V 505 Mon: One of the most massive binaries

From 59 spectra collected at Asiago from 1969 to 1976, we obtain the spectroscopic orbit of the binary V 505 Mon. The rather long periodP=53.7805 days and semiamplitudeK ₁=83±4 km s^–1 of the primary component imply a fairly large mass of the secondary (m ₂3.2±0.4m ). Apparently also lines of this latter have been recorded, thus indicating highly massive components (m ₁50,R ₁=26,m ₂27,R ₂=14, in solar units) in a detached system (separation 255R ). The already reported variation of 0.15 mag., with period about one day, together with H emission, we detected, point toward a possible massive X-ray progenitor.     

Period variations of Algol-type eclipsing binaries AD And,TW Cas and IV Cas

We present new analyses of variations in O-C diagrams of three Algol-type eclipsing binary stars:AD And,TW Cas and IV Cas.We have used all published minima times(including visual and photographic)as well as newly determined ones from our and Super Wasp observations.We determined orbital parameters of 3~(rd) bodies in the systems with statistically significant errors,using our code based on genetic algorithms and Markov chain Monte Carlo simulations.We confirmed the multiple nature of AD And and the triple-star model of TW Cas,and we proposed a quadruple-star model of IV Cas.     

The spectroscopic orbits of three double-lined eclipsing binaries: I. BG Ind,IM Mon,RS Sgr

We present the spectroscopic orbit solutions of three double-lines eclipsing binaries, BG Ind, IM Mon and RS Sgr. The first precise radial velocities (RVs) of the components were determined using high resolution echelle spectra obtained at Mt. John University Observatory in New Zealand. The RVs of the components of BG Ind and RS Sgr were measured using Gaussian fittings to the selected spectral lines, whereas two-dimensional cross-correlation technique was preferred to determine the RVs of IM Mon since it has relatively short orbital period among the other targets and so blending of the lines is more effective. For all systems, the Keplerian orbital solution was used during the analysis and also circular orbit was adopted because the eccentricities for all targets were found to be negligible. The first precise orbit analysis of these systems gives the mass ratios of the systems as 0.894, 0.606 and 0.325, respectively for BG Ind, IM Mon and RS Sgr. Comparison of the mass ratio values, orbital sizes and minimum masses of the components of the systems indicates that all systems should have different physical, dynamical and probable evolutionary status.     

Giantic Roundchroms of Binary Systems SX Cas and 22 Vul

The IUE observations do not favor the chromospheric origin of typical chromospheric emission lines, of the doublet 2800 MgII first of all, in close binary systems SX Cas and 22 Vul, both with a cool giant-supergiant as primary, and a hot B7–B8 star as secondary. Here, it is shown that the concept of common chromospheres – roundchroms can explain the unusual fluxes of chromospheric emission lines in these systems. The hot components of these binaries – B type stars, themselves are assumed to represent local binary systems with a white dwarf and an accretion disc: the latter being the source of generation of transition zone type high excitation emission lines 1240 NV, 1400 SiIV, 1550 CIV, etc. It is concluded, that roundchroms of giant sizes, of order of 100 R⊙ and larger, are not rare events for the RS CVn type binary systems. This revised version was published online in July 2006 with corrections to the Cover Date.     

Period studies of classical Algol-type binaries II: UX Leo,RW Mon,EQ Ori,XZ UMa and AX Vul

This study presents an investigation of the orbital period variations of five Algol type binaries, UX Leo, RW Mon, EQ Ori, XZ UMa and AX Vul based on all available minima times. The O–C diagrams of all systems exhibit a periodic variation superimposed on a downward parabolic segment. The mass loss due to magnetic braking effect in the cooler components is assumed to account for the parabolic variation with a downward shape, while it is suggested that the light-time effect (LITE) due to an unseen component around the eclipsing binaries explains the tilted sinusoidal changes in their O–C diagrams. The orbital period decrease rates for the systems are estimated as approximately between about 0.7 and 2.5 s per century. It is clearly seen that mass loss effect is more dominant than the expected mass transfer for classical Algols in this study. The minimum mass of the probable third bodies around the eclipsing pairs was calculated to be ?0.5 M_⊙ except for UX Leo, in which it was estimated to be approximately 0.9 M_⊙. In order to search for third lights in the light curves of five systems, the V-light curves of the systems were analyzed and their physical and photometric parameters were determined. For UX Leo, a significant third light contribution was determined. We found a very small third light that can be tested using multi-color light curves, for RW Mon, EQ Ori and XZ UMa, while a third light for AX Vul could not be exposed.     

A photometric study of the neglected eclipsing binaries: V405 Cep,V948 Her,KR Mon and UZ Sge

CCD multi-band light curves of the neglected eclipsing binaries V405 Cep, V948 Her, KR Mon and UZ Sge were obtained and analysed using the Wilson–Devinney code. New geometric and absolute parameters were derived and used to determine their current evolutionary state. V405 Cep, V948 Her and KR Mon are detached systems with their components in almost the same evolutionary stage. UZ Sge is a classical Algol system with a tertiary companion around it. Moreover, since the systems V405 Cep, V948 Her and UZ Sge contain an early type component, their light curves were examined for possible pulsation behaviour.     

Evolution of close binaries and origin of Algol-type systems

The evolution of close binary systems was followed for ten systems with the initial mass of the primary in the range 1–4M and with different initial mass ratios and initial separations. A brief discussion of the evolution of the contact component is presented for two separate cases: when the primary reaches its Roche lobe during central hydrogen burning (case A) and after the exhaustion of hydrogen in the center (case B).The models obtained are compared with observed semi-detached systems separately for massive (with total mass greater than 5M ) and low mass (with total mass below 4M ) binaries. It is shown that the contact components of the observed massive binaries are probably burning hydrogen in the core. On the contrary, the majority of contact components of the observed low-mass binaries are burning hydrogen in the shell. The observed distribution of such binaries as a function of different luminosity excesses of contact components seems to indicate that their origin is connected with case A rather than with case B.     

A photometric study of the contact binaries V523 Cas and TY UMa

Broad-band V and I photometry of the short-period W UMa-type contact binaries V523 Cas and TY UMa are reported. From the light curves, the system parameters have been determined and evidence is presented for extensive spot activity in both systems, with V523 Cas being the more active system. A compilation of all the available photoelectric and CCD-based timings of eclipse minima is made; the O–C diagrams show evidence for an increasing period in the case of V523 Cas and a decreasing period in TY UMa. In addition we derive a more accurate astrometric position for V523 Cas from our CCD images.     

Synthetic light curve solutions for the short-period eclipsing binaries ST Aqr,DO Cas,and TX Cet

Synthetic light curve solutions of the short-period binary systems ST Aqr, DO Cas, and TX Cet are presented. Their evolutionary state is briefly discussed.     

The present status of periodic orbits

Recent results on periodic orbits are presented and it is shown that the periodic orbits can be used in the study of planetary systems and triple or multiple stellar systems. Triple stellar systems are stable even for close approaches of the three components. Also stable triple systems exist with nearly zero angular momentum. For the planetary systems a global view is obtained from which it is clear which configurations are stable or unstable and also what factors affect the stability. Also, the relation between resonance and instability is studied by making use of periodic orbits.     

First period analyses of five neglected Algol-type eclipsing binaries: TT And, V342 Aql, RW Cap, BZ Cas and TW Lac

We present the first study of the orbital period variations of five neglected Algol-type eclipsing binaries TT And, V342 Aql, RW Cap, BZ Cas and TW Lac, using their O–C diagrams gathered from all available times of eclipse minima. These O–C diagrams indicate that short term periodic variations superimposed on secular period increases as expected in mass transferring Algols. However, due to short time coverage of the data, the secular period increase is not clear in the case of BZ Cas and V342 Aql. The secular period increase is interpreted in terms of the combined effect of mass transfer between the components of the system and the mass loss by a stellar wind from the system. The mass transfer rates from the less massive secondary components to the more massive primaries for non-conservative cases would be about 10⁻⁷M/yr and 10⁻⁸M/yr for RW Cap and V342 Aql, respectively, and 10⁻⁹M/yr for TT And and TW Lac. Therefore, the Algol systems RW Cap and V342 Aql have the largest mass transfer rate, which could be in Case AB type, while those of the Algol systems TT And and TW Lac display the slow mass transfer rate and they could be in Case B type. The sinusoidal forms of the orbital period variations of all five Algol systems can be due to either by the light-time effects due to unseen components in these systems, or by the cyclic magnetic activity effects of the cool secondary components. The possible third bodies in all five Algol binaries would have masses larger than one solar mass. If these hypothetical large massive third bodies were normal stars, they should be detectable. Therefore, new photometric and spectroscopic observations of these systems and careful analyses of those data are required. Otherwise, the cyclic magnetic activity effects of the secondary components could be the basis of a working hypothesis in explaining the cyclic period variations of these systems.     

Disk wind in young binaries and the origin of the cyclic activity of young stars

We present the results of our numerical simulations of the cyclic brightness modulation in young binary systems with eccentric orbits and low-mass secondary components. We suggest that the binary components accrete matter from the remnants of the protostellar cloud, with the main accretor (according to current models) being the low-mass component. The brightness variations of the primary are attributable to the periodic extinction variations on the line of sight caused by the disk wind from the secondary and by the common envelope produced by this wind. The distribution of matter in the envelope was calculated in the ballistic approximation. When calculating the optical effects produced by the dust component of the disk wind, we adopted the dust-to-gas mass ratio of 1:100 characteristic of the interstellar medium and the optical parameters of the circumstellar dust typical of young stars. Our calculations show that the theoretical light curves for binaries with elliptical orbits exhibit a wider variety of shapes than those for binaries with circular orbits. In this case, the parameters of the photometric minima (their depth, duration, and shape of the light curve) depend not only on the disk-wind parameters and the orbital inclination of the binary to the line of sight, but also on the longitude of the periastron. We investigate the modulation of the scattered radiation from the common envelope with orbital phase in the single-scattering approximation. The modulation amplitude is shown to be at a maximum when the system is seen edge-on and to be also nonzero in binaries seen pole-on. We discuss possible applications of the theory to young stellar objects. In particular, several model light curves have been found to be similar to those of candidate FU Orionis stars (FUORs).     

The Sun and the transcendental world of binaries

The theory of gravity says that a binary with orbital frequency ν should be a source of gravitational waves at the double frequency and higher harmonics. This implies that long-term exposure of an ensemble of binaries to gravity waves with frequency ν _G can result in (a) a lack of binaries with frequencies near frequency ν _G /2 and its higher harmonics (the effect of unstable orbits) and/or (b) an excess of binaries whose orbital frequencies are “absolutely” incommensurable with ν _G /2 and its higher harmonics (the effect of stable orbits). It is assumed that the stable-orbit frequencies are almost equal to multiples of πν _G /2 and ν _G /2π, where π plays the role of a “perfect” factor ensuring the best antiresonance of binaries. The statistical analysis of frequencies of 5774 Galactic close binary systems (CBSs) with periods P less than 10 days is based on calculating the resonance spectrum that indicates the best common multiple for a given set of frequencies with allowance for the factor π. The CBS distribution turns out to be modulated by the frequency ν _G = 104.4(5) μHz, and this effect is the most pronounced for superfast and compact rotators, such as cataclysmic variables (CVs) and related objects. The frequency ν _G is, within the error, equal to the “enigmatic” frequency ν₀ = 104.160(1) μHz com discovered earlier in the power spectra of the Sun and brightness variations of some extragalactic sources. This confirms the existence of a “coherent cosmic oscillation” of the Universe with frequency ν₀(ν _G ). The new astrophysical phenomenon naturally explains an “CV period gap” at frequencies ≈πν _G /3 (P ≈ 153 min) and maxima at the neighboring frequencies ≈πν _G /2 and ≈πν _G /4 (P ≈ 102 and ≈204 min, respectively). The remarkable and “mysterious” role of the transcendental number π for the world of binaries is emphasized, and the mystery of physical nature of the “universal” oscillation ν₀(ν _G ) is highlighted.     

Evolutionary status of UV Piscium and its comparison with other short period RS CVn binaries

From the derived elements of UV Piscium, the evolutionary status of both of its components are compared with the Schaller et al. models and also with other main sequence systems having spectral types of late F to K range. From these models the ages of the components of UV Psc are determined. The Rossby number, which is a measure of chromospheric activity, has been derived from the convective turnover time scales and also from the age estimates.     

The Divnoe meteorite: Petrology,chemistry, oxygen isotopes and origin

Abstract— The Divnoe meteorite is an olivine-rich primitive achondrite with subchondritic chemistry and mineralogy. It has a granoblastic, coarse-grained, olivine groundmass (CGL: coarse-grained lithology) with relatively large pyroxene-plagioclase poikilitic patches (PP) and small fine-grained domains of an opaque-rich lithology (ORL). Both PP and ORL are inhomogeneously distributed and display reaction boundaries with the groundmass. Major silicates, olivine (Fa_20–28) and orthopyroxene (Fs_20–28 Wo_0.5–2.5), display systematic differences in composition between CGL and ORL as well as a complicated pattern of variations within CGL. Accessory plagioclase has low K content and displays regular igneous zoning with core compositions An_40–45 and rims An_32–37. The bulk chemical composition of Divnoe is similar to that of olivine-rich primitive achondrites, except for a depletion of incompatible elements and minor enrichment of refractory siderophiles. Oxygen isotope compositions for whole-rock and separated minerals from Divnoe fall in a narrow range, with mean δ¹⁸O = +4.91, δ¹⁷O = +2.24, and Δ¹⁷O = ?0.26 ± 0.11. The isotopic composition is not within the range of any previously recognized group but is very close to that of the brachinites. To understand the origin of Divnoe lithologies, partial melting and crystallization were modelled using starting compositions equal to that of Divnoe and some chondritic meteorites. It was found that the Divnoe composition could be derived from a chondritic source region by ～20 wt% partial melting at T ～ 1300 °C and log(fO₂) = IW-1.8, followed by ～60 wt% crystallization of the partial melt formed, and removal of the still-liquid portion of the partial melt. Removal of the last partial melt resulted in depletion of the Divnoe plagioclase in Na and K. In this scenario, CGL represents the residue of partial melting, and PP is a portion of the partial melt that crystallized in situ. The ORL was formed during the final stages of partial melting by reaction between gaseous sulfur and residual olivine in the source region. A prominent feature of Divnoe is fine μm-scale chemical variations within olivine grains, related to lamellar structures the olivines display. The origin of these structures is not known.