Showing papers by "European Southern Observatory published in 1973"
01 Jan 1973
TL;DR: In this article, the present state of the luminosity calibrations in the MK system is reviewed with reference to recent work based on proper motions and radial velocities, and on trigonometric parallaxes, resulting in evidence for corrections of about 0.4 mag.
Abstract: Attention is drawn to important systematic effects in the calibration procedure due to the accidental errors in the measured luminosity criteria. The present state of the luminosity calibrations in the MK system is reviewed with reference to recent work based on proper motions and radial velocities, and on trigonometric parallaxes, resulting in evidence for corrections of about — 0.4 mag. for the K0–K5, III stars. Brief reference is made to the developments with regard to the M v (K) system.
10 citations
01 Jan 1973
TL;DR: Methodological problems and hardware/software requirements of efficient automatic classification of objective prism stellar spectra are described on the basis of experience from ‘microphotometer-computer’ classification.
Abstract: Methodological problems and hardware/software requirements of efficient automatic classification of objective prism stellar spectra are described on the basis of experience from ‘microphotometer-computer’ classification. Significant advances in hardware (two-dimensional scanners, on-line computers) as well as in software (image processing techniques) have now brought high-speed, exhaustive, automatic classification within reach. Some astronomical implications of automatic spectral surveys are discussed.
2 citations
01 Jan 1973
TL;DR: In this article, a calibration en magnitudes absolues de the classification stellaire BCD (classification a trois parametres λ 1, D, Ф b ) is used for determining le module de distance du Grand Nuage de Magellan.
Abstract: La calibration en magnitudes absolues de la classification stellaire BCD (classification a trois parametres λ 1, D, Ф b ) a ete utilisee pour determiner le module de distance du Grand Nuage de Magellan. La methode qui est decrite fait intervenir les parametres spectrophotometriques de supergeantes B et A du Grand Nuage et donne une valeur du module de distance independante des autres determinations, en particulier de celles qui sont basees sur les variables RR Lyrae et les Cepheides. La valeur trouvee pour la distance est un peu plus faible que celles generalement admises. Elle ne repose encore que sur un petit nombre de mesures et de nouvelles observations sont en cours; il semble cependant douteux que l’on arrive a des valeurs beaucoup plus grandes. Par ailleurs, les observations ont montre que le parametre λ 1 etait encore sensible a la luminosite pour des etoiles B et A plus brillantes que M = −8 et la calibration du diagramme λ 1 D en magnitudes absolues peut etre prolongee jusqu’a M = −9.
2 citations
01 Aug 1973
TL;DR: The globular cluster NGC 4590 has been observed at Haute Provence Observatory (photographic photometry, 80 cm reflector, F/6) and at the European Southern Observatory (image-tube, 152cm reflector and F/15).
Abstract: The globular cluster NGC 4590 has been observed at Haute Provence Observatory (photographic photometry, 80-cm reflector, F/6) and at the European Southern Observatory (image-tube, 152-cm reflector, F/15).
A sequence of red magnitudes, m r (λ eff ≅6400 A) has been established around the cluster. It comprises 28 stars with magnitudes between 11.66 and 16.50.
Five new variable stars were discovered in a one square degree field, centered on the cluster.
Four other variable stars (No. 39, 40, 41, and 42) were discovered in the cluster.
01 Jan 1973
TL;DR: In this article, the central region of the IC 2944 cluster has been investigated and the Fabry-Perot measurements have been made in 5 points within the nebulosity.
Abstract: An investigation has been made of the central region of the cluster IC 2944. For about 70 stars UBV photometry has been made. For the brighter of those stars also Hβ has been measured. Slit spectra of intermediate dispersion (73 A mm−1) have been made for the 40 brightest stars. Coude spectra (12 A mm−1) have been obtained for 8 stars. Fabry-Perot measurements have been made in 5 points within the nebulosity. The number of blue stars is shown to be extremely high. Down to visual magnitude 11.5 the cluster seems to contain only O and B stars, the majority of spectral class earlier than B3. The Fabry-Perot measurements give evidence of high internal gas motion. Evidently the gas is thin, visible only because of the great number of hot stars.
01 Jan 1973
TL;DR: In this paper, the physical characteristics of the Wolf-Rayet stars and their relation to other objects of early type have been discussed, and observations of later years have been used to make the discussion more complete by including observations from later years.
Abstract: In taking up the subject of the relation between different types of early type stars one inevitably comes on ground set foot upon before by C. S. Beals. Already in 1940 he published an extensive paper entitled ‘On the Physical Characteristics of the Wolf-Rayet Stars and Their Relation to Other Objects of Early Type’ (Beals, 1940). The purpose of the present contribution is mainly to make the discussion more complete by including observations of later years.