WFI J161953.3+031909: eclipsing ER UMa-type and Z Cam-type star in the period gap

TL;DR

This paper reports the discovery of WFI J161953.3+031909 as the first eclipsing Z Cam star in the period gap, likely an ER UMa star with supercycles, providing insights into high mass-transfer rates in this evolutionary stage.

Contribution

It identifies a unique eclipsing star exhibiting both ER UMa and Z Cam states in the period gap, refining its orbital period and suggesting new avenues for understanding disk behavior.

Findings

First eclipsing Z Cam star in the period gap

Likely an ER UMa star with 60-80 day supercycles

Refined orbital period to 0.099419808 days

Abstract

WFI J161953.3+031909 was considered to be an eclipsing novalike object in the period gap. Using the Zwicky Transient Facility (ZTF) public database, I found that this object is the first eclipsing Z Cam star in the period gap, and is also most likely an ER UMa star with supercycles of 60-80 d. The longest outburst (most likely a superoutburst) comprised 35-46% of the supercycle in the extreme case. If superhumps are confirmed, this becomes the second object showing both ER UMa and Z Cam states after NY Ser. These objects have anomalously high mass-transfer rates despite that they are in the period gap. I refined the orbital period to be 0.099419808(8) d. We can expect to learn from WFI J161953.3+031909 using eclipses what is actually happening in the ER UMa-type and Z Cam-type disk. I also provide a revised classification of an eclipsing IW And star for BMAM-V383 = IPHAS J200822.55+300341.6 by detecting an IW And-type standstill.