A Far-ultraviolet Atlas of Low-resolution Hubble Space Telescope Spectra of T Tauri Stars

TL;DR

This paper provides a comprehensive FUV spectral atlas of 91 pre-main sequence stars, revealing correlations among emission lines and accretion indicators, and offering insights into star-disk interactions and accretion processes.

Contribution

It introduces a new FUV spectral atlas of T Tauri stars, highlighting correlations among emission lines and accretion diagnostics, and distinguishes accreting from non-accreting stars based on H2 emission.

Findings

Strong correlations among FUV emission lines and accretion luminosity.

H2 emission indicates active accretion in T Tauri stars.

FUV and optical diagnostics can estimate FUV fluxes from optical data.

Abstract

We present a far-ultraviolet (FUV) spectral atlas consisting of spectra of 91 pre-main sequence stars. Most stars in this sample were observed with the Space Telescope Imaging Spectrograph (STIS) and Advanced Camera for Surveys (ACS) on the \emph{Hubble Space Telescope} (\emph{HST}). We find strong correlations among the \ion{O}{1} $\lambda$1304 triplet, %\ion{C}{2} $\lambda$1335, the \ion{Si}{4} $\lambda\lambda$1394/1403 doublet, the \ion{C}{4} $\lambda$1549 doublet, and the \ion{He}{2} $\lambda$1640 line luminosities. For classical T Tauri stars (CTTSs), we also find strong correlations between these lines and the accretion luminosity, suggesting that these lines form in processes related to accretion. These FUV line fluxes and X-ray luminosity correlate loosely with large scatters. The FUV emission also correlates well with H$\alpha$, H$\beta$, and \ion{Ca}{2} K line luminosities. These correlations between FUV and optical diagostics can be used to obtain rough estimates of FUV line fluxes from optical observations. Molecular hydrogen (H$_{2}$) emission is generally present in the spectra of actively accreting CTTSs but not the weak-lined T Tauri stars (WTTSs) that are not accreting. The presence of H$_2$ emission in the spectrum of HD 98800 N suggests that the disk should be classified as actively accreting rather than a debris disk. The spectra in the atlas are available at http://archive.stsci.edu/prepds/ttauriatlas.