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Roberts L.C.,Jet Propulsion Laboratory | Mason B.D.,U.S. Naval Observatory | Neyman C.R.,California Association for Research in Astronomy | Wu Y.,University of Toronto | And 29 more authors.
Astronomical Journal | Year: 2015

HD 8673 hosts a massive exoplanet in a highly eccentric orbit (e = 0.723). Based on two epochs of speckle interferometry a previous publication identified a candidate stellar companion. We observed HD 8673 multiple times with the 10 m Keck II telescope, the 5 m Hale telescope, the 3.63 m Advanced Electro-Optical System telescope, and the 1.5 m Palomar telescope in a variety of filters with the aim of confirming and characterizing the stellar companion. We did not detect the candidate companion, which we now conclude was a false detection, but we did detect a fainter companion. We collected astrometry and photometry of the companion on six epochs in a variety of filters. The measured differential photometry enabled us to determine that the companion is an early M dwarf with a mass estimate of 0.33-0.45 M . The companion has a projected separation of 10 AU, which is one of the smallest projected separations of an exoplanet host binary system. Based on the limited astrometry collected, we are able to constrain the orbit of the stellar companion to a semimajor axis of 35-60 AU, an eccentricity 0.5, and an inclination of 75-85. The stellar companion has likely strongly influenced the orbit of the exoplanet and quite possibly explains its high eccentricity. © 2015. The American Astronomical Society. All rights reserved..

Pott J.-U.,University of California at Los Angeles | Pott J.-U.,California Association for Research in Astronomy | Pott J.-U.,Max Planck Institute for Astronomy | Perrin M.D.,University of California at Los Angeles | And 6 more authors.
Astrophysical Journal | Year: 2010

With the Keck Interferometer, we have studied at 2 μm the innermost regions of several nearby, young, dust-depleted "transitional" disks. Our observations target five of the six clearest cases of transitional disks in the Taurus/Auriga star-forming region (DM Tau, GM Aur, LkCa 15, UX Tau A, and RY Tau) to explore the possibility that the depletion of optically thick dust from the inner disks is caused by stellar companions rather than the more typical planet-formation hypothesis. At the 99.7% confidence level, the observed visibilities exclude binaries with flux ratios of at least 0.05 and separations ranging from 2.5 to 30 mas (0.35-4AU) over ≳94% of the area covered by our measurements. All targets but DM Tau show near-infrared (NIR) excess in their spectral energy distribution (SED) higher than our companion flux ratio detection limits. While a companion has previously been detected in the candidate transitional disk system CoKu Tau/4, we can exclude similar mass companions as the typical origin for the clearing of inner dust in transitional disks and of the NIR excess emission. Unlike CoKu Tau/4, all our targets show some evidence of accretion. We find that all but one of the targets are clearly spatially resolved, and UX Tau A is marginally resolved. Our data are consistent with hot material on small scales (0.1AU) inside of and separated from the cooler outer disk, consistent with the recent SED modeling. These observations support the notion that some transitional disks have radial gaps in their optically thick material, which could be an indication for planet formation in the habitable zone (∼ a fewAU) of a protoplanetary disk. © 2010 The American Astronomical Society.

Agency: NSF | Branch: Standard Grant | Program: | Phase: MAJOR RESEARCH INSTRUMENTATION | Award Amount: 4.00M | Year: 2014

While astronomical images can offer breathtaking records of the appearance of the Universe, far greater information is obtained by dividing a light beam according to color (a technique known as spectroscopy). This approach can yield important details about the physical properties of the source: its temperature, chemical composition, density, mass, and velocity, among others. Constructing very efficient, wide spectral coverage, high-resolution mapping spectrographs is therefore an effective approach to getting the most from our very largest ground-based telescopes. Dr. H. Lewis (California Association for Research in Astronomy together with the California Institute of Technology and the University of California) proposes to complete the development of the Keck Cosmic Web Imager spectrograph for the 10-m Keck II telescope atop Mauna Kea, Hawaii with new optics optimized for the red portion of the spectrum. The final instrument will provide an extraordinary platform for carrying out sensitive assessments of galaxy formation and evolution in the first few hundred million years after the Big Bang, to study the interstellar medium in external galaxies, to probe star clusters and nebulae in our own Milky Way galaxy, and to track the process of star formation within those clusters.

The Keck Cosmic Web Imager (KCWI) is designed to provide seeing-limited visible band, integral field spectroscopy with moderate to high spectral resolution (up to R = 20,000), selectable slicer scales and fields of view, high efficiency, and excellent sky subtraction. KCWI will benefit from the Keck II telescopes large, 10-m aperture and excellent site, providing a dual-channel, modular implementation. The blue channel of KCWI is nearly complete; the red channel to be funded through this proposal will extend the spectral coverage to the entire optical window from 3500 to 10500 angstroms and enable scientists to address several of the key questions relating to the process of the formation and evolution of external galaxies, and thereby of the development of matter in the universe.

Funding for the development of the red channel of the Keck Cosmic Web Imager is being provided by NSFs Division of Astronomical Sciences through its participation in the Major Research Instrumentation program.

Agency: NSF | Branch: Standard Grant | Program: | Phase: ADVANCED TECHNOLOGIES & INSTRM | Award Amount: 684.00K | Year: 2012

Although the advent of adaptive optics (AO) has ushered in an era of dramatic discoveries that make use of the superb resolution of large ground-based telescopes, lack of knowledge of the point spread function (PSF) still stands as a fundamental limitation. Extragalactic, galactic and solar system AO science programs currently rely on non-synchronous PSF calibration stars, which results in increased random and systematic errors in astrometry, photometry, morphology and kinematics. The future of quantitative AO science, and the goal of the project proposed by Dr. Peter Wizinowich and his collaborators at the California Association for Research in Astronomy, lies in reconstructing synchronous PSF knowledge based on real-time telemetry collected from the telescope and AO system.

This proposal will develop PSF determination tools for on-axis both natural and laser guide-star AO science observations and demonstrate the quantitative science improvements that can be realized with these tools using the 10-m diameter Keck telescopes. The significantly improved capabilities produced through this program will be directly available to astronomers at the California Institute of Technology, the University of California, and the University of Hawaii through their time allocation committees, while the entire U.S. community will benefit due to their access to Keck through NASA and the NSF Telescope System Instrumentation Program. Moreover, success at the Keck Observatory would enable PSF determination to become a reality for AO on large telescopes worldwide, as the algorithms and techniques will be made publically available. Keck will also reinforce its role in the training of AO experts and continue to offer educational programs and services to work with local residents, educators and especially students, including its strong participation in the Akamai Workforce Initiative aimed at local Hawaiian students.

Funding for the development of real-time PSF assessment techniques is being provided by NSFs Division of Astronomical Sciences through its Advanced Technologies and Instrumentation program.

Barro G.,University of California at Santa Cruz | Trump J.R.,Pennsylvania State University | Koo D.C.,University of California at Santa Cruz | Dekel A.,Hebrew University of Jerusalem | And 28 more authors.
Astrophysical Journal | Year: 2014

We present Keck-I MOSFIRE near-infrared spectroscopy for a sample of 13 compact star-forming galaxies (SFGs) at redshift 2 ≤ z ≤ 2.5 with star formation rates of SFR ∼ 100 M⊙ yr-1 and masses of log(M/M⊙) ∼10.8. Their high integrated gas velocity dispersions of σint km s-1, as measured from emission lines of Hα and [O III], and the resultant M ∗-σint relation and M ⋆-Mdyn all match well to those of compact quiescent galaxies at z ∼ 2, as measured from stellar absorption lines. Since log(M ∗/Mdyn) =-0.06 ± 0.2 dex, these compact SFGs appear to be dynamically relaxed and evolved, i.e., depleted in gas and dark matter (<13%), and present larger σint than their non-compact SFG counterparts at the same epoch. Without infusion of external gas, depletion timescales are short, less than ∼300 Myr. This discovery adds another link to our new dynamical chain of evidence that compact SFGs at z ≳ 2 are already losing gas to become the immediate progenitors of compact quiescent galaxies by z ∼ 2. © 2014. The American Astronomical Society. All rights reserved.

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