Evidence of abrupt changes in the orbital periods of two cataclysmic variables

TL;DR

This study presents evidence of sudden orbital period changes in two cataclysmic variables, detected through eclipse timing, with no clear explanation for these abrupt shifts.

Contribution

It provides the first observational evidence of abrupt orbital period changes in cataclysmic variables using eclipse timing data.

Findings

Orbital period of HS 2325+8205 increased by 22.15 ms.

Orbital period of EP Dra increased by 4.51 ms.

No subsequent behavioral changes observed after the shifts.

Abstract

We report evidence from eclipse timing that two otherwise apparently normal cataclysmic variables have experienced abrupt changes in their orbital periods. The orbital period of HS 2325+8205 increased by 22.15 msec (1.3 x 10-6 of the orbital period) around 1 February 2011 and the orbital period of EP Dra increased by 4.51 msec (7.2 x 10-7 of the orbital period) around 7 December 2001. In neither case was there any apparent change in the subsequent behaviour of the system. These changes are currently unexplained.