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Serlemitsos, P. J.

Publications and source records attributed to Serlemitsos, P. J..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

A complete X-ray sample of the high-latitude /absolute value of b greater than 20 deg/ sky from HEAO 1 A-2 - Log N-log S and luminosity functions

An all-sky survey of X-ray sources was performed, complete to a limiting sensitivity of 3.1 x 10 to the -11 ergs/sq cm/s in the 2-10 keV band. The complete sample has allowed construction of luminosity functions based on a flux-limited sample for clusters of galaxies and active galactic nuclei. Integration of the best-fit luminosity functions indicates that clusters of galaxies contribute about 4% of the 2-10 keV DXRB, and active galactic nuclei about 20%. It is predicted that many of the objects seen in the deep survey should be local, relatively low luminosity active galactic nuclei and clusters of galaxies.

Piccinotti, G.↗
NASA NTRS1981

The X-ray spectrum of AM Herculis from 0.1 to 150 keV

No significant flux at 100 keV was detected in the observations by the HEAO 1 satellite (March and April of 1978) and in several OSO 7 observations. The spectrum above 2 keV can be fitted by a composite thermal bremsstrahlung model that includes an approximation to the albedo expected from the white dwarf. The bremsstrahlung kT sub e from this model (30.9 + or - 4.5 keV) implies a white dwarf mass in excess of 0.6 solar mass. An emission feature at 6.5 + or - 0.15 keV and equivalent width of 0.8 + or - 0.1 keV is confirmed; it is thought that this might be due to fluorescence from the white dwarf by the bremsstrahlung from a small thin shocked region. It is noted that the continuum could also have been steepened at high energy in scattering in the accretion column, but the line photons cannot have gone through the same optical depths.

Rothschild, R. E.↗
NASA NTRS1981

Broad band X-ray telescope (BBXRT)

An approach along with corroborating measurements for significantly enhancing the potential of Si(Li) spectrophotometry in X-ray astronomy is presented. The key new element is an unconventional X-ray mirror that meets qualifications of low cost, light weight, and large throughput over a broad energy band at moderate angular resolution. The potential for other applications is also discussed.

Serlemitsos, P. J.↗
NASA NTRS1981

A 5.57 hour modulation of the X-ray flux from 4U 1822-37

The X-ray flux of 4U 1822-37 is shown to be modulated with the 5.57 hr period of its optical counterpart. The X-ray light curve is two component, with a smooth sinusoidal-like 25% semiamplitude modulation and a 30 minute dip of approximately 0.2 in phase following the other minimum; the dip center occurs 0.04 in phase after the optical minimum. The X-ray spectrum is a relatively flat power law up to 17 keV, above which it steepens; iron emission is detected at 6.7 keV with a 4 keV FWHM and an equivalent width of 1100 eV. An excess below 2 keV is consistent with either a 0.25 keV thermal component of 350 eV equivalent width iron L emission. Modeling the eclipse for a 0.5-0.7 solar radius companion gives a system inclination of 70-79 deg and a spherical cloud radius of 0.2-0.3 solar radius. Models for the long-term modulation are considered, and a comparison of the properties of 4U 1822-37 with those of Cyg X-3 shows that they are similar systems.

White, N. E.↗
NASA NTRS1981

A complete X-ray sample of the high latitude sky from HEAO-1 A-2: log N lo S and luminosity functions

An experiment was performed in which a complete X-ray survey of the 8.2 steradians of the sky at galactic latitudes where the absolute value of b is 20 deg down to a limiting sensitivity of 3.1 x ten to the minus 11th power ergs/sq cm sec in the 2-10 keV band. Of the 85 detected sources 17 were identified with galactic objects, 61 were identified with extragalactic objects, and 7 remain unidentified. The log N - log S relation for the non-galactic objects is well fit by the Euclidean relationship. The X-ray spectra of these objects were used to construct log N - log S in physical units. The complete sample of identified sources was used to construct X-ray luminosity functions, using the absolute maximum likelihood method, for clusters galaxies and active galactic nuclei.

Piccinotti, G.↗
NASA NTRS1981

X-ray spectra of the Crab pulsar and Nebula

The X-ray spectra of the Crab pulsar and Crab Nebula are analyzed. Observations were made with OSO 8 on March 17-18, 1978, with all spacecraft telemetry assigned to one detector during seven dwell mode experiments. A resolution of 1.25 ms was obtained for pulse-height-analyzed counts in 64 channels. Progressive hardening and subsequent softening of the spectrum across the pulse was found. The fraction of the pulsed flux, exhibiting a spectral variability of about 0.14 was concentrated solely in the region between the two peaks. A model is suggested in which the pulsed X-ray emission from the Crab pulsar consists of two components: one is physically related to the double-peaked gamma-ray pulse and possibly to radio and optical pulses, but has no spectral dependence on the pulse phase, while the other exhibits spectral variability with the pulse phase but is confined to the interpeak emission seen with X-ray energies.

Pravdo, S. H.↗
NASA NTRS1981

Observation of the core of the Perseus cluster with the Einstein solid state spectrometer - Cooling gas and elemental abundances

Solid State Spectrometer observations of the core of the Perseus cluster have resulted in the detection of X-ray emission lines due to Si, S, and Fe. Analysis of the spectrum indicates that the X-ray emission has at least two characteristic temperatures. This is interpreted in the framework of radiative accretion in the core of the cluster. The derived parameters are a cooling time less than or approximately equal to 2 x 10 to the ninth years for the low-temperature gas, a mass accretion rate of approximately 300 solar masses per year, and a characteristic size of 10-20 kpc for the cool gas. The Fe abundance in the core (approximately 0.4) is similar to the Fe abundance averaged over the whole cluster, indicating that Fe emission is not strongly concentrated about NGC 1275. The Si and S abundances are consistent with solar values.

Mushotzky, R. F.↗
NASA NTRS1981

A 5.57 hour modulation of the X-ray flux of 4U1822-37: A new model for CYG X-3

The X-ray flux of 4U1822-37 is shown to be modulated with the 5.57 hour period of its optical counterpart. The X-ray light curve is two component with a smooth sinusoidal like 25 percent semiamplitude modulation and a 30 minute dip approximately 0.2 in phase following the other minimum. The X-ray spectrum is a relatively flat power law up to 17 keV, above which its steepens. Iron emission is detected at 6.7 keV with a 4 keV FWHM and an equivalent width of 1100 eV. There is an excee below 2 keV that is consistent with either a 0.25 keV thermal component or 350 eV equivalent width iron L emission. A slight softening of the spectrum is seen during both X-ray minima. The dip is interpreted as the partial occultation of an extended cloud of optically thick highly ionized material surrounding the central X-ray source. Modeling the eclipse gives a system inclination of 70-79 deg and a spherical cloud radius of 0.2-0.3 solar radius. Models for the long term modulation are considered. The properties of this source are compared to those of Cyg X-3. It is concluded that they are similar systems.

White, N. E.↗
NASA NTRS1981

X-ray spectra of the Crab pulsar and nebula

The spectrum of the Crab pulsar was measued from 2 to 50 keV as a function of pulse phase and a progressive hardening and subsequent softening of the spectrum across the pulse was found. The fraction of the pulsed flux which exhibits spectral variability is 0.14 and is concentrated solely in the region between the two peaks. A model is suggested in which the pulsed X-ray emission from the Crab pulsar consists of two components: one which has no spectral dependence with pulse phase and which is physically related to the double peaked gama ray pulse and, perhaps, the radio and optical pulses; and another component which exhibits spectral variability with pulse phase is confined to and comprises the interpeak emission, and which is only seen at X-ray energies. These results and studies of the binary X-ray pulsar Hercules X-1 suggest a phenomonological similarity. If the spectrally varying component in the Crab pulsar arises from a hot, magnetized plasma near the neutron star surface then higher energy spectral observations of this phase region might reveal spectral features which can be used to determine the surface field strength.

Pravdo, S. H.↗
NASA NTRS1980

The HEAO A-2 survey of Abell clusters and the X-ray luminosity function

A statistically complete sample of 225 Abell clusters has been examined. Twelve new identifications of clusters with X-ray sources have been made. It is found that (1) Lx is roughly correlated with richness for richness classes 0, 1, and 2; (2) Lx is well correlated with Rood-Sastry type and only loosely correlated with Bautz-Morgan type; and (3) the cluster contribution to the X-ray background is less than or equal to 5% between 2 and 10 keV.

Mckee, J. D.↗
NASA NTRS1980

Observation of the core of the Perseus cluster with the Einstein solid state spectrometer: Cooling gas and elemental abundances

Solid State Spectrometer observations of the core of the Perseus cluster have resulted in the detection of X-ray emission lines due to Si, S, and Fe. Analysis of the spectrum indicates that the X-ray emission has at least two characteristic temperatures. This is interpreted in the framework of radiative accretion in the core of the cluster. The derived parameters are a cooling time tc less than 2 x 109 yrs for the low temperature gas, a mass accretion rate of approximately 300 Mo/yr and a characteristic size of 10 to 20 Kpc for the cool gas. The Fe abundance in the core, approximately 0.4, is similar to the Fe abundance averaged over the whole cluster indicating that Fe emission is not strongly concentrated about NGC 1275. The Si and S abundances are consistent with solar values.

Mushotzky, R. F.↗
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

The X-ray spectrum of QSO 0241 + 622

The X-ray spectrum of QSO 0241 + 622 in the range 2-50 keV measured with the Goddard Space Flight Center proportional counters on OSO 8 is presented. The quasar is similar to 3C 273 in the proportion of energy emitted in various bands, excluding the radio, if reported radiation above 50 keV from its direction is indeed associated with QSO 0241 + 622. Comparisons are made between the two quasars in a discussion of possible energy generation scenarios. Implications concerning quasar contributions to the diffuse background are discussed.

Worrall, D. M.↗
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

The X-ray pulsars 4U 1145-61 and 1E 1145.1-6141

Observations of the neighboring X-ray pulsars 4U 1145-61 and 1E 1145.1-6141 obtained by OSO 8, HEAO 1 and the Einstein Observatory between 1975 and 1979 are reported. A temporal analysis of Einstein Solid State Spectrometer and Monitor Proportional Counter data, OSO 8 A and C detector data and HEAO 1 A-2(3) experiment data confirms the presence of two periodicites at 291 and 297 sec in the region, with the shorter period located within 3 arcmin of 4U 1145-61. Observations indicate the spectrum of 4U 1145-61 to obey a power law with an index of 1.5 out to at least 60 keV, with little variation with pulse phase, and a 500-eV EW iron line at 6.7 keV. The spectrum of the other source is found to be more absorbed. Similarities between the pulsars are noted, and it is suggested that they may be the result of pulsar formation in a homogeneous cloud of progenitors.

White, N. E.↗
NASA NTRS1980

X-ray observations of Algol

The Solid State Spectrometer on Einstein has been used to study Algol. Two observations six months apart were made, both including a primary optical eclipse. No corresponding X-ray eclipses were seen. During the second observation the source was flaring and was on the average a factor of three brighter. The spectrum on both occasions was consistent with a two-component thermal equilibrium model with temperatures of approximately 7.5 and 40 million degrees. Attempts to insert a third component indicate the temperature distribution to be bimodal. Models for the X-ray emission are discussed and it is suggested that it most likely originates from an active corona surrounding the K star.

White, N. E.↗
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.↗