Search Publications
Comparison of Gaia and Hipparcos parallaxes of close visual binary stars and the impact on determinations of their masses
Hussein, Abdallah M.; Al-Wardat, Mashhoor Ahmad; Al-Naimiy, Hamid M. +1 more
Precise measurement of the fundamental parameters of stellar systems, including mass and radius, depends critically on how well the stellar distances are known. Astrometry from space provides parallax measurements of unprecented accuracy, from which distances can be derived, initially from the Hipparcos mission, with a further refinement of that a…
Dynamical Study of the Exoplanet Host Binary System HD 106515
Rica, F. M.; Barrena, R.; Henríquez, J. A. +2 more
HD 106515 AB (STF1619 AB) is a high common proper motion and common radial velocity binary star system composed of two G-type bright stars located at 35 pc and separated by about 7 arcsec. This system was observed by the Hipparcos satellite with a precision in distance and proper motion of 3 and 2%, respectively. The system includes a circumprimar…
Complex Analysis of the Stellar Binary HD25811: A Subgiant System
Al-Wardat, Mashhoor A.; Widyan, Hatem S.; Al-thyabat, Ahmed
The visually close binary system HD25811 is analysed to estimate its physical and geometrical parameters in addition to its spectral type and luminosity class. The method depends on obtaining the best fit between the entire observational spectral energy distribution (SED) of the system and synthetic SEDs created by atmospheric modelling of the ind…
Verification of the Spectral Classification of Stars Using the Hipparcos Catalogue
Deb, D.; Chakraborty, P.
The spectral classifications of the stars from spectral data have been corrected from time to time and new spectral and luminosity classes have been assigned. Identifying stars with wrong spectral and luminosity classification has been a stupendous task from the huge catalogue of stars. In this work we describe a simple statistical technique to id…
The Angular Diameter and Fundamental Parameters of Sirius A
Tuthill, P. G.; Davis, J.; Ireland, M. J. +3 more
The Sydney University Stellar Interferometer (SUSI) has been used to make a new determination of the angular diameter of Sirius A. The observations were made at an effective wavelength of 694.1nm and the new value for the limb-darkened angular diameter is 6.048+/-0.040mas (+/-0.66%). This new result is compared with previous measurements and is fo…
High-resolution Spectroscopy and Spectropolarimetry of Some Late F- / Early G-type Sun-like Stars as Targets for Zeeman Doppler Imaging
Hart, R.; Burton, D.; Marsden, S. C. +4 more
High-resolution spectroscopy and spectropolarimetry have been undertaken at the Anglo-Australian Telescope in order to identify suitable targets for magnetic studies of young Sun-like stars, for the proxy study of early solar evolution. This study involved the investigation of some variable late F- / early G-type Sun-like stars originally identifi…
Kinematics of M-Type Giant Semi-Regular Variables from the Hipparcos Catalogue
Yeşilyaprak, C.; Aslan, Z.
The kinematics of M-type (O-rich) giant semi-regular (SR) variable stars were examined. They were grouped with respect to their relative parallax errors (ɛπ/π) in order to study the stars having relatively better parallax, and with the period limit (70 d). The spatial and velocity distributions were examined and the results were compare…
Cosmic Helium Production
Flynn, Chris
K-dwarfs are very long lived, slowly evolving stars, so that their present day helium Y and metal content (metallicity Z) is essentially the same as when they were born. K-dwarfs thus contain a fossil record of the amount of helium and metals which has been produced in successive stellar generations over the lifetime of the Galaxy. We here estimat…
The Geneva-Copenhagen Survey of the Solar Neighbourhood
Pont, F.; Holmberg, J.; Nordström, B. +3 more
We report on a new survey of metallicities, ages, and Galactic orbits for a complete, magnitude-limited, and kinematically unbiased all-sky sample of 16682 nearby F- and G-dwarfs. Our~63000 new, accurate radial velocities for nearly 13500 of the stars, combined with Hipparcos parallaxes and Tycho-2 proper motions, complete the kinematic data for 1…
Comprehensive Analysis of RGU Photometry in the Direction to M5
Bilir, S.; Karaali, S.; Buser, R.
The RGU-photographic investigation of an intermediate latitude field in the direction to the Galactic centre is presented. 164 extra-galactic objects, identified by comparison of Minnesota and Basel charts, are excluded from the program. Also, a region with size 0.104 square-degrees, contaminated by cluster (M5) stars and affected by background li…