Planetary detection limits taking into account stellar noise - I. Observational strategies to reduce stellar oscillation and granulation effects

By Xavier Dumusque, S. Udry, C. Lovis, Nuno C. Santos, M. Monteiro. 2010

223 citations recorded by the source corpus.

Context. Stellar noise produced by oscillations, granulation phenomena (granulation, mesogranulation, and supergranulation), and activity affects radial velocity measurements. The signature of the corresponding effect in radial velocity is small, around the meterper-second, but already too large for the detection of Earth-mass planets in habitable zones. Aims. We address the important role played by observational strategies in averaging out the radial velocity signature of stellar noise. We also derive the planetary mass detection limits expected in the presence of stellar noise. Methods. We start with HARPS asteroseismology measurements for four stars (β Hyi, α Cen A, μ Ara, and τ Ceti) available in the ESO archive and very precise measurements of α Cen B. This sample covers different spectral types from G2 to K1 and different evolutionary stages, from subgiant to dwarf stars. Since data span between 5 and 8 days, only stellar noise sources with timescales shorter than this time span will be extracted from these observations. Therefore, we are able to study oscillation modes and granulation phenomena without being significantly affected by activity noise present on longer timescales. For those five stars, we generate synthetic radial velocity measurements after fitting the corresponding models of stellar noise in Fourier space. These measurements allow us to study the radial velocity variation due to stellar noise for different observational strategies as well as the corresponding planetary mass detection limits. Results. Applying three measurements per night of 10 min exposure each, 2 h apart, seems to most efficiently average out the stellar noise considered. For quiet K1V stars such as α Cen B, this strategy allows us to detect planets of about three times the mass of Earth with an orbital period of 200 days, corresponding to the habitable zone of the star. Moreover, our simulations suggest that planets smaller than typically 5 M⊕ can be detected with HARPS over a wide range of separations around most non-active solar-type dwarfs. Since activity is not yet included in our simulation, these detection limits correspond to a case, which exists, where the host star has few magnetic features and stellar noise is dominated by oscillation modes and granulation phenomena. For our star sample, a trend between spectral type and surface gravity and the level of radial velocity variation is also identified by our simulations.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/a1e30c473714ef518cfc8975c7bdc6b72612a4db

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Citations in the corpus

THE KEPLER-10 PLANETARY SYSTEM REVISITED BY HARPS-N: A HOT ROCKY WORLD AND A SOLID NEPTUNE-MASS PLANET (2014, background): “With this low activity level, we do not expect the RVs to be significantly affected (Dumusque et al. 2011a).”
SOAP 2.0: A TOOL TO ESTIMATE THE PHOTOMETRIC AND RADIAL VELOCITY VARIATIONS INDUCED BY STELLAR SPOTS AND PLAGES (2014, background): “…are affected by solartype oscillations (Arentoft et al. 2008; Kjeldsen et al. 2005; Bouchy et al. 2005; Mayor et al. 2003), granulation phenomena (Dumusque et al. 2011b; Lindegren & Dravins 2003; Dravins 1982), and activity signals (Robertson et al. 2014; Jeffers et al. 2013; Meunier & Lagrange…”
The planet search programme at the ESO CES and HARPS - IV. The search for Jupiter analogues around solar-like stars (2012, background): “While the Sun has an oscillation timescale of∼5 min, its granulation14 has lifetime.25 min (see Dumusque et al. 2011b for adequate observing strategies).”
The Solar Twin Planet Search. I. Fundamental parameters of the stellar sample (2014, methodology): “The motivation for using 15 minute minimum total exposure times for a visit is to average the five-minutep-mode oscillations of Sun-like stars to below 1 m s−1 (e.g., Mayor et al. 2003; Lovis et al. 2006; Dumusque et al. 2011).”
Long-term magnetic activity of a sample of M-dwarf stars from the HARPS program I. Comparison of activity indices (2011, background): “…the signals induced by intrinsic sources (e.g. oscillations, rotating spots and plages, inhibition of convection) become more significant (e.g. Saar & Donahue 1997; Santos et al. 2000; Paulson et al. 2002; Bouchy et al. 2004; Meunier et al. 2010; Dumusque et al. 2011a,b; Boisse et al. 2011).”
The HARPS search for Earth-like planets in the habitable zone - I. Very low-mass planets around HD 20794, HD 85512, and HD 192310 (2011, background): “Dumusque et al. (2011b) show that longer-period granulation noise and RV-jitter caused by spots and activity are best averaged out by evenly sampling over the observational A58, page 3 of 16 season.”
State of the Field: Extreme Precision Radial Velocities (2016, background): “The typical magnitude of stellar jitter is 1 – 3 m s−1 for chromospherically quiet stars (Dumusque et al. 2011).”
Limits on Planetary Companions from Doppler Surveys of Nearby Stars (2016, background): “These effects can be mitigated by observational strategies that average over the relevant timescales with multiple RV measurements taken per night (Dumusque et al. 2011a, 2011b).”
A Gaussian process framework for modelling stellar activity signals in radial velocity data (2015, background): “While observational strategies can be devised to mitigate nui-sance RV signals associated with stellar oscillation and granulation (Dumusque et al. 2011), activity-induced signals pose a bigger challenge.”