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

[vsnet-grb-info 42970] GRB 260527A/EP260527a: 6 GHz VLA observations
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44838 SUBJECT: GRB 260527A/EP260527a: 6 GHz VLA observations DATE: 26/06/05 10:05:25 GMT FROM: muskan.yadav(a)students.uniroma2.eu M. Yadav, R. Ricci, E. Troja (U Rome) report: We observed the field of EP260527a (Yang et al., GCN 44718), likely associated with the short GRB 260527A (Svinkin et al., GCN 44722, Yu et al., GCN 44724; Kawakubo et al., GCN 44726, Wang et al., GCN 44735, Svinkin et al., GCN 44744, Cheung et al., GCN 44757) with Very Large Array in C-band at the centre frequency of 6 GHz with a bandwidth of 4 GHz in two epochs on May 29th 2026 (2.01 days after the trigger) and June 4th 2026 (8.05 days after the trigger). Data were calibrated and imaged using standard procedures in CASA (6.6.6.18). 1331+305 (3C286) was used for flux density and bandpass calibration and J1224+0330 was used for complex gain calibration. The radio source reported by Schroeder et al. (GCN 44740) is detected in our first epoch at a consistent position and flux level, and is seen to fade below detection threshold in our second epoch, yielding a preliminary 3-sigma upper limit of ~30 uJy/beam. We therefore confirm this source as the radio counterpart of EP260527a. We thank the VLA staff for executing the observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44838. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42969] GRB 260604C: GOTO detections of the optical afterglow
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44837 SUBJECT: GRB 260604C: GOTO detections of the optical afterglow DATE: 26/06/05 09:47:43 GMT FROM: Ben Gompertz at U of Birmingham <b.gompertz(a)bham.ac.uk> B. P. Gompertz, S. Moran, D. O’Neill, A. Kumar, G. Ramsay, R. Starling, K. Ackley, M. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson, T. Killestein and M. Pursiainen, on behalf of the GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to GRB 260604C, discovered by Fermi/GBM and SVOM (Fermi GBM Team, GCN 44822; Gotz et al., GCN 44823). Observations were taken in the GOTO-L filter (400 - 700nm) with 4x90s exposures. Images were processed immediately after acquisition using the GOTO pipeline. The optical counterpart (Lipunov et al., GCN 44827; Konno et al., GCN 44828; Zhu et al., GCN 44832, Becerra et al., GCN 44834; Hellot et al., GCN 44835) was detected in three epochs: | mid-time(UT) | t-t0(hr) | ABmag | | 2026-06-04 23:46:15 | 3.46 | 18.45 ± 0.04 | | 2026-06-05 00:54:05 | 4.59 | 18.70 ± 0.08 | | 2026-06-05 02:00:28 | 5.70 | 19.06 ± 0.12 | Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/44837. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42968] GRB 260604C: Correction to GCN 44828
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44836 SUBJECT: GRB 260604C: Correction to GCN 44828 DATE: 26/06/05 08:46:15 GMT FROM: Ruslan Konno at Weizmann Institute of Science <ruslankonno(a)gmail.com> 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), S. Fainer (WIS), A. Krassilchtchikov (WIS), Y. M. Shani (WIS), E. Segre (WIS), A. Gal-Yam (WIS), and S. Spitzer (WIS) report on behalf of the LAST Collaboration. This is a correction to the GCN Circular "GRB 260604C: LAST detection of optical counterpart candidate" (GCN 44828). The photometry within the circular was erroneously listed in the reverse order. The correct photometry is | Tmid-T0 (h) | Mag (AB) | | ------------ | ------------ | | 0.33 | 16.42 +/- 0.02 | | 0.45 | 16.63 +/- 0.02 | | 0.57 | 16.85 +/- 0.02 | | 0.75 | 17.12 +/- 0.02 | A correction of the archival circular has been requested, apologies for any confusion. View this GCN Circular online at https://gcn.nasa.gov/circulars/44836. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42967] GRB 260604C: Kilonova-Catcher optical afterglow detection
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44835 SUBJECT: GRB 260604C: Kilonova-Catcher optical afterglow detection DATE: 26/06/05 08:27:06 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> R. Hellot, D. Christen, M. Freeberg (KNC), D. Turpin (CEA-Saclay/Irfu), C. Andrade(UMN), S. Antier (IJCLab), M. Coughlin (UMN),S. Karpov (FZU), P. Hello (IJCLAB), M. Pillas (IAP) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 260604C detected by Fermi/GBM (Fermi GBM team, GCN 44822) and SVOM (Götz et al., GCN 44823) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with a CDK17 telescope located at AITP San Pedro Chile Observatory operated by R. Hellot and D. Cristen and the A1 CDK17 telescope located at the Alnitak Observatory operated by M. Freeberg. Our observations started at TGRB+1.0 hours and were taken with sdss-r and Rc filters. In our stacked frames, subtracted from the PanSTARRS DR2 template image, we clearly detect the optical counterpart (Lipunov et al., GCN 44825; GCN 44826; GCN 44827; Konno et al., GCN 44828; Zhu et al., GCN 44832; Becerra et al., GCN 44834). We report part of our follow-up results in the table below : | Tmid-TGRB (hrs) | Exp (s) | Filter | Magnitude | Instrument | | ------------ | --------- |------------ |---------------- |------------ | | 1.47 | 15 x 180s | Rc (Vega) | 17.43 +/- 0.03 | A1/CDK17 | | 3.17 | 8 x 300s | r (AB) | 18.41 +/- 0.05 | AITP/CDK17 | | 4.01 | 11 x 180s | Rc (Vega) | 18.43 +/- 0.06 | A1/CDK17 | All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the sloan filters were calibrated using the PanSTARRS DR1 catalog. Images obtained with the Johnson-cousins filters were calibrated using the GAIA DR3 synphot catalog. We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/) View this GCN Circular online at https://gcn.nasa.gov/circulars/44835. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42966] GRB 260604C: Kilonova-Catcher optical afterglow detection
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44835 SUBJECT: GRB 260604C: Kilonova-Catcher optical afterglow detection DATE: 26/06/05 08:27:06 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> R. Hellot, D. Christen, M. Freeberg (KNC), D. Turpin (CEA-Saclay/Irfu), C. Andrade(UMN), S. Antier (IJCLab), M. Coughlin (UMN),S. Karpov (FZU), P. Hello (IJCLAB), M. Pillas (IAP) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 260604C detected by Fermi/GBM (Fermi GBM team, GCN 44822) and SVOM (Götz et al., GCN 44823) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with a CDK17 telescope located at AITP San Pedro Chile Observatory operated by R. Hellot and D. Cristen and the A1 CDK17 telescope located at the Alnitak Observatory operated by M. Freeberg. Our observations started at TGRB+1.0 hours and were taken with sdss-r and Rc filters. In our stacked frames, subtracted from the PanSTARRS DR2 template image, we clearly detect the optical counterpart (Lipunov et al., GCN 44825; GCN 44826; GCN 44827; Konno et al., GCN 44828; Zhu et al., GCN 44832; Becerra et al., GCN 44834). We report part of our follow-up results in the table below : | Tmid-TGRB (hrs) | Exp (s) | Filter | Magnitude | Instrument | | ------------ | --------- |------------ |---------------- |------------ | | 1.47 | 15 x 180s | Rc (Vega) | 17.43 +/- 0.03 | A1/CDK17 | | 3.17 | 8 x 300s | r (AB) | 18.41 +/- 0.05 | AITP/CDK17 | | 4.01 | 11 x 180s | Rc (Vega) | 18.43 +/- 0.06 | A1/CDK17 | All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the sloan filters were calibrated using the PanSTARRS DR1 catalog. Images obtained with the Johnson-cousins filters were calibrated using the GAIA DR3 synphot catalog. We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/) View this GCN Circular online at https://gcn.nasa.gov/circulars/44835. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42965] GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44834 SUBJECT: GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations DATE: 26/06/05 04:19:38 GMT FROM: Rosa Leticia Becerra Godínez at Instituto de Astronomía, UNAM <rbecerra(a)astro.unam.mx> Rosa L. Becerra (UNAM), Sarah Antier (IJCLAB), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), 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), Antonio de Ugarte Postigo (LAM), and Sofia Bisero (CEA Saclay) report: We imaged the field of GRB 260604C (Fermi Team, GCN Circ. 44822, Gotz et al., GCN Circ. 44823) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-06-05 03:41 to 03:51 UTC (from 7.34 to 7.52 hours after the trigger) and obtained 3, 3, 3, 3 and 6 minutes of exposure in the g, r, i, z and y filters respectively. The data were reduced, coadded and analysed with the ASU COLIBRÍ pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We detected the optical counterpart reported by Lipunov et al. (GCN Circ. 44827), at preliminary magnitudes of: g = 19.69 +/- 0.04 r = 19.56 +/- 0.03 i = 19.38 +/- 0.04 z = 19.21 +/- 0.06 y = 19.26 +/- 0.08 These values are consistent with those reported by MASTER (Lipunov et al., GCN Circ. 44827), LAST (Gotz et al., GCN Circ. 44828), Jinshan (Zhu et al., GCN Circ. 44832). Comparing to the observations with LAST at about 0.75 hours, we estimate a temporal decay index of about -1.2. Moreover, the detections in all filters and the values in the colours, suggest a low-redshift event. We also notice the presence of a red galaxy with g = 21.69 +/- 0.02, r = 20.15 +/- 0.01, z = 19.10 +/- 0.01 and a photo-z = 0.343 +/- 0.031 (DESI Legacy Survey catalog; Dey et al. 2019) at 18.9" from the optical counterpart position. This corresponds to a Pcc ≈ 0.16 and a projected offset of 95 kpc, which makes an association very unlikely. We also comment that the light curve and analysis reported by the Fermi/GBM Team (GCN Circ. 44822, 44831) suggests hard emission with a duration that cannot completely rule out a Type I burst. Further observations and analysis are ongoing. We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/44834. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42964] The EP-WXT trigger 01709266798 is likely a flaring star
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44833 SUBJECT: The EP-WXT trigger 01709266798 is likely a flaring star DATE: 26/06/05 03:12:02 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.-Z. Li (YNAO), X. Tian (GXU), C.-L. Guo and C.-C. Jin (NAOC) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709266798 at the time of 2026-06-05T02:51:45, is likely a stellar flare associated with BD+33 2401 (High Proper Motion Star). The estimated flux of the flare is around 1.6 x 10^(-10) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 7.1 x 10^(31) erg/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/44833. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42963] GRB 260604C: Jinshan optical observations
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44832 SUBJECT: GRB 260604C: Jinshan optical observations DATE: 26/06/05 02:52:57 GMT FROM: Zipei Zhu at NAOC <zpzhu(a)nao.cas.cn> Z.P. Zhu, X. Liu, D. Xu, J. An,S.Q. Jiang, L.B. He (NAOC), S.Y. Fu, A.D. Zhu, L. Lei (HUST), J.Z. Liu (XAO) report: We observed the field of GRB260604C detected by Fermi-GBM (Fermi GBM team, GCN 44822) and SVOM (Gotz et al, GCN 44823), using the JinShan 100B telescope located at Altay, Xinjiang, China. Observation started at 2026-06-04T20:32:14 UT, i.e., about 13 min post-burst, and a series of r-band frames were obtained. The previously reported optical counterpart (Lipunov et al, GCN 44827; Konno et al, GCN 44828) is detected in our first single frame with a brightness of R = 16.1 +/- 0.1, calibrated with Pan-STARRS DR2 stars in the field and not corrected for Galactic extinction. We acknowledge the excellent support from T.Q. Chen, and J.F. Zhang for enabling these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44832. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42962] GRB 260604C: Fermi GBM Observation
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44831 SUBJECT: GRB 260604C: Fermi GBM Observation DATE: 26/06/05 02:49:32 GMT FROM: eliza.neights(a)gmail.com E. Neights (GWU, NASA GSFC) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 20:18:44.41 UT on 04 June 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260604C (trigger 802297129/260604846), which was also detected by SVOM ECLAIRs (Gotz et al. 2026, GCN 44823), MASTER (Lipunov et al. 2026, GCN 44827), and LAST (Konno et al. 2026, GCN 44828). The Fermi GBM on-ground location is consistent with the SVOM ECLAIRs position. The angle from the Fermi LAT boresight is 102 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 6.4 s (50-300 keV). The time-averaged spectrum from T0-2.2 to T0+12.0 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.03 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 551 +/- 2 keV. The event fluence (10-1000 keV) in this time interval is (2.55 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+4.5 s in the 10-1000 keV band is 44.1 +/- 0.6 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 394 +/- 3 keV, alpha = -0.95 +/- 0.01 and beta = -2 +/- 0.03. 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/44831. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42961] EP260602d: J-band upper limit with WINTER
by GCN Circulars 04 Jun '26

04 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44830 SUBJECT: EP260602d: J-band upper limit with WINTER DATE: 26/06/05 01:19:18 GMT FROM: Geoffrey Mo at Caltech / Carnegie Observatories <gmo(a)mit.edu> Tanishk Mohan (IITB), Geoffrey Mo (Caltech/Carnegie), Tomas Ahumada (NOIRLab), Benjamin Schneider (LAM), Robert Stein (UMD), Viraj Karambelkar (Columbia), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of EP260602d (Cao et al., GCN 44796) in the near-infrared J band with the Palomar 1-m telescope, equipped with the 1.2-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024). Observations began at 2026-06-03T08:06:13 UTC in the J band (10.88 hr after the EP trigger), consisting of 15*120 sec exposures. The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565) We do not detect any new source in the WXT localization (Aryan et al., GCN 44813; Cao et al., GCN 44796) after image subtraction performed relative to J-band images from the UKIRT Hemisphere survey (Dye et al., 2017). We obtain the following 5-sigma upper limit: J = 19.4 mag (AB). WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research. View this GCN Circular online at https://gcn.nasa.gov/circulars/44830. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0