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Serlemitsos, P.

Publications and source records attributed to Serlemitsos, P..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Status of the Micro-X Sounding Rocket X-Ray Spectrometer

Micro-X is a sounding rocket borne X-ray telescope that utilizes transition edge sensors to perform imaging spectroscopy with a high level of energy resolution. Its 2.1m focal length X-ray optic has an effective area of 300 sq cm, a field of view of 11.8 arcmin, and a bandpass of 0.12.5 keV. The detector array has 128 pixels and an intrinsic energy resolution of 4.5 eV FWHM. The integration of the system has progressed with functional tests of the detectors and electronics complete, and performance characterization of the detectors is underway. We present an update of ongoing progress in preparation for the upcoming launch of the instrument.

X-ray astronomy↗
NASA NTRS1993

BBXRT observations of supernova remnants

The Broad Band X-ray Telescope (BBXRT) was designed to perform sensitive, moderate resolution spectroscopy of cosmic X-ray sources in the 0.3-10 keV band from the Space Shuttle. During its nine-day flight in December, 1990, the BBXRT observed a variety of supernova remnants and related objects. We present results from some of these observations, emphasizing the ability of the BBXRT to perform spatially-resolved spectroscopy. The improved specral resolution and efficiency over previous instruments makes possible measurements of previously undetectable lines, and the broad bandpass allows simultaneous measurements of lines from oxygen through iron.

Petre, R.↗
NASA NTRS1992

BBXRT and Ginga observations of the Seyfert 1 galaxy MRK 335

We present new X-ray observations of Mrk 335 in the 0.4-10 keV band using the broadband X-ray telescope (BBXRT) and in the 2-18 keV band with Ginga. The BBXRT data show a gradual steepening of the spectrum to softer energies. We suggest that the nuclear emission can be explained by a self-consistent pair cascade model. The Ginga data show evidence for variability in absorption, uncorrected with flux changes of the continuum source. The inconsistency between the opacity observed at the iron K edge and at softer X-ray energies implies that the absorber has an ionization state BeXV.

Turner, T. J.↗
NASA NTRS1979

Extended-bandwidth X-ray observations of Cygnus X-1

An energy- and time-resolved observation of Cyg X-1, sensitive from 0.15 to 20 keV, is reported which was performed to investigate the spectrum and time variability of the flux at low X-ray energies. Data in the band from 1.5 to 42 keV, obtained in two previous rocket flights, are reanalyzed to search for any energy dependence of the time signature. No such energy dependence is found, so the explanation of the observed low-energy excess of Cyg X-1 as emission from an extended region separate from the high-energy source is rendered untenable. The evident stability of the power-law spectrum of Cyg X-1 through the observed shot-noise variation is shown to suggest that the spectrum has a Comptonization origin. It is concluded that there is no obvious analogy to be made between Cyg X-1 and X-ray bursters.

Priedhorsky, W.↗
NASA NTRS1979

Elemental abundances in a type I SNR

The solid state spectrometer on the HEAO-2 X-ray observatory observed the X-ray spectrum of Tycho's SNR. The observations show a relative excess of line emission from Si, S, and Ar by or = 6 compared to that expected from a plasma of solar composition in collisional equilibrium and by a factor of or = 3 compared to Cas A. Similar excesses are not found for line emission from Mg and Fe. The data suggest that the SN observed by Tycho in 1572 produced significant amounts of Si group elements but did not eject large amounts of Fe as predicted by some models of Type I SN events.

Becker, R. H.↗
NASA NTRS1979

The cosmic X-ray experiment aboard HEAO-1

The cosmic X-ray experiment aboard the HEAO-1 observatory is described, The instrument consists of six gas proportional counters of three types nominally covering the energy ranges of 0.15 keV, 1.2-20 keV, and 2.5-60 keV. The two low energy detectors have about 400 sq cm open area each while the four others have about 800 sq cm each. A novel feature of this experiment is the dual field of view collimators that allow the unambiguous determination of instrument internal background and diffuse X-ray brightness. Instrument characteristics and early performance are discussed.

Rothschild, R.↗
NASA NTRS1978

The fluctuating and isotropic components of the cosmic X-ray background

Spatial fluctuations in the surface brightness of the extragalactic hard X-ray sky that are characteristic of distant unresolved discrete sources as well as the possible clumpiness of a hot universal plasma are being studied with the HEAO-1 A-2 experiment. The energy spectrum for this fluctuating component is directly compared to that of the isotropic background. The spectra of identified extragalactic objects recently obtained with experiments aboard both OSO-8 and HEAO-1 are used for examining the contribution of such sources to this fluctuating component of the background.

Boldt, E.↗
NASA NTRS1977

OSO-8 X-ray observations of AM Herculis

Results are reported for hard X-ray observations of the binary system AM Her, which were coincident with soft X-ray and ground-based optical measurements. In the 2-60-keV band, variability was detected with an eclipse during phases 0.5 to 0.7 with respect to the 0.12892-day optical minima, synchronous with the known soft X-ray eclipse. The 2-60-keV uneclipsed flux was 9.5 by 10 to the -10th power erg/sq cm per sec, of which 86% lies above 10 keV. Thus, AM Her contains a hard source located near the similarly eclipsed soft X-ray source. The X-ray data are interpreted in terms of thermal bremsstrahlung from accretion onto a white dwarf.

Swank, J.↗
NASA NTRS1975

What is special about Cygnus X-1 - Black holes in theory and observation: X-ray observations

Of the eight X-ray sources now known which may be associated with binary stellar systems, Cygnus X-1 is the most likely candidate for being a black hole. 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 (Rothschild et al., 1974) are superposed on shot-noise fluctuations (Terrell, 1972) arising from 'events' of durations on the order of a second. Possible spectral-temporal correlations are investigated which indicate new measurements that need to be made in future experiments.

Boldt, E.↗
NASA NTRS1972

Spectral classification of X-ray sources

The use of special detectors to measure and classify spectral X-ray sources in the region of a few keV and above, is discussed. Two sources, Cygnus X-2 and Cygnus X-3 were measured.

Serlemitsos, P.↗
NASA NTRS1970

Hard X-rays from Sco X-1

Hard X rays from Sco X-1, discussing high energy excess with large temporal variations

Boldt, E.↗