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Photocenter Shift Effect in Double Stars of Gaia DR2 Database

100%

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

tom 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.

The Optical Gravitational Lensing Experiment. Catalog of High Proper Motion Stars Towards the Magellanic Clouds

100%

Soszyński I. , Żebruń K. , Udalski A. , Woźniak P. R. , Szymański M. , Kubiak M. , Pietrzyński G. , Szewczyk O. , Wyrzykowski Ł.

tom Vol. 52, No. 2

129--142

We present a Catalog of high proper motion (HPM) stars detected in the foreground of central parts of the Magellanic Clouds. The Catalog contains 2161 objects in the 4.5 square degree area towards the LMC, and 892 HPM stars in the 2.4 square degree area towards the SMC. The Catalog is based on observations collected during four years of the OGLE-II microlensing survey. The Difference Image Analysis (DIA) of the images provided candidate HPM stars with proper motion as small as 4 mas/yr. These appeared as pseudo-variables, and were all measured astrometrically on all CCD images, providing typically about 400 data points per star. The reference frame was defined by the majority of background stars, most of them members of the Magellanic Clouds. The reflex motion due to solar velocity with respect to the local standards of rest is clearly seen. The largest proper motion in our sample is 363 mas/yr. Parallaxes were measured with errors smaller than 20% for several stars.

Stellar Kinematics Near the Galactic Center - Possible Test for a Binary Black Hole

100%

Jaroszyński M.

tom Vol. 50, No. 1

67--78

We consider consequences of the presence of a binary black hole system in the center of our Galaxy. We show that the existence of such a system with total mass ≈2.6×106 Msolar and semimajor axis ≈0.001 pc is not excluded on theoretical grounds and it may have characteristic evolution time of a few billions years. We simulate astrometric measurements of proper motion of stars in the vicinity of the black hole system and check whether such observations are sufficient to discover the binary nature of the central mass. We show that such findings require astrometric accuracy about ten times higher than presently available; the Keck Interferometer, will be able to place stringent observational limits on the presence of a black hole binary in the Galactic center.

The Optical Gravitational Lensing Experiment. The Catalog of Stellar Proper Motions toward the Magellanic Clouds

75%

Poleski R. , Soszyński I. , Udalski A. , Szymański M. K. , Kubiak M. , Pietrzyński G. , Wyrzykowski Ł. , Ulaczyk K.

tom Vol. 62, No. 1

1-22

We present a catalog of over 6.2 million stars with measured proper motions. All these stars are observed in the direction of the Magellanic Clouds within the brightness range 12