Rotational modulation of chromospheric variations of main-sequence stars

Stimets, R.W.; Giles, Robert H.

doi:10.1086/183397

Cited by 17 publications

(9 citation statements)

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“…The mass of αCenA was taken as 1.1 M ⊙ and αCenB as 0.91 M ⊙ following Pourbaix, Neuforge‐Verheecke & Noels (1999) and the mass of 70OphA as 0.89 M ⊙ , from Eggenberger et al (2008). The rotation periods are from Donahue et al (1996) for the Sun, Barnes (2007) for α Cen, and from Stimets & Giles (1980) and Noyes et al (1984) for 70 Oph A. The last row is based on the supposition that the true period of 70 Oph A is twice the measured period, which may be a higher frequency harmonic of the true period, as we observed for some cluster stars.…”

Section: Calibration Of Gyrochronolgy: the Age Of Field Starsmentioning

confidence: 99%

Stellar rotation in the Hyades and Praesepe: gyrochronology and braking time-scale

Delorme

Cameron

Hebb

et al. 2011

Monthly Notices of the Royal Astronomical Society

171

248

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We present the results of photometric surveys for stellar rotation in the Hyades and in Praesepe, using data obtained as part of the SuperWASP exoplanetary transit‐search programme. We determined accurate rotation periods for more than 120 sources whose cluster membership was confirmed by common proper motion and colour–magnitude fits to the clusters’ isochrones. This allowed us to determine the effect of magnetic braking on a wide range of spectral types for expected ages of ∼600 Myr for the Hyades and Praesepe. Both clusters show a tight and nearly linear relation between J−Ks colour and rotation period in the F, G and K spectral range. This confirms that loss of angular momentum was significant enough that stars with strongly different initial rotation rates have converged to the same rotation period for a given mass, by the ages of Hyades and Praesepe. In the case of the Hyades, our colour–period sequence extends well into the M dwarf regime and shows a steep increase in the scatter of the colour–period relation, with identification of numerous rapid rotators from ∼0.5 M⊙ down to the lowest masses probed by our survey (∼0.25 M⊙). This provides crucial constraints on the rotational braking time‐scales and further clears the way to use gyrochronology as an accurate age measurement tool for main‐sequence stars.

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Section: Calibration Of Gyrochronolgy: the Age Of Field Starsmentioning

confidence: 99%

Stellar rotation in the Hyades and Praesepe: gyrochronology and braking time-scale

Delorme

Cameron

Hebb

et al. 2011

Monthly Notices of the Royal Astronomical Society

171

248

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“…As a result, Stimets and Giles (1980) and Vaughan et.al., (1981) have for the first time succeeded in measuring directly the At these wavelengths, the photospheric flux increases rapidly with increasing effective temperature. However, this effect does not account completely for the temperature·dependence of the emission flux.…”

Section: Evidence For Stellar Dynamos In Main Sequence Starsmentioning

confidence: 91%

Late-Type Ca II Emission-Line Stars in the Southern Hemisphere

Collier

1983

Astrophysics and Space Science Library

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The results of a photometric and spectroscopic study of twenty-three late-type southern stars with strong Ca II H and K emission are presented.The presence of photometric variability, with similar properties to the photometric wave phenomenon seen in the RS Canum Venaticorum binaries, is noted in thirteen of the fifteen stars for which extensive photometry was obtained.Of twenty stars for which high-resolution radial velocity measurements were obtained, ten are found to be single-lined and seven are found to be double-lined spectroscopic binaries.Orbital periods are determined for eight previously-unknown binaries.The periods range from 0.66 up to 53.9 days. ca II H and K spectra of ten of the program stars yield line surface fluxes in the range in the H and·K emission cores. The high proportion of single-lined RS CVn binaries in the sample is discussed in terms of selection effects.The space density of RS CVn systems with mass ratios less than q ~ 0.8 is found to be at least equal to that of the q ~ 0.8 systems. This implies a total space density of at systems in the Galactic plane is found to be 1.9 x 10 pc by this method, in reasonable agreement with the observed .value.ii CONTENTS

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“…On a shorter timescale, these emissions are correlated with active regions. As active regions are not symmetrically distributed in longitude and can last for several rotation periods, it is common for chromospheric emissions to be rotationally modulated, and thus accurate stellar rotation periods can be derived as well (Stimets and Giles, 1980;Vaughan et al, Hallam and Wolff, 1981).…”

Section: Starspot Cyclesmentioning

confidence: 99%

Climatic oscillations during the Precambrian era

Zahnle

Walker

1987

Climatic Change

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A remarkably regular cyclicity with a fundamental period of -11-12 cycles is preserved in the 680 million year old Elatina formation of South Australia. All but one of the many periods present can be interpreted as resulting from the combined influences of the sunspot cycle and the lunar nodal tide -in particular, beating between these two cycles gives rise to a long period phase alternation. Available paleontological evidence is used to constrain the lunar distance 680 Ma ago, thereby constraining the length of the lunar nodal tide. We then infer from the beat period that the sunspot cycle was 10.8_+0.2 years, which is in agreement with independent astronomical evidence suggesting that the sunspot cycle would then have been some 3-10% shorter than it is at present. Although this interpretation is not consistent with the 12.0 year sunspot cycle counted by Williams and Sonett (1985), we demonstrate that unavoidable random errors made in discriminating unusually indistinct varves gives rise to a systematic overcount of varves of this magnitude. The clarity of this evidence for solar and lunar signals in the climate 680 Ma ago lends support to reports of their importance today.

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Rotational modulation of chromospheric variations of main-sequence stars

Cited by 17 publications

References 0 publications

Stellar rotation in the Hyades and Praesepe: gyrochronology and braking time-scale

Stellar rotation in the Hyades and Praesepe: gyrochronology and braking time-scale

Late-Type Ca II Emission-Line Stars in the Southern Hemisphere

Climatic oscillations during the Precambrian era

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