The Recurrent Nova RS Ophiuchi

Page contents

Introduction

Quiescient Accretion Phase

Nova Outburst

Movie of Nova Outburst

References

Introduction

RS Ophiuchi is a recurrent nova with a period of about 22 years, timescale, consisting of a wind accreting binary system with a white dwarf (WD) very close to the Chandrasekhar limit and a red giant star (RG). The system is considered a prime candidate to evolve into an SNIa. For its most recent outbursts in 1985 and 2006, exquisite multiwavelength observational data are available.

We present a three dimensional hydrodynamic simulation of the quiescent accretion and the subsequent explosive phase. In combination with recent multi-cycle nova models, our results suggests that the WD in RS Oph will increase in mass. Several speculative outcomes then seem plausible. The WD may reach the Chandrasekhar limit and explode as an SN Ia. Alternatively, the mass loss of the RG could result in a smaller Roch volume, a common envelope phase, and a narrow WD + WD system. Angular momentum loss due to graviational wave emission could trigger the merger of the two WDs and -- perhaps -- an SN Ia via the double degenerate scenario.

Quiescient Accretion Phase

The computed circumstellar mass distribution in the quiescent phase is highly structured with a mass enhancement in the orbital plane of about a factor of 2 as compared to the poleward directions. For v_RG = 20 km/s and for nearly isothermal flows, we derive a mass transfer rate to the WD of 10% of the mass loss of the RG. For an RG mass loss of 10^-7 solar masse per year, we found the orbit of the system to decay by 3% per million years. With the derived mass transfer rate, multi-cycle nova models provide a qualitatively correct recurrence time, amplitude, and fastness of the nova.

Density structure during the accretion phase. Shown is density (logarithmic scale, g/cm3) in the orbital plane and in a plane perpendicular to the orbit for the entire computational domain (1015 cm a side, top) and a zoom around the accreting WD (1013 cm a side, bottom). The RG is shown in red, the WD in blue.

Nova Outburst

The simulated nova remnant evolves aspherically, propagating faster toward the poles. The shock velocities derived from the simulations are in agreement with those derived from observations.

Density structure of the nova remnant. Shown are density (logarithmic scale, g/cm3) and velocity (cm/s) in the orbital plane (left) and in a plane perpendicular to the orbit (right) at 29 hours (top) and 21 days (bottom) after the explosion. The RG is shown in red, the WD in blue.

Movie of Nova Outburst

The movie shows the relaxed flow in density during the accretion phase and the subsequent nova blast wave. The big panel on the left shows the orbital plane on a scale of 7*10¹⁴ cm a side. The right panels show the full domain, 10¹⁵ cm a side, in the orbital plane (upper panel) and normal to the orbital plane (lower panel). The time lapse covers a period of 21 days. The same logarithmic colour map applies to all three panels and covers the density range between 10^-18g/cm³ and 10^-13 g/cm³.
Available as avi format (9.5MB) or quicktime format (9.9MB).

References

R. Walder and D. Folini and S. N. Shore
3D simulations of RS Oph: from accretion to nova blast
Astronomy and Astrophysics Letter, in press
(Available as a 1.0MB gzipped pdf-file)