On the identity of Tsesevich's "YY Dra"

TL;DR

This paper reexamines the historical identification of the variable star YY Dra, suggesting it was likely misidentified and is actually the known star DO Dra, highlighting issues in historical variable star records and the importance of accurate identification.

Contribution

The study critically analyzes Tsesevich's original identification of YY Dra, proposing that the star was misclassified and is actually DO Dra, emphasizing the need for careful historical data interpretation.

Findings

Tsesevich's original variables were misidentified or lost.

YY Dra likely corresponds to DO Dra based on historical and observational analysis.

Historical plate collections are crucial but often incomplete due to WWII destruction.

Abstract

Hill et al. (2022, arXiv:2203.00221) recently published analysis of the intermediate polar DO Dra (YY Dra) using TESS, ASAS-SN and ZTF data. They also attempted a search for the "lost" variable YY Dra using modern catalogs of variable stars and found no corresponding one. This search drew our renewed attention and we studied the original discovery paper of YY Dra by Tsesevich (Zessewitch). We found that two out of four variables reported by him were either lost or improperly studied. The coordinate offset from the correct position in another object was much larger than the expected error. Using the information of the published period and epoch of YY Dra, we suspect that Tsesevich used a couple of plates on which the object was invisible to derive the period rather than from a completely phased light curve. DO Dra sometimes spends high states around 14 mag for a month to several months and it would not be surprising if Tsesevich observed DO Dra in such a state and suspected it to be an Algol, urging him to examine the plate archive to obtain the moments when the variable was undetected. We suspect that Tsesevich indeed observed DO Dra, rather than a different, lost eclipsing variable. The final conclusion of this matter is almost impossible to reach due to the consequence of the World War II, destructing the large part of plate collections. Until the humanity becomes wise enough to restore this destruction and wise enough to be able to avoid further destruction of human achievements, the designation YY Dra would better be conserved as a record of our negative history and unambiguous DO Dra would better be used to designate the intermediate polar 3A 1148+719.