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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Classical Spin-Orbit Coupling and Periastron Advance in a Binary Pulsar

We report on radio timing observations of PSR J0045-7319, and eccentric pulsar/B star 51-day binary in the Small Magellanic Cloud. Significant deviations from a simple Keplerian orbit, observed as precessions of the periastron longitude and orbital plane, are identified with classical spin-orbit coupling and apsidal advance, for the fist time in a binary pulsar. Both precessions result from the B star's rotationally-induced gravitational quadropole moment, however, the orbital plane precession requires the B star's spin axis to be inclined with respect to the orbital angular momentum. We constrain this inclination angle (theta) to be 25(deg) <(theta)<41(deg). Under the conventional assumption that the pre-supernova angular momenta were aligned, our observations provide the most direct evidence yet for an asymmetric supernova.

radio timing psr j0045-7319 pulsars binary pulsars↗
NASA NTRS1972

Photodetachment of an electron from selenide ion - The electron affinity and spin-orbit coupling constant for SeH.

The relative cross section for the gas phase photodetachment of an electron from SeH(-) was determined in the wavelength region 428 to 578 nm. An ion cyclotron resonance spectrometer was used to generate, trap, and detect the negative ions, and a 1000-W xenon arc lamp with a grating monochromator was employed as the light source. The cross section exhibited two sharp thresholds, whose positions remained unchanged for the photodetachment of SeD(-). As a result of these thresholds, the electron affinity and the spin-orbit coupling constant were evaluated.

Smyth, K. C.↗
NASA NTRS2004

Measurement of Gravitational Spin-Orbit Coupling in a Binary Pulsar System

In relativistic gravity, a spinning pulsar will precess as it orbits a compact companion star. We have measured the effect of such precession on the average shape and polarization of the radiation from PSR B1534+12. We have also detected, with limited precision, special-relativistic aberration of the revolving pulsar beam due to orbital motion. Our observations fix the system geometry, including the misalignment between the spin and orbital angular momenta, and yield a measurement of the precession timescale consistent with the predictions of General Relativity.

Stairs, I. H.↗
NASA NTRS1980

Theoretical treatment of the spin-orbit coupling in the rare gas oxides NeO, ArO, KrO, and XeO

Off-diagonal spin-orbit matrix elements are calculated as a function of internuclear distance for the rare gas oxides NeO, ArO, KrO, and XeO using the full microscopic spin-orbit Hamiltonian, including all one- and two-electron integrals, and POL-CI wave functions comparable to those of Dunning and Hay (1977). A good agreement was found when comparing these results in detail with the calculations of Cohen, Wadt and Hay (1979) that utilize an effective one-electron one-center spin-orbit operator. For the rare gas oxide molecules, it is suggested that the numerical results are a more sensitive test of the wave functions (particularly to the extent of charge transfer) than the exact evaluation of all terms in the full spin-orbit operator.

Langhoff, S. R.↗
NASA NTRS1999

XTE Observations of PSR 1259-63 and a Test of Spin Orbit Coupling in the 4U0115+63 System

During this report period, Mallory Roberts went to GSFC to analyze the data from two minor outbursts, which occurred from 4UO115+63. Unfortunately, the outbursts were not of sufficient duration to do a unique orbital determination (which was the scientific goal of the experiment). As this report is being written, 4UO115+63 is undergoing its first major outburst in four years. We are planning on adding our RXTE PCA data to any public ASM or PCA data that is obtained through the duration of this outburst, and combining it with our BATSE data from 1994 and 1995 outbursts in order to learn something about the orbital evolution in this system. We have formed a collaboration with colleagues at MIT who are working on the ASM data for this outburst. Thus, work on the original data will continue, with no further funding, and we are hopeful that some important questions with regard to the orbital timing will finally be resolved. The PSR 1259-63 data were originally analyzed by Barry Giles, who reported that no pulsations or flux were seen from this source near apastron. Recently, a new background model for low-count rate sources has been developed for the PCA. We intend to use this new background model to reanalyze these data to see if we can improve the upper limit to the flux. This work will also continue with no further funding.

Cominsky, Lynn R.↗
NASA NTRS2004

Theory of electrically controlled resonant tunneling spin devices

We report device concepts that exploit spin-orbit coupling for creating spin polarized current sources using nonmagnetic semiconductor resonant tunneling heterostructures, without external magnetic fields. The resonant interband tunneling psin filter exploits large valence band spin-orbit interaction to provide strong spin selectivity.

spin filters↗
NASA NTRS1973

Bombardment as a cause of the lunar asymmetry.

The moon is asymmetric in crustal thickness and also in the distribution of maria and gamma radioactivity. Early bombardment of the moon by planetesimals, in both heliocentric and geocentric orbits, is examined as a possible cause of the asymmetries. The presence of a massive companion (earth) causes a spin-orbit coupled moon to be bombarded nonuniformly. The most pronounced local concentration of impacts would have occurred on the west limb of the moon, when it orbited close to the earth, if low-eccentricity heliocentric planetesimals were still abundant in the solar system at that time. A very intense bombardment of this type could have redistributed crustal material on the moon, thinning the west limb crust appreciably. This would have caused a change in position of the principal axes of inertia, and a reorientation of the spin-orbit coupled moon such that the thinnest portion of its crust turned toward one of the poles. Erupting lavas would have preferentially flooded such a thin-crusted, low-lying area. This would have caused another readjustment of principal moments, and a reorientation of the moon such that the mare areas tipped toward the equator.

Wood, J. A.↗
NASA NTRS1995

Kramers' Restricted Closed Shell CCSD Theory

A Kramers' restricted version of the closed shell coupled cluster singles doubles theory is presented. The theory may be used in conjunction with 2 or 4-component relativistic reference wavefunctions. The intrinsic treatment of the spin-orbit coupling doubles the number of independent quantities (amplitudes and integrals) relative to a spin-independent formalism. The number of operations required to evaluate the equations is four times larger than in the optimal spin-independent closed shell formalism.

Visscher, Lucas↗
NASA NTRS2004

Electrically controlled spin device concepts

We discuss spin device concepts that exploit spin-orbit coupling in nonmagnetic semiconductor heterostructures, including the resonant interband tunneling spin filter, the bi-directional spin pump,, the bulk inversion asymmetry enhanced spin filter, and resonant spin lifetime devices.

Chang, Y.-C.↗
NASA NTRS2018

On the 2018 Outburst of the Accreting Millisecond X-Ray Pulsar Swift J1756.9-2508 As Seen with NICER

We report on the coherent timing analysis of the 182 Hz accreting millisecond X-ray pulsar SwiftJ1756.92508during its 2018 outburst as observed with the Neutron Star Interior Composition Explorer (NICER). Combiningour NICER observations with Rossi X-ray Timing Explorer observations of the 2007 and 2009 outbursts, we alsostudied the long-term spin and orbital evolution of this source. We find that the binary system is well describedby a constant orbital period model, with an upper limit on the orbital period derivative of Pb < 7.4 ´ 10-13 ss1.Additionally, we improve upon the source coordinates through astrometric analysis of the pulse arrival times,finding R.A.=17h56m57 18±0 08 and decl.=25°0627 8±3 5, while simultaneously measuring thelong-term spin frequency derivative as n = -7.3 ´ 10-16 Hzs1. We briefly discuss the implications of thesemeasurements in the context of the wider population of accreting millisecond pulsars. We reported on the coherent timing analysis of the 2018 outburst of Swift J1756 as observed with NICER. Consistent with analyses of the previous outbursts (Krimm et al. 2007b; Patruno et al. 2010), we find that the X-ray pulsations have energy dependent amplitudes; the fractional amplitude of the fundamental increases with energy, whereas the fractional amplitude of the harmonic shows a slight decline with energy. This energy dependent behavior is not unusual in AMXPs (Patruno & Watts 2012) and can be interpreted in terms of the thermal emission from the stellar hotspot and reprocessing in the accretion column (e.g., Gierliński et al. 2002; Ibragimov & Poutanen 2009). The pulse arrival times of the 2018 outburst are well described by a timing model consisting of a circular orbit with a constant spin frequency. The pulse phases with respect to this model do not show spurious residuals with time or orbital phase, and no evidence is found that the pulse arrival times exhibit an additional delay associated with passing through the gravitational well of the companion star (Shapiro delay). We note, however, that the expected Shapiro delay is given as (Shapiro et al. 1971) Equation (5) where Φ is the orbital phase, G is the gravitational constant, c is the speed of light, and i is the inclination. Even for the maximum allowed companion mass, ${M}_{C}=0.030\,{M}_{\odot }$ (Krimm et al. 2007b, but see Section 4.2 for more details) and an inclination of 90°, the largest delay we can expect is only 4 μs. As this time-delay is smaller than the uncertainty on our phase residuals by nearly two orders of magnitude (see Figure 1), we are not sensitive to Shapiro delays in Swift J1756. Comparing our measurements for the 2018 outburst with those of the 2007 and 2009 outbursts as observed with RXTE, we analyzed the long-term evolution of this source. We found that the binary system is consistent with having a constant orbital period and that the pulsar shows a spin frequency derivative of $\dot{\nu }=-7.3\times {10}^{-16}\,\mathrm{Hz}\,{{\rm{s}}}^{-1}$. 4.1. Spin-down Evolution The long-term spin frequency derivative measured in Swift J1756 is of the same order as the spin frequency derivatives measured in other AMXPs (Hartman et al. 2008; Patruno 2010; Riggio et al. 2011). This frequency change is most likely driven by the neutron star's loss of rotational energy. If so, then the spin-down luminosity is given as Equation (6) where I represents the neutron star moment of inertia. The long-term spin-down of a neutron star is usually assumed to be dominated by the braking torque associated with a spinning magnetic field. Assuming this mechanism is responsible for the observed spin-down in Swift J1756, we can compute the magnetic dipole moment as (Spitkovsky 2006) Equation (7) where α is the misalignment angle between the rotational and magnetic poles. Considering α = 0°–90°, we then find a magnetic field strength of $B\simeq (4\mbox{--}6)\times {10}^{8}$ G at the stellar magnetic poles. This magnetic field strength estimate is in line with those obtained for other accreting millisecond pulsars (see Mukherjee et al. 2015 and references therein). 4.2. Orbit Evolution The observed long-term binary evolution of Swift J1756 is consistent with this source having a constant orbital period and a lower limit on the evolutionary timescale of Equation (8) Binary evolution theory predicts that systems of this type evolve due to angular momentum loss through gravitational radiation (Kraft et al. 1962; Rappaport et al. 1982; Verbunt 1993). For conservative mass transfer, the binary period derivative is given by di Salvo et al. (2008), Equation (9) where MNS is the neutron star mass, $q={M}_{C}/{M}_{\mathrm{NS}}$ is the binary mass ratio, and −1/3 < n < 1 is the mass–radius index of the companion star. Depending on the source inclination, Krimm et al. (2007b) derived a companion mass of ${M}_{C}\,=0.007\mbox{--}0.022\,{M}_{\odot }$ for a neutron star mass of 1.4 ${M}_{\odot }$. For a neutron star mass of 2.2 ${M}_{\odot }$, the allowed range increased to ${M}_{C}=0.009\mbox{--}0.030\,{M}_{\odot }$. In both cases, they assumed an upper limit on the inclination of i < 85°, motivated by the fact that Swift J1756 does not show eclipses in its light curve. Accounting for the extreme cases of stellar masses and n, the binary may either be contracting or expanding. In either case, however, the rate of change is limited to $| {\dot{P}}_{b}| \lesssim 7\times {10}^{-14}$ s s−1, which is well below the upper limit obtained in this work. Although the binary evolution timescale we obtain for Swift J1756 is consistent with theory, it is worth noting that this is not generally true for low-mass X-ray binaries (see Patruno et al. 2017, for a comprehensive discussion). The AMXP SAX J1808.4–3658, in particular, has been found to evolve on a much shorter timescale, with a first derivative on the orbital period of $3.5\times {10}^{-12}$ s s−1 (Hartman et al. 2008; Patruno et al. 2012; Sanna et al. 2017a). Two models have been proposed to explain this discrepancy: highly nonconservative mass transfer due to irradiation of the companion star by the pulsar (di Salvo et al. 2008; Burderi et al. 2009), and spin–orbit coupling in the companion star (Hartman et al. 2008, 2009). While the latter depends on the companion star, and may vary from source to source, the former should operate in all AMXPs (see also Patruno 2017; Sanna et al. 2017c), including Swift J1756. The spin-down luminosity impinging on the companion star can be estimated as Equation (10) where ${\dot{E}}_{\mathrm{abl}}$ is the ablation luminosity, RL2 is the Roche lobe radius of the companion (Eggleton 1983), and a the binary separation. The irradiation fraction is $f={\dot{E}}_{\mathrm{abl}}/{\dot{E}}_{\mathrm{sd}}$, which, accounting for the range of allowed neutron star and companion masses, evaluates to f = 0.15%–0.35%. The associated mass loss for the companion is given by Equation (11) such that, assuming an efficiency of η = 100%, ${\dot{M}}_{C}\,\sim -3\times {10}^{-10}\,{M}_{\odot }$ yr−1. The effect of this mass loss on the orbital period follows through the relation (Frank et al. 2002) Equation (12) giving a period derivative due to mass loss of ${\dot{P}}_{b,\mathrm{ML}}\,=5\times {10}^{-12}$ s s−1. This value is well above our limit on the period derivative. Hence, in order for this mechanism to be consistent with our observations of Swift J1756, the efficiency at which the companion star converts the incident luminosity into mass loss must be η < 15%. This value is very different from the 40% required in SAX J1808.4–3658 (Patruno et al. 2016) and is instead in line with the <5% efficiency determined for IGR J00291+5934 (Patruno 2017). This work was supported by NASA through the NICER mission and the Astrophysics Explorers Program, and made use of data and software provided by the High Energy Astrophysics Science Archive Research Center (HEASARC). P.B. was supported by an NPP fellowship at NASA Goddard Space Flight Center. D.A. acknowledges support from the Royal Society.

Bult, Peter↗
NASA NTRS1995

The Duffin-Kemmer-Petiau oscillator

In view of current interest in relativistic spin-one systems and the recent work on the Dirac Oscillator, we introduce the Duffin-Kemmer-Petiau (DKP) equation obtained by using an external potential linear in r. Since, in the non-relativistic limit, the spin 1 representation leads to a harmonic oscillator with a spin-orbit coupling of the Thomas form, we call the equation the DKP oscillator. This oscillator is a relativistic generalization of the quantum harmonic oscillator for scalar and vector bosons. We show that it conserves total angular momentum and that it is exactly solvable. We calculate and discuss the eigenspectrum of the DKP oscillator in the spin 1 representation.

Nedjadi, Youcef↗
NASA NTRS1971

Transition moments, Franck-Condon factors, and lifetimes of forbidden transitions - Calculation of the intensity of the Cameron system of CO.

Discussion of the factors affecting the intensity of forbidden transitions in diatomic molecules. It is shown that using Franck-Condon factors to predict relative band intensities is less reliable for forbidden transitions than it is for allowed transitions. The intensity of the 0,0 and 1,0 bands of the a super 3 pi-super 1 sigma Cameron system of CO are calculated using perturbation theory. The intensity arises from spin-orbit mixing of the A super 1 pi state with the a super 3 pi state. From the known spin-orbit coupling constant of the a super 1 pi state and the known intensity of the fourth positive A super 1 pi-super 1 sigma transition, the oscillator strengths of the 0,0 and 1,0 bands are calculated to be 1.63 x 10 to the minus 7th power and 1.99 x 10 to the minus 7th power. Lifetimes of various rotational levels are shown to range from 2.9 to several hundred milliseconds.-

James, T. C.↗
NASA NTRS1972

Angular dependence of electron impact excitation cross sections of O2.

Study of the electron-impact excitation spectrum of O2 at 20 and 45 eV impact energies and at scattering angles ranging from 10 to 90 deg. The angular behavior of the differential scattering cross sections for excitation of the a super 1 delta sub g, b super 1 sigma sub g (+), B super 3 sigma sub u (-) states for the 9.97-eV ('longest' band) and the 10.29-eV ('second' band) transitions, for the broad feature at 6.1 eV energy-loss, and for elastic scattering is determined. The experimentally measured relative differential and integral cross sections for these processes are approximately normalized to the absolute scale. The intensities of the different transitions in optical and electron-impact spectra are compared, and the importance of spin-orbit coupling and exchange processes is discussed. It is found that the energy-loss feature at 6.1 eV in the electron-impact spectrum is mostly due to the excitation of the c super 1 sigma sub u (-) state, and not the A super 3 sigma sub u (+) state, as had been previously thought.

Trajmar, S.↗
NASA NTRS1973

Rotation of solid bodies in the solar system

The effects of elastic distortion, nonprincipal axis rotation, precessing orbits, and internal dissipation on the rotation of a solid solar system body, which is in the gravitational field of an exterior body, are relatively easily analyzed by a Hamiltonian theory developed here. Examples of applications include the Chandler wobble, wobble of the moon, spin-orbit coupling, generalized Cassini laws, and tidal evolution.

Peale, S. J.↗