大样本恒星演化研究组知识库

Context. Symbiotic systems (i.e. a white dwarf + red giant star, WD + RG), which experience mass loss and form circumstellar material (CSM), have been suggested as being a possible progenitor system of type Ia supernovae (SNe Ia). After a supernova explosion, the supernova ejecta may interact with the CSM or the RG secondary. X-ray/radio emission (excess UV photons) is expected from the interaction between supernova ejecta and the CSM (RG secondary). However, no X-ray or radio emission that has originated from this type of system has been observationally detected, and only four SNe Ia have shown any possible signal of excess UV emission. These observational discrepancies need to be interpreted. 

Aims. We seek to determine the luminosity of these emissions, using detailed binary evolution algorithms to obtain the parameters of binary systems at themoment of the supernova explosion. 

Methods. We carried out a series of binary stellar evolution calculations, in which the effect of tidally enhanced wind on the evolution of WD + RG systems is incorporated. The WDs increase their mass to the Chandrasekhar mass limit, and then explode as SNe Ia. Based on the binary evolution results, we estimated the X-ray/radio (the excess UV) luminosity from the interactions between supernova ejecta and the CSM (the secondary) using a variety of published standard models. 

Results. We found that the X-ray flux may be high enough to be detected for a nearby SN Ia from a symbiotic system, while the radio flux is more likely to de detected when the companion is an asymptotic giant branch (AGB) star, and for a first giant branch (FGB) companion, the radio flux is generally lower than the detection limit. For two well observed SNe Ia, 2011fe and 2014J, almost all symbiotic systems are excluded by X-ray observations, but WD + FGB systemsmay not be ruled out by radio observations. The excess UV luminosity that results from the collision of supernova ejecta with the RG secondary may be high enough to be detected if the secondary fills its Roche lobe at the moment of a supernova explosion. 

Conclusions. The X-ray/radio emissions are more prevalent in SNe Ia from WD + AGB systems, although SNe Ia from such systems are rare. The UV luminosityfrom the collision of supernova ejecta to RG secondary is high enough, but only one in every few hundred SNe Ia manifests the signal from the collision.