DETECTING PLANETS AROUND VERY LOW MASS STARS WITH THE RADIAL VELOCITY METHOD

By A. Reiners, J. Bean, K. Huber, S. Dreizler, A. Seifahrt, S. Czesla. 2009

148 citations recorded by the source corpus.

The detection of planets around very low-mass stars with the radial velocity (RV) method is hampered by the fact that these stars are very faint at optical wavelengths where the most high-precision spectrometers operate. We investigate the precision that can be achieved in RV measurements of low mass stars in the near-infrared (NIR) Y-, J-, and H-bands, and we compare it to the precision achievable in the optical assuming comparable telescope and instrument efficiencies. For early-M stars, RV measurements in the NIR offer no or only marginal advantage in comparison with optical measurements. Although they emit more flux in the NIR, the richness of spectral features in the optical outweighs the flux difference. We find that NIR measurement can be as precise as optical measurements in stars of spectral type ∼M4, and from there the NIR gains in precision toward cooler objects. We studied potential calibration strategies in the NIR finding that a stable spectrograph with a ThAr calibration can offer enough wavelength stability for m s−1 precision. Furthermore, we simulate the wavelength-dependent influence of activity (cool spots) on RV measurements from optical to NIR wavelengths. Our spot simulations reveal that the RV jitter does not decrease as dramatically toward longer wavelengths as often thought. The jitter strongly depends on the details of the spots, i.e., on spot temperature and the spectral appearance of the spot. At low temperature contrast (∼200 K), the jitter shows a decrease toward the NIR up to a factor of 10, but it decreases substantially less for larger temperature contrasts. Forthcoming NIR spectrographs will allow the search for planets with a particular advantage in mid- and late-M stars. Activity will remain an issue, but simultaneous observations at optical and NIR wavelengths can provide strong constraints on spot properties in active stars.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/aaf472d370bbbbb18c765b4202d2bb28a94bff23

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Citations in the corpus

THE NIRSPEC ULTRACOOL DWARF RADIAL VELOCITY SURVEY (2010, background): “Both Mahadevan & Ge (2009) and Reiners et al. (2010) provide a summary of future prospects for calibrating NIR echelle spectra using gas absorption cells and emission line lamps.”
Spectrum radial velocity analyser (SERVAL). High-precision radial velocities and two alternative spectral indicators (2017, background): “…wavelengths: first, the contrast grows too high in that active regions no longer contribute to the observed spectrum in a significant way; and second that the intensity of spectral features at short wavelengths also differs dramatically between active and quiet regions (Reiners et al. 2010).”
CARMENES input catalogue of M dwarfs. I. Low-resolution spectroscopy with CAFOS (2015, background): “The heterogeneities on the stellar surface of the almost-fully convective, rotating, M dwarfs, such as dark spots, may induce spurious radial-velocity variations at visible wavelengths (Bonfils et al. 2007; Reiners et al. 2010; Barnes et al. 2011; Andersen& Korhonen 2015; Robertson et al. 2015).”
CARMENES instrument overview (2014, background): “A set of simulations has been carried out to determine the best wavelength range for RV observations of M dwarfs (Reiners et al. 2010).”
THE HARPS-TERRA PROJECT. I. DESCRIPTION OF THE ALGORITHMS, PERFORMANCE, AND NEW MEASUREMENTS ON A FEW REMARKABLE STARS OBSERVED BY HARPS (2012, background): “Also, the wavelength dependence of the RMS illustrates the importance of moving to redder wavelengths to efficiently searh for low mass companions around cool stars (Reiners et al. 2010).”
The CARMENES Search for Exoplanets around M Dwarfs: A Low-mass Planet in the Temperate Zone of the Nearby K2-18 (2018, background): “This enables the comparison between the blue part and the red part of the spectrum, where, unlike a wavelengthindependent Keplerian signal, RV signals due to activity are wavelength dependent (Reiners et al. 2010).”
The habitable-zone planet finder: a stabilized fiber-fed NIR spectrograph for the Hobby-Eberly Telescope (2012, background): “Here the NIR (and choice of slow rotators) helps, since the RV signal induced by star spots is less than in the optical.(21) The high resolution of the HPF also enables line-bisectors to be used to disentangle activity from planets.”