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1.
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
2.
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
3.
HD 115781 and HD 116204 (BL CVn and BM CVn) are shown to be RS CVn binaries with periods near 20 days. HD 115781 is double-lined;
the primary type is about K1III, while the secondary is probably a late-type subgiant. The masses of the two components are equal within observational error.
There is substantial photometric variability with a period half the orbital period; it is attributed to ellipsoidal variation.
HD 116204 is also of type K1III. It shows exceptionally strong Ca II H and K emission, together with an emission-line spectrum typical of RS CVn stars in
theIUE ultraviolet region, but Hα is an absorption line. The secondary star in the HD 116204 system has not been detected. The primary
shows photometric variations, presumably due to starspots, with a period 5 per cent longer than the orbital period. 相似文献
4.
C. V. S. R. Sarma M. B. K. Sarma N. B. Sanwal 《Journal of Astrophysics and Astronomy》1989,10(3):307-346
The extensiveUBV observations of SV Camelopardalis by Patkos (1982) have been analysed to derive the orbital elements of the system. The data
were corrected for the effect of third body (Sarma, Sarma & Abhyankar 1985) and for the ‘RS CVn’ distortion wave (Sarma, Vivekanandarao
& Sarma 1988). The cleaned data were used to obtain a preliminary solution by a modified version of Wellmann method (Sarma
& Abhyankar 1979) from which we concluded that the primary eclipse is a transit. The final orbital elements of SV Cam were
obtained by the modified version (Sarma 1988; Sarmaet al. 1987) of WINK program by Wood (1972). The colour and median brightness variation are discussed. From the spectroscopic mass
functionf(m) = 0.118 M⊙ (Hiltner 1953), the absolute dimensions of the components are found to be 0.826 Mbd & 0.592 M⊙ and 1.236 R⊙ & 0.778 R⊙ for the primary and secondary components, respectively. The age of the binary system is estimated to be 6.0 ± 1.0 × 108 years 相似文献
5.
Douglas S. Hall Gregory W. Henry Dietmar Böhme Peter A. Brooks Sandy Chang Ales Dolzan George L. Fortier Robert E. Fried Russell M. Genet Bruce S. Grim James Hannon Darrel B. Hoff Kevin Krisciunas Howard J. Landis Howard P. Louth Larry P. Lovell Paul Nielsen Bobby E. Powell Harry D. Powell Don Pray Thomas R. Renner Charles W. Rogers Stephen Shervais Douglas M. Slauson Samuel Slote Harold J. Stelzer Arthur J. Stokes Jack C. Troeger Louis C. Turner Norman F. Wasson Kenneth W. Zeigler 《Journal of Astrophysics and Astronomy》1991,12(4):281-287
We present photoelectric photometry of λ And never before published, obtained between February 1982 and December 1990 at 29
different observatories. Then we combine it with all other photometry available to us (previously published, contained in
the I.A.U. Commission 27 Archives, and obtained with the Vanderbilt 16-inch automatic telescope but not yet published), to
yield a 14.8-year data base. Analysis reveals a long-term cycle in mean brightness, with a full range of 0m.15 and a period of 11.4 ± 0.4 years. Because most of our new photometry was concentrated in the 1983-84 observing season,
we analyze that one well-defined light curve with a two-spot model. Spot A keeps a 0m.04 amplitude throughout four rotation cycles whereas the amplitude of spot B diminishes from 0m.09 down almost to 0m.03. The spot rotation periods were 55d.9 ± 0d.6 and 520d.8 ± 1d.0, respectively. 相似文献
6.
7.
C. V. S. R. Sarma P. Vivekananda Rao M. B. K. Sarma 《Journal of Astrophysics and Astronomy》1991,12(1):49-67
The light outside the eclipses of the totally eclipsing RS CVn binary SV Camelopardalis (SV Cam) is Fourier analysed and the
amplitudes of the distortion waves have been derived. The distribution of the percentage contributions of these amplitudes
inV, B andU colours with respect to the luminosities of the binary components indicates that the hotter component is the source of the
distortion waves. These distortion waves, attributed to star spots, are modelled according to Budding (1977) and spot parameters
like longitude, latitude, temperature and size are obtained. From this study it is noticed that while symmetric waves with
two minima could be fitted satisfactorily, asymmetric waves with more than two minima could not be fitted well. From the longitudes
of the minima of the best fitted curves, migration periods of four spot groups are determined. Assuming synchronism between
rotation and orbital periods, the rotation periods of the four spot groups are derived from their migration periods. The period
of rotation of one of the spot groups having direct motion is found to be 0d.5934209 while the periods of the other three spot groups having retrograde motion are 0d.5926588, 0d.592607 and 0d.5924688. As the latitudes of these spots are known from modelling parameters, the latitude having a rotation period equal
to that of the orbital period (co-rotating latitude) is found to be about 30° 相似文献
8.
P. Vivekananda Rao M. B. K. Sarma B. V. N. S. Prakash Rao 《Journal of Astrophysics and Astronomy》1991,12(3):225-263
Results of analysis of photoelectric observations of the RS CVn eclipsing binary WY Cancri in the standard passbands ofUBV during 1973-74, 1976-79 and inUBVRI during 1984-86 are reported. A preliminary analysis of the eclipses suggested the primary eclipse to be transit. A study
of the percentage contribution of the distortion wave amplitudes in all the colours with respect to the luminosities of both
components, showed the hotter component to be the source of the distortion wave. The clean (wave removed) light curves of
different epochs have not merged, suggesting residual effects of spot activity. The reason for this is attributed to the presence
of either (1) polar spots or (2) small spots uniformly distributed all over the surface of the hotter component. This additional
variation is found to have a periodicity of about 50 years or more. The distortion waves in yellow colour are modelled according
to Budding’s (1977) method. For getting the best fit of the observations and theory, it was found necessary to assume three
or four spots on the surface of the hot component. Out of these four spot groups, three are found to have direct motion with
migration periods of 1.01, 1.01 and 2.51 years while the fourth one has a retrograde motion with a migration period of 3.01
years. From these periods and the latitudes of the spots derived from the model a co-rotating latitude of 4ℴ is obtained.
The temperatures of these spots are found to be lower than that of the photosphere by about 700ℴK to 800ℴK. Assuming the light
curve of 1985-86, which is the brightest of all the observed seasons, to be least affected by the spots, the light curves
of the other seasons are all brought up to the quadrature level of this season by applying suitable corrections. The merged
curves in theUBVRI colours are analysed for the elements by the Wilson-Devinney method. This analysis yielded the following absolute elements:
相似文献
9.
Padmakar K. P. Singh S. A. Drake S. K. Pandey 《Monthly notices of the Royal Astronomical Society》2000,314(4):733-742
We have carried out BVR photometric and H spectroscopic observations of the star HD 61396 during 1998 March 20 to 1999 April 3. We have discovered regular optical photometric variability from this star, with an inferred period of 31.95±0.10 d, and an amplitude of 0.18 mag. A possible period of 35.34±0.12 d, as determined with Hipparcos , cannot be completely ruled out, however. Modelling of its photometric light curve with two circular spots indicates that 521 per cent of the stellar surface is covered by dark starspots which are 830 K cooler than the surrounding photosphere, and produce the observed rotational modulation of the optical flux. Optical spectroscopy reveals a variable H emission feature, indicating that it is an unusually active star.
In addition, we have analysed archival X-ray data of HD 61396, obtained from serendipitous observations with the ROSAT X-ray observatory, and we also discuss the radio properties of this star, based on both published Green Bank and unpublished VLA observations. The strong photometric variability and H emission, the relatively hard X-ray spectrum, and the high X-ray and radio luminosities imply that HD 61396 is most likely to be a member of the RS CVn class of evolved active binary stars. Its X-ray and radio luminosities place it among the five most luminous active binaries detected so far. 相似文献 10.
G. J. Anders ‡ D. W. Coates ‡ K. Thompson‡ J. L. Innis†‡ 《Monthly notices of the Royal Astronomical Society》1999,310(2):377-386
The Wilson–Devinney program is used to model 27 light curves (our own and others) for CF Tuc. We find new parameters for the binary system, and estimate the longitudes and radii of the spots on the cooler secondary star. We also find a strong tendency for spots on the cooler star to appear in a limited range of longitudes, rather than to migrate fairly rapidly as for other RS CVn systems. There is evidence that the mean light level of the cooler star is varying cyclically.
The orbital period clearly changes discontinuously. We discuss this, and the apparently cyclic variations in mean light level, in relation to the model proposed by Applegate. 相似文献 11.
The eclipsing binary UV Piscium was observed with the standardUBV filters during 1976-77, 1977-78 and 1978-79 observing seasons with the 1.22-m reflecting telescope of the Japal-Rangapur
Observatory. A wave-like distortion on the light curve noticed by Carr (1969), Oliver (1974), Sadik (1979) and Zeiliket al. (1982a) is confirmed by the present observations. Combining our observations with those of Carr, Oliver and Sadik, it is
found that the distortion wave is moving towards decreasing orbital phase with a period of about 1200 days. The source of
the observed distortion wave is found to be the hotter component. 相似文献
12.
I. Yu. Alekseev 《Astrophysics》2005,48(1):20-31
The first results are reported from a search for activity cycles in stars similar to the sun based on modelling their spotting with an algorithm developed at the Crimean Astrophysical Observatory. Of the more than thirty program stars, 10 manifested a cyclical variation in their central latitudes and total starspot area. The observed cycles have durations of 4–15 years, i.e., analogous to the 11 year Schwabe sunspot cycle. Most of the stars have a rough analog of the solar butterfly pattern, with a reduction in the average latitude of the spots as their area increases. A flip-flop effect during the epoch of the maximum average latitude is noted in a number of these objects (e.g., the analog LQ Hya of the young sun or the RS CVn-type variable V711 Tau), as well as a reduction in the photometric rotation period of a star as the spots drift toward the equator, an analog of the differential rotation effect in the sun. Unlike in the sun, the observed spot formation cycles do not correlate uniquely with other indicators of activity— chromospheric emission in the CaII HK lines (Be Cet, EK Dra, Dx Leo), H line emission (LQ Hya, VY Ari, EV Lac), or cyclical flare activity (EV Lac). In V833 Tau, BY Dra, EK Dra, and VY Ari short Schwabe cycles coexist with long cycles that are analogous to the Gleissberg solar cycle, in which the spotted area can approach half the entire area of the star.Translated from Astrofizika, Vol. 48, No. 1, pp. 29–43 (February 2005). 相似文献
13.
14.
UBVRI photometric observations and models of spotting are presented for four noneclipsing RS CVn systems: IN Com (G5III/IV), IL Com (F8V+F8V), UX Ari (K01V+G5V), and V711 Tau (K1IV+G5V). A low amplitude variability caused by cold (T=1700K)spots which can occupy up to 19% of the star's surface is confirmed for the little-studied star IL Com. Long-term light curves are constructed and the stellar magnitudes and color indices of the unspotted photospheres are estimated for IN com, UX Ari, and V711 Tau. It is shown that UX Ari becomes bluer with decreasing brightness, so its variability cannot be fully explained in terms of cold spots. Models of spotting on In Com and V711 Tau are constructed from the full set of available photometric observations. The spots on both of these variables lie at middle latitudes and occupy up to 22% (In Com) and 33% (V711 Tau) of the stars' surfaces. Both stars manifest a tendency for the width of the spots to decrease as their area increases. This is a crude analog of the Maunder butterflies. These stars experience cyclical spot activity and have a differential rotation of the type found on the sun. 相似文献
15.
We discuss the observed orbital period modulations in close binaries, and focus on the mechanism proposed by Applegate relating the changes of the stellar internal rotation associated with a magnetic activity cycle with the variation of the gravitational quadrupole moment of the active component; the variation of this quadrupole moment in turn forces the orbital motion of the binary stars to follow the activity level of the active star. We generalize this approach by considering the details of this interaction, and develop some illustrative examples in which the problem can be easily solved in analytical form. Starting from such results, we consider the interplay between rotation and magnetic field generation in the framework of different types of dynamo models, which have been proposed to explain solar and stellar activity. We show how the observed orbital period modulation in active binaries may provide new constraints for discriminating between such models. In particular, we study the case of the prototype active binary RS Canum Venaticorum, and suggest that torsional oscillations — driven by a stellar magnetic dynamo — may account for the observed behaviour of this star. Further possible applications of the relationship between magnetic activity and orbital period modulation, related to the recent discovery of binary systems containing a radio pulsar and a convecting upper main-sequence or a late-type low-mass companion, are discussed. 相似文献
16.
C. banolu G. Ta E. Sipahi S. Evren 《Monthly notices of the Royal Astronomical Society》2007,376(2):573-579
We present new photometric two-colour observations of the double-lined close binary star VZ CVn. Combining two data sets obtained in 1971–72 and in 2006, the physical parameters of both components were derived. After removing the light variations due to the eclipses and proximity effects, a periodic variation in the more massive component with a dominant period of 1.068 76 d could be detected in the first photometric data set. In accordance with its position on the Hertzsprung–Russell diagram and both its pulsation period and pulsation constant of 0.62 d, the primary component of VZ CVn should be an excellent γ Doradus candidate. The less massive secondary component seems to have smaller radius with respect to its mass. Both components appear to have lower luminosities with respect to their masses; hence, their radiative properties seem to be different. The evolutionary status of the components is also discussed. 相似文献
17.
Mariela C. Vieytes Pablo J. D. Mauas Rodrigo F. Díaz † 《Monthly notices of the Royal Astronomical Society》2009,398(3):1495-1504
We study the differences in chromospheric structure induced in K stars by stellar activity, to expand our previous work for G stars, including the Sun as a star. We selected six stars of spectral type K with 0.82 < B − V < 0.90 , including the widely studied Epsilon Eridani and a variety of magnetic activity levels. We computed chromospheric models for the stars in the sample, in most cases in two different moments of activity. The models were constructed to obtain the best possible match with the Ca ii K and the Hβ observed profiles. We also computed in detail the net radiative losses for each model to constrain the heating mechanism that can maintain the structure in the atmosphere. We find a strong correlation between these losses and S
18.
I. S. Veselovsky A. V. Dmitriev A. V. Suvorova M. V. Tarsina 《Journal of Astrophysics and Astronomy》2000,21(3-4):423-429
The cyclic evolution of the heliospheric plasma parameters is related to the time-dependent boundary conditions in the solar
corona. &#x201C;Minimal&#x201D; coronal configurations correspond to the regular appearance of the tenuous, but hot
and fast plasma streams from the large polar coronal holes. The denser, but cooler and slower solar wind is adjacent to coronal
streamers. Irregular dynamic manifestations are present in the corona and the solar wind everywhere and always. They follow
the solar activity cycle rather well. Because of this, the direct and indirect solar wind measurements demonstrate clear variations
in space and time according to the minimal, intermediate and maximal conditions of the cycles. The average solar wind density,
velocity and temperature measured at the Earth&#x2019;s orbit show specific decadal variations and trends, which are of
the order of the first tens per cent during the last three solar cycles. Statistical, spectral and correlation characteristics
of the solar wind are reviewed with the emphasis on the cycles. 相似文献
19.
Data on the variability of the continuum optical emission are used for the first time to estimate the degree of spotting in
stars with activity levels similar to that of the sun. It is shown that the amount of spotting increases gradually from the
sun to the highly spotted stars for which Alekseev and Gershberg constructed the zonal model for the distribution of spots.
A close relationship is found between spotting and the power of the x-ray emission from stars with widely varying levels of
activity.
__________
Translated from Astrofizika, Vol. 50, No. 2, pp. 233–241 (May 2007). 相似文献
20.
V. V. Neustroev S. Zharikov 《Monthly notices of the Royal Astronomical Society》2008,386(3):1366-1379
We present high- and medium-resolution spectroscopic observations of the cataclysmic variable BF Eridani (BF Eri) during its low and bright states. The orbital period of this system was found to be 0.270881(3) d. The secondary star is clearly visible in the spectra through the absorption lines of the neutral metals Mg i , Fe i and Ca i . Its spectral type was found to be K3±0.5. A radial velocity study of the secondary yielded a semi-amplitude of K
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