# Prediction of a red nova outburst in KIC 9832227

## TL;DR

This paper predicts an imminent red nova in KIC 9832227 by analyzing its contact binary system's orbital timing, suggesting a merger around 2022, and introduces a method to identify similar precursors in our galaxy.

## Contribution

It develops a novel observational approach to identify red nova precursors using orbital timing signatures, and applies it to KIC 9832227, providing the first candidate prediction for an upcoming red nova.

## Key findings

- KIC 9832227 is a contact binary with decreasing orbital period.
- Estimated merger date is around the year 2022.
- Evidence of a third component influencing timing data.

## Abstract

We present the first identification of a candidate precursor for an imminent red nova. Our prediction is based on the example of the precursor to the red nova V1309 Sco, which was retrospectively found to be a contact binary with an exponentially decreasing period. We explore the use of this distinctive timing signature to identify precursors, developing the observational and analysis steps needed. We estimate that our Galaxy has roughly 1-10 observable precursors. Specifically, we lay out the observational case for KIC 9832227, which we identified as a tentative candidate two years ago (Molnar et al. 2015, AAS Meeting Abstracts 415.05). Orbital timing over the past two years has followed the tentative exponential fit. As of late 2015, the period time derivative went beyond the range found in other systems (dP/dt < 1x10^{-8}), a necessary criterion for a serious candidate. We estimate time of merger is the year 2022.2(7). Double absorption line spectra confirm directly the 0.458 d light curve period is a contact binary system and yield a mass ratio m_B/m_A = 0.228(3). Closer analysis of the Kepler timing data shows evidence of a component C with orbital period P_C = 590(8) days and m_C x sin i_C = 0.11 solar masses. An alternative interpretation of the long term timing trend, light travel time delay due to orbit around a distant component D, is ruled out by the spectroscopic data for any nondegenerate star. Additional measurements are needed to test further the merging hypothesis and to utilize fully this fortuitous opportunity.