LIGO/Virgo/KAGRA S250725j
GCN Circular 41595
Sean MacBride (University of Zurich), Shreya Anand (Stanford University), Erin Howard, Ian Sullivan, David Wang, Lynne Jones, Peter Yoachim, Eric Bellm (University of Washington), Bob Armstrong (Lawrence Livermore National Laboratory), Michael Wood-Vasey (University of Pittsburgh), Alex Drlica-Wagner, Ken Herner (Fermi National Accelerator Laboratory), Gautham Narayan (University of Illinois), Tatiana Acero Cuellar, Federica Bianco (University of Delaware), Bruno Sánchez (Aix Marseille Université), John Banovetz (Lawrence Berkeley National Laboratory), Kris Mortensen, Paulina Venegas, Yijung Kang, Yousuke Utsumi, and Tiago Ribeiro (NSF-DOE Vera C Rubin Observatory), reporting on behalf of NSF-DOE Vera C Rubin Observatory:
We observed the localization region of the binary black hole merger S250725j, reported by LIGO/Virgo/KAGRA (GCN 41154, GCN 41168) with the 9.6 square degree field of view LSST Camera mounted on the 8.4-m Simonyi Survey Telescope at the Vera C. Rubin Observatory. This is the first Target-of-Opportunity observation by Rubin Observatory.
Rubin Observatory is conducting a Science Validation (SV) survey as part of its commissioning activities [1]. During this period, data quality and acquisition rate are variable. Not all data products that will be available during the Legacy Survey of Space and Time (LSST) operations are currently available [2].
Observations were conducted as a part of commissioning the Rubin Target-of-Opportunity (ToO) system. We used the SCiMMA Hopskotch infrastructure to send the alert data from LVK to Rubin Observatory infrastructure [3]. The observing strategy for this gravitational wave event follows the community recommendation for a binary black-hole merger candidate of this distance and sky condition [4]. The observing strategy calls for multiple epochs of observation, but weather conditions have prevented further observations.
The localization region of S250725j is not inside the SV survey footprint, so no prior Rubin images of this region were available. We obtained two visits in each of the u, r, and i bands with 30s exposures. Observations were taken on the night of July 29, 2025, beginning at 02:28:07.875 UTC and concluding at 03:20:18.800 UTC. We observed with nine 9.6 square degree pointings centered on the following ICRS coordinates:
| RA | DEC |
|---|---|
| 230.604 | -38.402 |
| 232.198 | -35.510 |
| 232.568 | -41.024 |
| 233.614 | -32.596 |
| 234.198 | -38.132 |
| 235.633 | -35.209 |
| 236.925 | -32.268 |
| 237.769 | -37.776 |
We covered 94% of the total localization area in all three bands, reaching a median depth of 24.1 mag in r band, 23.8 mag in the i band, and 23.6 in u band.
Due to the lack of prior Rubin observations of the region, we performed image differencing against DECam templates from DES DR2 [5]. To support the usage of DECam templates, we devised a custom image processing task to create DECam templates from DES templates for use with LSSTCam observations. Apart from the DECam template task, we utilize the standard LSST data release production pipeline to obtain difference images and photometry on difference image sources [6].
With only a single epoch of observations at Rubin observatory, we are unable to characterize viable candidates from Rubin observations alone. Here, we report on candidates reported in GCN 41206 and GCN 41177.
We detect four candidates reported by the DESGW collaboration (GCN 41206), and two candidates reported by the GW-MMADS collaboration (GCN 41177, two candidates recovered by both collaborations). AT2025sib, AT2025srk, and AT2025srm are detected in both r and i band difference images. At the position of AT2025srm and AT2025sib there is a galaxy in the DES template images, and a point source present in the difference images. AT2025srk shows a point source present in the LSSTCam images, but not the DES templates. We caution that AT2025shz may be a variable star, as there is a point source at the location in the DES templates.
| AT name | Observation Date | RA | Dec | r | unc_r | i | unc_i |
|---|---|---|---|---|---|---|---|
| AT2025sib | 2025-07-29 | 235.548892 | -35.002876 | 20.95 | 0.03 | 20.76 | 0.03 |
| AT2025srk | 2025-07-29 | 234.755524 | -36.425993 | 21.17 | 0.04 | 21.31 | 0.06 |
| AT2025srm | 2025-07-29 | 232.987656 | -36.816564 | 21.90 | 0.05 | 22.99 | 0.21 |
| AT2025shz | 2025-07-29 | 231.072434 | -37.622634 | 22.25 | 0.07 | 21.97 | 0.11 |
Analysis of these candidates is ongoing.
This material is based upon work supported in part by the National Science Foundation through Cooperative Agreements AST-1258333 and AST-2241526 and Cooperative Support Agreements AST-1202910 and 2211468 managed by the Association of Universities for Research in Astronomy (AURA), and the Department of Energy under Contract No. DE-AC02-76SF00515 with the SLAC National Accelerator Laboratory managed by Stanford University. Additional Rubin Observatory funding comes from private donations, grants to universities, and in-kind support from LSST-DA Institutional Members.
[1] https://sitcomtn-005.lsst.io, §6
[3] www.scimma.org
[4] www.inspirehep.net/literature/2846480
GCN Circular 41213
B. Godson, N. Habeeb, K. Ackley, D. O’Neill, A. Kumar, G. Ramsay, M. J. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration:
We report on historical observations of counterpart candidate AT 2025sib (Hall et al. GCN 41177, McMahon et al. GCN 41206) with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024).
We find evidence of emission of the source starting at 2025-07-13 08:51 with a 3-sigma observation of L = 20.2 +/- 0.3 AB mag, with our final observation on 2025-07-21 10:11 with L = 20.8 +/- 0.3 AB mag at 3-sigma. We cannot rule out the variable nature of this source and find no evidence of the decay reported in Hall et al. GCN 41177 at these early times. We note that the source appears coincident with an object in the 2MASS Point Source Catalog, 2MASS15421160-3500115 (Cutri et al 2003).
GOTO last covered the field of S250725j serendipitously during survey mode on 2025-07-21. We did not perform follow-up for S250725j due to poor weather conditions at GOTO-South. In addition, we find no evidence of pre-detection emission for the other sources reported in GCN 41177, GCN 41206.
Continued analysis of additional candidates is ongoing.
Difference imaging was performed using deeper template observations. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction.
GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC).
GCN Circular 41206
Isaac McMahon, Sean MacBride, Marcelle Soares-Santos (UZH), Nora Sherman (Boston U.), Simran Kaur (U. of Michigan/UZH), Lillian Joseph (Benedictine U.), Ken Herner, Tom Diehl (Fermilab), reporting on behalf of the Dark Energy Survey Gravitational Wave (DESGW) Team:
At 2025-07-25 23:13:43 UTC and 2025-07-28 23:13:54 UTC, the Dark Energy Camera (DECam) began the first and second epoch of observations in response to the LVK alert issued for the candidate gravitational-wave event S250725j (GCN 41154). We observed nine fields centered on the following ICRS coordinates:
| RA | DEC |
|---|---|
| 231.833836 | -37.23415 |
| 234.585764 | -35.2584 |
| 232.520774 | -35.64614 |
| 233.935432 | -36.84845 |
| 236.026051 | -36.42542 |
| 230.4476 | -35.99735 |
| 233.180871 | -34.0649 |
| 236.640727 | -34.83446 |
| 229.723284 | -37.58219 |
These pointings cover the 90% localization region of candidate gravitational-wave event S250725j.
All fields were observed in DECam g, r, i, z filters with 90-second exposures. The limiting magnitudes achieved for epoch 1 were 23.2 in g, 22.9 in r, and 22.6 in i, and 21.6 in z. The limiting magnitudes achieved for epoch 2 were 22.5 in g, 22.6 in r, and 22.3 in i, and 21.6 in z.
We process the images with our difference imaging pipeline (Herner et al. 2020) using DES and public DECam images as templates. We employ the autoscan machine learning code (Goldstein et al 2015) to reject subtraction artifacts. Candidates were initially selected by requiring at least two high signal to noise detections, which were separated in time in order to reject moving objects. We also require an autoscan score of at least 0.7 on at least one of those detections. We also match our candidates against the ALLWISE, Milliquas, and Quaia AGN catalogs (Secrest et al 2015, Flesch 2023, Storey-Fisher et al 2024) within the LVK localization volume to determine if any correspond to known active galactic nuclei.
After candidate selection we report the 3 high confidence candidates listed below, including 2 nuclear candidates (likely active galactic nuclei) and 1 likely supernova. Further observations are ongoing, and we encourage followup of the 3 candidates identified herein.
| TYPE | ID | ATNAME | RA | DEC | MAG_G | MAG_G_ERR | MAG_R | MAG_R_ERR | MAG_I | MAG_I_ERR | MAG_Z | MAG_Z_ERR |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| SN_LIKE | 3141695 | AT2025srk | 234.755524 | -36.425993 | 21.51 | 0.02 | 21.0 | 0.02 | 21.27 | 0.03 | 22.06 | 0.27 |
| AGN_LIKE | 3237805 | AT2025srl | 234.90473 | -36.726032 | 23.55 | 0.19 | N/A | N/A | 19.74 | 0.01 | N/A | N/A |
| AGN_LIKE | 3141486 | AT2025srm | 232.987656 | -36.816564 | 22.43 | 0.06 | 22.07 | 0.04 | 22.74 | 0.17 | 21.21 | 0.05 |
Additionally, we also recover two of the candidates reported by GW-MMADS (GCN 41177). The candidate AT2025sib is of particular note, as its photometric redshift of z=0.07 reported by 2MASS (Bilicki et al 2014) lies within the LVK 90% volume.
| TYPE | ID | ATNAME | RA | DEC | MAG_G | MAG_G_ERR | MAG_R | MAG_R_ERR | MAG_I | MAG_I_ERR | MAG_Z | MAG_Z_ERR |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| AGN_LIKE | 3141729 | AT2025shz | 231.072453 | -37.6226 | 22.77 | 0.08 | 22.36 | 0.08 | N/A | N/A | N/A | N/A |
| SN_LIKE | 3141898 | AT2025sib | 235.548953 | -35.002893 | 21.72 | 0.04 | 20.7 | 0.02 | N/A | N/A | 20.72 | 0.07 |
The DECam Search & Discovery Program for Optical Signatures of Gravitational Wave Events (DESGW) is carried out by the Dark Energy Survey (DES) collaboration in partnership with wide-ranging groups in the community. DESGW uses data obtained with the Dark Energy Camera (DECam), which was constructed by the DES collaboration with support from the Department of Energy and member institutions, and utilizes data as distributed by the Science Data Archive at NOIRLAB. NOIRLAB is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. We thank the Cerro Tololo observatory staff for their support in acquiring these observations.
GCN Circular 41177
Xander Hall (CMU), Lei Hu (CMU), Tomás Cabrera (CMU), Antonella Palmese (CMU), Igor Andreoni (UNC), Keerthi Kunnumkai (CMU), Brendan O’Connor (CMU), on behalf of the Gravitational Wave MultiMessenger Astronomy DECam Survey (GW-MMADS) team
DECam observed the southern high probability area of the LVK gravitational wave candidate S250725j (GCN 41154) using the wide-field Dark Energy Camera (DECam) on the 4m Blanco telescope. Observations started at 2025-07-25 23:13:43 UTC (Prop ID: 2025A-227091; PI Soares-Santos) and covered the highest 90% probability region of the event (GCN 41168).
We run the SFFT difference imaging (Hu et al. 2022) on the available images, filter out likely stars and moving objects, visually inspect the remaining transients, and remove transients showing SNR>5 detections predating the gravitational wave alert from ATLAS forced photometry. We reported on TNS new transients within the LVK 99% CI area, and we report here those matched to a NED galaxy (GCN 41165):
| id | AT name | ra | dec | discovery_date (UT) | mag_g | mag_g_err | mag_g-mag_r | NED separation |
|---|---|---|---|---|---|---|---|---|
| T202507251524174m373721 | AT 2025shz | 231.072434 | -37.622634 | 2025-07-25 23:29:54.630 | 22.63 | 0.06 | 0.37 | 17.0” |
| T202507251542117m350010* | AT 2025sib | 235.548892 | -35.002876 | 2025-07-25 23:15:43.009 | 22.5 | 0.1 | 0.7 | 2.1” |
| T202507251538092m361517 | AT 2025sia | 234.538140 | -36.254760 | 2025-07-25 23:19:38.393 | 21.74 | 0.03 | 1.06 | 1.1” |
* - We note that these transients may have tentative low SNR pre-detections from ATLAS forced photometry.
We note that AT 2025shz cannot be excluded as a variable star and that it shows an extremely quick rise in the rz filters between two observations in the same night with a rise of several mag/day. We also note that AT 2025sib, shows a gradual decline in the grz filters between two observations with an average decline of ~0.5 mag/day.
Further analysis is underway.
We thank the CTIO and NOIRLab staff for supporting these observations and the data calibration.
GCN Circular 41168
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 S250725j (GCN Circular 41154). 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/S250725j
For the Bilby.multiorder.fits,0 sky map, the 90% credible region is well fit by an ellipse with an area of 19 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(15h32m, -36d06m, 3.23d, 1.84d, 158.46d)
Marginalized over the whole sky, the a posteriori luminosity distance estimate is 380 +/- 93 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
GCN Circular 41165
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 S250725j-3-Initial 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 594 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/S250725j/3
Top 20 List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250725j/3/20
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 J152748.68-355739.1 | 231.95286 | -35.96088 | G | 452.82 | null | null | null | 13.128 | 0.132 | 10.686 | 0.006 | 4.47e-06 | 4.56e-08 |
| WISEA J153844.18-344009.1 | 234.68409 | -34.66922 | G | 480.22 | null | null | null | 12.995 | 0.143 | 10.976 | 0.010 | 3.62e-06 | 3.52e-08 |
| WISEA J153525.42-344743.9 | 233.85592 | -34.79554 | G | 524.15 | null | null | null | 13.715 | 0.214 | 11.189 | 0.018 | 3.34e-06 | 2.91e-08 |
| WISEA J152653.58-355046.3 | 231.72329 | -35.84620 | G | 431.02 | null | null | null | 13.223 | 0.157 | 10.966 | 0.009 | 4.06e-06 | 2.89e-08 |
| WISEA J154628.27-340002.3 | 236.61826 | -34.00070 | G | 425.21 | null | null | null | 13.479 | 0.169 | 9.563 | 0.006 | 1.10e-06 | 2.79e-08 |
| WISEA J153024.70-351033.1 | 232.60293 | -35.17588 | G | 529.76 | null | null | null | 12.578 | 0.113 | 11.182 | 0.008 | 2.90e-06 | 2.58e-08 |
| WISEA J153324.20-354028.6 | 233.35085 | -35.67462 | G | 435.53 | null | null | null | 13.377 | 0.171 | 11.600 | 0.011 | 5.94e-06 | 2.45e-08 |
| WISEA J153416.18-351536.7 | 233.56786 | -35.26055 | G | 415.65 | null | null | null | 13.472 | 0.230 | 11.551 | 0.011 | 5.56e-06 | 2.18e-08 |
| WISEA J153550.83-352815.7 | 233.96181 | -35.47105 | G | 452.48 | null | null | null | 12.155 | 0.114 | 11.835 | 0.011 | 5.59e-06 | 2.01e-08 |
| WISEA J152918.46-355636.4 | 232.32692 | -35.94346 | G | 469.28 | null | null | null | 13.745 | 0.216 | 11.703 | 0.011 | 4.59e-06 | 1.97e-08 |
| WISEA J153406.90-352554.3 | 233.52878 | -35.43177 | G | 444.26 | 0.49 | null | null | 12.177 | 0.090 | 12.031 | 0.023 | 5.84e-06 | 1.68e-08 |
| WISEA J153130.18-350639.3 | 232.87576 | -35.11092 | G | 419.28 | 0.79 | null | null | 12.607 | 0.111 | 11.785 | 0.011 | 4.73e-06 | 1.49e-08 |
| WISEA J153144.43-352246.2 | 232.93514 | -35.37951 | G | 474.13 | null | null | null | 12.991 | 0.145 | 12.199 | 0.016 | 4.99e-06 | 1.38e-08 |
| WISEA J153031.02-350955.4 | 232.62929 | -35.16539 | G | 478.85 | null | null | null | 13.515 | 0.194 | 12.117 | 0.015 | 4.17e-06 | 1.28e-08 |
| WISEA J153512.75-350712.9 | 233.80314 | -35.12027 | G | 470.25 | null | null | null | 13.554 | 0.177 | 12.400 | 0.011 | 5.07e-06 | 1.18e-08 |
| WISEA J152932.42-350115.2 | 232.38508 | -35.02090 | G | 538.67 | null | null | null | 13.523 | 0.198 | 11.824 | 0.007 | 2.30e-06 | 1.16e-08 |
| WISEA J154625.51-332529.0 | 236.60631 | -33.42475 | G | 445.85 | null | null | null | 12.552 | 0.113 | 10.145 | 0.007 | 6.91e-07 | 1.13e-08 |
| WISEA J153354.06-351626.2 | 233.47529 | -35.27397 | G | 397.36 | null | null | null | 13.103 | 0.132 | 12.174 | 0.012 | 5.35e-06 | 1.08e-08 |
| WISEA J153959.24-350547.6 | 234.99684 | -35.09658 | G | 378.08 | null | null | null | 13.710 | 0.194 | 11.652 | 0.010 | 3.45e-06 | 1.05e-08 |
| WISEA J153052.19-345946.7 | 232.71748 | -34.99631 | G | 454.26 | 0.79 | null | null | 12.909 | 0.128 | 12.253 | 0.014 | 4.22e-06 | 1.01e-08 |
Table 1: Top 20 galaxies in NED-LVS that fall in the 90% probability volume for S250725j 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).
GCN Circular 41154
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
We identified the compact binary merger candidate S250725j during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-07-25 04:09:44.252 UTC (GPS time: 1437451802.252). The candidate was found by the GstLAL [1] analysis pipeline.
S250725j is an event of interest because its false alarm rate, as estimated by the online analysis, is 4.3e-11 Hz, or about one in 1e3 years. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S250725j
The classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<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%. [2] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [2] 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 source chirp mass falls with highest probability in the bin (11.0, 22.0) 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:
* bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [3], distributed via GCN and SCiMMA notices about 22 seconds after the candidate event time.
* bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [3], distributed via GCN and SCiMMA notices about 4 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 28 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(15h34m, -35d25m, 3.97d, 2.25d, 153.93d)
Marginalized over the whole sky, the a posteriori luminosity distance estimate is 478 +/- 107 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] 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
[2] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe
[3] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013