Starspot evolution, differential rotation, and magnetic cycles in the chromospherically active binaries lambda andromedae, sigma Geminorum, II Pegasi, and V711 Tauri

Henry, Gregory W.; Eaton, J. A.; Hamer, Jamesia; Hall, D. S.

doi:10.1086/192149

Cited by 193 publications

(258 citation statements)

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“…The projected filling factors were a minimum of f s = 35% at photometric phase of 0.5 and a maximum of f s = 50% at 0.75 phase. Comparing these values with the optical photometry of Henry et al (1995) obtained at the same time shows the star was at nearly the same brightness at these two phases. These observations show that the lack of the expected anticorrelation of the TiO absorption with brightness is not limited to just And and may be present in other RS CVn and related chromospherically active stars as well.…”

Section: Discussionmentioning

confidence: 55%

“…In addition, the mean light level of the star varies on a timescale of several years. Henry et al (1995) attribute the long-term brightness changes as arising from an $11 yr starspot cycle, similar to the 11 yr sunspot cycle.…”

Section: Observationsmentioning

confidence: 93%

“…Rotational periods determined from Ca ii H and K studies (Baliunas & Dupree 1982) and spot modeling of light curves show different periods at different epochs. For And, Henry et al (1995) have identified at least 11 spot regions for observing runs over an interval of $16 yr. They found corresponding rotational periods between P rot = 53.1 and 55.3 days, and they interpreted these difference as the sequential reappearance of spots at different stellar latitudes having correspondingly different periods.…”

Section: Evidences For Differential Rotationmentioning

confidence: 99%

“…Combining our 5 yr (1996)(1997)(1998)(1999)(2000)(2001) of continuous photometry of And with those of Henry et al (1995) and with several observation seasons from Villanova University Observatory, we have more than 26 yr of photometry. This is one of the longest observation intervals for an active star.…”

Section: Possible Activity Cycle Of Andmentioning

confidence: 99%

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Wing Near-Infrared, TiO-Band, andV-Band Photometry of Chromospherically Active Star Andromedae

Mirtorabi

Wasatonic

Guinan

2003

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As a pilot program, Wing near-IR, TiO-band, and V-band photometry is being conducted of the RS Canum Venaticorum type, chromospherically active, G8 IV-III star Andromedae. The objective is to investigate a possible relationship between variation of the $54 day rotationally starspot modulated visual light curve and TiO absorption strength. The TiO ( , 0, 0) absorption band strength at = 719 nm is very sensitive to temperature for cool stars and manifests itself in cooler starspot regions (T 4000 K). TiO photometry has an advantage over conventional photometry in that it provides unambiguous measures of the fractional cool starspot coverage. In addition, as the stars rotate, the variation in the TiO index yields information about the longitudinal distribution of the starspots. Importantly, combining the TiO photometry with the V-band and near-IR light curves allows the discrimination of white-light faculae (=hot spot) and cool starspot contributions. Initial results of this study indicate that the observed V-band and near-IR continua light variations found for And primarily arise from bright spot (plage) features rather than dark starspots as is usually assumed. This is in contrast to current theories that the visual light variation is solely due to dark spots. Models using both bright and dark spot features have been developed and are being used to fit the light and TiO-index curves. The models account for cool/hot spot characteristics such as projected filling factor and temperature. The long-term variation of V light and TiO index have been investigated to search for any activity cycles.

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Section: Discussionmentioning

confidence: 55%

Section: Observationsmentioning

confidence: 93%

Section: Evidences For Differential Rotationmentioning

confidence: 99%

Section: Possible Activity Cycle Of Andmentioning

confidence: 99%

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Wing Near-Infrared, TiO-Band, andV-Band Photometry of Chromospherically Active Star Andromedae

Mirtorabi

Wasatonic

Guinan

2003

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“…They are detached systems consisting of a G or K subgiant, and a dwarf or subgiant of spectral type F or G. Their phenomenology has been described in several reviews (e.g., Rodonò 1992;Guinan & Gimenez 1993). Long-term optical monitoring has revealed cycles of 10−20 yr in several systems (e.g., Rodonò et al 1995;Henry et al 1995;Oláh et al 1997;Lanza et al 1998;Rodonò et al 2000;Lanza et al 2001;Lanza et al 2002;Lanza et al 2006;Berdyugina & Henry 2007). Recently, Buccino & Mauas (2009) have investigated chromospheric cycles in some RS CVn systems using long-term UV data from the IUE satellite; and Messina (2008) has discussed the long-term variability of the optical colours of several systems finding in some cases evidence of a predominance of the faculae at the maximum of activity.…”

Section: Stellar Cycles From Photospheric Proxiesmentioning

confidence: 99%

Stellar magnetic cycles

Lanza

2009

Proc. IAU

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Abstract. The solar activity cycle is a manifestation of the hydromagnetic dynamo working inside our star. The detection of activity cycles in solar-like stars and the study of their properties allow us to put the solar dynamo in perspective, investigating how dynamo action depends on stellar parameters and stellar structure. Nevertheless, the lack of spatial resolution and the limited time extension of stellar data pose limitations to our understanding of stellar cycles and the possibility to constrain dynamo models. I briefly review some results obtained from disc-integrated proxies of stellar magnetic fields and discuss the new opportunities opened by space-borne photometry made available by MOST, CoRoT, Kepler, and GAIA, and by new ground-based spectroscopic or spectropolarimetric observations. Stellar cycles have a significant impact on the energetic output and circumstellar magnetic fields of late-type active stars which affects the interaction between stars and their planets. On the other hand, a close-in massive planet could affect the activity of its host star. Recent observations provide circumstantial evidence of such an interaction with possible consequences for stellar activity cycles.

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The Catania Automatic Photoelectric Telescope on Mt. Etna: asystematic study of magnetically active stars

et al. 2001

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Starspot evolution, differential rotation, and magnetic cycles in the chromospherically active binaries lambda andromedae, sigma Geminorum, II Pegasi, and V711 Tauri

Cited by 193 publications

References 0 publications

Wing Near-Infrared, TiO-Band, andV-Band Photometry of Chromospherically Active Star Andromedae

Wing Near-Infrared, TiO-Band, andV-Band Photometry of Chromospherically Active Star Andromedae

Stellar magnetic cycles

The Catania Automatic Photoelectric Telescope on Mt. Etna: asystematic study of magnetically active stars

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