| 1. |
- Creevey, O. L., et al.
(författare)
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Fundamental properties of the Population II fiducial stars HD 122563 and Gmb 1830 from CHARA interferometric observations
- 2012
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 545, s. A17-
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Tidskriftsartikel (refereegranskat)abstract
- We have determined the angular diameters of two metal-poor stars, HD 122563 and Gmb 1830, using CHARA and Palomar Testbed Interferometer observations. For the giant star HD 122563, we derive an angular diameter theta(3D) = 0.940 +/- 0.011 milliarcseconds (mas) using limb-darkening from 3D convection simulations and for the dwarf star Gmb 1830 (HD 103095) we obtain a 1D limb-darkened angular diameter theta(1D) = 0.679 +/- 0.007 mas. Coupling the angular diameters with photometry yields effective temperatures with precisions better than 55 K (T-eff = 4598 +/- 41 K and 4818 +/- 54 K - for the giant and the dwarf star, respectively). Including their distances results in very well-determined luminosities and radii (L = 230 +/- 7 L-circle dot, R = 24.1 +/- 1.1 R-circle dot and L = 0.213 +/- 0.002 L-circle dot, R = 0.665 +/- 0.014 R-circle dot, respectively). We used the CESAM2k stellar structure and evolution code in order to produce models that fit the observational data. We found values of the mixing-length parameter alpha (which describes 1D convection) that depend on the mass of the star. The masses were determined from the models with precisions of < 3% and with the well-measured radii excellent constraints on the surface gravity are obtained (log g = 1.60 +/- 0.04, 4.59 +/- 0.02 dex, respectively). The very small errors on both log g and T-eff provide stringent constraints for spectroscopic analyses given the sensitivity of abundances to both of these values. The precise determination of T-eff for the two stars brings into question the photometric scales for metal-poor stars.
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| 2. |
- Wittkowski, M., et al.
(författare)
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CalVin 3 - A New Release of the ESO Calibrator Selection Tool for the VLT Interferometer
- 2011
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Ingår i: The Messenger. - : ESO. ; 145, s. 7-9
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Tidskriftsartikel (refereegranskat)abstract
- Interferometric observations require frequent measurements of calibration stars of known diameter to estimate the instrumental transfer function. ESO offers the preparation tool CalVin to select suitable calibrators from an underlying list of calibrators. The latest version 3, first released in January 2011, offers major improvements in the number of available calibrators, the functionality of the search tool, as well as in terms of performance and ease of use. It has been developed in a collaboration between ESO and the French Jean-Marie Mariotti Center (JMMC).
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| 3. |
- Guirado, J. C., et al.
(författare)
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VLTI/AMBER detection of a K=9.5 very low mass star
- 2013
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Ingår i: Memorie della Societa Astronomica Italiana. ; 84:4, s. 1044-
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Konferensbidrag (refereegranskat)abstract
- The precise determination of both the dynamical mass and infrared photometry of the close companion to AB Dor A, AB Dor C (0.090 solar masses), has provided an important benchmark for calibration of theoretical evolutionary models of low-mass young stars. However, comparison of the observed magnitudes of AB Dor C with these models suggests that they could overpredict the flux of this object, a trend also found in other young systems. One of the ambiguities remaining in AB Dor C is the possible binary nature of this star; in fact, should AB Dor C be close binary (about 10 mas separation), it could reconcile observations and models. We will report on VLTI/AMBER observations of AB Dor C addressed to discriminate between both scenarios: AB Dor C as a single object or a binary brown dwarf. We used a non-standard "off-axis" fringe tracking that allowed the detection of AB Dor C. This is, to our knowledge, one of the weakest objects detected by an infrared interferometer (Ks=9.5).
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