scholarly journals Long-term stellar activity variations and their effect on radial-velocity measurements

2021 ◽  
Author(s):  
Jean C Costes ◽  
Christopher A Watson ◽  
Ernst de Mooij ◽  
Steven H Saar ◽  
Xavier Dumusque ◽  
...  
Keyword(s):  
Extrasolar Planets ◽  
Blue Shift ◽  
Convective Zone ◽  
Fundamental Parameter ◽  
Activity Levels ◽  
Stellar Activity ◽  
Gaussian Fit ◽  
Orbital Periods ◽  
Zone Depth

Abstract Long-term stellar activity variations can affect the detectability of long-period and Earth-analogue extrasolar planets. We have, for 54 stars, analysed the long-term trend of five activity indicators: log $R^{\prime }_\mathrm{{HK}}$, the cross-correlation function (CCF) bisector span, CCF full-width-at-half-maximum, CCF contrast, and the area of the Gaussian fit to the CCF; and studied their correlation with the RVs. The sign of the correlations appears to vary as a function of stellar spectral type, and the transition in sign signals a noteworthy change in the stellar activity properties where earlier type stars appear more plage dominated. These transitions become more clearly defined when considered as a function of the convective zone depth. Therefore, it is the convective zone depth (which can be altered by stellar metallicity) that appears to be the underlying fundamental parameter driving the observed activity correlations. In addition, for most of the stars, we find that the RVs become increasingly red-shifted as activity levels increase, which can be explained by the increase in the suppression of convective blue-shift. However, we also find a minority of stars where the RVs become increasingly blue-shifted as activity levels increase. Finally, using the correlation found between activity indicators and RVs, we removed RV signals generated by long-term changes in stellar activity. We find that performing simple cleaning of such long-term signals enables improved planet detection at longer orbital periods.

scholarly journals Stellar activity analysis of Barnard’s Star: Very slow rotation and evidence for long-term activity cycle

2019 ◽  
Author(s):  
B Toledo-Padrón ◽  
J I González Hernández ◽  
C Rodríguez-López ◽  
A Suárez Mascareño ◽  
R Rebolo ◽  
...  
Keyword(s):  
Time Series ◽  
Spectroscopic Data ◽  
Rotation Period ◽  
Photometric Data ◽  
Activity Level ◽  
Slow Rotation ◽  
Activity Levels ◽  
Stellar Activity

Abstract The search for Earth-like planets around late-type stars using ultra-stable spectrographs requires a very precise characterization of the stellar activity and the magnetic cycle of the star, since these phenomena induce radial velocity (RV) signals that can be misinterpreted as planetary signals. Among the nearby stars, we have selected Barnard’s Star (Gl 699) to carry out a characterization of these phenomena using a set of spectroscopic data that covers about 14.5 years and comes from seven different spectrographs: HARPS, HARPS-N, CARMENES, HIRES, UVES, APF, and PFS; and a set of photometric data that covers about 15.1 years and comes from four different photometric sources: ASAS, FCAPT-RCT, AAVSO, and SNO. We have measured different chromospheric activity indicators (Hα, Ca II HK and Na I D), as well as the FWHM of the cross-correlation function computed for a sub-set of the spectroscopic data. The analysis of Generalized Lomb-Scargle periodograms of the time series of different activity indicators reveals that the rotation period of the star is 145 ± 15 days, consistent with the expected rotation period according to the low activity level of the star and previous claims. The upper limit of the predicted activity-induced RV signal corresponding to this rotation period is about 1 m/s. We also find evidence of a long-term cycle of 10 ± 2 years that is consistent with previous estimates of magnetic cycles from photometric time series in other M stars of similar activity levels. The available photometric data of the star also support the detection of both the long-term and the rotation signals.

scholarly journals Towards the characterization of the hot Neptune/super-Earth population around nearby bright stars

2008 ◽  
Vol 4 (S253) ◽  
pp. 502-505 ◽  
Author(s):  
C. Lovis ◽  
M. Mayor ◽  
F. Bouchy ◽  
F. Pepe ◽  
D. Queloz ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Extrasolar Planets ◽  
Large Population ◽  
Long Term Stability ◽  
Data Points ◽  
Solar Type ◽  
Low Mass ◽  
Orbital Periods

AbstractThe HARPS search for low-mass extrasolar planets has been ongoing for more than 4 years, targeting originally about 400 bright FGK dwarfs in the solar neighbourhood. The published low-mass planetary systems coming from this survey are fully confirmed by subsequent observations, which demonstrate the sub-m/s long-term stability reached by HARPS. The complex RV curves of these systems have led us to focus on a smaller sample of stars, accumulating more data points per star. We perform a global search in our data to assess the existence of the large population of ice giants and super-Earths predicted by numerical simulations of planet formation. We indeed detect about 45 candidates having minimum masses below 30 M⊕ and orbital periods below 50 days. These numbers are preliminary since the existence of these objects has to be confirmed by subsequent observations. However, they indicate that about 30% of solar-type stars may have such close-in, low-mass planets. Some emerging properties of this low-mass population are presented. We finally discuss the prospects for finding transiting objects among these candidates, which may possibly yield the first nearby, transiting super-Earth.

scholarly journals Extrasolar planets and brown dwarfs around AF-type stars

2019 ◽  
Vol 621 ◽  
pp. A87 ◽  
Author(s):  
S. Borgniet ◽  
A.-M. Lagrange ◽  
N. Meunier ◽  
F. Galland ◽  
L. Arnold ◽  
...  
Keyword(s):  
Main Sequence ◽  
Extrasolar Planets ◽  
Giant Planet ◽  
High Amplitude ◽  
Stellar Mass ◽  
Occurrence Rate ◽  
Substellar Companions ◽  
Orbital Periods ◽  
The Impact

Context. The impact of stellar mass on the properties of giant planets is still not fully understood. Main-sequence (MS) stars more massive than the Sun remain relatively unexplored in radial velocity (RV) surveys, due to their characteristics which hinder classical RV measurements. Aims. Our aim is to characterize the close (up to ~2 au) giant planet (GP) and brown dwarf (BD) population around AF MS stars and compare this population to stars with different masses. Methods. We used the SOPHIE spectrograph located on the 1.93 m telescope at Observatoire de Haute-Provence to observe 125 northern, MS AF dwarfs. We used our dedicated SAFIR software to compute the RV and other spectroscopic observables. We characterized the detected substellar companions and computed the GP and BD occurrence rates combining the present SOPHIE survey and a similar HARPS survey. Results. We present new data on two known planetary systems around the F5-6V dwarfs HD 16232 and HD 113337. For the latter, we report an additional RV variation that might be induced by a second GP on a wider orbit. We also report the detection of 15 binaries or massive substellar companions with high-amplitude RV variations or long-term RV trends. Based on 225 targets observed with SOPHIE and/or HARPS, we constrain the BD frequency within 2–3 au around AF stars to be below 4% (1σ). For Jupiter-mass GPs within 2–3 au (periods ≤103 days), we find the occurrence rate to be 3.7−1+3% around AF stars with masses <1.5 M⊙, and to be ≤6% (1σ) around AF stars with masses >1.5 M⊙. For periods shorter than 10 days, we find the GP occurrence rate to be below 3 and 4.5% (1σ), respectively. Our results are compatible with the GP frequency reported around FGK dwarfs and are compatible with a possible increase in GP orbital periods with stellar mass as predicted by formation models.

Mediators of Estimates of Brief Time Intervals in Elderly Domiciled Males

1986 ◽  
Vol 21 (3) ◽  
pp. 211-225 ◽  
Author(s):  
David Licht ◽  
John B. Morganti ◽  
Milton F. Nehrke ◽  
Gary Heiman
Keyword(s):  
Production Method ◽  
Passage Time ◽  
Future Research ◽  
Value Of Time ◽  
Activity Levels ◽  
Time Intervals ◽  
Time To Death ◽  
Institutional Settings ◽  
Time Estimates

Conflicting interpretations questioning whether brief intervals of real time are perceived as passing more or less rapidly with increasing age have been reported. Reasons for these inconsistent results lie in semantic confusions, in variations in methodology, and in the effects of other mediating variables. The present study examined relationships between age, value of time over both the short and the long term, perceived time to death, self-perceived activity levels, and estimates of brief time intervals in a sample of older institutionalized males. The production method was used to obtain the estimates of time passage. Time intervals were increasingly underestimated with advancing age, indicating that time units are shorter with increasing age. While a number of other variables were interrelated, the only other factor consistently related to time estimates was the short-term value of time. Implications for future research and for interventions in institutional settings are discussed.

scholarly journals Technology for monitoring everyday prosthesis use: a systematic review

2020 ◽  
Author(s):  
Alix Chadwell ◽  
Laura Diment ◽  
Encarna Micó Amigo ◽  
Dafne Zuleima Morgado Ramirez ◽  
Alexander Dickinson ◽  
...  
Keyword(s):  
Upper Limb ◽  
Lower Limb ◽  
Battery Life ◽  
Activity Levels ◽  
Everyday Activity ◽  
Prosthetic Devices ◽  
Clinical Scores ◽  
Standard Clinical Practice ◽  
The Cost

BackgroundUnderstanding how prostheses are used in everyday life is central to the design, provision and evaluation of prosthetic devices and associated services. This paper reviews the scientific literature on methodologies and technologies that have been used to assess the daily use of both upper- and lower-limb prostheses. It discusses the types of studies that have been undertaken, the technologies used to monitor physical activity, the benefits of monitoring daily living and the barriers to long-term monitoring.MethodsA systematic literature search was conducted in PubMed, Web of Science, Scopus, CINAHL and EMBASE of studies that monitored the activity of prosthesis-users during daily-living.Results60 lower-limb studies and 9 upper-limb studies were identified for inclusion in the review. The first studies in the lower-limb field date from the 1990s and the number has increased steadily since the early 2000s. In contrast, the studies in the upper-limb field have only begun to emerge over the past few years. The early lower-limb studies focused on the development or validation of actimeters, algorithms and/or scores for activity classification. However, most of the recent lower-limb studies used activity monitoring to compare prosthetic components. The lower-limb studies mainly used step-counts as their only measure of activity, focusing on the amount of activity, not the type and quality of movements. In comparison, the small number of upper-limb studies were fairly evenly spread between development of algorithms, comparison of everyday activity to clinical scores, and comparison of different prosthesis user populations. Most upper-limb papers reported the degree of symmetry in activity levels between the arm with the prosthesis and the intact arm.ConclusionsActivity monitoring technology used in conjunction with clinical scores and user feedback, offers significant insights into how prostheses are used and whether they meet the user’s requirements. However, the cost, limited battery-life and lack of availability in many countries mean that using sensors to understand the daily use of prostheses and the types of activity being performed has not yet become a feasible standard clinical practice. This review provides recommendations for the research and clinical communities to advance this area for the benefit of prosthesis users.

scholarly journals Bilateral compartment syndrome of the lower limbs after urological surgery in the lithotomy position: a clinical case

2019 ◽  
Vol 18 ◽  
Author(s):  
José Maciel Caldas dos Reis ◽  
Lauro José Mendes Queiroz ◽  
Pablo Ferreira Mello ◽  
Renan Kleber Costa Teixeira ◽  
Fábio de Azevedo Gonçalves
Keyword(s):  
Compartment Syndrome ◽  
Wound Closure ◽  
Early Recognition ◽  
Acute Compartment Syndrome ◽  
Lower Limbs ◽  
Lithotomy Position ◽  
Activity Levels ◽  
Urological Surgery ◽  
Baseline Activity

Abstract Acute compartment syndrome of the lower extremities after urological surgery in the lithotomy position is a rare but potentially devastating clinical and medicolegal problem. We report the case of a 67-year-old male who underwent laparoscopic prostatectomy surgery to treat cancer, spending 180 minutes in surgery. Postoperatively, the patient developed acute compartment syndrome of both legs, needing emergency bilateral four-compartment fasciotomies, with repeated returns to the operating room for second-look procedures. The patient also exhibited delayed wound closure. He regained full function within 6 months, returning to unimpaired baseline activity levels. This report aims to highlight the importance of preoperative awareness of this severe complication which, in conjunction with early recognition and immediate surgical management, may mitigate long-term adverse sequelae and improve postoperative outcomes.

scholarly journals Adolescent wine consumption is inversely associated with long-term weight gain: results from follow-up of 20 or 22 years

2019 ◽  
Vol 18 (1) ◽  
Author(s):  
Pratiksha Poudel ◽  
Kamila Ismailova ◽  
Lars Bo Andersen ◽  
Sofus C. Larsen ◽  
Berit L. Heitmann
Keyword(s):  
Weight Gain ◽  
Alcohol Consumption ◽  
Smoking Status ◽  
Alcoholic Beverage ◽  
Activity Levels ◽  
Inverse Association ◽  
Wine Consumption ◽  
The Relationship

Abstract Background Several studies have suggested a link between the type of alcoholic beverage consumption and body weight. However, results from longitudinal studies have been inconsistent, and the association between adolescent alcohol consumption long-term weight gain has generally not been examined. Methods The study was based on data from 720 Danish adolescents aged between 15 to 19 years at baseline from the Danish Youth and Sports Study (YSS). Self-reported alcohol use, height, weight, smoking, social economic status (SES) and physical activity levels were assessed in baseline surveys conducted in 1983 and 1985, and in the follow up survey which was conducted in 2005. Multiple linear regression analyses were used to examine the association between alcohol consumption in adolescence and subsequent weight gain later in midlife. Results There was no significant association between total alcohol consumption during adolescence and change in BMI into midlife (P = 0.079) (β − 0.14; 95% CI -0.28, 0.005). Wine consumption was found to be inversely associated to subsequent BMI gain (P = 0.001) (β − 0.46; 95% CI -0.82, − 0.09) while the results were not significant for beer and spirit. The relationship did not differ by gender, but smoking status was found to modify the relationship, and the inverse association between alcohol and BMI gain was seen only among non-smokers (P = 0.01) (β − 0.24; 95% CI -0.41, − 0.06) while no association was found among smokers. Neither adolescent nor attained socioeconomic status in adulthood modified the relationship between alcohol intake and subsequent BMI gain. Conclusion Among non-smoking adolescents, consumption of alcohol, and in particular wine, seems to be associated with less weight gain until midlife. Trial registration The YSS cohort was retrospectively registered on August 2017. (Study ID number: NCT03244150).

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.

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