Yazar "Steer, I." seçeneğine göre listele

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    Öğe
    Effective Temperatures of Selected Main-Sequence Stars with the Most Accurate Parameters
    (Astronomical Soc Pacific, 2015) Soydugan, Faruk; Eker, Z.; Soydugan, Esin; Bilir, S.; Gokce, E. Y.; Steer, I.; Tuysuz, M.
    In this study we investigate the distributions of the properties of detached double-lined binaries (DBs) in the mass luminosity, mass radius, and mass-effective temperature diagrams. We have improved the classical mass luminosity relation based on the database of DBs by Eker et al. (2014a). Based on the accurate observational data available to us we propose a method for improving the effective temperatures of eclipsing binaries with accurate mass and radius determinations.
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    Öğe
    Interrelated main-sequence mass-luminosity, mass-radius, and mass-effective temperature relations
    (Oxford Univ Press, 2018) Eker, Z.; Bakis, V.; Bilir, S.; Soydugan, Faruk; Steer, I.; Soydugan, Esin; Bakis, H.
    Absolute parameters of 509 main-sequence stars selected from the components of detached eclipsing spectroscopic binaries in the solar neighbourhood are used to study mass-luminosity, mass-radius, and mass-effective temperature relations (MLR, MRR, and MTR). The MLR function is found better if expressed by a six-piece classical MLR (L proportional to M-alpha) rather than a fifth or a sixth degree polynomial within the mass range of 0.179 < M/M-circle dot <= 31. The break points separating the mass ranges with classical MLR do not appear to us to be arbitrary. Instead, the data indicate abrupt changes along the mass axis in the mean energy generation per unit of stellar mass. Unlike the MLR function, the MRR and MTR functions cannot be determined over the full range of masses. A single-piece MRR function is calibrated from the radii of stars with M <= 1.5M(circle dot), while a second single-piece MTR function is found for stars with M > 1.5M(circle dot). The missing part of the MRR is computed from the MLR and MTR, while the missing part of the MTR is computed from the MLR and MRR. As a result, we have interrelated the MLR, MRR, and MTR, which are useful in determining the typical absolute physical parameters of main-sequence stars of given masses. These functions are also useful to estimate typical absolute physical parameters from typical T-eff values. Thus, we were able to estimate the typical absolute physical parameters of main-sequence stars observed in the Sejong Open cluster Survey, based on that survey's published values for T-eff. Since typical absolute physical parameters of main-sequence stars cannot normally be determined in such photometric surveys, the interrelated functions are shown to be useful to compute such missing parameters from similar surveys.
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    MAIN-SEQUENCE EFFECTIVE TEMPERATURES FROM A REVISED MASS-LUMINOSITY RELATION BASED ON ACCURATE PROPERTIES
    (Iop Publishing Ltd, 2015) Eker, Z.; Soydugan, Faruk; Soydugan, Esin; Bilir, S.; Gokce, E. Yaz; Steer, I.; Tuysuz, M.
    The mass-luminosity (M-L), mass-radius (M-R), and mass-effective temperature (M-T-eff) diagrams for a subset of galactic nearby main-sequence stars with masses and radii accurate to <= 3% and luminosities accurate to <= 30% (268 stars) has led to a putative discovery. Four distinct mass domains have been identified, which we have tentatively associated with low, intermediate, high, and very high mass main-sequence stars, but which nevertheless are clearly separated by three distinct break points at 1.05, 2.4, and 7 M-circle dot within the studied mass range of 0.38-32 M-circle dot. Further, a revised mass-luminosity relation (MLR) is found based on linear fits for each of the mass domains identified. The revised, mass-domain based MLRs, which are classical (L proportional to M-alpha), are shown to be preferable to a single linear, quadratic, or cubic equation representing an alternative MLR. Stellar radius evolution within the main sequence for stars with M > 1 M-circle dot is clearly evident on the M-R diagram, but it is not clear on the M-T-eff diagram based on published temperatures. Effective temperatures can be calculated directly using the well known Stephan-Boltzmann law by employing the accurately known values of M and R with the newly defined MLRs. With the calculated temperatures, stellar temperature evolution within the main sequence for stars with M>1 M-circle dot is clearly visible on the M-T-eff diagram. Our study asserts that it is now possible to compute the effective temperature of a main-sequence star with an accuracy of similar to 6%, as long as its observed radius error is adequately small (<1%) and its observed mass error is reasonably small (<6%).