scholarly journals A Radial velocity survey of spatially resolved young, low-mass binaries

2018 ◽  
Vol 618 ◽  
pp. A5 ◽  
Author(s):  
Stephen Durkan ◽  
Markus Janson ◽  
Simona Ciceri ◽  
Wolfgang Brandner ◽  
Joshua Schlieder ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Solar Neighborhood ◽  
Activity Level ◽  
Activity Levels ◽  
Old Field ◽  
Triple Systems ◽  
Chromospheric Activity ◽  
Low Mass ◽  
Orbital Periods ◽  
Moving Groups

The identification and characterisation of low-mass binaries is of importance for a range of astrophysical investigations. Low-mass binaries in young (∼10–100 Myr) moving groups (YMGs) in the solar neighborhood are of particular significance as they provide unique opportunities to calibrate stellar models and evaluate the ages and coevality of the groups themselves. Low-mass M-dwarfs have pre-main sequence life times on the order of ∼100 Myr and therefore are continually evolving along a mass-luminosity track throughout the YMG phase, providing ideal laboratories for precise isochronal dating, if a model-independent dynamical mass can be measured. AstraLux lucky imaging multiplicity surveys have recently identified hundreds of new YMG low-mass binaries, where a subsample of M-dwarf multiples have estimated orbital periods less than 50 yr. We have conducted a radial velocity survey of a sample of 29 such targets to complement the astrometric data. This will allow enhanced orbital determinations and precise dynamical masses to be derived in a shorter timeframe than possible with astrometric monitoring alone, and allow for a more reliable isochronal analysis. Here we present radial velocity measurements derived for our sample over several epochs. We report the detection of the three-component spectroscopic multiple 2MASS J05301858-5358483, for which the C component is a new discovery, and forms a tight pair with the B component. Originally identified as a YMG member, we find that this system is a likely old field interloper, whose high chromospheric activity level is caused by tidal spin-up of the tight BC pair. Two other triple systems with a tight pair exist in the sample, 2MASS J04244260-0647313 (previously known) and 2MASS J20163382-0711456, but for the rest of the targets we find that additional tidally synchronized companions are highly unlikely, providing further evidence that their high chromospheric activity levels are generally signatures of youth.

scholarly journals Chromospheric activity in bright contact binary stars

2020 ◽  
Vol 635 ◽  
pp. A89
Author(s):  
T. Mitnyan ◽  
T. Szalai ◽  
A. Bódi ◽  
L. Kriskovics ◽  
K. Vida ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Activity Level ◽  
Physical Parameters ◽  
Activity Levels ◽  
Sampled Data ◽  
Data Set ◽  
Chromospheric Activity ◽  
First Case ◽  
Mass Ratios ◽  
Contact Binaries

Context. Studying chromospheric activity of contact binaries is an effective way of revealing the magnetic activity processes of these systems. One efficient but somewhat neglected method for this purpose is to follow the changes of the Hα line profiles via optical spectroscopy. Aims. Our goal is to perform a comprehensive preliminary analysis based on the optical spectral signs of chromospheric activity on the largest sample of contact binaries to date. Methods. We collected optical echelle spectra on 12 bright contact binaries in 17 nights. We derived new radial velocity curves from our observations. For quantifying the apparent chromospheric activity levels of the systems, we subtracted self-constructed synthetic spectra from the observed ones and measured the equivalent widths of the residual Hα-profiles at each observed epoch. Our well-sampled data set allowed us to study the short-term variations of chromospheric activity levels as well as to search for correlations between them and some basic physical parameters of the systems. Results. Fitting the radial velocity curves, we re-determined the mass ratios and systemic velocities of all observed objects. We found that chromospheric activity levels of the studied systems show various changes during the orbital revolution: we see either flat, one-peaked, or two-peaked distributions of equivalent width vs. the orbital phase. The first case means that the activity level is probably constant, while the latter two cases suggest the presence of one or two active longitudes at the stellar surfaces. Our correlation diagrams show that mean chromospheric activity levels may be related to the orbital periods, B−V color indices, inverse Rossby numbers, and temperature differences of the components. At the same time, no clear trend is visible with respect to the mass ratios, inclinations, or fill-out factors of the systems. A- and W-type contact binaries in our sample show similar distributions on each of the studied correlation diagrams.

scholarly journals The HARPS search for southern extra-solar planets

2021 ◽  
Vol 654 ◽  
pp. A104
Author(s):  
N. Unger ◽  
D. Ségransan ◽  
D. Queloz ◽  
S. Udry ◽  
C. Lovis ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Bayesian Model ◽  
Model Comparison ◽  
Informed Choice ◽  
Activity Level ◽  
Monte Carlo Algorithm ◽  
Echelle Spectrograph ◽  
Orbital Parameters ◽  
Bayesian Model Comparison ◽  
Orbital Periods

Context. We present precise radial-velocity measurements of five solar-type stars observed with the HARPS Echelle spectrograph mounted on the 3.6-m telescope in La Silla (ESO, Chile). With a time span of more than 10 yr and a fairly dense sampling, the survey is sensitive to low mass planets down to super-Earths on orbital periods up to 100 days. Aims. Our goal was to search for planetary companions around the stars HD 39194, HD 93385, HD 96700, HD 154088, and HD 189567 and use Bayesian model comparison to make an informed choice on the number of planets present in the systems based on the radial velocity observations. These findings will contribute to the pool of known exoplanets and better constrain their orbital parameters. Methods. A first analysis was performed using the Data & Analysis Center for Exoplanets online tools to assess the activity level of the star and the potential planetary content of each system. We then used Bayesian model comparison on all targets to get a robust estimate on the number of planets per star. We did this using the nested sampling algorithm POLYCHORD. For some targets, we also compared different noise models to disentangle planetary signatures from stellar activity. Lastly, we ran an efficient Markov chain Monte Carlo algorithm for each target to get reliable estimates for the planets’ orbital parameters. Results. We identify 12 planets within several multiplanet systems. These planets are all in the super-Earth and sub-Neptune mass regime with minimum masses ranging between 4 and 13 M⊕ and orbital periods between 5 and 103 days. Three of these planets are new, namely HD 93385 b, HD 96700 c, and HD 189567 c.

scholarly journals Catalog for the ESPRESSO blind radial velocity exoplanet survey

2019 ◽  
Vol 629 ◽  
pp. A80 ◽  
Author(s):  
S. Hojjatpanah ◽  
P. Figueira ◽  
N. C. Santos ◽  
V. Adibekyan ◽  
S. G. Sousa ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Rotational Velocity ◽  
Spectroscopic Characterization ◽  
Solar Neighborhood ◽  
Activity Level ◽  
Contamination Level ◽  
Echelle Spectrograph ◽  
Chemical Abundances ◽  
Blind Search

Aims. One of the main scientific drivers for ESPRESSO, Échelle SPectrograph, is the detection and characterization of Earth-class exoplanets. With this goal in mind, the ESPRESSO guaranteed time observations (GTO) Catalog identifies the best target stars for a blind search for the radial velocity (RV) signals caused by Earth-class exoplanets. Methods. Using the most complete stellar catalogs available, we screened for the most suitable G, K, and M dwarf stars for the detection of Earth-class exoplanets with ESPRESSO. For most of the stars, we then gathered high-resolution spectra from new observations or from archival data. We used these spectra to spectroscopically investigate the existence of any stellar binaries, both bound or background stars. We derived the activity level using chromospheric activity indexes using log (R′HK), as well as the projected rotational velocity v sin i. For the cases where planet companions are already known, we also looked at the possibility that additional planets may exist in the host’s habitable zone using dynamical arguments. Results. We estimated the spectroscopic contamination level, v sin i, activity, stellar parameters and chemical abundances for 249 of the most promising targets. Using these data, we selected 45 stars that match our criteria for detectability of a planet like Earth. The stars presented and discussed in this paper constitute the ESPRESSO GTO catalog for the RV blind search for Earth-class planets. They can also be used for any other work requiring a detailed spectroscopic characterization of stars in the solar neighborhood.

From the Sun to solar-type stars: radial velocity, photometry, astrometry and logR′HK time series for late-F to early-K old stars

2019 ◽  
Vol 15 (S354) ◽  
pp. 286-294
Author(s):  
Nadège Meunier ◽  
Anne-Marie Lagrange
Keyword(s):  
Radial Velocity ◽  
Large Range ◽  
Magnetic Activity ◽  
Activity Levels ◽  
The Sun ◽  
Lower Mass ◽  
Solar Type ◽  
Low Mass ◽  
Average Activity ◽  
The Impact

AbstractSolar simulations and observations showed that the detection of Earth twins around Sun-like stars is difficult in radial velocities with current methods techniques. The Sun has proved to be very useful to test processes, models, and analysis methods. The convective blueshift effect, dominating for the Sun, decreases towards lower mass stars, providing more suitable conditions to detect low mass planets. We describe the basic processes at work and how we extended a realistic solar model of radial velocity, photometry, astrometry and LogR′HK variability, using a coherent grid of stellar parameters covering a large range in mass and average activity levels. We present selected results concerning the impact of magnetic activity on Earth-mass planet detectability as a function of stellar type. We show how such realistic simulations can help characterizing the effect of stellar activity on RV and astrometric exoplanet detection.

scholarly journals The Diversity of Low-mass Exoplanets Characterized via Transit Timing

2015 ◽  
Vol 11 (A29A) ◽  
pp. 40-50 ◽  
Author(s):  
Daniel Jontof-Hutter ◽  
Eric B. Ford ◽  
Jason F. Rowe ◽  
Jack. J. Lissauer ◽  
Daniel C. Fabrycky
Keyword(s):  
Radial Velocity ◽  
Low Mass ◽  
Orbital Periods

AbstractTransit timing variations (TTV) in multi-transiting systems enables precise characterizations of low-mass planets and their orbits. The range of orbital periods and incident fluxes with detailed TTV constraints complements the radial velocity sample for low-mass planets, pushing exoplanet characterization to the regime sub-Earth size planets and out to Mercury-like distances. This has revealed an astonishing diversity in the density of super-Earth mass planets. We summarize these and other contributions to exoplanet science from TTVs.

scholarly journals Hα ACTIVITY OF OLD M DWARFS: STELLAR CYCLES AND MEAN ACTIVITY LEVELS FOR 93 LOW-MASS STARS IN THE SOLAR NEIGHBORHOOD

2013 ◽  
Vol 764 (1) ◽  
pp. 3 ◽  
Author(s):  
Paul Robertson ◽  
Michael Endl ◽  
William D. Cochran ◽  
Sarah E. Dodson-Robinson
Keyword(s):  
Solar Neighborhood ◽  
Activity Levels ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
Low Mass

scholarly journals The White Dwarf Binary Pathways Survey −III. Contamination from hierarchical triples containing a white dwarf

2020 ◽  
Vol 494 (1) ◽  
pp. 915-922 ◽  
Author(s):  
F Lagos ◽  
M R Schreiber ◽  
S G Parsons ◽  
A Zurlo ◽  
D Mesa ◽  
...  
Keyword(s):  
White Dwarf ◽  
Binary Stars ◽  
Main Sequence Stars ◽  
Triple Systems ◽  
Compact Binary ◽  
Tidal Forces ◽  
Eccentric Orbits ◽  
Low Mass ◽  
Orbital Periods ◽  
Binary Evolution

ABSTRACT The White Dwarf Binary Pathways Survey aims at increasing the number of known detached A, F, G, and K main-sequence stars in close orbits with white dwarf companions (WD+AFGK binaries) to refine our understanding about compact binary evolution and the nature of Supernova Ia progenitors. These close WD+AFGK binary stars are expected to form through common envelope evolution, in which tidal forces tend to circularize the orbit. However, some of the identified WD+AFGK binary candidates show eccentric orbits, indicating that these systems are either formed through a different mechanism or perhaps they are not close WD+AFGK binaries. We observed one of these eccentric WD+AFGK binaries with SPHERE and find that the system TYC 7218-934-1 is in fact a triple system where the WD is a distant companion. The inner binary likely consists of the G-type star plus an unseen low-mass companion in an eccentric orbit. Based on this finding, we estimate the fraction of triple systems that could contaminate the WD+AFGK sample. We find that less than 15 per cent of our targets with orbital periods shorter than 100 d might be hierarchical triples.

scholarly journals The BANYAN All-Sky Survey for Brown Dwarf Members of Young Moving Groups

2015 ◽  
Vol 10 (S314) ◽  
pp. 49-53
Author(s):  
Jonathan Gagné ◽  
David Lafrenière ◽  
René Doyon ◽  
Jacqueline K. Faherty ◽  
Lison Malo ◽  
...  
Keyword(s):  
Brown Dwarfs ◽  
Solar Neighborhood ◽  
Brown Dwarf ◽  
Low Gravity ◽  
Low Mass Stars ◽  
Sky Survey ◽  
Future Version ◽  
Bona Fide ◽  
Low Mass ◽  
Moving Groups

AbstractWe describe in this work the BASS survey for brown dwarfs in young moving groups of the solar neighborhood, and summarize the results that it generated. These include the discovery of the 2MASS J01033563–5515561 (AB)b and 2MASS J02192210–3925225 B young companions near the deuterium-burning limit as well as 44 new low-mass stars and 69 new brown dwarfs with a spectroscopically confirmed low gravity. Among those, ~20 have estimated masses within the planetary regime, one is a new L4 γ bona fide member of AB Doradus, three are TW Hydrae candidates with later spectral types (L1–L4) than all of its previously known members and six are among the first contenders for low-gravity ≥ L5 β/γ brown dwarfs, reminiscent of WISEP J004701.06+680352.1, PSO J318.5338–22.8603 and VHS J125601.92–125723.9 b. Finally, we describe a future version of this survey, BASS-Ultracool, that will specifically target ≥ L5 candidate members of young moving groups. First experimentations in designing the survey have already led to the discovery of a new T dwarf bona fide member of AB Doradus, as well as the serendipitous discoveries of an L9 subdwarf and an L5 + T5 brown dwarf binary.

scholarly journals Later sleep timing predicts accelerated summer weight gain among elementary school children: a prospective observational study

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Jennette P. Moreno ◽  
Javad Razjouyan ◽  
Houston Lester ◽  
Hafza Dadabhoy ◽  
Mona Amirmazaheri ◽  
...  
Keyword(s):  
Physical Activity ◽  
Observational Study ◽  
Sleep Duration ◽  
Obesity Prevention ◽  
Prospective Observational Study ◽  
Light Exposure ◽  
Activity Level ◽  
Activity Levels ◽  
School Year ◽  
Children’S Sleep

Abstract Objectives and background Social demands of the school-year and summer environment may affect children’s sleep patterns and circadian rhythms during these periods. The current study examined differences in children’s sleep and circadian-related behaviors during the school-year and summer and explored the association between sleep and circadian parameters and change in body mass index (BMI) during these time periods. Methods This was a prospective observational study with 119 children ages 5 to 8 years with three sequential BMI assessments: early school-year (fall), late school-year (spring), and beginning of the following school-year in Houston, Texas, USA. Sleep midpoint, sleep duration, variability of sleep midpoint, physical activity, and light exposure were estimated using wrist-worn accelerometry during the school-year (fall) and summer. To examine the effect of sleep parameters, physical activity level, and light exposure on change in BMI, growth curve modeling was conducted controlling for age, race, sex, and chronotype. Results Children’s sleep midpoint shifted later by an average of 1.5 h during summer compared to the school-year. After controlling for covariates, later sleep midpoints predicted larger increases in BMI during summer, (γ = .0004, p = .03), but not during the school-year. Sleep duration, sleep midpoint variability, physical activity levels, and sedentary behavior were not associated with change in BMI during the school-year or summer. Females tended to increase their BMI at a faster rate during summer compared to males, γ = .06, p = .049. Greater amounts of outdoor light exposure (γ = −.01, p = .02) predicted smaller increases in school-year BMI. Conclusions Obesity prevention interventions may need to target different behaviors depending on whether children are in or out of school. Promotion of outdoor time during the school-year and earlier sleep times during the summer may be effective obesity prevention strategies during these respective times.

scholarly journals Choroidal Thickness and Volume Modifications Induced by Aerobic Exercise in Healthy Young Adults

2020 ◽  
Author(s):  
Gema Insa-Sánchez ◽  
Lorena Fuentes-Broto ◽  
Alberto Cobos ◽  
Elvira Orduna Hospital ◽  
Francisco Segura ◽  
...  
Keyword(s):  
Physical Activity ◽  
Young Adults ◽  
Physical Exercise ◽  
Choroidal Thickness ◽  
Activity Level ◽  
Enhanced Depth Imaging ◽  
Activity Levels ◽  
Imaging Protocol ◽  
Post Exercise ◽  
Physical Activity Levels

<b><i>Introduction:</i></b> Our aim was to evaluate the changes in choroidal thickness (CT) and volume (CV) following aerobic physical exercise in healthy young adults. <b><i>Methods:</i></b> This study included 72 eyes from healthy volunteers between 22 and 37 years old. Using the International Physical Activity Questionnaire, total physical activity was computed. Measurements using an autorefractometer, ocular biometry, and spectral-domain optical coherence tomography using the Enhanced Depth Imaging protocol were taken. OCT was performed as a baseline measurement and after performing 10 min of dynamic physical exercise (3 and 10 min post-exercise). The choroidal layer was manually segmented, and the CT and CV in different areas from the Early Treatment Diabetic Retinopathy Study grid were obtained. <b><i>Results:</i></b> In healthy adults, at 3 min post-exercise, CT was higher in the subfoveal, the 3-mm nasal, and the 6-mm superior areas. Between 3 and 10 min post-exercise, the CT was reduced in all areas, and in some areas, the values were even smaller than the baseline measurements. The CV values showed changes after exercise similar to those of thickness. The total CV recovery after exercise was related to sex and physical activity level. <b><i>Conclusion:</i></b> Individuals with higher physical activity habits had greater CV at rest than those with lower physical activity levels. During exercise, healthy young people adjust CT and CV. At 3 min post-exercise, CT and CV increase. Women and individuals with greater physical activity levels reduce their total CV more than others during recovery.

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