# Activity and telluric contamination in HARPS observations of Alpha Centauri B

## TL;DR

This paper analyzes HARPS observations of Alpha Centauri B to understand stellar activity and telluric contamination, proposing procedures that improve data quality and provide insights into spectral line behavior.

## Contribution

It introduces methods to identify and mitigate telluric contamination in high-precision radial velocity data of Alpha Centauri B.

## Key findings

- Discarded about 5% of data due to contamination
- Improved RMS of measurements by a factor of 2
- Quantified behavior of 345 spectral lines

## Abstract

The Alpha Centauri system is the primary target for planet search as it is the closest star system composed of a solar twin Alpha Centauri A, a K-dwarf Alpha Centauri B and an M-dwarf Proxima Centauri, which has a confirmed planet in the temperate zone. Alpha Centauri A & B were monitored intensively with the HARPS spectrograph for over 10 years, providing high-precision radial velocity measurements. In this work we study the available data to better understand the stellar activity and other contaminating signals. We highlight the importance of telluric contamination and its impact on the radial velocity measurements. Our suggested procedures lead to discarding about 5% of HARPS data, providing a dataset with an RMS improved by a factor of 2. We compile and quantify the behaviour of 345 spectral lines with a wide range of line shapes and sensitivity to activity.