An astro-comb calibrated solar telescope to search for the radial velocity signature of Venus

Phillips, David F.; Glenday, Alex; Dumusque, X.; Buchschacher, N.; Cameron, A. Collier; Cecconi, M.; Charbonneau, David; Cosentino, R.; Ghedina, A.; Haywood, R. D.; Latham, David W.; Li, Chih‐Hao; Lodi, M.; Molinari, E.; Pepe, F.; Sasselov, Dimitar; Szentgyorgyi, Andrew; Udry, S.; Walsworth, Ronald L.

doi:10.1117/12.2232452

Cited by 32 publications

(22 citation statements)

References 27 publications

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“…The HARPS-N spectrograph at the TNG is a crossdispersed echelle spectrograph spanning the visible range (Cosentino et al 2012). During the day, a custom-built solar telescope connected to HARPS-N provides a nearcontinuous stream of disk-integrated solar spectra (Dumusque et al 2015, Phillips et al 2016). This instrument, in operation since 2015, works in combination with the HARPS-N spectrograph to observe the Sun as a star, giving unprecedented temporal coverage (about one exposure every five minutes, with a typical daily coverage of 6 hours) of the solar spectrum with resolving power R = 115000 and optical bandwidth spanning 383 nm -690 nm.…”

Section: Solar Telescope At Harps-nmentioning

confidence: 99%

“…Numerous ground and space-based instruments, such as Global Oscillations Network Group (GONG, Harvey et al 1988), the SOlar Radiation and Climate Experiment (SORCE, Rottman 2005), and the Solar Dynamics Observatory (SDO, Pesnell et al 2012), perform detailed observations of the Sun's surface. In parallel with these instruments, a custom-built solar telescope installed at the Telescopio Nazionale Galileo (TNG) on La Palma makes disk-integrated, spectroscopic measurements of the Sun as a star using the state-of-the-art High Radial velocity Planet Searcher for the Northern Hemisphere (HARPS-N) spectrograph (Dumusque et al 2015, Phillips et al 2016). This al-lows us to observe the Sun as we would any other star in high-precision RV exoplanet surveys.…”

Section: Introductionmentioning

confidence: 99%

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HARPS-N Solar RVs Are Dominated by Large, Bright Magnetic Regions

Milbourne

Haywood

Phillips

et al. 2019

ApJ

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State of the art radial-velocity (RV) exoplanet searches are currently limited by RV signals arising from stellar magnetic activity. We analyze solar observations acquired over a 3-year period during the decline of Carrington Cycle 24 to test models of RV variation of Sun-like stars. A purpose-built solar telescope at the High Accuracy Radial velocity Planet Searcher for the Northern hemisphere (HARPS-N) provides disk-integrated solar spectra, from which we extract RVs and log R HK . The Solar Dynamics Observatory (SDO) provides disk-resolved images of magnetic activity. The Solar Radiation and Climate Experiment (SORCE) provides near-continuous solar photometry, analogous to a Kepler light curve. We verify that the SORCE photometry and HARPS-N log R HK correlate strongly with the SDO-derived magnetic filling factor, while the HARPS-N RV variations do not. To explain this discrepancy, we test existing models of RV variations. We estimate the contributions of the suppression of convective blueshift and the rotational imbalance due to brightness inhomogeneities to the observed HARPS-N RVs. We investigate the time variation of these contributions over several rotation periods, and how these contributions depend on the area of active regions. We find that magnetic active regions smaller than 60 Mm 2 do not significantly suppress convective blueshift. Our area-dependent model reduces the amplitude of activity-induced RV variations by a factor of two. The present study highlights the need to identify a proxy that correlates specifically with large, bright magnetic regions on the surfaces of exoplanet-hosting stars.

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Section: Solar Telescope At Harps-nmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

HARPS-N Solar RVs Are Dominated by Large, Bright Magnetic Regions

Milbourne

Haywood

Phillips

et al. 2019

ApJ

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“…Using the solar telescope (Phillips et al 2016) operating with the HARPS-N spectrograph at the Telescopio Nazionale Galileo (TNG, Cosentino et al 2012), we extract high-resolution disk-integrated solar spectra (Dumusque et al 2015). We now have more than 50,000 high-SNR solar exposures spanning over 4 years of observing (Collier Cameron et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Testing the Spectroscopic Extraction of Suppression of Convective Blueshift

Miklos

Milbourne

Haywood

et al. 2020

ApJ

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Efforts to detect low-mass exoplanets using stellar radial velocities (RVs) are currently limited by magnetic photospheric activity. Suppression of convective blueshift is the dominant magnetic contribution to RV variability in low-activity Sun-like stars. Due to convective plasma motions, the magnitude of RV contributions from the suppression of convective blueshift is related to the depth of formation of photospheric spectral lines of a given species used to compute the RV time series. Meunier et al. (2017a,b), used this relation to demonstrate a method for spectroscopic extraction of the suppression of convective blueshift in order to isolate RV contributions, including planetary RVs, that contribute equally to the timeseries for each spectral line. Here, we extract disk-integrated solar RVs from observations over a 2.5 year time span made with the solar telescope integrated with the HARPS-N spectrograph at the Telescopio Nazionale Galileo (La Palma, Canary Islands, Spain). We apply the methods outlined by Meunier et al. (2017a,b). We are not, however, able to isolate physically meaningful contributions of the suppression of convective blueshift from this solar dataset, potentially because our dataset is from solar minimum when the suppression of convective blueshift may not sufficiently dominate activity contributions to RVs. This result indicates that, for low-activity Sun-like stars, one must include additional RV contributions from activity sources not considered in the Meunier et al. 2017 model at different timescales as well as instrumental variation in order to reach the sub-meter per second RV sensitivity necessary to detect low-mass planets in orbit around Sun-like stars.

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“…The thorium oxide lamps that are available have impurities that severely compromise their utility for PRV calibration. The PRV community is currently experimenting with several alternative calibrators, especially laser frequency combs (LFCs) 25,26 , passively stabilized etalons 27 and actively stabilized etalons 28 . The design of the calibration system was based on the assumption that the optical system would inject an image of a hollow cathode lamp or diffused incandescent bulb into the input fibers of the GCCFIB.…”

Section: Calibration Lamp System (Gccls) Optical Designmentioning

confidence: 99%

“…We also did an in-depth ghost analysis, focusing in particular on "Littrow ghosts" produced by the volume phase holographic (VPH) grating 25 . These investigations prompted us to change the blue camera VPH from a pure VPH grating to a VPH grism.…”

Section: Spectrograph Optical Designmentioning

confidence: 99%

The GMT-Consortium Large Earth Finder (G-CLEF): an optical Echelle spectrograph for the Giant Magellan Telescope (GMT)

et al. 2016

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The GMT-Consortium Large Earth Finder (G-CLEF) will be a cross-dispersed, optical band echelle spectrograph to be delivered as the first light scientific instrument for the Giant Magellan Telescope (GMT) in 2022. G-CLEF is vacuumenclosed and fiber-fed to enable precision radial velocity (PRV) measurements, especially for the detection and characterization of low-mass exoplanets orbiting solar-type stars. The passband of G-CLEF is broad, extending from 3500Å to 9500Å. This passband provides good sensitivity at blue wavelengths for stellar abundance studies and deep red response for observations of high-redshift phenomena. The design of G-CLEF incorporates several novel technical innovations. We give an overview of the innovative features of the current design. G-CLEF will be the first PRV spectrograph to have a composite optical bench so as to exploit that material's extremely low coefficient of thermal expansion, high in-plane thermal conductivity and high stiffness-to-mass ratio. The spectrograph camera subsystem is divided into a red and a blue channel, split by a dichroic, so there are two independent refractive spectrograph cameras. The control system software is being developed in model-driven software context that has been adopted globally by the GMT. G-CLEF has been conceived and designed within a strict systems engineering framework. As a part of this process, we have developed a analytical toolset to assess the predicted performance of G-CLEF as it has evolved through design phases.

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An astro-comb calibrated solar telescope to search for the radial velocity signature of Venus

Cited by 32 publications

References 27 publications

HARPS-N Solar RVs Are Dominated by Large, Bright Magnetic Regions

HARPS-N Solar RVs Are Dominated by Large, Bright Magnetic Regions

Testing the Spectroscopic Extraction of Suppression of Convective Blueshift

The GMT-Consortium Large Earth Finder (G-CLEF): an optical Echelle spectrograph for the Giant Magellan Telescope (GMT)

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