Speaker
Description
We present our radial-velocities (RVs) with the iSHELL spectrograph at the NASA Infrared Telescope facility. Replacing the 25 year old CSHELL instrument, iSHELL offers improvements in spectral grasp (~40x), resolution (70,000 versus 46,000), throughput, optics, and detector characteristics. Our primary goal with iSHELL is to characterize the precise radial-velocity performance of the methane isotopologue absorption gas cell in the calibration unit. Over the last two years, we've obtained 3-12 epochs of bright nearby RV standards as well as RV variables of our own. A new flexible telluric model allows for dynamic abundance ratios in Earth's atmosphere, and physically-motivated analytic fringing models account for internal reflections from the optics in the instrument. We've demonstrated 6 m/s precision on Barnard’s star over one year, sufficient to confirm Neptune-mass planets around M Dwarfs discovered by the NASA TESS mission. With further development on the the non-standard blaze and line spread functions present in iSHELL data, we aim to achieve 3-5 m/s long-term precision, sufficient to detect terrestrial mass planets in the habitable zone of nearby M Dwarfs.
