145,893 research outputs found
Photon Bunching at TeV Energies
Harwit, Protheroe, and Biermann (1999) recently proposed that Bose-Einstein
photon bunching might significantly affect the interpretation of Cerenkov
counts of TeV gamma photons. Here, we show that a combination of two recent
results of Aharonian et al. (2000) and Aharonian et al. (2001) permits us to
set new, more stringent upper limits of on the fractional amount
of photon bunching in the 7-10 TeV radiation from Markarian 501. Potential
bunching at even higher energies should nevertheless continue to be
investigated for this and other TeV sources, since a clear understanding of TeV
energy spectra is required to unambiguously determine the spectral energy
density of the mid-infrared extragalactic background
NASA-ARC 91.5-cm airborne infrared telescope
A 91.5 cm aperture telescope installed aboard NASA-Lockheed C-141A aircraft for the performance of infrared astronomy is described. A unique feature of the telescope is that its entire structure is supported by a 41 cm spherical air bearing which effectively uncouples it from aircraft angular motion, and with inertial stabilization and star tracking, limits tracking errors to less than 1 arc second in most applications. A general description of the system, a summary of its performance, and a detailed description of an offset tracking mechanism is presented
Tentative Detection of the Rotation of Eris
We report a multi-week sequence of B-band photometric measurements of the
dwarf planet Eris using the {\it Swift} satellite. The use of an observatory in
low-Earth orbit provides better temporal sampling than is available with a
ground-based telescope. We find no compelling evidence for an unusually slow
rotation period of multiple days, as has been suggested previously. A
1.08 day rotation period is marginally detected at a modest level of
statistical confidence (97%). Analysis of the combination of the
data with the ground-based B-band measurements of \citet{2007AJ....133...26R}
returns the same period (1.08 day) at a slightly higher statistical
confidence (99%).Comment: Accepted to Icarus 2008-Aug-19. 19 pages total, including 4 figures
and 1 tabl
G conditioning suit Patent
Conditioning suit for normal function of astronaut cardiovascular system in gravity environmen
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