Planets and brown dwarfs around A–F main-sequence stars: performances of radial-velocity surveys with HARPS and first detections

2010 ◽  
Vol 41 ◽  
pp. 99-102 ◽  
Author(s):  
M. Desort ◽  
A.-M. Lagrange ◽  
F. Galland ◽  
S. Udry ◽  
M. Mayor
Keyword(s):  
Radial Velocity ◽  
Main Sequence ◽  
Brown Dwarfs ◽  
Main Sequence Stars

scholarly journals The CORALIE survey for southern extrasolar planets

2019 ◽  
Vol 625 ◽  
pp. A71 ◽  
Author(s):  
E. L. Rickman ◽  
D. Ségransan ◽  
M. Marmier ◽  
S. Udry ◽  
F. Bouchy ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Main Sequence ◽  
Extrasolar Planets ◽  
Brown Dwarfs ◽  
Main Sequence Stars ◽  
Period Range ◽  
Orbital Parameters ◽  
Long Period ◽  
Long Term Trends

Context. Since 1998, a planet-search around main sequence stars within 50 pc in the southern hemisphere has been underway with the CORALIE spectrograph at La Silla Observatory. Aims. With an observing time span of more than 20 yr, the CORALIE survey is able to detect long-term trends in data with masses and separations large enough to select ideal targets for direct imaging. Detecting these giant companion candidates will allow us to start bridging the gap between radial-velocity-detected exoplanets and directly imaged planets and brown dwarfs. Methods. Long-term precise Doppler measurements with the CORALIE spectrograph reveal radial-velocity signatures of massive planetary companions and brown dwarfs on long-period orbits. Results. In this paper, we report the discovery of new companions orbiting HD 181234, HD 13724, HD 25015, HD 92987 and HD 50499. We also report updated orbital parameters for HD 50499b, HD 92788b and HD 98649b. In addition, we confirm the recent detection of HD 92788c. The newly reported companions span a period range of 15.6–40.4 yr and a mass domain of 2.93–26.77 MJup, the latter of which straddles the nominal boundary between planets and brown dwarfs. Conclusions. We report the detection of five new companions and updated parameters of four known extrasolar planets. We identify at least some of these companions to be promising candidates for imaging and further characterisation.

scholarly journals Properties which cannot be explained by Planetary Nebulae's progenitors

1997 ◽  
Vol 180 ◽  
pp. 367-367
Author(s):  
Noam Soker
Keyword(s):  
Main Sequence ◽  
Brown Dwarfs ◽  
Giant Planets ◽  
Main Sequence Stars ◽  
Substellar Objects ◽  
Earth Like Planets ◽  
Low Mass ◽  
Inner Region ◽  
Central Stars

Stellar binary companions account for bipolar PNe (∼ 11% of all PNe1), and some ellipticalls (22%2). The rest of axisymmetrical PNe (40% to 60% of all PNe) are due to substellar objects (planets and brown dwarfs)3. This classification of axi symmetrical PNe suggests that substellar objects are commonly present within several × AU around main sequence stars, and that several substellar objects must be present around most main sequence stars3. Some substellar and low mass stellar companions will enter the primary envelope only as the primary reaches the upper AGB. Thus, the early mass loss episode will be spherical, leading to the formation of a spherical halo around an elliptical inner region. Gas giant planets and brown dwarfs close to the primary, will not allow Earth-like planets to have stable orbits. Systems with no Jupiter-like planets will allow Earth-like planets to be present. These stars will form spherical PNe (10%-20% of all PNe, including spherically ejected PNe that have been deformed by the ISM through which they move4). Systems with substellar objects at large separation, as Jupiter in the solar system, will also allow Earth-like planets to be present. These systems will form PNe with spherical halo. Therefore, life may have been present in planets around the central stars of round PNe and elliptical PNe with round halos.

scholarly journals A Spectroscopic and Photometric Survey for Pre-Main Sequence Binaries

2001 ◽  
Vol 200 ◽  
pp. 165-168 ◽  
Author(s):  
Eike W. Guenther ◽  
Viki Joergens ◽  
Ralph Neuhäuser ◽  
Guillermo Torres ◽  
Natalie Stout Batalha ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Main Sequence ◽  
Spectroscopic Binaries ◽  
Main Sequence Stars ◽  
Current State ◽  
Short Period ◽  
Velocity Variations ◽  
The Masses ◽  
Stellar Masses ◽  
Crucial Test

We give here an overview of the current state of our survey for pre-main sequence spectroscopic binaries. Up to now we have taken 739 spectra of 250 pre-main sequence stars. We find that 8% of the stars show significant radial velocity variations, and are thus most likely spectroscopic binaries. In addition to the targets showing radial velocity variations, 6% of the targets are double-lined spectroscopic binaries i.e., the total fraction of spectroscopic binaries is expected to be about 14%. All short-period SB2s are monitored photometrically in order to search for eclipses. An eclipsing SB2 would allow the direct measurement of the masses of both stellar components. Measurements of the stellar masses together with determinations of the stellar radii are a crucial test of evolutionary tracks of pre-main sequence stars.

scholarly journals The GAPS Programme with HARPS-N at TNG

2018 ◽  
Vol 616 ◽  
pp. A155 ◽  
Author(s):  
A. F. Lanza ◽  
L. Malavolta ◽  
S. Benatti ◽  
S. Desidera ◽  
A. Bignamini ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Cross Correlation ◽  
Main Sequence ◽  
Activity Level ◽  
P Value ◽  
Main Sequence Stars ◽  
Stellar Spectrum ◽  
Stellar Activity ◽  
Binary Weighted ◽  
Low Activity

Aims. Stellar activity is the ultimate source of radial-velocity (hereinafter RV) noise in the search for Earth-mass planets orbiting late-type main-sequence stars. We analyse the performance of four different indicators and the chromospheric index log R′HK in detecting RV variations induced by stellar activity in 15 slowly rotating (υ sin i ≤ 5 km s−1), weakly active (log R′HK ≤ −4.95) solar-like stars observed with the high-resolution spectrograph High Accuracy Radial velocity Planet Searcher for the Northern hemisphere (HARPS-N). Methods. We consider indicators of the asymmetry of the cross-correlation function (CCF) between the stellar spectrum and the binary weighted line mask used to compute the RV, that is the bisector inverse span (BIS), ΔV, and a new indicator Vasy(mod) together with the full width at half maximum (FWHM) of the CCF. We present methods to evaluate the uncertainties of the CCF indicators and apply a kernel regression (KR) between the RV, the time, and each of the indicators to study their capability of reproducing the RV variations induced by stellar activity. Results. The considered indicators together with the KR prove to be useful to detect activity-induced RV variations in ~47 ± 18 percent of the stars over a two-year time span when a significance (two-sided p-value) threshold of one percent is adopted. In those cases, KR reduces the standard deviation of the RV time series by a factor of approximately two. The BIS, the FWHM, and the newly introduced Vasy(mod) are the best indicators, being useful in 27 ± 13, 13 ± 9, and 13 ± 9 percent of the cases, respectively. The relatively limited performances of the activity indicators are related to the very low activity level and υ sin i of the considered stars. For the application of our approach to sun-like stars, a spectral resolution allowing λ/Δλ ≥ 105 and highly stabilized spectrographs are recommended.

scholarly journals A Tale on Two Close Binaries in Pegasus

2014 ◽  
Vol 23 (2) ◽  
Author(s):  
H. V. Şenavcı ◽  
M. Yılmaz ◽  
Ö. Baştürk ◽  
İ. Özavcı ◽  
Ş. Çalışkan ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Main Sequence ◽  
Curve Analysis ◽  
Velocity Curve ◽  
Close Binaries ◽  
Main Sequence Stars ◽  
Radial Velocity Curve ◽  
Contact Binaries ◽  
Effective Temperatures

AbstractWe present the simultaneous light and radial velocity curve analysis of two contact binaries in Pegasus using the Wilson-Devinney code. The following absolute astrophysical parameters are determined: masses, radii and effective temperatures. BB Peg is a W-subtype W UMa-type binary, components of which are main sequence stars with 0.50

scholarly journals Spectroscopic and Photometric Observations of the Southern, Intermediate-Age Clusters NGC 2477 and NGC 2660

1980 ◽  
Vol 85 ◽  
pp. 235-236
Author(s):  
James E. Hesser ◽  
Horace A. Smith
Keyword(s):  
Radial Velocity ◽  
Main Sequence ◽  
Meridional Circulation ◽  
Main Sequence Stars ◽  
Image Tube ◽  
Giant Stars ◽  
Photometric Observations ◽  
Blue Straggler ◽  
The Mean

47 A mm−1 image-tube spectra show that the turnoff region and blue straggler stars in NGC 2477 are not, in general, rapid rotators, as postulated by Hartwick and Hesser (1974) to explain, via mixing induced by meridional circulation, the widely differing photometric metallicity estimates based upon uvbyβ photometry of the main-sequence stars and DDO photometry of the giant stars. However, the discrepant metallicity estimates are largely reconciled by recent revisions in the reddening corrections for the DDO system (Boyle 1979, Janes 1979); and by small color corrections of the type described by Muzzio (1978) and Schmidt and Taylor (1979) applied to the β-photometry. The mean radial velocity is found to be 5.6 kms−1 while the mean Vsini is 105 km s−1. Star “m” is spectroscopically confirmed to be an Am star.

scholarly journals Planetary Systems

1999 ◽  
Vol 172 ◽  
pp. 313-316
Author(s):  
Pawel Artymowicz
Keyword(s):  
Radial Velocity ◽  
Main Sequence ◽  
Direct Evidence ◽  
Planetary System ◽  
Planetary Systems ◽  
Main Sequence Stars ◽  
The Past ◽  
Exoplanetary Systems ◽  
Beta Pictoris

AbstractThe past decade brought direct evidence of the previously surmised exoplanetary systems. A variety of planetary system types exist those around pulsars, around both young and old main-sequence stars (as evidenced by planetesimal disks of the Beta Pictoris-type), and the mature giant exoplanets found in radial velocity surveys. The surprising diversity of the exoplanetary systems is addressed by several theories of their origin.

Stellar Kinematics in Star-Forming Regions

1984 ◽  
Vol 88 ◽  
pp. 263-264
Author(s):  
Robert D. Mathieu ◽  
David W. Latham ◽  
Lee Hartmann
Keyword(s):  
Radial Velocity ◽  
Measurement Errors ◽  
Main Sequence ◽  
Stellar Kinematics ◽  
Late Type ◽  
Stellar Rotation ◽  
Main Sequence Stars ◽  
Central Wavelength ◽  
Star Forming ◽  
Star Forming Regions

High-precision radial-velocity studies of three young, star-forming regions - λ Orionis, NGC 2264 and Taurus-Auriga - are under way; study of the Orion cluster (with L. Marschall, in conjunction with the Yale proper-motion study) is beginning this winter. Single-order (~50 A, central wavelength 5200A) echelle spectra have been obtained for late-type pre-main sequence stars. Due to the spectral peculiarities and stellar rotation associated with pre-main sequence stars, our radial-velocity precisions are often somewhat poorer than those obtained for late-type dwarfs or giants. Measurement errors of 0.7-1.5 km/sec are typical, although some stars do not permit any radial velocity measurement at all. We summarize preliminary findings for each region:

scholarly journals Properties of abundance gradient along the Galactic disk and the role of LAMOST

2013 ◽  
Vol 9 (S298) ◽  
pp. 304-309
Author(s):  
J.L. Hou ◽  
L. Chen ◽  
J.C. Yu ◽  
J. Sellwood ◽  
C. Pryor
Keyword(s):  
Radial Velocity ◽  
Main Sequence ◽  
Milky Way ◽  
Galactic Disk ◽  
Open Cluster ◽  
Dynamical Evolution ◽  
Open Clusters ◽  
Main Sequence Stars ◽  
Abundance Gradient

AbstractIn this paper, we present our recent work on the evolution of abundance gradients along the Milky Way disk based on the Geneva Copenhagen Survey (GCS) and Radial Velocity Experiment (RAVE) data. We will also discuss the role of the LAMOST Milky Way disk survey in clarifying the properties of metallicity breaks observed through open clusters and young tracers along the Milky Way disk. It is believed that the Galactic disk forms inside-out, in which the stellar population at increasing radii is younger and more metal poor. This picture is consistent with most Galactic Chemical Evolution (GCE) models which also predict a tight correlation between the metallicity and age of stars at a given radius. However, it is only a result of “steady state" and no dynamical evolution effects were taken into account. We have selected two stellar samples from GCS and RAVE, each sample contains about 10,000 local thin-disk, main-sequence stars. We use the guiding radius which is determined by the conservation of z-direction angular momentum, to eliminate the blurring effects. And also use the effective temperature of the main sequence stars as a proxy of stellar age. It is shown that the metallicity gradient flattens as the age increases. This is not consistent with our previous GCE prediction, but can be explained by radial mixing effects. In order to further demonstrate the abundance breaks observed in the Galactic disk we have proposed, and have been carrying out, an open cluster survey project based on LAMOST. We plan to observe at least 400 open clusters in the northern Galactic sky. From the observations, we will get uniform parameters for those clusters with radial velocity and metallicities. We anticipate that this uniform open cluster sample could clarify the observed abundance break around the Milky Way disk corotation radius and also give a more robust result concerning the evolution of the abundance gradient.

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