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1.
Our knowledge of the solar system encourages us to believe that we might expect exomoons to be present around some known exoplanets. With present hardware and existing optical astronomy methods, we do not expect to be able to find exomoons for at least 10 years, and even then, it will be a hard task to detect them. Using data from the Exoplanet Orbit Database(EOD) we find stars with Jovian exoplanets within 50 light years. Most of them will be fully accessible by the new radio telescope, the Five-hundred-meter Aperture Spherical radio Telescope(FAST), under construction which is now in the test phase. We suggest radio astronomy based methods to search for possible exomoons around two exoplanets.  相似文献   

2.
The detailed processes giving maser line radiation from various molecules in space are not well understood, as can be seen from many recent detailed studies of maser line emission with high spatial and velocity resolution, and with polarization measurements. We now propose an improved maser mechanism based on amplification of the original molecular line emission by stimulated emission in Rydberg Matter (RM) clouds in HII regions, containing clusters H N and (H2) N . This mechanism will amplify the molecular lines, depending on the position, velocity, cluster size and state of excitation of the clusters in the RM cloud. RM will only support certain frequencies, corresponding to rotational transitions of the clusters. The bond lengths in the RM clusters are known within 1% from radio frequency emission measurements in the laboratory, and it is now shown that all the commonly studied maser lines agree well with stimulated emission transitions in several types of RM clusters simultaneously. This may explain the strongly varying intensities of neighboring or related maser lines, an important effect that is not well understood previously. It is also pointed out that the magnetic field due to RM is of the same order of magnitude as observed from the Zeeman splitting in maser lines; thus, the molecules that are the original sources of the lines may be embedded in the RM clouds, for example in dense HII regions that are likely to be RM regions.  相似文献   

3.
We present spectroscopic CCD observations of R Canis Majoris obtained in 1993. A total of 19 plates for Hα line were secured and reduced with the IRAF for radial velocities. A new radial velocity curve has been analyzed with collected light curves by the method of the Wilson and Devinney Differential Correction. The solution set including mass ratio q = 0.17 is determined as a unique solution by cross checking simultaneous adjustment of radial velocity and light curves, mass-luminosity relation, and distance. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

4.
In order to make an in-depth comparison between theory and observations, we analyse the light and velocity curves of various hydrodynamical models simulating RRab stars. The observations are represented by empirical formulae, derived in this and our earlier papers. It is shown that the overwhelming majority of the models tested do not follow the empirical relations regarding the shape of the light curves and the physical parameters. In almost all cases the luminosities predicted from the model light curves are significantly lower than the corresponding model values. The overall discrepancy of the models is an important indication of the limitation of the applicability of the present theoretical light and velocity curves in the determination of the physical parameters of these stars. In transforming the theoretical data to the observed light curves in V colour and in computing the observed radial velocities, it is shown that both bolometric correction and tracing the line-forming regions have considerable effects on the evaluation of the observed quantities. In an effort to resolve the discrepancy between theory and observations, it is suggested that a proper evaluation of the bolometric correction and radial velocity based on complete dynamical atmosphere models may be a useful step in this direction.  相似文献   

5.
Anharmonic oscillations of rotating stars have been studied by various authors in literature to explain the observed features of certain variable stars. However, there is no study available in literature that has discussed the combined effect of rotation and tidal distortions on the anharmonic oscillations of stars. In this paper, we have created a model to determine the effect of rotation and tidal distortions on the anharmonic radial oscillations associated with various polytropic models of pulsating variable stars. For this study we have used the theory of Rosseland to obtain the anharmonic pulsation equation for rotationally and tidally distorted polytropic models of pulsating variable stars. The main objective of this study is to investigate the effect of rotation and tidal distortions on the shapes of the radial velocity curves for rotationally and tidally distorted polytropic models of pulsating variable stars. The results of the present study show that the rotational effects cause more deviations in the shapes of radial velocity curves of pulsating variable stars as compared to tidal effects.  相似文献   

6.
Synthesis methods for light and radial velocity curves allow one to find the physical parameters of the components of binary systems of different types. We describe the basics of a new light curve synthesis algorithm for binaries that contain stars with extended expanding atmospheres. The algorithm can be used to study, e.g., light curves of binaries that contain Wolf-Rayet stars.  相似文献   

7.
In our previous work, we developed a model to study the effects of rotation and/or tidal distortions on anharmonic radial oscillations and hence on the radial velocity curves of the polytropic models of pulsating variable stars.We considered the first three modes(fundamental and the next two higher modes) for the polytropic models of index 1.5 and 3.0 in that work.In the present paper, we are further extending our previous work to study the effect of the interaction of various modes on anharmonic radial oscillations and hence on radial velocity curves of the rotationally and/or tidally distorted polytropic models of pulsating variable stars.For this purpose, we have considered the following cases:(i) fundamental mode(ii) fundamental and the first mode,(iii) fundamental and the next two modes and finally(iv) fundamental and the next three higher modes of pulsation in our study.The objective of this paper is also to investigate whether the interaction of various modes affects the results of our previous study or not.The results of this study show that the interaction of the fundamental mode with higher modes appreciably changes the shape of the radial velocity curve of rotationally distorted and rotationally and tidally distorted polytropic models of pulsating variable stars.  相似文献   

8.
Lissajous diagrams are used to detect phase lags between radial velocity curves associated with different ions. Present in many kind of variable stars, this effect provides an important tool to study the atmosphere dynamics. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

9.
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10.
B andV light curves for one epoch and radial velocity curves of three different epochs have been analyzed to revise the solution of TX UMa. The solution has been adjusted simultaneously in the light curves and radial velocity curves by the method of Wilson and Devinney's differential correction. The primary star's surface rotation rate to synchronous rate is determined as 1.768 from one of the radial velocity curves. The absolute dimension of the system has been deduced based on the simultaneous solution. The primary star is well fitted to the evolutionary track for a single star while the secondary star, while filling its Roche lobe, is fitted to the evolutionary track for a close binary system.  相似文献   

11.
Line profiles and radial velocity curves for optical stars in X-ray binaries are calculated taking into account ellipticity of the optical star and X-ray heating effect.  相似文献   

12.
The Monitor project is a photometric monitoring survey of nine young (1–200 Myr) clusters in the solar neighbourhood to search for eclipses by very low mass stars and brown dwarfs and for planetary transits in the light curves of cluster members. It began in the autumn of 2004 and uses several 2- to 4-m telescopes worldwide. We aim to calibrate the relation between age, mass, radius and where possible luminosity, from the K dwarf to the planet regime, in an age range where constraints on evolutionary models are currently very scarce. Any detection of an exoplanet in one of our youngest targets (≲10 Myr) would also provide important constraints on planet formation and migration time-scales and their relation to protoplanetary disc lifetimes. Finally, we will use the light curves of cluster members to study rotation and flaring in low-mass pre-main-sequence stars.
The present paper details the motivation, science goals and observing strategy of the survey. We present a method to estimate the sensitivity and number of detections expected in each cluster, using a simple semi-analytic approach which takes into account the characteristics of the cluster and photometric observations, using (tunable) best-guess assumptions for the incidence and parameter distribution of putative companions, and we incorporate the limits imposed by radial velocity follow-up from medium and large telescopes. We use these calculations to show that the survey as a whole can be expected to detect over 100 young low and very low mass eclipsing binaries, and ∼3 transiting planets with radial velocity signatures detectable with currently available facilities.  相似文献   

13.
We have detected asymmetry in the symbiotic star CH Cyg through the measurement of precision closure phase with the Integrated Optics Near-Infrared Camera (IONIC) beam combiner, at the infrared optical telescope array interferometer. The position of the asymmetry changes with time and is correlated with the phase of the 2.1-year period found in the radial velocity measurements for this star. We can model the time-dependent asymmetry either as the orbit of a low-mass companion around the M giant or as an asymmetric, 20 per cent change in brightness across the M giant. We do not detect a change in the size of the star during a 3-year monitoring period neither with respect to time nor with respect to wavelength. We find a spherical dust shell with an emission size of 2.2 ± 0.1 D * full width at half-maximum around the M giant star. The star to dust flux ratio is estimated to be 11.63 ± 0.3. While the most likely explanation for the 20 per cent change in brightness is non-radial pulsation, we argue that a low-mass companion in close orbit could be the physical cause of the pulsation. The combined effect of pulsation and low-mass companion could explain the behaviour revealed by the radial velocity curves and the time-dependent asymmetry detected in the closure-phase data. If CH Cyg is a typical long secondary period variable then these variations could be explained by the effect of an orbiting low-mass companion on the primary star.  相似文献   

14.
We present the first light curves of V505 Sgr in the infrared (IR) J and K bands. The light curves are analysed with a code based on Roche geometry and stellar model atmosphere fluxes in order to determine a new set of stellar and orbital parameters. From the visual–IR photometry we find no evidence of IR excess in the system. We study the effect of the non-synchronous rotation of the primary star in the light and radial velocity curves. The distance of the system is estimated as  112 ± 4 pc  , in close agreement with the Hipparcos parallax.  相似文献   

15.
We have carried out a photometric and spectroscopic survey of bright high-amplitude δ Scuti (HADS) stars. The aim was to detect binarity and multiperiodicity (or both) in order to explore the possibility of combining binary star astrophysics with stellar oscillations. Here, we present the first results for 10, predominantly southern, HADS variables. We detected the orbital motion of RS Gru with a semi-amplitude of ∼6.5 km s−1 and 11.5 d period. The companion is inferred to be a low-mass dwarf star in a close orbit around RS Gru. We found multiperiodicity in RY Lep from both photometric and radial velocity data and detected orbital motion in the radial velocities with hints of a possible period of 500–700 d. The data also revealed that the amplitude of the secondary frequency is variable on the time-scale of a few years, whereas the dominant mode is stable. Radial velocities of AD CMi revealed cycle-to-cycle variations, which might be due to non-radial pulsations. We confirmed the multiperiodic nature of BQ Ind, while we obtained the first radial velocity curves of ZZ Mic and BE Lyn. The radial velocity curve and the O–C diagram of CY Aqr are consistent with the long-period binary hypothesis. We took new time series photometry on XX Cyg, DY Her and DY Peg, with which we updated their O–C diagrams.  相似文献   

16.
Despite recent progress in the modeling of alkali atmospheres like those around the Moon and Mercury, many problems still exist. It is proposed that Rydberg Matter (RM) clusters containing Na and K atoms are the main part of the alkali atmospheres of the Moon and Mercury, forming large clouds. RM clusters are studied in the laboratory with laser fragmentation and laser spectroscopy methods. Due to the very large collision cross sections of Rydberg atoms and RM clusters, the atmospheres are not collision free, as normally assumed based on the low densities of free alkali atoms. The non-escaping radial density variation for the Na atoms, observed, e.g., on the Moon, and the Maxwellian velocity distributions observed on Mercury are caused by a true atmosphere with collisional equilibration; this process is not possible in an exosphere. Fast alkali atoms are released from the RM clusters already at large heights by solar photons and charged particle impact. The kinetic temperatures derived for the atmospheres agree with the quantized energy release. The cluster model predicts that the rate of loss from the surface is much smaller than for a purely atomic model, since the transient storage is in the RM cluster form in the atmosphere and not at the surface. The conductance of the atmosphere is of the order of 100 S due to the facile collisional ionization of the RM clusters. The apparent depletion of K in the atmosphere of Mercury is explained.  相似文献   

17.
Spectra in the wavelength range 4230–9150 Å and the first light curves of Z Vul in the infrared J, H and K bands are presented. Our infrared JHK light curves and radial velocities, together with published radial velocity and UBV data are analyzed in order to determine a new set of stellar parameters. This allows us to determine new absolute parameters of the stellar components, the interstellar reddening and the distance to the system. We discuss the rotation of the primary star, finding that must be rotating faster than synchronous. From the visual–infrared photometry we find no evidence of IR excess in the system.  相似文献   

18.
We summarize the results of our survey of rotation curves for edge-on galaxies. The observations were carried out with the 6-m Special Astrophysical Observatory telescope. Over the four years of our observations, we obtained spectra for 306 galaxies from the FGC catalog (Karachentsev et al. 1993). Rotation curves and radial velocities are given for 135 galaxies. The median radial velocity of the galaxies studied is 7800 km s?1. Together with the observations performed by other authors with different instruments, this survey allowed us to produce a homogeneous sample of edge-on galaxies from the RFGC catalog (Karachentsev et al. 1999) uniformly distributed over the entire sky and to analyze the velocity field of galaxies on scales up to 100 Mpc.  相似文献   

19.
The EF Boo eclipsing binary system is studied in the context of optical light curves and radial velocity curves published in the literature. The best‐solution leads to an over‐contact configuration of W–subclass of WUMa systems with a fill‐out factor of 28%. Absolute parameters based on simultaneous solution of light and radial velocity curves are presented. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

20.
Four eclipsing binaries, which show apparent changes of period, have been studied with respect to a possible presence of the light–time effect. With a least squares method we calculated new light elements of these systems, the mass function of the predicted third body, and its minimum mass. We discuss the probability of the presence of such bodies in terms of mass function, changes in radial velocity and third light in solution of light curves.  相似文献   

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