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

[vsnet-grb-info 39676] EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
by GCN Circulars 30 Aug '25

30 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41611 SUBJECT: EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up DATE: 25/08/30 14:16:50 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.D. Liang (NAOC), K. R. Ni (CCNU), X. Tian(GXU), W. D. Zhang (NAOC) 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 EP250830a. The transient triggered EP-WXT (ID: 01709200995) at 2025-08-30T03:57:09 (UTC), whcih is about 25 s after the trigger of GRB 250830B by MAXI (GCN 41602). The WXT position of the source is R.A. = 105.723 deg, DEC = -64.816 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic), spatially consistent with GRB 250830B. The 0.5-4 keV spectrum can be fitted with an absorbed powerlaw model with Galactic hydrogen column density fixed to 1.1 x 10^21 cm^-2 and a photon index of 1.6 (+/- 0.2), and a peak flux of approximately 1 x 10^-9 erg/s/cm^2. We proposed a follow-up observation with the Swift XRT that was performed at 2025-08-30T07:00:13, approximately 3.05 h after the trigger. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 105.73708 deg, DEC = -64.85286 deg (J2000) with an uncertainty of 5 arcsec in radius (90% C.L. statistical and systematic). The integrated 0.3-10 keV spectrum can be fitted with an absorbed powerlaw model with fixed identity Galactic hydrogen column density and a photon index of 0.9 (+/-0.5), and an averaged flux of 2.5 x 10^-12 erg/s/cm^2. We gratefully acknowledge the support of the Swift team. 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/41611. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39675] LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
by GCN Circulars 30 Aug '25

30 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41610 SUBJECT: LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations DATE: 25/08/30 14:05:37 GMT FROM: Satoshi Sugita at Aoyama Gakuin U. <sugita(a)phys.aoyama.ac.jp> T. Mihara, N. Kawai (RIKEN), M. Nakajima, H. Negoro, K. Takagi (Nihon U.), S. Sugita, M. Serino, Y. Kawakubo, H. Hiramatsu, Y. Kondo (AGU) report on behalf of the MAXI team: We examined MAXI/GSC all-sky X-ray images (2-20 keV) after compact binary merger candidate S250830bp at 2025-08-30 10:24:18.852 UTC (GCN 41606, 41607). At the trigger time of S250830bp, the high-voltage of MAXI/GSC was on, but the FOV was out of the 90% credible region of the Bilby skymap. The credible region was observed about 3 minutes before the GW trigger time with GSC, and the first one-orbit (92 min) scan observation after the event covered 100% of the 90% credible region from 11:52:34 to 11:53:19 UTC (T0+5296 to T0+5341 sec). No significant new source was found in the region in those observations. A typical 1-sigma averaged upper limit obtained in one scan observation is 20 mCrab at 2-20 keV. If you require information about X-ray flux by MAXI/GSC at specific coordinates, please contact the submitter of this circular by email. View this GCN Circular online at https://gcn.nasa.gov/circulars/41610. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39674] LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
by GCN Circulars 30 Aug '25

30 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41609 SUBJECT: LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume DATE: 25/08/30 14:01:52 GMT FROM: Maria Brozzetti at Università degli Studi di Perugia <marialisa.brozzetti(a)ligo.org> M. L. Brozzetti (UniPG/INFN), G. Dálya (L2IT/EotvosU), G. Greco (INFN), M. Bawaj (UniPG/INFN), T. Matcovich (UniPG/INFN), S. Cutini (INFN) , R. De Pietri (UniPR/INFN), Marica Branchesi (GSSI) On behalf of the GLADEnet Team. We analyzed the completeness of the GLADE+ [1] catalog within the 90% credible localization volume of the S250830bp event from the 4-Update alert from the GCN Circular 41606. The completeness value is 6.6e-1 in the B-band using the last released skymap : [Bilby.multiorder.fits,0](https://gracedb.ligo.org/api/superevents/S250830bp…, which means that the catalogue contains 66% of the total light in the B-band expected from galaxies in the localization volume. A total of 517 galaxies are identified within the 90% gravitational volume. The complete list of galaxies can be downloaded from the GLADEnet webpage [2] : [https://virgo.pg.infn.it/gladenet/catalogs/](https://virgo.pg.infn.it/glade… GLADEnet allows for the interactive visualization of the 90% localization area and its intersection with regions of high extinction as defined in GLADE+. Furthermore, the first 1000 galaxies can be explored interactively, enabling users to filter galaxies based on their 3D probability density or their absolute B magnitude. The ligo.skymap cross-match method [3,4] is used to obtain the list of galaxies. References: [1]GLADE+: An Extended Galaxy Catalogue for Multimessenger Searches with Advanced Gravitational-wave Detectors G. Dálya et al. MNRAS, 514,1, pp.1403-1411, 2022 [2] GLADEnet: A progressive web app for multi-messenger cosmology and electromagnetic follow-ups of gravitational-wave sources M. L. Brozzetti, G. Dálya, G. Greco, M. Bawaj, T. Matcovich, M. Branchesi, T. Boch, M. Baumann, S. Cutini, R. De Pietri et al. (4 more) A&A, 684, A44 (2024) [3] Singer, L. P., Chen, H.-Y., Holz, D. E., et al. 2016, Astropys. J. Lett., 829, L15. doi:10.3847/2041-8205/829/1/L15 [4] Singer, L. P., Chen, H.-Y., Holz, D. E., et al. 2016, Astropys. J. Supp., 226, 10. doi:10.3847/0067-0049/226/1/10 View this GCN Circular online at https://gcn.nasa.gov/circulars/41609. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39673] LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
by GCN Circulars 30 Aug '25

30 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41608 SUBJECT: LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume DATE: 25/08/30 13:49:57 GMT FROM: David Cook at Caltech/IPAC-NED <dcook(a)ipac.caltech.edu> David O. Cook (Caltech/IPAC), Rick Ebert (Caltech/IPAC), George Helou (Caltech/IPAC), Joseph M. Mazzarella (Caltech/IPAC), Marion Schmitz (Caltech/IPAC), and Leo Singer (NASA/GSFC) On behalf of the NASA/IPAC Extragalactic Database (NED) Team. We spatially cross-matched the LVK S250830bp-4-Update sky localization with the NED Local Volume Sample (NED-LVS; Cook et al. 2023), which is a subset of NED with a redshift or redshift-independent distance less than 1000 Mpc. We find 72 galaxies within the 90% containment volume, and we list here the top 20 galaxies sorted by the joint probability of the 3D localization and the WISE W1 luminosity (an observable proxy for stellar mass). For the full or top 20 list of galaxies in the 90% volume go either to the NED Gravitational Wave Followup service at https://ned.ipac.caltech.edu/uri/NED::GWF/ or click on the following links: Full List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250830bp/4 Top 20 List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250830bp/4/20 The NED-GWF service provides downloadable galaxy lists and visualizations for candidate host galaxies. For each GW alert, these products are automatically generated and made available within minutes to expedite efficient electromagnetic follow-up observations. The NED top 20 list is sorted by the joint probability of the 3D localization and the WISE W1 luminosity, but users can sort on additional pre-computed prioritization metrics (star formation rate, P_3D * P_SFR; and specific star formation rate, P_3D * P_sSFR; etc.) which are available via downloading the entire galaxy list inside the event's probability volume. | objname| ra| dec|objtype| DistMpc|DistMpc_unc| m_NUV| m_NUV_unc| m_Ks| m_Ks_unc| m_W1| m_W1_unc| P_3D|P_3D_LumW1| |-------------------------|--------------|--------------|-------|-----------|-----------|------------|------------|------------|------------|------------|------------|--------|----------| |WISEA J215127.50-771123.7| 327.86462| -77.18992| G| 452.47| 0.65| null| null| 12.307| 0.126| 10.624| 0.006|1.78e-05| 2.49e-06| |WISEA J214848.24-774454.9| 327.20101| -77.74860| G| 463.54| null| null| null| 13.779| 0.215| 12.525| 0.010|5.02e-05| 1.28e-06| |WISEA J214657.45-773648.1| 326.73941| -77.61338| G| 462.69| null| null| null| 13.264| 0.192| 12.822| 0.014|5.09e-05| 9.83e-07| |WISEA J215919.74-775235.8| 329.83229| -77.87662| G| 451.54| 0.65| null| null| 12.506| 0.114| 12.064| 0.008|1.84e-05| 6.79e-07| |WISEA J213625.95-773427.9| 324.10814| -77.57443| G| 382.59| null| null| null| 13.364| 0.175| 12.873| 0.009|5.20e-05| 6.48e-07| |WISEA J214445.54-771938.0| 326.18978| -77.32723| G| 452.13| null| 21.430| 0.312| 13.324| 0.160| 13.240| 0.012|4.93e-05| 6.16e-07| |WISEA J213608.67-772811.0| 324.03613| -77.46974| G| 356.09| null| null| null| 13.524| 0.185| 12.576| 0.014|4.08e-05| 5.79e-07| |WISEA J215658.48-774037.0| 329.24368| -77.67696| G| 403.25| null| null| null| 13.090| 0.145| 12.789| 0.009|3.68e-05| 5.55e-07| |WISEA J213700.75-773426.0| 324.25313| -77.57391| G| 325.21| 0.65| 20.310| 0.217| 12.016| 0.075| 11.838| 0.006|2.20e-05| 5.14e-07| |WISEA J213454.05-772745.8| 323.72522| -77.46275| G| 372.81| null| null| null| 13.059| 0.143| 13.016| 0.016|4.75e-05| 4.92e-07| |WISEA J215146.52-780557.3| 327.94386| -78.09927| G| 368.25| 0.65| null| null| 12.882| 0.135| 12.228| 0.010|2.20e-05| 4.63e-07| |WISEA J213733.97-780150.6| 324.39156| -78.03074| G| 345.10| null| 20.443| 0.108| 13.417| 0.204| 11.831| 0.007|1.74e-05| 4.63e-07| |WISEA J212943.06-775542.2| 322.42945| -77.92839| G| 372.02| 0.65| null| null| 12.273| 0.114| 12.187| 0.009|1.85e-05| 4.12e-07| |WISEA J213608.13-772733.1| 324.03389| -77.45922| G| 319.73| 0.65| 21.351| 0.351| 12.228| 0.076| 11.985| 0.007|2.01e-05| 3.96e-07| |WISEA J212913.11-773431.7| 322.30466| -77.57550| G| 378.32| 0.65| 20.656| 0.234| 13.354| 0.165| 12.886| 0.013|2.92e-05| 3.50e-07| |WISEA J213641.68-775334.3| 324.17371| -77.89287| G| 411.08| null| 21.445| 0.179| 13.521| 0.179| 13.546| 0.029|4.09e-05| 3.18e-07| |WISEA J213632.95-765253.9| 324.13731| -76.88165| G| 460.55| 0.65| null| null| 12.341| 0.134| 12.450| 0.009|1.07e-05| 2.86e-07| |WISEA J213724.56-773623.7| 324.35235| -77.60660| G| 536.58| null| null| null| 13.729| 0.212| 13.039| 0.022|1.35e-05| 2.84e-07| |WISEA J215903.81-773020.5| 329.76589| -77.50571| G| 426.05| null| null| null| 13.020| 0.144| 12.826| 0.010|1.74e-05| 2.83e-07| |WISEA J212501.23-771251.5| 321.25514| -77.21431| G| 436.36| null| null| null| 13.307| 0.143| 12.903| 0.015|1.69e-05| 2.66e-07| Table 1: Top 20 galaxies in NED-LVS that fall in the 90% probability volume for S250830bp sorted by the joint probability of 3D position and WISE W1 luminosity (P_3D * P_LumW1). Galaxy is the NED preferred name. RA and Dec are the Equatorial coordinates in degrees (J2000). Objtype is the object type of the galaxy candidate. Distance is the distance to the galaxy in Mpc. m_NUV and mErr_NUV are the apparent magnitude and error from GALEX. m_Ks and mErr_Ks are the apparent magnitude and error from 2MASS. m_W1 and mErr_W1 are the apparent magnitude and error from AllWISE. P_3D is the probability that the galaxy is in the volume given the distance of GW event. P_3D_LumW1 is the joint probability within the volume weighted by the WISE1 luminosity of the galaxy (P_3D * P_LumW1). View this GCN Circular online at https://gcn.nasa.gov/circulars/41608. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39672] LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
by GCN Circulars 30 Aug '25

30 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41607 SUBJECT: LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification DATE: 25/08/30 12:55:43 GMT FROM: Colm Talbot at University of Chicago <talbotcolm(a)gmail.com> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S250830bp (GCN Circular 41606). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN and SCiMMA notices, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250830bp Assuming the candidate is astrophysical, the updated classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), BNS (<1%), or NSBH (<1%). Based on posterior support from parameter estimation [1], under the assumption that the candidate S250830bp is astrophysical in origin, the probability that at least one of the compact objects is consistent with a neutron star mass above one solar mass (HasNS) is <1%. [2] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [2] HasRemnant is assumed to be zero when the heavier component mass is below 1 solar mass. Both HasNS and HasRemnant consider the support of several neutron star equations of state for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. The probability that the lighter compact object is below 1 solar mass (HasSSM) is <1%. For the Bilby.multiorder.fits,0 sky map, the 90% credible region is well fit by an ellipse with an area of 4 deg2 described by the following DS9 region (right ascension, declination, semi-major axis, semi-minor axis, position angle of the semi-minor axis): icrs; ellipse(21h43m, -77d36m, 1.36d, 0.88d, 15.49d) Marginalized over the whole sky, the a posteriori luminosity distance estimate is 427 +/- 69 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. PRD 108, 123040 (2023) doi:10.1103/PhysRevD.108.123040 [2] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe View this GCN Circular online at https://gcn.nasa.gov/circulars/41607. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39671] LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
by GCN Circulars 30 Aug '25

30 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41606 SUBJECT: LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate DATE: 25/08/30 10:55:06 GMT FROM: Pedro Jeronimo Santos da Silva <pedro.jeronimo(a)unesp.br> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250830bp during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-08-30 10:24:18.852 UTC (GPS time: 1440584676.852). The candidate was found by the Aframe [1], cWB [2], cWB BBH [3], GstLAL [4], MBTA [5], MLy [6], PyCBC Live [7], and SPIIR [8] analysis pipelines. S250830bp is an event of interest because its false alarm rate, as estimated by the online analysis, is 3.2e-10 Hz, or about one in 1e2 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250830bp The classification of the GW signal, in order of descending probability, is BBH (84%), NSBH (16%), Terrestrial (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that at least one of the compact objects is consistent with a neutron star mass (HasNS) is <1%. [9] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [9] Both HasNS and HasRemnant consider the support of several neutron star equations of state for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is 16%. The source chirp mass falls with highest probability in the bin (5.5, 11.0) solar masses, assuming the candidate is astrophysical in origin. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * amplfi.multiorder.fits,0, an initial localization generated by AMPLFI [10], distributed via GCN and SCiMMA notices about 24 seconds after the candidate event time. * bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [11], distributed via GCN and SCiMMA notices about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,0. For the bayestar.multiorder.fits,0 sky map, the 90% credible region is 11 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 429 +/- 100 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Marx et al. PRD 111, 042010 (2025) doi:10.1103/PhysRevD.111.042010 [2] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 [3] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [4] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. PRD 109, 042008 (2024) doi:10.1103/PhysRevD.109.042008 [5] Alléné et al. CQG 42, 105009 (2025) doi:10.1088/1361-6382/add234 [6] Skliris et al. PRD 110, 104034 (2024) doi:10.1103/PhysRevD.110.104034 [7] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [8] Chu et al. PRD 105, 024023 (2022) doi:10.1103/PhysRevD.105.024023 [9] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [10] Chatterjee et al. MLST 5, 045030 (2024) doi:10.1088/2632-2153/ad8982 [11] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/41606. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39670] EP-WXT trigger 01709200994: Liverpool Telescope upper limits
by GCN Circulars 30 Aug '25

30 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41605 SUBJECT: EP-WXT trigger 01709200994: Liverpool Telescope upper limits DATE: 25/08/30 10:11:26 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris and N. Habeeb (U of Leicester) report on behalf of a larger collaboration: We observed the field of the EP-WXT trigger 01709200994 with the 2m Liverpool Telescope using the IO:O instrument. We obtained 6x150s exposures in each of the SDSS r’ and SDSS g’ filters starting at 2025-08-29 23:55:21 UT, approximately 3.0 hours after the X-ray detection. We performed image subtraction on the stacked images using reference images from Pan-STARRS and also compared the stacked and reference images manually. We detect no new sources in either the subtractions or stacked images. This is consistent with 01709200994 being a stellar flare (Ni et al., GCN 41599; Perez-Garcia et al., GCN 41603). We derive 3-sigma upper limits of r’ > 22.6 and g’ > 22.4 with photometry calibrated to Pan-STARRS and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/41605. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39669] GRB 250830B: Swift ToO observations
by GCN Circulars 30 Aug '25

30 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41604 SUBJECT: GRB 250830B: Swift ToO observations DATE: 25/08/30 07:01:14 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the MAXI-detected event GRB 250830B. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021858 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the MAXI event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41604. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39668] EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
by GCN Circulars 30 Aug '25

30 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41603 SUBJECT: EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6 DATE: 25/08/30 05:46:00 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct(a)iaa.es> I. Perez-Garcia, S.-Y. Wu, E. Fernandez-Garcia, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy and A. J. Castro-Tirado (IAA-CSIC, Granada), P. J. Meintjes and H. J. van Heerden (UFS, South Africa), A. Martin-Carrillo and L. Hanlon (UCD, Ireland), M. Gritsevich (Univ. of Helsinki) and C. J. Perez del Pulgar (UMA, Malaga), on behalf of a larger collaboration, report: Following the detection of EP-WXT trigger 01709200994 (Ni et al. GCNC 41599), the BOOTES-6/DPRT 0.6m robotic telescope at Boyden Observatory in Maselspoort (South Africa) responded to the alert on Aug 29, 21:51 UT (i.e. 54 min after detection and 2 min after notification). Within the reported EP-FXT error circle we find the star LP 524-48 decreasing in brightness from 14.2 to 14.6 mag in clear filter (using Gaia DR3 Gmag magnitude as reference) during a 1 hour time interval, confirming this event as due to a stellar flare, as already suggested by the EP team. We thank the staff at Boyden Observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/41603. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 39667] GRB 250830B: MAXI/GSC detection
by GCN Circulars 30 Aug '25

30 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41602 SUBJECT: GRB 250830B: MAXI/GSC detection DATE: 25/08/30 05:37:22 GMT FROM: Hitoshi Negoro at Nihon University/MAXI team <negoro.hitoshi(a)nihon-u.ac.jp> T. Usuki (Ehime U.), H. Negoro, M. Nakajima, K. Takagi, H. Takahashi, H. Nishio (Nihon U.), T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, Y. Kawakubo, H. Hiramatsu, Y. Kondo, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima, Y. Ishihara (Chuo U.), M. Shidatsu, C. Kang, T. Nakamoto (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.), S. Yamada (Tohoku U),report on behalf of the MAXI team: The MAXI/GSC nova alert system triggered on a bright uncatalogued X-ray transient source at 03:56:44 UT on August 30, 2025. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (105.209 deg, -64.628 deg) = (07 00 50, -64 37 40) (J2000) with a 90% C.L. statistical error of 0.33 deg and an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 225 +- 36 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (R.A., Dec) = (105.751, -63.592) deg = (07 03 00, -63 35 31) (J2000) (R.A., Dec) = (104.300, -63.666) deg = (06 57 11, -63 39 57) (J2000) (R.A., Dec) = (104.713, -65.344) deg = (06 58 51, -65 20 38) (J2000) (R.A., Dec) = (106.255, -65.266) deg = (07 05 01, -65 15 57) (J2000) There was no significant excess flux in the previous transit at 02:23 UT and in the next transit at 05:30 UT with an upper limit of 20 mCrab for each. We requested Swift/XRT followup observation. View this GCN Circular online at https://gcn.nasa.gov/circulars/41602. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0