Temporal Variability in Carbon Monoxide Abundances in Young Stellar Objects and Implications for the Early Solar System

Abstract

Observations of young stellar objects (YSOs) provide a unique window into protoplanetary chemistry. In particular, high-resolution near-infrared observations of carbon monoxide (CO) gas toward YSOs and evaluation of carbon and oxygen isotopes have yielded valuable insights into protoplanetary processes with implications for the early solar nebula [1-7]. While each spectral observation is a snapshot in a several-million-years timescale, YSOs have interestingly been observed to vary in several important parameters over timescales of months to a few years. For example, observations of late-stage solar-type disks reveal up to 50% variability in infrared (IR) fluxes, possibly due to the stellar companions or magnetic fields [8], and 70% of Class I and II YSOs studied in Orion show IR variability in amplitude, possibly due to gas extinction or warps in disk geometry [9]. Significant light-curve variations have further been found in YSOs of the Lynds 1688 region, attributed to possible structural changes in the inner disk [10], and IR photometric variability in nearly 100 YSOs in Cygnus observed over a few years could be due to changes in disk dynamics [11]. Here we present our intial variability analysis of gas-phase CO observations toward a range of solar-type and massive YSOs, with separations in observations of each YSO target ranging from months to a few years. This study is centered on exploring how key molecular reservoirs may vary in the very shortterm in evolving systems, and how these variations may differ between solar-type and massive YSOs.

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