[Paper Review] The Place of Recurrent Novae among the Symbiotic Stars

J. Mikołajewska|ArXiv.org|Mar 26, 2008

Astronomical Observations and Instrumentation3 citations

TL;DR

This paper establishes that recurrent novae with red giant companions—specifically RS Oph and T CrB—qualify as symbiotic stars due to shared physical properties, including orbital parameters, mass transfer mechanisms, and accretion disc activity. The key finding is that these systems host the most massive white dwarfs (1.1–1.4 M⊙) among symbiotics, enabling their recurrent nova outbursts and potential Type Ia supernova progenitor status.

ABSTRACT

The observational properties of recurrent novae indicate that they can be divided into two subclasses:systems with a dwarf and a red giant secondary, respectively. The second type -- which includes RS Oph -- bears many similarities to symbiotic stars.

Motivation & Objective

• To determine the physical and orbital similarities between recurrent novae with red giant secondaries and classical symbiotic stars.
• To assess whether Roche-lobe overflow is the dominant mass transfer mechanism in these systems, especially given their short orbital periods.
• To investigate the role of unstable accretion discs in driving both Z And-type activity and recurrent nova eruptions in symbiotic recurrent novae (SyRNe).
• To clarify the evolutionary status of SyRNe, particularly the high white dwarf masses and their implications for Type Ia supernova formation.

Proposed method

• Analysis of updated orbital parameters (periods, mass ratios, component masses) from 70 symbiotic systems, including 5 new galactic systems and 3 spectroscopic orbits.
• Comparison of orbital and stellar parameters (e.g., white dwarf mass, giant mass) between SyRNe (RS Oph, T CrB) and classical symbiotics.
• Examination of light curves for ellipsoidal variability to infer Roche-lobe filling status of cool giants.
• Evaluation of spectroscopic data (e.g., vrot sin i) and kinematic features (e.g., jets, bipolar outflows) to assess accretion disc presence and dynamics.
• Use of mass-luminosity relations and evolutionary models to assess the thermal state and accretion history of hot components.
• Cross-analysis of outburst light curves (e.g., AG Peg, RX Pup) to compare recurrence timescales and luminosity evolution with SyRNe.

Experimental results

Research questions

• RQ1 Do recurrent novae with red giant companions share fundamental physical characteristics with classical symbiotic stars?
• RQ2 Is Roche-lobe overflow the dominant mass transfer mechanism in symbiotic recurrent novae, particularly in systems with short orbital periods?
• RQ3 What is the role of unstable accretion discs in driving both Z And-type activity and recurrent nova outbursts in SyRNe?
• RQ4 Why do SyRNe host the most massive white dwarfs among symbiotics, and what are the implications for their evolution and supernova potential?

Key findings

• RS Oph and T CrB have orbital periods of 453 and 227 days, respectively, placing them in the shorter-period tail of galactic S-type symbiotic systems.
• The white dwarfs in SyRNe are the most massive known in symbiotic systems, with masses of 1.1–1.4 M⊙, sufficient to trigger Type Ia supernovae.
• The cool giants in SyRNe are less massive (0.6–0.8 M⊙) than in other symbiotics, making them the least massive donors in the symbiotic class.
• Ellipsoidal light curve variability confirms that the cool giant in T CrB fills its Roche lobe, providing strong evidence for Roche-lobe overflow.
• In RS Oph, complex light curves with a moving bump and no secondary minimum suggest possible Roche-lobe overflow, though the evidence is less direct than in T CrB.
• Both Z And-type activity and the high/low states in SyRNe are driven by unstable disc accretion, but in SyRNe, hydrogen burning is unstable, leading to recurrent nova outbursts.