2025-12-16 カリフォルニア工科大学（Caltech）
This artist’s concepts shows a hypothesized event known as a superkilonova. A massive star explodes in a supernova (left), which generates elements like carbon and iron. In the aftermath, two neutron stars are born (middle), at least one of which is believed to be less massive than our Sun. The neutron stars spiral together, sending gravitational waves rippling through the cosmos, before merging in a dramatic kilonova (right). Kilonovae seed the universe with the heaviest elements, such as gold at platinum, which glow with red light.Credit: Caltech/K. Miller and R. Hurt (IPAC)
＜関連情報＞
- https://www.caltech.edu/about/news/possible-superkilonova-exploded-not-once-but-twice
- https://iopscience.iop.org/article/10.3847/2041-8213/ae2000
- https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.161101
ZTF25aLetterbjmnps (AT2025ulz) と S250818k: サブスレッショルド太陽重力波トリガーによるスーパーキロノバ候補 ZTF25abjmnps (AT2025ulz) and S250818k: A Candidate Superkilonova from a Subthreshold Subsolar Gravitational-wave Trigger
Mansi M. Kasliwal, Tomás Ahumada, Robert Stein, Viraj Karambelkar, Xander J. Hall, Avinash Singh, Christoffer Fremling, Brian D. Metzger, Mattia Bulla, Vishwajeet Swain,…
The Astrophysical Journal Letters Published: 2025 December 15
DOI:10.3847/2041-8213/ae2000
Abstract
On 2025 August 18, the LIGO–Virgo–KAGRA collaboration reported gravitational waves from a subthreshold 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, ZTF 25abjmnps (AT2025ulz), which 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 ZTF 25abjmnps and S250818k. Theoretical models have been proposed wherein subsolar 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 multiwavelength dataset in the context of the superkilonova picture. Future higher-significance gravitational-wave detections of subsolar neutron star mergers with extensive electromagnetic follow-up would conclusively resolve this tantalizing multimessenger association.
GW170817: 連星中性子星からの重力波の観測 GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
B. P. Abbott, R. Abbott, T. D. Abbott, F. Acernese, K. Ackley, C. Adams, T. Adams, P. Addesso, R. X. Adhikari et al. (LIGO Scientific Collaboration and Virgo Collaboration)
Physical Review Letters Published 16 October, 2017
DOI: https://doi.org/10.1103/PhysRevLett.119.161101
Abstract
On August 17, 2017 at 12∶41:04 UTC the Advanced LIGO and Advanced Virgo gravitational-wave detectors made their first observation of a binary neutron star inspiral. The signal, GW170817, was detected with a combined signal-to-noise ratio of 32.4 and a false-alarm-rate estimate of less than one per 8.0×104 years. We infer the component masses of the binary to be between 0.86 and 2.26 ⊙, in agreement with masses of known neutron stars. Restricting the component spins to the range inferred in binary neutron stars, we find the component masses to be in the range 1.17–1.60 ⊙, with the total mass of the system 2.74+0.04−0.01⊙. The source was localized within a sky region of 28 deg2 (90% probability) and had a luminosity distance of 40+8−14 Mpc, the closest and most precisely localized gravitational-wave signal yet. The association with the -ray burst GRB 170817A, detected by Fermi-GBM 1.7 s after the coalescence, corroborates the hypothesis of a neutron star merger and provides the first direct evidence of a link between these mergers and short -ray bursts. Subsequent identification of transient counterparts across the electromagnetic spectrum in the same location further supports the interpretation of this event as a neutron star merger. This unprecedented joint gravitational and electromagnetic observation provides insight into astrophysics, dense matter, gravitation, and cosmology.
