A revised gyro-age for M67 from<i>Kepler/K2-Campaign-5</i>light curves

González, Guillermo

doi:10.1093/mnras/stw2237

Cited by 9 publications

(7 citation statements)

References 18 publications

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“…We estimate the grass level in this frequency region to be less than ∼15 µmag, which underlines the high quality of the K2 data, which, at least in the case of the analyzed data set, are comparable in this respect to data from the original Kepler mission. Note, though, that the noise level increases significantly towards lower frequencies, which substantiates the above mentioned results of Douglas et al (2016) and Gonzalez (2016).…”

Section: Period Analysissupporting

confidence: 89%

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K2 observations of 95 Vir: δ Scuti pulsations in a chromospherically active star

Paunzen

Hümmerich

Bernhard

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We have searched for photometric variability in 95 Vir, a fast rotating, chromospherically active early F-type star, which was observed in the framework of Campaign 6 of the Kepler K2 mission. Available literature information on 95 Vir were procured, and well-established calibrations were employed to verify the derived astrophysical parameters. We have investigated the location of our target star in the M Bol versus log T eff diagram, which provides information on evolutionary status. We have discussed our results in detail, drawing on literature information and the theoretical predictions of state-of-the-art pulsation models, with the aim of unraveling the underlying variability mechanisms. From an analysis of 3400 long-cadence measurements, we have identified two main frequencies and several harmonics in our target star. We attribute the main frequency, f 1 = 9.53728 d −1 , to δ Scuti pulsations. The origin of the secondary signal, f 2 = 1.07129 d −1 , is less clear. We have investigated three possible interpretations of the low-frequency variation: binarity, pulsation and rotational modulation. Current evidence favours an interpretation of f 2 as a signature of the rotational period caused by the presence of cool star spots, which goes along well with the observed chromospheric activity. However, phase-resolved spectroscopy is needed to verify this assumption. We briefly consider other chromospherically active δ Scuti stars that have been presented in the literature. A search for star spot-induced photometric variability in these objects might be of great interest, as well as an investigation of the interplay between chromospheric and pulsational activity.

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Section: Period Analysissupporting

confidence: 89%

“…The presence of significant low-frequency power in K2 data, which is unrelated to intrinsic stellar variability, has been established (e.g. Douglas et al 2016;Gonzalez 2016). Bearing in mind the time baseline of only ∼79 days, we are therefore inclined to regard these frequencies as spurious detections.…”

Section: Period Analysismentioning

confidence: 98%

K2 observations of 95 Vir: δ Scuti pulsations in a chromospherically active star

Paunzen

Hümmerich

Bernhard

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…One possibility is to use rotation measurements from K2 observations of the ∼4.0 Gyr cluster M67. However, inconsistent results for the rotation distribution in this cluster have been found (Barnes et al 2016;Gonzalez 2016a;Gonzalez 2016b), andEsselstein et al (2018) showed that accurately determining the rotation periods from the available data is challenging, especially given their long 20-35 day rotation periods and the limited 75 day observation window. Another problem with using M67 is that the age of the cluster is uncertain, and many age determinations are based on the gyrochonology method, which for our purpose is not useful.…”

Section: Observational Constraintsmentioning

confidence: 99%

The active lives of stars: A complete description of the rotation and XUV evolution of F, G, K, and M dwarfs

Johnstone

Bartel

Güdel

2021

A&A

172

217

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Aims. We study the evolution of the rotation and the high energy X-ray, extreme ultraviolet (EUV), and Ly-α emission for F, G, K, and M dwarfs, with masses between 0.1 and 1.2 M⊙, and provide a freely available set of evolutionary tracks for use in planetary atmosphere studies. Methods. We develop a physical rotational evolution model constrained by observed rotation distributions in young stellar clusters. Using rotation, X-ray, EUV, and Ly-α measurements, we derive empirical relations for the dependences of high energy emission on stellar parameters. Our description of X-ray evolution is validated using measurements of X-ray distributions in young clusters. Results. A star’s X-ray, EUV, and Ly-α evolution is determined by its mass and initial rotation rate, with initial rotation being less important for lower mass stars. At all ages, solar mass stars are significantly more X-ray luminous than lower mass stars and stars that are born as rapid rotators remain highly active longer than those born as slow rotators. At all evolutionary stages, habitable zone planets receive higher X-ray and EUV fluxes when orbiting lower mass stars due to their longer evolutionary timescales. The rates of flares follow similar evolutionary trends with higher mass stars flaring more often than lower mass stars at all ages, though habitable zone planets are likely influenced by flares more when orbiting lower mass stars. Conclusions. Our results show that single decay laws are insufficient to describe stellar activity evolution and highlight the need for a more comprehensive description based on the evolution of rotation that also includes the effects of short-term variability. Planets at similar orbital distances from their host stars receive significantly more X-ray and EUV energy over their lifetimes when orbiting higher mass stars. The common belief that M dwarfs are more X-ray and EUV active than G dwarfs is justified only when considering the fluxes received by planets with similar effective temperatures, such as those in the habitable zone.

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“…The sample, presented in Table 1, was chosen from a list built with M67 objects that have high membership probabilities, calculated using proper motion from Yadav et al (2008), previous spectroscopic studies by Pasquini et al (2008), and further studies of radial velocity by Geller et al (2015). Furthermore, we verified objects that may have about 1M ⊙ and some photometric modulation from Kepler K2, as analysed by Barnes et al (2016) and Gonzalez (2016).…”

Section: Sample and Analysismentioning

confidence: 99%

Li abundances for solar twins in the open cluster M67

Carlos

Meléndez

Nascimento

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We determine lithium (Li) abundances for solar twins in the M67 open cluster to add valuable information about the correlation between Li depletion and stellar age and, then, better understand stellar structure and evolution. We use high resolution and good signal-to-noise ratio spectra to characterize Li depletion in three solar twins from M67, using spectral synthesis in the region of the asymmetric 6707.75Å Li I feature. The mean Li abundance value of A(Li)= 1.6 ± 0.2 dex for our sample of M67 solar twins (our three stars plus a fourth solar twin from a previous analysis in the literature) presents Li abundance expected for its age. Also, the scatter estimated from the standard deviation of the Li abundances in this work is similar to the typical scatter found in a sample of field solar twins presented in the literature.

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A revised gyro-age for M67 fromKepler/K2-Campaign-5light curves

Cited by 9 publications

References 18 publications

K2 observations of 95 Vir: δ Scuti pulsations in a chromospherically active star

K2 observations of 95 Vir: δ Scuti pulsations in a chromospherically active star

The active lives of stars: A complete description of the rotation and XUV evolution of F, G, K, and M dwarfs

Li abundances for solar twins in the open cluster M67

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