VROOMM: a new high-resolution echelle spectrograph for Observatoire du Mont Mégantic

VROOMM is an optical (360nm - 930 nm) high-resolution échelle spectrograph currently in its design phase for the 1.6-meter telescope of the Observatoire du Mont-Mégantic (OMM) in Québec, Canada. Specifically designed for precision radial velocity (RV) measurements of relatively faint stars, the instrument features a 4K photon-counting EMCCD, octagonal fibers, and a double scrambler, all housed in a thermally stabilized vacuum cryostat. Designed for a resolution exceeding 80 000, the spectrograph aims to provide RV measurements with precision tailored for specific cases. The first scenario involves using the EMCCD like a normal CCD without electron amplification, enabling follow-up observations of terrestrial planets, super-Earths, and mini-Neptunes orbiting relatively bright M dwarfs. The second case employs photon counting, utilizing the electron-multiplying mode of the EMCCD to achieve 100−200 m/s velocimetry through cross-correlation of extremely low signal-to-noise ratio data. This innovative approach opens up observations of stars as faint as rsdss=19-20, an unexplored realm in RV studies. The main science niche for this mode is the confirmation of brown dwarfs orbiting cool stars and stellar dynamics within open clusters and young associations. Typically observed at low resolution, these targets face challenges in achieving RV precision better than a few km/s. VROOMM’s photon counting capability presents a novel solution for obtaining high-precision radial velocities in this challenging regime. We detail the unique features and capabilities of each operation mode, emphasizing the novel contributions of VROOMM in advancing precision RV measurements for a diverse range of exoplanet systems.