Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe red supergiant and supernova rate problems: implications for core-collapse supernova physics
122
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Mapping supernovae to their progenitors is fundamental to understanding the collapse of massive stars. We investigate the red supergiant problem, which concerns why red supergiants with masses $sim16$-$30 M_odot$ have not been identified as progenitors of Type IIP supernovae, and the supernova rate problem, which concerns why the observed cosmic supernova rate is smaller than the observed cosmic star formation rate. We find key physics to solving these in the compactness parameter, which characterizes the density structure of the progenitor. If massive stars with compactness above $xi_{2.5} sim 0.2$ fail to produce canonical supernovae, (i) stars in the mass range $16$-$30 M_odot$ populate an island of stars that have high $xi_{2.5}$ and do not produce canonical supernovae, and (ii) the fraction of such stars is consistent with the missing fraction of supernovae relative to star formation. We support this scenario with a series of two- and three-dimensional radiation hydrodynamics core-collapse simulations. Using more than 300 progenitors covering initial masses $10.8$-$75 M_odot$ and three initial metallicities, we show that high compactness is conducive to failed explosions. We then argue that a critical compactness of $sim 0.2$ as the divide between successful and failed explosions is consistent with state-of-the-art three-dimensional core-collapse simulations. Our study implies that numerical simulations of core collapse need not produce robust explosions in a significant fraction of compact massive star initial conditions.
rate research
Read More
We use the Sloan Digital Sky Survey II Supernova Survey (SDSS-II SNS) data to measure the volumetric core collapse supernova (CCSN) rate in the redshift range (0.03<z<0.09). Using a sample of 89 CCSN we find a volume-averaged rate of (1.06 +/- 0.19) x 10**(-4)/(yr Mpc**3) at a mean redshift of 0.072 +/- 0.009. We measure the CCSN luminosity function from the data and consider the implications on the star formation history.
We use three years of data from the Supernova Legacy Survey (SNLS) to study the general properties of core-collapse and type Ia supernovae. This is the first such study using the rolling search technique which guarantees well-sampled SNLS light curves and good efficiency for supernovae brighter than $i^primesim24$. Using host photometric redshifts, we measure the supernova absolute magnitude distribution down to luminosities $4.5 {rm mag}$ fainter than normal SNIa. Using spectroscopy and light-curve fitting to discriminate against SNIa, we find a sample of 117 core-collapse supernova candidates with redshifts $z<0.4$ (median redshift of 0.29) and measure their rate to be larger than the type Ia supernova rate by a factor $4.5pm0.8(stat.) pm0.6 (sys.)$. This corresponds to a core-collapse rate at $z=0.3$ of $[1.42pm 0.3(stat.) pm0.3(sys.)]times10^{-4}yr^{-1}(h_{70}^{-1}Mpc)^{-3}$.
We investigate a method to construct parametrized progenitor models for core-collapse supernova simulations. Different from all modern core-collapse supernova studies, which rely on progenitor models from stellar evolution calculations, we follow the methodology of Baron & Cooperstein (1990) to construct initial models. Choosing parametrized spatial distributions of entropy and electron fraction as a function of mass coordinate and solving the equation of hydrostatic equilibrium, we obtain the initial density structures of our progenitor models. First, we calculate structures with parameters fitting broadly the evolutionary model s11.2 of Woosley et al. (2002). We then demonstrate the reliability of our method by performing general relativistic hydrodynamic simulations in spherical symmetry with the isotropic diffusion source approximation to solve the neutrino transport. Our comprehensive parameter study shows that initial models with a small central entropy ($lesssim 0.4,k_B$ nucleon$^{-1}$) can explode even in spherically symmetric simulations. Models with a large entropy ($gtrsim 6,k_B$ nucleon$^{-1}$) in the Si/O layer have a rather large explosion energy ($sim 4times 10^{50}$ erg) at the end of the simulations, which is still rapidly increasing.
How do massive stars explode? Progress toward the answer is driven by increases in compute power. Petascale supercomputers are enabling detailed three-dimensional simulations of core-collapse supernovae. These are elucidating the role of fluid instabilities, turbulence, and magnetic field amplification in supernova engines.
The recent discovery that the Fe-K line luminosities and energy centroids observed in nearby SNRs are a strong discriminant of both progenitor type and circumstellar environment has implications for our understanding of supernova progenitor evolution. Using models for the chemical composition of core-collapse supernova ejecta, we model the dynamics and thermal X-ray emission from shocked ejecta and circumstellar material, modeled as an $r^{-2}$ wind, to ages of 3000 years. We compare the X-ray spectra expected from these models to observations made with the Suzaku satellite. We also model the dynamics and X-ray emission from Type Ia progenitor models. We find a clear distinction in Fe-K line energy centroid between core-collapse and Type Ia models. The core-collapse supernova models predict higher Fe-K line centroid energies than the Type Ia models, in agreement with observations. We argue that the higher line centroids are a consequence of the increased densities found in the circumstellar environment created by the expansion of the slow-moving wind from the massive progenitors.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
