 | 18.5 | 198 | MASTER-OAFA | C | 40 | 18.7 | 245 | MASTER-OAFA | C | 40 | 18.6 | 296 | MASTER-OAFA | C | 50 | 18.7 | 362 | MASTER-OAFA | C | 70 | 19.0 | 443 | MASTER-OAFA | C | 80 | 19.0 | 539 | MASTER-OAFA | C | 100 | 19.1 | 656 | MASTER-OAFA | C | 120 | 19.1 | 794 | MASTER-OAFA | C | 140 | 19.2 | 955 | MASTER-OAFA | C | 170 | 19.2 | 1138 | MASTER-OAFA | C | 180 | 19.2 | 1324 | MASTER-OAFA | C | 180 | 19.1 | 1511 | MASTER-OAFA | C | 180 | 19.1 | 1697 | MASTER-OAFA | C | 180 | 19.1 | 1884 | MASTER-OAFA | C | 180 | 19.1 | 2070 | MASTER-OAFA | C | 180 | 19.1 | 2257 | MASTER-OAFA | C | 180 | 19.1 | 2443 | MASTER-OAFA | C | 180 | 19.1 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40614. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38649] GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
by GCN Circulars 03 Jun '25

03 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40613 SUBJECT: GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916 DATE: 25/06/03 01:51:05 GMT FROM: David Palmer at LANL <palmer(a)lanl.gov> T. M. Parsotan (GSFC), R. Brivio (INAF-OAB), R. Gupta (NASA GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL) and C. Salvaggio (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team: At 01:10:23 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250603A (trigger=1320335). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 129.918, -39.268 which is RA(J2000) = 08h 39m 40s Dec(J2000) = -39d 16' 05" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 18 sec with a possible short spike at T0+16 sec. The peak count rate was ~1,300 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 01:12:04.7 UT, 101.7 seconds after the BAT trigger. No source was detected in the 2.5-s promptly available image. We are waiting for the full dataset to detect and localise the XRT counterpart. Although the initial 2.5s of XRT data do not show a clear X-ray afterglow, the high significance of the BAT image (7.82 sigma) gives us confidence that this is an astrophysical source. Further analysis awaits the full downlinked dataset. We note the presence of Fermi-GBM event at ~T+10 minutes (GBM trigger: 770606412) with a position consistent (to its 25Â° error radius) with this source location. Given the location of the BAT detection at 1.42Â° from the Galactic plane, persistent flux over 10 minutes would suggest a Galactic transient. If so, we would name it Swift J0839.7-3916 . Burst Advocate for this burst is T. M. Parsotan (tyler.parsotan AT nasa.gov) Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/40613. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38648] GRB 250602A: Fermi GBM Observation
by GCN Circulars 03 Jun '25

03 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40612 SUBJECT: GRB 250602A: Fermi GBM Observation DATE: 25/06/03 01:47:35 GMT FROM: Jacob Smith at Fermi-GBM Team <jrs0118(a)uah.edu> Jacob Smith (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: At 03:04:31.31 UT on 02 June 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250602A (trigger 770526276/250602128). which was also detected by Fermi-LAT (A. Holzmann Airasca, et al. 2025, GCN 40611). The Fermi GBM on-ground location is consistent with the Fermi-LAT position. The angle from the Fermi LAT boresight is 111 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 14.6 s (50-300 keV). The time-averaged spectrum from T0+0.003 to T0+8.768 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.9 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 120 +/- 10 keV. The event fluence (10-1000 keV) in this time interval is (1.7 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.0 s in the 10-1000 keV band is 5.8 +/- 0.3 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 102 +/- 22 keV, alpha = -0.7 +/- 0.3 and beta = -2.2 +/- 0.2. 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/40612. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38647] GRB 250602A: Fermi-LAT detection
by GCN Circulars 02 Jun '25

02 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40611 SUBJECT: GRB 250602A: Fermi-LAT detection DATE: 25/06/02 20:13:59 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta(a)nasa.gov> A. Holzmann Airasca (UniTrento and INFN Bari), S. Lopez (CNRS / IN2P3), R. Gupta (NASA GSFC), F. Longo (University and INFN, Trieste), N. Di Lalla (Stanford Univ.), and J. Racusin (NASA GSFC) report on behalf of the Fermi-LAT Collaboration: On June 02, 2025, Fermi-LAT detected high-energy emission from GRB 250602A, which was also detected by Fermi-GBM (trigger 770526276 / 250602128, GCN 40602). The best LAT on-ground location is found to be: RA, Dec = 111.9, 56.9 (J2000) with an error radius of 0.4 deg (90 % containment, statistical error only). This was 111 deg from the LAT boresight at the time of the GBM trigger (T0 = 03:04:31.31 UT). The data from the Fermi-LAT shows a significant increase in the event rate that is spatially and temporally correlated with the GBM emission with high significance. The photon flux above 100 MeV in the time interval 3000 - 8000 s after the GBM trigger is (8.2 ± 3.2) E-7 ph/cm2/s. The estimated photon index above 100 MeV is -2.17 ± 0.33. The highest-energy photon is a 1.6 GeV event which is observed ~ 4800 seconds after the GBM trigger. The Fermi-LAT point of contact for this burst is Rahul Gupta (rahul.gupta(a)nasa.gov) The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/40611. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38646] GRB 250602A: DDOTI Optical Upper Limit
by GCN Circulars 02 Jun '25

02 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40610 SUBJECT: GRB 250602A: DDOTI Optical Upper Limit DATE: 25/06/02 19:56:39 GMT FROM: sahil.atri(a)students.uniroma2.eu Sahil Atri (U Roma), Rosa L. Becerra (U Roma), Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM), Margarita Pereyra (UNAM) and Eleonora Troja (U Roma) report: We observed the field of GRB 250602A detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 40602) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) on the night of 2025-06-02 UTC. DDOTI observed the Fermi/GBM error region, covering about 88% of the statistical error region (Fermi GBM Team, GCN Circ. 40602). DDOTI observed the field of GRB 250602A from 04:05 UTC to 06:05 UTC (from T+1.01 h to T+ 3.02 h after the trigger) and obtained a total exposure of 50 minutes, alternating with other scientific programs. Comparing our observations to the USNO-B1 and Pan-STARRS PS1 DR2 catalogues, we detect no uncatalogued fading sources within the observed field down to a 10-sigma limiting AB magnitude of: w > 20.0 This value is not corrected for the Galactic extinction. We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/40610. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38645] GRB 250530C: Swift-BAT refined analysis
by GCN Circulars 02 Jun '25

02 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40609 SUBJECT: GRB 250530C: Swift-BAT refined analysis DATE: 25/06/02 19:11:33 GMT FROM: Mike Moss at NASA GSFC <mikejmoss3(a)gmail.com> D. Sadaula (GSFC/UMBC), S. D. Barthelmy (GSFC), R. Caputo (NASA/GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+885 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250530C (trigger #1319125) (Caputo, et al., GCN Circ. 40585). The BAT ground-calculated position is RA, Dec = 55.146, -22.457 deg which is RA(J2000) = 03h 40m 35.1s Dec(J2000) = -22d 27' 26.1" with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 96%. The mask-weighted light curve displays a complex structure with multiple dim pulses. The T90 (15-350 keV) is 42.86 +- 6.04 sec (estimated error including systematics). The time-averaged spectrum from T-29.77 to T+21.26 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.32 +- 0.17. The fluence in the 15-150 keV band is 8.5 +- 0.9 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T-0.28 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/1319125 View this GCN Circular online at https://gcn.nasa.gov/circulars/40609. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38644] GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
by GCN Circulars 02 Jun '25

02 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40608 SUBJECT: GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj DATE: 25/06/02 16:07:14 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie> A. Martin-Carrillo (UCD), B. Schneider (LAM), L. Izzo (INAF/OACN and DARK/NBI), A. de Ugarte Postigo (LAM), G. Corcoran (UCD), B. Gompertz (U. Birmingham), D. B. Malesani (DAWN/NBI and Radboud), R. H. Rasmussen (NOT and Aarhus Univ.), report on behalf of a larger collaboration. We carried out spectroscopic observations of AT2025mgj (Andreoni et al., GCN 40566), a candidate optical counterpart to GRB 250521C (Fermi GBM team, GCN 40515), using the ALFOSC camera mounted on the Nordic Optical Telescope (NOT). We obtained 4x900 s exposures starting at 21:16 UT on 2025-05-31 (10.3 days after the Fermi trigger) with a wavelength coverage of 3800-9500 AA. The spectrum shows a blue, featureless continuum, peaking at around 4500 AA. Redward of the peak, the continuum is consistent with a power law F_lambda propto lambda^-2.7. The overall shape does not resemble a power-law spectrum, which would be typical of GRB afterglows, nor a SN spectrum, given the lack of any features. Although the spectrum does not fully resemble those of dwarf novae in outbursts, the spectral energy distribution is overall consistent with previous examples (e.g. Aviles et al. 2018, doi:10.14482/INDES.30.1.303.661). In summary, our spectroscopic observations confirm that AT2025mgj is not associated with GRB250521C, as already suggested by Busmann et al. (GCN 40597) and Gillanders et al. (GCN 40605) based on photometric observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/40608. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38643] GRB 250601A: EP-FXT follow-up observation and afterglow candidates
by GCN Circulars 02 Jun '25

02 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40607 SUBJECT: GRB 250601A: EP-FXT follow-up observation and afterglow candidates DATE: 25/06/02 15:46:51 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Q. C. Liu (THU), X. Y. Zhou (PRIC), H. L. Peng (NNU), B. B. Zhang (BNU) and Y. Liu (NAO,CAS) report on behalf of the Einstein Probe (EP) team : We performed a follow-up observation of GRB 250601A (detected through on-broad trigger of Fermi/GBM, Fermi, GCN #40596, and localized by Swift/BAT, DeLaunay, GCN #40600; followed by Swift/XRT, Page et al., GCN #40604), with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation began at 2025-06-02T02:10:26 (T-TGRB ~ 8.7 hrs) with an exposure time of about 5.8 ks. Two uncatalogued sources were detected by FXT-A and FXT-B in the 3-sigma Swift/BAT error circle with a radius of 493 arcsecond centered at RA, DEC = 90.0709 deg, -57.2892 deg, as listed below (the FXT flux is taken from FXT-B module). EP J060023.3-571631 has a separation of 11.6 arcsecond from the XRT source 3, and EP J060048.7-571413 has a separation of 4.8 arcsecond from the XRT source 2. Source name | RA | DEC | Estimated Flux | SNR | Dist from Swift/BAT | | deg | deg | (erg/s/cm^2) | | offset (in arcmin) | EP J060023.3-571631 | 90.0971 | -57.2752 | 3.2(+/-1.2) x 10^-14 | 4.1 | 1.19 | EP J060048.7-571413 * | 90.2037 | -57.2368 | 1.0(+/-0.2) x 10^-13 | 9.4 | 5.33 | Note: * EP J060048.7-571413 was also detected by Swift/XRT (GCN #40604) in a ~4.6 ks observation conducted at T-TGRB ~ 4.8 hrs, with a flux of ~ 4e-13 erg/s/cm^2. The source thus exhibits a decreasing trend in the X-ray flux within the two epochs. The above observation was made with the EP-FXT instrument. 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). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES. View this GCN Circular online at https://gcn.nasa.gov/circulars/40607. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38642] GRB 250601A: Swift/XRT candidate afterglow
by GCN Circulars 02 Jun '25

02 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40606 SUBJECT: GRB 250601A: Swift/XRT candidate afterglow DATE: 25/06/02 15:13:44 GMT FROM: Chiara Salvaggio at INAF OABrera <chiara.salvaggio(a)inaf.it> C. Salvaggio (INAF-OAB), S. B. Cenko (GSFC), B. Sbarufatti (INAF-OAB) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/GBM, Swift/BAT-GUANO detected burst GRB 250601A (GCN 40596, 40600). Two XRT sources have been previously reported in GCN 40604. One of the two sources (source 2) has an eROSITA counterpart, while XRT source 3 is a new transient. Therefore we consider source 3 a candidate afterglow for GRB 250601A. Source 3: RA (J2000.0): 90.0936 = 06:00:22.47 Dec (J2000.0): -57.2778 = -57:16:40.0 Error: 5.7 arcsec (radius, 90% conf.) Count-rate: (3.6 [+1.6, -1.3])e-3 ct s^-1 Distance: 60 arcsec from Swift/BAT position. Flux: (1.00 [+0.45, -0.35])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) More Swift/XRT observations are planned to (un)confirm the afterglow detection. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00021844. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40606. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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