HR 7578 - A K dwarf double-lined spectroscopic binary with peculiar abundances

Fekel, Francis C.; Beavers, W. I.

doi:10.1086/160905

Cited by 14 publications

(17 citation statements)

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“…via a bootstrap algorithm (Wang et al 2012). Our best-fit orbital solution is in excellent agreement with the one found by Fekel & Beavers (1983) and of much higher accuracy.…”

Section: Resultssupporting

confidence: 78%

Searching for Earth-mass planets around α Centauri: precise radial velocities from contaminated spectra

Bergmann

Endl

Hearnshaw

et al. 2014

International Journal of Astrobiology

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This work is part of an ongoing project which aims to detect terrestrial planets in our neighbouring star system α Centauri using the Doppler method. Owing to the small angular separation between the two components of the α Cen AB binary system, the observations will to some extent be contaminated with light coming from the other star.We are accurately determining the amount of contamination for every observation by measuring the relative strengths of the H-α and NaD lines. Furthermore, we have developed a modified version of a well established Doppler code that is modelling the observations using two stellar templates simultaneously. With this method we can significantly reduce the scatter of the radial velocity measurements due to spectral cross-contamination and hence increase our chances of detecting the tiny signature caused by potential Earth-mass planets. After correcting for the contamination we achieve radial velocity precision of ∼ 2.5 m s −1 for a given night of observations.We have also applied this new Doppler code to four southern double-lined spectroscopic binary systems (HR159, HR913, HR7578, HD181958) and have successfully recovered radial velocities for both components simultaneously.

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“…via a bootstrap algorithm (Wang et al 2012). Our best-fit orbital solution is in excellent agreement with the one found by Fekel & Beavers (1983) and of much higher accuracy.…”

Section: Resultssupporting

confidence: 78%

Searching for Earth-mass planets around α Centauri: precise radial velocities from contaminated spectra

Bergmann

Endl

Hearnshaw

et al. 2014

International Journal of Astrobiology

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“…One binary, HR 7578 = V4200 Sgr, is rather reminiscent of HD 18955. It consists of a pair of K2-K3 dwarfs that have an orbit with a period of 46.82 days and an eccentricity of 0.69 (Fekel & Beavers 1983). The calculated pseudosynchronous period is 7.5 days.…”

Section: Discussionmentioning

confidence: 99%

Chromospherically Active Stars. XXII. HD 18955, A Massive K Dwarf Binary

2004

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HD 18955 is a double-lined spectroscopic binary with a period of 43.3214 days and a high eccentricity of 0.761. The spectral types of the components are K0 V and K2-K3 V. The secondary is a typical early K dwarf, although its minimum mass is greater than canonical values. However, this larger mass is consistent with other early K dwarf, spectroscopic binary results. The primary is anomalous, being substantially underluminous for its radius and mass, which are equal to or slightly greater than solar values. A lack of lithium argues that the components are not pre-main-sequence stars. The large minimum masses of both components suggest that the system has a high orbital inclination. Our photometric observations around the times of conjunction show no evidence of eclipses, but considering the uncertainties in the ephemerides, there is only a 50% chance that our photometric observations would have detected the primary eclipse and almost no chance that we covered the secondary eclipse. Hence, eclipses remain a real possibility in this system. Photometric variations with an amplitude of 0.02 mag reveal a period of 7.55 days, which is assumed to be the primary star's rotation period. Thus, given the spectral types of the stars, this system is a BY Draconis type variable. With v sin i values of 5 km s À1 for both components, the two stars are rotating more rapidly than typical K dwarf field stars, but the observed rotation period is still substantially longer than the predicted pseudosynchronous rotation period of 4.6 days for the primary.

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“…As illustrated in the figure, there are two stars (one in the calibration set and the other in the testing set) for which the predicted temperatures differ significantly from the tabulated temperatures (marked with an open circle). Those two stars are HR 7578, a spectroscopic binary (Fekel & Beavers 1983), and HD 188512 (Alshain), a variable star that is evolving off the main sequence (Corsaro et al 2012).…”

Section: S 4 Nmentioning

confidence: 99%

A PCA approach to stellar effective temperatures

Bermejo

Ramos

Prieto

2013

A&A

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Context. The derivation of the effective temperature of a star is a critical first step in a detailed spectroscopic analysis. Spectroscopic methods suffer from systematic errors related to model simplifications. Photometric methods may be more robust, but are exposed to the distortions caused by interstellar reddening. Direct methods are difficult to apply, since fundamental data of high accuracy are hard to obtain. Aims. We explore a new approach in which the spectrum is used to characterize a star's effective temperature based on a calibration established by a small set of standard stars. Methods. We perform principal component analysis on homogeneous libraries of stellar spectra, then calibrate a relationship between the principal components and the effective temperature using a set of stars with reliable effective temperatures. Results. We find that our procedure gives excellent consistency when spectra from a homogenous set of observations are used. Systematic offsets may appear when combining observations from different sources. Using as reference the spectra of stars with high-quality spectroscopic temperatures in the Elodie library, we define a temperature scale for FG-type disk dwarfs with an internal consistency of about 50 K, in excellent agreement with temperatures from direct determinations and widely used scales based on the infrared flux method.

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HR 7578 - A K dwarf double-lined spectroscopic binary with peculiar abundances

Cited by 14 publications

References 0 publications

Searching for Earth-mass planets around α Centauri: precise radial velocities from contaminated spectra

Searching for Earth-mass planets around α Centauri: precise radial velocities from contaminated spectra

Chromospherically Active Stars. XXII. HD 18955, A Massive K Dwarf Binary

A PCA approach to stellar effective temperatures

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