Disks Of Young Stars Research Articles

THE MOTIONS OF THE A STARS AT THE NORTH GALACTIC POLE

ABSTRACT OLIN J. EGGEN Mount Stromlo and Siding Spring Observatories Received July 8, 1969 The extensive hotometric and nsdial velocity material for A-type stars near the NGP, collecte by Peri , is discnssed in li ht of his difficnlty in deriving Kz. New proper motions are erived ior many o the stars. These proper motions permit a separation of yonng and old disk objects on the basis of their (U, V) motion. Peri 's conclusion that there are two types of A stars at the NGP is shown to he the expected result from the mixture of old and young disk stars in his sample, which contains objects of types B6 to FO. The youn disk stars extend to only 300 parsecs above the galactic plane and the old isk population contributes 20 percent of the stars to this height. Perry's sample of stars extends beyond 500 parsecs and is almost evenly divided between the two disk - tin us.

STELLAR GROUPS IN THE OLD DISK POPULATION

Our horizon of some 300 parsecs, within which we can accumulate relatively accurate data, includes a large range of objects very young stars, born within this horizon and still there; somewhat older stars, born in this region and revisiting because of nearly circular orbits about the center; still older stars, passing through from outer or inner reaches for the first or a rare visit; and very old stars, that may not be strangers to any part of the Galaxy, including regions away from the plane where younger objects can never reach. We now have methods sufficiently accurate to sort these objects into relatively well-defined age groups, and these, coupled with the luminosity estimates and the available apparent motions, permit us to at least partially untangle the space motions of the various age groups. One of the outstanding features of the motions of young disk stars is that they are mainly members of a few stellar groups. It is also becoming clear that the old disk population also consists of many such groups.

SCO XR-1 a member of the upper Scorpius complex

view Abstract Citations (9) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS SCO X-1 as a member of the upper Scorpius complex. Eggen, O. J. Abstract Three stars that share the proper motioi~ of Sco XR-1, together with Sco XR-1 itself, are probably members of the Scorpius-Centaurus association of young disk stars. The resulting luminosity of Sco XR-1 is near +6 mag Publication: The Astrophysical Journal Pub Date: October 1969 DOI: 10.1086/180426 Bibcode: 1969ApJ...158L..31E full text sources ADS | data products SIMBAD (8) GCPD (1)