scholarly journals Periodic Variability of the Brown Dwarf Kelu-1

2003 ◽  
Vol 211 ◽  
pp. 457-458
Author(s):  
F. J. Clarke ◽  
C. G. Tinney ◽  
S. T. Hodgkin
Keyword(s):  
Radial Velocity ◽  
Rotation Period ◽  
Velocity Measurements ◽  
Brown Dwarf ◽  
Photometric Variability ◽  
Spectroscopic Observations ◽  
Significant Variability ◽  
Show Evidence ◽  
Molecular Lines ◽  
Rule Out

We present results of two observing campaigns aimed at characterising variability of the L2 brown dwarf Kelu-1. The first campaign in March 2000 detected photometric variability at the 1.2% level, with a strong period of 1.8 hours. Followup spectroscopic observations with the VLT in February 2002 show no evidence of significant variability in the dust sensitive molecular lines, but do show evidence for variability in the EW(Hα) with a period of 1.8 hours. Radial velocity measurements rule out a close substellar companion. Kelu-1 appears to be a single brown dwarf with a rotation period of 1.8 hours.

scholarly journals A possible dividing line between massive planets and brown-dwarf companions

2010 ◽  
Vol 6 (S276) ◽  
pp. 117-120 ◽  
Author(s):  
Johannes Sahlmann ◽  
Damien Ségransan ◽  
Didier Queloz ◽  
Stéphane Udry
Keyword(s):  
Radial Velocity ◽  
Formation Process ◽  
Brown Dwarfs ◽  
Mass Range ◽  
Velocity Measurements ◽  
Brown Dwarf ◽  
The One ◽  
The Individual ◽  
Dividing Line

AbstractBrown dwarfs are intermediate objects between planets and stars. The lower end of the brown-dwarf mass range overlaps with the one of massive planets and therefore the distinction between planets and brown-dwarf companions may require to trace the individual formation process. We present results on new potential brown-dwarf companions of Sun-like stars, which were discovered using CORALIE radial-velocity measurements. By combining the spectroscopic orbits and Hipparcos astrometric measurements, we have determined the orbit inclinations and therefore the companion masses for many of these systems. This has revealed a mass range between 25 and 45 Jupiter masses almost void of objects, suggesting a possible dividing line between massive planets and sub-stellar companions.

scholarly journals Direct Imaging Of Long Period Radial Velocity Targets With NICI

2013 ◽  
Vol 8 (S299) ◽  
pp. 66-67
Author(s):  
Graeme S. Salter ◽  
Chris G. Tinney ◽  
Robert A. Wittenmyer ◽  
James S. Jenkins ◽  
Hugh R.A. Jones ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Near Infrared ◽  
Minimum Mass ◽  
Post Processing ◽  
Velocity Measurements ◽  
Brown Dwarf ◽  
Direct Imaging ◽  
Parameter Spaces ◽  
Long Period ◽  
Imaging Parameter

AbstractWe are finally entering an era where radial velocity and direct imaging parameter spaces are starting to overlap. Radial velocity measurements provide us with a minimum mass for an orbiting companion (the mass as a function of the inclination of the system). By following up these long period radial velocity detections with direct imaging we can determine whether a trend seen is due to an orbiting planet at low inclination or an orbiting brown dwarf at high inclination. In the event of a non-detection we are still able to put a limit on the maximum mass of the orbiting body. The Anglo-Australian Planet Search is one of the longest baseline radial velocity planet searches in existence, amongst its targets are many that show long period trends in the data. Here we present our direct imaging survey of these objects with our results to date. ADI Observations have been made using NICI (Near Infrared Coronagraphic Imager) on Gemini South and analysed using an in house, LOCI-like, post processing.

scholarly journals Rapid spectroscopic and photometric variability in the Be star Alpha Eridani

1994 ◽  
Vol 162 ◽  
pp. 106-107
Author(s):  
N.V. Leister ◽  
E. Janot-Pacheco ◽  
M.T.C. Buck ◽  
M.P. Dias ◽  
A.M. Hubert ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Time Scale ◽  
Preliminary Report ◽  
Photometric Variability ◽  
Spectroscopic Observations ◽  
Photometric And Spectroscopic Observations ◽  
Be Star ◽  
Spotted Star ◽  
Activity Cycles ◽  
Comprehensive Study

We present here a preliminary report on the analysis of simultaneous photometric and spectroscopic observations of the Be star α Eri, taken during 1992 at the Laboratório Nacional de Astrofísica. α Eri (Archenar, HR472, HD10144, B3–4 III-IV) is the brightest Be star in the sky. It shows activity cycles in a time scale of a few years. Balona et al. (1987) presented a comprehensive study of the star based on photometric and spectroscopic observations. They found a periodicity of 1.26 days in both radial velocity and light variations and argued that a spotted star rotating at this period is the simplest working model that explains the observations.

scholarly journals Searching for Photometric Variability across the L, T & Y Dwarf Sequence

2013 ◽  
Vol 8 (S299) ◽  
pp. 301-302
Author(s):  
A. Rajan ◽  
P. A. Wilson ◽  
J. Patience ◽  
F. Pont ◽  
R. J. De Rosa
Keyword(s):  
Spectral Range ◽  
Rotation Period ◽  
Brown Dwarfs ◽  
Cloud Layer ◽  
Significant Fraction ◽  
Similar Process ◽  
Brown Dwarf ◽  
Photometric Variability

AbstractTo investigate the atmospheres of ultracool brown dwarfs with temperatures covering the range of transiting and directly imaged planets, we have monitored a sample of 76 L, T and Y brown dwarfs for infrared photometric variability. This survey was conducted in the J-band using both the SOFI camera on the 3.5-m NTT and the SWIRC camera on the 6.5-m MMT. Each target was observed for a period ranging from 2.0 hours to 6.0 hours, covering a significant fraction of the expected rotation period. Breakup of the iron and silicate clouds into a patchy cloud layer has been suggested as an explanation for the variability of several objects identified at the L/T transition, and a similar process with sulfide clouds may be manifest in T/Y transition objects; our data provides the first test of these patchy cloud scenarios across the entire brown dwarf spectral range.

scholarly journals Orbital and spectral analysis of the benchmark brown dwarf HD 4747B

2019 ◽  
Vol 631 ◽  
pp. A107 ◽  
Author(s):  
S. Peretti ◽  
D. Ségransan ◽  
B. Lavie ◽  
S. Desidera ◽  
A.-L. Maire ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Brown Dwarfs ◽  
Evolutionary Models ◽  
High Contrast ◽  
Imaging Data ◽  
Velocity Measurements ◽  
Brown Dwarf ◽  
Contrast Imaging ◽  
Semi Major Axis ◽  
Dynamical Mass

Context. The study of high-contrast imaged brown dwarfs and exoplanets depends strongly on evolutionary models. To estimate the mass of a directly imaged substellar object, its extracted photometry or spectrum is used and adjusted with model spectra together with the estimated age of the system. These models still need to be properly tested and constrained. HD 4747B is a brown dwarf close to the H burning mass limit, orbiting a nearby (d = 19.25 ± 0.58 pc), solar-type star (G9V); it has been observed with the radial velocity method for over almost two decades. Its companion was also recently detected by direct imaging, allowing a complete study of this particular object. Aims. We aim to fully characterize HD 4747B by combining a well-constrained dynamical mass and a study of its observed spectral features in order to test evolutionary models for substellar objects and to characterize its atmosphere. Methods. We combined the radial velocity measurements of High Resolution Echelle Spectrometer (HIRES) and CORALIE taken over two decades and high-contrast imaging of several epochs from NACO, NIRC2, and SPHERE to obtain a dynamical mass. From the SPHERE data we obtained a low-resolution spectrum of the companion from Y to H band, and two narrow band-width photometric measurements in the K band. A study of the primary star also allowed us to constrain the age of the system and its distance. Results. Thanks to the new SPHERE epoch and NACO archival data combined with previous imaging data and high-precision radial velocity measurements, we were able to derive a well-constrained orbit. The high eccentricity (e = 0.7362 ± 0.0025) of HD 4747B is confirmed, and the inclination and the semi-major axis are derived (i = 47.3 ± 1.6°, a = 10.01 ± 0.21 au). We derive a dynamical mass of mB = 70.0 ± 1.6 MJup, which is higher than a previous study but in better agreement with the models. By comparing the object with known brown dwarfs spectra, we derive a spectral type of L9 and an effective temperature of 1350 ± 50 K. With a retrieval analysis we constrain the oxygen and carbon abundances and compare them with the values from the HR 8799 planets.

scholarly journals WASP-166b: a bloated super-Neptune transiting a V  = 9 star

2019 ◽  
Vol 488 (3) ◽  
pp. 3067-3075 ◽  
Author(s):  
Coel Hellier ◽  
D R Anderson ◽  
A H M J Triaud ◽  
F Bouchy ◽  
A Burdanov ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Rotation Axis ◽  
Rotation Period ◽  
Magnetic Activity ◽  
Stellar Rotation ◽  
Velocity Measurements

Abstract We report the discovery of WASP-166b, a super-Neptune planet with a mass of 0.1 MJup (1.9 MNep) and a bloated radius of 0.63 RJup. It transits a V = 9.36, F9V star in a 5.44-d orbit that is aligned with the stellar rotation axis (sky-projected obliquity angle λ = 3 ± 5 deg). Variations in the radial-velocity measurements are likely the result of magnetic activity over a 12-d stellar rotation period. WASP-166b appears to be a rare object within the ‘Neptune desert’.

scholarly journals Late-Type Ca II Emission-Line Stars in the Southern Hemisphere

1983 ◽  
Vol 71 ◽  
pp. 75-76
Author(s):  
A.C. Collier
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Spectroscopic Study ◽  
Emission Line ◽  
Wave Phenomenon ◽  
Spectroscopic Binaries ◽  
Late Type ◽  
Velocity Measurements ◽  
Photometric Variability ◽  
Rs Canum Venaticorum Binaries

ABSTRACTThe results of a photometric and spectroscopic study of twenty-three late-type southern stars with strong Ca II H and K emission are presented.The presence of photometric variability, with similar properties to the photometric wave phenomenon seen in the RS Canum Venaticorum binaries, is noted in thirteen of the fifteen stars for which extensive photometry was obtained. Of twenty stars for which high resolution radial velocity measurements were obtained, ten are found to be single-lined and seven are found to be double-lined spectroscopic binaries. The periods range from 0.66 up to 53-9 days.

scholarly journals The CARMENES search for exoplanets around M dwarfs

2019 ◽  
Vol 627 ◽  
pp. A49 ◽  
Author(s):  
M. Zechmeister ◽  
S. Dreizler ◽  
I. Ribas ◽  
A. Reiners ◽  
J. A. Caballero ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Near Infrared ◽  
Radial Velocities ◽  
Slow Rotation ◽  
M Dwarfs ◽  
Photometric Variability ◽  
Photometric Measurements ◽  
The Masses ◽  
Rule Out

Context. Teegarden’s Star is the brightest and one of the nearest ultra-cool dwarfs in the solar neighbourhood. For its late spectral type (M7.0 V), the star shows relatively little activity and is a prime target for near-infrared radial velocity surveys such as CARMENES. Aims. As part of the CARMENES search for exoplanets around M dwarfs, we obtained more than 200 radial-velocity measurements of Teegarden’s Star and analysed them for planetary signals. Methods. We find periodic variability in the radial velocities of Teegarden’s Star. We also studied photometric measurements to rule out stellar brightness variations mimicking planetary signals. Results. We find evidence for two planet candidates, each with 1.1 M⊕ minimum mass, orbiting at periods of 4.91 and 11.4 d, respectively. No evidence for planetary transits could be found in archival and follow-up photometry. Small photometric variability is suggestive of slow rotation and old age. Conclusions. The two planets are among the lowest-mass planets discovered so far, and they are the first Earth-mass planets around an ultra-cool dwarf for which the masses have been determined using radial velocities.

Spectroscopic Observations of Visual Double Stars

1965 ◽  
Vol 5 ◽  
pp. 109-111
Author(s):  
Frederick R. West
Keyword(s):  
Radial Velocity ◽  
High Dispersion ◽  
Velocity Difference ◽  
Spectrograph Slit ◽  
Spectroscopic Observations ◽  
Double Stars ◽  
Visual Double Stars ◽  
Relative Orbit ◽  
Two Component ◽  
Star Images

There are certain visual double stars which, when close to a node of their relative orbit, should have enough radial velocity difference (10-20 km/s) that the spectra of the two component stars will appear resolved on high-dispersion spectrograms (5 Å/mm or less) obtainable by use of modern coudé and solar spectrographs on bright stars. Both star images are then recorded simultaneously on the spectrograph slit, so that two stellar components will appear on each spectrogram.

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