Engineering topics

Szymkowiak, A. E.

Publications and source records attributed to Szymkowiak, A. E..

43 records · Page 3

NASA NTRS1980

X-ray spectral constraints on the broad-line cloud geometry of NGC 4151

X-ray spectral data from NGC 4151 taken with the Einstein Solid-State Spectrometer (SSS) and the HEAO 1 A-2 experiment cannot be simply reconciled with absorption from a uniform column of cold gas. The SSS data can, however, be explained in terms of a clumped absorber with approximately 10% uncovered fraction and factor-of-two overabundances in Z equal to or greater than 14 elements relative to solar oxygen. It is shown that these and previously reported spectral and variability data can be quantitatively reconciled with absorption arising in the cold clouds responsible for the broad optical line emission if the cloud dimensions are small compared to the central source size. It is suggested that the lack of significant X-ray absorption observed from much higher luminosity Seyferts and quasars is a natural consequence of the proposed picture for NGC 4151.

Holt, S. S.↗

NASA NTRS1980

Is the remnant of SN 1006 Crablike

The solid-state spectrometer on the Einstein Observatory and the GSFC cosmic X-ray spectrometer on OSO 8 have observed the X-ray spectrum of SN 1006. The data can be well represented by a power-law model with alpha = 1.2, similar to the spectrum of the Crab Nebula. This is in contrast to the radio and X-ray maps of SN 1006 which show a shell structure more typical of SNR with thermal X-ray emission. The X-ray spectrum is suggestive of nonthermal synchrotron emission, raising the possibility that the remnant of SN 1006 contains a source of relativistic electrons.

Becker, R. H.↗

NASA NTRS1980

X-ray spectral constraints on the broad-line cloud geometry of NGC 4151

X-ray spectral data from NGC 4151 taken with the Einstein Solid-State Spectrometer (SSS) and the HEAO-1 A-2 experiment cannot be simply reconciled with absorption from a uniform column of cold gas. The SSS data can, however, be explained in terms of a clumped absorber with approximately 10% uncovered fraction and factor-of-two overabundances in Z equal to or greater than 14 elements relative to solar oxygen. It is shown that these and previously reported spectral and variability data can be quantitatively reconciled with absorption arising in the cold clouds responsible for the broad optical line emission if the cloud dimensions are small compared to the central source size. It is suggested that the lack of significant X-ray absorption observed from much higher luminosity Seyferts and quasars is a natural consequence of our picture for NGC 4151.

Holt, S. S.↗

NASA NTRS1980

Is the remnant of SN1006 crab-like?

The solid state spectrometer on the Einstein Observatory and the GSFC cosmic X-ray spectrometer on OSO-8 observed the X-ray spectrum of SN1006. The data can be well-represented by a power-law model with alpha = 1.2, similar to the spectrum of the Crab nebula. This is in contrast to the radio and X-ray maps of SN1006 which show a shell structure more typical of SNR with thermal X-ray emission. The X-ray spectrum is suggestive of nonthermal synchrotron emission, raising the possibility that the remnant of SN1006 contains a source of relativistic electrons.

Becker, R. H.↗

NASA NTRS1980

X-ray spectroscopy of supernova remnants

The information which can be obtained from X-ray spectroscopy of supernova remnants is considerd. The fitting of X-ray detector counts to models of the incident spectrum is discussed, and the types of thermal emission models generally employed are presented, including the power law, black body, and thermal bremsstrahlung models of the continua and models of the emission of a hot, optically thin plasma in collisional equilibrium. Observations of 12 supernova remnants made with the Solid State Spectrometer on board the Einstein Observatory are reported, and metal abundances inferred from the lines of the eight remnants showing thermal spectra are summarized. Questions raised by the failure to observe the overabundance of Fe predicted by stellar evolution and hydrodynamic modeling are discussed, and the need to develop more detailed models of the conditions in a supernova remnant in order to interpret the X-ray spectra is noted.

Szymkowiak, A. E.↗

NASA NTRS1979

HEAO 1 observations of the X-ray pulsar 4U 1626-67

Results are reported for an observation of the 7-s pulsar 4U 1626-67 with the A-2 experiment on HEAO 1. The phase-averaged X-ray spectrum between 0.7 and 60 keV is complex, as are the constituent spectra, which change radically as a function of pulse phase. Included in this spectral change is the sudden appearance and subsequent decay of a continuum or emission feature with a mean energy of 19 keV, which contains about one-half the power in this spectral range. Pulse-timing results include a new determination of the pulse period and a factor of 8 reduction in the upper limit for the light travel time for orbital periods between 1 and 7 hours. These findings are discussed and compared with the general nature of pulsar spectra.

Pravdo, S. H.↗

NASA NTRS1979

HEAO 1 observations of the X-ray pulsar 4U1626-67

Results of an observation of the 7-s pulsar 4U1626-67 with the A2 experiments on HEAO 1 are reported. The phase-averaged X-ray spectra which change radically as a function of pulse phase. Included in this spectral change is the sudden appearance and subsequent decay of a continuum or emission feature with a mean energy of 19 keV which contains about 1/2 the power in this spectral range. Pulse timing results include a new determination of the pulse period and a factor 8 reduction in the upper limit for the light travel time for orbital periods between 1 and 7 hours. The findings for this system are discussed and compared with the general nature of pulsar spectra.

Pravdo, S. H.↗