Preprint
ZTF25abjmnps (AT2025ulz) and S250818k: A Candidate Superkilonova from a Sub-threshold Sub-Solar Gravitational Wave Trigger
ArXiv.org
27 Oct 2025
Abstract
On August 18, 2025, the LIGO-Virgo-KAGRA collaboration reported gravitational waves from a sub-threshold binary neutron star merger. If astrophysical, this event would have a surprisingly low chirp mass, suggesting that at least one neutron star was below a solar mass. The Zwicky Transient Facility mapped the coarse localization and discovered a transient, ZTF25abjmnps (AT2025ulz), that was spatially and temporally coincident with the gravitational wave trigger. The first week of follow-up suggested properties reminiscent of a GW170817-like kilonova. Subsequent follow-up suggests properties most similar to a young, stripped-envelope, Type IIb supernova. Although we cannot statistically rule out chance coincidence, we undertake due diligence analysis to explore the possible association between ZTF25abjmnps and S250818k. Theoretical models have been proposed wherein sub-solar neutron star(s) may form (and subsequently merge) via accretion disk fragmentation or core fission inside a core-collapse supernova i.e. a ``superkilonova". Here, we qualitatively discuss our multi-wavelength dataset in the context of the superkilonova picture. Future higher significance gravitational wave detections of sub-solar neutron star mergers with extensive electromagnetic follow-up would conclusively resolve this tantalizing multi-messenger association.
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Details
- Title
- ZTF25abjmnps (AT2025ulz) and S250818k: A Candidate Superkilonova from a Sub-threshold Sub-Solar Gravitational Wave Trigger
- Creators
- Mansi M KasliwalTomas AhumadaRobert SteinViraj KarambelkarXander J HallAvinash SinghChristoffer FremlingBrian D MetzgerMattia BullaVishwajeet SwainSarah AntierMarion PillasMalte BusmannJames FreeburnSergey KarpovAleksandra BochenekBrendan O'ConnorDaniel A PerleyDalya AklShreya AnandAndrew ToivonenSam RoseTheophile Jegou du LazChang LiuKaustav DasSushant Sharma ChaudharyTyler BarnaAditya Pawan SaikiaIgor AndreoniEric C BellmVarun BhaleraoS. Bradley CenkoMichael W CoughlinDaniel GruenDaniel KasenAdam A MillerSamaya NissankeAntonella PalmeseJesper SollermanNiharika SravanG. C AnupamaSmaranika BanerjeeSudhanshu BarwayJoshua S BloomTomas CabreraTracy ChenChris CopperwheatAlessandra CorsiRichard DekanyNicholas EarleyMatthew GrahamPatrice HelloGeorge HelouLei HuYves KiniAshish MahabalFrank MasciTanishk MohanNatalya PletskovaJosiah PurdumYu-Jing QinNabeel RehemtullaAnirudh SalgundiYuankun Wang
- Publication Details
- ArXiv.org
- Resource Type
- Preprint
- Language
- English
- Academic Unit
- Physics
- Other Identifier
- 991022127347904721