title: The CIDA-QUEST large-scale survey of Orion OB1: evidence for rapid disk dissipation in a dispersed stellar population.
abstract: We are conducting a large-scale, multiepoch, optical photometric survey [Centro de Investigaciones de Astronomia-Quasar Equatorial Survey Team (CIDA-QUEST)] covering about 120 square degrees to identify the young low-mass stars in the Orion OB1 association. We present results for an area of 34 square degrees. Using photometric variability as our main selection criterion, as well as follow-up spectroscopy, we confirmed 168 previously unidentified pre-main sequence stars that are about 0.6 to 0.9 times the mass of the sun (Mo), with ages of about 1 million to 3 million years (Ori OB1b) and about 3 million to 10 million years (Ori OB1a). The low-mass stars are spatially coincident with the high-mass (at least 3 Mo) members of the associations. Indicators of disk accretion such as Halpha emission and near-infrared emission from dusty disks fall sharply from Ori OB1b to Ori OB1a, indicating that the time scale for disk dissipation and possibly the onset of planet formation is a few million years.
authors.affiliation: Centro de Investigaciones de Astronomia, Apartado Postal 264, Mérida 5101-A, Venezuela. briceno@cida.ve
authors.forename: C
authors.initials: C
authors.lastname: Briceño
authors.forename: A K
authors.initials: AK
authors.lastname: Vivas
authors.forename: N
authors.initials: N
authors.lastname: Calvet
authors.forename: L
authors.initials: L
authors.lastname: Hartmann
authors.forename: R
authors.initials: R
authors.lastname: Pacheco
authors.forename: D
authors.initials: D
authors.lastname: Herrera
authors.forename: L
authors.initials: L
authors.lastname: Romero
authors.forename: P
authors.initials: P
authors.lastname: Berlind
authors.forename: G
authors.initials: G
authors.lastname: Sánchez
authors.forename: J A
authors.initials: JA
authors.lastname: Snyder
authors.forename: P
authors.initials: P
authors.lastname: Andrews