Go to ...

Астрофизический семинар ИНАСАН № 162 (4 декабря 2008 г.,11:00)

Опубликовано: 04/12/2008

Докладчик: S. Roeser (Center for Astronomy, University of Heidelberg (Germany))

Название доклада: “Extending the ICRS to fainter stars – the PPMX catalogue”

Краткое содержание доклада:

In the time span between Hipparcos and Gaia, a major effort in astrometry is the extension and densification of the International Celestial Reference System (ICRS), represented at the bright end by the Hipparcos catalogue. Above all, inertial proper motions are a pre-requisite for studying kinematics and dynamics of the Galaxy, especially in the Solar neighbourhood.

I will briefly discuss the situation of ground-based astrometry and photometry – especially of large sky-surveys – in the pre-Gaia era.The wealth of data available at present enabled the construction of a new compilation catalogue. This catalogue, PPM-Extended (PPMX) contains positions, proper motions, as well as optical and infrared photometry for some 18 million stars down to an approximate limiting magnitude of V = 16. For the brightest part of PPMX, the 4.5 million stars that have measurements in the Astrographic Catalogue from the beginning of the last century, the accuracy of the proper motions is better than 2 mas/y.

Докладчик: E. Schilbach (Center for Astronomy, University of Heidelberg (Germany))

Название доклада: “Open clusters and “field” O-stars”

Краткое содержание доклада:

Being very young objects (age < 15 Myr), O-stars are expected to be located not too far from the places where they formed. Also, it is commonly accepted that stars are forming in groups. However, there are many O-stars which appear isolated on the sky: e.g., in the recent O-star catalogue by Sota et al. (2007) about 30 percent of the O-stars are classified as ``field'' stars.

We studied the relation between young open clusters and “field” O-stars by dynamical backtracing of the orbits of O-stars and open clusters. For about 80% of the investigated “field” O-stars we could show that, with high probability, these stars were ejected from young open clusters or protoclusters over the past 10 Myr.

The study is based on the best presently available information on proper motions (PPMX, R”oser et al.~2008), radial velocities (CRVAD2, Kharchenko et al.~2007), and Galactic open clusters (COCD, Kharchenko et al.~2005a,b).