uvby Paper Abstracts


Balona L.A. (1984, MNRAS 211, 973)

Abstract

Using the Kurucz model atmospheres as a guide, we calibrate effective temperatures and bolometric corrections for early-type stars in terms of the Stromgren co and beta indices. These are placed on an empirical scale by adjusting the zero points for best agreement with measurements by Code et al. The form of the mass calibration is determined from evolutionary calculations and the zero point adjusted for best agreement with empirical determinations. A mass discrepancy problem arises when these masses are compared with those determined from model atmospheres.


Balona L.A. (1994, NMNRAS 268, 119)

Abstract

We discuss the determination of effective temperature, bolometric correction and surface gravity using Stromgren indices. We use synthetic colours to define the functional relationship over a wide range of surface gravity, and calibrate the relationship by means of stars with well-determined effective temperatures and surface gravities. The calibrations are presented as interpolation formulae, valid for O-F stars. We find that the latest evolutionary computations predict masses that agree with those from detached eclipsing binaries to within 7 per cent. We discuss the position of the zero-age main sequence from the models relative to that observed in two young open clusters. There is a serious discrepancy between the surface gravity calculated from model atmospheres and from evolutionary models.


Gray R.O. (1991, A&A 252, 237)

Abstract

This paper is the second in a series of papers which derives an empirical calibration of the Stromgren uvby beta photometric system for the A, F and early G supergiants. This paper considers the F and early G supergiants. A calibration which gives the intrinsic colour (b-y)o in terms of a temperature parameter, [m1] and a gravity parameter delta [c1] is derived. This calibration is subjected to tests to determine the presence of systematic errors. It is also used to derive colour excesses for a set of classical Cepheid variable stars, which are compared to other estimates in the literature. Finally, the (b-y)o index is calibrated against the effective temperatures of Luck & Bond (1989), and the sensitivity of the calibration to metal abundance is discussed.


Gray R.O. (1992, A&A 265, 704)

Abstract

This paper, the third in a series, deals with calibration of Stromgren photometry for the A and early F supergiants. We derive a gravity parameter, delta G, which can be used to separate photometrically supergiants of different luminosity classes. delta G is used in conjunction with [m1] to derive a simple calibration which gives the intrinsic colour, (b-y)o of the supergiant. This calibration is tested and compared with other reddening estimates for A and F supergiants in the literature. Finally, we derive a semi-empirical effective temperature calibration for the A and F supergiants.


Napiwotzki R., et al. (1993, AA 268, 653)

Abstract

The determination of stellar temperatures and surface gravities by means of the Stromgren photometric system is examined in the region. We used a sample of stars with independently derived temperature and gravities. We compare our results with Castelli (1991) and present new temperature calibrations for normal stars ([u-b],(b-y)o, and Johnson (B-V)o) and for Ap stars ([u-b] and [c1]).

The use of integrated fluxes and especially the infrared flux method (IRFM) for determining stellar temperatures is discussed. SDurface gravities of B and A stars, derived by fitting theoretical profiles to the Balmer lines, are used to check the calibrations.


Olsen E.H. (1988, AA 189, 173)

Abstract

Several calibrations of Stromgren uvby-beta photometry with respect to the intrinsic colour (b-y)o exist for F-type stars. These calibration are complementary, since they are valid for different ranges of heavy element abundance. A new comprehensive intrinsic colour calibration is presented. It is valid for all F0-G2 stars of luminosity classes III-V, except possibly the most extreme population II stars. The calibration is based on 1231 stars. The rms scatter around the calibration is 0.009 (one star).


Schuster W.J., Nissen P.E. (1989, A&A 221, 65)

Abstract

The uvby beta photometry of 711 hight-velocity and metal-poor stars by Schuster and Nissen (1988, Paper I) has been used to derive new (b-y)o - beta and [Fe/H] calibrations. The interstellare color excess, E(b-y), can be determined with a standard deviation of 0.01 for beta values down to 2.55. The standard deviation of [Fe/H] increases from about 0.15 dex at [Fe/H]~-0.5 to about 0.30 dex at [Fe/H]~-2.5. The calibrations are particularly useful for metal-poor, late-F and G stars, and will be used to study the age-metallicity-kinematic relations of halo and old disk population stars. The error of E(b-y) for unresolved binary stars is shown to be negligible whereas the error of [Fe/H] is of the order of +0.10 to + 0.25 dex. Errors in beta due to radial velocity shifts of the H Beta line are shown to be negligible for the particular set of beta observations in Paper I. The derived reddenings and metallicities for stars from Paper I agree very well with data from the survey of proper motions stars by Laird et al. (1988) for the large majority of the 132 stars in common between the two works. However, about 10% of the stars have significant differences in the derived reddenings, which lead to differences in [Fe/H] of typically +0.40 dex. The [Fe/H] values for stars in Paper I do not agree particularly well with the [Fe/H] values of Sandage and Fouts (1987). From a comparison of data for 258 stars in common the standard deviation of the [Fe/H] values of Sandage and Fouts is estimated to be 0.35 dex. This error should be taken into account when deriving the intrinsic relations between kinematical parameters and metallicity from the data of Sandage and Fouts.


Smalley B., Dworetsky M.M. (1995, A&A 293, 446)

Abstract

We present an investigation into the determination of fundamental values of Tefff and log g. A re-evaluation of the fundamental values of T eff determined by Code et al. (1976) using modern flux measurements is presented, but there are no significant changes. A determination of fundamental values of Tefff for four binary systems with fundamental log g value has been performed. Medium-resolution Hbeta profiles of the fundamental stars have been obtained and compared to theoretical profiles in order to provide estimates of the parameters that have not been obtained in a fundamenta manner. We have calculated a table of synthetic beta indices which explicitly include the effects of metal-line blocking. We find that these beta indices are in good agreement with the photometric values. A comparison of theoretical uvby colours is also presented, and found to be in very good agreement with the photometric colours.


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Last update: 7 Novembre 1995