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Multiple Period Search for K, M and C Type Semiregular Variables in TÜBITAK National Observatory
Yeşilyaprak, Cahit; Sahin, Timur; Iskender, Ahmet
In this study, periods obtained from long-term multi-bands (Johnson V and R filters) photometric observations of some K, M and C spectral type semiregular (SR) variables obtained with the T40 telescope (40 cm) and SSP5A photometer at TÜBITAK National Observatory (TNO) between 1998 and 2005 were examined. We have found that some of these SR variabl…
Analysis of RGU Photometry in Selected Area 51
Bilir, S.; Karaali, S.; Buser, R.
A low-latitude anticenter field (l=189 °, b=+21 °) is investigated by using the full calibration tools of RGU photometry. The observed RGU data are reduced to the standard system and the separation of dwarfs and evolved stars is carried out by an empirical method. Stars are categorized into three metallicity classes, i.e. -0.25<[M/H]≤+0.50, $-1…
Is There an Age of the Universe Problem after the Hipparcos Data?
Özer, Murat
We have reanalyzed the age of the universe problem under the assumption that the lower limit on the age of the globular clusters is ∼11 Gyr, as predicted by the recent Hipparcos data. We find that the globular cluster and the expansion ages in a standard l=0 universe are consistent only if the present value H0 of the Hubble constant is …
Kinematics of RS CVn and W UMa binaries in the Hipparcos catalogue.
Yesilyaprak, C.; Özdemir, T.; Aslan, Z. +1 more
Space motions of RS CVn and W UMa binaries have been calculated using parallaxes and proper motions from Hipparcos catalogue and radial velocities from the literature. The authors have calculated the mean motions and velocity dispersions. They have excluded those binaries with relative parallax errors ≥0.5. The comparison of the asymmetric drift, …