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Results for “Periodic orbits”

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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Orbital period changes in Centaurus X-3

Two new times of mid-X-ray eclipse for Cen X-3 are presented on the basis of pulse arrival time analyses of pointed observations with SAS 3. When combined with all other published eclipse times based on Doppler delay measurements, the results show that the 2.1d binary period is decreasing at an average rate of 1.8 x 10 to the -6th/yr. The decrease, however, is seen as having significant fluctuations about a smooth, linear decrease. The changes observed in the orbital period can be accounted for by mass loss from the system through the L2 point, although the rates required are implausibly high. It is also shown that the long-term overall orbital decay can readily be interpreted as the result of torques exerted by the tidally distorted companion star (Krzeminski's star) on the orbiting neutron star. It is noted that the inferred asynchronism between the orbital frequency and the rotation frequency of the companion star may be maintained by mass and angular momentum loss in a stellar wind or by a tidal instability related to the Darwin effect. However, this would not provide a natural explanation for any short-term deviations from a constant rate of orbital decay.

Kelley, R. L.↗
NASA NTRS1989

Inhibition of quantum transport due to 'scars' of unstable periodic orbits

A new quantum mechanism for the suppression of chaotic ionization of highly excited hydrogen atoms explains the appearance of anomalously stable states in the microwave ionization experiments of Koch et al. A novel phase-space representation of the perturbed wave functions reveals that the inhibition of quantum transport is due to the selective excitation of wave functions that are highly localized near unstable periodic orbits in the chaotic classical phase space. The 'scarred' wave functions provide a new basis for the quantum description of a variety of classically chaotic systems.

Jensen, R. V.↗
NASA NTRS2018

Solar Sail Transfers from Invariant Objects to L5 Periodic Orbits

The rising interest in a mission to the Sun-Earth L5 point for heliophysics or Trojan asteroid search and the development of solar sails has opened the question of using solar radiation pressure for such a mission. Different solar sail trajectories to the Sun-Earth L5 point are constructed. Different invariant objects in the neighbourhood of Earth are considered for departure: equilibrium points, families of periodic orbits and their associated invariant manifold. Using a multi-objective genetic algorithm, differential correction and the optimal control solver PSOPT the transfers are obtained. The approach followed results in fast solar sail transfers which can be used for the preliminary design of a mission to the Sun-Earth L5 point.

Fernandez, Alvaro↗
NASA NTRS2021

Speckle Observations of TESS Exoplanet Host Stars: Understanding the Binary Exoplanet Host Star Orbital Period Distribution

We present high-resolution speckle interferometric imaging observations of TESS exoplanet host stars using the NN-EXPLORE Exoplanet and Stellar Speckle Imager instrument at the 3.5 m WIYN telescope. Eight TESS objects of interest that were originally discovered by Kepler were previously observed using the Differential Speckle Survey Instrument. Speckle observations of 186 TESS stars were carried out, and 45 (24%) likely bound companions were detected. This is approximately the number of companions we would expect to observe given the established 46% binarity rate in exoplanet host stars. For the detected binaries, the distribution of stellar mass ratio is consistent with that of the standard Raghavan distribution and may show a decrease in high-q systems as the binary separation increases. The distribution of binary orbital periods, however, is not consistent with the standard Ragahavan model, and our observations support the premise that exoplanet-hosting stars with binary companions have, in general, wider orbital separations than field binaries. We find that exoplanet-hosting binary star systems show a distribution peaking near 100 au, higher than the 40–50 au peak that is observed for field binaries. This fact led to earlier suggestions that planet formation is suppressed in close binaries.

Stellar Speckle Imager↗
NASA NTRS1990

1H 0709-360 - A cataclysmic variable with an orbital period inside the 'period gap'

The discovery is reported of the second cataclysmic variable with a binary period lying well inside the nominal 2-3 hr period gap. The object, 1H 0709-360, is an X-ray source which has been identified on the basis of positional data from the instruments of the HEAO 1 survey. The X-ray source was also detected by the Uhuru and Ariel 5 surveys. Multicolor photometry has revealed eclipsing behavior at an orbital period of 2.444 hr. Radial velocity measurements show modulations at the same period, with an offset between the spectroscopic and photometric conjunctions. Both the eclipse profile and a clear rotational disturbance in the radial velocities of emission lines during eclipse provide unambiguous evidence for the existence of an accretion disk. Thus the object cannot be an AM Herculis variable, a conclusion supported by the absence of circular polarization. Instead, the evidence suggests that the object could be a DQ Herculis magnetic variable that is close to synchronism. The evolutionary implications of this rare object are discussed.

Tuohy, I. R.↗
NASA NTRS2001

Earth Observing-1 Advanced Imager Flight Performance Assessment: Investigating Dark Current Stability Over One-Half Orbit Period during the First 60 Days

The stability of the EO-1 Advanced Land Imager dark current levels over the period of one-half orbit is investigated. A series of two-second dark current collections, over the course of 40 minutes, was performed during the first sixty days the instrument was in orbit. Analysis of this data indicates only two dark current reference periods, obtained entering and exiting eclipse, are required to remove ALI dark current offsets for 99.9% of the focal plane to within 1.5 digital numbers for any observation on the solar illuminated portion of the orbit.

Mendenhall, J. A.↗
NASA NTRS1980

Analytic construction of periodic orbits about the collinear points

A third-order analytical solution for halo-type periodic motion about the collinear points of the circular-restricted problem is presented. The three-dimensional equations of motion are obtained by a Lagrangian formulation. The solution is constructed using the method of successive approximations in conjunction with a technique similar to the Lindstedt-Poincare method. The theory is applied to the sun-earth system.

Richardson, D. L.↗
NASA NTRS1975

Periodic orbits in the Planar General Three-Body Problem

The article contains a numerical study of periodic solutions of the Planar General Three-Body Problem. Several new periodic solutions have been discovered and are described. In particular, there is a continuous family with variable masses, extending all the way from the elliptic restricted problem to the general problem with three equal masses. All our examples have special symmetry properties which are described in detail. Finally we also suggest some important applications to the natural satellites of the solar system.

Broucke, R.↗
NASA NTRS1977

Further studies of the pulsation period and orbital elements of Centaurus X-3

The long- and short-term variability of the 4.8-s pulsation and the 2.1-day orbital periods of Centaurus X-3 are studied. The pulsation period decreases over 4 yr with a fractional change of -0.00028 per yr, but with rms fluctuations of 0.0002 s. In August-September 1972, a continuous transition from speedup to slowdown was observed. The orbital period also decreases over 4 yr with decrease of approximately 8 millionths per yr, and with significant fluctuations of the order of 0.00001 day over months. The orbital eccentricity is found to be about 0.0008. The pulsation-period variability is found to be consistent with a near balance between the Alfven and corotation radii in an accretion-disk model. The orbital-period variability is interpreted in terms of tidal circularization and possible mass transfer and loss.

Fabbiano, G.↗
NASA NTRS2019

A ~60 day Super-orbital Period Originating from the Ultraluminous X-ray Pulsar in M82

Ultraluminous X-ray (ULX) pulsars are a new class of object powered by apparent super-critical accretion onto magnetized neutron stars. Three sources in this class have been identified so far; M82X-2, NGC 5907 ULX-1, and NGC 7793 P13 have been found to have two properties in common; ∼1 s spin periods, and for NGC 5907 ULX-1 and NGC 7793 P13 periodic X-ray flux modulations on timescales of ∼60–80 days. M82 X-2 resides in a crowded field that includes the ULX M82 X-1 separated from X-2 by 5″, as well as other bright point sources. A 60 day modulation has been observed from the region, but the origin has been difficult to identify; both M82 X-1 and X-2 have been suggested as the source. In this paper we present the analysis of a systematic monitoring campaign by Chandra, the only X-ray telescope capable of resolving the crowded field. From a simple Lomb–Scargle periodogram analysis and a more sophisticated Gaussian Process analysis we find that only X-2 exhibits a periodic signal around 60 days, supporting previous claims that it is the origin. We also construct a phase-averaged flux profile of the modulations from higher-cadence Swift/XRT data and find that the flux variations in the Chandra data are fully consistent with the flux profile. Since the orbit of the neutron star and its companion is known to be 2.5 days, the ∼60 day period must be super-orbital in origin. The flux of the modulations varies by a factor of ∼100 from the minimum to the maximum, with no evidence for spectral variations, making the origin difficult to explain.

Individual galaxies↗
NASA NTRS1990

The orbital period of 4U/MXB 1636-53 (V801 Arae)

The results of CCD photometry of the optical counterpart (V801 Arae) of the X-ray burst source 4U/MXB 1636-53, obtained between 1984 and 1988 are reported. From these data, and additional measurements discussed previously, a linear orbital ephemeris P(orb) = 3.803878 + or - 0.000022 h covering the interval between 1980 and 1988 is derived. The results confirm that substantial night-to-night variations occur in the shape of the light curve, superposed on the periodic brightness variations. No evidence is found for a relation between orbital phase and the delays of optical bursts relative to the coincident X-ray bursts. The variation with orbital phase of the corresponding ratios of optical to X-ray burst fluences and peak fluxes does not follow the average optical light curve. These results suggest that substantial long-term changes occur in the spatial distribution of reprocessing matter in the binary system.

Van Paradijs, J.↗
NASA NTRS1987

Do slow orbital periodicities appear in the record of earth's magnetic reversals?

Time-series spectral analysis has been performed on the dates of geomagnetic reversals of the last 20 Myr BP and earlier. Possible evidence is found from the presence of high spectral peaks for two very long periodicities, 0.4 Myr and 1.3 Myr, that may be associated with slow variations of the earth's orbital eccentricity as predicted by Berger. However, statistical significance tests and a number of other arguments do not confirm the two detections.

Stothers, Richard B.↗
NASA NTRS1993

Effect of parking orbit period on aerocapture for manned Mars missions

Aerocapture has previously been identified as a critical technology for manned Mars missions. A wide range of parking orbits is available into which an aerobraking vehicle could be captured, and earlier authors have advocated different target orbits for various reasons. The choice of the parking orbit impacts the amount of energy which must be dissipated during the atmospheric trajectory. The effect of this choice on the entry corridor width, the required vehicle L/D, and the aerothermal environment are explored in this paper.

Lyne, James E.↗
NASA NTRS1980

Variations in the Nimbus-7 scanning multichannel microwave radiometer cold reference antenna signals and temperatures during two orbital periods

The observed effects of solar radiance on the Nimbus 7 scanning multichannel microwave radiometer (SMMR) cold reference signal are discussed. Unexpected diurnal responses in this signal sometimes larger than the typical cold reference signal resulted from acquisition of the solar disc. Solar heating of the SMMR components as a function of orbital locations was correlated with the cold reference radiances for two sets of sequential orbit six months apart.

Gloersen, P.↗