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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
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NASA NTRS1973

Millisecond time scale atmospheric light pulses associated with solar and magnetospheric activity.

By using a wide-angle photomultiplier system a class of millisecond time scale diffuse atmospheric light emission of terrestrial origin has been discovered. These fast atmospheric pulsation events also show damped oscillations around 10-kHz frequency, which distinguishes them from ordinary lightning-type events. Evidence is presented for the enhancement in the rate of these events induced by solar flare activity.

Ogelman, H.↗
NASA NTRS1973

A portable millisecond-integration-time photoelectric photometer.

Portable equipment for recording millisecond-integration-time photoelectric photometric data is described. Digital data are reliably recorded on standard 6.35 mm audio grade magnetic tape via a quadradial audio grade tape deck. The system is designed specifically for recording lunar occulations of stars, but the data recording technique is independent of the data source. Recovery of the data is made via minicomputer.

Mcgraw, J. T.↗
NASA NTRS1983

High-resolution X-ray and radio maps of the millisecond pulsar

The 1.5 millisecond pulsar (PSR1937+214) discovered in the radio source 4C21.53 is more closely located and characterized. High-resolution radio maps of the region were obtained with the Very Large Array, and no evidence was found in the morphology of 4C21.53 to connect it with the pulsar, which was determined to be at a different distance. A high-resolution imager X-ray map of the region was made using the Einstein Observatory, and no detectable X-ray emission could be associated with either 4C21.53 or the pulsar. From the stringent upper limit on X-ray emissions, substantial differences in the magnetospheric structure of the pulsar compared to that of other radio pulsars are inferred.

Becker, R. H.↗
NASA NTRS1983

On neutron star structure and the millisecond pulsar

The millisecond pulsar is the first observed example of a neutron star spinning rapidly enough to approach the Jacobi bifurcation point and thus affords the possibility of constraining neutron star physics. The pulsar must be rotating below the critical frequency at which its equilibrium configuration would become nonaxisymmetric, since the lifetime of this configuration against decay by gravitational radiation is very short. This critical frequency may be used to set a lower limit of 2 x 10 to the 14th g/cu cm on the density of the star. If the mass is 0.5-1.5 solar mass, several of the stiffer neutron star equations of state may be ruled out, and the radius should be less than 16 km. The condition for axisymmetry also imposes an upper limit on the rotation rate to which neutron stars may be spun up by accretion disks in binary systems.

Harding, A. K.↗
NASA NTRS1984

Voyager observations of Jovian millisecond radio bursts

Voyager Planetary Radio Astronomy data collected over 30-day intervals centered on the two close encounters with Jupiter were utilized to study the characteristics of millisecond-duration radio bursts (s-bursts) at frequencies between 5 and 15 MHz. In this frequency range, s-bursts are found to occur almost independently of Central Meridian Longitude and to depend entirely on the phase of Io with respect to the observer's planetocentric line of sight. Individual bursts typically cover a total frequency range of about 1.5 to 3 MHz, and they are usually strongly circularly polarized. Most bursts in a particular s-burst storm will exhibit the same polarization sense (either right-hand or left-hand), and there is some evidence for a systematic pattern in which one polarizations sense is preferred over the other as a function of Io phase and Central Meridian Longitude. These data are all suggestive of a radio source that is located along the instantaneous Io flux tube and that extends over a linear dimension of 5000 km along the field lines in both the northern and southern Hemispheres.

Alexander, J. K.↗
NASA NTRS1983

Genesis stories for the millisecond pulsar

Theoretical models proposed to explain the origin of the millisecond pulsar (MP) PSR 1937+214 are reviewed, examining their ability to explain its low surface dipole magnetic field (B), its low birth temperature (less than 10 to the 8th K), the absence of a companion or remnant, and its low velocity perpendicular to the Galactic plane. The models discussed are a single isolated explosion forming a rapidly spinning neutron star, spin-up of a dead pulsar by accretion from a companion, collapse of an accreting spinning white dwarf, and fusion of a tight binary composed of two old neutron stars. Although all of the models have difficulties in explaining one or more of the MP characteristics, the second model is found to be most probable in the light of present knowledge. The lack of a companion is explained by its tidal disruption after it had fed the accreting pre-pulsar for 1 Gyr or more and its mass had decreased to about 0.01 solar mass. Neutron stars accreting in this way have been observed in Galactic-bulge X-ray sources.

Ruderman, M. A.↗
NASA NTRS1984

Voyager observations of Jovian millisecond radio bursts

Voyager Planetary Radio Astronomy data collected over 30-day intervals centered on the two close encounters with Jupiter were utilized to study the characteristics of millisecond-duration radio bursts (s-bursts) at frequencies between 5 and 15 MHz. In this frequency range, s-bursts are found to occur almost independently of Central Meridian Longitude and to depend entirely on the phase of Io with respect to the observer's planetocentric line of sight. Individual bursts typically cover a total frequency range of about 1.5 to 3 MHz, and they are usually strongly circularly polarized. Most bursts in a particular s-burst storm will exhibit the same polarization sense (either right-hand or left-hand), and there is some evidence for a systematic pattern in which one polarizations sense is preferred over the other as a function of Io phase and Central Meridian Longitude. These data are all suggestive of a radio source that is located along the instantaneous Io flux tube and that extends over a linear dimension of 5000 km along the field lines in both the Northern and Southern Hemispheres. Previously announced in STAR as N84-17109

Alexander, J. K.↗
NASA NTRS1984

Superfluidity in millisecond pulsars

The evidence for superfluidity in the Vela pulsar, the Crab pulsar and PSR 0525 + 21 is reviewed, and the prospects for observing similar consequences of superfluidity in the already-discovered millisecond pulsars are examined. Inter alia, the likelihood of observing glitches, the expected postglitch behavior, and pulsar heating by energy dissipation due to the creep of neutron vortex lines in pinned superfluid regions of the crust are considered.

Pines, D.↗
NASA NTRS1985

Durability of the accretion disk of millisecond pulsars

Pulsars with pulsation periods in the millisecond range are thought to be neutron stars that have acquired an extraordinarily short spin period through the accretion of stellar material spiraling down onto the neutron star from a nearby companion. Nearly all the angular momentum and most of the mass of the companion star is transferred to the neutron star. During this process, wherein the neutron star consumes its companion, it is required that a disk of stellar material be formed around the neutron star. In conventional models it is supposed that the disk is somehow lost when the accretion phase is finished, so that only the rapidly spinning neutron star remains. However, it is possible that, after the accretion phase, a residual disk remains in stable orbit around the neutron star. The end result of such an accretion process is an object that looks much like a miniature (about 100 kilometers), heavy version of Saturn: a central object (the neutron star) surrounded by a durable disk.

Michel, F. C.↗
NASA NTRS1986

Solar microwave millisecond spike at 2.84 GHz

Using the high time resolution of 1 ms, the data of solar microwave millisecond spike (MMS) event was recorded more than two hundred times at the frequency of 2.84 GHz at Beijing (Peking) Observatory since May 1981. A preliminary analysis was made. It can be seen from the data that the MMS-events have a variety of the fast activities such as the dispersed and isolated spikes, the clusters of the crowded spikes, the weak spikes superimposed on the noise background, and the phenomena of absorption. The marked differences from that observed with lower time resolution are presented. Using the data, a valuable statistical analysis was made. There are close correlations between MMS-events and hard X-ray bursts, and fast drifting bursts. The MMS events are highly dependent on the type of active regions and the magnetic field configuration. It seems to be crucial to find out the accurate positions on the active region where the MMS-events happen and to make co-operative observations at different bands during the special period when specific active regions appear on the solar disk.

Fu, Qi-Jun↗
NASA NTRS1986

Electron-cyclotron maser and solar microwave millisecond spike emission

An intense solar microwave millisecond spike emission (SMMSE) event was observed on May 16, 1981 by Zhao and Jin at Beijing Observatory. The peak flux density of the spikes is high to 5 x 100,000 s.f.u. and the corresponding brightness temperature (BT) reaches approx. 10 to the 15th K. In order to explain the observed properties of SMMSE, it is proposed that a beam of electrons with energy of tens KeV injected from the acceleration region downwards into an emerging magnetic arch forms so-called hollow beam distribution and causes electron-cyclotron maser (ECM) instability. The growth rate of second harmonic X-mode is calculated and its change with time is deduced. It is shown that the saturation time of ECM is t sub s approx. equals 0.42 ms and only at last short stage (delta t less than 0.2 t sub s) the growth rate decreases to zero rather rapidly. So a SMMSE with very high BT will be produced if the ratio of number density of nonthermal electrons to that of background electrons, n sub s/n sub e, is larger than 4 x .00001.

Li, Hong-Wei↗
NASA NTRS1988

Millisecond optical photometry of the DQ Herculis objects

The results of millisecond optical photometry of the DQ Herculis stars EX Hya, H2252-035, V1223 Sgr, and AE Aqr obtained at the Las Campanas Observatory and Cerro Tololo Inter-American Observatory during the years 1985, 1986, and 1987 are reported. The data for coherent and incoherent features are searched for. Coherent features (other than those previously known) were not detected for frequencies between 0.1 and 250 Hz at 4-sigma upper limits of 0.05-0.4 percent. Evidence is not found for 1-3 s, quasi-coherent features. Such features have been detected in the optical emission of the AM Her objects AN UMa, EF Eri, and E1405-451. Because of the similarities between AM Her and DQ Her objects, it was suggested that such quasi-coherent features might also be found in the DQ Her objects.

Imamura, James N.↗
NASA NTRS1988

A search for optical millisecond pulsars in globular clusters

A search for millisecond optical pulsars in several bright, compact globular clusters was conducted. The sample included M28, and the X-ray clusters 47 Tuc, NGC 6441, NGC 6624, M22, and M15. The globular cluster M28 contains the recently discovered 327 Hz radio pulsar. Upper limits of 4 sigma to pulsed emission of (1-20) solar luminosities were found for the globular clusters tested, and 0.3 solar luminosity for the M28 pulsar for frequencies up to 500 Hz.

Middleditch, J. H.↗
NASA NTRS1989

Was the millisecond pulsar in SN1987A spun up or born spinning fast?

It is argued here that the millisecond pulsar in SN1987A has been spun up by accretion. The accreted angular momentum in this case comes from the mixed mantle and helium core of the ejecta, of which roughly 0.1 solar mass fell back during the first day after the explosion. This sizable mass, and hence angular momentum, of the reimploded material is at least partly a consequence of the blue supergiant nature of the progenitor star.

Woosley, S. E.↗
NASA NTRS1989

Evolution of wide binary millisecond pulsars in globular clusters

The evolution of a binary radio pulsar in a wide orbit about a low-mass degenerate dwarf companion in a globular cluster environment is investigated. An extensive series of numerical scattering experiments is used to study encounters between such a pulsar and passing cluster field stars. A wide range of initial orbital periods from 3 to 1000 days is considered with a corresponding range of masses for the degenerate dwarf companions. The calculative results are summarized in the form of scattering cross sections. In particular, cross sections are presented for three final 'channels' in which the end product of the encounter is an isolated neutron star. Cross sections for inducing various orbital eccentricities into initially circular orbits are also derived. The implications of the results for the formation of the single millisecond pulsars in M28 and M15 and for the nearly circular obit of the M4 binary radio pulsar are discussed.

Rappaport, S.↗
NASA NTRS1989

Is the sub-millisecond pulsar strange?

The possibility that the submillisecond pulsar from supernova 1987A is composed of strange matter is theoretically discussed. It is shown that for a range of hadron parameters, the maximum rotation rate of secularly stable strange stars may exceed that of the half-millisecond pulsar and the nonrotating maximum mass is greater than 1.52 solar mass. The low-mass companion(s) to SN1987A, inferred from the periodic modulations of the optical signal, can be accounted for by stable strange-matter lump(s) ejected from the young strange star.

Frieman, Joshua A.↗
NASA NTRS1990

Electron-positron heating and the eclipsing millisecond pulsar PSR 1957 + 20

The companion in the eclipsing millisecond PSR 1957 + 20 appears to be strongly heated by the pulsar and may also be rapidly losing mass due to that heating. A new mechanism is presented by which the heating may be accomplished: diffusion of mildly relativistic electron-positron pairs from the pulsar's relativistic wind through a thermal wind issuing from the companion. Wave-particle scattering regulates the depth at which the pairs deposit their energy; requirements of self-consistency place bounds on the wave spectrum and pair distribution function. If the pairs carry over about 10 percent of the pulsar spin-down luminosity, and the companion's heavy element abundance is subsolar, the heating rate can be adequate to drive a wind with sufficient momentum flux to explain the eclipse geometry. Annihilation photons then heat the companion beneath its photosphere and supply a significant part of the power for the optical luminosity. This model also suggests that the eclipse duration decreases sharply above a critical photon frequency.

Krolik, Julian H.↗