Paper Abstracts

Buser R. (1978, A&A, 62, 425)


Improved transformation equations for the UBV and RGU systems have been derived from synthetic colors computed from detailed spectral energy distributions of main-sequence stars. The effects of interstellar reddening have been accounted for, including the variations of the reddening parameters of the two systems due to (1) different degrees of extinction, and (2) the intrinsic colors of stars.

Earlier transformations by different authors are briefly discussed and are shown to be affected by inadequacies that have been removed in the present analysis. The revised mean RGU standard main sequence and the zero-age main-sequence have been computed.

Bessel M.S. (1995, PASP 107, 672)


The photometry of Landolt has been transformed onto the Cousins (SAAO) system by using polynomial fits to photometry of 230 common stars. The accuracy of the fits are within 0.01 mag for (B-V), (V-R) and (V-I) and 0.02 mag for (U-B). The BVRI photometry of Bessell and Weis has also been transformed.

Bessel M.S., Weis E.W. (1987, PASP 99, 642)


Cubic transformations have been derived between colors measured in the Cousins and the Kron systems using measurements of common stars with spectral types from A0 V to M6 V. Polynomial fits are also derived for the mean main sequence for late-type dwarfs.

Cramer N. (1984, A&A, 132, 283)


The relation linking the Geneva and Johnson U, B, V intrinsic colours of B-type stars of classes V to III are defined via estimators based on the Geneva reddening-free X and Y parameters. These estimators allow the direct intercomparison of the properties of these three photometric frameworks of analysis. A new Teff vs X relation is defined and, in a first application of the relation above, is compared with existing Teff vs Johnson (U, B, V) relations.

Caldwell J.A.R., et al. (1993, SAAO Circ. 15, 1)


Polynomial relations are given for the prediction of one photometric colour from another, based on accurate and homogeneous photometry.

Fernie J.D. (1983, PASP 95, 782)


The transformation in (V-R), (V-I) and (R-I) between the photometric systems of Johnson and Kron-Cousins are investigated using the new Johnson UBVRI standards now appearing in . Transformations for very red stars are determined separately from other data.

Meylan G., Hauck B. (A&A Suppl. 46, 281


The relations between temperature parameters of various photometric systems are given. The photometries concerned are the following: UBVB1B2V1G (Geneva), UBV (Johnson), uvby-beta (Strömgren), UPXYZVS (Vilnius), UBVRIJKLMNH (Johnson), UVBGRI (Stebbins and Whitford). The effects due to the different luminosity classes and to blanketing (Am, Ap and population II dwarf stars) are taken into account.

Natali E., et al. (1994, A&A 289, 756)


We present an analysis derived from the UBVRI photometry of 12 open clusters, that shows a linear relationship between the color indices (B-I) and (B-V). Due to this characteristics the (B-I) color index is a more sensitive estimator of the effective stellar temperatures with respect to the widely used (B-V), and it is less affected by the absorption bands of H2 molecules in low mass stars. Furthermore, from the two colors (B-I) vs (B-V) diagrams we derive a new method yielding a parameter that estimates the interstellar reddening fro each cluster.

Ruelas_Mayorga R.A., Noriega-Mendoza H.


A set of infrared standard stars for the South African Astronomical Observatory (SAAO) are observed from the Observatorio Astronomico Nacional (OAN) located at San Pedro Martir (SPM) in northern Mexico. A number of linear transformation equations is obtained; in them, there is a slight need for a colour term which implies that both sets of filters have slightly different values for their effective wavelengths. Values for the OAN mean extinction coefficients are calculated. They are larger that the values reported in Carrasco et al. (1991); they might, however, be due to the ash and debris deposited on the atmosphere by recent volcanic eruptions. We also calculate a set of colour transformations to the homogeneous IR photometric system proposed by Bessell and Brett (1988).

Taylor B.J. (1986, ApJS 60, 577)


Transformation among VRI systems are commonly beset by Paschen-jump effects, for which fully satisfactory allowance has not previously been made. This paper describes two new techeniques which are based on the work of Gutierrez-Moreno, and which allow fully for the effects of the Paschen jump. Values of E(V-R)/E(B-V) and E(R-I)/E(B-V) are also given for the Cousins system for a wide range of temperatures. These and the new techniques contribute to a set of new transformation relations which apply for most VRI systems; the status of the remaining systems is reviewed, and future work needed for them is described. Two major sources of Cousins VRI data underlie the new relations; the consistency of these sources is reviewed and found generally satisfactory, although more work on this question is needed. Finally, three tables of transformed standard-star and other data are given for the Cousins and Johnson systems, and a description of ways to reproduce the latter is presented.

Turner D.G. (1990, PASP 102, 1331)


Transfromation relations are derived for the conversion of Stromgren colors for early-type stars into equivalent Johnson system colors. The relation

(U-B) = 0.675 (u-b) - 0.938

is valid for O and B stars of all luminosity classes and A and F stars of luminosity classes III to V. The relation

(B-V) = 1.584 (b-y) + 0.681 m1 - 0.116

is valid for O and B stars of all luminosity classes and A stars of luminosity classes III to V. No significant reddening corrections appear to be necessary with these relations, which are accurate to 0.016 and 0.022 in the transformed values of (B-V)> and (U-B), respectively. Examples are given of color-dependant and magnitude-dependent effects in published UBV data. Such problems have important consequences for the distance scale of cluster cepheids.
Last update: 7 Novembre 1995