Intermediate Luminosity Optical Transients (ILOTs) from merging giants. (arXiv:1904.11331v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Segev_R/0/1/0/all/0/1">Ran Segev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sabach_E/0/1/0/all/0/1">Efrat Sabach</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Soker_N/0/1/0/all/0/1">Noam Soker</a> (Technion, Israel)
We study the formation of intermediate luminosity optical transients (ILOTs)
from the merger of two cool giant stars. For the two stars to merge when both
are in their giant phases the stars must have close masses at their zero age
main sequence, and the orbital separation must be in the right range. After the
two giants merge, the two cores spirals-in toward each other within a common
envelope. This process ejects mass that powers radiation by recombination and
by collision with previously ejected mass. Using the stellar evolution
numerical code MESA for two binary systems with stellar masses of (15,15.75Mo)
and (31,31.5Mo), we find that the merger of the two cores releases
gravitational energy that marginally ejects the entire common envelope. This
implies that in many cases the two cores merge, i.e., a fatal common envelope
evolution, leading to a somewhat more luminous ILOT. Overall, we estimate that
a typical ILOT from merger of two cool giant stars lasts for several months to
several years and has a typical average luminosity of
L(ILOT)=10^6(M(CE)/10Mo)Lo, where M(CE) is the common envelope mass. Due to the
merger-driven massive outflow, we expect dust formation and a very red ILOT,
possibly even an infrared luminous and undetectable in the visible. As the
giants cannot launch jets, we expect the descendant nebula formed by the merger
process to have an elliptical morphology but with no bipolar lobes.
We study the formation of intermediate luminosity optical transients (ILOTs)
from the merger of two cool giant stars. For the two stars to merge when both
are in their giant phases the stars must have close masses at their zero age
main sequence, and the orbital separation must be in the right range. After the
two giants merge, the two cores spirals-in toward each other within a common
envelope. This process ejects mass that powers radiation by recombination and
by collision with previously ejected mass. Using the stellar evolution
numerical code MESA for two binary systems with stellar masses of (15,15.75Mo)
and (31,31.5Mo), we find that the merger of the two cores releases
gravitational energy that marginally ejects the entire common envelope. This
implies that in many cases the two cores merge, i.e., a fatal common envelope
evolution, leading to a somewhat more luminous ILOT. Overall, we estimate that
a typical ILOT from merger of two cool giant stars lasts for several months to
several years and has a typical average luminosity of
L(ILOT)=10^6(M(CE)/10Mo)Lo, where M(CE) is the common envelope mass. Due to the
merger-driven massive outflow, we expect dust formation and a very red ILOT,
possibly even an infrared luminous and undetectable in the visible. As the
giants cannot launch jets, we expect the descendant nebula formed by the merger
process to have an elliptical morphology but with no bipolar lobes.
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