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1.
The discovery of a planetary companion to the intermediate-mass late-type giant star HD173416 from precise Doppler surveys of G and K giants at Xingiong station and Okayama Astrophysical Observatory (OAO) is presented in this letter. The planet has a minimum mass of 2.7 MJ an eccentricity of 0.21, a semimajor axis of 1.16 AU and an orbital period of 324 days. 相似文献
2.
《Astronomische Nachrichten》2012,333(8)
Hα profile variations of HD 82286 in 2010. The spectral lines from the secondary star appearas increased scatter around the primary‐star lines (see K. G. Strassmeier et al., this issue, p. 663) 相似文献
3.
We study the usage of the X-ray light curve, column density towards the hard X-ray source, and emission measure (density square times volume), of the massive binary system η Carinae to determine the orientation of its semimajor axis. The source of the hard X-ray emission is the shocked secondary wind. We argue that, by itself, the observed X-ray flux cannot teach us much about the orientation of the semimajor axis. Minor adjustment of some unknown parameters of the binary system allows to fit the X-ray light curve with almost any inclination angle and orientation. The column density and X-ray emission measure, on the other hand, impose strong constrains on the orientation. We improve our previous calculations and show that the column density is more compatible with an orientation where for most of the time the secondary – the hotter, less massive star – is behind the primary star. The secondary comes closer to the observer only for a short time near periastron passage. The 10-week X-ray deep minimum, which results from a large decrease in the emission measure, implies that the regular secondary wind is substantially suppressed during that period. This suppression is most likely resulted by accretion of mass from the dense wind of the primary luminous blue variable star. The accretion from the equatorial plane might lead to the formation of a polar outflow. We suggest that the polar outflow contributes to the soft X-ray emission during the X-ray minimum; the other source is the shocked secondary wind in the tail. The conclusion that accretion occurs at each periastron passage, every five and a half years, implies that accretion had occurred at a much higher rate during the Great Eruption of η Car in the 19th century. This has far reaching implications for major eruptions of luminous blue variable stars. 相似文献
4.
自1995年第一颗类太阳恒星周围的系外行星发现以来,随着已发现的系外行星数目的增多,对系外行星性质的统计分析变得重要和有意义。截至2011年6月9日,共发现系外行星555颗。以这些系外行星的轨道参数为依据,对系外行星的性质进行统计分析,得出了一些有意义的结论。同时简要介绍现有的行星形成与演化模型并依据得出的行星统计性质对其进行检验,这对于系外行星的进一步探测具有一定的指导作用。 相似文献
5.
Precision Doppler measurements from the Keck High-Resolution Echelle Spectrograph reveal periodic Keplerian velocity variations in the stars HD 16141 and HD 46375. HD 16141 (G5 IV) has a period of 75.8 days and a velocity amplitude of 11 m s-1, yielding a companion having Msini=0.22 M(JUP) and a semimajor axis of a=0.35 AU. HD 46375 (K1 IV-V) has a period of 3.024 days and a velocity amplitude of 35 m s-1, yielding a companion with Msini=0.25 M(JUP), a semimajor axis of a=0.041 AU, and an eccentricity of 0.04 (consistent with zero). These companions contribute to the rising planet mass function toward lower masses. 相似文献
6.
The Hill stability criterion is applied to analyse the stability of a planet in the binary star system of HD 41004 AB, with the primary and secondary separated by 22 AU, and masses of 0.7 M⊙ and 0.4 M⊙, respectively. The primary hosts one planet in an S‐type orbit, and the secondary hosts a brown dwarf (18.64 MJ) on a relatively close orbit, 0.0177 AU, thereby forming another binary pair within this binary system. This star‐brown dwarf pair (HD 41004 B+Bb) is considered a single body during our numerical calculations, while the dynamics of the planet around the primary, HD 41004 Ab, is studied in different phase‐spaces. HD 41004 Ab is a 2.6 MJ planet orbiting at the distance of 1.7 AU with orbital eccentricity 0.39. For the purpose of this study, the system is reduced to a three‐body problem and is solved numerically as the elliptic restricted three‐body problem (ERTBP). The Hill stability function is used as a chaos indicator to configure and analyse the orbital stability of the planet, HD 41004 Ab. The indicator has been effective in measuring the planet's orbital perturbation due to the secondary star during its periastron passage. The calculated Hill stability time series of the planet for the coplanar case shows the stable and quasi‐periodic orbits for at least ten million years. For the reduced ERTBP the stability of the system is also studied for different values of planet's orbital inclination with the binary plane. Also, by recording the planet's ejection time from the system or collision time with a star during the integration period, stability of the system is analysed in a bigger phase‐space of the planet's orbital inclination, ≤ 90°, and its semimajor axis, 1.65–1.75 AU. Based on our analysis it is found that the system can maintain a stable configuration for the planet's orbital inclination as high as 65° relative to the binary plane. The results from the Hill stability criterion and the planet's dynamical lifetime map are found to be consistent with each other. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
7.
This study is concerned with the stability of motion of the circumbinary exoplanet Kepler-413b. The analysis is performed within the framework of a flat restricted three-body problem. The stability diagram is plotted in the plane of initial conditions “pericentric distance—eccentricity” using mass calculations of Lyapunov exponents. According to the diagram, the Kepler-413b planet is located in a stable resonance cell, confined by the mean-motion resonances 6: 1 and 7: 1 with a central binary star, which agrees with the conclusions of Kostov et al. (2014) based on calculations of the MEGNO parameter. It is shown that the value of the critical semimajor axis acquired from the empirical formula of Holman and Wiegert (1999) almost coincides with the value obtained directly from the stability diagram; at low and moderate eccentricities of the planetary orbit, the position of the calculated boundary of the chaos zone is in close agreement with the boundary predicted by Shevchenko’s theory (2015). If the planet were in the instability zone, its characteristic Lyapunov time would be only ~1 year. In accordance with the conclusions of Kostov et al. (2014), it has been shown that the planet Kepler-413b is outside the habitability zone of the system. 相似文献
8.
We have computed a combined spectroscopic-interferometric orbit for the nearby binary Gliese 600 discovered by us. The orbital period is 2.78 years, and the semimajor axis is 100 mas (0.1″). Its M0 V components are almost identical and have a mass of 0.5M ⊙. The mass ratio is uncertain because of the low radialvelocity semiamplitude (7 km s?1) associated with the low orbital inclination (37°). The orbital parallax of the binary (52±11 mas) matches its dynamical and photometric parallaxes but differs significantly from the Hipparcos parallax (44.3±1.6) mas; the latter was probably distorted by the orbital motion that was not taken into account. 相似文献
9.
Ren-Xin Xu Department of Astronomy School of Physics Peking University Beijing 《中国天文和天体物理学报》2006,6(5)
Efforts are made to understand the timing behaviors (e.g., the jumps in the projected pulsar semimajor axis at the periastron passages) observed in the 13-year monitoring of PSR B1259-63. Planet-like objects are suggested to orbit around the Be star, which may gravitationally perturb the (probably low mass) pulsar when it passes through periastron. An accretion disk should exist outside the pulsar's light cylinder, which creates a spindown torque on the pulsar due to the propeller effect. The observed negative braking index and the discrepant timing residuals close to periastron could be related to the existence of a disk with a varying accretion rate. A speculation is presented that the accretion rate may increase on a long timescale in order to explain the negative braking index. 相似文献
10.
Dissociation and ionization of hydrogen molecules and ionization of hydrogen atoms due to extreme UV radiation from the parent star are accompanied by the formation of a concurrent photoelectron flux with excess kinetic energy. These dissociation and ionization processes are the main source of atomic and molecular ions in the thermospheres of extrasolar planets, such as the “hot Jupiter” HD 209458b. The ionization processes are the most important part of contemporary aeronomic models of planetary atmospheres in the Solar System and extrasolar systems (Johnson et al., 2008; Yelle et al., 2008). We estimate the contribution of the dissociation and ionization processes due to the stellar UV radiation and the concurrent photoelectron flux to the formation of extended ionospheres around extrasolar giant planets. As opposed to models of other researchers, we calculated the ionization rates due to the concurrent photo-electron flux for the first time. It is established that, in contrast to a widely used parametrization of the photoelectron contribution (Cecchi-Pestellini et al., 2006; 2009), the rate of secondary ionization due to the photoelectrons depends appreciably on the altitude, approaching the photoionization rate in the lower layers of the thermosphere. The calculated ionization rate in the thermosphere of the extrasolar giant planet (EGP) orbiting close to its parent star is a necessary link when modeling an aeronomic model and estimating the rate of the EGP atmospheric loss. 相似文献
11.
On the migration of a system of protoplanets 总被引：1，自引：0，他引：1
W. Kley † 《Monthly notices of the Royal Astronomical Society》2000,313(4):L47-L51
The evolution of a system consisting of a protoplanetary disc with two embedded Jupiter-sized planets is studied numerically. The disc is assumed to be flat and non-self-gravitating; this is modelled by the planar (two-dimensional) Navier–Stokes equations. The mutual gravitational interaction of the planets and the star, and the gravitational torques of the disc acting on the planets and the central star are included. The planets have an initial mass of one Jupiter mass M Jup each, and the radial distances from the star are one and two semimajor axes of Jupiter, respectively.
During the evolution a joint wide annular gap is created by the planets. Both planets increase their mass owing to accretion of gas from the disc: after about 2500 orbital periods of the inner planet it has reached a mass of 2.3 MJup , while the outer planet has reached a mass of 3.2 M Jup . The net gravitational torques exerted by the disc on the planets result in an inward migration of the outer planet on time-scales comparable to the viscous evolution time of the disc. The semimajor axis of the inner planet remains constant as there is very little gas left in its vicinity to induce any migration. When the distance of close approach eventually becomes smaller than the mutual Hill radius, the eccentricities increase strongly and the system may become unstable.
If disc depletion occurs rapidly enough before the planets come too close to each other, a stable system similar to our own Solar system may remain. Otherwise the orbits may become unstable and produce systems like υ And. 相似文献
During the evolution a joint wide annular gap is created by the planets. Both planets increase their mass owing to accretion of gas from the disc: after about 2500 orbital periods of the inner planet it has reached a mass of 2.3 M
If disc depletion occurs rapidly enough before the planets come too close to each other, a stable system similar to our own Solar system may remain. Otherwise the orbits may become unstable and produce systems like υ And. 相似文献
12.
We report the detection of extended IR emission at 10.8 and 18.2 μm around the Vega-like source HD 141569. Mid-IR imaging with OSCIR on Keck II shows emission from dust extending out to 100 AU from the B9.5 Ve star. Our modeling of the dust places an upper limit of approximately 2 μm on the diameter of the mid-IR-emitting particles if they are Mie spheres of astronomical silicates. Comparison of our mid-IR images to the near-IR (1.1 μm) NICMOS images of HD 141569 (Weinberger et al. 1999) shows that the mid-IR emission originates at smaller distances from the star than the scattered near-IR light, as also previously observed for the archetype Vega-like source beta Pictoris. 相似文献
13.
R. Schwarz Á. Süli R. Dvorak E. Pilat-Lohinger 《Celestial Mechanics and Dynamical Astronomy》2009,104(1-2):69-84
Today there are more than 340 extra-solar planets in about 270 extra-solar systems confirmed. Besides the observed planets there exists also the possibility of a Trojan planet moving in the same orbit as the Jupiter-like planet. In our investigation we take also into account the habitability of a Trojan planet and whether such a terrestrial planet stays in the habitable zone. Its stability was investigated for multi-planetary systems, where one of the detected giant planets moves partly or completely in the habitable zone. By using numerical computations, we studied the orbital behaviour up to 107 years and determined the size of the stable regions around the Lagrangian equilibrium points for different dynamical models for fictitious Trojans. We also examined the interaction of the Trojan planets with a second or third giant planet, by varying its semimajor axis and eccentricity. We have found two systems (HD 155358 and HD 69830) that can host habitable Trojan planets. Another aim of this work was to determine the size of the stable region around the Lagrangian equilibrium points in the restricted three body problem for small mass ratios μ of the primaries μ ≤ 0.001 (e.g. Neptune mass of the secondary and smaller masses). We established a simple relation for the size depending on μ and the eccentricity. 相似文献
14.
Gliese 22 is a hierarchical triple red dwarf system formed by two close components, Aa and Ab, and a distant component, B, which is moving around the center of mass of the first two.The possible existence of a fourth very low-mass object (15 Jupiter mass) orbiting around component B was reported by Docobo et al. (Docobo, J.A. et al. [2007]. IAU Commun. 26, 3-4). In this probable scenario with four bodies, component B would be in reality two: star Ba and the new object, Bb.Two full three-dimensional accurate (circular and elliptical) solutions for the orbit of Bb have been obtained, along with an improved arrangement of the system masses. In addition, such a multiple system is analyzed by means of a (2 + 2)-body model considering its evolution during 10 Myr. In particular, we have studied its apsidal motion in order to eventually find any evidence of chaotic behavior. The nature of the new object as a giant planet or a brown star is also discussed. 相似文献
15.
《Astronomische Nachrichten》2012,333(7)
A case study for the restricted 3‐body problem showing the osculating semimajor axis for the first 50 binary orbits (see B. Quarles et al., this issue, p. 551) (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
16.
A. A. Tokovinin R. F. Griffin Yu. Yu. Balega E. A. Pluzhnik S. Udry 《Astronomy Letters》2000,26(2):116-121
A combined spectroscopic-interferometric orbit is computed for the primary component of the visual binary star HR 7272=ADS 12101. The orbital period is 3.55 years; semimajor axis 0.″074. Radial velocities of both components were determined by correlation techniques; their semi-amplitudes are 6.6 and 8.4 km s?1. Because those amplitudes are so modest, the correlation dips are never well resolved, and the mass ratio and orbital parallax remain poorly determined. Adopting normal masses for the components, we obtain the dynamical parallax; the Hipparcos parallax for this star seems to have a large error, probably because the orbital motion was not taken into account. The visual component B belongs to this system and has a constant radial velocity. 相似文献
17.
R. C. North T. R. Marsh C. K. J. Moran U. Kolb R. C. Smith R. Stehle 《Monthly notices of the Royal Astronomical Society》2000,313(2):383-391
We have discovered that the spectrum of the well-known dwarf nova EM Cyg is contaminated by light from a K25V star (in addition to the K-type mass donor star). The K25V star contributes approximately 16 per cent of the light from the system and if not taken into account has a considerable effect upon radial velocity measurements of the mass donor star. We obtain a new radial velocity amplitude for the mass donor star of K 2 =202±3 km s1 , compared with the value of K 2 =135±3 km s1 obtained in Stover, Robinson & Nather's classic study of EM Cyg. The revised value of the amplitude, combined with a measurement of rotational broadening of the mass donor, v sin i =140±6 km s1 , leads to a new mass ratio of q M 2 M 1 =0.88±0.05. This solves a long-standing problem with EM Cyg, because Stover et al.'s measurements indicated a mass ratio q >1, a value that should have led to dynamically unstable mass transfer for the secondary mass deduced by Stover et al. The revised value of the mass ratio, combined with the orbital inclination i =67±2°, leads to masses of 0.99±0.12 M
We discuss whether the K star could be physically associated with EM Cyg or not, and present the results of the spectroscopic study. 相似文献
We discuss whether the K star could be physically associated with EM Cyg or not, and present the results of the spectroscopic study. 相似文献
18.
New series of rigid Earth nutations for the angular momemtum axis, the rotation axis and the figure axis, named RDAN97, are
computed using the torque approach. Besides the classical J2 terms coming from the Moon and the Sun, we also consider several
additional effects: terms coming from J3 and J4 in the case of the Moon, direct and indirect planetary effects, lunar inequality,
J2 tilt, planetary‐tilt, effects of the precession and nutations on the nutations, secular variations of the amplitudes, effects
due to the triaxiality of the Earth, new additional out‐of‐phase terms coming from second order effect and relativistic effects.
Finally, we obtain rigid Earth nutation series of 1529 terms in longitude and 984 terms in obliquity with a truncation level
of 0.1 μ (microarcsecond) and 8 significant digits. The value of the dynamical flattening used in this theory is HD=(C-A)/C=0.0032737674
computed from the initial value pa=50′.2877/yr for the precession rate. These new rigid Earth nutation series are then compared
with the most recent models (Hartmann et al., 1998; Souchay and Kinoshita, 1996, 1997; Bretagnon et al., 1997, 1998. We also
compute a benchmark series (RDNN97) from the numerical ephemerides DE403/LE403 (Standish et al., 1995) in order to test our
model. The comparison between our model (RDAN97) and the benchmark series (RDNN97) shows a maximum difference, in the time
domain, of 69 μas in longitude and 29 μas in obliquity. In the frequency domain, the maximum differences are 6 μas in longitude
and 4 μ as in obliquity which is below the level of precision of the most recent observations (0.2 mas in time domain (temporal
resolution of 1 day) and 0.02 mas in frequency domain).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
R. F. Griffin 《Monthly notices of the Royal Astronomical Society》2006,368(3):1359-1361
In a recent paper Fuhrmann et al. presented radial-velocity measurements of HD 75767 and derived an orbit that was an improvement on the one published by Sanford in 1931; an orbit published in 1991 was, however, overlooked, and the actual calculation of the new elements is open to criticism. A joint solution of all the available data provides a better result than any of the three constituent sets separately; the period is determined to a precision more than 100 times better than in the recent orbit, and a very small but definite eccentricity is reliably documented for the first time. The eccentricity is probably caused (or maintained) by the visual companion. Fuhrmann et al.'s conclusion that the secondary object in the spectroscopic orbit is a white dwarf does not seem inescapable; indeed, the object appears quite likely to be a lower-main-sequence star. 相似文献
20.
A model of Cyg X-3, as a binary cocooned star system with two sources of X-rays, one above the polar caps of the neutron star — the usual pulsar radiation — and the other around the equatorial plane of the magneto-bounding surface formed due to the interaction of the infalling plasma and the magnetic field of the neutron star, is made. The X-ray, -ray, and IR radiation light curves are considered from the shadow effect. An upper limit on the mass of the neutron star is estimated from the consideration of periodic derivative purely due to mass loss. A comparison is made with the results of Elsneret al. (1980) and Ghoshet al. (1981), which they derived from the consideration of period derivative purely from apsidal motion. 相似文献