Stellar jitter from variable gravitational redshift: implications for radial velocity confirmation of habitable exoplanets

Heather M. Cegla, Christopher Watson, Tom Marsh, Sergiy Shelyag, Victoria Moulds, Stuart Littlefair, Mihalis Mathioudakis, Don Pollacco, Xavier Bonfils

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Abstract

A variation of gravitational redshift, arising from stellar radius fluctuations, will introduce astrophysical noise into radial velocity measurements by shifting the centroid of the observed spectral lines. Shifting the centroid does not necessarily introduce line asymmetries. This is fundamentally different from other types of stellar jitter so far identified, which do result from line asymmetries. Furthermore, only a very small change in stellar radius, ∼0.01 per cent, is necessary to generate a gravitational redshift variation large enough to mask or mimic an Earth-twin. We explore possible mechanisms for stellar radius fluctuations in low-mass stars. Convective inhibition due to varying magnetic field strengths and the Wilson depression of starspots are both found to induce substantial gravitational redshift variations. Finally, we investigate a possible method for monitoring/correcting this newly identified potential source of jitter and comment on its impact for future exoplanet searches.
Original languageEnglish
Pages (from-to)L54-L58
JournalMonthly Notices of the Royal Astronomical Society: Letters
Volume421
Issue number1
Early online date1 Mar 2012
DOIs
Publication statusE-pub ahead of print - 1 Mar 2012

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