Moment Of Supernova Explosion Research Articles

SALT observations of the supernova remnant MCSNR J0127−7332 and its associated Be X-ray binary SXP 1062 in the SMC

ABSTRACT We report the results of optical spectroscopy of the Small Magellanic Cloud supernova remnant (SNR) MCSNR J0127−7332 and the mass donor Be star, 2dFS 3831, in its associated high-mass X-ray binary SXP 1062 carried out with the Southern African Large Telescope. Using high-resolution long-slit spectra, we measured the expansion velocity of the SNR shell of ${\approx} 140 \, {\rm \, km\, s^{-1}}$, indicating that MCSNR J0127−7332 is in the radiative phase. We found that the observed line ratios in the SNR spectrum can be understood if the local interstellar medium is ionized by 2dFS 3831 and/or OB stars around the SNR. We propose that MCSNR J0127−7332 is the result of supernova explosion within a bubble produced by the stellar wind of the supernova progenitor and that the bubble was surrounded by a massive shell at the moment of supernova explosion. We estimated the age of MCSNR J0127−7332 to be ${\lesssim} 10\, 000$ yr. We found that the spectrum of 2dFS 3831 changes with orbital phase. Namely, the equivalent width of the H α emission line decreased by ≈40 per cent in ≈130 d after periastron passage of the neutron star and then almost returned to its original value in the next ≈100 d. Also, the spectrum of 2dFS 3831 obtained closest to the periastron epoch (about 3 weeks after the periastron) shows a noticeable emission line of He ii λ4686, which disappeared in the next 2 weeks. We interpret these changes as a result of the temporary perturbation and heating of the disc as the neutron star passes through it.

Subdwarf B stars as possible surviving companions in Type Ia supernova remnants

Although type Ia supernovae (SNe Ia) are so important in many astrophysical fields, a debate on their progenitor model is still endless. Searching the surviving companion in a supernova remnant (SNR) may distinguish different progenitor models, since a companion still exists in the remnant for the single-degenerate (SD) model, but does not for the double degenerate (DD) model. However, some recent surveys do not discover the surviving companions in the remnant of SN 1006 and Kepler's supernova, which seems to disfavor the SD model. Such a result could be derived from an incorrect survey target. Here, based on the common-envelope wind SD model for SNe Ia, in which the initial binary system consists of a white dwarf (WD) and a main-sequence (MS) star, we found that the companion at the moment of supernova explosion may be a MS, red-giant (RG) or subdwarf B (sdB) star if a spin-down timescale of less than $10^{\rm 7}$ yr is assumed. We show the properties of the companions at the moment of supernova explosion, which are key clues to search the surviving companions in SNRs. Here, we suggest that the sdB star may be the surviving companion in some SNRs, even if the progenitor systems are the WD + MS systems. The SNe Ia with the sdB companions may contribute to all SNe Ia as much as 22\%.

The X-ray/radio and UV luminosity expected from symbiotic systems as the progenitor of SNe Ia

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) via some published standard models. 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 systems may not be ruled out by radio observations. The excess UV luminosity resulting 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 supernova explosion. 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 luminosity from the collision of supernova ejecta to RG secondary is high enough, but only 1 in every few hundred SNe Ia manifests the signal from the collision.

Abundances of59Co and59Ni in the cosmic ray flux

Two main hypotheses for the origin of Galactic cosmic rays are the "supernova" and "superbubble" origin hypotheses. We analyse the evidence for the superbubble hypothesis provided by the measurements of the relativive abundances of isotopes of cobalt and nickel in the cosmic ray flux. We compare the measured upper limit on the abundance of 59Ni in the cosmic ray flux with the 59Ni abundance predictions of the up-to-date stellar evolution models. Non-detection of 59Ni in the cosmic ray flux has previously been attributed to a large time delay of the order of 1e5 yr between the moment of supernova explosion and the onset of particle acceleration process. This large time delay was considered as an argument in favour of the "superbubble" scenario. We show that the recent calculation of the 59Ni yield of massive stars, which takes into account the initial mass range up to 120 solar masses and includes stellar rotation, results in prediction of low 59Ni abundance relative to its decay product 59Co. The predicted abundance is consistent with the upper bound on 59Ni abundance in the cosmic ray flux for the supernova parameters assumed. This result removes the necessity of decay of 59Ni in the time interval between the supernova explosion and the onset of acceleration process and restores the consistency of measurements of 59Ni / 59Co abundances with the "supernova" hypothesis of the CR origin.

Companion stars of Type Ia supernovae with different metallicities

Meng, Chen & Han (2009) comprehensively and systemically studied the WD + MS system by detailed binary evolution calculations. Following their studies, we have carried out a series of binary population synthesis studies about the properties of the companions of SNe Ia for different metallicities $Z$. We present the distributions of the masses, $M_{\rm 2}^{\rm SN}$, the radii, $R_{\rm 2}^{\rm SN}$, of companions, and the periods, $P_{\rm SN}$, and the ratios of separations to radii, $A/R_{\rm 2}^{\rm SN}$, of WD + MS systems for various $Z$ at the moment of supernova explosion. These arameters can be applied to constrain the numerical simulation of the interaction between the ejecta of a supernova and its companion. We also show the distributions of some integral properties of companions, i.e. the mass, the space velocity and the surface gravity, for various $Z$ after the interaction. The distributions may help to search companion in a supernova remnant. All the parameters above significantly change with $Z$. Incorporating the simulation results of interaction between supernovae ejecta and companions in Marietta et al. (2000) and Kasen et al. (2004) into our binary population synthesis study, we found that more than 75% of all supernovae have enough polarization signal which can be detected by spectropolarimetric observations. We also found that 13 to 14 per cent SNe Ia belong to the supernovae like 1991T, which is consistent with observations within errors. This may indicate that SNe 1991T-like have not any special properties in physics except for the viewing angle of an observer.

Color excesses of type Ia supernovae from the single-degenerate channel model

The single degenerate model is the most widely accepted progenitor model of type Ia supernovae (SNe Ia), in which a carbon-oxygen white dwarf (CO WD) accretes hydrogen-rich material from a main sequence or a slightly evolved star (WD+MS) to increase its mass, and explodes when its mass approaches the Chandrasekhar mass limit. During the mass transfer phase between the two components, an optically thick wind may occur and the material lost as wind may exist as circumstellar material (CSM). Searching for the CSM around a progenitor star is helpful for discriminating different progenitor models of SNe Ia. In addition, the CSM is a source of color excess. The purpose of this paper is to study the color excess produced from the single-degenerate progenitor model with an optically thick wind, and reproduce the distribution of color excesses of SNe Ia. Meng et al. systemically carried out binary evolution calculations of the WD +MS systems for various metallicities and showed the parameters of the systems before Roche lobe overflow and at the moment of supernova explosion in Meng & Yang. With the results of Meng et al., we calculate the color excesses of SNe Ia at maximum light via a simple analytic method. We reproduce the distribution of color excesses of SNe Ia by our binary population synthesis approach if the velocity of the optically thick wind is taken to be an order of magnitude of 10 km s−1. However, if the wind velocity is larger than 100 km s−1, the reproduction is bad.

The single degenerate channel for the progenitors of Type Ia supernovae

AbstractWe have carried out a detailed study of the single-degenerate channel for the progenitors of type Ia supernovae (SNe Ia). In the model, a carbon-oxygen white dwarf (CO WD) accretes hydrogen-rich material from an unevolved or a slightly evolved non-degenerate companion to increase its mass to Chandrasekhar mass limit. Incorporating the prescription of Hachisuet al. (1999a) for the accretion efficiency into Eggleton's stellar evolution code and assuming that the prescription is valid for all metallicities, we performed binary stellar evolution calculations for more than 25,000 close WD binary systems with various metallicities. The initial parameter spaces for SNe Ia are presented in an orbital period-secondary mass (logPi,M2i) plane for eachZ.Adopting the results above, we studied the birth rate of SNe Ia for variousZvia binary population synthesis. From the study, we see that for a highZ, SNe Ia occur systemically earlier and the peak value of the birth rate is larger if a single starburst is assumed. The Galactic birth rate from the channel is lower than (but comparable to) that inferred from observations.We also showed the distributions of the parameters of the binary systems at the moment of supernova explosion and the distributions of the properties of companions after supernova explosion. The former provides physics input to simulate the interaction between supernova ejecta and its companion, and the latter is helpful for searching the companions in supernova remnants.