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Öğe A Silent Revolution in Fundamental Astrophysics(Iop Publishing Ltd, 2022) Eker, Zeki; Soydugan, Faruk; Bakis, Volkan; Bilir, Selcuk; Steer, IanArbitrariness in the zeropoint of bolometric corrections is a paradigm that is nearly a century old and leads to two more paradigms. Bolometric corrections must always be negative, and the bolometric magnitude of a star ought to be brighter than its V magnitude. Both were considered valid before the IAU 2015 General Assembly Resolution B2, a revolutionary document that supersedes all three aforementioned paradigms. The purpose of this article is to initiate new insight into and a new understanding of the fundamental astrophysics and present new capabilities to obtain standard and more accurate stellar luminosities and gain more from accurate observations in the era after Gaia. The accuracy gained will aid in advancing stellar structure and evolution theories and also Galactic and extragalactic research, observational cosmology, and searches for dark matter and dark energy.Öğe On the zero point constant of the bolometric correction scale(Oxford University Press, 2021) Eker, Zeki; Bakiş, Volkan; Soydugan, Faruk; Bilir, SelçukArbitrariness attributed to the zero-point constant of the V-band bolometric corrections (BCV) and its relation to ‘bolometric magnitude of a star ought to be brighter than its visual magnitude’ and ‘bolometric corrections must always be negative’ was investigated. The falsehood of the second assertion became noticeable to us after IAU 2015 General Assembly Resolution B2, where the zero-point constant of bolometric magnitude scale was decided to have a definite value CBol(W) = 71.197 425 ... . Since the zero-point constant of the BCV scale could be written as C2 = CBol − CV, where CV is the zero-point constant of the visual magnitudes in the basic definition BCV = MBol − MV = mbol − mV, and CBol > CV, the zero-point constant (C2) of the BCV scale cannot be arbitrary anymore; rather, it must be a definite positive number obtained from the two definite positive numbers. The two conditions C2 > 0 and 0 < BCV < C2 are also sufficient for LV < L, a similar case to negative BCV numbers, which means that ‘bolometric corrections are not always negative’. In sum it becomes apparent that the first assertion is misleading causing one to understand bolometric corrections must always be negative, which is not necessarily true.Öğe Standard stellar luminosities: what are typical and limiting accuracies in the era after Gaia?(Oxford University Press, 2021) Eker, Zeki; Soydugan, Faruk; Bilir, Selçuk; Bakiş, VolkanMethods of obtaining stellar luminosities (L) have been revised and a new concept, standard stellar luminosity, has been defined. In this paper, we study three methods: (i) a direct method from radii and effective temperatures; (ii) a method using a mass–luminosity relation (MLR); and (iii) a method requiring a bolometric correction. If the unique bolometric correction (BC) of a star extracted from a flux ratio (fV/fBol) obtained from the observed spectrum with sufficient spectral coverage and resolution are used, the third method is estimated to provide an uncertainty (ΔL/L) typically at a low percentage, which could be as accurate as 1 per cent, perhaps more. The typical and limiting uncertainties of the predicted L of the three methods were compared. The secondary methods, which require either a pre-determined non-unique BC or MLR, were found to provide less accurate luminosities than the direct method, which could provide stellar luminosities with a typical accuracy of 8.2–12.2 per cent while its estimated limiting accuracy is 2.5 per cent.Öğe Updated MS Luminosity-Radius-Temperature-Mass Relations for Solar Neighborhood Galactic Disk Stars(Amer Inst Physics, 2018) Eker, Zeki; Bakis, Volkan; Bilir, Selcuk; Soydugan, Faruk; Steer, Ian; Soydugan, Esin; Bakis, HicranConventional mass- luminosity (M- L) relations are defined using 509 nearby main- sequence (MS) stars within the Solar neighborhood. A smooth mass- radius (M- R) relation was fixed from radii of MS stars appeared in literature having masses within the limits 0.179- 1.5 M. Similarly, a smooth mass- effective temperature (M- Teff) relation was derived for the main- sequence stars having masses within the limits 1.5- 31 M using their effective temperatures available. The omitted parts of M- R and M- Teff relations in the range from 0.179 to 31 M were computed according to Stephan- Boltzmann law, so inter- related M- L, M- R and M- Teff were achieved.Öğe Uzun dönemli RS CVn çift yıldızlarında ışıkkürenin ve renkkürenin aktivitesi(2008) Erdem, Ahmet; Demircan, Osman; Buddıng, Edwin; Eker, Zeki; Çiçek, Caner; Soydugan, Faruk; Soydugan, Esin[Abstract Not Available]
