Determining stellar accretion rates from Pa_α and Br_β emission lines with JWST NIRSpec Accretion of pre-main-sequence stars in NGC 3603

In this Letter, we present the first systematic spectroscopic measurements of the near-infrared (NIR) hydrogen recombination lines Paschen alpha (Paalphalambda = 1.875 mu m) and Brackett beta (Brbetalambda = 2.626 mu m), 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 LBrgamma 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 Paalpha and Brbeta. These relationships are: log10(Lacc/Lcircle dot) = 1.42(+/- 0.18) x log10(LPaalpha/Lcircle dot + 3.33(+/- 0.42) and log10(Lacc/Lcircle dot) = 1.47(+/- 0.18) x log10(LBr beta/Lcircle dot) + 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.