Jekyll2020-03-17T21:54:46+00:00http://core.gitpages.tpi.uni-jena.de/feed.xmlComputational RelativityCoRe collaboration website.Accretion-induced prompt black hole formation in asymmetric neutron star mergers, dynamical ejecta and kilonova signals2020-03-12T00:00:00+00:002020-03-12T00:00:00+00:00http://core.gitpages.tpi.uni-jena.de/papers/2020/03/12/paper-aipc<p>In <a href="https://arxiv.org/abs/2003.06015">2003.06015</a> we present new numerical relativity results of neutron star mergers with chirp mass 1.188M⊙ and mass ratios q=1.67 and q=1.8 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 ∼0.15M⊙, and it is significantly heavier than the remnant discs in equal-masses prompt collapse mergers. Massive dynamical ejecta of order ∼0.01M⊙ 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.</p>S.BernuzziIn 2003.06015 we present new numerical relativity results of neutron star mergers with chirp mass 1.188M⊙ and mass ratios q=1.67 and q=1.8 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 ∼0.15M⊙, and it is significantly heavier than the remnant discs in equal-masses prompt collapse mergers. Massive dynamical ejecta of order ∼0.01M⊙ 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.kiloHertz gravitational waves from binary neutron star remnants2019-10-01T00:00:00+00:002019-10-01T00:00:00+00:00http://core.gitpages.tpi.uni-jena.de/papers/2019/10/01/paper-nrpm<p>In <a href="https://arxiv.org/abs/1908.11418">1908.11418</a> we develop an analytical time-domain waveform model, labelled as NRPM, for postmerger signals informed by numerical relativity simulations. The model completes effective-one-body waveforms for quasi-circular nonspinning binaries in the kiloHertz regime. We show that a template-based analysis can detect postmerger signals with a minimal signal-to-noise ratios (SNR) of 8, corresponding to GW170817-like events for third-generation interferometers. Using Bayesian model selection and the complete inspiral-merger-postmerger waveform model it is possible to infer whether the merger outcome is a prompt collapse to a black hole or a remnant star. Furthermore, we demonstrate the feasibility of inferring the stiffness of the equation of state at extreme densities using the quasiuniversal relations deduced from numerical-relativity simulations.</p>M.BreschiIn 1908.11418 we develop an analytical time-domain waveform model, labelled as NRPM, for postmerger signals informed by numerical relativity simulations. The model completes effective-one-body waveforms for quasi-circular nonspinning binaries in the kiloHertz regime. We show that a template-based analysis can detect postmerger signals with a minimal signal-to-noise ratios (SNR) of 8, corresponding to GW170817-like events for third-generation interferometers. Using Bayesian model selection and the complete inspiral-merger-postmerger waveform model it is possible to infer whether the merger outcome is a prompt collapse to a black hole or a remnant star. Furthermore, we demonstrate the feasibility of inferring the stiffness of the equation of state at extreme densities using the quasiuniversal relations deduced from numerical-relativity simulations.Paper Neutrinospheres2019-08-14T00:00:00+00:002019-08-14T00:00:00+00:00http://core.gitpages.tpi.uni-jena.de/2019/08/14/paper-neutrinospheres<p>layout: post
author: A.Endrizzi
title: Thermodynamics conditions of matter in the neutrino decoupling region in neutron star mergers
categories: [Papers]
tags: [BNS, neutrinos, EOS]
image: assets/images/paper/190804952.png
link: https://arxiv.org/abs/1908.04952</p>
<p>In <a href="https://arxiv.org/abs/1908.04952">1908.04952</a> we analyse general relativistic merger simulations employing microphysical equations of state and approximate neutrino transport to investigate the thermodynamics conditions at which weak and thermal equilibrium freezes out (equilibrium surfaces), as well as conditions at which thetransition between diffusion and free-streaming regime occurs (diffusion surfaces). We find that the rest mass density and the neutrino energy are the most relevant quantities in determining the location of the decoupling surfaces. For example, for mean neutrinos energies, diffusion surfaces are located around 10^11 g ccm for all neutrino species (electron neutrinos and antineutrinos and mu-tau neutrinos). Equilibrium surfaces of electron neutrinos and antineutrinos are close to diffusion surfaces while for heavy flavor neutrinos they are significantly deeper (10^12 g ccm). Neutrinos streaming at infinity with different energies come from very different regions of the remnant: while low energy neutrinos (∼3 MeV) decouple at ρ∼10^13 g ccm, T∼10MeV and Ye~0.1 close to cold weak equilibrium, high energy neutrinos (∼50 MeV) decouple from the disk at ρ∼10^9 g ccm, T∼2 MeV and Ye~0.25. The presence of a massive NS or of a BH in the remnant influencesthe neutrino thermalization process. While in the former case neutrinos of all relevant energies thermalize and diffuse from the innermost part of the remnant, the lower maximum rest mass density in the BH-disk system does not allow a relevant portion of the neutrino spectrum to thermalize and diffuse.</p>
<p>In light of our results, the accurate modelling of neutrinos and of their emitted spectrum in BNS mergers requires the consistent inclusion of neutrino-matter interactions for a broad range of nuclear conditions, characterized by more than four order of magnitudes in rest mass densities, one order of magnitude in temperatures, and a factor of a few in electron fraction.</p>layout: post author: A.Endrizzi title: Thermodynamics conditions of matter in the neutrino decoupling region in neutron star mergers categories: [Papers] tags: [BNS, neutrinos, EOS] image: assets/images/paper/190804952.png link: https://arxiv.org/abs/1908.04952Thermodynamics conditions of matter in the neutrino decoupling region during neutron star mergers2019-08-14T00:00:00+00:002019-08-14T00:00:00+00:00http://core.gitpages.tpi.uni-jena.de/papers/2019/08/14/paper-nuspheres<p>In <a href="https://arxiv.org/abs/1908.04952">1908.04952</a> we analyse general relativistic merger simulations employing microphysical equations of state and approximate neutrino transport to investigate the thermodynamics conditions at which weak and thermal equilibrium freezes out (equilibrium surfaces), as well as conditions at which thetransition between diffusion and free-streaming regime occurs (diffusion surfaces). We find that the rest mass density and the neutrino energy are the most relevant quantities in determining the location of the decoupling surfaces. For example, for mean neutrinos energies, diffusion surfaces are located around 10^11 g ccm for all neutrino species (electron neutrinos and antineutrinos and mu-tau neutrinos). Equilibrium surfaces of electron neutrinos and antineutrinos are close to diffusion surfaces while for heavy flavor neutrinos they are significantly deeper (10^12 g ccm). Neutrinos streaming at infinity with different energies come from very different regions of the remnant: while low energy neutrinos (∼3 MeV) decouple at ρ∼10^13 g ccm, T∼10MeV and Ye~0.1 close to cold weak equilibrium, high energy neutrinos (∼50 MeV) decouple from the disk at ρ∼10^9 g ccm, T∼2 MeV and Ye~0.25. The presence of a massive NS or of a BH in the remnant influencesthe neutrino thermalization process. While in the former case neutrinos of all relevant energies thermalize and diffuse from the innermost part of the remnant, the lower maximum rest mass density in the BH-disk system does not allow a relevant portion of the neutrino spectrum to thermalize and diffuse. We conclude that the accurate modelling of neutrinos and of their emitted spectrum in BNS mergers requires the consistent inclusion of neutrino-matter interactions for a broad range of nuclear conditions, characterized by more than four order of magnitudes in rest mass densities, one order of magnitude in temperatures, and a factor of a few in electron fraction.</p>S.BernuzziIn 1908.04952 we analyse general relativistic merger simulations employing microphysical equations of state and approximate neutrino transport to investigate the thermodynamics conditions at which weak and thermal equilibrium freezes out (equilibrium surfaces), as well as conditions at which thetransition between diffusion and free-streaming regime occurs (diffusion surfaces). We find that the rest mass density and the neutrino energy are the most relevant quantities in determining the location of the decoupling surfaces. For example, for mean neutrinos energies, diffusion surfaces are located around 10^11 g ccm for all neutrino species (electron neutrinos and antineutrinos and mu-tau neutrinos). Equilibrium surfaces of electron neutrinos and antineutrinos are close to diffusion surfaces while for heavy flavor neutrinos they are significantly deeper (10^12 g ccm). Neutrinos streaming at infinity with different energies come from very different regions of the remnant: while low energy neutrinos (∼3 MeV) decouple at ρ∼10^13 g ccm, T∼10MeV and Ye~0.1 close to cold weak equilibrium, high energy neutrinos (∼50 MeV) decouple from the disk at ρ∼10^9 g ccm, T∼2 MeV and Ye~0.25. The presence of a massive NS or of a BH in the remnant influencesthe neutrino thermalization process. While in the former case neutrinos of all relevant energies thermalize and diffuse from the innermost part of the remnant, the lower maximum rest mass density in the BH-disk system does not allow a relevant portion of the neutrino spectrum to thermalize and diffuse. We conclude that the accurate modelling of neutrinos and of their emitted spectrum in BNS mergers requires the consistent inclusion of neutrino-matter interactions for a broad range of nuclear conditions, characterized by more than four order of magnitudes in rest mass densities, one order of magnitude in temperatures, and a factor of a few in electron fraction.Inferring prompt black-hole formation in neutron star mergers from gravitational-wave data2019-08-05T00:00:00+00:002019-08-05T00:00:00+00:00http://core.gitpages.tpi.uni-jena.de/papers/2019/08/05/paper-promptcoll<p>In <a href="https://arxiv.org/abs/1908.05442">1908.05442</a> we present two methods to infer the probability of prompt black hole formation in neutron star merger by analyzing the inspiral gravitational-wave signal solely. Both methods combine the posterior distribution from the gravitational-wave data analysis with numerical relativity results. One method relies on the use of phenomenological models for the equation of state and on the estimate of the collapse threshold mass. The other is based on the estimate of the tidal polarizability parameter that is correlated in an equation-of-state agnostic way with the prompt BH formation. Our approach helps interpreting events for which the LIGO-Virgo sensitivity at high frequencies is not sufficient to detect the signal corresponding to the merger and post-merger phases, like GW170817. By applying the methods to GW170817 data we find that they consistently predict a probability of ~ 50-70% for prompt black-hole formation, which however significantly decreases below 10% if the maximum mass constraint from PSR J0348+0432 or PSR J0740+6620 is imposed.</p>S.BernuzziIn 1908.05442 we present two methods to infer the probability of prompt black hole formation in neutron star merger by analyzing the inspiral gravitational-wave signal solely. Both methods combine the posterior distribution from the gravitational-wave data analysis with numerical relativity results. One method relies on the use of phenomenological models for the equation of state and on the estimate of the collapse threshold mass. The other is based on the estimate of the tidal polarizability parameter that is correlated in an equation-of-state agnostic way with the prompt BH formation. Our approach helps interpreting events for which the LIGO-Virgo sensitivity at high frequencies is not sufficient to detect the signal corresponding to the merger and post-merger phases, like GW170817. By applying the methods to GW170817 data we find that they consistently predict a probability of ~ 50-70% for prompt black-hole formation, which however significantly decreases below 10% if the maximum mass constraint from PSR J0348+0432 or PSR J0740+6620 is imposed.Spiral-wave wind for the blue kilonova2019-07-10T00:00:00+00:002019-07-10T00:00:00+00:00http://core.gitpages.tpi.uni-jena.de/papers/2019/07/10/paper-spiralwavewind<p>In <a href="https://arxiv.org/abs/1907.04872">1907.04872</a> we investigate the new mechanism of mass ejection from the BNS systems after merger. We find that the interaction between the remnant, should it survive, and the disk creates a characteristic spiral wave structure in the latter and drives the quasi-steady state outflow with total mass ~10^{-2} solar masses and fine-tuned velocity around 0.2c and high electron fraction of >0.25. This spiral-wave wind persists as long as remnant lives and dies out quickly after the BH formation. Its properties are robust with resolution and inclusion of the subgird turbulence.
Then we use the data from numerical relativity simulations to compute the kilonova models. We report that the combination of dynamical ejecta and spiral-wave wind can account for early-time observed light curves.</p>V.NedoraIn 1907.04872 we investigate the new mechanism of mass ejection from the BNS systems after merger. We find that the interaction between the remnant, should it survive, and the disk creates a characteristic spiral wave structure in the latter and drives the quasi-steady state outflow with total mass ~10^{-2} solar masses and fine-tuned velocity around 0.2c and high electron fraction of >0.25. This spiral-wave wind persists as long as remnant lives and dies out quickly after the BH formation. Its properties are robust with resolution and inclusion of the subgird turbulence. Then we use the data from numerical relativity simulations to compute the kilonova models. We report that the combination of dynamical ejecta and spiral-wave wind can account for early-time observed light curves.Dynamical ejecta data2019-05-30T00:00:00+00:002019-05-30T00:00:00+00:00http://core.gitpages.tpi.uni-jena.de/core-database/2019/05/30/data-ejecta<p>We release dynamical ejecta data from binary neutron star merger simulations of</p>
<blockquote>
<p>D. Radice, A. Perego, K. Hotokezaka, S. A. Fromm, S. Bernuzzi, and L. F. Roberts, Binary Neutron Star Mergers: Mass Ejection, Electromagnetic Counterparts, and Nucleosynthesis, ApJ 869:130 (2018), arXiv:1809.11161</p>
</blockquote>
<p>The outflows are extracted at a fixed coordinate sphere with radius 300 G/c^2 Msun (= 443 km). Only material unbound according to the geodesic criterion is considered to be part of the dynamical ejecta.</p>
<p>Data are relased on <a href="https://zenodo.org/record/3235675#.XPAjxENS-00">ZENODO</a></p>
<p>Included data:</p>
<ul>
<li><code class="highlighter-rouge">Table2.txt</code>: Table 2 of the paper in machine readable format</li>
<li><code class="highlighter-rouge">tabulated_nucsyn.h5</code>: nucleosynthesis yields from pre-computed parametrized trajectories. The first three indices of each dataset are Ye, entropy, and expansion timescale tau. For example <code class="highlighter-rouge">Y_final[iYe, ientr, itau, iiso]</code> gives the final abundance of isotope <code class="highlighter-rouge">iiso</code> with <code class="highlighter-rouge">A[iiso]</code> and <code class="highlighter-rouge">Z[iiso]</code> for a trajectory with initial Ye = <code class="highlighter-rouge">Ye[iYe]</code>, initial entropy <code class="highlighter-rouge">s[ientr]</code>, and expansion timescale <code class="highlighter-rouge">tau[itau]</code>.</li>
<li><code class="highlighter-rouge">[model].tar</code>: ejecta data for individual simulations. The naming convention is the same as in the paper.</li>
</ul>
<p>For each model we provide:</p>
<ul>
<li><code class="highlighter-rouge">outflow.txt</code>: angle integrated outflow rate and cumulated ejecta mass. Data are given in units with Msun = G = c = 1 (eg, the conversion factor for time to seconds is 4.9258e-6).</li>
<li><code class="highlighter-rouge">hist_entropy.dat</code>: histogram of the ejecta as a function of the entropy (in kb)</li>
<li><code class="highlighter-rouge">hist_vinf.dat</code>: histogram of the ejecta as a function of the asymptotic velocity (in units of c)</li>
<li><code class="highlighter-rouge">hist_ye.dat</code>: histogram of the ejecta as a function of the electron fraction Ye.</li>
<li><code class="highlighter-rouge">profile.txt</code>: time integrated ejecta profiles as a function of the polar angle.</li>
<li><code class="highlighter-rouge">hist_vinf_theta.h5</code>: histograms of the ejecta as a function of the asymptotic velocity and the polar angle.</li>
<li><code class="highlighter-rouge">hist_ye_theta.h5</code>: histograms of the ejecta as a function of the asymptotic velocity and the polar angle.</li>
<li><code class="highlighter-rouge">hist_ye_entropy_tau.h5</code>: histograms of the ejecta as a function of Ye, entropy, and expansion timescale tau.</li>
</ul>
<p>Additionally we distribute:</p>
<ul>
<li>Initial data generated with LORENE and associated EOS tables.</li>
<li>EOS tables used for the evolution</li>
<li>Parameter file used for each simulation</li>
</ul>
<p>For the multidimensional histograms the indices are ordered as specified in the file name, ie the file <code class="highlighter-rouge">hist_ye_theta.h5</code> tabulates the ejecta mass as a function of Ye (first index) and polar angle theta (second index).</p>CoRe-adminWe release dynamical ejecta data from binary neutron star merger simulations ofImproving the NRTidal model for binary neutron star systems2019-05-15T00:00:00+00:002019-05-15T00:00:00+00:00http://core.gitpages.tpi.uni-jena.de/papers/2019/05/15/paper-nrtidalv2<p>In <a href="https://arxiv.org/abs/1905.06011">1905.06011</a> we present
an extension of the NRTidal model for binary neutron star (BNS) waveforms.
The upgrades are: (i) a new closed-form expression for the tidal contribution to the GW phase which
includes further analytical knowledge and is calibrated to more accurate numerical relativity data
than previously available; (ii) a tidal correction to the GW amplitude; (iii) an extension of the spinsector incorporating equation-of-state-dependent finite size effects at quadrupolar and octupolar
order; these appear in the spin-spin tail terms and cubic-in-spin terms, both at 3.5PN.
We add the new description to the precessing binary black hole waveform model IMRPhenomPv2
to obtain a frequency-domain precessing binary neutron star model. In addition, we extend the
SEOBNRv4_ROM and IMRPhenomD aligned-spin binary black hole waveform models with the improved
tidal phase corrections. Focusing on the new IMRPhenomPv2_NRTidalv2 approximant, we test the
model by comparing with numerical relativity waveforms as well as hybrid waveforms combining
tidal effective-one-body and numerical relativity data. We also check consistency against a tidal
effective-one-body model across large regions of the BNS parameter space</p>T.DietrichIn 1905.06011 we present an extension of the NRTidal model for binary neutron star (BNS) waveforms. The upgrades are: (i) a new closed-form expression for the tidal contribution to the GW phase which includes further analytical knowledge and is calibrated to more accurate numerical relativity data than previously available; (ii) a tidal correction to the GW amplitude; (iii) an extension of the spinsector incorporating equation-of-state-dependent finite size effects at quadrupolar and octupolar order; these appear in the spin-spin tail terms and cubic-in-spin terms, both at 3.5PN. We add the new description to the precessing binary black hole waveform model IMRPhenomPv2 to obtain a frequency-domain precessing binary neutron star model. In addition, we extend the SEOBNRv4_ROM and IMRPhenomD aligned-spin binary black hole waveform models with the improved tidal phase corrections. Focusing on the new IMRPhenomPv2_NRTidalv2 approximant, we test the model by comparing with numerical relativity waveforms as well as hybrid waveforms combining tidal effective-one-body and numerical relativity data. We also check consistency against a tidal effective-one-body model across large regions of the BNS parameter spaceBlack-hole remnants from black-hole–neutron-star mergers2019-03-19T00:00:00+00:002019-03-19T00:00:00+00:00http://core.gitpages.tpi.uni-jena.de/papers/2019/03/19/paper-bhnsremnant<p>In <a href="https://arxiv.org/abs/1903.11622">1903.11622</a> we construct a model for the remnant black hole produced by the collision of stellar-mass black holes and a neutron stars mergers (BHNS). We used a sample of numerical-relativity simulations and mapped the properties of the binary components to the mass and spin of the remnant black hole in a simple and physically accurate way.</p>
<p>As an application, we combine the remnant characterization with state-of-art population synthesis for binary formation. We predict that BHNS mergers produce a population of remnant black holes with masses narrowly distributed around 7M⊙ and 9M⊙. Assuming isotropic spin distribution of the initial BH implies that nonmassive accretion disks are favoured: no bright electromagnetic counterparts are expected in such mergers.</p>
<p>Our results will support LIGO-Virgo observations of BHNS systems as new sources of gravitational waves and the joint analysis with electromagnetic signals. While they predict (and will eventually explain) the lack of electromagnetic counterparts for these events, they also point out that a counterpart observation will heavily impact the most unknown physics: astrophysical spin distributions of the BH in the binary and the NS equation of state.</p>
<p>A python code of our model can be found <a href="https://git.tpi.uni-jena.de/core/bhnsremnant">here</a></p>S.BernuzziIn 1903.11622 we construct a model for the remnant black hole produced by the collision of stellar-mass black holes and a neutron stars mergers (BHNS). We used a sample of numerical-relativity simulations and mapped the properties of the binary components to the mass and spin of the remnant black hole in a simple and physically accurate way.Thermodynamics conditions of matter in neutron star mergers2019-03-19T00:00:00+00:002019-03-19T00:00:00+00:00http://core.gitpages.tpi.uni-jena.de/papers/2019/03/19/paper-thermodynamicsbns<p>In <a href="https://arxiv.org/abs/1903.07898">1903.07898</a> we explore the
properties of extreme matter along the general relativistic dynamics
of neutron star mergers. We consider 3 microphysical equations of
state and numerical relativity simulations including an approximate
neutrino transport scheme and construct time-dependent histograms of
the mass on a 3D hypersurfaces as distributed in density, temperature
and electron fraction bins (see figure below). For example, the matter
in a merger ending in a long-lived neutron star increases the initial
maximum density up to ∼3-4ρ0 (ρ0 is the nuclear saturation density),
and the multiple centrifugal bounces heat the initially cold matter to
several tens of MeV. Streams of hot matter with initial densities ∼2ρ0
move outwards and cool due to decompression and neutrino emission. The
remnant reaches temperatures up to 50 MeV, but the highest
temperatures are confined in an approximately spherical annulus at
∼ρ0. Such temperatures favour positron-neutron capture and lead to a
neutrino emission dominated by electron antineutrinos. Neutrinos are
trapped at the highest densities of the remnant core which is less
affected by weak interaction and only at longer timescales. A similar
dynamics is found if the remnant collapses to black hole. The main
difference bewteen the two case is found in the remnant disk. Both
discs are neutron rich and not isentropic, but they differ in size,
entropy and lepton fraction depending on the nature of the central
object. In presence of a black hole, disks are smaller and mostly
transparent to neutrinos; in presence of a massive neutron star, they
are more massive, geometrically and optically thick.</p>S.BernuzziIn 1903.07898 we explore the properties of extreme matter along the general relativistic dynamics of neutron star mergers. We consider 3 microphysical equations of state and numerical relativity simulations including an approximate neutrino transport scheme and construct time-dependent histograms of the mass on a 3D hypersurfaces as distributed in density, temperature and electron fraction bins (see figure below). For example, the matter in a merger ending in a long-lived neutron star increases the initial maximum density up to ∼3-4ρ0 (ρ0 is the nuclear saturation density), and the multiple centrifugal bounces heat the initially cold matter to several tens of MeV. Streams of hot matter with initial densities ∼2ρ0 move outwards and cool due to decompression and neutrino emission. The remnant reaches temperatures up to 50 MeV, but the highest temperatures are confined in an approximately spherical annulus at ∼ρ0. Such temperatures favour positron-neutron capture and lead to a neutrino emission dominated by electron antineutrinos. Neutrinos are trapped at the highest densities of the remnant core which is less affected by weak interaction and only at longer timescales. A similar dynamics is found if the remnant collapses to black hole. The main difference bewteen the two case is found in the remnant disk. Both discs are neutron rich and not isentropic, but they differ in size, entropy and lepton fraction depending on the nature of the central object. In presence of a black hole, disks are smaller and mostly transparent to neutrinos; in presence of a massive neutron star, they are more massive, geometrically and optically thick.