LIGO/Virgo/KAGRA S250205bk
GCN Circular 39148
Subject
LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate
Date
2025-02-05T11:12:59Z (4 months ago)
From
Lorenzo Asprea at INFN Torino <lorenzo.asprea@to.infn.it>
Via
Web form
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We identified the compact binary merger candidate S250205bk during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-02-05 10:35:41.575 UTC (GPS time: 1422786959.575). The candidate was found by the CWB-BBH [1], GstLAL [2], MBTA [3], PyCBC Live [4], and SPIIR [5] analysis pipelines.
S250205bk is an event of interest because its false alarm rate, as estimated by the online analysis, is 9.5e-10 Hz, or about one in 33 years. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S250205bk
The classification of the GW signal, in order of descending probability, is BBH (98%), NSBH (1%), Terrestrial (<1%), or BNS (<1%).
Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [6] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [6] 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 <1%.
Two sky maps are available at this time and can be retrieved from the GraceDB event page:
bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [7], distributed via GCN notice about 39 seconds after the candidate event time.
bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [7], distributed via GCN notice about 5 minutes after the candidate event time.
The preferred sky map at this time is bayestar.multiorder.fits,1. For the bayestar.multiorder.fits,1 sky map, the 90% credible region is well fit by an ellipse with an area of 101 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(09h24m, -06d08m, 14.43d, 2.23d, 119.13d)
Marginalized over the whole sky, the a posteriori luminosity distance estimate is 794 +/- 191 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] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018
[2] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625
[3] Aubin et al. CQG 38, 095004 (2021) doi:10.1088/1361-6382/abe913
[4] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a
[5] Chu et al. PRD 105, 024023 (2022) doi:10.1103/PhysRevD.105.024023
[6] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe
[7] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013
GCN Circular 39150
Subject
LIGO/Virgo/KAGRA S250205bk: Updated Sky localization
Date
2025-02-05T13:44:16Z (4 months ago)
From
Will Farr <will.farr@stonybrook.edu>
Via
Web form
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 S250205bk (GCN Circular 39148). 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/S250205bk
For the Bilby.multiorder.fits,0 sky map, the 90% credible region is well fit by an ellipse with an area of 66 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(09h27m, -03d55m, 10.95d, 1.92d, 118.01d)
Marginalized over the whole sky, the a posteriori luminosity distance estimate is 748 +/- 160 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
GCN Circular 39153
Subject
LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
Date
2025-02-05T16:24:42Z (4 months ago)
From
David Cook at Caltech/IPAC-NED <dcook@ipac.caltech.edu>
Via
Web form
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 S250205bk-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 2528 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/S250205bk/4
Top 20 List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250205bk/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 J093844.45+005715.7| 144.68526| 0.95433| G| 824.18| 0.23| 21.253| 0.083| 11.774| 0.018| 10.243| 0.023|1.80e-07| 4.17e-09|
|WISEA J092856.47-021335.7| 142.23530| -2.22658| G| 710.26| 0.65| null| null| 12.461| 0.067| 11.321| 0.023|4.40e-07| 2.79e-09|
|WISEA J093341.13-003004.3| 143.42148| -0.50123| G| 673.85| 0.10| null| null| 14.214| 0.130| 11.563| 0.006|3.58e-07| 1.64e-09|
|WISEA J091951.25-073541.7| 139.96363| -7.59489| G| 818.16| 0.65| null| null| 13.410| 0.148| 11.982| 0.023|3.24e-07| 1.48e-09|
|WISEA J091742.69-081416.0| 139.42792| -8.23772| G| 542.17| 0.65| null| null| 13.284| 0.131| 10.986| 0.006|2.82e-07| 1.42e-09|
|WISEA J093439.55+002752.0| 143.66484| 0.46446| G| 703.82| 0.09| 19.820| 0.033| 13.392| 0.182| 11.618| 0.022|2.88e-07| 1.37e-09|
|WISEA J092442.24-043058.7| 141.17604| -4.51631| G| 689.17| null| null| null| 13.275| 0.172| 12.531| 0.017|6.76e-07| 1.33e-09|
|WISEA J091817.00-080516.1| 139.57088| -8.08781| G| 630.66| null| null| null| 13.763| 0.181| 11.982| 0.009|4.12e-07| 1.12e-09|
|WISEA J093252.21-032932.6| 143.21754| -3.49244| G| 631.45| null| null| null| 13.036| 0.174| 11.604| 0.007|2.65e-07| 1.03e-09|
|WISEA J092320.48-045941.1| 140.83533| -4.99478| G| 729.41| 0.65| null| null| 13.622| 0.205| 12.955| 0.023|6.62e-07| 9.83e-10|
|WISEA J092952.72-015714.7| 142.46970| -1.95410| G| 845.32| null| null| null| 13.348| 0.154| 12.605| 0.014|2.92e-07| 8.03e-10|
|WISEA J093249.74-032936.8| 143.20729| -3.49361| G| 756.36| null| null| null| 13.293| 0.155| 12.100| 0.010|2.20e-07| 7.73e-10|
|WISEA J092004.03-082300.2| 140.01683| -8.38336| G| 650.64| null| null| null| 13.494| 0.163| 12.090| 0.009|2.85e-07| 7.47e-10|
|WISEA J092631.89-043419.8| 141.63296| -4.57217| G| 645.03| null| null| null| 13.754| 0.131| 13.015| 0.018|6.66e-07| 7.32e-10|
|WISEA J092955.58-003402.7| 142.48160| -0.56755| G| 712.37| 0.13| null| null| 12.886| 0.138| 12.029| 0.014|2.18e-07| 7.24e-10|
|WISEA J091833.08-082916.7| 139.63783| -8.48797| G| 660.03| null| null| null| 12.957| 0.126| 12.362| 0.017|3.38e-07| 7.10e-10|
|WISEA J091745.56-072447.9| 139.43988| -7.41339| G| 654.29| null| 22.017| 0.284| 13.320| 0.145| 12.674| 0.011|4.37e-07| 6.77e-10|
|WISEA J093033.14-034338.7| 142.63804| -3.72744| G| 647.19| null| 20.508| 0.159| 13.665| 0.191| 12.865| 0.013|4.95e-07| 6.29e-10|
|WISEA J093042.67-014550.9| 142.67791| -1.76427| G| 607.80| null| 21.811| 0.330| 12.959| 0.125| 12.547| 0.014|4.10e-07| 6.15e-10|
|WISEA J092150.45-071954.1| 140.46029| -7.33178| G| 661.45| null| null| null| 13.083| 0.146| 12.922| 0.018|4.54e-07| 5.73e-10|
Table 1: Top 20 galaxies in NED-LVS that fall in the 90% probability volume for S250205bk 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).