Galaktik OB Oymakları ve Çoklu Yıldız Sistemleri

OB oymakları yıldız oluşumunun devam ettiği veya kısa bir zaman önce sonlandığı genç yıldızların ve yoğun yıldızlararası maddenin oluşturduğu bölgelerdir. Bu bölgelerin araştırılması yıldız oluşumu ve evriminin ilk basamakları hakkında daha fazla bilgiye sahip olmamızı sağlar. Teorik çalışmalar yıldız oluşum bölgelerindeki yıldız oluşumu sonrasında oluşan en az bir bileşene sahip yıldız oranının %99 olduğunu göstermiştir. Bu da oluşan her 100 yıldızdan 99’unun çift veya çoklu sistem olduğuna işaret etmektedir. Bu çalışmada yıldız oluşum bölgelerindeki bazı çift ve çoklu yıldız sistemlerinin analiz sonuçları verilecek ve bu sistemlerin analizlerinde dikkat edilmesi gereken hususlar tartışılacaktır

Basic Parameters, Fundamental Relations and Bolometric Corrections of Solar Neighborhood Main-Sequence Stars

The published masses, radii and effective temperatures of 509 main-sequence stars chosen from the catalogue of detached double-lined eclipsing binaries with metal abundances 0.008 ≤ Z ≤ 0.040 in the solar neighborhood within the disk were used to calibrate interrelated mass-luminosity (MLR), mass-radius (MRR) and mass-effective temperature (MTR) relations. 34 more stars (20 binaries) from the same catalog with unpublished effective temperatures added after computing their effective temperatures using newly defined fundamental relations (MLR, MRR, MTR). Binaries compiled were searched if they have light ratios (L2/L1) in the V band together with trigonometric parallaxes and visual apparent magnitudes. 225 systems (440 stars) were found eligible to calculate bolometric corrections (BC). NASA/IPAC Galactic dust maps were used to estimate extinctions. Systems with unreliable extinctions (dusty regions and/or b ≤ 5°) were replaced with private determinations. The computed BC values were reduced again by choosing the systems with most accurate parallaxes (σπ/π< 0.07) for a calibration sample (322 stars). Main-sequence BC – Teff relation valid from 3000 to 30000 K in the form a cubic function is determined using the basic stellar parameters in the calibration sample

STUDY OF ECLIPSING BINARY AND MULTIPLE SYSTEMS IN OB ASSOCIATIONS. II. THE CYGNUS OB REGION: V443 Cyg, V456 Cyg, AND V2107 Cyg

Three presumably young eclipsing binary systems in the direction of the Cygnus OB1, OB3, and OB9 associations are studied. Component spectra are reconstructed and their orbits are determined using light curves and spectra disentangling techniques. V443 Cyg and V456 Cyg have circular orbits while the light curve of V2107 Cyg imposes a slightly eccentric orbit (e = 0.045 +/- 0.03). V443 Cyg harbors F-type stars, not young early-A stars as previously suggested in the literature based solely on photometry. It appears to be situated in the foreground (distance 0.6 +/- 0.2 kpc) of the young stellar populations in Cygnus. V456 Cyg, at a distance of 0.50 +/- 0.03 kpc, consists of a slightly metal-weak A-type star and an early-F star. The age of both systems, on or very near to the main sequence, remains uncertain by an order of magnitude. V2107 Cyg is a more massive system (8.9 +/- 2 and 4.5 +/- 1.2M(circle dot)) at 1.5 +/- 0.5 kpc and, also kinematically, a strong candidate-member of Cyg OB1. The more massive component is slightly evolved and appears to undergo non-radial beta Cep-type pulsations. The Doppler signal of the secondary is barely detectable. A more extensive, asteroseismological study is necessary to fix masses more precisely. Nevertheless, the position of the primary in the H-R diagram confines the age reasonably well to 20 +/- 5 Myr, indicating that for Cyg OB1 has a similar extent of star formation history as that established for Cyg OB2