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RE: Ancient LMC Supernovae
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Title: Supernova Remnants in the AKARI IRC Survey of the Large Magellanic Cloud
Authors: Ji Yeon Seok, Bon-Chul Koo, Takashi Onaka, Yoshifusa Ita, Ho-Gyu Lee, Jae-Joon Lee, Dae-Sik Moon, Itsuki Sakon, Hidehiro Kaneda, Hyung Mok Lee, Myung Gyoon Lee, Sung Eun Kim

We present the near- to mid-infared study of supernova remnants (SNRs) using the AKARI IRC Survey of the Large Magellanic Cloud (LMC). The LMC survey observed about a 10 square degree area of the LMC in five bands centred at 3, 7, 11, 15, and 24 \micron using the Infrared Camera (IRC) aboard AKARI. The number of SNRs in the survey area is 21, which is about a half of the known LMC SNRs. We systematically examined the AKARI images and identified eight SNRs with distinguishable infrared emission. All of them were detected at >~10 \micron and some at 3 and 7 \micron, too. We present their AKARI images and fluxes. In the 11/15 \micron versus 15/24 \micron colour-colour diagram, the SNRs appear to be aligned along a modified blackbody curve, representing thermal emission from dust at temperatures between 90 and 190 K. There is a good correlation between the 24 \micron and X-ray fluxes of the SNRs. It was also found that there is a good correlation between the 24 \micron and radio fluxes even if there is no direct physical connection between them. We considered the origin of the detected mid-infrared emission in individual SNRs. We conclude that the mid-infrared emissions in five SNRs that show morphologies similar to the X-rays are dominated by thermal emission from hot dust heated by X-ray emitting plasma. Their 15/24 \micron colour temperatures are generally higher than the Spitzer 24/70 \micron colour temperatures, which suggests that a single-temperature dust model cannot describe the full spectral energy distribution (SED) of the SNRs. It also implies that our understanding of the full SED is essential for estimating the dust destruction rate of grains by SNR shocks.

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Posts: 131433
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(SNR) 0509-67.5
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Huge explosions on Earth may be one-time deals, but their resounding echoes can give us another bang for our buck if conditions are right.
Strangely, the same is true in the depths of space.
Astronomers recently captured a supernova's blinding flash "echoing" off dust 400 light-years from the detonation site in the Large Magellanic Cloud which means earthly observers may have seen the original blast 400 years ago. Because a star's death rattle produced the light, scientists can use the new observations to effectively peer into the past.


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RE: Ancient LMC Supernovae
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Dust clouds glow thanks to delayed "light echoes" from a supernova, 400 years after light from the original event washed over Earth
(Images: X-ray: NASA/CXC/Rutgers/J Warren/J Hughes; Optical light echo: NOAO/AURA/NSF/Harvard/A Rest et al; LMC image: NOAO/AURA/NSF/S Points/C Smith/MCELS team)

Light radiating outwards from a supernova hits dust clouds along the way and is reflected towards Earth, providing a delayed echo or "replay" of the original explosion.
Credit: NASA/CXC/M.Weiss

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X-ray and optical images of aftermath of supernova
X-ray and optical images of aftermath of supernova

Astronomers have made the best ever determination of the power of a supernova explosion that was visible from Earth long ago. By observing the remnant of a supernova and a light echo from the initial outburst, they have established the validity of a powerful new method for studying supernovas.
 Using data from NASA's Chandra X-ray Observatory, ESA's XMM-Newton Observatory, and the Gemini Observatory, two teams of researchers studied the supernova remnant and its light echo, located in the Large Magellanic Cloud (LMC), a small galaxy about 160 000 light-years from Earth. They concluded that the supernova occurred about 400 years ago (in Earths time frame), and was unusually bright and energetic.

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N132D
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N132D
Credit: NASA/CXC/NCSU/K.J.Borkowski et al.
JPEG (198.1 kb) Tiff (15.5 MB) PS (6 MB)

This Chandra X-ray Observatory image shows the debris of a massive star explosion in the Large Magellanic Cloud, a small galaxy about 160,000 light years from Earth. The supernova remnant (SNR) shown here, N132D, is the brightest in the Magellanic clouds, and belongs to a rare class of oxygen-rich remnants. Most of the oxygen that we breathe on Earth is thought to have come from explosions similar to this one.
The colours in this image show low energy X-rays (red), intermediate energy X-rays (green) and high energy X-rays (blue). Substantial amounts of oxygen are detected in this image, particularly in the green regions near the centre of the image. The location of these oxygen-rich areas, detected in the Chandra image, is generally well matched with the oxygen-rich areas detected in Hubble Space Telescope images (not shown here). However, the expanding, ellipse-shaped shell of oxygen seen in N132D is not seen in either G292.0+1.8 or Puppis A, two oxygen-rich SNRs in the galaxy with similar ages to N132D (about 3,000 years, ten times older than Cas A). The origin of this shell is unknown, but it might have been created by a `nickel bubble' shortly after the supernova explosion, caused by radioactive energy input from nickel that was created by the explosion. The existence of such bubbles is predicted by theoretical work.

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Posts: 131433
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RE: Ancient LMC Supernovae
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Title: Spectral Identification of an Ancient Supernova using Light Echoes in the LMC
Authors: A. Rest, T. Matheson, S. Blondin, M. Bergmann, D. L. Welch, N. B. Suntzeff, R. C. Smith, K. Olsen, J. L. Prieto, A. Garg, P. Challis, C. Stubbs, M. Hicken, M. Modjaz, W. M. Wood-Vasey, A. Zenteno, G. Damke, A. Newman, M. Huber, K. H. Cook, S. Nikolaev, A. C. Becker, A. Miceli, R. Covarrubias, L. Morelli, G. Pignata, A. Clocchiatti, D. Minniti, R. J. Foley

We report the successful identification of the type of the supernova responsible for the supernova remnant SNR 0509-675 in the Large Magellanic Cloud (LMC) using Gemini spectra of surrounding light echoes. The ability to classify outbursts associated with centuries-old remnants provides a new window into several aspects of supernova research and is likely to be successful in providing new constraints on additional LMC supernovae as well as their historical counterparts in the Milky Way Galaxy (MWG). The combined spectrum of echo light from SNR 0509-675 shows broad emission and absorption lines consistent with a supernova (SN) spectrum. We create a spectral library consisting of 26 SNe Ia and 6 SN Ib/c that are time-integrated, dust-scattered by LMC dust, and reddened by the LMC and MWG. We fit these SN templates to the observed light echo spectrum using \chi˛ minimisation as well as correlation techniques, and we find that overluminous 91T-like SNe Ia with \dm15<0.9 match the observed spectrum best.

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Kepler supernova
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North Carolina State University astrophysicists have answered a long-standing question about the nature of one of our galaxy’s most famous supernova explosions, discovering a new class of supernova in the process.
Dr. Stephen Reynolds, astrophysicist in NC State’s College of Physical and Mathematical Sciences, along with colleague Dr. Kazik Borkowski and a team of scientists from NASA, Rutgers University, and the Naval Research Laboratories, set out to determine whether the Kepler supernova, which occurred in 1604 A.D., was a core collapse supernova or a thermonuclear supernova.
They revealed their results in a press conference today at the annual meeting of the American Astronomical Society.

A core collapse supernova occurs when a single, massive star (with a mass eight times greater – or more – than that of our sun) reaches the end of its life and explodes. Core collapse supernovae leave pulsars, rapidly spinning neutron stars, behind when they occur. They also tend to be surrounded by circumstellar medium – leftover elements from the star that collapsed, as well as large amounts of oxygen and small amounts of iron. These supernovae are usually located near “star-forming” sites along a galaxy’s edge.
Thermonuclear, or Type Ia, supernovae occur when a white dwarf star, which typically travels through space with a companion star that eventually “leaks” its own mass onto the dwarf, reaches its mass limit and explodes. These supernovae can be found all over a galaxy, are typically not associated with any circumstellar medium, and produce large amounts of iron.
The Kepler supernova has long puzzled scientists because it has features that are common to both types of supernova: The Kepler supernova’s location and the presence of a lot of iron are indicative of a Type Ia supernova, but the dense surroundings and nitrogen-enriched circumstellar medium are commonly associated with the aftermath of a core collapse.
Reynolds and his team used the powerful Chandra X-ray telescope to observe the Kepler supernova, and they discovered that Kepler is something entirely new: a Type Ia supernova in which the progenitor of the white dwarf star that created it had enough mass to create circumstellar medium.

We really don’t know much about Type Ia supernovae, and they’re really important to our understanding of the universe. We use the fact that they all have similar luminosities, or brightness, to calculate the distance of galaxies and to determine how much and how quickly the universe is expanding. Type Ia’s are also the source of the majority of iron in the universe, and can give us a lot of information about its chemical history. A new class of Type Ia supernova will have huge implications for our ability to understand the source of the elements that create our universe” - Dr. Stephen Reynolds.

Source:      North Carolina State University

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Posts: 131433
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DEM L238 and DEM L249
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Evidence for a significant new class of supernova has been found with the European Space Agency's XMM-Newton and NASA's Chandra X-ray Observatory. These results strengthen the case for a population of stars that evolve rapidly and are destroyed by thermonuclear explosions. Such ‘prompt’ supernovas could be valuable tools for probing the early history of the cosmos.

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Posts: 131433
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DEML238 & DEML249
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DEM L238 and DEM L249 are two supernova remnants in the Large Magellanic Cloud. X-ray data from NASA's Chandra and ESA's XMM-Newton observatories suggest that the stars responsible for these debris fields were unusually young when they were destroyed by thermonuclear explosions.
The large field-of-view is a composite image of DEM L238 (right) and DEM L249, Chandra X-ray data in blue and optical data in white. The image reveals how DEM L238 appears in the three bands of X-ray emission (low energy X-rays are shown in red, medium energies in green and high energies in blue.) The central region of DEM L238 is green which indicates that it is rich in iron. This overabundance of iron identifies this object as a so-called Type Ia supernova, one possible explosive death of a star.

deml238_xrayopt
Expand (53kb, 560 x 389)
Credit: X-ray: NASA/CXC/NCSU/K.Borkowski; Optical: NOAO/CTIO/MCELS

Position (2000): RA 05h 34m 08.80s Dec -70ş 34' 28.00"

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Posts: 131433
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N49
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This is a composite image of N49, the brightest supernova remnant in optical light in the Large Magellanic Cloud. The Chandra X-ray image (blue) shows million-degree gas in the center. Much cooler gas at the outer parts of the remnant is seen in the infrared image from Spitzer (red). While astronomers expected that dust particles were generating most of the infrared emission, the study of this object indicates that much of the infrared is instead generated in heated gas.

n49_291106
Credit: X-ray: NASA/CXC/Caltech/S.Kulkarni et al.; Optical: NASA/STScI/UIUC/Y.H.Chu & R.Williams et al.; IR: NASA/JPL-Caltech/R.Gehrz et al.

Position(2000): RA 05h 25m 25.00s | Dec -65ş 59' 22.00"

The unique filamentary structure seen in the optical image by Hubble (white & yellow) has long set N49 apart from other well understood supernova remnants, as most supernova remnants appear roughly circular in visible light. Recent mapping of molecular clouds suggests that this supernova remnant is expanding into a denser region to the southeast, which would cause its asymmetrical appearance. This idea is confirmed by the Chandra data. Although X-rays reveal a round shell of emission, the X-rays also show brightening in the southeast, confirming the idea of colliding material in that area.

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