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The Extreme Stellar-signals Project. III. Combining Solar Data from HARPS, HARPS-N, EXPRES, and NEID

L. L. Zhao, X. Dumusque, E. B. Ford, J. Llama, A. M. J. Mortier, M. Bedell, K. Al Moulla, C. F. Bender, C. H. Blake, J. M. Brewer, A. Collier Cameron, R. Cosentino, P. Figueira, D. A. Fischer, A. Ghedina, M. Gonzalez, S. Halverson, S. Kanodia, D. W. Latham, A. S. J. Lin, G. Lo Curto, M. Lodi, S. E. Logsdon, C. Lovis, S. Mahadevan, A. Monson, J. P. Ninan, F. Pepe, R. M. Roettenbacher, A. Roy, N. C. Santos, C. Schwab, G. Stefánsson, A. E. Szymkowiak, R. C. Terrien, S. Udry, S. A. Weiss, F. Wildi, T. Wildi, J. T. Wright

We present an analysis of Sun-as-a-star observations from four different high-resolution, stabilized spectrographs-HARPS, HARPS-N, EXPRES, and NEID. With simultaneous observations of the Sun from four different instruments, we are able to gain insight into the radial velocity precision and accuracy delivered by each of these instruments and isolate instrumental systematics that differ from true astrophysical signals. With solar observations, we can completely characterize the expected Doppler shift contributed by orbiting Solar System bodies and remove them. This results in a data set with measured velocity variations that purely trace flows on the solar surface. Direct comparisons of the radial velocities measured by each instrument show remarkable agreement with residual intraday scatter of only 15-30 cm s-1. This shows that current ultra-stabilized instruments have broken through to a new level of measurement precision that reveals stellar variability with high fidelity and detail. We end by discussing how radial velocities from different instruments can be combined to provide powerful leverage for testing techniques to mitigate stellar signals.

Stellar activity; Solar activity; Spectrometers; Astronomical instrumentation; Radial velocity; Exoplanet detection methods

Acta Astronautica
Volume 166, Number 4, Page 17
2023 October

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia