SV Cam spot activity in February 2001 – March 2002

Abstract

Abstract. We present the analysis of new BVR light curves for the active star SV Cam. The Roche model with spotted areas on the hotter primary component fits satisfactorily all filter observations yielding two spots in intermediate latitudes and covering about 1.5% each of the stellar surface. Both are ∼1000 K cooler than surrounding photosphere. The comparison with an earlier season (January/February 2000) suggests that the spots probably evolved in area longitude and latitude but basic and preferred orientation from previous season is confirmed.Key words. stars: binaries: eclipsing IntroductionThe active star SV Cam (HD44982, p ∼ 0.59d, sp. ∼ F8, m V = 9.34) is an eclipsing binary and has been extensively studied since its discovery (Guthnick 1929) due to its asymmetry and overall shape of the light curves and magnetic activity on probably both components. For example Hilditch et al. (1979) gave some arguments in favour of the secondary being responsible for the distortion of light curves. Later on, Cellino et al. (1985) claimed that the hotter primary was an active and spotted component. Özeren et al. (2001) found an excess emission in hydrogen lines connected with the secondary, cooler component of the system and processes like surface plages and prominences. The spectral type of the component stars were derived as G2-3V and K4 by Hilditch et al. (1979) and Pojmański (1996) estimated a new mass ratio, 0.56, and he derived spectral types F5V and K0V from stellar masses for the components.Among the most recent studies, Albayrak et al. (2001) presented the light and period study of the system and suggested the parameters of the third body orbit. Considering the recent and oldest observations, Zboril (2002) Lehmann et al. (2002) and Kjurkchieva et al. (2002) offer slightly different mass ratios for the components. Given the spectral type and light curve solutions it is generally agreed that the secondary contributes less than 10% of the light.The spot properties are of great interest in general and in the case of fast rotators in particular. Since there is a difference in magnetic activity between the Sun and active stars, there may be a considerable difference in their field distribution. Present work on magnetic flux tubes suggests higher spot latitudes for rapidly rotating stars, and perhaps the SV Cam system is a good one to investigate spot properties and its overall activity due to bound and therefore fast rotation of the components. ObservationsNew observation in UBVR filters were obtained on 18 nights with two 0.6 m telescopes at the Skalnaté Pleso and Stará Lesná observatories in the season January 2001 -March 2002. The detectors were photometers OPTEC SSP-5, HAMAMATSU R4457 and EMI 9789 Q multipliers. The differential photometry was performed with the sequence 3xS-3xV-3xCH and sky background and all corrected for differential extinction. The comparison stars were SAO 1045 (S, standard) and SAO 1030 (CH, check). The extinction coefficients can be derived directly from the individual night or seasonal ...

Variation of the period and light curves of the solar-type contact binary EQ Tauri

“…Secondly, although Byrne (1996) analysed the reliability on polar spots, and criticized the existence of polar spots, polar spots often appear in Doppler imaging (see, for example, Strassmeier & Rice 1998; Lister, Collier Cameron & Bartus 1999; Vogt et al 1999; Jeffers, Collier Cameron & Barnes 2005). Thirdly, a high‐latitude spot is consistent with flux‐tube models, which predict higher spot latitudes with higher rotational angular velocity but with a larger depth of convective envelope as well (Zboril & Djurašević 2003). Although the latitude of the star‐spot cannot be reliably estimated from light curves alone (Lanza & Rodonò 1999), our work can still give one possible location of spots.…”

A compact flare eclipsed in the corona of SV Camelopardalis

“…SV Cam has been detected by ROSAT (Hempelmann et al 1997), but the low statistics of the observation did not allow us to clearly identify the presence of eclipses in the X-ray band. Optical observations reveal the presence of spots in the primary star, but the low luminosity of the secondary (∼15% of the total) does not allow us to identify such features on the cooler object (Hempelmann et al 1997;Kjurkchieva et al 2002;Zboril & Djurašević 2003, and references therein). The Hα and Ca IR triplet profiles are filled in due to chromospheric activity in the secondary star (Montes et al 1995;Pojmanski 1998;Kjurkchieva et al 2002).…”

Spurious 'active longitudes' in parametric models of heavily spotted eclipsing binaries

“…Another approach for the reconstruction of a surface brightness distribution is the ‘two‐spot’ model. The ‘two‐spot’ model can account for the light variations of chromospherically active stars, and examples of this model applied to SV Cam can be found in Budding & Zeilik (1987), Zelik et al (1988), Patkos & Hempelmann (1994), Djurašević (1998), Kjurkchieva, Marchev & Ogloza (2000), Albayrak et al (2001) and Zboril & Djurašević (2003). However, Doppler images of chromospherically active RS CVn stars (e.g.…”

“…Another approach for the reconstruction of a surface brightness distribution is the 'two-spot' model. The 'two-spot' model can account for the light variations of chromospherically active stars and examples of this model applied to SV Cam can be found in: Zboril & Djurašević (2003), Albayrak et al (2001), Kjurkchieva et al (2000), Djurasevic (1998), Patkos & Hempelmann (1994), Budding & Zeilik (1987) and Zelik et al (1988). However Doppler images of chromospherically active RS CVn stars (e.g.…”