Frequency-comb-calibrated Laser Heterodyne Radiometry for Precision Radial Velocity Measurements

Area of Science:

• Solar Physics
• Stellar Activity
• Spectroscopy

Background:

• Disk-integrated solar observations offer unique insights into stellar activity.
• Radial velocity measurements are key to understanding stellar behavior and exoplanet detection.
• Existing methods face challenges in precision and accuracy.

Purpose of the Study:

• To introduce and evaluate a novel approach for disk-integrated solar spectroscopy.
• To assess the capabilities of this new method for precise solar radial velocity measurements.
• To quantify uncertainty sources impacting radial velocity measurements.

Main Methods:

• Utilized a near-infrared laser heterodyne radiometer (LHR) coupled with optical frequency comb calibration.
• Recorded solar spectra of the Fe I 1565 nm transition over a six-week period.
• Employed daily measurements of the absolute line center for stability assessment.

Main Results:

• Achieved high spectral resolution (∼800,000) and signal-to-noise ratio (∼2600).
• Demonstrated sub-meter-per-second radial velocity precision within a single day.
• Quantified principal uncertainty sources affecting radial velocity measurements.

Conclusions:

• The comb-calibrated LHR approach enables precision disk-integrated solar spectroscopy.
• This method offers high absolute frequency accuracy and long-term stability.
• Future modifications can further enhance its utility for stellar variability studies.