共查询到20条相似文献,搜索用时 0 毫秒
1.
R. D. Jeffries 《Monthly notices of the Royal Astronomical Society》1998,295(4):825-833
The short-period, eclipsing, magnetically active binary system XY UMa has been observed over several orbital cycles at X-ray wavelengths. The X-ray light curves vary owing to obvious flares and other lower level activity on time-scales of days. These data caution against deducing coronal structure on the basis of a single orbit of X-ray data. In contrast to similar binary systems, XY UMa shows no significant X-ray eclipses. This is interpreted as evidence for either extended (> 1 R ⊙ ) coronae or a compact corona at high, uneclipsed latitudes on the primary star. The extended coronal scenario is favoured by some observational features of other systems such as extended radio coronae, long-duration X-ray flares and cool prominences, but unfavoured by others such as high coronal densities from EUV spectroscopy. A high-latitude compact corona might be associated with the high-latitude starspots seen in many active stars. Nearly simultaneous optical light curves suggest that some equatorial spots were present at the time of the X-ray observations, but fewer than in previous or subsequent years and that high-latitude spots must also be present. It is speculated that the lack of X-ray eclipses and dearth of equatorial, compact coronal regions are associated with a minimum in XY UMa's magnetic activity cycle. 相似文献
2.
A total of 704 previously published photoelectricB colour observations of the multiple system HR 4560 are analyzed by means of the light curve models NDE (Popper and Etzel, 1981) and WINK (Wood, 1972) in an iterative procedure. As a result, we have found that componentC of the multiplpe system ADS 8347 is the most probable origin of the observed eclipses. Some relevant astrophysical parameters of the component stars which indicate a normal Main-Sequence binary star have also been estimated. 相似文献
3.
《New Astronomy》2020
In this study, photometry was conducted for the W UMa type eclipsing binary BB Peg through V and R Johnson filters during several nights in September and October 2016. The light curves were obtained at Dr. Mojtahedi Observatory, of the University of Birjand, Iran. Data reduction was performed using IRIS software. Orbital parameters were obtained by analyzing the light curves using PHOEBE software. The radial velocity information was then used to obtain the absolute parameters of the system. Some minimum light times were obtained forthe system and variations in the orbital period of BB Peg were analyzed by adding the new minimum light times to the O-C diagram to obtain a new ephemeris for the system. The period change appeared to be due to the light-time effect. A justifiable fit was obtained using the third and fourth stars. However, this fit was not confirmed and it may need revision when further data are obtained. The variation could be attributed to other sources, such as magnetic cycles or non-conservative mass transfer from the system. 相似文献
4.
UBV light curves of AO Cam were analyzed with Wilson and Devinney's model. The system was found to be a contact configuration with a degree of overcontact of 1.4%. The mass ratio of the system is about 1.30, and the inclination is 75
.
0
9. The primary eclipse appears to be an occultation. Thus AO Cam has the characteristics of a W-type W UMa system. Its location in a period-spectral type diagram suggests that the system may be a zero-age contact system. 相似文献
5.
Due to its extreme mass ratio, the system AW UMa is considered as one of the most interesting contact binaries. In the present paper, a total of 1289 observations in VRI band were carried out from on 2006 March 7, 8, and 9 at Piszkesteto, Mountain Station of the Konkoly observatory (Hungary). VRI light curves were constructed and a photometric solution of these light curves was obtained by means of Willson-Devinney code. The results show that the primary component is more massive and hotter than the primary component by ~140 K. A secular period decrease with a rate dP/dE=2.436×10?10 day/cycle was detected. Based on the physical parameters of the system, we investigate the evolutionary state of the components. The primary component is above the zero age main sequence (ZAMS) track, while the secondary component has a larger radius and luminosity than expected from its ZAMS mass. 相似文献
7.
Liu Xue-fu
K. C. Leung
Tan Hui-song
《Chinese Astronomy and Astrophysics》1988,12(4):298-303New UBV photometric observations of IU Aur were made at McDonald Observatory in December 1984 and January 1985, showing that the eclipse depth had kept on increasing and the light minimum time had shown periodic changes. Orbital elements were obtained using the Wilson-Devinney method. The inclination is now close to 90°. The continuous variation of inclination over the last few decades suggests the presence of a third body. Absolute parameters of IU Aur were calculated with the help of Mammano's spectral data. 相似文献
8.
F. Sánchez-Bajo E. García-Melendo J. M. Gómez-Forrellad 《Astrophysics and Space Science》2007,312(3-4):151-159
New ephemeris and the absolute parameters—masses, radii and luminosities—of the contact systems VW LMi and BX Dra have been
obtained, by means of the analysis of the minima data available in the literature (for the determination of the ephemeris)
and combining the previously published spectroscopic information and the results of the Wilson-Devinney method using photometric
data (for the determination of the absolute parameters). The VW LMi O−C analysis confirms the multiplicity of the system detected previously from the spectroscopic data. Masses of the VW LMi contact
system primary and secondary components are 1.67 ± 0.02M
⊙ and 0.70 ± 0.02M
⊙, respectively. The corresponding radii are 1.709 ± 0.007R
⊙ and 1.208 ± 0.006R
⊙, respectively. For the BX Dra contact system the masses are 2.19 ± 0.13M
⊙ and 0.63 ± 0.06M
⊙, and the radii, 2.13 ± 0.04R
⊙ and 1.26 ± 0.03R
⊙, for the primary and secondary, respectively. In both cases, the estimated luminosities seem to be slightly greater that
the values derived from the Hipparcos distances. 相似文献
9.
《Chinese Astronomy and Astrophysics》1982,6(2):167-171
We have obtained photoelectric light cureves in B and V of the eclipsing binary XY Leonis. Comapring our results with those of Koch of 1956, we have found obvious changes in the shape of the light curve. We have obtained one princiapl and two secondary minimum epochs and thereby further confirmed the periodic character in the change in period of this binary. 相似文献
10.
The light curve andU, B andV observations of the system XY Cep have been presented. Photoelectric and absolute elements of the system have been determined. It is a semi-detached system. 相似文献
11.
The absolute elements of the system XY Ceti have been obtained on the basis of the spectroscopic elements given by Popper (1971) and the photoelectric elements derived by us. The colours of the components have been obtained. Both components are found to lie fairly on the Main Sequence. The primary component of the system, however, is slightly more evolved as it shows a tendency to drift away from the Main Sequence. The spectral classes now assigned are A5V (primary) and A7V (secondary). The values of Roche constants indicate that the system is a detached one. 相似文献
12.
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
13.
Photoelectric observations in B and V for the FZ Del system are presented and its light curves are analyzed. Absolute parameters
are obtained. The system shows a near contact subgaint secondary component with a likely K1 spectral type. The O-C curve is
presented and probably a secular orbital period variations is detected on a timescale of about 6.9×106 yrs, suggesting thermal timescale mass transfer. A new light elements for the system have been obtained. The system can be
considered as an early stage of conservative case of mass transfer.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
14.
Sixty-one blue spectrograms of TX UMa were obtained in the years 1969–1970, mainly in phases close to the primary minimum of the eclipsing system. The radial velocity curve displays clear rotational effect from which much higher than synchronous rotational velocity of the blue (B8V) component has been formally derived. However, this discrepancy is probably due to the presence of the tenous accretion disk around the primary. The disk is apparently fed by the intermittent mass transfer as indicated by the occasional changes of orbital period of the system. From all available radial velocity data an improved set of spectroscopic orbital elements is derived. The behaviour of the spectral lines in and out of the primary minimum is compared. Metallic lines of the cold (F7IV) secondary component are clearly seen exclusively in phases 0.988 to 0.012.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
15.
Three color photoelectric observations of the close binary system XZ Cep at the Abastumani Astrophysical Observatory are reported.
These data cover the entire light curve and represent, up to now, the best and most extensive observations of this star. The
positions of the components of XZ Cep on a mass-log g diagram show that it is in a phase following a rapid transfer of mass.
The theoretical light curves are not fully consistent with the observed curves at phases of 0.35-0.40 and 0.6-0.9. This is
evidently because of the influence of gaseous flows in the system. The existence of circumstellar matter and gas flows at
phases of 0.7-0.9 are also confirmed by spectral data and by changes in the intrinsic polarization of XZ Cep. In addition,
a polarimetric study of the star indicates that two or more interstellar clouds with different properties lie between XZ Cep
and us. A detailed study of the photoelectric data presented here is also extremely interesting for the confirmation of the
latter idea. 相似文献
16.
DifferentialUBV observations of the small amplitude (0.12 mag inV) single-lined active binary V350 Lac are presented. It was observed that the light minima occur in conjunction time. A shift of the light curve (0.05 in orbital phase) towards lower phases could be due to a small error in the light elements. The primary minimum is about 0.04 mag deeper than the secondary. It was shown that different depths of two light minima are not produced by the reflection effect but due primarily to gravity darkening on the tidally elongated and synchronously rotating visible component. An O'Connel effect observed as the brighter primary maximum could be an indication of starspot activity or gas streaming between the components. 相似文献
17.
Ö. L. Deĝirmenci Ö. Gülmen C. Sezer N. Güdür A. Erdem 《Astrophysics and Space Science》1996,241(2):327-332
Photoelectric B and V light curves of the eclipsing binary V1425 Cygni were analyzed by the method of Wilson-Devinney. The system was found to be a semi-detached binary where the secondary component (less massive and cooler) fills its Roche lobe. 相似文献
18.
In this paper, we give theBV photoelectric light curves of the Algol-type eclipsing binary EU Hydrae. We have analysed its period by means of the times of minima determined from this observation and the times of minima which other observers published. The period was found to gradually decrease with a change rate dP/dE = -3
.
d
29 × 10–10. The obtained light curves have been solved using Wilson-Devinney's synthetic light-curve program. The results demonstrate that EU Hydrae is a detached system, the secondary component fills the Roche-lobe, its mass ratio is 0.205. EU Hya may evolve to be a semidetached system in which the secondary component fills the Roche-lobe. 相似文献
19.
《New Astronomy》2016
The present study is an analysis of V-band CCD observations of new W UMa contact binary OQ Dra. To carry out the analysis, Primary and secondary minimum were obtained and new epoch was calculated. The computed period of system was 0.33967 day. Light curve analysis was performed using Binary Maker 3 and PHOEBE that uses the latest Wilson–Devinney code. We obtained photometric mass ratio of qptm = 0.55.O’Connell effect also was seen in the fitted model. Finally, the best model was achieved by introducing 2 spots on each component. 相似文献