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We investigate the evolution of accretion luminosity $L_{rm acc}$ and stellar luminosity ${L_ast}$ in pre-mainsequence stars. We make the assumption that when the star appears as a Class II object, the major phase of accretion is long past, and the accretion disc has entered its asymptotic phase. We use an approximate stellar evolution scheme for accreting pre-mainsequence stars based on Hartmann, Cassen & Kenyon, 1997. We show that the observed range of values $k = L_{rm acc}/L_ast$ between 0.01 and 1 can be reproduced if the values of the disc mass fraction $M_{rm disc}/M_*$ at the start of the T Tauri phase lie in the range 0.01 -- 0.2, independent of stellar mass. We also show that the observed upper bound of $L_{rm acc} sim L_ast$ is a generic feature of such disc accretion. We conclude that as long as the data uniformly fills the region between this upper bound and observational detection thresholds, then the degeneracies between age, mass and accretion history severely limit the use of this data for constraining possible scalings between disc properties and stellar mass.
We present Halpha spectropolarimetry observations of a sample of 10 bright T Tauri stars, supplemented with new Herbig Ae/Be star data. A change in the linear polarisation across Halpha is detected in most of the T Tauri (9/10) and Herbig Ae (9/11) o
We have used the high sensitivity and resolution of the IRAM interferometer to produce sub-arcsecond 12CO 2-1 images of 9 protoplanetary disks surrounding T Tauri stars in the Taurus-Auriga cloud (7 singles and 2 binaries). The images demonstrate the
We have analysed the [OI]6300 A line in a sample of 131 young stars with discs in the Lupus, Chamaeleon and signa Orionis star forming regions, observed with the X-shooter spectrograph at VLT. The stars have mass accretion rates spanning from 10^{-12
In Spitzer observations of Tauri stars and their disks, PAH features are detected in less than 10% of the objects, although the stellar photosphere is sufficiently hot to excite PAHs. To explain the deficiency, we discuss PAH destruction by photons a
The Small Magellanic Cloud (SMC) is an excellent laboratory to study the formation of solar-mass stars in a low-metallicity environment, similar to the conditions expected in the early phases of galactic evolution. Here we present preliminary results