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

[vsnet-grb-info 42209] EP260214b: ATCA 6 GHz detection
by GCN Circulars 23 Mar '26

23 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44088 SUBJECT: EP260214b: ATCA 6 GHz detection DATE: 26/03/23 15:25:11 GMT FROM: Aishwarya L Thakur at INAF-IAPS, Rome <aishth(a)outlook.com> G. Gianfagna, G. Bruni, A. L. Thakur, M. Fanelli, L. Piro (INAF-IAPS) report: We re-observed the Fast X-ray Transient EP260214b (J Yang et al., GCN 43744, H Yang et al., GCN 43779) with the Australian Telescope Compact Array (ATCA) radio telescope using the 4-cm receiver. Observations were performed on March 20 2026 (at a mean epoch of ~34 days after the EP trigger and 17 days after our last observation; see Gianfagna et al., GCN 43924) for a total of 5 hours. Data were reduced and imaged with standard CASA procedures. The final 6 GHz image has an RMS of 12 uJy/beam. We detect radio emission at a flux density of ~0.04 mJy at a position consistent with the optical counterpart (He et al.). GCN 43745, Watson et al. GCN 43747, Le Floch et al. GCN 43749, Pérez-Fournon et al. GCN 43750, Russeil et al. 43752,Li et al. GCN 43755, Vijayjumar et al. GCN 43757, Becerra et al. GCN 43758, Yang et al. GCN 43760, Aaryan et al. GCN 43762, Bochenek et al. GCN 43764, Kar et al. GCN 43774, Volnova et al. GCN 43775). Further ATCA observations are planned. The Australia Telescope Compact Array is part of the Australia Telescope National Facility (grid.421683.a), which is funded by the Australian Government for operation as a National Facility managed by CSIRO. We acknowledge the Gomeroi people as the traditional owners of the Observatory site. View this GCN Circular online at https://gcn.nasa.gov/circulars/44088. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42208] EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
by GCN Circulars 23 Mar '26

23 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44087 SUBJECT: EP260321a: Early TRT rising followed by JinShan decaying and then re-rising DATE: 26/03/23 11:26:51 GMT FROM: liuxing(a)nao.cas.cn X. Liu, D. Xu (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan, K. Noysena (NARIT), J. An, Z.P. Zhu, N.C. Sun, W.X. Li, Z. Fan, S.Q. Jiang, L.B. He (NAOC), S.Y. Fu (HUST), J.Z. Liu (XAO) report on behalf of a large group: Upon the alert of EP260321a detected by Einstein Probe (Huang et al., GCN 44068), we observed the field of EP260321a using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at New South Wales, Australia (SBO), and then using the 100B telescope of the JinShan project, located at Altay, Xinjiang, China. The TRT observation started at 12:52:13 UT on 2026-03-21, i.e., 21.9 mins after the EP-WXT trigger. No uncatalogued optical transient is detected within the EP-FXT error cicle (Huang et al., GCN 44068) down to R ~ 20.5 mag. We noticed the brightening of the catalogued blue point-like source (R.A. 09:59:42.880, Dec. 00:25:06.29, J2000), if compared with PanSTARRS and Legacy Survey, in the outskirt of the galaxy, SDSS J095942.88+002506.2, with a redshift z = 0.0343 in the DESI Legacy Survey DR1 spectroscopic catalogue, mentioned by Kinder (Lee et al., GCN 44070) and then spectroscopically confirmed at VLT/MUSE (Tanvir et al., GCN 44082). The point source has R ~ 19.0 (Vega) at a median time of 27.6 mins post-trigger, calibrated with PanSTARRS in which the source has r = 19.85 +/- 0.03 mag (AB). The JinShan 100B telescope observed the field in g- and r- bands in the nights of 2026-03-21 and 2026-03-22. In the first night, the blue source decayed a bit to g ~ 18.9 (AB and hereafter) at 2.3 hrs post-trigger and r ~ 19.3 mag at 2.8 hrs post-trigger. And the g-band brightening, if subtracted using the PanSTARS templates, is more prominent than in the r-band, suggesting the transient itself is also quite blue. Together with the rather deep ZTF pre-EP upper limit (Ahumada et al., GCN 44084), the TRT observation, and the Kinder first observation (Lee et al., GCN 44070), the transient shows a fast rising around the EP trigger time and then starts to decay around the first Kinder observation. The decaying behavior is consistent with the cooling of Shock Break-Out (SBO) of a SN-like event (Huang et al., GCN 44075) and a thermal-like spectrum at VLT/MUSE (Tanvir et al., GCN 44082). In the second night, the blue source re-brightened to g ~ 18.5 at 28.5 hrs post-trigger and r ~ 18.8 mag at 29.0 hrs post-trigger, which are also brighter than the second Kinder observation that is a bit earlier than the second JinShan (Aryan et al. GCN 44081). This indicates that a SN-like main component is emerging and will likely continue to brighten to a peak in the coming days. View this GCN Circular online at https://gcn.nasa.gov/circulars/44087. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42207] GRB 260321A: EP-FXT follow-up observation
by GCN Circulars 23 Mar '26

23 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44086 SUBJECT: GRB 260321A: EP-FXT follow-up observation DATE: 26/03/23 03:51:16 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Z.-C. Zou, Y. H. Jiang (NJU), J. P. Chen (SYSY), Y. J. Yi (BNU) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of the SVOM/ECLAIRs-detected burst GRB 260321A (SVOM/sb26032123; Brunet et al., GCN 44071) starting at 2026-03-22T15:23:32 UTC, approximately 21 hours after the SVOM trigger, with a total exposure time of 4565 s. Four uncataloged sources are detected within the ECLAIRs error circle. Preliminary analysis on these sources is automatically conducted, and the details are listed as follows. EPF_J143847.8+314542 RA (J2000): 219.6990 Dec (J2000): 31.7616 Flux: 9.265 x 10^-14 erg/s/cm2 (observed, 0.5-10 keV) Flux_err: 3.498 x 10^-14 erg/s/cm2 (1 sigma) EPF_J143759.7+314425 RA (J2000): 219.4989 Dec (J2000): 31.7404 Flux: 2.9252 x 10^-14 erg/s/cm2 (observed, 0.5-10 keV) Flux_err: 1.2651 x 10^-14 erg/s/cm2 (1 sigma) EPF_J143833.9+314628 RA (J2000): 219.6440 Dec (J2000): 31.7719 Flux: 5.9349 x 10^-14 erg/s/cm2 (observed, 0.5-10 keV) Flux_err: 2.0193 x 10^-14 erg/s/cm2 (1 sigma) EPF_J143845.7+313613 RA (J2000): 219.6902 Dec (J2000): 31.6037 Flux: 8.0698 x 10^-14 erg/s/cm2 (observed, 0.5-10 keV) Flux_err: 1.9625 x 10^-14 erg/s/cm2 (1 sigma) 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/44086. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42206] The EP-WXT trigger 01709259045 is likely a flaring star
by GCN Circulars 23 Mar '26

23 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44085 SUBJECT: The EP-WXT trigger 01709259045 is likely a flaring star DATE: 26/03/23 02:46:01 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.L. Hua (PMO, CAS), T. Zhao, W. Chen, Y. Liu (NAOC, CAS) on behalf of the Einstein Probe team The EP-WXT trigger 01709259045 at the time of 2026-03-22T23:47:38, is likely a stellar flare associated with 2MASS J15570856+2749007. The estimated flux of the flare is around 6e-11 erg/s/cm^2 in 0.5-4 keV, corresponding to an X-ray luminosity of around 4.31e+32 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/44085. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42205] EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
by GCN Circulars 22 Mar '26

22 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44084 SUBJECT: EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a DATE: 26/03/22 23:06:20 GMT FROM: Tomas Ahumada <tomas.ahumada(a)noirlab.edu> T. Ahumada (NOIRLab), X. J. Hall (CMU), D. A. Perley (LJMU) on behalf of the Zwicky Transient Facility We report the Zwicky Transient Facility detection of ZTF26aaonmha (AT 2026gzf), the candidate optical counterpart to EP260321a (Huang et al., GCNs 44068, 44075) announced by Lee et al (GCN 44070, see also Aryan et al., GCN 44081, Tanvir et al. GCN 44082). The ZTF detection was observed at 2026-03-22 07:35:25 (~19 hr after the EP-trigger) in the ZTF-g band at a magnitude of 19.7 +/- 0.2 mag. The region was also observed in ZTF-r band at 2026-03-22 07:12:13, but resulted in a non-detection limit of 19.6 mag. The source has no previous activity in the ZTF survey, with the most recent upper limit of g = 20.2 mag on 2026-03-21 08:06:02 (4.5 hr before the X-ray detection). The ZTF non-detection prior to the EP detection, together with the post-EP ZTF trigger, strongly supports the optical association. We additionally note that the source is detected in the Rubin alert stream, although we caution that the alerts show a dipole structure and could be spurious detections. The variability in the Rubin data fluctuates in around r = 23.8 mag, with the most prominent pre-EP detection at r = 21.1 mag, ~25 days before the X-ray flare. The combined Rubin and ZTF lightcurve can be found at https://babamul.caltech.edu/objects/LSST/314003014107006318 We are pursuing and encouraging follow-up observations to classify the source and validate the X-ray and optical association. Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Award #2407588 and a partnership including Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; University of Wisconsin at Milwaukee, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; Operations are conducted by Caltech's Optical Observatory (COO) and Caltech/IPAC. View this GCN Circular online at https://gcn.nasa.gov/circulars/44084. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42204] EP260321a: GOTO detection of blue variable source
by GCN Circulars 22 Mar '26

22 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44083 SUBJECT: EP260321a: GOTO detection of blue variable source DATE: 26/03/22 21:30:52 GMT FROM: Shane Moran at University of Leicester <shane.moran(a)leicester.ac.uk> S. Moran, A. Kumar, G. Ramsay, D. O'Neill, K. Ulaczyk, S. Moran, B. P. Gompertz, R. Starling, M. Wortley, M. Kennedy, K. Ackley, M. Dyer, J. Lyman, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson, T. Killestein, M. Pursiainen, on behalf of GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) that serendipitously covered the field of EP/WXT detected EP260321a (WXT01709259023; Huang et al., GCNs 44068, 44075). Observations covering the localisation area were taken at 2026-03-22 11:25:46 UT (+22.92h post trigger) utilising GOTO-South. Each observation consisted of 4x45s exposures in the GOTO L-band (400-700 nm). We detect the previously reported variable source (Lee et al. GCN 44070, Tanvir et al. GCN 44082) with L = 19.51 ± 0.1 AB mag. 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/44083. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42203] EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
by GCN Circulars 22 Mar '26

22 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44082 SUBJECT: EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343 DATE: 26/03/22 19:50:53 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> N. R. Tanvir (Leicester), L. Izzo (INAF/OACN), A. J. Levan (Radboud and Warwick), D. Xu (NAOC), G. Corcoran (UCD), P. G. Jonker (Radboud), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), G. Pugliese (API), A. de Ugarte Postigo (LAM), K. Wiersema (Hertfordshire), report on behalf of the Stargate collaboration: We observed the field of EP260321a (Huang et al., GCNs 44068, 44075) with the ESO VLT UT1 (Antu) and UT4 (Yepun), obtaining R-band imaging with the FORS2 instrument (mid-time 00:44 UT on 2026-02-22; 12.23 hr after the EP trigger), and integral field spectroscopy with the MUSE instrument on UT4 (mid-time 05:29 UT on 2026-02-22; 16.98 hr after the EP trigger). Within the refined EP/FXT error circle (Huang et al., GCN 44075), the blue, historically variable source coincident with the outskirts of a galaxy at z = 0.0343, noted by Lee et al. (GCN 44070), is prominent. We measure a magnitude of R = 19.5, which is within the range of archival values, but is significantly brighter than reported by Lee et al. (GCN 44070). The source itself is consistent with being marginally resolved in 0.7" seeing imaging, though this may be due to contamination from the underlying galaxy. Our spectroscopy shows the variable source (covering the wavelength range 4750 - 9300 Å) to be characterised by a blue power-law continuum, with very strong narrow emission lines at z = 0.0343 (e.g., [O III] 5008 EW ~ 500 Å). No absorption features are detected at either z = 0 or z = 0.0343. While the emission lines are visible across the entire galaxy, they are strongly spatially concentrated at the location of the blue variable object, with fluxes approximately twenty times brighter than at the galaxy nucleus. This makes it unlikely for the source to be a random foreground superposition, suggesting that it lies itself within the galaxy at z = 0.0343. At this redshift, our measured flux corresponds to an absolute magnitude of approximately M_R = -16.8, and the past variability (Lee et al., GCN 44070) appears to be consistent with previous outbursts to a comparable flux level. It is possible that past variability was due to LBV-like outbursts from a star embedded within a dense, luminous cluster (as evidenced by the strong emission line component). The short-term variability following the outburst (Lee et al., GCN 44070; Aryan et al., GCN 44081), coupled with the location within the revised FXT error circle, suggest that this source is the optical counterpart of EP260321a. It is unclear if the current outburst is related to a further LBV flare or the terminal collapse of the star, as may be suggested by the possible shock breakout properties of the X-ray outburst (Huang et al., GCN 44075). Under this interpretation, this would make EP260321a the first example of an X-ray transient progenitor detected prior to explosion. We encourage further monitoring of this object at all wavelengths in order to clarify its enigmatic nature. We acknowledge excellent support of the ESO observing staff at Paranal, in particular Abel de Burgos Sierra, Alonso Luna Ruiz Fernandez, Elyar Sedaghati, Enrico Congiu, Israel Blanchard, and Rodrigo Palominos. We also thank the visitor observers on UT4, Silvia Piranomonte and Eleonora Parlanti, for generously allowing the execution of our observation. View this GCN Circular online at https://gcn.nasa.gov/circulars/44082. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42202] EP260321a: further Kinder optical observations
by GCN Circulars 22 Mar '26

22 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44081 SUBJECT: EP260321a: further Kinder optical observations DATE: 26/03/22 15:49:58 GMT FROM: Janet Chen at National Central University <janetstars(a)gmail.com> A. Aryan, M.-H. Lee, T.-W. Chen, W.-J. Hou (all NCU), S. Yang (HNAS), A. K. H. Kong (NTHU), T. Moriya (NAOJ), S. J. Smartt, J. Gillanders (both Oxford), Y. J. Yang (NYUAD), A. Dutta, Y.-H. Lee, A. Sankar.K, Y.-C. Pan, C.-C. Ngeow, C.-H. Lai, C.-S. Lin H.-C. Lin, H.-Y. Hsiao, J.-K. Guo (all NCU), Z. N. Wang, D. C. Qiang, L. L. Fan (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the fast X-ray transient EP260321a (Huang et al., GCN 44068) using the 1m LOT at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen et al., 2025, ApJ, 983, 86, doi:10.3847/1538-4357/adb428). The first LOT epoch of observations started at 11:34 UTC on the 22nd of March 2026 (MJD 61121.482), 23.07 hr after the EP-WXT trigger. We used Kinder pipeline (Yang et al. A&A 646, A22) to perform template subtraction with the DESI Legacy Survey (Dey et al. 2019, AJ 157, 168) DR10 image. In the difference image, we still detected this stellar source SDSS J095942.88+002506.2 (Lee et al., GCN 44070), but no other new transient has emerged. Moreover, we used AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform PSF photometry for this variable star (without template subtraction). The details of the observations and the measured magnitude (in the AB system) are as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | (med/avg.) Airmass LOT | r | 61121.482 | 23.07 | 300 * 6 | 19.18 +/- 0.04 | 0".96 | 1.27 LOT | g | 61121.520 | 23.99 | 300 * 2 | 18.77 +/- 0.04 | 1".11 | 1.17 Our 3-sigma upper limit for the observed field is r = 23.4 mag. EP260321a was identified as a possible supernova shock-breakout candidate in the EP refined analysis (Huang et al., GCN 44075). However, no optical counterpart has been reported to date (Lee et al., GCN 44070; Ma et al., GCN 44074; Aguilar-Ruiz et al., GCN 44076; Liang et al., GCN 44079). For comparison, in SN 2008D the optical counterpart was detected only ~1.4 hr after the initial X-ray detection (Soderberg et al. 2008). Given the similar X-ray duration to SN 2008D and the continued absence of any optical counterpart, we suspect that the EP260321a X-ray emission more likely originates from the variable star itself. If it is a Galactic X-ray binary, the spectrum suggests a supersoft (WD) accretor, but the X-ray flux is weak; a strong local stellar flare is also plausible. The presented magnitudes are calibrated using the field stars from the ATLAS-RefCat2 catalog from MAST (Tonry J. L. et al. 2018, ApJ, 867, 105) and are not corrected for the expected Galactic foreground extinctions of A_r = 0.06 mag and A_g = 0.08 mag, in the direction of the transient (Schlafly & Finkbeiner 2011). The methodology, details on the Lulin observatory telescopes, and a compilation of our optical follow-up campaign for FXTs discovered within the first year of operation of the Einstein-Probe mission can be found in Aryan et al. 2025, ApJS, 281, 20, doi:10.3847/1538-4365/adfc69. View this GCN Circular online at https://gcn.nasa.gov/circulars/44081. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42201] GRB 260321A: SVOM/VT optical upper limits
by GCN Circulars 22 Mar '26

22 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44080 SUBJECT: GRB 260321A: SVOM/VT optical upper limits DATE: 26/03/22 14:10:30 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, Y. N. Ma, C. Wu, Z. H. Yao, Y. L. Qiu, L. P. Xin, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu), M. Brunet (IRAP), O. Godet (IRAP) report on behalf of the SVOM/VT team. SVOM/VT performed an observation with automatic slew to the field of GRB 260321A triggered by SVOM/ECLAIRs (sb26032123, Brunet et al., GCN 44071). The observation started at 2026-03-21T18:57:18 UTC, i.e., about 45 minutes post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. No credible sources were detected within the error box of ECLAIRs (Brunet et al., GCN 44071), compared to the Legacy survey catalog. The 5 sigma upper limits in AB magnitude are derived as follows: Mid time | Band | Exposure Time | 5 sigma upper limit 1.13 hour VT_B 53*50 sec > 22.7 mag 1.12 hour VT_R 42*50 sec > 22.5 mag More detailed analysis is still ongoing. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/44080. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42200] EP260321a: Las Cumbres upper limit
by GCN Circulars 22 Mar '26

22 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44079 SUBJECT: EP260321a: Las Cumbres upper limit DATE: 26/03/22 13:12:22 GMT FROM: aujust(a)mail.ustc.edu.cn Runduo Liang, Wenxiong Li (NAOC), Iair Arcavi (TAU), Ido Keinan (TAU), David Sand (U of Arizona) We observed the position of EP260321a (GCN 44068, GCN 44075) with a Las Cumbres 1m telescope at Cerro Tololo Inter-American Observatory, Chile, about 11.25 hours after the Einstein Probe WXT trigger. We took 2x300s exposures in the broad optical r-band. We didn’t detect any uncataloged source within the EP-FXT refined position down to a 3-sigma limiting r-band mag of ~20.8. The presented magnitudes are calibrated with Pan-STARRS sources in the field and not corrected for Galactic extinction. Additional follow-up is encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/44079. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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