scholarly journals Radius Determination for Nine Short Period Cepheids

1985 ◽  
Vol 82 ◽  
pp. 34-37
Author(s):  
G. Burki
Keyword(s):  
Small Amplitude ◽  
Radial Velocities ◽  
Short Period

From November, 1981 to March, 1982, nine Pop I and Pop II cepheids of periods between 1.5 and 4.2 days have been monitored, in Geneva photometry from La Silla Observatory (Chile) and in radial velocities from the Haute-Provence Observatory (France). These cepheids are listed in Table 1. Figure 1 shows an example of the light, colour and velocity curves for EU Tau, a small amplitude cepheid with a period of 2.10 days.

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 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.

scholarly journals Spectroscopic Binaries in the Open Cluster M67

1992 ◽  
Vol 135 ◽  
pp. 155-157 ◽  
Author(s):  
David W. Latham ◽  
Robert D. Mathieu ◽  
Alejandra A.E. Milone ◽  
Robert J. Davis
Keyword(s):  
Circular Orbit ◽  
Main Sequence ◽  
Open Cluster ◽  
Radial Velocities ◽  
Spectroscopic Binaries ◽  
Eccentric Orbit ◽  
Circular Orbits ◽  
Blue Stragglers ◽  
Short Period ◽  
Blue Straggler

AbstractFor almost 400 members of M67 we have accumulated about 5,000 precise radial velocities. Already we have orbital solutions for more than 32 spectroscopic binaries in M67. Many of these orbits were derived by combining the Palomar and CfA observations, thus extending the time coverage to more than 20 years. The distribution of eccentricity versus period shows evidence for tidal circularization on the main sequence. The transition from circular orbits is fairly clean. Excluding the blue stragglers, the first eccentric orbit has a period of 11.0 days, while the last circular orbit has a period of 12.4 days. For longer periods the distribution of eccentricity is the same as for field stars. The blue straggler S1284 has an eccentric orbit despite its short period of 4.2 days.

scholarly journals HR 7308, A Short Period Cepheid With Variable Amplitude

1980 ◽  
Vol 58 ◽  
pp. 429-430
Author(s):  
G. Burki ◽  
M. Mayor
Keyword(s):  
Small Amplitude ◽  
Variable Amplitude ◽  
Short Period

HR 7308 is a F6 lb-11 star of 6th magnitude. Semi-regular photometric variations were detected by Breger (1969) , Percy et al. (1979) find that this star is a new small-amplitude Cepheid, and Burki and Mayor (1980) obtain a period of 1.49107 d. and detect a strongly variable amplitude.

Structural Characterization of Composition-Modulated ZnSel-xTex Epitaxial Films

1995 ◽  
Vol 417 ◽  
Author(s):  
S. P. Ahrenkiel ◽  
M. H. Bode ◽  
M. M. Al-Jassim ◽  
H. Luo ◽  
S. H. Xin ◽  
...  
Keyword(s):  
Cross Sections ◽  
Small Amplitude ◽  
Molecular Beam ◽  
Growth Direction ◽  
Epitaxial Films ◽  
Modulation Amplitude ◽  
Transmission Electron ◽  
Short Period ◽  
Strain Modulation

AbstractWe examine the microstructure of short-period (14–31 Å) composition modulations in epitaxial ZnSel-xTex ([email protected]) films grown by molecular-beam epitaxy (MBE) on vicinal (001) GaAs. Transmission electron microscope (TEM) images of cross-sections reveal highly-periodic contrast along the growth direction throughout the full thicknesses of the films (over 2 μm) that corresponds to a nearly sinusoidal variation between Se- and Te-rich compositions. Growth of ZnSe1-xTex at 285°C on substrates tilted 4° toward [1111 maximizes the strength and regularity of the modulation. Using dynamical electron-diffraction simulations, we estimate a modulation amplitude of [email protected](7) in a sample showing strong modulation. We assume a small amplitude of strain modulation to fit the experimental data.

scholarly journals HD 213885b: a transiting 1-d-period super-Earth with an Earth-like composition around a bright (V = 7.9) star unveiled by TESS

2019 ◽  
Vol 491 (2) ◽  
pp. 2982-2999 ◽  
Author(s):  
Néstor Espinoza ◽  
Rafael Brahm ◽  
Thomas Henning ◽  
Andrés Jordán ◽  
Caroline Dorn ◽  
...  
Keyword(s):  
Bulk Composition ◽  
Radial Velocities ◽  
Minimum Mass ◽  
Good Target ◽  
Short Period

ABSTRACT We report the discovery of the 1.008-d, ultrashort period (USP) super-Earth HD 213885b (TOI-141b) orbiting the bright (V = 7.9) star HD 213885 (TOI-141, TIC 403224672), detected using photometry from the recently launched TESS mission. Using FEROS, HARPS, and CORALIE radial velocities, we measure a precise mass of 8.8 ± 0.6 M⊕ for this 1.74 ± 0.05 R⊕ exoplanet, which provides enough information to constrain its bulk composition – similar to Earth’s but enriched in iron. The radius, mass, and stellar irradiation of HD 213885b are, given our data, very similar to 55 Cancri e, making this exoplanet a good target to perform comparative exoplanetology of short period, highly irradiated super-Earths. Our precise radial velocities reveal an additional 4.78-d signal which we interpret as arising from a second, non-transiting planet in the system, HD 213885c, whose minimum mass of 19.9 ± 1.4 M⊕ makes it consistent with being a Neptune-mass exoplanet. The HD 213885 system is very interesting from the perspective of future atmospheric characterization, being the second brightest star to host an USP transiting super-Earth (with the brightest star being, in fact, 55 Cancri). Prospects for characterization with present and future observatories are discussed.

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.

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