A Radio Survey of Older T Tauri Stars in the eta Chamaeleontis Cluster

Abstract

A radio continuum survey of X-ray-identified weak-lined T Tauri stars (WTTs) in the newly-discovered ´ Chamaeleontis cluster has been completed using the Australia Telescope Compact Array (ATCA). The 10 known WTTs in the cluster form a unique sample of codistant late-type pre-main-sequence stars with ages of ~8 Myr and masses ranging from 0.1 - 1.0 M_sun. Our survey detected none of the 10 X-ray-emitting WTTs with 3¾ sensitivity limits at 4.8 and 8.6 GHz (6.2 and 3.5 cm) of typically 0.4 mJy, corresponding to a radio luminosity of 4.5 x 10^15 erg Hz^-1 s^-1. Rotation periods for these stars indicate that they are not, as a group, fast-rotating stars. The non-detection in the radio bands supports the findings of other radio surveys of inhomogeneous samples of young stars, where radio emission is fairly common (10{30%) among very young T Tauri stars across all late spectral types, but confined to rapidly-rotating F-G-K stars amongst older zero-age main sequence stars. Rotation, more than youth, appears to be the key to radio emission in young stars.