Geometry of Deformed Boson Algebras

Phase-space realisations of an infinite parameter family of quantum deformations of the boson algebra in which the $q$-- and the $qp$--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 $0\rlap.{''}3$ 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, $T(r)\propto r^{-0.5}$ and $\Sigma(r) \propto r^{-1}$. These properties are consistent with an irradiated gaseous accretion disk of mass $\sim0.03~{\rm M_{\odot}}$ with an accretion rate $\sim10^{-8}~{\rm M_{\odot}yr^{-1}}$ and viscosity parameter $\alpha = 0.01$. 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