231 research outputs found
Estimates of black-hole natal kick velocities from observations of low-mass X-ray binaries
The birth kicks of black holes, arising from asymmetric mass ejection or
neutrino emission during core-collapse supernovae, are of great interest for
both observationally constraining supernova models and population-synthesis
studies of binary evolution. Recently, several efforts were undertaken to
estimate black hole birth kicks from observations of black-hole low-mass X-ray
binaries. We follow up on this work, specifically focussing on the highest
estimated black-hole kick velocities. We find that existing observations do not
require black hole birth kicks in excess of approximately 100 km/s, although
higher kicks are not ruled out
The orbit of GW170817 was inclined by less than 28 degrees to the line of sight
We combine the gravitational-wave measurement of the effective distance to
the binary neutron star merger GW170817, the redshift of its host galaxy NGC
4993, and the latest Hubble constant measurement from the Dark Energy Survey to
constrain the inclination between the orbital angular momentum of the binary
and the line of sight to degrees (less than 28 degrees at 90%
confidence). This provides a complementary constraint on models of potential
afterglow observations.Comment: Revised and expanded, to match version accepted by ApJ Letter
Parameter estimation on gravitational waves from multiple coalescing binaries
Future ground-based and space-borne interferometric gravitational-wave
detectors may capture between tens and thousands of binary coalescence events
per year. There is a significant and growing body of work on the estimation of
astrophysically relevant parameters, such as masses and spins, from the
gravitational-wave signature of a single event. This paper introduces a robust
Bayesian framework for combining the parameter estimates for multiple events
into a parameter distribution of the underlying event population. The framework
can be readily deployed as a rapid post-processing tool
Constraining the masses of microlensing black holes and the mass gap with Gaia DR2
Context: Gravitational microlensing is sensitive to compact-object lenses in
the Milky Way, including white dwarfs, neutron stars or black holes, and could
potentially probe a wide range of stellar remnant masses. However, the mass of
the lens can be determined only in very limited cases, due to missing
information on both source and lens distances and their proper motions.
Aims: We aim at improving the mass estimates in the annual parallax
microlensing events found in the 8 years of OGLE-III observations towards the
Galactic Bulge (Wyrzykowski et al. 2016) with the use of Gaia Data Release 2
(DR2).
Methods: We use Gaia DR2 data on distances and proper motions of non-blended
sources and recompute the masses of lenses in parallax events. We also identify
new events in that sample which are likely to have dark lens; the total number
of such events is now 18.
Results: The derived distribution of masses of dark lenses is consistent with
a continuous distribution of stellar remnant masses. A mass gap between
neutron-star and black-hole masses in the range between 2 and 5 solar masses is
not favoured by our data, unless black holes receive natal-kicks above 20-80
km/s. We present 8 candidates for objects with masses within the putative mass
gap, including a spectacular multi-peak parallax event with mass of
located just at 600 pc. The absence of an
observational mass gap between neutron stars and black holes, or, conversely,
the evidence for black hole natal kicks if a mass gap is assumed, can inform
future supernova modelling efforts.Comment: 12 pages, published as Wyrzykowski&Mandel, 2020, A&A, 636, A2
Merging stellar-mass binary black holes
The LIGO and Virgo detectors have recently directly observed gravitational
waves from several mergers of pairs of stellar-mass black holes, as well as
from one merging pair of neutron stars. These observations raise the hope that
compact object mergers could be used as a probe of stellar and binary
evolution, and perhaps of stellar dynamics. This colloquium-style article
summarizes the existing observations, describes theoretical predictions for
formation channels of merging stellar-mass black-hole binaries along with their
rates and observable properties, and presents some of the prospects for
gravitational-wave astronomy.Comment: Colloquium-style article solicited by Reviews of Modern Physics;
comments appreciate
Double Neutron Star Populations and Formation Channels
In the past five years, the number of known double neutron stars (DNS) in the
Milky Way has roughly doubled. We argue that the observed sample can be split
into three distinct sub-populations based on their orbital characteristics: (i)
short-period, low-eccentricity binaries; (ii) wide binaries; and (iii)
short-period, high-eccentricity binaries. These sub-populations also exhibit
distinct spin period and spindown rate properties. We focus on sub-population
(iii), which contains the Hulse-Taylor binary. Contrary to previous analysis,
we demonstrate that, if they are the product of primordial binary evolution,
the and distribution of these systems requires that the
second-born NSs must have been formed with small natal kicks (25 km
s) and have pre-SN masses narrowly distributed around 3.2 M.
These constraints challenge binary evolution theory and further predict closely
aligned spin and orbital axes, inconsistent with the Hulse-Taylor binary's
measured spin-orbit misalignment angle of 20. Motivated by
the similarity of these DNSs to B2127+11C, a DNS residing in the globular
cluster M15, we argue that this sub-population is consistent with being formed
in, and then ejected from, globular clusters. This scenario provides a pathway
for the formation and merger of DNSs in stellar environments without recent
star formation, as observed in the host galaxy population of short gamma ray
bursts and the recent detection by LIGO of a merging DNS in an old stellar
population.Comment: 8 pages, 4 figures, 1 table, accepted for publication in ApJ
Accelerating gravitational wave parameter estimation with multi-band template interpolation
Parameter estimation on gravitational wave signals from compact binary
coalescence (CBC) requires the evaluation of computationally intensive waveform
models, typically the bottleneck in the analysis. This cost will increase
further as low frequency sensitivity in later second and third generation
detectors motivates the use of longer waveforms.
We describe a method for accelerating parameter estimation by exploiting the
chirping behaviour of the signals to sample the waveform sparsely for portions
where the full frequency resolution is not required. We demonstrate that the
method can reproduce the original results with a waveform mismatch of , but with a waveform generation cost up to times
lower for computationally costly frequency-domain waveforms starting from below
8 Hz
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