9 research outputs found
Numerical Relativity Simulations of the Neutron Star Merger GW170817: Long-Term Remnant Evolutions, Winds, Remnant Disks, and Nucleosynthesis
We present a systematic numerical-relativity study of the dynamical ejecta,
winds and nucleosynthesis in neutron star merger remnants. Binaries with the
chirp mass compatible with GW170817, different mass ratios, and five
microphysical equations of state (EOS) are simulated with an approximate
neutrino transport and a subgrid model for magnetohydrodynamics turbulence up
to 100 milliseconds postmerger. Spiral density waves propagating from the
neutron star remnant to the disk trigger a wind with mass flux
persisting for the entire simulation as long
as the remnant does not collapse to black hole. This wind has average electron
fraction and average velocity c and thus is a
site for the production of weak -process elements (mass number ).
Disks around long-lived remnants have masses ,
temperatures peaking at MeV near the inner edge, and a
characteristic double-peak distribution in entropy resulting from shocks
propagating through the disk. The dynamical and spiral-wave ejecta computed in
our targeted simulations are not compatible with those inferred from AT2017gfo
using two-components kilonova models. Rather, they indicate that
multi-component kilonova models including disk winds are necessary to interpret
AT2017gfo. The nucleosynthesis in the combined dynamical ejecta and spiral-wave
wind in the comparable-mass long-lived mergers robustly accounts for all the
-process peaks, from mass number to actinides in terms of solar
abundances. Total abundandes are weakly dependent on the EOS, while the mass
ratio affect the production of first peak elements.Comment: 20 pages, 13 figures, 3 table
Predicting electromagnetic counterparts using low-latency gravitational-wave data products
Searches for gravitational-wave counterparts have been going in earnest since GW170817 and the discovery of AT2017gfo. Since then, the lack of detection of other optical counterparts connected to binary neutron star or black hole–neutron star candidates has highlighted the need for a better discrimination criterion to support this effort. At the moment, low-latency gravitational-wave alerts contain preliminary information about binary properties and hence whether a detected binary might have an electromagnetic counterpart. The current alert method is a classifier that estimates the probability that there is a debris disc outside the black hole created during the merger as well as the probability of a signal being a binary neutron star, a black hole–neutron star, a binary black hole, or of terrestrial origin. In this work, we expand upon this approach to both predict the ejecta properties and provide contours of potential light curves for these events, in order to improve the follow-up observation strategy. The various sources of uncertainty are discussed, and we conclude that our ignorance about the ejecta composition and the insufficient constraint of the binary parameters by low-latency pipelines represent the main limitations. To validate the method, we test our approach on real events from the second and third Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO)–Virgo observing runs
Accretion-induced prompt black hole formation in asymmetric neutron star mergers, dynamical ejecta and kilonova signals
We present new numerical relativity results of neutron star mergers with
chirp mass and mass ratios and using
finite-temperature equations of state (EOS), approximate neutrino transport and
a subgrid model for magnetohydrodynamics-induced turbulent viscosity. The EOS
are compatible with nuclear and astrophysical constraints and include a new
microphysical model derived from ab-initio calculations based on the
Brueckner-Hartree-Fock approach. We report for the first time evidence for
accretion-induced prompt collapse in high-mass-ratio mergers, in which the
tidal disruption of the companion and its accretion onto the primary star
determine prompt black hole formation. As a result of the tidal disruption, an
accretion disc of neutron-rich and cold matter forms with baryon masses
, and it is significantly heavier than the remnant discs in
equal-masses prompt collapse mergers. Massive dynamical ejecta of order
also originate from the tidal disruption. They are neutron
rich and expand from the orbital plane with a crescent-like geometry.
Consequently, bright, red and temporally extended kilonova emission is
predicted from these mergers. Our results show that prompt black hole mergers
can power bright electromagnetic counterparts for high-mass-ratio binaries, and
that the binary mass ratio can be in principle constrained from multimessenger
observations.Comment: 20 pages, 21 figures, 4 table
Economic consequences of investing in anti-HCV antiviral treatment from the Italian NHS perspective : a real-world-based analysis of PITER data
OBJECTIVE:
We estimated the cost consequence of Italian National Health System (NHS) investment in direct-acting antiviral (DAA) therapy according to hepatitis C virus (HCV) treatment access policies in Italy.
METHODS:
A multistate, 20-year time horizon Markov model of HCV liver disease progression was developed. Fibrosis stage, age and genotype distributions were derived from the Italian Platform for the Study of Viral Hepatitis Therapies (PITER) cohort. The treatment efficacy, disease progression probabilities and direct costs in each health state were obtained from the literature. The break-even point in time (BPT) was defined as the period of time required for the cumulative costs saved to recover the Italian NHS investment in DAA treatment. Three different PITER enrolment periods, which covered the full DAA access evolution in Italy, were considered.
RESULTS:
The disease stages of 2657 patients who consecutively underwent DAA therapy from January 2015 to December 2017 at 30 PITER clinical centres were standardized for 1000 patients. The investment in DAAs was considered to equal €25 million, €15 million, and €9 million in 2015, 2016, and 2017, respectively. For patients treated in 2015, the BPT was not achieved, because of the disease severity of the treated patients and high DAA prices. For 2016 and 2017, the estimated BPTs were 6.6 and 6.2 years, respectively. The total cost savings after 20 years were €50.13 and €55.50 million for 1000 patients treated in 2016 and 2017, respectively.
CONCLUSIONS:
This study may be a useful tool for public decision makers to understand how HCV clinical and epidemiological profiles influence the economic burden of HCV
L'Italia come modello per l'Europa e per il mondo nelle politiche sanitarie per il trattamento dell'epatite cronica da HCV
The World Health Organization foresees the
elimination of HCV infection by 2030. In light of this and the curre
nt, nearly worldwide, restriction in direct-acting agents
(DAA) accessibility due to their high price, we aimed to evaluate
the cost-effectiveness of two alternative DAA treatment
policies: Policy 1 (universal): treat all patients, regardless of the fibrosis stage; Policy 2 (prioritized): treat only priori
tized
patients and delay treatment of the
remaining patients until reaching stage F3. T
he model was based on patient’s data
from the PITER cohort. We demonstrated that extending HC
V treatment of patients in any fibrosis stage improves health
outcomes and is cost-effective
Predicting electromagnetic counterparts using low-latency gravitational-wave data products
International audienceSearches for gravitational-wave counterparts have been going in earnest since GW170817 and the discovery of AT2017gfo. Since then, the lack of detection of other optical counterparts connected to binary neutron star or black hole–neutron star candidates has highlighted the need for a better discrimination criterion to support this effort. At the moment, low-latency gravitational-wave alerts contain preliminary information about binary properties and hence whether a detected binary might have an electromagnetic counterpart. The current alert method is a classifier that estimates the probability that there is a debris disc outside the black hole created during the merger as well as the probability of a signal being a binary neutron star, a black hole–neutron star, a binary black hole, or of terrestrial origin. In this work, we expand upon this approach to both predict the ejecta properties and provide contours of potential light curves for these events, in order to improve the follow-up observation strategy. The various sources of uncertainty are discussed, and we conclude that our ignorance about the ejecta composition and the insufficient constraint of the binary parameters by low-latency pipelines represent the main limitations. To validate the method, we test our approach on real events from the second and third Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO)–Virgo observing runs