Topics concerning state variable feedback in automatic control systems. Part 1 - Specification. Part 2 - Sensitivity. Part 3 - Intentional nonlinearities. Part 4 - Unavailable states

Specifications, sensitivity, intentional nonlinearities, and unavailable states concerned with state variable feedback in automatic control system

Externally Dispersed Interferometry for Precision Radial Velocimetry

Externally Dispersed Interferometry (EDI) is the series combination of a fixed-delay field-widened Michelson interferometer with a dispersive spectrograph. This combination boosts the spectrograph performance for both Doppler velocimetry and high resolution spectroscopy. The interferometer creates a periodic spectral comb that multiplies against the input spectrum to create moire fringes, which are recorded in combination with the regular spectrum. The moire pattern shifts in phase in response to a Doppler shift. Moire patterns are broader than the underlying spectral features and more easily survive spectrograph blurring and common distortions. Thus, the EDI technique allows lower resolution spectrographs having relaxed optical tolerances (and therefore higher throughput) to return high precision velocity measurements, which otherwise would be imprecise for the spectrograph alone.Comment: 7 Pages, White paper submitted to the AAAC Exoplanet Task Forc

Masses, Luminosities, and Orbital Coplanarities of the mu Orionis Quadruple Star System from PHASES Differential Astrometry

mu Orionis was identified by spectroscopic studies as a quadruple star system. Seventeen high precision differential astrometry measurements of mu Ori have been collected by the Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES). These show both the motion of the long period binary orbit and short period perturbations superimposed on that caused by each of the components in the long period system being themselves binaries. The new measurements enable the orientations of the long period binary and short period subsystems to be determined. Recent theoretical work predicts the distribution of relative inclinations between inner and outer orbits of hierarchical systems to peak near 40 and 140 degrees. The degree of coplanarity of this complex system is determined, and the angle between the planes of the A-B and Aa-Ab orbits is found to be 136.7 +/- 8.3 degrees, near the predicted distribution peak at 140 degrees; this result is discussed in the context of the handful of systems with established mutual inclinations. The system distance and masses for each component are obtained from a combined fit of the PHASES astrometry and archival radial velocity observations. The component masses have relative precisions of 5% (component Aa), 15% (Ab), and 1.4% (each of Ba and Bb). The median size of the minor axes of the uncertainty ellipses for the new measurements is 20 micro-arcseconds. Updated orbits for delta Equulei, kappa Pegasi, and V819 Herculis are also presented.Comment: 12 Pages, Accepted for publication in A

Orbital Solutions and Absolute Elements of the Short-Period Eclipsing Binary ES Librae

We have obtained new differential UBV photoelectric photometry and radial velocities of both components of the short-period eclipsing binary ES Lib. The system has a circular orbit with a period of 0.883040928 days and is seen at an inclination of 70.1°. With the Wilson-Devinney analysis program, we obtained a simultaneous solution of our photometric and spectroscopic observations that resulted in masses of M1 = 2.30 ± 0.03 M⊙ and M2 = 0.97 ± 0.01 M⊙ and the equal-volume radii of R1 = 2.69 ± 0.02 R⊙ and R2 = 1.83 ± 0.01 R⊙ for the primary and secondary, respectively. The secondary is oversized and overluminous for its mass. The effective temperatures of the primary and secondary are 8500 K (fixed) and 5774 ± 57 K, respectively. Despite the very large temperature difference, our photometric and spectroscopic data indicate that ES Lib is not semidetached but rather require it to be in an overcontact state, where both components exceed their critical Roche lobes. Given its nonthermal equilibrium state, if the overcontact solution correctly characterizes the system, the change from being semidetached to overcontact may have occurred recently. While the asymmetry of the light curves can be modeled well with a large, hot starspot or a large, cool one on the secondary component, we prefer the latter interpretation because cool spots are a typical feature on many contact binaries

Detectability of Terrestrial Planets in Multi-Planet Systems: Preliminary Report

We ask if Earth-like planets (terrestrial mass and habitable-zone orbit) can be detected in multi-planet systems, using astrometric and radial velocity observations. We report here the preliminary results of double-blind calculations designed to answer this question.Comment: 10 pages, 0 figure

Orbital and physical parameters of eclipsing binaries from the ASAS catalogue - IV. A 0.61 + 0.45 M_sun binary in a multiple system

We present the orbital and physical parameters of a newly discovered low-mass detached eclipsing binary from the All-Sky Automated Survey (ASAS) database: ASAS J011328-3821.1 A - a member of a visual binary system with the secondary component separated by about 1.4 seconds of arc. The radial velocities were calculated from the high-resolution spectra obtained with the 1.9-m Radcliffe/GIRAFFE, 3.9-m AAT/UCLES and 3.0-m Shane/HamSpec telescopes/spectrographs on the basis of the TODCOR technique and positions of H_alpha emission lines. For the analysis we used V and I band photometry obtained with the 1.0-m Elizabeth and robotic 0.41-m PROMPT telescopes, supplemented with the publicly available ASAS light curve of the system. We found that ASAS J011328-3821.1 A is composed of two late-type dwarfs having masses of M_1 = 0.612 +/- 0.030 M_sun, M_2 = 0.445 +/- 0.019 M_sun and radii of R_1 = 0.596 +/- 0.020 R_sun, R_2 = 0.445 +/- 0.024 R_sun, both show a substantial level of activity, which manifests in strong H_alpha and H_beta emission and the presence of cool spots. The influence of the third light on the eclipsing pair properties was also evaluated and the photometric properties of the component B were derived. Comparison with several popular stellar evolution models shows that the system is on its main sequence evolution stage and probably is more metal rich than the Sun. We also found several clues which suggest that the component B itself is a binary composed of two nearly identical ~0.5 M_sun stars.Comment: 12 pages, 7 figures, 7 tables, to appear in MNRA

Interferometric Observations of RS Ophiuchi and the Origin of the Near-IR Emission

We report observations of the recurrent nova RS Oph using long-baseline near-IR interferometry. We are able to resolve emission from the nova for several weeks after the February 2006 outburst. The near-IR source initially expands to a size of approximately 5 milli-arcseconds. However, beginning around day 10 the IR source appears to begin to shrink, reaching approximately 2 milli-arcseconds by day 100. We combine our measured angular diameters with previously available interferometric and photometric data to derive an emission measure for the source, and hence are able to determine the mass-loss rate of the nova in the days following the outburst.Comment: 17 pages, 4 figures. Accepted for publication in Ap

PHASES High Precision Differential Astrometry of delta Equulei

delta Equulei is among the most well-studied nearby binary star systems. Results of its observation have been applied to a wide range of fundamental studies of binary systems and stellar astrophysics. It is widely used to calibrate and constrain theoretical models of the physics of stars. We report 27 high precision differential astrometry measurements of delta Equulei from the Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES). The median size of the minor axes of the uncertainty ellipses for these measurements is 26 micro-arcseconds. These data are combined with previously published radial velocity data and other previously published differential astrometry measurements using other techniques to produce a combined model for the system orbit. The distance to the system is determined to within a twentieth of a parsec and the component masses are determined at the level of a percent. The constraints on masses and distance are limited by the precisions of the radial velocity data; we outline plans improve this deficiency and discuss the outlook for further study of this binary.Comment: Accepted by AJ. Complete versions of tables 2-7 now available at http://stuff.mit.edu/~matthew1/deltaEquTables/ (removed from astroph server

Exoplanet Characterization and the Search for Life

Over 300 extrasolar planets (exoplanets) have been detected orbiting nearby stars. We now hope to conduct a census of all planets around nearby stars and to characterize their atmospheres and surfaces with spectroscopy. Rocky planets within their star's habitable zones have the highest priority, as these have the potential to harbor life. Our science goal is to find and characterize all nearby exoplanets; this requires that we measure the mass, orbit, and spectroscopic signature of each one at visible and infrared wavelengths. The techniques for doing this are at hand today. Within the decade we could answer long-standing questions about the evolution and nature of other planetary systems, and we could search for clues as to whether life exists elsewhere in our galactic neighborhood.Comment: 7 pages, 2 figures, submitted to Astro2010 Decadal Revie