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1. An Exo-Kuiper Belt and An Extended Halo around HD 191089 in Scattered Light

Author

Pauline Arriaga, Bin Ren, Sloane Wiktorowicz, Alexandra Z. Greenbaum, Rémi Soummer, Arthur Vigan, Christophe Pinte, Robert J. De Rosa, Inseok Song, Laurent Pueyo, Jean-Baptiste Ruffio, Johan Mazoyer, Fredrik T. Rantakyrö, Juan Sebastián Bruzzone, Thomas M. Esposito, Tara Cotten, Patrick Ingraham, Travis Barman, Christopher C. Stark, Sandrine Thomas, J. Kent Wallace, Magaret Moerchen, Jeffrey Chilcote, Julien Rameau, Franck Marchis, Adam C. Schneider, Megan Ansdell, Malena Rice, Christian Marois, Li-Wei Hung, Stanimir Metchev, Lisa Poyneer, Bruce Macintosh, Charles A. Poteet, S. Mark Ammons, René Doyon, James E. Larkin, Kimberly Ward-Duong, Tushar Mittal, Pascale Hibon, Gaspard Duchene, Michael P. Fitzgerald, Quinn Konopacky, Maxwell A. Millar-Blanchaer, Glenn Schneider, Joanna Bulger, Jérôme Maire, Mamadou N'Diaye, Katherine B. Follette, Rebecca Oppenheimer, J. Brendan Hagan, James R. Graham, Eric L. Nielsen, Marie Ygouf, Christine Chen, Paul Kalas, Jennifer Patience, Abhijith Rajan, Marshall D. Perrin, Stephen J. Goodsell, Schuyler Wolff, Anand Sivaramakrishnan, Dean C. Hines, Vanessa P. Bailey, Dmitry Savransky, Elodie Choquet, D. M. Palmer, John H. Debes, Jason J. Wang, Francois Menard, Dominic M. Ryan, Colin Norman, Benjamin L. Gerard, Department of Physics and Astronomy [Baltimore], Johns Hopkins University (JHU), Department of Mathematics and Statistics [Baltimore], Loyola University [Maryland, Baltimore], Caltech Department of Astronomy [Pasadena], California Institute of Technology (CALTECH), Laboratoire d'Astrophysique de Marseille (LAM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), Jet Propulsion Laboratory (JPL), California Institute of Technology (CALTECH)-NASA, Space Telescope Science Institute (STSci), Department of Astronomy [Berkeley], University of California [Berkeley], University of California-University of California, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Yale University [New Haven], Steward Observatory, University of Arizona, Lawrence Livermore National Laboratory (LLNL), Department of Physics and Astronomy [UCLA, Los Angeles], University of California [Los Angeles] (UCLA), Lunar and Planetary Laboratory [Tucson] (LPL), University of Western Ontario (UWO), Subaru Telescope, National Astronomical Observatory of Japan (NAOJ), University of Notre Dame [Indiana] (UND), University of Georgia [USA], Institut de Recherche sur les Exoplanètes (iREX), Université de Montréal [Montréal], Amherst College, Gemini Observatory [Southern Operations Center], Association of Universities for Research in Astronomy (AURA), University of Victoria [Canada] (UVIC), National Research Council of Canada (NRC), Department of Astronomy [Ann Arbor], University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, Natural Sounds and Night Skies Division, Large Synoptic Survey Telescope (LSST), Search for Extraterrestrial Intelligence Institute (SETI), University of California [San Diego] (UC San Diego), University of California, Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), Stanford University [Stanford], Department of Physics and Astronomy [Stony Brook], Stony Brook University [SUNY] (SBU), State University of New York (SUNY)-State University of New York (SUNY), Department of Earth and Planetary Science [UC Berkeley] (EPS), American Geophysical Union, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), American Museum of Natural History (AMNH), Arizona State University [Tempe] (ASU), School of Physics and Astronomy [Clayton], Monash University [Clayton], Department of Astronomy [Ithaca], Cornell University, Department of Astronomy and Astrophysics [UCSC Santa Cruz], University of California [Santa Cruz] (UCSC), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Infrared Processing and Analysis Center (IPAC), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), NASA-California Institute of Technology (CALTECH), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université de Montréal (UdeM), Stanford University, Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Cornell University [New York], University of California [Berkeley] (UC Berkeley), University of California (UC)-University of California (UC), University of California (UC), American Geophysical Union [Washington], Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), University of California [Santa Cruz] (UC Santa Cruz), and Universiteit Leiden

Subjects
010504 meteorology & atmospheric sciences, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Phase (waves), FOS: Physical sciences, techniques: image processing, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Ring (chemistry), stars: individual (HD 191089), 01 natural sciences, Power law, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Earth and Planetary Astrophysics (astro-ph.EP), Physics, Debris disk, Range (particle radiation), Scattering, protoplanetary disks, Astronomy and Astrophysics, stars: imaging, Astrophysics - Solar and Stellar Astrophysics, radiative transfer, 13. Climate action, Space and Planetary Science, Halo, Astrophysics::Earth and Planetary Astrophysics, Intensity (heat transfer), Astrophysics - Earth and Planetary Astrophysics
Abstract

We have obtained Hubble Space Telescope STIS and NICMOS, and Gemini/GPI scattered light images of the HD 191089 debris disk. We identify two spatial components: a ring resembling Kuiper Belt in radial extent (FWHM: ${\sim}$25 au, centered at ${\sim}$46 au), and a halo extending to ${\sim}$640 au. We find that the halo is significantly bluer than the ring, consistent with the scenario that the ring serves as the "birth ring" for the smaller dust in the halo. We measure the scattering phase functions in the 30{\deg}-150{\deg} scattering angle range and find the halo dust is both more forward- and backward-scattering than the ring dust. We measure a surface density power law index of -0.68${\pm}$0.04 for the halo, which indicates the slow-down of the radial outward motion of the dust. Using radiative transfer modeling, we attempt to simultaneously reproduce the (visible) total and (near-infrared) polarized intensity images of the birth ring. Our modeling leads to mutually inconsistent results, indicating that more complex models, such as the inclusion of more realistic aggregate particles, are needed., Comment: 29 pages, 18 figures, ApJ accepted

Published
2019
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2. Direct Imaging of the HD 35841 Debris Disk: A Polarized Dust Ring from Gemini Planet Imager and an Outer Halo from HST/STIS

Author

Bruce Macintosh, Juan Sebastián Bruzzone, Abhijith Rajan, Julien Rameau, Quinn Konopacky, Jérôme Maire, Pauline Arriaga, Bin Ren, Lisa Poyneer, Inseok Song, Rémi Soummer, Sandrine Thomas, Adam C. Schneider, Rebecca Oppenheimer, Christine Chen, Paul Kalas, James R. Graham, Alexandra Z. Greenbaum, David Palmer, J. Kent Wallace, James E. Larkin, Jason J. Wang, Sloane J. Wiktorowicz, Robert J. De Rosa, Eugene Chiang, Gaspard Duchêne, Thomas M. Esposito, Stephen J. Goodsell, Laurent Pueyo, Schuyler Wolff, Joanna Bulger, Marshall D. Perrin, Eric L. Nielsen, Patrick Ingraham, Pascale Hibon, Jeffrey Chilcote, Vanessa P. Bailey, Tara Cotten, Johan Mazoyer, Stanimir Metchev, Dominic M. Ryan, S. Mark Ammons, Kimberly Ward-Duong, Dmitry Savransky, René Doyon, Li-Wei Hung, Maxwell A. Millar-Blanchaer, Franck Marchis, Jennifer Patience, Malena Rice, Elodie Choquet, Travis Barman, Michael P. Fitzgerald, Christian Marois, Fredrik T. Rantakyrö, Anand Sivaramakrishnan, Megan Ansdell, Katherine B. Follette, Lawrence Berkeley National Laboratory [Berkeley] (LBNL), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Department of Mathematics [Berkeley], University of California [Berkeley], University of California-University of California, Search for Extraterrestrial Intelligence Institute (SETI), Caltech Department of Astronomy [Pasadena], California Institute of Technology (CALTECH), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Johns Hopkins University (JHU), Space Telescope Science Institute (STSci), Department of Physics and Astronomy [UCLA, Los Angeles], University of California [Los Angeles] (UCLA), Department of Earth and Planetary Science [UC Berkeley] (EPS), Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), Stanford University, Physics and Astronomy Department, Amherst College, European Southern Observatory [Santiago] (ESO), European Southern Observatory (ESO), Laboratoire Universitaire d'Astrophysique de Nice (LUAN), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Arizona State University [Tempe] (ASU), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), California Institute of Technology (CALTECH)-NASA, Stanford University [Stanford], and Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astronomy & Astrophysics, 01 natural sciences, circumstellar matter, 010305 fluids & plasmas, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Gemini Planet Imager, Surface brightness, planetary systems [infrared], 010303 astronomy & astrophysics, individual [stars], Astrophysics::Galaxy Astrophysics, Physics, Earth and Planetary Astrophysics (astro-ph.EP), Debris disk, Scattering, high angular resolution [techniques], Astronomy and Astrophysics, Planetary system, Radiation pressure, 13. Climate action, Space and Planetary Science, astro-ph.EP, Spectral energy distribution, Halo, Astrophysics::Earth and Planetary Astrophysics, Astronomical and Space Sciences, Astrophysics - Earth and Planetary Astrophysics
Abstract

We present new high resolution imaging of a light-scattering dust ring and halo around the young star HD 35841. Using spectroscopic and polarimetric data from the Gemini Planet Imager in H-band (1.6 microns), we detect the highly inclined (i=85 deg) ring of debris down to a projected separation of ~12 au (~0.12") for the first time. Optical imaging from HST/STIS shows a smooth dust halo extending outward from the ring to >140 au (>1.4"). We measure the ring's scattering phase function and polarization fraction over scattering angles of 22-125 deg, showing a preference for forward scattering and a polarization fraction that peaks at ~30% near the ansae. Modeling of the scattered-light disk indicates that the ring spans radii of ~60-220 au, has a vertical thickness similar to that of other resolved dust rings, and contains grains as small as 1.5 microns in diameter. These models also suggest the grains have a low porosity, are more likely to consist of carbon than astrosilicates, and contain significant water ice. The halo has a surface brightness profile consistent with that expected from grains pushed by radiation pressure from the main ring onto highly eccentric but still bound orbits. We also briefly investigate arrangements of a possible inner disk component implied by our spectral energy distribution models, and speculate about the limitations of Mie theory for doing detailed analyses of debris disk dust populations., Accepted to AJ. 22 pages, 11 figures, 3 tables

Published
2018
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3. Orbits for the Impatient: A Bayesian Rejection Sampling Method for Quickly Fitting the Orbits of Long-Period Exoplanets

Author

Sarah Blunt, Bruce Macintosh, Quinn Konopacky, Christian Marois, Dominic M. Ryan, James R. Graham, Julien Rameau, Jason J. Wang, Adam C. Schneider, Gaspard Duchêne, Eric L. Nielsen, Laurent Pueyo, Robert J. De Rosa, and Franck Marchis

Subjects
Physics, Orbital elements, Earth and Planetary Astrophysics (astro-ph.EP), 010504 meteorology & atmospheric sciences, Rejection sampling, Bayesian probability, Brown dwarf, FOS: Physical sciences, Astronomy and Astrophysics, Markov chain Monte Carlo, Astrometry, Orders of magnitude (angular velocity), 01 natural sciences, Exoplanet, Statistics::Computation, symbols.namesake, Space and Planetary Science, 0103 physical sciences, symbols, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Algorithm, 0105 earth and related environmental sciences, Astrophysics - Earth and Planetary Astrophysics
Abstract

We describe a Bayesian rejection sampling algorithm designed to efficiently compute posterior distributions of orbital elements for data covering short fractions of long-period exoplanet orbits. Our implementation of this method, Orbits for the Impatient (OFTI), converges up to several orders of magnitude faster than two implementations of MCMC in this regime. We illustrate the efficiency of our approach by showing that OFTI calculates accurate posteriors for all existing astrometry of the exoplanet 51 Eri b up to 100 times faster than a Metropolis-Hastings MCMC. We demonstrate the accuracy of OFTI by comparing our results for several orbiting systems with those of various MCMC implementations, finding the output posteriors to be identical within shot noise. We also describe how our algorithm was used to successfully predict the location of 51 Eri b six months in the future based on less than three months of astrometry. Finally, we apply OFTI to ten long-period exoplanets and brown dwarfs, all but one of which have been monitored over less than 3% of their orbits, producing fits to their orbits from astrometric records in the literature., 32 pages, 28 figures, Accepted to AJ

Published
2017

4. Modeling the afterglow of the possible Fermi-GBM event associated with GW150914

Author

Brian J. Morsony, Jared C. Workman, and Dominic M. Ryan

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Brightness, 010308 nuclear & particles physics, Gravitational wave, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, LIGO, Afterglow, Space and Planetary Science, 0103 physical sciences, Radio frequency, Gamma-ray burst, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, Event (particle physics), Fermi Gamma-ray Space Telescope
Abstract

We model the possible afterglow of the Fermi GBM event associated with LIGO detection GW150914, under the assumption that the gamma-ray are produced by a short GRB-like relativistic outflow. We model GW150914-GBM as both a weak, on-axis short GRB and normal short GRB seen far off axis. Given the large uncertainty in the position of GW150914, we determine that the best chance of finding the afterglow is with ASKAP or possibly the MWA, with the flux from an off-axis short GRB reaching 0.2 - 4 mJy (0.12 - 16 mJy) at 150 MHz (863.5 MHz) by 1 - 12 months after the initial event. At low frequencies, the source would evolve from a hard to soft spectrum over several months. The radio afterglow would be detectable for several months to years after it peaks, meaning the afterglow may still be detectable and increasing in brightness NOW (mid-July 2016). With a localization from the MWA or ASKAP, the afterglow would be detectable at higher radio frequencies with the ATCA and in X-rays with Chandra or XMM., Comment: 7 pages, 4 figures, 1 table. Accepted by ApJL

Published
2016
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5. Astrometric confirmation and preliminary orbital parameters of the young exoplanet 51 Eridani b with the Gemini Planet Imager

Author

Inseok Song, Patrick Ingraham, James R. Graham, Sarah Blunt, Gautam Vasisht, David Lafrenière, Jason J. Wang, Julien Rameau, Mara Johnson-Groh, Gaspard Duchêne, Christian Marois, Adam C. Schneider, Marshall D. Perrin, Laurent Pueyo, Franck Marchis, Ashley Chontos, Rebecca Oppenheimer, Jennifer Patience, Abhijith Rajan, Benjamin L. Gerard, Pauline Arriaga, Eric L. Nielsen, Dominic M. Ryan, Maxwell A. Millar-Blanchaer, Vanessa P. Bailey, Thomas M. Esposito, Paul Kalas, Jean-Baptiste Ruffio, Katie M. Morzinski, Fredrik T. Rantakyrö, Bruce Macintosh, Kimberly Ward-Duong, Katherine B. Follette, Alexandra Z. Greenbaum, Stephen J. Goodsell, Schuyler Wolff, Debby Tran, Stanimir Metchev, Quinn Konopacky, Pascale Hibon, Michael P. Fitzgerald, S. Mark Ammons, René Doyon, Jeffrey Chilcote, Anand Sivaramakrishnan, Daniel C. Fabrycky, Robert J. De Rosa, Rahul Patel, Tara Cotten, and Jérôme Maire

Subjects
010504 meteorology & atmospheric sciences, Epoch (astronomy), detection [planets and satellites], FOS: Physical sciences, Astrophysics, Astronomy & Astrophysics, 01 natural sciences, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Gemini Planet Imager, 10. No inequality, 010303 astronomy & astrophysics, planetary systems, individual [stars], Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Physics, Orbital elements, Earth and Planetary Astrophysics (astro-ph.EP), Astronomy and Astrophysics, Planetary system, Exoplanet, Orbit, Space and Planetary Science, Orbital motion, astro-ph.EP, Astrophysics::Earth and Planetary Astrophysics, Astronomical and Space Sciences, Astrophysics - Earth and Planetary Astrophysics
Abstract

We present new Gemini Planet Imager observations of the young exoplanet 51 Eridani b which provide further evidence that the companion is physically associated with 51 Eridani. Combining this new astrometric measurement with those reported in the literature, we significantly reduce the posterior probability that 51 Eridani b is an unbound foreground or background T-dwarf in a chance alignment with 51 Eridani to $2\times10^{-7}$, an order of magnitude lower than previously reported. If 51 Eridani b is indeed a bound object, then we have detected orbital motion of the planet between the discovery epoch and the latest epoch. By implementing a computationally efficient Monte Carlo technique, preliminary constraints are placed on the orbital parameters of the system. The current set of astrometric measurements suggest an orbital semimajor axis of $14^{+7}_{-3}$ AU, corresponding to a period of $41^{+35}_{-12}$ years (assuming a mass of $1.75$ $M_{\odot}$ for the central star), and an inclination of $138^{+15}_{-13}$ deg. The remaining orbital elements are only marginally constrained by the current measurements. These preliminary values suggest an orbit which does not share the same inclination as the orbit of the distant M-dwarf binary, GJ 3305, which is a wide physically bound companion to 51 Eridani., Comment: 7 pages, 1 table, 4 figures, accepted for publication in ApJ Letters (November 4, 2015). Additional text added to section 4 during referee stage, and minor corrections during proofing

Published
2015
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7. Scale height — A parameter for characterizing atmosphere

Author

Kevin M. Lee and Dominic M. Ryan

Subjects
Physics, Gravity (chemistry), Ideal gas law, General Physics and Astronomy, Scale height, Astrophysics, Stellar classification, Education, law.invention, Atmosphere, Acceleration, law, Terrestrial planet, Astrophysics::Earth and Planetary Astrophysics, Hydrostatic equilibrium, Astrophysics::Galaxy Astrophysics
Abstract

Scale height is a parameter used to describe how something fades away with increasing distance. It is exclusively applied to atmospheres1 of terrestrial planets and moons in this paper, but it is used in many other contexts, e.g., describing the distances of various types of stars from the galactic disk.2 It brings together diverse concepts such as hydrostatic equilibrium, the ideal gas law, and the acceleration due to gravity to describe the extent to which an atmosphere hugs its parent body.

Published
2015
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8. Identification of a novel aspartic protease (Asp 2) as beta-secretase

Author

David Simmons, David J. Powell, Christopher Southan, Conrad Gerald Chapman, Dominic M. Ryan, David R. Howlett, Frank S. Walsh, Israel S. Gloger, David G. Tew, Thomas D. Meek, Kay Elizabeth Murphy, Gary Christie, Colin Dingwall, Trudi S. Smith, and Ishrut Hussain

Subjects
Molecular Sequence Data, Cathepsin D, Biology, Transfection, Hippocampus, Cell Line, Cellular and Molecular Neuroscience, Amyloid beta-Protein Precursor, Alzheimer Disease, mental disorders, Endopeptidases, Papain, Amyloid precursor protein, Animals, Aspartic Acid Endopeptidases, Humans, Amino Acid Sequence, Molecular Biology, Sequence Homology, Amino Acid, Endoplasmic reticulum, Cell Membrane, Cell Biology, Middle Aged, Molecular biology, Transmembrane protein, Recombinant Proteins, Beta-secretase 1, Alpha secretase, Amino Acid Substitution, COS Cells, biology.protein, Mutagenesis, Site-Directed, Verubecestat, Female, Amyloid Precursor Protein Secretases, Amyloid precursor protein secretase, Sequence Alignment
Abstract

The Alzheimer's disease beta-amyloid peptide (Abeta) is produced by excision from the type 1 integral membrane glycoprotein amyloid precursor protein (APP) by the sequential actions of beta- and then gamma-secretases. Here we report that Asp 2, a novel transmembrane aspartic protease, has the key activities expected of beta-secretase. Transient expression of Asp 2 in cells expressing APP causes an increase in the secretion of the N-terminal fragment of APP and an increase in the cell-associated C-terminal beta-secretase APP fragment. Mutation of either of the putative catalytic aspartyl residues in Asp 2 abrogates the production of the fragments characteristic of cleavage at the beta-secretase site. The enzyme is present in normal and Alzheimer's disease (AD) brain and is also found in cell lines known to produce Abeta. Asp 2 localizes to the Golgi/endoplasmic reticulum in transfected cells and shows clear colocalization with APP in cells stably expressing the 751-amino-acid isoform of APP.

Published
1999

9. Individual, Model-independent Masses of the Closest Known Brown Dwarf Binary to the Sun.

Author

E. Victor Garcia, S. Mark Ammons, Maissa Salama, Ian Crossfield, Eduardo Bendek, Jeffrey Chilcote, Vincent Garrel, James R. Graham, Paul Kalas, Quinn Konopacky, Jessica R. Lu, Bruce Macintosh, Eduardo Marin, Christian Marois, Eric Nielsen, Benoît Neichel, Don Pham, Robert J. De Rosa, Dominic M. Ryan, and Maxwell Service

Subjects
VERY large telescopes, MONTE Carlo method, BARYCENTRIC dynamical time, MARKOV chain Monte Carlo
Abstract

At a distance of ∼2 pc, our nearest brown dwarf neighbor, Luhman 16 AB, has been extensively studied since its discovery 3 years ago, yet its most fundamental parameter—the masses of the individual dwarfs—has not been constrained with precision. In this work, we present the full astrometric orbit and barycentric motion of Luhman 16 AB and the first precision measurements of the individual component masses. We draw upon archival observations spanning 31 years from the European Southern Observatory (ESO) Schmidt Telescope, the Deep Near-Infrared Survey of the Southern Sky (DENIS), public FORS2 data on the Very Large Telescope (VLT), and new astrometry from the Gemini South Multiconjugate Adaptive Optics System (GeMS). Finally, we include three radial velocity measurements of the two components from VLT/CRIRES, spanning one year. With this new data sampling a full period of the orbit, we use a Markov chain Monte Carlo algorithm to fit a 16-parameter model incorporating mutual orbit and barycentric motion parameters and constrain the individual masses to be for the T dwarf and for the L dwarf. Our measurements of Luhman 16 AB’s mass ratio and barycentric motion parameters are consistent with previous estimates in the literature utilizing recent astrometry only. The GeMS-derived measurements of the Luhman 16 AB separation in 2014–2015 agree closely with Hubble Space Telescope (HST) measurements made during the same epoch, and the derived mutual orbit agrees with those measurements to within the HST uncertainties of 0.3–0.4 mas. [ABSTRACT FROM AUTHOR]

Published
2017
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10. ASTROMETRIC CONFIRMATION AND PRELIMINARY ORBITAL PARAMETERS OF THE YOUNG EXOPLANET 51 ERIDANI b WITH THE GEMINI PLANET IMAGER.

Author

Robert J. De Rosa, Eric L. Nielsen, Sarah C. Blunt, James R. Graham, Quinn M. Konopacky, Christian Marois, Laurent Pueyo, Julien Rameau, Dominic M. Ryan, Jason J. Wang, Vanessa Bailey, Ashley Chontos, Daniel C. Fabrycky, Katherine B. Follette, Bruce Macintosh, Franck Marchis, S. Mark Ammons, Pauline Arriaga, Jeffrey K. Chilcote, and Tara H. Cotten

Published
2015
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