36,484 research outputs found
Geometry of Deformed Boson Algebras
Phase-space realisations of an infinite parameter family of quantum
deformations of the boson algebra in which the -- and the --deformed
algebras arise as special cases are studied. Quantum and classical models for
the corresponding deformed oscillators are provided. The deformation parameters
are identified with coefficients of non-linear terms in the normal forms
expansion of a family of classical Hamiltonian systems. These quantum
deformations are trivial in the sense that they correspond to non-unitary
transformations of the Weyl algebra. They are non-trivial in the sense that the
deformed commutators consistently quantise a class of non-canonical classical
Poisson structures.Comment: 20 pages, late
Radio Continuum Sources Associated with AB Aur
We present high angular resolution, high-sensitivity Very Large Array
observations at 3.6 cm of the Herbig Ae star AB Aur. This star is of interest
since its circumstellar disk exhibits characteristics that have been attributed
to the presence of an undetected low mass companion or giant gas planet. Our
image confirms the continuum emission known to exist in association with the
star, and detects a faint protuberance that extends about to its
SE. Previous theoretical considerations and observational results are
consistent with the presence of a companion to AB Aur with the separation and
position angle derived from our radio data. We also determine the proper motion
of AB Aur by comparing our new observations with data taken about 17 years ago
and find values consistent with those found by Hipparcos.Comment: 6 pages, 1 figur
Unveiling the nature and interaction of the intermediate/high-mass YSOs in IRAS 20343+4129
In order to elucidate the nature of the brightest infrared sources associated
with IRAS 20343+4129, IRS1 and IRS3, we observed with the Submillimeter Array
(SMA) the 1.3 mm continuum and CO(2-1) emission of the region. Faint millimeter
dust continuum emission was detected toward IRS1, and we derived an associated
gas mass of ~0.8 Msun. The IRS1 spectral energy distribution agrees with IRS1
being an intermediate-mass Class I source of about 1000 Lsun, whose
circumstellar material is producing the observed large infrared excess. We have
discovered a high-velocity CO bipolar outflow in the east-west direction, which
is clearly associated with IRS1, and the outflow parameters are similar to
those of intermediate-mass young stellar objects. Associated with the blue
large scale CO outflow lobe, detected with single-dish observations, we only
found two elongated low-velocity structures on either side of IRS3. The
large-scale outflow lobe is almost completely resolved out by the SMA. Our
detected low-velocity CO structures are coincident with elongated H2 emission
features. The strongest millimeter continuum condensations in the region are
found on either side of IRS3, where the infrared emission is extremely weak,
and the CO and H2 elongated structures follow the border of the millimeter
continuum emission that is facing IRS3. All these results suggest that the dust
is associated with the walls of an expanding cavity driven by IRS3, estimated
to be a B2 star. Within and beyond the expanding cavity, the millimeter
continuum sources can be sites of future low-mass star formation.Comment: 12 pages, 7 figures, accepted for publication in A&
VLA Imaging of the Disk Surrounding the Nearby Young Star TW Hya
The TW Hya system is perhaps the closest analog to the early solar nebula. We
have used the Very Large Array to image TW Hya at wavelengths of 7mm and 3.6 cm
with resolutions 0.1 arcseconds (about 5 AU) and 1.0 arcseconds (about 50 AU),
respectively. The 7mm emission is extended and appears dominated by a dusty
disk of radius larger than 50 AU surrounding the star. The 3.6 cm emission is
unresolved and likely arises from an ionized wind or gyrosynchrotron activity.
The dust spectrum and spatially resolved 7mm images of the TW Hya disk are
fitted by a simple model with temperature and surface density described by
radial power laws, and . These
properties are consistent with an irradiated gaseous accretion disk of mass
with an accretion rate and viscosity parameter . The estimates of
mass and mass accretion rates are uncertain as the gas-to-dust ratio in the TW
Hya disk may have evolved from the standard interstellar value.Comment: 13 pages, 3 figures, accepted by ApJ Letter
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