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Frost, K. J.

Publications and source records attributed to Frost, K. J..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

High energy X-ray observations of COS-B gamma-ray sources from OSO-8

During the three years between satellite launch in June 1975 and turn-off in October 1978, the high energy X-ray spectrometer on board OSO-8 observed nearly all of the COS-B gamma-ray source positions given in the 2CG catalog (Swanenburg et al., 1981). An X-ray source was detected at energies above 20 keV at the 6-sigma level of significance in the gamma-ray error box containing 2CG342 - 02 and at the 3-sigma level of significance in the error boxes containing 2CG065 + 00, 2CG195 + 04, and 2CG311 - 01. No definite association between the X-ray and gamma-ray sources can be made from these data alone. Upper limits are given for the 2CG sources from which no X-ray flux was detected above 20 keV.

Dolan, J. F.↗
NASA NTRS1985

Temporal and spectral characteristics of solar flare hard X-ray emission

Solar Maximum Mission observations of three flares that impose stringent constraints on physical models of the hard X-ray production during the impulsive phase are presented. Hard X-ray imaging observations of the flares on 1980 November 5 at 22:33 UT show two patches in the 16 to 30 keV images that are separated by 70,000 km and that brighten simultaneously to within 5 s. Observations to O V from one of the footprints show simultaneity of the brightening in this transition zone line and in the total hard X-ray flux to within a second or two. These results suggest but do not require the existence of electron beams in this flare. The rapid fluctuations of the hard X-ray flux within some flares on the time scales of 1 s also provide evidence for electron beams and limits on the time scale of the energy release mechanism. Observations of a flare on 1980 June 6 at 22:34 UT show variations in the 28 keV X-ray counting rate from one 20 ms interval to the next over a period of 10 s. The hard X-ray spectral variations measured with 128 ms time resolution for one 0.5 s spike during this flare are consistent with the predictions of thick-target non-thermal beam model.

Dennis, B. R.↗
NASA NTRS1984

Space research in the era of the space station

The historical development of U.S. space technology is examined as a basis for future programs planned in the field of astrophysics, meteorological and land sciences, and planetary exploration. The background of the NASA space station project is described, as well as other current programs: Voyager II for Uranus and Neptune exploration, Galileo mission for sending probes into the Jovian atmosphere, Venus Radar Mapper, Mars Geochemistry and Climatology Orbiter, and the International Solar Polar mission. Recent advances in in-orbit assembly, refurbishment and repairs are discussed through the example of the Solar Maximum mission spacecraft repair in 1984 and the use of the RMS tool. The U.S. space observatory project with a 20-meter reflector telescope, currently in the early definition stage, is also discussed. Finally, the Soviet Salyut and Soyuz missions, together with the Soviet Union's study of long term flight conditions are mentioned as possible comparison with the NASA work.

Frost, K. J.↗
NASA NTRS1984

Fast variations in high-energy X-rays from solar flares and their constraints on nonthermal models

The results of a quantitatve analysis of quantitative the temporal properties of over 7000 hard X-ray solar flares are presented. The data were obtained with the Hard X-ray Burst Spectrometer of the SMM satellite. The data reveal examples of hundreds of fast spikes with durations of less than 1 s. The spectra of a well-observed fast spike were compared with the predicted spectra of a detailed nonthermal electron beam model, in order to determine upper limits for electron beam parameters and path lengths. The theoretical spectra were found to be consistent with the observed spectra when the separation of between the accretion site and the thick target was greater than 10 to the 8th cm. It is shown that if the separation is much greater than 3 x 10 to the 9th cm, the electrons with high pitch angles (greater than 60 deg) are either not emitted or are mirrored before they reach the footpoints.

Kiplinger, A. L.↗
NASA NTRS1984

The high-energy X-ray spectrum of Centaurus XR-3 observed from OSO 8

Observations of the X-ray binary Cen XR-3 in the 20-120 keV energy range by means of OSO 8's high energy X-ray spectrometer, during July 16-19, 1975, and July 5-14 and 28-29, 1978, indicate that the source was in a high luminosity state during 1975 and a low luminosity one in 1978. While mean orbital light curves appear similar in shape in both years, orbit-to-orbit intensity variations are noted. Spectral, luminosity, and the 4.84 sec modulation are characterized. Cen XR-3 may be a system in which mass transfer by Roche lobe overflow, and by accretion from a stellar wind, are both effective in the production of observable X-ray radiation.

Dolan, J. F.↗
NASA NTRS1983

Recurrent pulse trains in the solar hard X-ray flare of 1980 June 7

This study presents a detailed examination of the solar hard X-ray and gamma-ray flare of 1980 June 7 as seen by the Hard X-Ray Burst Spectrometer on SMM. The hard X-ray profile is most unusual in that it is characterized by an initial pulse train of seven intense hard X-ray spikes. However, the event is unique among the 6300 events observed by HXRBS in that the temporal signature of this pulse train recurs twice during the flare. Examinations of the hard X-ray data in conjunction with radio and gamma-ray observations show that the 28-480 keV X-ray emission is simultaneous with the 17 GHz microwave fluxes within 128 ms and that the 3.5-6.5 MeV prompt gamma-ray line emission is coincident with secondary maxima of the microwave and X-ray fluxes. Although the absence of spatially resolved hard X-ray observations leaves other possibilities open, a parameterization of the event as a set of seven sequentially firing loops is presented that offers many satisfying explanations of the observations.

Kiplinger, A. L.↗
NASA NTRS1983

Space station architectural issues - The view from science

The evolution from current missions in space from Shuttle-directed to space station-directed is projected, with consideration given to space station missions that will affect the station architecture. The Shuttle science mission is basically to support astronomy and astrophysics work into the 1990s, particularly in launching and refurbishing satellites such as the SMM, the Space Telescope, and the Gamma Ray Observatory. Various new observational facilities are being planned and may be carried by the Shuttle for assembly in orbit. The assembly crews could live on a space station if sufficient capabilities and size were built into the station. The construction of large instruments in orbit, instruments that cannot be launched by any current booster, could permit enough data to be gathered to successfully characterize the evolution of the Universe.

Mcdonald, F. B.↗
NASA NTRS1983

Characteristics of gamma-ray line flares as observed in hard X-ray emissions and other phenomena

Solar Maximum Mission observations of gamma-ray lines from solar flares indicate that energetic proton and heavy ions are accelerated during the impulsive phase. Attention is given to the characteristics of flares from which gamma-ray lines have been observed, as well as intense, hard X-ray flares lacking gamma-ray line emissions. It is found that most of the gamma-ray line flares produced intense, type II and IV radio bursts, and that the time profiles of the high energy hard X-rays are delayed for several seconds relative to those of low energy hard X-rays. The hard X-ray spectral of the gamma-ray line flares are generally flatter (harder) than those of flares without gamma-ray emission.

Bai, T.↗
NASA NTRS1983

Microwave and hard X-ray observations of a solar flare with a time resolution better than 100 ms

Simultaneous microwave and X-ray observations are presented for a solar flare detected on 1980 May 8 starting at 1937 UT. The X-ray observations were made with the Hard X-ray Burst Spectrometer on the Solar Maximum Mission and covered the energy range from 28-490 keV with a time resolution of 10 ms. The microwave observations were made with the 5 and 45 foot antennas at the Itapetinga Radio Obervatory at frequencies of 7 and 22 GHz, with time resolutions of 100 ms and 1 ms respectively. Detailed correlation analysis of the different time profiles of the event show that the major impulsive in the X-ray flux preceded the corresponding microwave peaks at 22 GHz by about 240 ms. For this particular burst the 22 GHz peaks preceded the 7 GHz by about 1.5s. Observed delays of the microwave peaks are too large for a simple electron beam model but they can be reconciled with the speeds of shock waves in a thermal model. Previously announced in STAR as N82-30215

Kaufmann, P.↗
NASA NTRS1983

The hard X-ray burst spectrometer event listing 1980, 1981 and 1982

A comprehensive reference for the hard X-ray bursts detected with the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission for the time of launch on February 14, 1980 to March 1983 is provided. Over 6300 X-ray events were detected in the energy range from 30 to approx 500 keV with the vast majority being solar flares. The listing includes the start time, peak time, duration and peak rate of each event.

Dennis, B. R.↗
NASA NTRS1983

Millisecond time variations in hard X-ray solar flares

The results of a search for fast spikes in 2830 hard X-ray solar flares as observed with the hard X-ray burst spectrometer on the Solar Maximum Mission (SMM) are presented. Hundreds of fast spikes with durations of less than 1 sec have been detected at time resolutions of 128 msec and 10 msec. Fast spikes have been detected with rise and decay times as short as 20 msec and with widths as short as 45 msec. They are the fastest hard X-ray variations yet seen from the sun. The observations of such fast variations place new constraints on the physical nature of the source, and these observations and constraints are discussed in terms of nonthermal and thermal models of flares.

Kiplinger, A. L.↗
NASA NTRS1983

Gamma-ray burst high time-resolution spectral observations made with the Solar Maximum Mission

The gamma-ray bursts of April 19 and 21, 1980, and March 1, 1981, are characterized on the basis of observations obtained at 25-500 keV and time resolution 128 msec using the hard-X-ray-burst spectrometer of the SMM satellite. The data are presented graphically, and the parameters determined by fitting three theoretical models to the data for each phase (rising phase, decay phase, and valleys between pulses) are given in tables. Models used are thin thermal bremsstrahlung with or without absorption lines, thermal synchrotron with or without absorption lines, and power law with exponential cutoff.

Desai, U. D.↗
NASA NTRS1982

The impulsive and gradual phases of a solar limb flare as observed from the solar maximum mission satellite

Simultaneous observations of a solar limb flare in the X-ray and ultraviolet regions of the spectrum are presented. Temporal and spectral X-ray observations were obtained for the 25-300 keV range while temporal, spectral, and spatial X-ray observations were obtained for the 30-0.3 keV range. The ultraviolet observations were images with a 10 arcsec spatial resolution in the line of O V and Fe XXI. The hard X-ray and O V data indicate that the impulsive phase began in the photosphere or chromosphere and continued for several minutes as materials was ejected into the corona. Impulsive excitation was observed up to 30,000 km above the solar surface at specific points in the flare loop. The Fe XXI observations indicate a preheating before the impulsive phase and showed the formation of hot post-flare loops. This later formation was confirmed by soft X-ray observations. These observations provide limitations for current flare models and will provide the data needed for initial conditions in modeling the concurrent coronal transient.

Poland, A. I.↗
NASA NTRS1982

Microwave and hard X-ray observations of a solar flare with a time resolution of better than 100 MS

Simultaneous microwave and X-ray observations are presented for a solar flare detected on 1980 May 8 starting at 1937 UT. The X-ray observations were made with the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission and covered the energy range from 28-490 keV with a time resolution of 10 ms. The microwave observations were made with the 5 and 45 foot antennas at the Itapetinga Radio Observatory at frequencies of 7 and 22 GHz, with time resolutions of 100 ms and 1 ms respectively. Detailed correlation analysis of the different time profiles of the event show that the major impulsive in the X-ray flux preceded the corresponding microwave peaks at 22 GHz by about 240ms. For this particular burst the 22 GHz peaks preceded the 7 GHz by about 1.5s. Observed delays of the microwave peaks are too large for a simple electron beam model but they can be reconciled with the speeds of shock waves in a thermal model.

Kaufmann, P.↗
NASA NTRS1982

Time variations of an absorption feature in the spectrum of the gamma-ray burst on 1980 April 19

The photon number spectrum integrated over the impulsive part of the event is shown to fit a thermal bremsstrahlung function with a temperature of 330 + or - 70 keV at energies between 151 and 487 keV. At lower energies, the data points lie considerably below this function, indicating a broad absorption feature extending down to values less than or equal to 28 keV, the lowest energy measured. The upper energy of this absorption feature varies from 100 to 150 keV on a time scale less than or equal to 0.5 s. This event is interpreted as a typical gamma ray burst, even though it is still considered remotely possible that it is of solar origin. The spectral features, together with their variability, are interpreted in terms of electron interactions at the cyclotron resonance frequency in magnetic fields of 10 to the 12th - 10 to the 13th gauss close to the surface of a neutron star.

Dennis, B. R.↗
NASA NTRS1981

Properties of solar flare electrons, deduced from hard X-ray and spatially resolved microwave observations

An important question concerning an understanding of impulsive solar flares is related to the energetic electrons responsible for the microwave and the hard X-ray emission. A description is presented of an investigation in which spatially resolved microwave observations of an impulsive flare and hard X-ray data from the Solar Maximum Mission (SMM) are used to test the hypothesis that the two types of emission come from the same basic electron population. The considered observations are found to imply that the microwaves and hard X-rays were not produced by a common population of electrons with either a Maxwellian or single power-law energy distribution. It is suggested that the calculations should be repeated when observations of stronger events become available, for which a better determination of the X-ray spectrum is possible. The possibility is considered that microwaves and moderately hard X-rays come from spatially different regions.

Marsh, K. A.↗
NASA NTRS1981

High energy X-ray observations of CYG X-3 from from OSO-8: Further evidence of a 34.1 day period

The X-ray source Cyg X-3 (=4U2030+40) was observed with the high energy X-ray spectrometer on OSO-8 for two weeks in 1975 and in 1976 and for one week in 1977. No change in spectral shape and intensity above 23 keV was observed from year to year. No correlation is observed between the source's intensity and the phase of the 34.1 day period discovered by Molteni, et al. (1980). The pulsed fraction of the 4.8 hour light curve between 23 and 73 keV varies from week to week, however, and the magnitude of the pulsed fraction appears to be correlated with the 34.1 day phase. No immediate explanation of this behavior is apparent in terms of previously proposed models of the source.

Dolan, J. F.↗