ABSTRACT
Asteroseismology using space-based telescopes is vital to our understanding of stellar structure and evolution. CoRoT, Kepler, and TESS space telescopes have detected large numbers of ...solar-like oscillating evolved stars. Solar-like oscillation frequencies have an important role in the determination of fundamental stellar parameters; in the literature, the relations between the two is established by the so-called scaling relations. In this study, we analyse data obtained from the observation of 15 evolved solar-like oscillating stars using the Kepler and ground-based telescopes. The main purpose of the study is to determine very precisely the fundamental parameters of evolved stars by constructing interior models using asteroseismic parameters. We also fit the reference frequencies of models to the observational reference frequencies caused by the He ii ionization zone. The 15 evolved stars are found to have masses and radii within ranges of 0.79–1.47 M⊙ and 1.60–3.15 R⊙, respectively. Their model ages range from 2.19 to 12.75 Gyr. It is revealed that fitting reference frequencies typically increase the accuracy of asteroseismic radius, mass, and age. The typical uncertainties of mass and radius are ∼3–6 and ∼1–2 per cent, respectively. Accordingly, the differences between the model and literature ages are generally only a few Gyr.
ABSTRACT
Planets and planet candidates are subjected to great investigation in recent years. In this study, we analyse 20 planet and planet-candidate host stars at different evolutionary phases. We ...construct stellar interior models of the host stars with the mesa e.volution code and obtain their fundamental parameters under influence of observational asteroseismic and non-asteroseismic constraints. Model mass range of the host stars is 0.74–1.55 $\rm M_{\odot }$. The mean value of the so-called large separation between oscillation frequencies and its variation about the minima shows the diagnostic potential of asteroseismic properties. Comparison of variations of model and observed large separations versus the oscillation frequencies leads to inference of fundamental parameters of the host stars. Using these parameters, we revise orbital and fundamental parameters of 34 planets and four planet candidates. According to our findings, radius range of the planets is 0.35–16.50 $\rm R_{{\oplus }}$. The maximum difference between the transit and revised radii occurs for Kepler-444b-f is about 25 per cent.
So-called scaling relations based on oscillation frequencies have the potential to reveal the mass and radius of solar-like oscillating stars. In the derivation of these relations, it is assumed that ...the first adiabatic exponent at the surface (
$\Gamma _{\rm \negthinspace 1s}$
) of such stars is constant. However, by constructing interior models for the mass range 0.8–1.6 M⊙, we show that
$\Gamma _{\rm \negthinspace 1s}$
is not constant at stellar surfaces for the effective temperature range with which we deal. Furthermore, the well-known relation between large separation and mean density also depends on
$\Gamma _{\rm \negthinspace 1s}$
. Such knowledge is the basis for our aim of modifying the scaling relations. There are significant differences between masses and radii found from modified and conventional scaling relations. However, a comparison of predictions of these relations with the non-asteroseismic observations of Procyon A reveals that new scaling relations are effective in determining the mass and radius of stars. In the present study, solar-like oscillation frequencies of 89 target stars (mostly Kepler and CoRoT) were analysed. As well as two new reference frequencies (νmin1 and νmin2) found in the spacing of solar-like oscillation frequencies of stellar interior models, we also take into account νmin0. In addition to the frequency of maximum amplitude, these frequencies have a very strong diagnostic potential in the determination of fundamental properties. The present study applies the derived relations from the models to the solar-like oscillating stars, and computes their effective temperatures using purely asteroseismic methods. There are in general very close agreements between effective temperatures from asteroseismic and non-asteroseismic (spectral and photometric) methods. For the Sun and Procyon A, for example, the agreement is almost total.
Summary
Background
The efficacy and safety of certolizumab pegol (CZP) in moderate‐to‐severe Crohn's disease were demonstrated in two 26‐week double‐blind studies (PRECiSE 1 & 2).
Aim
To report the ...safety and efficacy outcomes of long‐term, CZP therapy from PRECiSE 3, in which patients received treatment up to 7 years treatment.
Methods
Patients completing PRECiSE 1 or 2 were eligible to enter PRECiSE 3 in which they received CZP 400 mg, open‐label, every 4 weeks (without additional induction therapy) for up to 7 years, for up to 91 doses from study start. Safety (adverse events, including infections and malignancies) and efficacy (Harvey–Bradshaw Index, faecal calprotectin, C‐reactive protein) were prospectively monitored. Remission was analysed using observed cases, last observation carried forward imputation and nonresponder imputation.
Results
A total of 595 patients entered the study; 117 (20%) completed 7 years. Discontinuation rates were 29.2%, 13.6%, 16.1%, 7.9%, 5.0%, 4.5% and 3.9% (years 1–7 respectively). During 1920 patient‐years of exposure to CZP, no new safety signals were observed. Incidence rates (new cases/100 patient‐years) for serious infections and malignant neoplasms were 4.37 and 1.06 respectively. No lymphoproliferative malignancies were reported. Clinical remission rates were ≥68% at each year (observed cases); rates by last observation carried forward and nonresponder imputation were 58% and 45% at year 1, 56% and 26% at year 3 and 55% and 13% at year 7 respectively.
Conclusion
Certolizumab pegol was well tolerated in the long‐term treatment of Crohn's disease, with sustained remission in some patients continuing in the study for up to 7 years. ClinicalTrials.gov identifier NCT00552058.
Aims.
Both components of the bright eclipsing binary
α
Dra have been resolved using long baseline interferometry and the secondary component has been shown to contribute approximately 15% of the ...total flux; however, a spectroscopic detection of the companion star has so far been unsuccessful. We aim for a firm spectroscopic detection of the secondary component of
α
Dra using state-of-the-art spectroscopic analysis methods for very high-quality spectroscopic observations. This will allow the determination of fundamental and atmospheric properties of the components in the system with high precision and accuracy.
Methods.
To achieve our goals, we use a combined data set from interferometry with the Navy Precision Optical Interferometer (NPOI), photometry with the TESS space observatory, and high-resolution spectroscopy with the H
ERMES
fibre-fed spectrograph at the La Palma observatory. We use the method of spectral disentangling to search for the contribution of a companion star in the observed composite H
ERMES
spectra, to separate the spectral contributions of both components, and to determine orbital elements of the
α
Dra system. TESS light curves are analysed in an iterative fashion with spectroscopic inference of stellar atmospheric parameters to determine fundamental stellar properties and their uncertainties. Finally, NPOI interferometric measurements are used for determination of the orbital parameters of the system and angular diameters of both binary components.
Results.
We report the first firm spectroscopic detection of the secondary component in
α
Dra and deliver disentangled spectra of both binary components. The components’ masses and radii are inferred with high precision and accuracy, and are
M
A
= 3.186 ± 0.044
M
⊙
,
R
A
= 4.932 ± 0.036
R
⊙
, and
M
B
= 2.431 ± 0.019
M
⊙
,
R
B
= 2.326 ± 0.052
R
⊙
for the primary and secondary components, respectively. Combined astrometric and spectroscopic analysis yields the semi-major axis of the system, which is ultimately used to derive the dynamical parallax of
π
= 11.48 ± 0.13 mas, and the distance
d
= 87.07 ± 1.03 pc to the
α
Dra system. Evolutionary analysis of both binary components with M
ESA
stellar structure and evolution models suggests the primary is an evolved post-TAMS A-type star, while the companion is a main-sequence A-type star with a convective core mass of
M
cc
= 0.337 ± 0.011
M
⊙
. Positions of both binary components in the Kiel- and HR-diagrams suggest a value of the convective core overshooting parameter
f
ov
well below 0.010
H
p
, and we infer the age of the system to be 310 ± 25 Myr.
Conclusions.
The inferred near-core mixing properties of both components do not support a dependence of the convective core overshooting on the stellar mass. At the same time, the
α
Dra system provides extra support to hypothesise that the mass discrepancy in eclipsing spectroscopic double-lined binaries is associated with inferior atmospheric modelling of intermediate- and high-mass stars, and less so with the predictive powerof stellar structure and evolution models as to the amount of near-core mixing and mass of the convective core.
ABSTRACT
We present the results of a systematic search of the Transiting Exoplanet Survey Satellite (TESS) 2-min cadence data for new rapidly oscillating Ap (roAp) stars observed during the Cycle 2 ...phase of its mission. We find seven new roAp stars previously unreported as such and present the analysis of a further 25 roAp stars that are already known. Three of the new stars show multiperiodic pulsations, while all new members are rotationally variable stars, leading to almost 70 per cent (22) of the roAp stars presented being α2 CVn-type variable stars. We show that targeted observations of known chemically peculiar stars are likely to overlook many new roAp stars, and demonstrate that multiepoch observations are necessary to see pulsational behaviour changes. We find a lack of roAp stars close to the blue edge of the theoretical roAp instability strip, and reaffirm that mode instability is observed more frequently with precise, space-based observations. In addition to the Cycle 2 observations, we analyse TESS data for all-known roAp stars. This amounts to 18 further roAp stars observed by TESS. Finally, we list six known roAp stars that TESS is yet to observe. We deduce that the incidence of roAp stars amongst the Ap star population is just 5.5 per cent, raising fundamental questions about the conditions required to excite pulsations in Ap stars. This work, coupled with our previous work on roAp stars in Cycle 1 observations, presents the most comprehensive, homogeneous study of the roAp stars in the TESS nominal mission, with a collection of 112 confirmed roAp stars in total.
The large separations between the oscillation frequencies of solar-like stars are measures of stellar mean density. The separations have been thought to be mostly constant in the observed range of ...frequencies. However, detailed investigation shows that they are not constant, and their variations are not random but have very strong diagnostic potential for our understanding of stellar structure and evolution. In this regard, frequencies of the minimum large separation are very useful tools. From these frequencies, in addition to the large separation and frequency of maximum amplitude, Yildiz et al. recently have developed new methods to find almost all the fundamental stellar properties. In the present study, we aim to find metallicity and helium abundances from the frequencies, and generalize the relations given by Yildiz et al. for a wider stellar mass range and arbitrary metallicity (Z) and helium abundance (Y). We show that the effect of metallicity is significant for most of the fundamental parameters. For stellar mass, for example, the expression must be multiplied by ... For arbitrary helium abundance, ... Methods for determination of Z and Y from pure asteroseismic quantities are based on amplitudes (differences between maximum and minimum values of ...) in the oscillatory component in the spacing of oscillation frequencies. Additionally, we demonstrate that the difference between the first maximum and the second minimum is very sensitive to Z. It also depends on ... and small separation between the frequencies. Such a dependence leads us to develop a method to find Z (and Y) from oscillation frequencies. The maximum difference between the estimated and model Z values is about 14 per cent. It is 10 per cent for Y. (ProQuest: ... denotes formulae/symbols omitted.)
The large separations between the oscillation frequencies of solar-like stars are measures of stellar mean density. The separations have been thought to be mostly constant in the observed range of ...frequencies. However, detailed investigation shows that they are not constant, and their variations are not random but have very strong diagnostic potential for our understanding of stellar structure and evolution. In this regard, frequencies of the minimum large separation are very useful tools. From these frequencies, in addition to the large separation and frequency of maximum amplitude, Yıldız et al. recently have developed new methods to find almost all the fundamental stellar properties. In the present study, we aim to find metallicity and helium abundances from the frequencies, and generalize the relations given by Yıldız et al. for a wider stellar mass range and arbitrary metallicity (Z) and helium abundance (Y). We show that the effect of metallicity is significant for most of the fundamental parameters. For stellar mass, for example, the expression must be multiplied by (Z/Z⊙)0.12. For arbitrary helium abundance, M ∝ (Y/Y⊙)0.25. Methods for determination of Z and Y from pure asteroseismic quantities are based on amplitudes (differences between maximum and minimum values of Δν) in the oscillatory component in the spacing of oscillation frequencies. Additionally, we demonstrate that the difference between the first maximum and the second minimum is very sensitive to Z. It also depends on
${\nu _{\rm min}}_1/{\nu _{\rm max}}$
and small separation between the frequencies. Such a dependence leads us to develop a method to find Z (and Y) from oscillation frequencies. The maximum difference between the estimated and model Z values is about 14 per cent. It is 10 per cent for Y.
It is already stated in the previous studies that the radius of the giant planets is affected by stellar irradiation. The confirmed relation between radius and incident flux depends on planetary mass ...intervals. In this study, we show that there is a single relation between radius and irradiated energy per gram per second (l
−), for all mass intervals. There is an extra increase in radius of planets if l
− is higher than 1100 times energy received by the Earth (l
⊕). This is likely due to dissociation of molecules. The tidal interaction as a heating mechanism is also considered and found that its maximum effect on the inflation of planets is about 15 per cent. We also compute age and heavy element abundances from the properties of host stars, given in the TEPCat catalogue (Southworth 2011). The metallicity given in the literature is as Fe/H. However, the most abundant element is oxygen, and there is a reverse relation between the observed abundances Fe/H and O/Fe. Therefore, we first compute O/H from Fe/H by using observed abundances, and then find heavy element abundance from O/H. We also develop a new method for age determination. Using the ages we find, we analyse variation of both radius and mass of the planets with respect to time, and estimate the initial mass of the planets from the relation we derive for the first time. According to our results, the highly irradiated gas giants lose 5 per cent of their mass in every 1 Gyr.
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