Binary incidence among the BY Draconis variables

Bopp, B. W.; Fekel, Francis C.

doi:10.1086/112079

Cited by 88 publications

(40 citation statements)

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“…HD 216803 (TW PsA, HR8721, Gl879) is classified as a BY Dra star (Bopp & Fekel 1977). It is a K5 dwarf with a rotation period of 10.3 days but with a small projected rotational velocity of 2.6 km s −1 (Vogt et al 1983), indicating an inclination of approximately 30 • .…”

Section: The Target Starsmentioning

confidence: 99%

“…Bopp & Fekel 1977;Edwards 1983;Shkolnik et al 2003). The differential gravitational pull from a companion may cause a longitude-and latitude-dependent relationship between rotation rate and activity level, and may also contribute to an inhomogeneous chemical abundance by introducing tidal waves which affect the chemical stratification.…”

Section: Introductionmentioning

confidence: 99%

“…Our sample consist of about 30 known active G-M stars, with known photometric variations attributed to rotational modulation of star spots, including both binaries and -supposedly -single stars. Most of our sample stars belong to the BY Draconis variables, which are defined from their variability due to changing star spot coverage (Bopp & Fekel 1977). Several aspects need to be investigated to properly analyze the sample, including (1) timeresolved RV monitoring and (2) line bisector analysis, (3) monitoring of activity indexes, (4) determination of fundamental atmospheric parameters, and (5) accurate photospheric abundance analysis.…”

Section: Introductionmentioning

confidence: 99%

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Binarity, activity and metallicity among late-type stars

Dall¹,

Bruntt²,

Strassméier

2005

A&A

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We present the first in a series of papers that attempt to investigate the relation between binarity, magnetic activity, and chemical surface abundances of cool stars. In the current paper, we lay out and test two abundance analysis methods and apply them to two well-known, active, single stars, HD 27536 (G8IV-III) and HD 216803 (K5V), presenting photospheric fundamental parameters and abundances of Li, Al, Ca, Si, Sc, Ti, V, Cr, Fe, Co and Ni. The abundances from the two methods agree within the errors for all elements except calcium in HD 216803, which means that either method yields the same fundamental model parameters and the same abundances. Activity is described by the radiative loss in the Ca ii H and K lines with respect to the bolometric luminosity, through the activity index R HK . Binarity is established by very precise radial velocity (RV) measurements using HARPS spectra. The spectral line bisectors are examined for correlations between RV and bisector shape to distinguish between the effects of stellar activity and unseen companions. We show that HD 27536 exhibit RV variations mimicking the effect of a low-mass (m ∼ 4 M J ) companion in a relatively close (a ∼ 1 AU) orbit. The variation is strongly correlated with the activity, and consistent with the known photometric period P = 306.9 d, demonstrating a remarkable coherence between R HK and the bisector shape, i.e. between the photosphere and the chromosphere. We discuss the complications involved in distinguishing between companion and activity induced RV variations.

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Section: The Target Starsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Binarity, activity and metallicity among late-type stars

Dall¹,

Bruntt²,

Strassméier

2005

A&A

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“…For instance, close binaries (a < ∼ 0.1 AU) experience a tidal torque which acts to synchronize their rotation with the orbital motion of the system, in addition to any magnetic torque they experience due to stellar winds (Zahn 1989;1994); thus, as they evolve along the main-sequence, components in the closest binaries tend to rotate faster (on average) than single stars of similar mass and age. Observations of RS CVn and BY Dra systems have shown Zahn's theoretical framework to be correct (Hall 1976;Bopp & Fekel 1977;Fekel et al 1986). Binary/multiple systems must therefore be avoided, where the data allow, in establishing gyrochronology ages of stars (see Meibom et al 2006, for a more thorough discussion).…”

Section: Introductionmentioning

confidence: 99%

New rotation periods in the open cluster NGC 1039 (M 34), and a derivation of its gyrochronology age

James

Barnes

Meibom

et al. 2010

A&A

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Aims. Employing photometric rotation periods for solar-type stars in NGC 1039 [M 34], a young, nearby open cluster, we use its mass-dependent rotation period distribution to derive the cluster's age in a distance independent way, i.e., the so-called gyrochronology method. Methods. We present an analysis of 55 new rotation periods, using light curves derived from differential photometry, for solar type stars in the open cluster NGC 1039 [M 34]. We also exploit the results of a recently-completed, standardized, homogeneous BV Ic CCD survey of the cluster, performed by the Indiana Group of the WIYN open cluster survey, in order to establish photometric cluster membership and assign B − V colours to each photometric variable. We describe a methodology for establishing the gyrochronology age for an ensemble of solar-type stars. Empirical relations between rotation period, photometric colour and stellar age (gyrochronology) are used to determine the age of M 34. Based on its position in a colour-period diagram, each M 34 member is designated as being either a solid-body rotator (interface or I-star), a differentially rotating star (convective or C-star) or an object which is in some transitory state in between the two (gap or g-star). Fitting the period and photometric colour of each I-sequence star in the cluster, we derive the cluster's mean gyrochronology age. Results. Of the photometric variable stars in the cluster field, for which we derive a period, 47 out of 55 of them lie along the loci of the cluster main sequence in V/B − V and V/V − I space. We are further able to confirm kinematic membership of the cluster for half of the periodic variables [21/55], employing results from an on-going radial velocity survey of the cluster. For each cluster member identified as an I-sequence object in the colour-period diagram, we derive its individual gyrochronology age, where the mean gyro age of M 34 is found to be 193 ± 9 Myr. Conclusions. Using differential photometry, members of a young open cluster can be easily identified in a colour−magnitude diagram from their periodic photometric variability alone. Such periodicity can be used to establish a period-colour distribution for the cluster, which for M 34, we have used to derive its gyrochronology age of 193 ± 9 Myr. Formally, our gyro age of M 34 is consistent (within the errors) with that derived using several distance-dependent, photometric isochrone methods (250 ± 67 Myr).

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“…; 5, Bopp & Fekel (1977);6, Shkolnik et al (2010);7, Harlow (1996); 8, Law et al (2006); 9, Gizis et al (2002). Karmn Name SpT pEW(Hα) Ref.…”

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CARMENES input catalogue of M dwarfs

Jeffers

Schöfer

Lamert

et al. 2018

A&A

139

141

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CARMENES is a spectrograph for radial velocity surveys of M dwarfs with the aim of detecting Earth-mass planets orbiting in the habitable zones of their host stars. To ensure an optimal use of the CARMENES Guaranteed Time Observations, in this paper we investigate the correlation of activity and rotation for approximately 2200 M dwarfs, ranging in spectral type from M0.0 V to M9.0 V. We present new high-resolution spectroscopic observations with FEROS, CAFE, and HRS of approximately 500 M dwarfs. For each new observation, we determined its radial velocity and measured its Hα activity index and its rotation velocity. Additionally, we have multiple observations of many stars to investigate if there are any radial velocity variations due to multiplicity. The results of our survey confirm that early-M dwarfs are Hα inactive with low rotational velocities and that late-M dwarfs are Hα active with very high rotational velocities. The results of this high-resolution analysis comprise the most extensive catalogue of rotation and activity in M dwarfs currently available.

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Binary incidence among the BY Draconis variables

Cited by 88 publications

References 0 publications

Binarity, activity and metallicity among late-type stars

Binarity, activity and metallicity among late-type stars

New rotation periods in the open cluster NGC 1039 (M 34), and a derivation of its gyrochronology age

CARMENES input catalogue of M dwarfs

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