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

[vsnet-grb-info 37196] The EP-WXT trigger 01709131290 is likely a flaring star
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39187 SUBJECT: The EP-WXT trigger 01709131290 is likely a flaring star DATE: 25/02/07 03:34:16 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> M. J. Liu, D. Y. Li, M. H. Zhang, H. N. Yang (NAOC, CAS), Z. Y. Liu (USTC), Q. C. Shui (IHEP, CAS), W. D. Zhang, W. M. Yuan (NAOC, CAS) report on behalf of the Einstein Probe team: The EP-WXT trigger (ID: 01709131290) on 2025-02-06 09:52:08 (UTC) is likely a stellar flare associated with a star UCAC4 185-006985. The estimated flux of the flare is around 1.9 x 10^-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 5.5 x 10^31 erg/s. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard 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/39187. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37195] GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39186 SUBJECT: GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection DATE: 25/02/07 03:20:08 GMT FROM: Camila Angulo Valdez at UNAM <camiangulo(a)astro.unam.mx> Camila Angulo (UNAM), Alan M. Watson (UNAM), Noémie Globus (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Rosa L. Becerra (Università degli Studi di Roma Tor Vergata), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), and Benjamin Schneider (LAM) report: We imaged the field of GRB 250207A detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 39181) and Swift/BAT (Ferro et al., GCN Circ.39182) with the DDRAGO wide-field camera on the COLIBRÍ (SVOM/F-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed from 2025-02-07 02:34 to 02:55 UTC (78 to 99 min after the burst), with a midpoint of 88.5 minutes after the event, and obtained 960 seconds of exposure in the r filter in good weather conditions. The data were reduced and stacked using custom software and then calibrated against the PS1 catalog and analysed using STDPipe (Karpov 2021). At the position of the afterglow detected by XRT and UVOT (Ferro et al., GCN Circ. 39182), we detect a source with r = 18.90 +/- 0.01 and confirm fading relative to the UVOT observation. Our magnitude is not corrected for Galactic extinction. Further observations are planned. We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/39186. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37194] LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39185 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume DATE: 25/02/07 03:18:00 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 S250206dm-6-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 31227 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/S250206dm/6 Top 20 List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250206dm/6/20 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 J022843.33+542030.5| 37.18021| 54.34178| G| 408.50| null| null| null| 13.098| 0.150| 9.250| 0.006|5.79e-07| 6.59e-10| |WISEA J022348.88+533854.6| 35.95371| 53.64847| G| 361.18| null| null| null| 12.653| 0.121| 10.626| 0.007|8.66e-07| 2.14e-10| |WISEA J161708.84-674024.7| 244.28700| -67.67294| G| 314.35| null| null| null| 12.878| 0.112| 9.322| 0.006|2.82e-07| 1.72e-10| |WISEA J022200.27+503737.1| 35.50117| 50.62697| G| 288.27| null| null| null| 12.566| 0.105| 9.223| 0.006|2.54e-07| 1.52e-10| |WISEA J024516.51+542758.5| 41.31871| 54.46631| G| 365.18| null| null| null| 12.190| 0.129| 10.967| 0.007|7.65e-07| 1.50e-10| | MCG -01-57-002| 335.01662| -3.45381| G| 254.69| 0.65| null| null| null| null| 9.016| 0.006|2.74e-07| 1.45e-10| |WISEA J025225.08+545415.7| 43.10437| 54.90433| G| 333.19| null| null| null| 12.932| 0.105| 10.581| 0.006|5.48e-07| 1.36e-10| |WISEA J023404.21+543420.9| 38.51758| 54.57247| G| 387.94| 0.60| null| null| 11.605| 0.091| 11.228| 0.010|6.76e-07| 1.14e-10| |WISEA J022610.54+530728.2| 36.54379| 53.12453| G| 369.10| null| null| null| 13.505| 0.153| 11.533| 0.008|9.77e-07| 1.10e-10| |WISEA J023155.31+513044.0| 37.98038| 51.51228| G| 322.72| null| null| null| 13.525| 0.153| 10.101| 0.006|3.26e-07| 1.06e-10| |WISEA J024025.00+541511.8| 40.10413| 54.25331| G| 377.15| null| null| null| 13.153| 0.114| 11.550| 0.010|8.57e-07| 1.02e-10| |WISEA J162759.57-693615.7| 246.99817| -69.60428| G| 281.76| 0.65| null| null| 12.713| 0.125| 10.256| 0.006|4.57e-07| 9.55e-11| |WISEA J021556.19+534832.3| 33.98408| 53.80906| G| 289.71| null| null| null| 12.281| 0.088| 10.334| 0.006|4.55e-07| 9.46e-11| |WISEA J154439.56-665529.0| 236.16450| -66.92469| G| 344.93| null| null| null| 12.631| 0.201| 8.871| 0.006|8.13e-08| 9.16e-11| |WISEA J023620.33+544551.7| 39.08458| 54.76433| G| 260.69| 0.40| null| null| 11.288| 0.099| 10.411| 0.006|5.59e-07| 9.04e-11| |WISEA J025232.69+543416.1| 43.13625| 54.57122| G| 251.14| null| null| null| 14.027| 0.191| 10.414| 0.007|5.55e-07| 8.88e-11| |WISEA J021942.98+525320.0| 34.92904| 52.88886| G| 471.43| null| null| null| 12.998| 0.153| 11.105| 0.012|3.29e-07| 8.85e-11| |WISEA J155633.83-693531.5| 239.14079| -69.59225| G| 320.59| null| null| null| 13.038| 0.134| 10.118| 0.007|2.65e-07| 8.10e-11| |WISEA J222605.71-063926.9| 336.52379| -6.65744| G| 305.80| null| 19.372| 0.067| 13.615| 0.206| 9.569| 0.006|1.76e-07| 8.08e-11| | 3C 445| 335.95638| -2.10357| G| 250.91| 0.79| null| null| null| null| 9.765| 0.006|2.98e-07| 7.70e-11| Table 1: Top 20 galaxies in NED-LVS that fall in the 90% probability volume for S250206dm 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/39185. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37193] LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39184 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification DATE: 25/02/07 02:51:46 GMT FROM: Will Farr <will.farr(a)stonybrook.edu> 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 S250206dm (GCN Circular 39175). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,1, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250206dm Based on posterior support from parameter estimation [1], under the assumption that the candidate S250206dm is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is >99%. [2] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is 15%. [2] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is 59%. For the Bilby.multiorder.fits,1 sky map, the 90% credible region is 910 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 348 +/- 114 Mpc (a posteriori mean +/- standard deviation). At the time of the candidate, the Virgo detector was being brought online and was not in observing mode. However, it was determined that the Virgo detector was sufficiently sensitive to inform our estimate of the sky localization. Investigations are ongoing to understand how the operational state of Virgo at the time of the event impacts this analysis. The estimated sky localization may change based on these studies, but this skymap represents our best understanding of the event at this time. 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. (2023) arXiv:2307.13380 [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/39184. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37192] LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39183 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations DATE: 25/02/07 02:04:13 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA) and R. Hamburg (USRA) report on behalf of the Fermi-GBM Team: For S250206dm (GCN 39175; GCN 39178) and using the updated Bilby skymap, Fermi-GBM was observing 35.7% of the localization probability at event time. There was no Fermi-GBM onboard trigger around the event time of the LIGO/Virgo/KAGRA (LVK) detection of GW trigger S250206dm. An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM also identified no counterpart candidates. The GBM targeted search, the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around merger time, and also identified no counterpart candidates. Part of the LVK localization region is behind the Earth for Fermi, located at an RA=24.7, Dec=-4.2 with a radius of 67.9 degrees. We therefore set upper limits on impulsive gamma-ray emission for the GW localization region visible to Fermi at merger time. Using the representative soft, normal, and hard GRB-like templates described in arXiv:1612.02395, we set the following 3 sigma flux upper limits over 10-1000 keV, weighted by GW localization probability (in units of 10^-7 erg/s/cm^2): Timescale Soft Normal Hard ------------------------------------ 0.128 s: 1.5 2.4 5.1 1.024 s: 0.44 0.72 1.3 8.192 s: 0.08 0.17 0.31 Assuming the median luminosity distance of 358.7 Mpc from the GW detection, we estimate the following intrinsic luminosity upper limits over the 1 keV-10 MeV energy range (in units of 10^50 erg/s): Timescale Soft Normal Hard ------------------------------------ 0.128s: 0.71 1.02 2.95 1.024s: 0.09 0.14 0.47 8.192s: 0.02 0.02 0.04 View this GCN Circular online at https://gcn.nasa.gov/circulars/39183. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37191] GRB 250207A: Swift detection of a burst with optical counterpart
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39182 SUBJECT: GRB 250207A: Swift detection of a burst with optical counterpart DATE: 25/02/07 01:34:53 GMT FROM: Jamie Kennea at Penn State <jak51(a)psu.edu> M. Ferro (INAF-OAB), R. Gupta (NASA GSFC), J. A. Kennea (PSU), K. L. Page (U Leicester) and B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team: At 01:16:07 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250207A (trigger=1287821). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 16.115, -12.159 which is RA(J2000) = 01h 04m 28s Dec(J2000) = -12d 09' 30" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 30 sec. The peak count rate was ~3847 counts/sec (15-350 keV), at ~6 sec after the trigger. The XRT began observing the field at 01:17:53.2 UT, 105.9 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 16.0892, -12.1633 which is equivalent to: RA(J2000) = 01h 04m 21.41s Dec(J2000) = -12d 09' 47.9" with an uncertainty of 5.9 arcseconds (radius, 90% containment). This location is 92 arcseconds from the BAT onboard position, within the BAT error circle. Despite the onboard localisation, no X-ray source was detected in 85 s of promptly-downlinked data, suggesting that the initial centroid may equally have been a cosmic ray. This position should therefore be treated with caution. The initial flux in the 2.5 s image was 7.54e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 113 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 01:04:21.41 = 16.08919 DEC(J2000) = -12:09:52.5 = -12.16458 with a 90%-confidence error radius of about 0.74 arc sec. This position is 4.6 arc sec. from the center of the XRT error circle. The estimated magnitude is 15.04 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.027. Burst Advocate for this burst is M. Ferro (matteo.ferro AT inaf.it). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/39182. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37190] GRB 250207A: Fermi GBM Final Real-time Localization
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39181 SUBJECT: GRB 250207A: Fermi GBM Final Real-time Localization DATE: 25/02/07 01:26:45 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 01:16:03 UT on 7 Feb 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250207A (trigger 760583768.15163 / 250207053). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 11.8, Dec = -13.3 (J2000 degrees, equivalent to J2000 00h 47m, -13d 18'), with a statistical uncertainty of 3.2 degrees. The angle from the Fermi LAT boresight is 47.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250207053/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250207053/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250207053/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39181. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37189] Fermi-LAT Gamma-ray Observations of IceCube-250203A
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39180 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-250203A DATE: 25/02/07 00:54:06 GMT FROM: Simone Garrappa at Weizmann Institute of Science <simone.garrappa(a)weizmann.ac.il> S. Garrappa (Weizmann Institute of Science), C. Bartolini (INFN Bari), L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and P. M. Veres (Ruhr University Bochum) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC250203A neutrino event (GCN 39132) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 2025-02-03 03:59:29.20 UTC (T0) with J2000 position RA = 253.30 (+0.49, -0.49) deg, Decl. = -1.31 (+0.48, -0.44) deg 90% PSF containment. No cataloged gamma-ray sources are found within the 90% IC250203A localization error (The Fourth Fermi-LAT catalog, 4FGL-DR4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC250203A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IceCube best-fit position, the >100 MeV flux upper limit (95% confidence) is <1.1e-9 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), <7.6e-09(<1.0e-7) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this source, the Fermi-LAT contact person is S. Garrappa (simone.garrappa at weizmann.ac.il). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/39180. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37188] LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39179 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations DATE: 25/02/07 00:26:56 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> N. Kawai, T. Mihara, (RIKEN), H. Negoro, M. Nakajima, K. Takagi (Nihon U.), S. Sugita, M. Serino, Y. Kawakubo, H. Hiramatsu, H. Nishikawa, 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 S250206dm at 2025-02-06 21:25:30.439 UTC (GCN #39175, 39178). At the trigger time of S250206dm, the high-voltage of MAXI/GSC was off, and it was turned on at T0+786 sec (+13.1 min). The first one-orbit (92 min) scan observation with GSC after the event covered 52% of the 90% credible region of the Bilby skymap from 21:38:56 to 22:48:26 UTC (T0+806 to T0+4976 sec). No significant new source was found in the region in the one-orbit scan observation. 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/39179. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 37187] LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39178 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification DATE: 25/02/07 00:05:38 GMT FROM: Divyajyoti NLN <divyajyoti.nln(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) data around the time of the compact binary merger (CBC) candidate S250206dm (GCN Circular 39175). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250206dm Based on posterior support from parameter estimation [1], under the assumption that the candidate S250206dm is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is >99%. [2] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is 17%. [2] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is 52%. For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 1626 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 359 +/- 125 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. (2023) arXiv:2307.13380 [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/39178. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0