Yazar "Yaz, E." seçeneğine göre listele

Listeleniyor 1 - 2 / 2
  • [ X ]
    Öğe
    New absolute magnitude calibrations for detached binaries
    (Wiley-V C H Verlag Gmbh, 2008) Bilir, S.; Ak, T.; Soydugan, Esin; Soydugan, Faruk; Yaz, E.; Ak, N. Filiz; Eker, Z.
    Lutz-Kelker bias corrected absolute magnitude calibrations for the detached binary systems with main-sequence components are presented. The absolute magnitudes of the calibrator stars were derived at intrinsic colours of Johnson-Cousins and 2MASS (Two Micron All Sky Survey) photometric systems. As for the calibrator stars, 44 detached binaries were selected from the Hipparcos catalogue, which have relative observed parallax errors smaller than 15% (sigma(pi)/pi <= 0.15). The calibration equations which provide the corrected absolute magnitude for optical and near-infrared pass bands are valid for wide ranges of colours and absolute magnitudes: -0.18 < (B - V)(0) < 0.91, -1.6 < M-V < 5.5 and -0.15 < (J - H)(0) < 0.50, -0-02 < (H - K-s)(0) < 0. 13, 0 < M-J < 4, respectively. The distances computed using the luminosity-colours (LCs) relation with optical (B V) and near-infrared (J H K-s) observations were compared to the distances found from various other methods. The results show that new absolute magnitude calibrations of this study can be used as a convenient statistical tool to estimate the true distances of detached binaries out of Hipparcos' distance limit. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA. Weinheim
  • [ X ]
    Öğe
    New absolute magnitude calibrations for W Ursa Majoris type binaries
    (Wiley-V C H Verlag Gmbh, 2009) Eker, Z.; Bilir, S.; Yaz, E.; Demircan, O.; Helvaci, M.
    Parallaxes of W UMa stars in the Hipparcos catalogue have been analyzed. 31 W UMa stars. which have the most accurate parallaxes (sigma(pi)/pi < 0.15) which are neither associated with a photometric tertiary nor with evidence of a Visual companion, were selected for re-calibrating the Period-Luminosity-Color (PLC) relation of W UMa stars. Using the Lutz-Kelker (LK) bias corrected (most probable) parallaxes. periods (0.26 < P < 0.87, P in days), and colors (0.04 < (B - V)(0) < 1.28) of the 31 selected W UMa, the PLC relation have been revised and re-calibrated. The difference between the old (revised but no( bias corrected) and the new (LK bias corrected) relations are almost negligible in predicting the distances of W UMa stars Up to about 100 pc. But, it increases and may become intolerable as distances of stars increase. Additionally, using (J - H)(0) and (H -K(s))(0) colors from 2MASS (Two Micron All Sky Survey) data, a PLC relation working with infrared data was derived. It can be used with infrared colors in the range -0.01 < (J-H)(0) < 0.58, and -0.10 < (H - K(s))(0) < 0.18. Despite of the fact that the 2MASS data refer to single epoch observations which are not guaranteed to be taken at maximum brightness of the W UMa stars. the established relation has been found surprisingly consistent and reliable in predicting LK corrected distances of W UMa stars. (C) 2009 WILEY-VCH Verlag GmbH & Co, KGaA, Weinheim