scholarly journals The fiber-fed spectrograph, a tool to detect planets

1999 ◽  
Vol 170 ◽  
pp. 13-21 ◽  
Author(s):  
D. Queloz ◽  
M. Casse ◽  
M. Mayor
Keyword(s):  
Radial Velocity ◽  
Precision Measurements ◽  
Velocity Measurements ◽  
Calibration Technique ◽  
The Stability ◽  
Very High

AbstractThe use of fibers to feed spectrographs is a very efficient way to increase the precision of radial velocity measurements. It has already proved to be successful with the very first detection by the ELODIE fiber-fed spectrograph of the planet orbiting the star 51 Peg. The basic key properties of fibers in the very high radial velocity precision measurements context are described in this review. The ELODIE spectrograph is used to illustrate the thorium simultaneous calibration technique. The use and the effects of a double-scrambler to increase the stability of the slit illumination are also discussed.

scholarly journals High Precision Photometry from EulerCam and TRAPPIST: The Case of WASP-42, WASP-49 and WASP-50

2012 ◽  
Vol 8 (S293) ◽  
pp. 119-121
Author(s):  
Monika Lendl ◽  
Michaël Gillon ◽  
Didier Queloz
Keyword(s):  
Radial Velocity ◽  
High Precision ◽  
Extrasolar Planets ◽  
High Accuracy ◽  
Velocity Measurements ◽  
Very High

AbstractTransiting extrasolar planets provide unmatched insights into the structure and composition of close-in planets. When a planet transits its host star, its radius is known, which together with radial velocity measurements, allows accessing the planetary density. We present results obtained using the Euler and TRAPPIST telescopes that aim at reaching very high accuracy on the parameters derived from transit lightcurves. Here, we show the case of the recently discovered WASP-42b and WASP-49b and new observations of WASP-50b.

scholarly journals Precise Radial-velocity Measurements with a Cassegrain Spectrograph, II: Radial-velocity Determination and Applications

1999 ◽  
Vol 170 ◽  
pp. 68-72 ◽  
Author(s):  
I. V. Ilyin ◽  
R. Duemmler
Keyword(s):  
Radial Velocity ◽  
Data Reduction ◽  
High Accuracy ◽  
Radial Velocities ◽  
Velocity Measurements ◽  
Echelle Spectrograph ◽  
The Stability ◽  
Stability Issues

AbstractWe present our measurements of radial velocities of two stars suspected to have a substellar companion by using observations made with a cassegrain échelle spectrograph. The stability issues and details of the data reduction are discussed in Ilyin & Duemmler (paper I, these proceedings). The results obtained here show that relatively high accuracy of radial velocity determinations is also attainable for cassegrain spectrographs.

scholarly journals CAFE2: an upgrade to the CAFE high-resolution spectrograph. Commissioning results and new public pipeline

2019 ◽  
Vol 491 (3) ◽  
pp. 4496-4508 ◽  
Author(s):  
J Lillo-Box ◽  
J Aceituno ◽  
S Pedraz ◽  
G Bergond ◽  
D Galadí-Enríquez ◽  
...  
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Room Temperature ◽  
Velocity Measurements ◽  
Dwarf Stars ◽  
New Public ◽  
The Stability ◽  
Reduced Data ◽  
Calar Alto ◽  
Active Temperature

ABSTRACT CAFE is a high-resolution spectrograph with high-precision radial velocity capabilities mounted at the 2.2 m telescope of Calar Alto Observatory. It suffered from strong degradation after 4 yr of operations and it has now been upgraded. The upgrades of the instrument (now named CAFE2) aimed at recovering the throughput and improving the stability due to the installation of a new grating, an active temperature control in the isolated coudé room, and a new scrambling system. In this paper, we present the results of the new commissioning of the instrument and a new pipeline (CAFExtractor) that provides the user with fully reduced data including radial velocity measurements of FGK dwarf stars. The commissioning results show a clear improvement in the instrument performance. The room temperature is now stabilized down to 5 mK during one night and below 50 mK over two months. CAFE2 now provides 3 m s−1 precision on the reference ThAr frames and the on-sky tests provide a radial velocity precision of 8 m s−1 during one night (for S/N > 50). The throughput of the instrument is now back to nominal values with an efficiency of around 15 per cent at 550 nm. The limiting magnitude of the instrument for a 1 h exposure and S/N = 20 is V = 15. With all these properties, CAFE enters into the small family of high-resolution spectrographs at 2–4 m telescopes capable of reaching radial velocity precisions below 10 m s−1.

Modeling of External Pressure Gradient Influence on the Stability of Disturbances in the Boundary Layers of Compressed Gas

2013 ◽  
Vol 8 (4) ◽  
pp. 64-75
Author(s):  
Sergey Gaponov ◽  
Natalya Terekhova
Keyword(s):  
Mach Number ◽  
Pressure Gradient ◽  
Boundary Layers ◽  
Leading Edge ◽  
External Pressure ◽  
Transition To Turbulence ◽  
Compressed Gas ◽  
High Mach ◽  
The Stability ◽  
Very High

This work continues the research on modeling of passive methods of management of flow regimes in the boundary layers of compressed gas. Authors consider the influence of pressure gradient on the evolution of perturbations of different nature. For low Mach number M = 2 increase in pressure contributes to an earlier transition of laminar to turbulent flow, and, on the contrary, drop in the pressure leads to a prolongation of the transition to turbulence. For high Mach number M = 5.35 found that the acoustic disturbances exhibit a very high dependence on the sign and magnitude of the external gradient, with a favorable gradient of the critical Reynolds number becomes smaller than the vortex disturbances, and at worst – boundary layer is destabilized directly on the leading edge

scholarly journals Precision stellar radial velocity measurements with FIDEOS at the ESO 1-m telescope of La Silla

2018 ◽  
Vol 477 (4) ◽  
pp. 5041-5051 ◽  
Author(s):  
L Vanzi ◽  
A Zapata ◽  
M Flores ◽  
R Brahm ◽  
M Tala Pinto ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Velocity Measurements

STUDIES ON HOMOGENEOUS FIRST ORDER GAS REACTIONS: II. THE DECOMPOSITION OF THE ISOMERIC ESTERS BUTYLIDENE DIACETATE AND ETHYLIDENE DIPROPIONATE

1932 ◽  
Vol 6 (4) ◽  
pp. 417-427 ◽  
Author(s):  
C. C. Coffin
Keyword(s):  
Activation Energy ◽  
Degrees Of Freedom ◽  
Maximum Energy ◽  
Velocity Measurements ◽  
First Order ◽  
Gas Reactions ◽  
Points Of View ◽  
The Stability ◽  
Future Work ◽  
Internal Degrees Of Freedom

The gaseous decompositions of the esters butylidene diacetate and ethylidene dipropionate have been studied from points of view previously outlined in papers on the decomposition of ethylidene diacetate (2, 3). The decomposition velocities have been measured at initial pressures of from 5 to 56 cm. of mercury and at temperatures between 211 and 265 °C. The reactions are homogeneous and of the first order. They agree with the Arrhenius equation and give 100% yields (within experimental error) of an aldehyde and an anhydride. The preparation of the compounds and improvements in the technique of the velocity measurements are described.While the specific velocities of the three reactions at any temperature are somewhat different, their activation energies are the same. It is suggested that in the case of such simple reactions, which are strictly localized within the molecular structure, the activation energy can be identified as the maximum energy that the reactive bonds may possess and still exist; i.e., it may be taken as a measure of the stability of the bonds which are broken in the reaction. The suggestion is also made that for a series of reactions which have the same activation energy, the specific velocities can be taken as a relative measure of the number of internal degrees of freedom that contribute to the energy of activation. On the basis of these assumptions it becomes possible to use reaction-velocity measurements for the investigation of intramolecular energy exchange. The theoretical significance of the data is further discussed and the scope of future work in this connection is indicated.The monomolecular velocity constants (sec−1) of the decomposition of ethylidene diacetate, ethylidene dipropionate and butylidene diacetate are given respectively by the equations [Formula: see text], [Formula: see text], and [Formula: see text].

scholarly journals Spectroscopic Orbit of the Eclipsing Binary BD +52°2009

1999 ◽  
Vol 170 ◽  
pp. 325-330
Author(s):  
B. Khalesseh
Keyword(s):  
Correlation Function ◽  
Light Curve ◽  
Radial Velocity ◽  
Physical Model ◽  
Cross Correlation ◽  
Cross Correlation Function ◽  
Physical Parameters ◽  
Mass Ratio ◽  
Velocity Measurements ◽  
Eclipsing Binary

AbstractNew radial velocity measurements of the Algol-type eclipsing binary BD +52 °2009, based on Reticon observations, are presented. The velocity measures are based on fitting theoretical profiles, generated by a physical model of the binary, to the observed cross-correlation function (ccf). Such profiles match this function very well, much better in fact than Gaussian profiles, which are generally used. Measuring the ccf’s with Gaussian profiles yields the following results: mp sin3i = 2.55 ± 0.05m⊙, ms sin3i = 1.14 ± 0.03m⊙, (ap + as) sin i = 7.34 ± 0.05R⊙, and mp/ms = 2.23 ± 0.05. However, measuring the ccf’s with theoretical profiles yields a mass ratio of 2.33 and following results: mp sin3i = 2.84 ± 0.05m⊙, ms sin3i = 1.22 ± 0.03m⊙, (ap + as) sin i = 7.56 ± 0.05R⊙. The system has a semi-detached configuration. By combining the solution of a previously published light curve with the spectroscopic orbit, one can obtain the following physical parameters: mp = 2.99m⊙, ms3 = 1.28m⊙, < Tp >= 9600K, < Ts >= 5400K, < Rp >= 2.35R⊙, < Rs >= 2.12R⊙. The system consists of an A0 primary and a G2 secondary.

A Theoretical Analysis of Floating Bush Journal Bearing With Axial Oil Film Rupture Being Considered

2002 ◽  
Vol 124 (3) ◽  
pp. 494-505 ◽  
Author(s):  
Kiyoshi Hatakenaka ◽  
Masato Tanaka ◽  
Kenji Suzuki
Keyword(s):  
Steady State ◽  
Reynolds Equation ◽  
Speed Ratio ◽  
Shaft Speed ◽  
Film Rupture ◽  
State Behavior ◽  
Oil Film ◽  
Rotordynamic Coefficients ◽  
The Stability ◽  
Very High

A new modified Reynolds equation is derived with centrifugal force acting on the hydrodynamic oil film being considered. This equation, together with a cavitation model, is used to obtain the steady-state equilibrium and calculate the rotordynamic coefficients of lightly loaded floating bush journal bearings operating at very high shaft speeds. The bush-to-shaft speed ratio and the linear cross-coupling spring coefficients of the inner oil film is found to decrease with the increase in shaft speed as the axial oil film rupture develops in the inner oil film. The present model can give reasonable explanation to the steady-state behavior and the stability behavior of the bearing observed in actual machines.

The stability of onoratoite, Sb8O11Cl2, in the supergene environment

2014 ◽  
Vol 78 (7) ◽  
pp. 1671-1675 ◽  
Author(s):  
Adam J. Roper ◽  
Peter Leverett ◽  
Timothy D. Murphy ◽  
Peter A. Williams
Keyword(s):  
Significant Influence ◽  
Secondary Phase ◽  
Low Ph ◽  
Stable Phase ◽  
Supergene Zone ◽  
A Value ◽  
Solubility Studies ◽  
The Stability ◽  
Very High

AbstractSynthesis and solubility studies of onoratoite have been undertaken to determine the role of this rare secondary phase in the immobilization of Sb and the conditions responsible for its formation in the supergene zone. Solubility studies were undertaken at 298.15 K. A value of ΔGfθ (Sb8O11Cl2, s, 298.15 K) = –2576 ±12 kJ mol–1 was derived. Calculations involving sénarmontite, Sb2O3, klebelsbergite, Sb4O4SO4(OH)2 and schafarzikite, FeSb2O4, show that onoratoite is a thermodynamically stable phase only at negligible activities of SO42–(aq) and low activities of Fe2+(aq), at low pH and very high activities of Cl–(aq). This explains why onoratoite is such a rare secondary phase and why it cannot exert any significant influence on the dispersion of Sb in the supergene environment.

scholarly journals Densified Pupil Spectrograph as High-precision Radial Velocimetry: From Direct Measurement of the Universe’s Expansion History to Characterization of Nearby Habitable Planet Candidates

2022 ◽  
Vol 163 (2) ◽  
pp. 63
Author(s):  
Taro Matsuo ◽  
Thomas P. Greene ◽  
Mahdi Qezlou ◽  
Simeon Bird ◽  
Kiyotomo Ichiki ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Direct Measurement ◽  
High Precision ◽  
Resolving Power ◽  
Line Of Sight ◽  
High Dispersion ◽  
Velocity Measurements ◽  
Habitable Planet ◽  
Airy Disk

Abstract The direct measurement of the universe’s expansion history and the search for terrestrial planets in habitable zones around solar-type stars require extremely high-precision radial-velocity measures over a decade. This study proposes an approach for enabling high-precision radial-velocity measurements from space. The concept presents a combination of a high-dispersion densified pupil spectrograph and a novel line-of-sight monitor for telescopes. The precision of the radial-velocity measurements is determined by combining the spectrophotometric accuracy and the quality of the absorption lines in the recorded spectrum. Therefore, a highly dispersive densified pupil spectrograph proposed to perform stable spectroscopy can be utilized for high-precision radial-velocity measures. A concept involving the telescope’s line-of-sight monitor is developed to minimize the change of the telescope’s line of sight over a decade. This monitor allows the precise measurement of long-term telescope drift without any significant impact on the Airy disk when the densified pupil spectra are recorded. We analytically derive the uncertainty of the radial-velocity measurements, which is caused by the residual offset of the lines of sight at two epochs. We find that the error could be reduced down to approximately 1 cm s−1, and the precision will be limited by another factor (e.g., wavelength calibration uncertainty). A combination of the high-precision spectrophotometry and the high spectral resolving power could open a new path toward the characterization of nearby non-transiting habitable planet candidates orbiting late-type stars. We present two simple and compact highly dispersed densified pupil spectrograph designs for cosmology and exoplanet sciences.

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