EXORCISM: A Spectroscopic Survey of Young Eruptive Variables (EXor and Candidates)
Journal
Date Issued
2022
Author(s)
Abstract
We present an optical/near-IR survey of 11 variable young stars (EXors and EXor candidates) aimed at deriving and monitoring their accretion properties. About 30 optical and near-infrared spectra ( R∼1500-2000 ) were collected between 2014 and 2019 with the Large Binocular Telescope (LBT). From the spectral analysis we have derived the accretion luminosity (L acc ) and mass accretion rate ( Ṁacc ), the visual extinction (A V), the temperature and density of the permitted line formation region (T, n H), and the signature of the outflowing matter. Two sources (ASASSN-13db and iPTF15afq) have been observed in outburst and quiescence, three during a high level of brightness (XZ Tau, PV Cep, and NY Ori), and the others in quiescence. These latter have L acc and Ṁacc in line with the values measured in classical T Tauri stars of similar mass. All sources observed more than once present L acc and Ṁacc variability. The most extreme case is ASASSN-13db, for which Ṁacc decreases by two orders of magnitude from the outburst peak in 2015 to quiescence in 2017. Also, in NY Ori L acc decreases by a factor 25 in one year. In 80% of the sample we detect the [O i] 6300 Å line, a tracer of mass loss. From the variability of the Hα/[O i] 6300 Å ratio, we conclude that mass accretion variations are larger than mass loss variations. From the analysis of the H i recombination lines, a correlation is suggested between the density of the line formation region, and the level of accretion activity of the source.
Volume
929
Issue
2
Start page
129
Issn Identifier
0004-637X
Rights
open.access
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