Neutral Gas within 20,000 Schwarzschild radii of Sagittarius A*
  Murchikova et al 2019 discovered a disk of cool ionized gas within 20,000
Schwarzschild radii of the Milky Way's Galactic Center black hole Sagittarius
A*. They further demonstrated that the ionizing photon flux in the region is
enough to keep the disk ionized, but there is not ample excess of this
radiation. This raised the possibility that some neutral gas could also be in
the region shielded within the cool ionized clumps. Here we present ALMA
observations of a broad 1.3 millimeter hydrogen recombination line H30alpha: n
= 31 -> 30, conducted during the flyby of the S0-2 star by Sgr A*. We report
that the velocity-integrated H30alpha line flux two month prior to the S0-2
pericenter passage is about 20% larger than it was one month prior to the
passage. The S0-2 is a strong source of ionizing radiation moving at several
thousand kilometers per second during the approach. Such a source is capable of
ionising parcels of neural gas along its trajectory, resulting in variation of
the recombination line spectra from epoch to epoch. We conclude that there are
at least (6.6 +- 3.3) x 10^{-6} Msun of neutral gas within 20,000 Schwarzschild
radii of Sgr A*.
