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

[vsnet-grb-info 41462] Swift trigger 1436759 is not an astrophysical event
by GCN Circulars 11 Jan '26

11 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43369 SUBJECT: Swift trigger 1436759 is not an astrophysical event DATE: 26/01/11 09:22:31 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> R. Brivio (INAF-OAB), A. Mei (INAF-OAB), K. L. Page (U Leicester), T. M. Parsotan (GSFC), C. Salvaggio (INAF-OAB), B. Sbarufatti (INAF-OAB) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: The downlinked data showed no obvious light curve structure, and the lack of the scaled map at the time prevented full verification of the low image significance of the event in the BAT data. The XRT began observing the field at 09:03:15.2 UT, 112.0 seconds after the BAT trigger. No source was detected in 930 s of promptly downlinked data. UVOT took a finding chart exposure of 250 seconds with the U filter starting 172 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 25% of the BAT error circle. The typical 3-sigma upper limit has been about 19.2 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the BAT error circle. The list of sources is typically complete to about 18.0 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.111. View this GCN Circular online at https://gcn.nasa.gov/circulars/43369. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41461] EP260110a: KAIT optical upper limit
by GCN Circulars 11 Jan '26

11 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43368 SUBJECT: EP260110a: KAIT optical upper limit DATE: 26/01/11 06:29:36 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of EP260110a (Zhang et al., GCN 43363; 43367) starting at 12:19, Jan 10 UT, about 21 minutes after the burst. A set of 20s, 40s and 60s clear (roughly R) filter images were obtained. In our coadd image, we did not detect any new source within the EP-WXT error circle (Zhang et al., GCN 43367) down to a limiting mag of 21.0 mag (Vega) at a mid-time of 1.0 hours after the burst. Our result is consistent with the upper limit reported by other groups (Perez-Garcia et al., GCN 43364; Kang et al., GCN 43365; Antier et al., GCN43366). View this GCN Circular online at https://gcn.nasa.gov/circulars/43368. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41460] EP260110a: refined analysis of the EP-WXT and EP-FXT observations
by GCN Circulars 11 Jan '26

11 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43367 SUBJECT: EP260110a: refined analysis of the EP-WXT and EP-FXT observations DATE: 26/01/11 04:43:42 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> B. Zhang, J. P. Feng (USTC), Y. Wu (NJU), F. F. Song(YNAO, CAS), A. Li (BNU), C. Y. Wang (THU), G. Y. Zhao (SYSU), Y. Liu (NAOC, CAS) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP260110a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Zhang et al., GCN 43363). The refined analysis of the WXT data shows that the event started at T0=2026-01-10T 11:56:58(UTC), and lasted for approximately 85 seconds, after which the WXT light curve was interrupted due to the autonomous follow-up observation. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.59×10^20 cm^-2 and a photon index of 0.83(-0.51/+0.56). The derived average unabsorbed 0.5-4 keV flux is 2.64(-0.88/+1.15)×10^(-10) erg/s/cm^2. The Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously at 2026-01-10T12:00:52(UTC, T0+234 s). The exposure time of this observation is 4576s. On-ground analysis of the FXT data found an uncatalogued source at R.A. = 199.4321, DEC = 65.8490 (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic), which is consistent with the WXT position. The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.59×10^20 cm^-2 and a photon index of 2.02 (-0.14/+0.14). The derived average unabsorbed 0.5-10 keV flux is 1.52 (-0.19/+0.22)×10^(-12) erg/s/cm^2. We performed one target-of-opportunity (ToO) follow-up observations with FXT at 2026-01-10T16:23:31 (UTC, T0+15,993 s) with an exposure time of 3,032s. The average FXT 0.5-10 keV spectrum of the ToO observation can be fitted with an absorbed power law, with a fixed Galactic hydrogen column density of 1.59×10^20 cm^-2, and a photon index of 2.11 (-0.84/+1.00) . The derived average unabsorbed 0.5-10 keV flux is 1.15 (-0.57/+1.33)×10^(-13) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. No optical counterpart of EP260110a has been detected so far (Perez-Garcia et al., GCN 43364; Kang et al., GCN 43365; Antier et al., GCN43366) , and further mutil-band follow-up observations are encouraged to explore the nature of EP260110a. 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/43367. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41459] EP 260110a: COLIBRÍ optical observations
by GCN Circulars 10 Jan '26

10 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43366 SUBJECT: EP 260110a: COLIBRÍ optical observations DATE: 26/01/10 17:31:28 GMT FROM: antier(a)ijclab.in2p3.fr Sarah Antier (IJCLAB), Dalya Akl (NYUAD), Edilberto Aguilar-Ruiz (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Rosa L. Becerra (UNAM), 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), Nikos Mandarakas (LAM), Kin Ocelotl López (UNAM), 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 Antonio de Ugarte Postigo (LAM): We imaged the field of the EP 260110a using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-01-10 12:17:40 to 13:21 UTC (from 18 min after the trigger) and obtained about 50 minutes of simultaneous exposure in the r and z filters. The data were reduced, coadded, and analyzed with the two COLIBRÍ pipelines, and were also analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we do not detect any new source against Legacy at the WXT and FXT localization error box (Zhang et al., GCN Circ. 43363) down to the following 5-sigma limit: r > 22.8 z > 21.8 This upper limit is consistent with the ones reported by Perez-Garcia et al. GCN Circ. 43364 and Kang at al. Circ. 43365. 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 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/43366. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41458] EP260110a: SVOM/C-GFT upper limit
by GCN Circulars 10 Jan '26

10 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43365 SUBJECT: EP260110a: SVOM/C-GFT upper limit DATE: 26/01/10 14:51:46 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Z. Kang (CHO), C. WU, L.P. Xin, X.H. Han, P.P. Zhang, X.M. Lu (NAOC), Z.W. Li (CHO), Y. Lv (CHO), R.S. Zhang, Y.J. Xiao, Y.L. Qiu, J. Wang, J.S. Deng, L. Huang, J.Y. Wei (NAOC) report on behalf of the SVOM/C-GFT team: We observed the field of EP260110a, detected by EP/WXT (Zhang et al., GCN 43363), using the LATIOS instrument on the SVOM/C-GFT. Observations started at 2026-01-10T12:20:27 UTC, ~22.07 min after the trigger. A series of i-band images were obtained. After preliminary processing, no credible candidate was detected within the error box provided by EP/FXT (Zhang et al., GCN 43363) in our images. The three-sigma upper limit is: | Date-Obs (mid-time) | Mid_t - T0 (min) | Exposure Time (s) | Band | Upper Limit (AB) | |---------------------|----------------|-------------------|------|------------------| | 2026-01-10T12:20:57 | 22.57 | 2×30 | i | 18.6 | The photometry was calibrated against nearby Pan-STARRS1 stars and no correction for Galactic dust extinction was applied. This result is consistent with Perez-Garcia et al., GCN 43364. We thank the observation assistants Yin-Huai Hao and Chun-Lei Guo at Jilin observatory for their excellent support. The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching. View this GCN Circular online at https://gcn.nasa.gov/circulars/43365. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41457] EP260110a: SVOM/C-GFT upper limit
by GCN Circulars 10 Jan '26

10 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43365 SUBJECT: EP260110a: SVOM/C-GFT upper limit DATE: 26/01/10 14:51:46 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Z. Kang (CHO), C. WU, L.P. Xin, X.H. Han, P.P. Zhang, X.M. Lu (NAOC), Z.W. Li (CHO), Y. Lv (CHO), R.S. Zhang, Y.J. Xiao, Y.L. Qiu, J. Wang, J.S. Deng, L. Huang, J.Y. Wei (NAOC) report on behalf of the SVOM/C-GFT team: We observed the field of EP260110a, detected by EP/WXT (Zhang et al., GCN 43363), using the LATIOS instrument on the SVOM/C-GFT. Observations started at 2026-01-10T12:20:27 UTC, ~22.07 min after the trigger. A series of i-band images were obtained. After preliminary processing, no credible candidate was detected within the error box provided by EP/FXT (Zhang et al., GCN 43363) in our images. The three-sigma upper limit is: | Date-Obs (mid-time) | Mid_t - T0 (min) | Exposure Time (s) | Band | Upper Limit (AB) | |---------------------|----------------|-------------------|------|------------------| | 2026-01-10T12:20:57 | 22.57 | 2×30 | i | 18.6 | The photometry was calibrated against nearby Pan-STARRS1 stars and no correction for Galactic dust extinction was applied. This result is consistent with Perez-Garcia et al., GCN 43364. We thank the observation assistants Yin-Huai Hao and Chun-Lei Guo at Jilin observatory for their excellent support. The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching. View this GCN Circular online at https://gcn.nasa.gov/circulars/43365. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41456] EP260110a: BOOTES-5/JGU optical upper limit
by GCN Circulars 10 Jan '26

10 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43364 SUBJECT: EP260110a: BOOTES-5/JGU optical upper limit DATE: 26/01/10 13:26:38 GMT FROM: I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg(a)iaa.es> I. Perez-Garcia, E. J. Fernandez-Garcia, M. D. Caballero-Garcia, S.-Y. Wu, R. Sanchez-Ramirez, S. Guziy and A. J. Castro-Tirado (IAA-CSIC, Granada), I. M. Carrasco (SMA), M. Gritsevich (Univ. of Helsinki), C. Perez del Pulgar (Univ. of Malaga), Y.-D. Hu (GXU), S. Jeong (ADD, Daejeon), G. Garcia-Segura and D. Hiriart (IA-UNAM, Ensenada), D. R. Xiong (Yunnan Observatories of CAS, Kunming), and W. H. Lee (UNAM, Mexico DF), on behalf of a larger collaboration, report: Following the detection of EP260110a by EP (Zhang et al., GCN 43363), the 0.6m BOOTES-5/JGU robotic telescope at San Pedro Martir Observatory (Mexico) automatically responded to this high-energy event starting on Jan 10, 12:18:31 UT (i.e. 20 min after detection). Nothing is detected down to 17.3 in this first image. On a coadd image (12 x 60sec) at 12:41:13 UT (mid exposure time), nothing is detected down to 20.1 mag (clear filter) within the FXT error region. All photometric calibration was done using Gaia Gmag band. We would like to thank the staff at San Pedro Martir Observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/43364. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41455] EP260110a: Einstein Probe detection of an X-ray transient
by GCN Circulars 10 Jan '26

10 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43363 SUBJECT: EP260110a: Einstein Probe detection of an X-ray transient DATE: 26/01/10 12:53:09 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> B.Zhang, J. P. Feng (USTC), Y. Wu (NJU), F. F. Song(YNAO, CAS), A. Li (BNU), C. Y. Wang (THU), G. Y. Zhao (SYSU). Y. Liu (NAOC, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260110a. The transient triggered EP-WXT (ID: 01709251242) at 2026-01-10T11:58:23 (UTC). The WXT position of the source is R.A. = 199.406 deg, DEC = 65.845 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 199.4371 deg, DEC = 65.8476 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). Further information will be updated when the telemetry data is received. 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/43363. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41454] GRB 260109C: LCO optical upper limits
by GCN Circulars 09 Jan '26

09 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43362 SUBJECT: GRB 260109C: LCO optical upper limits DATE: 26/01/09 21:27:52 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> D. Turpin, (CEA/Irfu) C. Wu, X.-H. Han, L.-P. Xin (NAOC), A. Saccardi, J. T. Palmerio (CEA/Irfu) report on behalf of the SVOM mission team: We observed the field of the possible GRB 260109C detected by Swift/BAT (Parsotan et al., GCN 43359) with the LCO 1m telescope at the Siding Spring Observatory (SSO) equipped with the Sinistro instrument. Our observation started at 2026-01-09 13:16:04 about 29 minutes after the Swift/BAT trigger time. We obtained 2 epochs of 3x200s exposures in the PanSTARRS z filters. No any uncatalogued source was identified in our stacked frames in agreement with the non detection of the Kilonova-Catcher group in the Rc band (Freeberg et al., GCN 43360). When stacking the our two series of observations, we measure the following upper limits (5 sigma) calibrated against the SkyMapper DR4 catalog, and not corrected for Galactic extinction: z = 19.6 (AB) T_mid - T0 = 40 min This project is funded by the SVOM collaboration. The transient detection and photometric calibration were performed with the STDPipe pipeline (Karpov et al., 2022). View this GCN Circular online at https://gcn.nasa.gov/circulars/43362. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41453] GRB 260109C: Kilonova-Catcher optical upper limit
by GCN Circulars 09 Jan '26

09 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43361 SUBJECT: GRB 260109C: Kilonova-Catcher optical upper limit DATE: 26/01/09 21:03:55 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> M. Freeberg (KNC), D. Turpin (CEA-Saclay/Irfu), C. Andrade(UMN), S. Antier (OCA/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 260109C detected by Swift/BAT (Parsotan et al., GCN 43359) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the iT30 itelescope located at the Siding Spring Observatory and operated by M. Freeberg. Our observations started at TGRB+34.5 min and were taken with Rc filter. In our stacked frames, subtracted from the SkyMapper DR4 template image, we do not detect any optical counterpart in the Swift/BAT error radius. We report our follow-up results in the table below: +---------------+----------+-----------+----------------+-------------+ | Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument | +===============+==========+===========+================+=============+ | 0.83 | 6 x 300s | Rc (Vega) | 20.8 (5 sigma) | iT30 | +---------------+----------+-----------+----------------+-------------+ All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). 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/43361. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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