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Lucky planets: how circum-binary planets survive the supernova in one of the inner-binary components

by Fedde Fagginger Auer, Simon Portegies Zwart

Submission summary

As Contributors: Simon Portegies Zwart
Arxiv Link: https://arxiv.org/abs/2101.08033v1 (pdf)
Code repository: http://amusecode.org
Date submitted: 2021-01-21 14:26
Submitted by: Portegies Zwart, Simon
Submitted to: SciPost Astronomy
Academic field: Astronomy
Specialties:
  • Solar and Stellar Astrophysics
Approaches: Theoretical, Computational

Abstract

Since the discovery of exoplanets around pulsars, there has been a debate on their origin. Popular scenarios include in situ formation or the dynamical capture of a planet in a dense stellar system. The possibility of a planet surviving its host star's supernova is often neglected, because a planet in orbit around a single exploding star is not expected to survive the supernova. A circum-binary planet, however, may stand a chance in staying bound when one of the binary components explodes. We investigate the latter and constrain the distribution of post-supernova orbital parameters of circum-binary planets. This is done by performing population synthesis calculations of binary stars until the first supernova. Just before the supernova, we add a planet in orbit around the binary to study its survivability. In our supernova model, the exploding star's mass is assumed to change instantaneously, and we apply a velocity kick to the newly formed remnant. The mass loss and velocity kick affect the orbits of the two stars and the planet. Only $2 \cdot 10^{-3}$ of systems survive the supernova while keeping the circum-binary planet bound. The surviving planetary orbits are wide ($a \apgt 10$ au) and eccentric ($e \apgt 0.3$). It turns out much more likely ($3\cdot 10^{-2}$ system fraction) that the newly formed compact object is ejected from the system, leaving the planet bound to its companion star in a highly eccentric orbit (typically $\apgt 0.9$). We expect that the Milky way Galaxy hosts at most $10$ x-ray binaries that are still orbited by a planet, and $\aplt 150$ planets that survived in orbit around the compact object's companion. These numbers should be convolved with the fraction of massive binaries that is orbited by a planet.

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Submission 2101.08033v1 on 21 January 2021

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