336 research outputs found

    Robo-AO Discovery and Basic Characterization of Wide Multiple Star Systems in the Pleiades, Praesepe, and NGC 2264 Clusters

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    We identify and roughly characterize 66 candidate binary star systems in the Pleiades, Praesepe, and NGC 2264 star clusters based on robotic adaptive optics imaging data obtained using Robo-AO at the Palomar 60" telescope. Only \sim10% of our imaged pairs were previously known. We detect companions at red optical wavelengths having physical separations ranging from a few tens to a few thousand AU. A 3-sigma contrast curve generated for each final image provides upper limits to the brightness ratios for any undetected putative companions. The observations are sensitive to companions with maximum contrast \sim6m^m at larger separations. At smaller separations, the mean (best) raw contrast at 2 arcsec is 3.8m^m (6m^m), at 1 arcsec is 3.0m^m (4.5m^m), and at 0.5 arcsec is 1.9m^m (3m^m). PSF subtraction can recover close to the full contrast in to the closer separations. For detected candidate binary pairs, we report separations, position angles, and relative magnitudes. Theoretical isochrones appropriate to the Pleiades and Praesepe clusters are then used to determine the corresponding binary mass ratios, which range from 0.2-0.9 in q=m2/m1q=m_2/m_1. For our sample of roughly solar-mass (FGK type) stars in NGC 2264 and sub-solar-mass (K and early M-type) primaries in the Pleiades and Praesepe, the overall binary frequency is measured at \sim15.5% ±\pm 2%. However, this value should be considered a lower limit to the true binary fraction within the specified separation and mass ratio ranges in these clusters, given that complex and uncertain corrections for sensitivity and completeness have not been applied.Comment: Accepted to A

    Characterizing the Cool KOIs. VI. H- and K-band Spectra of Kepler M Dwarf Planet-Candidate Hosts

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    We present H- and K-band spectra for late-type Kepler Objects of Interest (the "Cool KOIs"): low-mass stars with transiting-planet candidates discovered by NASA's Kepler Mission that are listed on the NASA Exoplanet Archive. We acquired spectra of 103 Cool KOIs and used the indices and calibrations of Rojas-Ayala et al. to determine their spectral types, stellar effective temperatures and metallicities, significantly augmenting previously published values. We interpolate our measured effective temperatures and metallicities onto evolutionary isochrones to determine stellar masses, radii, luminosities and distances, assuming the stars have settled onto the main-sequence. As a choice of isochrones, we use a new suite of Dartmouth predictions that reliably include mid-to-late M dwarf stars. We identify five M4V stars: KOI-961 (confirmed as Kepler 42), KOI-2704, KOI-2842, KOI-4290, and the secondary component to visual binary KOI-1725, which we call KOI-1725 B. We also identify a peculiar star, KOI-3497, which has a Na and Ca lines consistent with a dwarf star but CO lines consistent with a giant. Visible-wavelength adaptive optics imaging reveals two objects within a 1 arc second diameter; however, the objects' colors are peculiar. The spectra and properties presented in this paper serve as a resource for prioritizing follow-up observations and planet validation efforts for the Cool KOIs, and are all available for download online using the "data behind the figure" feature.Comment: Accepted for publication in the Astrophysical Journal Supplement Series (ApJS). Data and table are available in the sourc

    Robotic Laser-Adaptive-Optics Imaging of 715 Kepler Exoplanet Candidates using Robo-AO

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    The Robo-AO Kepler Planetary Candidate Survey is designed to observe every Kepler planet candidate host star with laser adaptive optics imaging to search for blended nearby stars, which may be physically associated companions and/or responsible for transit false positives. In this paper we present the results from the 2012 observing season, searching for stars close to 715 representative Kepler planet candidate hosts. We find 53 companions, 44 of which are new discoveries. We detail the Robo-AO survey data reduction methods including a method of using the large ensemble of target observations as mutual point-spread-function references, along with a new automated companion-detection algorithm designed for large adaptive optics surveys. Our survey is sensitive to objects from 0.15" to 2.5" separation, with contrast ratios up to delta-m~6. We measure an overall nearby-star-probability for Kepler planet candidates of 7.4% +/- 1.0%, and calculate the effects of each detected nearby star on the Kepler-measured planetary radius. We discuss several KOIs of particular interest, including KOI-191 and KOI-1151, which are both multi-planet systems with detected stellar companions whose unusual planetary system architecture might be best explained if they are "coincident multiple" systems, with several transiting planets shared between the two stars. Finally, we detect 2.6-sigma evidence for <15d-period giant planets being 2-3 times more likely be found in wide stellar binaries than smaller close-in planets and all sizes of further-out planets.Comment: Accepted by ApJ. Minor updates & improved statistical analysis; no changes to results. 15 pages, 13 figure

    eOrganic: The organic agriculture community of practice for eXtension

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    eOrganic is the organic agriculture community of practice (CoP) and resource area for eXtension. eOrganic\u27s primary community of interest (CoI) is organic farmers and the agricultural professionals who support them. The 250 members of the eOrganic CoP include farmers, researchers, certifiers, and extension/other agricultural professionals. eOrganic\u27s mission is to build a diverse national CoP and use web technologies to synthesize existing information, emerging science, and practical knowledge into information resources and training materials for its CoI. eOrganic strategies to achieve that mission include collaborative publication, stakeholder engagement, community development, projectmanagement, evaluation, and fundraising. eOrganic\u27s public site currently offers 240 articles, 250 videos, 80 webinars and broadcasts, and 100 frequently asked questions (FAQs). eOrganic CoP members have answered more than 1000 \u27Ask an Expert\u27 questions. eOrganic authors collaboratively develop articles in eOrganic\u27s collaborative workspace, which undergo review by two anonymous reviewers andNational Organic Program (NOP) compliance review. eOrganic will offer online courses in 2012. eOrganic stakeholders evaluated eOrganic articles and videos in 2010 and overall they stated that they were relevant, science-based, and useful. Three quarters of webinar and broadcast participants said the webinar improved their understanding of the topic, and 83% said they would recommend the webinar to others. Sixty-nine percent of webinar survey respondents stated that they changed practices or provided others with information as the result of the webinar. eOrganic surveyed active CoP members in 2011. Members view eOrganic as important because it is the only national organic agriculture resource with direct ties to university research and they considered all of eOrganic\u27s core activities important. eOrganic is supported by small grants from eXtension and subawards in more than 20 U.S. Department of Agriculture (USDA), National Institute of Food and Agriculture (NIFA) research/extension projects. To enhance its financial sustainability, eOrganic will work to solidify its partnership with NIFA programs and diversify its funding sources to include course fees and underwriters

    Gattini 2010: Cutting Edge Science at the Bottom of the World

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    The high altitude Antarctic sites of Dome A and the South Pole offer intriguing locations for future large scale optical astronomical Observatories. The Gattini project was created to measure the optical sky brightness, large area cloud cover and aurora of the winter-time sky above such high altitude Antarctic sites. The Gattini-DomeA camera was installed on the PLATO instrument module as part of the Chinese-led traverse to the highest point on the Antarctic plateau in January 2008. This single automated wide field camera contains a suite of Bessel photometric filters (B, V, R) and a long-pass red filter for the detection and monitoring of OH emission. We have in hand one complete winter-time dataset (2009) from the camera that was recently returned in April 2010. The Gattini-South Pole UV camera is a wide-field optical camera that in 2011 will measure for the first time the UV properties of the winter-time sky above the South Pole dark sector. This unique dataset will consist of frequent images taken in both broadband U and B filters in addition to high resolution (R similar to 5000) long slit spectroscopy over a narrow bandwidth of the central field. The camera is a proof of concept for the 2m-class Antarctic Cosmic Web Imager telescope, a dedicated experiment to directly detect and map the redshifted lyman alpha fluorescence or Cosmic Web emission we believe possible due to the unique geographical qualities of the site. We present the current status of both projects

    Behavior specification in a software design system

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    A technique for software system behavior specification appropriate for use in designing systems with concurrency is presented. The technique is based upon a generalized ability to define events, or significant occurrences in a software system, and then indicate whatever constraints the designer might wish to see imposed upon the ordering or simultaneity of those events. Constructs implementing this technique in the DREAM software design system are presented and illustrated. The relationship of this technique to other behavior specification techniques is also discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25196/1/0000635.pd

    The Infrared Imaging Spectrograph (IRIS) for TMT: Instrument Overview

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    We present an overview of the design of IRIS, an infrared (0.84 - 2.4 micron) integral field spectrograph and imaging camera for the Thirty Meter Telescope (TMT). With extremely low wavefront error (<30 nm) and on-board wavefront sensors, IRIS will take advantage of the high angular resolution of the narrow field infrared adaptive optics system (NFIRAOS) to dissect the sky at the diffraction limit of the 30-meter aperture. With a primary spectral resolution of 4000 and spatial sampling starting at 4 milliarcseconds, the instrument will create an unparalleled ability to explore high redshift galaxies, the Galactic center, star forming regions and virtually any astrophysical object. This paper summarizes the entire design and basic capabilities. Among the design innovations is the combination of lenslet and slicer integral field units, new 4Kx4k detectors, extremely precise atmospheric dispersion correction, infrared wavefront sensors, and a very large vacuum cryogenic system.Comment: Proceedings of the SPIE, 9147-76 (2014

    Elusive Majority of Young Moving Groups. I. Young Binaries and Lithium-rich Stars in the Solar Neighborhood

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    Young stars in the solar neighborhood serve as nearby probes of stellar evolution and represent promising targets to directly image self-luminous giant planets. We have carried out an all-sky search for late-type (≈K7–M5) stars within 100 pc selected primarily on the basis of activity indicators from the Galaxy Evolution Explorer and ROSAT. Approximately 2000 active and potentially young stars are identified, of which we have followed up over 600 with low-resolution optical spectroscopy and over 1000 with diffraction-limited imaging using Robo-AO at the Palomar 1.5 m telescope. Strong lithium is present in 58 stars, implying ages spanning ≈10–200 Myr. Most of these lithium-rich stars are new or previously known members of young moving groups including TWA, β Pic, Tuc-Hor, Carina, Columba, Argus, AB Dor, Upper Centaurus Lupus, and Lower Centaurus Crux; the rest appear to be young low-mass stars without connections to established kinematic groups. Over 200 close binaries are identified down to 0.”2—the vast majority of which are new—and will be valuable for dynamical mass measurements of young stars with continued orbit monitoring in the future
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