It is very easy to use a Planck distribution to show that a color index is a temperature parameter, but it is more difficult to calibrate such a color index in terms of temperature because only a few Teff values are determined. A pioneering work is that of Kuiper (1938), who derived a temperature scale according to spectral type (from A0 to M2 for dwarfs and from G0 to M8 for giants) and a Becker index. The first study giving a relation between Teff and a photoelectric color index is that of Popper (1959) in which the author derives a relation between Teff and B-V for the A and F stars and for G8 to K5 (dwarf and giant) stars. On this occasion, Popper shows the relation between temperature parameters of two photometric systems, R-I from the six-color system of Stebbins and Whitford, and B-V. This work was followed by a quantity of others from numerous authors in various systems, one of the most important being that of Johnson (1966). The purpose of the present study is not to review all the relations to be found in the literature but to define a set of stars which can be used to determine a calibration of a photometric parameter in terms of Teff.

Photometric abundance determinations using blanketing in the ultraviolet and violet spectral regions as well as the intensity of strong lines and bands is the most important tool in the study of chemical composition of faint and distant stars. However, this method requires the calibration of different photometric quantities in terms of abundance at given temperatures and luminosities. Two principal methods of calibration are in use. One of them uses stars with abundances determined from high dispersion spectra by curve of growth or model atmosphere analysis of the spectral lines. The other one uses synthetic spectra based on model atmospheres which are integrated to imitate the narrow band photometric indices. This paper will summarize the results of the application of both of these methods to calibrate a number of the important photometric systems. Most attention will be given to the late-type stars, which demonstrate the strongest photometric abundance effects.

The use of photometric and spectroscopic criteria, calibrated by model-atmosphere calculations, for determining effective temperatures, surface gravities and chemical compositions of stars is illustrated and commented on. The accuracy that can be obtained today in such calibrations is discussed, as well as possible ways of improving this accuracy further for different types of stars.

This paper is an attempt to provide the background information necessary to find data outside of one's specialized field. The most important computer readable catalogs pertaining to the different stellar parameters are reviewed.

At a time when so much of the prestigious astronomical research is devoted to new and highly speculative phenomena, it has been rewarding to see and hear the cautions and accurate approach to the measuring and interpreting of stellar quantities. It has been shown by many speakers, perhaps clearest of all by our participant of honor Professor Popper, how insufficient attention to calibration problems can lead to erroneous results.

We are preparing a microfiche, at the Stellar Data Center in Strasbourg, concerning standard stars in various systems which will be included with the proceedings of this meeting. In the first part of the microfiche we will present a list of stars which are standards in spectroscopic, photometric systems or for which fundamental determinations of temperature, gravity, radius or mass have been made or for which spectrophotometry has been done, fluxes measured or [Fe/H] determined. If a star is a standard in one of these systems an X will be placed in the column opposite its name.

The Space Telescope (ST) will require many types of standard sources for a diverse range of calibrations to be performed after launch. The scientific instruments are sensitive to a wide range of wavelengths from 1050 to 11,000Å and encompass a broad range of measurement capabilities including astrometry, photometry, imaging, polarimetry, and spectroscopy. To verify proper operations of each instrument and to provide quantitative calibrations, a diverse range of standard sources and fields are required. In order to select targets that satisfy the requirements of the Instrument Definition Teams and the long term responsibilities of the Science Institute, six groups containing a total of 25 astronomers are defining the calibration targets to be observed after launch. The six categories of ST standard sources are:

1. 1) Ultraviolet Spectrophotometric

2. 2) Ground Based Spectrophotometric and Photometric

3. 3) Wavelength

4. 4) Astrometric

5. 5) Polarimetric

6. 6) Spatially Flat Field

The data in these categories will be collected from the literature or through new observing programs as appropriate. These six reports of the working groups outline the calibrations and proposed targets for all of the scientific instruments on ST. The collected data on each set of standard sources should be published in the refereed literature.

With the possible exception of the Hyades, M67 is the best-studied star cluster. Accurate photoelectric photometry exists well down onto the main sequence and proper motion studies have isolated cluster stars from the field. From photometry and spectroscopy, its composition is determined to be almost exactly the same as the Sun, with an age about one-half billion years less. This similarity to the Sun permits an accurate determination of distance to M67 independently of other distance measurements. Using the Sun as a reference, the distance modulus of M67 is found to be 9.48 mag. An extensive analysis of possible sources of error leads to an uncertainty (standard error) of ± 0.15 mag., with the chief sources of error being the color index of the Sun, the composition of the cluster, and its age. The M67 distance uncertainty compares favorably with Hanson's (1975) Hyades modulus of 3.29 ± 0.08.

The visual surface brightness relation is applied to the determination of parallaxes of white dwarfs on the assumption, borne out by previous studies of white dwarfs of known parallax, that these show only a small range of linear diameters.

The nearby stars are most favored for determining precise absolute magnitudes and for calibrating spectral-type, luminosity relations and color, luminosity relations. To demonstrate the main problems we discuss the (Mv,B-V) relation since (B-V) data are available for most of our candidates. At Yale Observatory van Altena is compiling a new catalog of trigonometric parallaxes. We feel deeply indebted to van Altena for making available to us a preliminary version of this catalog.

This paper presents a brief review of the various applications carried out with the statistical-parallax algorithm based on the principle of maximum likelihood.

High signal-to-noise Reticon spectra for 87 members of 8 open clusters and associations together with 37 stars having reliable parallaxes (early A-type stars with reliable trigonometric parallaxes, eclipsing binaries, and visual binaries) have been used to calibrate the W(Hγ)-Mv relation for spectral types 0 to early A of luminosity classes III-V. The new calibration has a mean probable dispersion of ±0.28 mag. The distance modulus of the Pleiades is 5.54 ± 0.06 mag, which is in excellent agreement with other, recent determinations, as are the distance moduli for all the calibrating clusters. The use of visual-binary parallaxes implies a Hyades distance modulus of about 3.0 which is significantly smaller than the Hanson (1980) value of 3.30 mag. Although no spectral-type corrections are necessary, stellar evolution probably affects the construction of the new calibration and special care should be taken when determining distance moduli from slightly evolved cluster sequences or for individual stars. Systematic departures from the calibration may be present for stars with Vsin i ≥ 220–250 km/sec. Significant residuals are found between our values of W(Hγ) and those of Petrie in the range 1–13 Å equivalent width, which are due in part to systematic errors in Petrie's W(Hγ) measures. Our distance modulus of 11.11 mag for NGC 2244 is in excellent agreement with the photometric distance. The new calibration is compared to other early type star calibrations for main sequence stars. It is 1.2 mag brighter than Petrie's (1965) Hγ calibration at spectral type 06 and 0.7 mag brighter at A3. For types B1 and earlier the new calibration averages 0.4 mag brighter than the Balona and Crampton (1974) Hγ calibration. There is generally good agreement with the Blaauw (1963) MK calibration although the latter is 0.4 mag brighter at spectral type BO. The Crawford (1978) Hβ calibration is up to 0.5 mag brighter for the earlier spectral types and 0.4 mag fainter for later types. More complete discussions of the Hγ-luminosity calibration are available in Millward and Walker (1984, 1985).

The existence of a tight linear correlation between the stellar absolute magnitude Mv and the Mg II k-line emission width log WMg II k (kms−1) is confirmed using IUE high-resolution (0.2A) data for 100 late-type stars. A least-squares fit to the data gives the relation:

A general model of gaseous streams in semidetached systems is proposed from the study of the eclipsing binary symbiotic stars CI Cyg and V 1329 Cyg. The influence of gaseous streams on the determination of the masses of semidetached systems is shown.

High signal-to-noise ratio spectrometric observations of the large light-ratio eclipsing binary IQ Per (B7 + A2) have been obtained with the coudé Reticon spectrograph of the 2.7 m reflector at McDonald Observatory. Absorption lines of the secondary are seen at the 4481 Å MgII line and the 4549 Å TiII + FeII blend. Radial velocities of both components have been measured by cross-correlation techniques and spectroscopic orbits have been computed. The fitted orbits have an eccentricity (0.075 ± 0.007) that is consistent with the photometric orbit of Hall, Gertken and Burke (1970). Young's (1975) “provisional” estimate of K2 is about 14% too small. Absolute dimensions and masses have been computed from Hall et al.'s (1970) photometric orbit and the new spectroscopic orbit. Additionally, V-R photometric observations obtained by M. Frueh at McDonald Obs. have been analysed by Popper with light curve synthesis techniques (WINK and EBOP). The relative radii of the new photometric orbits differ by less than 2% from the previous orbits, and the other orbital elements also show excellent agreement. The absolute dimensions and masses are (3.51 ± 0.04m⊙, 2.46 ± 0.04 R⊙) for the primary and (1.73 ± 0.02m⊙, 1.50 ± 0.03 R⊙) for the secondary. Both stars are near the zero-age main sequence. The value of ω has changed significantly between the epoch of Hall, Gertken, and Burke's (1970) observations and my own due to apsidal motion. The apsidal motion period is estimated to be in the interval 90 ≤ τ ≤ 180 yr.

In the Hertzsprung-Russell diagram, which is not well known for the binary stars, we can use the unit-mass brightness instead of the brightness itself. For each component this parameter can be obtained using the photometry and the orbital elements of the system. It is only through the orbital constant that the parallax comes in the calculation. This new diagram can be applied to any component of binary stars which orbit and class are known. By using a mass luminosity relationship one can define the zero-age main sequence on the diagram. The evolved stars can thus easily be noticed on the diagram; the mean age of the solar vicinity binary systems should be about 1010 years.

147 of the best known visual binary stars have been used for an independent calibration of the main sequence in the interval −0m.15 ≤B-V≤0m.80. The (Mv, B-V) diagram is found to be equal to the composite open cluster diagram for the age group between 8.35 and 8.43 × 108 years - very hot stars excepted. The cosmic scatter of the main sequence is discussed. It appears that only a small number of visual binaries in our sample are simple binary systems.

We have rediscussed the synchronism between rotation and revolution in close binaries by an inspection of the published projected rotational velocities V sin i of about 250 early-type (from 0 to F5) eclipsing and double-lined spectroscopic binaries. Corrections of the V sin i - values (which are mainly taken from the catalog of Uesugi and Fukuda, 1982) for the aspect effect is straightforward for the eclipsing binaries with analyzed light-curves; in the other cases we have estimated the value of the orbital inclination angle i from the primary's minimum mass M1 sin3 i on the assumption that its mass follows Straižys and Kuriliené's (1981) mass-spectrum relations for different luminosity classes. For the components of non-eclipsing binaries, for which the absolute radii are not directly known, we have adopted values of the absolute radii in accordance with Straižys and Kuriliené's (1981) radius-spectrum relations for different luminosity classes. By using our estimates of the radii, for each component we have evaluated the synchronized velocity Vk (corresponding to the mean orbital angular velocity) and the pseudosynchronized velocity Ve, which corresponds to a synchronization with the instantaneous orbital angular velocity at periastron of an eccentric orbit; in close binaries with appreciably eccentric orbits synchronization is attained with V/Vk>1 and it is probably quickly reached at periastron (Hut 1981).

Statistical algorithms have been appplied to a set of stellar low-dispersion IUE spectra in order to derive objective spectral classification schemes in the UV. This paper describes how standard stars can be selected, particularly in the context of the VPB approach. Comparisons to existing schemes proved quite satisfactory.

A study of the distribution of spectral types of Solar Type Stars (STS) in the revised MKJ and MSS classifications is made on 3919 F8-K3 HD spectral-type stars brighter than mv=10. By means of the solar color indices U-B and B-V 697 STS were selected. The spectral types G3V and G5V have the highest percentages in MSS and MKJ, respectively, confirming statistically the results published by Keenan and Pitts (1980) and by Hardorp (1982). The distribution of the color indices U-B and B-V in the revised G2V spectral type shows that these are good selection criteria for STS and are in the range 0.06 ≤ U-B ≤ 0.10 and 0.58 ≤ B-V ≤ 0.65.