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Reading papers on Supernova

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harrycostas

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G'day from the land of ozzzzzz

The day will come when we shall detect the Gravitational Waves (GW) during the phase changes in supernova, this may lead to unlocking the secrets and allow us to understand supernova events.

According to the paer we see one supernova per 2 years.

TOPICAL REVIEW: The gravitational-wave signature of core-collapse supernovae
Mar-09
http://adsabs.harvard.edu/abs/2009CQGra..26f3001O
http://adsabs.harvard.edu/cgi-bin/nph-d ... db_key=AST
We review the ensemble of anticipated gravitational-wave (GW) emission processes in stellar core collapse and postbounce core-collapse supernova evolution. We discuss recent progress in the modeling of these processes and summarize most recent GW signal estimates. In addition, we present new results on the GW emission from postbounce convective overturn and protoneutron star g-mode pulsations based on axisymmetric radiation-hydrodynamic calculations. Galactic core-collapse supernovae are very rare events, but within 3 5 Mpc from Earth, the rate jumps to 1 in ~2 years. Using the set of currently available theoretical gravitational waveforms, we compute upper-limit optimal signal-to-noise ratios based on current and advanced LIGO/GEO600/VIRGO noise curves for the recent SN 2008bk which exploded at ~3.9 Mpc. While initial LIGOs cannot detect GWs emitted by core-collapse events at such a distance, we find that advanced LIGO-class detectors could put significant upper limits on the GW emission strength for such events. We study the potential occurrence of the various GW emission processes in particular supernova explosion scenarios and argue that the GW signatures of neutrino-driven, magneto-rotational, and acoustically-driven core-collapse SNe may be mutually exclusive. We suggest that even initial LIGOs could distinguish these explosion mechanisms based on the detection (or non-detection) of GWs from a galactic core-collapse supernova.
 
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harrycostas

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G'day

Can stars form from the fragments of a supernova?

If that can be so.

Why not the remanant core of a supernova?

http://arxiv.org/abs/0907.3667
Star Formation Triggered by Supernova Explosions in Young Galaxies

Authors: Takanori Nagakura, Takashi Hosokawa, Kazuyuki Omukai
(Submitted on 21 Jul 2009)

Abstract: We study the evolution of supernova remnants in a low-metallicity medium $Z/Z_{\odot} = 10^{-4}$ -- $10^{-2}$ in the early universe, using one-dimensional hydrodynamics with non-equilibrium chemistry. Once a post-shock layer is able to cool radiatively, a dense shell forms behind the shock. If this shell becomes gravitationally unstable and fragments into pieces, next-generation stars are expected to form from these fragments. To explore the possibility of this triggered star formation, we apply a linear perturbation analysis of an expanding shell to our results and constrain the parameter range of ambient density, explosion energy, and metallicity where fragmentation of the shell occurs. For the explosion energy of $10^{51}{\rm ergs} (10^{52}{\rm ergs})$, the shell fragmentation occurs for ambient densities higher than $\gtrsim 10^{2} {\rm cm^{-3}}$ (10 ${\rm cm^{-3}}$, respectively). This condition depends little on the metallicity in the ranges we examined. We find that the mode of star formation triggered occurs only in massive ($\gtrsim 10^{8}M_{\odot}$) haloes.
 
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harrycostas

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G'day

There has always been an interest in finding where the matter comes from, particularly compact matter. Either from the disc or from the core of a compact star. This paper may answer that, and this may explain another form of star formation.

http://arxiv.org/abs/0907.5040
Discovery of Extremely High Velocity "Molecular Bullets" in the HH 80-81 High-Mass Star-Forming Region

Authors: Keping Qiu, Qizhou Zhang
(Submitted on 29 Jul 2009)

Abstract: We present Submillimter Array 1.3 mm waveband continuum and molecular line observations of the HH 80-81 high-mass star-forming region. The dust continuum emission reveals two dominant peaks MM1 and MM2, and line emission from high-density tracers suggests the presence of another core MC. Molecular line emission from MM1, which harbors the exciting source of the HH 80-81 radio jet, yields a hot molecular core at a gas temperature of 110 K. The two younger cores MM2 and MC both appear to power collimated CO outflows. In particular, the outflow arising from MM2 exhibits a jet-like morphology and a broad velocity range of 190 km/s. The outflow contains compact and fast moving molecular clumps, known as "molecular bullets" first discovered in low-mass class 0 protostellar outflows. These "bullets" cannot be locally entrained or swept up from the ambient gas, but are more likely ejected from the close vicinity of the central protostar. The discovery of this remarkable outflow manifests an episodic, disk-mediated accretion for massive star formation.
 
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harrycostas

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G'day

Do you ever wonder what happens to the dust ejected from a supernova?

Most papers talk about the collapse of a core during a supernova. The problem is this, you first need a compact core to generate the power to form jets and eject matter out. We see this in the hour glass images of supernova. So! what I'm trying to say is this. The compact core goes through a process of rejuvination during the supernova where normal matter degenerates and feeds into the core via a process of magnetic reconnection. Thus creating a dynamo effect.

This paper is interesting

Dust in Supernovae; Formation and Evolution
Mar-09
http://adsabs.harvard.edu/abs/2009arXiv0903.0217K
http://adsabs.harvard.edu/cgi-bin/nph-d ... db_key=PRE
Core--collapsed supernovae (CCSNe) have been considered to be one of sources of dust in the universe. What kind and how much mass of dust are formed in the ejecta and are injected into the interstellar medium (ISM) depend on the type of CCSNe, through the difference in the thickness (mass) of outer envelope. In this review, after summarizing the existing results of observations on dust formation in CCSNe, we investigate formation of dust in the ejecta and its evolution in the supernova remnants (SNRs) of Type II--P and Type IIb SNe. Then, the time evolution of thermal emission from dust in the SNR of Type IIb SN is demonstrated and compared with the observation of Cas A. We find that the total dust mass formed in the ejecta does not so much depend on the type; $\sim 0.3-0.7 M_{\odot}$ in Type II--P SNe and $\sim 0.13 M_{\odot}$ in Type IIb SN. However the size of dust sensitively depends on the type, being affected by the difference in the gas density in the ejecta: the dust mass is dominated by grains with radii larger than 0.03 $\mu$m in Type II-P, and less than 0.006 $\mu$m in Type IIb, which decides the fate of dust in the SNR. The surviving dust mass is $\sim 0.04-0.2 M_{\odot}$ in the SNRs of Type II--P SNe for the ambient hydrogen density of $n_{\rm H}=10.0-1.0$ cm$^{-3}$, while almost all dust grains are destroyed in the SNR of Type IIb. The spectral energy distribution (SED) of thermal emission from dust in SNR well reflects the evolution of dust grains in SNR through erosion by sputtering and stochastic heating. The observed SED of Cas A SNR is reasonably reproduced by the model of dust formation and evolution for Type IIb SN.
 
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harrycostas

Guest
G'day from the land of ozzzzz

This paper is quite informative without heavy maths and big words so to speak and easy to read.

Some Recent Progress on the Studies of Supernova Remnants
http://arxiv.org/abs/0909.0386
Authors: Jian-Wen Xu
(Submitted on 2 Sep 2009)

Abstract: We briefly reviewed some recent progress on the studies of supernova remnants (SNRs), including the radio SNRs (the structure, polarization, spectrum etc.), observational characteristics of X-ray emission, pulsar wind nebulae (PWNe), association properties between SNR and PSR, interaction of SNR and interstellar medium (ISM), cosmos ray and the SNRs in external galaxies, etc.. Correspondingly to the continue improvement of space and spectrum resolution of the on-ground and in-space astronomical equipments at wavelengthes as radio, optical, X-ray and so on, we know about SNRs more and deeper.
 
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harrycostas

Guest
G'day

The problem of core collapse is that the process is difficult to ivesticate and for this reason remains an unknown. The mechanism via gravitational/electromagnetic waves may give us more light to the subject. Particularly EM reconnection feeding the core with degenerate matter.

this link is interesting.

Probing the Core-Collapse Supernova Mechanism with Gravitational Waves
May-09
http://adsabs.harvard.edu/abs/2009arXiv0905.2797O
http://adsabs.harvard.edu/cgi-bin/nph-d ... db_key=PRE
The mechanism of core-collapse supernova explosions must draw on the energy provided by gravitational collapse and transfer the necessary fraction to the kinetic and internal energy of the ejecta. Despite many decades of concerted theoretical effort, the detailed mechanism of core-collapse supernova explosions is still unknown, but indications are strong that multi-D processes lie at its heart. This opens up the possibility of probing the supernova mechanism with gravitational waves, carrying direct dynamical information from the supernova engine deep inside a dying massive star. I present a concise overview of the physics and primary multi-D dynamics in neutrino-driven, magnetorotational, and acoustically-driven core-collapse supernova explosion scenarios. Discussing and contrasting estimates for the gravitational-wave emission characteristics of these mechanisms, I argue that their gravitational-wave signatures are clearly distinct and that the observation (or non-observation) of gravitational waves from a nearby core-collapse event could put strong constraints on the supernova mechanism.
 
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harrycostas

Guest
G'day
Although this paper is in favor of a static universe. We still have the contraction and expansion explained by the physical nature of the object. Clusters of galaxies may show contraction over millions of light years and also sho expansion over millions of light years via observational huge giant jets (solitons) that reform galaxies near and far. NASAand others images show such effects.

http://vixra.org/abs/0909.0009
Discovery of a New Dimming Effect Specific to Supernovae and Gamma-Ray Bursts

Authors: Thomas B. Andrews

Because type Ia supernovae (SNs) are anomalously dimmed with respect to the at (qo = 0.5) Friedman Expanding Universe model, I was surprised to find that the brightest cluster galaxies (BCGs) are not anomalously dimmed. Based on the absence of anomalous dimming in BCGs, the following conclusions were reached:

⋅ Since the light from the SNs and BCGs traverses the same space, the current hypothesis of an accelerated expansion of the universe to explain the anomalous dimming of SNs is disproved.
⋅ The cause of the anomalous dimming must be specific to the SNs.

The first conclusion is important since current research in dark energy and the cosmological constant was initiated based on the accelerated expansion hypothesis. The disproof of this hypothesis, therefore, casts serious doubts on the existence of dark energy and the cosmological constant. The second conclusion indicates that the occurrence of anomalous dimming depends on a basic difference between the SNs and BCGs. The only difference besides the obvious - that SNs are exploding stars and the BCGs are galaxies - is that the light curves of the SNs are limited in duration. Due on this difference, I discovered that SNs light curves are broadened at the observer by a new Hubble redshift effect. Since the total energy of the light curve is then spread over a longer time period, the apparent luminosity is reduced at the observer, causing the observed anomalous dimming of SNs. I also show that BCGs are not anomalously dimmed because their absolute luminosity is approximately constant over the time required for the light to reach the observer. The above conclusions also apply to Gamma Ray Bursts (GRBs) since gamma-ray "light" curves are limited in duration. Finally, the light curve broadening effect can be used to determine if the universe is expanding or static. In the expanding universe model, a light curve broadening effect is predicted due to time-dilation for the SNs, GRBs and BCGs. Consequently, if the universe is expanding, two light curve broadening effects should occur for the SNs and GRBs. However, if the universe is static, only one light curve broadening effect will occur for the SNs and GRBs. Fortunately, Golhaber has measured the width's of SNs light curves and conclusively showed that only one light curve broadening effect occurs. Consequently, the expanding universe model is logically falsified.
 
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MeteorWayne

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Since the article has not been submitted even to the friendly Crothers journal, (in fact the link indicates no journal submission at all; IOW, it's a web posting) it is a bunch of fluff.
 
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harrycostas

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G'day MeteorWayne

The science within is more important then the journal entry.

We should not be blind or too qick to critisize papers without first understanding the science.

What part of the science do you disagree with?
 
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