Observing and modelling the young solar analogue EK Draconis: starspot distribution, elemental abundances, and evolutionary status. (arXiv:2101.07248v2 [astro-ph.SR] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Senavci_H/0/1/0/all/0/1">H.V. Şenavcı</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kilicoglu_T/0/1/0/all/0/1">T. Kılıçoğlu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Isik_E/0/1/0/all/0/1">E. Işık</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hussain_G/0/1/0/all/0/1">G.A.J. Hussain</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Montes_D/0/1/0/all/0/1">D. Montes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bahar_E/0/1/0/all/0/1">E. Bahar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Solanki_S/0/1/0/all/0/1">S.K. Solanki</a>
Observations and modelling of stars with near-solar masses in their early
phases of evolution is 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 $[{rm Fe/H}]=0.03$, 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 $M_odot$ 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-day-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.
Observations and modelling of stars with near-solar masses in their early
phases of evolution is 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 $[{rm Fe/H}]=0.03$, 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 $M_odot$ 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-day-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.
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