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

[vsnet-grb-info 43120] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43119] GRB 260429A: cubesat Avion detection
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44962 SUBJECT: GRB 260429A: cubesat Avion detection DATE: 26/06/17 08:30:39 GMT FROM: Andrey Bogomolov at Moscow State University <aabboogg(a)srd.sinp.msu.ru> From Andrey Bogomolov at Moscow State University <aabboogg(a)srd.sinp.msu.ru> A. Bogomolov, V. Bogomolov, A. Iyudin, S. Svertilov, N. Vasiliev on behalf of the MSU “Sozvezdie-270” team, report: At 2026-04-29 ~23:24:02 UT the short GRB 260429A (Fermi GBM detection: GCN #44425, GCN #44430, SVOM detection: GCN #44439, IPN triangulation: GCN #44459) was detected by the DeCoR-3 instrument on the cubesat Avion of the Moscow University project “Sozvezdie-270” [1]. Total amount of photons detected by Avion is 69 (energy band >30 keV), it corresponds to a fluence of ~6.2*10^(-7) erg/cm^2 in the range 30-500 keV. LC in the energy range of 30-500 keV is a single episode of ~0.5 sec duration with a maximum flux of ~16 phot/(cm^2*s). А total duration (T90) of the burst is less than ~0.5 s. The light curve obtained by Avion is available here: https://swx.sinp.msu.ru/models/grb_cat/data/pictures/GRB260429A_LC_Avion.png Parameters of GRB 260429A as well as other GRBs detected by Moscow University cubesats are listed at: https://swx.sinp.msu.ru/models/grb_cat/grb.php?lang=en Avion is one of 5 cubesats of the Moscow University project “Sozvezdie-270” [1] launched on 2023 June 27. The payload of Avion is a set of scintillation gamma-ray detectors DeCoR [2], the energy range is >30 keV, the time resolution is 0.5s. [1] Svertilov et al. 2023 https://link.springer.com/chapter/10.1007/978-3-031-50248-4_21 [2] Bogomolov et al. 2022 Universe 8, 282 https://www.mdpi.com/2218-1997/8/5/282 View this GCN Circular online at https://gcn.nasa.gov/circulars/44962. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43118] GRB 260429A: cubesat Avion detection
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44962 SUBJECT: GRB 260429A: cubesat Avion detection DATE: 26/06/17 08:30:39 GMT FROM: Andrey Bogomolov at Moscow State University <aabboogg(a)srd.sinp.msu.ru> From Andrey Bogomolov at Moscow State University <aabboogg(a)srd.sinp.msu.ru> A. Bogomolov, V. Bogomolov, A. Iyudin, S. Svertilov, N. Vasiliev on behalf of the MSU “Sozvezdie-270” team, report: At 2026-04-29 ~23:24:02 UT the short GRB 260429A (Fermi GBM detection: GCN #44425, GCN #44430, SVOM detection: GCN #44439, IPN triangulation: GCN #44459) was detected by the DeCoR-3 instrument on the cubesat Avion of the Moscow University project “Sozvezdie-270” [1]. Total amount of photons detected by Avion is 69 (energy band >30 keV), it corresponds to a fluence of ~6.2*10^(-7) erg/cm^2 in the range 30-500 keV. LC in the energy range of 30-500 keV is a single episode of ~0.5 sec duration with a maximum flux of ~16 phot/(cm^2*s). А total duration (T90) of the burst is less than ~0.5 s. The light curve obtained by Avion is available here: https://swx.sinp.msu.ru/models/grb_cat/data/pictures/GRB260429A_LC_Avion.png Parameters of GRB 260429A as well as other GRBs detected by Moscow University cubesats are listed at: https://swx.sinp.msu.ru/models/grb_cat/grb.php?lang=en Avion is one of 5 cubesats of the Moscow University project “Sozvezdie-270” [1] launched on 2023 June 27. The payload of Avion is a set of scintillation gamma-ray detectors DeCoR [2], the energy range is >30 keV, the time resolution is 0.5s. [1] Svertilov et al. 2023 https://link.springer.com/chapter/10.1007/978-3-031-50248-4_21 [2] Bogomolov et al. 2022 Universe 8, 282 https://www.mdpi.com/2218-1997/8/5/282 View this GCN Circular online at https://gcn.nasa.gov/circulars/44962. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43117] GRB260616C: MAXI/GSC detection
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44961 SUBJECT: GRB260616C: MAXI/GSC detection DATE: 26/06/17 03:18:02 GMT FROM: Wataru Iwakiri at Chiba University <iwakiri.wataru.buz(a)gmail.com> W. Iwakiri (Chiba U.),M. Serino(AGU), H. Negoro, M. Nakajima, K. Saito, T. Yokoyama, M. Wada (Nihon U.), T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, Y. Kawakubo, H. Hiramatsu, A. Yoshida (AGU), Y. Tsuboi, Y. Ishihara, H. Ogaki (Chuo U.), M. Shidatsu, C. Kang, M. Uenishi, T. Usuki, S. Yatsuzuka, H. Aoe (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara, S. Kobayashi (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), T. Kawamuro (Osaka U.), S. Yamada (Tohoku U), S. Ogawa (TUS) report on behalf of the MAXI team: The MAXI/GSC detected a bright uncatalogued X-ray transient source at 14:47 UT on June 16 2026. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (67.745 deg, 9.294 deg) = (04 30 58, +09 17 38) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.39 deg and 0.3 deg, respectively. The roll angle of long axis from the north direction is 22.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 148 +- 33 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (66.883, 10.254) deg = (04 27 31, +10 15 14) (J2000) (66.471, 9.596) deg = (04 25 53, +09 35 45) (J2000) (68.604, 8.290) deg = (04 34 24, +08 17 23) (J2000) (69.019, 8.945) deg = (04 36 04, +08 56 42) (J2000) A marginal excess of about 50 mCrab may be present in the previous and next MAXI scans at 13:14 UT and 16:20 UT, respectively. However, these scans were obtained during a period of large background variations, and the significance of the excesses is currently unclear. The possible presence of X-ray activity over multiple scans raises the possibility that this event is a new X-ray transient source rather than a GRB. We therefore tentatively name the source MAXI J0430+092. Multi-wavelength follow-up observations are encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/44961. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43116] GRB260616C: MAXI/GSC detection
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44961 SUBJECT: GRB260616C: MAXI/GSC detection DATE: 26/06/17 03:18:02 GMT FROM: Wataru Iwakiri at Chiba University <iwakiri.wataru.buz(a)gmail.com> W. Iwakiri (Chiba U.),M. Serino(AGU), H. Negoro, M. Nakajima, K. Saito, T. Yokoyama, M. Wada (Nihon U.), T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, Y. Kawakubo, H. Hiramatsu, A. Yoshida (AGU), Y. Tsuboi, Y. Ishihara, H. Ogaki (Chuo U.), M. Shidatsu, C. Kang, M. Uenishi, T. Usuki, S. Yatsuzuka, H. Aoe (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara, S. Kobayashi (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), T. Kawamuro (Osaka U.), S. Yamada (Tohoku U), S. Ogawa (TUS) report on behalf of the MAXI team: The MAXI/GSC detected a bright uncatalogued X-ray transient source at 14:47 UT on June 16 2026. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (67.745 deg, 9.294 deg) = (04 30 58, +09 17 38) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.39 deg and 0.3 deg, respectively. The roll angle of long axis from the north direction is 22.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 148 +- 33 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (66.883, 10.254) deg = (04 27 31, +10 15 14) (J2000) (66.471, 9.596) deg = (04 25 53, +09 35 45) (J2000) (68.604, 8.290) deg = (04 34 24, +08 17 23) (J2000) (69.019, 8.945) deg = (04 36 04, +08 56 42) (J2000) A marginal excess of about 50 mCrab may be present in the previous and next MAXI scans at 13:14 UT and 16:20 UT, respectively. However, these scans were obtained during a period of large background variations, and the significance of the excesses is currently unclear. The possible presence of X-ray activity over multiple scans raises the possibility that this event is a new X-ray transient source rather than a GRB. We therefore tentatively name the source MAXI J0430+092. Multi-wavelength follow-up observations are encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/44961. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43115] GRB 260616A: Fermi-LAT detection
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44960 SUBJECT: GRB 260616A: Fermi-LAT detection DATE: 26/06/16 23:28:45 GMT FROM: N. Di Lalla at Stanford University <niccolo.dilalla(a)stanford.edu> S. Lopez (CNRS / IN2P3), N. Di Lalla (Stanford University), R. Gupta (NASA/GSFC), F. Longo (University and INFN, Trieste), D. Depalo (Politecnico & INFN Bari), N. Omodei (Stanford University), and J. Valverde (Marquette University) report on behalf of the Fermi-LAT collaboration: At 03:21:54 UT on 16 June 2026, Fermi-LAT detected high-energy emission from GRB 260616A, which was also detected by Fermi-GBM (trigger 803272919/ 260616140, GCN #44948). The best LAT on-ground location is found to be RA, Dec = 93.53, -32.07 (J2000) with an error radius of 0.54 deg (90 % containment, statistical error only). This was 111 deg from the LAT boresight at the time of the trigger. The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the trigger with high significance. The photon flux above 100 MeV in the time interval 500 - 3000 s after the GBM trigger is (1.8 ± 0.6)E-6 ph/cm2/s. The estimated photon index above 100 MeV is -2.4 ± 0.4. The highest energy photon has an energy of 724 MeV and occurs at 1690 s after trigger time. The Fermi-LAT point of contact for this burst is Samantha López (lpsamy18(a)gmail.com) 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/44960. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43114] GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44959 SUBJECT: GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening DATE: 26/06/16 20:04:25 GMT FROM: Dimple at University of Birmingham <dimplepanchal96(a)gmail.com> Dimple (U. Birmingham), B. P. Gompertz (U. Birmingham), A. Bochenek (LJMU), D. A. Perley (LJMU), D. O’Neill (U. Birmingham), D. B. Malesani (DAWN/NBI and Radboud) and A. Martin-Carrillo (UCD) report on behalf of a larger collaboration: We have conducted nightly griz observations of the optical afterglow (O’Neill et al., GCNs 44903, 44914; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCNs 44910, 44955; Akl et al., GCNs 44911, 44930; Moskvitin et al., GCNs 44918, 44929; Jackson-Horne et al., GCN 44919; Izzo et al., GCN 44920; Li et al., GCN 44921; Bochenek et al., GCNs 44927, 44932; Pankov et al., GCN 44946; Angulo et al., GCN 44958) of GRB 260610B (Fermi GBM Team, GCN 44901; Yu et al., GCN 44944) with the IO:O optical camera on the 2m robotic Liverpool Telescope. In our two most recent epochs we detect the optical rebrightening first suggested by Gillanders et al. between their t-t0 = 3.3 and 4.3 day epochs (GCN 44955) in all filters. The measured g- and r-band AB magnitudes are: | t-t0(d) | filter | mag | | 3.99 | g | 21.71 ± 0.07 | | 3.97 | r | 21.34 ± 0.07 | | 5.08 | g | 21.49 ± 0.08 | | 5.09 | r | 21.02 ± 0.07 | These observations indicate that GRB 260610B continues experiencing a rebrightening episode beyond 5 days after trigger. We detect no change in g-r colour when comparing our observations to the earliest Liverpool Telescope epoch (Bochenek & Perley, GCN 44927), suggesting an achromatic rebrightening, inconsistent with expectations for an emerging supernova. The above magnitudes are calibrated against nearby Pan-STARRS objects and are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44959. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43113] GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44958 SUBJECT: GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening DATE: 26/06/16 19:58:21 GMT FROM: Rosa Leticia Becerra Godínez at Instituto de Astronomía, UNAM <rbecerra(a)astro.unam.mx> Camila Angulo (UNAM), Marion Guelfand (CPPM), Rosa L. Becerra (UNAM), Nikos Mandarakas (LAM), Antonio de Ugarte Postigo (LAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Dalya Akl (NYUAD), Jean-Luc Atteia (IRAP),Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), and Alan M. Watson (UNAM) report: We reimaged the field of AT 2026owq (O'Neill et al., GCN Circ. 44903, 44914; Watson et al., GCN Circ. 44905; Zhu et al., GCN Circ. 44909; Gillanders et al., GCN Circ. 44910; Akl et al., GCNs 44911, 44930; Moskvitin et al., GCNs 44918, 44929; Jackson-Horne et al., GCN Circ. 44919; Izzo et al., GCN Circ. 44920; Li et al., GCN Circ. 44921; Bochenek et al., GCNs 44927, 44932; Pankov et al., GCN Circ. 44946; Gillanders et al., GCN Circ. 44995), which is the optical counterpart of GRB 260610B (Fermi GBM team, GCN Circ. 44901), using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. In our latest epoch, we observed from 2026-06-16 07:26 to 08:41 UTC (from 5.32 to 5.37 days after the GRB trigger) and obtained 6, 4, 5, and 14 minutes of exposure in the g, r, i, and z filters, respectively. The data were reduced, coadded, calibrated, and analysed with the COLIBRÍ pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR2 catalog, is in the AB system, and is not corrected for Galactic extinction. We detect the source AT2026owq with preliminary magnitudes of: g = 21.52 +/- 0.13, r = 21.02 +/- 0.10, i = 20.69 +/- 0.09, z = 20.43 +/- 0.10. Compared with previous observations reported for this event, we also observe the rebrightening/flattening first reported by the Pan-STARRS team (Gillanders et al., GCN Circ. 44995), beginning approximately 80 hours after the trigger and visible in all of our filters. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and México (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, México. View this GCN Circular online at https://gcn.nasa.gov/circulars/44958. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43112] GRB GRB260614A: AstroSat CZTI detection
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44957 SUBJECT: GRB GRB260614A: AstroSat CZTI detection DATE: 26/06/16 19:06:22 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> A. Goyal (IITB), A. Arya (IITB), Harsha K. H. (IUCAA), S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), G. Waratkar (Caltech/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 GRB 260614A which was also detected by Fermi (GBM team, GCN Circ. 44935), GECAM (Xing-Hao Luo et. al., GCN Circ. 44940). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2026-06-14 10:06:15.64. The measured peak count rate associated with the burst is 57 (+28, -14) counts/s above the background in the combined data of three quadrants (out of four), with a total of 391 (+196, -206) counts. The local mean background count rate was 221 (+3, -3) counts/s. We measure a T90 of 20 (+3, -12) s from the cumulative CZT light curve. CZTI data products like interactive and downloadable light curves for this GRB can be found at:https://astrosat.iucaa.in/cift/cift_products/ET20260614T100614/ET20260614T100614_details.html 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/44957. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43111] EP260616a: EP-WXT detection of a fast X-ray transient
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44956 SUBJECT: EP260616a: EP-WXT detection of a fast X-ray transient DATE: 26/06/16 16:27:09 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> D. Y. Li (NAO, CAS), J. H. Wu (GZHU), T. Y. Liu, Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe team: We report on the detection of a fast X-ray transient, designated EP260616a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient event started at 2026-06-16T07:05:16 (UTC). The position of the source is R.A. = 256.059 deg, DEC = -32.305 deg (J2000) with an uncertainty of 2.2 arcmin in radius (90% C.L. statistical and systematic). No onboard alert or automated X-ray follow-up observation was triggered at this position due to the low Galactic latitude. The start time and the position of the transient is consistent with that of GRB 260616B detected by Fermi/GBM (GCN 44953). The average 0.5-4 keV spectrum can be fitted by an absorbed power law with a photon index of 1.8 (+0.3/-0.3). The column density is fixed at the Galactic value of 3.4 x 10^21 cm^-2. The derived average unabsorbed 0.5-4 keV flux is 4.1 (+/-0.5) x 10^-10 erg/s/cm^2. The peak flux is around 3.4 x 10^-9 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Follow-up observations by EP-FXT will be arranged. 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/44956. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0