14 research outputs found
Neutron Star Mergers and the Quark Matter Equation of State
As neutron stars merge they can approach very high nuclear density. Here, we summarized recent results for the evolution and gravitational wave emission from binary-neutron star mergers using a a variety of nuclear equations of state with and without a crossover transition to quark matter. We discuss how the late time gravitational wave emission from binary neutron star mergers may possibly reveal the existence of a crossover transition to quark matter
Interpolated kilonova spectra models: necessity for a phenomenological, blue component in the fitting of AT2017gfo spectra
In this work, we present a simple interpolation methodology for spectroscopic
time series, based on conventional interpolation techniques (random forests)
implemented in widely-available libraries. We demonstrate that our existing
library of simulations is sufficient for training, producing interpolated
spectra that respond sensitively to varied ejecta parameter, post-merger time,
and viewing angle inputs. We compare our interpolated spectra to the AT2017gfo
spectral data, and find parameters similar to our previous inferences using
broadband light curves. However, the spectral observations have significant
systematic short-wavelength residuals relative to our models, which we cannot
explain within our existing framework. Similar to previous studies, we argue
that an additional blue component is required. We consider a radioactive
heating source as a third component characterized by light, slow-moving,
lanthanide-free ejecta with , c,
and cm/g. When included as part of our radiative
transfer simulations, our choice of third component reprocesses blue photons
into lower energies, having the opposite effect and further accentuating the
blue-underluminosity disparity in our simulations. As such, we are unable to
overcome short-wavelength deficits at later times using an additional
radioactive heating component, indicating the need for a more sophisticated
modeling treatment.Comment: 11 pages, 7 figures, presenting at April APS session F13.0000
Surrogate light curve models for kilonovae with comprehensive wind ejecta outflows and parameter estimation for AT2017gfo
The electromagnetic emission resulting from neutron star mergers have been
shown to encode properties of the ejected material in their light curves. The
ejecta properties inferred from the kilonova emission has been in tension with
those calculated based on the gravitational wave signal and numerical
relativity models. Motivated by this tension, we construct a broad set of
surrogate light curve models derived for kilonova ejecta. The four-parameter
family of two-dimensional anisotropic simulations and its associated surrogate
explore different assumptions about the wind outflow morphology and outflow
composition, keeping the dynamical ejecta component consistent. We present the
capabilities of these surrogate models in interpolating kilonova light curves
across various ejecta parameters and perform parameter estimation for AT2017gfo
both without any assumptions on the outflow and under the assumption that the
outflow must be representative of solar r-process abundance patterns. Our
parameter estimation for AT2017gfo shows these surrogate models help alleviate
the ejecta property discrepancy while also illustrating the impact of
systematic modeling uncertainties on these properties, urging further
investigation.Comment: 15 pages, 6 figures, data available in Zenodo
(https://zenodo.org/record/7335961) and GitHub
(https://github.com/markoris/surrogate_kne
A comparative study to analyze the cost of curative care at primary health center in Ahmedabad
Objectives: To determine the unit cost of curative care provided at Primary Health Centers (PHCs) and to examine the variation in unit cost in different PHCs. Materials and Methods: The present study was carried out in three PHCs of Ahmedabad district namely Sanathal, Nandej, and Uperdal, between 1 April, 2006 and 31 March, 2007. For estimating the cost of a health program, information on all the physical and human resources that were basic inputs to the PHC services were collected and grouped into two categories, non-recurrent (capital resources vehicles, buildings, etc.) and recurrent resources (salaries, drugs, vaccines, contraceptives, maintenance, etc.). To generate the required data, two types of schedules were developed, daily time schedule and PHC/SC (Subcenter) information schedule. Results: The unit cost of curative care was lowest (Rs. 29.43) for the Sanathal PHC and highest (Rs. 88.26) for the Uperdal PHC, followed by the Nandej PHC with Rs. 40.88, implying severe underutilization of curative care at the Uperdal PHC. Conclusions: Location of health facilities is a problem at many places. As relocation is not possible or even feasible, strengthening of infrastructure and facilities at these centers can be taken up immediately
Binary neutron star mergers of quark matter based nuclear equations of state
With observations of gravitational wave signals from binary neutron star mergers (BNSM) by LIGO-Virgo-KAGRA (LVK) Collaboration and NICER, the nuclear equation of state (EOS) is becoming increasingly testable by complementary numerical simulations. Numerous simulations currently explore the EOS at different density regimes for the constituent neutron stars specifically narrowing the uncertainty in the sub-nuclear densities. In this paper we summarize the three-dimensional general relativistic-hydrodynamics based simulations of BNSMs for EOSs with a specific emphasis on the quark matter EOS at the highest densities
Binary neutron star mergers as a probe of quark-hadron crossover equations of state
It is anticipated that the gravitational radiation detected in future
gravitational wave (GW) detectors from binary neutron star (NS) mergers can
probe the high-density equation of state (EOS). We perform the first
simulations of binary NS mergers which adopt various parametrizations of the
quark-hadron crossover (QHC) EOS. These are constructed from combinations of a
hadronic EOS (), where
and are the baryon number density and the nuclear saturation
density, respectively. At the crossover densities ()
the QHC EOSs continuously soften, while remaining stiffer than hadronic and
first-order phase transition EOSs, achieving the stiffness of strongly
correlated quark matter. This enhanced stiffness leads to significantly longer
lifetimes of the postmerger NS than that for a pure hadronic EOS. We find a
dual nature of these EOSs such that their maximum chirp GW frequencies
fall into the category of a soft EOS while the dominant peak
frequencies () of the postmerger stage fall in between that of a soft
and stiff hadronic EOS. An observation of this kind of dual nature in the
characteristic GW frequencies will provide crucial evidence for the existence
of strongly interacting quark matter at the crossover densities for QCD.Comment: 8 pages, 3 figure
Neutron Star Mergers and the Quark Matter Equation of State
As neutron stars merge they can approach very high nuclear density. Here, we summarized recent results for the evolution and gravitational wave emission from binary-neutron star mergers using a a variety of nuclear equations of state with and without a crossover transition to quark matter. We discuss how the late time gravitational wave emission from binary neutron star mergers may possibly reveal the existence of a crossover transition to quark matter