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1.
In the present work we have presented and analysedB andV light curves and the (B-V)-colour curve of the short period (RS CVn type) binary system UV Psc, and derived absolute information from the available data.x 2 minimization procedures were utilized to a large extent in fitting light and colour curves.The solutions show the binary to be at a distance of about 90 pc with two detached components which are close to the main sequence (G2 and K0). The inclination of the orbit is close to 90°Photometric irregularities present in the light curve are briefly considered in relation to current ideas on RS CVn systems, and the colour information indicates a locally hotter (rather than cooler) region is responsible for the irregularities.  相似文献   

2.
We present photoelectric photometry of this bright long-period RS CVn binary and use it, along with earlier photometry, to derive the photometric period and discuss the changing light curve shape. The best ephemeris for times of minimum light is 2443829.2+53.d95E. Because times of minimum and maximum extending back to those of Calder in 1933–37 can be phased together properly, the principal dark region must have maintained its identify for almost 50 yr. Over the last five years the brightness range has been 3 m .70<V<4 m .05. During 1980–81 shallow secondary minima developed at phases where maxima occurred in previous years. λ And remains the only wellestablished case of non synchronous rotation among the known RS CVn binaries.  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.
Investigating more than 270 nightly mean magnitudes of the long-period RS CVn binary HK Lac, we can draw some conclusions about the nature of its complicated light variations. The mean brightness, the apparent photometric period, and the shape of the light curve all show strong variations. Analysis with a starspot model, assuming two large spots and a general uniform spottedness, indicates two comparably large spots which appear to have maintained their separate identities for the last 15 yr and drifted in longitude separation from each other smoothly by only about 45°. The phase of the two spots indicates both are rotating very nearly synchronously with the orbital motion, one slightly (0.025%) faster and the other slightly (0.080%) slower. the latitudes of the two spots, one farther above the equator and one closer to the equator, are consistent with solar-type differential rotation and yield an estimate of 25±12° for the co-rotating latitude. A correlation between mean spot latitude and instantaneous photometric period yields another estimate of 31±2°, in agreement with the first.  相似文献   

5.
A study of the relationship between soft X-ray luminosity and Hei 10830 equivalent width in RS CVn binaries and very active late-type Main-Sequence stars is made. Long-period RS CVns and very active F and G Main-Sequence stars show strong dependence on their X-ray luminosities. This is attributed to the dominance of coronal excitation of the line in these stars. Short-period RS CVn binaries have lower Hei 10830 absorption compared to their X-ray emission. This phenomenon is explained by the presence of Hei emission region also in their chromospheres.On leave from Indian Institute of Astrophysics, Bangalore, India.  相似文献   

6.
We give the results of our J, H, K photometry on 41 RS CVn systems and the data on 40 RS CVn systems identified with IRAS point sources. For those systems in which the components have individual spectral types, we discuss their infrared color excess. We found only very few systems showed infrared excesses. (UX Ari, Z Her and HR 1099 in the near infrared and SZ Psz at 12μm).

For systems having fluxes at 12 and 25μm and K magnitudes, we plotted a color-color diagram and found the majority of points to be lying close to the black body line. These observations are in conflict with Biermann and Hall's statement [1] that infrared excess is a general characteristic of RS CVn systems.  相似文献   


7.
The problem of ionization for magnesium and radiation field in k and h MgII doublet in common envelopes – roundchroms – formed around the RS CVn type systems is examined. It is shown that: a) The roundchroms are completely opaque in the lines of k and h MgII doublet; b) F, G or K type cool stars as secondary in such binaries ensure the complete ionization of magnesium atoms within the whole volume of roundchrom; c) The density of k and h MgII doublet radiation field in the main volume of roundchrom is extremely high, on four-five orders of magnitude, than is derived for its outer boundary. These results have direct relation to the observed saddle-like and very broad shapes of k and h MgII emission lines in the spectrum of RS CVn type close binaries. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

8.
For 37 components belonging to 31 RS CVn binary systems, we measured the rotation using Reticon data on the 2.1 McDonald Reflector. Combining our previous data for 38 components, we made a statistical analysis on the question of synchronous rotation. Our results show that, while the great majority show synchronous rotation, exceptions are found in all period groups, contradicting the generally held view that all short period and normal period RS CVn stars have synchronous rotation and all long period ones do not.  相似文献   

9.
Due to the extensive photoelectric observations made at the Ege University Observatory in 1988, we have found no evidence for any eclipse in the light curve of this newly classified RS CVn system V775 Her. The shapes and behaviour of the light curves obtained at different time intervals clearly suggest the existence of a migrating wave, which is typical of that seen in most RS CVn binaries. The amplitude of the wave-like distortion seems to be slightly less than 0.1 mag. The migration period for the wave-like distortion is roughly found to be between 8 and 10 months.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.  相似文献   

10.
We made polarization measurement on 30 RS CVn systems using the Berger polarimeter of McDonald Observatory in July-December 1984, of which 26 systems were measured for the first time. The results are given here. They show that for most RS CVn systems, the optical linear polarization is weak, generally below 0.45%, averaging about 0.20%. Some systems, like AR Lac, HR 5110, HD 8357, HK Lac, HR 7275 and HR 7428 have polarization above 0.03%, which showed time variations by factors between 10 and 30. For HD 8357 and ER Vul, there is a clear connection between the polarization and the orbital phase.  相似文献   

11.
Spectrophotometric observations of the RS CVn binary UX Arietis have been presented. The comparison of the observed fluxes with model atmospheres indicates that during the four phases observed, the temperature does not vary significantly. However, brightness variation of 0 m .23 are thought to be due to change in the surface emitting regions.  相似文献   

12.
Infrared observations in the J, H, and K bands were made on eleven RS CVn systems. Infrared (IR) excess 0.3 mag in the J, H, and K bands was observed from the three systems UX Ari, HR 1099 and CrB. Similar observations were also made on the RS CVn candidates HD 26354, 39937, 42449, 51268, and 86005.The IR excess in the RS CVn systems for which near infrared photometric data are available is found to be correlated with the maximum of optical wave amplitude of these systems.The observed excess cannot be explained on the basis of a single process such as: (i) emission from cool spots on the photosphere; (ii) free-free emission from an optically thin circumstellar plasma; or (iii) dust grain emission from circumstellar material.On leave from TIFR, Bombay, India.  相似文献   

13.
We present multifrequency observations of the active binary RS CVn. Ultraviolet observations were obtained from the IUE data bank. Optical observations were made at the Observatorio del Roque de los Muchachos (La Palma), while the infrared observations were obtained at the Observatorio del Teide (Tenerife).The continuum of RS CVn shows that both components behave in good agreement with normal values for their spectral type and luminosity class, when observed data are corrected for small spot effects. No significant circumstellar reddening is detected.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.  相似文献   

14.
We correct the correction brought by Bartoliniet al. (1982) to the identification of the star BD+37° 442.  相似文献   

15.
HD 201270/1 is a composite-spectrum binary whose components have spectral types close to G8 III and A2 V. They are in a circular orbit with a period of only 40 days. Photometric variability of RS CVn character is therefore not unlikely  相似文献   

16.
Differential BVR photometric observations of the three RS CVn binary stars: V711 Tau, UX Ari and IM Peg obtained during the period November 26, 1994–February 24, 1995 using the 0.35 m reflector telescope equipped with photoelectric photometer are presented. Analysis of light curves shows significant changes in shape, amplitude as well as the phases of minimum light of all the three binaries. The amplitude of IM Peg, in particular, is found to have reached a larger value in the present epoch of observation than reported earlier.  相似文献   

17.
We discuss representative cases of X-ray spectra of active stars obtained with ASCA and BeppoSAX. We focus in particular on our own observations of the RS CVn binaries γ And and UX Ari, of the BY Dra eclipsing binary HD9770, and of the young stars AB Dor and HD35850. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

18.
我们用美国McDonald天文台2.1米反光镜Coude Reticon观测,对31个RS CVn型双星系统的37颗子星的自转进行了测量。并结合以前测得的38颗子星的数据,对RS CVn型星是否同步作了统计分析,结果表明,绝大多数都显示出同步自转性质;但无论是短周期、正常周期还是长周期组的,都有少数与同步自转不一致的例子。这与过去认为短周期和正常周期的呈同步自转,而长周期的呈非同步自转的结论不一致。  相似文献   

19.
Complete infraredJ andK light curves of the RS CVn system XY UMa have been obtained at the beginning of 1989. We point out some interesting morphological changes observed in these light curves.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.  相似文献   

20.
Photoelectric photometry has been obtained for CF Octantis on 39 nights. The object is a member of the RS CVn class and has a highly active chromosphere. A 20.15 ±0.06 d period has been found from theB andV magnitudes, which is interpreted as the rotational modulation of the light from a non-uniformly spotted star. The amplitude of this spot wave is observed to vary slowly between ΔV about 0m.l and 0m.3, which may be evidence for an activity cycle of 9 ±3 years.  相似文献   

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