Journal article
LIGO/Virgo/KAGRA Neutron Star Merger Candidate S250206dm: Zwicky Transient Facility Observations
Publications of the Astronomical Society of the Pacific, v 138(3), 34101
01 Mar 2026
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Abstract
We present the searches conducted with the Zwicky Transient Facility (ZTF) in response to S250206dm, a bona fide event with an online false alarm rate of one in 25 yr, detected by the International Gravitational Wave Network. Although the event is significant, the nature of the compact objects involved remains unclear, with at least one likely neutron star. ZTF covered 68% of the last refined Bilby localization region, though we did not identify any likely optical counterpart. We describe the ZTF strategy, potential candidates, and the observations that helped rule out candidates, including sources circulated by other collaborations. Similar to Ahumada et al., we perform a frequentist analysis, using simsurvey, as well as Bayesian analysis, using nimbus, to quantify the efficiency of our searches. We find that, given the nominal up-to-date distance to this event of 373 ± 104 Mpc, our efficiencies are above 10% for KNe brighter than −17.5 absolute magnitude. Assuming the optical counterpart known as kilonova (KN) lies within the ZTF footprint, our limits constrain the brightest end of the KN parameter space. Through dedicated radiative transfer simulations of KNe from binary neutron star (BNS) and black hole–neutron star mergers, we exclude parts of the BNS KN parameter space. Up to 35% of the models with high wind ejecta mass (Mwind ≈ 0.13 M⊙) are ruled out when viewed face-on ( cosθobs=1.0 ). Finally, we present a joint analysis using the combined coverage from ZTF and the Gravitational Wave Multimessenger Dark Energy Camera Survey. The joint observations cover 73% of the Bilby localization region, and the combined efficiency has a stronger impact on rising and slowly fading models, allowing us to rule out 55% of the high-mass KN models viewed face-on.
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- Title
- LIGO/Virgo/KAGRA Neutron Star Merger Candidate S250206dm: Zwicky Transient Facility Observations
- Creators
- Tomás Ahumada - California Institute of TechnologyShreya Anand - Kavli Institute for Particle Astrophysics and CosmologyMattia Bulla - University of FerraraVaidehi Gupta - University of MinnesotaMansi Kasliwal - California Institute of TechnologyRobert Stein - Goddard Space Flight CenterViraj Karambelkar - California Institute of TechnologyEric C Bellm - University of WashingtonTheophile Jegou du LazMichael W Coughlin - University of MinnesotaIgor Andreoni - University of North Carolina at Chapel HillSmaranika Banerjee - Stockholm UniversityAleksandra Bochenek - Liverpool CollegeK-Ryan Hinds - Liverpool CollegeLei Hu - Carnegie Mellon UniversityAntonella Palmese - Carnegie Mellon UniversityDaniel Perley - Liverpool CollegeNatalya Pletskova - Drexel UniversityAnirudh Salgundi - Indian Institute of Technology BombayAvinash Singh - Stockholm UniversityJesper Sollerman - Stockholm UniversityVishwajeet Swain - Indian Institute of Technology BombayAvery Wold - California Institute of TechnologyVarun Bhalerao - Indian Institute of Technology BombayS. Bradley Cenko - Joint Space Science InstituteDavid O Cook - California Institute of TechnologyChris Copperwheat - Liverpool CollegeMatthew Graham - California Institute of TechnologyDavid L Kaplan - University of Wisconsin–MilwaukeeLeo P Singer - Goddard Space Flight CenterNiharika Sravan - Drexel UniversityMalte Busmann - Ludwig-Maximilians-Universität MünchenJulius Gassert - Ludwig-Maximilians-Universität MünchenDaniel Gruen - Excellence Cluster OriginsJulian Sommer - Ludwig-Maximilians-Universität MünchenYajie Zhang - Ludwig-Maximilians-Universität MünchenAriel Amsellem - Carnegie Mellon UniversityTomás Cabrera - Carnegie Mellon UniversityXander J Hall - Carnegie Mellon UniversityKeerthi Kunnumkai - Carnegie Mellon UniversityBrendan O’Connor - Carnegie Mellon UniversityTyler Barna - University of MinnesotaFelipe Fontinele NunesAndrew Toivonen - University of MinnesotaArgyro Sasli - University of MinnesotaFrank J Masci - Infrared Processing and Analysis CenterTracy X Chen - California Institute of TechnologyRichard Dekany - California Institute of TechnologyJosiah Purdum - California Institute of TechnologyAntoine Le Calloch - University of MinnesotaG. C Anupama - Indian Institute of AstrophysicsSudhanshu Barway - Indian Institute of Astrophysics
- Publication Details
- Publications of the Astronomical Society of the Pacific, v 138(3), 34101
- Publisher
- IOP Publishing
- Number of pages
- 26
- Grant note
- NSF: 2308193., AST 2505775, PHY- 748 2117997, PHY- 758 2010970., PHY-2010970, PHY-2308862 NASA: 24-ADAP24-0159 University of Ferrara: FIRD 2024 Knut och Alice Wallenbergs Stiftelse: Gravity Meets Light UKRI: ST/W001934/1, ST/X005933/1 David and Lucile Packard Foundation
M.M.K., S.A. and T.A. acknowledge generous support from the David and Lucile Packard Foundation. M.B. acknowledges the Department of Physics and Earth Science of the University of Ferrara for the financial support through the FIRD 2024 grant M.W.C., A.T., A.S. and T.B. acknowledges support from the National Science Foundation with grant No. PHY-2010970. A.T. acknowledges support from the National Science Foundation with grant Nos. PHY-2308862 and PHY-2117997 A.P. and L.H. acknowledges support by National Science Foundation grant No. 2308193. I.A. acknowledges support from the National Science Foundation Award AST 2505775 and NASA grant 24-ADAP24-0159 A. S.ngh acknowledges support from the Knut and Alice Wallenberg Foundation through the "Gravity Meets Light" project. C.M.C. acknowledges support from UKRI with grant numbers ST/X005933/1 and ST/W001934/1 A. S. acknowledges support from the National Science Foundation with grant number PHY-2010970. M.B. is supported by a Student Grant from the Wubben Stiftung Wissenschaft. G.C.A. thanks the Indian National Science Academy for support under the INSA Senior Scientist Programme. A.T. acknowledges support from the National Science Foundation with grant Nos. PHY-2308862 and PHY-2117997.
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Physics
- Web of Science ID
- WOS:001710402800001
- Other Identifier
- 991022167717804721