Astrophys. J., 661, 1119-1128 (2007/June-1)
25 Orionis: a kinematically distinct 10 Myr old group in Orion OB1a.
BRICENO C., HARTMANN L., HERNANDEZ J., CALVET N., VIVAS A.K., FURESZ G. and SZENTGYORGYI A.
Abstract (from CDS):
We report here on the photometric and kinematic properties of a well-defined group of nearly 200 low-mass pre-main-sequence stars, concentrated within ∼1° of the early-B star 25 Ori, in the Orion OB1a subassociation. We refer to this stellar aggregate as the 25 Orionis group. The group also harbors the Herbig Ae/Be star V346 Ori and a dozen other early-type stars with photometry, parallaxes, and some with IR excess emission, indicative of group membership. The number of high- and low-mass stars is in agreement with expectations from a standard initial mass function. The velocity distribution for the low-mass stars shows a narrow peak at 19.7 km/s, offset ~-10 km/s from the velocity characterizing the younger stars of the Ori OB1b subassociation, and -4 km/s from the velocity of widely spread young stars of the Ori OB1a population; this result provides new and compelling evidence that the 25 Ori group is a distinct kinematic entity, and that considerable space and velocity structure is present in the Ori OB1a subassociation. The low-mass members follow a well-defined band in the color-magnitude diagram, consistent with an isochronal age of ∼7-10 Myr. The ∼2 time drop in the overall Li I equivalent widths and accretion fraction between the younger Ori OB1b and the 25 Ori group is consistent with the latter being significantly older. In a simple-minded kinematic evolution scenario, the 25 Ori group may represent the evolved counterpart of the younger σ Ori cluster. The 25 Ori stellar aggregate is the most populous ∼10 Myr sample yet known within 500 pc, setting it as an excellent laboratory to study the evolution of solar-like stars and protoplanetary disks.
Galaxy: Open Clusters and Associations: Individual: Name: Orion OB1 - Stars: Kinematics - Stars: Pre-Main-Sequence
VizieR on-line data:
<Available at CDS (J/ApJ/661/1119): table2.dat>
Table 2: CVSO NNN (Nos 198-258) added.
View the reference in ADS
To bookmark this query, right click on this link: simbad:2007ApJ...661.1119B and select 'bookmark this link' or equivalent in the popup menu