scholarly journals juliet: a versatile modelling tool for transiting and non-transiting exoplanetary systems

2019 ◽  
Vol 490 (2) ◽  
pp. 2262-2283 ◽  
Author(s):  
Néstor Espinoza ◽  
Diana Kossakowski ◽  
Rafael Brahm
Keyword(s):  
Radial Velocity ◽  
Model Comparison ◽  
Computing Time ◽  
Radial Velocities ◽  
Stellar Rotation ◽  
Velocity Measurements ◽  
Nested Sampling ◽  
Rotation Periods ◽  
Exoplanetary Systems ◽  
Versatile Tool

ABSTRACT Here we present juliet, a versatile tool for the analysis of transits, radial velocities, or both. juliet is built over many available tools for the modelling of transits, radial velocities, and stochastic processes (here modelled as Gaussian Processes; GPs) in order to deliver a tool/wrapper which can be used for the analysis of transit photometry and radial-velocity measurements from multiple instruments at the same time, using nested sampling algorithms which allows it to not only perform a thorough sampling of the parameter space, but also to perform model comparison via Bayesian evidences. In addition, juliet allows us to fit transiting and non-transiting multiplanetary systems, and to fit GPs which might share hyperparameters between the photometry and radial velocities simultaneously (e.g. stellar rotation periods), which might be useful for disentangling stellar activity in radial-velocity measurements. Nested Sampling, Importance Nested Sampling, and Dynamic Nested Sampling is performed with publicly available codes which in turn give juliet multithreading options, allowing it to scale the computing time of complicated multidimensional problems. We make juliet publicly available via GitHub.

scholarly journals The empirical period-radius relation for pulsating stars: a synthesis based on photometric and radial velocity measurements

1986 ◽  
Vol 118 ◽  
pp. 273-274
Author(s):  
G. Burki
Keyword(s):  
Radial Velocity ◽  
Stellar Evolution ◽  
Variable Stars ◽  
Radial Velocities ◽  
Velocity Measurements ◽  
Pulsating Stars ◽  
Powerful Test ◽  
The Mean

The relation existing between the radius and the period for the pulsating stars of a given class constitutes a powerful test for the theory of stellar evolution and for the identification of the pulsation modes. In recent years, several authors have determined the mean radius of a lot of pulsating stars of various classes by applying the Baade-Wesselink method. Fig. 1 presents the resulting general logP - logR diagram grouping these determinations. The sources for the radii are given by Burki and Meylan (1986). The variable stars in known binaries have been excluded since the presence of a companion biases the radius calculation (Burki, 1984). The determinations marked by arrows are based on the radial velocities by CORAVEL (1m telescope at the Haute-Provence Observatory, France) or/and on the photometry in the Geneva system (40cm and 70cm telescopes at La Silla Observatory, Chile).

scholarly journals Dealing with activity in RV planet searches

2015 ◽  
Vol 11 (A29A) ◽  
pp. 193-195
Author(s):  
Isabelle Boisse
Keyword(s):  
Time Series ◽  
Radial Velocity ◽  
Radial Velocities ◽  
Velocity Measurements ◽  
Stellar Activity ◽  
The Future

AbstractPrecise radial velocity measurements of a star allow to search for planets. But this method has to face with irregularly time series. Stellar variabilities: pulsation, granulation, stellar activity on a short and long timescale, also modify the measure of the radial velocities. There is indeed a growing literature of controversies on how a signal is interpreted as a planet or due to stellar activity. I present how the star variations change the measured RVs, which techniques and indices are used by several teams to disentangle activity and planets, and the future options that are being studied.

scholarly journals The LAMOST spectroscopic survey of planetary nebulae in M31 and M33

2016 ◽  
Vol 12 (S323) ◽  
pp. 388-389
Author(s):  
Maosheng Xiang ◽  
Xiaowei Liu ◽  
Meng Zhang ◽  
Haibo Yuan ◽  
Zhiying Huo
Keyword(s):  
Radial Velocity ◽  
Planetary Nebulae ◽  
Radial Velocities ◽  
Velocity Measurements ◽  
The Galaxy ◽  
Galaxy Center ◽  
Projected Distance

AbstractWe present LAMOST observations and radial velocity measurements of about 1500 planetary nebulae (PNe) in M31 and M33. Most of the PNe are previously known, but 36 of them are newly discovered in the outskirts of M31, and the furthest one has a projected distance larger than 50 kpc away from the galaxy center. Eighteen objects in the area of M33 are probably newly discovered PNe, and quite a few of them are associated with previously known clusters. For all the 1500 PNe, homogeneous radial velocities are measured from the LAMOST spectra, with a typical uncertainty of a few km s−1.

scholarly journals Precise radial velocities of giant stars

2019 ◽  
Vol 625 ◽  
pp. A22 ◽  
Author(s):  
Katja Reichert ◽  
Sabine Reffert ◽  
Stephan Stock ◽  
Trifon Trifonov ◽  
Andreas Quirrenbach
Keyword(s):  
Radial Velocity ◽  
Statistical Power ◽  
Radial Velocities ◽  
Dynamical Stability ◽  
Published Data ◽  
Data Sets ◽  
Velocity Data ◽  
Velocity Measurements ◽  
Velocity Variations ◽  
Radial Velocity Data

Context. Radial-velocity variations of the K giant star Aldebaran (α Tau) were first reported in the early 1990s. After subsequent analyses, the radial-velocity variability with a period of ∼629 d has recently been interpreted as caused by a planet of several Jovian masses. Aims. We want to further investigate the hypothesis of an extrasolar planet around Aldebaran. Methods. We combine 165 new radial-velocity measurements from Lick Observatory with seven already published data sets comprising 373 radial-velocity measurements. We perform statistical analyses and investigate whether a Keplerian model properly fits the radial velocities. We also perform a dynamical stability analysis for a possible two-planet solution. Furthermore, the possibility of oscillatory convective modes as cause for the observed radial-velocity variability is discussed. Results. As best Keplerian fit to the combined radial-velocity data we obtain an orbit for the hypothetical planet with a smaller period (P = 607 d) and a larger eccentricity (e = 0.33 ± 0.04) than the previously proposed one. However, the residual scatter around that fit is still large, with a standard deviation of 117 ms−1. In 2006/2007, the statistical power of the ∼620 d period showed a temporary but significant decrease. Plotting the growth of power in reverse chronological order reveals that a period around 620 d is clearly present in the newest data but not in the data taken before ∼2006. Furthermore, an apparent phase shift between radial-velocity data and orbital solution is observable at certain times. A two-planet Keplerian fit matches the data considerably better than a single-planet solution, but poses severe dynamical stability issues. Conclusions. The radial-velocity data from Lick Observatory do not further support but in fact weaken the hypothesis of a substellar companion around Aldebaran. Oscillatory convective modes might be a plausible alternative explanation of the observed radial-velocity variations.

scholarly journals Precision Radial Velocities in the Near Infrared with TEDI

2008 ◽  
Vol 4 (S253) ◽  
pp. 157-161 ◽  
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.

scholarly journals Detecting planetary signals with Bayesian methods

2009 ◽  
Vol 5 (H15) ◽  
pp. 693-693
Author(s):  
Samuli Kotiranta ◽  
Mikko Tuomi
Keyword(s):  
Radial Velocity ◽  
Bayesian Methods ◽  
Bayesian Model ◽  
Model Comparison ◽  
Planetary System ◽  
Velocity Measurements ◽  
Bayesian Model Comparison

AbstractIn this paper we present an application of Bayesian model comparison to the radial velocity measurements of suspected extra-solar planetary system host star.

scholarly journals Spin-orbit alignment and magnetic activity in the young planetary system AU Mic

2020 ◽  
Vol 641 ◽  
pp. L1 ◽  
Author(s):  
E. Martioli ◽  
G. Hébrard ◽  
C. Moutou ◽  
J.-F. Donati ◽  
É. Artigau ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Template Matching ◽  
Near Infrared ◽  
Rotation Axis ◽  
Magnetic Activity ◽  
Radial Velocities ◽  
Model Parameters ◽  
Correlation Technique ◽  
Spin Orbit ◽  
Stellar Rotation

We present high-resolution near-infrared spectropolarimetric observations using the SPIRou instrument at Canada-France-Hawaii Telescope (CFHT) during a transit of the recently detected young planet AU Mic b, with supporting spectroscopic data from iSHELL at NASA InfraRed Telescope Facility. We detect Zeeman signatures in the Stokes V profiles and measure a mean longitudinal magnetic field of ¯Bℓ = 46.3 ± 0.7 G. Rotationally modulated magnetic spots likely cause long-term variations of the field with a slope of dBℓ/dt = −108.7 ± 7.7 G d−1. We apply the cross-correlation technique to measure line profiles and obtain radial velocities through CCF template matching. We find an empirical linear relationship between radial velocity and Bℓ, which allows us to estimate the radial-velocity induced by stellar activity through rotational modulation of spots for the five hours of continuous monitoring of AU Mic with SPIRou. We model the corrected radial velocities for the classical Rossiter-McLaughlin effect, using MCMC to sample the posterior distribution of the model parameters. This analysis shows that the orbit of AU Mic b is prograde and aligned with the stellar rotation axis with a sky-projected spin-orbit obliquity of λ = 0°−15°+18°. The aligned orbit of AU Mic b indicates that it formed in the protoplanetary disk that evolved into the current debris disk around AU Mic.

scholarly journals La Mesure Des Vitesses Radiales Avec Un Prisme Objectif Associe A Un Telescope De Schmidt

1984 ◽  
Vol 78 ◽  
pp. 291-294
Author(s):  
Ch. Fehrenbach ◽  
R. Burnage
Keyword(s):  
Radial Velocity ◽  
Correlation Method ◽  
Probable Error ◽  
Radial Velocities ◽  
Galactic Latitude ◽  
Velocity Measurements ◽  
Schmidt Telescope ◽  
Special Machine ◽  
Objective Prism

AbstractRadial velocity measurements with an objective-prism mounted on a Schmidt telescope.A 62 cm diameter objective-prism is mounted on the CNRS-University of Liège Schmidt telescope at the Haute Provence Observatory. The field is 4 x 4° and the limiting magnitude is 12.5 on IllaJ hyper-sensitised plates. The dispersion is 200 A mm-1 at 4220 A. The plates are measured with a special machine and data are reduced by means of a computer with a correlation method. Stars of all spectral types are measured. The probable error is of some 4 km sec -1 over a mean of at least 3 plates. Already several lists of radial velocities of stars belonging to field situated at -30° of galactic latitude have been published. We have also started radial velocity observations for the Hipparcos Program.

Coravel Measurements of IAU and Southern Potential Radial-Velocity Standard Stars. A Zero Point Discussion

1984 ◽  
Vol 88 ◽  
pp. 299-310
Author(s):  
M. Mayor ◽  
E. Maurice
Keyword(s):  
Radial Velocity ◽  
Observational Data ◽  
Zero Point ◽  
Variable Stars ◽  
Radial Velocities ◽  
Variable Velocity ◽  
Velocity Measurements ◽  
Similar Difference ◽  
Systematic Effects ◽  
Velocity Variations

AbstractRadial velocity measurements have been carried out since 1981 with the spectrometer CORAVEL at ESO, La Silla. Almost one thousand measurements of IAU radial velocity standard stars and of potential southern standard stars have been acquired by the different observers (mean precision per measurement 0.2 km/s).Among the measured IAU standard stars, at least four have shown clear radial-velocity variations from 1981 to 1984 (HD 36673, 156014, 44131, 115521).The comparison between CORAVEL mean velocities and IAU values reveals a difference of approximately 0.8 km/s between bright (mv <4.3) and faint IAU (mv >4.3) standards (Vr(IAUB) - Vr(IAUF) = +0.8 km/s). A similar difference also appears when comparing IAU standard velocities and those measured with the Victoria spectrometer, Fletcher et al. (1982).Thus, IAU standard stars not only include radial-velocity variable stars (intrinsic variables and SB) but they also present zero-point systematic effects.In the present paper we correct the radial velocities of the bright IAU standard stars so that they now belong to the same system as the faint ones. After elimination of variable velocity stars and stars showing large differences between IAU values and recent radial-velocity determinations, an homogeneous list of 34 IAU standard stars is obtained. These revised radial velocities are based on IAU values and new determinations obtained with the Victoria spectrometer and with CORAVEL at La Silla. These stars are distributed between the declinations δ = -82° and δ = +28°.This paper uses observational data in advance of the publication by CORAVEL observers of the 7th of the series of papers: “Radial velocities of southern stars obtained with the photoelectric scanner CORAVEL”.

scholarly journals Precise Radial-velocity Measurements with a Cassegrain Spectrograph, II: Radial-velocity Determination and Applications

1999 ◽  
Vol 170 ◽  
pp. 68-72 ◽  
Author(s):  
I. V. Ilyin ◽  
R. Duemmler
Keyword(s):  
Radial Velocity ◽  
Data Reduction ◽  
High Accuracy ◽  
Radial Velocities ◽  
Velocity Measurements ◽  
Echelle Spectrograph ◽  
The Stability ◽  
Stability Issues

AbstractWe present our measurements of radial velocities of two stars suspected to have a substellar companion by using observations made with a cassegrain échelle spectrograph. The stability issues and details of the data reduction are discussed in Ilyin & Duemmler (paper I, these proceedings). The results obtained here show that relatively high accuracy of radial velocity determinations is also attainable for cassegrain spectrographs.

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