Poster Presentation
The early-phase protostellar disk around the VeLLO, IRAS16253-2429
Presenter: Tien-Hao Hsieh (Academia Sinica Institute of Astronomy and Astrophysics (ASIAA))
We present ALMA cycle 4 results toward the Very Low Luminosity Object (VeLLO), IRAS 16253-2429 (hereafter IRAS 16253). IRAS 16253 was considered as a proto-brown dwarf binary system, but the new observation identifies it as a single protostar down to 0.09” (~12 au). Our previous result suggests that IRAS 16253 has experienced a past accretion burst with a mass accretion rate > 1.5*10-5 Msun yr-1 within 10,000 yr. This result, together with the detection of bipolar outflows, implies an existence of gravitational unstable disk which has delivered a 0.002 - 0.003 solar mass of material on to the central protostar in the past burst. We find a tiny dusty disk with a size of ~20 au through the 1.3 mm continuum emission. Rotational supported disk with a size of ~80 au is found from CO (2–1) and C18O (2–1) observations. The mass of the central star derived from the rotation curve of the gaseous disk is ~0.07 Msun, which is already close to the stellar mass. The mass ratio between the central star+disk system and natal core (0.2–0.5 Msun) is 15–40%. This implies that the central object have enough mass reservoir to form a low-mass star with hydrogen burning. The mass of the gaseous disk is estimated to be ~0.005 Msun, ~7% of that of the protostar, and is about 2 times larger than that of the accreted material during the past burst.
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