Spectrum radial velocity analyser (SERVAL)

Context. The CARMENES survey is a high-precision radial velocity (RV) programme that aims to detect Earth-like planets orbiting low-mass stars. Aims. We develop least-squares fitting algorithms to derive the RVs and additional spectral diagnostics implemented in the SpEctrum Radial Velocity AnaLyser (SERVAL), a publicly available python code. Methods. We measured the RVs using high signal-to-noise templates created by coadding all available spectra of each star. We define the chromatic index as the RV gradient as a function of wavelength with the RVs measured in the echelle orders. Additionally, we computed the differential line width by correlating the fit residuals with the second derivative of the template to track variations in the stellar line width. Results. Using HARPS data, our SERVAL code achieves a RV precision at the level of 1 m/s. Applying the chromatic index to CARMENES data of the active star YZ CMi, we identify apparent RV variations induced by stellar activity. The differential line width is found to be an alternative indicator to the commonly used full width half maximum. Conclusions. We find that at the red optical wavelengths (700–900 nm) obtained by the visual channel of CARMENES, the chromatic index is an excellent tool to investigate stellar active regions and to identify and perhaps even correct for activity-induced RV variations.

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Lyα Observations of High Radial Velocity Low-mass Stars Ross 1044 and Ross 825

The Astrophysical Journal ◽

10.3847/1538-4357/ab48de ◽

2019 ◽

Vol 886 (1) ◽

pp. 19 ◽

Cited By ~ 1

Author(s):

Adam C. Schneider ◽

Evgenya L. Shkolnik ◽

Travis S. Barman ◽

R. Parke Loyd

Keyword(s):

Radial Velocity ◽

Low Mass Stars ◽

Low Mass

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The CARMENES search for exoplanets around M dwarfs

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833423 ◽

2018 ◽

Vol 620 ◽

pp. A171 ◽

Cited By ~ 15

Author(s):

R. Luque ◽

G. Nowak ◽

E. Pallé ◽

D. Kossakowski ◽

T. Trifonov ◽

...

Keyword(s):

Bimodal Distribution ◽

Photometric Data ◽

M Dwarfs ◽

Visual Channel ◽

Low Mass Stars ◽

Short Period ◽

Low Mass ◽

Periodic Signals ◽

M Stars ◽

Host Stars

We announce the discovery of two planetary companions orbiting around the low-mass stars Ross 1020 (GJ 3779, M4.0V) and LP 819-052 (GJ 1265, M4.5V). The discovery is based on the analysis of CARMENES radial velocity (RV) observations in the visual channel as part of its survey for exoplanets around M dwarfs. In the case of GJ 1265, CARMENES observations were complemented with publicly available Doppler measurements from HARPS. The datasets reveal two planetary companions, one for each star, that share very similar properties: minimum masses of 8.0 ± 0.5 M⊕ and 7.4 ± 0.5 M⊕ in low-eccentricity orbits with periods of 3.023 ± 0.001 d and 3.651 ± 0.001 d for GJ 3779 b and GJ 1265 b, respectively. The periodic signals around 3 d found in the RV data have no counterpart in any spectral activity indicator. Furthermore, we collected available photometric data for the two host stars, which confirm that the additional Doppler variations found at periods of approximately 95 d can be attributed to the rotation of the stars. The addition of these planets to a mass-period diagram of known planets around M dwarfs suggests a bimodal distribution with a lack of short-period low-mass planets in the range of 2–5 M⊕. It also indicates that super-Earths (>5 M⊕) currently detected by RV and transit techniques around M stars are usually found in systems dominated by a single planet.

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

The Astrophysical Journal ◽

10.1088/0004-637x/710/1/432 ◽

2010 ◽

Vol 710 (1) ◽

pp. 432-443 ◽

Cited By ~ 116

Author(s):

A. Reiners ◽

J. L. Bean ◽

K. F. Huber ◽

S. Dreizler ◽

A. Seifahrt ◽

...

Keyword(s):

Radial Velocity ◽

Low Mass Stars ◽

Low Mass

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Precision Radial Velocities in the Near Infrared with TEDI

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308026355 ◽

2008 ◽

Vol 4 (S253) ◽

pp. 157-161 ◽

Cited By ~ 1

Author(s):

James P. Lloyd ◽

Agnieszka Czeszumska ◽

Jerry Edelstein ◽

David Erskine ◽

Michael Feuerstein ◽

...

Keyword(s):

Radial Velocity ◽

Near Infrared ◽

Radial Velocities ◽

Velocity Measurements ◽

M Dwarfs ◽

Low Mass Stars ◽

Habitable Zones ◽

Low Mass ◽

Transit Method

AbstractThe TEDI (TripleSpec - Exoplanet Discovery Instrument) is a dedicated instrument for the near-infrared radial velocity search for planetary companions to low-mass stars with the goal of achieving meters-per-second radial velocity precision. Heretofore, such planet searches have been limited almost entirely to the optical band and to stars that are bright in this band. Consequently, knowledge about planetary companions to the populous but visibly faint low-mass stars is limited. In addition to the opportunity afforded by precision radial velocity searches directly for planets around low mass stars, transits around the smallest M dwarfs offer a chance to detect the smallest possible planets in the habitable zones of the parent stars. As has been the the case with followup of planet candidates detected by the transit method requiring radial velocity confirmation, the capability to undertake efficient precision radial velocity measurements of mid-late M dwarfs will be required. TEDI has been commissioned on the Palomar 200” telescope in December 2007, and is currently in a science verification phase.

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The Milky Way evolution under the RAVE perspective

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315008686 ◽

2015 ◽

Vol 11 (S317) ◽

pp. 320-323

Author(s):

Georges Kordopatis ◽

Keyword(s):

Radial Velocity ◽

Milky Way ◽

Solar Neighbourhood ◽

Low Mass Stars ◽

Medium Resolution ◽

Low Mass

AbstractThe RAdial Velocity Experiment (RAVE) collected from 2003 to 2013 medium resolution spectra for 5ċ105 low-mass stars of our Galaxy, improving our understanding of the Milky Way evolution and of its properties outside the Solar neighbourhood. This proceeding gives an overview of RAVE results obtained in the last two years.

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Radial Velocities and Rotational Velocities of Late-Type Stars in the Coma Ber Cluster

Symposium - International Astronomical Union ◽

10.1017/s0074180900091956 ◽

1980 ◽

Vol 85 ◽

pp. 243-244

Author(s):

M. Mayor ◽

J. C. Mermilliod

Keyword(s):

Radial Velocity ◽

Radial Velocities ◽

Late Type ◽

Low Mass Stars ◽

Red Dwarfs ◽

Low Mass ◽

The Mean ◽

Average Dispersion

Stars with spectral types later than or equal to F5V in the Coma Ber cluster have been measured from 1977 to 1979 with the spectrometer CORAVEL (A. Baranne et al. 1980). The aims of this investigation were to clarify the membership based on radial velocity for some faint stars, to study the binarity of the low mass stars of the cluster, and to obtain the distribution of the rotational velocities for the red dwarfs. 391 measurements have been made for 34 stars. The average dispersion over the mean VR of each star is 0.6 kms−1.

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Astrometric exoplanet surveys in practice

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316002878 ◽

2015 ◽

Vol 11 (A29A) ◽

pp. 217-218

Author(s):

Johannes Sahlmann

Keyword(s):

Radial Velocity ◽

Brown Dwarfs ◽

Giant Planets ◽

Low Mass Stars ◽

Low Mass ◽

Host Stars

AbstractConversely to the transit photometry and radial velocity methods, the astrometric discovery of exoplanets is still limited by the sensitivity of available instruments. Ground-based surveys are now sensitive to giant planets in orbit around nearby low-mass stars and brown dwarfs. In 2014, ESA's Gaia mission began its survey, which is expected to discover thousands of giant exoplanets by detecting the astrometric orbital motions of the host stars.

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Analysis of the chromosphere and corona of low-activity early-M dwarfs

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319009931 ◽

2019 ◽

Vol 15 (S354) ◽

pp. 355-362

Author(s):

Gaetano Scandariato ◽

E. González Álvarez ◽

J. Maldonado ◽

A. Suárez Mascareño ◽

Keyword(s):

Active Regions ◽

Limiting Factors ◽

Activity Levels ◽

M Dwarfs ◽

Low Mass Stars ◽

Balmer Series ◽

Emission Fluxes ◽

Low Mass ◽

Low Activity

AbstractWhile most of the exoplanets have been found orbiting around solar-type stars, low-mass stars have recently been recognized as ideal exo-life laboratory. Currently, stellar activity is one of the limiting factors for the characterization of Earth-twins and for assessing their habitability: understanding the activity of M dwarfs is thus crucial. In this contribution I present the spectroscopic analysis of the quiet early-M dwarfs monitored within the HADES (HArps-n red Dwarf Exoplanet Survey) radial velocity survey. The spectra allow us to analyze simultaneously the Ca ii H&K doublet and the Hydrogen Balmer series, while the intensive follow up gives us a large number of spectra ( 100) for each target. We complement this dataset with ground-based follow-up photometry and archival X-ray data. I present our results on the activity-rotation-stellar parameters and flux-flux relationships, and discuss the correlation of emission fluxes at low activity levels and the evolution timescales of active regions.

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Radial velocity studies of cool stars

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2013.0088 ◽

2014 ◽

Vol 372 (2014) ◽

pp. 20130088 ◽

Cited By ~ 1

Author(s):

Hugh R. A. Jones ◽

John Barnes ◽

Mikko Tuomi ◽

James S. Jenkins ◽

Guillem Anglada-Escude

Keyword(s):

Radial Velocity ◽

Current View ◽

Velocity Data ◽

M Dwarfs ◽

Low Mass Stars ◽

Robust Detection ◽

Dwarf Planets ◽

Low Mass ◽

M Dwarf ◽

Radial Velocity Data

Our current view of exoplanets is one derived primarily from solar-like stars with a strong focus on understanding our Solar System. Our knowledge about the properties of exoplanets around the dominant stellar population by number, the so-called low-mass stars or M dwarfs, is much more cursory. Based on radial velocity discoveries, we find that the semi-major axis distribution of M dwarf planets appears to be broadly similar to those around more massive stars and thus formation and migration processes might be similar to heavier stars. However, we find that the mass of M dwarf planets is relatively much lower than the expected mass dependency based on stellar mass and thus infer that planet formation efficiency around low-mass stars is relatively impaired. We consider techniques to overcome the practical issue of obtaining good quality radial velocity data for M dwarfs despite their faintness and sustained activity and emphasize (i) the wavelength sensitivity of radial velocity signals, (ii) the combination of radial velocity data from different experiments for robust detection of small amplitude signals, and (iii) the selection of targets and radial velocity interpretation of late-type M dwarfs should consider H α behaviour.

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