Very low-luminosity Class I/Flat outflow sources in Sigma Orionis: Clues to alternative formation mechanisms for very low-mass stars

Autor(en)

Basmah Riaz, E. Whelan, M. Thompson, E. Vorobyov, N. Lodieu

Abstrakt

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(en)

Institut für Astrophysik

Externe Organisation(en)

University of Maryland, College Park, Eberhard Karls Universität Tübingen, University of Hertfordshire, Consiglio Nazionale delle Ricerche

Journal

American Astronautical Society. Proceedings of the Annual Meeting

Band

225

Publikationsdatum

01-2015

Peer-reviewed

Ja

ÖFOS 2012

103004 Astrophysik

Link zum Portal

https://ucrisportal.univie.ac.at/de/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