We have recently published observations of significant flux density variations at 1.3 cm in HÂ ii regions in the star forming regions Sgr B2 Main and North ( De Pree et al .
2014 ) .
To further study these variations , we have made new 7 mm continuum and recombination line observations of Sgr B2 at the highest possible angular resolution of the Karl G. Jansky Very Large Array ( VLA ) .
We have observed Sgr B2 Main and North at 42.9 GHz and at 45.4 GHz in the BnA configuration ( Main ) and the A configuration ( North ) .
We compare these new data to archival VLA 7 mm continuum data of Sgr B2 Main observed in 2003 and Sgr B2 North observed in 2001 .
We find that one of the 41 known ultracompact and hypercompact HÂ ii regions in Sgr B2 ( K2-North ) has decreased \sim 27 % in flux density from 142 \pm 14 mJy to 103 \pm 10 mJy ( 2.3 \sigma ) between 2001 and 2012 .
A second source , F3c-Main has increased \sim 30 % in flux density from 82 \pm 8 mJy to 107 \pm 11 mJy ( 1.8 \sigma ) between 2003 and 2012 .
F3c-Main was previously observed to increase in flux density at 1.3 cm over a longer time period between 1989 and 2012 ( De Pree et al .
2014 ) .
An observation of decreasing flux density , such as that observed in K2-North , is particularly significant since such a change is not predicted by the classical hypothesis of steady expansion of HÂ ii regions during massive star accretion .
Our new observations at 7 mm , along with others in the literature , suggest that the formation of massive stars occurs through time-variable and violent accretion .