The solar neighborhood. XXVI. AP Col: The closest (8.4pc) pre-main-sequence star

Abstract

We present the results of a multi-technique investigation of the M4.5Ve flare star AP Col, which we discover to be the nearest pre-main-sequence star. These include astrometric data from the CTIO 0.9 m, from which we derive a proper motion of 342.0 ± 0.5masyr-1, a trigonometric parallax of 119.21 ± 0.98mas (8.39 ± 0.07pc), and photometry and photometric variability at optical wavelengths. We also provide spectroscopic data, including radial velocity (22.4 ± 0.3kms-1), lithium equivalent width (EW) (0.28 ± 0.02 Å), Hα EW (-6.0 to -35), vsin i (11 ± 1kms-1), and gravity indicators from the Siding Spring 2.3m WiFeS, Lick 3m Hamilton echelle, and Keck-I HIRES echelle spectrographs. The combined observations demonstrate that AP Col is the closer of only two known systems within 10pc of the Sun younger than 100Myr. Given its space motion and apparent age of 12-50Myr, AP Col is likely a member of the recently proposed ∼ 40Myr old Argus/IC 2391 Association. © 2011. The American Astronomical Society. All rights reserved.