Variability in gas-phase co reservoirs in massive young stellar cores and binaries

Abstract

High-resolution observations of young stellar objects (YSOs) are exciting windows into protoplanetary chemistry. Near-infrared observations of carbon monoxide (CO) gas toward YSOs and evaluation of carbon and oxygen isotopes therin have provided insights into protoplanetary processes with implications for the evolution of carbon in the early solar nebula [1-7]. Each YSO observation reveals a snapshot in a ~million-yr timescale of disk evolution; yet, YSOs have also been observed to vary significantly in timescales of months to a few years. For example, infrared fluxes in late-stage solar-type disks show up to 50% variability [8], and 70% of Class I and II YSOs in Orion vary in infrared amplitudes [9]. Structural changes in the inner disk could also influence lightcurve variations in certain YSOs [10], and disk dynamics could lead to photometric variability in within a few years [11]. Our preliminary analysis on abundance variation in CO using archival VLT-CRIRES data revealed that [¹³CO]/[C¹⁸O] ratios for low-mass YSOs could vary significantly (~53% to 63%) [12]. Here we present ongoing results of short-term variability in gas-phase CO toward a range of massive YSOs using high-resolution spectra observed at NASA's IRTF observatory. This study explores a range of environments: solar-type and massive YSO cores, as well as binary pairs – unique targets that inform chemical evolution in systems with stellar multiplicity.

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