3,053 research outputs found
Searching for binary coalescences with inspiral templates: Detection and parameter estimation
There has been remarkable progress in numerical relativity recently. This has
led to the generation of gravitational waveform signals covering what has been
traditionally termed the three phases of the coalescence of a compact binary -
the inspiral, merger and ringdown. In this paper, we examine the usefulness of
inspiral only templates for both detection and parameter estimation of the full
coalescence waveforms generated by numerical relativity simulations. To this
end, we deploy as search templates waveforms based on the effective one-body
waveforms terminated at the light-ring as well as standard post-Newtonian
waveforms. We find that both of these are good for detection of signals.
Parameter estimation is good at low masses, but degrades as the mass of the
binary system increases.Comment: 14 pages, submitted to proceedings of the NRDA08 meeting, Syracuse,
Aug. 11-14, 200
Black holes in the low mass gap: Implications for gravitational wave observations
Binary neutron-star mergers will predominantly produce black-hole remnants of
mass , thus populating the putative \emph{low mass gap}
between neutron stars and stellar-mass black holes. If these low-mass black
holes are in dense astrophysical environments, mass segregation could lead to
"second-generation" compact binaries merging within a Hubble time. In this
paper, we investigate possible signatures of such low-mass compact binary
mergers in gravitational-wave observations. We show that this unique population
of objects, if present, will be uncovered by the third-generation
gravitational-wave detectors, such as Cosmic Explorer and Einstein Telescope.
Future joint measurements of chirp mass and effective spin
could clarify the formation scenario of compact objects in the
low mass gap. As a case study, we show that the recent detection of GW190425
(along with GW170817) favors a double Gaussian mass model for neutron stars,
under the assumption that the primary in GW190425 is a black hole formed from a
previous binary neutron star merger.Comment: 8 pages, 4 figures, 1 table. v4: matches the version accepted for
publication in Phys. Rev.
Comparison of Gravitational Wave Detector Network Sky Localization Approximations
Gravitational waves emitted during compact binary coalescences are a
promising source for gravitational-wave detector networks. The accuracy with
which the location of the source on the sky can be inferred from gravitational
wave data is a limiting factor for several potential scientific goals of
gravitational-wave astronomy, including multi-messenger observations. Various
methods have been used to estimate the ability of a proposed network to
localize sources. Here we compare two techniques for predicting the uncertainty
of sky localization -- timing triangulation and the Fisher information matrix
approximations -- with Bayesian inference on the full, coherent data set. We
find that timing triangulation alone tends to over-estimate the uncertainty in
sky localization by a median factor of for a set of signals from
non-spinning compact object binaries ranging up to a total mass of , and the over-estimation increases with the mass of the system. We
find that average predictions can be brought to better agreement by the
inclusion of phase consistency information in timing-triangulation techniques.
However, even after corrections, these techniques can yield significantly
different results to the full analysis on specific mock signals. Thus, while
the approximate techniques may be useful in providing rapid, large scale
estimates of network localization capability, the fully coherent Bayesian
analysis gives more robust results for individual signals, particularly in the
presence of detector noise.Comment: 11 pages, 7 Figure
Early Advanced LIGO binary neutron-star sky localization and parameter estimation
2015 will see the first observations of Advanced LIGO and the start of the
gravitational-wave (GW) advanced-detector era. One of the most promising
sources for ground-based GW detectors are binary neutron-star (BNS)
coalescences. In order to use any detections for astrophysics, we must
understand the capabilities of our parameter-estimation analysis. By simulating
the GWs from an astrophysically motivated population of BNSs, we examine the
accuracy of parameter inferences in the early advanced-detector era. We find
that sky location, which is important for electromagnetic follow-up, can be
determined rapidly (~5 s), but that sky areas may be hundreds of square
degrees. The degeneracy between component mass and spin means there is
significant uncertainty for measurements of the individual masses and spins;
however, the chirp mass is well measured (typically better than 0.1%).Comment: 4 pages, 2 figures. Published in the proceedings of Amaldi 1
Supplement: Going the Distance: Mapping Host Galaxies of LIGO and Virgo Sources in Three Dimensions Using Local Cosmography and Targeted Follow-up
This is a supplement to the Letter of Singer et al.
(https://arxiv.org/abs/1603.07333), in which we demonstrated a rapid algorithm
for obtaining joint 3D estimates of sky location and luminosity distance from
observations of binary neutron star mergers with Advanced LIGO and Virgo. We
argued that combining the reconstructed volumes with positions and redshifts of
possible host galaxies can provide large-aperture but small field of view
instruments with a manageable list of targets to search for optical or infrared
emission. In this Supplement, we document the new HEALPix-based file format for
3D localizations of gravitational-wave transients. We include Python sample
code to show the reader how to perform simple manipulations of the 3D sky maps
and extract ranked lists of likely host galaxies. Finally, we include
mathematical details of the rapid volume reconstruction algorithm.Comment: For associated data release, see
http://asd.gsfc.nasa.gov/Leo.Singer/going-the-distanc
Spaceborne radar observations: A guide for Magellan radar-image analysis
Geologic analyses of spaceborne radar images of Earth are reviewed and summarized with respect to detecting, mapping, and interpreting impact craters, volcanic landforms, eolian and subsurface features, and tectonic landforms. Interpretations are illustrated mostly with Seasat synthetic aperture radar and shuttle-imaging-radar images. Analogies are drawn for the potential interpretation of radar images of Venus, with emphasis on the effects of variation in Magellan look angle with Venusian latitude. In each landform category, differences in feature perception and interpretive capability are related to variations in imaging geometry, spatial resolution, and wavelength of the imaging radar systems. Impact craters and other radially symmetrical features may show apparent bilateral symmetry parallel to the illumination vector at low look angles. The styles of eruption and the emplacement of major and minor volcanic constructs can be interpreted from morphological features observed in images. Radar responses that are governed by small-scale surface roughness may serve to distinguish flow types, but do not provide unambiguous information. Imaging of sand dunes is rigorously constrained by specific angular relations between the illumination vector and the orientation and angle of repose of the dune faces, but is independent of radar wavelength. With a single look angle, conditions that enable shallow subsurface imaging to occur do not provide the information necessary to determine whether the radar has recorded surface or subsurface features. The topographic linearity of many tectonic landforms is enhanced on images at regional and local scales, but the detection of structural detail is a strong function of illumination direction. Nontopographic tectonic lineaments may appear in response to contrasts in small-surface roughness or dielectric constant. The breakpoint for rough surfaces will vary by about 25 percent through the Magellan viewing geometries from low to high Venusian latitudes. Examples of anomalies and system artifacts that can affect image interpretation are described
Mojave remote sensing field experiment
The Mojave Remote Sensing Field Experiment (MFE), conducted in June 1988, involved acquisition of Thermal Infrared Multispectral Scanner (TIMS); C, L, and P-band polarimetric radar (AIRSAR) data; and simultaneous field observations at the Pisgah and Cima volcanic fields, and Lavic and Silver Lake Playas, Mojave Desert, California. A LANDSAT Thematic Mapper (TM) scene is also included in the MFE archive. TM-based reflectance and TIMS-based emissivity surface spectra were extracted for selected surfaces. Radiative transfer procedures were used to model the atmosphere and surface simultaneously, with the constraint that the spectra must be consistent with field-based spectral observations. AIRSAR data were calibrated to backscatter cross sections using corner reflectors deployed at target sites. Analyses of MFE data focus on extraction of reflectance, emissivity, and cross section for lava flows of various ages and degradation states. Results have relevance for the evolution of volcanic plains on Venus and Mars
Report of the panel on the land surface: Process of change, section 5
The panel defined three main areas of study that are central to the Solid Earth Science (SES) program: climate interactions with the Earth's surface, tectonism as it affects the Earth's surface and climate, and human activities that modify the Earth's surface. Four foci of research are envisioned: process studies with an emphasis on modern processes in transitional areas; integrated studies with an emphasis on long term continental climate change; climate-tectonic interactions; and studies of human activities that modify the Earth's surface, with an emphasis on soil degradation. The panel concluded that there is a clear requirement for global coverage by high resolution stereoscopic images and a pressing need for global topographic data in support of studies of the land surface
Time evolution of a non-singular primordial black hole
There is growing notion that black holes may not contain curvature
singularities (and that indeed nature in general may abhor such spacetime
defects). This notion could have implications on our understanding of the
evolution of primordial black holes (PBHs) and possibly on their contribution
to cosmic energy. This paper discusses the evolution of a non-singular black
hole (NSBH) based on a recent model [1]. We begin with a study of the
thermodynamic process of the black hole in this model, and demonstrate the
existence of a maximum horizon temperature T_{max}, corresponding to a unique
mass value. At this mass value the specific heat capacity C changes signs to
positive and the body begins to lose its black hole characteristics. With no
loss of generality, the model is used to discuss the time evolution of a
primordial black hole (PBH), through the early radiation era of the universe to
present, under the assumption that PBHs are non-singular. In particular, we
track the evolution of two benchmark PBHs, namely the one radiating up to the
end of the cosmic radiation domination era, and the one stopping to radiate
currently, and in each case determine some useful features including the
initial mass m_{f} and the corresponding time of formation t_{f}. It is found
that along the evolutionary history of the universe the distribution of PBH
remnant masses (PBH-RM) PBH-RMs follows a power law. We believe such a result
can be a useful step in a study to establish current abundance of PBH-MRs.Comment: To appear in Int. J. Mod. Phys.
- …