The Messenger: a galactic centre gravitational-wave beacon. (arXiv:1903.10698v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Abramowicz_M/0/1/0/all/0/1">Marek Abramowicz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bejger_M/0/1/0/all/0/1">Michal Bejger</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gourgoulhon_E/0/1/0/all/0/1">Eric Gourgoulhon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Straub_O/0/1/0/all/0/1">Odele Straub</a>

Our existence in the Universe resulted from a rare combination of
circumstances. The same must be true for any advanced extraterrestrial
civilisation. If there exist any in the Milky Way, they are likely scattered
over large distances in space and time, however, they must be aware of the
unique property of the Galactic centre: it hosts the closest massive black hole
to anyone in the Galaxy. A sufficiently advanced civilisation may have placed
material in orbit around this black hole to study it, extract energy from it,
and/or for communication purposes. In either case, its orbital motion will
necessarily be a source of gravitational waves. Here we show that a
Jupiter-mass “Messenger” on the innermost stable circular orbit around the
black hole can be sustained for a few billion years by the energy output of a
single star and emits an unambiguously artificial (continuous) gravitational
wave signal that will be observable with LISA-type detectors.

Our existence in the Universe resulted from a rare combination of
circumstances. The same must be true for any advanced extraterrestrial
civilisation. If there exist any in the Milky Way, they are likely scattered
over large distances in space and time, however, they must be aware of the
unique property of the Galactic centre: it hosts the closest massive black hole
to anyone in the Galaxy. A sufficiently advanced civilisation may have placed
material in orbit around this black hole to study it, extract energy from it,
and/or for communication purposes. In either case, its orbital motion will
necessarily be a source of gravitational waves. Here we show that a
Jupiter-mass “Messenger” on the innermost stable circular orbit around the
black hole can be sustained for a few billion years by the energy output of a
single star and emits an unambiguously artificial (continuous) gravitational
wave signal that will be observable with LISA-type detectors.

http://arxiv.org/icons/sfx.gif