# Towards a Self-calibrating, Empirical, Light-Weight Model for Tellurics in High-Resolution Spectra

## TL;DR

This paper introduces SELENITE, a lightweight, self-calibrating empirical model for telluric correction in high-resolution spectra, eliminating the need for standard star observations or imprecise line data, thus enabling precise radial velocity measurements.

## Contribution

The paper presents SELENITE, a novel empirical model that accurately corrects telluric contamination without requiring line data or additional observations, streamlining high-precision spectroscopic analysis.

## Key findings

- Achieves residuals of about 1% of continuum in spectra.
- Fits data with a reduced chi squared of 1.17 on B stars.
- Fitting process takes seconds on standard laptops.

## Abstract

To discover Earth analogs around other stars, next generation spectrographs must measure radial velocity (RV) with 10 cm/s precision. To achieve 10cm/s precision, however, the effects of telluric contamination must be accounted for. The standard approaches to telluric removal are: (a) observing a standard star and (b) using a radiative transfer code. Observing standard stars, however, takes valuable observing time away from science targets. Radiative transfer codes, meanwhile, rely on imprecise line data in the HITRAN database (typical line position uncertainties range from a few to several hundred m/s) and require difficult-to-obtain measurements of water vapor column density for best performance. To address these issues, we present SELENITE: a SELf-calibrating, Empricial, Light-Weight liNear regressIon TElluric model for high-resolution spectra. The model exploits two simple observations: (a) water tellurics grow proportionally to precipitable water vapor and therefore proportionally to each other and (b) non-water tellurics grow proportionally to airmass. Water tellurics can be identified by looking for pixels whose growth correlates with a known calibration water telluric and modelled by regression against it, and likewise non-water tellurics with airmass. The model doesn't require line data, water vapor measurements and additional observations (beyond one-time calibration observations), achieves fits with a reduced chi squared of 1.17 on B stars and 2.95 on K dwarfs, and leaves residuals of 1% (B stars) and 1.1% (K dwarfs) of continuum. Fitting takes seconds on laptop PCs: SELENITE is light-weight enough to guide observing runs.