arXiv subjects

Patrick O. Slane

Publications and source records attributed to Patrick O. Slane.

57 records · Page 4Linked to original sources

arXiv2000

Discovery of X-ray Emission from G328.4+0.2, a Crab-Like Supernova Remnant

G328.4+0.2 is a moderately small (5 arcmin x 5arcmin) Galactic radio supernova remnant (SNR) at a distance of at least 17 kpc that has been long suggested to be Crab-like. Here we report on the detection with ASCA of the X-ray emission from the SNR. The X-ray source is faint with an observed flux of (6.0 +/- 0.8)E-13 erg/s/cm^2 over the 2-10 keV band. The emission is heavily cut-off at low energies and no flux is detected below 2 keV. Spectral analysis confirms that the column density to the source is indeed large, N_H ~ 1E23 atoms/cm^2, and consistent with the total column density of hydrogen through the Galaxy at this position. Good fits to the spectrum can be obtained for either thermal plasma or nonthermal power-law models, although the lack of detected line emission as well as other evidence argues against the former interpretation. The power-law index we find, α_P = 2.9 (+0.9,-0.8), is consistent with other Crab-like SNRs. In the radio band G328.4+0.2 is nearly as luminous as the Crab Nebula, yet in the X-ray band luminosity it is some 70 times fainter. Nevertheless its inferred soft X-ray band luminosity is greater than all but the brightest pulsar-powered synchrotron nebulae and implies that G328.4+0.2 contains a rapidly spinning, as yet undetected, pulsar that is losing energy at a rate of approximately 1E38 erg/s.

astro-ph↗

arXiv1999

Nucleosynthesis and Mixing in Cassiopeia A

We present results from the first light observations of the Cassiopeia A (Cas A) supernova remnant (SNR) by the Chandra X-ray Observatory. The X-ray spectrum varies on all spatial scales down to the instrumental limit (0.02 pc at the SNR). Based on representative spectra from four selected regions we investigate the processes of nucleosynthesis and mixing in Cas A. We make the first unequivocal identification of iron-rich ejecta produced by explosive silicon-burning in a young Galactic SNR. Elsewhere in the remnant we see silicon-rich ejecta from explosive oxygen-burning. Remarkably, our study finds that the Fe-rich ejecta lies outside the Si-rich material, leading to the conclusion that bulk motions of the ejecta were extensive and energetic enough in Cas A to cause a spatial inversion of a significant portion of the supernova core during the explosion. It is likely that this inversion was caused by ``Fe''-rich ejecta emerging in plumes from the rising bubbles in the neutrino-driven convection layer. In addition the radioactive decay energy from $^{56}$Ni may have contributed to the subsequent evolution of the material. We have also discovered faint, well-defined filaments with featureless X-ray spectra that are possibly the sites of cosmic ray acceleration in Cas A.

astro-ph↗

arXiv1998

Study of the Composite Supernova Remnant MSH 11-62

We present the analysis of the X-ray data collected during an observation of the supernova remnant (SNR) MSH 11-62 by the Advanced Satellite for Cosmology and Astrophysics (ASCA). We show that MSH 11-62 is a composite remnant whose X-ray emission comes from two distinct contributions. Nonthermal, synchrotron emission, localized to a region of radius (~~)3' (consistent with a point source) dominates the total flux above 2 keV. A second contribution comes from a thermal component, extended up to a radius of (~~)6' and detected only at energies below 2keV. The spatial and spectral analysis imply the presence of a neutron star losing energy at a rate of about (10**36 - 10**37) ergs/s. No pulsed emission is detected and we set a limit on the pulsed fraction of 10%. This is consistent with the lack of a radio pulsar in the remnant, which may indicate that the pulsed emission from the rapidly rotating compact object that should be powering the synchrotron nebula is beamed and our viewing direction is unfavorable. In either event, the central neutron star deposits much of its spin-down energy into the surrounding synchrotron nebula where, through direct imaging with broadband satellites such as ASCA, it is possible to study the energetics and evolution of the compact remnant.

astro-ph↗