High-Resolution Ultraviolet Radiation Fields of Classical T Tauri Stars*

Abstract

The far-ultraviolet (FUV; 912 -1700Å) radiation field from accreting central stars in Classical T Tauri systems influences the disk chemistry during the period of giant planet formation. The FUV field may also play a critical role in determining the evolution of the inner disk (r < 10 AU), from a gasand dust-rich primordial disk to a transitional system where the optically thick warm dust distribution has been depleted. Previous efforts to measure the true stellar+accretion-generated FUV luminosity (both hot gas emission lines and continua) have been complicated by a combination of low-sensitivity and/or low-spectral resolution and did not include the contribution from the bright Lyα emission line. In this work, we present a high-resolution spectroscopic study of the FUV radiation fields of 16 T Tauri stars whose dust disks display a range of evolutionary states. We include reconstructed Lyα line profiles and remove atomic and molecular disk emission (from H 2 and CO fluorescence) to provide robust measurements of both the FUV continuum and hot gas lines (e.g., Lyα, N V, C IV, He II) for an appreciable sample of T Tauri stars for the first time. We find that the flux of the typical Classical T Tauri Star FUV radiation field at 1 AU from the central star is ∼ 10 7 times the average interstellar radiation field. The Lyα emission line contributes an average of 88% of the total FUV flux, with the FUV continuum accounting for an average of 8%. Both the FUV continuum and Lyα flux are strongly correlated with C IV flux, suggesting that accretion processes dominate the production of both of these components. On average, only ∼ 0.5% of the total FUV flux is emitted between the Lyman limit (912Å) and the H 2 (0 -0) absorption band at 1110Å. The total and component-level high-resolution radiation fields are made publicly available in machine-readable format.

A self-consistent model for the evolution of the gas produced in the debris disc of β Pictoris

“…These Xrays are not present around main sequence stars but there could be some remnants in the youngest systems (Rigliaco et al 2015). Indeed, the flux of a typical classical T Tauri star FUV radiation field at 1 AU from the central star is 10 7 times the interstellar radiation field (France et al 2014).…”

Volatile-carbon locking and release in protoplanetary disks

“…3. The ultraviolet range of spectra used in this study for TW Hya (red curve, France et al 2014;Cleeves et al 2015) and HD 100546 (blue curve, Bruderer et al 2012), compared with blackbody photospheres for pre main sequence model stars with an age of 10 Myr (black curves, Tognelli et al 2011). The two curves labelled 4000 K+UV show a 4000 K stellar photosphere with a 10 000 K blackbody added for the accretion ratesṀ = 10 −9 and 10 −8 M yr −1 .…”

The 1600 Å Emission Bump in Protoplanetary Disks: A Spectral Signature of H2O Dissociation∗

“…Following the discussion in §3.2, previous correlations between C IV and the accretion rate may have been driven in part by an overestimated extinction correction, but this plot demonstrates that L(FUV Cont) and L(C IV) are strongly correlated over more than three decades of C IV luminosity. The FUV continuum has been shown to not be a direct extension of the NUV Balmer continuum in most CTTS France et al 2014b), but instead is likely contributed by specific high-temperature pre-shock regions where accretion columns are impacting the protostellar surface, likely with a small geometric filling faction over the stellar surface (e.g., Ingleby et al 2013). Models of the FUV accretion continuum generation would be valuable inputs to studies of disk photochemistry and the photoevaporative evolution of gas disks.…”

“…c Intrinsic Lyα luminosity values with error bars were taken from the literature France et al 2014b). Lyα values without error bars were extrapolated from direct H 2 fluorescence measurements based on the L(Lyα) vs. L(H 2 ) relationship (see Section 3.1.2).…”