Engineering topics

Slane, P.

Publications and source records attributed to Slane, P..

7 records

NASA NTRS2011

Properties and Spatial Distribution of Dust Emission in the Crab Nebula

The nature and quantity of dust produced in supernovae (SNe) is still poorly understood. Recent IR observations of freshly-formed dust in supernova remnants (SNRs) have yielded significantly lower dust masses than predicted by theoretical models and observations high-redshift galaxies. The Crab Nebula's pulsar wind is thought to be sweeping up freshly-formed SN dust along with the SN ejecta. The evidence for this dust was found in the form of an IR bump in the integrated spectrum of the Crab and in extinction against the synchrotron nebula that revealed the presence of dust in the filament cores. We present the first spatially-resolved emission spectra of dust in the Crab Nebula acquired with the Spitzer Space Telescope. The IR spectra are dominated by synchrotron emission and show forbidden line emission from both sides of the expanding nebula, including emission from [S III], [Si II], [Ne II], [Ne III], [Ne V], [Ar III], [Ar V], [Fe II], and [Ni II]. We extrapolated a synchrotron spectral data cube from the Spitzer 3.6 and 4.5 micron images, and subtracted this contribution from our 15-40 micron spectral data to produce a map of the residual continuum emission from dust. The emission appears to be concentrated along the ejecta filaments and is well described by astronomical silicates at an average temperature of 65 K. The estimated mass of dust in the Crab Nebula is 0.008 solar masses.

Sonneborn, G.↗

NASA NTRS2001

B-MINE: The Balloon-Borne Microcalorimeter Nuclear Line Explorer

B-MINE is a concept for a balloon mission designed to probe the deepest regions of a supernova explosion by detecting 44Ti emission at 68 keV with spatial and spectral resolutions that are sufficient to determine the extent and velocity distribution of the 44Ti emitting region. The payload introduces the concept of focusing optics and microcalorimeter spectroscopy to nuclear line emission astrophysics. B-MINE has a thin, plastic foil telescope multilayered to maximize the reflectivity in a 20 keV band centered at 68 keV and a microcalorimeter array optimized for the same energy band. This combination provides a reduced background, an energy resolution of 50 eV and a 3 sigma sensitivity in 10 (exp 6) s of 3.3 x 10(exp -7) ph cm(exp -2) s(exp -1) at 68 keV. During the course of a long duration balloon flight, B-MINE could carry out a detailed study of the 44Ti emission line centroid and width in CAS A.

Silver, E.↗

NASA NTRS1999

An X-Ray Study of the Evolution of the CTB1 Supernova Remnant

The subject grant supported an X-ray study of the evolution of CTB1, a supernova remnant with a centrally brightened morphology in X-rays and a curious optical structure suggesting the possibility of evolution in a stellar wind cavity. The primary questions to be answered in the study were: 1) is the X-ray emission thermal, and thus associated with hot gas in the remnant interior, or nonthermal, presumably driven by an unseen pulsar; 2) if the emission is thermal, is the ionization timescale of the hot gas consistent with a dynamically young SNR, such as might be expected for a cavity explosion, or is it consistent with dynamically older remnant whose centrally enhanced X-ray profile is the result of thermal conduction with a radiative shell, or perhaps evaporation of cool clouds being slowly heated in the SNR interior?

Slane, P.↗

NASA NTRS1997

Using the Tycho catalogue for AXAF: Guiding and aspect reconstruction for half-arcsecond X-ray images

The Advanced X-ray Astrophysics Facility (AXAF) will carry a high resolution mirror, two imaging detectors, and two sets of transmission gratings. The Tycho catalog from the Hipparcos mission will serve as a primary part of the AXAF Guide and Aspect Star Catalog (AGASC). The incorporation of Tycho into AGASC will provide: accurate positions and magnitudes for target acquisition and guidance; the necessary colors for magnitude transformations to the AXAF aspect camera system; high internal astrometric accuracy for half-arcsecond, post-facto image reconstruction; and an external astrometric system.

Green, P. J.↗

NASA NTRS1994

1ES 1113+432: Luminous, soft X-ray outburst from a nearby cataclysmic variable (AR Ursae Majoris)

A remarkable X-ray transient from the Einstein Slew Survey, 1 ES 1113+432, is identified with a nearby, short-period cataclysmic variable. Wenzel (1993) has confirmed that the optical counterpart is the variable star, AR UMa (cataloged as 'semiregular'), erroneously reported 5.7 min southeast of the true position. One of the Einstein slew observations recorded a flux of 43 IPC counts/s, which is an order of magnitude above the flux observed from the brightest cataclysmic variables in other X-ray surveys. The outburst spectrum is extremely 'soft,' with an implied blackbody temperature of approximately 22 eV. The optical counterpart (V = 16.5) exhibits a strong UV component, TiO bands from an M star, and broadened Balmer emission lines. Optical states as bright as V approx. 13 were found on photographs from the Harvard Plate Library, confirming outburst behavior in the optical counterpart. The historical photographic record suggests that 1ES 1113+432 remains in a low-accretion state most of the time. Both of the soft X-ray spectrum and the transitions between high and low-accretion states are suggestive of the AM Her (magnetic) subclass. Photometric observations in the I band show 0.18 mag modulations at a period of 0.966 hr. These are interpreted as ellipsiodal variations in the secondary star for a binary period of 1.932 hr, which is near the lower boundary of the 'period gap' in the histogram, of orbital periods of accreting white dwarfs. Thus 1ES 1113+432 provides the rare opportunity to study a secondary star in a cataclysmic binary that has evolved through the period gap. The optical spectral features from the secondary imply a spectral type of approximately M6 and a distance of approximately 88 pc. The peak luminosity in the soft X-ray component (unabsorbed) is then estimated to be 3 X 10(exp 33) ergs/s, assuming emission from a blackbody slab with a temperature of 22 eV. While this luminosity is higher than previous measures of the soft X-ray component, it does not exceed the amount of radiation that could be emitted from the accretion-heated surface of a white dwarf.

Remillard, R. A.↗

NASA NTRS1992

Grazing incidence X-ray reflectivity - Studies for the AXAF observatory

The energy bandwidth and total throughput of a grazing incidence optics system is a strong function of the X-ray reflectivity of the surface coating. In support of the Advanced X-ray Astrophysics Facility (AXAF), studies are underway to evaluate and characterize the reflectivity of potential AXAF coatings. Here we report on results obtained for Au, Ir, and Ni coatings produced by electron-beam evaporation, evaporation with ion-assist, and sputtering. Effects of coating thickness and deposition angle have been evaluated at 6.4 and 8.1 keV; the highest reflectivities are those of the thinner, about 200 A vs about 700 A, coatings. While considerable variations exist, the best Ir samples have higher reflectivity than any of the Au coatings. Data results have been compared with models for theoretical reflectivity, particularly with regard to the effective density of the coatings. Independent measurements of the coating densities have been carried out for comparison with the reflectivity results.

Slane, P.↗

NASA NTRS1989

Measurement of the effects of particulate contamination on X-ray reflectivity

Because particles of sizes larger than a few tenths microns adversely affect high resolution X-ray telescopes by scattering and absorbing X-rays, the cleanliness required to maintain the about 1 percent overall calibration precision desired for the Advanced X-ray Astrophysics Facility (AXAF) is being investigated. At the grazing angles used for the AXAF mirrors, each particle shadows a surface area about 100 times its geometric area, necessitating glass occlusion specifications much more stringent than typically stipulated for visible-light particulate contamination. On test flats coated with gold, controlled levels of contamination have been deposited spanning the range from 5 x 10 to the -5th to 0.005 fractional area covered, and the absorption component of extinction has been measured over a range of grazing angles and X-ray energies to verify the predicted effects of particulate contamination.

Slane, P.↗