B. Garcia

Spectroscopic binary frequency among CNO stars

Analyse des variations de vitesse radiale a travers un echantillon de 35 etoiles OB avec des anomalies de CH. Les resultats de Bolton et Rogers (1978) sont confirmes: les etoiles OBN apparaissent de preference dans les systemes binaires de courte periode, en contraste avec les etoiles OBC

SPECTRAL MORPHOLOGY IN THE OPEN CLUSTERS TRUMPLER 14 AND TRUMPLER 15

A total of 21 and 14 stars in the fields of the open clusters Tr 15 and Tr 14, respectively, have been observed in order to provide spectral types derived through the MK process. The spectroscopic parallaxes for those groups have also been obtained, finding that Tr 15 is almost at the same distance from the sun as Tr 16 but that Tr 14 is possibly more distant. This cluster, with its high concentration of O-type stars, is also the youngest of both groups studied in this work and may be younger than Tr 16.

Spectroscopic binaries in the open cluster Collinder 228

A radial velocity study of the members of the open cluster Collinder 228 is presented. For a total of 55 stars in the field of the cluster, an average of 10 spectra per star, is obtained and used to derive preliminary orbital elements for six new spectroscopic binaries. With the same observational material, projected axial rotation velocities are derived for stars later than O9 on the main sequence. A statistical discussion based on the above data indicated that the minimum proportion of binaries among the main sequence members of Collinder 228 in the spectral range O9-B3, is 31 percent while the average projected axial rotation of the cluster members with respect to the average rotation for field stars of the same types is 0.89 + or - 0.12. Several early-type SB2 systems of potential astrophysical interest are pointed out. 20 refs.

Rapid Temporal Variations of Interstellar Absorption Lines in the Carina Nebula

Two observations of the complex interstellar absorption-line profiles in the UV spectrum of CPD -59°2603, obtained 22 months apart in the R ~ 110,000 mode of the Space Telescope Imaging Spectrograph on the Hubble Space Telescope, reveal substantial variations in the intensities of several high-velocity components, including the virtual disappearance of one of them. These are the first observations of interstellar temporal variations in dominant ions to our knowledge. The most probable interpretation is motion across the line of sight of discrete absorbing features in the near foreground of the O-type star, within the Carina Nebula. Ground-based survey data also indicate that the extreme interstellar profiles throughout this region originate relatively near the most massive stars, suggesting an origin related to their stellar winds. The morphological similarity of these profiles to a low-ionization, narrow-line system in a quasi-stellar object (QSO) spectrum is pointed out. Time variability may provide a critical test among different interpretations of such QSO systems.

THE OPEN CLUSTER NGC 6193: ANOTHER CLUSTER RICH IN SPECTROSCOPIC BINARIES

From spectrographic observations of probable members of NGC 6193 the authors have obtained radial velocities, projected axial rotational velocities, and approximate spectral types. They computed the average axial rotation with respect to the field stars for the members of NGC 6193 as 0.67±0.08 and an average heliocentric radial velocity for the cluster of -33.1 km sec-1. Six new spectroscopic binaries and a He-rich star were discovered. The authors compare the high incidence of spectroscopic binaries among the main-sequence members of NGC 6193 with clusters of similar average axial rotation.

The ratio of total to selective absorption in the Carina OB2 association

Several previous studies in and around the Great Carina nebula (NGC 3372) have strongly indicated an abnormal interstellar extinction law with a high ratio of total to selective absorptionR. In the present study, newUBV photometric data and accurate MK spectral-types of stars in the region of the Carina OB2 association are used to show that (1) Car OB2 is a genuine stellar association located at a distance of 3.2 kpc, and (2) the interstellar extinction law seems to be normal throughout most of the region. A representative value ofR = Av/E(B − V) = 3.0 is derived for Car OB2 from the variable extinction method.

Frequency of Binaries in the Open Cluster Trumpler 14

We present new spectroscopic data for nine objects among the brightest stars in the field of the open cluster Trumpler 14. Radial velocities were measured from around 80 new spectrograms in order to provide more information about the binary nature of these objects. From this material, we conclude that at least two of the stars in the sample are radial-velocity variables, one of them showing double He i features.

Radial velocities in the open cluster IC 2602

We have determined radial velocities for 31 stars in the field of the open cluster IC 2391, and derived the percentage of probable radial-velocity variables. We improved the orbit of one previously known spectroscopic binary, and confirmed the existence of two double-line binaries. We discussed with such data the membership to the cluster, the average cluster radial velocity and compared the incidence of short-period binaries among the Main-Sequence members of IC 2391 with the incidence for other clusters with similar average axial rotation of its members.

Radial velocities in the open cluster Trumpler 14

In this paper we present radial velocity measurements of probable members of Trumpler 14, a very young open cluster associated with the Carina Nebula. We have found 4 double-line spectroscopic binaries and 2 single-line spectroscopic binaries. We have succeeded in deriving orbital elements for the SB1s. All the binaries are of potential astrophysical interest and are worth further observational efforts.

Further Study of the High‐Velocity Interstellar Medium in the Carina Nebula

We present new spectroscopic data for 12 stars in the field of Trumpler 16 and for 18 stars in Collinder 228, to analyze the behavior of the Ca ii and Na i interstellar lines and to study the high radial velocity components. The purpose was to provide a finer map of the small angular scale changes in previously observed high-velocity components. We have found three striking new high-velocity profiles in Tr 16 and one probable case in Cr 228. However, the most important result is that as fainter members of the complex are observed, smaller fractions of high-velocity profiles are found, perhaps indicating that such profiles in the earlier spectral type, more massive stars are formed in their near vicinities, in an interaction between their stellar winds and surrounding interstellar material.