Starspots as the cause of the intrinsic light variations in RS Canum Venaticorum type stars

Eaton, J. A.; Hall, D. S.

doi:10.1086/156800

Cited by 147 publications

(57 citation statements)

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“…It allowed for detecting spot appearance and disappearance on time scales from a few to a hundred days. A zonal model with (near-)equatorial inhomogeneous bands of spots was considered by Eaton and Hall (1979) and Alekseev and Gershberg (1996).…”

Section: Light-curve Modellingmentioning

confidence: 99%

Starspots: A Key to the Stellar Dynamo

Berdyugina

2005

Living Rev. Solar Phys.

567

530

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Magnetic activity similar to that of the Sun is observed on a variety of cool stars with external convection envelopes. Stellar rotation coupled with convective motions generate strong magnetic fields in the stellar interior and produce a multitude of magnetic phenomena including starspots in the photosphere, chromospheric plages, coronal loops, UV, X-ray, and radio emission and flares. Here I review the phenomenon of starspots on different types of cool stars, observational tools and diagnostic techniques for studying starspots as well as starspot properties including their temperatures, areas, magnetic field strengths, lifetimes, active latitudes and longitudes, etc. Evolution of starspots on various time scales allows us to investigate stellar differential rotation, activity cycles, and global magnetic fields. Together these constitute the basis for our understanding of stellar and solar dynamos and provide valuable constraints for theoretical models.

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Section: Light-curve Modellingmentioning

confidence: 99%

Starspots: A Key to the Stellar Dynamo

Berdyugina

2005

Living Rev. Solar Phys.

567

530

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“…Optical light curves show a distintive modulation outside eclipse attributed to cool starspots that are regarded as stellar counterparts of sunspots or sunspot groups (Eaton & Hall 1979). By modelling their surface distribution and their time variations it is possible to derive information on active longitudes and activity cycles.…”

Section: Sz Piscium (Hd 219113; Sao 128041; Bd+01mentioning

confidence: 99%

Long-term starspot evolution, activity cycle and orbital period variation of SZ Piscium

Lanza

Rodonò

Mazzola

et al. 2001

A&A

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Abstract.A sequence of V -band light curves of the active close binary SZ Piscium (F8 V-IV+ K1 IV), extending from 1957 to 1998, is presented and analysed to derive the spot distribution and evolution on the component stars. In our modelling approach the Roche geometry and Kurucz's atmospheric models were adopted. The resulting maps of the spot surface distribution were regularized by means of the Maximum Entropy and Tikhonov criteria to take full advantage of the increased geometrical resolution during eclipses. By comparing the maps obtained with these two criteria, it was possible to discriminate between surface features actually required by the data and artifacts introduced by the regularization process. Satisfactory fits were obtained assuming spots on both components and the unspotted V -band luminosity ratio: L1/L2 = 0.35 ± 0.035. The derived yearly spot distributions indicate that the spot patterns consist of two components, one uniformly and the other non-uniformly distributed in longitude, the latter suggesting the presence of preferential longitudes. Starspots at latitudes higher than ∼75• were not required to reproduce the photometric modulation. For the spot pattern on the less luminous F8 V primary component there are only some hints of the possible presence of spots around the substellar point facing the K1 IV secondary component. On the more luminous and larger secondary component there is clear evidence for the presence of three active longitudes. A stable active longitude around the substellar point facing the primary star appears to be quite compact with an extension of ∼40• on several maps. The other two active longitudes display irregular changes of the spot area and location. The variation of the total spotted area on the secondary component shows sizeable fluctuations and a possible short-term cycle of about 13 yr, which is more clearly apparent in the variation of the spotted area unevenly distributed in longitude. A longer-term cycle of about 30 yr with a markedly non-sinusoidal variation might also be present. The spatial association between photospheric spots and chromospheric plages (as detected in the UV lines) appears significant for the active region around the substellar point in the K1 IV component. A possible connection between magnetic activity and orbital period variation is suggested by comparing the variation of the total spotted area with the O−C diagram of the primary eclipse times. The time span covered by the available data is, however, not long enough for us to draw any definite conclusions.

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“…Milone 1977;Milone & Naftilan 1980). Eaton & Hall (1979) proposed a model in which the more massive star is so heavily spotted that its average surface flux, despite its higher temperature, is fainter than that of the cooler star, and it is responsible for the intrinsic variability of the system. Moreover, from long-term broadband photometric monitoring, Evren (1989) found that both components are active.…”

Section: Introductionmentioning

confidence: 99%

Hαspectroscopy and $\vec{BV}$ photometry of RT Lacertae

Frasca

Çakırlı²,

Catalano

et al. 2002

A&A

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Abstract. Contemporaneous spectroscopic and photometric BV observations of the RS CVn type eclipsing binary RT Lacertae were performed in summer 2000. The photometric observations were obtained at the Ege University Observatory, while the spectroscopic ones were carried out at Catania Astrophysical Observatory in the spectral range 5860-6700Å. We obtained a high quality radial velocity curve of the system that allowed us to give more accurate values of the orbital parameters. A steady decrease of the barycentric velocity from 1920 to 2000 has been pointed out and has been discussed in the context of a third body hypothesis. Through the subtraction of a "synthetic" spectrum, built up with spectra of inactive standard stars, we detected Hα excess emission which fills in the photospheric absorption profiles of both components. With the exception of a few spectra, taken close to the eclipses, in which some extra absorption or a faint double-peaked broad emission appears, there is no further evidence of circumstellar matter in this system, as suggested in previous works. The hotter and more massive star appears also as the more active at a chromospheric level, since it has a Hα flux about ten times greater than the companion, on average. Rotational modulation of the Hα emission has been detected in both stars. The hemisphere of the more massive star facing the observer at phase 0. p 75 appears brighter (in Hα) than that seen at phase 0. p 25, while for the less massive G9 IV star the maximum Hα emission is seen around phase 0. p 0-0. p 1. From the analysis of the contemporaneous light curve (Lanza et al. 2002), the more massive G5 IV star results to be more active than the companion at a photospheric level, in agreement with the chromospheric behaviour observed in Hα. In addition, the starspots of the G5 IV star are mainly located in the Hα brighter hemisphere, suggesting a close spatial association of spots and plages in this star. The G9 IV star displays instead the maximum Hα emission at the phase of maximum visibility of the smaller spotted area found from the light-curve analysis. The minimum Hα emission occurs when the more heavily spotted region is visible.

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Starspots as the cause of the intrinsic light variations in RS Canum Venaticorum type stars

Cited by 147 publications

References 0 publications

Starspots: A Key to the Stellar Dynamo

Starspots: A Key to the Stellar Dynamo

Long-term starspot evolution, activity cycle and orbital period variation of SZ Piscium

Hαspectroscopy and $\vec{BV}$ photometry of RT Lacertae

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