scholarly journals The orbital periods of subdwarf B binaries produced by the first stable Roche Lobe overflow channel

2013 ◽  
Vol 434 (1) ◽  
pp. 186-193 ◽  
Author(s):  
Xuefei Chen ◽  
Zhanwen Han ◽  
Jan Deca ◽  
Philipp Podsiadlowski
Keyword(s):  
Roche Lobe ◽  
Orbital Periods ◽  
Overflow Channel

scholarly journals Evolutionary Scenarios for Double Degenerate Systems

1996 ◽  
Vol 158 ◽  
pp. 459-460
Author(s):  
P. B. Marks ◽  
M. J. Sarna ◽  
R. C. Smith
Keyword(s):  
Mass Transfer ◽  
Orbital Period ◽  
White Dwarf ◽  
Massive Star ◽  
Roche Lobe ◽  
Orbital Parameters ◽  
Common Envelope ◽  
Orbital Periods ◽  
Two Phases ◽  
The Masses

There are presently eight double degenerate systems with well determined orbital parameters, their periods being either a few hours or a few days (Marsh, Dhillon & Duck 1995; Marsh 1995). The masses of the primaries and secondaries lie in the range 0.15… 0.45M⊙.We calculate two evolutionary scenarios (Sarna, Marks & Smith 1996); the first is Algol-type evolution with two phases of stable mass transfer, and the second involves first a stage of common envelope (CE) evolution followed by a stage of stable mass transfer. In both calculations we assume non-conservative mass transfer by which we mean that the total mass and angular momentum of the system are not conserved. For both scenarios we start our calculations after the first stage of mass transfer has finished. In all calculations the primary is the initially more massive star that filled its Roche lobe and transferred material to the secondary during the first phase of mass transfer, hence the secondary is the star that fills its Roche lobe in our calculations. The system’s orbital period decreases and then increases until the system detaches; we are left with a detached white dwarf/white dwarf binary with an orbital period of the order of hours or of days (see Table 1). There must exist some bifurcation period below which the systems evolve towards orbital periods of the order of hours and above which the systems evolve to periods of the order of several days.

scholarly journals Black widow formation by pulsar irradiation and sustained magnetic braking

2020 ◽  
Vol 500 (2) ◽  
pp. 1592-1603
Author(s):  
Sivan Ginzburg ◽  
Eliot Quataert
Keyword(s):  
Main Sequence ◽  
High Energy ◽  
Roche Lobe ◽  
Main Sequence Stars ◽  
Black Widow ◽  
High Energy Radiation ◽  
Night Side ◽  
Low Mass ◽  
Magnetic Braking ◽  
Orbital Periods

ABSTRACT Black widows are millisecond pulsars with low-mass companions, a few per cent the mass of the sun, on orbits of several hours. These companions are presumably the remnants of main-sequence stars that lost their mass through a combination of Roche lobe overflow and ablation by the host pulsar’s high-energy radiation. While ablation itself is too weak to significantly reduce the mass of the companion star, the ablated wind couples to its magnetic field, removes orbital angular momentum, and thus maintains stable Roche lobe overflow. We use the mesa stellar evolution code, complemented by analytical estimates, to track initially main-sequence companions as they are reduced to a fraction of their original mass by this ablation-driven magnetic braking. We argue that magnetic braking remains effective even for low-mass companions. A key ingredient of our model is that the irradiating luminosity of the pulsar Lirr deposits energy in the companion’s atmosphere and thereby slows down its Kelvin–Helmholtz cooling. We find that the high-energy luminosities measured by Fermi  $L_{\rm irr}=0.1\rm {-}3$ L⊙ can explain the span of black widow orbital periods. The same Lirr range reproduces the companions’ night-side temperatures, which cluster around 3000 K, as inferred from optical light curves.

From the Oort cloud to Halley-type comets

1999 ◽  
Vol 173 ◽  
pp. 327-338 ◽  
Author(s):  
J.A. Fernández ◽  
T. Gallardo
Keyword(s):  
Total Population ◽  
Complex Function ◽  
Dynamical Evolution ◽  
Oort Cloud ◽  
Capture Process ◽  
Influx Rate ◽  
Short Period ◽  
Dynamical Properties ◽  
Orbital Periods ◽  
Probability Of Capture

AbstractThe Oort cloud probably is the source of Halley-type (HT) comets and perhaps of some Jupiter-family (JF) comets. The process of capture of Oort cloud comets into HT comets by planetary perturbations and its efficiency are very important problems in comet ary dynamics. A small fraction of comets coming from the Oort cloud − of about 10−2− are found to become HT comets (orbital periods < 200 yr). The steady-state population of HT comets is a complex function of the influx rate of new comets, the probability of capture and their physical lifetimes. From the discovery rate of active HT comets, their total population can be estimated to be of a few hundreds for perihelion distancesq <2 AU. Randomly-oriented LP comets captured into short-period orbits (orbital periods < 20 yr) show dynamical properties that do not match the observed properties of JF comets, in particular the distribution of their orbital inclinations, so Oort cloud comets can be ruled out as a suitable source for most JF comets. The scope of this presentation is to review the capture process of new comets into HT and short-period orbits, including the possibility that some of them may become sungrazers during their dynamical evolution.

scholarly journals The Role of Saturn's Oblateness in the Mimas-Tethys Resonance

1974 ◽  
Vol 62 ◽  
pp. 71-76
Author(s):  
R. Greenberg
Keyword(s):  
Saturn’S Satellites ◽  
Orbital Periods

Saturn's satellites Mimas and Tethys appear to be involved in a unique resonance. All orbit-orbit resonances, by definition, have the satellites' conjunction librating about some specific longitude. Equivalently, their orbital periods, measured relative to that longitude, are commensurable. Most orbit-orbit resonances are of the eccentricity-type; the conjunctions librate about the longitude of an apse of one orbit. The Mimas-Tethys resonance is of the inclination type.

scholarly journals X-ray variability of the HMXB Cen X-3: evidence for inhomogeneous accretion flows.

2020 ◽  
Author(s):  
G Sanjurjo-Ferrín ◽  
J M Torrejón ◽  
K Postnov ◽  
L Oskinova ◽  
J J Rodes-Roca ◽  
...  
Keyword(s):  
Equivalent Width ◽  
Compact Star ◽  
Timing Analysis ◽  
Roche Lobe ◽  
The Other ◽  
Emission Lines ◽  
High Mass ◽  
X Ray ◽  
Accretion Flows ◽  
Inner Radius

Abstract Cen X-3 is a compact high mass X-ray binary likely powered by Roche lobe overflow. We present a phase-resolved X-ray spectral and timing analysis of two pointed XMM-Newton observations. The first one took place during a normal state of the source, when it has a luminosity LX ∼ 1036 erg s−1. This observation covered orbital phases φ = 0.00 − 0.37, i.e. the egress from the eclipse. The egress lightcurve is highly structured, showing distinctive intervals. We argue that different intervals correspond to the emergence of different emitting structures. The lightcurve analysis enables us to estimate the size of such structures around the compact star, the most conspicuous of which has a size ∼0.3R*, of the order of the Roche lobe radius. During the egress, the equivalent width of Fe emission lines, from highly ionized species, decreases as the X-ray continuum grows. On the other hand, the equivalent width of the Fe Kα line, from near neutral Fe, strengthens. This line is likely formed due to the X-ray illumination of the accretion stream. The second observation was taken when the source was 10 times X-ray brighter and covered the orbital phases φ = 0.36 − 0.80. The X-ray lightcurve in the high state shows dips. These dips are not caused by absorption but can be due to instabilities in the accretion stream. The typical dip duration, of about 1000 s, is much longer than the timescale attributed to the accretion of the clumpy stellar wind of the massive donor star, but is similar to the viscous timescale at the inner radius of the accretion disk.

scholarly journals The White Dwarf Mass and Orbital Period Distribution in Zero-Age Cataclysmic Binaries

1989 ◽  
Vol 114 ◽  
pp. 440-442
Author(s):  
M. Politano ◽  
R. F. Webbink
Keyword(s):  
Star Formation ◽  
White Dwarf ◽  
Galactic Disk ◽  
Orbital Energy ◽  
Orbital Parameter ◽  
Orbital Parameters ◽  
Cataclysmic Binaries ◽  
Magnetic Braking ◽  
Orbital Periods ◽  
The Individual

A zero-age cataclysmic binary (ZACB) we define as a binary system at the onset of interaction as a cataclysmic variable. We present here the results of calculations of the distributions of white dwarf masses and of orbital periods in ZACBs, due to binaries present in a stellar population which has undergone continuous, constant star formation for 1010 years.Distributions of ZACBs were calculated for binaries formed t years ago, for log t = 7.4 (the youngest age at which viable ZACBs can form) to log t = 10.0 (the assumed age of the Galactic disk), in intervals of log t = 0.1. These distributions were then integrated over time to obtain the ZACB distribution for a constant rate of star formation. To compute the individual distributions for a given t, we require the density of systems forming (number of pre-cataclysmics forming per unit volume of orbital parameter space), n£(t), and the rates at which the radii of the secondary and of its Roche lobe are changing in time, s (t) and L, s (t), respectively. In calculating nf(t), we assume that the distribution of the orbital parameters in primordial (ZAMS) binaries may be written as the product of the distribution of masses of ZAMS stars (Miller and Scalo 1979), the distribution of mass ratios in ZAMS binaries (cf. Popova, et al., 1982), and the distribution of orbital periods in ZAMS binaries (Abt 1983). In transforming the the orbital parameters from progenitor (ZAMS) to offspring (ZACB) binaries, we assume that all of the orbital energy deposited into the envelope during the common envelope phase leading to ZACB formation goes into unbinding that envelope. R.L, s (t) is determined from orbital angular momentum loss rates due to gravitational radiation (Landau and Lifshitz 1951) and magnetic braking (γ = 2 in Rappaport, Verbunt, and Joss 1983). We turn off magnetic braking if the secondary is completely convective.

scholarly journals X-Ray Sources in Close Binary Systems

1974 ◽  
Vol 3 ◽  
pp. 89-107
Author(s):  
M. J. Rees
Keyword(s):  
Binary Systems ◽  
Close Binary ◽  
Rapid Variability ◽  
X Ray ◽  
Close Binary Systems ◽  
General Order ◽  
Typical Distances ◽  
Astronomical Research ◽  
Orbital Periods ◽  
Galactic Sources

The discovery by Giacconi and his colleagues of variable X-ray sources in close binary systems certainly ranks as one of the highlights of astronomical research during the last 3 years. These remarkable objects have already been extensively studied, by optical and radio observations as well as in the X-ray band; and they seem likely to prove as significant and far-reaching in their implications as pulsars.The ‘Third Uhuru Catalogue’ (Giacconi et al., 1973a) contains about 160 sources, of which about 100 lie in our Galaxy. Their distribution over the sky (together with other arguments) suggests that these sources have luminosities of the general order 1036–1038 erg s−1, and that their typical distances are ˜ 10kpc. These galactic sources generally display rapid variability. Little else is known about most of them, but they are probably of the same general class as systems such as Her X1, Cen X3, Cyg X1 and Cyg X3. These sources have been investigated in detail, and in all cases one infers a system where the X-ray source is orbiting around a relatively ordinary star. Six sources have been optically identified, and there are some others whose binary nature is established by the occurrence of an X-ray eclipse. Orbital periods range from 4.8 h (Cyg X3) up to ˜ 10 days.

scholarly journals Dynamical evolution of Oort cloud comets to near-Earth space

2006 ◽  
Vol 2 (S236) ◽  
pp. 43-54 ◽  
Author(s):  
Olga A. Mazeeva
Keyword(s):  
Dynamical Evolution ◽  
Absolute Magnitude ◽  
Oort Cloud ◽  
Outer Solar System ◽  
Earth Space ◽  
Near Earth Space ◽  
Long Period ◽  
Order Of Magnitude ◽  
Orbital Periods ◽  
Stellar Perturbations

AbstractThe dynamical evolution of 2⋅105 hypothetical Oort cloud comets by the action of planetary, galactic and stellar perturbations during 2⋅109 years is studied numerically. The evolution of comet orbits from the outer (104 AU <a<5⋅104 AU, a is semimajor axes) and the inner Oort cloud (5⋅103 AU <a<104 AU) to near-Earth space is investigated separately. The distribution of the perihelion (q) passage frequency in the planetary region is obtained calculating the numbers of comets in every interval of Δ q per year. The flux of long-period (LP) comets (orbital periods P>200 yr) with perihelion distances q<1.5 AU brighter than visual absolute magnitude H10=7 is ∼ 1.5 comets per year, and ∼18 comets with H10<10.9. The ratio of all LP comets with q<1.5 AU to ‘new’ comets is ∼5. The frequency of passages of LP comets from the inner Oort cloud through region q<1.5 AU is ∼3.5⋅10−13 yr−1, that is roughly one order of magnitude less than frequency of passages of LP comets from the outer cloud (∼5.28⋅10−12 yr−1). We show that the flux of ‘new’ comets with 15<q<31 AU is higher than with q<15 AU, by a factor ∼1.7 for comets from the outer Oort cloud and, by a factor ∼7 for comets from the inner cloud. The perihelia of comets from the outer cloud previously passed through the planetary region are predominated in the Saturn-Uranus region. The majority of inner cloud comets come in the outer solar system (q>15 AU), and a small fraction (∼0.01) of them can reach orbits with q<1.5 AU. The frequency of transfer of comets from the inner cloud (a<104 AU) to the outer Oort cloud (a>104 AU), from where they are injected to the region q<1.5 AU, is ∼6⋅10−14 yr−1.

scholarly journals By Draconis and RS Canum Venaticorum Stars: The Discoveries of Classical Photometry and Spectroscopy

1980 ◽  
Vol 5 ◽  
pp. 847-848 ◽  
Author(s):  
Bernard W. Bopp
Keyword(s):  
Spectroscopic Binaries ◽  
Physical Parameters ◽  
Late Type ◽  
Double Line ◽  
Strong Emission ◽  
Rs Cvn Stars ◽  
Ceti Type ◽  
The Common ◽  
Orbital Periods ◽  
Detached Binaries

Physically quite dissimilar, the BY Dra and RS CVn stars have the common characteristic of extraordinarily high levels of stellar surface activity.The RS CVn group, as defined by Hall, consists of detached binaries both components of types F, G, or K. The orbital periods are from a few days to a few weeks, and the mass ratios are generally near unity. Spectroscopically, the stars are remarkable in that they show very strong Ca II H and K emission outside eclipse. Masses and radii are known for many of these systems; physical parameters indicate these systems contain a moderately evolved subgiant, with mass slightly greater than 1 M⊚. The ages (which may be verified by data on visual companions) are a few 10 years.In contrast, the BY Dra variables are late-type dwarfs, with spectral types ranging from dK5e to dM4e. The e designation indicates the presence of Balmer emission, which is generally visible in moderate strength at Ha and only very weakly present in the blue. The BY Dra stars do exhibit strong emission at H and K, however, and also show UV Ceti-type flares. Approximately 75% of the BY Dra variables are known as double-line spectroscopic binaries.

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