MOST detects g-modes in the late-type Be star beta Canis Minoris (B8 Ve)

The Microvariability and Oscillations of Stars ( MOST) satellite has detected low-amplitude light variations (Delta m similar to 1 mmag) in the Be star beta CMi (B8 Ve). The observations lasted 41 days and the variations have typical periods similar to 0.3 days. We demonstrate that the dominant frequencies are consistent with prograde high-order g-modes of m = - 1 excited by the Fe bump of opacity in an intermediate-mass (approximate to 3.5 M-.) star with a nearly critical rotation period of 0.38 days. This is the first detection of nonradial g-mode pulsations in a Be star later than B6 leading to the possibility that pulsations are excited in all classical Be stars.