Determining stellar accretion rates from Paα and Brβ emission lines with JWST NIRSpec

Abstract

In this Letter, we present the first systematic spectroscopic measurements of the near-infrared (NIR) hydrogen recombination lines Paschen alpha (Paαλ = 1.875 μm) and Brackett beta (Brβλ = 2.626 μm), produced by pre-main-sequence (PMS) stars. Such stars include T Tauri and Herbig AeBe stars, located in the massive Galactic star-forming region NGC 3603. We used measurements obtained from JWST NIRSpec, using multi-object spectroscopy (MOS) mode. Based on the existing empirical relations between Lacc and LBrγ from the literature, we used our new measurements to formulate, for the first time, an empirical relationship between the accretion luminosity, Lacc, of the stars and the line luminosities, Lline, of both Paα and Brβ. These relationships are: log10(Lacc/L⊙) = 1.42(±0.18) × log10(LPaα/L⊙ + 3.33(±0.42) and log10(Lacc/L⊙) = 1.47(±0.18) × log10(LBrβ/L⊙) + 4.60(±0.57). These new relationships are key to establishing rough estimates of the accretion rates for large samples of PMS stars with JWST.