Consistency of the Infrared Variability of Sgr A* over 22 years
  We report new infrared measurements of the supermassive black hole at the
Galactic Center, Sgr A*, over a decade that was previously inaccessible at
these wavelengths. This enables a variability study that addresses variability
timescales that are ten times longer than earlier published studies. Sgr A* was
initially detected in the near-infrared with adaptive optics observations in
2002. While earlier data exists in form of speckle imaging (1995 - 2005), Sgr
A* was not detected in the initial analysis. Here, we improved our speckle
holography analysis techniques. This has improved the sensitivity of the
resulting speckle images by up to a factor of three. Sgr A* is now detectable
in the majority of epochs covering 7 years. The brightness of Sgr A* in the
speckle data has an average observed K magnitude of 16.0, which corresponds to
a dereddened flux density of $3.4$ mJy. Furthermore, the flat power spectral
density (PSD) of Sgr A* between $\sim$80 days and 7 years shows its
uncorrelation in time beyond the proposed single power-law break of $\sim$245
minutes. We report that the brightness and its variability is consistent over
22 years. This analysis is based on simulations using Witzel et al. (2018)
model to characterize infrared variability from 2006 to 2016. Finally, we note
that the 2001 periapse of the extended, dusty object G1 had no apparent effect
on the near-infrared emission from accretion flow onto Sgr A*. The result is
consistent with G1 being a self-gravitating object rather than a disrupting gas
cloud.
