Periodic accretion instabilities in the protostar L1634IRS 7.
HODAPP K.W. and CHINI R.
Abstract (from CDS):
The small molecular cloud Lynds 1634 contains at least three outflow sources. We found one of these, IRS 7, to be variable with a period of 37.14±0.04 days and an amplitude of approximately 2 mag in the Ksband. The light curve consists of a quiescent phase with little or no variation, and a rapid outburst phase. During the outburst phase, the rapid variation in brightness generates light echoes that propagate into the surrounding molecular cloud, allowing a measurement of the distance to IRS 7 of 404 pc±35 pc. We observed only a marginally significant change in the H - K color during the outburst phase. The K-band spectrum of IRS 7 shows CO bandhead emission but its equivalent width does not change significantly with the phase of the light curve. The H21-0 S(1) line emission does not follow the variability of the continuum flux. We also used the imaging data for a proper motion study of the outflows originating from the IRS 7 and the far-infrared source IRAS 05173-0555, and confirm that these are indeed distinct outflows.