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High resolution molecular line observations of CS, HCO+, C18O and N2H+ wereobtained toward the starless globule FeSt 1-457 in order to investigate itskinematics and chemistry. The HCO+ and CS spectra show clear self-reversed andasymmetric profiles across the face of the globule. The sense of the observedasymmetry is indicative of the global presence of expansion motions in theouter layers of the globule. These motions appear to be subsonic andsignificantly below the escape velocity of the globule. Comparison of ourobservations with near-infrared extinction data indicate that the globule isgravitationally bound. Taken together these considerations lead us to suggestthat the observed expansion has its origin in an oscillatory motion of theouter layers of the globule which itself is likely in a quasi-stable state nearhydrostatic equilibrium. Analysis of the observed linewidths of CO and N2H+confirm that thermal pressure is the dominant component of the cloud's internalsupport. A simple calculation suggests that the dominant mode of pulsationwould be an l = 2 mode with a period of 0.3 Myr. Deformation of the globule dueto the large amplitude l = 2 oscillation may be responsible for thedouble-peaked structure of the core detected in high resolution extinctionmaps. Detailed comparison of the molecular-line observations and extinctiondata provides evidence for significant depletion of C18O and perhaps HCO+ whileN2H+ may be undepleted to a cloud depth of about 40 magnitudes of visualextinction.

The Dynamical State fo the Starless Dense Core FeSt 1-457: A Pulsating Globule?