Bias and robustness of eccentricity estimates from radial velocity data

ABSTRACT Eccentricity is a parameter of particular interest as it is an informative indicator of the past of planetary systems. It is however not always clear whether the eccentricity fitted on radial velocity data is real or if it is an artefact of an inappropriate modelling. In this work, we address this question in two steps: we first assume that the model used for inference is correct and present interesting features of classical estimators. Secondly, we study whether the eccentricity estimates are to be trusted when the data contain incorrectly modelled signals, such as missed planetary companions, non-Gaussian noises, correlated noises with unknown covariance, etc. Our main conclusion is that data analysis via posterior distributions, with a model including a free error term gives reliable results provided two conditions. First, convergence of the numerical methods needs to be ascertained. Secondly, the noise power spectrum should not have a particularly strong peak at the semiperiod of the planet of interest. As a consequence, it is difficult to determine if the signal of an apparently eccentric planet might be due to another inner companion in 2:1 mean motion resonance. We study the use of Bayes factors to disentangle these cases. Finally, we suggest methods to check if there are hints of an incorrect model in the residuals. We show on simulated data the performance of our methods and comment on the eccentricities of Proxima b and 55 Cnc f.

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Search for the Companion in the β CrB Spectrum

International Astronomical Union Colloquium ◽

10.1017/s0252921100020455 ◽

1993 ◽

Vol 138 ◽

pp. 169-172

Author(s):

R. Faraggiana ◽

M. Gerbaldi

Keyword(s):

Radial Velocity ◽

Velocity Data ◽

The Past ◽

Spectroscopic Analyses ◽

System P ◽

Double Nature ◽

Radial Velocity Data

Spectroscopic analyses of the β CrB spectrum have been performed in the past without taking into consideration the double nature of this well-known cool Ap star (e.g. Hiltner, 1945; Hack, 1958; Adelman, 1973). Recently, Kamper et al. (1990) have re-examined the astrometric (interferometric and visual) and spectroscopic (radial velocity) data and have given an improved orbit for the β CrB system (P=10.55 yr) and the passage at periastron at 1991.02.

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Kinematics of Disk Stars in the Solar Neighbourhood

Highlights of Astronomy ◽

10.1017/s1539299600022310 ◽

1998 ◽

Vol 11 (1) ◽

pp. 574-574

Author(s):

A.E. Gómez ◽

S. Grenier ◽

S. Udry ◽

M. Haywood ◽

V. Sabas ◽

...

Keyword(s):

Dispersion Relation ◽

Radial Velocity ◽

Velocity Dispersion ◽

Tangential Velocity ◽

Thin Disk ◽

The Other ◽

Proper Motions ◽

Velocity Data ◽

Kinematic Data ◽

Radial Velocity Data

Using Hipparcos parallaxes and proper motions together with radial velocity data and individual ages estimated from isochones, the velocity ellipsoid has been determined as a function of age. On the basis of the available kinematic data two different samples were considered: a first one (7789 stars) for which only tangential velocities were calculated and a second one containing 3104 stars with available U, V and W velocity components and total velocities ≤ 65 km.s-1. The main conclusions are: -Mixing is not complete at about 0.8-1 Gyr. -The shape of the velocity ellipsoid changes with time getting rounder from σu/σv/σ-w = 1/0.63/0.42 ± 0.04 at about 1 Gyr to1/0.7/0.62 ±0.04 at 4-5 Gyr. -The age-velocity-dispersion relation (from the sample with kinematical selection) rises to a maximum, thereafter remaining roughly constant; there is no dynamically significant evolution of the disk after about 4-5 Gyr. -Among the stars with solar metallicities and log(age) > 9.8 two groups are identified: one has typical thin disk characteristics, the other is older than 10 Gyr and lags the LSR at about 40 km.s-1 . -The variation of the tangential velocity with age(without selection on the tangential velocity) shows a discontinuity at about 10 Gyr, which may be attributed to stars typically of the thick disk populations for ages > 10 Gyr.

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THEPOSTERIORDISTRIBUTION OF sin(i) VALUES FOR EXOPLANETS WITHMTsin(i) DETERMINED FROM RADIAL VELOCITY DATA

The Astrophysical Journal ◽

10.1088/0004-637x/739/1/26 ◽

2011 ◽

Vol 739 (1) ◽

pp. 26 ◽

Cited By ~ 21

Author(s):

Shirley Ho ◽

Edwin L. Turner

Keyword(s):

Radial Velocity ◽

Velocity Data ◽

Radial Velocity Data

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An Efficient Dual-Resolution Approach for Ensemble Data Assimilation and Tests with Simulated Doppler Radar Data

Monthly Weather Review ◽

10.1175/2007mwr2120.1 ◽

2008 ◽

Vol 136 (3) ◽

pp. 945-963 ◽

Cited By ~ 31

Author(s):

Jidong Gao ◽

Ming Xue

Keyword(s):

High Resolution ◽

Data Assimilation ◽

Radial Velocity ◽

Computational Cost ◽

Radar Data ◽

Horizontal Resolution ◽

Velocity Data ◽

Background Error ◽

Cross Covariance ◽

Radial Velocity Data

Abstract A new efficient dual-resolution (DR) data assimilation algorithm is developed based on the ensemble Kalman filter (EnKF) method and tested using simulated radar radial velocity data for a supercell storm. Radar observations are assimilated on both high-resolution and lower-resolution grids using the EnKF algorithm with flow-dependent background error covariances estimated from the lower-resolution ensemble. It is shown that the flow-dependent and dynamically evolved background error covariances thus estimated are effective in producing quality analyses on the high-resolution grid. The DR method has the advantage of being able to significantly reduce the computational cost of the EnKF analysis. In the system, the lower-resolution ensemble provides the flow-dependent background error covariance, while the single-high-resolution forecast and analysis provides the benefit of higher resolution, which is important for resolving the internal structures of thunderstorms. The relative smoothness of the covariance obtained from the lower 4-km-resolution ensemble does not appear to significantly degrade the quality of analysis. This is because the cross covariance among different variables is of first-order importance for “retrieving” unobserved variables from the radar radial velocity data. For the DR analysis, an ensemble size of 40 appears to be a reasonable choice with the use of a 4-km horizontal resolution in the ensemble and a 1-km resolution in the high-resolution analysis. Several sensitivity tests show that the DR EnKF system is quite robust to different observation errors. A 4-km thinned data resolution is a compromise that is acceptable under the constraint of real-time applications. A data density of 8 km leads to a significant degradation in the analysis.

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Precipitation cloud identification based on faster-RCNN for Doppler weather radar

EURASIP Journal on Wireless Communications and Networking ◽

10.1186/s13638-021-01896-5 ◽

2021 ◽

Vol 2021 (1) ◽

Author(s):

Yuanbo Ran ◽

Haijiang Wang ◽

Li Tian ◽

Jiang Wu ◽

Xiaohong Li

Keyword(s):

Radial Velocity ◽

Vertical Direction ◽

Weather Radar ◽

Radar Reflectivity ◽

Convective Precipitation ◽

Horizontal Wind ◽

Doppler Weather Radar ◽

Velocity Data ◽

Precipitation Processes ◽

Radial Velocity Data

AbstractPrecipitation clouds are visible aggregates of hydrometeor in the air that floating in the atmosphere after condensation, which can be divided into stratiform cloud and convective cloud. Different precipitation clouds often accompany different precipitation processes. Accurate identification of precipitation clouds is significant for the prediction of severe precipitation processes. Traditional identification methods mostly depend on the differences of radar reflectivity distribution morphology between stratiform and convective precipitation clouds in three-dimensional space. However, all of them have a common shortcoming that the radial velocity data detected by Doppler Weather Radar has not been applied to the identification of precipitation clouds because it is insensitive to the convective movement in the vertical direction. This paper proposes a new method for precipitation clouds identification based on deep learning algorithm, which is according the distribution morphology of multiple radar data. It mainly includes three parts, which are Constant Altitude Plan Position Indicator data (CAPPI) interpolation for radar reflectivity, Radial projection of the ground horizontal wind field by using radial velocity data, and the precipitation clouds identification based on Faster-RCNN. The testing result shows that the method proposed in this paper performs better than the traditional methods in terms of precision. Moreover, this method boasts great advantages in running time and adaptive ability.

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The CORAVEL Radial Velocity Data Base

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317006834 ◽

2017 ◽

Vol 13 (S334) ◽

pp. 271-272

Author(s):

Stéphane Udry ◽

Maxime Marmier ◽

Michel Mayor ◽

Johannes Andersen ◽

Birgitta Nordström

Keyword(s):

Radial Velocity ◽

Data Base ◽

Radial Velocities ◽

Velocity Data ◽

Radial Velocity Data

AbstractFrom 1977 to 1999, thousands of accurate radial velocities in both hemispheres were made on a large variety of programmes with the two CORAVEL scanners. The data base of ~350000 individual observations will now be made available to complement the Gaia data.

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The Radial Velocity Curve of V652 Her (BD+13°3224)

International Astronomical Union Colloquium ◽

10.1017/s0252921100090679 ◽

1985 ◽

Vol 87 ◽

pp. 109-115

Author(s):

P.W. Hill ◽

C.S. Jeffery

Keyword(s):

Radial Velocity ◽

Time Resolution ◽

High Frequency ◽

Velocity Curve ◽

Velocity Data ◽

Effective Surface ◽

Radial Velocity Curve ◽

Minimum Radius ◽

Helium Star ◽

Radial Velocity Data

AbstractNew radial velocity data for the pulsating extreme helium star V652 Her (BD+13°3224) have been obtained with a time resolution of 100 s. High frequency structure in the radial velocity curve is detected, and a comparison with previous data suggests that the detailed shape of the velocity curve is variable. The data imply that the effective surface gravity must increase by a factor of 4 at minimum radius.

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