The fundamental definition of “radial velocity”

Lindegren, L.; Dravins, Dainis

doi:10.1051/0004-6361:20030181

Cited by 181 publications

(167 citation statements)

References 70 publications

Supporting

Mentioning

163

Contrasting

Order By: Relevance

“…It is adopted for this purpose because it closely corresponds to the conventional interpretation of the astrometric parameters. However, when the astrometric parameters are to be interpreted in terms of the barycentric space velocity of the source, some of these effects may come into play (Lindegren & Dravins 2003).…”

Section: Astrometric Modelmentioning

confidence: 99%

The astrometric core solution for theGaiamission

Lindegren

Lammers

Hobbs

et al. 2012

A&A

370

624

View full text Add to dashboard Cite

Context. The Gaia satellite will observe about one billion stars and other point-like sources. The astrometric core solution will determine the astrometric parameters (position, parallax, and proper motion) for a subset of these sources, using a global solution approach which must also include a large number of parameters for the satellite attitude and optical instrument. The accurate and efficient implementation of this solution is an extremely demanding task, but crucial for the outcome of the mission. Aims. We aim to provide a comprehensive overview of the mathematical and physical models applicable to this solution, as well as its numerical and algorithmic framework. Methods. The astrometric core solution is a simultaneous least-squares estimation of about half a billion parameters, including the astrometric parameters for some 100 million well-behaved so-called primary sources. The global nature of the solution requires an iterative approach, which can be broken down into a small number of distinct processing blocks (source, attitude, calibration and global updating) and auxiliary processes (including the frame rotator and selection of primary sources). We describe each of these processes in some detail, formulate the underlying models, from which the observation equations are derived, and outline the adopted numerical solution methods with due consideration of robustness and the structure of the resulting system of equations. Appendices provide brief introductions to some important mathematical tools (quaternions and B-splines for the attitude representation, and a modified Cholesky algorithm for positive semidefinite problems) and discuss some complications expected in the real mission data. Results. A complete software system called AGIS (Astrometric Global Iterative Solution) is being built according to the methods described in the paper. Based on simulated data for 2 million primary sources we present some initial results, demonstrating the basic mathematical and numerical validity of the approach and, by a reasonable extrapolation, its practical feasibility in terms of data management and computations for the real mission.

show abstract

Section: Astrometric Modelmentioning

confidence: 99%

The astrometric core solution for theGaiamission

Lindegren

Lammers

Hobbs

et al. 2012

A&A

370

624

View full text Add to dashboard Cite

show abstract

“…The effect is now corrected down to a level of just a few 0.1 m/s, using the differential pressure sensitivity of the argon and thorium lines. The HARPS pipeline also corrects the radial velocities to the Solar System barycentric reference frame (Lindegren & Dravins 2003). That correction is computed at the weightedmean time of the exposure, which is measured by a photometer that diverts a small fraction of the stellar flux.…”

Section: A New Data Setmentioning

confidence: 99%

The HARPS search for southern extra-solar planets

Mayor¹,

Bonfils

Forveille

et al. 2009

A&A

368

397

View full text Add to dashboard Cite

The GJ 581 planetary system is already known to harbour three planets, including two super-Earth planets that straddle its habitable zone. We report the detection of an additional planet -GJ 581e -with a minimum mass of 1.9 M ⊕ . With a period of 3.15 days, it is the innermost planet of the system and has a ∼5% transit probability. We also correct our previous confusion about the orbital period of GJ 581d (the outermost planet) with a one-year alias, benefitting from an extended time span and many more measurements. The revised period is 66.8 days, and positions the semi-major axis inside the habitable zone of the low mass star. The dynamical stability of the 4-planet system imposes an upper bound on the orbital plane inclination. The planets cannot be more massive than approximately 1.6 times their minimum mass.

show abstract

“…There are many physical mechanisms that affect spectroscopic radial velocities (Lindegren & Dravins 2003). For instance, the convective shifts caused by motions in stellar atmospheres depend on stellar lines and on the temperature and gravity.…”

Section: Next Stepsmentioning

confidence: 99%

The catalogue of radial velocity standard stars forGaia

Soubiran

Jasniewicz

Chemin

et al. 2013

A&A

128

142

View full text Add to dashboard Cite

The Radial Velocity Spectrograph (RVS) on board Gaia needs to be calibrated using stable reference stars known in advance. The catalogue presented here was built for that purpose. It includes 1420 radial velocity standard star candidates selected on strict criteria to fulfil the Gaia-RVS requirements. A large programme of ground-based observations has been underway since 2006 to monitor these stars and verify their stability, which has to be better than 300 m s −1 over several years. The observations were done on the echelle spectrographs ELODIE and SOPHIE on the 1.93-m telescope at Observatoire de Haute-Provence (OHP), NARVAL on the Télescope Bernard Lyot at Observatoire du Pic du Midi and CORALIE on the Euler-Swiss Telescope at La Silla. Data from the OHP and Geneva Observatory archives have also been retrieved as have HARPS spectra from the ESO archive. We provide a mean radial velocity in the SOPHIE scale for each star, derived from the combination of velocities measured with those instruments, after having carefully estimated their differences in zero points. In total, 10214 radial velocity measurements have been obtained for the 1420 stars. With a mean time baseline of 6.35 years, 92.9% of the candidates fulfil a target stability criterion of 300 m s −1 . Three hundred forty-three stars are found to be constant at the level of 100 m s −1 over 10 years. Comparisons with earlier catalogues show excellent agreement for FGK stars, with zero-point differences lower than 100 m s −1 and a remarkably low rms scatter of 33 m s −1 in one case, suggesting that the precision of the catalogue presented here is better than this value. This catalogue will likely be useful for other large-scale spectroscopic surveys, such as APOGEE, Gaia-ESO, HERMES, and LAMOST.

show abstract

The fundamental definition of “radial velocity”

Cited by 181 publications

References 70 publications

The astrometric core solution for theGaiamission

The astrometric core solution for theGaiamission

The HARPS search for southern extra-solar planets

The catalogue of radial velocity standard stars forGaia

Contact Info

Product

Resources

About