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

[vsnet-grb-info 37588] EP250225a: the candidate optical counterpart is an AGN
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39573 SUBJECT: EP250225a: the candidate optical counterpart is an AGN DATE: 25/03/03 15:25:46 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> D. B. Malesani (DAWN/NBI and Radboud Univ.), D. Mata-Sanchez (IAC and ULL), A. Martin-Carrillo (UCD), A. J. Levan (Radboud Univ.), P. G. Jonker (Radboud Univ.), report on behalf of a larger collaboration: We observed again the variable object (Malesani et al., GCN 39516) located inside the X-ray localization of the fast X-ray transient EP250225a (Jiang et al., GCN 39475; Jiang et al., GCN 39529) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. The observation mid time was 2025 Feb 27.93 UT (2.42 days after the trigger) and a total of 5x300 s was secured in the r band. The object is detected with a flux consistent with our previous observation (Malesani et al., GCN 39516) to within ~0.1 mag, and still brighter than the archival value from the Legacy Survey. Image subtraction confirms no significant variability between the two NOT epochs. A spectrum of this source was secured with the Gran Telescopio Canarias (GTC). Observations started on 2025 Feb 28.98 UT (3.47 days after the trigger), and consisted of a single 1800 s exposure with grism R1000R, yielding usable data in the wavelength range 5000-9000 AA. Detection of two broad features (FWHM ~ 3500 km s^-1), identified as Hbeta and Hgamma, as well as of narrow [O III] 5008, allows us to measure a redshift z = 0.587. The large velocities and the point-like PSF indicate that this is an active galactic nucleus. Given the slow variability and the AGN nature of this source, its relationship to EP250225b is unclear, and the two may well be unrelated. We acknowledge significant support from the observing staff at the NOT, in particular, Alejandra Diaz Teodori (NOT and Turku Univ.), Roar Rasmussen (NOT and Aarhus Univ.), and Saskia Schlagenhauf (QUB), and at the GTC, in particular Antonio Cabrera-Lavers (GTC). View this GCN Circular online at https://gcn.nasa.gov/circulars/39573. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37587] EP250302a: Kinder optical follow-up observations
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39572 SUBJECT: EP250302a: Kinder optical follow-up observations DATE: 25/03/03 14:21:48 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> A. Aryan, T.-W. Chen, C.-S. Lin (all NCU), A. K. H. Kong (NTHU), 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, H.-Y. Hsiao, 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 EP250302a (Zhu et al., GCN 39550; Dai et al., GCN 39556) using the 40cm SLT 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 r band started at 18:30 UT on the 2nd of March 2025 (MJD = 60736.771), ~2.91 hrs after the EP trigger. We took a total of 12 frames in r-band spanning a period of about 2.91hr to 5.22hr since the EP-WXT trigger. The optical counterpart candidate proposed by Zhu et al., (GCN 39550 ) and confirmed by several other observations (Busmann et al., GCN 39551; Leonini et al., GCN 39553; Wu et al., GCN 39555; Xin et al., GCN 39558; Adami et al., GCN 39560; Yang et al., GCN 39561; Becerra et al., GCN 39562; and Izzo et al., GCN 39564), was clearly detected in almost each of the individual frame (besides the last frame). We utilized the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform PSF photometry on individual frames. The details of the observation and measured photometry from the first frame (in the AB system) were as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | Seeing | Airmass SLT | r | 60736.771 | 2.91 | 300 * 1 | 19.60 +/- 0.05 | 1".25 | 1.14 The presented magnitude was calibrated using the field stars from the Pan-STARRS1 catalog and was not corrected for the expected Galactic foreground extinction corresponding to a reddening of A_r = 0.06 mag, respectively, in the direction of the transient (Schlafly & Finkbeiner 2011). View this GCN Circular online at https://gcn.nasa.gov/circulars/39572. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37586] LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39571 SUBJECT: LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search DATE: 25/03/03 13:51:37 GMT FROM: Zsuzsa Marka at IceCube/Columbia University <zsuzsa(a)astro.columbia.edu> IceCube Collaboration (http://icecube.wisc.edu/) reports: We have performed a search for track-like muon neutrino candidate events detected by IceCube consistent with the sky localization of the low-significance gravitational-wave candidate event S250302av in a time range of 1000 seconds centered on the alert event time (2025-03-02 13:57:15 UTC to 2025-03-02 14:13:55 UTC) [1,2]. During this time period, IceCube was collecting good quality data. A single hypothesis test was conducted using a Bayesian approach to quantify the joint GW + neutrino event significance, which assumes a binary merger scenario and accounts for known astrophysical priors, such as GW source distance, in the statistical significance estimation [3]. Two track-like events were found in spatial and temporal coincidence with the gravitational-wave candidate S250302av calculated from the map circulated in the S250302av-2-Preliminary notice. This represents an overall p-value of 0.0084 for the Bayesian search. The p-value measures the consistency of the observed track-like events with the known atmospheric backgrounds for this single map (not accounting for statistical trials from multiple GW events). Further details are available at https://gcn.nasa.gov/missions/icecube and at https://roc.icecube.wisc.edu/public/LvkNuTrackSearch. Properties of the coincident event are shown below: dt(s) RA(deg) Dec(deg) Angular uncertainty(deg) p-value(Bayesian) ------------------------------------------------------------------------------------- 76.86 114.87 3.25 1.16 0.0298 211.98 191.11 58.45 5.39 0.0137 where: dt = Time of track event minus time of GW trigger (sec) Angular uncertainty = Angular uncertainty of track event: the radius of a circle representing 90% CL containment by area. p-value = the individual p-value for the specific track event from this search. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu [1] M. G. Aartsen et al 2020 ApJL 898 L10 [2] Abbasi et al. Astrophys.J. 944 (2023) 1, 80 [3] I. Bartos et al. 2019 Phys. Rev. D 100, 083017 View this GCN Circular online at https://gcn.nasa.gov/circulars/39571. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37585] EP250302a: Swift/UVOT detection
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39570 SUBJECT: EP250302a: Swift/UVOT detection DATE: 25/03/03 12:58:05 GMT FROM: Sam Shilling at Lancaster University <shilling.sam(a)gmail.com> S. P. R. Shilling (Lancaster U.) and A. A. Breeveld (UCL-MSSL) reports on behalf of the Swift UVOT team: Swift/UVOT observed the field of EP250302a (Dai et al., GCN 39556) for 1029 seconds in the U-band starting at 16:36:56 UT, 1 hour after the detection by Einstein Probe WXT. A source consistent with the EP-FXT position (Dai et al., GCN 39556) is detected and appears to be fading. The preliminary detection magnitudes reported below are calculated using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373). The magnitude at the start of the observation is 17.64 +/- 0.05 (1 hour post trigger) and decays to 18.88 +/- 0.12 (~2 hours post trigger). We note that an X-ray source at the EP-FXT position was independently observed by the Swift/XRT (Page et al., GCN 39557). We also note that, in addition to the Swift/UVOT, various other facilities have observed an optical counterpart at this position (Zhu et al., GCN 39550; Busmann et al., GCN 39551; Leonini et al., GCN 39553; Wu et al., GCN 39555; Xin et al., GCN 39558; Lipunov et al., GCN 39559; Adami et al., GCN 39560; Becerra et al., GCN 39562; Pankov et al., GCN 39565; Reguitti et al., GCN 39568; Komesh et al., GCN 39569). View this GCN Circular online at https://gcn.nasa.gov/circulars/39570. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37584] EP250302a: NUTTelA-TAO Early Measurments
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39569 SUBJECT: EP250302a: NUTTelA-TAO Early Measurments DATE: 25/03/03 12:18:23 GMT FROM: Toktarkhan Komesh at Nazarbayev University <toktarkhan.komesh(a)nu.edu.kz> T. Komesh (NU), Z. Abdullayev (NU), Z. Maksut (NU), D. Berdikhan (NU), B. Grossan (UCB, NU), M. Krugov (FAI) and E. Abdikamalov (NU) report on behalf of the Energetic Cosmos Laboratory: The Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) pointed at EP250302a on receipt of an automated GCN / EP position alert, observing in Sloan g' and r' bands, with the Burst Simultaneous Three-Channel Imager (BSTI; Grossan, Kumar & Smoot 2019, JHEA, 32, 14). We started observations at 15:42:43 UT on 2025-03-02, 399 seconds after the Einstein Probe trigger (Dai et al., GCN 39556). Observations were made in partially cloudy conditions. A new and changing source consistent with the XRT position (Page et al., GCN 38761) was detected. We report the following photometric values for the optical transient: tc-t0(s) g'(mag) err r'(mag) err exposure_time (s) -------------------------------------------------------------- 424 - 18.36 0.08 50 628 - 18.35 0.08 300 928 - 18.80 0.13 300 1273 - 18.76 0.07 240 1513 - 18.55 0.06 240 1753 - 18.12 0.04 240 1993 - 17.71 0.03 240 2233 - 17.58 0.02 240 2686 - 17.48 0.03 240 2926 - 17.54 0.02 240 3166 - 17.58 0.02 240 3406 - 17.65 0.02 240 3646 - 17.68 0.03 240 3886 - 17.73 0.03 240 4126 - 17.85 0.03 240 4366 - 17.88 0.04 240 4606 - 17.95 0.03 240 4846 - 18.08 0.04 240 5086 - 18.11 0.03 240 5326 - 18.18 0.04 240 5566 - 18.32 0.04 240 5806 - 18.47 0.04 240 6046 - 18.56 0.04 240 6348 18.93 0.05 18.56 0.04 240 6588 18.99 0.06 18.76 0.04 240 6828 19.01 0.05 18.86 0.05 240 7068 19.05 0.05 18.86 0.05 240 7308 19.06 0.05 18.90 0.05 240 7548 19.12 0.05 18.94 0.05 240 7788 19.28 0.07 19.01 0.06 240 8028 19.43 0.08 19.01 0.06 240 8269 19.53 0.08 19.19 0.07 240 8509 19.34 0.06 19.19 0.06 240 tc-t0 = trigger time minus image center time. Calibration was done with 4 bright Pan-STARRS catalog stars on our images. Our results are in agreement with those reported in previously published circulars (Zhu et. al, GCN 39550; Wu et. al, GCN 39555; Xin et. al, GCN 39558; Pankov et al., GCN 39565). We caution the reader that these are preliminary results, without color or other corrections, and will likely change in small measure. Please also note that times are approximate. ---------------------------------- NU = Nazarbayev University, Astana, Kazakhstan UCB = University of California, Berkeley, USA FAI = Fesenkov Astrophysical Institute, Kazakhstan This research has been funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP26103591). The NUTTelA-TAO Team acknowledges the support of the staff of the Assy-Turgen Astrophysical Observatory, Almaty, Kazakhstan, and the Fesenkov Astrophysical Institute, Almaty, Kazkhstan. View this GCN Circular online at https://gcn.nasa.gov/circulars/39569. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37583] EP250302a: optical observation from the INAF Asiago Observatory
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39568 SUBJECT: EP250302a: optical observation from the INAF Asiago Observatory DATE: 25/03/03 11:27:12 GMT FROM: Andrea Reguitti at INAF - Osservatorio Astronomico di Brera <andreareguitti(a)gmail.com> A. Reguitti (INAF-OAB) reports on behalf of the CIBO (Coordinamento Italiano Burst Ottici) collaboration: We observed the field of EP250302a (Zhu et al., GCN 39550) from the INAF - Padova Astronomical Observatory located in Asiago (Italy) with the 67/92 Schmidt robotic telescope. The observation was carried in the Sloan-i filter, started on 2025 March 02 at 20:01:15 UT (i.e. 4.4 hr after the burst), and lasted for 15 minutes. In our stacked images, the optical counterpart is detected at the coordinates reported by Zhu et al., GCN 39550: i = 19.98+-0.17 mag (AB; calibrated against the PS1 catalogue), at a mid-time of about 4.5 hours after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/39568. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37582] EP250302a: REM NIR upper limits
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39567 SUBJECT: EP250302a: REM NIR upper limits DATE: 25/03/03 10:11:26 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio(a)inaf.it> R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of EP250302a (Dai et al., GCN 39556) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the J, H, and K bands, started on 2025 March 03 at 02:15:53 UT (i.e. 10.66 hr after the burst), and lasted for about 1 hour. From preliminary analysis, we do not find any counterpart at the position of the reported optical afterglow (Zhu et al., GCN 39550; Busmann et al., GCN 39551; Leonini et al., GCN 39553; Wu et al., GCN 39555; Xin et al., GCN 39558; Adami et al., GCN 39560; Yang et al., GCN 39561; Becerra et al., GCN 39562; Izzo et al., GCN 39564; Pankov et al., 39565) down to the following 3sigma limit: H > 16.1 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 11.09 hours after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/39567. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37581] IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39566 SUBJECT: IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect DATE: 25/03/03 09:56:46 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> K. Labzina, K.Zhirkov, V.Lipunov, E.Gorbovskoy, G.Antipov, D.Vlasenko, A.Kuznetsov, N.Tyurina, P.Balanutsa, A.Chasovnikov, D.Kuvshinov, V.Topolev,Ya.Kechin,Yu.Tselik, K.Minkina(Lomonosov Moscow State University, SAI, Physics Department), O.Gress, N.Budnev, O.Ershova (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), D.Buckley (SAAO), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started IceCube-241113 (IceCube, Zegarelli et al. GCN#38200) to the IceCube Alert 241113.02 (trigger No 30891383, 13h 04m 46.32s , +08d 29m 27.6s, R=0.53) errorbox 477 sec after notice time and 554 sec after trigger time at 2024-11-13 00:31:35 UT, with upper limit up to 16.0 mag. (Lipunov et al. GCN#38186) MASTER cover map: https://master.sai.msu.ru/site/master2/observ.php?id=2668204 We analyzed MASTER archive images since 2012 of the sources, that can be related with this event. We detected blazar J131155.76+085340.9 inside 3 sigma https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=&-out.add=_r&-out.add=… and we detected its brightening up to 16.9m during last nights observations. The MASTER archive light curve from 2010 year is available at http://observ.pereplet.ru/MASTER_IC241113A.jpg Light curve shows that after neutrino alert the blazar J131155.76+085340.9 was in a dim state 20.2m, after which, within an half hour, it increased its brightness to 16.9m. This, we report observation of an Zhirkov effect, discovered earlier (The Astrophysic Jornal Letters, 896, L19, 2020 https://ui.adsabs.harvard.edu/abs/2020ApJ...896L..19L/abstract ). View this GCN Circular online at https://gcn.nasa.gov/circulars/39566. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37580] EP250302a: Mondy Observations and Optical Light Curve
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39565 SUBJECT: EP250302a: Mondy Observations and Optical Light Curve DATE: 25/03/03 09:54:00 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), A. Moskvitin (SAO RAS), E. Klunko (ISTP) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of a fast X-Ray transient EP250302a (Zhu et. al, GCN 39550; Busmann et. al, GCN 39551; Leonini et. al, GCN 39553; Wu et. al, GCN 39555; Dai et. al, GCN 39556; Page et. al, GCN 39557; Xin et. al, GCN 39558; Lipunov et. al, GCN 39559; Adami et. al, GCN 39560; Yang et al., GCN 39561; Becerra et al., GCN 39562; Izzo et al., GCN 39564) in the R filter with the AZT-33IK 1.5-meter telescope of Mondy observatory. The observations began on 2025-03-02 (UT) 15:50:41.578, i.e. 0.01083 days since trigger. The optical counterpart (firstly reported by Zhu et. al, GCN 39550) is clearly detected in each image of an exposure of 120 sec. The optical light curve displays variable behavior. Initially, the light curve fades until ~1.5e-2 days since trigger, then it is brightening until it reaches peak magnitude of R = 17.26 +/- 0.03 mag at 2025-03-02 (UT) 16:14:42 (0.02751 days since trigger). The further brightness evolution is a decay by the times indicated in Adami et. al, GCN 39560. Our photometry is based on nearby stars from the USNO-B1.0 catalog (see the list below) and has not been corrected for the Galactic extinction. Ref. stars RA Dec R2 11:18:11.14 +33:32:45.34 15.74 11:17:47.64 +33:30:50.19 17.69 The light curve image is available at: http://grb.rssi.ru/EP250302a/EP250302a_LC.jpg View this GCN Circular online at https://gcn.nasa.gov/circulars/39565. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37579] EP250302a: VLT/MUSE optical redshift z = 1.131
by GCN Circulars 03 Mar '25

03 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39564 SUBJECT: EP250302a: VLT/MUSE optical redshift z = 1.131 DATE: 25/03/03 09:11:58 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> L. Izzo (INAF/OACn and DARK/NBI), R. A. J. Eyles-Ferris (Univ. Leicester), D. Xu (NAOC), A. Saccardi (CEA/Irfu), B. Schneider (LAM), D. B. Malesani (DAWN/NBI and Radboud Univ.), J. T. Palmerio (CEA/Irfu), N. R. Tanvir (Univ. Leicester), P. G. Jonker (Radboud Univ.), S. D. Vergani (CNRS - Paris Observatory/LUX), A. J. Levan (Radboud Univ. and Warwick Univ.), report on behalf of the Stargate collaboration: We observed the optical/NIR counterpart (Zhu et al., GCN 39550; Busmann et al., GCN 39551; Leonini et al., GCN 39553; Wu et al., GCN 39555; Xin et al., GCN 39558; Adami et al., GCN 39560; Becerra et al., GCN 39562) of the fast X-ray transient EP250302a (Dai et al., GCN 39556) using the ESO VLT UT4 (Yepun) equipped with the MUSE integral-field spectrograph. The observation mid-epoch is 2025 March 3.193 UT (13.03 hr after the initial high-energy trigger), the total exposure time is 76.5 min, and the covered wavelength range is 4750-9300 AA. The optical counterpart (Zhu et al., GCN 39550) is well detected in the wavelength-stacked “white light” image, as well as in continuum spectroscopy. We also observe several clear absorption features, which we interpret as due to Mg I (2853), Mg II (2804, 2796), and Fe II (2600, 2587, 2383, 2374, 2344), all at a common redshift z = 1.131. Given the overall good S/N of the spectrum, and the fact that there are no features left un-identified, we consider z = 1.131 to be most likely the redshift of EP250302a. Our spectra do not cover the blue region where the z = 0.549 features reported by Yang et al. (GCN 39561) would fall, so we cannot confirm the presence of that system, which could be an intervening absorber. No emission lines at z = 0.549 appear in our data. Thanks to the large MUSE field of view (1' x 1'), further to the optical transient, two neighboring bright galaxies were covered in our observation, including the one noted by Busmann et al. (GCN 39551) and Yang et al. (GCN 39561). For them, we measure the following redshifts: 1) RA = 11:18:05.26, Dec = +33:35:05.6: z = 0.127 from Na I D, Mg b, Hbeta, G band absorption; 2) RA = 11:18:01.03, Dec = +33:35:30.8: z = 0.127 from Halpha, [N II] and [S II] emission. We conclude that these objects are not physically associated with EP250302a. We thank Malte Busmann and Brendan O’Connor for sharing a finding chart of the field, and the ESO observing staff in Paranal, in particular Claudia Cid, Monika Petr-Gotzens, and Jonathan Smoker, for efficiently carrying out these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39564. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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