Chromospheric CA II H and K and H-alpha emission in single and binary stars of spectral types F6-M2

Strassmeier, K. G.; Fekel, Francis C.; Bopp, B. W.; Dempsey, Robert C.; Henry, Gregory W.

doi:10.1086/191414

Cited by 206 publications

(188 citation statements)

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“…The main error source is the errors on V − R, while the error from measuring the fluxes in the spectra are around 0.02 on log R HK for both stars. Strassmeier et al (1990) found log R HK = −3.85 for HD 27536. Taking into account the differences in derived T eff and V − R, the present result and the findings of Strassmeier et al (1990) are similar: using their parameters, our values of log R HK would shift by +0.21.…”

Section: Radial Velocities Bisectors and Activity Indexesmentioning

confidence: 98%

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: Radial Velocities Bisectors and Activity Indexesmentioning

confidence: 98%

Binarity, activity and metallicity among late-type stars

Dall¹,

Bruntt²,

Strassméier

2005

A&A

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“…The Sun and Sun-like stars with convection zones in their outer envelopes, have long been known to exhibit emission line and X-ray activity, associated with hot gas in chromospheres, transition regions, and coronae (e.g., Pizzolato et al 2003;Strassmeier et al 1990;Wright et al 2011). Understanding this activity, and understanding how the solar case relates to the activity observed across the HR diagram is a long-standing puzzle.…”

Section: Introductionmentioning

confidence: 99%

Convection and differential rotation properties of G and K stars computed with the ASH code

Matt

Cao

Brown³

et al. 2011

Astron Nachr

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The stellar luminosity and depth of the convective envelope vary rapidly with mass for G-and K-type main sequence stars. In order to understand how these properties influence the convective turbulence, differential rotation, and meridional circulation, we have carried out 3D dynamical simulations of the interiors of rotating main sequence stars, using the anelastic spherical harmonic (ASH) code. The stars in our simulations have masses of 0.5, 0.7, 0.9, and 1.1 M , corresponding to spectral types K7 through G0, and rotate at the same angular speed as the Sun. We identify several trends of convection zone properties with stellar mass, exhibited by the simulations. The convective velocities, temperature contrast between up-and downflows, and meridional circulation velocities all increase with stellar luminosity. As a consequence of the trend in convective velocity, the Rossby number (at a fixed rotation rate) increases and the convective turnover timescales decrease significantly with increasing stellar mass. The three lowest mass cases exhibit solar-like differential rotation, in a sense that they show a maximum rotation at the equator and minimum at higher latitudes, but the 1.1 M case exhibits anti-solar rotation. At low mass, the meridional circulation is multi-cellular and aligned with the rotation axis; as the mass increases, the circulation pattern tends toward a unicellular structure covering each hemisphere in the convection zone.

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“…Fast rotation of the star is similar to FK Comae type stars, but Bl is weaker, compared to FK Comae (60 to 272G) (Korhonen et al 2009). The star is also in a different activity level with emission components in Hα and CaII H&K lines not so strong as in FK Comae (Korhonen et al 2009, Strassmeier et al 1990.…”

Section: Observations Results and Conclusionmentioning

confidence: 97%

The Hertzsprung-gap giant 31 Comae in 2013: Magnetic field and activity indicators

et al. 2013

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Abstract. We have observed the giant star 31 Comae in April and May 2013 with the spectropolarimeter Narval at Pic du Midi Observatory, France. 31 Comae is a single, rapidly rotating giant with rotational period ∼ 6.8 d and vsini ∼ 67 km/s. We present measurements and discuss variability of the longitudinal magnetic field (Bl), spectral activity indicators Hα , CaII H&K, Ca II IR triplet and evolutionary status. Our future aim is to perform a Zeeman-Doppler imaging study for the star.

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Chromospheric CA II H and K and H-alpha emission in single and binary stars of spectral types F6-M2

Cited by 206 publications

References 0 publications

Binarity, activity and metallicity among late-type stars

Binarity, activity and metallicity among late-type stars

Convection and differential rotation properties of G and K stars computed with the ASH code

The Hertzsprung-gap giant 31 Comae in 2013: Magnetic field and activity indicators

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