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Rothschild, R. E.

Publications and source records attributed to Rothschild, R. E..

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Iron line emission from a high-temperature plasma in Cassiopeia A

The letter reports a measurement of the X-ray spectrum of Cas A with a proportional counter on board OSO-8. The high-energy data (greater than 7 keV) are found to agree equally well with a power law having a number index of about 4.5 and with a thermal spectrum having kT of about 3.9 keV. A narrow iron line predicted by the thermal model is also observed; this line is centered at about 6.67 keV and has an equivalent width of approximately 1270 eV. The low-energy data (below 6 keV) are not fully accounted for by the above thermal spectrum, but are fitted well by an additional low-temperature thermal component with kT not exceeding 0.7 keV and an atomic hydrogen column density of approximately 10 to the 22nd power per sq cm. The iron abundance in the plasma at an electron temperature of 40 keV is estimated from the observed line-to-continuum ratio, and it is shown that a normal cosmic iron abundance is adequate to explain the observation.

Pravdo, S. H.↗
NASA NTRS1976

X-ray observations of the Vela pulsar: Statistics and spectrum

The Vela pulsar was observed in the range 2-60 keV by the GSFC proportional counter experiment onboard OSO-8 with temporal resolution sufficient to make possible a sensitive search for pulsed X-rays at the radio pulsar period. A statistical analysis yielded 8 per cent as the 3 sigma upper limit on the pulsed fraction. The energy spectrum is fit well by a structureless power law with number index 2.21 + or - 0.2 and absorption by a hydrogen column density of N sub H equals 2.9 + or - 2.0 times ten to the twenty-second power per sq.cm.

Pravdo, S. H.↗
NASA NTRS1976

Spectral variability in the X-ray pulsar GX 1+4

Observations of the galactic center region, hard X-ray source GX 1+4 by the GSFC X-ray spectroscopy experiment on OSO-8 confirm that GX 1+4 is a slow X-ray pulsar. The amount of absorption by cold matter in the spectrum of GX 1+4 varies significantly within a 24 hour period, behavior typical of many X-ray binary systems. The light curve for the pulsations from GX 1+4 appears to be energy dependent.

Becker, R. H.↗
NASA NTRS1976

Iron line emission from a high temperature plasma in Cas A

The X-ray spectrum of Cassiopeia A was observed for several days by the proportional counter experiment on board OSO-8. The high energy ( 5 keV) data are fit well by a thermal spectrum. A narrow iron line which is predicted by the thermal model is also observed. The low energy (2-5 keV) data show an excess over the high temperature component which is consistent with the presence of an additional low temperature thermal component. Iron abundance in the source relative to normal cosmic abundance is discussed, as in the relation of this observation to shock wave and multi-component thermal models for supernova remnants.

Pravdo, S. H.↗
NASA NTRS1976

Cosmic X-ray observations with OSO-8

The GSFC Cosmic X-ray Spectroscopy experiment aboard OSO-8 has operated successfully since launch providing spectral and temporal data on X-ray sources in tha energy range 2-60 keV. Analysis of quick look data shows a variety of spectral features, some stable, others variable, which will increase understanding of the nature of individual sources. In particular, observed emission and absorption features that can be attributed to iron will result in abundance measures of this important element in sources such as some X-ray binaries, the supernova remnant Cas A, and the nucleus of the galaxy Cen A.

Serlemitsos, P. J.↗
NASA NTRS1976

Her X-1 spectral evidence for a strong magnetic field

The steep high energy cutoff observed in the spectrum for Her X-1 is analyzed in terms of the severely modified Thomson scattering that dominates the radiative transfer in a highly magnetized plasma near the surface of a neutron star. The data are shown to indicate a field of about 10 to the 13th power G near the magnetic poles and the stopping of accreting matter by nuclear collisions in the neighboring plasma.

Boldt, E. A.↗
NASA NTRS1976

OSO-8 observations of Hercules X-1

The X-ray binary Her X-1 was observed by the GSFC cosmic X-ray detectors aboard OSO-8 between August 26 and September 3, 1975. The results reported are based on quick look tapes which contain less than 10% of the total time spent on source. Spectra were observed during different phases of the binary period including the anomalous low state (dip) in X-ray intensity. The normal high spectra is well represented by a power law with a short cutoff above approximately 25 keV. A significant and varying enhancement in the intensity around 6.7 keV was observed, suggesting the presence of an iron line. Absorption was seen in the spectrum immediately following eclipse. The dip spectrum is found to be considerably flattened. Also spectra are presented for different phases of the pulse period.

Pravdo, S. H.↗
NASA NTRS1976

OSO-8 GSFC results on Cen X-3

Spectra of Cen X-3 during eclipse, in transition out of eclipse, and during several later phases of the binary orbit were obtained from quick look data of the July 16-25, 1975 observation by the Goddard X-ray spectroscopy experiment on OSO-8. In the high state there was no absorption turn over. Pulsations were present at least to 23 keV. The spectrum at the pulse minimum was flatter above 7 keV than that of the pulse peak. In transition out of eclipse Cen X-3 emerged above a small low energy flux seen during eclipse. The observations appear to indicate absorption by cold and ionized matter and the presence of iron in the companion's atmosphere. Decreased intensities were observed at late phases of some binary orbits in some cases corresponding to dips. Absorption appears although the low energy component remains. Variable features may be interpretable as absorption and emission by iron and possibly other trace elements.

Swank, J. H.↗
NASA NTRS1976

High resolution measurements of Cyg X-1 from rockets

Cyg X-1 was observed on two occasions (Oct. 4, 1973 and Oct. 3, 1974) by the Goddard X-ray rocket payload. This payload consisted of two gas proportional counters (xenon-methane with 710 sq cm and argon-methane with 610 sq cm using the same 128 channel pulse height analyzer and having 320 micro sec temporal resolution on the 1973 flight and 160 micro sec resolution on the 1974 flight. During both flights, bursts of 1 ms duration were observed with very high statistical certainty. To date all 13 of these bursts were analyzed for spectral and temporal character, and the results of this analysis are presented. The spectra of overall X-ray emission from both flights is also presented. In a source known for its variability, it is remarkable that the spectra taken one year apart are virtually identical.

Rothschild, R. E.↗
NASA NTRS1976

The observation program for the GSFC cosmic X-ray spectroscopy experiment

The cosmic X-ray spectroscopy experiment on OSO-8 will observe seven X-ray binary sources in its first six months of operation. If possible, each of these sources will be observed for one or more binary orbits so that the X-ray spectrum of each object can be observed through all phases of its orbit. For the two pulsing binaries, Her X-1 and Cen X-3, spectral variations over the pulse period will be studied. Simultaneous radio observations of Cyg X-1 and Cyg X-3 will search for any correlation between radio and X-ray emission. During the first year of operation, the detectors will observe over 50% of the known X-ray sources.

Becker, R. H.↗
NASA NTRS1975

Spectral variability of Cygnus X-3

Spectra of Cyg X-3 from 1.7 to 40 keV, obtained about a year apart using the same rocket payload, show large spectral differences. The two observations suggest that while the luminosity of this source remains roughly the same, its spectrum can vary from a featureless blackbody distribution to a flat spectrum which includes strong iron line emission at approximately 6.7 keV. The flux in the line is 0.018 (plus or minus 0.004) photons per sq cm/sec, corresponding to an equivalent continuum width of 1.2 keV.

Serlemitsos, P. J.↗
NASA NTRS1975

The Her X-1 spectrum: A measure of the field near the magnetic poles of a neutron star

The steep high energy cutoff observed in the spectrum for Her X-1 was analyzed in terms of the severely modified Thomson scattering that dominates the radiative transfer in a highly magnetized plasma near the surface of a neutron star. The data indicate a field of about 1013 G near the magnetic poles and the stopping of accreting matter by nuclear collisions in the neighboring plasma.

Boldt, E. A.↗
NASA NTRS1975

Spectral variability of Cyg X-3

The 1.7-40 keV spectra of Cyg X-3 obtained about a year apart, using the same rocket payload, show large spectral differences. The two observations suggest that while the luminosity of this source remains roughly the same, its spectrum can vary from a featureless blackbody distribution to a flat spectrum which includes strong iron line emission at approximately 6.7 keV. The flux in the line corresponds to an equivalent continuum width of 1.2 keV.

Serlemitsos, P. J.↗
NASA NTRS1975

Performance of and planned improvements to a mountain altitude cosmic ray mass spectrometer

A cosmic ray mass spectrometer with superconducting magnet, wire spark chambers, and time-of-flight scintillation counters has been operated at an altitude of 2750 meters. Various specifications of the spectrometer are presented and the method of event analysis described. Corrections to the data, resolutions and efficiencies of the spark chambers, and momentum resolution are discussed. Recent and planned improvements of the apparatus are indicated.

Jones, J. J.↗
NASA NTRS1974

What is special about Cygnus X-1?

The X-ray evidence from several experiments is reviewed, with special emphasis on those characteristics which appear to distinguish Cygnus X-1 from other compact X-ray emitting objects. Data are examined within the context of a model in which millisecond bursts are superposed upon shot-noise fluctuations arising from events of durations on the order of a second. Possible spectral-temporal correlations are investigated which provide additional evidence that Cygnus X-1 is very likely a black hole.

Boldt, E. A.↗
NASA NTRS1974

A new measurement of the Hercules X-1 X-ray pulse profile

Report on measurements of a triple-peaked 1.24-sec pulse profile in a 1-minute rocket-borne exposure to Her X-1, in contrast to the double-peaked profiles expected from models which maximize the X-ray emission at the magnetic equator of an accreting neutron star. The profile exhibits statistically significant energy dependence, with the emission greater than about 12 keV having narrower peaks which appear to lag (by approximately 5% of the pulse period) the corresponding peaks at lower energies. Approximately one-third of the total emission from the source is nonpulsed.

Holt, S. S.↗
NASA NTRS1974

A new measurement of the Her X-1 X-ray pulse profile

A triple peaked 1.24 sec. pulse profile in a 1-minute rocket borne exposure to Her X-1 was measured, in contrast to the doublepeaked profiles expected from models which maximize the X ray emission at the magnetic equator of an accreting neutron star. The profile exhibits statistically significant energy dependence, with the emission approximately greater than 12 keV having narrower peaks which lag (by approximately 5% of the pulse period) the corresponding peaks at lower energies. Approximately one third of the total emission from the source is nonpulsed.

Holt, S. S.↗