Cross-Correlation Spectrocsopy Using Coravel

1984 ◽  
Vol 88 ◽  
pp. 35-48
Author(s):  
M. Mayor
Keyword(s):  
Magnetic Fields ◽  
Radial Velocity ◽  
Mass Exchange ◽  
Orbital Period ◽  
Cross Correlation ◽  
Correlation Spectroscopy ◽  
Radial Velocities ◽  
Total Absence ◽  
Oscillation Modes ◽  
Visual Binaries

AbstractSeveral studies are reviewed to illustrate the possibilities of cross-correlation spectroscopy to derive rotational velocities, macroturbulence, metallicities, magnetic fields and information on oscillation modes.The validity of radial-velocities of SB2 systems derived from the cross-correlation device has sometimes been criticized. The total absence of any basis to this criticism can easily be demonstrated. Indeed, this method is well suited to the study of SB2 with low radial velocity amplitudes, as for example, visual binaries.Finally, as a result of different radial-velocity surveys carried out with CORAVEL, the eccentricity-period relations are discussed, showing the concurrent influence of the tidal circularization, circularization by mass-exchange and the dependence of the initial eccentricity distribution with the orbital period.

scholarly journals TODCOR: A Two-Dimensional Correlation of a Composite Spectrum to Derive the Radial Velocities of its Components

1992 ◽  
Vol 135 ◽  
pp. 164-166
Author(s):  
Tsevi Mazeh ◽  
Shay Zucker
Keyword(s):  
Radial Velocity ◽  
Cross Correlation ◽  
Radial Velocities ◽  
Two Dimensional ◽  
One Dimensional ◽  
Independent Variables ◽  
Doppler Shifts ◽  
Correlation Algorithm ◽  
Potential Difficulty ◽  
The One

Cross correlation is a frequently used technique to obtain the Doppler shifts of digitized celestial spectra. This method, suggested by Tonry & Davis (1979), cross correlates the observed spectrum against an assumed template, and obtains the stellar radial velocity by the location of the correlation maximum (Wyatt 1985). The technique finds the correct radial velocity even for extremely low S/N spectra.Spectra composed of two components present a potential difficulty to this technique. The cross correlation of these spectra usually displays a double peak which can not be resolved whenever the relative velocity of the two components is small. To overcome this difficulty, we developed TODCOR — a new TwO-Dimensional CORrelation algorithm which can simultaneously derive the Doppler shifts of the two components.TODCOR assumes that the observed spectrum is a combination of two known spectra with unknown shifts. Following the one-dimensional technique, the algorithm calculates the correlation of the observed spectrum against a set of combinations of two templates, with all possible shifts. The correlation, thus, is a two-dimensional function, whose two independent variables are the radial velocities of the two components. The location of the maximum of this function corresponds to the actual Doppler shifts of the two components.

scholarly journals Radial Velocity Observations of Binary Stars

1983 ◽  
Vol 62 ◽  
pp. 93-103
Author(s):  
C. D. Scarfe
Keyword(s):  
Radial Velocity ◽  
Binary Stars ◽  
Velocity Measurement ◽  
Cross Correlation ◽  
Radial Velocities ◽  
Measuring Instruments ◽  
Great Stability ◽  
Visual Binary Stars ◽  
Radial Velocity Measurement

AbstractThis review considers three main areas, leaving several others to be discussed in more detail in the contributed papers of this session.1.The need for spectrographs and measuring instruments of great stability for long-term projects such as radial velocity observations of visual binary stars.2.The use of cross-correlation devices, both analog (radial velocity scanners) and digital, for radial velocity measurement.3.The use of comparison spectra impressed directly onto the starlight and of polarisation instruments as means to very precise radial velocities.

scholarly journals Radial Velocities of SS Cygni

1979 ◽  
Vol 53 ◽  
pp. 489-493
Author(s):  
R. J. Stover
Keyword(s):  
Radial Velocity ◽  
Emission Line ◽  
Absorption Line ◽  
Orbital Period ◽  
Radial Velocities ◽  
Orbital Elements ◽  
Velocity Measurements ◽  
Light Spectrum ◽  
Minimum Light ◽  
Spectroscopic Binary

SS Cygni was found by Joy (1956) to be a spectroscopic binary with an orbital period of about 6-1/2 hours. At minimum light it has mv=12 and is the brightest member of the dwarf nova class of variables. The minimum light spectrum reveals faint, narrow absorption lines of a G- or K-type star along with strong, broad emission lines of hydrogen, helium, and calcium which are produced by an accretion disk surrounding a white dwarf star. Joy’s radial velocities were not very accurate. Nevertheless, he was able to estimate the orbital elements, finding 115 km/s for the absorption line K-velocity and 122 km/s for the emission line K-velocity. In addition, he derived an orbital period of 0276244. Later minimum light observations by Walker and Chincarini (1968) were too few to be able to improve the orbital elements. Kiplinger (1979) refined the emission line radial velocities but was not able to remeasure the faint absorption line spectrum. This paper presents new radial velocity measurements of both the emission and absorption line spectra of SS Cygni at minimum light, and is the first thorough investigation of this star’s radial velocity variations in more than 20 years. The accuracy of the radial velocity curves has been greatly improved. We also find that Joy’s orbital period is in error by nearly two minutes.

scholarly journals High precision radial-velocity measurements of late-type evolved stars

1999 ◽  
Vol 170 ◽  
pp. 204-210 ◽  
Author(s):  
I.N. Cummings ◽  
J.B. Hearnshaw ◽  
P.M. Kilmartin ◽  
A.C. Gilmore
Keyword(s):  
Radial Velocity ◽  
High Precision ◽  
Spectral Type ◽  
Cross Correlation ◽  
Radial Velocities ◽  
High Dispersion ◽  
Late Type ◽  
Velocity Measurements ◽  
Evolved Stars ◽  
Type K

AbstractHigh dispersion spectra for 44 southern evolved stars of spectral type K or M have been obtained. From these observations relative radial velocities of 50 m/s precision have been obtained by the method of digital cross-correlation. This method of achieving precise relative radial velocities for late-type stars, and the problems encountered in its use, are discussed. Using this method, statistically significant radial-velocity variations have been found. Two of the observed stars have their precise radial velocities presented and the potential mechanisms of their variation examined.

scholarly journals Comparison of Selected Methods for Radial Velocity Measurements

2006 ◽  
Vol 2 (S240) ◽  
pp. 486-489
Author(s):  
Štefan Parimucha ◽  
Petr Škoda
Keyword(s):  
Radial Velocity ◽  
Line Profile ◽  
Cross Correlation ◽  
Radial Velocities ◽  
Be Stars ◽  
Velocity Measurements ◽  
Stellar Spectra ◽  
Advantages And Disadvantages ◽  
Profile Fitting ◽  
Correlation Line

AbstractWe present a comparison of selected methods for measuring radial velocities in stellar spectra. We compare cross-correlation, line-profile fitting with Gauss, Lorentz and Voigt functions and a less-known mirroring method. We discuss their applicability and precision and indicate their advantages and disadvantages. The mirroring method proved to be useful for the analysis of Be stars, but is not implemented in any major astronomical packages.

scholarly journals Search for associations containing young stars (SACY)

2020 ◽  
Vol 645 ◽  
pp. A30
Author(s):  
S. Zúñiga-Fernández ◽  
A. Bayo ◽  
P. Elliott ◽  
C. Zamora ◽  
G. Corvalán ◽  
...  
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Cross Correlation ◽  
Young Stars ◽  
Radial Velocities ◽  
Spectroscopic Binaries ◽  
Substellar Objects ◽  
Apparent Variation ◽  
Stellar Associations

Context. Nearby young associations offer one of the best opportunities for a detailed study of the properties of young stellar and substellar objects thanks to their proximity (<200 pc) and age (∼5−150 Myr). Previous works have identified spectroscopic (<5 au) binaries, close (5−1000 au) visual binaries, and wide or extremely wide (1000−100 000 au) binaries in the young associations. In most of the previous analyses, single-lined spectroscopic binaries (SB1) were identified based on radial velocities variations. However, this apparent variation may also be caused by mechanisms unrelated to multiplicity. Aims. We seek to update the spectroscopy binary fraction of the Search for Associations Containing Young stars (SACY) sample, taking into consideration all possible biases in our identification of binary candidates, such as activity and rotation. Methods. Using high-resolution spectroscopic observations, we produced ∼1300 cross-correlation functions (CCFs) to disentangle the previously mentioned sources of contamination. The radial velocity values we obtained were cross-matched with the literature and then used to revise and update the spectroscopic binary (SB) fraction in each object of the SACY association. In order to better describe the CCF profile, we calculated a set of high-order cross-correlation features to determine the origin of the variations in radial velocities. Results. We identified 68 SB candidates from our sample of 410 objects. Our results hint that at the possibility that the youngest associations have a higher SB fraction. Specifically, we found sensitivity-corrected SB fractions of 22−11+15% for ϵ Cha, 31−14+16% for TW Hya and 32−8+9% for β Pictoris, in contrast to the five oldest associations we have sampled (∼35−125 Myr) which are ∼10% or lower. This result seems independent of the methodology used to asses membership to the associations. Conclusions. The new CCF analysis, radial velocity estimates, and SB candidates are particularly relevant for membership revision of targets in young stellar associations. These targets would be ideal candidates for follow-up campaigns using high-resolution techniques to confirm binarity, resolve orbits, and, ideally, calculate dynamical masses. Additionally, if the results on the SB fraction in the youngest associations were confirmed, it could hint at a non-universal multiplicity among SACY associations.

scholarly journals Astrometric Radial Velocities From Hipparcos

1998 ◽  
Vol 11 (1) ◽  
pp. 564-564
Author(s):  
D. Dravins ◽  
L. Lindegren ◽  
S. Madsen ◽  
J. Holmberg
Keyword(s):  
Radial Velocity ◽  
High Precision ◽  
Radial Velocities ◽  
Radial Motion ◽  
Spectral Lines ◽  
Parallel Program ◽  
Stellar Surface ◽  
Space Astrometry ◽  
Stellar Motion ◽  
Surface Convection

Abstract Space astrometry now permits accurate determinations of stellar radial motion, without using spectroscopy. Although the feasibility of deducing astrometric radial velocities from geometric projection effects was realized already by Schlesinger (1917), only with Hipparcos has it become practical. Such a program has now been carried out for the moving clusters of Ursa Major, Hyades, and Coma Berenices. Realized inaccuracies reach about 300 m/s (Dravins et al. 1997). Discrepancies between astrometric and spectroscopic radial velocities reveal effects (other than stellar motion) that affect wavelength positions of spectral lines. Such are caused by stellar surface convection, and by gravitational redshifts. A parallel program (Gullberg & Dravins 1997) is analyzing high-precision spectroscopic radial velocities for different spectral lines in these stars, using the ELODIE radial-velocity instrument atHaute-Provence.

scholarly journals Fluorescence Cross-Correlation Spectroscopy Yields True Affinity and Binding Kinetics of Plasmodium Lactate Transport Inhibitors

2021 ◽  
Vol 14 (8) ◽  
pp. 757
Author(s):  
Iga Jakobowska ◽  
Frank Becker ◽  
Stefano Minguzzi ◽  
Kerrin Hansen ◽  
Björn Henke ◽  
...  
Keyword(s):  
Rate Constants ◽  
Cross Correlation ◽  
Fluorescent Protein ◽  
Correlation Spectroscopy ◽  
Confocal Imaging ◽  
Binding Kinetics ◽  
Acceptor Site ◽  
Lactate Transport ◽  
Entry Site ◽  
Hydrogen Bond Acceptor

Blocking lactate export in the parasitic protozoan Plasmodium falciparum is a novel strategy to combat malaria. We discovered small drug-like molecules that inhibit the sole plasmodial lactate transporter, PfFNT, and kill parasites in culture. The pentafluoro-3-hydroxy-pent-2-en-1-one BH296 blocks PfFNT with nanomolar efficiency but an in vitro selected PfFNT G107S mutation confers resistance against the drug. We circumvented the mutation by introducing a nitrogen atom as a hydrogen bond acceptor site into the aromatic ring of the inhibitor yielding BH267.meta. The current PfFNT inhibitor efficiency values were derived from yeast-based lactate transport assays, yet direct affinity and binding kinetics data are missing. Here, we expressed PfFNT fused with a green fluorescent protein in human embryonic kidney cells and generated fluorescent derivatives of the inhibitors, BH296 and BH267.meta. Using confocal imaging, we confirmed the location of the proposed binding site at the cytosolic transporter entry site. We then carried out fluorescence cross-correlation spectroscopy measurements to assign true Ki-values, as well as kon and koff rate constants for inhibitor binding to PfFNT wildtype and the G107S mutant. BH296 and BH267.meta gave similar rate constants for binding to PfFNT wildtype. BH296 was inactive on PfFNT G107S, whereas BH267.meta bound the mutant protein albeit with weaker affinity than to PfFNT wildtype. Eventually, using a set of PfFNT inhibitor compounds, we found a robust correlation of the results from the biophysical FCCS binding assay to inhibition data of the functional transport assay.

scholarly journals Tidally induced stellar oscillations: converting modelled oscillations excited by hot Jupiters into observables

2020 ◽  
Vol 500 (2) ◽  
pp. 2711-2731
Author(s):  
Andrew Bunting ◽  
Caroline Terquem
Keyword(s):  
Radial Velocity ◽  
Orbital Period ◽  
Planetary Systems ◽  
Velocity Signal ◽  
Convective Flux ◽  
Hot Jupiters ◽  
Stellar Oscillations ◽  
Orbital Periods ◽  
Hot Jupiter

ABSTRACT We calculate the conversion from non-adiabatic, non-radial oscillations tidally induced by a hot Jupiter on a star to observable spectroscopic and photometric signals. Models with both frozen convection and an approximation for a perturbation to the convective flux are discussed. Observables are calculated for some real planetary systems to give specific predictions. The photometric signal is predicted to be proportional to the inverse square of the orbital period, P−2, as in the equilibrium tide approximation. However, the radial velocity signal is predicted to be proportional to P−1, and is therefore much larger at long orbital periods than the signal corresponding to the equilibrium tide approximation, which is proportional to P−3. The prospects for detecting these oscillations and the implications for the detection and characterization of planets are discussed.

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