41 research outputs found
Common envelope ejection in massive binary stars - Implications for the progenitors of GW150914 and GW151226
The recently detected gravitational wave signals (GW150914 and GW151226) of
the merger event of a pair of relatively massive stellar-mass black holes (BHs)
calls for an investigation of the formation of such progenitor systems in
general. We analyse the common envelope (CE) stage of the "traditional"
formation channel in binaries where the first-formed compact object undergoes
an in-spiral inside the envelope of its evolved companion star and ejects the
envelope in that process. We calculate envelope binding energies of donor stars
with initial masses between 4 and 115 Msun for metallicities of Z=Zsun/2 and
Z=Zsun/50, and derive minimum masses of in-spiralling objects needed to eject
these envelopes. We find that CE evolution, besides from producing WD-WD and
NS-NS binaries, may, in principle, also produce massive BH-BH systems with
individual BH component masses up to ~50-60 Msun, in particular for donor stars
evolved to giants. However, the physics of envelope ejection of massive stars
remains uncertain. We discuss the applicability of the energy-budget formalism,
the location of the bifurcation point, the recombination energy and the
accretion energy during in-spiral as possible energy sources, and also comment
on the effect of inflated helium cores. Massive stars in a wide range of
metallicities and with initial masses up to at least 115 Msun may possibly shed
their envelopes and survive CE evolution, depending on their initial orbital
parameters, similarly to the situation for intermediate mass and low-mass stars
with degenerate cores. We conclude that based on stellar structure
calculations, and in the view of the usual simple energy budget analysis,
events like GW150914 and GW151226 could possibly be produced from the CE
channel. Calculations of post-CE orbital separations, however, and thus the
estimated LIGO detection rates, remain highly uncertain. [Abridged]Comment: 13 pages, 7 figures, A&A accepte
The interaction of core-collapse supernova ejecta with a stellar companion
The progenitors of many core-collapse supernovae (CCSNe) are expected to be
in binary systems. By performing a series of three-dimensional hydrodynamical
simulations, we investigate how CCSN explosions affect their binary companion.
We find that the amount of removed stellar mass, the resulting impact velocity,
and the chemical contamination of the companion that results from the impact of
the SN ejecta, strongly increases with decreasing binary separation and
increasing explosion energy. Also, it is foud that the impact effects of CCSN
ejecta on the structure of main-sequence (MS) companions, and thus their long
term post-explosion evolution, is in general not be dramatic.Comment: 5 pages, 3 figures, poster contribution: IAU Symposium 346 "High Mass
X-ray Binaries: illuminating the passage from massive binaries to merging
compact objects", Vienna, Austria, 27-31 August 2018. arXiv admin note:
substantial text overlap with arXiv:1509.0363
The interaction of core-collapse supernova ejecta with a companion star
The progenitors of many CCSNe are expected to be in binary systems. After the
SN explosion, the companion may suffer from mass stripping and be shock heated
as a result of the impact of the SN ejecta. If the binary system is disrupted,
the companion is ejected as a runaway and hypervelocity star. By performing a
series of 3D hydrodynamical simulations of the collision of SN ejecta with the
companion star, we investigate how CCSN explosions affect their companions. We
use the BEC code to construct the detailed companion structure at the time of
SN explosion. The impact of the SN blast wave on the companion is followed by
means of 3D SPH simulations using the Stellar GADGET code. For main-sequence
(MS) companions, we find that the amount of removed mass, impact velocity, and
chemical contamination of the companion that results from the impact of the SN
ejecta, strongly increases with decreasing binary separation and increasing
explosion energy. Their relationship can be approximately fitted by power laws,
which is consistent with the results obtained from impact simulations of
SNe~Ia. However, we find that the impact velocity is sensitive to the momentum
profile of the outer SN ejecta and, in fact, may decrease with increasing
ejecta mass, depending on the modeling of the ejecta. Because most companions
to Ib/c CCSNe are in their MS phase at the moment of the explosion, combined
with the strongly decaying impact effects with increasing binary separation, we
argue that the majority of these SNe lead to inefficient mass stripping and
shock heating of the companion star following the impact of the ejecta. Our
simulations show that the impact effects of Ib/c SN ejecta on the structure of
MS companions, and thus their long-term post-explosion evolution, is in general
not dramatic. We find that at most 10% of their mass is lost, and their
resulting impact velocities are less than 100 km/s.Comment: Accepted for publication in Astronomy and Astrophysics, some minor
typographical errors are fixed, the affiliation of second author is correcte
Progenitors of gravitational wave mergers: Binary evolution with the stellar grid-based code ComBinE
The first gravitational wave detections of mergers between black holes and
neutron stars represent a remarkable new regime of high-energy transient
astrophysics. The signals observed with LIGO-Virgo detectors come from mergers
of extreme physical objects which are the end products of stellar evolution in
close binary systems. To better understand their origin and merger rates, we
have performed binary population syntheses at different metallicities using the
new grid-based binary population synthesis code ComBinE. Starting from newborn
pairs of stars, we follow their evolution including mass loss, mass transfer
and accretion, common envelopes and supernova explosions. We apply the binding
energies of common envelopes based on dense grids of detailed stellar structure
models, make use of improved investigations of the subsequent Case BB
Roche-lobe overflow and scale supernova kicks according to the stripping of the
exploding stars. We demonstrate that all the double black hole mergers,
GW150914, LVT151012, GW151226, GW170104, GW170608 and GW170814, as well as the
double neutron star merger GW170817, are accounted for in our models in the
appropriate metallicity regime. Our binary interaction parameters are
calibrated to match the accurately determined properties of Galactic double
neutron star systems, and we discuss their masses and types of supernova
origin. Using our default values for the input physics parameters, we find a
double neutron star merger rate of about 3.0 Myr^-1 for Milky-Way equivalent
galaxies. Our upper limit to the merger-rate density of double neutron stars is
R=400 yr^-1 Gpc^-3 in the local Universe (z=0).Comment: 36 pages, 26 figures, 8 tables, plus 9 pages appendix. Accepted 2018
August 6 by MNRAS after revision according to referee report (in particular,
including further discussions on the progenitor binary of GW170817
Progenitors of gravitational wave mergers: Binary evolution with the stellar grid-based code ComBinE
The first gravitational wave detections of mergers between black holes and neutron stars represent a remarkable new regime of high-energy transient astrophysics. The signals observed with LIGO-Virgo detectors come from mergers of extreme physical objects which are the end products of stellar evolution in close binary systems. To better understand their origin and merger rates, we have performed binary population syntheses at different metallicities using the new grid-based binary population synthesis code ComBinE. Starting from newborn pairs of stars, we follow their evolution including mass loss, mass transfer and accretion, common envelopes and supernova explosions. We apply the binding energies of common envelopes based on dense grids of detailed stellar structure models, make use of improved investigations of the subsequent Case BB Roche-lobe overflow and scale supernova kicks according to the stripping of the exploding stars. We demonstrate that all the double black hole mergers, GW150914, LVT151012, GW151226, GW170104, GW170608 and GW170814, as well as the double neutron star merger GW170817, are accounted for in our models in the appropriate metallicity regime. Our binary interaction parameters are calibrated to match the accurately determined properties of Galactic double neutron star systems, and we discuss their masses and types of supernova origin. Using our default values for the input physics parameters, we find a double neutron star merger rate of about 3.0 Myr-1 for Milky-Way equivalent galaxies. Our upper limit to the merger-rate density of double neutron stars is R≃400 yr-1 Gpc-3 in the local Universe (z=0)
Properties and applications of a predicted population of runaway He-sdO/B stars ejected from single degenerate He-donor SNe
This study builds on previous works, producing the most extensive prediction
of the properties of such a hypothetical population to date, taking into
account both Chandrasekhar and non-Chandrasekhar mass events. These results are
then used to define criteria for membership of this population and characterise
putative subpopulations
This study contains 6x10^6 individual ejection trajectories out of the
Galactic plane calculated with the stellar kinematics framework SHyRT, which
are analysed with regard to their bulk observational properties. These are then
put into context with the only previously identified population member US\,708
and applied to a number of other possible candidate objects.
We find that two additional previously observed objects possess properties to
warrant a designation as candidate objects. Characterisation of these object
with respect to the predicted population finds all of them to be extreme in at
least one astrometric observable. We find that current observations support a
Galactic SN rate on the order of ~3x10^-7/yr to ~2x10^-6/yr, three orders of
magnitude below the inferred Galactic SN Ia rate and two orders of magnitude
below the formation rate of predicted He-donor progenitors. The number of
currently observed population members suggests that the He-donor scenariois not
a dominant contributor to the number of observed SNe Ia. However, we find that,
even at the low event rate suggested, the majority of possibly detectable
population members is still undetected. The extreme nature of current
population members suggests that a still larger number of objects has simply
evaded detection up to this point, hinting at a higher contribution than is
currently supported by observation. - abridged -Comment: 26 pages, 23 figures, 5 tables - accepted in A&
Can Neutron Star Mergers Alone Explain the r-process Enrichment of the Milky Way?
© 2023. The Author(s). Published by the American Astronomical Society. This is an open access article under the terms of the Creative Commons Attribution License, https://creativecommons.org/licenses/by/4.0/Comparing Galactic chemical evolution models to the observed elemental abundances in the Milky Way, we show that neutron star mergers can be a leading r-process site only if at low metallicities such mergers have very short delay times and significant ejecta masses that are facilitated by the masses of the compact objects. Namely, black hole–neutron star mergers, depending on the black hole spins, can play an important role in the early chemical enrichment of the Milky Way. We also show that none of the binary population synthesis models used in this Letter, i.e., COMPAS, StarTrack, Brussels, ComBinE, and BPASS, can currently reproduce the elemental abundance observations. The predictions are problematic not only for neutron star mergers, but also for Type Ia supernovae, which may point to shortcomings in binary evolution models.Peer reviewe
Ein Mikroventil und ein Verfahren zur Herstellung desselben
Ein Mikroventil weist einen Ventilsitz mit einer Ventiloeffnung und eine Ventilklappe zum Verschliessen der Ventiloeffnung des Mikroventils mit einem Abdeckabschnitt der Ventilklappe auf. In einem geschlossenen Zustand des Mikroventils befindet sich der Abdeckabschnitt der Ventilklappe in einer Ventilsitzebene. Die Ventilklappe ist in einer Schicht einstueckig gebildet wobei die Schicht derart eingespannt ist dass zumindest ein Teil der Schicht in dem geschlossenen Zustand aus der Ventilsitzebene ausgelenkt ist und die Ventilklappe auf den Ventilsitz gedrueckt wird
Predicted spatial and velocity distributions of ejected companion stars of helium accretion-induced thermonuclear supernovae
Context. Thermonuclear supernovae (SNe), a subset of which are the highly important SNe Type Ia, remain one of the more poorly understood phenomena known to modern astrophysics. In recent years, the single degenerate helium (He) donor channel, where a white dwarf star accretes He-rich matter from a hydrogen-depleted companion, has emerged as a promising candidate progenitor scenario for these events. An unresolved question in this scenario is the fate of the companion star, which would be evident as a runaway hot subdwarf O/B stars (He sdO/B) in the aftermath of the SN event.
Aims. Previous studies have shown that the kinematic properties of an ejected companion provide an opportunity to closer examine the properties of an SN progenitor system. However, with the number of observed objects not matching predictions by theory, the viability of this mechanism is called into question. In this study, we first synthesize a population of companion stars ejected by the aforementioned mechanism, taking into account predicted ejection velocities, the inferred population density in the Galactic mass distribution, and subsequent kinematics in the Galactic potential. We then discuss the astrometric properties of this population.
Methods. We present 106 individual ejection trajectories, which were numerically computed with a newly developed, lightweight simulation framework. Initial conditions were randomly generated, but weighted according to the Galactic mass density and ejection velocity data. We then discuss the bulk properties (Galactic distribution and observational parameters) of our sample.
Results. Our synthetic population reflects the Galactic mass distribution. A peak in the density distribution for close objects is expected in the direction of the Galactic centre. Higher mass runaways should outnumber lower mass ones. If the entire considered mass range is realised, the radial velocity distribution should show a peak at 500 km s−1. If only close US 708 analogues are considered, there should be a peak at (∼750 − 850) km s−1. In either case, US 708 should be a member of the high-velocity tail of the distribution.
Conclusions. We show that the puzzling lack of confirmed surviving companion stars of thermonuclear SNe, though possibly an observation-related selection effect, may indicate a selection against high mass donors in the SD He donor channel