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Photocenter Shift Effect in Double Stars of Gaia DR2 Database

López Oriona A., Ling J. F., Sánchez Sellero C.

Acta Astronomica

2020

Vol. 70, No. 1

19--32

In order to check the performance of the Gaia satellite when detecting double stars, we attempted to discover a photocenter shift affecting Gaia's second data release (Gaia DR2). We analyzed data of bona-fide double stars from "Double and Multiple System Annex" catalog and matched them with the Gaia DR2 catalog. We tried to derive a relationship between measurements of visual magnitude and signs of binarity based on parallaxes and proper motions. A comprehensive study of parallaxes indicates the presence of the photocenter shift effect. Due to the proper motion two-dimensional nature, we conducted only a simply study which implies that a real photocenter shift may affect double stars appearing in the Gaia DR2 catalog as single sources.

High Proper Motion Objects toward the Inner Milky Way: Characterization of Newly Identified Nearby Stars from the VISTA Variables in the Vía Láctea Survey

Gromadzki M., Kurtev R., Beamán J. C., Tekola A., Ramphul R., Ivanov V. D., Minniti D., Folkes S. L., Vaisanen P., Kniazev A. Y., Borissova J., Parsons S. G., Villanueva V.

Acta Astronomica

2016

Vol. 66, No. 3

293--306

The census of the Solar neighborhood is still incomplete, as demonstrated by recent discoveries of many objects within 5-10 pc from the Sun. The area around the mid-plane and bulge of the Milky Way presents the most difficulties in searches for such nearby objects, and is therefore deficient in the known population. This is largely due to high stellar densities encountered. Spectroscopic, photometric and kinematic characterization of these objects allows better understanding of the local mass function, the binary fraction, and provides new interesting targets for more detailed studies. We report the spectroscopic follow-up and characterization of twelve bright high proper motion objects, identified from the VISTA Variables in Vía Láctea survey (VVV). We used the 1.9-m telescope of the South African Astronomical Observatory (SAAO) for low-resolution optical spectroscopy and spectral classification, and the MPG/ESP 2.2-m telescope Fiber-fed Extended Range Optical Spectrograph (FEROS) high-resolution optical spectroscopy to obtain the radial and space velocities for three of them. Six of our objects have co-moving companions. We derived optical spectral types and photometric distances, and classified all of them as K and M dwarfs within 27-264 pc from the Sun. Finally, we found that one of the sources, VVV J141421.23-602326.1 (a co-moving companion of VVV J141420.55-602337.1), appears to be a rare massive white dwarf located close to the ZZ Cet instability strip in the CMD and CC diagrams. Many of the objects in our list are interesting targets for exoplanet searches.