Protostellar Accretion

Accreting young stars require simultaneous continuum and line diagnostics from the atmospheric cutoff through K band.

These measurements link accretion luminosity, extinction, and outflow strength for the same state of the source. They constrain how young stars gain mass and lose angular momentum.

X-shooter spectra of accreting young stellar objects around the Balmer jump. The observed spectra, non-accreting templates, and accretion-continuum fits separate photospheric and accretion emission.
Source: Alcala et al. 2014, A&A, 561, A2, Figure 4; ZShooter SRD Section 2.3.10.

Science Drivers

• The blue spectrum measures the Balmer continuum and Balmer jump.

• H, He I 1.083 um, Pa beta, Br gamma, and O I lines measure accretion, extinction, winds, and outflows.

Instrument Requirements

• Simultaneous 0.31 to 2.45 um spectra avoid biases from accretion variability between separate optical and NIR observations.

Observing Requirements

• The reference target is r ≈ 20 at S/N = 10 and R ≈ 10,000, with ≈ 5 km/s radial-velocity precision.