scholarly journals Stellar activity of planetary host star HD 189733

2008 ◽  
Vol 4 (S253) ◽  
pp. 462-465
Author(s):  
I. Boisse ◽  
C. Moutou ◽  
A. Vidal-Madjar ◽  
F. Bouchy ◽  
F. Pont ◽  
...  
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
High Precision ◽  
Velocity Gradient ◽  
Orbital Motion ◽  
Spectral Lines ◽  
Stellar Surface ◽  
Stellar Activity ◽  
Orbital Parameters

AbstractExoplanet search programs need to study how to disentangle radial-velocity (RV) variations due to Doppler motion and the noise induced by stellar activity. We monitored the active K2V HD 189733 with the high-resolution SOPHIE spectrograph (OHP, France). We refined the orbital parameters of HD 189733b and put limitations on the eccentricity and on a long-term velocity gradient. We subtracted the orbital motion of the planet and compared the variability of activity spectroscopic indices (HeI, Hα, Ca II H&K lines) to the evolution of the RV residuals and the shape of spectral lines. All are in agreement with an active stellar surface in rotation. We used such correlations to correct for the RV jitter due to stellar activity. This results in achieving a high precision on the orbital parameters, with a semi-amplitude: K=200.56±0.88m⋅s−1 and a derived planet mass of MP=1.13±0.03 MJup.

scholarly journals Astrometric Radial Velocities From Hipparcos

1998 ◽  
Vol 11 (1) ◽  
pp. 564-564
Author(s):  
D. Dravins ◽  
L. Lindegren ◽  
S. Madsen ◽  
J. Holmberg
Keyword(s):  
Radial Velocity ◽  
High Precision ◽  
Radial Velocities ◽  
Radial Motion ◽  
Spectral Lines ◽  
Parallel Program ◽  
Stellar Surface ◽  
Space Astrometry ◽  
Stellar Motion ◽  
Surface Convection

Abstract Space astrometry now permits accurate determinations of stellar radial motion, without using spectroscopy. Although the feasibility of deducing astrometric radial velocities from geometric projection effects was realized already by Schlesinger (1917), only with Hipparcos has it become practical. Such a program has now been carried out for the moving clusters of Ursa Major, Hyades, and Coma Berenices. Realized inaccuracies reach about 300 m/s (Dravins et al. 1997). Discrepancies between astrometric and spectroscopic radial velocities reveal effects (other than stellar motion) that affect wavelength positions of spectral lines. Such are caused by stellar surface convection, and by gravitational redshifts. A parallel program (Gullberg & Dravins 1997) is analyzing high-precision spectroscopic radial velocities for different spectral lines in these stars, using the ELODIE radial-velocity instrument atHaute-Provence.

A Study of the Orbital and Intrinsic Variability of the Double-Lined Spectroscopic Binary β Centauri

2002 ◽  
Vol 185 ◽  
pp. 86-87
Author(s):  
M. Ausseloos ◽  
C. Aerts ◽  
K. Uytterhoeven
Keyword(s):  
High Resolution ◽  
Orbital Motion ◽  
High Signal ◽  
Mass Ratio ◽  
Eccentric Orbit ◽  
Intrinsic Variability ◽  
Signal To Noise ◽  
Orbital Parameters ◽  
Spectroscopic Binary ◽  
First Time

AbstractWe introduce our observational study of the orbital motion of β Cen. Using 463 high signal-to-noise, high-resolution spectra obtained over a timespan of 12 years it is shown that the radial velocity of β Cen varies with an orbital period of 357.0 days. We derive for the first time the orbital parameters of β Cen and find a very eccentric orbit (e = 0.81) and similar component masses with a mass ratio M1/M2 = 1.02. Both the primary and the secondary exhibit periodic line-profile variations.

scholarly journals The Long-term Variation in the RV Tauri Star U Mon

1995 ◽  
Vol 155 ◽  
pp. 409-410 ◽  
Author(s):  
Karen R. Pollard ◽  
P. L. Cottrell
Keyword(s):  
High Resolution ◽  
Light Curve ◽  
Radial Velocity ◽  
Tauri Star ◽  
Short Term ◽  
Instability Strip ◽  
Term Variation ◽  
Velocity Variations

The RV Tauri stars are semiregular pulsating variables located in the brightest part of the Cepheid II instability strip. They have a characteristic light curve of alternating deep and shallow minima. A subset of the RV Tauri stars (the RVb subclass) exhibit long-term (500 to 2600 day) light and radial velocity variations. Although it is well established that the short-term variations are due to pulsations, the long-term behaviour is not well understood.BVRI photometry and high-resolution spectra of U Mon (the brightest member of the RVb subclass) were obtained at the Mt John University Observatory (MJUO) between 1990 Aug and 1994 May. The light and colour curves obtained clearly show the long-term variation in U Mon (Fig. 1(a) and (b)). The reddest colours occur slightly later than the long-term minimum in the light curve. The short-term light and colour variations are ‘damped’ at the long-term minimum.

scholarly journals Proxima’s orbit around α Centauri

2017 ◽  
Vol 598 ◽  
pp. L7 ◽  
Author(s):  
P. Kervella ◽  
F. Thévenin ◽  
C. Lovis
Keyword(s):  
Radial Velocity ◽  
High Precision ◽  
Orbital Period ◽  
Triple System ◽  
Orbital Motion ◽  
The Sun ◽  
Proper Motions ◽  
Velocity Measurements ◽  
Degree Of Confidence ◽  
High Degree

Proxima and α Centauri AB have almost identical distances and proper motions with respect to the Sun. Although the probability of such similar parameters is, in principle, very low, the question as to whether they actually form a single gravitationally bound triple system has been open since the discovery of Proxima one century ago. Owing to HARPS high-precision absolute radial velocity measurements and the recent revision of the parameters of the α Cen pair, we show that Proxima and α Cen are gravitationally bound with a high degree of confidence. The orbital period of Proxima is ≈ 550 000 yr. With an eccentricity of 0.50+0.08-0.09, Proxima comes within 4.3+1.1-0.9 kau of α Cen at periastron, and is currently close to apastron (13.0+0.3-0.1 kau). This orbital motion may have influenced the formation or evolution of the recently discovered planet orbiting Proxima, as well as circumbinary planet formation around α Cen.

scholarly journals A Search for Planetary-Mass Companions to Nearby Stars

1989 ◽  
Vol 8 ◽  
pp. 109-110
Author(s):  
Bruce Campbell
Keyword(s):  
Mass Spectrum ◽  
Radial Velocity ◽  
High Precision ◽  
Low Level ◽  
Planetary Mass ◽  
Nearby Stars

AbstractNine of 18 stars observed with a high precision radial velocity technique show long term, low level variations which imply the presence of companions in the range of 1 to 10 Jupiter masses. These companions could represent the tip of the planetary-mass spectrum.

scholarly journals A weak spectral signature of water vapour in the atmosphere of HD 179949 b at high spectral resolution in the L band

2020 ◽  
Vol 494 (1) ◽  
pp. 108-119 ◽  
Author(s):  
Rebecca K Webb ◽  
Matteo Brogi ◽  
Siddharth Gandhi ◽  
Michael R Line ◽  
Jayne L Birkby ◽  
...  
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Semimajor Axis ◽  
Spectral Lines ◽  
Lapse Rate ◽  
High Spectral Resolution ◽  
High Resolution Spectroscopy ◽  
Spectral Signature ◽  
Orbital Inclination ◽  
L Band

ABSTRACT High-resolution spectroscopy ($R\, \geqslant \, 20\, 000$) is currently the only known method to constrain the orbital solution and atmospheric properties of non-transiting hot Jupiters. It does so by resolving the spectral features of the planet into a forest of spectral lines and directly observing its Doppler shift while orbiting the host star. In this study, we analyse VLT/CRIRES ($R=100\, 000$) L-band observations of the non-transiting giant planet HD 179949 b centred around 3.5 ${\mu {m}}$. We observe a weak (3.0σ, or S/N = 4.8) spectral signature of H2O in absorption contained within the radial velocity of the planet at superior-conjunction, with a mild dependence on the choice of line list used for the modelling. Combining this data with previous observations in the K band, we measure a detection significance of 8.4 σ for an atmosphere that is most consistent with a shallow lapse-rate, solar C/O ratio, and with CO and H2O being the only major sources of opacity in this wavelength range. As the two sets of data were taken 3 yr apart, this points to the absence of strong radial-velocity anomalies due, e.g. to variability in atmospheric circulation. We measure a projected orbital velocity for the planet of KP = (145.2 ± 2.0) km s−1 (1σ) and improve the error bars on this parameter by ∼70 per cent. However, we only marginally tighten constraints on orbital inclination ($66.2^{+3.7}_{-3.1}$ deg) and planet mass ($0.963^{+0.036}_{-0.031}$ Jupiter masses), due to the dominant uncertainties of stellar mass and semimajor axis. Follow ups of radial-velocity planets are thus crucial to fully enable their accurate characterization via high-resolution spectroscopy.

scholarly journals Disentangling planetary orbits from stellar activity in radial-velocity surveys

2014 ◽  
Vol 13 (2) ◽  
pp. 155-157 ◽  
Author(s):  
R. D. Haywood ◽  
A. Collier Cameron ◽  
D. Queloz ◽  
S.C.C. Barros ◽  
M. Deleuil ◽  
...  
Keyword(s):  
Radial Velocity ◽  
High Accuracy ◽  
Stellar Surface ◽  
Stellar Activity ◽  
The Earth ◽  
Planetary Orbits ◽  
Low Mass ◽  
Do So

AbstractThe majority of extra-solar planets have been discovered (or confirmed after follow-up) through radial-velocity (RV) surveys. Using ground-based spectrographs such as High Accuracy Radial Velocity Planetary Search (HARPS) and HARPS-North, it is now possible to detect planets that are only a few times the mass of the Earth. However, the presence of dark spots on the stellar surface produces RV signals that are very similar in amplitude to those caused by orbiting low-mass planets. Disentangling these signals has thus become the biggest challenge in the detection of Earth-mass planets using RV surveys. To do so, we use the star's lightcurve to model the RV variations produced by spots. Here we present this method and show the results of its application to CoRoT-7.

scholarly journals The GAPS Programme at TNG

2020 ◽  
Vol 638 ◽  
pp. A5 ◽  
Author(s):  
I. Carleo ◽  
L. Malavolta ◽  
A. F. Lanza ◽  
M. Damasso ◽  
S. Desidera ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Near Infrared ◽  
Semimajor Axis ◽  
Young Stars ◽  
Homogeneous Sample ◽  
Stellar Activity ◽  
Orbital Parameters ◽  
Hot Jupiters ◽  
Multi Band ◽  
Hot Jupiter

Context. The existence of hot Jupiters is still not well understood. Two main channels are thought to be responsible for their current location: a smooth planet migration through the protoplanetary disk or the circularization of an initial highly eccentric orbit by tidal dissipation leading to a strong decrease in the semimajor axis. Different formation scenarios result in different observable effects, such as orbital parameters (obliquity and eccentricity) or frequency of planets at different stellar ages. Aims. In the context of the GAPS Young Objects project, we are carrying out a radial velocity survey with the aim of searching and characterizing young hot-Jupiter planets. Our purpose is to put constraints on evolutionary models and establish statistical properties, such as the frequency of these planets from a homogeneous sample. Methods. Since young stars are in general magnetically very active, we performed multi-band (visible and near-infrared) spectroscopy with simultaneous GIANO-B + HARPS-N (GIARPS) observing mode at TNG. This helps in dealing with stellar activity and distinguishing the nature of radial velocity variations: stellar activity will introduce a wavelength-dependent radial velocity amplitude, whereas a Keplerian signal is achromatic. As a pilot study, we present here the cases of two known hot Jupiters orbiting young stars: HD 285507 b and AD Leo b. Results. Our analysis of simultaneous high-precision GIARPS spectroscopic data confirms the Keplerian nature of the variation in the HD 285507 radial velocities and refines the orbital parameters of the hot Jupiter, obtaining an eccentricity consistent with a circular orbit. Instead, our analysis does not confirm the signal previously attributed to a planet orbiting AD Leo. This demonstrates the power of the multi-band spectroscopic technique when observing active stars.

scholarly journals EXPRES. III. Revealing the Stellar Activity Radial Velocity Signature of ϵ Eridani with Photometry and Interferometry

2021 ◽  
Vol 163 (1) ◽  
pp. 19
Author(s):  
Rachael M. Roettenbacher ◽  
Samuel H. C. Cabot ◽  
Debra A. Fischer ◽  
John D. Monnier ◽  
Gregory W. Henry ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Current Data ◽  
Stellar Surface ◽  
Inversion Algorithm ◽  
Stellar Activity ◽  
Activity Component ◽  
Beam Combiner ◽  
Debris Disk ◽  
Flexible Models ◽  
High Cadence

Abstract The distortions of absorption line profiles caused by photospheric brightness variations on the surfaces of cool, main-sequence stars can mimic or overwhelm radial velocity (RV) shifts due to the presence of exoplanets. The latest generation of precision RV spectrographs aims to detect velocity amplitudes ≲ 10 cm s−1, but requires mitigation of stellar signals. Statistical techniques are being developed to differentiate between Keplerian and activity-related velocity perturbations. Two important challenges, however, are the interpretability of the stellar activity component as RV models become more sophisticated, and ensuring the lowest-amplitude Keplerian signatures are not inadvertently accounted for in flexible models of stellar activity. For the K2V exoplanet host ϵ Eridani, we separately used ground-based photometry to constrain Gaussian processes for modeling RVs and TESS photometry with a light-curve inversion algorithm to reconstruct the stellar surface. From the reconstructions of TESS photometry, we produced an activity model that reduced the rms scatter in RVs obtained with EXPRES from 4.72 to 1.98 m s−1. We present a pilot study using the CHARA Array and MIRC-X beam combiner to directly image the starspots seen in the TESS photometry. With the limited phase coverage, our spot detections are marginal with current data but a future dedicated observing campaign should allow for imaging, as well as allow the stellar inclination and orientation with respect to the debris disk to be definitively determined. This work shows that stellar surface maps obtained with high-cadence, time-series photometric and interferometric data can provide the constraints needed to accurately reduce RV scatter.

scholarly journals The Texas High-Precision Radial-velocity Programs

1999 ◽  
Vol 170 ◽  
pp. 113-120
Author(s):  
William D. Cochran ◽  
Artie P. Hatzes
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
High Precision ◽  
Line Profile ◽  
Planetary Systems ◽  
Profile Measurement ◽  
European Southern Observatory ◽  
University Of Texas ◽  
The University ◽  
Search Program

AbstractSeveral different high-precision radial-velocity programs are now underway at The University of Texas. This paper discusses the aspects of these programs that are related to the problem of detection of extrasolar planetary systems. This includes the McDonald Observatory Planetary Search program on the McDonald 2.7-m Harlan Smith Telescope, an accompanying program of high-resolution stellar line profile measurement, the European Southern Observatory planetary search program, the Keck Hyades survey, and the Hobby∙Eberly Telescope planet surveys. Here, we summarize each of these programs, and present recent results from each.

Sign in / Sign up

Export Citation Format

Share Document