E. H. Wishnow

A Systematic Change with Time in the Size of Betelgeuse

The diameter of Betelgeuse (α Orionis) has been measured at a wavelength of 11.15 μm using the Infrared Spatial Interferometer over the past 15 years. During this 1993-2009 time period the stars size has decreased systematically by 15%.

The Nonspherical Shape of Betelgeuse in the Mid-Infrared

Three-telescope interferometric observations from the Infrared Spatial Interferometer (ISI) are reported at spatial frequencies that resolve the size and shape of the star Betelgeuse (α Ori) at a wavelength of 11.15 μm with a bandwidth of 0.18 cm-1. The data include closure phase measurements, the first such measurements of a stellar disk in the mid-infrared. The data indicate a clear asymmetry of the stellar surface at these wavelengths. Mechanisms for generating the observed asymmetry via an elliptical shape or a hot spot near the southern limb of the star are discussed.

THE DUST SURROUNDING W HYDRAE

Dust shells surrounding the star W Hydrae have been resolved and measured at a wavelength of 11.15 ?m, using the Infrared Spatial Interferometer. Two different models for the star and dust shells are used to fit the data, one for recent data taken over short time spans and another for the combined data of 15 years. Modeling of the data shows the presence of two dust shells with diameters of approximately 100 mas and 250 mas. The inner dust shell is seen to expand over the year 2008. The observations are consistent with a stellar diameter of 50 mas.

THE NON-UNIFORM, DYNAMIC ATMOSPHERE OF BETELGEUSE OBSERVED AT MID-INFRARED WAVELENGTHS

We present an interferometric study of the continuum surface of the red supergiant star Betelgeuse at 11.15 μm wavelength, using data obtained with the Berkeley Infrared Spatial Interferometer each year between 2006 and 2010. These data allow an investigation of an optically thick layer within 1.4 stellar radii of the photosphere. The layer has an optical depth of ∼1 at 11.15 μm, and varies in temperature between 1900 K and 2800 K and in outer radius between 1.16 and 1.36 stellar radii. Electron–hydrogen-atom collisions contribute significantly to the opacity of the layer. The layer has a non-uniform intensity distribution that changes between observing epochs. These results indicate that large-scale surface convective activity strongly influences the dynamics of the inner atmosphere of Betelgeuse and mass-loss processes.

Observation of a Burst of High-Velocity Dust from α Herculis

Interferometric observations of α Herculis at a wavelength of 11.15 μm over the period 1989-2004 show large visibility variations. These variations are interpreted as an ejection of approximately 10-6 M☉ of material in 1990 that has subsequently expanded and dissipated. The expansion rate is approximately 75 km s-1, much larger than previous observations. No substantial material has been emitted during the subsequent 14 years.

ASYMMETRIES AND OUTFLOWS IN THE CIRCUMSTELLAR DUST OF MIRA A

Asymmetries and motions in the dust shell surrounding Mira A (o Ceti) are reported. Measurements were taken with the UC Berkeley Infrared Spatial Interferometer (ISI), a three-element interferometer operating at 11.15 μm. At the time of these observations, it was in a linear, east-west configuration with a maximum baseline of 12 m and thus had a resolution of better than 100 mas. Three years of data (2003-2005) are presented and permit observation of the movement of dust shells over time. Fits are made to the visibility and closure-phase curves, which are then used to create one-dimensional profiles of the dust shells. Asymmetries in the circumstellar dust have been observed, and several possible explanations for these asymmetries are explored.

Submillimeter spectrum of low-temperature hydrogen - The pure translational band of H2 and the R(0) line of HD

The pure translational absorption spectrum of hydrogen gas has been measured from 20 to 100 cm −1 at temperatures in the range 24-37 K. Superposed on the broad translational band is the sharp rotational line R(0) of HD, present in the gas in natural abundance. From the intensity of the line, the electric dipole moment is determined to be (0.81 ± 0.05) × 10 -3 debye. The measurements are of relevance to the infrared opacity and to the D/H ratio of the atmospheres of the giant planets

A method for generating a synthetic spectrum within Zemax

A method using non-sequential Zemax to produce a pixelated synthetic spectrum is described. This simulation was developed for the Keck Planet Finder (KPF) instrument, and will prove useful for engineering performance analyses (stability, stray light, order cross-talk, distortion, etc.). It has also provided a set of synthetic spectra to be used during the development of the data pipeline. Various aspects concerning the construction of the spectrum are described, including: converting a model from sequential to non-sequential Zemax, the creation of Zemax coating files for echelle blaze functions, and the generation of spectrum source files (solar, thorium-argon, incandescent, Fabry-Perot etalon and laser frequency comb).

Collimated focal ratio degradation testing for highly multiplexed fiber systems-an improvement to a standard test.

A simple method for determining the focal ratio degradation of optical fibers has been developed. The method involves splitting the light from the test fiber and recording ring patterns that have traveled over two different, and known, optical paths. This new method will be valuable for testing many fibers as will be needed for new multiobject astronomical spectrographs.

The Evolving Shapes of o Ceti and R Leonis

The sizes and shapes of the stars o Ceti and R Leonis have been measured in the mid-infrared. The observations were made using the UC Berkeley Infrared Spatial Interferometer (ISI), and they reveal details about the size, shape and asymmetry of both stars over several epochs in 2006. The star o Ceti appears to be rather symmetric, while the shape of R Leonis appears more consistent with a uniform disk plus a point source that provides approximately 9% additional intensity somewhere in the southern half of the star.