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 Precise Radial Velocity Measurements with a Cassegrain Spectrograph, I: Wavelength calibration

1999 ◽  
Vol 170 ◽  
pp. 63-67
Author(s):  
I. V. Ilyin ◽  
R. Duemmler
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Cross Correlation ◽  
Time Dependent ◽  
Instrumental Effects ◽  
Velocity Measurements ◽  
Echelle Spectrograph ◽  
Optical Telescope ◽  
La Palma ◽  
Observational Strategy

AbstractWe briefly describe the instrumental effects which affect the accuracy of the radial velocity measurements. We have implemented several methods to correct for the instability effects and improve the accuracy of the measurements. These include modifications of the observational strategy and a time-dependent wavelength solution as well as a discussion of the error of the offset from cross-correlation. These methods are applied to observations obtained with the high resolution échelle spectrograph SOFIN mounted at the Cassegrain focus of the alt-azimuth 2.56-m Nordic Optical Telescope, La Palma, Canary Islands.

scholarly journals Study of Spectroscopic Binaries with the Objective Prism Method

1983 ◽  
Vol 62 ◽  
pp. 104-107
Author(s):  
Frank Gieseking
Keyword(s):  
Radial Velocity ◽  
Frequency Distribution ◽  
Radial Velocities ◽  
Spectroscopic Binaries ◽  
Steep Decrease ◽  
Visual Magnitude ◽  
Objective Prism ◽  
The Individual ◽  
Large Telescopes

The frequency distribution of SB’s over apparent visual magnitude emerging from the catalogue of Batten et. al. (1978) shows a very steep decrease of the number of spectroscopically detected SB’s already for such bright stars of magnitude 7. Considering the number of all stars in the individual magnitude intervals, we find a kind of completeness parameter of the spectroscopic surveys: If we scale it somewhat optimistically at 100% between 0 and 3 mag, we see a 50% decrease of the completeness of our knowledge of stellar radial velocities already for stars fainter than 4.5 mag.This situation is mainly due to the fact that the measurement of radial velocities with conventional slit spectrographs is extremely laborious, requiring long exposure times at large telescopes for the exposure of only one spectrum at a time. – Therefore more efficient methods for radial velocity determinations of fainter stars are urgently needed.

scholarly journals EUVE J0825-16.3 and EUVE J1501-43.6: Two dMe Double–Lined Spectroscopic Binaries

2006 ◽  
Vol 2 (S240) ◽  
pp. 690-696
Author(s):  
D. Montes ◽  
I. Crespo-Chacón ◽  
M.C. Gálvez ◽  
M.J. Fernández-Figueroa
Keyword(s):  
High Resolution ◽  
Orbital Period ◽  
Binary Systems ◽  
Cross Correlation ◽  
Rotational Velocity ◽  
Spectroscopic Binaries ◽  
Balmer Lines ◽  
First Time ◽  
Orbital Solution ◽  
Similar Intensity

AbstractHigh-resolution echelle spectroscopic observations taken with the FEROS spectrograph at the ESO 2.2-m telescope confirm the binary nature of the dMe stars EUVE J0825−16.3 and EUVE J1501−43.6, previously reported by Christian & Mathioudakis (2002). In these binary systems, emission of similar intensity from both components is detected in the Na i D1 & D2, He i D3, Ca II H&K, Ca II IRT and Balmer lines. We have determined precise radial velocities by cross-correlation with radial velocity standard stars, which have allowed us to obtain for the first time the orbital solution of these systems. Both binaries consist of two nearly equal M0V components with an orbital period shorter than 3.5 days. We have analyzed the behaviour of the chromospheric activity indicators (variability and possible flares). In addition, we have determined its rotational velocity and kinematics.

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 follow-up for confirmation and characterization of transiting exoplanets

2008 ◽  
Vol 4 (S253) ◽  
pp. 129-139 ◽  
Author(s):  
François Bouchy ◽  
Claire Moutou ◽  
Didier Queloz ◽  
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Space Mission ◽  
High Resolution Spectroscopy

AbstractRadial Velocity follow-up is essential to establish or exclude the planetary nature of a transiting companion as well as to accurately determine its mass. Here we present some elements of an efficient Doppler follow-up strategy, based on high-resolution spectroscopy, devoted to the characterization of transiting candidates. Some aspects and results of the radial velocity follow-up of the CoRoT space mission are presented in order to illustrate the strategy used to deal with the zoo of transiting candidates.

scholarly journals K2-141 b

2018 ◽  
Vol 612 ◽  
pp. A95 ◽  
Author(s):  
O. Barragán ◽  
D. Gandolfi ◽  
F. Dai ◽  
J. Livingston ◽  
C. M. Persson ◽  
...  
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
High Precision ◽  
Orbital Period ◽  
Total Mass ◽  
Iron Composition ◽  
Short Period

We report on the discovery of K2-141 b (EPIC 246393474 b), an ultra-short-period super-Earth on a 6.7 h orbit transiting an active K7 V star based on data from K2 campaign 12. We confirmed the planet’s existence and measured its mass with a series of follow-up observations: seeing-limited MuSCAT imaging, NESSI high-resolution speckle observations, and FIES and HARPS high-precision radial-velocity monitoring. K2-141 b has a mass of 5.31 ± 0.46 M⊕ and radius of 1.54−0.09+0.10 R⊕, yielding a mean density of 8.00−1.45+1.83 g cm−3 and suggesting a rocky-iron composition. Models indicate that iron cannot exceed ~70% of the total mass. With an orbital period of only 6.7 h, K2-141 b is the shortest-period planet known to date with a precisely determined mass.

scholarly journals Precision versus Accuracy: some astrophysical and operational limitations

1999 ◽  
Vol 170 ◽  
pp. 52-57
Author(s):  
R. E. M. Griffin
Keyword(s):  
High Resolution ◽  
Wavelength Range ◽  
Spectral Type ◽  
Cross Correlation ◽  
Systematic Errors ◽  
Radial Velocities ◽  
High Dispersion ◽  
Low Level ◽  
Separate Category ◽  
Wide Wavelength Range

AbstractThe measurement of accurate radial velocities for A- or B-type dwarfs poses a separate category of problems: the small number of suitable lines, the wide wavelength range over which such lines are distributed, thermal broadening, rotational broadening, line distortions caused by rotating spots, spectrum variations due to obvious duplicity, and low-level velocity variations due to undetected companion spectra. Moreover, the fact that A- and B-type spectra fall into very distinct groups, each with its own sub-set of the above problems, means that it may be both difficult and unsatisfactory to specify velocity standards, since intrinsic uncertainties caused by differences in spectral type may exceed the measuring errors. The investigation summarized here into the nature and magnitude of some of these intrinsic errors employs wide spans of high-resolution, high-dispersion spectra of Sirius and Vega as ‘natural’ templates. Attention is also drawn to systematic errors which may arise (a) when modelling a cross-correlation ‘dip’ and (b) whenever a spectrum or a cross-correlation dip is measured in the unavoidable presence of another such spectrum or dip.

scholarly journals The Keck I/HIRES and TNG/SARG Radial Velocity Survey of Speckle Binaries

2011 ◽  
Vol 7 (S282) ◽  
pp. 472-473
Author(s):  
Milena Ratajczak ◽  
Maciej Konacki ◽  
Shrinivas R. Kulkarni ◽  
Matthew W. Muterspaugh
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Binary Stars ◽  
Radial Velocities ◽  
High Signal ◽  
Signal To Noise ◽  
Echelle Spectrograph ◽  
Data Set ◽  
Multiple Star ◽  
Triple Star

AbstractA sample of about 160 speckle binary stars was observed with the Keck I telescope and its Échelle HIRES spectrograph over the years 2003-2007 in an effort to detect substellar and planetary companions to components of binary and multiple star systems. This data set was supplemented with the data obtained at the TNG telescope equipped with the SARG Échelle spectrograph over the years 2006-2007. The high-resolution (R = 65000 for HIRES and R = 86000 for SARG) and high signal-to-noise (typically 75-150) spectra were used to derive radial velocities of the components of the observed speckle binaries. Here, we present a summary of this effort, which includes the discovery of new triple star systems and improved orbital solutions of a few known binaries.

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 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.

Sign in / Sign up

Export Citation Format

Share Document