Kavli Affiliate: Gregory J. Herczeg
| First 5 Authors: Pedro Henrique Nogueira, Alice Zurlo, Sebastián Pérez, Camilo González-Ruilova, Lucas A. Cieza
| Summary:
Episodic accretion is a low-mass pre-main sequence phenomenon characterized
by sudden outbursts of enhanced accretion. These objects are classified into
two: protostars with elevated levels of accretion that lasts for decades or
more, called FUors, and protostars with shorter and repetitive bursts, called
EXors. HBC 494 is a FUor object embedded in the Orion Molecular Cloud. Earlier
Atacama Large (sub-)Millimeter Array (ALMA) continuum observations showed an
asymmetry in the disk at 0.”2 resolution. Here, we present follow-up
observations at ~0.”03, resolving the system into two components: HBC 494 N
(primary) and HBC 494 S (secondary). No circumbinary disk was detected. Both
disks are resolved with a projected separation of ~0.”18 (75 au). Their
projected dimensions are 84+/-1.8 x 66.9+/-1.5 mas for HBC 494 N and 64.6+/-2.5
x 46.0+/-1.9 mas for HBC 494 S. The disks are almost aligned and with similar
inclinations. The observations show that the primary is ~5 times brighter/more
massive and ~2 times bigger than the secondary. We notice that the northern
component has a similar mass to the FUors, while the southern has to EXors. The
HBC 494 disks show individual sizes that are smaller than single eruptive YSOs.
In this work, we also report 12CO, 13CO, and C18O molecular line observations.
At large scale, the 12CO emission shows bipolar outflows, while the 13CO and
C18O maps show a rotating and infalling envelope around the system. At a
smaller scale, the 12CO and 13CO moment zero maps show cavities within the
continuum disks’ area, which may indicate continuum over-subtraction or
slow-moving jets and chemical destruction along the line-of-sight.
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