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1.
We consider a model for the cyclic activity of young binary stars that accrete matter from the remnants of a protostellar
cloud. If the orbit of such a binary system is inclined at a small angle to the line of sight, then the streams of matter
and the density waves excited in the circumbinary disk can screen the primary component of the binary from the observer. To
study these phenomena by the SPH (smoothed particle hydrodynamics) method, we have computed grids of hydrodynamic models for
binary systems based on which we have constructed the light curves as a function of the orbital phase. The main emphasis is
on investigating the properties of the brightness oscillations. Therefore, the model parameters were varied within the following
ranges: the component mass ratio q = M
2: M
1 = 0.2–0.5 and the eccentricity = 0–0.7. The parameter that defined the binary viscosity was also varied. We adopted optical
grain characteristics typical of circumstellar dust. Our computations have shown that bimodal oscillations are excited in
binaries with eccentric orbits, provided that the binary components do not differ too much in mass. In this case, the ratios
of the periods and amplitudes of the bimodal oscillations and their shape depend strongly on the inclination of the binary
plane and its orientation relative to the observer. Our analysis shows that the computed light curves can be used in interpreting
the cyclic activity of UX Ori stars. 相似文献
2.
We consider a model of cyclic brightness variations in a young star with a low-mass (q = M
2/M
1 ≤ 0.1) companion that accretes matter from the remnants of a protostellar cloud (circumbinary disk). We assume that the orbit
of the companion is circular and that its plane does not coincide with the disk plane. We have computed grids of hydrodynamic
models for such a binary by the SPH method based on which we have investigated the circumstellar extinction variations produced
by the streams of matter and density waves excited in the circumbinary disk by the orbital motion of the companion. We show
that, depending on the inclination and orientation of the binary’s line of nodes relative to the observer, the brightness
of the primary component can undergo various (in shape and depth) oscillations with a period equal to the orbital one. In
contrast to the models with coplanar circular orbits, the accretion rate onto the components of a binary with a noncoplanar
orbit depends on the orbital phase. The results of our computations can be used to study the cyclic activity of UX Ori stars
and young eclipsing binaries with anomalously long eclipses. 相似文献
3.
Photoelectric observations of the RS CVn type non-eclipsing binary UX Arietis obtained at Nizamiah Observatory during the
observing seasons of 1975–76, 1981–82 and 1982–83 are presented. The light curve of UX Ari showed a distortion wave with an
amplitude inV varying from 0.02 mag during 1975–76 to 0.15 mag during 1982–83. An analysis of the available data shows that the light maximum
is almost constant. It is also evident that the light-curve minimum decreases as the wave amplitude increases. The constant
light at maximum,V = 6.51 ± 0.03 indicates the unspotted photospheric brightness. It is also suggested that the variation in meanV brightness is mainly due to spot activity and not due to intrinsic variation. 相似文献
4.
We present new photometric data and analyze long-term UBV observations of three candidates for protoplanetary nebulae—F supergiants with infrared excesses at high Galactic latitudes—IRAS
18095+2704, IRAS 19386+0155, and IRAS 19500-1709. All these stars exhibit quasi-periodic low-amplitude variations caused by
pulsations against the background of long-term brightness trends. For IRAS 18095+2704=V887 Her, we have found a pulsation
period of 109 days and revealed a linear brightness trend—the star brightens at constant (within the limits of the measurement
errors) yearly mean color indices. The light curve of IRAS 19386+0155=V1648 Aql in 2000–2008 is represented by a wave with
a fundamental period of 102 days whose modulation with a close period of 98 days leads to variations with a variable amplitude.
V1648 Aql also shows a systematic rise in V brightness along with a reddening. IRAS 19500–1709=V5112 Sgr exhibits irregular pulsations with periods of 39 and 47 days.
The long-term variability component of V5112 Sgr may indicate that the star is binary. 相似文献
5.
D. Manzoori 《Astronomische Nachrichten》2016,337(6):652-661
New standardized V ‐band light curves (LCs) for the eclipsing binary SV Cam have been modeled using the PHOEBE program (v. 0.31a). Absolute parameters of the stellar components were then determined, enabling them to be positioned on the mass‐radius diagram. Analysis of eclipse minima timing data (O – C diagrams) indicated two cyclic periods of 48.0 and 23.3 yr. These cyclic variations of the orbital period are interpreted in terms of motion of a third body around the system and magnetic activity cycle modulating the orbital period of SV Cam via the Applegate (1992) mechanism. The use of the Applegate model for SV Cam has been checked by examining the long term brightness variation and calculating some important parameters of this system. The results of these calculations favor the modulation of the orbital period by the Applegate mechanism. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
We present a new method to solve the problem of initial orbit determination of any binary system. This method is mainly based
on the material available for an observer, for example relative positions at a given time of the couple in the “plane of sky”,
namely the tangent plane to the celestial sphere at the position of the primary component. The problem of orbit determination
is solved by splitting in successive stages in order to decorrelate the parameters of each other as much as possible. On one
hand, the geometric problem is solved using the first Kepler’s law from a single observing run and, on the other hand, dynamical
parameters are then inferred from the fit of the Kepler’s equation. At last, the final stage consists in determining the main
physical parameters involved in the secular evolution of the system, that is the spin axis and the J2 parameter of the primary if we assume that it is a quasi-spherical body. As a matter of fact there is no need to make too
restrictive initial assumptions (such as circular orbit or zero eccentricity) and initial guesses of parameters required by
a non-linear least-squares Levenberg–Marquardt algorithm are finally obtained after each stage. Such a protocol is very useful
to study systems like binary asteroids for which all of the parameters should be considered a priori as unknowns. As an example of application, we used our method to estimate the set of the Pluto–Charon system parameters from
observations collected in the literature since 1980. 相似文献
7.
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). 相似文献
8.
Vlad Turcu Alexandru Pop Alexandru Marcu Dan Moldovan 《Astrophysics and Space Science》2011,331(1):105-113
The interest in the study of the Algol binary system Y Leonis is justified not only by its light curve having a very deep
primary minimum, and pulsating character of its primary component, but also by the complex behavior of its O–C curve which is featured by the presence of long and short time scale modulations. Taking into account the previously inferred
K spectral type of the secondary component, one may expect that one of the involved periodicities could be related to magnetic
cycles of this star. We gave the Wilson-Devinney solution of the eclipse light curve using our observational data obtained
during 2009. The long- and short-term photometric variability of Y Leo is approached both through literature data and new
CCD data. Even though these data are scarce, they revealed significant variability in the maximum and minimum brightness of
this binary system at long time-scale. The nature of the rapid photometric variations during the deepest phase of primary
minima can hardly be explained only by weak δ Scuti pulsations of the primary component which is still visible in partial eclipses. 相似文献
9.
D. G. Yakin V. F. Suleimanov N. V. Borisov V. V. Shimanskii I. F. Bikmaev 《Astronomy Letters》2011,37(12):845-857
We present the results of our photometric and spectroscopic studies of the new eclipsing cataclysmic variable star 1RXS J180834.7+101041.
Its spectrum exhibits double-peaked hydrogen and helium emission lines. The Doppler maps constructed from hydrogen lines show
a nonuniform distribution of emission in the disk similar to that observed in IP Peg. This suggests that the object can be
a cataclysmic variable with tidal density waves in the disk. We have determined the component masses (M
WD = 0.8 ± 0.22M
⊙ and M
RD = 0.14 ± 0.02M
⊙) and the binary inclination (i = 78° ± 1.5°) based on well-known relations between parameters for cataclysmic variable stars. We have modeled the binary
light curves and showed that the model of a disk with two spots is capable of explaining the main observed features of the
light curves. 相似文献
10.
We present a photometric study of the near contact binary BX And. UBV photometric observations have been carried out in 1996,
1997, 1998 and 2000. The observations made in 1998 and 2000 yielded two complete light curves in each color. The intrinsic
color indices indicate that primary component has a temperature of ∼6690 K corresponding to spectral type of ∼F4.
The photometric mass ratio of the system was well determined. The corresponding light curves were analyzed by Wilson–Devinney
code. From combining the photometric solution with spectroscopic elements, the absolute parameters were determined. Finally,
the position of both components in H–R, M–L, and M–R diagrams are given. 相似文献
11.
Diana Kjurkchieva Dragomir Marchev Tatiana Khruzina Gojko Djurašević 《Astrophysics and Space Science》2006,306(4):217-229
UBVRI photometry and spectroscopic observations around the Hα line of the cataclysmic star UX UMa are presented. The analysis of the 9-year photometry shows that the out-of-eclipse brightness
of the system and the depth of the eclipse changes in different time scales while the width of the eclipse remains constant.
The observed features of the light curves as well as the features of the two-peaked Hα profiles were attributed to an inhomogeneity of the accretion disk. “Spiral arm” model for a fitting of the light curves
of UX UMa is proposed. It reproduces well the observational data. The obtained azimuthal extent of the spiral arms is of ∼90°
and their light contribution is about 17–30of the total V flux of the disk. The obtained two dense structures at the outer
disk covering partially the inner hot disk and the white dwarf at orbital phases ∼0.7 and ∼0.2 is in agreement with the predictions
of the theoretical computations. 相似文献
12.
V2213 Cyg was discovered as a variable star by Pavlenko (1999) in 1998. We present our photometry of V2213 Cyg from 1998–2003
based on CCD observations with the K-380 Cassegrain telescope of CrAO and the 60 cm Zeiss telescope of SAI. Observations have
been carried out mostly in R and sometimes in B and V Johnson system. The total amount of data is 2270 points, covering ∼50 nights. We classify this binary as a W UMa-type contact
system. Using all data we determined the orbital period to be 0.350079 ± 0.000007 day. The mean brightness varies between
R = 14.35 and 14.05. The mean 1999–2003 orbital light curve has two humps and a primary minimum (I), which is 0.04 mag brighter
than the deeper secondary one (II). The mean humps have slightly different height. The difference between two individual maxima
varies within 0.1 mag, which may indicate an activity of the components. The highest hump is an asymmetrical one: it has sort
of a shoulder at phases 0.75–0.80, before entering the less deep primary minimum (phase 0.0). The system is rather reddened,
its colour indices are: B−V ∼ 0.8 and V−R ∼ 0.7, and give a spectral class of V2213 Cyg earlier than K. 相似文献
13.
Elena Pavlenko Kirill Antoniuk Sergei Yu. Shugarov Nataly A. Katysheva Lenie Muzhdabaeva Vyacheslav Mikhajlov 《Astrophysics and Space Science》2005,296(1-4):461-464
We present results of multicolour photometry of the nova-like binary MV Lyr in the years 2002–2003, corresponding to the transition
of the star from its low (V = 17.8) to high (V = 12.3) brightness state. The transition lasted at most 200 days. During the first ∼50 days MV Lyr brightened at the rate
0.06 mag/day, and during the next ∼150 days at the rate 0.01 mag/day. The brightening was accompanied by a blue shift from
0.45 to 0.05 in V−R, interpreted as an increase of the accretion disk contribution to the total light. During the transition MV Lyr displayed
well-known ‘quasi-orbital’ light variations and fast quasi-periodic oscillations with a typical time scale of tens of minutes. 相似文献
14.
The eclipsing binary NN Vir is a short period system showing an EW-type light curve. Photometric observations of NN Vir were
done by Gomez–Ferrellad and Garcia–Melendo (1997) at Esteve Duran Observatory. The first spectroscopic observations of this
system were obtained by Rucinski and Lu (1999). The radial velocity and light curves analysis was made with the latest version
of the Wilson program (1998), and the geometric and physical elements of the system are derived. From the simultaneous solutions
of the system, we determined the masses and radii of the components: 1.89 M
⊙ and 1.65 R
⊙ for the primary component; 0.93 M
⊙ and 1.23 R
⊙ for the secondary component. We estimated effective temperatures of 7030 K for the primary and 6977 K for the secondary component. 相似文献
15.
L. V. Tambovtseva 《Astrophysics》2008,51(2):218-225
A model of a young binary system with companions of unequal mass whose orbital plane is inclined at a large angle to the line
of sight is examined. The system components are assumed to accrete matter from the remains of the protostellar cloud. It is
found that eclipsing of the primary component by the disk wind of the secondary can be observed when the plane of the orbit
is inclined at a large angle to the line of sight or even when the binary system is observed pole-on.
__________
Translated from Astrofizika, Vol. 51, No. 2, pp. 267–275 (May 2008). 相似文献
16.
U. Mukherjee H. Raichur B. Paul S. Naik N. Bhatt 《Journal of Astrophysics and Astronomy》2006,27(4):411-423
We report here results from detailed timing and spectral studies of the high mass X-ray binary pulsar 4U 1538-52 over several
binary periods using observations made with the Rossi X-ray Timing Explorer (RXTE) and BeppoSAX satellites. Pulse timing analysis
with the 2003 RXTE data over two binary orbits confirms an eccentric orbit of the system. Combining the orbitial parameters
determined from this observation with the earlier measurements we did not find any evidence of orbital decay in this X-ray
binary. We have carried out orbital phase resolved spectroscopy to measure changes in the spectral parameters with orbital
phase, particularly the absorption column density and the iron line flux. The RXTE-PCA spectra in the 3–20 keV energy range
were fitted ∼6.4 keV, whereas the BeppoSAX spectra needed only a power law and Gaussian emission line at ∼6.4 keV in the restricted
energy range of 0.3–10.0 keV. An absorption along the line of sight was included for both the RXTE and BeppoSAX data. The
variation of the free spectral parameters over the binary orbit was investigated and we found that the variation of the column
density of absorbing material in the line of sight with orbital phase is in reasonable agreement with a simple model of a
spherically symmetric stellar wind from the companion star. 相似文献
17.
In addition to the detection of an asteroid moon or a binary asteroid, the knowledge of the satellite’s true orbit is of high importance to derive fundamental physical parameters of the binary system such as its mass and to shed light on its possible formation history and dynamical evolution (prograde/retrograde orbit, large/small eccentricity or inclination, etc.). A new methodology for preliminary orbit determination of binary asteroids – and visual binaries in general – is proposed. It is based on Thiele–Innes method combined with a ‘trial and error’ Monte-Carlo technique. This method provides the full set of solutions (bundle of orbits, with the 7 orbital elements) even for a reduced number of observations. The mass is a direct by-product of this orbit determination, from which one can next infer the bulk-density and porosity. In addition to the bundle of orbits, the method provides the marginal probability densities of the foreseen parameters. Such error analysis – since it avoids linear approximation – can be of importance for the prediction of the satellite’s position in the plane-of-sky during future stellar occultations or subsequent observations, but also for the analysis of the orbit’s secular evolution. After briefly describing the method, we present the algorithm and its application to some practical cases, with particular emphasis on asteroids binaries and applications on orbital evolution. 相似文献
18.
A. V. Meshcheryakov M. G. Revnivtsev M. N. Pavlinsky I. Khamitov I. F. Bikmaev 《Astronomy Letters》2010,36(10):738-751
The variability of the optical and X-ray fluxes from the binary GS 1826-238 is investigated. An epoch-folding analysis of
the optical data obtained with the RTT-150 telescope in 2003–2004 has revealed periodic brightness variations in the source
with a period P
orb = 2.24940 ± 0.00015 h with a high statistical significance. When estimating the detection significance of the periodic signal,
we have specially taken into account the presence of a powerful aperiodic component (“red noise”) in the source’s brightness
variability. The source’s power density spectra in the frequency range ∼10−5–0.01 Hz have been obtained. We have detected a statistically significant break in the power density spectrum of GS 1826-238
at a frequency ν
br ≈ (8.48 ± 0.14) × 10−5 Hz in both optical and X-ray energy bands. We have estimated the orbital period of the binary GS 1826-238 using the correlation
between the break frequency in the power density spectrum and the orbital period of binaries, P
orb ∝ 1/ν
br, found by Gilfanov and Arefiev (2005): P
orb = 3.7 ± 0.8 h and P
orb = 11.3 ± 5.9 h when using Sco X-1 and 1H 16267-273, respectively, as reference sources. It seems to us that the method for
estimating the orbital periods of low-mass X-ray binaries using the correlation P
orb ∝ 1/ν
br may turn out to be very promising, especially for persistent low-luminosity X-ray binaries. 相似文献
19.
Multicolor photometric data are presented for the asynchronous polar V1500 Cyg during 2000–2009, i.e., 23–35 years after its
outburst. Some examples of individual light curves of the system are shown. An analysis of these reveals large variations
in its brightness and color with the phase of the orbital period owing to a “reflection effect” caused by reradiation from
the side of the red dwarf facing the hot white dwarf and heated by its hard ultraviolet radiation. The variations in the O-C
residuals and in the maximum intensity with the phase of the synodic period are illustrated. It is found that the amplitude
A of the orbital fluctuations increases in proportion to the intensity I at a rate dA/dI=0.64. This behavior of V1500 Cyg
is most likely caused by periodic shading of the illuminated part of the red dwarf, where the degree of shading depends on
the phase of the synodic cycle. 相似文献
20.
UBV photometry of HR 1099 obtained during the 1979-80 and 1980-81 observing seasons is presented. An analysis of the available
data shows that the brightness at the light curve maximum increases as the wave amplitude increases, while the brightness
at the light minimum remains almost the same. In terms of the starspot model it implies that there is always a hemisphere
of the active component that is nearly ’saturated’ with spots and that spots occupy a larger fraction of the stellar surface
when the wave amplitude is smaller. The continuous migration attributed to the photometric wave by various authors is far
from certain. The amplitude of the wave has a sharp rise followed by slow decay with a period around 5–6 yr. It is found that
the two-spot model proposed by Dorren and Guinan (1982) is inadequate to describe all the observed photometric peculiarities
of HR 1099. 相似文献