# # Program information file # PROGRAM_ID 2021A073 PROGRAM_TITLE LAERTES: L-Band Accretion Estimator Reconnaissance of TTS Emission Spectra PROGRAM_INV1 Will Fischer PROGRAM_INV2 Tracy Beck PROGRAM_INV3 James Muzerolle PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT stellar PROGRAM_ABSTRACT_BEG The disk accretion rates of accreting young stars are important inputs for understanding how stars and planets get their masses. These are best measured from the UV/optical continuum, but these wavelengths are not accessible for the most embedded T Tauri stars [TTS] or in their precursors, the protostars. Instead, IR emission lines can be used as indirect tracers. At 4.05 microns, Brackett alpha is a strong emission line in accreting young stars and will be readily accessible to JWST spectroscopy, but it has not been fully calibrated as an accretion indicator. We propose 1.7-4.2 micron SpeX LXD_short spectroscopy of 29 TTS with the 0.8 arcsec slit. These observations will be nearly simultaneous with HST observations of the targets expected to be made in the 2021A semester as part of the ULLYSES public director's discretionary program. This will allow the Brackett alpha line to be calibrated with nearly simultaneous measurements of the UV/optical continuum in these stars. It will also provide an important archival dataset for the community by extending the wavelength coverage of the HST observations to the thermal IR. PROGRAM_ABSTRACT_END