  We examine properties of the population of SOHO/STEREO (dwarf) Kreutz
sungrazing comets from 2004 to 2013, including the arrival rates, peculiar
gaps, and a potential relationship to the spectacular comet C/2011 W3
(Lovejoy). Selection effects, influencing the observed distribution, are
largely absent among bright dwarf sungrazers, whose temporal sequence implies
the presence of a swarm, with the objects brighter at maximum than apparent
magnitude 3 arriving at a peak rate of about 4.6 per year in late 2010, while
those brighter than magnitude 2 at a peak rate of about 4.3 per year in early
2011, both a few times the pre-swarm rate. The entire population of SOHO/STEREO
Kreutz sungrazers also peaked about one year before the appearance of C/2011
W3. Orbital data show, however, that all bright dwarf sungrazers moved in paths
similar to that of comet C/1843 D1, deviating 10 deg or more from the orbit of
C/2011 W3 in the angular elements. The evidence from the swarm and the overall
elevated arrival rates suggests the existence of a fragmented sizable sungrazer
that shortly preceded C/2011 W3 but was independent of it. On the other hand,
these findings represent another warning signal that the expected 21st-century
cluster of spectacular Kreutz comets is on its way to perihelion, to arrive
during the coming decades. It is only in this sense that we find a parallel
link between C/2011 W3 and the spikes in the population of SOHO/STEREO Kreutz
sungrazers.
