Dwarf Novae in the OGLE Data. II. Forty New Dwarf Novae in the OGLE-III Galactic Disk Fields

TL;DR

This paper reports the discovery of forty new dwarf novae in the OGLE-III Galactic disk fields, classifying their types, estimating supercycle lengths, and analyzing their outburst behaviors, contributing to the understanding of cataclysmic variable star populations.

Contribution

It introduces forty newly identified dwarf novae, estimates their supercycle lengths, and questions the validity of the ER UMa class as a separate category.

Findings

Supercycle lengths range from 20 to 90 days.

No significant difference between SU UMa and ER UMa types.

Negative supercycle period change observed in one star.

Abstract

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.