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

[vsnet-grb-info 42896] EP260601a: Einstein Probe detection of an X-ray transient
by GCN Circulars 02 Jun '26

02 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44766 SUBJECT: EP260601a: Einstein Probe detection of an X-ray transient DATE: 26/06/02 11:52:06 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> G. J. Yang (NAO, CAS), Z. X. Li, G. L. Huang, J. Y. Cao (IHEP, CAS), Y. Wang (PMO, CAS; UCB), W. D. Zhang (NAO, 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 EP260601a. The transient triggered EP-WXT (ID: 01709266307) at 2026-06-01T19:13:22 UTC. The WXT position of the source is R.A. = 257.649 deg, Dec = -1.647 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The preliminary analysis of the WXT data shows that the burst started at T_0 = 2026-06-01T19:12:41 UTC. The light curve shows an initial flare lasting approximately 100 s, followed by tail emission. During the flare, the unabsorbed 0.5-4 keV flux was 5.2 (-1.7/+3.6) x 10^-08 erg cm^-2 s^-1. The time-averaged WXT 0.5-4 keV spectrum over the entire detected emission can be described by an absorbed power law, with the hydrogen column density left as a free parameter. The best-fit hydrogen column density is 6.7 (-1.5/+1.6) x 10^21 cm^-2. The best-fit photon index is 1.2 (-0.3/+0.3). The unabsorbed 0.5-4 keV flux is 2.4 (-0.2/+0.3) x 10^-10 erg cm^-2 s^-1. A follow-up observation with the Follow-up X-ray Telescope (FXT) onboard EP is scheduled. 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/44766. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42895] EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
by GCN Circulars 02 Jun '26

02 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44765 SUBJECT: EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations DATE: 26/06/02 11:05:28 GMT FROM: Marion G <marion.guelfand(a)gmail.com> Marion Guelfand (CPPM), Camila Angulo (UNAM), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), 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) and Antonio de Ugarte Postigo (LAM) report: We observed the field of the EP-WXT Trigger 01709266307 (EP260601a) with the DDRAGO two-channel wide-field imager mounted on the COLIBRÍ telescope. We observed from 2026-06-02 08:36 UTC to 09:00 UTC (from 13.38 to 13.39 hours after the trigger) and obtained 20 minutes of simultaneous exposure in the r and z filters, respectively. The data were reduced and coadded with the COLIBRI pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the Pan-STARRS-DR2 catalog, is in the AB system, and is not corrected for Galactic extinction. We detected the optical counterpart reported by Liu et al., GCN Circ. 44764. The preliminary magnitude derived for that source is: r = 21.93 +/- 0.15 z = 21.07 +/- 0.12 The source is fading between the two observations. Further observations 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/44765. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42894] EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
by GCN Circulars 02 Jun '26

02 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44764 SUBJECT: EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection DATE: 26/06/02 10:23:04 GMT FROM: liuxing(a)nao.cas.cn X. Liu, Z.P. Zhu, 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 EP-WXT Trigger 01709266307 (EP260601a) detected by Einstein Probe (EP), using the JinShan 100B telescope located at Altay, Xinjiang, China. A series of r-band frames were obtained. An uncatalogued and decaying source is detected within the EP/WXT error circle at coordinates R.A. (J2000) = 17:10:38.24 Dec. (J2000) = -01:38:42.4 with an uncertainty of ~ 1.0 arcsec. The source had r ~ 18.4 mag at a median time of ~ 0.73 hr post-trigger, calibrated with Pan-STARRS DR2 and not corrected for Galactic extinction of A_V ~ 1.15 mag. We thus think the source is the optical counterpart of EP260601a. We also note the presence of a faint source with g ~ 25.2 mag in the Legacy Survey DR10 image at the above position, which could be the host of EP260601a. 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/44764. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42893] GRB 260601A: Glowbug gamma-ray detection of a short burst
by GCN Circulars 02 Jun '26

02 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44763 SUBJECT: GRB 260601A: Glowbug gamma-ray detection of a short burst DATE: 26/06/02 01:04:27 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260601A, which was also detected by Fermi/GBM (GCN 44755, 44760) and CALET (Trigger ID Num 1464346716). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-06-01 11:00:11.408 with a duration of 0.26 s and a total significance of about 77 sigma. The light curve comprises a triple-peaked structure. The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/44763. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42892] GRB 260531B: Glowbug gamma-ray detection
by GCN Circulars 01 Jun '26

01 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44762 SUBJECT: GRB 260531B: Glowbug gamma-ray detection DATE: 26/06/01 22:31:42 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260531B, which was also detected by Fermi/GBM (GCN 44747) and GECAM-B (GCN 44754). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-05-31 13:57:58.840 with a duration of 8.2 s and a total significance of about 31.6 sigma. The light curve comprises a complex multi-peaked structure. The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/44762. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42891] GRB 260516D: VLA radio detection
by GCN Circulars 01 Jun '26

01 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44761 SUBJECT: GRB 260516D: VLA radio detection DATE: 26/06/01 21:56:18 GMT FROM: Daniel Perley at Liverpool JMU <d.a.perley(a)ljmu.ac.uk> Daniel A. Perley (LJMU), Genevieve Schroeder (Cornell), and Anna Y. Q. Ho (Cornell) report: We observed the location of the X-ray flash GRB 260516D (Brunet et al., GCN 44649; Brunet et al., 44667) using the Karl G. Jansky Very Large Array on 2026-05-22 between 10:46-11:33 UT (approximately 5.6 days after the GRB trigger) using the X-band receivers (mean frequency 10 GHz). A source is detected at the location of the optical transient (Li et al., GCN 44654) with a flux density of 34.9 +/- 8.8 uJy. The inferred luminosity of 2.9 x 10^30 erg/s/Hz is characteristic of GRB afterglows at the equivalent rest-frame post-GRB time, but at the low end of the distribution. We thank the NRAO staff for scheduling and executing these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44761. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42890] GRB 260601A: Fermi GBM Observation
by GCN Circulars 01 Jun '26

01 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44760 SUBJECT: GRB 260601A: Fermi GBM Observation DATE: 26/06/01 18:13:56 GMT FROM: A. Holzmann Airasca at University of Trento and INFN Bari <a.holzmannairasca(a)unitn.it> A. Holzmann Airasca (UniTrento and INFN Bari) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 11:00:12.44 UT on 01 June 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260601A (trigger 802004417/260601458). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 15.06, Dec = 44.38 (J2000 degrees, equivalent to J2000 1h 0m, +44d 22'), with a statistical uncertainty of 2.03 degrees. (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a mixture of two Gaussians, one with a radius of 1.8 degrees (52% contribution) and one with a radius of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]). The angle from the Fermi LAT boresight is 30 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 0.8 s (50-300 keV). The time-averaged spectrum from T0-0.07 to T0+0.34 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.63 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 960 +/- 30 keV. The event fluence (10-1000 keV) in this time interval is (2.08 +/- 0.06)E-06 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.064 s in the 10-1000 keV band is 40 +/- 1 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 750 +/- 20 keV, alpha = -0.57 +/- 0.05 and beta = -2.0 +/- 0.2. 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/44760. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42889] EP260530a/AT 2026nwl: COLIBRÍ optical observations
by GCN Circulars 01 Jun '26

01 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44759 SUBJECT: EP260530a/AT 2026nwl: COLIBRÍ optical observations DATE: 26/06/01 17:34:44 GMT FROM: globus(a)astro.unam.mx Noémie Globus (UNAM), Damien Dornic (CPPM), Alan M. Watson (UNAM), Rosa L. Becerra (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), , Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (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) and Antonio de Ugarte Postigo (LAM) report: We observed the field of the Einstein Probe X-ray transient EP260530a (Wu et al., ATel #17824) with the DDRAGO two-channel wide-field imager mounted on the COLIBRÍ telescope. The observations targeted the optical counterpart candidate, AT 2026nwl, discovered by GOTO (TNS Astronomical Transient Report No. 306622) and associated with EP260530a. We observed from 2026-06-01 04:59 to 06:02 UTC (from (55.93 to 56.97 hours after the GOTO discovery) and obtained 11, 23, 10, 24, and 20 minutes of exposure in the g, r, i, z, and y filters, respectively. The data were reduced and coadded with the COLIBRÍ ASU 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 detect the optical counterpart previously reported by GOTO (AT 2026nwl). The source is measured at the following preliminary magnitudes: g = 15.22 +/- 0.01, r = 15.33 +/- 0.01, i = 15.41 +/- 0.01, z = 15.52 +/- 0.01, y = 15.58 +/- 0.01. The source is brighter than the magnitude of L = 17.03 at 2026-05-29 21:04 UTC reported by the GOTO team (TNS Astronomical Transient Report 306622), but fainter than the unfiltered magnitude of 14.46 at 2026-05-31 05:24 UTC reported by Sokolovsky et al (TNS Astronomical Transient Report 306654). If the transient has a simple rise and decay, this suggests that it has already reached its maximum. The source shows blue colors, consistent with both a CV and an FBOT. During the 55 minutes of our observations, the source shows a smooth rise from r = 15.35 to r = 15.28 followed by a smooth fall again to r = 15.36. Similar behavior is also seen in the other filters. This variability is reminiscent of that seen in CVs. We encourage spectroscopic observations to determine the redshift of this source and its likely nature. 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/44759. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42888] GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
by GCN Circulars 01 Jun '26

01 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44758 SUBJECT: GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search DATE: 26/06/01 15:40:07 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet, O. Godet (IRAP), D. Turpin (CEA) report on behalf of the SVOM/ECLAIRs team The SVOM/ECLAIRs telescope detected a transient source, labelled GRB 260530C, starting at 2026-05-30T00:13:15.62 UTC (trigger time T0), through an on-ground search with the event-by-event data downloaded through the X-band ground station. The burst was detected within several energy ranges and timescales. The best detection is obtained by the Image Trigger with a signal-to-noise ratio of 6.8 within 8-120 keV over a time window of 20.48 seconds starting at T0-20.48s. The burst that triggered ECLAIRs onground shows a double peak structure. The burst duration is estimated to be around 25s in the 4-120 keV energy band through imaging. The localization of the source is RA, Dec = 196.655, 26.384 degrees: RA (J2000) = 13h 06m 37.2s Dec (J2000) = 26d23m02.4s with a 90% C.L. radius of 12.8 arcmin (including systematic error of 6 arcmin added in quadrature). We note that no bright catalogued X-ray sources are found in the error box. The time-averaged spectrum from T0-20.5 s to T0+4.5 s in the energy range 5-120 keV is best fitted by a powerlaw model with alpha = -1.10 +/- 0.16. With this model, the 4-120 keV fluence is (3.2 +0.3/-1.0) e-7 erg/cm^2 and the 4-120 keV photon flux is 0.26 +0.02/-0.08 ph/cm^2/s. All the quoted errors are at the 68% confidence level. A SVOM ToO observation has been requested to follow-up this trigger with both MXT and VT instruments. The results of these observations will be reported later in a future Circular. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM/ECLAIRs point of contact for this burst is: Marius Brunet (IRAP) (marius.brunet at utoulouse.fr) View this GCN Circular online at https://gcn.nasa.gov/circulars/44758. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42887] AT2026nik: EP-FXT X-ray counterpart
by GCN Circulars 01 Jun '26

01 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44749 SUBJECT: AT2026nik: EP-FXT X-ray counterpart DATE: 26/05/31 21:01:15 GMT FROM: Jonathan Quirola at Radboud University <jaquirola1990(a)gmail.com> J. Quirola-Vasquez (Radboud), P. G. Jonker (Radboud), A. A. Chrimes (ESA/ESTEC), A. J. Levan (Radboud & Warwick), A Inkenhaag (Bath), D. Coppejans (Warwick), P. Groot (Radboud/UCT/SAAO): We observed the field of AT2026nik (AstroNotes: 2026-151, 2026-152) with the Follow-up X-ray Telescope (FXT) aboard the Einstein Probe mission. The observation was carried out from 2026 May 29 18:45:25.9 to May 30 00:22:29.8 UT, with a total exposure time of 7.2 ks using Modules A and B. After stacking the data from both modules, we detected an X-ray source with a significance of S/N ≈ 5.5 at the position (with an uncertainty of 10"): RA = 11:22:52.1 Dec = -06:13:21.7 No X-ray source is reported at this position in the ROSAT, eROSITA, Swift-XRT, XMM-Newton, or Chandra catalogs, according to the STONKS Multi-Mission X-ray Catalog (Quintin et al. 2024). The position of the detected X-ray source is consistent with that of AT2026nik, suggesting that it is the X-ray counterpart of the transient. The source has a net count rate of 2.58e-3 counts/s. Assuming a Galactic hydrogen column density of N_H = 4e20 cm-2 and a power-law spectrum with photon index Γ = 1.5, we estimate an absorbed X-ray flux of approximately 5.8e-14 erg/cm2/s. AT2026nik exhibited a blue, nearly featureless optical spectrum (P. Pessi and J. Wise; AstroNotes: 2026-151, 2026-152), with a tentative detection of the interstellar Mg II absorption doublet at z = 0.182. Assuming this redshift, the inferred X-ray luminosity is approximately L_X~5.4e42 erg/s, consistent with that observed in AT2018cow and other LFBOTs at a similar epoch (e.g., Margutti et al. 2019). The blue optical spectrum and the newly detected X-ray counterpart support the classification of AT2026nik as a luminous fast blue optical transient (LFBOT). We thank the Einstein Probe staff for their execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44749. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0