Companion Point Research Articles

Faults & failures

In the old joke, at the end of an orchestra recital the critic leaps to his feet, crying "Encore, encore!" When his companion points out the mediocrity of the performance, the critic replies, "I know. I want them to do it again until they get it right." An unsettling replay of that joke was enacted on 12 May and in the following weeks when, just seconds into launch, a test flight of the Theater High Altitude Area Defense System (Thaad) self-destructed after a short circuit in a thrust controller. It was the system’s fifth test failure in a row, yet just a few hours later, bloodied but unbowed, a spokesman for the Department of Defense (DOD) told reporters: "We will continue to test the program until we get it right."

Orbital Decay, Spin-down, and Pulse-Phase--resolved Spectroscopy of LMC X-4 from GINGA and ROSAT Observations

view Abstract Citations (44) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Orbital Decay, Spin-down, and Pulse-Phase--resolved Spectroscopy of LMC X-4 from GINGA and ROSAT Observations Woo, Jonathan W. ; Clark, George W. ; Levine, Alan M. ; Corbet, Robin H. D. ; Nagase, Fumiaki Abstract We report pulse-timing and pulse-phase resolved spectrum analysis of LMC X-4 observations by the X-ray satellites Ginga in 1988 and ROSAT in 1991 extending over a combined energy range from 0.2 to 37 keV. The results, when combined with previous results of X-ray observations dating back to 1977, yield marginal evidence of orbital decay with an average rate of change in the orbital period of P_orb_/P_orb_ = (-5.3 +/- 2.7) x 10^-7^ yr^-1^. This low decay rate and the relatively small radius of the companion point to the conclusion that the companion is still in the hydrogen core-burning stage of its evolution. The pulse period increased between the two observations at an average rate of P_pulse_ = (1.91+/- 0.001) x 10^-3^ s yr^-1^. At other times, the spin period has both decreased and increased. The neutron star must therefore be in the condition of approximate spin equilibrium wherein its period is close to the Kepler period at the inner edge of the accretion disk. For a disk- accreting pulsar with the luminosity (~10^38.6^ ergs s^-1^) and spin period (~13.5 s) of LMC X-4, this condition implies that its magnetic dipole moment is exceptionally large, of the order of 10^31.5^ G cm^3^. The pulse-phase resolved combined pulse-height distributions are well fitted with a model spectrum consisting of the sum of four components, a Planck function (PF), thermal bremsstrahlung (TB), power law (PL), and iron K-line (FE), multiplied by a photoelectric absorption factor, an exponential high-energy cutoff and a cyclotron resonance attenuation factor. The pulse profiles of the TB and PL (E > 15 keV) energy fluxes are single-peaked with pulse fractions of ~0.12 and ~0.16, respectively, but ~180^deg^ different in phase. The Fe-line flux also exhibits a single peak pulse profile. Its pulse fraction is ~0.37, and its peak lags that of the FL peak by ~140^deg^. The PL (E > 15 keV) profile is attributed to a pencil-beam-like anisotropy in the emission and the TB profile to a fan-beam-like anisotropy with the condition that the sum of the spin axis inclination and the angle between the spin and magnetic dipole axes is less than 90^deg^. The PF component shows no significant pulse variation and is attributed to emission from the accretion disk. Publication: The Astrophysical Journal Pub Date: August 1996 DOI: 10.1086/177655 Bibcode: 1996ApJ...467..811W Keywords: STARS: BINARIES: ECLIPSING; STARS: PULSARS: INDIVIDUAL ALPHANUMERIC: LMC X-4; X-RAYS: STARS; STARS: NEUTRON full text sources ADS | data products SIMBAD (5) NED (1) HEASARC (1)

Narrative and Logical Strategies in Socio-cognitive Interaction between Children

This study is an analysis of the "meaning giving" process in children when they have to classify empirical objects. There are three stages to the experiment: (1) the children performed a classification task individually; (2) they performed it with a companion; (3) in the individual control situation they performed it again but alone. The aim of this research project was to establish: (1) how children change the meanings they give to objects when they move from an individual situation to a social one; and (2) the role of the two children's different classification strategies in the negotiation of shared meanings. The sample consisted of 72 6-year-old children. Three different classification criteria were distinguished: category; function; and narrative. The results showed that children who used narrative criteria in the first phase ("narrative children") modified them during the second phase in favour of more categorial criteria. Analysis of the interactional process revealed that narrative children were significantly more willing than "logical children" (who had used categorial criteria in the first phase) to come to terms with their companion's point of view. In the third phase both types of children changed their classification strategies, in part absorbing their companion's classification approach. We conclude that: (1) the personal approach to giving a meaning to objects influences the individual child's interaction strategies; and (2) the experience of comparison and social conflict modifies attribution of meaning in narrative and logical children.

Gravitational lensing of quasars as seen by the Hubble Space Telescope Snapshot Survey

Results from the ongoing HST Snapshot Survey are presented, with emphasis on 152 high-luminosity, z greater than 1 quasars. One quasar among those observed, 1208 + 1011, is a candidate lens system with subarcsecond image separation. Six other quasars have point sources within 6 arcsec. Ground-based observations of five of these cases show that the companion point sources are foreground Galactic stars. The predicted lensing frequency of the sample is calculated for a variety of cosmological models. The effect of uncertainties in some of the observational parameters upon the predictions is discussed. No correlation of the drift rate with time, right ascension, declination, or point error is found.

A Preliminary Study of a Physical Basis of Bird Navigation

The bird navigation theory as presented implies an organ or organs in the bird's physiology which are sensitive to the effect of its motion through the vertical component of the earth's magnetic field and to the effort exerted to overcome the coriolis force, due to the earth's rotation. Both these influences involve a set of lines which together form a navigational gridwork. By correlating its instantaneous land speed with the two above effects, a bird can fly to its home which is a unique point in this gridwork, or to related companion points existing in the gridwork at positions other than its home. Experimentation with homing pigeons between the home and spurious home points (conjugate or companion points) has yielded data which supports the theory.