1,828 research outputs found
An X-ray Synchrotron Shell and a Pulsar: The Peculiar Supernova Remnant G32.4+0.1
We present a deep Chandra observation of the shell supernova remnant
G32.4+0.1, whose featureless X-ray spectrum has led to its classification as an
X-ray synchrotron-dominated supernova remnant (SNR). We find a partial shell
morphology whose outline is quite circular, with a radius of about 11 pc at an
assumed distance of 11 kpc. Thermal and power-law spectral models for three
relatively bright regions provided equally good fits, but the absence of
spectral lines required ionization timescales from thermal fits that are
inconsistent with mean densities derived from emission measures. We thus
confirm the nonthermal, i.e., synchrotron, origin of X-rays from G32.4+0.1.
Shock velocities needed to accelerate electrons to the required TeV energies
are >~1000 km/s, giving remnant ages <~5,000 -- 9,000 yr. There is no obvious
X-ray counterpart to the radio pulsar PSR J1850--0026, but its position adjoins
a region of X-ray emission whose spectrum is somewhat harder than that of other
regions of the shell, and which may be a pulsar-wind nebula (PWN), though its
spectrum is steeper than almost all known X-ray PWNe. The distance of the
pulsar from the center of symmetry of the shell disfavors a birth in a
supernova event at that location only a few thousand years before: either the
pulsar (and putative PWN) are not associated with the shell SNR, requiring a
coincidence of both position and (roughly) absorbing column density, or the SNR
is much older, making the origin of nonthermal emission problematic.Comment: 13 pages, 9 figures; accepted for publication in the Astrophysical
Journa
X-Ray Emitting Ejecta of Supernova Remnant N132D
The brightest supernova remnant in the Magellanic Clouds, N132D, belongs to
the rare class of oxygen-rich remnants, about a dozen objects that show optical
emission from pure heavy-element ejecta. They originate in explosions of
massive stars that produce large amounts of O, although only a tiny fraction of
that O is found to emit at optical wavelengths. We report the detection of
substantial amounts of O at X-ray wavelengths in a recent 100 ks Chandra ACIS
observation of N132D. A comparison between subarcsecond-resolution Chandra and
Hubble images reveals a good match between clumpy X-ray and optically emitting
ejecta on large (but not small) scales. Ejecta spectra are dominated by strong
lines of He- and H-like O; they exhibit substantial spatial variations
partially caused by patchy absorption within the LMC. Because optical ejecta
are concentrated in a 5 pc radius elliptical expanding shell, the detected
ejecta X-ray emission also originates in this shell.Comment: 5 pages, 6 figures, ApJ Letters, in pres
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