First-Overtone CO Variability in Young Stellar Objects

摘要

We have monitored the 2.3 μm v = 2 CO bands toward young stellar objects that are predominantly of low luminosity (L < 10,000 L) and show evidence of mass loss. The CO emission can be highly variable, on timescales as short as a few days. In DG Tau, the bands have been observed to disappear and reappear and may also have a periodic modulation. For the BN object, the equivalent width has varied by a factor of 3; and for V1331 Cyg, the equivalent width doubled in 9 days. Changes in equiva- lent width also occurred in SSV 13, AS 353A, and 1548C27, while WL 16 and S106 have not shown variations.