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Charles, P.

Publications and source records attributed to Charles, P..

15 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Validation of predictive performance models for supersonic gas-jet nozzles at the Laboratory for Laser Energetics

We present results characterizing the neutral-density distributions produced by the supersonic nozzles used in experiments on the OMEGA-60 and OMEGA-EP laser systems at the University of Rochester’s Laboratory for Laser Energetics (LLE). Axisymmetric Fluent® simulations using LLE nozzle specifications capture the viscous effects, gas expansion, and shock waves that complicate flow predictions for offsets above the nozzle exit. Here, these simulations show good agreement with neutral-density measurements obtained using a four-wave shearing interferometer. An analytical form is given for the plateau length. Fits to simulation data for boundary layer thickness, mean plateau density, and density ramps are given as functions of nozzle offset and nozzle backing pressure for a number of nozzles and gases.

47 OTHER INSTRUMENTATION↗
NASA NTRS1980

The coronae of 40 Eridani

High-resolution X-ray and radio images of the 40 Eridani triple star system have been obtained. The X-ray image, obtained with the Einstein Observatory, shows a corona of approximately solar intensity at the position of the K1 V star; the dM4e flare star is a strong X-ray source estimated at 2 x 10 to the 28th ergs/s. The hot white dwarf 40 Eridani B shows no X-ray signal down to a level of 8 x 10 to the 26th ergs/s. A VLA 4885 MHz radio image shows no evidence of signal from any of the three stars, down to the 0.95 mJy level.

Cash, W.↗
NASA NTRS1980

The X-ray superbubble in Cygnus

It is shown that Cyg X-6 and Cyg X-7 are part of a large X-ray ring, 13 degrees in diameter. At a distance of 2 kpc, this X-ray source lies behind the Great Rift of Cygnus, and as such has radiation from its central region absorbed. The diameter of the emitting region is 450 pc. The X-ray source is associated with a ring of elongated H-alpha filaments which enclose the Cygnus X radio source. At the center of this region lies the highly luminous Cygnus OB2 association.

Cash, W.↗
NASA NTRS1979

X-ray and optical variability in 2A1052+606 - A new RS CVn-type system

The paper discusses a star with RS CVn-type characteristics discovered as a result of an accurate X-ray location. The RS CVn binaries have been found to be a new class of soft X-ray sources from the HEAO 1 low energy sky survey. The source was detected at energies below 1 keV and evidence is presented for variability on time scales of approximately 1 day. The strong soft X-ray source was observed at a position consistent with 2A1052+606 and the X-ray light curve shows that the source underwent a strong soft X-ray flare. Subsequent spectrophotometry revealed variable H(alpha) and possibly CaII H,K emission which strongly supports its classification as an RS CVn system.

Charles, P.↗
NASA NTRS1979

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.

Klein, R. I.↗
NASA NTRS1979

A precise position and optical identification for 4U 2129+47 - X-ray heating and a 5.2 hour binary period

A precise (20 arcsec) position and an optical counterpart are presented for the weak X-ray source 4U 2129+47. The optical counterpart shows weak but distinct He II 4686-A and C III-N III 4640-4650-A emission. Both H-beta and Ca II H and K are sometimes visible in absorption. Numerous plates and spectrophotometric observations from the 1978 observing season show that the blue magnitude varies from 16.7 to 18.0 in a period of 5.2382 hours. The light curve is sinusoidal in appearance, but with sharply defined V-shaped minima. It is proposed that most of the optical emission from this system originates at the X-ray heated face of the normal star and hence that this system is analogous to HZ Her/Her X-1. This is one of the few intrinsically faint optical counterparts of X-ray sources that show clear evidence of binary nature. The observations suggest a distance of 1.2-1.6 kpc for the source, and a consequent X-ray luminosity of approximately 10 to the 34.8 ergs/s.

Thorstensen, J.↗
NASA NTRS1979

X-ray emission from an Ap star /Phi Herculis/ and a late B star /Pi Ceti/

Using the HEAO 1 soft X-ray sky survey, a search was conducted for X-ray emission from 18 stars in the spectral range B5-A7. The detection of 0.25 keV X-ray sources consistent with the positions of Pi Ceti, a normal B7 V star, and Phi Herculis, a classic Ap star was reported. The detection of these stars argues for large mass motions in the upper layers of stars in this spectral range, and argues against radiative diffusion as the source of abundance anomalies in Ap stars.

Cash, W.↗
NASA NTRS1979

2A 0526-328 - An X-ray-emitting cataclysmic variable

The weak hard X-ray source 2A 0526-328 is identified with a previously unknown cataclysmic variable on the basis of its optical emission-line spectrum and a precise X-ray location. This star has a V magnitude of about 11 and spectral properties similar to dwarf novae at minimum light and AM Her, but shows no polarization. It is likely to be a Z Camelopardalis-type system in a very extended standstill (i.e., 'novalike' or UX Ursae Majoris-type) or a recurrent nova that has not erupted in recent times.

Charles, P.↗
NASA NTRS1979

Discovery of X-rays from the 40 Eridani system

The detection of a point source of soft X-rays (H0405-08) consistent with the position of the nearby triple star system 40 Eridani is reported. The source, which has a temperature near 10 million K, has a flux of 3 x 10 to the -11th erg/sqcm-sec at earth, implying a luminosity of 9(+ or -3) x 10 to the 28th erg/s at the distance of 40 Eridani. The likely source of the bulk of the X-rays is considered, including the K1 dwarf, the DA white dwarf, the dwarf M4 flare star, or accretion onto the white dwarf.

Cash, W.↗
NASA NTRS1979

Evidence for a massive X-ray halo around Markarian 541

Mkn 541, a Type I Seyfert galaxy, has been detected as an X-ray source with the rotating modulation collimator on SAS 3. The galaxy, which is identified as the optical counterpart of 4U 2351+06, has an X-ray flux of 3 x 10 to the -11th erg/sq cm per sec, which corresponds to a luminosity of 2 x 10 to the 44th erg/s at 240 Mpc. Evidence is presented that the X-rays are emitted in a volume of diameter 150 kpc. A variety of possible emission mechanisms are investigated, and it is suggested that the X-rays are caused by thermal bremsstrahlung from 500 billion solar masses of hot gas trapped in the gravitational well of Mkn 541, which implies that the mass of the galaxy exceeds 5 trillion solar masses. The hot gas can be explained as the accumulated ejecta of the Seyfert nucleus.

Cash, W.↗
NASA NTRS1979

HEAO-1 soft X-ray observations of Sirius

The soft X-ray intensity, spectrum, and variability of Sirius as determined with the HEAO A-2 experiment are reported. The X-ray spectrum of Sirius is shown to be extremely soft, and an upper limit of 200,000 K is established for the temperature of the emitting plasma. Observational constraints on models of coronal emission from a hot envelope surrounding either Sirius A or Sirius B are briefly considered

Lampton, M.↗
NASA NTRS1978

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

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.

Walter, F.↗
NASA NTRS1978

X-ray and radio emission from the compact galaxy III Zw 2

X-rays from the compact galaxy III Zw 2 have been detected with the rotating modulation collimator on board SAS 3. The (2-10-keV) flux is (4.3 + or - 0.5) by 10 to the -11th power erg/sq cm per sec, which corresponds to a luminosity of 1.4 by 10 to the 45th power erg/s at 530 Mpc. Subsequent radio observations between 1.46 and 90 GHz were made at the NRAO Very Large Array and 36-foot (11-m) installations. The radio spectrum rises sharply toward higher frequencies and, below about 100 GHz, is indicative of a self-absorbed synchrotron spectrum from an extremely compact, rapidly evolving object.

Schnopper, H. W.↗
NASA NTRS1978

The optical counterpart of Aquila X-1 /3U 1908+00/

We have discovered a highly variable star very close to the center of the SAS 3 error circle for the flaring X-ray source Aquila X-1 (3U 1908+00). Photographic photometry over the last 4 years shows covariability; the optical counterpart brightens from B greater than 20 to B approximately 17 mag during times of X-ray outburst, thus establishing the identification. Spectrophotometry of this star during its quiescent state shows spectral features of a K0 star with no obvious peculiarities; its distance must be at least 1.7 kpc.

Thorstensen, J.↗