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Using a wavelength-generalized version of the Garstang (1991) model, we evaluate overhead sky glow as a function of distance up to 300 km, from a variety of lamp types, including common gas discharge lamps and several types of LED lamps. We conclude for both professional, and especially cultural (visual), astronomy, that low-pressure sodium and narrow-spectrum amber LED lamps cause much less sky glow than all broad-spectrum sources., Published in Highlights of Astronomy, v16 p756, 2015. Presented at the XXVIIIth IAU General Assembly, Aug 2012. Prepared in collaboration with the Max-Planck-Institut fur Astronomie, Heidelberg, Germany, the Planetary Science Institute, Tucson, AZ, and the National Park Service, Bishop, CA.

Astrometric measurements are presented for seven nearby stars with previously detected planets: six M dwarfs (GJ 317, GJ 667C, GJ 581, GJ 849, GJ 876, and GJ 1214) and one K dwarf (BD-10 -3166). Measurements are also presented for six additional nearby M dwarfs without known planets, but which are more favorable to astrometric detections of low mass companions, as well as three binary systems for which we provide astrometric orbit solutions. Observations have baselines of 3 to 13 years, and were made as part of the RECONS long-term astrometry and photometry program at the CTIO/SMARTS 0.9 m telescope. We provide trigonometric parallaxes and proper motions for all 16 systems, and perform an extensive analysis of the astrometric residuals to determine the minimum detectable companion mass for the 12 M dwarfs not having close stellar secondaries. For the six M dwarfs with known planets, we are not sensitive to planets, but can rule out the presence of all but the least massive brown dwarfs at periods of 2 12 years. For the six more astrometrically favorable M dwarfs, we conclude that none have brown dwarf companions, and are sensitive to companions with masses as low as 1 M(jup) for periods longer than two years. These results complement previously published M dwarf planet occurrence rates by providing astrometrically determined upper mass limits on potential super-Jupiter companions at orbits of two years and longer. As part of a continuing survey, these results are consistent with the paucity of super-Jupiter and brown dwarf companions we find among the over 250 red dwarfs within 25 pc observed longer than five years in our astrometric program., Published in The Astronomical Journal, v148 n91 p1-12, November 2014. The original document contains color images.

We present in this paper the data collection and reduction for the YSOVAR(Young Stellar Object VARiability) programs, representing nearly 800 hr of Spitzer time studying the variability of young stars in 12 different clusters. We also describe the assembly of broad collections of ancillary data for these clusters. There are approximately 29,000 unique objects of any sort matched to 39,000 [3.6] or [4.5] light curves in the YSOVAR data set. The goals of the broader YSOVAR program include: to obtain the first extensive mid-infrared time series photometry of young stars to help reveal the structure of the inner disc region of YSOs, provide new constraints on accretion and extinction variability, assess timescales of mid-IR variability from seconds to years, identify new young eclipsing binaries, help identify new very low-mass substylar members of the surveyed clusters, constrain the short- and long-term stability of hot spots of the surfaces of YSOs, and determine rotational periods for objects too embedded for such monitoring in the optical. In this paper, we set the stage for several planned papers., Published in The Astronomical Journal v148 n92 Nov 2014.

Determining the distance to the open cluster M29 (NGC 6913) has proven difficult, with distances determined by various authors differing by a factor of two or more. To solve this problem, we have initiated a new photometric investigation of the cluster in the Vilnius seven-color photometric system, supplementing it with available data in the BV and JHKs photometric systems and spectra of the nine brightest stars of spectral classes O and B. Photometric spectral classes and luminosities of 260 stars in a 15' x 15' area down to V = 19 mag are used to investigate the interstellar extinction run with distance and to estimate the distance of the Great Cygnus Rift, approximately 800 pc. The interstellar reddening law in the optical and near-infrared regions is found to be close to normal, with the ratio of extinction to color excess R(BV) = 2.87. The extinction A(V) of cluster members is between 2.5 and 3.8 mag, with a mean value of 2.97 mag, or E(B-V) = 1.03. The average distance of eight stars of spectral types O9 B2 is 1.54 +/- 0.15 kpc. Two stars from the seven brightest stars are field stars: HDE 229238 is a background B0.5 supergiant and HD 194378 is a foreground F star. In the intrinsic color magnitude diagram, seven fainter stars of spectral classes B3 B8 are identified as possible members of the cluster. The 15 selected members of the cluster of spectral classes O9 B8, together with the isochrones from the Padova database, give the age of the cluster as 5 +/- 1 Myr., The Astronomical Journal, 148:89 (9pp), 2014 November. The original document contains color images.

We discuss the status of coherent integration with the Navy Prototype Optical Interferometer (NPOI) Armstrong et al. (1998). Coherent integration relies on being able to phase reference interferometric measurements, which in turn relies on making measurements at multiple wavelengths. We first discuss the generalized group-delay approach, then the meaning of the resulting complex visibilities and then demonstrate how coherent integration can be used to perform very precise measurement of stellar diameters. The phase of the complex visibility is particularly attractive as a data product because it is not biased in the same way that visibility amplitudes are. We demonstrate how single-baseline phases can be used to make accurate measurements of magnitude differences and separations of binary stars., Published in Resolving the Future of Astronomy with Long-Baseline Interferometry ASP Conference Series, v487, 2014. The original document contains color images. Prepared in collaboration with the New Mexico Institute of Mining and Technology, Socorro, and Seabrook Engineering, Seabrook, MD. Sponsored in part by the Oceanographer of the Navy.

Determining the distance to the open cluster M29 (NGC 6913) has proven difficult, with distances determined by various authors differing by a factor of two or more. To solve this problem, we have initiated a new photometric investigation of the cluster in the Vilnius seven-color photometric system, supplementing it with available data in the BV and JHKs photometric systems and spectra of the nine brightest stars of spectral classes O and B. Photometric spectral classes and luminosities of 260 stars in a 15 ' 15 ' area down to V = 19 mag are used to investigate the interstellar extinction run with distance and to estimate the distance of the Great Cygnus Rift, 800 pc. The interstellar reddening law in the optical and near-infrared regions is found to be close to normal, with the ratio of extinction to color excess RBV = 2.87. The extinction AV of cluster members is between 2.5 and 3.8 mag, with a mean value of 2.97 mag, or EB V = 1.03. The average distance of eight stars of spectral types O9 B2 is 1.54 0.15 kpc. Two stars from the seven brightest stars are field stars: HDE 229238 is a background B0.5 supergiant and HD 194378 is a foreground F star. In the intrinsic color magnitude diagram, seven fainter stars of spectral classes B3 B8 are identified as possible members of the cluster. The 15 selected members of the cluster of spectral classes O9 B8 plotted on the log L/LO versus log Teff diagram, together with the isochrones from the Padova database, give the age of the cluster as 5 1 Myr., Published in the Astronomical Journal, v148 n89, Nov 2014. The original document contains color images. Prepared in collaboration with the Institute of Theoretical Physics and Astronomy, Vilnius University, Vilnius, Lithuania, the Vatican Observatory Research Group, Steward Observatory, Tucson, AZ, the INAF Astronomical Observatory of Padova, Asiago, Italy, the Space Telescope Science Institute, Baltimore, MD, and the University School Ignatianum, Cracow, Poland.

Surveys of massive O- and B-type stars suggest a significantly higher multiplicity fraction than for Solar-type primaries, but coverage over the complete separation range is incomplete. Understanding the distribution of the separation of these companions is important when considering the formation and survivability of disks and proto-planetary systems around these massive stars. We detail the status of an ongoing volume-limited (D 75 parsecs) multiplicity survey of B-type stars covering this important separation range between 1 and 15AU, complemented by AO observations to resolve wider companions. The angular resolution provided by the Navy Prototype Optical Interferometer (NPOI) allows for the detection of close (5 700mas) binaries with a magnitude difference reaching delta R of 3. With our large, unbiased volume-limited sample of 69 targets, these observations will allow for the first constraint on the multiplicity of these massive stars over this separation range. This survey will be complementary to both previous spectroscopic surveys and speckle interferometry observations. Newly resolved companions within this study will make ideal targets for follow-up interferometric observations to detect orbital motion and determine their orbital parameters. Future interferometers will extend this work to closer, fainter companions around both these targets and intrinsically fainter A-type stars., The original document contains color images. Published in Resolving the Future of Astronomy with Long-Baseline Interferometry, ASP Conference Series, v487, 2014. Prepared in collaboration with the College of Engineering, Mathematics and Physical Sciences, School of Physics, University of Exeter, Exeter, UK, the Lowell Observatory, Flagstaff, AZ, the National Research Council Canada, Herzberg Institute of Astrophysics, Victoria, BC, Canada, and the University of California Observatories/Lick Observatory, University of California, Santa Cruz. Sponsored in part by the Oceanographer of the Navy.

The latest science results from the Navy Prototype Optical Interferometer (NPOI) are summarized. Major areas reviewed include 1) recent results on NPOI imaging and orbits of radio star systems, with emphasis on the delineation of the Algol triple system; 2) NPOI observations that complement speckle interferometry programs by measurement of those portions of the orbits inaccessible at the resolution of speckle; 3) revised orbits for systems of particular astrophysical interest such as delta Sco; and 4) applications of advanced coherent integration techniques to the determination of ultraprecise stellar angular diameters in exoplanet and other systems., Published in Resolving the Future of Astronomy with Long-Baseline Interferometry, ASP Conference Series, v487, 2014. The original document contains color images. Sponsored in part by the Oceanographer of the Navy.

We present new BVIC photometry for 350 Pleiades proper motion members with 9V 17. Importantly, our new catalog includes a large number of K- and early M-type stars, roughly doubling the number of low-mass stars with well-calibrated Johnson/Cousins photometry in this benchmark cluster. We combine our new photometry with existing photometry from the literature to define a purely empirical isochrone at Pleiades age ( 100 Myr) extending from V = 9 to 17. We use the empirical isochrone to identify 48 new probable binaries and 14 likely nonmembers.The photometrically identified single stars are compared against their expected positions in the color magnitude diagram (CMD). At 100 Myr, the mid K and early M stars are predicted to lie above the zero-age main sequence (ZAMS) having not yet reached the ZAMS.We find in the B V versus V CMDthat mid K and early M dwarfs are instead displaced below (or blueward of) the ZAMS. Using the stars previously reported rotation periods, we find a highly statistically significant correlation between rotation period and CMD displacement, in the sense that the more rapidly rotating stars have the largest displacements in the B V CMD., The Astronomical Journal, v148 n30, p1-10, 2014. The original document contains color images.

We present the Coordinated Synoptic Investigation of NGC 2264, a continuous 30 day multi-wavelength photometric monitoring campaign on more than 1000 young cluster members using 16 telescopes. The unprecedented combination of multi-wavelength, high-precision, high-cadence, and long-duration data opens a new window into the time domain behavior of young stellar objects. Here we provide an overview of the observations, focusing on results from Spitzer and CoRoT. The highlight of this work is detailed analysis of 162 classical T Tauri stars for which we can probe optical and mid-infrared flux variations to 1% amplitudes and sub-hour timescales. We present a morphological variability census and then use metrics of periodicity, stochasticity, and symmetry to statistically separate the light curves into seven distinct classes, which we suggest represent different physical processes and geometric effects. We provide distributions of the characteristic timescales and amplitudes and assess the fractional representation within each class. The largest category (20%) are optical dippers with discrete fading events lasting 1-5 days. The degree of correlation between the optical and infrared light curves is positive but weak; notably, the independently assigned optical and infrared morphology classes tend to be different for the same object. Assessment of flux variation behavior with respect to (circum)stellar properties reveals correlations of variability parameters with Ha emission and with effective temperature. Overall, our results point to multiple origins of young star variability, including circumstellar obscuration events, hot spots on the star and for disk, accretion bursts, and rapid structural changes in the inner disk., Published in The Astronomical Journal, v147 n82 47pp, April 2014. The original document contains color images.

The Navy Precision Optical Interferometer, located near Flagstaff, Arizona, is a ground-based interferometer that collects, transports, and modulates stellar radiation from up to six primary flat collectors, known as siderostats, through a common vacuum relay system to a combiner. In the combiner, the modulated beams are superimposed, fringes obtained, and data recorded for further analysis to produce precise star positions or stellar details. The current number of observable stellar objects for the astrometric interferometer can increase from 6000 to at least 47,000 with the addition of full-aperture 20-deg down-tilting beam compressors in each optical train. Such an aperture increase, from the current 12.5 to 35 cm, opens the sky to many additional and fainter stars. Engineering analysis of our beam compressor primary mirror shows that the maximum allowable sag, 21 nm, occurs prematurely at 2.8-deg down-tilt angle. Furthermore, at the operational down-tilt angle of 20 deg, the wavefront deformation increases to 155 nm. We present a finite element analysis technique and design modification concept to reduce tilt-induced deformation on the mirror surface. This work is a first pass to determine the feasibility for a mechanical solution path forward. From this analysis, we found that four outwardly applied 17.8-N forces on the rear surface of the mirror could reduce sag from 155 to 32 nm at 20-deg down-tilt angle., Published in Optical Engineering v53 n1 015102-1 - 015102-9. The original document contains color images.

Although the processes involved in single star formation have a wide variety of observational and theoretical constraints (e.g., McKee & Ostriker 2007), the complex physics involved in the formation of binary and especially multiple star systems is much less understood (e.g., Halbwachs et al. 2003; Tokovinin 2008; Duchene & Kraus 2013). Prompt fragmentation of a collapsing prestellar core is favored as setting the initial conditions for multiple star systems (e.g., Tohline 2002), though how this depends upon the initial conditions of the cloud core (e.g., metallicity, mass, etc.) is not well understood. Once initial fragments form, subsequent fragmentation (possibly within a disk), accretion from the remnant cloud core, N-body dynamics, and possibly orbital migration have been proposed to play competing roles in setting the final properties of multiple star systems (e.g., Bate 2000; Bonnell 2001; Delgado-Donate et al., Pub. in The Astronomical Journal, v147 n26 1-9p, Feb 2014. The original document contains color images.

Context. Binary post-asymptotic giant branch (post-AGB) stars are interesting laboratories to study both the evolution of binaries as well as the structure of circumstellar disks. Aims. A multiwavelength high angular resolution study of the prototypical object 89 Herculis is performed with the aim of identifying and locating the different emission components seen in the spectral energy distribution. Methods. A large interferometric data set, collected over the past decade and covering optical and near-infrared wavelengths, is analyzed in combination with the spectral energy distribution and flux-calibrated optical spectra. In this first paper only simple geometric models are applied to fit the interferometric data. Combining the interferometric constraints with the photometry and the optical spectra, we re-assess the energy budget of the post-AGB star and its circumstellar environment. Results. We report the first (direct) detection of a large (35-40%) optical circumstellar flux contribution and spatially resolve its emission region. Given this large amount of reprocessed and/or redistributed optical light, the fitted size of the emission region is rather compact and fits with(in) the inner rim of the circumbinary dust disk. This rim dominates our K band data through thermal emission and is rather compact, emitting significantly already at a radius of twice the orbital separation. We interpret the circumstellar optical flux as due to a scattering process, with the scatterers located in the extremely puffed-up inner rim of the disk and possibly also in a bipolar outflow seen pole-on. A non-local thermodynamic equilibrium gaseous origin in an inner disk cannot be excluded but is considered highly unlikely. Conclusions. This direct detection of a significant amount of circumbinary light at optical wavelengths poses several significant questions regarding our understanding of both post-AGB binaries and the physics in their circumbinary disks., Published in Astronomy & Astrophysics, v559, A111, 2013. The original document contains color images.

Magnitudes and color indices in the Vilnius seven-color system were determined for 1752 stars down to V = 19.5 mag in the direction of the open cluster M 29 (NGC 6913). The region is centered at R.A = 20:24, DEC = +38:30 (J2000) and covers an area of 1.5 sq. deg. The photometric data are used to classify about 70% of stars in spectral and luminosity classes and peculiarity types., Published in Baltic Astronomy, v22 p181-221, 2013.

Aims. A close companion of Orionis A was found in 2000 with the Navy Precision Optical Interferometer (NPOI), and shown to be a physical companion. Because the primary is a supergiant of type O, for which dynamical mass measurements are very rare, the companion was observed with NPOI over the full 7-year orbit. Our aim was to determine the dynamical mass of a supergiant that, due to the physical separation of more than 10 AU between the components, cannot have undergone mass exchange with the companion. Methods. The interferometric observations allow measuring the relative positions of the binary components and their relative brightness. The data collected over the full orbital period allows all seven orbital elements to be determined. In addition to the interferometric observations, we analyzed archival spectra obtained at the Calar Alto, Haute Provence, Cerro Armazones, and La Silla observatories, as well as new spectra obtained at the VLT on Cerro Paranal. In the high-resolution spectra we identified a few lines that can be associated exclusively to one or the other component for the measurement of the radial velocities of both. The combination of astrometry and spectroscopy then yields the stellar masses and the distance to the binary star. Results. The resulting masses for components Aa of 14.0 2.2 M sun and Ab of 7.4 1.1 M sun are low compared to theoretical expectations, with a distance of 294 21 pc which is smaller than a photometric distance estimate of 387 54 pc based on the spectral type B0III of the B component. If the latter (because it is also consistent with the distance to the Orion OB1 association) is adopted, the mass of the secondary component Ab of 14 3 M sun would agree with classifying a star of type B0.5IV. It is fainter than the primary by about 2.2 0.1 magnitudes in the visual. The primary mass is then determined to be 33 10 M sun., Published in Astronomy & Astrophysics, v554 A52, 2013. The original document contains color images. Prepared in cooperation with European Southern Observatory, Garching, Germany, European Southern Observatory, Santiago, Chile, Dr. Karl Remeis Sternwarte & ECAP, University of Erlangen-Nuremberg, Bamberg, Germany, the Institute of Astro- and Particle Physics, University of Innsbruck, Innsbruck, Austria, ZAH, Landessternwarte Heidelberg-K nigstuhl, Heidelberg, Germany, and the Lowell Observatory, Flagstaff, AZ.

Observations of binary stars are the bread-and-butter for optical interferometers. An easy exploit for the unrivaled angular resolution of long baseline interferometers, the measurement of the orbits of double-lined spectroscopic binaries affords the determination of fundamental parameters of stars as well as their distance from Earth. Interferometry thus extends the reach of using spectroscopic binaries to non-eclipsing pairs, as a special but unlikely geometry for seeing eclipses, which also allow the determination of high-precision stellar masses, is no longer required., Published in Central European Astrophysics Bulletin v37 n1 p127-135, 2012. The original document contains color images. ISSN 1845-8319.

We present results from an ongoing multiwavelength radial velocity (RV) survey of the Taurus-Auriga star-forming region as part of our effort to identify pre-main-sequence giant planet hosts. These 1-3 Myr old T Tauri stars present significant challenges to traditional RV surveys. The presence of strong magnetic fields gives rise to large, cool star spots. These spots introduce significant RV jitter which can mimic the velocity modulation from a planet-mass companion. To distinguish between spot-induced and planet-induced RV modulation, we conduct observations at 6700 Angstroms and 2.3 microns and measure thewavelength dependence (if any) in theRVamplitude. CSHELL observations of the known exoplanet host Gl 86 demonstrate our ability to detect not only hot Jupiters in the near-infrared but also secular trends from more distant companions. Observations of nine very young stars reveal a typical reduction in RV amplitude at the longer wavelengths by a factor of 2-3. While we cannot confirm the presence of planets in this sample, three targets show different periodicities in the two wavelength regions. This suggests different physical mechanisms underlying the optical and the K-band variability., The Astrophysical Journal, 761:164 (17pp), 2012 December 20. The original document contains color images.

We report parallax measurements for 70 ultracool dwarfs (UCDs) including 11 late-M, 32 L, and 27 T dwarfs. In this sample, 14 M and L dwarfs exhibit low surface gravity features, 6 are close binary systems, and 2 are metal-poor subdwarfs. We combined our new measurements with 114 previously published UCD parallaxes and optical mid- IR photometry to examine trends in spectral-type/absolute magnitude, and color color diagrams. We report new polynomial relations between spectral type and MJHK. Including resolved L/T transition binaries in the relations, we find no reason to differentiate between a bright (unresolved binary) and a faint (single source) sample across the L/T boundary. Isolating early T dwarfs, we find that the brightening of T0 T4 sources is prominent inMJ where there is a [1.2 1.4] mag difference., The original document contains color images. The Astrophysical Journal, 752:56 (22pp), 2012 June 10

The highly eccentric Be binary system δ Sco reached periastron during early 2011 July, when the distance between the primary and secondary was a few times the size of the primary disk in the H band. This opened a window of opportunity to study how the gaseous disks around Be stars respond to gravitational disturbance. We first refine the binary parameters with the best orbital phase coverage data from the Navy Precision Optical Interferometer. Then we present the first imaging results of the disk after the periastron, based on seven nights of five telescope observations with the MIRC combiner at the CHARA array. We found that the disk was inclined 27 deg.6 +- 6 deg.0 from the plane of the sky, had a half-light radius of 0.49 mas (2.2 stellar radii), and consistently contributed 71.4% +- 2.7% of the total flux in the H band from night to night, suggesting no ongoing transfer of material into the disk during the periastron. The new estimation of the periastron passage is UT 2011 July 3 07:00 +- 4:30. Re-analysis of archival VLTI-AMBER interferometry data allowed us to determine the rotation direction of the primary disk constraining it to be inclined either 119 deg or 171 deg relative to the orbital plane of the binary system. We also detect inner disk asymmetries that could be explained by spot-like emission with a few percent of the disk total flux moving in Keplerian orbits, although we lack sufficient angular resolution to be sure of this interpretation and cannot yet rule out spiral density waves or other more complicated geometries., Published in Astrophysical Journal, v757 n29 p1-17, 20 September 2012. The original document contains color images.

The Defense Advanced Research Projects Agency (DARPA) has constructed the 3.5-meter Space Surveillance Telescope (SST) on North Oscura Peak in the White Sands Missile Range. The primary goal of the SST program is the monitoring of the Earth?s geosynchronous belt for microsatellites and debris. At the end of DARPA?s demonstration period, the SST will undergo an Air Force Space Command utilization study. The DARPA press release announcing the existence of SST included the words ?SST may also provide the science community a unique asset for astronomical surveys?. This paper presents the preliminary results from rapid cadence science collections (1-sec integrations every 2.5-sec) of a 9.5 square degree area centered near the open cluster M67., Presented at the Annual Advanced Maui Optical and Space Surveillance (AMOS) Technologies Conference (13th) held in Maui, Hawaii on 11-14 September 2012. The original document contains color images.

By selecting astrometric and photometric data from the Sloan Digital Sky Survey (SDSS), the Lepine & Shara Proper Motion North Catalog (LSPM-North), the Two Micron All Sky Survey (2MASS), and the USNO-B1.0 catalog, we use a succession of methods to isolate white dwarf (WD) candidates for follow-up spectroscopy. Our methods include reduced proper motion diagram cuts, color cuts, and atmospheric model adherence. We present spectroscopy of 26WDs obtained from the CTIO 4 m and APO 3.5 m telescopes. Additionally, we confirm 28WDs with spectra available in the SDSS DR7 database but unpublished elsewhere, presenting a total of 54 WDs. We label one of these as a recovered WD while the remaining 53 are new discoveries. We determine physical parameters and estimate distances based on atmospheric model analyses. Three new WDs are modeled to lie within 25 pc. Two additional WDs are confirmed to be metal-polluted (DAZ). Follow-up time series photometry confirms another object to be a pulsating ZZ Ceti WD., Published in The Astronomical Journal, 143:103 (12pp), April 2012. The original document contains color images.

We present new orbital measurements of the pre-main-sequence triple system, V807 Tau, using adaptive optics imaging at the Keck Observatory. We computed an orbit for the close pair, V807 Tau Ba--Bb, with a period of 12.312 + or - 0.058 years and a semi-major axis of 38.59 + or - 0.16 mas. By modeling the center of mass motion of the components in the close pair relative to the wide component, V807 Tau A, we measured a mass ratio of 0.843 + or - 0.050 for Bb/Ba. Combined with the total mass from the relative orbit, we derived individual masses of MBa = 0.564+ or - 0.018 (d/140 pc) cubed solar mass and MBb = 0.476 + or - 0.017 (d/140 pc) cubed solar mass at an average distance of 140 pc to the Taurus star-forming region. We computed spectral energy distributions to determine the luminosities of the three components. We also measured their spectral types, effective temperatures, and rotational velocities based on spatially resolved spectra obtained at the Keck Observatory. If the rotational axes are aligned, then the projected rotational velocities imply that V807 Tau Ba and Bb are rotating much faster than V807 Tau A. The uncertainty in the stellar effective temperatures and distance to the system currently limit the comparison of our dynamical mass measurements with predictions based on evolutionary tracks for pre-main-sequence stars. We also report preliminary results from a program to map the 3.6 cm radio emission from V807 Tau using the Very Long Baseline Array. With continued monitoring, these observations will provide a precise parallax for placing the dynamical masses on an absolute scale., Published in The Astrophysical Journal, v756 article 120 (14pp), 2012 September 10. The original document contains color images.

Eclipsing binaries (EBs) provide critical laboratories for empirically testing predictions of theoretical models of stellar structure and evolution. Pre-main-sequence (PMS) EBs are particularly valuable, both due to their rarity and the highly dynamic nature of PMS evolution, such that a dense grid of PMS EBs is required to properly calibrate theoretical PMS models. Analyzing multi-epoch, multi-color light curves for 2400 candidate Orion Nebula Cluster (ONC) members from our Warm Spitzer Exploration Science Program YSOVAR, we have identified 12 stars whose light curves show eclipse features. Four of these 12 EBs are previously known. Supplementing our light curves with follow-up optical and near-infrared spectroscopy, we establish two of the candidates as likely field EBs lying behind the ONC. We confirm the remaining six candidate systems, however, as newly identified ONC PMS EBs. These systems increase the number of known PMS EBs by over 50% and include the highest mass (theta 1 Ori E, for which we provide a complete set of well-determined parameters including component masses of 2.807 and 2.797 Mass compared to the Sun) and longest-period (ISOY J053505.71-052354.1, P 20 days) PMS EBs currently known. In two cases (theta 1 Ori E and ISOY J053526.88-044730.7), enough photometric and spectroscopic data exist to attempt an orbit solution and derive the system parameters. For the remaining systems, we combine our data with literature information to provide a preliminary characterization sufficient to guide follow-up investigations of these rare benchmark systems., Published in The Astrophysical Journal, 753:149 (17pp), July 10, 2012. The original document contains color images.

The potential existence of a giant planet orbiting within a few au of a stellar remnant has profound implications for both the survival and possible regeneration of planets during post-main-sequence stellar evolution. This paper reports Hubble Space Telescope Fine Guidance Sensor and US Naval Observatory relative astrometry of GD66, a white dwarf thought to harbour a giant planet between 2 and 3 au based on stellar pulsation arrival times. Combined with existing infrared data, the precision measurements here rule out all stellar-mass and brown dwarf companions, implying that only a planet remains plausible, if orbital motion is indeed the cause of the variations in pulsation timing., Published in Monthly Notices of the Royal Astronomical Society, v424 p519-523, 2012. The original document contains color images.

Observations with milliarcsecond resolution using the Navy Optical Interferometer have been obtained for a number of stellar systems which include high-mass binaries, eclipsing binaries, and radio stars. These observations also reveal the previously unseen companions in single-lined spectroscopic binaries via directly measured flux ratios. We will present examples of published and ongoing research efforts of these systems to illustrate how an optical interferometer contributes to our knowledge of stars, their environment, and companions. These studies include a conclusive revealing of the previously unseen companion in the single-lined binary phi Herculis, the direct determination of orbital parameters in the wide and close orbits of Algol, and revealing the orbit of beta Lyrae with spatially resolved images of the H-alpha emission., Published in Journal of Astronomy and Space Sciences, v29 n1 p63-67, 2012. The original document contains color images.

Here we report the first attempts to observe a stellar occultation from the Stratospheric Observatory for Infrared Astronomy. We predicted and will attempt to observe the stellar occultations by Pluto and Charon on 23 June 2011 UT and by Pluto and Hydra on 27 June 2011 UT. We shall provide details on the predictions, preparation, and any successful observations and initial results and implications for the Pluto system., EPSC-DPS Joint Meeting 2011 v6, EPSC-DPS2011-1374. The original document contains color images.

In the spring of 2009, the Kepler Mission commenced high-precision photometry on nearly 156,000 stars to determine the frequency and characteristics of small exoplanets, conduct a guest observer program, and obtain asteroseismic data on a wide variety of stars. On 2010 June 15, the Kepler Mission released most of the data from the first quarter of observations. At the time of this data release, 705 stars from this first data set have exoplanet candidates with sizes from as small as that of Earth to larger than that of Jupiter. Here we give the identity and characteristics of 305 released stars with planetary candidates. Data for the remaining 400 stars with planetary candidates will be released in 2011 February. More than half the candidates on the released list have radii less than half that of Jupiter. Five candidates are present in and near the habitable zone; two near super-Earth size, and three bracketing the size of Jupiter. The released stars also include five possible multi-planet systems. One of these has two Neptune-size (2.3 and 2.5 Earth radius) candidates with near-resonant periods., The Astrophysical Journal, 728:117 (20pp), 2011 February 20. The original document contains color images.

We present orbital parameters for six double-lined spectroscopic binaries (iota Pegasi, omega Draconis, 12 Bootis, V1143 Cygni, beta Aurigae, and Mizar A) and two double-lined triple star systems (kappa Pegasi and eta Virginis). The orbital fits are based upon high-precision radial velocity (RV) observations made with a dispersed Fourier Transform Spectrograph, or dFTS, a new instrument that combines interferometric and dispersive elements. For some of the double-lined binaries with known inclination angles, the quality of our RV data permits us to determine the masses M1 and M2 of the stellar components with relative errors as small as 0.2%., The Astronomical Journal, v142 n6, 2011. The original document contains color images.

A current investigation is underway into the possible collision between a circumstellar disk and the secondary star in the delta Scorpii binary system. Delta Scorpii is a prime candidate for a disk-star collision since the primary star has a circumstellar disk and the secondary star has a highly elliptical orbit with a period of approximately 10.5 years making the periastron passage very close to the primary star. The Navy Prototype Optical Interferometer (NPOI) was used to spatially resolve the two stars as well as the circumstellar disk around the primary. A revised orbit with new orbital parameters has been calculated using observations obtained between 2005 and 2010. Our results indicate periastron passage will occur on 2011-07-03., Sponsored in part by the Oceanographer of the Navy. Presented at the International Astronomical Union (IAU) Symposium on Active OB Stars: Structure, Evolution, Mass Loss, and Critical Limits, held in Paris, France on 19-23 July 2010. Published in the Proceedings of the International Astronomical Union (IAU) Symposium, n272 p278-279, 2010.

We present the results of eight-color CCD photometry of 674 stars in the direction of the open cluster Tombaugh 5 in Camelopardalis. The stars are observed in the Vilnius system supplemented by the broad-band I filter the field is of 22' diameter, the limiting magnitude is V = 17.7 mag. The catalog contains the coordinates, V magnitudes, seven color indices, two-dimensional spectral types determined from photometric parameters, interstellar extinctions and distances. The color-magnitude diagram plotted for 480 individually dereddened stars is used to identify cluster members and to determine the distance (1.74 kpc) and age (200-250 Myr) of the cluster. The faintest cluster stars classified are of spectral class GO. The cluster contains two blue stragglers of spectral classes B2-B4, both of them seem to be visual binaries. The extinction Av for the cluster stars is non-uniform, being spread between 2 and 3 mag, with a mean value of 2.42 mag. The extinction vs. distance dependence can be modeled by the Parenago exponential curve with two dust concentrations in the Camelopardalis dark clouds at about 150 pc and the Cam OBI association clouds at 0.9-1.0 kpc.

In anticipation of the possible collision between a circumstellar disk and the secondary star in the highly eccentric binary system Scorpii, high angular resolution interferometric observations have been acquired aimed at revising the binary parameters. The Navy Prototype Optical Interferometer (NPOI) was used to spatially resolve the binary components in 2000 and over a period between 2005 and 2010. The interferometric observations are used to obtain the angular separations and orientations of the two stellar components at all epochs for which data has been obtained, including 2005 and 2006, for which based on previous studies there was some uncertainty as if the signature of binarity can be clearly detected. The results of this study represent the most complete and accurate coverage of the binary orbit of this system to date and allow for the revised timing of the upcoming periastron passage that will occur in 2011 to be obtained., Prepared in cooperation with Central Michigan University, and with European Southern Observatory, Munich, Germany. The original document contains color images.

Recent searches by unbiased, wide-field surveys have uncovered a group of extremely luminous optical transients. The initial discoveries of SN 2005ap by the Texas Supernova Search and SCP-06F6 in a deep Hubble pencil beam survey were followed by the Palomar Transient Factory confirmation of host redshifts for other similar transients. The transients share the common properties of high optical luminosities (peak magnitudes -21 to -23), blue colors, and a lack of H or He spectral features. The physical mechanism that produces the luminosity is uncertain, with suggestions ranging from jet-driven explosion to pulsational pair instability. Here, we report the most detailed photometric and spectral coverage of an ultra-bright transient (SN 2010gx) detected in the Pan-STARRS 1 sky survey. In common with other transients in this family, early-time spectra show a blue continuum and prominent broad absorption lines of Oii. However, about 25 days after discovery, the spectra developed type Ic supernova features, showing the characteristic broad Fe ii and Si ii absorption lines. Detailed, post-maximum follow-up may show that all SN 2005ap and SCP-06F6 type transients are linked to supernovae Ic. This poses problems in understanding the physics of the explosions: there is no indication from late-time photometry that the luminosity is powered by Ni56, the broad light curves suggest very large ejected masses, and the slow spectral evolution is quite different from typical Ic timescales. The nature of the progenitor stars and the origin of the luminosity are intriguing and open questions., Published in The Astrophysical Journal Letters, v724 n1 pL16-L21,20 November 2010. The original document contains color images.

We present the early UV and optical light curve of Type IIP supernova (SN) 2010aq at z = 0.0862, and compare it to analytical models for thermal emission following SN shock breakout in a red supergiant star. SN 2010aq was discovered in joint monitoring between the Galaxy Evolution Explorer (GALEX) Time Domain Survey (TDS) in the NUV and the Pan-STARRS1 Medium Deep Survey (PS1 MDS) in the g, r, i, and z bands. The GALEX and Pan-STARRS1 observations detect the SN less than 1 day after the shock breakout, measure a diluted blackbody temperature of 31,000 +/- 6000 K 1 day later, and follow the rise in the UV/optical light curve over the next 2 days caused by the expansion and cooling of the SN ejecta. The high signal-to-noise ratio of the simultaneous UV and optical photometry allows us to fit for a progenitor star radius of 700 +/- 200R(Sun) , the size of a red supergiant star. An excess in UV emission two weeks after shock breakout compared with SNe well fitted by model atmosphere-code synthetic spectra with solar metallicity is best explained by suppressed line blanketing due to a lower metallicity progenitor star in SN 2010aq. Continued monitoring of PS1 MDS fields by the GALEX TDS will increase the sample of early UV detections of Type II SNe by an order of magnitude and probe the diversity of SN progenitor star properties., The Astrophysical Journal Letters, v720 n1 pL77-L81, 2010 September 1. The original document contains color images.

The Kepler Mission, launched on 2009 March 6, was designed with the explicit capability to detect Earth-size planets in the habitable zone of solar-like stars using the transit photometry method. Results from just 43 days of data along with ground-based follow-up observations have identified five new transiting planets with measurements of their masses, radii, and orbital periods. Many aspects of stellar astrophysics also benefit from the unique, precise, extended, and nearly continuous data set for a large number and variety of stars. Early results for classical variables and eclipsing stars show great promise. To fully understand the methodology, processes and eventually the results from the mission, we present the underlying rationale that ultimately led to the flight and ground system designs used to achieve the exquisite photometric performance. As an example of the initial photometric results, we present variability measurements that can be used to distinguish dwarf stars from red giants., The Astrophysical Journal Letters, v713 ppL79-L86, 20 Apr 2010 . The original document contains color images.

We present photometric and spectroscopic observations of a luminous Type IIP Supernova (SN) 2009kf discovered by the Pan-STARRS 1 (PS1) survey and also detected by the Galaxy Evolution Explorer. The SN shows a plateau in its optical and bolometric light curves, lasting approximately 70 days in the rest frame, with an absolute magnitude of Mv = -18.4 mag. The P-Cygni profiles of hydrogen indicate expansion velocities of 9000 km/s at 61 days after discovery which is extremely high for a Type IIP SN. SN 2009kf is also remarkably bright in the near-ultraviolet (NUV) and shows a slow evolution 10-20 days after optical discovery. The NUV and optical luminosity at these epochs can be modeled with a blackbody with a hot effective temperature (T 16,000 K) and a large radius (R 1 x 100(exp 15) cm). The bright bolometric and NUV luminosity, the light curve peak and plateau duration, the high velocities, and temperatures suggest that 2009kf is a Type IIP SN powered by a larger than normal explosion energy. Recently discovered high-z SNe (0.7 z 2.3) have been assumed to be IIn SNe, with the bright UV luminosities due to the interaction of SN ejecta with a dense circumstellar medium. UV-bright SNe similar to SN 2009kf could also account for these high-z events, and its absolute magnitude Mnuv = -21.5 + or - 0.5 mag suggests such SNe could be discovered out to z 2.5 in the PS1 survey., Published in The Astrophysical Journal Letters, v717 n1 pL52-L56, 1 July 2010. The original document contains color images.

The Kepler Mission was launched on 2009 March 6, to undertake a search for Earth-size planets orbiting in the habitable zones of stars similar to the Sun. Kepler uses the transit photometry approach for this task (Borucki et al. 2010a). Kepler s commissioning process went very well and the system provides data of exceptional photometric quality (Koch et al. 2010a). Indeed, the final commissioning data, 9.7 days of science-like observations of 50,000 stars selected from the Kepler Input Catalog (KIC;Koch et al. 2010a), were of such high quality that they are now commonly, if incorrectly, referred to as the quarter 0 data., The Astrophysical Journal Letters, 713:L136-L139, 2010 April 20. The original document contains color images.

We report on the discovery and confirmation of Kepler-7b, a transiting planet with unusually low density. The mass is less than half that of Jupiter, M(p) = 0.43M(j), but the radius is 50% larger, R(p) = 1.48R(j). The resulting density, Rho(p) = 0.17 g cm( -3), is the second lowest reported so far for an extrasolar planet. The orbital period is fairly long, P = 4.886 days, and the host star is not much hotter than the Sun, T(eff) = 6000 K. However, it is more massive and considerably larger than the Sun, M(*) = 1.35M of the sun and R = 1.84R of the sun, and must be near the end of its life on the main sequence., Published in The Astrophysical Journal Letters, 713:L140-L144, 2010 April 20. Government or Federal Purpose Rights License.. The original document contains color images.

Early time-series photometry from NASA's Kepler spacecraft has revealed a planet transiting the star we term Kepler-4, at R.A. = 19h02m27.s68, declination = +50 deg 08 min 08 sec.7. The planet has an orbital period of 3.213 days and shows transits with a relative depth of 0.87 x 10(exp -3) and a duration of about 3.95 hr. Radial velocity (RV) measurements from the Keck High Resolution Echelle Spectrometer show a reflex Doppler signal of 9.3(+1.1 sub 1.9) m s-1, consistent with a low-eccentricity orbit with the phase expected from the transits. Various tests show no evidence for any companion star near enough to affect the light curve or the RVs for this system. From a transit-based estimate of the host star's mean density, combined with analysis of high-resolution spectra, we infer that the host star is near turnoff from the main sequence, with estimated mass and radius of 1.223(+0.053 sub 0.091) M and 1.487(+0.071 sub 0.084) R . We estimate the planet mass and radius to be {M(sub P), R(sub P)} = {24.5 +/- 3.8 M, 3.99 +/- 0.21 R}. The planet's density is near 1.9 g cm-3; it is thus slightly denser and more massive than Neptune, but about the same size., Published in The Astrophysical Journal Letters, v713 pL126-L130, April 20, 2010. The original document contains color images.

Kepler photometry has revealed two unusual transiting companions: one orbiting an early A-star and the other orbiting a late B-star. In both cases, the occultation of the companion is deeper than the transit. The occultation and transit with follow-up optical spectroscopy reveal a 9400 K early A-star, KOI-74 (KIC 6889235), with a companion in a 5.2 day orbit with a radius of 0.08 solar radius and a 10,000 K late B-star KOI-81 (KIC 8823868) that has a companion in a 24 day orbit with a radius of 0.2 solar radius. We infer a temperature of 12,250 K for KOI-74b and 13,500 K for KOI-81b. We present 43 days of high duty cycle, 30 minute cadence photometry, with models demonstrating the intriguing properties of these objects, and speculate on their nature., Published in The Astrophysical Journal Letters, v713 n2 pL150-L154, 2010 April 20. The original document contains color images.

The Kepler Mission began its 3.5 year photometric monitoring campaign in 2009 May on a select group of approximately 150,000 stars. The stars were chosen from the approximately half million in the field of view that are brighter than 16th magnitude. The selection criteria are quantitative metrics designed to optimize the scientific yield of the mission with regard to the detection of Earth-size planets in the habitable zone. This yields more than 90,000 G-type stars on or close to the main sequence, 20,000 of which are brighter than 14th magnitude. At the temperature extremes, the sample includes approximately 3000 M-type dwarfs and a small sample of O- and B-type MS stars (200). The small numbers of giants are included in the sample: approximately 5000 stars with surface gravities log(g) 3.5. We present a brief summary of the selection process and the stellar populations it yields in terms of surface gravity, effective temperature, and apparent magnitude. In addition to the primary, statistically derived target set, several ancillary target lists were manually generated to enhance the science of the mission, examples being: known eclipsing binaries, open cluster members, and high proper motion stars., Published in The Astrophysical Journal Letters,v713 n2 pgs.109-L114, 2010 April 20. Funding for this Discovery mission is provided by NASA's Science Mission Directorate. The original document contains color images.

The Kepler mission was designed to determine the frequency of Earth-sized planets in and near the habitable zone of Sun-like stars. The habitable zone is the region where planetary temperatures are suitable for water to exist on a planet's surface. During the first 6 weeks of observations, Kepler monitored 156,000 stars, and five new exoplanets with sizes between 0.37 and 1.6 Jupiter radii and orbital periods from 3.2 to 4.9 days were discovered. The density of the Neptune-sized Kepler-4b is similar to that of Neptune and GJ 436b, even though the irradiation level is 800,000 times higher. Kepler-7b is one of the lowest-density planets (0.17 gram per cubic centimeter) yet detected. Kepler-5b, -6b, and -8b confirm the existence of planets with densities lower than those predicted for gas giant planets., Published in SCIENCE, v327 p977-980, 19 February 2010. The original document contains color images.

High spatial resolution observations of the H(alpha)-emitting wind structure associated with the luminous blue variable star P Cygni were obtained with the Navy Prototype Optical Interferometer. These observations represent the most comprehensive interferometric data set on P Cyg to date. We demonstrate how the apparent size of the H(alpha)-emitting region of the wind structure of P Cyg compares between the 2005, 2007, and 2008 observing seasons and how this relates to the H(alpha) line spectroscopy. Using the data sets from 2005, 2007, and 2008 observing seasons, we fit a circularly symmetric Gaussian model to the interferometric signature from the H(alpha)-emitting wind structure of P Cyg. Based on our results, we conclude that the radial extent of the H(alpha)-emitting wind structure around P Cyg is stable at the 10% level. We also show how the radial distribution of the H(alpha) flux from the wind structure deviates from a Gaussian shape, whereas a two-component Gaussian model is sufficient to fully describe the H(alpha)-emitting region around P Cyg., Published in The Astronomical Journal, v139 n6 p2269-2278, Jun 2010.

The Kuiper belt is a collection of small bodies (Kuiper belt objects, KBOs) that lie beyond the orbit of Neptune and which are believed to have formed contemporaneously with the planets. Their small size and great distance make them difficult to study. KBO 55636 (2002 TX300) is a member of the water-ice-rich Haumea KBO collisional family. The Haumea family are among the most highly reflective objects in the Solar System. Dynamical calculations indicate that the collision that created KBO 55636 occurred at least 1Gyr ago. Here we report observations of a multi-chord stellar occultation by KBO 55636, which occurred on 9 October 2009 UT. We find that it has a mean radius of 143+/-5km (assuming a circular solution). Allowing for possible elliptical shapes, we find a geometric albedo of in the V photometric band, which establishes that KBO 55636 is smaller than previously thought and that, like its parent body, it is highly reflective. The dynamical age implies either that KBO 55636 has an active resurfacing mechanism, or that fresh water-ice in the outer Solar System can persist for gigayear timescales., Published in the journal NATURE, v465 n17 p897-900, June 2010. The original document contains color images.

We report on multi-frequency polarimetry very long baseline interferometry observations of active galactic nuclei using the Very Long Baseline Array. These observations are used to construct images of the Faraday rotation measure (RM) in J1613+342, Mrk 501, 3C 371, and BL Lac. Despite having resolved the jets in total intensity and polarization for three of these sources no RM gradients are found. This is in contrast to the large fraction of sources with RM gradients now claimed in the literature and invoked as evidence in support of helical magnetic fields. We propose objective criteria for establishing what constitutes an RM gradient. Furthermore, although we note the absence of simple, monotonic gradients, comparison with simulations could reveal systematic changes in the RM that may be masked by a varying jet orientation., Published in The Astrophysical Journal Letters, v722 i2 L183-L187, 2010. The original document contains color images.

We report on ancient white dwarfs found in the proper motion survey we are conducting at the Bok and USNO telescopes. To date we have surveyed approximately 2800 square degrees of sky and identified numerous WDs with Teff < or = 6000. A subset of these WDs are high velocity objects that most likely belong to the Galactic halo population. Where possible, we are acquiring trigonometric parallaxes to constrain the WD masses. We apply a new Bayesian modeling approach to these WDs that consistently incorporates precursor evolutionary timescales, the initial-final mass relation, WD interior and atmosphere models, and uses the observed magnitudes, distances, etc. to derive the distribution of WD age as a function of uncertainties in the observational parameters., Presented at the European White Dwarf Workshop (17th) held in Tubingen, Germnay on 16-20 August 2010. Published in AIP Conference Proceedings, Volume 1273, p141-145, 2010. The original document contains color images.

We report the discovery of three nearby old halo white dwarf (WD) candidates in the Sloan Digital Sky Survey (SDSS), including two stars in a common proper motion binary system. These candidates are selected from our 2800 deg2 proper motion survey on the Bok and U.S. Naval Observatory Flagstaff Station 1.3m telescopes, and they display proper motions of 0".4-0".5 yr(exp -1). Follow-up MMT spectroscopy and near-infrared photometry demonstrate that all three objects are hydrogen-dominated atmosphere WDs with T(sub eff) approximately equal 3700-4100 K. For average mass WDs,these temperature estimates correspond to cooling ages of 9-10 Gyr, distances of 70-80 pc, and tangential velocities of 140-200 km s(exp -1). Based on the UVW space velocities, we conclude that they most likely belong to the halo. Furthermore, the combined main-sequence and WD cooling ages are 10-11 Gyr. Along with SDSS J1102+4113, they are the oldest field WDs currently known. These three stars represent only a small fraction of the halo WD candidates in our proper motion survey, and they demonstrate that deep imaging surveys like the Pan-STARRS and Large Synoptic Survey Telescope should find many old thick disk and halo WDs that can be used to constrain the age of the Galactic thick disk and halo., Pub. the Astrophysical Journal Letters, v715 n1, pL21-L25, 2010. The original document contains color images. Sponsored in part by NASA.

This paper reports Very Large Array observations at 325 and 1425 MHz (lambda 90 cm and lambda 20 cm) during and near the periastron passage of HD 80606b on HJD 2454424.86 (2007 November 20). We obtain flux density limits (3 sigma) of 1.7mJy and micro-Jy at 325 and 1425 MHz, respectively, equivalent to planetary luminosity limits of 2.3 x 10(exp 24) erg/s and 2.7 x 10(exp 23) erg/s. Unfortunately, these are several orders of magnitude above the nominal Jovian value (at 40 MHz) of 2 x 10(exp 18) erg/s. The motivation for these observations was that the planetary magnetospheric emission is driven by a stellar-wind-planetary-magnetosphere interaction so that the planetary luminosity would be elevated near periastron. We estimate that, near periastron, HD80606b might be as much as 3000 times more luminous than Jupiter. Recent transit observations of HD 80606b provide reasonably stringent constraints on the planetary mass and radius, and, because of the planet's highly eccentric orbit, its rotation period is likely to be "pseudo-synchronized" to its orbital period, allowing a robust estimate of the former. Consequently,we are able to make relatively robust estimates of the emission frequency of the planetary magnetospheric emission and find it to be around 60-90 MHz. While this is too low for our reported observations, we compare HD 80606b to other high-eccentricity systems and assess the detection possibilities for both near-term and more distant future systems., Published in The Astronomical Journal, v140 n6 p1929-1933, December 2010. Prepared in collaboration with NASA Lunar Science Institute, Moffett Field, CA; and NASA Goddard Space Flight Center, Greenbelt, MD. The original document contains color images.

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., Published in Proceedings of the SPIE, v7734 p77343K-1/77343K-9, 2010.

The Pan-STARRS 1 Telescope (PS1) is currently (2009 Aug) undergoing final commissioning efforts and starting to perform initial science observations for the PS1 survey mission. PS1 will greatly expand the known population of Brown Dwarfs, with discovery via photometry, proper-motion, and parallax., Published in the Highlights of Astronomy, v15 p818, 2009. Prepared in cooperation with University of Hawaii, Honolulu, and with Heidelberg, Germany.

In this paper, we discuss the detection of systematic biases in star positions of the USNO A1.0, A2.0, and B1.0 catalogs, as deduced from the residuals of numbered asteroid observations. We present a technique for the removal of these biases, and validate this technique by illustrating the resulting improvements in numbered asteroid residuals, and by establishing that debiased orbits predict omitted observations more accurately than do orbits derived from non-debiased observations. We also illustrate the benefits of debiasing to high-precision astrometric applications such as asteroid mass determination and collision analysis, including a refined prediction of the impact probability of 99942 Apophis. Specifically, we find the IP of Apophis to be lowered by nearly an order of magnitude to 4.5 x 10(exp -6) for the 2036 close approach., Published in Icarus, v210 p158-181, 2010.