An Improved Orbital Period for GY Cancri Based on Two K2 Campaigns

TL;DR

This paper refines the orbital period of GY Cancri using extensive K2 satellite data and additional observations, significantly improving the ephemeris accuracy and analyzing brightness-related timing residuals.

Contribution

The study provides a more precise orbital period and ephemeris for GY Cancri by combining multiple datasets, with no evidence of period change.

Findings

Refined orbital period with reduced error over 18 years

No significant orbital period derivative detected

Detected correlation between brightness and eclipse timing residuals

Abstract

GY Cnc is a deeply eclipsing cataclysmic variable star with an orbital period of 4.21 hours that has shown several dwarf nova outbursts. The variable was continuously observed by the K2/Kepler satellite with a short cadence in Campaign 5 (C05) for 75 days during 2015. The star was again observed in 2017/2018 for 80 consecutive days during Campaign 16 (C16). 419 well-observed eclipses were measured over C5 and 446 timings were determined in C16. A new ephemeris was calculated combining the K2 data, previously published timings, new light curves from the KELT Follow-Up Network, and additional observations in the AAVSO database. We have refined the orbital period of GY Cnc and improved its ephemeris which had accumulated an error of about 300s over 18 years. A quadratic term was not found to be significant indicating that there is currently no detectable orbital period derivative. We observed a correlation between the quiescent system brightness and the eclipse timing residuals that are as large as +/-15s in the K2 data.