共查询到20条相似文献，搜索用时 31 毫秒
1.
A. E. Rosenbush 《Astronomische Nachrichten》1995,316(4):213-223
The results of photometry and polarimetry of the R Coronae Borealis type stars and other interesting objects are given. The observation of the former objects are obtained at the light maximum or at a brightness lower by 2-3 mag. The polarization of R CrB stars at light maximum has interstellar origin. The absolute magnitude of V 854 Cen is estimated to Msvw = −3m, and for Y Mus it is Mv > −3m.7. ρ Cas has a variable polarization and is probably a giant (Mv ≅ 0m) rather than a supergiant. Many early stars in its surroundings are photometrically and polarimetrically variable. The protoplanetary star BD −0°3679 has a polarization with the Rayleigh component. 相似文献
2.
N. D. Melikian 《Astrophysics》1996,39(4):321-326
The results of polarimetric observations of long-period Mira variables obtained over the past 30 years at the Byurakan observatory are presented. Analysis of these observations shows that there is a real correlation between the degree of light polarization and the brightness of these stars. The maximum degree of polarization is observed at the middle of the ascending branch of the light curve. The degree of polarization is correlated with the period of brightness variation. The average degree of polarization of Mira stars increases with an increase in their period up toP=380 days.Translated fromAstrofizika, Vol. 39, No. 4, pp. 541–551, November, 1996. 相似文献
3.
In an attempt to discover planetary eclipses, we observed the open cluster NGC 7086. On one night we observed the cluster and standard stars through the B and V filters, enabling us to make a colour-magnitude diagram. Plots of the differential magnitudes were inspected for variability, but no planetary eclipses were found. New variable stars were discovered and their light curves show some of them to be eclipsing binary stars. The location on the colour-magnitude diagram of some of the variable stars is consistent with cluster membership. 相似文献
4.
Observations of 35 long-period variables have been done mainly at the Byurakan Astrophysical Observatory during the last years.
A polarimetric monitoring of 34 stars has been carried out with simultaneous photometric measurements for some of them. Photometric
data in the UBVR bands have been obtained for the star Y Ori, which is the faintest one. The results show that the degree
of light polarization is correlated with the period and brightness of these stars. This indicates that the degree of light
polarization is connected with the mass loss as well. Finally the photoelectric observations of the stars Y Ori, T Cep, R
Gem, and R Boo show a short-term increase of their brightness in the decreasing branch of their light curves. The measured
(U-B) or (B-V) colors of detected rapid variations are bluer than the colors of the star measured before these events. It
is supposed that the change of polarization with time, the relatively blue colors of miras near their minimum brightness,
and the colors of detected rapid variations may be explained by the influence of a invisible blue companion, as in the case
of the star R Aqr.
Published in Astrofizika, Vol. 42, No. 3, pp. 341–350, July–September, 1999. 相似文献
5.
Based on analysis of photometric, colorimetric, and polarimetric data, we show that red variable stars of high luminosity are divided with respect to their period of brightness variation into two groups: I) binary stars with periods larger than 480 days; II) single stars with periods less than 480 days. The binary stars exhibit: a) large correlation coefficients between the V-band brightness variation and the U-B, B-V colors; b) comparatively smaller U-B colors (< 1.
m
5);c)strong variability of polarization parameters. Based on this division, we suspect that the star PZ Cas is a binary.Translated from Astrofizika, Vol. 37, No. 2, pp. 235–244, April–June, 1994.In conclusion, the author wishes to express deep gratitude to professor L. V. Mirzoyan for valuable comments. 相似文献
6.
N. D. Melikian 《Astrophysics》1999,42(4):408-418
Based on an analysis of light curves of 223 long-period variables of the Mira Ceti type, recorded using the HIPPARCOS space
telescope, it is shown that all the light curves of these stars can be divided by outward form into two groups: stars exhibiting
simple light curves of sinusoidal shape and stars with complicated light curves, with hump-shaped formations on the ascending
branch of the curve. Some observational parameters of the investigated stars display a tendency to separation into groups
of stars with complicated and simple light curves. Stars with complicated light curves have longer periods, they are brighter
in absolute bolometric magnitude, and there is a greater probability of detecting polarization in their light.
Translated from Astrofizika, Vol. 42, No. 4, pp. 541–554, October–December, 1999. 相似文献
7.
Fifteen Be, 5 Bn, and 1 B stars were monitored during 10 nights in March–April 1988 by means of photoelectricubvy photometry. At least 80% of the Be stars were found variable. Tentative periods between 0.3 and 4.3 days were derived for 13 stars of our entire sample. In all cases the stars are bluest when brightest. Variations in B0-B5e stars are, in average, of larger amplitude than in B5-B9e stars. Bn stars show, in general, variations of smaller amplitude than Be stars. We discuss these results in terms of the current models on short-term photometric variability. In addition, from the observed period distribution we deduce the existence of intrinsically slow Be rotators. We propose the rotation of slightly displaced poles of a weak global dipolar magnetic field as responsable for the rapid periodic light variations.Based on observations obtained at the European Southern Observatory, La Silla, Chile. 相似文献
8.
U, B, andV observations of RZ Eri have been reported. Colours of comparison stars BD-10°994, BD-10°996 and of the variable RZ Eri have been presented. The observations of RZ Eri do not indicate the distortion wave in the light curve beyond observational scatter. 相似文献
9.
With the advent of surveys generating multi-epoch photometry and the discovery of large numbers of variable stars, the classification of these stars has to be automatic. We have developed such a classification procedure for about 1700 stars from the variable star catalogue of the All-Sky Automated Survey 1–2 (ASAS 1–2) by selecting the periodic stars and by applying an unsupervised Bayesian classifier using parameters obtained through a Fourier decomposition of the light curve. For irregular light curves we used the period and moments of the magnitude distribution for the classification. In the case of ASAS 1–2, 83 per cent of variable objects are red giants. A general relation between the period and amplitude is found for a large fraction of those stars. The selection led to 302 periodic and 1429 semiperiodic stars, which are classified in six major groups: eclipsing binaries, 'sinusoidal curves', Cepheids, small amplitude red variables, SR and Mira stars. The type classification error level is estimated to be about 7 per cent. 相似文献
10.
Multicolor photometric and polarimetric observations of the eclipsing binary EK Cep at the Crimean Astrophysical Observatory
in 1995 and 2006–2007 are reported. Polarimetric observations were made of stars in the neighborhood of EK Cep. It is shown
that the observed linear polarization of EK Cep is determined by a variable circumstellar constituent, as well as by the interstellar
component. Various possible mechanisms for formation of the intrinsic polarization of binary stars are discussed.
Translated from Astrofizika, Vol. 52, No. 1, pp. 117–126 (February 2009). 相似文献
11.
《New Astronomy》2013
CCD time-series photometric observations are presented for the stars in the fields of the open clusters NGC7209, NGC1582 and Dolidze 18 in Johnson V, together with some photometric observations in R, and B. The results reveal 14 variable stars in the three clusters in total, among which 13 are newly-discovered variables. With color–magnitude diagrams and color–color diagram, memberships of the variable stars are estimated. With the derived light curves, scales of time and amplitude of variability of these variable stars are obtained. Together with the spectral types due to the estimation of color temperatures, possible types of the variable stars are preliminarily discussed. 相似文献
12.
J. L. Christiansen A. Derekas L. L. Kiss M. C. B. Ashley S. J. Curran D. W. Hamacher M. G. Hidas M. R. Thompson J. K. Webb T. B. Young 《Monthly notices of the Royal Astronomical Society》2008,385(4):1749-1763
We present a new catalogue of variable stars compiled from the data taken for the University of New South Wales Extrasolar Planet Search. From 2004 October to 2007 May, 25 target fields were each observed for one to four months, resulting in ∼87 000 high-precision light curves with 1600–4400 data points. We have extracted a total of 850 variable light curves, 659 of which do not have a counterpart in the General Catalogue of Variable Stars, the New Suspected Variables catalogue or the All Sky Automated Survey southern variable star catalogue. The catalogue is detailed here, and includes 142 Algol-type eclipsing binaries, 23 β Lyrae-type eclipsing binaries, 218 contact eclipsing binaries, 53 RR Lyrae stars, 26 Cepheid stars, 13 rotationally variable active stars, 153 uncategorized pulsating stars with periods <10 d, including δ Scuti stars, and 222 long period variables with variability on time-scales of >10 d. As a general application of variable stars discovered by extrasolar planet transit search projects, we discuss several astrophysical problems which could benefit from carefully selected samples of bright variables. These include (i) the quest for contact binaries with the smallest mass ratio, which could be used to test theories of binary mergers; (ii) detached eclipsing binaries with pre-main-sequence components, which are important test objects for calibrating stellar evolutionary models and (iii) RR Lyrae-type pulsating stars exhibiting the Blazhko effect, which is one of the last great mysteries of pulsating star research. 相似文献
13.
Bai Jian-yong Han Jin-lin Gao Xu-yang Wang Chen Zhang Li-yun 《Chinese Astronomy and Astrophysics》2013
We have performed radio polarization observation experiments of the stars V772 Her and β Per with the Urumqi 25 m radio telescope at the 6 cm waveband, and obtained light curves of the stars after data processing and calibration. A radio ?are from the star V772 Her was detected on 2011 April 13. The degree of linear polarization of this ?are is about 30%, and the polarization angle is about 4°. We have detected also the slowly-varying component of the radio radiation from β Per, as well as a short ?are superposed on it, which has a very weak linear polarization. 相似文献
14.
Linear polarization of radiation emitted by tidally distorted stars as a function of the binary system phase is computed, taking into account true absorption and the scattering of light on free and bound electrons within hot stellar atmospheres. Computations are made both for the linear distribution of true sources across the atmospheres and for radiative-stable model atmospheres presented by Kurcuzet al. (1974) and Kurucz (1979). Polarization variability was investigated as a function of wavelength . In a number of cases, polarization variability was found to be at an observable level. The most marked variability was expected in the ultraviolet range adjacent to the boundaries of the spectral series for H and He. Near the Lyman limit of approximately =912 Å for stars with an effective temperatureT
eff35 000 K and near the ionization boundary for HeII 226 Å for stars withT
eff>35 000 K, the amplitude of polarization variability is greater than in the case of pure electron atmospheres, sometimes reaching the level of 0.5–1%. For fairly long waves where the limb-darkening coefficient falls below a certain critical valueu
cr0.5, the plane of polarization is found to be turned by 90° as compared to the case of a pure electron atmosphere. For limb-darkening coefficients far from the value ofu
cr; the form of the polarization phase curves, as well as dependence on the parameters of a binary system, remain approximately the same as those in the case of pure electron scattering. 相似文献
15.
The properties of such phenomena as the appearance of humps at the ascending branch or double peaks in the light curve of
long-period pulsating stars are examined. The characteristics of humps and the average light curves are obtained for a group
of Mira-type stars and semiregular (SRa) variable stars. Correlations between the parameters of the light curves and the characteristics
of the humps for these stars are discussed. The results obtained here are compared with published theoretical models.
__________
Translated from Astrofizika, Vol. 50, No. 1, pp. 99–105 (February 2007). 相似文献
16.
We look for high‐amplitude variable young stars in the open clusters and associations of the Orion Belt. We use public data from the ASAS‐3 Photometric V ‐band Catalogue of the All Sky Automated Survey, infrared photometry from the 2MASS and IRAS catalogues, proper motions, and the Aladin sky atlas to obtain a list of the most variable stars in a survey area of side 5° centred on the bright star Alnilam (ε Ori) in the centre of the Orion Belt. We identify 32 highly variable stars, of which 16 had not been reported to vary before. They are mostly variable young stars and candidates (16) and background giants (8), but there are also field cataclysmic variables, contact binaries, and eclipsing binary candidates. Of the young stars, which typically are active Herbig Ae/Be and T Tauri stars with Hα emission and infrared flux excess, we discover four new variables and confirm the variability status of another two. Some of them belong to the well known σ Orionis cluster. Besides, six of the eight giants are new variables, and three are new periodic variables (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
17.
18.
The degree of polarization of light from stars in 44 O B associations as a function of interstellar absorption is investigated. It is shown that the character of the dependence of P on A
V for stars in associations and stars not in associations depends on the value of A
V: for A
V 2
m
.5 it has a linear character and is the same for both groups of stars. For A
V > 2
m
.5 the dependence of P on A
V for stars in and not in associations departs from linearity and for A
V = 4
m
.5 it reaches P
ass = 1.8% and P
nonass = 1%, respectively. Such a difference is explained by the additional depolarization in stellar associations. Such strong depolarization in associations may be due to the overall magnetic field of the Galaxy and to physical peculiarities in the association itself. 相似文献
19.
We have measured polarization of the 1.1 mm and 0.8 mm continuum emission for 3 pre-T Tauri stars and 2 T Tauri stars. Positive detections were made for NGC 1333 IRAS 4 and IRAS 16293-2422, while L1551 IRS 5 and HL Tau were only marginally detected. For GG Tau we measured a 2 upper limit of 3%. The polarization is interpreted in terms of thermal emission by magnetically aligned dust grains in circumstellar disks or envelopes. We have found a definite geometrical relation between the polarization and other circumstellar structure. 相似文献
20.
Regina E. Schulte-Ladbeck 《Astrophysics and Space Science》1994,221(1-2):347-356
I review polarimetric observations of presumably single, hot, luminous stars. The stellar types discussed are OB stars, B[e] supergiants, Luminous Blue Variables (LBV), Wolf-Rayet (W-R) stars, and type II supernovae (SN). It is shown that variable, intrinsic polarization is a common phenomenon in that part of the Hertzsprung-Russell (HR) diagram which these stars occupy. However, much observational work remains to be done before we can answer the most basic, statistical questions about the polarimetric properties of different groups of hot, luminous stars. Insight into the diagnostic power of polarization observations has been gained, but cannot be exploited without detailed models. Thus, while polarimetric observations do tell us that the mass-loss processes of all types of massive stars are time-dependent and anisotropic, the significance that this might have for the accuracy of their stellar parameters and evolutionary paths remains elusive. 相似文献