4,493 research outputs found
One-dimensional Excitations in Superfluid He and He-He Mixture Films Adsorbed in Porous Materials
A normal-fluid component varying as T is observed at very low
temperatures in superfluid He and He-He mixture films adsorbed in
alumina powder. The normal fluid appears to arise from thermally excited third
sound that has one-dimensional propagation characteristics. A Landau model of
third sound excitations in an infinite cylindrical pore by Saam and Cole
provides good agreement with the experimental measurements over a wide range of
He and He coverages. However, it is unclear why the powder substrate
can be modeled as having cylindrical pores.Comment: 5 pages, 6 figures, revtex4, to appear in PR
First detection of 22 GHz H2O masers in TX Camelopardalis
Simultaneous time monitoring observations of HO , SiO
= 1--0, 2--1, 3--2, and SiO = 0, = 1--0 lines were carried
out in the direction of the Mira variable star TX Cam with the Korean VLBI
Network single dish radio telescopes. For the first time, the HO maser
emission from TX Cam was detected near the stellar velocity at five epochs from
April 10, 2013 ( = 3.13) to June 4, 2014 ( = 3.89) including
minimum optical phases. The intensities of HO masers are very weak
compared to SiO masers. The variation of peak antenna temperature ratios among
SiO = 1, = 1--0, = 2--1, and = 3--2 masers is investigated
according to their phases. The shift of peak velocities of HO and SiO
masers with respect to the stellar velocity is also investigated according to
observed optical phases. The HO maser emission occurs around the stellar
velocity during our monitoring interval. On the other hand, the peak velocities
of SiO masers show a spread compared to the stellar velocity. The peak
velocities of SiO = 2--1, and = 3--2 masers show a smaller spread with
respect to the stellar velocity than those of SiO = 1--0 masers. These
simultaneous observations of multi-frequencies will provide a good constraint
for maser pumping models and a good probe for investigating the stellar
atmosphere and envelope according to their different excitation conditions.Comment: 10 page
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