Accurate effective temperatures of the metal-poor benchmark stars HD 140283, HD 122563, and HD 103095 from CHARA interferometry

Abstract

Large stellar surveys of the Milky Way require validation with reference to a set of "benchmark" stars whose fundamental properties are well-determined. For metal-poor benchmark stars, disagreement between spectroscopic and interferometric effective temperatures has called the reliability of the temperature scale into question. We present new interferometric measurements of three metal-poor benchmark stars, HD 140283, HD 122563, and HD 103095, from which we determine their effective temperatures. The angular sizes of all the stars were determined from observations with the PAVO beam combiner at visible wavelengths at the CHARA array, with additional observations of HD 103095 made with the VEGA instrument, also at the CHARA array. Together with photometrically derived bolometric fluxes, the angular diameters give a direct measurement of the effective temperature. For HD 140283 we find θ LD =0.324±0.005 mas, T eff =5787±48 K; for HD 122563, θ LD =0.926±0.011 mas, T eff =4636±37 K; and for HD 103095 θ LD =0.595±0.007 mas, T eff =5140±49 K. Our temperatures for HD 140283 and HD 103095 are hotter than the previous interferometric measurements by 253 K and 322 K, respectively. We find good agreement between our temperatures and recent spectroscopic and photometric estimates. We conclude some previous interferometric measurements have been affected by systematic uncertainties larger than their quoted errors.

Empirical Relations for the Accurate Estimation of Stellar Masses and Radii

“…All but three stars of Ligi et al (2016) have angular diameters of less than 1 mas. Karovicova et al (2018) suggested that the Ligi et al (2016) catalog could be overestimating R. In any case, this subsample is always a small percentage of the total sample.…”

SkyMapper stellar parameters for Galactic Archaeology on a grand-scale

“…Stars with reliably measured angular diameters would provide an equally good reference set (e.g. Karovicova et al 2018;White et al 2018), but only a handful of such objects are presently available, and because of their brightness they are also saturated in SkyMapper. We remark that the T eff scale we adopt has been tested against interferometric angular diameters confirming its accuracy (Casagrande et al 2014a;Karovicova et al 2018;White et al 2018).…”

Interferometric diameters of five evolved intermediate-mass planet-hosting stars measured with PAVO at the CHARA Array

“…Although the PAVO interferometric temperatures for these stars are significantly higher than previous interferometric determinations, they generally agree with the spectroscopic measurements given in Table 1. Only the temperature of 24 Sex disagrees with Bazot et al (2011), Huber et al (2012 and White et al (2013) are indicated by green squares, red giants from Huber et al (2012) are indicated by pink diamonds, and metal-poor stars from Karovicova et al (2018) are orange triangles. the value found by Mortier et al (2013) by 1.8σ, with the interferometric temperature being cooler by 161±90 K. We might therefore expect that the masses obtained using the interferometric measurements and constraints will generally agree with results in the literature.…”

“…Again, the K ′ -band measurement with Classic (0.861 ± 0.015 mas;Boyajian et al 2012) is larger. For HD 103095, there is only a 1.4σ difference between the VEGA (0.611±0.009 mas) and PAVO (0.595±0.007 mas) values(Karovicova et al 2018), both of which are substantially smaller than the value obtained from the FLUOR and Classic beam combiners (0.679 ± 0.015 mas;Creevey et al 2012). The PAVO diameter of HD 140283 (0.324 ± 0.005 mas;Karovicova et al 2018) is 2σ smaller than the VEGA measurement (0.353 ± 0.013 mas;Creevey et al 2015).…”