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Origin of 1I/’Oumuamua. II. An ejected exo-Oort cloud object?
(Submitted on 31 Oct 2018)
1I/’Oumuamua is the first detected interstellar interloper. We test the hypothesis that it is representative of a background population of exo-Oort cloud objects ejected under the effect of post-main sequence mass loss and stellar encounters. We do this by comparing the cumulative number density of interstellar objects inferred from the detection of 1I/’Oumuamua to that expected from these two clearing processes. We consider the 0.08–8 M⊙ mass range, take into account the dependencies with stellar mass, Galactocentric distance, and evolutionary state, and consider a wide range of size distributions for the ejected objects. Our conclusion is that 1I/’Oumuamua is likely not representative of this background population, strengthened by the consideration that our estimate is likely an overestimate because it assumes exo-Oort clouds are frequent but the parameter space to form them is actually quite restricted. We discuss whether the number density of free-floating, planetary-mass objects derived from gravitational microlensing surveys could be used as a discriminating measurement regarding 1I/’Oumuamua’s origin (given their potential common origin). We conclude that this is challenged by the mass limitation of the surveys and the resulting uncertainty of the mass distribution. The detection of interlopers may be one of the few observational constraints of the low end of the mass distribution of free-floaters, with the caveat that, as we conclude here and in Moro-Mart\’ın (2018), it might not be appropriate to assume they are representative of an isotropic background population, which makes the derivation of a number density very challenging.
Comments: Submitted to ApJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1811.00023 [astro-ph.EP] (or arXiv:1811.00023v1 [astro-ph.EP] for this version)
From: Amaya Moro-Martin
[v1] Wed, 31 Oct 2018 18:00:02 UTC (235 KB)