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.

scholarly journals A Campaign for the Detection of Earth-Mass Planets in the Habitable Zone of Alpha Centauri

2012 ◽  
Vol 8 (S293) ◽  
pp. 58-64
Author(s):  
Robert A. Wittenmyer ◽  
Michael Endl ◽  
Christoph Bergmann ◽  
John Hearnshaw ◽  
Stuart I. Barnes ◽  
...  
Keyword(s):  
New Zealand ◽  
High Resolution ◽  
Optical Fibre ◽  
Orbital Stability ◽  
High Signal ◽  
Habitable Zone ◽  
Signal To Noise ◽  
Echelle Spectrograph ◽  
Doppler Method ◽  
Iodine Cell

AbstractWe review the possible formation and orbital stability of Earth-mass or super Earth-mass planets around either of the stars Alpha Centauri A or B and describe a program at Mt John University Observatory using the Doppler method that aims to detect such planets. From New Zealand, we are able to observe the Alpha Centauri system year-round. This is critical in order to acquire data of sufficient quantity and phase coverage to detect the orbit of a terrestrial-mass planet in the habitable zone. Our observations are being made at high resolution (R = 70,000) and high signal-to-noise with the Hercules vacuum echelle spectrograph attached to the 1-m McLellan telescope by a 25-m long optical fibre and using an iodine cell. We discuss the velocity precision and instrumental stability required for success and outline the progress of the observations so far. At present we are collecting about 10,000 observations of each star, A and B, per year with a typical precision of 2.5 m/s per observation.

scholarly journals Chemical abundances of three new Ba stars from the Keck/HIRES spectra

2021 ◽  
Vol 21 (11) ◽  
pp. 278
Author(s):  
Shuai Liu ◽  
Liang Wang ◽  
Jian-Rong Shi ◽  
Zhen-Yu Wu ◽  
Hong-Liang Yan ◽  
...  
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Parameter Space ◽  
Thin Disk ◽  
High Signal ◽  
Velocity Data ◽  
Signal To Noise ◽  
Chemical Abundances ◽  
Radial Velocity Data

Abstract Based on high resolution, high signal-to-noise (S/N) ratio spectra from Keck/HIRES, we have determined abundances of 20 elements for 18 Ba candidates. The parameter space of these stars is in the range of 4880 ≤ T eff ≤ 6050 K, 2.56 ≤ log g ≤ 4.53 dex and − 0.27 ≤ [Fe/H] ≤ 0.09 dex. It is found that four of them can be identified as Ba stars with [s/Fe] > 0.25 dex (s: Sr, Y, Zr, Ba, La, Ce and Nd), and three of them are newly discovered, which include two Ba giants (HD 16178 and HD 22233) and one Ba subgiant (HD 2946). Our results show that the abundances of α, odd and iron-peak elements (O, Na, Mg, Al, Si, Ca, Sc, Ti, Mn, Ni and Cu) for our program stars are similar to those of the thin disk, while the distribution of [hs/ls] (hs: Ba, La, Ce and Nd, ls: Sr, Y and Zr) ratios of our Ba stars is similar to those of the known Ba objects. None of the four Ba stars show clear enhancement in carbon including the known CH subgiant HD 4395. It is found that three of the Ba stars present clear evidence of hosting stellar or sub-stellar companions from the radial velocity data.

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 Public HARPS radial velocity database corrected for systematic errors

2020 ◽  
Vol 636 ◽  
pp. A74 ◽  
Author(s):  
Trifon Trifonov ◽  
Lev Tal-Or ◽  
Mathias Zechmeister ◽  
Adrian Kaminski ◽  
Shay Zucker ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Signal To Noise Ratio ◽  
Auxiliary Information ◽  
Easy Access ◽  
High Signal ◽  
M Dwarfs ◽  
Data Set ◽  
New Public ◽  
Systematic Effects ◽  
User Friendly

Context. The High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph has been mounted since 2003 at the ESO 3.6 m telescope in La Silla and provides state-of-the-art stellar radial velocity (RV) measurements with a precision down to ∼1 m s−1. The spectra are extracted with a dedicated data-reduction software (DRS), and the RVs are computed by cross-correlating with a numerical mask. Aims. This study has three main aims: (i) Create easy access to the public HARPS RV data set. (ii) Apply the new public SpEctrum Radial Velocity AnaLyser (SERVAL) pipeline to the spectra, and produce a more precise RV data set. (iii) Determine whether the precision of the RVs can be further improved by correcting for small nightly systematic effects. Methods. For each star observed with HARPS, we downloaded the publicly available spectra from the ESO archive and recomputed the RVs with SERVAL. This was based on fitting each observed spectrum with a high signal-to-noise ratio template created by coadding all the available spectra of that star. We then computed nightly zero-points (NZPs) by averaging the RVs of quiet stars. Results. By analyzing the RVs of the most RV-quiet stars, whose RV scatter is < 5 m s−1, we find that SERVAL RVs are on average more precise than DRS RVs by a few percent. By investigating the NZP time series, we find three significant systematic effects whose magnitude is independent of the software that is used to derive the RV: (i) stochastic variations with a magnitude of ∼1 m s−1; (ii) long-term variations, with a magnitude of ∼1 m s−1 and a typical timescale of a few weeks; and (iii) 20–30 NZPs that significantly deviate by a few m s−1. In addition, we find small (≲1 m s−1) but significant intra-night drifts in DRS RVs before the 2015 intervention, and in SERVAL RVs after it. We confirm that the fibre exchange in 2015 caused a discontinuous RV jump that strongly depends on the spectral type of the observed star: from ∼14 m s−1 for late F-type stars to ∼ − 3 m s−1 for M dwarfs. The combined effect of extracting the RVs with SERVAL and correcting them for the systematics we find is an improved average RV precision: an improvement of ∼5% for spectra taken before the 2015 intervention, and an improvement of ∼15% for spectra taken after it. To demonstrate the quality of the new RV data set, we present an updated orbital solution of the GJ 253 two-planet system. Conclusions. Our NZP-corrected SERVAL RVs can be retrieved from a user-friendly public database. It provides more than 212 000 RVs for about 3000 stars along with much auxiliary information, such as the NZP corrections, various activity indices, and DRS-CCF products.

scholarly journals Airglow Derived Measurements of Q-Branch Transition Probabilities for Several Hydroxyl Meinel Bands

Atmosphere ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 637 ◽  
Author(s):  
Christoph Franzen ◽  
Patrick Joseph Espy ◽  
Niklas Hofmann ◽  
Robert Edward Hibbins ◽  
Anlaug Amanda Djupvik
Keyword(s):  
High Resolution ◽  
Spontaneous Emission ◽  
Transition Probabilities ◽  
High Signal ◽  
Hitran Database ◽  
Signal To Noise ◽  
Optical Telescope ◽  
Spectroscopic Observations ◽  
Emission Transition ◽  
Airglow Emissions

Spectroscopic measurements of the hydroxyl (OH) airglow emissions are often used to infer neutral temperatures near the mesopause. Correct Einstein coefficients for the various transitions in the OH airglow are needed to calculate accurate temperatures. However, studies from some studys showed experimentally and theoretically that the most commonly used Einstein spontaneous emission transition probabilities for the Q-branch of the OH Meinel (6,2) transition are overestimated. Extending their work to several Δv = 2 and 3 transitions from v′ = 3 to 9, we have determined Einstein coefficients for the first four Q-branch rotational lines. These have been derived from high resolution, high signal to noise spectroscopic observations of the OH airglow in the night sky from the Nordic Optical Telescope. The Q-branch Einstein coefficients calculated from these spectra show that values currently tabulated in the HITRAN database overestimate many of the Q-branch transition probabilities. The implications for atmospheric temperatures derived from OH Q-branch measurements are discussed.

scholarly journals Lithium Abundances in Bright Giant Stars

2000 ◽  
Vol 198 ◽  
pp. 364-365
Author(s):  
Agnès Lèbre ◽  
Patrick de Laverny ◽  
José Renan de Medeiros
Keyword(s):  
High Resolution ◽  
Binary Stars ◽  
Spectroscopic Data ◽  
Radial Velocities ◽  
European Southern Observatory ◽  
Binary Nature ◽  
Giant Stars

We present new high resolution spectroscopic data of the 6707.81 Å Li I line for 117 G and K Bright Giants (class of luminosity II). We derived Lithium abundances that we analysed along the stellar parameters: Teff, M* and Vsini. With the CORAVEL spectrometers (at Observatoire de Haute Provence [OHP] and at European Southern Observatory [ESO]), De Medeiros & Mayor (2000) obtained radial velocities and Vsini with an uncertainty of about 0.3 kms—1 and 2.0 kms—1, respectively. CORAVEL data also provide indication on the binary nature of our sample stars (32% are binary stars).

A Study of the Orbital and Intrinsic Variability of the Double-Lined Spectroscopic Binary β Centauri

2002 ◽  
Vol 185 ◽  
pp. 86-87
Author(s):  
M. Ausseloos ◽  
C. Aerts ◽  
K. Uytterhoeven
Keyword(s):  
High Resolution ◽  
Orbital Motion ◽  
High Signal ◽  
Mass Ratio ◽  
Eccentric Orbit ◽  
Intrinsic Variability ◽  
Signal To Noise ◽  
Orbital Parameters ◽  
Spectroscopic Binary ◽  
First Time

AbstractWe introduce our observational study of the orbital motion of β Cen. Using 463 high signal-to-noise, high-resolution spectra obtained over a timespan of 12 years it is shown that the radial velocity of β Cen varies with an orbital period of 357.0 days. We derive for the first time the orbital parameters of β Cen and find a very eccentric orbit (e = 0.81) and similar component masses with a mass ratio M1/M2 = 1.02. Both the primary and the secondary exhibit periodic line-profile variations.

scholarly journals The well correlated diffuse interstellar bands at λλ 6196, 6614 Å and their possible companions

2020 ◽  
Vol 496 (2) ◽  
pp. 2231-2240
Author(s):  
A Bondar
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
High Resolution ◽  
Aromatic Hydrocarbons ◽  
Correlation Coefficients ◽  
High Signal ◽  
Signal To Noise ◽  
B Stars ◽  
Diffuse Interstellar Bands ◽  
Polycyclic Aromatic ◽  
First Time

ABSTRACT Considered here is the interrelation between five diffuse interstellar bands (DIBs), λλ 5545, 6113, 6196, 6445 and 6614 Å. Two DIBs (λλ 6196 and 6614 Å) are already known as being well correlated with each other; their relation with three other weaker bands is investigated for the first time. To accomplish this task, high-resolution spectra (λ/δλ ≈100 000) with high signal-to-noise ratios (S/N) of 54 hot O–B stars with reddening 0.12–1.45 mag were used. Analysis of measured equivalent widths has allowed us to establish linear dependences and evaluate linear correlation coefficients as high as 0.968–0.988 between the intensities of these five DIBs. Such a degree of correlation may indicate their common origin. Several spacings in wavenumbers found between these DIBs correspond to the energies of vibrational transitions in some polycyclic aromatic hydrocarbons resulting in IR emissions at λλ 16.4, 11.3, 7.7, 6.2 and 3.3 μm.

scholarly journals The Composition of Warm Giants in M 71 and M 5

1988 ◽  
Vol 126 ◽  
pp. 497-498
Author(s):  
Catherine A. Pilachowski ◽  
Christopher Sneden
Keyword(s):  
High Resolution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
High Dispersion ◽  
High Signal ◽  
Signal To Noise

In 1979 a disturbing controversy arose in the field of globular cluster research when Cohen (1980) and Pilachowski, Canterna, and Wallerstein (1980) announced the results of the first high dispersion studies of the composition of giants in the globular clusters M 71 and 47 Tucanae. In contrast to earlier studies, which found metallicities of typically −0.3 and −0.5 dex, these investigators obtained values of −1.3 and −1.1. Since then, many have attempted to redetermine the abundances of M 71 and 47 Tuc to explain the discrepant results. These efforts have all suffered from the absence of high signal-to-noise, high resolution spectra of stars with temperatures above 4300 K.

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