Time Variable Broad Line Emission in NGC 4203: Evidence for Stellar
  Contrails
  Dual epoch spectroscopy of the lenticular galaxy, NGC 4203, obtained with the
Hubble Space Telescope (HST) has revealed that the double-peaked component of
the broad H{\alpha} emission line profile is time variable, increasing by a
factor of 2.2 in brightness between 1999 and 2010. Modeling the gas
distribution responsible for the double-peaked profiles indicates that a ring
is a more appropriate description than a disk and most likely represents the
contrail of a red supergiant star that is being tidally disrupted at a distance
of ~ 1500 AU from the central black hole. There is also a bright core of broad
H{\alpha} line emission that is not time variable and identified with a large
scale inflow from an outer radius ~1 pc. If the gas number density is > 10^6
cm^{-3}, as suggested by the absence of similarly broad [O I] and [O III]
emission lines, then the steady state inflow rate is ~ 2 x 10^{-2}
M{_{\sun}}/yr which exceeds the inflow requirement to explain the X-ray
luminosity in terms of radiatively inefficient accretion by a factor of ~6. The
central AGN is unable to sustain ionization of the broad line region, the
discrepancy is particularly acute in 2010 when the broad H{\alpha} emission
line is dominated by the contrail of the in-falling supergiant star. However,
ram pressure shock ionization produced by the interaction of the in-falling
supergiant with the ambient interstellar medium may help alleviate the ionizing
deficit by generating a mechanical source of ionization supplementing the
photoionization provided by the AGN.
