scholarly journals Migration of planets in circumbinary discs

2018 ◽  
Vol 616 ◽  
pp. A47 ◽  
Author(s):  
Daniel Thun ◽  
Wilhelm Kley
Keyword(s):  
Binary Stars ◽  
Special Focus ◽  
Two Dimensional ◽  
Mass Ratio ◽  
Orbital Elements ◽  
Lower Mass ◽  
Orbital Parameters ◽  
Current Location ◽  
Hydrodynamical Simulations ◽  
Grid Based

Aims. The discovery of planets in close orbits around binary stars raises questions about their formation. It is believed that these planets formed in the outer regions of the disc and then migrated through planet-disc interaction to their current location. Considering five different systems (Kepler-16, -34, -35, -38, and -413) we model planet migration through the disc, with special focus on the final orbital elements of the planets. We investigate how the final orbital parameters are influenced by the disc and planet masses. Methods. Using two-dimensional, locally isothermal, and viscous hydrodynamical simulations, we first model the disc dynamics for all five systems, followed by a study of the migration properties of embedded planets with different masses. To strengthen our results, we apply two grid-based hydrodynamical codes using different numerics (PLUTO and FARGO3D). Results. For all systems, we find that the discs become eccentric and precess slowly. We confirm the bifurcation feature in the precession period – gap-size diagram for different binary mass ratios. The Kepler-16, -35, -38, and -413 systems lie on the lower branch and Kepler-34 on the upper one. For systems with small binary eccentricity, we find a new non-monotonic, loop-like feature. In all systems, the planets migrate to the inner edge of the disc cavity. Depending on the planet-disc mass ratio, we observe one of two different regimes. Massive planets can significantly alter the disc structure by compressing and circularising the inner cavity and they remain on nearly circular orbits. Lower-mass planets are strongly influenced by the disc, their eccentricity is excited to high values, and their orbits are aligned with the inner disc in a state of apsidal corotation. In our simulations, the final locations of the planets are typically too large with respect to the observations because of the large inner gaps of the discs. The migrating planets in the most eccentric discs (around Kepler-34 and -413) show the largest final eccentricity in agreement with the observations.

scholarly journals Binary fraction of O and B-type stars from LAMOST data

2021 ◽  
Vol 21 (11) ◽  
pp. 272
Author(s):  
Feng Luo ◽  
Yong-Heng Zhao ◽  
Jiao Li ◽  
Yan-Jun Guo ◽  
Chao Liu
Keyword(s):  
Binary Stars ◽  
Cross Correlation ◽  
Stellar Populations ◽  
Mass Ratio ◽  
Stellar Spectra ◽  
Ob Stars ◽  
Orbital Parameters ◽  
Repeated Observations ◽  
Kolmogorov Smirnov ◽  
Fixed Power

Abstract Binary stars play an important role in the evolution of stellar populations . The intrinsic binary fraction (f bin) of O and B-type (OB) stars in LAMOST DR5 was investigated in this work. We employed a cross-correlation approach to estimate relative radial velocities for each of the stellar spectra. The algorithm described by Sana et al. (2013) was implemented and several simulations were made to assess the performance of the approach. The binary fraction of the OB stars is estimated through comparing the uni-distribution between observations and simulations with the Kolmogorov-Smirnov tests. Simulations show that it is reliable for stars most of whom have six, seven and eight repeated observations. The uncertainty of orbital parameters of binarity becomes larger when observational frequencies decrease. By adopting the fixed power exponents of π = −0.45 and κ = −1 for period and mass ratio distributions, respectively, we obtain that f bin = 0.4 − 0.06 + 0.05 for the samples with more than three observations. When we consider the full samples with at least two observations, the binary fraction turns out to be 0.37 − 0.03 + 0.03 . These two results are consistent with each other in 1σ.

scholarly journals Statistics of Binary Stars: Semi-Major Axes

1976 ◽  
Vol 73 ◽  
pp. 369-379
Author(s):  
V. Trimble ◽  
C. Cheung
Keyword(s):  
Binary Stars ◽  
Binary Systems ◽  
Major Axis ◽  
Small Mass ◽  
Close Binaries ◽  
Mass Ratio ◽  
Orbital Elements ◽  
Semi Major Axis ◽  
Mass Ratios ◽  
Show Evidence

We have examined the distribution of the semi-major axes of the binary systems in the Sixth Catalogue of the Orbital Elements of Spectroscopic Binary Systems (and its extensions) and the correlation of semi-major axis with other properties of the systems. The total distribution has a single peak near asini=107km. Evolved systems have wider separations and smaller mass ratios than unevolved systems. Among each type separately, the distribution of mass ratios is bimodal and small mass ratio is correlated with large separation. These data appear to show evidence of two mechanisms of binary system formation and of the process of mass transfer in close binaries.

The study of short orbital period of delta scuti pulsating variable stars

2019 ◽  
Vol 15 (S356) ◽  
pp. 407-407
Author(s):  
Abduselam Mohammed
Keyword(s):  
Time Delay ◽  
Orbital Period ◽  
Binary Stars ◽  
Arrival Time ◽  
Periodic Variation ◽  
Variable Stars ◽  
Orbital Elements ◽  
Pulsating Stars ◽  
Delta Scuti ◽  
Arrival Time Delay

AbstractAs a pulsating star moves in its binary orbit, the path length of the light between us and the star varies, leading to the periodic variation in the arrival time of the signal from the star to us (earth). With the consideration of pulsators light arrival time delay effects several new methods which allows using Kepler photometric data (light curves) alone to find binary stars have been recently developed. Among these modern techniques we used binarogram method and we identified that several δSct pulsating stars have companions. The application of these method on detecting long periods(i.e. longer than about 50 d) δSct pulsating stars is not new, but the uniqueness of this study is we verified that it is also applicable to detect and determine the orbital elements of short periods (i.e short orbital period) δSct pulsating stars. With this investigation, we identified the possible way to overcome effects of fictious peaks, even, on the maximum peaks helpful to verify weather the star has companion or not depend up on the existence of the time-delay. Then, we applied the technique on known binary stars and their orbital elements are previously published. Finally, we identified some new short orbital period δSct pulsating stars and obtained their orbital frequency and period with the same procedures. Because of with our attempts we succeeded and verified the applicability of the method (the Binarogram method) on these stars (i.e short orbital period) for the first time, we expect that our present study will play a great role for similar study and to improve our binary statistics.

Twin stars as tracers of binary evolution in the Kepler era

2021 ◽  
Author(s):  
Sara Bulut ◽  
Baris Hoyman ◽  
Ahmet Dervisoglu ◽  
Orkun Özdarcan ◽  
Ömür Cakilrli
Keyword(s):  
High Resolution ◽  
Internal Structure ◽  
Spectroscopic Analysis ◽  
Independent Method ◽  
Eclipsing Binaries ◽  
Physical Parameters ◽  
Evolutionary Status ◽  
Mass Ratio ◽  
Orbital Parameters ◽  
Binary Evolution

Abstract We present results of the combined photometric and spectroscopic analysis of four systems, which are eclipsing binaries with a twin–component (mass ratio q ≃ 1). These are exceptional tools to provide information for probing the internal structure of stars. None of the systems were previously recognized as twin binaries. We used a number of high–resolution optical spectra to calculate the radial velocities and later combined them with photometry to derive orbital parameters. Temperatures and metallicities of systems were estimated from high-resolution spectra. For each binary, we obtained a full set of orbital and physical parameters, reaching precision below 3 per cent in masses and radii for whole pairs. By comparing our results with PARSEC and MIST isochrones, we assess the distance, age and evolutionary status of the researched objects. The primary and/or secondary stars of EPIC 216075815 and EPIC 202843107 are one of the cases where asteroseismic parameters of δ Sct and γ Dor pulsators were confirmed by an independent method and rare examples of the twin–eclipsing binaries, therefore the following analyses and results concern the pulsating nature of the components.

scholarly journals Probing gas disc physics with LISA: simulations of an intermediate mass ratio inspiral in an accretion disc

2019 ◽  
Vol 486 (2) ◽  
pp. 2754-2765 ◽  
Author(s):  
A M Derdzinski ◽  
D D’Orazio ◽  
P Duffell ◽  
Z Haiman ◽  
A MacFadyen
Keyword(s):  
Small Deviation ◽  
Compact Object ◽  
Accretion Disc ◽  
Mass Ratio ◽  
Intermediate Mass ◽  
Laser Interferometer Space Antenna ◽  
Total Phase ◽  
Accretion Rates ◽  
Hydrodynamical Simulations ◽  
And Migration

Abstract The coalescence of a compact object with a $10^{4}\hbox{--}10^{7}\, {\rm M_\odot }$ supermassive black hole (SMBH) produces mHz gravitational waves (GWs) detectable by the future Laser Interferometer Space Antenna (LISA). If such an inspiral occurs in the accretion disc of an active galactic nucleus (AGN), the gas torques imprint a small deviation in the GW waveform. Here, we present two-dimensional hydrodynamical simulations with the moving-mesh code disco of a BH inspiraling at the GW rate in a binary system with a mass ratio q = M2/M1 = 10−3, embedded in an accretion disc. We assume a locally isothermal equation of state for the gas (with Mach number $\mathcal {M}=20$) and implement a standard α-prescription for its viscosity (with α = 0.03). We find disc torques on the binary that are weaker than in previous semi-analytic toy models, and are in the opposite direction: the gas disc slows down, rather than speeds up the inspiral. We compute the resulting deviations in the GW waveform, which scale linearly with the mass of the disc. The SNR of these deviations accumulates mostly at high frequencies, and becomes detectable in a 5 yr LISA observation if the total phase shift exceeds a few radians. We find that this occurs if the disc surface density exceeds $\Sigma _0 \gtrsim 10^{2-3}\rm g\, cm^{-2}$, as may be the case in thin discs with near-Eddington accretion rates. Since the characteristic imprint on the GW signal is strongly dependent on disc parameters, a LISA detection of an intermediate mass ratio inspiral would probe the physics of AGN discs and migration.

Electrochemical polymerization for two-dimensional conjugated polymers

2018 ◽  
Vol 6 (40) ◽  
pp. 10672-10686 ◽  
Author(s):  
Qing Zhang ◽  
Huanli Dong ◽  
Wenping Hu
Keyword(s):  
Conjugated Polymers ◽  
Electrochemical Polymerization ◽  
Research Progress ◽  
Future Research ◽  
Special Focus ◽  
Two Dimensional ◽  
Research Directions ◽  
Potential Applications ◽  
Future Research Directions ◽  
Recent Research Progress

This article places special focus on the recent research progress of the EP method in synthesizing CPs. In particular, their potential applications as 2D CPs are summarized, with a basic introduction of the EP method, its use in synthesizing CPs as well as the promising applications of the obtained CPs in different fields. Discussions of current challenges in this field and future research directions are also given.

scholarly journals Quality of carcass sides, yield and distribution of certain tissues in carcasses from pigs fattened in conventional way and on deep litter

2008 ◽  
Vol 62 (3-4) ◽  
pp. 179-188 ◽  
Author(s):  
Olga Kosovac ◽  
Branislav Zivkovic ◽  
Tatjana Smiljakovic ◽  
C. Radovic
Keyword(s):  
Conventional Method ◽  
Muscle Tissue ◽  
Special Focus ◽  
Housing Conditions ◽  
Lower Mass ◽  
Meat Yield ◽  
Group I ◽  
Pig Carcasses ◽  
Group Yield

Objective of this research was to present and compare results of the research of the effect of two fattening methods, on deep litter and conventional method (without litter). Slaughter properties have been determined with special focus on distribution of certain tissues in pig carcasses fattened in two different ways. Research was carried out on meat, fattening pig breeds - Swedish landrace. Research included 115 fatteners from single farm in Vojvodina. Depending on the housing conditions, two groups were formed: first group - group I (60 heads in group) was housed on deep litter, and the second - group II (55 heads in group), without litter. At the end of the trial, pigs were slaughtered and dissection was performed on cooled (+4?C) left carcass sides and meat yield determined using the method of partial dissection (Walstra and Merkus, 1996). Carcass sides were cut in 12 parts. Based on the meat quantity in four main carcass parts: leg, shoulder, back-loin part (BLP) and belly-rib part (BRP), which contain 75% of total musculature mass and mass of tenderloin of carcass side, meat percentage in carcass sides was calculated according to formulation (Manojlovic Danica et al., 1999). Fatteners housed on deep litter had statistically significantly (**p<0.01) lower mass of cool carcass sides (38.38 kg) compared to fatteners housed without litter (40.90 kg). Higher absolute and relative shares of leg (10.22 kg and 25.02%) were established and higher absolute yield of shoulder (5.35 kg ) in fatteners housed in boxes without litter (II group). Yield of muscle tissue in leg, shoulder, BLP and BRP was higher in fatteners of the II group (without litter) compared to pigs fattened on deep litter, and also statistically highly significant differences were established in share of muscle tissue in shoulder (**p<0.01) and considerable differences in regard to share of muscle tissue in BRP (*p<0.05). Meat yield of pig carcass sides was determined by method of partial dissection, for fatteners housed on deep litter it was 47,92%, and in case of fatteners housed without litter it was 53.89%. Established differences were very significant (**p<0.01).

scholarly journals Modeling Tidal Effects in Accretion Discs

1997 ◽  
Vol 163 ◽  
pp. 335-338
Author(s):  
Patrick Godon
Keyword(s):  
Equation Of State ◽  
White Dwarf ◽  
Accretion Discs ◽  
Time Dependent ◽  
Two Dimensional ◽  
Mass Ratio ◽  
Tidal Effects ◽  
Azimuthal Mode ◽  
Polytropic Equation

AbstractA two-dimensional time-dependent spectral code is used for the study of tidal effects in accretion discs. A cool disc around a white dwarf (characteristic of CV systems) is modeled under the assumption of a polytropic equation of state and a standard alpha viscosity prescription. For a mass ratio q < 0.1 (considered here) and under the assumption of a reflective inner boundary, tidal effects induce an eccentric (m=l azimuthal) mode in the disc together with an elliptic (m=2 azimuthal) mode in the inner disc.

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