Observing the Sun as a Star: Design and Early Results from the NEID Solar Feed

Creators: Lin, Andrea S. J.; Monson, Andrew; Mahadevan, Suvrath; Ninan, Joe P.; Halverson, Samuel; Nitroy, Colin; Bender, Chad F.; Logsdon, Sarah E.; Kanodia, Shubham; Terrien, Ryan C.; Roy, Arpita; Luhn, Jacob K.; Gupta, Arvind F.; Ford, Eric B.; Hearty, Fred; Laher, Russ R.; Hunting, Emily; McBride, William R.; Salazar Rivera, Noah Isaac; Rajagopal, Jayadev; Wolf, Marsha J.; Robertson, Paul; Wright, Jason T.; Blake, Cullen H.; Cañas, Caleb I.; Lubar, Emily; McElwain, Michael W.; Ramsey, Lawrence W.; Schwab, Christian; Stefansson, Gudmundur

Abstract

Efforts with extreme-precision radial velocity (EPRV) instruments to detect small-amplitude planets are largely limited, on many timescales, by the effects of stellar variability and instrumental systematics. One avenue for investigating these effects is the use of small solar telescopes which direct disk-integrated sunlight to these EPRV instruments, observing the Sun at high cadence over months or years. We have designed and built a solar feed system to carry out "Sun-as-a-star" observations with NEID, a very high precision Doppler spectrometer recently commissioned at the WIYN 3.5 m Telescope at Kitt Peak National Observatory. The NEID solar feed has been taking observations nearly every day since 2020 December; data is publicly available at the NASA Exoplanet Science Institute NEID Solar Archive: https://neid.ipac.caltech.edu/search_solar.php. In this paper, we present the design of the NEID solar feed and explanations behind our design intent. We also present early radial velocity (RV) results which demonstrate NEID's RV stability on the Sun over 4 months of commissioning: 0.66 m s⁻¹ rms under good sky conditions and improving to 0.41 m s⁻¹ rms under best conditions.

Additional Information

© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 December 10; revised 2022 February 4; accepted 2022 February 15; published 2022 March 22. Based on observations at Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. NEID and WIYN Data presented were obtained by the NEID spectrograph built by Penn State University and operated at the WIYN Observatory by NOIRLab, under the NN-EXPLORE partnership of the National Aeronautics and Space Administration and the National Science Foundation. WIYN is a joint facility of the University of Wisconsin–Madison, Indiana University, NSF's NOIRLab, the Pennsylvania State University, Purdue University, University of California, Irvine, and the University of Missouri. The authors are honored to be permitted to conduct astronomical research on Iolkam Du'ag (Kitt Peak), a mountain with particular significance to the Tohono O'odham. This research was supported by Heising-Simons Foundation grant # 2019-1177. This work was partially supported by funding from the Center for Exoplanets and Habitable Worlds. The Center for Exoplanets and Habitable Worlds and the Penn State Extraterrestrial Intelligence Center are supported by the Pennsylvania State University and the Eberly College of Science. CIC acknowledges support by NASA Headquarters under the NASA Earth and Space Science Fellowship Program through grant 80NSSC18K1114. Part of this work was performed for the Jet Propulsion Laboratory, California Institute of Technology, sponsored by the United States Government under the Prime Contract 80NM0018D0004 between Caltech and NASA. Computations for this research were performed on the Pennsylvania State Universitys Institute for Computational and Data Sciences Roar supercomputer. Processing of data included here used an allocation of computer time from the Research Computing High Performance Computing cluster at the University of Arizona, which is gratefully acknowledged. We acknowledge BJ Fulton and colleagues at the NASA Exoplanet Science Institute (NExScI) for their efforts in hosting the NEID Solar Data Archive. This research has made use of NASA's Astrophysics Data System Bibliographic Services. This research made use of Astropy (http://www.astropy.org), a community-developed core Python package for Astronomy Astropy Collaboration et al. (2013), Astropy Collaboration et al. (2018). Facility: NEID/WIYN 3.5 m. - Software: astropy (Astropy Collaboration et al. 2018), barycorrpy (Kanodia & Wright 2018), matplotlib (Hunter 2007), numpy (van der Walt et al. 2011), pandas (McKinney 2010), pvlib (Holmgren et al. 2018), scipy (Virtanen et al. 2020).

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