Tidal breakup of quadruple stars in the Galactic Centre
  The most likely origin of hypervelocity stars (HVSs) is the tidal disruption
of a binary star by the supermassive black hole (MBH) in the Galactic Centre
(GC). However, HE0437-5439, a $9$ M$_\odot$ B-type main-sequence star moving
with a heliocentric radial velocity of about $720$ km s$^{-1}$ at a distance of
$\sim 60$ kpc, and the recent discovered hypervelocity binary candidate (HVB),
traveling at $\sim 570$ km s$^{-1}$, challenge this standard scenario.
Recently, Fragione & Gualandris (2018) have demonstrated that the tidal breakup
of a triple star leads to an insufficient rate. Observations show that
quadruple stars made up of two binaries orbiting their common center of mass
(the so-called 2+2 quadruples) are $\approx 4\%$ of the stars in the solar
neighborhood. Although rarer than triples, 2+2 quadruple stars may have a role
in ejecting HVBs as due to their larger energy reservoir. We present a
numerical study of 2+2 quadruple disruptions by the MBH in the GC and find that
the production of HVBs has a probability $\lesssim 2-4\%$, which translates
into an ejection rate of $\lesssim 1$ Gyr$^{-1}$, comparable to the triple
disruption scenario. Given the low ejection rate, we suggest that alternative
mechanisms are responsible for the origin of HVBs, as the ejection from the
interaction of a young star cluster with the MBH in the GC and the origin in
the Large Magellanic Cloud.
