LINE BLANKETING AS RELATED TO LUMINOSITY AND TURBULENCE IN F5-TYPE STARSSmolinski, J.; Climenhaga, J. L.; Wright, K. O.
doi: 10.1086/129930pmid: N/A
From high-dispersion spectrograms the line blanketing has been determined for ten stars of type F5 by computer techniques in intervals of 25 Å over the spectral regions from 4025 Å to 4375 Å. All luminosity classes are included. The line blanketing is found to be considerably greater for the high-luminosity than for the low-luminosity stars. However, it is found to be less for the super-luminous star HD 231195 than for the other high-luminosity stars. It appears to reach a maximum value for stars of absolute magnitude between -4 and -7. The results are interpreted as being dependent on microturbulence and luminosity.
BASIC PARAMETERS OF THE OPEN CLUSTER NGC 2571.Clariá, J. J.
doi: 10.1086/129933pmid: N/A
Photoelectric measurements in the UBV system are presented for 49 stars in NGC 2571. The intensity of the Hfi line was measured for the five brightest cluster members and DDO photometric data were obtained for the possible red-giant member CD 2905941. The UBV-H analysis confirms that NGC 2571 is a genuine open cluster, with a minimum membership of 28 stars. The red-giant CD 2905941 is most probably not a cluster member. A uniform E(B- V) = was found for the cluster. A distance of (1.25 j 0.08) kpc, an age of 2.7 x 10 years, and other basic parameters were also derived. Key words: open clusters - UBV-H and DDO photometry
SPECTROPHOTOMETRY OF A LOW-LUMINOSITY EMISSION-LINE DWARF, G51-15.Liebert, J.
doi: 10.1086/129934pmid: N/A
Image-tube scans show that the low-luminosity, proper-motion star G51-15 has an M-dwarf absorption spectrum later than Wolf 359 (dM6) and spectroscopic "flare" -star characteristics. The Balmer lines and Ca ii H and K were seen in emission, and an ultraviolet continuum excess was evident. An absorption feature at 550O-556(), recently identified with CaOH, appears very strongly in this star. Key words: spectrophotometry - late-type stars - emission-line stars - flare stars
ACCRETION ONTO BINARY SYSTEMS: EFFECTS ON THE ORBITAL ELEMENTSRayburn, D. R.
doi: 10.1086/129936pmid: N/A
We have investigated the effects on the orbital elements of accretion onto a binary system from a nonrotating gas cloud. We give formulae for the rate of decrease of the semimajor axis and the rate of advance of periastron and we show, within the context of the model, that the eccentricity is secularly constant We compute the accretion ratio 9. 2P.. 1 as a flinction of the mass ratio 9)"2/ . We make a numerical estimate of the semimajor axis decay time scale and show that for a typical binary in a typical interstellar cloud it is of order 1 years. Finally we estimate that a few tens of percent of the binaries in the Galaxy have undergone such accretionary episodes. Key words: accretion - binary systems
SV CENTAURI - A TRULY CONTACT BINARY.Rucinski, S. M.
doi: 10.1086/129937pmid: N/A
A light-curve-synthesis program which implements interpolation in a grid of nongray model atmospheres has been used to determine the geometrical elements of SV Cen by simultaneous differentialcorrection fitting of the three-color light curves obtained in UBV by Irwin and Landolt (1972). Solutions with the mass ratio fixed at its spectroscopic value of 0.84 reveal an extraordinarily high degree of contact between the components (fill-out parameter f = 0.10 ::::: 0.02) and a rather high temperature of the less massive component relative to the more massive component. The large local temperature excess of the secondary star, X = A TIT = 0.78 :::: 0.03 (which results in temperatures 28,000 and 17,0000 K, for the less massive and more massive compounds, respectively) is difficult to understand in the framework of the contact model but might be related to the thermal-time-scale mass-transfer stage of the evolution of SV Cen. Key words: light-curve synthesis - mass transfer