scholarly journals Observing and modelling the young solar analogue EK Draconis: starspot distribution, elemental abundances, and evolutionary status

2021 ◽  
Vol 502 (3) ◽  
pp. 3343-3356
Author(s):  
H V Şenavcı ◽  
T Kılıçoğlu ◽  
E Işık ◽  
G A J Hussain ◽  
D Montes ◽  
...  
Keyword(s):  
Initial Conditions ◽  
Doppler Imaging ◽  
Evolutionary Status ◽  
Low Latitude ◽  
Surface Distribution ◽  
La Palma ◽  
Solar Abundances ◽  
Microturbulent Velocity ◽  
Solar Type ◽  
Process Elements

ABSTRACT Observations and modelling of stars with near-solar masses in their early phases of evolution are critical for a better understanding of how dynamos of solar-type stars evolve. We examine the chemical composition and the spot distribution of the pre-main-sequence solar analogue EK Dra. Using spectra from the HERMES Spectrograph (La Palma), we obtain the abundances of 23 elements with respect to the solar ones, which lead to a [Fe/H] = 0.03, with significant overabundance of Li and Ba. The s-process elements Sr, Y, and Ce are marginally overabundant, while Co, Ni, Cu, Zn are marginally deficient compared to solar abundances. The overabundance of Ba is most likely due to the assumption of depth-independent microturbulent velocity. Li abundance is consistent with the age and the other abundances may indicate distinct initial conditions of the pre-stellar nebula. We estimate a mass of 1.04 M⊙ and an age of $27^{+11}_{-8}$ Myr using various spectroscopic and photometric indicators. We study the surface distribution of dark spots, using 17 spectra collected during 15 nights using the CAFE Spectrograph (Calar Alto). We also conduct flux emergence and transport (FEAT) simulations for EK Dra’s parameters and produce 15-d-averaged synoptic maps of the likely starspot distributions. Using Doppler imaging, we reconstruct the surface brightness distributions for the observed spectra and FEAT simulations, which show overall agreement for polar and mid-latitude spots, while in the simulations there is a lack of low-latitude spots compared to the observed image. We find indications that cross-equatorial extensions of mid-latitude spots can be artefacts of the less visible southern-hemisphere activity.

scholarly journals The Evolutionary Status of Short-Period RS CVn and Related W UMa Eclipsing Binaries

1983 ◽  
Vol 71 ◽  
pp. 463-464 ◽  
Author(s):  
G. Russo ◽  
L. Milano ◽  
S. Mancuso
Keyword(s):  
Eclipsing Binaries ◽  
Evolutionary Status ◽  
Type Activity ◽  
Rs Cvn Stars ◽  
Short Period ◽  
Solar Type

Among the RS CVn stars showing solar-type activity, with spectral types ranging from F to K and total masses up to 4 M⊙, there are two peculiar groups with period less than one day:a)agroup with components well inside their Roche lobes (Short-Period-Group, hereinafter SPG) and b) a group with their components in a thin or marginal degree of contact, with lightcurves of W UMa-W type (hereinafter WWG).

scholarly journals Lithium in Cool Magnetic CP Stars: Some New Results of Observations, Using CAT (ESO) 2.6m (CrAO), (NOT) La Palma Telescopes

2000 ◽  
Vol 198 ◽  
pp. 489-494
Author(s):  
N. Polosukhina ◽  
D. Kurtz ◽  
M. Hack ◽  
P. North ◽  
I. Ilyin ◽  
...  
Keyword(s):  
Magnetic Star ◽  
Evolutionary Status ◽  
Mixing Processes ◽  
La Palma ◽  
Resonance Doublet

Lithium in cool magnetic CP stars in still poorly studied and estimations of the Li abundance in these stars are scarce. There is some evidence of variability of the LiI 6708 Â line, but this variability has not been studied systematicaly. Even the identification of the 6708 Â line with the LiI resonance doublet is still in doubt. This problem is important in the broader context of the Li abundance in various types of stars, as well as for deeper undersfanding of the magnetic star phonomenon itself. The reason for fhis is that the Li abundance in very sensitive to evolutionary status of the stars and their properties, such as the character and intensity of mixing processes.

scholarly journals Zeeman-Doppler imaging of active young solar-type stars

2016 ◽  
Vol 587 ◽  
pp. A28 ◽  
Author(s):  
T. Hackman ◽  
J. Lehtinen ◽  
L. Rosén ◽  
O. Kochukhov ◽  
M. J. Käpylä
Keyword(s):  
Doppler Imaging ◽  
Solar Type

scholarly journals Abundance Analysis of Alpha Ursae Minoris

1985 ◽  
Vol 82 ◽  
pp. 100-103
Author(s):  
Sunetra Giridhar
Keyword(s):  
Wavelength Range ◽  
Evolutionary Status ◽  
Spectrum Synthesis ◽  
Abundance Anomalies ◽  
Process Elements

AbstractWe have derived atmospheric abundances of the bright Cepheid a UMi in order to study the abundance anomalies in different elements. The atmospheric abundance of C, 0, Fe-peak elements Ca, Sc, Ti, Cr, Fe and heavier s-process elements Y, Ba, Ce and Sm have been derived using the method of spectrum synthesis. The abundance of carbon is derived using the C I lines in 4700A region, whereas for oxygen, the forbidden line at 6300.311A is employed. Abundances of the Fe-peak elements and s-process elements are obtained by synthesizing selected portions in the wavelength range 4330A - 4650A. The estimates of C/0 derived from the present investigation are compared with other Cepheids of similar period. The evolutionary status of a UMi is discussed in the light of these derived abundances.

scholarly journals How the planetary research helps to the stellar dynamo understanding

2012 ◽  
Vol 8 (S294) ◽  
pp. 471-475
Author(s):  
I. Boisse ◽  
M. Oshagh ◽  
C. Lovis ◽  
N. C. Santos ◽  
X. Dumusque ◽  
...  
Keyword(s):  
Planetary System ◽  
Magnetic Activity ◽  
Doppler Imaging ◽  
Habitable Zone ◽  
Stellar Activity ◽  
Term Variation ◽  
Solar Type ◽  
Low Mass ◽  
Stellar Dynamo

AbstractMost of the exoplanet science is dependent on the stellar knowledge. One of them that has to be understood is the magnetic activity when we search for planets with radial velocity or photometry measurements. The main shape of stellar activity and spots properties have to be understood, for example, to choose the best targets to search for low-mass planets in the habitable zone or to derive the accurate parameters of a planetary system. With that aim, we show in this presentation how these studies lead to give clues on spots latitudes and on the long term variation of stellar activity. The properties of magnetic activity on the low rotators solar-type stars are not easily reachable by other techniques (spectropolarimetry or Doppler imaging) and these studies should be used to constrain theories of stellar dynamo.

scholarly journals Spectroscopic Binaries Among λ Bootis-type Stars

2011 ◽  
Vol 7 (S282) ◽  
pp. 333-334
Author(s):  
Ernst Paunzen ◽  
Luciano Fraga ◽  
Ulrike Heiter ◽  
Ilian Kh. Iliev ◽  
Inga Kamp ◽  
...  
Keyword(s):  
Time Series ◽  
Parameter Estimation ◽  
Spectroscopic Binaries ◽  
Orbital Parameter ◽  
Evolutionary Status ◽  
Atmospheric Diffusion ◽  
Spectroscopic Binary ◽  
Accretion Process ◽  
Solar Abundances

AbstractThe small group of λ Bootis stars comprises late B to early F-type stars, with moderate to extreme (up to a factor 100) surface under-abundances of most Fe-peak elements and solar abundances of lighter elements (C, N, O, and S). The main mechanisms responsible for this phenomenon are atmospheric diffusion, meridional mixing, and accretion of material from their surroundings. Especially spectroscopic binary (SB) systems with λ Bootis-type components are very important to investigate the evolutionary status and accretion process in more details. Because also δ Scuti type pulsation was found for several members, it gives the opportunity to use the tools of astroseismology for further investigations. We present the results of our long term efforts of detailed abundance analysis, orbital parameter estimation and photometric time series analysis for five well investigated SB systems.

scholarly journals Magnetic Field Structure and Activity of the He-burning Giant 37 Comae

2013 ◽  
Vol 9 (S302) ◽  
pp. 367-368
Author(s):  
S. Tsvetkova ◽  
P. Petit ◽  
R. Konstantinova-Antova ◽  
M. Aurière ◽  
G. A. Wade ◽  
...  
Keyword(s):  
State Of The Art ◽  
Field Structure ◽  
Doppler Imaging ◽  
Evolutionary Status ◽  
Evolutionary Models ◽  
Chemical Abundance ◽  
Magnetic Field Structure ◽  
The Core ◽  
Type Giant ◽  
Structure And Activity

AbstractWe present the first magnetic map of the late-type giant 37 Com. The Least Squares Deconvolution (LSD) method and Zeeman Doppler Imaging (ZDI) inversion technique were applied. The chromospheric activity indicators Hα, S-index, Ca ii IRT and the radial velocity were also measured. The evolutionary status of the star has been studied on the basis of state-of-the-art stellar evolutionary models and chemical abundance analysis. 37 Com appears to be in the core Helium-burning phase.

scholarly journals Updated studies on exomoons in the HD 23079 system

2021 ◽  
Vol 38 ◽  
Author(s):  
O. Jagtap ◽  
B. Quarles ◽  
M. Cuntz
Keyword(s):  
Initial Conditions ◽  
Time Lag ◽  
Orbital Stability ◽  
Stability Limit ◽  
Outer Edge ◽  
Future Research ◽  
Tidal Interactions ◽  
System A ◽  
Solar Type ◽  
Outward Migration

Abstract We re-evaluate the outer edge of orbital stability for possible exomoons orbiting the radial velocity planet discovered in the HD 23079 system. In this system, a solar-type star hosts a Jupiter-mass planet in a nearly circular orbit in the outer stellar habitable zone. The outer stability limit of exomoons is deduced using N-body and tidal migration simulations considering a large range of initial conditions, encompassing both prograde and retrograde orbits. In particular, we extend previous works by evaluating many values in the satellite mean anomaly to identify and exclude regions of quasi-stability. Future observations of this system can make use of our results through a scale factor relative to the currently measured minimum mass. Using a constant time lag tidal model (Hut 1981), we find that plausible tidal interactions within the system are insufficient to induce significant outward migration toward the theoretical stability limit. While current technologies are incapable of detecting exomoons in this system, we comment on the detectability of putative moons through Doppler monitoring within direct imaging observations in view of future research capacities.

scholarly journals High-resolution spectroscopy of detached solar-type eclipsing binaries observed during the Kepler K2 mission

2020 ◽  
Vol 493 (2) ◽  
pp. 2329-2338
Author(s):  
B Hoyman ◽  
Ö Çakırlı
Keyword(s):  
Theoretical Models ◽  
Eclipsing Binaries ◽  
High Resolution Spectroscopy ◽  
Physical Parameters ◽  
Evolutionary Status ◽  
Low Mass Stars ◽  
Ongoing Effort ◽  
Stellar Parameter ◽  
Solar Type ◽  
Low Mass

ABSTRACT Solar-type stars in eclipsing binaries are proving to be a remarkable resource of knowledge for testing models of stellar evolution, as spectroscopic and photometric studies have opened up a window into their interiors. Until recently, many cases have been worked out with Kepler data. In an ongoing effort to elucidate this research, we examine five detached eclipsing binaries, selected from the Kepler catalogue. There is a well-known stellar parameter discrepancy for low-mass stars, in that the observed radii and masses are often larger and stars overluminous than predicted by theory by several per cent. In our samples, we found five double-lined binaries, with solar-type stars dominating the spectrum. The orbital and light-curve solutions were found for them, and compared with isochrones, in order to estimate absolute physical parameters and evolutionary status of the components. An important aspect of this work is that the calculated stellar radii and masses are consistent with theoretical models within the uncertainties, whereas the estimated temperatures from the disentangled spectra of the components are no different than predicted.

Sign in / Sign up

Export Citation Format

Share Document