Low-energy Detector Research Articles

X-Ray Observations of Stellar Coronae and Winds

Since the discovery in 1974 by Heise et al. (1975) with the ANS satellite of X-ray flares from YZ CMi and UV Cet, only a few attempts to observe X-rays from flare stars have succeeded. On the other hand, the discovery of X-ray emission from Capella by Catura, Acton and Johnson (1975) in a rocket flight has been followed by so many detections of RS CVn binaries by the low energy detectors (0.15 - 3 keV) of the HEAO A2 experiment that, while Catura et al. estimated that many variable soft X-ray sources probably exist, Walter, Charles and Bowyer (1978) could identify the RS CVn systems as a class of quiescent sources. They have higher temperatures than at first predicted, so they are ideal for detection in the energy range ¼ keV to a few keV, and the high space density provides many close candidates. Further information on these sources is now available from the GSFC Solid State Spectrometer Experiment on the Einstein Observatory, which with energy resolution of 140 eV can resolve the major complexes of line emission from Si, S, Fe and less abundant elements that are an important part of the emission of 10 million degree plasmas. The imaging experiments on the Einstein Observatory have detected X-ray emission from subsets of all types of stars, and results on the luminosities, variability and temperatures are just beginning to come out.

A search for X-ray bursts from extragalactic supernovae using the HEAO 1 satellite

The soft X-ray data from the low energy detectors of the HEAO 1 A-2 experiment are surveyed in the 0.15-3.0 keV range to search for X-ray bursts (less than 1 hour) from extragalactic supernovae predicted by Klein and Chevalier. To within the operating sensitivity of 0.08 photons per sq cm/s no events were discovered from the first 8 months of operation. This is consistent with the theoretical prediction that the probability of finding one such event is small. The HEAO 2 satellite should be capable of detecting supernovae out to 2000 Mpc; these events are of cosmological interest.

Soft X-ray emission from 2A 0311-227, an AM Herculis-type system

view Abstract Citations (18) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Soft X-ray emission from 2A 0311-227, an AM Herculis-type system. Charles, P. A. ; Mason, K. O. Abstract The low-energy detectors on board the HEAO 1 satellite have observed a variable soft X-ray source consistent with the location of 2A 0311-227. The maximum observed intensity is about 2 x 10 to the -11th erg/sq cm-sec. (0.18-0.43 keV) and the temperature must be less than 10 million K. The source is interpreted as a member of the AM Herculis class on the basis of the optical identification with a magnetic binary system. Publication: The Astrophysical Journal Pub Date: August 1979 DOI: 10.1086/183029 Bibcode: 1979ApJ...232L..25C Keywords: Magnetic Stars; Spaceborne Astronomy; Variable Stars; X Ray Sources; X Ray Stars; Binary Stars; Heao 2; Stellar Temperature; X Ray Spectra; Astrophysics; AM Herculis Stars:X Rays full text sources ADS |

An intense soft high-latitude X-ray source H2156-304 - A new BL Lacertae object

The discovery of an intense high-latitude soft X-ray source (designated H2156-304) detected with the low-energy detectors of the HEAO A-2 experiment is reported. The error box of the source includes a 14th mag starlike object that may be coincident with the radio source PKS 2155-304 and has been suggested as a BL Lac candidate. Intensity variations of H2156-304 on time scales of about 1 sec to 1 day are discussed, along with a probable flare from the source. The derived energy spectrum of the source is shown to be well fitted by either a two-temperature thermal model with temperatures of 16 million and 1.6 million K or a single power-law model with a spectral index of 2.4 + or - 0.3. Hydrogen column densities of approximately 2.5 x 10 to the 20th and 2.0 x 10 to the 20th H atoms/sq cm are obtained for the two-temperature and power-law models, respectively. The emission mechanism of H2156-304 is considered, and the characteristics of this source are compared with those of three known soft X-ray-emitting BL Lac objects.

Soft X-ray spectrum and structure of the supernova remnant G65.2+5.7

The HEAO 1 low energy detectors have observed the supernova remnant G65.2+5.7 in the energy range 0.2-2.5 keV. A strong, extended source of X-ray emission is observed coincident with the eastern side of the optical filamentary structure. The characteristic temperature of the emission is in the range 2-3.8 x 10 to the 6th K, and evidence is found for line emission at about 0.8 keV in the X-ray spectrum. These observations imply a shock velocity (425 km/s) and age (about 20,000 yr) that markedly disagree with the estimates from optical and radio observations.

The interstellar oxygen edge in the X-ray spectrum of the Crab Nebula

Measurement of the X-ray spectrum of the Crab Nebula by the HEAO 1 A-2 low-energy (0.15-3 keV) detectors is reported. The spectral restoration techniques described by Blissett and Cruise (1979) and Kahn and Blissett (1979) are used to demonstrate explicitly the existence of a 'negative' feature near 0.5 keV that is consistent with the edge expected due to absorption by interstellar oxygen. For a simple power-law model with photon index -2.08, the data require a column density of 3.0 + or - 0.1 x 10 to the 21st per sq cm and an oxygen abundance of 1.0 + or - 0.1 times the Brown and Gould (1970) value. Satisfactory fits can also be achieved with the more sophisticated Fireman (1974) models, but no model can be adjusted to fit the data without the inclusion of interstellar oxygen.

Soft X-ray emission from the vicinity of the dwarf nova AY Lyrae

THE discovery of a low-intensity soft X-ray source in a region of the sky containing the dwarf nova AY Lyrae is reported here. Figure 1 shows how the source, designated H1839 + 37, appeared in the superposition of HEAO A2 scanning data that were taken on 9 October 1977 with the low-energy detector LED1. (A complete description of the A2 experiment on HEAO 1 is given by Rothschild et al.1.) The source was detected only in the energy interval 0.18–0.43 keV. The peak in Fig. 1 represents an intensity of 0.014 ±0.0027 counts cm−2 s−1 (5σ). An upper limit to the temperature of H1839 + 37 was derived by comparing the ratio of the source counts in different energy bands. If a thermal bremsstrahlung spectrum is assumed, TBR ≤ 5 × 106 K, whereas a black-body fit implies TBL ≤ 1.4 × 106 K. A lower limit TBL ≥ 1×105K is set by the LED1 lower-level discriminator.

Evidence for X-ray emission from Kepler's supernova remnant

THE remnant of Kepler's supernova of 1604 AD has long eluded detection at X-ray wavelengths, principally because of its proximity to a source confused region in the direction of the galactic centre. We present here the first evidence for weak soft X-ray emission from Kepler's remnant, which was beyond the capability of earlier X-ray surveys1 but is now possible because of the increased sensitivity provided by the low energy detectors (LEDs) of the A 2 experiment on the HEAO 1 spacecraft. (The A 2 experiment on HEAO 1 is a collaborative effort led by E. Boldt of GSFC and G. Garmire of CIT, with collaborators at GSFC, CIT, JPL, and UCB). The LEDs are described in detail by Rothschild et al.2 Briefly, the data reported here were acquired using the LED1 narrow field of view (1.5° FWHM in the scan direction) which has an effective area of 175 cm2 and is sensitive to X-rays between 0.2 and 3 keV.

X-ray emission from RS CVn systems - A progress report

view Abstract Citations (51) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X-ray emission from RS CVn systems: a progress report. Walter, F. ; Charles, P. ; Bowyer, S. Abstract A report is given on progress made in a search for soft X-ray emission from RS CVn systems, using the low-energy detectors aboard HEAO 1. To date, nine systems have been seen. The properties of these systems are discussed. The failure to detect certain systems is considered. The possibility is discussed of discovering hitherto unknown RS CVn systems with soft X-ray observations. Publication: The Astronomical Journal Pub Date: December 1978 DOI: 10.1086/112361 Bibcode: 1978AJ.....83.1539W Keywords: Binary Stars; Heao 1; Spaceborne Astronomy; X Ray Sources; Radiant Flux Density; Stellar Radiation; Astrophysics; RS CVn Binaries:X Rays full text sources ADS | data products SIMBAD (13)

The X-ray drift chamber (XDC): Use of conventional MWPCs as drift chambers for detection with high energy resolution of soft X-rays with energy down to 500 eV

A new way of using conventional MWPCs for detection with good energy resolution of low-energy X-rays is suggested. The method is based on the measurement of the drift-time of the primary electrons and on the strong energy dependence of the absorption cross-section of low-energy X-rays. While the low-energy detection threshold is, as usual, determined by the thickness of the chamber entrance window and can be set below 500 eV with thin windows, the energy resolution is no longer dictated by the number of primary electrons, but instead by the accuracy of the drift-time measurement. The method is illustrated in the 3–6 keV energy region, using p He data collected with the high-pressure cylindrical MWPC used by the “Protonium” Collaboration in Exp. S142 at CERN. The use of this detection technique in a 4 π X-ray counter may allow substantial progress in the spectroscopy of low- Z exotic atoms.

X-ray emission from UX ARIETIS - RS Canum Venaticorum systems as a class of coronal X-ray sources

We report the discovery of a new source of soft X-rays, H0324+28, observed with the HEAO 1 low-energy detectors, which we identify with the RS Canum Venaticorum system UX Ari. The source luminosity is 2.1 x 10/sup 31/ ergs s/sup -1/ (0.15--2.8 keV) and it has a temperature of 10/sup 7/ K. We briefly review the nature of RS Canum Venaticorum systems, discuss a possible model involving maintenance of a corona by extensive flaring, and suggest possible observational tests. We conclude that RS Canum Venaticorum systems form a new class of low-luminosity X-ray sources.

The interplanetary acceleration of energetic nucleons

Co-rotating proton and electron streams are the dominant type of low-energy (0.1-10 MeV/nucleon) particle event observed at 1 A.U. The radial dependence of these events was studied between 1 and 4.6 A.U. using essentially identical low-energy detector systems on IMP 7, Pioneer 10 and Pioneer 11. It was expected that at a given energy, the intensity of these streams would decrease rapidly with heliocentric distance due to the effects of interplanetary adiabatic deceleration. Instead it was found that from event to event the intensity either remains roughly constant or increases significantly (more than an order of magnitude) between 1 and 3 A.U. It appears that interplanetary acceleration processes are the most plausible explanation. Several possible acceleration models are explored.

Repeated sharp flux dropouts observed at 6.6REduring a geomagnetic storm

A number of repeated rapid flux dropouts have been observed at 6.6 R/ subE/ by the NOAA low-energy proton detectors on board the ATS 6 satellite during the July 4--6, 1974, geomagnetic storm period. These rapid flux changes are caused by the fact that the outer boundary of the trapped radiation region moves back and forth past the satellite. Although a tilting field line configuration can cause the boundary to pass the satellite, as has frequently been reported in the literature, the boundary is shown to be distorted by a large surface wave traveling eastward around the earth. The maximum velocity of the wave was observed to be approx. =40 km/s. (AIP)

A superconducting thin-film low-energy particle detector

Techniques for constructing a superconducting thin-film particle detector have been developed. Detecting surfaces were fabricated by evaporating a 500 A tinindium film on a glass cover slide and scratching to obtain a 1 micron strip. At a point just below the T c and at current densities near I c , pulses due to single incident Ar, Ar+, He, and He+ particles were observed. Pulses were observed for helium and argon down to 200 eV and 150 eV respectively and up to approximately 800 eV. The response of the detector to ions and neutral particles was identical with near 100% efficiency. Calculated values for the size of normal regions of the film due to incident particles were of the same order of magnitude as those measured. Pulse height analysis indicated no dependence on incident particle energy. It was concluded that this lack of pulse height dependence on incident energy was due to an intrinsic fluctuation phenomenon of the superconducting film.

The decay of 33 70 Se37

The decay of70Se was studied using a 75 cm3 Ge(Li) detector, placed in an anti-compton shield, and a low-energy detector. Of the 36γ-rays observed 31 are placed in a levelscheme of70As, based on coincidence- and sumrelations. Conversion electrons of two low energy transitions were observed in order to determine their multipolarity. The halflife is measured (41.1 min). Spins and parities of the excited levels were deduced and compared with shell model predictions and logft values of theEC/β + branches were calculated.

Practical aspects of neutron activation determination of the platinum metals

Triple gamma coincidence counting of192Ir allowed the determination of Ir by instrumental neutron activation analysis down to 1 ppb in ultrabasic rocks and down to ca. 20 ppb in some high-furnace slags; the limiting factor for the latter matrix was the presence of124Sb. Radiochemical neutron activation analysis of the USGS standard rocks revealed that the Ir contents are up to three orders of magnitude lower than previously reported, except for the ultrabasic rocks. The factor of merit of several scintillation and semiconductor, gamma-ray detectors was determined for the neutron activation determination of Pd, Pt and Os. In the case of radiochemically pure sources, a NaI(Tl) wafer was preferred; in the presence of high-energy gamma-emitters, a Ge(Li) low-energy photon detector was superior.

Determination of the Position of GX2 + 5 with Copernicus

GX2 + 5 (2U1728–24) has been observed on two occasions, using the University College X-ray experiment on board Copernicus. Three of the X-ray detectors were used for the observations, the collimated proportional counter, sensitive in the range 1–3 A and the two grazing incidence telescopes which are sensitive in the ranges 3–9 A and 6-18 A respectively. The field of view of the 1–3 A detector is about 3 arc deg (FWHM); the two low energy detectors have three possible fields of view, 10, 2 and 1 arc min (FWHM) for the 3–9 A 10, 6 and 2 arc min (FWHM) for the 6–18 A detector. By scanning the approximate location of a source, its position can be determined from the count rates of the 3–9 A and 6–18 A detectors, while any variation in source intensity is monitored on the wide angle 1–3 A counter. A complete description the experiment, the measurement of the alignment of the X-ray reflecting mirror axes with respect to the Princeton Ultraviolet Experiment Fine Error Sensor (FES) and the instrument calibration will be given elsewhere.

Improved Isotope Tagging Detection Procedures for Synthetic Fibers Using the LEPD Detector

A new type of nuclear detector known as a low-energy photon detector (LEPD) has been developed by the nuclear industry which will enable textile firms to optimize the technique of neutron activatior analysis as applied to the tagging of synthetic textile monofilaments with rare earths and other elements. The sensitivity and resolution of the LEPD shows that, under various parameters, europium, samarium, gadolinium, terbium, dyprosium, holmium, erbium, ytterbium, lutetium, and palladium all are excellent textile tagging possibilities.

Rocket-borne celestial X-ray proportional counter system

Characteristics of a new sensitive broad-range thin-window gas-flow proportional counter system, designed primarily for the detection of low energy X rays in rocket-borne experiments, are presented. A space conserving, two-gas, stacked concept is utilized. The system consists of a methane-filled front counter on top of an argon-filled back counter. A single eggcrate, charged vane, collimator with a voltage on alternate vanes to eliminate background from cosmic electrons defines entry into both counters. To facilitate instrument calibration, a portable characteristic X-ray emitter for energies between 0.2 and 10 keV was developed. Some comments on its operation and performance are included.

Method for quality control of low-energy x-ray and gamma detectors

Method for quality control of low-energy x-ray and gamma detectors