The Long-Term Radial Velocity Stability of the COS G130M/1291 Mode
Abstract
We investigate the long-term radial velocity (RV) stability of one of the Far-UV (FUV) modes on the Cosmic Origins Spectrograph (COS). We do so by using a standard white dwarf, WD~0308-565, that has been observed over a large fraction of COS's operational lifetime of 17 years. We demonstrate that for modest signal-to-noise COS can return an RV stability of <3 km s−1 over a baseline of 15 years. For higher SNR and a smaller number of epochs, we obtain σV=600 m s−1. We also show that the absolute radial velocity accuracy for this target is consistent with results from ground-based optical spectroscopy. We discuss some observational strategies and astrophysical objects that may be well suited to pushing to the very RV limit of the instrument. Utilizing COS for precision RV work opens a new scientific avenue for space-based UV astronomy as COS approaches 20 years of operations and hints at what may be possible with the stability of a high-resolution UV spectrograph on future missions such as the Habitable Worlds Observatory.
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BibTeX
@misc{debes2026longterm,
title = {{The Long-Term Radial Velocity Stability of the COS G130M/1291 Mode}},
author = {John Debes and David M. French and Leonardo A. Dos Santos and Travis Fischer and Svea Hernandez and Ravi Sankrit},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.15819},
eprint = {2610.15819},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.15819},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The Long-Term Radial Velocity Stability of the COS G130M/1291 Mode
AU - John Debes
AU - David M. French
AU - Leonardo A. Dos Santos
AU - Travis Fischer
AU - Svea Hernandez
AU - Ravi Sankrit
PY - 2026
DA - 2026/10/11
PB - arXiv
DO - 10.48550/arxiv.2610.15819
UR - https://arxiv.org/abs/2610.15819
AB - We investigate the long-term radial velocity (RV) stability of one of the Far-UV (FUV) modes on the Cosmic Origins Spectrograph (COS). We do so by using a standard white dwarf, WD~0308-565, that has been observed over a large fraction of COS's operational lifetime of 17 years. We demonstrate that for modest signal-to-noise COS can return an RV stability of <3 km s^−1 over a baseline of 15 years. For higher SNR and a smaller number of epochs, we obtain σ_V=600 m s^−1. We also show that the absolute radial velocity accuracy for this target is consistent with results from ground-based optical spectroscopy. We discuss some observational strategies and astrophysical objects that may be well suited to pushing to the very RV limit of the instrument. Utilizing COS for precision RV work opens a new scientific avenue for space-based UV astronomy as COS approaches 20 years of operations and hints at what may be possible with the stability of a high-resolution UV spectrograph on future missions such as the Habitable Worlds Observatory.
ER -