Absolute Dimensions of the G7+k7 Eclipsing Binary Star Im Virginis: Discrepancies With Stellar Evolution Models

Morales, J. C.; Torres, Guillermo; Marschall, Laurence A.; Brehm, W.

doi:10.1088/0004-637x/707/1/671

Cited by 46 publications

(28 citation statements)

References 56 publications

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“…At this point we recall the findings of radius and temperature inconsistencies for active low-mass eclipsing binaries with model computations (e.g. Morales et al 2009Morales et al , 2010. Oversized stars with a temperature deficit caused by chromospheric activity could alter the true stellar position in the H-R diagram, thus affect the mass and age estimate.…”

Section: Rotation Induced Radial-velocity Variationsmentioning

confidence: 76%

Binary-induced magnetic activity?

Strassmeier

Carroll

Weber

et al. 2011

A&A

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Context. Multi-wavelength time-series observations with high cadence and long duration are needed to resolve and understand the many variations of magnetically active late-type stars, which is an approach often used to observe the Sun. Aims. We present a first and detailed study of the bright and active K0IV-III star HD 123351. Methods. We acquired a total of 955 high-resolution STELLA echelle spectra during the years 2006-2010 and a total of 2260 photometric VI C data points during 1998-2010. These data are complemented by some spectra from CFHT and KPNO. Results. The star is found to be a single-lined spectroscopic binary with a period of 147.8919 ± 0.0003 days and a large eccentricity of e = 0.8086 ± 0.0001. The rms of the orbital solution is just 47 m s −1 , making it the most precise orbit ever obtained for an active binary system. The rotation period is constrained from long-term photometry to be 58.32 ± 0.01 days. It shows that HD 123351 is a very asynchronous rotator, rotating five times slower than the expected pseudo-synchronous value. Two spotted regions persisted throughout the 12 years of our observations. We interpret them as active longitudes on a differentially rotating surface with a ΔP/P of 0.076. Four years of Hα, Ca ii H&K and He i D3 monitoring identifies the same main periodicity as the photometry but dynamic spectra also indicate that there is an intermittent dependence on the orbital period, in particular for Ca ii H&K in 2008. Line-profile inversions of a pair of Zeeman sensitive/insensitive iron lines yield an average surface magnetic-flux density of 542 ± 72 G. The time series for 2008 is modulated by the stellar rotation as well as the orbital motion, such that the magnetic flux is generally weaker during times of periastron and that the chromospheric emissions vary in anti-phase with the magnetic flux. We also identify a broad and asymmetric lithium line profile and measure an abundance of log n(Li) = 1.70 ± 0.05. The star's position in the H-R diagram indicates a mass of 1.2 ± 0.1 M and an age of 6-7 Gyr. Conclusions. We interpret the anti-phase relation of the magnetic flux with the chromospheric emissions as evidence that there are two magnetic fields present at the same time, a localized surface magnetic field associated with spots and a global field that is oriented towards the (low-mass) secondary component. We suggest that the inter-binary field is responsible for the magnetic-flux dilution at periastron. It is also likely to be responsible for the unexpected slow and asynchronous rotation of the primary star.

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Section: Rotation Induced Radial-velocity Variationsmentioning

confidence: 76%

Binary-induced magnetic activity?

Strassmeier

Carroll

Weber

et al. 2011

A&A

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“…Chabrier et al 2007;Morales et al 2010). Even in higher mass G-and K-dwarfs, strong magnetic activity in the stars results in disagreement with stellar models (Morales et al 2009). However, in wider separation M-dwarf DLEBs with magnetically inactive low-mass stars, the radii are still inflated (Irwin et al 2011;Doyle et al 2011), with no real convergence towards stellar models at longer periods (Birkby et al 2012).…”

Section: Discussionmentioning

confidence: 92%

Detection of carbon monoxide in the high-resolution day-side spectrum of the exoplanet HD 189733b

Kok

Brogi

Snellen

et al. 2013

A&A

219

170

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Context. After many attempts over more than a decade, high-resolution spectroscopy has recently delivered its first detections of molecular absorption in exoplanet atmospheres, both in transmission and thermal emission spectra. Targeting the combined signal from individual lines in molecular bands, these measurements use variations in the planet radial velocity to separate the planet signal from telluric and stellar contaminants. Aims. We apply high-resolution spectroscopy to probe molecular absorption in the day-side spectrum of the bright transiting hot Jupiter HD 189733b. Methods. We observed HD 189733b with the CRIRES high-resolution near-infrared spectograph on the Very Large Telescope during three nights, targeting possible absorption from carbon monoxide, water vapour, methane, and carbon dioxide, at 2.0 and 2.3 μm. Results. We detect a 5-σ absorption signal from CO at a contrast level of ∼4.5 × 10 −4 with respect to the stellar continuum, revealing the planet orbital radial velocity at 154 +4 −3 km s −1 . This allows us to solve for the planet and stellar mass in a similar way as for stellar eclipsing binaries, resulting in M s = 0.846 +0.068 −0.049 M and M p = 1.162 +0.058 −0.039 M Jup . No significant absorption is detected from H 2 O, CO 2 , or CH 4 and we determine upper limits on their line contrasts. Conclusions. The detection of CO in the day-side spectrum of HD 189733b can be made consistent with the haze layer proposed to explain the optical to near-infrared transmission spectrum if the layer is optically thin at the normal incidence angles probed by our observations, or if the CO abundance is high enough for the CO absorption to originate from above the haze. Our non-detection of CO 2 at 2.0 μm is not inconsistent with the deep CO 2 absorption from low-resolution NICMOS secondary eclipse data in the same wavelength range. If genuine, the absorption would be so strong that it blanks out any planet light completely in this wavelength range, leaving no high-resolution signal to be measured.

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“…This sometimes leads to introducing and/or calibrating some physical processes in evolutionary codes, such as convective core overshooting, or to varying the external convection efficiency through the mixing-length parameter (see e.g. Andersen 1991;Pols et al 1997;Ribas et al 2000;Torres et al 2006Torres et al , 2010Torres et al , 2014Morales et al 2009;Clausen et al 2009Clausen et al , 2010, and references therein).…”

Section: Introductionmentioning

confidence: 99%

Grid-based estimates of stellar ages in binary systems

Valle

Dell’Omodarme

Moroni

et al. 2015

A&A

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Aims. We investigate the performance of grid-based techniques in estimating the age of stars in detached eclipsing binary systems. We evaluate the precision of the estimates due to the uncertainty in the observational constraints -masses, radii, effective temperatures, and [Fe/H] -and the systematic bias caused by the uncertainty in convective core overshooting, element diffusion, mixing-length value, and initial helium content. Methods. We adopted the SCEPtER grid, which includes stars with mass in the range [0.8; 1.6] M and evolutionary stages from the zero-age main sequence to the central hydrogen depletion. Age estimates have been obtained by a generalisation of the maximum likelihood technique described in our previous work. Results. We showed that the typical 1σ random error in age estimates -due only to the uncertainty affecting the observational constraints -is about ±7%, which is nearly independent of the masses of the two stars. However, such an error strongly depends on the evolutionary phase and becomes larger and asymmetric for stars near the zero-age main sequence where it ranges from about +90% to −25%. The systematic bias due to the including convective core overshooting -for mild and strong overshooting scenariosis about 50% and 120% of the error due to observational uncertainties. A variation of ±1 in the helium-to-metal enrichment ratio ΔY/ΔZ accounts for about ±150% of the random error. The neglect of microscopic diffusion accounts for a bias of about 60% of the error due to observational uncertainties. We also introduced a statistical test of the expected difference in the recovered age of two coeval stars in a binary system. We find that random fluctuations within the current observational uncertainties can lead genuine coeval binary components to appear to be non-coeval with a difference in age as high as 60%.

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Absolute Dimensions of the G7+k7 Eclipsing Binary Star Im Virginis: Discrepancies With Stellar Evolution Models

Cited by 46 publications

References 56 publications

Binary-induced magnetic activity?

Binary-induced magnetic activity?

Detection of carbon monoxide in the high-resolution day-side spectrum of the exoplanet HD 189733b

Grid-based estimates of stellar ages in binary systems

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