A Comprehensive K2 and Ground-Based Study of CRTS J035905.9+175034, an Eclipsing SU UMa System with a Large Mass Ratio

TL;DR

This study provides a detailed analysis of the eclipsing SU UMa system CRTS J035905.9+175034, combining space-based K2 data and ground observations to determine its properties, superoutburst behavior, and mass ratio, challenging existing theoretical limits.

Contribution

It offers the first superoutburst observation of this system with Kepler, and determines its fundamental parameters, including a high mass ratio near theoretical limits, supporting the thermal-tidal instability model.

Findings

Superoutburst with precursor and superhumps observed

Mass ratio estimated at 0.281, near theoretical maximum

Eclipse and hot spot analysis supports thermal-tidal instability

Abstract

CRTS J035905.9+175034 is the first eclipsing SU UMa system for which a superoutburst has been observed by Kepler in the short-cadence mode. The light curve contains one superoutburst, eight normal outbursts (including a precursor to the superoutburst), and several minioutbursts that are present before -- but not after -- the superoutburst. The superoutburst began with a precursor normal outburst, and shortly after the peak of the precursor, the system developed large-amplitude superhumps that achieved their maximum amplitude after just three superhump cycles. The period excess of the initial superhump period relative to the orbital period implies a mass ratio of 0.281 +/- 0.015, placing it marginally above most theoretical predictions of the highest-possible mass ratio for superhump formation. In addition, our analysis of the variations in eclipse width and depth, as well as the hot spot amplitudes, generally provides substantiation of the thermal-tidal instability model. The K2 data, in conjunction with our ground-based time-resolved spectroscopy and photometry from 2014-2016, allows us to determine many of the fundamental parameters of this system.