RESUMEN
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M_{â}) and near-circular orbit (e≈0.02) of VFTS 243 suggest that the progenitor star experienced complete collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence level, the natal kick velocity (mass decrement) is â²10 km/s (â²1.0M_{â}), with a full probability distribution that peaks when ≈0.3M_{â} were ejected, presumably in neutrinos, and the black hole experienced a natal kick of 4 km/s. The neutrino-emission asymmetry is â²4%, with best fit values of â¼0-0.2%. Such a small neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
RESUMEN
Some compact objects observed in gravitational wave events have masses in the gap between known neutron stars (NSs) and black holes (BHs). The nature of these mass gap objects is unknown, as is the formation of their host binary systems. We report pulsar timing observations made with the Karoo Array Telescope (MeerKAT) of PSR J0514-4002E, an eccentric binary millisecond pulsar in the globular cluster NGC 1851. We found a total binary mass of 3.887 ± 0.004 solar masses (Mâ), and multiwavelength observations show that the pulsar's binary companion is also a compact object. The companion's mass (2.09 to 2.71 Mâ, 95% confidence interval) is in the mass gap, indicating either a very massive NS or a low-mass BH. We propose that the companion formed in a merger between two earlier NSs.
RESUMEN
Thompson et al (Reports, 1 November 2019, p. 637) interpreted the unseen companion of the red giant star 2MASS J05215658+4359220 as most likely a black hole. We argue that if the red giant's mass is ~1 solar mass, its companion can be a close binary consisting of two main-sequence stars. This would explain why no x-ray emission is detected from the system.
RESUMEN
This corrects the article DOI: 10.1103/PhysRevLett.121.131105.
RESUMEN
The prime candidate sources for the upcoming space-borne gravitational wave (GW) observatory LISA are the numerous Galactic tight binaries of white dwarfs (WDs) and neutron stars (NSs), many of which will coalesce and undergo mass transfer, leading to simultaneous emission of x rays and GWs. Here, detailed and coherent numerical stellar models are explored for the formation and evolution of these systems, including finite-temperature effects and complete calculations of mass transfer from a WD to a NS accretor. Evolutionary tracks of characteristic strain amplitude are computed, and the unique pattern of their evolution in the GW frequency-dynamical chirp mass parameter space enables a firm identification of the nature of the systems. Furthermore, it is demonstrated that a precise detection of the chirp allows determination of the NS mass to an accuracy of a few percent; with applications to constraining its equation of state, in particular for dual-line GW sources observed simultaneously at high and low frequencies.
RESUMEN
Many physically motivated extensions to general relativity (GR) predict substantial deviations in the properties of spacetime surrounding massive neutron stars. We report the measurement of a 2.01 ± 0.04 solar mass (Mâ) pulsar in a 2.46-hour orbit with a 0.172 ± 0.003 Mâ white dwarf. The high pulsar mass and the compact orbit make this system a sensitive laboratory of a previously untested strong-field gravity regime. Thus far, the observed orbital decay agrees with GR, supporting its validity even for the extreme conditions present in the system. The resulting constraints on deviations support the use of GR-based templates for ground-based gravitational wave detectors. Additionally, the system strengthens recent constraints on the properties of dense matter and provides insight to binary stellar astrophysics and pulsar recycling.
RESUMEN
Millisecond pulsars are old neutron stars that have been spun up to high rotational frequencies via accretion of mass from a binary companion star. An important issue for understanding the physics of the early spin evolution of millisecond pulsars is the impact of the expanding magnetosphere during the terminal stages of the mass-transfer process. Here, I report binary stellar evolution calculations that show that the braking torque acting on a neutron star, when the companion star decouples from its Roche lobe, is able to dissipate >50% of the rotational energy of the pulsar. This effect may explain the apparent difference in observed spin distributions between x-ray and radio millisecond pulsars and help account for the noticeable age discrepancy with their young white dwarf companions.
