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

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.

[1]  L. Ramsey,et al.  Stellar Activity Manifesting at a One-year Alias Explains Barnard b as a False Positive , 2021, The Astronomical Journal.

[2]  A. Szentgyorgyi,et al.  Separating planetary reflex Doppler shifts from stellar variability in the wavelength domain , 2020, Monthly Notices of the Royal Astronomical Society.

[3]  S. Udry,et al.  Three years of HARPS-N high-resolution spectroscopy and precise radial velocity data for the Sun , 2020, Astronomy & Astrophysics.

[4]  X. Dumusque,et al.  The spectral impact of magnetic activity on disc-integrated HARPS-N solar observations: exploring new activity indicators , 2020, 2004.09830.

[5]  L. Buchhave,et al.  A robust, template-free approach to precise radial velocity extraction , 2019, Monthly Notices of the Royal Astronomical Society.

[6]  X. Dumusque,et al.  Measuring precise radial velocities on individual spectral lines , 2019, Astronomy & Astrophysics.

[7]  X. Dumusque,et al.  Testing the Spectroscopic Extraction of Suppression of Convective Blueshift , 2019, The Astrophysical Journal.

[8]  R. Haywood,et al.  Sensitivity of low-degree solar p modes to active and ephemeral regions: frequency shifts back to the Maunder minimum , 2019, Monthly Notices of the Royal Astronomical Society: Letters.

[9]  Johannes L. Schönberger,et al.  SciPy 1.0: fundamental algorithms for scientific computing in Python , 2019, Nature Methods.

[10]  F. Pepe,et al.  Temporal evolution and correlations of optical activity indicators measured in Sun-as-a-star observations , 2019, Astronomy & Astrophysics.

[11]  D Sasselov,et al.  Three years of Sun-as-a-star radial-velocity observations on the approach to solar minimum , 2019, Monthly Notices of the Royal Astronomical Society.

[12]  A. Lagrange,et al.  Unexpectedly strong effect of supergranulation on the detectability of Earth twins orbiting Sun-like stars with radial velocities , 2019, Astronomy & Astrophysics.

[13]  F. Bouchy,et al.  HARPS-N Solar RVs Are Dominated by Large, Bright Magnetic Regions , 2019, The Astrophysical Journal.

[14]  Clifford W. Hansen,et al.  Pvlib Python: a Python Package for Modeling Solar Energy Systems , 2018, J. Open Source Softw..

[15]  Xavier Dumusque,et al.  Measuring precise radial velocities on individual spectral lines , 2018, Astronomy & Astrophysics.

[16]  Samuel P. Halverson,et al.  Overview of the spectrometer optical fiber feed for the habitable-zone planet finder , 2018, Astronomical Telescopes + Instrumentation.

[17]  Christopher J. Evans,et al.  Ground-based and Airborne Instrumentation for Astronomy VII , 2018 .

[18]  Jason Wright,et al.  The NEID precision radial velocity spectrometer: port adapter overview, requirements, and test plan , 2018, Astronomical Telescopes + Instrumentation.

[19]  Jason Wright,et al.  The NEID precision radial velocity spectrometer: optical design of the port adapter and ADC , 2018, Astronomical Telescopes + Instrumentation.

[20]  A. Tozzi,et al.  LOCNES: low cost NIR extended solar telescope , 2018, Astronomical Telescopes + Instrumentation.

[21]  Adrian M. Price-Whelan,et al.  Binary Companions of Evolved Stars in APOGEE DR14: Search Method and Catalog of ∼5000 Companions , 2018, The Astronomical Journal.

[22]  Jason Wright,et al.  Python Leap Second Management and Implementation of Precise Barycentric Correction (barycorrpy) , 2018, 1801.01634.

[23]  A. Lagrange,et al.  A new method of correcting radial velocity time series for inhomogeneous convection , 2017, 1708.03458.

[24]  Christian Schwab,et al.  A VERSATILE TECHNIQUE TO ENABLE SUB-MILLI-KELVIN INSTRUMENT STABILITY FOR PRECISE RADIAL VELOCITY MEASUREMENTS: TESTS WITH THE HABITABLE-ZONE PLANET FINDER , 2016, 1610.06216.

[25]  Basil Blank,et al.  A system to provide sub-milliKelvin temperature control at T~300K for extreme precision optical radial velocimetry , 2016, Astronomical Telescopes + Instrumentation.

[26]  Claire Poppett,et al.  KPF: Keck Planet Finder , 2016, Astronomical Telescopes + Instrumentation.

[27]  Jonay I. González Hernández,et al.  HARPS3 for a roboticized Isaac Newton Telescope , 2016, Astronomical Telescopes + Instrumentation.

[28]  C. Schwab,et al.  Design of NEID, an extreme precision Doppler spectrograph for WIYN , 2016, Astronomical Telescopes + Instrumentation.

[29]  Jeffrey D. Crane,et al.  The GMT-Consortium Large Earth Finder (G-CLEF): an optical Echelle spectrograph for the Giant Magellan Telescope (GMT) , 2016, Astronomical Telescopes + Instrumentation.

[30]  Nicolas Buchschacher,et al.  An astro-comb calibrated solar telescope to search for the radial velocity signature of Venus , 2016, Astronomical Telescopes + Instrumentation.

[31]  Jason Wright,et al.  A comprehensive radial velocity error budget for next generation Doppler spectrometers , 2016, Astronomical Telescopes + Instrumentation.

[32]  Andreas Seifahrt,et al.  Development and construction of MAROON-X , 2016, Astronomical Telescopes + Instrumentation.

[33]  C. Jurgenson,et al.  EXPRES: a next generation RV spectrograph in the search for earth-like worlds , 2016, Astronomical Telescopes + Instrumentation.

[34]  Tilo Steinmetz,et al.  State of the Field: Extreme Precision Radial Velocities , 2016, 1602.07939.

[35]  A. Collier Cameron,et al.  The Sun as a planet-host star: proxies from SDO images for HARPS radial-velocity variations , 2016, 1601.05651.

[36]  Steven Reece,et al.  A Gaussian process framework for modelling stellar activity signals in radial velocity data , 2015, 1506.07304.

[37]  J. Eastman,et al.  Barycentric Corrections at 1 cm s-1 for Precise Doppler Velocities , 2014, 1409.4774.

[38]  Arpita Roy,et al.  Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581 , 2014, Science.

[39]  Prasanth H. Nair,et al.  Astropy: A community Python package for astronomy , 2013, 1307.6212.

[40]  A. Collier Cameron,et al.  Planets and Stellar Activity: Hide and Seek in the CoRoT-7 system , 2013, Proceedings of the International Astronomical Union.

[41]  Christophe Lovis,et al.  Planetary detection limits taking into account stellar noise - I. Observational strategies to reduce stellar oscillation and granulation effects , 2010, 1010.2616.

[42]  G. R. Davies,et al.  Observations , 2009, Castlemaine Naturalist.

[43]  C. Moutou,et al.  The HARPS search for southern extra-solar planets XVII. Six long-period giant planets around BD -1 , 2008, 0810.4662.

[44]  Ian S. McLean,et al.  Ground-based and Airborne Instrumentation for Astronomy II , 2008 .

[45]  I. McLean,et al.  Ground-based and Airborne Instrumentation for Astronomy , 2006 .

[46]  M. Mayor,et al.  A Jupiter-mass companion to a solar-type star , 1995, Nature.

[47]  A. Wolszczan,et al.  Confirmation of Earth-Mass Planets Orbiting the Millisecond Pulsar PSR B1257 + 12 , 1994, Science.

[48]  D. Frail,et al.  A planetary system around the millisecond pulsar PSR1257 + 12 , 1992, Nature.

[49]  R. Bird,et al.  Simplified clear sky model for direct and diffuse insolation on horizontal surfaces , 1981 .

[50]  M. Langlois,et al.  Society of Photo-Optical Instrumentation Engineers , 2005 .