Starspot Lifetimes

Hall, D. S.; Busby, M R

doi:10.1007/978-94-009-0679-2_30

Cited by 22 publications

(20 citation statements)

References 17 publications

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“…Hall and Henry (1994) analysed several dozen spotted stars and concluded that lifetimes of relatively small spots are proportional to their sizes, which is consistent with sunspot properties. Lifetimes of relatively large spots are possibly limited by a shear of surface differential rotation.…”

Section: Lifetimesmentioning

confidence: 59%

Starspots: A Key to the Stellar Dynamo

Berdyugina

2005

Living Rev. Solar Phys.

577

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: Lifetimesmentioning

confidence: 59%

Starspots: A Key to the Stellar Dynamo

Berdyugina

2005

Living Rev. Solar Phys.

577

530

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“…The Sun has k = 0.189, but much lower values have been obtained for the components of close binaries. Observations have indicated a range between k ≈ 6 × 10 −4 and 0.18, with a mean value k = 3 × 10 −2 (Hall & Busby 1990). Thus, the rotation period of a starspot differs from P eq by ∆P = P λ − P eq , where…”

Section: O-c Differences Due To Migrating Starspotsmentioning

confidence: 99%

“…Hall & Busby 1990;Guinan & Giménez 1993). Although it is not clear whether such dark areas consist of a group of many small spots or of just one giant spot, the second option seems to prevail.…”

Section: O-c Differences Due To Non-migrating Starspotsmentioning

confidence: 99%

Starspots and photometric noise on observed minus calculated (O–C) diagrams

Kalimeris

Rovithis‐Livaniou

Rovithis

2002

A&A

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Abstract. The effects of starspots on the O-C diagrams of eclipsing binaries are investigated, with a special emphasis on contact binaries. It is shown that starspots modulate the O-C differences in a fundamentally different way than real orbital period variations. Migrating starspots can only introduce high frequency, low amplitude disturbances (generally less than 0.01 d), whose characteristics are numerically specified for typical contact binaries. It becomes evident that the observed systematic short timescale variations of the O-C diagrams of active contact binaries (even those like VW Cep) cannot be attributed to starspots. Furthermore, the basic property of non-linear modulation of O-C differences is emphasised. This non-linearity has serious consequences for the widespread traditional method of O-C diagram analysis. This traditional method is found inappropriate even on a fundamental level, and its mathematical and physical inconsistencies are reviewed.

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“…DQ/Q Ӎ 4 This is clear evidence of surface differential rotation on k 1 Ceti, and only the second after EK Dra (Messina & Guinan 2003) in which two spots were also simultaneously visible. All other inferences were based on apparent period changes (Hall & Busby 1990;Henry et al 1995;Gaidos et al 2000;Messina & Guinan 2003), the interpretation of subtle broadening effects in spectral lines, so far detectable only in the most rapidly rotating stars (Donati & Collier Cameron 1997;Donati et al 1999), or Doppler imaging from epoch to epoch (Collier Cameron 2002). (For general reviews of these techniques and their limitations, see Rice [2002], Gizon &Solanki [2004], andStrassmeier [2004]).…”

Section: Spot Modelingmentioning

confidence: 99%

Differential Rotation of the Active G5 V Star κ¹Ceti: Photometry from theMOSTSatellite

Ruciński

Walker

Matthews

et al. 2004

PUBL ASTRON SOC PAC

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ABSTRACT. About 30.5 days of nearly uninterrupted broadband photometry of the solar-type star k 1 Ceti, obtained with the MOST (Microvariability and Oscillations of Stars) satellite, shows evidence for two large starspots with different rotation periods of 8.9 and ∼9.3 days ( ). Ground-based measurements of Ca ii H and K emission DQ/Q Ӎ 4% in 2002 and 2003 reveal variations in chromospheric activity with a period of about 9.3 days. The data were obtained during the MOST commissioning phase. When the data are combined with historical observations, they indicate that the 9.3 day spot has been stable in its period for over 30 yr. The photometry, with a sampling rate of approximately once per minute, was also used to search for acoustic (p-mode) oscillations in the star. We detect no clear evidence for p-modes in the k 1 Ceti photometry, with a noise level around 7-9 mmag at frequencies in the range of 0.5-4 mHz (3 j detection limit of 21-27 mmag). There were no flares or planetary transits during 30.5 days of MOST monitoring with light amplitudes greater than 2 mmag (durations 1200 minutes) and 3 mmag (2-200 minute durations). While this rules out any close-in planets with Jupiter diameters ≥0.5 and orbital inclinations close to 90Њ, the scatter in differential radial velocities permit a close giant planet in a more highly inclined orbit.On-line material: machine-readable table

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Starspot Lifetimes

Cited by 22 publications

References 17 publications

Starspots: A Key to the Stellar Dynamo

Starspots: A Key to the Stellar Dynamo

Starspots and photometric noise on observed minus calculated (O–C) diagrams

Differential Rotation of the Active G5 V Star κ¹Ceti: Photometry from theMOSTSatellite

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Starspot Lifetimes

Cited by 22 publications

References 17 publications

Starspots: A Key to the Stellar Dynamo

Starspots: A Key to the Stellar Dynamo

Starspots and photometric noise on observed minus calculated (O–C) diagrams

Differential Rotation of the Active G5 V Star κ1Ceti: Photometry from theMOSTSatellite

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Differential Rotation of the Active G5 V Star κ¹Ceti: Photometry from theMOSTSatellite