We present two results on multiqubit Werner states, defined to be those states that are invariant under the collective action of any given single-qubit unitary that acts simultaneously on all the qubits. Motivated by the desire to characterize entanglement properties of Werner states, we construct a basis for the real linear vector space of Werner invariant Hermitian operators on the Hilbert space of pure states; it follows that any mixed Werner state can be written as a mixture of these basis operators with unique coefficients. Continuing a study of "polygon diagram" Werner states constructed in earlier work, with a goal to connect diagrams to entanglement properties, we consider a family of multiqubit states that generalize the singlet, and show that their 2-qubit reduced density matrices are separable.

David W. Lyons Cristina Mullican Adam Rilatt Jack D. Putnam

This article provides a brief overview of the Spitzer Space Telescope and discusses its initial scientific results on galactic and solar system science.

M. Werner G. Fazio G. Rieke T. Roellig D. Watson

We have used the Keck I telescope to resolve at mid-infrared wavelengths the dust emission from HD 56126 (IRAS 07134+1005), a post-Asymptotic Giant Branch carbon star with a detached dust shell. The gross morphology of the image can be explained by a strong wind which started to die about 1500 years ago. If the star had an effective temperature near 2600 K when it was losing a large amount of mass, then during the past 1500 years, the average value of dT/dt has been +2.2 K/yr. With such a time variation of the effective temperture of the star, the 11.7 micron image can be approximately reproduced if the mass loss rate varied as T^(-8.26), as proposed in recent models for dust-driven winds. Since the mass loss rate appears to be very sensitive to the effective temperature of the star, we speculate that the observed deviations from spherical symmetry of the dust shell can be explained by plausible variations in the surface temperature of the mass-losing star caused by rotation and/or magnetic fields.

M. Jura C. Chen M. W. Werner

We have used the Owens Valley Radio Observatory Millimeter Array to obtain a map of the J = (1-0) CO emission from the circumstellar shell around HD 179821, a highly evolved G-type star which will probably explode as a supernova in the next 100,000 yr. Very approximately, the gas presents as a circular ring with azimuthal variations in the CO brightness by about a factor of 2. Until about 1600 years ago, the star was a red hypergiant losing about 0.0003 M(Sun)/yr at an average outflow speed of 32 km/s. We propose that when HD 179821 explodes as a supernova, it may resemble Kepler's supernova remnant and thus some of the anisotropies in supernova remnants may be intrinsic. If the factors which cause the anisotropic mass loss in HD 179821 persist to the moment when the star explodes as a supernova, the newly-born pulsar may receive a momentum "kick" leading to a space motion near 700 km/s. Independent of the angular asymmetries, the radially detached shell around HD 179821 may be representative of environments which produce dust echoes from gamma-ray bursts.

M. Jura T. Velusamy M. W. Werner

We report on the identification of the lens responsible for microlensing event MACHO-LMC-20. As part of a \textit{Spitzer}/IRAC program conducting mid-infrared follow-up of the MACHO Large Magellanic Cloud microlensing fields, we discovered a significant flux excess at the position of the source star for this event. These data, in combination with high resolution near-infrared \textit{Magellan}/PANIC data has allowed us to classify the lens as an early M dwarf in the thick disk of the Milky Way, at a distance of $\sim 2$ kpc. This is only the second microlens to have been identified, the first also being a M dwarf star in the disk. Together, these two events are still consistent with the expected frequency of nearby stars in the Milky Way thin and thick disks acting as lenses.

Nitya Kallivayalil Brian M. Patten Massimo Marengo Charles Alcock Michael W. Werner Giovanni G. Fazio

We present infrared and millimeter observations of Barnard 335, the prototypical isolated Bok globule with an embedded protostar. Using Spitzer data we measure the source luminosity accurately; we also constrain the density profile of the innermost globule material near the protostar using the observation of an 8.0 um shadow. HHT observations of 12CO 2 --> 1 confirm the detection of a flattened molecular core with diameter ~10000 AU and the same orientation as the circumstellar disk (~100 to 200 AU in diameter). This structure is probably the same as that generating the 8.0 um shadow and is expected from theoretical simulations of collapsing embedded protostars. We estimate the mass of the protostar to be only ~5% of the mass of the parent globule.

Amelia M. Stutz Mark Rubin Michael W. Werner George H. Rieke John H. Bieging Jocelyn Keene Miju Kang Yancy L. Shirley K. Y. L. Su Thangasamy Velusamy David J. Wilner

Stabilizing the gain of a radio astronomy receiver is of great importance for sensitive radio intensity mapping. In this paper we discuss a stabilization method using a continuous-wave reference signal injected into the signal chain and tracked in a single channel of the spectrometer to correct for the gain variations of the receiver. This method depends on the fact that gain fluctuations of the receiver are strongly correlated across the frequency band, which we can show is the case for our experimental setup. This method is especially suited for receivers with a digital back-end with high spectral resolution and moderate dynamic range. The sensitivity of the receiver is unaltered except for one lost frequency channel. We present experimental results using a new 4-8.5 GHz receiver with a digital back-end that shows substantial reduction of the 1/ f noise and the 1/ f knee frequency.

Alexander W. Pollak Christian M. Holler Michael E. Jones Angela C. Taylor

The O VIII phenomenon describes the occurrence of ultra-high ionization absorption lines of the CNO elements (e.g. O VIII, N VII, C VI, and even Ne X) in the optical spectra hot of DO WDs.

K. Werner S. Dreizler J. W. Kruk M. L. Sitko

We try to understand recent data on proton-proton and deuteron-gold collisions at RHIC, employing a modified parton model approach.

K. Werner F. M. Liu T. Pierog

Fusion is defined for arbitrary lowest weight representations of $W$-algebras, without assuming rationality. Explicit algorithms are given. A category of quasirational representations is defined and shown to be stable under fusion. Conjecturally, it may coincide with the category of representations of finite quantum dimensions.

Werner Nahm