Very low-luminosity Class I/Flat outflow sources in Sigma Orionis: Clues to alternative formation mechanisms for very low-mass stars
- Author(s)
- Basmah Riaz, E. Whelan, M. Thompson, E. Vorobyov, N. Lodieu
- Abstract
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 spectrographat the Calar Alto 3.5-m telescope. The spectra for both sources showprominent emission in accretion- and outflow-associated lines. The meanaccretion 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 andestimated to be 1x10^{-9} Msun/yr. The activity rates are within therange observed for low-mass Class I protostars. We obtainedsub-millimetre continuum observations with the Submillimetre Common-UserBolometer Array (SCUBA-2) bolometer at the James Clerk MaxwellTelescope. Both objects are detected at a >5-sigma level in theSCUBA-2 850mu band. The bolometric luminosity of the targets as measuredfrom 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 Mayrit1082188, and is in the very low-mass range. The total dust+gas massderived from sub-millimetre fluxes is 36 M_Jup and 22 M_Jup for Mayrit1701117 and Mayrit 1082188, respectively. There is the possibility thatsome of the envelope material might be dissipated by the strong outflowsdriven by these sources, resulting in a final mass of the system closeto or below the sub-stellar limit. Given the membership of these objectsin a relatively evolved cluster of 3 Myr of age, we consider analternate formation mechanism in the context of the 'hybrid' model ofdisk fragmentation, followed by ejection of a gaseous clump.
- Organisation(s)
- Department of Astrophysics
- External organisation(s)
- University of Maryland, College Park, Eberhard Karls Universität Tübingen, University of Hertfordshire, Institute of Genetics and Biophysics "Adriano Buzzati-Traverso", CNR
- Journal
- American Astronautical Society. Proceedings of the Annual Meeting
- Volume
- 225
- Publication date
- 01-2015
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 103004 Astrophysics
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/very-lowluminosity-class-iflat-outflow-sources-in-sigma-orionis-clues-to-alternative-formation-mechanisms-for-very-lowmass-stars(52645c24-dcda-4428-bf34-3ea4ddda5827).html