Detecting planets around very cool dwarfs at near infrared wavelengths with the radial velocity technique

Rodler, F.; Burgo, C. del; Witte, S.; Helling, Christiane; Hauschildt, P. H.; Martín, E. L.; Álvarez, Carlos; Deshpande, Rohit

doi:10.1051/0004-6361/201015490

Cited by 20 publications

(31 citation statements)

References 39 publications

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“…Detailed simulations of the photon-limited RV precision in M dwarfs were carried out by Reiners et al (2010); Rodler et al (2011);Bottom et al (2013); Plavchan et al (2015); Figueira et al (2016). With only very few exceptions, these studies relied on synthetic spectra from model atmosphere simulations.…”

Section: Radial Velocity Information Contentmentioning

confidence: 99%

The CARMENES search for exoplanets around M dwarfs

Reiners

Zechmeister

Caballero

et al. 2018

A&A

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The CARMENES radial velocity (RV) survey is observing 324 M dwarfs to search for any orbiting planets. In this paper, we present the survey sample by publishing one CARMENES spectrum for each M dwarf. These spectra cover the wavelength range 520-1710 nm at a resolution of at least R > 80, 000, and we measure its RV, Hα emission, and projected rotation velocity. We present an atlas of high-resolution M-dwarf spectra and compare the spectra to atmospheric models. To quantify the RV precision that can be achieved in low-mass stars over the CARMENES wavelength range, we analyze our empirical information on the RV precision from more than 6500 observations. We compare our high-resolution M-dwarf spectra to atmospheric models where we determine the spectroscopic RV information content, Q, and signal-to-noise ratio. We find that for all M-type dwarfs, the highest RV precision can be reached in the wavelength range 700-900 nm. Observations at longer wavelengths are equally precise only at the very latest spectral types (M8 and M9). We demonstrate that in this spectroscopic range, the large amount of absorption features compensates for the intrinsic faintness of an M7 star. To reach an RV precision of 1 m s −1 in very low mass M dwarfs at longer wavelengths likely requires the use of a 10 m class telescope. For spectral types M6 and earlier, the combination of a red visual and a near-infrared spectrograph is ideal to search for low-mass planets and to distinguish between planets and stellar variability. At a 4 m class telescope, an instrument like CARMENES has the potential to push the RV precision well below the typical jitter level of 3-4 m s −1 .

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Section: Radial Velocity Information Contentmentioning

confidence: 99%

The CARMENES search for exoplanets around M dwarfs

Reiners

Zechmeister

Caballero

et al. 2018

A&A

Self Cite

201

111

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“…Several studies showed that the RV jitter will be divided by at least a factor of 2 due to the lower contrast between the dark spot regions and the quiet photosphere (Marchwinski et al (2015) & Reiners et al (2010; Rodler et al (2011), respectively for Sun-like stars & late M dwarfs). In this context, the new generation of high resolution/precision velocimeters working in the nIR domain (e.g., CARMENES 7 , SPIRou 8 , CRIRES+ 9 ) present a tremendous interest.…”

Section: Photosphere Occupancymentioning

confidence: 99%

Modelling the RV jitter of early-M dwarfs using tomographic imaging

Hébrard

Donati

Delfosse

et al. 2016

Mon. Not. R. Astron. Soc.

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In this paper we show how tomographic imaging (Zeeman Doppler Imaging, ZDI) can be used to characterize stellar activity and magnetic field topologies, ultimately allowing to filter out the radial velocity (RV) activity jitter of M-dwarf moderate rotators. This work is based on spectropolarimetric observations of a sample of five weakly-active early M-dwarfs (GJ 205, GJ 358, GJ 410, GJ479, GJ 846) with HARPS-Pol and NARVAL. These stars have v sin i and RV jitters in the range 1-2 km s −1 and 2.7-10.0 m s −1 rms respectively.Using a modified version of ZDI applied to sets of phase-resolved Least-Squares-Deconvolved (LSD) profiles of unpolarized spectral lines, we are able to characterize the distribution of active regions at the stellar surfaces. We find that darks spots cover less than 2% of the total surface of the stars of our sample. Our technique is efficient at modeling the rotationally modulated component of the activity jitter, and succeeds at decreasing the amplitude of this component by typical factors of 2-3 and up to 6 in optimal cases. From the rotationally modulated time-series of circularly polarized spectra and with ZDI, we also reconstruct the large-scale magnetic field topology. These fields suggest that bi-stability of dynamo processes observed in active M dwarfs may also be at work for moderately active M dwarfs. Comparing spot distributions with field topologies suggest that dark spots causing activity jitter concentrate at the magnetic pole and/or equator, to be confirmed with future data on a larger sample.

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“…As result, they found that the highest RV precision for M-dwarfs is attained in the Y-band around 1 μm and not in the J-, H-or K-band. For L-dwarfs, however, Rodler et al (2011) reported that the highest RV precision is attained in the J-band.…”

Section: Resultsmentioning

confidence: 99%

“…We note that and Rodler et al (2011) carried out theoretical RV precision studies of M-and L-dwarfs by adopting theoretical models of M-dwarfs (e.g. del ).…”

Section: Resultsmentioning

confidence: 99%

Search for radial velocity variations in eight M-dwarfs with NIRSPEC/Keck II

Rodler

Deshpande

Osorio

et al. 2012

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Context. Radial velocity (RV) measurements from near-infrared spectra have become a potentially powerful tool to search for planets around cool stars and sub-stellar objects. As part of a large survey to characterize M-dwarfs using NIRSPEC at Keck II, we obtained spectra of eight late M-dwarfs (spectral types M5.0-M8.0) during two or more observing epochs per target. These spectra were taken with intermediate spectral resolving powers (R ∼ 20 000) in the J-band. Aims. We search for relative RV variability in these late M-dwarfs and test the NIRSPEC capability of detecting short-period brown dwarf and massive planetary companions around low-mass stars in the J-band (≈1.25 μm). Additionally, we reanalyzed the data of the M8-type star vB10 (one of our targets), which had been presented in another article. Methods. To achieve a precise RV measurement stability, the NIRSPEC spectra were self-calibrated by making use of the telluric absorption lines, which are present in the observed spectra and were used as a long-term stable reference. In the modeling process a multi-parameter χ 2 -optimization was employed to generate an accurate description of the observation. The telluric lines allowed us to model the instrumental profile of the spectrograph and the determination of the Doppler shift of the stellar absorption lines. Results. For the entire M-dwarf sample, we found no evidence of relative RV variations induced by a short-period brown dwarf or massive planetary companion. The typical RV precision of the measurements is between 180 and 300 m s −1 , which is sufficient to detect hot Neptunes around M-dwarfs. Moreover, we found that the spurious RV shift detected previously of the star VB10 was caused by asymmetries in the instrumental profile between different observing epochs, which were not taken into account in the previous analysis.

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Detecting planets around very cool dwarfs at near infrared wavelengths with the radial velocity technique

Cited by 20 publications

References 39 publications

The CARMENES search for exoplanets around M dwarfs

The CARMENES search for exoplanets around M dwarfs

Modelling the RV jitter of early-M dwarfs using tomographic imaging

Search for radial velocity variations in eight M-dwarfs with NIRSPEC/Keck II

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