February 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 37556] Konus-Wind detection of GRB 250226A
by GCN Circulars 28 Feb '25

28 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39542 SUBJECT: Konus-Wind detection of GRB 250226A DATE: 25/02/28 22:10:03 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, A. Tsvetkova, M. Ulanov, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 250226A (Fermi-GBM detection: The Fermi GBM team, GCN 39479; Pathak and Meegan, GCN 39530; EP-WXT detection: Jiang et al., GCN 39482; INTEGRAL SPI-ACS and PICsIT detection: Thakur et al., GCN 39518) triggered Konus-Wind at T0=23700.486 s UT (06:35:00.486). The burst light curve shows a single emission episode which starts at ~T0-5 s and has a total duration of ~32 s. The emission is seen up to ~1 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250226_T23700/ As observed by Konus-Wind, the burst had a fluence of 1.17(-0.21,+0.28)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+0.438 s, of 3.45(-1.09,+1.18)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+24.832 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.16(-0.47,+0.68), the high energy photon index beta = -2.25(-0.38,+0.24), the peak energy Ep = 143(-28,+35) keV (chi2 = 64/97 dof). The spectrum near the maximum count rate (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.60(-0.36,+0.54), the high energy photon index beta = -2.00(-8,+0.17), the peak energy Ep = 190(-53,+331) keV (chi2 = 86/97 dof). Assuming the redshift z=3.315 (Zhu et al. GCN 39487) and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the following rest-frame parameters: the isotropic energy release E_iso is 2.80(-0.51,+0.67)x10^53 erg, the peak luminosity L_iso is 3.56(-1.12,+1.22)x10^53 erg/s, the rest-frame peak energy of the time-averaged spectrum Ep,i,z is 616(-119,+151) keV and the spectrum near the maximum count rate Ep,p,z is 822(-229,+1427) keV. With the obtained estimates, GRB 250226A is inside 68% prediction bands for both the 'Amati' and the 'Yonetoku' relations derived for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB250226_T23700/GRB250226A_rest_frame.pdf All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/39542. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37555] GRB 250225B: EIRSAT-1 GMOD Detection
by GCN Circulars 28 Feb '25

28 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39541 SUBJECT: GRB 250225B: EIRSAT-1 GMOD Detection DATE: 25/02/28 21:22:14 GMT FROM: Gabriel Finneran at School of Physics and Centre for Space Research, University College Dublin <gabriel.finneran(a)ucdconnect.ie> G. Finneran, C. McKenna, D. Murphy, C. de Barra, A. Ulyanov, P. McDermott, M. Doyle, R. Dunwoody, J. Mangan, G. Corcoran, L. Cotter, A. Empey, J. Fisher, F. Gibson Kiely, J. Thompson, D. McKeown, A. Martin-Carrillo, L. Hanlon, S. McBreen, on behalf of the EIRSAT-1 team: EIRSAT-1 reports the detection of the long gamma-ray burst GRB250225B by the Gamma-ray Module (GMOD) instrument, which was also detected by Swift BAT (GCN 39473), SVOM GRM (GCN 39493), Konus-Wind (GCN 39498), Fermi GBM (GCN 39502) and INTEGRAL SPI-ACS (GCN 39517). The GMOD detection was made starting at 2025-02-25 19:39:13.1 UTC. The GMOD light-curve for GRB250225B with 1.2s binning shows a peak consistent with the first peak seen by SVOM GRM, with a tentative detection of the second peak at around 60 seconds. The spacecraft location at the time of detection was 31.703 N, 135.873 W, at an altitude of 425.8km. The GMOD light curve for this event can be found here: https://grb.eirsat1.ie/250225B/250225B_LC_onboard_preliminary.png EIRSAT-1 is Ireland’s first satellite (Doyle et al. Proceedings of the 4th SSEA, 2022). It is a 2U CubeSat and carries onboard a number of experiments including the Gamma-Ray Module (GMOD), a novel, compact, gamma-ray detector (Murphy et al, Experimental Astronomy, 53, 961–990, 2022). GMOD consists of a 25 mm × 25 mm × 40 mm Cerium Bromide scintillator coupled to SiPMs and is designed to detect gamma-ray bursts in the ~ 60 keV - 1.5 MeV range. EIRSAT-1 was developed in University College Dublin with support from ESA’s Fly Your Satellite! programme and was launched on 1st December 2023. View this GCN Circular online at https://gcn.nasa.gov/circulars/39541. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37554] GRB 250226A: KAO Optical Upper Limit
by GCN Circulars 28 Feb '25

28 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39540 SUBJECT: GRB 250226A: KAO Optical Upper Limit DATE: 25/02/28 20:48:07 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), A. M. Abdelaziz (NRIAG), M. Abdelkareem (NRIAG), E. Amin (NRIAG), A. Pozanenko (IKI) report on behalf of IKI GRB-FuN: We performed optical observations of the field of GRB 250226A (The Fermi GBM team, GCN 39479; V.Lipunov et. al, GCN 39481; Jiang et. al, GCN 39482; An et. al, GCN 39486; Zhu et. al, GCN 39487; Magnani et. al, GCN 39488; Li et. al, GCN 39489; Li et. al, GCN 39492; Aryan et. al, GCN 39509; Zou et. al, GCN 39511; Jiang et. al, GCN 39513; Li et. al, GCN 39514; Junjie-Jin et. al, GCN 39515; Thakur et. al, GCN 39518; Poidevin et. al, GCN 39524; Pathak et. al, GCN 39530; Pankov et. al, GCN 39539) in the R filter with the 1.88-meter telescope of the Kottamia Astronomical Observatory (KAO). The observations started on (UT) 2025-02-28 00:30:36, i.e. ~1.78 days since trigger and consists of 39x150 sec exposures. We do not detect the optical counterpart in the stacked image. The preliminary upper limit is as follows: Date UT start t-T0 Exp. Filter UL(3sigma) (mid, days) (s) 2025-02-28 00:30:36 1.78084 39*150 R 22.3 The photometry is based on nearby stars from the USNO-B1.0 catalog and has not been corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39540. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37553] GRB 250226A: AbAO AS-32 Optical Upper Limit
by GCN Circulars 28 Feb '25

28 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39539 SUBJECT: GRB 250226A: AbAO AS-32 Optical Upper Limit DATE: 25/02/28 20:42:33 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), R. Ya. Inasaridze (AbAO), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of GRB 250226A (The Fermi GBM team, GCN 39479; V.Lipunov et. al, GCN 39481; Jiang et. al, GCN 39482; An et. al, GCN 39486; Zhu et. al, GCN 39487; Magnani et. al, GCN 39488; Li et. al, GCN 39489; Li et. al, GCN 39492; Aryan et. al, GCN 39509; Zou et. al, GCN 39511; Jiang et. al, GCN 39513; Li et. al, GCN 39514; Junjie-Jin et. al, GCN 39515; Thakur et. al, GCN 39518; Poidevin et. al, GCN 39524; Pathak et. al, GCN 39530) in the R filter with the 0.7-meter AS-32 telescope of the Abastumani Astrophysical Observatory. The observations started on (UT) 2025-02-28 00:25:49, i.e. ~1.76 days since trigger and consists of 70*60 sec exposures. We do not detect the optical counterpart in the stacked image. The preliminary upper limit is as follows: Date UT start t-T0 Exp. Filter UL(3sigma) (mid, days) (s) 2025-02-28 00:25:49 1.76796 70*60 R 21.4 The photometry is based on nearby stars from the USNO-B1.0 catalog and has not been corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39539. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37552] EP250227a: Global MASTER-Net observations report
by GCN Circulars 28 Feb '25

28 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39538 SUBJECT: EP250227a: Global MASTER-Net observations report DATE: 25/02/28 17:54:50 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the EP250227a ( EP Team et al., GCN 39532) errorbox 5473 sec after notice time and 1 days 45921 sec after trigger time at 2025-02-28 17:25:01 UT, with upper limit up to 17.1 mag. The observations began at zenith distance = 74 deg. The sun altitude is -46.8 deg. The galactic latitude b = 47 deg., longitude l = 320 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2795063 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 132351 | 2025-02-28 17:25:01 | MASTER-Tunka | (13h 36m 31.38s , -13d 41m 08.1s) | C | 60 | 17.1 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39538. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37551] EP250223A: Upper limits from Fermi-GBM Observations
by GCN Circulars 28 Feb '25

28 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39537 SUBJECT: EP250223A: Upper limits from Fermi-GBM Observations DATE: 25/02/28 17:47:57 GMT FROM: mariaedvige.ravasio(a)ru.nl M. E. Ravasio (Radboud Univ.), E. Burns (LSU), and P.G. Jonker (Radboud Univ.) report on behalf of the Fermi-GBM Team: Fermi-GBM had full spatial coverage of the transient EP250223A detected by EP-WXT (Lian et al., GCN 39429). There was no Fermi-GBM onboard trigger around the EP starting time T0=2025-02-23T15:02:05.66 UTC (Wang et al., GCN 39448). The GBM targeted search [1], the most sensitive, coherent search for GRB-like signals, was run in the time interval [T0-50;T0+500] s, seeking signals between 64 ms and 32.768 s in duration. No signal consistent with the EP transient both temporally and spatially is identified, as confirmed by visual inspection of the data. Assuming a “soft” spectral template (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7), and a duration of 8.192 s, we derive a sky-averaged flux upper limit of 3.1e-08 erg/cm2/s in the energy band 10-1000 keV. [1] Goldstein et al. 2019 arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/39537. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37550] EP250227a: TRT optical upper limit
by GCN Circulars 28 Feb '25

28 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39536 SUBJECT: EP250227a: TRT optical upper limit DATE: 25/02/28 17:28:36 GMT FROM: sqjiang at NAOC <sqjiang(a)bao.ac.cn> S.Q. Jiang (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), J. An, X. Liu, S.Y. Fu, Z.P. Zhu, D. Xu, Z. Fan, W.X. Li, Y.N. Wang, N.C. Sun (NAOC) report on behalf of a large collaboration: We observed the field of EP250227a detected by EP (Wen et al., GCN 39532), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Cerro Tololo Inter-American Observatory, Chile. Observations started at 04:10:11.093 UT on 2025-02-28, i.e., 0.98 days after the EP trigger, and a series of 300 s frames were obtained in the R band. No uncatalogued optical source is detected in the stacked R-band image within the EP/FXT error circle (Wen et al., GCN 39532), down to the 5-sigma limiting magnitude of R ~ 22.1, calibrated with LS-DR10 stars and not corrected for Galactic extinction, being consistent with the non-detections by NOT (Malesani et al., GCN 39533) and SLT (Aryan et al., GCN 39534). View this GCN Circular online at https://gcn.nasa.gov/circulars/39536. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37549] GRB 250225B: VLT/HAWKI near-infrared observations
by GCN Circulars 28 Feb '25

28 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39535 SUBJECT: GRB 250225B: VLT/HAWKI near-infrared observations DATE: 25/02/28 17:08:01 GMT FROM: Nusrin Habeeb at University of Leicester <nh312(a)leicester.ac.uk> B.C. Rayson (U. Leicester), N. Habeeb (U. Leicester), N. R. Tanvir (U. Leicester), R. A. J. Eyles-Ferris (U. Leicester), R. Brivio (INAF-OAB), M. Ferro (INAF-OAB), A J. Levan (Radboud and Warwick), D. B. Malesani (DAWN/NBI and Radboud) report on behalf of the Stargate collaboration: We observed the field of the GRB 250225B (Williams et al., GCN 39473) with the ESO Very Large Telescope UT4, equipped with the HAWK-I near-infrared camera. We obtained a 20 min exposure Ks band, starting at 09:12:18.45 UT on 2025-02-27, i.e. 1.56 days after the Swift trigger. The observations were obtained under good seeing conditions, with a measured seeing of 0.96″ in the Ks band. We detect the optical afterglow candidate reported by Schneider et al. (GCN 39494) and Yang et al. (GCN 39495) at coordinates: RA(J2000) = 20:24:33.81 DEC(J2000) = -41:28:25.4 Its Vega magnitude is Ks = 19.382 +- 0.057, calibrated using nearby stars in the 2MASS catalogue. From VISTA survey images, we measured a 2-sigma upper limit to be Ks(Vega) > 19.56. No other obviously variable sources are seen, to the depth of the VISTA comparison images. We thank the staff at the VLT, for the rapid execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39535. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37548] EP250227a: Optical upper limits with Kinder observations
by GCN Circulars 28 Feb '25

28 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39534 SUBJECT: EP250227a: Optical upper limits with Kinder observations DATE: 25/02/28 16:56:52 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> A. Aryan (NCU), A. K. H. Kong (NTHU), T.-W. Chen, H.-Y. Hsiao, C.-S. Lin (all NCU), J. Gillanders (Oxford), S. J. Smartt (Oxford/QUB), Y. J. Yang, A. Sankar. K, Y.-C. Pan, C.-C. Ngeow, W.-J. Hou, M.-H. Lee, H.-C. Lin, C.-H. Lai, J.-K. Guo (all NCU), S. Yang, L. L. Fan, Z. N. Wang, G. H. Sun (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 EP250227a (Wen et al., GCN 39532) using the 40cm SLT telescope at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al. 2024, arXiv:2406.09270). The first SLT epoch of observations in the i band started at 15:53 UT on the 27th of February 2025 (MJD = 60733.662), ~11.22 hrs after the EP trigger, while the first SLT epoch of observations in the r band started at 16:28 UT on the 27th of February 2025 (MJD = 60733.686), ~11.79 hrs after the EP trigger. We utilized the astroalign (Beroiz et al., 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al., 2022, ApJ, 935, 167) packages to align and stack the individual frames. We did not detect any uncataloged optical counterpart candidate within the EP-WXT localization error circle of radius 2.7 arcminutes. We further employed the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform PSF photometry on our stacked frames. The details of the observations and measured three sigma upper limits (in the AB system) were as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass SLT | i | 60733.662 | 11.22 | 300 * 6 | >21.1 | 1".47 | 1.80 SLT | r | 60733.686 | 11.79 | 300 * 12 | >21.5 | 1".46 | 1.49 The non-detection of any prominent optical counterpart is consistent with Malesani et al., (GCN 39533). The presented upper limits were calibrated using the field stars from the Pan-STARRS1 catalog and were not corrected for the expected Galactic foreground extinction corresponding to a reddening of A_i = 0.12 mag and A_r = 0.16 mag, respectively, in the direction of the transient (Schlafly & Finkbeiner 2011). View this GCN Circular online at https://gcn.nasa.gov/circulars/39534. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37547] EP250227a: NOT optical observations
by GCN Circulars 28 Feb '25

28 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39533 SUBJECT: EP250227a: NOT optical observations DATE: 25/02/28 16:36:03 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie> D. B. Malesani (DAWN/NBI and Radboud Univ.), A. Martin-Carrillo (UCD), A. J. Levan (Radboud Univ and Warwick Univ.), F. E. Bauer (PUC), P. G. Jonker (Radboud Univ), M. Alejandra Diaz Teodori (NOT and Turku Univ.), Roar H. Rasmussen (NOT and Aarhus Univ.), Saskia Schlagenhauf (QUB), report for a larger collaboration: We obtained observations of the field of the fast X-ray transient EP250227a (Wen et al. GCN 39532) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations started on 2025 Feb 28.126 UT (22.37 hr after the EP trigger) and were carried out in the r and z filters. No new source is visible within the EP/FXT X-ray error circle (Wen et al. GCN 39532), down to a 3-sigma limiting magnitude r > 23.7 AB, calibrated against nearby Pan-STARRS objects. At the edge of the error circle, we note the presence of a source, visible also in the Legacy Survey and whose brightness is consistent with the archival value. While this is a potential host galaxy for EP250227a, its chance association probability is not negligible. We also performed image subtraction on our stacked r-band image using the Legacy Survey as template. A single variable source is identified at coordinates (inconsistent with those of the EP/FXT error circle): R.A.(J2000) = 13:36:29.37 Dec.(J2000) = -13:49:00.16 This source is located about 1” to the NE of the nucleus of a galaxy visible in the Legacy Survey with magnitude r = 18.8. We measure for the variable source r = 22.5 +/- 0.1 AB. The nature of this source and its association with EP250227a are unclear at the moment. Further observations are planned and deep r-band photometry of the field is encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/39533. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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