WY Cnc Research Articles

Physical Properties of Three Eclipsing Binaries of V Crt, WY Cnc and CG Cyg with Radio Radiation

Radio radiation has been detected across the Hertzsprung Russell diagram. We selected three objects with radio radiation (a semi-detached eclipsing binary V Crt, and two detached binaries WY Cnc and CG Cyg) that show magnetic activity. We made new photometric observations using a SARA 60 cm and NAOC 85 cm optical telescopes. Then, we obtained their orbital and starspot parameters by analyzing our light curves and published radial velocities using the updated Wilson-Devinney program. We revised the ephemeris information for V Crt and WY Cnc by analyzing the orbital minimum times. The orbital periods increased by 2.8 (±2.1) ×10−9 d yr−1 for V Crt, which maybe caused by mass transfer. The orbital periods decreased by −8.641 (±0.004) ×10−8 d yr−1 for WY Cnc. Orbital period change for CG Cyg was also found and we used a third-body of M3 of 0.14 M⊙ and a period of approximately 59.20 (0.36) yr to explain that. We also analysed the possible second period oscillation of CG Cyg with a cycle about 18.31 (0.06) yr. The long period changes of WY Cnc and CG Cyg might be caused by magnetic activity or stellar wind, rather than mass transfer.

On the Origin of Orbital Period Change in WY Cancri: A Genuine Angular-Momentum Loss?

Abstract WY Cnc is a short-period ($ P$$ =$ 0.829 d) eclipsing RS Canum Venaticorum star, and both components are of the late-type stars. Recently, observations provided by photometric observations and light-time minima show that the orbital period of WY Cnc is experiencing a secular decrease at a rate of $ {d}P/{d}t$$ =$$-$ 1.2 $ \times$ 10$ ^{-7}$ d yr$ ^{-1}$ . In this letter, we consider whether the period change of WY Cnc can originate from angular-momentum loss. In calculations, we assumed that this source has a high wind loss rate of $ \sim$ 10$ ^{-10}$$ M_{\odot}$ yr$ ^{-1}$ . To account for the observation, magnetic braking demands a strong surface magnetic field of $ \gtrsim$ 10000 G, like that of Ap/Bp stars. Furthermore, if this source is perhaps surrounded by a circumbinary disk, and 6% of the wind loss feeds the disk, the tidal torque between the disk and the binary can account for the observed angular-momentum loss rate. Such a strong magnetic field, or an extremely high wind input fraction, seems to be highly unlikely.

Period Change and Possible Magnetic Braking in WY Cancri

Abstract In this paper, the orbital period change of the RS CVn-type binary system WY Cnc is analyzed through a detailed description of the $O-C$ curve by a weighted least-squares method. It is found that the period variation is suffering a secular period decrease at a rate of $dp/dt$$=$$-$1.20 $\times$ 10$^{-7}$dy$^{-1}$. Since WY Cnc is a typical detached binary system, and both components are late-type stars, the long-term period decrease may be caused by angular momentum loss via magnetic braking.

Long-term starspot activity of the eclipsing binaries BH Vir and WY Cnc

We present the results of multicolor photometry of the two spotted, short-period, late-type RS CVn stars BH Vir and WY Cnc. We have derived the parameters of the binaries’ components, and refined their masses, radii, and luminosities. A strong flare of WY Cnc was detected for the first time, and pre-flare variations of the star’s activity studied. Our observations and published data spanning 40 years are analyzed using a zone starspot model. We demonstrate that the spots are always concentrated near the equators and at intermediate latitudes, with maximum spotted areas as large as 29% for BH Vir and 21% for WY Cnc. The temperature differences between spotted regions and the quiet photosphere were 2300 K (BH Vir) and 1800 K (WY Cnc). The detected long-term brightness variations of BH Vir suggest the existence of an activity cycle with a probable period of 22 years. Both stars have starspots concentrated at two active longitudes separated by approximately half of the orbital period during all the studied seasons; these longitudes remained the same (0° and 184°) for BH Vir over 40 years, whereas they migrated in the direction of the stellar rotation at a rate of 3.8°/yr for WY Cnc, suggesting a cycle of 47 years for the migration of the active longitudes.

An investigation of the tidally driven period changes in detached binary systems throughO–Ctime series analysis: the case of RT And and WY Cnc

Detached binary systems are subjected to a variety of physical mechanisms which are able to change their period in a continuous way and in a broad band of timescales. Assuming that these changes should be detectable in O–C diagrams in a way specified by the physical theory of the underlying mechanisms, we carry out a preliminary study in a properly selected sample of detached binaries, where no mass transfer is expected. We are primarily interested in finding traces of tidal moments in observed orbital period changes (possibly coupled with stellar wind angular momentum losses). We focus our attempts on two short-period chromospherically active binaries (RT And and WY Cnc), whose expected period changes rates are found to be close to those derived by means of time series analysis. Emphasis is also given to systems which show a remarkably constant orbital period, in disagreement with the values expected by theory. †This paper was originally due to be published in the Special Issue: Close Binary Stars in Mod...

Long-term starspot activity of three short-period RS CVn stars: BH Vir, WY Cnc and CG Cyg

We present starspot analyses of CG Cyg, BH Vir and WY Cnc on the basis of our new photometric observations as well as published photometric data spanning almost 40 years. The spotted regions were concentrated at low latitudes up to 32°, the spots covered up to 29% of the stellar surface and all three stars show non-axisymmetric spot distributions (active longitude structures separated by approximately half the orbital period). We found that the variations in the brightness and spottedness of CG Cyg are probably cyclic with a period of about 20 years. We detected a large flare on WY Cnc (1.02×1035 erg in the B band) and analysed the WY Cnc spot activity before and during the flare.

Active Longitudes in Close Binaries

We examine the positions of the active longitudes in close binaries with respect to their companion stars on a sample of 12 systems. The primaries of four (five?) main sequence eclipsing binaries (RT And, CG Cyg, BH Vir, WY Cnc, and, possibly, UV Psc) show active longitudes at the quadrature positions. The K2 IV component of RS CVn has spots at all longitudes. Three subgiant binaries (AR Lac, SZ Psc and RT Lac have spots on both components, with pronounced active longitudes at the substellar points, and at other longitudes as well. Finally, three giant, non-eclipsing binaries (UZ Lib, HK Lac, IM Peg) have active longitudes at their substellar points and opposite to it. In case of main sequence systems probably their common magnetic field, for giants the tidal force, and, for subgiants both forces together, determine the positions of the active longitudes.

Spectroscopic and photometric observations of the short-period RS CVn-type star WY Cnc

Spectroscopic and photometric observations of the short-period RS CVn-type star WY Cnc

Spectroscopic and photometric observations of the short-period RS CVn-type star CG Cyg

High-resolution spectroscopic observations around the H α line and BVRI photometry of the eclipsing short-period RS CVn star WY Cnc are presented. The solutions of our radial velocity curves and light curves yielded the following values for masses and radii of the components: M 1 = 0.84 M ○. , M 2 = 0.46 M ○. , R 1 = 1.06 R ○. , R 2 = 0.65 R ○. . The measured rotational broadenings of the spectral lines correspond to equatorial velocities V 1 = 78 km s -1 and V 2 = 49 km s -1 . The distortions of our multicolor light curve of WY Cnc were reproduced by two cool spots on the primary star. An increase of the out-of-eclipse brightness by 0.1 mag in February 2001 was detected. Our spectra show H α line in emission from the secondary star. The chromospheric activity appeared also in the observed emission cores of the CaII H and K lines as well as the CaI 6494 line.

Do the Secular Variations in WY Cancri Mark the Spot Cycles?

I present optical photometry of the short-period eclipsing RS Canum Venaticorum binary WY Cancri taken after the most recent secular luminosity increase, in 1997. Data taken between the previous two secular luminosity increases, in 1988 and 1997, show a tendency for spots to migrate toward increasing longitude within an active longitude belt. These new data show a trend for spots to migrate in the opposite direction, toward decreasing longitude. Based on these trends, I suggest that WY Cnc shows cyclic behavior and that the previously observed secular luminosity increases in WY Cnc mark the start of new magnetic activity cycles in which the direction of longitudinal spot migration reverses. Continued observations will of course be necessary to confirm this hypothesis.

Time-resolved Spectroscopy of RS Canum Venaticorum Short-Period Systems. II. RT Andromedae, WY Cancri, and XY Ursae Majoris

We present the second part of the results of our spectroscopic study of orbital phase resolution of short-period active binaries. In this paper we present the observations of the binaries RT And, WY Cnc, and XY UMa, for which we obtained simultaneous low-resolution spectra in the Hα, Hβ, and Ca II infrared triplet (IRT; 8498 and 8542 A) lines, and higher resolution spectra in Hα for WY Cnc and XY UMa. Hα and Hβ emission excess was found in all the observed orbital phases of WY Cnc and XY UMa, while RT And showed Hα emission only during some orbital phases. We measure a clear Ca II (IRT) excess in all the spectra of the three binaries. The ratio of the flux excesses derived for these binaries, EHα/EHβ 1–3 and E8542/E8498 1–3, give low values typical of solar plage structures. In the higher resolution Hα spectra, we found emissions that can be associated with both stellar components of XY UMa and WY Cnc, indicating that the faint secondary stars in both binaries are active late-type dwarfs. Some Hα emission components, which could originate in extended structures between the stars, were detected in both systems.

Time-Resolved Spectroscopy of Short Period RS CVn Systems

AbstractWe have initiated a programme of spectroscopic observations of RS CVn short-period group, with orbital phase resolution. The systems of this group are all eclipsing binaries with both components at the Main Sequence, and most of them have similar spectral type components. The high rotational velocities and their short orbital periods (less than 1 day) hinder the spectroscopic study of these stars. We presents the first results yielded by Hα line observations of the systems XY UMa and WY Cnc. Both systems were observed during 1991 with reasonably wide orbital phase coverage. The analysis of the spectra is made by comparison with a binary model, constructed from the observed spectra of normal stars of the same spectral type as the RS CVn system components. The model accounts for the partial contribution of each component at any orbital phase within eclipses.

Spot modelling and elements of the RS CVn eclipsing binary WY Cancri

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: $$\begin{gathered} m_h = 0.86 \pm 0.03{\text{ }}M_ \odot \hfill \\ m_h = 0.51 \pm 0.03{\text{ }}M_ \odot \hfill \\ R_h = 0.99 \pm 0.02{\text{ }}R_ \odot \hfill \\ R_c = 0.65 \pm 0.02{\text{ }}R_ \odot \hfill \\ T_h = 5520^o K \pm 100^o K \hfill \\ T_c = 3740^o K \pm 20^o K \hfill \\ M_{h(bol)} = 4\mathop .\limits^m 96 \pm 0.10 \hfill \\ M_{c(bol)} = 7\mathop .\limits^m 58 \pm 0.15 \hfill \\ Spectral type hotter component = G5 \pm 1 \hfill \\ cooler component = K9 \pm 1 \hfill \\ \end{gathered} $$ For a mass ratio of 0.506 and with the derived fractional radii rh = 0.241 andr c = 0.157, both the components are found to be within their Roche lobes. Hence we have classified WY Cnc as a detached system. From their positions on the HR diagram it is concluded that both the components of WY Cnc belong to the main sequence.

Starspot Activity on Short-period RS CVn Stars

We have yet to understand the magnetic activity cycles of cool close binary systems of sunlike stars. Mutual tidal interactions, as well as magnetic ones, may result from a regime of dynamo models not yet tested, because these have been developed for single stars. To arrive at the basic physics, though, requires that we first examine the phenomenology of magnetic activity for binary systems. In particular, we would like to discover if such activity has a clearly-defined cycle, such as the sun exibits.Among the proxy indicators of magnetic activity are the Ca II H and K lines. Strassmeier et al. (1988) used the strength of these lines as the primary criterion for the inclusion of systems in The Catalog of Chromospherically Binary Stars. Of the RS CVn stars in the catalog, 12 have orbital periods of one day or shorter; 9 are eclipsing systems. As part of a decade-long program, we have focussed our observations and models on eight of the short-period group (Hall, 1976): XY UMa, UV Psc, SV Cam, RT And, CG Cyg, ER Vul, BH Vir, and WY Cnc. These close systems are tidally-locked in synchronous rotation and tidally-distorted into Roche lobe configurations.

Long-term starspot activity of short-period RS Canum Venaticorum stars. IV - WY CANCRI

The photometric distortion waves in the short-period RS CVn system WY CnC are parametrized by a dark, circular spot model for the active regions on the primary star. From recent observations and archival sources, the changes in positions and areas of the active regions are inferred. For light curves with simultaneous visual and red or infrared data, the average temperatures of the spotted regions relative to the photosphere are evaluated. In 1989, it is found that T(spot) = 3970 + or - 300 K for a primary star temperature of 5520 K. Some indication is found of a nonuniform temperature distribution in longitude across the spotted area at this time. The active regions tend to occur at low latitudes, in contrast to the high latitudes previously found for SV Cam, RT And, and BH Vir. It is found again that the active regions fall into preferred longitudes near 90 and 270 deg. 27 refs.

Infrared photometry of the RS CVn short-period systems - XY UMa and WY CNC

Infrared J and K light curves of two RS CVn short-period systems, XY UMa and WY Cnc, are presented. Both systems show similar variability in the infrared to that observed in the visual. From the colors an infrared excess is inferred for the primary component of both systems. A new determination of their geometrical elements is presented and the resulting parameters are compared to those previously obtained from visible photometry. The light curves show peculiarities that may indicate the presence of gas streams in the systems.

Four-color uvby photometry and starspot parameters of WY Cancri

Four color uvby observations of the short period RS CVn system WY Cnc were made in 1986 March. Three times of priminimum were determined. With the starspot assumption, the photometric distortion waves were analysed of the b and y observations, and of Chambliss' (1965) B and V observations, respectively. The analyses were based on the W-D program of 1983 edition and the differential correction computing code for spot parameters designed by ZHAI and CHEN (1988). Two spots were found on the primary component in each of the two epochs. TABLE 5 presents the starspot parameters and their errors. TABLE 6 are the Roche model parameters in which the new photometric mass ratio q is 0.454±0.005. The photometric results show that WY Cnc is a main sequence detached system.

The system WY Cnc and derivation of absolute information at the lower end of the Main Sequence

Photometric and spectrographic observations of the system WY Cnc are presented and analysed. It is concluded that the system consists of two Main Sequence stars: a G5 primary and a low mass secondary star with a mass of about 0.4M ⊙, corresponding to a spectral type of around M2. The possibility of deriving absolute information on this low mass Main Sequence object lends significance to this study. Also there is evidence concerning the role of scattering by the atmosphere of the cool comparison.

The eclipsing binary system WY Cnc.

The eclipsing binary system WY Cnc.