scholarly journals The SOPHIE search for northern extrasolar planets

2020 ◽  
Vol 636 ◽  
pp. L6 ◽  
Author(s):  
N. C. Hara ◽  
F. Bouchy ◽  
M. Stalport ◽  
I. Boisse ◽  
J. Rodrigues ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Extrasolar Planets ◽  
Statistical Significance ◽  
Rotation Period ◽  
Low Frequency ◽  
Stellar Rotation ◽  
Strong Candidate ◽  
A New Technique ◽  
Photometric Measurements ◽  
Three Body

Aims. Since 2011, the SOPHIE spectrograph has been used to search for Neptunes and super-Earths in the northern hemisphere. As part of this observational program, 290 radial velocity measurements of the 6.4 V magnitude star HD 158259 were obtained. Additionally, TESS photometric measurements of this target are available. We present an analysis of the SOPHIE data and compare our results with the output of the TESS pipeline. Methods. The radial velocity data, ancillary spectroscopic indices, and ground-based photometric measurements were analyzed with classical and ℓ1 periodograms. The stellar activity was modeled as a correlated Gaussian noise and its impact on the planet detection was measured with a new technique. Results. The SOPHIE data support the detection of five planets, each with m sin i ≈ 6 M⊕, orbiting HD 158259 in 3.4, 5.2, 7.9, 12, and 17.4 days. Though a planetary origin is strongly favored, the 17.4 d signal is classified as a planet candidate due to a slightly lower statistical significance and to its proximity to the expected stellar rotation period. The data also present low frequency variations, most likely originating from a magnetic cycle and instrument systematics. Furthermore, the TESS pipeline reports a significant signal at 2.17 days corresponding to a planet of radius ≈1.2 R⊕. A compatible signal is seen in the radial velocities, which confirms the detection of an additional planet and yields a ≈2 M⊕ mass estimate. Conclusions. We find a system of five planets and a strong candidate near a 3:2 mean motion resonance chain orbiting HD 158259. The planets are found to be outside of the two and three body resonances.

scholarly journals Decoding the radial velocity variations of HD 41248 with ESPRESSO

2020 ◽  
Vol 635 ◽  
pp. A13 ◽  
Author(s):  
J. P. Faria ◽  
V. Adibekyan ◽  
E. M. Amazo-Gómez ◽  
S. C. C. Barros ◽  
J. D. Camacho ◽  
...  
Keyword(s):  
Light Curve ◽  
Radial Velocity ◽  
Gaussian Process ◽  
Process Model ◽  
Moving Average ◽  
Rotation Period ◽  
Magnetic Activity ◽  
Noise Model ◽  
Stellar Rotation ◽  
Gaussian Process Model

Context. Twenty-four years after the discoveries of the first exoplanets, the radial-velocity (RV) method is still one of the most productive techniques to detect and confirm exoplanets. But stellar magnetic activity can induce RV variations large enough to make it difficult to disentangle planet signals from the stellar noise. In this context, HD 41248 is an interesting planet-host candidate, with RV observations plagued by activity-induced signals. Aims. We report on ESPRESSO observations of HD 41248 and analyse them together with previous observations from HARPS with the goal of evaluating the presence of orbiting planets. Methods. Using different noise models within a general Bayesian framework designed for planet detection in RV data, we test the significance of the various signals present in the HD 41248 dataset. We use Gaussian processes as well as a first-order moving average component to try to correct for activity-induced signals. At the same time, we analyse photometry from the TESS mission, searching for transits and rotational modulation in the light curve. Results. The number of significantly detected Keplerian signals depends on the noise model employed, which can range from 0 with the Gaussian process model to 3 with a white noise model. We find that the Gaussian process alone can explain the RV data while allowing for the stellar rotation period and active region evolution timescale to be constrained. The rotation period estimated from the RVs agrees with the value determined from the TESS light curve. Conclusions. Based on the data that is currently available, we conclude that the RV variations of HD 41248 can be explained by stellar activity (using the Gaussian process model) in line with the evidence from activity indicators and the TESS photometry.

scholarly journals Rotational and pulsational variability in the TESS light curve of HD 27463

2019 ◽  
Vol 490 (2) ◽  
pp. 2102-2111 ◽  
Author(s):  
V Khalack ◽  
C Lovekin ◽  
D M Bowman ◽  
O Kobzar ◽  
A David-Uraz ◽  
...  
Keyword(s):  
Rotation Period ◽  
Low Frequency ◽  
Balmer Line ◽  
Rotational Axis ◽  
Line Profiles ◽  
Stellar Rotation ◽  
Photometric Variability ◽  
Low Frequency Variability ◽  
Best Fitting ◽  
Frequency Variations

ABSTRACT The new photometric data on pulsating Ap star HD 27463 obtained recently with the Transiting Exoplanet Survey Satellite (TESS) are analysed to search for variability. Our analysis shows that HD 27463 exhibits two types of photometric variability. The low-frequency variability with the period P  = 2.834 274 ± 0.000 008 d can be explained in terms of axial stellar rotation assuming the oblique magnetic rotator model and presence of surface abundance/brightness spots, while the detected high-frequency variations are characteristics of δ Scuti pulsations. From the analysis of Balmer line profiles visible in two FEROS spectra of HD 27463 we have derived its effective temperature and surface gravity, finding values that are close to those published for this star in the TESS Input Catalogue (TIC). Knowing the rotation period and the v sin i value estimated from the fitting of Balmer line profiles we found that the rotational axis is inclined to the line of sight with an angle of $i=33\pm 8\deg$. Our best-fitting model of the observed pulsation modes results in an overshoot parameter value fov = 0.014 and values of global stellar parameters that are in good agreement with the data reported in the TIC and with the data derived from fitting Balmer line profiles. This model indicates an age of 5.0 ± 0.4 × 108 yr, which corresponds to a core hydrogen fraction of 0.33.

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 Eyes on K2-3: A system of three likely sub-Neptunes characterized with HARPS-N and HARPS

2018 ◽  
Vol 615 ◽  
pp. A69 ◽  
Author(s):  
M. Damasso ◽  
A. S. Bonomo ◽  
N. Astudillo-Defru ◽  
X. Bonfils ◽  
L. Malavolta ◽  
...  
Keyword(s):  
Time Series ◽  
Radial Velocity ◽  
Rotation Period ◽  
Doppler Signal ◽  
Stellar Rotation ◽  
Mass Measurements ◽  
Stellar Activity ◽  
Velocity Signal ◽  
M Dwarf ◽  
High Cadence

Context. M-dwarf stars are promising targets for identifying and characterizing potentially habitable planets. K2-3 is a nearby (45 pc), early-type M dwarf hosting three small transiting planets, the outermost of which orbits close to the inner edge of the stellar (optimistic) habitable zone. The K2-3 system is well suited for follow-up characterization studies aimed at determining accurate masses and bulk densities of the three planets. Aims. Using a total of 329 radial velocity measurements collected over 2.5 years with the HARPS-N and HARPS spectrographs and a proper treatment of the stellar activity signal, we aim to improve measurements of the masses and bulk densities of the K2-3 planets. We use our results to investigate the physical structure of the planets. Methods. We analysed radial velocity time series extracted with two independent pipelines using Gaussian process regression. We adopted a quasi-periodic kernel to model the stellar magnetic activity jointly with the planetary signals. We used Monte Carlo simulations to investigate the robustness of our mass measurements of K2-3 c and K2-3 d, and to explore how additional high-cadence radial velocity observations might improve these values. Results. Even though the stellar activity component is the strongest signal present in the radial velocity time series, we are able to derive masses for both planet b (Mb = 6.6 ± 1.1 M⊕) and planet c (Mc = 3.1−1.2+1.3 M⊕). The Doppler signal from K2-3 d remains undetected, likely because of its low amplitude compared to the radial velocity signal induced by the stellar activity. The closeness of the orbital period of K2-3 d to the stellar rotation period could also make the detection of the planetary signal complicated. Based on our ability to recover injected signals in simulated data, we tentatively estimate the mass of K2-3 d to be Md = 2.7−0.8+1.2 M⊕ M⊕. These mass measurements imply that the bulk densities and therefore the interior structures of the three planets may be similar. In particular, the planets may either have small H/He envelopes (<1%) or massive water layers, with a water content ≥50% of their total mass, on top of rocky cores. Placing further constraints on the bulk densities of K2-3 c and d is difficult; in particular, we would not have been able to detect the Doppler signal of K2-3 d even by adopting a semester of intense, high-cadence radial velocity observations with HARPS-N and HARPS.

scholarly journals HADES RV programme with HARPS-N at TNG

2018 ◽  
Vol 612 ◽  
pp. A89 ◽  
Author(s):  
A. Suárez Mascareño ◽  
R. Rebolo ◽  
J. I. González Hernández ◽  
B. Toledo-Padrón ◽  
M. Perger ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Rotation Period ◽  
Stellar Rotation ◽  
M Dwarfs ◽  
Velocity Signal ◽  
The Public ◽  
Rotation Periods ◽  
Chromospheric Emission ◽  
The Mean ◽  
Magnetic Cycles

We aim to investigate the presence of signatures of magnetic cycles and rotation on a sample of 71 early M-dwarfs from the HADES RV programme using high-resolution time-series spectroscopy of the Ca II H&K and Hα chromospheric activity indicators, the radial velocity series, the parameters of the cross correlation function and the V -band photometry. We used mainly HARPS-N spectra, acquired over 4 yr, and add HARPS spectra from the public ESO database and ASAS photometry light-curves as support data, extending the baseline of the observations of some stars up to 12 yr. We provide log10(R′HK) measurements for all the stars in the sample, cycle length measurements for 13 stars, rotation periods for 33 stars and we are able to measure the semi-amplitude of the radial velocity signal induced by rotation in 16 stars. We complement our work with previous results and confirm and refine the previously reported relationships between the mean level of chromospheric emission, measured by the log10(R′HK), with the rotation period, and with the measured semi-amplitude of the activity induced radial velocity signal for early M-dwarfs. We searched for a possible relation between the measured rotation periods and the lengths of the magnetic cycle, finding a weak correlation between both quantities. Using previous v sin i measurements we estimated the inclinations of the star’s poles to the line of sight for all the stars in the sample, and estimate the range of masses of the planets GJ 3998 b and c (2.5–4.9 and 6.3–12.5 M⊕), GJ 625 b (2.82 M⊕), GJ 3942 b (7.1–10.0 M⊕) and GJ 15A b (3.1–3.3 M⊕), assuming their orbits are coplanar with the stellar rotation.

scholarly journals Characterizing the Eccentricities of Transiting Extrasolar Planets with Kepler and CoRoT

2008 ◽  
Vol 4 (S253) ◽  
pp. 111-119
Author(s):  
Eric B. Ford ◽  
Knicole D. Colón
Keyword(s):  
Radial Velocity ◽  
Extrasolar Planets ◽  
Giant Planets ◽  
Physical Parameters ◽  
Tidal Dissipation ◽  
Transiting Planets ◽  
Photometric Observations ◽  
Short Period ◽  
Photometric Measurements ◽  
Rocky Planets

AbstractRadial velocity planet searches have revealed that many giant planets have large eccentricities, in striking contrast with the giant planets in the solar system and prior theories of planet formation. The realization that many giant planets have large eccentricities raises a fundamental question: Do terrestrial-size planets of other stars typically have significantly eccentric orbits or nearly circular orbits like the Earth? While space-based missions such as CoRoT and Kepler will be capable of detecting nearly Earth-sized planets, it will be extremely challenging to measure their eccentricities using radial velocity observations. We review several ways that photometric measurements of transit light curves can constrain the eccentricity of transiting planets. In particular, photometric observations of transit durations can be used to characterize the distribution of orbital eccentricities for various populations of transiting planets (e.g., nearly Earth-sized planets in the habitable zone) without relying on radial velocity measurements. Applying this technique to rocky planets to be found by CoRoT and Kepler will enable constraints on theories for the excitation of eccentricities and tidal dissipation. We also remind observers that several short-period transiting planets are known to have significant eccentricities and caution that assuming they are on a circular orbit can reduce the probability of detecting transits, impact planning for follow-up observations, and adversely affect measurements of the physical parameters of the star and planet.

scholarly journals Sectoral r modes and periodic radial velocity variations of Sun-like stars

2019 ◽  
Vol 623 ◽  
pp. A50 ◽  
Author(s):  
A. F. Lanza ◽  
L. Gizon ◽  
T. V. Zaqarashvili ◽  
Z.-C. Liang ◽  
K. Rodenbeck
Keyword(s):  
Radial Velocity ◽  
Rotation Axis ◽  
Rotation Period ◽  
Maximum Amplitude ◽  
Global Scale ◽  
Surface Velocity ◽  
The Sun ◽  
Stellar Rotation ◽  
Restoring Force ◽  
Transiting Planets

Context. Radial velocity (RV) measurements are used to search for planets orbiting late-type main-sequence stars and to confirm the transiting planets. Aims. The most advanced spectrometers are now approaching a precision of ~10 cm s−1, which implies the need to identify and correct for all possible sources of RV oscillations intrinsic to the star down to this level and possibly beyond. The recent discovery of global-scale equatorial Rossby waves in the Sun, also called r modes, prompted us to investigate their possible signature in stellar RV measurements. These r modes are toroidal modes of oscillation whose restoring force is the Coriolis force; they propagate in the retrograde direction in a frame that co-rotates with the star. The solar r modes with azimuthal orders 3 ≤ m ≲ 15 were identified unambiguously because of their dispersion relation and their long e-folding lifetimes of hundreds of days. Methods. In this paper, we simulate the RV oscillations produced by sectoral r modes with 2 ≤ m ≤ 5 by assuming a stellar rotation period of 25.54 days and a maximum amplitude of the surface velocity of each mode of 2 m s−1. This amplitude is representative of the solar measurements except for the m = 2 mode, which has not yet been observed on the Sun. Results. Sectoral r modes with azimuthal orders m = 2 and 3 would produce RV oscillations with amplitudes of 76.4 and 19.6 cm s−1 and periods of 19.16 and 10.22 days, respectively, for a star with an inclination of the rotation axis to the line of sight i = 60°. Therefore, they may produce rather sharp peaks in the Fourier spectrum of the radial velocity time series that could lead to spurious planetary detections. Conclusions. Sectoral r modes may represent a source of confusion in the case of slowly rotating inactive stars that are preferential targets for RV planet search. The main limitation of the present investigation is the lack of observational constraints on the amplitude of the m = 2 mode on the Sun.

scholarly journals The HADES RV programme with HARPS-N at TNG

2019 ◽  
Vol 625 ◽  
pp. A126 ◽  
Author(s):  
M. Pinamonti ◽  
A. Sozzetti ◽  
P. Giacobbe ◽  
M. Damasso ◽  
G. Scandariato ◽  
...  
Keyword(s):  
Time Series ◽  
Activity Index ◽  
Rotation Period ◽  
Gaussian Process Regression ◽  
Formation Mechanisms ◽  
Stellar Rotation ◽  
Dwarf Planets ◽  
Depth Analysis ◽  
Low Mass ◽  
Photometric Measurements

Context. Small rocky planets seem to be very abundant around low-mass M-type stars. Their actual planetary population is however not yet precisely understood. Currently, several surveys aim to expand the statistics with intensive detection campaigns, both photometric and spectroscopic. Aims. The HADES program aims to improve the current statistics through the in-depth analysis of accurate radial-velocity (RV) monitoring in a narrow range of spectral sub-types, with the precision needed to detect small planets with a few Earth masses. Methods. We analyse 106 spectroscopic HARPS-N observations of the active M0-type star GJ 685 taken over the past five years. We combine these data with photometric measurements from different observatories to accurately model the stellar rotation and disentangle its signals from genuine Doppler planetary signals in the RV data. We run an MCMC analysis on the RV and activity index time series to model the planetary and stellar signals present in the data, applying Gaussian Process regression technique to deal with the stellar activity signals. Results. We identify three periodic signals in the RV time series, with periods of 9, 24, and 18 d. Combining the analyses of the photometry of the star with the activity indexes derived from the HARPS-N spectra, we identify the 18 d and 9 d signals as activity-related, corresponding to the stellar rotation period and its first harmonic, respectively. The 24 d signal shows no relation to any activity proxy, and therefore we identify it as a genuine planetary signal. We find the best-fit model describing the Doppler signal of the newly found planet, GJ 685 b, corresponding to an orbital period Pb = 24.160−0.047+0.061 d and a minimum mass MP sin i = 9.0−1.8+1.7 M⊕. We also study a sample of 70 RV-detected M-dwarf planets, and present new statistical evidence of a difference in mass distribution between the populations of single- and multi-planet systems, which can shed new light on the formation mechanisms of low-mass planets around late-type stars.

On the Configuration of the Magnetic Field of β CrB

1976 ◽  
Vol 32 ◽  
pp. 613-622
Author(s):  
I.A. Aslanov ◽  
Yu.S. Rustamov
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Radial Velocity ◽  
Magnetic Field Strength ◽  
Complex Shape ◽  
Rotation Period ◽  
Field Variation ◽  
Magnetic Field Variation ◽  
Secular Variations ◽  
The Magnetic Field

SummaryMeasurements of the radial velocities and magnetic field strength of β CrB were carried out. It is shown that there is a variability with the rotation period different for various elements. The curve of the magnetic field variation measured from lines of 5 different elements: FeI, CrI, CrII, TiII, ScII and CaI has a complex shape specific for each element. This may be due to the presence of magnetic spots on the stellar surface. A comparison with the radial velocity curves suggests the presence of a least 4 spots of Ti and Cr coinciding with magnetic spots. A change of the magnetic field with optical depth is shown. The curve of the Heffvariation with the rotation period is given. A possibility of secular variations of the magnetic field is shown.

Pre-pregnancy body mass index is associated with offspring body composition in adulthood before adiposity-related disorders: a retrospective cohort

2020 ◽  
pp. 1-17
Author(s):  
Ilana Eshriqui ◽  
Angélica Marques Martins Valente ◽  
Luciana Dias Folchetti ◽  
Bianca de Almeida-Pititto ◽  
Sandra Roberta G. Ferreira
Keyword(s):  
Body Mass Index ◽  
Body Composition ◽  
Body Mass ◽  
Body Fat ◽  
Retrospective Cohort ◽  
Statistical Significance ◽  
Directed Acyclic Graphs ◽  
Health Study ◽  
Appendicular Skeletal Muscle ◽  
Three Body

Abstract Objective: To investigate the association between maternal pre-pregnancy body mass index (BMI) and offspring body composition in adulthood. Design: Retrospective cohort. Undergraduates of nutrition or nutritionists were recruited at the baseline of the Nutritionists’ Health Study between 2014 and 2017. Maternal pre-pregnancy BMI and current life aspects were self-reported through online questionnaires. Three body compartments were DXA-determined. The following variables were obtained: body-fat (%), fat mass index (FMI) (kg/m2), android-to-gynoid fat ratio, visceral adipose tissue (VAT) (cm3), appendicular skeletal muscle mass index (ASMI) (kg/m2), total bone and femur mineral content (g) and density (g/cm2). Linear regression adjusted according to directed acyclic graphs recommendation was performed. Setting: São Paulo, Brazil. Participants: Healthy non-pregnant women (aged 20-45 years) (n=150). Results: Median age and BMI were 22 years (IQR=20; 29) and 22.3 kg/m2 (IQR=20.4; 25.3). Pre-pregnancy BMI≥25 kg/m2 was reported by 14.7% of mothers. In fully adjusted models, maternal pre-pregnancy BMI was associated with their daughters’ body-fat % (β=0.31; 95%CI=0.0004; 0.63), FMI (β=0.17; 95%CI=0.03; 0.30, android-to-gynoid ratio (β=0.01; 95%CI=0.004; 0.02) and VAT (β=0.09; 95%CI=0.02; 0.16), but not with total bone density (β=0.001; 95%CI=-0.003; 0.006) and content (β=7.13; 95%CI=-4.19; 18.46). Direct association with ASMI was also detected, but lost statistical significance when participants whose mothers were underweight were excluded. Conclusions: Maternal pre-pregnancy body mass index was directly associated with offspring general and visceral adiposity but seem not to be associated with bone mass. Results reinforce importance of avoiding excess of maternal adiposity, as an attempt to break the vicious cycle of obesity transmission.

Sign in / Sign up

Export Citation Format

Share Document