A Volume-Limited Photometric Survey of 114 Γ Doradus Candidates

Henry, Gregory W.; Fekel, Francis C.; Henry, Stephen M.

doi:10.1088/0004-6256/142/2/39

Cited by 35 publications

(27 citation statements)

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“…Their periods range from 0.3 to 1.7 d, though two cases are known at longer periods, up to 2.7 d (Henry et al 2007(Henry et al , 2011. Our periods are compatible with this range.…”

Section: Group 4 Of Periodic Variables: γ Dor Candidatessupporting

confidence: 78%

Stellar variability in open clusters

Mowlavï¹,

Barblan²,

Saesen³

et al. 2013

A&A

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Aims. We analyze the population of periodic variable stars in the open cluster NGC 3766 based on a 7-year multiband monitoring campaign conducted on the 1.2 m Swiss Euler telescope at La Silla, Chili. Methods. The data reduction, light curve cleaning, and period search procedures, combined with the long observation time line, allowed us to detect variability amplitudes down to the millimagnitude (mmag) level. The variability properties were complemented with the positions in the color-magnitude and color-color diagrams to classify periodic variable stars into distinct variability types. Results. We find a large population (36 stars) of new variable stars between the red edge of slowly pulsating B (SPB) stars and the blue edge of δ Sct stars, a region in the Hertzsprung-Russell (HR) diagram where no pulsation is predicted to occur based on standard stellar models. The bulk of their periods ranges from 0.1 to 0.7 d, with amplitudes between 1 and 4 mmag for the majority of them. About 20% of stars in that region of the HR diagram are found to be variable, but the number of members of this new group is expected to be higher, with amplitudes below our mmag detection limit. The properties of this new group of variable stars are summarized and arguments set forth in favor of a pulsation origin of the variability, with g-modes sustained by stellar rotation. Potential members of this new class of low-amplitude periodic (most probably pulsating) A and late-B variables in the literature are discussed. We additionally identify 16 eclipsing binary, 13 SPB, 14 δ Sct, and 12 γ Dor candidates, as well as 72 fainter periodic variables. All are new discoveries. Conclusions. We encourage searching for this new class of variables in other young open clusters, especially in those hosting a rich population of Be stars.

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“…Their periods range from 0.3 to 1.7 d, though two cases are known at longer periods, up to 2.7 d (Henry et al 2007(Henry et al , 2011. Our periods are compatible with this range.…”

Section: Group 4 Of Periodic Variables: γ Dor Candidatessupporting

confidence: 78%

Stellar variability in open clusters

Mowlavï¹,

Barblan²,

Saesen³

et al. 2013

A&A

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“…Some suggested mechanisms for periodic variability of late-A/early-F dwarfs are ellipsoidal distortions due to a close binary, surface features causing brightness modulations, and/or δ Sct or γ Dor pulsations (see Henry et al 2011 and references therein). González & Levato (2009) included these two stars as part of a long term spectroscopic survey looking for binaries in Blanco 1.…”

Section: Potential γ Doradus Blanco 1 Starsmentioning

confidence: 99%

Evaluating Gyrochronology on the Zero-Age-Main-Sequence: Rotation Periods in the Southern Open Cluster Blanco 1 From the Kelt-South Survey

Cargile

James

Pepper

et al. 2014

ApJ

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We report periods for 33 members of Blanco 1 as measured from Kilodegree Extremely Little Telescope-South light curves, the first reported rotation periods for this benchmark zero-age-main-sequence open cluster. The distribution of these stars spans from late-A or early-F dwarfs to mid-K with periods ranging from less than a day to ∼8 days. The rotation period distribution has a morphology similar to the coeval Pleiades cluster, suggesting the universal nature of stellar rotation distributions. Employing two different gyrochronology methods, we find an age of 146 +13 −14 Myr for the cluster. Using the same techniques, we infer an age of 134 +9 −10 Myr for the Pleiades measured from existing literature rotation periods. These rotation-derived ages agree with independently determined cluster ages based on the lithium depletion boundary technique. Additionally, we evaluate different gyrochronology models and quantify levels of agreement between the models and the Blanco 1/Pleiades rotation period distributions, including incorporating the rotation distributions of clusters at ages up to 1.1 Gyr. We find the Skumanich-like spin-down rate sufficiently describes the rotation evolution of stars hotter than the Sun; however, we find cooler stars rotating faster than predicted by a Skumanich law, suggesting a mass dependence in the efficiency of stellar angular momentum loss rate. Finally, we compare the Blanco 1 and Pleiades rotation period distributions to available nonlinear angular momentum evolution models. We find they require a significant mass dependence on the initial rotation rate of solar-type stars to reproduce the observed range of rotation periods at a given stellar mass and are furthermore unable to predict the observed over-density of stars along the upper envelope of the clusters' rotation distributions.

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“…Our current understanding is that they pulsate in high-order gravity (g) modes (Kaye et al 1999a), excited by a flux modulation mechanism induced by the upper convective layer (Guzik et al 2000;Dupret et al 2004;. Typical γ Dor periods are between 8 h and 3 d. From the ground, about 70 bona fide and 88 candidate γ Dor pulsators have been detected (Balona et al 1994;Handler 1999;De Cat et al 2006;Henry et al 2011, among other papers).…”

Section: Introductionmentioning

confidence: 99%

TheKeplercharacterization of the variability among A- and F-type stars

Uytterhoeven

Moya

Grigahcène

et al. 2011

A&A

333

316

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Context. The Kepler spacecraft is providing time series of photometric data with micromagnitude precision for hundreds of A-F type stars. Aims. We present a first general characterization of the pulsational behaviour of A-F type stars as observed in the Kepler light curves of a sample of 750 candidate A-F type stars, and observationally investigate the relation between γ Doradus (γ Dor), δ Scuti (δ Sct), and hybrid stars. Methods. We compile a database of physical parameters for the sample stars from the literature and new ground-based observations. We analyse the Kepler light curve of each star and extract the pulsational frequencies using different frequency analysis methods. We construct two new observables, "energy" and "efficiency", related to the driving energy of the pulsation mode and the convective efficiency of the outer convective zone, respectively. Results. We propose three main groups to describe the observed variety in pulsating A-F type stars: γ Dor, δ Sct, and hybrid stars. We assign 63% of our sample to one of the three groups, and identify the remaining part as rotationally modulated/active stars, binaries, stars of different spectral type, or stars that show no clear periodic variability. 23% of the stars (171 stars) are hybrid stars, which is a much higher fraction than what has been observed before. We characterize for the first time a large number of A-F type stars (475 stars) in terms of number of detected frequencies, frequency range, and typical pulsation amplitudes. The majority of hybrid stars show frequencies with all kinds of periodicities within the γ Dor and δ Sct range, also between 5 and 10 d −1 , which is a challenge for the current models. We find indications for the existence of δ Sct and γ Dor stars beyond the edges of the current observational instability strips. The hybrid stars occupy the entire region within the δ Sct and γ Dor instability strips and beyond. Non-variable stars seem to exist within the instability strips. The location of γ Dor and δ Sct classes in the (T eff , log g)-diagram has been extended. We investigate two newly constructed variables, "efficiency" and "energy", as a means to explore the relation between γ Dor and δ Sct stars. Conclusions. Our results suggest a revision of the current observational instability strips of δ Sct and γ Dor stars and imply an investigation of pulsation mechanisms to supplement the κ mechanism and convective blocking effect to drive hybrid pulsations. Accurate physical parameters for all stars are needed to confirm these findings.

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A Volume-Limited Photometric Survey of 114 Γ Doradus Candidates

Cited by 35 publications

References 100 publications

Stellar variability in open clusters

Stellar variability in open clusters

Evaluating Gyrochronology on the Zero-Age-Main-Sequence: Rotation Periods in the Southern Open Cluster Blanco 1 From the Kelt-South Survey

TheKeplercharacterization of the variability among A- and F-type stars

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