X-Shooter study of accretion in Chamaeleon I

C F Manara,G J Herczeg,D Fedele,P S Teixeira

doi:10.1051/0004-6361/201527224

Abstract

We present the analysis of 34 new VLT/X-Shooter spectra of young stellar objects in the Chamaeleon I star forming region, together with four more spectra of stars in Taurus and two in Chamaeleon II. The broad wavelength coverage and accurate flux calibration of our spectra allow us to estimate stellar and accretion parameters for our targets by fitting the photospheric and accretion continuum emission from the Balmer continuum down to 700 nm. The dependence of accretion with stellar properties for this sample is consistent with previous results from the literature. The accretion rates for transitional disks are consistent with those of full disks in the same region. The spread of mass accretion rates at any given stellar mass is found to be smaller than in many studies, but is larger than that derived in the Lupus clouds using similar data and techniques. Differences in the stellar mass range and in the environmental conditions between our sample and that of Lupus may account for the discrepancy in scatter between Chamaeleon I and Lupus. Complete samples in Chamaeleon I and Lupus are needed to determine whether the difference in scatter of accretion rates and the lack of evolutionary trends are robust to sample selection.

Highlights

During the first Myr of evolution toward the main sequence, the disk around young stellar objects (YSOs) evolves and is dispersed mainly by disk accretion processes and photoevaporation (Alexander et al 2014)
We present the analysis of 34 new VLT/X-Shooter spectra of young stellar objects in the Chamaeleon I star-forming region, together with four more spectra of stars in Taurus and two in Chamaeleon II
In this paper we present a study of a large sample of 34 Class II YSOs in the Chamaeleon I star-forming region (d = 160 pc, Luhman 2008) observed with X-Shooter, and of a few additional targets in Taurus and Chamaeleon II

Summary

Introduction

During the first Myr of evolution toward the main sequence, the disk around young stellar objects (YSOs) evolves and is dispersed mainly by disk accretion processes and photoevaporation (Alexander et al 2014). Observations of accretion in YSOs mostly focus on determining the amount of material accreted onto the central star per unit time. This mass accretion rate (Macc, e.g., Hartmann et al 1998) may be compared to the stellar and disk properties to test the predictions of models of disk evolution. Accretion has sometimes been found to correlate with age (e.g., Hartmann et al 1998; Sicilia-Aguilar et al 2010; Antoniucci et al 2014), ages of individual young stars in a given

Results

Discussion

Conclusion