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

[vsnet-grb-info 38066] GRB 250403A: SVOM/VT optical observation
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40045 SUBJECT: GRB 250403A: SVOM/VT optical observation DATE: 25/04/04 11:49:37 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> L.P. Xin, Y. L. Qiu, C. Wu, H. L. Li, J . Z. H. Yao, Y. Xu, P. P. Zhang, W. J. Xie, J. Wang, X. H. Han, Y. J. Xiao, H. B. Cai, Y. N. Yi, J. Y. Wei (NAOC), Y. Julakanti, R. A. J. Eyles-Ferris (U. Leicester) report on behalf of the SVOM team: SVOM performed a Target of Opportunity observation of GRB 250403A detected by Fermi/GBM (Fermi GBM team, GCN 40025) and SVOM/ECLAIRs (Julakanti et al., GCN 40026) in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The optical afterglow (Starling et al., GCN. 40028; Wu et al., GCN 40029; Du et al., GCN 40031; Li et al., GCN 40032; Julakanti et al., GCN 40034; Ghosh et al., GCN 40039; Jiang et al., GCN 40041, Pérez-Fournon et al., GCN 40043, Brivio et al., GCN 40044) was detected with a brightness of VT_R=21.26 +/- 0.07 (AB) mag and VT_B=21.78 +/- 0.07 (AB) at the mid time of 14.26 hours after the burst. 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/40045. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38065] GRB 250403A: REM NIR afterglow detection
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40044 SUBJECT: GRB 250403A: REM NIR afterglow detection DATE: 25/04/04 10:49:24 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 GRB 250403A detected by SVOM/ECLAIRs (Julakanti et al., GCN 40026) and Fermi/GBM (Fermi GBM team, GCN 40025) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, and K bands, started on 2025 April 03 at 23:27:03 UT (i.e. 8.2 hr after the burst), and lasted for about 1 hour. From preliminary photometry, we detect the NIR counterpart at the position of the optical afterglow (Starling et al., GCN. 40028; Wu et al., GCN 40029; Du et al., GCN 40031; Li et al., GCN 40032; Julakanti et al., GCN 40034; Ghosh et al., GCN 40039; Jiang et al., GCN 40041, Pérez-Fournon et al., GCN 40043) with the following magnitude: H = 16.3 +/- 0.3 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 8.6 hours after the trigger. The afterglow is not detected in our r-band observations down to the following 3sigma limit: r > 20.7 (AB; calibrated against the Pan-STARRS catalogue), at a mid-time of 8.7 hours after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/40044. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38064] GRB 250403A: LCO optical counterpart detection
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40043 SUBJECT: GRB 250403A: LCO optical counterpart detection DATE: 25/04/04 10:34:53 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia (ULL), and A. López-Oramas (IAC and ULL) We report on Las Cumbres Observatory Global Telescope network (LCOGT) observations of GRB 250403A, detected by Fermi GBM (Fermi GBM team, GCN circ. 40025), SVOM/ECLAIRs (Julakanti et al., GCN circ. 40026), and Swift XRT (Dichiara et al., GCN circ. 40037) We observed the field of GRB 250403A with two LCOGT 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at Sutherland Observatory (South Africa) in the SDSS r, i, g, and u filters, starting at 2025-04-03 22:00:46 UTC, about 6.76 hours after the Fermi and SVOM triggers. A source is clearly detected in the four filters at the position of the optical counterpart first reported by GOTO (Starling et al., GCN circ. 40028) and detected also by WU et al. (GCN circ. 40029), Du et al. (GCN circ. 40031), Li et al. (GCN circ. 40032), Julakanti et al. (GCN circ. 40034), Ghosh et al. (GCN circ. 40039), and Jiang et al. (GCN circ. 40041). The r, i, and g images were calibrated against Pan-STARRS DR2 stars and the u image was calibrated against stars from the Gaia DR3 synthetic photometry catalog generated from the Gaia BP/RP mean spectra (Gaia Collaboration, 2022). We measure the following preliminary magnitudes, that are not corrected for Galactic extinction: Date | UT start | mag | error | filter | exposure time (sec) --------------------------------------------------------------------- 2025-04-03 22:00:46 20.34 0.08 r 300 2025-04-03 23:00:56 20.39 0.08 i 300 2025-04-03 23:08:52 20.97 0.08 g 300 2025-04-04 00:14:01 21.44 0.16 u 600 We note that a faint source, morphologically classified as point-like, is detected in the Legacy Surveys (LS) DR10 images at the position of the optical counterpart of GRB 250403A, with coordinates RA, Dec (J2000) = 194.6157, -24.3795, and magnitudes in the LS DR10 catalog of g = 24.16, r = 24.17, i = 23.88, and z = 24.34. This work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT observing programme IAC2025A-009, SGLF). View this GCN Circular online at https://gcn.nasa.gov/circulars/40043. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38063] IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40042 SUBJECT: IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect DATE: 25/04/04 10:05:05 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> K. Labzina, K.Zhirkov, V.Lipunov, E.Gorbovskoy, A.Kuznetsov, G.Antipov, D.Vlasenko, A.Kuznetsov, N.Tyurina, P.Balanutsa, A.Chasovnikov, V.Topolev, Ya.Kechin, V.Senik (Lomonosov MSU), O.Gress, N.Budnev, O.Ershova (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), D.Buckley (SAAO), A.Sosnovskij (Crao RAS), 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 AstrophysicsObservatory) MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the IC250330A alert(IceCube GCN# 39943, trigger No 49427574, 20h 29m 18.48s, +10d 58m 33.6s, R=0.51deg) errorbox 91 sec after notice time (148 sec after trigger time) at 2025-03-30 08:33:34 UT, with upper limit up to 19.2m (Lipunov et al.GCN# 39942) MASTER cover map: https://master.sai.msu.ru/site/master2/observ.php?id=2828042 We analyzed MASTER archive images since 2010 of possible sources, that can be related with this event. There is blazar PKS 2032+107 inside 3 sigma https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=&-out.add=_r&-out.add=… We detected the blazar in a dim state with m=15.4m 4 minutes after the alarm, and 3 minutes later, it brightened to 14.6m. After it an hour later, blazar returned to its original state. MASTER archive light curve from 2010 year is available at http://observ.pereplet.ru/IC/MASTER_IC250330.jpg 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/40042. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38062] GRB 250403A: JinShan optical observations
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40041 SUBJECT: GRB 250403A: JinShan optical observations DATE: 25/04/04 09:10:46 GMT FROM: sqjiang at NAOC <sqjiang(a)bao.ac.cn> S.Q. Jiang, Z.P. Zhu, X. Liu, J. An, D. Xu (NAOC), S.Y. Fu (HUST), J.Z. Liu (XAO) report on behalf of a large collaboration: We observed the field of GRB 250403A detected by SVOM/ECLAIRs (Julakanti et al., GCN 40026) and Fermi/GBM (Fermi GBM team, GCN 40025), using the 100cm-C telescope (100C) of the JinShan project, located at Altay, Xinjiang, China. Observations started at 18:03:34.11 UT on 2025-04-03, i.e., 2.80 hr after the SVOM/ECLAIRs trigger, and a series of 600 s frames were obtained in the Sloan r- and i- bands. The optical afterglow (Starling et al., GCN 40028; Wu et al., GCN 40029; Du et al., GCN 40031; Li et al., GCN 40032; Julakanti et al., GCN 40034; Ghosh et al., GCN 40039) of GRB 250403A is clearly detected in our stacked images. Preliminary photometry results are as follows: T_mid(hr) Filter Mag(AB) MagErr 4.06 r 19.77 0.05 4.73 i 20.11 0.06 calibrated with nearby Legacy Survey stars and not corrected for Galactic extinction. We acknowledge the excellent support from T.Q. Chen and Z.K. Feng for enabling these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/40041. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38061] GRB 250402A: EP-FXT afterglow detection
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40040 SUBJECT: GRB 250402A: EP-FXT afterglow detection DATE: 25/04/04 09:08:48 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> D. Turpin, B. Cordier (CEA), H. Q. Cheng (NAO, CAS), R.-Z. Li (YNAO, CAS), Q. C. Zhao, Z. H. Yang (IHEP, CAS), Y. Liu (NAO, CAS), W. Yuan (NAO, CAS) on behalf of the SVOM and Einstein Probe teams We performed a follow-up observation of GRB 250402A (Chen et al., GCN 40014) with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation started at 2025-04-03 20:30:51 (T-TGRB ~ 21.4 hr) for about 4.6ks of exposure in total. A bright uncatalogued X-ray source is detected by both FXT-A and FXT-B at the position (J2000) RA, DEC = 213.4094, -5.9295 (error=10", 90% C.L.), 2.1 arcminute away from the SVOM/ECLAIRs position (Chen et al., GCN 40014). This position is consistent with the x-ray and optical afterglow positions reported by SVOM/VT (Xin et al., GCN 40015), SVOM/MXT (Maggi et al., GCN 40019), the LCO telescope (Pérez-Fournon et al., GCN 40020), VLT/X-shooter (Schneider et al., GCN 40022), SVOM/COLIBRI (FM-GFT, Magnani et al., GCN 40023) and Swift/XRT (Dichiara et al., GCN 40027). The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 7.2 x 10^21 cm^-2 and a photon index of 2.16 (-0.22/+0.25). The derived average observed 0.5-10 keV flux is 1.31 (-0.12/+0.16) x 10^(-12) erg/s/cm^2. 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/40040. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38060] GRB 250403A: Optical counterpart detection by LCO.
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40039 SUBJECT: GRB 250403A: Optical counterpart detection by LCO. DATE: 25/04/04 08:44:09 GMT FROM: ankur ghosh at CAPP, University of Johannesburg <ghosh.ankur1994(a)gmail.com> Ankur Ghosh, Soebur Razzaque (CAPP, University of Johannesburg), Alexander Moskvitin, Yulia Sotnikova (SAO RAS), Naveen Dukiya (ARIES), Rahul Gupta (NASA GSFC) on behalf of a larger collaboration. We observed the field of the GRB 250403A triggered by Fermi (Fermi GBM team, GCN 40025) in the V, r filter of the 1-meter Sinistro telescope at the Las Cumbres Observatory Global Telescope (LCOGT) node located at Teide Observatory, Tenerife, Canary Islands, Spain. The 1-m Sinistro telescope is equipped with a 4K x 4K CCD (FOV: 26 x 26 arcmin, scale: 0.39 arcsec/pixel). Observations began on March 29, 2025, starting 1.49 hours after the GRB trigger. We clearly detect the optical transient (OT) reported by GCNs (Julakanti et al. 2025, GCN 40026, Starling et al., GCN 40028; Wu et al., GCN 40029; Du et al., GCN 40031; Li et al., GCN 40032, Julakanti et al. 2025, GCN 40034) in our r band image. ------------------------------------------------------------------------------------------------- |Date| |UTstart| |t-T0 (hours)| |Exp (sec)| |Filter| |Magnitude| -------------------------------------------------------------------------------------------------- 2025-04-04 00:11:21.696 8.93 1 x 900 r r = 20.83 +/- 0.07 -------------------------------------------------------------------------------------------------- The field was calibrated against nearby APASS stars, with magnitudes converted using Lupton (2005) equations, and has not been corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40039. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38059] EP250402a: EP-FXT follow-up observations
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40038 SUBJECT: EP250402a: EP-FXT follow-up observations DATE: 25/04/04 08:39:01 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.-Z. Li (YNAO, CAS), H. Q. Cheng (NAO, CAS), Q. C. Zhao, Z. H. Yang (IHEP, CAS), Y. Liu (NAO, CAS) report on behalf of the Einstein Probe team: The X-ray transient EP250402a was detected by EP-WXT (Li et al., GCN 40017). Two follow-up observations were conducted by EP-FXT. The first follow-up observation was performed at 2025-04-03T07:25:06 (UTC), about 18.93 hours after the trigger, with an exposure time of 1 ks. On-ground analysis of the EP-FXT data identified an uncatalogued X-ray source at the coordinates (J2000): R.A., Dec. = 172.1798, -47.2954 deg, with an uncertainty of about 10 arcsec (radius, 90% confidence level, including both statistical and systematic errors). This source lies within the EP-WXT error circle (Li et al., GCN 40017). The 0.5-10 keV spectrum can be fitted with an absorbed power-law model, with the column density nH fixed at the Galactic value of 1.43e21 cm^-2, and a photon index of 2.9 (+1.2, -1.0). The unabsorbed 0.5-10 keV flux is 1.9 (+1.2, -0.7) e-13 erg/s/cm^2. The second follow-up observation was performed at 2025-04-03T17:11:45 (UTC), about 28.71 hours after the trigger, with an exposure time of 4.4 ks. The 0.5-10 keV spectrum can also be fitted with an absorbed power-law model, with nH fixed at the Galactic value of 1.43e21 cm^-2, and a photon index fixed at 2.9. The unabsorbed 0.5-10 keV flux is 9.1 (+5.0, -3.5) e-14 erg/s/cm^2. All uncertainties quoted above are at the 90% confidence level. 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/40038. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38058] GRB 250403A: Swift-XRT observations
by GCN Circulars 03 Apr '25

03 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40037 SUBJECT: GRB 250403A: Swift-XRT observations DATE: 25/04/04 03:32:07 GMT FROM: Simone Dichiara at Pennsylvania State University <sbd5667(a)psu.edu> S. Dichiara (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB), K.L. Page and P.A. Evans (U.Leicester) reports on behalf of the Swift-XRT team: We have analysed 401 s of XRT data for the GRB 250402A detected by Fermi GBM (Fermi team, GCN circ. 40025) and SVOM/ECLAIRs (SVOM trigger sb25040305; Julakanti et al., GCN circ. 40026), from T0+7.62 ks to T0+8.02 ks after the SVOM/ECLAIRs trigger. The data are entirely in Photon Counting (PC) mode. We find an uncatalogued X-ray source 3.1 sigma above the RASS limit, consistent with the reported optical counterpart (Starling et al., GCN 40028, Chao et al., GCN 40029, Guowang et al., GCN 40031, Li et al., GCN 40032). Details of this source are given below: Source 1: RA (J2000.0): 194.6162 = 12:58:27.90 Dec (J2000.0): -24.3800 = -24:22:47.9 Error: 3.7 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: 0.29 (±0.07) ct s-1 Flux: 1.2 (±0.3) ×10-11 erg cm-2 s-1 (observed, 0.3-10 keV) This XRT position is 2.5 arcsec away from the optical position (Starling et al., GCN 40028). The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/SVOM/SVOM_FIELD00010/. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40037. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38057] GRB 250322A: 10 GHz VLA radio upper limits
by GCN Circulars 03 Apr '25

03 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40036 SUBJECT: GRB 250322A: 10 GHz VLA radio upper limits DATE: 25/04/04 01:52:21 GMT FROM: Genevieve Schroeder at Cornell University <genevieveschroeder(a)u.northwestern.edu> G. Schroeder (Cornell), T. Laskar (Utah), W. Fong, J. Rastinejad (Northwestern) report: We observed the position of the short GRB 250322A (Gupta et al., GCN 39835; Tembhurnikar et al., GCN 39849; Ridnaia et al., GCN 39873) with the Karl G. Jansky Very Large Array (VLA) under program 25A-063 (PI Schroeder) beginning on 2025 March 25 at 22:07 UT (3.25 days post-burst) for 1 hour at a mean frequency of 10 GHz. Based on preliminary analysis, we do not detect any radio emission at or near the position of the XRT afterglow (Perri et al., GCN 39855), to a 3 sigma limit of 20 microJy. We additionally do not detect the putative host galaxy in our image (Martin-Carrillo et al., GCN 39842; Becerra et al., GCN 39844; 39845l; Kilpatrick & Fong, GCN 39846; Fong et al., GCN 39852, Schneider et al., GCN 39863). Assuming a redshift of z = 0.42 (Fong et al., GCN 39852; Yang et al. GCN 39859), these observations imply a limit on the radio-inferred star formation rate of < 18 M_sol/year (following the formalism of Greiner et al. 2016). Using the putative host redshift, the lack of radio afterglow detection implies a radio luminosity of < 1.3e29 erg/Hz/s, which is a factor of >~4 lower than the median radio luminosity of radio-detected short GRBs at a similar epoch and rest frame time (Laskar et. al. 2022). Overall, this limit places GRB 250322A in the bottom 25% of radio-observed short GRBs with redshift determinations, in terms of radio luminosity. We thank the VLA staff for quickly approving and executing these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/40036. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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