Bibcode
Riaz, B.; Whelan, E.; Thompson, M.; Vorobyov, E.; Lodieu, N.
Referencia bibliográfica
American Astronomical Society, AAS Meeting #225, #449.07
Fecha de publicación:
1
2015
Número de citas
0
Número de citas referidas
0
Descripción
We present an optical through sub-millimetre multi-wavelength study of
two very low-luminosity Class I/Flat systems, Mayrit 1701117 and Mayrit
1082188, in the sigma Orionis cluster. We performed moderate resolution
(R 1000) optical ( 0.4-0.9mu) spectroscopy with the TWIN spectrograph
at the Calar Alto 3.5-m telescope. The spectra for both sources show
prominent emission in accretion- and outflow-associated lines. The mean
accretion rate measured from multiple line diagnostics is 6.4x10^{-10}
Msun/yr for Mayrit 1701117, and 2.5x10^{-10} Msun/yr for Mayrit 1082188.
The outflow mass loss rates for the two systems are similar and
estimated to be 1x10^{-9} Msun/yr. The activity rates are within the
range observed for low-mass Class I protostars. We obtained
sub-millimetre continuum observations with the Submillimetre Common-User
Bolometer Array (SCUBA-2) bolometer at the James Clerk Maxwell
Telescope. Both objects are detected at a >5-sigma level in the
SCUBA-2 850mu band. The bolometric luminosity of the targets as measured
from the observed spectral energy distribution over 0.8-850mu is
0.18+/-0.04 Lsun for Mayrit 1701117, and 0.16+/-0.03 Lsun for Mayrit
1082188, and is in the very low-mass range. The total dust+gas mass
derived from sub-millimetre fluxes is 36 M_Jup and 22 M_Jup for Mayrit
1701117 and Mayrit 1082188, respectively. There is the possibility that
some of the envelope material might be dissipated by the strong outflows
driven by these sources, resulting in a final mass of the system close
to or below the sub-stellar limit. Given the membership of these objects
in a relatively evolved cluster of 3 Myr of age, we consider an
alternate formation mechanism in the context of the `hybrid' model of
disk fragmentation, followed by ejection of a gaseous clump.