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Post Info TOPIC: Supernova remnant
Blobrana


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Posts: 131433
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RE: Supernova remnant
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G347.3-0.5
Credit: Chandra: NASA/CXC/SAO/P.Slane et al.; XMM-Newton: ESA/RIKEN/J.Hiraga et al.; Chandra: NASA/CXC/Univ. of Utrecht/J.Vink et al.; XMM-Newton: ESA/Univ. of Utrecht/J.Vink et al.
JPEG (287.1 kb) Tiff (46.3 MB) PS (2.8 MB)

These images of two supernova remnants, G347.3-0.5 and RCW 86, show the result of combining data from NASA's Chandra X-ray Observatory and ESA's XMM-Newton. In each image, XMM-Newton has obtained data from a much wider field-of-view, while Chandra has been used to concentrate on key areas of interest to researchers (outlined in the boxes).

RCW 86 (right panel) may be the one of the earliest stellar explosions ever recorded. The formation of the remnant appears to coincide with a supernova observed by Chinese astronomers (and perhaps the Romans) in 185 AD. Together, the Chandra and XMM-Newton data show the expanding ring of debris that was created after a massive star in the Milky Way collapsed onto itself and exploded. Both the Chandra and XMM-Newton images show low-energy X-rays in red, medium energies in green and high energies in blue. The Chandra observations focused on the northeast (left-hand) and southwest (lower right) side of RCW 86, and show that X-ray radiation is produced both by high-energy electrons accelerated in a magnetic field (blue) as well as heat from the blast itself (red).

As in the case of RCW 86, it is believed that the Chinese may have witnessed the supernova that caused G347.3-0.5, but a couple of centuries later in 393 A.D. According to the Chinese records, a bright star in the location of G347.3-0.5 was visible for months and rivalled the brilliance of Jupiter. X-rays from G347.3-0.5 are dominated by radiation from extremely high-energy electrons in a magnetized shell rather than radiation from a hot gas. The remnant is also a source of very high-energy gamma rays. The bright point-like source on the lower section of the image (which only shows the upper portion of the entire remnant) is similar to other known neutron stars and indicates that G347.3-0.5 is the result of a core-collapse of a massive star. In both the Chandra and XMM-Newton images, the intensity of X-rays is represented by the brightness of the colour.

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Blobrana


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Posts: 131433
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SNR DA 530
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Title: Chandra View of DA 530: A Sub-Energetic Supernova Remnant with a Pulsar Wind Nebula?
Authors: Bing Jiang, Yang Chen, Q. Daniel Wang
(Version v2)

Based on a Chandra ACIS observation, we report the detection of an extended X-ray feature close to the centre of the remnant DA 530 with 5.3 sigma above the background within a circle of 20'' radius. This feature, characterised by a power-law with the photon index gamma=1.6 ±0.8 and spatially coinciding with a nonthermal radiosource, most likely represents a pulsar wind nebula. We have further examined the spectrum of the diffuse X-ray emission from the remnant interior with a background-subtracted count rate of ~0.06 counts s^-1 in 0.3-3.5 keV. The spectrum of the emission can be described by a thermal plasma with a temperature of ~0.3-0.6 keV and a Si over-abundance of >~7 solar. These spectral characteristics, together with the extremely low X-ray luminosity, suggest that the remnant arises from a supernova with an anomalously low mechanical energy (<10^50 ergs). The centrally-filled thermal X-ray emission of the remnant may indicate an early thermalisation of the SN ejecta by the circum-stellar medium. Our results suggest that the remnant is likely the product of a core-collapsed SN with a progenitor mass of 8-12 Msun. Similar remnants are probably common in the Galaxy, but have rarely been studied.

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Blobrana


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Posts: 131433
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RE: Supernova remnant RCW 103
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When stars are more massive than about 8 times the Sun, they end their lives in a spectacular explosion called a supernova. The outer layers of the star are hurtled out into space at thousands of miles an hour, leaving a debris field of gas and dust. Where the star once was located, a small, incredibly dense object called a neutron star is often found. While only 10 miles or so across, the tightly packed neutrons in such a star contain more mass than the entire Sun.

RCW 103
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Credit: NASA/CXC/Penn State/G.Garmire et al
JPEG (227.5 kb) Tiff (50.9 MB) PS (1.9 MB)

A new X-ray image shows the 2,000 year-old-remnant of such a cosmic explosion, known as RCW 103, which occurred about 10,000 light years from Earth. In Chandra's image, the colours of red, green, and blue are mapped to low, medium, and high-energy X-rays. At the center, the bright blue dot is likely the neutron star that astronomers believe formed when the star exploded. For several years astronomers have struggled to understand the behaviour of the this object, which exhibits unusually large variations in its X-ray emission over a period of years. New evidence from Chandra implies that the neutron star near the centre is rotating once every 6.7 hours, confirming recent work from XMM-Newton. This is much slower than a neutron star of its age should be spinning. One possible solution to this mystery is that the massive progenitor star to RCW 103 may not have exploded in isolation. Rather, a low-mass star that is too dim to see directly may be orbiting around the neutron star. Gas flowing from this unseen neighbour onto the neutron star might be powering its X-ray emission, and the interaction of the magnetic field of the two stars could have caused the neutron star to slow its rotation.

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Blobrana


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Posts: 131433
Date:
RE: Supernova remnant
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Title: Chandra X-Ray Study of Galactic Supernova Remnant G299.2-2.9
Authors: Sangwook Park (Penn State), Patrick O. Slane (CfA), John P. Hughes (Rutgers), Koji Mori (Miyazaki), David N. Burrows, Gordon P. Garmire (Penn State)

We report on observations of the Galactic supernova remnant (SNR) G299.2-2.9 with the Chandra X-Ray Observatory. The high resolution images with Chandra resolve the X-ray-bright knots, shell, and diffuse emission extending beyond the bright shell. Interior to the X-ray shell is faint diffuse emission occupying the central regions of the SNR. Spatially-resolved spectroscopy indicates a large foreground absorption (N_{
m H} ~ 3.5 x  10^{21} cm^{-2}), which supports a relatively distant location (d  ~ 5 kpc) for the SNR. The blast wave is encountering a highly inhomogeneous ambient medium with the densities ranging over more than an order of magnitude (n_0 ~ 0.1 - 4 cm^{-3}). Assuming the distance of d ~ 5 kpc, we derive a Sedov age of \tau ~ 4500 yr and an explosion energy of E_0 ~ 1.6 \times 10^{50} ergs. The ambient density structure and the overall morphology suggest that G299.2-2.9 may be a limb-brightened partial shell extending to ~7 pc radius surrounded by fainter emission extending beyond that to a radius of ~9 pc. This suggests the SNR exploded in a region of space where there is a density gradient whose direction lies roughly along the line of sight. The faint central region shows strong line emission from heavy elements of Si and Fe, which is caused by the presence of the overabundant stellar ejecta there. We find no evidence for stellar ejecta enriched in light elements of O and Ne. The observed abundance structure of the metal-rich ejecta supports a Type Ia origin for G299.2-2.9.

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Blobrana


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Posts: 131433
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RE: Supernova remnant G337.2+0.1
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Title: XMM detection of the supernova remnant G337.2+0.1
Authors: Jorge A. Combi, Juan F. Albacete Colombo, Gustavo E. Romero, Paula Benaglia
(revised v2)

We report the first XMM detection of the SNR candidate G337.2+0.1 (=AX J1635.9-4719). The object shows centrally filled and diffuse X-ray emission. The emission peaks in the hard 3.0-10.0 keV band. A spatially resolved spectral study confirms that the column density of the central part of the SNR is about N_{H}~5.9 ± 1.5*10^22 cm^-2 and its X-ray spectrum is well represented by a single power-law with a photon index Gamma=0.96 ± 0.56. The non-detection of line emission in the central spectrum is consistent with synchrotron radiation from a population of relativistic electrons. Detailed spectral analysis indicates that the outer region is highly absorbed and quite softer than the inner region, with N_H~16.2(±5.2)*10^22 cm^-2 and kT=4.4(±2.8) keV. Such characteristics are already observed in other X-ray plerions. Based on the morphological and spectral X-ray information, we confirm the SNR nature of G337.2+0.1, and suggest that the central region of the source is a pulsar wind nebula (PWN), originated by an energetic though yet undetected pulsar, that is currently losing energy at a rate of ~ 10^36 erg s^-1.

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Blobrana


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Posts: 131433
Date:
Supernova Remnant Containing a Compact Object: G15.9+0.2
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Title: A New Young Galactic Supernova Remnant Containing a Compact Object: G15.9+0.2
Authors: S.P. Reynolds, K.J. Borkowski, U. Hwang, I. Harrus, R. Petre, G. Dubner

We identify the radio-emitting shell-type supernova remnant G15.9+0.2 as a relatively young remnant containing an X-ray point source that may be its associated neutron star. The integrated spectrum of the remnant shell obtained from our 30 ks exploratory Chandra observation shows very strong lines that require elevated element abundances from ejecta, in particular of sulphur. A plane-shock model fit gives a temperature kT = 0.9 (0.8, 1.0) keV, an ionisation timescale n_et = 6 (4, 9) x 10^10 cm^-3 s, and a sulphur abundance of 2.1 (1.7, 2.7) times solar (90% confidence limits). Two-component models with one solar and one enriched component are also plausible, but are not well constrained by the data. Various estimates give a remnant age of order 10^3 yr, which would make G15.9+0.2 among the dozen or so youngest remnants in the Galaxy. The sparse point source spectrum is consistent with either a steep Gamma ~ 4 power law or a kT ~ 0.4 keV blackbody. The spectrum is absorbed by a H column density N_H ~ 4 x 10^22 cm^-2 similar to that required for the remnant shell. The implied 2--9.5 keV source luminosity is about 10^33 ergs s^-1 for an assumed distance of 8.5 kpc consistent with the high absorption column. We suggest that the point source is either a rotation-powered pulsar or a compact central object (CCO).

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Blobrana


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Posts: 131433
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Supernova remnant RCW86
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The combined image from the Chandra and XMM-Newton X-ray observatories of RCW 86 shows the expanding ring of debris that was created after a massive star in the Milky Way collapsed onto itself and exploded. Both the Chandra and XMM images show low energy X-rays in red, medium energies in green and high energies in blue. The Chandra observations focused on the northeast (left-hand) side of RCW 86, and show that X-ray radiation is produced both by high-energy electrons accelerated in a magnetic field (blue) as well as heat from the blast itself (red).

supernovarem rcw86
Expand (315kb, 658 x 592)
Credit: Chandra: NASA/CXC/Univ. of Utrecht/J.Vink et al. XMM-Newton: ESA/Univ. of Utrecht/J.Vink et al.

Position (2000) RA 14h 45m 02.30s | Dec -62º 20' 32.00"

Properties of the shell in the Chandra image, along with the remnant's size and a basic understanding of how supernovas expand, were used to help determine the age of RCW 86. The new data revealed that RCW 86 was created by a star that exploded about 2,000 years ago in the constellation Circinus. This age matches observations of a new bright star by Chinese astronomers in 185 A.D. (and possibly Romans as well) and may be the oldest known recordings of a supernova. Supernova explosions in galaxies like ours are rare, and none have been recorded in hundreds of years.

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Blobrana


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Posts: 131433
Date:
Hydrogen Deuteride
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Title: Spitzer observations of hydrogen deuteride
Authors: David A. Neufeld (JHU), Joel D. Green (Rochester), David J. Hollenbach (NASA/Ames), Paule Sonnentrucker (JHU), Gary J. Melnick (CfA), Edwin A. Bergin (U. Michigan), Ronald L. Snell (U. Mass.), William J. Forrest (Rochester), Dan M. Watson (Rochester), Michael J. Kaufman (San Jose State U.)

Researchers report the detection of interstellar hydrogen deuteride (HD) toward the supernova remnant IC443, and the tentative detection of HD toward the Herbig Haro objects HH54 and HH7 and the star forming region GGD37 (Cepheus A West).
Their detections are based upon spectral line mapping observations of the R(3) and R(4) rotational lines of HD, at rest wavelengths of 28.502 and 23.034 micron respectively, obtained using the Infrared Spectrograph onboard the Spitzer Space Telescope.
The HD R(4)/R(3) line intensity ratio promises to be a valuable probe of the gas pressure in regions where it can be observed. The derived HD/H2 abundance ratios are 1.19(+0.35/-0.24)E-5, 1.80(+0.54/-0.32)E-5, and 1.41(+0.46/-0.33)E-5 respectively (68.3% confidence limits, based upon statistical errors alone) for IC443 (clump C), HH54, and HH7. If HD is the only significant reservoir of gas-phase deuterium in these sources, the inferred HD/H2 ratios are all consistent with a gas-phase elemental abundance [n(D)/n(H)](gas) ~ 7.5E-6, a factor 2 - 3 below the values obtained previously from observations of atomic deuterium in the local bubble and the Galactic halo.
However, similarly low gas-phase deuterium abundances have been inferred previously for molecular gas clouds in the Orion region, and in atomic clouds along sight-lines within the Galactic disk to stars more distant than 500 pc from the Sun.

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Blobrana


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Posts: 131433
Date:
CXOU J061705.3+222127
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Observations with the Chandra X-ray Observatory has revealed important new details of a neutron star that is spewing out a wake of high-energy particles as it races through space. The deduced location of the neutron star on the edge of a supernova remnant, and the peculiar orientation of the neutron star wake, pose mysteries that remain unresolved.

"Like a kite flying in the wind, the behaviour of this neutron star and its wake tell us what sort of gas it must be ploughing through. Yet we're still not sure how the neutron star got to its present location" - Bryan Gaensler of the Harvard-Smithsonian Centre for Astrophysics (CfA) in Cambridge, Mass., and lead author of a paper accepted to The Astrophysical Journal.

ic443
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Credit NASA

The neutron star, known as CXOU J061705.3+222127, appears to lie near the outer edge of an expanding bubble of hot gas associated with the supernova remnant IC 443. Presumably, the neutron star was created at the time of the supernova -- approximately 30,000 years ago -- and propelled away from the site of the explosion at about 500,000 miles per hour.
However, the neutron star's wake is oriented almost perpendicularly to the direction expected if the neutron star were moving away from the centre of the supernova remnant. This apparent misalignment had previously raised doubts about the association of the speeding neutron star with the supernova remnant.
Gaensler and his colleagues provide strong evidence that the neutron star was indeed born in the same explosion that created the supernova remnant. First, the shape of the neutron star's wake indicates it is moving a little faster than the speed of sound in the remnant's multimillion-degree gas. The velocity that one can then calculate from this conclusion closely matches the predicted pace of the neutron star. In contrast, if the neutron star were outside the confines of the remnant, its inferred speed would be a sluggish 20,000 miles per hour. Also, the measured temperature of the neutron star matches that of one born at the same time of the supernova remnant.
What then, could cause the misaligned, or wayward, neutron star wake?
The authors speculate that perhaps the doomed progenitor star was moving at a high speed before it exploded, so that the explosion site was not at the observed centre of the supernova remnant. Fast moving gusts of gas inside the supernova remnant have further pushed the neutron star's wake out of alignment.
Observations of J0617 in the next 10 years should put this idea to the test.

"If the neutron star was born off-center and if the wake is being pushed around by cross-winds, the neutron star should be moving close to vertically, away from the center of the supernova remnant. Now we wait and see/i]" - Bryan Gaensler.

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Blobrana


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Posts: 131433
Date:
IC443
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Title: The X-ray Structure of the Pulsar Bow Shock G189.22+2.90 in the Supernova Remnant IC 443
Authors: B. M. Gaensler, S. Chatterjee, P. O. Slane, E. van der Swaluw, F. Camilo, J. P. Hughes

Researchers present a deep observation with the Chandra X-ray Observatory of the neutron star bow shock G189.22+2.90 in the supernova remnant (SNR) IC 443.
Their data confirms the cometary morphology and central point source seen previously, but also reveal considerable new structure. Specifically, they find that the X-ray nebula consists of two distinct components: a "tongue" of bright emission close to the neutron star, enveloped by a larger, fainter "tail".
The researchers interpret the tongue and tail as delineating the termination shock and the post-shock flow, respectively, as previously identified also in the pulsar bow shock G359.23-0.82 ("the Mouse"). However, for G189.22+2.90 the tongue is much less elongated than for the Mouse, while the tail is much broader. These differences are consistent with the low Mach number, M >~ 2, expected for a neutron star moving through the hot gas in a SNR's interior, supporting the case for a physical association between G189.22+2.90 and IC 443. They resolve the stand-off distance between the star and the head of the bow shock, which allows them to estimate a space velocity for the neutron star of ~230 km/s, independent of distance.
They detected thermal emission from the neutron star surface at a temperature of 102 ±22 eV, which is consistent with the age of SNR IC 443 for standard neutron star cooling models. They also identify two compact knots of hard emission located 1-2 arcsec north and south of the neutron star.

IC 443
A multiwavelength view of the SNR IC 443 and the PWN G189.22+2.90. Red shows 670-nm emission from the Second Palomar Observatory Sky Survey; green shows 1.4-GHz radio data taken by the DRAO Synthesis Telescope (Leahy 2004); blue shows 0.1–2.4 keV X-ray data taken by the ROSAT PSPC (Asaoka & Aschenbach 1994).
The white contours show 8.5-GHz Very Large Array data on G189.22+2.90 at a resolution of 9'' ×8'' (O2001), with contour levels drawn at 20%, 50% and 80% of the peak of 3.7 mJy beam-1. The bright star to the west of IC 443 is nu Gem.

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