# The eShel Spectrograph: A Radial-velocity Tool at the Wise Observatory

## TL;DR

The paper presents the installation and performance evaluation of the eShel spectrograph at Wise Observatory, demonstrating its capability for precise radial velocity measurements suitable for binary star studies.

## Contribution

It introduces the eShel spectrograph setup, a new algorithm UNICOR for systematics removal, and showcases its application in binary star orbital solutions.

## Key findings

- Achieves better than 200 m/s radial velocity precision for F-K stars.
- Performance close to photon-noise limit for exposures over 10^7 counts.
- Effective for studying spectroscopic binaries brighter than magnitude 11.

## Abstract

The eShel, an off-the-shelf, fiber-fed echelle spectrograph ($R \approx 10,000$), was installed on the 1m telescope at the Wise observatory in Israel. We report the installation of the multi-order spectrograph, and describe our pipeline to extract stellar radial velocity from the obtained spectra. We also introduce a new algorithm---UNICOR, to remove radial-velocity systematics that can appear in some of the observed orders. We show that the system performance is close to the photon-noise limit for exposures with more than $10^7$ counts, with a precision that can get better than 200 m/s for F--K stars, for which the eShel spectral response is optimal. This makes the eShel at Wise a useful tool for studying spectroscopic binaries brighter than $m_V=11$. We demonstrate this capability with orbital solutions of two binaries from projects being performed at Wise.