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SN 1987A
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Title: Evidence for two neutrinos bursts from SN1987A
Author: R. Valentim, J. E. Horvath, E. M. Rangel

The SN1987A in the Giant Magellanic Cloud was an amazing and extraordinary event because it was detected in real time for different neutrinos experiments (s) around the world. Approximate ~25 events were observed in three different experiments: Kamiokande II (KII) ~12, Irvine-Michigan-Brookhaven (IMB) ~8 e Baksan ~5, plus a contrived burst at Mont Blanc (Liquid Scintillator Detector - LSD) later dismissed because of energetic requirements (Aglietta et al. 1988). The neutrinos have an important play role into the neutron star newborn: at the moment when the supernova explodes the compact object remnant is freezing by neutrinos (~99% energy is lost in the few seconds of the explosion). The work is motivated by neutrinos' event in relation arrival times where there is a temporal gap between set of events (~6s). The first part of dataset came from the ordinary mechanism of freezing and the second part suggests different mechanism of neutrinos production. We tested two models of cooling for neutrinos from SN1987A: 1st an exponential cooling is an ordinary model of cooling and 2nd a two-step temperature model that it considers two bursts separated with temporal gap. Our analysis was done with Bayesian tools (Bayesian Information Criterion - BIC) The result showed strong evidence in favour of a two-step model against one single exponential cooling (lnB_ij>5.0), and suggests the existence of two neutrino bursts at the moment the neutron star was born.

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Supernova 1987A
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The Dawn of a New Era for Supernova 1987A

In February 1987, on a mountaintop in Chile, telescope operator Oscar Duhalde stood outside the observatory at Las Campanas and looked up at the clear night sky. There, in a hazy-looking patch of brightness in the sky - the Large Magellanic Cloud (LMC), a neighboring galaxy - was a bright star he hadn't noticed before.
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RE: (SN) 1987A
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The Dawn of a New Era for Supernova 1987A

Since that finding, an armada of telescopes, including the Hubble Space Telescope, has studied the supernova. Hubble wasn't even in space when SN 1987A was found. The supernova, however, was one of the first objects Hubble observed after its launch in 1990. Hubble has continued to monitor the exploded star for nearly 30 years, yielding insight into the messy aftermath of a star's violent self-destruction. Hubble has given astronomers a ring-side seat to watch the brightening of a ring around the dead star as the supernova blast wave slammed into it.
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Title: Turning off the lights: Supernova SN1987A 30 years on
Author: Richard de Grijs

Decades-long repeat observations of supernova SN1987A offer us unique, real-time insights into the violent death of a massive star and its long-term environmental effects, until its eventual switch-off.

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Supernova 1987A
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Title: Neutrinos from SN 1987a. A Puzzle Revisited
Author: Gerd Schatz (Universitaet Heidelberg and Karlsruhe Institute of Technology)

The smallest of the four detectors which claim to have observed neutrinos from SN 1987a registered the events more than 4 h earlier than the other three ones. This claim is not usually accepted because it is difficult to understand that the other (and larger) detectors did not register any events at the same time. It is shown that microlensing of the neutrinos by a star in-between the supernova (SN) and Earth can enhance the neutrino intensity at the position of one detector by more than an order of magnitude with respect to the other detectors. Such a configuration is improbable but not impossible. Essential for this enhancement is the small source diameter, of order 100 km. So if two bursts of neutrinos were emitted by SN 1987a at a separation of about 4 h it could be explained easily that the smallest detector observed the first burst while the other ones missed it and vice versa.

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RE: (SN) 1987A
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Title: The Destruction of the Circumstellar Ring of SN 1987A
Author: Claes Fransson, Josefin Larsson, Katia Migotto, Dominic Pesce, Peter Challis, Roger A. Chevalier, Kevin France, Robert P. Kirshner, Bruno Leibundgut, Peter Lundqvist, Richard McCray, Jason Spyromilio, Francesco Taddia, Anders Jerkstrand, Seppo Mattila, Nathan Smith, Jesper Sollerman, J. Craig Wheeler, Arlin Crotts, Peter Garnavich, Kevin Heng, Stephen S. Lawrence, Nino Panagia, Chun S. J. Pun, George Sonneborn, Ben Sugerman

We present imaging and spectroscopic observations with HST and VLT of the ring of SN 1987A from 1994 to 2014. After an almost exponential increase of the shocked emission from the hotspots up to day ~8,000 (~2009), both this and the unshocked emission are now fading. From the radial positions of the hotspots we see an acceleration of these up to 500-1000 km/s, consistent with the highest spectroscopic shock velocities from the radiative shocks. In the most recent observations (2013 and 2014), we find several new hotspots outside the inner ring, excited by either X-rays from the shocks or by direct shock interaction. All of these observations indicate that the interaction with the supernova ejecta is now gradually dissolving the hotspots. We predict, based on the observed decay, that the inner ring will be destroyed by ~2025.

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Supernova 1987A
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Star Explosion Is Lopsided, Finds NASA's NuSTAR

NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, has found evidence that a massive star exploded in a lopsided fashion, sending ejected material flying in one direction and the core of the star in the other.
The findings offer the best proof yet that star explosions of this type, called Type II or core-collapse supernovae, are inherently asymmetrical, a phenomenon that had been difficult to prove before now.

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RE: (SN) 1987A
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Title: Dark Matter Balls Help Supernovae to Explode
Author: Colin D. Froggatt, Holger B. Nielsen

As a solution to the well-known problem that the shock wave potentially responsible for the explosion of a supernova actually tends to stall, we propose a new energy source arising from our model for dark matter. Our earlier model proposed that dark matter should consist of cm-large white dwarf-like objects kept together by a skin separating two different sorts of vacua. These dark matter balls or pearls will collect in the middle of any star throughout its lifetime. At some stage during the development of a supernova the balls will begin to take in neutrons and then other surrounding material. By passing into a ball nucleons fall through a potential of order 10 MeV, causing a severe production of heat - of order 10 foe for a solar mass of material eaten by the balls. The temperature in the iron core will thereby be raised, splitting up the iron into smaller nuclei. This provides a mechanism for reviving the shock wave when it arrives and making the supernova explosion really occur. The onset of the heating due to the dark matter balls would at first stop the collapse of the supernova progenitor. This opens up the possibility of there being {\em two} collapses giving two neutrino outbursts, as apparently seen in the supernova SN1987A - one in Mont Blanc, and one 4 hours 43 minutes later in both IMB and Kamiokande.

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Posts: 129912
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Supernova remnant 1987A
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Supernova remnant 1987A continues to reveal its secrets

A team of astronomers led by the International Centre for Radio Astronomy Research (ICRAR) have succeeded in observing the death throws of a giant star in unprecedented detail.
In research published in the Astrophysical Journal today, a team of astronomers in Australia and Hong Kong have succeeded in using the Australia Telescope Compact Array, CSIRO radio telescope in northern New South Wales, to make the highest resolution radio images of the expanding supernova remnant at millimetre wavelengths.

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RE: (SN) 1987A
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Title: The morphology of the ejecta in Supernova 1987A: a study over time and wavelength
Authors: Josefin Larsson, Claes Fransson, Karina Kjaer, Anders Jerkstrand, Robert P. Kirshner, Bruno Leibundgut, Peter Lundqvist, Seppo Mattila, Richard McCray, Jesper Sollerman, Jason Spyromilio, J. Craig Wheeler

We present a study of the morphology of the ejecta in Supernova 1987A based on images and spectra from the HST as well as integral field spectroscopy from VLT/SINFONI. The HST observations were obtained between 1994 - 2011 and primarily probe the outer hydrogen-rich zones of the ejecta. The SINFONI observations were obtained in 2005 and 2011 and instead probe the [Si I]/[Fe II] emission from the inner regions. We find a strong temporal evolution of the morphology in the HST images, from a roughly elliptical shape before ~5,000 days, to a more irregular, edge-brightened morphology thereafter. We demonstrate that this transition is a natural consequence of the change in the dominant energy source powering the ejecta, from radioactive decay before ~5,000 days to X-ray input from the circumstellar interaction thereafter. The [Si I]/[Fe II] images display a more uniform morphology, which may be due to a remaining significant contribution from radioactivity in the inner ejecta and the higher abundance of these elements in the core. Both the H-alpha and the [Si I]/[Fe II] line profiles show that the ejecta are distributed fairly close to the plane of the inner circumstellar ring, which is assumed to define the rotational axis of the progenitor. The H-alpha emission extends to higher velocities than [Si I]/[Fe II] as expected. There is no clear symmetry axis for all the emission and we are unable to model the ejecta distribution with a simple ellipsoid model with a uniform distribution of dust. Instead, we find that the emission is concentrated to clumps and that the emission is distributed somewhat closer to the ring in the north than in the south. This north-south asymmetry may be partially explained by dust absorption. We compare our results with explosion models and find some qualitative agreement, but note that the observations show a higher degree of large-scale asymmetry.

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