High-resolution ALMA Study of the Proto-brown-dwarf Candidate L328-IRS

This paper presents our observational attempts to precisely measure the central mass of a proto-brown dwarf candidate, L328-IRS, in order to investigate whether L328-IRS is in the substellar mass regime. Observations were made for the central region of L328-IRS with the dust continuum and CO isotopo...

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Bibliographic Details
Published in:The Astrophysical journal 2018-10, Vol.865 (2), p.131
Main Authors: Lee, Chang Won, Kim, Gwanjeong, Myers, Philip C., Saito, Masao, Kim, Shinyoung, Kwon, Woojin, Lyo, A-Ran, Soam, Archana, Kim, Mi-Ryang
Format: Article
Language:English
Subjects:
Accretion disks
Astrophysics
Brown dwarf stars
brown dwarfs
Inclination angle
ISM: individual objects (L328, L328-IRS)
Luminosity
Outflow
Radio telescopes
stars: low-mass
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Summary:This paper presents our observational attempts to precisely measure the central mass of a proto-brown dwarf candidate, L328-IRS, in order to investigate whether L328-IRS is in the substellar mass regime. Observations were made for the central region of L328-IRS with the dust continuum and CO isotopologue line emission at Atacama Large Millimeter/submillimeter Array (ALMA) band 6, discovering the detailed outflow activities and a deconvolved disk structure of a size of ∼87 × 37 au. We investigated the rotational velocities as a function of the disk radius, finding that its motions between 130 and 60 au are partially fitted with a Keplerian orbit by a stellar object of ∼0.30 M , while the motions within 60 au do not follow any Keplerian orbit at all. This makes it difficult to lead a reliable estimation of the mass of L328-IRS. Nonetheless, our ALMA observations were useful enough to well constrain the inclination angle of the outflow cavity of L328-IRS as ∼66°, enabling us to better determine the mass accretion rate of ∼8.9 × 10−7 M yr−1. From assumptions that the internal luminosity of L328-IRS is mostly due to this mass accretion process in the disk, or that L328-IRS has mostly accumulated the mass through this constant accretion rate during its outflow activity, its mass was estimated to be ∼0.012-0.023 M , suggesting L328-IRS to be a substellar object. However, we leave our identification of L328-IRS as a proto-brown dwarf to be tentative because of various uncertainties, especially regarding the mass accretion rate.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/aadcf6