Dwarf Novae in the OGLE Data. II. Forty New Dwarf Novae in the OGLE-III
  Galactic Disk Fields
  We report the discovery of forty erupting cataclysmic variable stars in the
OGLE-III Galactic disk fields: seventeen objects of U Gem type, four of Z Cam
type, and nineteen stars showing outbursts and superoutbursts typical for SU
UMa type dwarf novae. In the case of five stars we were able to estimate their
supercycle lengths. The obtained lengths are in the range 20-90 d, generally
between the typical SU UMa type variables and a few objects classified as the
ER UMa type variables. Since there is no significant difference between the two
types but a higher mass-transfer rate resulting in more frequent outbursts and
superoutbursts in the ER UMa type stars, we propose to discard this type as a
separate class of variables. We note that in one of the SU UMa type stars,
OGLE-GD-DN-039, we found a negative supercycle period change, in contrast to
other active systems of this type. Two of the new OGLE objects showed
long-duration WZ Sge-like superoutbursts followed by a sequence of echo
outbursts. All stars reported in this paper are part of the OGLE-III Catalog of
Variable Stars.
