[Paper Review] Precise radial velocities of Proxima Centauri

M. Kürster, A. P. Hatzes+4 more|arXiv (Cornell University)|Mar 2, 1999

Stellar, planetary, and galactic studies3 citations

TL;DR

This study presents precise radial velocity measurements of Proxima Centauri over four years using the ESO CES spectrograph, achieving a mean precision of 54 m s⁻¹. No periodic signal indicative of a sub-stellar companion was detected, and upper limits on companion mass range from 1.1 to 22 M_{Jup} at orbital periods between 0.75 and 3000 days, excluding brown dwarfs or massive planets within 0.69 AU.

ABSTRACT

We present differential radial velocity measurements of Proxima Centauri collected over 4 years with the ESO CES with a mean precision of $54 ms^{-1}$. We find no evidence of a periodic signal that could corroborate the existence of a sub-stellar companion. We put upper limits (97% confidence) to the companion mass ranging from 1.1 to 22 M_{Jup} at orbital periods of 0.75 to 3000 d, i.e. separations 0.008-2 AU from Prox Cen. Our mass limits concur with limits found by precise astrometry (Benedict et al. 1998a and priv. comm.) which strongly constrain the period range 50-600 d to 1.1-0.22 M_{Jup}. Combining both results we exclude a brown dwarf or supermassive planet at separations 0.008-0.69 AU from Prox Cen. We also find that, at the level of our precision, the RV data are not affected by stellar activity.

Motivation & Objective

• To search for periodic radial velocity variations in Proxima Centauri that could indicate the presence of a sub-stellar companion.
• To determine the upper mass limits for potential planetary or brown dwarf companions based on radial velocity data.
• To assess whether stellar activity could mimic or affect radial velocity signals at the current precision level.
• To combine radial velocity results with prior astrometric constraints to further restrict the parameter space for companions.
• To test the reliability of radial velocity measurements at 54 m s⁻¹ precision for detecting low-mass companions around nearby M-dwarfs.

Proposed method

• Acquired differential radial velocity measurements of Proxima Centauri using the ESO CES spectrograph over a 4-year baseline.
• Employed high-precision radial velocity techniques with a mean precision of 54 m s⁻¹ to detect small Doppler shifts.
• Analyzed the data for periodic signals using standard radial velocity analysis methods to identify potential planetary companions.
• Calculated 97% confidence upper limits on companion mass as a function of orbital period, ranging from 0.75 to 3000 days.
• Compared results with prior astrometric constraints from Benedict et al. (1998a) to jointly constrain the orbital parameter space.
• Assessed the impact of stellar activity on radial velocity measurements by examining the data for non-periodic or variable trends.

Experimental results

Research questions

• RQ1 Is there a periodic radial velocity signal in Proxima Centauri consistent with a sub-stellar companion?
• RQ2 What are the upper mass limits for a companion to Proxima Centauri at various orbital periods, given the radial velocity precision?
• RQ3 To what extent is the radial velocity data affected by stellar activity at the 54 m s⁻¹ precision level?
• RQ4 How do radial velocity constraints compare with prior astrometric limits from Benedict et al. (1998a)?
• RQ5 Can the combination of radial velocity and astrometric data exclude the presence of brown dwarfs or massive planets in the inner system?

Key findings

• No periodic radial velocity signal was detected in the 4-year data set, providing no evidence for a sub-stellar companion.
• Upper mass limits for companions range from 1.1 M_{Jup} at 0.75 days to 22 M_{Jup} at 3000 days, with 97% confidence.
• The radial velocity data show no significant correlation with stellar activity indicators, indicating that activity does not affect measurements at the 54 m s⁻¹ level.
• Combined with astrometric constraints, the results exclude a brown dwarf or supermassive planet within 0.69 AU of Proxima Centauri.
• The joint constraints from radial velocity and astrometry strongly limit the orbital parameter space, particularly for periods between 50 and 600 days.
• The upper mass limit for companions in the 50–600 day range is constrained to 1.1–0.22 M_{Jup}, consistent with astrometric limits.