16,348 research outputs found
Current problems in the zodiacal light
Photometric observations of zodiacal ligh
A program of ground-based studies of the zodiacal light
Nonzodiacal light sources of polarization in nightglow, and polarization due to airglow line emission
Polarimetric observations of Comet Kohoutek (1973f)
Radio, optical, and visual observations were made of Comet Kohoutek (1973f) using facilities of the National Radio Astronomy Observatory (NRAO) and of the Hawaii Night Sky Observatory, State University of New York at Albany (SUNYA). Transit observations were made using the NRAO 300 ft radio telescope on six consecutive days beginning November 24, 1973. Observations were carried out in the continuum at 11 cm using the 4-feed system at different position angles. The data were recorded on magnetic tape and were computer reduced. Results were negative, with an rms error of 62 milli flux units, giving an upper limit of 180 mfu for the 11 cm continuum emission from the Comet. This relatively high detection limit resulted from a combination of interference and bad weather that affected these pre-perihelion observations. No observations could be scheduled near or after perihelion
Zodiacal light Summary report
Survey in form of tables and graphs of surface brightness and degree of polarization of zodiacal light as function of elongation in plane of elliptic - related bibliograph
Preliminary study of contaminant particulates around Skylab
Techniques originally developed for the Skylab T025 contamination experiment were applied to S052 white-light coronagraph data in a preliminary study to investigate particulates around Skylab. Periods were selected which contained some contamination, even though there were no apparent dumps or vents during these periods. Velocity and size distributions were determined from optical data for particles within 200 meters of the spacecraft. Both photographic (61 particle tracks) and video (34 particles) observations yield an upper limit on particle radius of 100 micrometers. Selected photometric data from the S073 zodiacal light experiment during mission SL-2 were also examined for evidence of contamination
Photoelectric polarimetry of the tail of comet Ikey-Seki (1975 VIII)
Post-perihelion measurements of Comet 1965 VIII made on four nights in October-November 1965 using a Fabry photometer atop 3,052 m Mt. Haleakala, Hawaii are described. Detailed results of observations at 5300A on October 29, 1965 are presented
Dissipation of dark matter
Fluids often display dissipative properties. We explore dissipation in the
form of bulk viscosity in the cold dark matter fluid. We constrain this model
using current data from supernovae, baryon acoustic oscillations and the cosmic
microwave background. Considering the isotropic and homogeneous background
only, viscous dark matter is allowed to have a bulk viscosity
Pas, also consistent with the expected integrated Sachs-Wolfe effect
(which plagues some models with bulk viscosity). We further investigate the
small-scale formation of viscous dark matter halos, which turns out to place
significantly stronger constraints on the dark matter viscosity. The existence
of dwarf galaxies is guaranteed only for much smaller values of the dark matter
viscosity, Pas.Comment: 10 pages, 3 figures, published in PR
Direct measurement of xenon flashtube opacity
Opacity measurement of xenon flash tube - optical mase
Papapetrou Energy-Momentum Tensor for Chern-Simons Modified Gravity
We construct a conserved, symmetric energy-momentum (pseudo-)tensor for
Chern-Simons modified gravity, thus demonstrating that the theory is Lorentz
invariant. The tensor is discussed in relation to other gravitational
energy-momentum tensors and analyzed for the Schwarzschild, Reissner-Nordstrom,
and FRW solutions. To our knowledge this is the first confirmation that the
Reissner-Nordstrom and FRW metrics are solutions of the modified theory.Comment: 8 pages; typos corrected, references fixed, some calculations
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