24 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
Treatment Status and Use of Psychoactive Substances in Deceased Drug Users
Background: Studies on drug use are limited by the study populations available, which usually only include drug users in treatment settings. Therefore, the knowledge base is limited on drug users not entering treatment for drug use disorder (DUD). Using registers from departments of forensic medicine enables research on decedents with DUD, irrespective of treatment status. Objectives: The aim of this study is to characterize and compare drug users not receiving treatment and drug users receiving treatment, in relation to cause of death, toxicological findings, and use of nonprescribed medication. Methods: Retrospective register-based study on deceased drug users with supplemental data from the Registry of Drug Abusers Undergoing Treatment and the Register of Medicinal Product Statistics in 2 observation periods: 2001â2002 and 2011â2012. Results: Two-thirds of the population were not receiving treatment at the time of death in both observation periods. Drug users receiving treatment were more likely to die from accidental poisonings than drug users not receiving treatment. There was no difference in mean age at the time of death between the 2 groups, and both groups were older in the second observation period. There was no difference in toxicological findings according to treatment status and the 2 groups did not differ in the presence of nonprescribed medication found in the blood at the time of death. Discussion/Conclusions: The proportion of drug users that received treatment prior to death has not increased, and deceased drug users are mostly not in treatment for their drug use at the time of death
The interaction of core-collapse supernova ejecta with a companion star
Context. The progenitors of many core-collapse supernovae (CCSNe) are expected to be in binary systems. After the SN explosion in a binary, the companion star 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 by the SN explosion, the companion star is ejected as a runaway star, and in some cases as a hypervelocity star. Aims. By performing a series of three-dimensional (3D) hydrodynamical simulations of the collision of SN ejecta with the companion star, we investigate how CCSN explosions affect their binary companion. Methods. We use the BEC stellar evolution code to construct the detailed companion structure at the moment of SN explosion. The impact of the SN blast wave on the companion star is followed by means of 3D smoothed particle hydrodynamics (SPH) simulations using the STELLAR GADGET code. Results. For main-sequence (MS) companion stars, 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. Their relationship can be approximately fitted by power laws, which is consistent with the results obtained from impact simulations of Type Ia SNe. 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 companion stars to Type 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. Conclusions. Our simulations show that the impact effects of Type Ib/c SN ejecta on the structure of MS companion stars, 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-1
Packaging of bio-MEMS: strategies, technologies and applications
International audienceBiomicroelectromechanical systems (bio-MEMS) are MEMS which are designed for medical or biological applications. As with other MEMS, bio-MEMS frequently, have to be packaged to provide an interface to the macroscale world of the user. Bio-MEMS can be roughly divided in two groups. Bio-MEMS can be pure technical systems applied in a biological environment or technical systems which integrate biological materials as one functional component of the system. In both cases, the materials which have intimate contact to biological matter have to be biocompatible to avoid unintentional effects on the biological substances, which in case of medical implants, could harm the patient. In the case of biosensors, the use of nonbiocompatible materials could interfere with the biological subcomponents which would affect the sensor's performance. Bio-MEMS containing biological subcomponents require the use of âbiocompatibleâ technologies for assembly and packaging; e.g., high temperatures occurring, for instance, during thermosonic wire bonding and other thermobonding processes would denature the bioaffinity layers on biosensor chips. This means that the use of selected or alternative packaging and assembly methods, or new strategies, is necessary for a widerange of bio-MEMSapplications. This paper provides an overview of some of the strategies, technologies, and applications in the field of bio-MEMS packaging. It includes the following: 1) strategies for the partitioning of subsystems with integrated microsystems for (bio)chemical analysis/synthesis; 2) methods for microassembly of bio-MEMS; 3) technologies for bonding of polymer bio-MEMS components; 4) packaging of miniature medical devices; 5) packaging of biosensors for in vitro applications; 6) packaging of micropumps as a bio-MEMS component. The applications discussed are derived from different fields to demonstrate the plethora of bio-MEMS considerations. In commercial production, packaging is possibly the major cost factor of bio-MEMS-based products, and its development requires special attention
Formation of double neutron star systems
Double neutron star (DNS) systems represent extreme physical objects and the endpoint of an exotic journey of stellar evolution and binary interactions. Large numbers of DNS systems and their mergers are anticipated to be discovered using the Square-Kilometre-Array searching for radio pulsars and high-frequency gravitational wave detectors (LIGO/VIRGO), respectively. Here we discuss all key properties of DNS systems, as well as selection effects, and combine the latest observational data with new theoretical progress on various physical processes with the aim of advancing our knowledge on their formation. We examine key interactions of their progenitor systems and evaluate their accretion history during the high-mass X-ray binary stage, the common envelope phase and the subsequent Case BB mass transfer, and argue that the first-formed NSs have accreted at most . We investigate DNS masses, spins and velocities, and in particular correlations between spin period, orbital period and eccentricity. Numerous Monte Carlo simulations of the second supernova (SN) events are performed to extrapolate pre-SN stellar properties and probe the explosions. All known close-orbit DNS systems are consistent with ultra-stripped exploding stars. Although their resulting NS kicks are often small, we demonstrate a large spread in kick magnitudes which may, in general, depend on the past interaction history of the exploding star and thus correlate with the NS mass. We analyze and discuss NS kick directions based on our SN simulations. Finally, we discuss the terminal evolution of close-orbit DNS systems until they merge and possibly produce a short -ray burst
PSR J1755-2550: A young radio pulsar with a massive, compact companion
Radio pulsars found in binary systems with short orbital periods are usually
fast spinning as a consequence of recycling via mass transfer from their
companion stars; this process is also thought to decrease the magnetic field of
the neutron star being recycled. Here, we report on timing observations of the
recently discovered binary PSR J17552550 and find that this pulsar is an
exception: with a characteristic age of 2.1 Myr, it is relatively young;
furthermore, with a spin period of 315 ms and a surface magnetic field strength
at its poles of 0.8810 G the pulsar shows no sign of having been
recycled. Based on its timing and orbital characteristics, the pulsar either
has a massive white dwarf (WD) or a neutron star (NS) companion. To distinguish
between these two cases, we searched radio observations for a potential
recycled pulsar companion and analysed archival optical data for a potential WD
companion. Neither work returned conclusive detections. We apply population
synthesis modelling and find that both solutions are roughly equally probable.
Our population synthesis also predicts a minimum mass of 0.90 M for
the companion star to PSR J17552550 and we simulate the systemic runaway
velocities for the resulting WDNS systems which may merge and possibly produce
Ca-rich supernovae. Whether PSR J17552550 hosts a WD or a NS companion star,
it is certainly a member of a rare subpopulation of binary radio pulsars.Comment: 13 pages, 11 figures, accepted by MNRA
Formation of double neutron star systems
Double neutron star (DNS) systems represent extreme physical objects and the endpoint of an exotic journey of stellar evolution and binary interactions. Large numbers of DNS systems and their mergers are anticipated to be discovered using the Square-Kilometre-Array searching for radio pulsars and high-frequency gravitational wave detectors (LIGO/VIRGO), respectively. Here we discuss all key properties of DNS systems, as well as selection effects, and combine the latest observational data with new theoretical progress on various physical processes with the aim of advancing our knowledge on their formation. We examine key interactions of their progenitor systems and evaluate their accretion history during the high-mass X-ray binary stage, the common envelope phase and the subsequent Case BB mass transfer, and argue that the first-formed NSs have accreted at most . We investigate DNS masses, spins and velocities, and in particular correlations between spin period, orbital period and eccentricity. Numerous Monte Carlo simulations of the second supernova (SN) events are performed to extrapolate pre-SN stellar properties and probe the explosions. All known close-orbit DNS systems are consistent with ultra-stripped exploding stars. Although their resulting NS kicks are often small, we demonstrate a large spread in kick magnitudes which may, in general, depend on the past interaction history of the exploding star and thus correlate with the NS mass. We analyze and discuss NS kick directions based on our SN simulations. Finally, we discuss the terminal evolution of close-orbit DNS systems until they merge and possibly produce a short -ray burst