scholarly journals Kinematics of Short-Period Mira Variables - A Progress Report

1989 ◽  
Vol 106 ◽  
pp. 56-56
Author(s):  
J. Hron
Keyword(s):  
Stellar Populations ◽  
Progress Report ◽  
Radial Velocities ◽  
Correlation Technique ◽  
Echelle Spectrograph ◽  
Mira Variables ◽  
Short Period ◽  
First Results ◽  
Visual Magnitude

First results of an observing program recently started at the Figl Observatory for Astrophysics, Austria, are presented. Radial velocities derived by a correlation technique from the TiO bandheads near 7050 Å will be used to identify the stellar populations present among the short period (P ≤ 200d) Mira variables. From the first observations with the Reticon-equipped Echelle Spectrograph of the FOA (resolution 0.3 Å at 7000 Å) we conclude that for Mira stars with a limiting visual magnitude of about 10m velocities can be determined with an external accuracy of 6 km/s.

scholarly journals Absolute Radial Velocities by Cross-Correlation with Synthetic Spectra

1999 ◽  
Vol 170 ◽  
pp. 91-97 ◽  
Author(s):  
J. Skuljan ◽  
J. B. Hearnshaw ◽  
P. L. Cottrell
Keyword(s):  
Cross Correlation ◽  
Zero Point ◽  
Radial Velocities ◽  
Correlation Technique ◽  
Late Type ◽  
Echelle Spectrograph ◽  
Stellar Spectra ◽  
Synthetic Spectra ◽  
Cross Correlation Technique ◽  
The Continuum

AbstractPrecise absolute radial velocities have been measured for several hundred late-type stars at Mt John University Observatory with the 1-m telescope, fiber-fed échelle spectrograph, and Thomson CCD. Six échelle orders in the green (5000−5600 Å) are used. Many delicate steps have been undertaken in order to maintain exactly the same conditions, both in recording and reducing the spectra, over a period of 18 months. A cross-correlation technique with theoretical spectra computed by R. L. Kurucz has been chosen to determine the absolute radial velocities. Blue sky spectra have been used to monitor systematic zero-point fluctuations from one observing run to another. An additional correlation between the measured velocities and average number of A/D units in the continuum has been discovered and used for fine adjustments, significantly improving the results. A random uncertainty of 10–20 ms−1 has been achieved for stellar spectra having intrinsically constant radial velocities.

scholarly journals A Study of the Short-Period Cepheid EU Tauri

1985 ◽  
Vol 82 ◽  
pp. 98-99
Author(s):  
W. P. Gieren
Keyword(s):  
Light Curve ◽  
Velocity Curve ◽  
Radial Velocities ◽  
Correlation Technique ◽  
Fourier Decomposition ◽  
Classical Cepheid ◽  
Photometric Observations ◽  
Short Period ◽  
Johnson System ◽  
Better Than

EU Tauri is a classical Cepheid with one of the shortest period known. A Fourier decomposition study of its V light curve by Simon S Lee (1981) revealed a peculiar position in phase-period diagrams, very similar to the star SU Cas which is probably an overtone pulsator (Gieren, 1982). This suggested the possibility that EU Tau might be another galactic overtone pulsator. In order to investigate this question, some 100 new photometric observations of this star on the UBVRI (Johnson) system were obtained with the #2 0.9m telescope of KPNO. Simultaneously, 43 CCD spectra of the star were secured on the Coudé feed telescope of KPNO which were measured for radial velocities using a correlation technique. These velocities have an internal accuracy of better than 0.5 km/s and define a complete velocity curve of EU Tau.

scholarly journals An unusually low density ultra-short period super-Earth and three mini-Neptunes around the old star TOI-561

2020 ◽  
Author(s):  
G Lacedelli ◽  
L Malavolta ◽  
L Borsato ◽  
G Piotto ◽  
D Nardiello ◽  
...  
Keyword(s):  
Transit Time ◽  
Time Variation ◽  
Planetary System ◽  
Radial Velocities ◽  
Low Density ◽  
Outer Planets ◽  
Short Period ◽  
The Stability

Abstract Based on HARPS-N radial velocities (RVs) and TESS photometry, we present a full characterisation of the planetary system orbiting the late G dwarf After the identification of three transiting candidates by TESS, we discovered two additional external planets from RV analysis. RVs cannot confirm the outer TESS transiting candidate, which would also make the system dynamically unstable. We demonstrate that the two transits initially associated with this candidate are instead due to single transits of the two planets discovered using RVs. The four planets orbiting TOI-561 include an ultra-short period (USP) super-Earth (TOI-561 b) with period Pb = 0.45 d, mass Mb = 1.59 ± 0.36 M⊕ and radius Rb = 1.42 ± 0.07 R⊕, and three mini-Neptunes: TOI-561 c, with Pc = 10.78 d, Mc = 5.40 ± 0.98 M⊕, Rc = 2.88 ± 0.09 R⊕; TOI-561 d, with Pd = 25.6 d, Md = 11.9 ± 1.3 M⊕, Rd = 2.53 ± 0.13 R⊕; and TOI-561 e, with Pe = 77.2 d, Me = 16.0 ± 2.3 M⊕, Re = 2.67 ± 0.11 R⊕. Having a density of 3.0 ± 0.8 g cm−3, TOI-561 b is the lowest density USP planet known to date. Our N-body simulations confirm the stability of the system and predict a strong, anti-correlated, long-term transit time variation signal between planets d and e. The unusual density of the inner super-Earth and the dynamical interactions between the outer planets make TOI-561 an interesting follow-up target.

scholarly journals Progress Report on the Southern Proper Motion Program

1995 ◽  
Vol 166 ◽  
pp. 357-357
Author(s):  
I. Platais ◽  
T. M. Girard ◽  
V. Kozhurina-Platais ◽  
R. A. Mendez ◽  
W. F. Van Altena ◽  
...  
Keyword(s):  
Reference Frame ◽  
Proper Motion ◽  
Systematic Errors ◽  
Progress Report ◽  
Model Choice ◽  
Plate Model ◽  
Field Independent ◽  
The Status ◽  
First Results ◽  
Galaxy Model

We present the status of the Yale/San Juan Southern Proper Motion program (SPM) which is the southern hemisphere extension of the Lick Observatory Northern Proper Motion program with respect to faint galaxies (Platais et al., 1993). To date, measurements and reductions in the South Galactic Pole region comprising ≈ 1000 square-degrees on the sky have been finished. At this stage of the SPM program particular attention has been paid to the plate model choice along with an assessment of and accounting for systematic errors. For our establishing of a secondary reference frame we have noticed the presence of a potentially dangerous effect, so–called field–independent coma which is caused by lens decentering. We acknowledge the superb Hipparcos preliminary positions without which such analysis would be virtually impossible. The SPM data at the SGP region have also been used to constrain a multi–component Galaxy model. First results of this analysis are presented.

scholarly journals Radial-velocity search and statistical studies for short-period planets in the Pleiades open cluster

2020 ◽  
Vol 72 (6) ◽  
Author(s):  
Takuya Takarada ◽  
Bun’ei Sato ◽  
Masashi Omiya ◽  
Yasunori Hori ◽  
Michiko S Fujii
Keyword(s):  
Radial Velocity ◽  
Open Cluster ◽  
Open Clusters ◽  
Occurrence Rate ◽  
High Dispersion ◽  
Echelle Spectrograph ◽  
Upper Limit ◽  
Stringent Constraint ◽  
Short Period ◽  
Statistical Studies

Abstract We report on a radial-velocity search for short-period planets in the Pleiades open cluster. We observed 30 Pleiades member stars at the Okayama Astrophysical Observatory with the High Dispersion Echelle Spectrograph. To evaluate and mitigate the effects of stellar activity on radial-velocity (RV) measurements, we computed four activity indicators (full width at half maximum, Vspan, Wspan, and SHα). Among our sample, no short-period planet candidates were detected. Stellar intrinsic RV jitter was estimated to be 52 m s−1, 128 m s−1, and 173 m s−1 for stars with $v$ sin i of 10 km s−1, 15 km s−1, and 20 km s−1, respectively. We determined the planet occurrence rate from our survey and set the upper limit to 11.4% for planets with masses 1–13 MJUP and period 1–10 d. To set a more stringent constraint on the planet occurrence rate, we combined the result of our survey with those of other surveys targeting open clusters with ages in the range 30–300 Myr. As a result, the planet occurrence rate in young open clusters was found to be less than 7.4%, 2.9%, and 1.9% for planets with an orbital period of 3 d and masses of 1–5, 5–13, and 13–80 MJUP, respectively.

scholarly journals The Young Massive Star Cluster Westerlund 2 Observed with MUSE. I. First Results on the Cluster Internal Motion from Stellar Radial Velocities

2018 ◽  
Vol 156 (5) ◽  
pp. 211 ◽  
Author(s):  
Peter Zeidler ◽  
Elena Sabbi ◽  
Antonella Nota ◽  
Anna Pasquali ◽  
Eva K. Grebel ◽  
...  
Keyword(s):  
Massive Star ◽  
Star Cluster ◽  
Radial Velocities ◽  
Internal Motion ◽  
First Results

scholarly journals Adaptation of Docobo’s Method for the Calculation of Orbits of Spectroscopic-Interferometric Binaries with Mixed Data

1992 ◽  
Vol 135 ◽  
pp. 220-222
Author(s):  
J.A. Docobo ◽  
J.F. Ling ◽  
C. Prieto
Keyword(s):  
Observational Data ◽  
Radial Velocities ◽  
Polar Coordinates ◽  
Mixed Data ◽  
Short Period ◽  
Visual Binaries

AbstractBased on Docobo’s method for the calculation of orbits of visual binaries, an algorithm is presented for the calculation of short-period orbits when observational data comprise radial velocities and polar coordinates. The method is applied to some examples.

Spectroscopic Binaries in the Halo

1992 ◽  
Vol 135 ◽  
pp. 158-160 ◽  
Author(s):  
David W. Latham ◽  
Tsevi Mazeh ◽  
Robert P. Stefanik ◽  
Robert J. Davis ◽  
Bruce W. Carney ◽  
...  
Keyword(s):  
Proper Motion ◽  
Main Sequence ◽  
Radial Velocities ◽  
Spectroscopic Binaries ◽  
Variable Velocity ◽  
Short Period ◽  
The Galaxy ◽  
Elliptical Orbits

AbstractFor almost 1500 stars in the Carney-Latham survey of proper-motion stars we have accumulated about 20,000 precise radial velocities. Already we have orbital solutions for more than 150 spectroscopic binaries in this sample, and about 100 additional binary candidates with variable velocity. We find that among the metal-poor halo field stars in this sample the frequency of short-period spectroscopic binaries is indistinguishable from that of the disk. The distribution of eccentricity versus period shows evidence for tidal circularization on the main sequence. For the binaries more metal poor than [m/H] = −1.6 there is a clean transition from circular to elliptical orbits at a period of about 19 days. For longer periods the distribution of eccentricity is the same as for stars in the disk of the Galaxy.

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