X-Shooter spectroscopy of young stellar objects: IV -- Accretion in low-mass stars and sub-stellar objects in Lupus

摘要: We present X-Shooter/VLT observations of a sample 36 accreting low-mass stellar and sub-stellar objects (YSOs) in the Lupus star forming region, spanning range mass from ~0.03 to ~1.2Msun, but mostly with 0.1Msun < Mstar 0.5Msun. Our aim is twofold: firstly, analyse relationship between excess-continuum line emission accretion diagnostics, and, secondly, investigate properties terms physical central object. The luminosity (Lacc), it rate (Macc), derived by modelling excess emission, UV near-IR, as continuum slab hydrogen. flux (Ll) large number lines H, He, CaII, etc., observed simultaneously ~330nm 2500nm, were computed. all well correlated Lacc. provide empirical relationships Lacc 39 lines, which have lower dispersion compared previous literature. measurements extend Pab Brg values about two orders magnitude than those reported studies. confirm that different methodologies measure Macc yield significantly results: Ha profile may underestimate 0.6 0.8dex respect continuum-excess measures. Such differences explain likely spurious bi-modal other YSOs derive 2e-12 -- 4e-8 Msun/yr conclude proportional Mstar^1.8(+/-0.2), factor 2 A indicate conditions gas are similar over more 5 Macc.