58 research outputs found
A super-Eddington wind scenario for the progenitors of type Ia supernovae: binary population synthesis calculations
The super-Eddington wind scenario has been proposed as an alternative way for
producing type Ia supernovae (SNe Ia). The super-Eddington wind can naturally
prevent the carbon--oxygen white dwarfs (CO WDs) with high mass-accretion rates
from becoming red-giant-like stars. Furthermore, it works in low-metallicity
environments, which may explain SNe Ia observed at high redshifts. In this
article, we systematically investigated the most prominent single-degenerate
WD+MS channel based on the super-Eddington wind scenario. We combined the
Eggleton stellar evolution code with a rapid binary population synthesis (BPS)
approach to predict SN Ia birthrates for the WD+MS channel by adopting the
super-Eddington wind scenario and detailed mass-accumulation efficiencies of
H-shell flashes on the WDs. Our BPS calculations found that the estimated SN Ia
birthrates for the WD+MS channel are ~0.009-0.315*10^{-3}{yr}^{-1} if we adopt
the Eddington accretion rate as the critical accretion rate, which are much
lower than that of the observations (<10% of the observed SN Ia birthrates).
This indicates that the WD+MS channel only contributes a small proportion of
all SNe Ia. The birthrates in this simulation are lower than previous studies,
the main reason of which is that new mass-accumulation efficiencies of H-shell
flashes are adopted. We also found that the critical mass-accretion rate has a
significant influence on the birthrates of SNe Ia. Meanwhile, the results of
our BPS calculations are sensitive to the values of the common-envelope
ejection efficiency.Comment: 14 pages, 9 figures, 1 table, accepted for publication in Astronomy
and Astrophysic
A 34.5 day quasi-periodic oscillation in gamma-ray emission from the blazar PKS 2247-131
Since 2016 October, the active galaxy PKS 2247-131 has undergone a gamma-ray
outburst, which we studied using data obtained with the Fermi Gamma-ray Space
Telescope. The emission arises from a relativistic jet in PKS 2247-131, as an
optical spectrum only shows a few weak absorption lines, typical of the BL
Lacertae sub-class of the blazar class of active galactic nuclei. Here we
report a ~34.5 day quasi-periodic oscillation (QPO) in the emission after the
initial flux peak of the outburst. Compared to one-year time-scale QPOs,
previously identified in blazars in Fermi energies, PKS 2247-131 exhibits the
first clear case of a relatively short, month-like oscillation. We show that
this QPO can be explained in terms of a helical structure in the jet, where the
viewing angle to the dominant emission region in the jet undergoes periodic
changes. The time scale of the QPO suggests the presence of binary supermassive
black holes in PKS 2247-131.Comment: 6 pages, 4 figure
Optical and Ultraviolet Observations of the Very Young Type IIP SN 2014cx in NGC 337
Extensive photometric and spectroscopic observations are presented for SN
2014cx, a type IIP supernova (SN) exploding in the nearby galaxy NGC 337. The
observations are performed in optical and ultraviolet bands, covering from -20
to +400 days from the peak light. The stringent detection limit from
prediscovery images suggests that this supernova was actually detected within
about 1 day after explosion. Evolution of the very early-time light curve of SN
2014cx is similar to that predicted from a shock breakout and post-shock
cooling decline before reaching the optical peak. Our photometric observations
show that SN 2014cx has a plateau duration of ~ 100 days, an absolute V-band
magnitude of ~ -16.5 mag at t~50 days, and a nickel mass of 0.056+-0.008 Msun.
The spectral evolution of SN 2014cx resembles that of normal SNe IIP like SN
1999em and SN 2004et, except that it has a slightly higher expansion velocity
(~ 4200 km/s at 50 days). From the cooling curve of photospheric temperature,
we derive that the progenitor has a pre-explosion radius of ~ 640 Rsun,
consistent with those obtained from SNEC modeling (~ 620 Rsun) and
hydrodynamical modeling of the observables (~ 570 Rsun). Moreover, the
hydrodynamical simulations yield a total explosion energy of ~ 0.4*10e51 erg,
and an ejected mass of ~ 8 Msun. These results indicate that the immediate
progenitor of SN 2014cx is likely a red supergiant star with a mass of ~ 10
Msun.Comment: 47 pages, 12 figures and 7 tables. Accepted by Ap
Circumstellar Material Ejected Violently by A Massive Star Immediately before its Death
Type II supernovae represent the most common stellar explosions in the
Universe, for which the final stage evolution of their hydrogen-rich massive
progenitors towards core-collapse explosion are elusive. The recent explosion
of SN 2023ixf in a very nearby galaxy, Messier 101, provides a rare opportunity
to explore this longstanding issue. With the timely high-cadence flash spectra
taken within 1-5 days after the explosion, we can put stringent constraints on
the properties of the surrounding circumstellar material around this supernova.
Based on the rapid fading of the narrow emission lines and luminosity/profile
of emission at very early times, we estimate that the progenitor
of SN 2023ixf lost material at a mass-loss rate over the last 2-3 years before explosion.
This close-by material, moving at a velocity , accumulates a compact CSM shell at the radius smaller than cm from the progenitor. Given the high mass-loss rate and
relatively large wind velocity presented here, together with the pre-explosion
observations made about two decades ago, the progenitor of SN 2023ixf could be
a short-lived yellow hypergiant that evolved from a red supergiant shortly
before the explosion.Comment: 10 pages, 6 figures in main body, accepted for publication in Science
Bulleti
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