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Topic: Radial velocities


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  Radial Velocities
In order for our points to coincide with the radial velocity curve, we have had to shift them in phase by -0.06 with respect to the van der Hooft et al.
Unfortunately, their radial velocities (and other groups') are not published in tabular form.
Radial velocities from 1996 February 25 (quiescent period) do not deviate as much, but nevertheless have a steeper gradient than the curve similar to 1995 May 2 data.
www.atnf.csiro.au /pasa/18_1/buxton/paper/node5.html   (430 words)

  
 radial velocity method
If a star is accompanied by a planet, the radial velocity of the star will periodically change as the star moves toward and then away from a distant observer.
A number of groups around the world are now using the radial velocity method, with a precision in the range 3 to 10 m/s in the search for extrasolar planets (see extrasolar planets, searches).
To determine the value of i, and therefore the true mass, radial velocity measurements must be combined with astrometric observations which track the movement of the host star across the sky.
www.daviddarling.info /encyclopedia/R/radialvelmeth.html   (495 words)

  
 The fundamental definition of "radial velocity"   (Site not responding. Last check: 2007-10-21)
Accuracy levels of metres per second require the fundamental concept of "radial velocity" for stars and other distant objects to be examined, both as a physical velocity, and as measured by spectroscopic and astrometric techniques.
Already in a classical (non-relativistic) framework the line-of-sight velocity component is an ambiguous concept, depending on whether, e.g., the time of light emission (at the object) or that of light detection (by the observer) is used for recording the time coordinate.
However, it is not a physical velocity, and cannot be accurately transformed to a kinematic or astrometric radial velocity without additional assumptions and data in modelling the process of light emission from the source, the transmission of the signal through space, and its recording by the observer.
www.edpsciences.org /articles/aa/abs/2003/15/aah3961/aah3961.html   (425 words)

  
 SDSS DR3 - Data products: Spectra - Quality of stellar radial velocities
Radial velocities (RVs) are stored as redshifts (multiply z by the speed of light to get the RV in km/s) and were measured by cross-correlation to a set of stellar templates.
This calibration has been checked by obtaining a special plate of known radial velocity standards in the cluster M67, and the velocities are in agreement with an absolute error of less than 4 km/s.
The relative rms velocity error is magnitude (signal-to-noise) dependent, but repeated observations of the same stars have shown the errors to be about 5 km/s (one sigma rms) for stars brighter than about g = 18.2 mag, degrading to errors of 25 km/s for stars with g = 20.3 mag.
www.sdss.org /dr3/products/spectra/radvelocity.html   (427 words)

  
 Astron. Astrophys. 336, L17-L20 (1998)
Our sample of radial velocities was obtained with the CORAVEL radial velocity spectrometers installed at the Swiss telecope at the Haute Provence Observatory in France and at the Danish 1.5 meter telescope at La Silla, Chile (Baranne et al., 1979).
Thanks to the fact that AC Her is one of the stablest RV Tauri stars known we could correct the total velocity set for the pulsation amplitude by using the pulsation period determination of 75.47 days by Zsoldos (1993).
The radial velocity measurements of AC Her (asterisk) folded on the 1194 days period, together with the best fit as discussed in the text.
aa.springer.de /papers/8336002/2300l17/sc2.htm   (432 words)

  
 Discharge measurement index part 2   (Site not responding. Last check: 2007-10-21)
The depth is measured using of a sounding reel, and the velocity is measured by setting the meter at the proper position in the vertical.
Estimate the depth and observe the velocity at 0.2 of the estimated depth.
The ratio is known between the velocity of selected points in the vertical and the mean velocity in the vertical.
wwwrcamnl.wr.usgs.gov /sws/fieldmethods/QMeas.tmp/index2.htm   (4913 words)

  
 Interpreting Doppler Radar Velocities: straight line winds and rotation
The radial velocity pattern on the right is what the radar would see if the wind speed was uniform at 50 knots and the wind was blowing from the west towards the east.
The Doppler radial velocity display again shows the zero line down the middle of the box since winds along this line are perpendicular to the radar beam.
This Doppler velocity pattern corresponds to an axisymmetric divergent flow where the center of the downburst is in the center of the box 65 nautical miles north of the radar.
ww2010.atmos.uiuc.edu /(Gh)/guides/rs/rad/ptrn/ptrn3.rxml   (434 words)

  
 COMMISSION 30: RADIAL VELOCITIES (VITESSES RADIALES)
The velocity dispersions suggest that this newly-discovered ultra-cool population of M dwarfs is young.
Radial velocities in Praesepe and Coma Berenices were also obtained by Abt and Willmarth (1999ApJ...521..682A) Those studies present orbital elements for spectroscopic binaries.
Radial velocities for 303 giant stars in the globular clusters M3, M13, M15, and M92 were presented by Soderberg et al.
www.ctio.noao.edu /science/iauc30/C30rep.html   (3917 words)

  
 Dainis Dravins (Lund Observatory)
Although radial velocities are normally determined through spectroscopy, the accuracies in space astrometry now permit their determination also from purely geometric measurements.
These originate from correlated velocity and brightness patterns: rising (blueshifted) elements are hot (bright), and a convective blueshift results from a larger contribution of such blueshifted photons than of redshifted ones from the sinking and cooler (darker) gas.
Accuracy levels of meters per second require the fundamental concept of "radial velocity" to be precisely defined, in particular with respect to relativistic velocity effects and measurements made inside gravitational fields.
www.astro.lu.se /~dainis/HTML/ASTROMET.html   (958 words)

  
 Fort Dodge Iowa Automated Flight Service Station, Nexrad HTM   (Site not responding. Last check: 2007-10-21)
Radial velocity is a measure of the speed of particles toward or away from the radar antenna.
A radial velocity of zero does not necessarily indicate there is no air motion, but rather there is none in the direction of the radar antenna.
Radial velocity is calculated from the frequency shift of the returned signal.
www.dodgenet.com /%7Eweavers/afss/nexrad.htm   (1104 words)

  
 Dainis Dravins (Lund Observatory)
As the cluster moves in the radial direction, it appears to contract or expand at a rate equal to the relative rate of change in distance.
Differences between astrometric and spectroscopic velocities permit to better understand physical processes on stellar surfaces (convective lineshifts); stellar interior structure (gravitational redshifts); and to understand which spectral features are the best sensors for the true stellar center-of-mass motion and/or its variations, e.g.
The radial velocity determined through purely geometric methods does, in principle, depend on the coordinate frames and timescales chosen, why there is a need for a stringent definition for the fundamental concept of "astrometric radial velocity".
www.astro.lu.se /~dainis/HTML/HIPPARCOS.html   (998 words)

  
 Radial velocities of Hipparcos southern B8-F2 type stars   (Site not responding. Last check: 2007-10-21)
Radial velocities have been determined for a sample of B8-F2 type stars observed by the Hipparcos satellite.
Radial velocities have been measured using a cross-correlation method, the templates being a grid of synthetic spectra.
The obtained precision depends on effective temperature and projected rotational velocity of the star as well as on a possible asymmetry of the correlation peak generally due to secondary components.
www.edpsciences.org /articles/aas/abs/1999/06/ds1639/ds1639.html   (248 words)

  
 MAST:IUE NEWSIPS Radial Velocity Studies   (Site not responding. Last check: 2007-10-21)
Figure 2 exhibits the variation of radial velocity with wavelength in the range 1170--1410 Angstroms for large-aperture images of tau Sco and white dwarfs.
The radial velocities of the tau Sco images have been shifted to match the mean curve for the white dwarfs.
The large range in RV offsets is a consequence of calibration errors in the zero points calculated by IUESIPS, which are as a function of epoch (Study 1), of and different centerings of the image in the large aperture.
archive.stsci.edu /iue/newsips/radvel   (1134 words)

  
 Radial velocities (from Milky Way Galaxy) --¬† Encyclop√¶dia Britannica
Radial velocities, measured along the line of sight spectroscopically using the Doppler effect, are not known for all of the recognized stars near the Sun.
The radial velocities of the rest are not known either because of faintness or because of problems resulting from the nature of…
Because it has direction as well as magnitude, velocity is known as a vector quantity and cannot be specified completely by a number, as can be done with time or length, which are scalar quantities.
www.britannica.com /eb/article-68093?tocId=68093   (1031 words)

  
 Radial velocities and orbit
Radial velocities for AG Dor were determined from cross-correlations with spectra of the radial velocity standard star HR1829 (
Its radial velocities were measured from the residual spectra after subtraction of a reference spectrum (Sect.
The uncertainties of the zero point and the periods are such that we achieve a phase accuracy of 0001 for UX For and 0003 for AG Dor.
www.aip.de /~wasi/research/AG_Dor/A+A/node4.html   (479 words)

  
 Origins: Library
Radial velocity measurements favor finding large planets located close to their parent star.
Figure 4-8 shows the range of planet-masses and star-planet distances which radial velocity techniques are likely to probe.
The limits to planetary detection by the radial velocities are unknown.
origins.jpl.nasa.gov /library/exnps/ch04_3.html   (555 words)

  
 Astron. Astrophys. 318, 416-428 (1997)
Radial velocities are calculated from the spectra with an on-line reduction procedure using numerical correlation with a binary mask imitating a F0 dwarf.
Although our main effort concerned radial velocities, we also obtained photometry for most objects in the sample, since the existing data were not sufficient to compute reliable reddenings and distances.
Mean values for magnitudes and radial velocities were calculated either by fitting a 2nd to 5th order Fourier curve on the data when the number of measurements was sufficient, or by fitting the curve of another well-measured cepheid of similar period (a method described in Pont et al.
aa.springer.de /papers/7318002/2300416/sc2.htm   (969 words)

  
 Interpreting Doppler Radar Velocities: speed shear wind patterns
Doppler velocity patterns (right) correspond to vertical wind profiles (left), where the wind barbs indicate wind speed and direction from the ground up to 24,000 feet.
Note on the radial velocity field that the maximum inbound velocity is to the west and maximum outbound to the east while to the north and south the radar measures zero radial velocity.
The maximum radial velocities are observed where the radar beam points directly toward or away from the wind direction.
ww2010.atmos.uiuc.edu /(Gh)/guides/rs/rad/ptrn/ptrn1.rxml   (462 words)

  
 Measurement Of Stellar Radial Velocities Utilizing Amateur Astronomical Equipment
To explore the measurement of stellar radial velocities using specific amateur astronomical equipment, allowing the amateur astronomer to generate accurate scientific results that fall within the published radial velocity requirements for a specific star or other extended object.
The calculated radial velocity is +15.53 km/sec and is well within the published accuracy of the instrument of +- 6 km/sec and therefore very close in value to the published radial velocity of this star +21 km/sec.
The calculated radial velocity is +23.19 km/sec and is well within the published error of the instrument of +- 6 km/sec1 and therefore very close in value to the published radial velocity of this star +21.01 km/sec.
users.ameritech.net /delprop/rvpaper1.htm   (1022 words)

  
 Radial velocities and axial rotation of a sample of chemically peculiar stars.
Radial velocities and axial rotation of a sample of chemically peculiar stars.
As part of a systematic project we have determined radial velocities and projected rotational velocities for a sample of 186 chemically peculiar stars which have been observed by the Hipparcos' satellite.
The purpose is to provide necessary data to study the space velocities of peculiar stars.
www.cs.wisc.edu /niagara/data/nasa/A+AS_118_231.xml   (109 words)

  
 Catalogue of Stellar Radial Velocities
The ISGCRV is intended as a continuation of the General Catalogue of Stellar Radial Velocities (Wilson 1953, GCRV).
Velocities from the referees have also been included, but are listed in Figure 3 on page 8.
In any case, the referees should not be held responsible for any of the catalog's contents, although we acknowledge their work and hope that we have made good use of it.
www.cs.wisc.edu /niagara/data/nasa/3047B.xml   (1341 words)

  
 Astrometric vs. Spectroscopic Radial Velocities   (Site not responding. Last check: 2007-10-21)
One important purpose of the Moon observations is to connect stellar observations to the JPL ephemeris, bringing the velocities of the stars to a common and near-absolute frame of reference.
Note that the convective signature is independent of the radial velocity itself of the star, drift in wavelength zero-point (at time scale of the order of the integration time), gravitational redshifts, etc. A major instrumental requirement is that the wavelength scale has a high degree of internal integrity.
This, the astrometric, radial velocity could be perceived as being the true center of mass motion in the line of sight.
www.obs-hp.fr /www/lettre-ohp/no-18/gullberg.html   (1843 words)

  
 Exhibits: Astronomy in California 1850-1950
Campbell changed the direction of Lick Observatory research from that of pioneering astrophysical investigation to the steady accumulation of radial velocity data when he assumed the Directorship in 1901.
The spectroscopic radial velocity program that he planned, organized, and directed became the backbone of Lick Observatory for almost 30 years.
The data on stellar radial velocities that came out of the "doppler" program were Campbell's main contribution to astronomy.
www.chabotspace.org /vsc/exhibits/califastronomy/lickartifacts.asp   (411 words)

  
 Astron. Astrophys. 322, 730-746 (1997)
The correction for internal velocity dispersion was made according to Tully and Fouqué (1985).
Heliocentric radial velocities from optical or radio measurements are corrected to the centroid of the Local Group according to Yahil et al.
Radio velocities come essentially from 21-cm line measurements; they have been homogenized and tested for scale, zero-point errors, and reference effect (Bottinelli et al.
aa.springer.de /papers/7322003/2300730/sc2.htm   (780 words)

  
 Precision Radial Velocities: Techniques and Applications   (Site not responding. Last check: 2007-10-21)
Differential velocities between various classes of lines reveal detail about velocity fields and shocks in the atmospheres of Cepheids and provide the raw information needed to construct detailed physical models.
As a first order correction to the Barnes-Evans/Baade-Wesselink method, it is suggested that the amplitude of radial velocity curves be reduced by 10% to better match the motion of the optical continuum forming region.
The shape and amplitude of the radial velocity curve of $\delta$ Cep is shown to have been extremely constant over most of the last century.
www.aas.org /publications/baas/v25n2/aas182/abshtml/S6303.html   (221 words)

  
 [47.04] Radial Velocities of Cepheids and RR Lyraes   (Site not responding. Last check: 2007-10-21)
[47.04] Radial Velocities of Cepheids and RR Lyraes
Radial velocities of variable stars, in particular RR Lyraes and Cepheids, are of great astrophysical importance.
Some years ago, we began a program designed to determine radial velocities of a number of these stars in support of surface brightness distance determinations.
www.aas.org /publications/baas/v33n2/aas198/722.htm   (168 words)

  
 6.2 Determination of Velocity Dispersion and Radial Velocity
The line of sight velocity distribution of the stars in the galaxy (the broadening function) is Gaussian.
The iteration solves for all these three variables, although the radial velocity is not expected to change much.
Therefore, it was tested which template star observations would give the lowest velocity dispersions, and the three best, one observation of each of the stars HD77236, HD176047, and BD were actually used in the Fourier fitting.
www.astro.ku.dk /~milvang/Master/more/thesis/node57.html   (688 words)

  
 Stellar Radial Velocities with SOAR   (Site not responding. Last check: 2007-10-21)
The velocity precision that is science relevant is strongly dependent on the spectral properties and the measurement technique that is applied on them.
In binary mass function determination each radial velocity measurement are naturally time-correlated in the form of a periodic function, therefore the error of individual measurements are less relevant for the science goals since they are combined in some meaningful way.
The internal precision of the velocity measurements is evaluated by synthesizing statistically independent sets of spectra (for each seeing, R, magnitude triplet in a grid) and measuring the velocity scatter for each set.
www.pa.msu.edu /soar/SAC/radvel.html   (504 words)

  
 Wavelength Calibration
The telluric lines are obviously stationary relative to the observer while the photospheric lines are formed in an object moving with a radial velocity relative to the observer.
The difference a-d is the offset of the wavelength of photospheric lines relative to the atmospheric lines and it is due to the non zero radial velocity of the star relative to the observer.
Table 3.3: Measured radial velocities for the T Tauri stars with photospheric lines in their Pa Beta spectra (uncertainties in the measurements within brackets) and values found in the literature.
www.astro.up.pt /users/dfmf/Thesis/Hypertext/node39.html   (887 words)

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