Remnant evolution after a carbon–oxygen white dwarf merger

By Sung-Chul Yoon, Philipp PodsiadlowskiStephan Rosswog. 2007

215 citations recorded by the source corpus.

We systematically explore the evolution of the merger of two carbon-oxygen (CO) white dwarfs. The dynamical evolution of a 0.9Msolar + 0.6Msolar CO white dwarf merger is followed by a 3D smoothed particle hydrodynamics (SPH) simulation. The calculation uses a state-of-the-art equation of state that is coupled to an efficient nuclear reaction network that accurately approximates all stages from helium burning up to nuclear statistical equilibrium. We use an elaborate prescription in which artificial viscosity is essentially absent, unless a shock is detected, and a much larger number of SPH particles than earlier calculations. Based on this simulation, we suggest that the central region of the merger remnant can, once it has reached quasi-static equilibrium, be approximated as a differentially rotating CO star, which consists of a slowly rotating cold core and a rapidly rotating hot envelope surrounded by a centrifugally supported disc. We construct a model of the CO remnant that mimics the results of the SPH simulation using a 1D hydrodynamic stellar evolution code and then follow its secular evolution, where we include the effects of rotation on the stellar structure and the transport of angular momentum. The influence of the Keplerian disc is implicitly treated by considering mass accretion from the disc on to the hot envelope. The stellar evolution models indicate that the growth of the cold core is controlled by neutrino cooling at the interface between the core and the hot envelope, and that carbon ignition in the envelope can be avoided despite high effective accretion rates. This result suggests that the assumption of forced accretion of cold matter that was adopted in previous studies of the evolution of double CO white dwarf merger remnants may not be appropriate. Specifically we find that off-centre carbon ignition, which would eventually lead to the collapse of the remnant to a neutron star, can be avoided if the following conditions are satisfied. (1) When the merger remnant reaches quasi-static equilibrium, the local maximum temperature at the interface between the core and the envelope must be lower than the critical limit for carbon ignition. (2) Angular momentum loss from the central merger remnant should not occur on a time-scale shorter than the local neutrino cooling time-scale at the interface. (3) The mass accretion rate from the centrifugally supported disc must be sufficiently low to 10-5Msolaryr-1). Our results imply that at least some products of double CO white dwarfs merger may be considered good candidates for the progenitors of Type Ia supernovae. In this case, the characteristic time delay between the initial dynamical merger and the eventual explosion would be ~105yr.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/7502370b85110513e82582f51086feb84cf235ca

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Citations in the corpus

Fast Radio Bursts from Magnetars Born in Binary Neutron Star Mergers and Accretion Induced Collapse (2019, background): “…a non-degenerate binary companion (e.g., Nomoto et al. 1979; Taam & van den Heuvel 1986; Canal et al. 1990; Nomoto & Kondo 1991; Tauris et al. 2013; Schwab et al. 2015; Brooks et al. 2017) or following the merger of two white dwarfs in a binary system (e.g., Yoon et al. 2007; Schwab et al. 2016).”
RATES AND DELAY TIMES OF TYPE Ia SUPERNOVAE (2009, background): “Some new studies have found that some mergers might produce Type Ia supernovae, but the merger conditions must be severely refined (Yoon et al. 2007).”
SUB-CHANDRASEKHAR WHITE DWARF MERGERS AS THE PROGENITORS OF TYPE Ia SUPERNOVAE (2010, methodology): “Any nuclear processing happened at the core-envelope interface, as likely would any subsequent ignition (Nomoto & Iben 1985; Yoon et al. 2007).”
Constraining the Type Ia Supernova Progenitor: The Search for Hydrogen in Nebular Spectra (2006, background): “Nonetheless, theoretical loopholes remain (e.g., Piersanti et al. 2003; Yoon et al. 2007), and the observational sample of nearby double-degenerate systems is not complete (Nelemans et al. 2005).”
Short-duration gamma-ray bursts with extended emission from protomagnetar spin-down (2007, methodology): “Specifically, the accretion disk produced by a WD-WD merger prior to collapse (e.g., Yoon et al. 2007) may accrete onto the NS at later times, powering a bipolar outflow similar to that produced during the prompt accretion episode; in this case, the delay until EE reflects the accretion timescale…”
On the Progenitors of Type Ia Supernovae (2018, unknown): “…in this scenario the accretion is of carbon- and oxygen-rich material (thus avoiding altogether nova eruptions and helium shell flashes), it has been shown that at least under some conditions the merger can lead to central carbon ignition and an SN Ia (e.g., Yoon et al. 2007; Sato et al. 2015).”
SURFACE DETONATIONS IN DOUBLE DEGENERATE BINARY SYSTEMS TRIGGERED BY ACCRETION STREAM INSTABILITIES (2009, background): “Most studies of dynamically unstable DD systems focus on the evolution of the post-merger object and, assuming that the final object has a mass larger than the Chandrasekhar limit, on how the merged remnant may eventually lead to a Type Ia SNe (Livio 2000; Yoon et al. 2007).”
Supernova Type Ia progenitors from merging double white dwarfs - Using a new population synthesis model (2012, background): “A serious concern about the DD scenario is whether the collapse of the remnant would lead to a supernova or to a neutron star through accretion-induced collapse (see Nomoto & Iben 1985; Saio & Nomoto 1985; Piersanti et al. 2003; Yoon et al. 2007; Pakmor et al. 2010, 2012; Shen et al. 2012).”
A circumbinary disc in the final stages of common envelope and the core-degenerate scenario for Type Ia supernovae (2011, background): “Most simulations and calculations of double degenerate merger (e.g., Yoon et al. 2007) assume the merger to occur a long time after the CE phase, when the two WDs are already cold.”
NORMAL TYPE Ia SUPERNOVAE FROM VIOLENT MERGERS OF WHITE DWARF BINARIES (2012, background): “Ways to avoid the transformation of the carbon-oxygen white dwarf into an oxygen-neon white dwarf have been proposed (e.g. Yoon et al. 2007), but without conclusive results.”
Violent mergers of nearly equal-mass white dwarf as progenitors of subluminous Type Ia supernovae (2011, background): “The evolution of the binary is qualitatively similar to previous studies of merging double degenerate systems (e.g. Guerrero et al. 2004; Yoon et al. 2007; Lorén-Aguilar et al. 2009).”
Delay Time Distribution Measurement of Type Ia Supernovae by the Subaru/XMM-Newton Deep Survey and Implications for the Progenitor (2008, unknown): “A merger of two white dwarfs may result in an accretion induced collapse rather than a SN Ia (Saio & Nomoto 1985), but theoretical uncertainties are still quite large (Piersanti et al. 2003; Yoon et al. 2007).”
THE LONG-TERM EVOLUTION OF DOUBLE WHITE DWARF MERGERS (2011, methodology): “…of the merging process (Benz et al. 1990; Rasio & Shapiro 1995; Segretain et al. 1997; Guerrero et al. 2004; Lorén-Aguilar et al. 2005, 2009; Yoon et al. 2007; Dan et al. 2011; Raskin et al. 2011) find that the tidally disrupted WD is instead converted into material that is supported…”