Photometry of the RS CVn Binary II Peg

Mohin, S.; Raveendran, A. V.; Mekkaden, M. V.

doi:10.1007/978-94-010-9433-7_67

Cited by 12 publications

(26 citation statements)

References 4 publications

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“…They collected and homogenized data from several sources listed in their Table 10 and added new observations obtained by their automated telescopes 1 . We added data for the years 1982-1991 obtained by Mohin & Raveendran (1993), who also used 10 Tau as a comparison star.…”

Section: The Photometric Data Setmentioning

confidence: 99%

Long-term starspot evolution, activity cycle, and orbital period variation of V711 Tauri (HR 1099)

Lanza

Piluso

Rodonò

et al. 2006

A&A

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The long-term optical photometry of V711 Tau (HR 1099) from 1975 to 2001 is analysed with different techniques to provide information on the activity of this widely studied RS CVn-type binary. Pooled variance analysis gives a characteristic timescale of evolution for the photospheric pattern of starspots of the order of 100-200 days, while periodogram analysis of seasonal photometric data reveals that the rotational modulation period is 2.837 ± 0.094 d, without significant changes during the 26 analysed years. Considering subsets of the entire data sequence along which the rotational modulation of the optical flux stays stable, a set of 66 light curves is obtained. They are modelled by means of inversion techniques based on Maximum Entropy and Tikhonov regularizations to derive the distributions in longitude and the total amount of the spotted area on the more luminous K1 IV component that dominates the optical variability of the system. An extensive comparison with published Doppler Imaging maps shows the advantages and drawbacks of inversion techniques based solely on optical photometry. The large-scale structure of the longitudinal distribution of the spotted area is correctly reproduced, although individual starspots revealed by Doppler Imaging cannot be detected because of the limited spatial resolution of the photometric imaging. On the other hand, the variation of the total spotted area is best reconstructed from optical photometry and shows an activity cycle with a period of 19.5 ± 2.0 yr, upon which a short-term modulation might be superposed having variable amplitude and phase and a mean duration of approximately 3-5 years. The distributions of the spotted area versus longitude show the presence of one dominant preferential longitude from 1975 to 1989; afterwards, two preferential longitudes with comparable spotted areas are detected. Their migration rates with respect to the orbital reference frame are variable versus time, possibly as a consequence of a variable drift rate of the respective non-axisymmetric dynamo modes. The variation of the orbital period of the system appears to be correlated with the magnetic activity of the K1 IV component. Specifically, the decrease of the orbital period that occurred around 1990 coincides with a re-configuration of the stellar magnetic field, as indicated by the simultaneous variation of its different proxies. In combination with previous studies, these results allow us to discriminate among different theoretical models proposed to explain the connection between magnetic activity and orbital dynamics.Key words. stars: activity -stars: starspots -stars: magnetic fields -stars: late-type -stars: binaries: spectroscopicstars: individual: V711 Tauri -stars: individual: HR 1099 IntroductionV711 Tauri (HR1099, HD 22468) is one of the most extensively studied members of the RS CVn class of magnetically active close binaries. It is a detached, non-eclipsing SB2 system, consisting of a K1 subgiant star, filling about 80% of its Roche lobe, and a G5 dwarf star on...

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Section: The Photometric Data Setmentioning

confidence: 99%

Long-term starspot evolution, activity cycle, and orbital period variation of V711 Tauri (HR 1099)

Lanza

Piluso

Rodonò

et al. 2006

A&A

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“…Both DM UMa and II Peg are • 1301 against the corresponding ∆V obtained at VBO over 1984VBO over -2007. Filled circles represent data from Mohin & Raveendran (1992, 1994, and open circles represent unpublished data. single-lined binaries, and hence the variations in (B − V) colour with V can be attributed entirely to the active components of the respective binary systems.…”

Section: (B -V ) Variationmentioning

confidence: 99%

Bluer colour of UX Arietis at fainter visual magnitudes

Rosario

Raveendran

Mekkaden

2007

A&A

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Aims. The RS CVn star UX Ari appears bluer when it is fainter, which is unusual for a spotted star; we aim to resolve this unusual behaviour of the object. Also the data available in the literature indicate that the mean V magnitude of UX Ari varies by about 25 years; we want to confirm whether this is indeed true. Methods. The most important parameter in understanding the colour variation is the relative brightnesses of the component stars of UX Ari. We use all spectroscopic information available in the literature to obtain a reasonable value for this parameter. We also present new BV photometry of UX Ari obtained on 58 nights during 2001-07. Results. The V magnitudes of UX Ari we obtained are significantly fainter than those reported in the literature, and they are not consistent with a 25-year period for the mean light level. The increased fractional contribution by the hotter G-type component to the total light in the blue spectral region as the active star becomes faint, seems to be the real cause for the bluer colour of UX Ari at fainter visual magnitudes.

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“…Recent papers containing extensive photometric analysis of this star are by Mohin & Raveendran (1993a) and Henry et al (1995). The knowledge of the orbital inclination is very important for the latitude determination of starspots, and this parameter(i = 30 • ) has been obtained with high accuracy by Fekel (1983) and Donati et al (1990).…”

Section: V711 Taumentioning

confidence: 99%

New BVR photometry of six prominent RS Canum Venaticorum binaries

Padmakar

Pandey

1999

Astron. Astrophys. Suppl. Ser.

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Abstract.A new BV R photometry of six prominent RS CVn stars: V711 Tau, UX Ari, IM Peg, II Peg, σ Gem and λ And, carried out during 1995-97, is presented. The new results reveal significant evolution in the shape as well as in the amplitude of light curves of these binaries. The traditional two-starspot model has been used to obtain the spot parameters from the observed light curves of the stars. Changes in spot area and their location on stellar surface can be noticed from extracted spot parameters. Some of these stars are found to have significant variation in (B − V ) and (V −R) colour indices. The (V − R) colour index variation found in IM Peg, II Peg and λ And have been used for determining starspot effective temperatures.

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Photometry of the RS CVn Binary II Peg

Cited by 12 publications

References 4 publications

Long-term starspot evolution, activity cycle, and orbital period variation of V711 Tauri (HR 1099)

Long-term starspot evolution, activity cycle, and orbital period variation of V711 Tauri (HR 1099)

Bluer colour of UX Arietis at fainter visual magnitudes

New BVR photometry of six prominent RS Canum Venaticorum binaries

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