Prediction of a red nova outburst in KIC 9832227

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.

• The paper predicts an impending red nova outburst in the KIC 9832227 binary system by analyzing its exponentially decreasing orbital period, similar to the V1309 Sco precursor.
• Analysis indicates an exponential orbital period decline in KIC 9832227, fitting a model that predicts the merger and outburst around 2022.2 0.7, echoing the behavior of V1309 Sco before its nova.
• Precise timing measurements revealed timing variations suggesting a third stellar component in KIC 9832227, while photometric and spectroscopic data indicate a contact binary with a mass ratio of approximately 0.228.

Prediction of a Red Nova Outburst in KIC 9832227: An Overview

The study "PREDICTION OF A RED NOVA OUTBURST IN KIC 9832227" by Molnar et al. presents a sophisticated analysis of the binary star system KIC 9832227, proposing it as a candidate for an impending red nova event. This paper stands out in its application of observational data and modeling techniques aimed at predicting such rare astrophysical phenomena.

Key Findings

The central objective of the paper is the prediction of a red nova outburst based on the decreasing orbital period of a contact binary system. The authors draw parallels to the well-documented case of V1309 Sco, where an exponential decrease in the orbital period preceded a merger and subsequent nova outburst. In essence, the paper leverages prior observational insights to identify potential precursors to similar future events.

Several critical results underpin the authors' argument for KIC 9832227 being a red nova precursor:

• Exponential Orbital Period Decline: The analysis indicates that the orbital period of KIC 9832227 is decreasing exponentially, a characteristic signature seen in the V1309 Sco precursor prior to its outburst. The fitted model predicts the merger and outburst to occur in 2022.2 ± 0.7.
• Mass Ratio and Binary Characteristics: Spectroscopic and photometric data suggest a contact binary system with a mass ratio of approximately 0.228. This subverts theoretical expectations regarding the Darwin instability threshold, which traditionally predicts merger at much lower mass ratios.
• Detection of a Third Body: The periodic timing variations within the Kepler data of KIC 9832227 suggest the presence of a third stellar component, component C, with an orbital period of roughly 590 days and a minimum mass of 0.11 M☉.

Methodological Approach

The authors employ several robust observational data sets, including historical data from the Northern Sky Variability Survey (NSVS), ASAS, and extensive observations from the Kepler spacecraft. Additionally, they incorporate recent photometric and spectroscopic followups from Apache Point Observatory and Wyoming Infrared Observatory, as well as calibrated differential photometry from Calvin College.

The use of a least-squares light curve fitting and phase modeling technique, as opposed to traditional eclipse timing, affords precision in the face of timing noise induced by starspot activity. The strategy effectively refines orbital timing measurements, thereby enabling a more reliable assessment of period changes and substantiating the claim of a diminishing period.

Theoretical and Practical Implications

The prediction of a red nova outbreak not only holds significant implications for understanding late-stage stellar evolution in contact binaries but also highlights the role of precise timing observations in predictive astrophysical modeling. The formalism used reinforces the understanding that certain period derivatives can act as reliable harbingers of stellar mergers.

As high-cadence and all-sky survey data proliferate, such predictive models hold promise for more regularly anticipating transient celestial events. The characterization of red nova precursors, as proposed in this study, provides an observational framework that could be leveraged to detect similar systems poised for dynamical evolution and energetic outbursts.

Future Prospects

While the study confirms KIC 9832227 as a promising nova precursor, future work will need to focus on more detailed theoretical underpinnings of the merger process in contact binaries, alongside continued monitoring of KIC 9832227 and other similar systems. Such efforts would not only solidify the anticipated link between timing observations and red nova events but could also unravel more sophisticated aspects of binary star evolution and merger dynamics.

In conclusion, the prediction of a red nova in KIC 9832227 exemplifies the intersection of phenomenological modeling, robust observational strategies, and the promising potential for predictive astronomy. As the timeline to the predicted 2022 outburst narrows, enhancements in both prediction accuracy and theoretical grounding will be instrumental in advancing the field.