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[vsnet-grb-info 40905] GRB 251125B: Fermi GBM Final Real-time Localization
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42836 SUBJECT: GRB 251125B: Fermi GBM Final Real-time Localization DATE: 25/11/25 20:34:30 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 20:23:45 UT on 25 Nov 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251125B (trigger 785795030.880336 / 251125850). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 237.5, Dec = 57.5 (J2000 degrees, equivalent to J2000 15h 50m, 57d 30'), with a statistical uncertainty of 3.1 degrees. The angle from the Fermi LAT boresight is 45.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251125850/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251125850/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251125850/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42836. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40904] EP251124b: Global MASTER-Net observations report
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42835 SUBJECT: EP251124b: Global MASTER-Net observations report DATE: 25/11/25 15:54:29 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-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP251124b ( EP Team et al., GCN 42834) errorbox 186 sec after notice time and 80214 sec after trigger time at 2025-11-25 15:39:56 UT, with upper limit up to 15.3 mag. The observations began at zenith distance = 68 deg. The sun altitude is -21.6 deg. The galactic latitude b = 17 deg., longitude l = 162 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3051627 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 80245 | 2025-11-25 15:39:56 | MASTER-Kislovodsk | (06h 13m 18.49s , +52d 39m 59.0s) | C | 60 | 15.3 | 80245 | 2025-11-25 15:39:56 | MASTER-Kislovodsk | (06h 13m 25.72s , +52d 17m 24.8s) | C | 60 | 13.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/42835. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40903] EP251124b: EP-WXT detection of a fast X-ray transient
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42834 SUBJECT: EP251124b: EP-WXT detection of a fast X-ray transient DATE: 25/11/25 15:33:27 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J. P. Feng, B. Zhang (USTC), X. X. Sun (NAO, CAS), Q. C. Liu (THU), D. F. Hu, Y. L. Hua (PMO, CAS), C. C. Jin (NAO, CAS), on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP251124b. The transient was detected by EP-WXT at 2025-11-24T17:23:02 (UTC). The WXT position of the source is R.A. = 93.493 deg, DEC = 52.694 deg (J2000) with an uncertainty of 2.6 arcmin in radius (90% C.L. statistical and systematic). The transient event lasts for ～240 seconds, the average 0.5-4 keV spectrum can be fitted with an absorbed power-law model, with fixed galactic nH of 1.51 x 10^21 cm^-2 and a photon index of 1.72 (-0.78, +0.83). The unabsorbed average 0.5-4 keV flux is estimated to be 2.97 (-0.95, +1.51) x 10^-10 erg/s/cm2. The peak flux reaches around 4.8e-9 erg/s/cm2. The uncertainties are at the 90% confidence level for the above parameters. The transient was discovered by the ground analysis of the delayed telemetry data. The follow-up observation of EP-FXT has been scheduled. 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/42834. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40902] EP251124a: Xinglong GWAC-F60A optical observation
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42833 SUBJECT: EP251124a: Xinglong GWAC-F60A optical observation DATE: 25/11/25 09:48:40 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, L. P. Xin, Y. L. Qiu, C. Wu, J. Wang, X. H. Han, P. P. Zhang, H. L. Li, Z. H. Yao, J. Y. Wei (NAOC) report on behalf of SVOM follow-up team: We observed the field of EP251124a triggered by EP/WXT (Zhou et al., GCN 42816; GCN 42832) using the GWAC-F60A telescope located at Xinglong observatory, China. We obtained a series of frames in R-band, starting at 2025-11-24T11:22:30 UTC, about 12.42 minutes after the trigger. No uncataloged sources were detected in our single or stacked images within the error box provided by EP/FXT (Zhou et al., GCN 42816) and Swift/XRT (Evans et al., GCN 42827), the three sigma limit is: mid-time | exposure time | band | upper limit ----------- -|-----------------|-------|------------- 19.5 minutes | 10*50 sec | R | 19.5 mag None of the known sources showed significant brightness variations within EP/FXT and Swift/XRT errorbox compared with USNO-B1.0 catalog. Our results are consistent with GIT (Mohan et al., GCN 42817), Kinder (Wang et al., GCN 42824), MASTER (Lipunov et al., GCN 42828), and NOT (van Hoof et al., GCN 42829). Our photometry was not corrected for Galactic extinction. We thank the staff at Xinglong observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/42833. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40901] EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42832 SUBJECT: EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7 DATE: 25/11/25 09:23:49 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H.Zhou (PMO, CAS), J.-Y. Cao (IHEP), H.-N. Yang, and Z.-X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: Refined analysis of the WXT data shows that EP251124a (GCN #42816) is associated with the Cluster of Galaxies AWM 7. The estimated flux is ~6.17e-11 erg/cm2/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/42832. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40900] Fermi GRB 251125A: Global MASTER-Net observations report
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42831 SUBJECT: Fermi GRB 251125A: Global MASTER-Net observations report DATE: 25/11/25 01:15:21 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-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 251125A ( Fermi GBM team, GCN 42830) errorbox 29 sec after notice time and 35 sec after trigger time at 2025-11-25 01:00:14 UT, with upper limit up to 18.2 mag. The observations began at zenith distance = 58 deg. The sun altitude is -35.2 deg. MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 251125A errorbox 58 sec after notice time and 64 sec after trigger time at 2025-11-25 01:00:43 UT, with upper limit up to 19.3 mag. The observations began at zenith distance = 65 deg. The sun altitude is -25.5 deg. The galactic latitude b = 44 deg., longitude l = 259 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3051146 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 40 | 2025-11-25 01:00:14 | MASTER-Kislovodsk | (10h 47m 41.84s , -02d 16m 18.0s) | C | 10 | 16.6 | 69 | 2025-11-25 01:00:43 | MASTER-SAAO | (10h 46m 14.24s , -02d 25m 57.0s) | C | 10 | 17.6 | 69 | 2025-11-25 01:00:43 | MASTER-SAAO | (10h 48m 05.24s , -02d 41m 35.6s) | C | 10 | 17.7 | 70 | 2025-11-25 01:00:44 | MASTER-Kislovodsk | (10h 47m 41.88s , -02d 16m 25.2s) | C | 10 | 16.7 | 103 | 2025-11-25 01:01:12 | MASTER-SAAO | (10h 46m 14.21s , -02d 25m 59.4s) | C | 20 | 18.1 | 103 | 2025-11-25 01:01:12 | MASTER-SAAO | (10h 48m 05.20s , -02d 41m 35.0s) | C | 20 | 18.5 | 106 | 2025-11-25 01:01:14 | MASTER-Kislovodsk | (10h 47m 41.94s , -02d 16m 40.7s) | C | 20 | 17.2 | 147 | 2025-11-25 01:01:51 | MASTER-SAAO | (10h 46m 14.28s , -02d 25m 58.7s) | C | 30 | 18.5 | 147 | 2025-11-25 01:01:51 | MASTER-SAAO | (10h 48m 05.23s , -02d 41m 33.9s) | C | 30 | 18.8 | 146 | 2025-11-25 01:01:54 | MASTER-Kislovodsk | (10h 47m 41.97s , -02d 16m 43.6s) | C | 20 | 17.2 | 181 | 2025-11-25 01:01:54 | MASTER-Kislovodsk | (10h 47m 41.96s , -02d 16m 43.7s) | C | 90 | 18.2 | Coadd 195 | 2025-11-25 01:02:38 | MASTER-Kislovodsk | (10h 47m 41.94s , -02d 16m 44.6s) | C | 30 | 17.5 | 201 | 2025-11-25 01:02:40 | MASTER-SAAO | (10h 46m 14.26s , -02d 25m 58.4s) | C | 40 | 18.8 | 201 | 2025-11-25 01:02:40 | MASTER-SAAO | (10h 48m 05.20s , -02d 41m 33.1s) | C | 40 | 18.9 | 250 | 2025-11-25 01:03:28 | MASTER-Kislovodsk | (10h 47m 41.92s , -02d 16m 45.1s) | C | 40 | 17.8 | 265 | 2025-11-25 01:03:39 | MASTER-SAAO | (10h 46m 14.24s , -02d 25m 58.5s) | C | 50 | 18.9 | 265 | 2025-11-25 01:03:39 | MASTER-SAAO | (10h 48m 05.17s , -02d 41m 32.9s) | C | 50 | 19.0 | 315 | 2025-11-25 01:04:28 | MASTER-Kislovodsk | (10h 47m 41.90s , -02d 16m 45.0s) | C | 50 | 17.8 | 315 | 2025-11-25 01:04:28 | MASTER-Kislovodsk | (10h 52m 01.99s , -02d 40m 47.8s) | C | 50 | 12.0 | 340 | 2025-11-25 01:04:48 | MASTER-SAAO | (10h 46m 14.20s , -02d 25m 58.8s) | C | 60 | 19.1 | 340 | 2025-11-25 01:04:48 | MASTER-SAAO | (10h 48m 05.12s , -02d 41m 32.9s) | C | 60 | 19.3 | 395 | 2025-11-25 01:05:38 | MASTER-Kislovodsk | (10h 47m 41.86s , -02d 16m 44.4s) | C | 70 | 18.1 | 480 | 2025-11-25 01:07:08 | MASTER-Kislovodsk | (10h 51m 53.78s , -02d 19m 53.0s) | C | 60 | 17.8 | 560 | 2025-11-25 01:08:28 | MASTER-Kislovodsk | (10h 51m 23.73s , -00d 26m 51.2s) | C | 60 | 18.0 | 639 | 2025-11-25 01:09:48 | MASTER-Kislovodsk | (10h 36m 38.70s , -02d 21m 11.9s) | C | 60 | 17.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/42831. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40899] GRB 251125A: Fermi GBM Final Real-time Localization
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42830 SUBJECT: GRB 251125A: Fermi GBM Final Real-time Localization DATE: 25/11/25 01:09:58 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 00:59:38 UT on 25 Nov 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251125A (trigger 785725183.783164 / 251125041). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 161.9, Dec = -7.6 (J2000 degrees, equivalent to J2000 10h 47m, -7d 35'), with a statistical uncertainty of 7.6 degrees. The angle from the Fermi LAT boresight is 37.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251125041/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251125041/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251125041/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42830. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40898] EP251124a: NOT r- and z-band optical upper limits
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42829 SUBJECT: EP251124a: NOT r- and z-band optical upper limits DATE: 25/11/24 23:32:52 GMT FROM: Agnes van Hoof at Radboud University <agnes.vanhoof(a)ru.nl> A. P. C. van Hoof (Radboud), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), J. N. D. van Dalen (Radboud), P. G. Jonker (Radboud), Shilpa Bijavara Seshashayana (NOT and Malmo Univ.), report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP251124a (Zhou et al., GCN 42816) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were obtained in the r (3x300 s) and z (3x200 s) bands, starting on 2025-11-24 at 21:34:32 UTC (10.4 hr after the WXT trigger). No new source is detected within any of the X-ray error circles provided by EP/FXT (Zhou et al., GCN 42816) and Swift/XRT (Evans et al., GCN 42827). From the stacked images we obtain the following 3-sigma upper limits: r > 24.4 z > 23.0 These upper limits are in AB magnitudes and were calibrated using nearby stars from the Pan-STARRS catalog and are not corrected for Galactic extinction. The upper limits are consistent with previously reported upper limits in r-band (Mohan et al., GCN 42817; Wang et al., GCN 42824). View this GCN Circular online at https://gcn.nasa.gov/circulars/42829. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40897] EP251124a: Global MASTER-Net observations report
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42828 SUBJECT: EP251124a: Global MASTER-Net observations report DATE: 25/11/24 21:09:29 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-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP251124a ( EP Team et al., GCN 42816) errorbox 21097 sec after notice time and 28845 sec after trigger time at 2025-11-24 19:10:50 UT, with upper limit up to 18.2 mag. The observations began at zenith distance = 7 deg. The sun altitude is -58.5 deg. The galactic latitude b = -15 deg., longitude l = 147 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3050758 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 28935 | 2025-11-24 19:10:50 | MASTER-Kislovodsk | (02h 53m 11.63s , +41d 55m 39.9s) | C | 180 | 18.2 | 28935 | 2025-11-24 19:10:50 | MASTER-Kislovodsk | (02h 53m 47.32s , +41d 32m 52.8s) | C | 180 | 12.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/42828. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40896] EP251124a: Swift-XRT observations
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42827 SUBJECT: EP251124a: Swift-XRT observations DATE: 25/11/24 17:36:48 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi (INAF-IASFPA) , A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N. Burrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro (INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Einstein Probe/WXT-detected source EP251124a, collecting 2.5 ks of Photon Counting (PC) mode data between T0+5.1 ks and T0+11 ks after the trigger. The field is full of extended emission due to a cluster of galaxies. We have detected 3 sources. These have been automatically classified as follows: * 0 likely counterparts * 0 candidate counterparts * 3 uncatalogued X-ray sources * 0 known X-ray sources Uncatalogued X-ray sources -------------------------- Source 2 (SWIFT J025449.9+413724): ================================== RA (J2000.0): 43.7081 = 02 54 49.94 Dec (J2000.0): +41.6234 = +41 37 24.2 Error: 5.4 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 3.0 arcmin from the Einstein Probe/WXT position. Mean rate: (-1.0 +/- -1.0)e0 ct s^-1 Mean flux: (-2.1 +/- -2.1)e-11 erg cm^-2 s^-1 Peak rate: (8.5 [+3.4, -3.0])e-3 ct s^-1 Peak flux: (1.80 [+0.71, -0.63])e-13 erg cm^-2 s^-1 ECF: 2.12e-11 erg cm^-2 ct^-1 assuming NH=2.22e+22 cm^-2, gamma=5.93 determined from a spectral fit. LSXPS UL: 1.0e-02 ct/sec, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. A SIMBAD object `2MASX J02544959+4137278' is 5.1" away. There is 1 2MASS object within the source's 3-sigma error radius. Source 3 (SWIFT J025510.5+413444): ================================== RA (J2000.0): 43.7940 = 02 55 10.56 Dec (J2000.0): +41.5789 = +41 34 44.0 Error: 5.7 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 2.8 arcmin from the Einstein Probe/WXT position. Mean rate: (-1.0 +/- -1.0)e0 ct s^-1 Mean flux: (-1.6 +/- -1.6)e-10 erg cm^-2 s^-1 Peak rate: (3.8 [+2.5, -2.2])e-3 ct s^-1 Peak flux: (6.0 [+4.0, -3.4])e-13 erg cm^-2 s^-1 ECF: 1.57e-10 erg cm^-2 ct^-1 assuming NH=2.84e+21 cm^-2, gamma=0.31 determined from a spectral fit. LSXPS UL: 1.6e-02 ct/sec, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. Source 6 (SWIFT J025445.0+413429): ================================== RA (J2000.0): 43.6876 = 02 54 45.02 Dec (J2000.0): +41.5749 = +41 34 29.6 Error: 5.4 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 2.0 arcmin from the Einstein Probe/WXT position. Mean rate: 0.0245 [+0.0084, -0.0071] ct s^-1 Mean flux: (8.9 [+3.1, -2.6])e-13 erg cm^-2 s^-1 Peak rate: 0.043 [+0.022, -0.018] ct s^-1 Peak flux: (1.56 [+0.81, -0.66])e-12 erg cm^-2 s^-1 ECF: 3.63e-11 erg cm^-2 ct^-1 assuming NH=1.20e+21 cm^-2, gamma=1.87 determined from a spectral fit. LSXPS UL: 3.2e-02 ct/sec, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. All fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated. 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/EP/EP_FIELD00083. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42827. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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