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

TL;DR

This study measures mass accretion rates in Herbig Ae/Be stars using X-shooter spectra, revealing variability and applicability of T Tauri star calibrations, with implications for understanding star formation processes.

Contribution

First application of multi-diagnostic spectral analysis to Herbig Ae/Be stars with simultaneous broad wavelength coverage.

Findings

Mass accretion rates range from 2x10^-9 to 2x10^-7 M_sun/yr.

Detected accretion variability of 0.10-0.40 dex over days to weeks.

Most calibrations for T Tauri stars are applicable, some need re-calibration.

Abstract

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 M_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 2x10^-9 to 2x10^-7 M_sun/yr. 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 M_acc variability in details. Our study shows that the majority of the calibrational 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.