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

[vsnet-grb-info 39210] LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
by GCN Circulars 25 Jul '25

25 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41154 SUBJECT: LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate DATE: 25/07/25 04:48:19 GMT FROM: Hanlin Song and Junjie Zhao at Peking University and Henan Academy of Sciences <hanlin(a)stu.pku.edu.cn> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250725j during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-07-25 04:09:44.252 UTC (GPS time: 1437451802.252). The candidate was found by the GstLAL [1] analysis pipeline. S250725j is an event of interest because its false alarm rate, as estimated by the online analysis, is 4.3e-11 Hz, or about one in 1e3 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250725j The classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that at least one of the compact objects is consistent with a neutron star mass (HasNS) is <1%. [2] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [2] Both HasNS and HasRemnant consider the support of several neutron star equations of state for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. The source chirp mass falls with highest probability in the bin (11.0, 22.0) solar masses, assuming the candidate is astrophysical in origin. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [3], distributed via GCN and SCiMMA notices about 22 seconds after the candidate event time. * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [3], distributed via GCN and SCiMMA notices about 4 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,1. For the bayestar.multiorder.fits,1 sky map, the 90% credible region is well fit by an ellipse with an area of 28 deg2 described by the following DS9 region (right ascension, declination, semi-major axis, semi-minor axis, position angle of the semi-minor axis): icrs; ellipse(15h34m, -35d25m, 3.97d, 2.25d, 153.93d) Marginalized over the whole sky, the a posteriori luminosity distance estimate is 478 +/- 107 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] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. PRD 109, 042008 (2024) doi:10.1103/PhysRevD.109.042008 [2] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [3] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/41154. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39209] GRB 250725A: Enhanced Swift-XRT position
by GCN Circulars 25 Jul '25

25 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41153 SUBJECT: GRB 250725A: Enhanced Swift-XRT position DATE: 25/07/25 04:33:59 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 1662 s of XRT Photon Counting mode data and 1 UVOT images for GRB 250725A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 35.47933, -82.79122 which is equivalent to: RA (J2000): 02h 21m 55.04s Dec (J2000): -82d 47' 28.4" with an uncertainty of 2.2 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41153. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39208] GRB 250725A: Swift detection of a burst
by GCN Circulars 25 Jul '25

25 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41152 SUBJECT: GRB 250725A: Swift detection of a burst DATE: 25/07/25 02:16:19 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> P. A. Evans (U Leicester), N. P. M. Kuin (UCL-MSSL), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team: At 01:51:36 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250725A (trigger=1336720). Swift slewed to the burst after a short delay due to an observing constraint. The BAT on-board calculated location is RA, Dec 35.385, -82.784 which is RA(J2000) = 02h 21m 32s Dec(J2000) = -82d 47' 02" 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 20 sec. The peak count rate was ~8700 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 02:03:56.8 UT, 740.4 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 35.47808, -82.79131 which is equivalent to: RA(J2000) = 02h 21m 54.74s Dec(J2000) = -82d 47' 28.7" with an uncertainty of 3.5 arcseconds (radius, 90% containment). This location is 49 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (9.21 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.9 (+2.24/-1.95) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 879 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.115. Burst Advocate for this burst is P. A. Evans (pae9 AT leicester.ac.uk). 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/41152. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39207] Swift GRB250725.08: Global MASTER-Net OT detection
by GCN Circulars 25 Jul '25

25 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41151 SUBJECT: Swift GRB250725.08: Global MASTER-Net OT detection DATE: 25/07/25 02:09:35 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> D. Buckley (South African Astronomical Observatory), V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik, D. Vlasenko, G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), O.A. Gress, N.M. Budnev, O.Ershova (Irkutsk State University, API), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich (Blagoveschensk Educational State University) MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the GRB250725.08 33 sec after notice time and 53 sec after trigger time at 2025-07-25 01:52:29 UT. On our first (10s exposure) set we found 1 optical transient within Swift error-box (ra=35.3833 dec=-82.7836 r=0.05) brighter than 16.0. T-Tmid Date Time Expt. Ra Dec Mag ---------|---------------------|-------|-----------------|-----------------|------- 58 2025-07-25 01:52:29 10 (02h 21m 55.91s , -82d 47m 28.0s) 15.6 The 5-sigma upper limit has been about 16.0mag The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/41151. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39206] GRB 250725A: Fermi GBM Final Real-time Localization
by GCN Circulars 25 Jul '25

25 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41150 SUBJECT: GRB 250725A: Fermi GBM Final Real-time Localization DATE: 25/07/25 02:01:58 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 01:51:34 UT on 25 Jul 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250725A (trigger 775101099.80868 / 250725077). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 31.5, Dec = -85.4 (J2000 degrees, equivalent to J2000 02h 06m, -85d 24'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 22.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250725077/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250725077/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250725077/… View this GCN Circular online at https://gcn.nasa.gov/circulars/41150. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39205] Fermi trigger No 775101099: Global MASTER-Net observations report
by GCN Circulars 25 Jul '25

25 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41149 SUBJECT: Fermi trigger No 775101099: Global MASTER-Net observations report DATE: 25/07/25 02:00:36 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) started inspect of the Fermi GRB250725.08 (trigger No 775101099,02h 08m 43.20s , -85d 24m 00.0s, R=1.74) errorbox 13 sec after notice time and 47 sec after trigger time at 2025-07-25 01:52:22 UT, with upper limit up to 19.0 mag. The observations began at zenith distance = 64 deg. The sun altitude is -50.5 deg. MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB250725.08 errorbox 20 sec after notice time and 54 sec after trigger time at 2025-07-25 01:52:29 UT, with upper limit up to 17.0 mag. The observations began at zenith distance = 53 deg. The sun altitude is -46.5 deg. The galactic latitude b = -32 deg., longitude l = 301 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2947370 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 52 | 2025-07-25 01:52:22 | MASTER-OAFA | (02h 25m 24.07s , -83d 05m 36.9s) | C | 10 | 18.2 | 60 | 2025-07-25 01:52:29 | MASTER-SAAO | (02h 09m 37.42s , -82d 51m 47.1s) | P/ | 10 | 16.1 | 60 | 2025-07-25 01:52:29 | MASTER-SAAO | (02h 24m 15.37s , -83d 06m 32.9s) | P\\ | 10 | 16.5 | 68 | 2025-07-25 01:52:38 | MASTER-OAFA | (02h 25m 23.82s , -83d 05m 36.2s) | C | 10 | 18.3 | 89 | 2025-07-25 01:52:54 | MASTER-OAFA | (02h 25m 23.31s , -83d 05m 34.7s) | C | 20 | 18.7 | 94 | 2025-07-25 01:52:58 | MASTER-SAAO | (02h 09m 37.12s , -82d 51m 49.2s) | P/ | 20 | 16.8 | 94 | 2025-07-25 01:52:58 | MASTER-SAAO | (02h 24m 15.31s , -83d 06m 34.5s) | P\\ | 20 | 17.0 | 116 | 2025-07-25 01:53:20 | MASTER-OAFA | (02h 25m 22.79s , -83d 05m 34.2s) | C | 20 | 18.7 | 133 | 2025-07-25 01:53:37 | MASTER-SAAO | (02h 24m 14.91s , -83d 06m 36.1s) | P\\ | 20 | 17.0 | 147 | 2025-07-25 01:53:46 | MASTER-OAFA | (02h 25m 21.97s , -83d 05m 32.7s) | C | 30 | 19.0 | 183 | 2025-07-25 01:54:22 | MASTER-OAFA | (02h 25m 21.21s , -83d 05m 31.3s) | C | 30 | 19.0 | 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/41149. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39204] Swift GRB250725.08: Global MASTER-Net observations report
by GCN Circulars 25 Jul '25

25 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41148 SUBJECT: Swift GRB250725.08: Global MASTER-Net observations report DATE: 25/07/25 01:58:44 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 GRB250725.08 (trigger No 1336720,02h 21m 32.40s , -82d 47m 02.4s, R=0.05) errorbox 23 sec after notice time and 45 sec after trigger time at 2025-07-25 01:52:22 UT, with upper limit up to 18.3 mag. The observations began at zenith distance = 64 deg. The sun altitude is -50.5 deg. MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB250725.08 errorbox 30 sec after notice time and 53 sec after trigger time at 2025-07-25 01:52:29 UT, with upper limit up to 17.0 mag. The observations began at zenith distance = 53 deg. The sun altitude is -46.5 deg. The galactic latitude b = -34 deg., longitude l = 300 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2947351 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 51 | MASTER-OAFA | C | 10 | 18.2 | 58 | MASTER-SAAO | P/ | 10 | 16.1 | 58 | MASTER-SAAO | P\\ | 10 | 16.5 | 67 | MASTER-OAFA | C | 10 | 18.3 | 92 | MASTER-SAAO | P/ | 20 | 16.8 | 92 | MASTER-SAAO | P\\ | 20 | 17.0 | 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/41148. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39203] EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
by GCN Circulars 24 Jul '25

24 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41147 SUBJECT: EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz DATE: 25/07/24 17:27:21 GMT FROM: stephane.corbel(a)cea.fr Author: N. Grollimund, S. Corbel (Univ. Paris Cité & CEA Saclay), A. Coleiro, F. Cangemi (Univ. Paris Cité), J. Rodriguez (CEA Saclay) on behalf of a larger team. We observed the field of EP250702a (GCN 40906) with the MeerKAT radio telescope (proposal ID MKT-24172; PI: Corbel) using the S-band receivers, at a central frequency of 3.06 GHz. We conducted our observations from 2025-07-21 23:34:37 UTC, with a total on-source time of 11 min. We used J1939-6342 for flux and bandpass calibration, and J1822-0938 for complex gain calibration. We detect a point source with a flux density of 147 +/- 19 uJy at the position of EP250702a, with an RMS noise level of ~15 uJy/beam. Our observation, in combination with the detection of a ~100 uJy point source reported in GCN 40985, implies that the flux of EP250702a increased by ~50% at 3 GHz between 2025-07-04 and 2025-07-21. Averaging the fitted positions from all of our S-band observations, we find a refined radio position for the source: R.A. = 18:58:45.549 +/- 0.01s, Dec. = -7:52:26.54 +/- 0.15’'. This position is consistent with the radio position reported by VLA in GCN 41053, as well as the NIR and X-ray counterparts (GCNs 40924, 40906). Further observations are planned. We thank the SARAO staff for rapidly scheduling these observations. The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation. This work has made use of the "MPIfR S-band receiver system" designed, constructed and maintained by funding of the MPI für Radioastronomie and the Max-Planck-Society. View this GCN Circular online at https://gcn.nasa.gov/circulars/41147. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39202] SVOM J195836+32283 is not a real source
by GCN Circulars 24 Jul '25

24 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41146 SUBJECT: SVOM J195836+32283 is not a real source DATE: 25/07/24 15:39:42 GMT FROM: Diego Gotz at CEA <diego.gotz(a)cea.fr> D. Götz (CEA Saclay), P. Maggi (ObAS) on behalf of the SVOM/MXT Team report: A careful re-analysis of the entire MXT data set of the field of SVOM J195836+32283, including a SVOM follow-up ToO observation, started on July 22nd 2025 at 11:26:07 U.T. for a net exposure of 7 ks, indicates that the new transient source SVOM J195836+32283, announced in GCN Circular 41131, is in reality an artifact due to single reflection photons induced by the bright X-ray source Cyg X-1, which lies at 2.7 degrees from the source position, outside the MXT field of view. View this GCN Circular online at https://gcn.nasa.gov/circulars/41146. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39201] EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
by GCN Circulars 24 Jul '25

24 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41145 SUBJECT: EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz DATE: 25/07/24 06:13:17 GMT FROM: Arvind Balasubramanian <arvind6895(a)gmail.com> A. Balasubramanian (IIA), L. Resmi (IIST), D. Eappachen (IIA), S K Jagan (IIST), V. Bhalerao (IITB), B. Zhang (HKU), G.C. Anupama (IIA), H Sun (NAO, CAS), D. K. Sahu (IIA), and W. Yuan (NAO, CAS) report: We observed the field of the X-ray transient EP250702a/GRB250702 B,D,E (GCNs 40906, 40883, 40886, 40890, 40891) with upgraded Giant Metrewave Radio Telescope under the joint uGMRT ToO proposals 48_059 (PI: D. Eappachen) and 48_167 (PI: L. Resmi) on 12th July 2025 in band 5 (1.26 GHz) for a total of 4 hours starting from 19:30 UTC. In our preliminary analysis, we detect a point source with a flux density of ~90 uJy at the position of EP250702a. We used 3C48 for the flux calibration and J1911+201 for complex gain and phase calibration. The CAPTURE-CASA6 pipeline was used for data calibration and imaging. We thank the staff of the GMRT that made these observations possible. GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. View this GCN Circular online at https://gcn.nasa.gov/circulars/41145. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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