We present the first results from an ongoing survey for multiplicity among the bright stars using the Navy Precision Optical Interferometer (NPOI). We first present a summary of NPOI observations of known multiple systems, including the first detection of the companion of beta Scuti with precise relative astrometry, to illustrate the instrument's detection sensitivity for binaries at magnitude differences Delta m less than or similar to 3 over the range of angular separation 3-860 milliarcseconds (mas). A limiting Delta m(700) similar to 3.5 is likely for binaries where the component spectral types differ by less than two. Model fits to these data show good agreement with published orbits, and we additionally present a new orbit solution for one of these stars, sigma Her. We then discuss early results of the survey of bright stars at delta >= -20 degrees. This survey, which complements previous surveys of the bright stars using speckle interferometry, initially emphasizes bright stars of spectral types F0 through K2. We report observations of 41 stars of apparent visual magnitude m(V) <= 4.30, all having been observed on multiple nights. Analysis of these data produces fitted angular separations, position angles, and component magnitude differences for six previously known visual binaries. Three additional systems were examined as possible binaries, but no conclusive detection could be made. No evidence of close stellar companions within our detection limit of Delta m approximate to 3 was found for the remaining 32 stars observed; however, uniform-disk angular diameters are reported for 11 of the resolved stars in this last group.

The 62-6! and 52-5! E transitions of CH3OH have been mapped toward the Orion-KL region with an angular resolution of 3" and a frequency resolution of 12 kHz ( = 0.15 km s). There are at least 16 masers of flux density greater than 3 Jy. These are distributed in a 40" long crescent shaped region, extending from NW to SE around the “hot core.” The radial velocities and positions of some of these masers agree with a peak of the Sq-?! A transition of CH3OH, near 95 GHz. The most intense 62-6! E maser is unresolved; the flux density of 103 Jy and size of less than I'.T give a brightness temperature of greater than 10 K. The FWHP line widths, including the instrumental resolution, range from less than 0.15 km s (unresolved) to 1 km s. What have been previously cataloged as spatially extended individual masers are most likely blends of maser components with slightly different radial velocities. The E-type masers in Orion appear to cluster on scale sizes of less than 3". From a multiline analysis and our limits to maser source sizes, the column densities in the regions with the most intense lines are greater than 2 x 10 cm. The spatial distribution and the observed velocities suggest that the methanol masers arise from high column density gas adjacent to the Hot Core. The masers may be located very near the interface of the high-velocity outflow and the surrounding dense gas. Subject headings: ISM: kinematics and dynamics — ISM: molecules — ISM: structure — masers

The Navy Precision Optical Interferometer (NPOI) has two purposes: wide angle precise astrometry and high-resolution imaging, both at visible wavelengths. It operates with up to six 12-cm diameter apertures simultaneously, with baseline lengths (distances between array elements) from 16m to 79m, and disperses the combined light into 16 spectral channels. It has been operational since first fringes were found in 1994; six-beam operations began in 2001. The NPOI is undergoing upgrades in numerous areas: control system and data acquisition improvements, a second beam combiner, additional array stations for both longer and shorter baselines, and supplemental delay lines to improve sky coverage for the longer baselines. Future possibilities include the installation of four fixed 1.8m telescopes as well as up to six moveable lightweight 1.4m telescopes. Observing programs, including programs led by outside investigators, cover a broad range of stellar astrophysics as well as observations of geostationary satellites.

TANAMI (Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry) is a monitoring program to study the parsec-scale structures and dynamics of relativistic jets in active galactic nuclei (AGN) of the Southern Hemisphere with the Long Baseline Array and associated telescopes. Extragalactic jets south of -30 degrees declination are observed at 8.4 GHz and 22 GHz every two months at milliarcsecond resolution. The initial TANAMI sample is a hybrid radio and gamma-ray selected sample since the combination of VLBI and gamma-ray observations is crucial to understand the broadband emission characteristics of AGN.

We report progress on the United States Naval Observatory, Navy Prototype Optical Interferometer, Astrometric Catalog (UNAC). This catalog uses observations from eight astrometric observation runs (Jan. 2005 - Nov. 2009) at the Navy Prototype Optical Interferometer (NPOI). The goal of the first release of the UNAC is to provide an astrometric catalog of at least 100 bright (V < 6) stars with precise positions accurate to < 16 milliarcseconds. In this paper we report on some of the data processing methods used to obtain absolute astrometric positions from optical interferometer data. We also discuss plans for assessing the accuracy of our interferometrically derived absolute astrometric positions.

Submitted by Alan Marscher & Svetlana Jorstad (Boston U.), David Murphy, David Meier, Robert Preston, & Stephen Unwin (JPL), Kenneth Kellermann, Joan Wrobel, & Jonathan Romney (NRAO), Daniel Homan (Denison U.), Matthew Lister (Purdue U.), Glenn Piner (Whittier College), Lincoln Greenhill & Mark Reid (SAO), Gregory Taylor (U. New Mexico), Ann Wehrle (Space Science Institute), David Roberts (Brandeis U.), Anthony Readhead (Caltech), Markus Bottcher (Ohio U.), Markos Georganopoulos (U. Maryland), Steven Bloom (HampdenSydney Col.), Kenneth Johnston (US Naval Obs.), C.C. Cheung (NASA/GSFC), Thomas Krichbaum (Max-Planck-Institut fur Radioastronomie), M. Tsuboi (ISAS/JAXA, Japan), M. Inoue (NAOJ, Japan), S. Kameno (Kagoshima U., Japan)

The discovery of extrasolar planets is one of the greatest achievements of modern astronomy. The detection of planets that vary widely in mass demonstrates that extrasolar planets of low mass exist. In this paper, we describe a mission, called Darwin, whose primary goal is the search for, and characterization of, terrestrial extrasolar planets and the search for life. Accomplishing the mission objectives will require collaborative science across disciplines, including astrophysics, planetary sciences, chemistry, and microbiology. Darwin is designed to detect rocky planets similar to Earth and perform spectroscopic analysis at mid-infrared wavelengths (6-20 mum), where an advantageous contrast ratio between star and planet occurs. The baseline mission is projected to last 5 years and consists of approximately 200 individual target stars. Among these, 25-50 planetary systems can be studied spectroscopically, which will include the search for gases such as CO(2), H(2)O, CH(4), and O(3). Many of the key technologies required for the construction of Darwin have already been demonstrated, and the remainder are estimated to be mature in the near future. Darwin is a mission that will ignite intense interest in both the research community and the wider public.

The fundamental properties of the spacetime fabric of the local Universe cannot be determined without an observable, ultra-accurate standard of inertiality, which can be applied to any celestial object from high-z quasars to an exoplanet orbiting a nearby star. The only currently plausible method of setting such a standard is the establishment of an inertial reference frame based on grid stars anchored by extragalactic sources. An astronomical reference frame at 1 μas accuracy covering the entire sky will make it possible to observe and measure (rather than speculate) a wide range of physical and cosmological phenomena, essentially promoting new observational science. To name a few, it will allow for the first time the direct detection of the acceleration of the Solar System within the Milky Way and the Local Group toward the Virgo cluster. Meaningful experimental constraints will be put on the broadband power of the relic gravitational waves, to constrain the mass function of free-floating planets and comets, to resolve the puzzles of the origin of radiation from radio-loud quasars and the coronal activity in tight RS CVn binaries, and obtain more accurate tests of alternative gravitation theories. All of this will be accomplished by observing the motion and relative position of a large number of stars and distant "fixed" quasars.

We present the results of an experiment to image the interacting binary star beta Lyrae with data from the Navy Prototype Optical Interferometer using a differential phase technique to correct for the effects of the instrument and atmosphere on the interferometer phases. We take advantage of the fact that the visual primary of beta Lyrae and the visibility calibrator we used are both nearly unresolved and nearly centrally symmetric, and consequently have interferometric phases near zero. We used this property to correct for the effects of the instrument and atmosphere on the phases of beta Lyrae and to obtain differential phases in the channel containing the H alpha emission line. Combining the H alpha-channel phases with information about the line strength, we recovered complex visibilities and imaged the H alpha emission using standard radio interferometrymethods. Our images show the position of the H alpha-emitting regions relative to the continuum photocenter as a function of orbital phase, indicating a major axis line of nodes along Omega = 249 degrees +/- 4 degrees. The orbit is smaller than previously predicted, a discrepancy that can be alleviated if we assume that the system is at a larger distance, or if the stellar continuum contribution to the H alpha channel was underestimated. We do not detect a jet in the H alpha images, which may be due to the limited resolution of the observations along the direction perpendicular to the orbital plane. We find that the differential phase results are consistent with those obtained from a more standard analysis using squared visibilities (V(2)s) and closure phases, which also indicate an H alpha disk radius of 0.6 +/- 0.1 mas, and Delta V 1.30 +/- 0.1 and Delta R = 1.20 +/- 0.1 mag for the magnitude difference between the stars.

After a brief review of rotation among upper main sequence stars and von Zeipel’s vZ24 theory for the interiors, we describe our interferometric measurements of two bright A stars, Altair and Vega. The Navy Prototype Optical Interferometer (jointly operated by the US Naval Observatory, the Naval Research Laboratory and Lowell Observatory) which works at visible wavelengths has implemented baselines of sufficient length to initiate true imaging of the disks of the brightest A stars. We report here measurements of Altair, the third brightest A star in the sky. “Closure phase” techniques show that Altair deviates dramatically from a normal limb-darkened isk, indicating a strongly asymmetric intensity distribution. A oche model provides a good fit to the data, indicating that Altair is rotating at about 90% of its breakup (angular) velocity. We find that a gravity darkening law exponent appropriate for a radiative star is required by the observations and we describe the potential of this object for testing the assumption of solid body rotation throughout its envelope. We will also describe recent measurements of Vega which confirm the proposed interpretation of spectral line measurements indicating that this star is also rapidly rotating, but seen nearly pole on.

This paper provides an overview of technology development for the Terrestrial Planet Finder Interferometer (TPF-I). TPF-I is a mid-infrared space interferometer being designed with the capability of detecting Earth-like planets in the habitable zones around nearby stars. The overall technology roadmap is presented and progress with each of the testbeds is summarized.

The instrumental status of the Navy Prototype Optical Interferometer (NPOI) since the last SPIE meeting in 2006 is summarized. along with the results of the current science programs. The commissioning of new stations and plans for greatly increased telescope apertures arc discussed, along with other instrumentation upgrades. Recent results in the areas of wide-angle astrometry, binary starss, physical modeling Of the circumstellar disks of early-type stars, improvements in coherent averaging, and phase-reference imaging are also reviewed.

During the last few years, considerable effort has been directed towards large-scale (>> 1 Billion US) missions to detect and characterize earth-like planets around nearby stars, such as the Terrestrial Planet Finder Interferometer (TPF-I) and Darwin missions. However, technological and budgetary issues as well as shifting science priorities will likely prevent these missions from entering Phase A until the next decade. The secondary eclipse technique using the Spitzer Space Telescope has been used to directly measure the temperature and emission spectrum of extrasolar planets. However, only a small fraction of known extrasolar planets are in transiting orbits. Thus, a simplified nulling interferometer, which produces an artificial eclipse or occultation, and operates in the near- to mid-infrared (e.g. 3 to 8 or 10 microns), can characterize the atmospheres of this much larger sample of the known but non-transiting exoplanets. Many other scientific problems can be addressed with a system like this, including imaging debris disks, active galactic nuclei, and low mass companions around nearby stars. We discuss the rationale for a probe-scale mission in the600-800 Million range, which we name here as the Small Prototype Planet Finding Interferometer (SPPFI).

Over 500 counterparts of ICRF sources were observed during 24 deep CCD observing runs as part of the USNO CCD Astrograph Catalog (UCAC) project, providing a direct link to Tycho-2 stars. For some sources a positional accuracy of 10 mas is achieved. A sample of 12 extragalactic ICRF sources are being observed at the Naval Observatory Flagstaff Station (NOFS) 1.55-meter telescope over several years to monitor optical position stability. First high resolution imaging of selected sources are obtained at the Lick 3-meter AO system to correlate source structure with optical-radio centroid offsets. As part of the Space Interferometry Mission (SIM) preparatory science about 240 bright QSO's are monitored for photometric variability in B,V,R and I. The USNO Robotic Astrometric Telescope (URAT) will be able to combine deep CCD imaging of all ICRF2 target areas and millions of compact galaxies with a stellar, astrometric, all-sky survey of multiple epochs.