Non-standard modeling of a possible blue straggler star, KIC 11145123. (arXiv:2110.06926v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Hatta_Y/0/1/0/all/0/1">Yoshiki Hatta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sekii_T/0/1/0/all/0/1">Takashi Sekii</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Takata_M/0/1/0/all/0/1">Masao Takata</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Benomar_O/0/1/0/all/0/1">Othman Benomar</a>
Non-standard modeling of KIC 11145123, a possible blue straggler star, has
been asteroseismically carried out based on a scheme to compute stellar models
with the chemical compositions in their envelopes arbitrarily modified,
mimicking effects of some interactions with other stars through which blue
straggler stars are thought to be born. We have constructed a non-standard
model of the star with the following parameters: $M=1.36M_{odot}$,
$Y_{mathrm{init}}=0.26$, $Z_{mathrm{init}}=0.002$, and
$f_{mathrm{ovs}}=0.027$, where $f_{mathrm{ovs}}$ is the extent of
overshooting described as an exponentially decaying diffusive process. The
modification is down to the depth of $r/Rsim0.6$ and the extent $Delta X$,
which is a difference in surface hydrogen abundance between the
envelope-modified and unmodified models, is $0.06$. The residuals between the
model and the observed frequencies are comparable with those for the previous
models computed assuming standard single-star evolution, suggesting that it is
possible that the star was born with an relatively ordinary initial helium
abundance of $sim0.26$ compared with that of the previous models
($sim0.30$–$0.40$), then experienced some modification of the chemical
compositions, and gained helium in the envelope. Detailed analyses of the
non-standard model have implied that the elemental diffusion in the deep
radiative region of the star might be much weaker than that assumed in current
stellar evolutionary calculations; we need some extra mechanisms inside the
star, rendering the star a much more intriguing target to be further
investigated.
Non-standard modeling of KIC 11145123, a possible blue straggler star, has
been asteroseismically carried out based on a scheme to compute stellar models
with the chemical compositions in their envelopes arbitrarily modified,
mimicking effects of some interactions with other stars through which blue
straggler stars are thought to be born. We have constructed a non-standard
model of the star with the following parameters: $M=1.36M_{odot}$,
$Y_{mathrm{init}}=0.26$, $Z_{mathrm{init}}=0.002$, and
$f_{mathrm{ovs}}=0.027$, where $f_{mathrm{ovs}}$ is the extent of
overshooting described as an exponentially decaying diffusive process. The
modification is down to the depth of $r/Rsim0.6$ and the extent $Delta X$,
which is a difference in surface hydrogen abundance between the
envelope-modified and unmodified models, is $0.06$. The residuals between the
model and the observed frequencies are comparable with those for the previous
models computed assuming standard single-star evolution, suggesting that it is
possible that the star was born with an relatively ordinary initial helium
abundance of $sim0.26$ compared with that of the previous models
($sim0.30$–$0.40$), then experienced some modification of the chemical
compositions, and gained helium in the envelope. Detailed analyses of the
non-standard model have implied that the elemental diffusion in the deep
radiative region of the star might be much weaker than that assumed in current
stellar evolutionary calculations; we need some extra mechanisms inside the
star, rendering the star a much more intriguing target to be further
investigated.
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