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Cruddace, R.

Publications and source records attributed to Cruddace, R..

18 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Rosat detections of X-ray emission from young B-type stars

We present first results of a series of pointings of the Rosat HRI at visual binaries consisting of a B-star with a later-type companion. The binaries selected for this study are very likely physical pairs. Dating of the B-type stars with respect to the zero-age main sequence, as well as spectroscopic observations of the late-type stars, provides evidence for the extreme youth of these systems with ages typically near or below 10 exp 8 yr. Surprisingly, the late-B component was in many cases detected as an X-ray source, in contrast to previous findings that X-ray emission among late-B field stars is rather uncommon.

Schmitt, J. H. M. M.↗
NASA NTRS1985

Sounding rockets shot from the Shuttle

The Space Shuttle-launched sounding rocket Spartan-1 will map the structure of two extended X-ray sources: the hot gas pervading the Perseus cluster of galaxies, and the central core of the Milky Way. Spartan-1 contains two large X-ray proportional counter detectors sensitive to the 1-15 A wavelength range. A new generation of instruments destined for X-ray telescope focal planes will yield high resolution imaging and spectroscopy, over observation times sometimes exceeding one day/source, in the course of a long-term Spartan research program that will encompass planetary, solar, and UV astronomy missions.

Cruddace, R.↗
NASA NTRS1976

An ultrasoft X-ray source in Coma Berenices

An intense soft X-ray source with an extraordinary spectrum has been observed in Coma Berenices, 4 deg northeast of and not associated with the Coma cluster of galaxies. Two spectra, obtained at different times in a sounding-rocket flight, indicate that the source temperature in thermal models is less than 1 million K; a power-law model requires photon power-law indices steeper than n = -3. The intensity in the 44-165 A band is of the order of 5 by 10 to the -10th power erg/sq cm/sec, but no flux is present at energies 0.3-2.1 keV to a limit of 1 by 10 to the -10th power erg/sq cm/sec. The lack of bright stars or a supernova remnant in the error box implies that this may be a new class of soft X-ray sources.

Margon, B.↗
NASA NTRS1975

A sensitive search for soft X-rays from Arcturus and Procyon

Sensitive X-ray observations have been obtained of alpha Boo and alpha CMi using rocket-borne large area proportional counters. No flux was detected from either star, yielding limits on intrinsic luminosity in the 75-2000 eV band (6-165 A) as stringent as 10 to the 28-th power ergs per sec depending upon assumed coronal temperature. These are at least an order of magnitude better limits than previously reported values. Upper limits are also set on a mass loss rate of three billionths solar mass per year and on an emission measure of less than 3 times 10 to the 53-rd power per cu cm. If these stars are typical, then giants and subgiants cannot be responsible for a significant fraction of the soft component of the diffuse X-ray background.

Cruddace, R.↗
NASA NTRS1975

The soft X-ray spectrum of the Perseus cluster

The X-ray spectrum of the Perseus cluster in the range 0.1-4.0 keV has been observed. Contrary to the results of previous low-energy rocket observations, no large flux of soft X-rays was found. The X-ray spectrum from 0.1 to 56 keV is consistent with bremsstrahlung from an intracluster gas with T approximately equal to 100 million K. attenuated by the interstellar column density inferred from 21-cm observations. The low-energy X-ray spectrum is not consistent with a nonthermal power-law model with the same slope as that observed at higher energies. The mass of hot intracluster gas required to produce the observed X-ray flux is a small fraction of the gravitational binding mass. The soft X-ray flux, when combined with limits on the radio flux, implies that the cluster is not gravitationally bounded by ionized gas at any temperature.

Davidsen, A.↗
NASA NTRS1975

Large area extreme ultraviolet focusing collector

A grazing incidence one-dimensional focusing collector for use in the extreme ultraviolet is described. The collector has a field of view of 1 x 50 deg, a focal length of 3015 cm, and a total unobstructed area of 224 sq cm. The instrument employs an interchangeable detector package of either channel-electron multipliers or proportional counters which yield a limiting sensitivity of 1.0 photons/sq cm sec A at 170 A and 0.05 photons/sq cm sec A at 90 A, respectively, for one second integrations. The design and calibration of the instrument are described in detail. Data obtained by this instrument during recent rocket flights are presented.

Henry, P.↗
NASA NTRS1975

Soft X-ray spectroscopy of three extragalactic sources

Soft X-ray spectra (0.5 to 5 KeV) acquired with a rocket-borne argon-methane proportional counter are reported for M87, 3C 273, and NGC 4151. The counter sensitivity range allowed derivation of simultaneous information on the magnitude of soft X-ray absorption and the slope of the hard X-ray spectrum. Error estimation techniques for the free parameters of X-ray spectra are analyzed, and the results are applied to the spectra previously reported for these sources. It is shown that the technique used to analyze the previous spectra can drastically underestimate the magnitude of errors, and it is concluded that the proposed division of extragalactic X-ray sources into two groups according to the magnitude of absorption in their spectra is premature.

Margon, B.↗
NASA NTRS1974

A search for a cosmological component of the soft X-ray background in the direction of M31

Results of an experiment to search for absorption of the soft diffuse X-ray background by M31, the Andromeda Nebula, are presented. Both X-ray and 21-cm observations were obtained with high spatial resolution; the X-ray detector had a 2-degree field of view, and the 21-cm data were taken with 20-minute resolution. The results establish that at least 48 percent of the soft X-ray flux has a local source, but that the remainder may be of distant origin and therefore of cosmological significance.

Margon, B.↗
NASA NTRS1974

Observation of X-ray emission from M31

Observation of X-ray emission from M31 in the 0.5- to 5.0-keV band, using rocket-borne proportional counters. The integrated flux corresponds to (2.2 plus or minus 0.6) x 10 to the 39th ergs/sec at M31, and is confined chiefly to a region coinciding with the optical image of the galaxy. The spectrum has a slope similar to the bright Galactic X-ray sources. The intensity, spectral, and spatial data suggest that the bulk of X-ray emission from M31, and by inference from most normal galaxies, is due to a small group of highly luminous sources, in agreement with the Galactic X-ray luminosity function.

Bowyer, S.↗
NASA NTRS1972

The spectra of ten galactic X-ray sources in the southern sky.

Data on 10 galactic X-ray sources located between 320 and 20 deg galactic longitude were obtained during a rocket flight from Brazil in June 1969. Detailed spectra of these sources have been compared with bremsstrahlung, blackbody, and power-law models, each including interstellar absorption. Six of the sources were fitted well by one or more of these models. In only one case were the data sufficient to distinguish the best model. Three of the sources were not fitted by any of the models, which suggests that more complex emission mechanisms are applicable. A comparison of our results with those of previous investigations provides evidence that five of the sources vary in intensity by a factor of two or more, and that three have variable spectra.

Cruddace, R.↗
NASA NTRS1972

Anomalous minima in Cen X-3.

Report of an observation made with a rocket-borne argon-methane proportional counter, which was equipped with a 'Mylar' window and was sensitive to X rays in the range from 0.2 to 10 keV. During a scan of the galactic plane, the detector passed directly over the location of Cen X-3 at a roll rate of 1 deg per second. An extended minimum of X-ray flux was observed. It is concluded that the anomalous effect is intrinsic to the source.

Margon, B.↗
NASA NTRS1971

The spectra of ten galactic X-ray sources in the southern sky

Data on ten galactic X-ray sources were obtained during a rocket flight from Brazil in June 1969. Detailed spectra of these sources have been compared with bremsstrahlung, black body, and power law models, each including interstellar absorption. Six of the sources were fitted well by one or more of these models. In only one case were the data sufficient to distinguish the best model. Three of the sources were not fitted by any of the models, which suggests that more complex emission mechanisms are applicable. A comparison of our results with those of previous investigations provides evidence that five of the sources vary in intensity by a factor of 2 or more, and that three have variable spectra. New or substantially improved positions have been derived for four of the sources observed.

Cruddace, R.↗