2019ApJ...877...21W

The accretion-driven outbursts of young FU Orionis-type stars may be a common stage of pre-main-sequence evolution and can have a significant impact on the circumstellar environment as it pertains to the growth of solids and eventually planets. This episodic accretion is thought to be sustained by additional gas infalling from the circumstellar envelope and disk. We present APEX observations of the CO gas in the envelope around V883 Orionis, a young outbursting star. The observations mapped the ¹²CO(4-3), ¹²CO(3-2), and ¹³CO(3-2) lines with the FLASH⁺ instrument and the ¹²CO(6-5) line with the SEPIA instrument. We detected high signal-to-noise emission extending out to radii >10,000 au and calculated integrated fluxes of 1100 Jy km s^–1 for ¹²CO(6-5), 2400 Jy km s^–1 for ¹²CO(4-3), 1600 Jy km s^–1 for ¹²CO(3-2), and 450 Jy km s^–1 for ¹³CO(3-2). We used the thermochemical code PRODIMO to test several models and find the data are best described by an envelope structure with M_env ≃ 0.2-0.4 M_☉ and a mass-infall rate of {dot}M_inf=1–2×10^–6M_☉yr^–1. We infer that the observed envelope and outflow structure around V883 Ori could be caused by multiple outbursts, consistent with episodic accretion.