754 research outputs found
The Proper Motion of the Central Compact Object RX J0822-4300 in the Supernova Remnant Puppis A
Using the High Resolution Camera (HRC) aboard the Chandra X-ray Observatory,
we have re-examined the proper motion of the central compact object RX
J0822-4300 in the supernova remnant Puppis A. New data from 2010 August,
combined with three archival data sets from as early as 1999 December, provide
a baseline of 3886 days (more than 10 1/2 years) to perform the measurement.
Correlating the four positions of RX J0822-4300 measured in each data set
implies a projected proper motion of mu 71 \pm 12 masy. For a distance of 2 kpc
this proper motion is equivalent to a recoil velocity of 672 \pm 115 km/s. The
position angle is found to be 244 \pm 11 degrees. Both the magnitude and
direction of the proper motion are in agreement with RX J0822-4300 originating
near the optical expansion center of the supernova remnant. For a displacement
of 371 \pm 31 arcsec between its birth place and today's position we deduce an
age of (5.2 \pm 1.0) 10^3 yrs for RX J0822-4300. The age inferred from the
neutron star proper motion and filament motions can be considered as two
independent measurements of the same quantity. They average to 4450 \pm 750 yrs
for the age of the supernova remnant Puppis A.Comment: Accepted for publication in the Astrophysical Journa
Direct Measurement of Neutron-Star Recoil in the Oxygen-Rich Supernova Remnant Puppis A
A sequence of three Chandra X-ray Observatory High Resolution Camera images
taken over a span of five years reveals arc-second-scale displacement of RX
J0822-4300, the stellar remnant (presumably a neutron star) near the center of
the Puppis A supernova remnant. We measure its proper motion to be
0.165+/-0.025 arcsec/yr toward the west-southwest. At a distance of 2 kpc, this
corresponds to a transverse space velocity of ~1600 km/s. The space velocity is
consistent with the explosion center inferred from proper motions of the
oxygen-rich optical filaments, and confirms the idea that Puppis A resulted
from an asymmetric explosion accompanied by a kick that imparted roughly
3*10^49 ergs of kinetic energy (some 3 percent of the kinetic energy for a
typical supernova) to the stellar remnant. We discuss constraints on
core-collapse supernova models that have been proposed to explain neutron star
kick velocities
The First X-Ray Proper-Motion Measurements of the Forward Shock in the Northeastern Limb of SN 1006
We report on the first X-ray proper-motion measurements of the
nonthermally-dominated forward shock in the northeastern limb of SN 1006, based
on two Chandra observations taken in 2000 and 2008. We find that the proper
motion of the forward shock is about 0.48 arcsec/yr and does not vary around
the rim within the ~10% measurement uncertainties. The proper motion measured
is consistent with that determined by the previous radio observations. The mean
expansion index of the forward shock is calculated to be ~0.54 which matches
the value expected based on an evolutionary model of a Type Ia supernova with
either a power-law or an exponential ejecta density profile. Assuming pressure
equilibrium around the periphery from the thermally-dominated northwestern rim
to the nonthermally-dominated northeastern rim, we estimate the ambient density
to the northeast of SN 1006 to be about 0.085/cm^3.Comment: Accepted for publication in The Astrophysical Journal Letter
Far-flung Filaments of Ejecta in the Young Supernova Remnant G292.0+1.8
New optical images of the young SNR G292.0+1.8, obtained from the 0.9-m
telescope at CTIO, show a more extensive network of filaments than had been
known previously. Filaments emitting in [O III] are distributed throughout much
of the 8 arcmin diameter shell seen in X-ray and radio images, including a few
at the very outermost shell limits. We have also detected four small complexes
of filaments that show [S II] emission along with [OIII]. In a single long-slit
spectrum we find variations of almost an order of magnitude in the relative
strengths of oxygen and sulfur lines, which must result from abundance
variations. None of the filaments, with or without [S II], shows any evidence
for hydrogen, so all appear to be fragments of pure SN ejecta. The [S II]
filaments provide the first evidence for undiluted products of oxygen burning
in the ejecta from the supernova that gave rise to G292.0+1.8. Some oxygen
burning must have occurred, but the paucity of [S II]-emitting filaments
suggests that either the oxygen burning was not extensive or that most of its
products have yet to be excited. Most of the outer filaments exhibit radial,
pencil-like morphologies that suggest an origin as Rayleigh-Taylor fingers of
ejecta, perhaps formed during the explosion. Simulations of core-collapse
supernovae predict such fingers, but these have never before been so clearly
observed in a young SNR. The total flux from the SNR in [OIII] 5007 is 5.4 *
10**-12 ergs/cm**2/s. Using a distance of 6 kpc and an extinction correction
corresponding to E(B-V) = 0.6 (lower than previous values but more consistent
both with our data and radio and X-ray estimates of NH), this leads to a
luminosity of 1.6 * 10**35 ergs/s in the 5007 Ang. line.Comment: 32 pages including 10 figures, and 3 tables, accepted for publication
in AJ. Vol 132, July 2006. Higher resolution versions of the figures and a
pdf of the manuscript can be found at
http://www-int.stsci.edu/~long/papers/g292_optical
Supernova Remnants in the Irregular Galaxy NGC4449
The nearby irregular galaxy NGC4449 has a star formation rate of about 0.4
solar masses/yr and should host of order 70 SNRs younger than 20,000 years, a
typical age for SNRs expanding into to an ISM with unit density to reach the
radiative phase. We have carried out an optical imaging and spectroscopic
survey in an attempt to identify these SNRs. This task is challenging because
diffuse gas with elevated ratios of [SII]:H-alpha is omnipresent in NGC4449,
{causing confusion when using this common diagnostic for SNRs. Using
narrow-band interference-filter images, we first identified 49 objects that
have elevated [SII]:H-alpha ratios compared to nearby HII regions. Using
Gemini-N and GMOS, we then obtained high-resolution spectra of 30 of these SNR
candidates, 25 of which have [SII]:H-alpha ratios greater than 0.5. Of these,
15 nebulae are almost certainly SNRs, based on a combination of
characteristics: higher [OI]:H-alpha ratios and broader line widths than
observed from HII regions. The remainder are good candidates as well, but need
additional confirmation. Surprisingly, despite having superior imaging and
spectroscopic data sets to examine, we are unable to confirm most of the
candidates suggested by Leonidaki (2013). While NGC4449 is likely an extreme
case because of the high surface brightness and elevated [SII]:H-alpha ratio of
diffuse gas, it highlights the need for sensitive high-resolution optical
spectroscopy, or high spatial resolution radio or X-ray observations that can
ensure accurate SNR identifications in external galaxies
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