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Observational astronomy has changed drastically in the last decade: manually driven target-by-target instruments have been replaced by fully automated robotic telescopes. Data acquisition methods have advanced to the point that terabytes of data are flowing in and being stored on a daily basis. At the same time, the vast majority of analysis tools in stellar astrophysics still rely on manual expert interaction. To bridge this gap, we foresee that the next decade will witness a fundamental shift in the approaches to data analysis: case-by-case methods will be replaced by fully automated pipelines that will process the data from their reduction stage, through analysis, to storage. While major effort has been invested in data reduction automation, automated data analysis has mostly been neglected despite the urgent need. Scientific data mining will face serious challenges to identify, understand and eliminate the sources of systematic errors that will arise from this automation. As a special case, we present an artificial intelligence (AI) driven pipeline that is prototyped in the domain of stellar astrophysics (eclipsing binaries in particular), current results and the challenges still ahead., Comment: 10 pages; Decadal Survey 2010 White Paper on Theory, Computation, and Laboratory Astrophysics

Spectroscopic and eclipsing binary systems offer the best means for determining accurate physical properties of stars, including their masses and radii. The data available for low-mass stars have yielded firm evidence that stellar structure models predict smaller radii and higher effective temperatures than observed, but the number of systems with detailed analyses is still small. In this paper we present a complete reanalysis of one of such eclipsing systems, CM Dra, composed of two dM4.5 stars. New and existing light curves as well as a radial velocity curve are modeled to measure the physical properties of both components. The masses and radii determined for the components of CM Dra are M1=0.2310+/-0.0009 Msun, M2=0.2141+/-0.0010 Msun, R1=0.2534+/-0.0019 Rsun, and R2=0.2396+/-0.0015 Rsun. With relative uncertainties well below the 1% level, these values constitute the most accurate properties to date for fully convective stars. This makes CM Dra a valuable benchmark for testing theoretical models. In comparing our measurements with theory, we confirm the discrepancies reported previously for other low-mass eclipsing binaries. These discrepancies seem likely to be due to the effects of magnetic activity. We find that the orbit of this system is slightly eccentric, and we have made use of eclipse timings spanning three decades to infer the apsidal motion and other related properties., Comment: 19 pages, 9 figures. Accepted for publication in ApJ

Achieving maximum scientific results from the overwhelming volume of astronomical data to be acquired over the next few decades will demand novel, fully automatic methods of data analysis. Artificial intelligence approaches hold great promise in contributing to this goal. Here we apply neural network learning technology to the specific domain of eclipsing binary (EB) stars, of which only some hundreds have been rigorously analyzed, but whose numbers will reach millions in a decade. Well-analyzed EBs are a prime source of astrophysical information whose growth rate is at present limited by the need for human interaction with each EB data-set, principally in determining a starting solution for subsequent rigorous analysis. We describe the artificial neural network (ANN) approach which is able to surmount this human bottleneck and permit EB-based astrophysical information to keep pace with future data rates. The ANN, following training on a sample of 33,235 model light curves, outputs a set of approximate model parameters (T2/T1, (R1+R2)/a, e sin(omega), e cos(omega), and sin i) for each input light curve data-set. The whole sample is processed in just a few seconds on a single 2GHz CPU. The obtained parameters can then be readily passed to sophisticated modeling engines. We also describe a novel method polyfit for pre-processing observational light curves before inputting their data to the ANN and present the results and analysis of testing the approach on synthetic data and on real data including fifty binaries from the Catalog and Atlas of Eclipsing Binaries (CALEB) database and 2580 light curves from OGLE survey data. [abridged], Comment: 52 pages, accepted to ApJ

The distance to the Large Magellanic Cloud (LMC) is crucial for the calibration of the Cosmic Distance Scale. We derive a distance to the LMC based on an analysis of ground-based photometry and HST-based spectroscopy and spectrophotometry of the LMC eclipsing binary system HV2274. Analysis of the optical light curve and HST/GHRS radial velocity curve provides the masses and radii of the binary components. Analysis of the HST/FOS UV/optical spectrophotometry provides the temperatures of the component stars and the interstellar extinction of the system. When combined, these data yield a distance to the binary system. After correcting for the location of HV2274 with respect to the center of the LMC, we find d(LMC) = 45.7 +/- 1.6 kpc or DM(LMC) = 18.30 +/- 0.07 mag. This result, which is immune to the metallicity-induced zero point uncertainties that have plagued other techniques, lends strong support to the ``short'' LMC distance scale as derived from a number of independent methods., Comment: 6 pages, including 2 pages of figures. Newly available optical (B and V) photometry has revealed -- and allowed the elimination of -- a systematic error in the previously reported determination of E(B-V) for HV2274. The new result is E(B-V) = 0.12 mag (as compared to the value of 0.083 reported in the original submission) and produces a DECREASE in the distance modulus of HV2274 by 0.12 mag. ApJ Letters, in press

IUE (International Ultraviolet Explorer) observations were made around the orbits of three Algol-type binaries: R Arae, U Cephei and Algol. These stars were selected to represent, respectively, the rapid, moderate and slow phases of mass transfer and mass loss in Algols. The data was obtained to derive maps of gas flow and mass loss, to study accretion processes and kinetic heating, and to investigate the importance of magnetic fields in these systems. Continuous observations were made from GSFC and VILSPA over 4 1/3 consecutive days during 10 to 14 Sep. 1989. A total of 100 spectra are obtained. This is the first time that Algol systems are observed continuously over their orbits with IUE. Initial results from this program are discussed.

The IUE spectra of the close binary star HD 47755 have been examined in order to determine its geometry, chemical composition, and light curve. UBV fluxes in the spectra, when dereddened for E(B-V) = 0.09 yield an effective temperature of 16,500 K. The ratio of the mean radii of the stars is found to agree well with an old blueband spectrophotometric value. Eclipses in the binary have been observed and a complex green light curve is derived. It is suggested that the wind from at least one of the components of HD 47755 is the source of the complexity in the light curve. The geometry of the HD 47755 is compared to that of V 641 Mon, A definite cluster member of NGC 2264. The interstellar line spectrum is found to be similar to that of V 641 Mon and the column densities for a few interstellar ions are given in a table. Evaluation of the nonastrometric evidence indicates that HD 47755 is also a member of NGC 2264.

Several high- and low-dispersion IUE spectra are described for the hot, massive close binary HD 47732. The stellar silicon lines do not show theoretically expected strength, the weakness being attributed to incipicent emission. A weak stellar wind is measurable with an expansion velocity of about 500 km/s. There is difficulty in fitting a model atmosphere to all of the IUE continuum and visible band and IR measures. These difficulties are resolved by appealing to a 22,500 K model atmosphere and a distinctive interstellar extinction law. Numerous V band measures show the polarization to be variable, but not strongly in a phased-locked way. This suggests sporadic outbursts of gas feeding the shell. Several seasonal V band light curves are discussed, and the seasonal variations among them are attributed to variable developments of a systemic shell which scatters the photospheric light and dilutes to a variable degree the light variation due to ellipticity of figure of the component stars.

This hot, double line, ellipsoidal variable member of NGC 2264 has been shown previously to be either a semi-detached or contact close binary. Low-resolution IUE spectra are best fitted to a Kurucz model atmosphere for very small (approximately 0.08 mag) E(B-V). The familiar interstellar absorption dip near lambda 2200 is apparently absent. A suitable model atmosphere can be fitted to the IUE fluxes, but flux excesses (compared to the model) appear for all the published U through L magnitudes. The spectrum of the B through L excess appears to follow a .0001 lambda dependence. It is shown that this cannot be interpreted as arising from another star fortuitously observed in the visible band or IR. Ground based polarization measures indicate V641 Mon to be a polarization variable. Previous and new V light curves show the amplitude of light variability itself to be variable by about a factor of 2. It is suggested that all these observed characteristics are best explained by postulating "third light" and identifying part of it with Rayleigh scattered starlight very near to the stars. From this same region there arise circumstellar absorptions which give rise to nontheoretical strengths for Si II and Si III lines.

Low- and high-dispersion ultraviolet spectra obtained by the IUE of the early B-type close binary V Puppis are reported. The continuum derived from the low-dispersion images is consistent with a solar abundance model of effective temperature 25,000 K and log surface gravity 4.0. The high-dispersion spectra show shallow double lines, representing Doppler-resolved stellar lines, which are broadened as expected for the fast rotational velocities given by Levato (1974). The equivalent widths of the silicon lines, however, do not agree with the temperature derived for the star, while the silicon and carbon absorptions indicate a disordered photosphere in the presence of circumstellar gas. Several interstellar lines are also observed for the first time.