Kavli Affiliate: Pau Amaro Seoane
| First 5 Authors: Pau Amaro Seoane, Pau Amaro Seoane, , ,
| Summary:
Sagittarius A* (Sgr A*), the supermassive black hole at the center of the
Milky Way, exhibits daily energetic flares characterized by non-thermal
emission in the infrared and X-ray bands. While the underlying accretion flow
is a Radiatively Inefficient Accretion Flow (RIAF) peaking at radio
frequencies, the mechanism powering these non-thermal transients remains
debated. Stellar dynamics predict a population of faint brown dwarfs orbiting
Sgr A*. These objects are progenitors of Extremely Large Mass Ratio Inspirals
(XMRIs), crucial sources of low-frequency gravitational waves for the future
Laser Interferometer Space Antenna (LISA) mission. We investigate whether the
tidal stripping of brown dwarfs provides a viable fueling mechanism for the
observed flares. Here we present high-resolution hydrodynamic simulations of
grazing tidal interactions coupled with a parameterized non-thermal radiation
model. We demonstrate that the dynamics of the tidal fallback and subsequent
viscous evolution naturally reproduce the fundamental temporal characteristics
of observed flares: the peak luminosity and the characteristic 1-hour duration.
We show that this fueling mechanism is dynamically viable and energetically
consistent, placing strong constraints on the required efficiency of the
non-thermal emission process, suggesting extreme radiative inefficiency. These
findings provide compelling evidence for a hidden population of brown dwarfs in
the Galactic Center. Crucially, the observed high flare frequency implies tight
orbits characteristic of advanced inspirals. This establishes a direct link
between electromagnetic transients and active gravitational wave sources,
alerting the LISA consortium years in advance to the presence of specific XMRI
systems promising exceptionally high signal-to-noise ratios for precision tests
of general relativity.
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