  We present the longest, by a factor of two, near-infrared lightcurve from Sgr
A* - the supermassive black hole in the Galactic center. Achieved by combining
Keck and VLT data from one common night, which fortuitously had simultaneous
Chandra and SMA data, this lightcurve is used to address two outstanding
problems. First, a putative quasi-periodicity of ~20 min reported by groups
using ESO's VLT is not confirmed by Keck observations. Second, while the
infrared and mm-regimes are thought to be related based on reported time lags
between lightcurves from the two wavelength domains, the reported time lag of
20 min inferred using the Keck data of this common VLT/Keck night only is at
odds with the lag of ~100 min reported earlier. With our long lightcurve, we
find that (i) the simultaneous 1.3 millimeter observations are in fact
consistent with a ~100 min time lag, (ii) the different methods of NIR
photometry used by the VLT and Keck groups lead to consistent results, (iii)
the Lomb-Scargle periodogram of the whole NIR lightcurve is featureless and
follows a power-law with slope -1.6, and (iv) scanning the lightcurve with a
sliding window to look for a transient QPO phenomenon reveals for a certain
part of the lightcurve a 25 min peak in the periodogram. Using Monte Carlo
simulations and taking the number of trials into account, we find it to be
insignificant.
