Lithium Enrichment Signatures of Planetary Engulfment Events in Evolved Stars. (arXiv:2002.05275v1 [astro-ph.SR])

Lithium Enrichment Signatures of Planetary Engulfment Events in Evolved Stars. (arXiv:2002.05275v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Soares_Furtado_M/0/1/0/all/0/1">M. Soares-Furtado</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cantiello_M/0/1/0/all/0/1">Matteo Cantiello</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+MacLeod_M/0/1/0/all/0/1">Morgan MacLeod</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ness_M/0/1/0/all/0/1">Melissa K. Ness</a>

Planetary engulfment events have long been proposed as a lithium (Li)
enrichment mechanism contributing to the population of Li-rich giants
$(A(mathrm{Li}) geq 1.5$ dex). Using $GALAH$ survey data and MESA stellar
models, we calculate the strength and duration of the Li enrichment signature
produced in the convective envelope of a host star that has engulfed a hot
Jupiter (HJ) companion. We consider solar-metallicity stars in the mass range
of $1.0-2.0~mathrm{M_{odot}}$ and the Li supplied by a HJ of
$1.0~mathrm{M_{J}}$. We explore engulfment events that occur near the main
sequence turn-off (MSTO) and out to orbital separations of
$R_{star}{sim}~0.1~mathrm{AU}= 22~mathrm{R_{odot}}$. We map our results
onto the Hertzsprung-Russell (H-R) Diagram, revealing the parameter space where
planetary engulfment events produce significant Li enrichment signatures. We
also map the associated survival times of these signatures, which range across
9 orders of magnitude. Our calculations indicate that if the HJ engulfment
event occurs near the MSTO or on the subgiant branch, Li enrichment can be
measured at a $5sigma$ confidence level and with strengths that exceed
meteoritic abundance measurements. Moreover, for stars of
$1.4~mathrm{M_{odot}}$, these signatures are predicted to survive for up to 1
Gyr. We determine that Li enrichment beyond the subgiant branch must be
produced by other mechanisms, such as the Cameron-Fowler process or accretion
of material from an AGB companion.

Planetary engulfment events have long been proposed as a lithium (Li)
enrichment mechanism contributing to the population of Li-rich giants
$(A(mathrm{Li}) geq 1.5$ dex). Using $GALAH$ survey data and MESA stellar
models, we calculate the strength and duration of the Li enrichment signature
produced in the convective envelope of a host star that has engulfed a hot
Jupiter (HJ) companion. We consider solar-metallicity stars in the mass range
of $1.0-2.0~mathrm{M_{odot}}$ and the Li supplied by a HJ of
$1.0~mathrm{M_{J}}$. We explore engulfment events that occur near the main
sequence turn-off (MSTO) and out to orbital separations of
$R_{star}{sim}~0.1~mathrm{AU}= 22~mathrm{R_{odot}}$. We map our results
onto the Hertzsprung-Russell (H-R) Diagram, revealing the parameter space where
planetary engulfment events produce significant Li enrichment signatures. We
also map the associated survival times of these signatures, which range across
9 orders of magnitude. Our calculations indicate that if the HJ engulfment
event occurs near the MSTO or on the subgiant branch, Li enrichment can be
measured at a $5sigma$ confidence level and with strengths that exceed
meteoritic abundance measurements. Moreover, for stars of
$1.4~mathrm{M_{odot}}$, these signatures are predicted to survive for up to 1
Gyr. We determine that Li enrichment beyond the subgiant branch must be
produced by other mechanisms, such as the Cameron-Fowler process or accretion
of material from an AGB companion.

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