Measuring the mass accretion rates of Herbig Ae/Be stars with X-shooter?

摘要

We present the results of our observations of eight magnetic Herbig Ae/Be stars obtained with the X-shooter spectrograph mounted on UT2 at the VLT. X-shooter provides a simultaneous, medium-resolution and high-sensitivity spectrum over the entire wavelength range from 300 to 2500 nm. We estimate the mass accretion rates (?_acc) of the targets from 13 different spectral diagnostics using empiric calibrations derived previously for T Tauri-type stars and brown dwarfs. We have estimated the mass accretion rates of our targets, which range from 2 × 10–9 to 2 × 10–7 M_⊙ yr–1. Furthermore, we have found accretion rate variability with amplitudes of 0.10–0.40 dex taking place on time scales from one day to tens of days. Additional future night-to-night observations need to be carried out to investigate the character of ?_acc variability in details. Our study shows that the majority of the calibration relations can be applied to Herbig Ae/Be stars, but several of them need to be re-calibrated on the basis of new spectral data for a larger number of Herbig Ae/Be stars (? 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)