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

[vsnet-grb-info 37608] EP250302A: 1.3m DFOT optical afterglow detection
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39593 SUBJECT: EP250302A: 1.3m DFOT optical afterglow detection DATE: 25/03/04 15:36:13 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Amit K. Ror, Kuntal Misra, and Shashi B. Pandey (ARIES) report: We observed the field of EP250302A detected by EP-WXT (Trigger ID: 01709132186) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2025-03-02 at 20:15:46 UT, i.e., ~ 4.66 hours after the EP-WXT trigger. We have taken multiple frames with an exposure time of 300 s in the R filter. We stacked the images after the alignment. We clearly detected optical afterglow in our stacked image within the error box of the EP/WXT coordinates (GCN 39550). We obtained the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hour) Filter Exp time (s) magnitude ========================================================================= 2025-03-02 20:15:46 ~4.66 hour R 300*12 19.990 +- 0.004 Our detection is consistent with Zhu et al. 2025 (GCN 39550); Busmann et al. 2025 (GCN 39551); Leonini et al. 2025 (GCN 39553); WU et al. 2025 (GCN 39555); Xin et al. 2025 (GCN 39558); Lipunov et al. 2025 (GCN 39559); Adami et al. 2025 (GCN 39560); Yang et al. 2025 (GCN 39561); Becerra et al. 2025 (GCN 39562); Izzo et al. 2025 (GCN 39564); Pankov et al. 2025(GCN 39565); Reguitti et al. 2025 (GCN 39568); Komesh et al. 2025 (GCN 39569); Shilling et al. 2025 (GCN 39570); Aryan et al. 2025 (GCN 39572); Eappachen wt al. 2025 (GCN 39575); Moskvitin et al. 2025(GCN 39576); Wu et al. 2025 (GCN 39578) and Pankov et al. 2025 (GCN 39586). The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalog. This circular may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39593. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37607] IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39592 SUBJECT: IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/03/04 14:56:45 GMT FROM: Jessie Thwaites at IceCube/U Wisc-Madison <thwaites(a)wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-250302A (https://gcn.nasa.gov/circulars/39549) in a time range of 1000 seconds centered on the alert event time (2025-03-02 03:12:32.900 UTC to 2025-03-02 03:29:12.900 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-250302A. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-250302A is 1.4e-01 GeV cm^-2 in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 3e+02 GeV and 1e+05 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2025-03-01 03:20:52.900 UTC to 2025-03-03 03:20:52.900 UTC). In this case, we report a p-value of 1.00, consistent with no significant excess of track events. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-250302A is 1.6e-01 GeV cm^-2 in a 2 day time window. 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] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/39592. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37606] EP250304a: refined analysis of the EP-WXT and EP-FXT observations
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39591 SUBJECT: EP250304a: refined analysis of the EP-WXT and EP-FXT observations DATE: 25/03/04 14:33:38 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.J. Zhang (THU), C. Y. Dai (NJU), W. Chen, W. X. Wang (NAO, CAS), Y. Liu (NAO, CAS) report on behalf of the Einstein Probe team: The X-ray transient EP250304a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Chen et al., GCN 39580), and followed up by several telescopes (Xu et al, GCN 39583, Page et al., GCN 39584, Saccardi et al., GCN 39585, Shilling et al., 39587), with an optical counterpart detected at a redshift of 0.200 (Saccardi et al., GCN 39585). Refined analysis of the WXT data shows that the event started at T0=2025-03-04T01:29:49 (UTC) and lasted for about 1200 s. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 5 x 10^20 cm^-2 and a photon index of 2.2 (-/+0.1). The derived average unabsorbed 0.5-4 keV flux is 5.3(-/+0.4) x 10^(-10) erg/s/cm^2. The Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously about 200 seconds after T0. On-ground analysis of the FXT data found an uncatalogued source at R.A. = 208.3953, DEC = -42.8050 (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic), which is consistent positionally with the WXT transient. The FXT observation suffered from significant pile up at the begining of the observation. The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 5 x 10^20 cm^-2 and a photon index of 2.11 (-/+0.05). The derived average unabsorbed 0.5-10 keV flux is 1.75 (-/+0.06) x 10^(-10) erg/s/cm^2 during the time interval from 500 to 1200 seconds after the start of the observation. Further FXT observation started about 4000 seconds after the trigger and showed an average unabsorbed 0.5-10 keV flux of 6.5 (-2.3/+3.5) x 10^(-12) erg/s/cm^2 with an exposure time of about 300 seconds. The uncertainties are at the 90% confidence level for the above parameters. 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/39591. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37605] Konus-Wind detection of GRB 250222A
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39590 SUBJECT: Konus-Wind detection of GRB 250222A DATE: 25/03/04 13:35:08 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long GRB 250222A (SVOM-GRM detection: Wang et al., GCN 39454; IPN triangulation: Svinkin et al., GCN 39588) triggered Konus-Wind (KW) at T0=51862.905 s UT (14:24:22.905). The burst light curve shows a bright, multi-peaked pulse, with the duration of ~2.5 s, followed by a weaker, decaying emission. The total duration of the burst is ~13 s. The emission is seen up to ~10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250222_T51862/ As observed by Konus-Wind, the burst had a fluence of (1.79 ± 0.19)x10^-5 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 0.064 s, of (1.53 ± 0.20)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+16.640 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.51 (-0.22,+0.26), the high energy photon index beta = -2.28 (-0.14,+0.11), the peak energy Ep = 173 (-21,+23) keV, chi2 = 98/97 dof. The spectrum near the peak count rate (measured from T0 to T0+0.256 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = 0.40 (-0.61,+1.09), the high energy photon index beta = -1.97 (-0.13,+0.10), the peak energy Ep = 169 (-39,+46) keV, chi2 = 42/43 dof. All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/39590. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37604] EP250304a: REM NIR upper limits
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39589 SUBJECT: EP250304a: REM NIR upper limits DATE: 25/03/04 13:00:46 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio(a)inaf.it> R. Brivio, M. Ferro (INAF-OAB), D. B. Malesani (DAWN/NBI and Radboud), P. D’Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of EP250304a (Chen et al., GCN 39580) 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 04 at 01:46:18 UT (i.e. 0.23 hr after the burst), and lasted for about 2 hours. From preliminary analysis, we do not find any NIR counterpart at the position of the reported optical afterglow (Liu et al., GCN 39583; Saccardi et al., GCN 39585) down to the following 3sigma limit: J > 17.5 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 1.46 hours after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/39589. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37603] IPN triangulation of GRB 250222A
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39588 SUBJECT: IPN triangulation of GRB 250222A DATE: 25/03/04 12:59:51 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, Y. Zhang, C. Wang, S. Xiong, J. Wei, and B. Cordier on behalf of the SVOM-GRM team, E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM team, S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu on behalf of the Swift-BAT team, report: The long-duration GRB 250222A (SVOM-GRM detection: Wang et al., GCN 39454) was detected by SVOM (GRM), Konus-Wind, and INTEGRAL (SPI-ACS) at about 51859 s UT (14:24:19). Fermi (GBM) and Swift (BAT) were taking data, but shows no rate increase at the burst time. We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 359.336 (23h 57m 21s) +0.946 ( +0d 56' 47") Corners: 335.308 (22h 21m 14s) +25.783 (+25d 47' 00") 352.637 (23h 30m 33s) +12.776 (+12d 46' 35") 6.156 (00h 24m 37s) -19.368 (-19d 22' 04") 2.915 (00h 11m 40s) -9.794 ( -9d 47' 40") --------------------------------------------- The error box area is 38.5 sq. deg, and its maximum dimension is 54 deg (the minimum one is 3 deg). The Sun distance was 25 deg. This localization may be improved. The SVOM (GRM) localization (GCN 39454) is inconsistent with the IPN localization and also with burst non-detection by Fermi (GBM) and Swift (BAT). A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB250222_T51862/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/39588. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37602] EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39587 SUBJECT: EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve DATE: 25/03/04 12:18:09 GMT FROM: Sam Shilling at Lancaster University <shilling.sam(a)gmail.com> S. P. R. Shilling (Lancaster U.) reports on behalf of the Swift UVOT team: Swift/UVOT observed the field of EP250304a (Chen et al., GCN 39580) for a total of 2 ks in the U-band starting at 02:48:13 UT, 1.25 hours after the detection by Einstein Probe WXT. An optical source consistent with the EP-FXT position (Chen et al., GCN 39580) is detected and appears to be rising in brightness. 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 19.29 +/- 0.09 (1.25 hours post trigger) and rises to 18.91 +/- 0.15 (~2.75 hours post trigger). We note that an X-ray source at this position was independently observed by the Swift/XRT (Page et al., GCN 39584). We also note that, in addition to the Swift/UVOT detection, an optical counterpart at this position has been detected by the TRT (Liu et al., GCN 39583) but has not been detected by MASTER (Lipunov et al., GCN 39581). Finally, that the source has a spectroscopic redshift, observed with the VLT/X-shooter, of z=0.2 (Saccardi et al., GCN 39585). View this GCN Circular online at https://gcn.nasa.gov/circulars/39587. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37601] EP250302a: Mondy Continued Optical Observations
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39586 SUBJECT: EP250302a: Mondy Continued Optical Observations DATE: 25/03/04 10:06:19 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP), A. Moskvitin (SAO RAS) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of a fast X-Ray transient EP250302a (Dai et al., GCN 39556; Page et al., GCN 39557) in the R filter with the 1.5-meter telescope of Sayan Solar Observatory (Mondy). The observations began on 2025-03-03 (UT) 19:29:15, i.e. ~1.18 days since trigger. The optical source (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., GCN 39565; Reguitti, GCN 39568; Komesh et al., GCN 39569; Shilling and Breeveld, GCN 39570; Aryan et al., GCN 39572; Moskvitin et. al, GCN 39576; Wu et. al, GCN 39578) is detected in the stacked image of 28*120 seconds. The preliminary photometry is as follows: Date UT start t-T0 Exptime Filter OT Err. UL (mid, days) (s) (3sigma) 2025-03-03 19:29:15 1.18136 28*120 R 22.12 0.14 23.4 The photometry is based on nearby stars from the USNO-B1.0 catalog (R2 magnitudes) and has not been corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39586. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37600] EP250304a: VLT/X-shooter redshift z = 0.200
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39585 SUBJECT: EP250304a: VLT/X-shooter redshift z = 0.200 DATE: 25/03/04 09:54:03 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> A. Saccardi (CEA/Irfu), Z. P. Zhu (NAOC), B. Schneider (LAM), D. Xu (NAOC), L. Izzo (INAF/OAC and DARK/NBI), A. J. Levan (Radboud and Warwick), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), N. R. Tanvir (U. Leicester), S. D. Vergani (CNRS - Paris Observatory/LUX) report on behalf of the Stargate collaboration: We observed the optical counterpart (Liu et al., GCN 39583; see also Page et al., GCN 39584) of the fast X-ray transient EP250304a (Chen et al., GCN 39580) using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. In a 30-s r-band image taken with the acquisition camera (mid-time 2025 Mar 4.302 UT, or 5.7 hr after trigger), we detect the optical counterpart with a magnitude r = 20.97 +/- 0.03 (AB), calibrated against nearby stars from the SkyMapper catalog (Wolf et al. 2018, doi:10.4225/41/593620ad5b574). Our spectra cover the wavelength range 3000-21000 AA, and consist of 4 exposures of 600 s each. The observation mid time was 2025 Mar 4.3248 UT (6.254 hr after the GRB). In a preliminary reduction of the spectra, we detect continuum over the entire covered wavelength range. We detect emission lines in the VIS arm, which we identify as Halpha and [O III] 5007 AA at the common redshift of z = 0.200. We also identify the Mg II doublet (2796,2804) in absorption at a consistent redshift. The spectrum continues to rise towards the blue end down to the cut-off of the UVB arm (~3100 AA). This spectral shape is qualitatively similar to what was seen in EP250108a / AT2025kg (e.g., Zhu et al., GCN 38908). We encourage further follow-up of this potentially interesting target. We acknowledge expert support from the ESO staff in Paranal, in particular Diego Parraguez. View this GCN Circular online at https://gcn.nasa.gov/circulars/39585. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37599] EP250304a: Swift-XRT detection of a fading X-ray source
by GCN Circulars 04 Mar '25

04 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39584 SUBJECT: EP250304a: Swift-XRT detection of a fading X-ray source DATE: 25/03/04 09:18:19 GMT FROM: K.L. Page at U Leicester <klp5(a)leicester.ac.uk> K.L. Page, P.A. Evans (U.Leicester) and J. DeLaunay (PSU) report on behalf of the Swift XRT Team: On 2025 March 04 at 02:59 UT, Swift started observing EP250304a, 5.2 ks after the Einstein Probe trigger (GCN Circ. 39580). A fading X-ray source was identified, at a position of RA, Dec = 208.39408, -42.8046, which is equivalent to RA (J2000): 13h 53m 34.58s Dec (J2000): -42d 48′ 16.7″ with an uncertainty of 4.1 arcsec (radius, 90% confidence). This is consistent with the FXT position (GCN Circ. 39580), as well as the TRT optical counterpart given in GCN Circ. 39583. The mean observed X-ray flux in the first snapshot was (3.5 +/- 0.4) x 10^-12 erg cm^-2 s^-1 (0.3 - 10 keV). By the time of the second snapshot, at 10.3 ks after the trigger, the source was no longer detected, having faded to a 3-sigma upper limit of 2.1 x 10^-12 erg cm^-2 s^-1. View this GCN Circular online at https://gcn.nasa.gov/circulars/39584. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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