Aspherical supernova explosions and formation of compact black hole low-mass X-ray binaries

It has been suggested that black-hole low-mass X-ray binaries (BHLMXBs) with short orbital periods may have evolved from BH binaries with an intermediate-mass secondary, but the donor star seems to always have higher effective temperatures than measured in BHLMXBs (Justham, Rappaport & Podsiadlowski 2006). Here we suggest that the secondary star is originally an intermediate-mass (\sim 2-5 M_{\sun}) star, which loses a large fraction of its mass due to the ejecta impact during the aspherical SN explosion that produced the BH. The resulted secondary star could be of low-mass (\la 1 M_{\sun}). Magnetic braking would shrink the binary orbit, drive mass transfer between the donor and the BH, producing a compact BHLMXB.Comment: 4 pages, accepted for publication in MNRAS Letter

Thermal Timescale Mass Transfer and the Evolution of White Dwarf Binaries

The evolution of binaries consisting of evolved main sequence stars (1 < M_d/Msun < 3.5) with white dwarf companions (0.7 < M_wd/Msun < 1.2) is investigated through the thermal mass transfer phase. Taking into account the stabilizing effect of a strong, optically thick wind from the accreting white dwarf surface, we have explored the formation of several evolutionary groups of systems for progenitors with initial orbital periods of 1 and 2 days. The numerical results show that CO white dwarfs can accrete sufficient mass to evolve to a Type Ia supernova and ONeMg white dwarfs can be built up to undergo accretion induced collapse for donors more massive than about 2 Msun. For donors less massive than ~2 Msun the system can evolve to form a He and CO or ONeMg white dwarf pair. In addition, sufficient helium can be accumulated (~0.1 Msun) in systems characterized by 1.6 < M_d/Msun < 1.9 and 0.8 < M_wd/Msun < 1 such that sub Chandrasekhar mass models for Type Ia supernovae, involving off center helium ignition, are possible for progenitor systems evolving via the Case A mass transfer phase. For systems characterized by mass ratios > 3 the system likely merges as a result of the occurrence of a delayed dynamical mass transfer instability. A semi-analytical model is developed to delineate these phases which can be easily incorporated in population synthesis studies of these systems.Comment: 9 pages, 6 figures, Latex, emulateapj style, ApJ accepte

Dynamical Formation of Close Binaries in Globular Clusters II: Cataclysmic Variables

We answer the long-standing question of which production mechanism is responsible for the cataclysmic variables (CVs) in globular clusters. Arguments have been given that range from mostly primordial presence to a significant contribution of later dynamical formation in close stellar encounters. We conclude, based on a thorough analysis of a homogeneous {\it Chandra} data set, that the majority of CVs in globulars has a dynamical origin.Comment: submitted to ApJL; comments welcom

Donor Stars in Black-Hole X-Ray Binaries

We study theoretically the formation of black-hole (BH) X-ray binaries. Consistency of the models with the observed relative numbers of systems with low-mass (<2 M_sun) and intermediate-mass (~2 M_sun - M_{BH}) donors leads to severe constraints on the evolutionary parameters of the progenitors. In particular, we find that (i) BH progenitor masses cannot exceed about 2 M_{BH}; (ii) high values of the common-envelope efficiency parameter (alpha_{CE} > 1) are required, implying that energy sources other than orbital contraction must be invoked to eject the envelope; (iii) the mass-loss fraction in helium-star winds is limited to be <50%. Outside of this limited parameter space for progenitors we find that either BH X-ray binary formation cannot occur at all or donors do not have the full range of observed masses. We discuss the implications of these results for the structure of massive hydrogen-rich stars, the evolution of helium-stars, and BH formation. We also consider the possible importance of asymmetric kicks.Comment: 29 pages, 6 figures, accepted for publication in The Astrophysical Journa

Supernova Kicks, Magnetic Braking, and Neutron-Star Binaries

We consider the formation of low-mass X-ray binaries containing accreting neutron stars via the helium-star supernova channel. The predicted relative number of short-period transients provides a sensitive test of the input physics in this process. We investigate the effect of varying mean kick velocities, orbital angular momentum loss efficiencies, and common envelope ejection efficiencies on the subpopulation of short-period systems, both transient and persistent. Guided by the thermal-viscous disk instability model in irradiation-dominated disks, we posit that short-period transients have donors close to the end of core-hydrogen burning. We find that with increasing mean kick velocity the overall short-period fraction, s, grows, while the fraction, r, of systems with evolved donors among short-period systems drops. This effect, acting in opposite directions on these two fractions, allows us to constrain models of LMXB formation through comparison with observational estimates of s and r. Without fine tuning or extreme assumptions about evolutionary parameters, consistency between models and current observations is achieved for a regime of intermediate average kick magnitudes of about 100-200 km/s, provided that (i) orbital braking for systems with donor masses in the range 1-1.5 solar masses is weak, i.e., much less effective than a simple extrapolation of standard magnetic braking beyond 1.0 solar mass would suggest, and (ii) the efficiency of common envelope ejection is low.Comment: 24 pages, AAATeX, accepted for publication in The Astrophysical Journa

Проект установки получения 9-этоксикарбазола

Цель работы – спроектировать установку поучения 9-этоксикарбазола с мощностью 66 тонн в год. Объектом разработки является алкилирование карбазола этиленхлоргидрином в присутствии ацетона и гидроксида натрия. Целью проектирования является разработка комплекса взаимосвязанных процессов, обеспечивающих выработку требуемого продукта нужного качества.The work purpose – to design lecture installation 9 ethoxydibenzo-pyrroles with a power of 66 tons per year. Object of development is the dibenzo-pyrrole alkylation etilenkhlorgidriny in the presence of acetone and sodium hydroxide. The purpose of projection is development of a complex of the interdependent processes providing development of the required product of the necessary quality

The Unusual Binary Pulsar PSR J1744-3922: Radio Flux Variability, Near-infrared Observation and Evolution

PSR J1744-3922 is a binary pulsar exhibiting highly variable pulsed radio emission. We report on a statistical multi-frequency study of the pulsed radio flux variability which suggests that this phenomenon is extrinsic to the pulsar and possibly tied to the companion, although not strongly correlated with orbital phase. The pulsar has an unusual combination of characteristics compared to typical recycled pulsars: a long spin period (172 ms); a relatively high magnetic field strength (1.7x10^10 G); a very circular, compact orbit of 4.6 hours; and a low-mass companion (0.08 Msun). These spin and orbital properties are likely inconsistent with standard evolutionary models. We find similarities between the properties of the PSR J1744-3922 system and those of several other known binary pulsar systems, motivating the identification of a new class of binary pulsars. We suggest that this new class could result from either: a standard accretion scenario of a magnetar or a high-magnetic field pulsar; common envelope evolution with a low-mass star and a neutron star, similar to what is expected for ultra-compact X-ray binaries; or, accretion induced collapse of a white dwarf. We also report the detection of a possible K'=19.30(15) infrared counterpart at the position of the pulsar, which is relatively bright if the companion is a helium white dwarf at the nominal distance, and discuss its implications for the pulsar's companion and evolutionary history.Comment: 18 pages, 8 figures, accepted for publication of Ap

Dynamical Formation of Close Binary Systems in Globular Clusters

We know from observations that globular clusters are very efficient catalysts in forming unusual short-period binary systems or their offspring, such as low-mass X-ray binaries (LMXBs; neutron stars accreting matter from low-mass stellar companions), cataclysmic variables (CVs; white dwarfs accreting matter from stellar companions), and millisecond pulsars (MSPs; rotating neutron stars with spin periods of a few ms). Although there has been little direct evidence, the overabundance of these objects in globular clusters has been attributed by numerous authors to the high densities in the cores, which leads to an increase in the formation rate of exotic binary systems through close stellar encounters. Many such close binary systems emit X-radiation at low luminosities (L_x < 10^{34} erg/s) and are being found in large numbers through observations with the Chandra X-ray Observatory. Here we present conclusive observational evidence for a link between the number of close binaries observed in X-rays in a globular cluster and the stellar encounter rate of the cluster. We also make an estimate of the total number of LMXBs in globular clusters in our Galaxy.Comment: 11 pages, 1 b&w figure, 1 color figur