Browsing by FAS Department "Astronomy"

Now showing items 1-20 of 945

    • 1.3 mm Wavelength VLBI of Sagittarius A*: Detection of Time-Variable Emission on Event Horizon Scales 

      Fish, Vincent L.; Doeleman, Sheperd Samuel; Beaudoin, Christopher; Blundell, Raymond; Bolin, David E.; Bower, Geoffrey C.; Chamberlin, Richard; Freund, Robert; Friberg, Per; Gurwell, Mark Andrew; Honma, Mareki; Inoue, Makoto; Krichbaum, Thomas P.; Lamb, James; Marrone, Daniel P.; Moran, James M.; Oyama, Tomoaki; Plambeck, Richard; Primiani, Rurik A.; Rogers, Alan E. E.; Smythe, Daniel L.; SooHoo, Jason; Strittmatter, Peter; Tilanus, Remo P. J.; Titus, Michael; Weintroub, Jonathan; Wright, Melvyn; Woody, David; Young, Ken Harbour; Ziurys, Lucy M. (IOP Publishing, 2011)
      Sagittarius A*, the ~4 × 106 M ☉ black hole candidate at the Galactic center, can be studied on Schwarzschild radius scales with (sub)millimeter wavelength very long baseline interferometry (VLBI). We report on 1.3 mm ...

    • A 1.9 Earth Radius Rocky Planet and the Discovery of a Non-Transiting Planet in the Kepler-20 System 

      Buchhave, Lars A.; Dressing, Courtney D.; Dumusque, Xavier; Rice, Ken; Vanderburg, Andrew Michael; Mortier, Annelies; Lopez-Morales, Mercedes; Lopez, Eric; Lundkvist, Mia S.; Kjeldsen, Hans; Affer, Laura; Bonomo, Aldo S.; Charbonneau, David; Cameron, Andrew Collier; Cosentino, Rosario; Figueira, Pedro; Fiorenzano, Aldo F. M.; Harutyunyan, Avet; Haywood, Raphaelle D.; Johnson, John Asher; Latham, David Winslow; Lovis, Christophe; Malavolta, Luca; Mayor, Michel; Micela, Giusi; Molinari, Emilio; Motalebi, Fatemeh; Nascimbeni, Valerio; Pepe, Francesco; Phillips, David F.; Piotto, Giampaolo; Pollacco, Don; Queloz, Didier; Sasselov, Dimitar D.; Ségransan, Damien; Sozzetti, Alessandro; Udry, Stéphane; Watson, Chris (American Astronomical Society, 2016)
      Kepler-20 is a solar-type star (V = 12.5) hosting a compact system of five transiting planets, all packed within the orbital distance of Mercury in our own solar system. A transition from rocky to gaseous planets with a ...

    • 23 GHz VLBI Observations of SN 2008ax 

      Marti-Vidal, I.; Alberdi, A.; Ros, E.; Shapiro, Irwin Ira; Beswick, R.J.; Pedlar, A.; Immler, S.; Panagia, N.; Van Dyk, S.; Marcaide, J. M.; Guirado, J. C.; Perrez-Torres, M. A.; Muxlow, T. W. B.; Argo, M. K.; Stockdale, C. J.; Sramek, R. A.; Weiler, K. W. (EDP Sciences, 2009)
      We report on phase-referenced 23 GHz Very-Long-Baseline-Interferometry (VLBI) observations of the type IIb supernova SN 2008ax, made with the Very Long Baseline Array (VLBA) on 2 April 2008 (33 days after explosion). These ...

    • 230 GHz VLBI observations of M87: event-horizon-scale structure at the enhanced very-high-energy γ-ray state in 2012 

      Akiyama, Kazunori; Lu, Ru-Sen; Fish, Vincent; Doeleman, Sheperd S.; Broderick, Avery; Dexter, Jason; Hada, Kazuhiro; Kino, Motoki; Nagai, Hiroshi; Honma, Mareki; Johnson, Michael D.; Algaba, Juan; Asada, Keiichi; Brinkerink, Christiaan; Blundell, Raymond; Bower, Geoffrey; Cappallo, Roger; Crew, Geoffrey; Dexter, Matt; Dzib, Sergio; Freund, Robert; Friberg, Per; Gurwell, Mark Andrew; Ho, Paul; Inoue, Makoto; Krichbaum, Thomas; Loinard, Laurent; MacMahon, David; Marrone, Daniel; Moran, James M.; Nakamura, Masanori; Nagar, Neil; Ortiz-Leon, Gisela; Plambeck, Richard; Pradel, Nicolas; Primiani, Rurik A.; Rogers, Alan; Roy, Alan; SooHoo, Jason; Tavares, Jonathan-León; Tilanus, Remo; Titus, Michael; Wagner, Jan; Weintroub, Jonathan; Yamaguchi, Paul Isami; Young, Ken Harbour; Zensus, Anton; Ziurys, Lucy (IOP Publishing, 2015)
      We report on 230 GHz (1.3 mm) VLBI observations of M87 with the Event Horizon Telescope using antennas on Mauna Kea in Hawaii, Mt. Graham in Arizona and Cedar Flat in California. For the first time, we have acquired 230 ...

    • 3-Cm Fine Structure Masers: A Unique Signature of Supermassive Black Hole Formation via Direct Collapse in the Early Universe 

      Dijkstra, Mark; Sethi, Shiv; Loeb, Abraham (American Astronomical Society, 2016)
      The direct collapse black hole (DCBH) scenario describes the isothermal collapse of a pristine gas cloud directly into a massive, M_BH=10^4-10^6 M_sun black hole. In this paper we show that large HI column densities of ...

    • 3c 220.3: A Radio Galaxy Lensing a Submillimeter Galaxy 

      Haas, Martin; Leipski, Christian; Barthel, Peter; Wilkes, Belinda Jane; Vegetti, Simona; Bussmann, R. Shane; Willner, Steven P.; Westhues, Christian; Ashby, Matthew L N; Chini, Rolf; Clements, David L.; Fassnacht, Christopher D.; Horesh, Assaf; Klaas, Ulrich; Koopmans, Léon V. E.; Kuraszkiewicz, Joanna; Lagattuta, David J.; Meisenheimer, Klaus; Stern, Daniel; Wylezalek, Dominika (IOP Publishing, 2014)
      Herschel Space Observatory photometry and extensive multiwavelength follow-up have revealed that the powerful radio galaxy (PRG) 3C 220.3 at z = 0.685 acts as a gravitational lens for a background submillimeter galaxy (SMG) ...

    • A 4% Geometric Distance to the Galaxy NGC4258 from Orbital Motions in a Nuclear Gas Disk 

      Herrnstein, J.; Moran, James M.; Greenhill, Lincoln Jared; Diamond, P.; Inoue, M.; Nakai, N.; Miyoshi, M.; Henkel, C.; Riess, A. (Springer Nature, 1999)
      The accurate measurement of extragalactic distances is a central challenge of modern astronomy, being required for any realistic description of the age, geometry and fate of the Universe. The measurement of relative ...

    • The 4.5 µm full-orbit phase curve of the hot Jupiter HD 209458B 

      Zellem, Robert T.; Lewis, Nikole K.; Knutson, Heather A.; Griffith, Caitlin A.; Showman, Adam P.; Fortney, Jonathan J.; Cowan, Nicolas B.; Agol, Eric; Burrows, Adam; Charbonneau, David; Deming, Drake; Laughlin, Gregory; Langton, Jonathan (IOP Publishing, 2014)
      The hot Jupiter HD 209458b is particularly amenable to detailed study as it is among the brightest transiting exoplanet systems currently known (V-mag = 7.65; K-mag = 6.308) and has a large planet-to-star contrast ratio. ...

    • 8.4 GHz VLBI Observations of SN 2004et in NGC 6946 

      Martí-Vidal, I.; Marcaide, J. M.; Alberdi, A.; Guirado, J. C.; Lara, L.; Pérez-Torres, M. A.; Ros, E.; Argo, M. K.; Beswick, R. J.; Muxlow, T. W. B.; Pedlar, A.; Shapiro, Irwin; Stockdale, C. J.; Sramek, R. A.; Weiler, K. W.; Vinko, J. (EDP Sciences, 2007-05-25)
      We report on 8.4 GHz very-long-baseline-interferometry (VLBI) observations of the type II-P supernova SN2004et in the spiral galaxy NGC 6946, made on 20 February 2005 (151 days after explosion). The Very Large Array (VLA) ...

    • AAS WorldWide Telescope: Seamless, Cross-Platform Data Visualization Engine for Astronomy Research, Education, and Democratizing Data 

      Rosenfield, Philip; Fay, Jonathan; Gilchrist, Ronald; Chenzhou, Cui; Weigel, David; Robitaille, Thomas; Otor, Oderah Justin; Goodman, Alyssa (The American Astronomical Society, 2018-05-11)
      The American Astronomical Society's WorldWide Telescope (WWT) project enables terabytes of astronomical images, data, and stories to be viewed and shared among researchers, exhibited in science museums, projected into ...

    • Absence of a Thick Atmosphere on the Terrestrial Exoplanet LHS 3844b 

      Kreidberg, Laura; Hu, Renyu; Schaefer, Laura; Deming, Drake; Stevenson, Kevin B.; Dittmann, Jason; Vanderburg, Andrew; Berardo, David; Guo, Xueying; Stassun, Keivan; Crossfield, Ian; Charbonneau, David; Loeb, Abraham; Ricker, George; Seager, Sara; Vanderspek, Roland; Koll, Daniel; Morley, Caroline; Latham, David (Springer Science and Business Media LLC, 2019-08-19)
      The majority of terrestrial planets in the Galaxy orbit small stars with radii less than 60% that of the Sun1,2. Theoretical models predict that these planets are more vulnerable to at- mospheric escape and collapse than ...

    • Absolute polarization angle calibration using polarized diffuse Galactic emission observed by BICEP 

      Matsumura, Tomotake; Ade, Peter; Barkats, Denis; Barron, Darcy; Battle, John O.; Bierman, Evan M.; Bock, James J.; Chiang, H. Cynthia; Crill, Brendan P.; Dowell, C. Darren; Duband, Lionel; Hivon, Eric F.; Holzapfel, William L.; Hristov, Viktor V.; Jones, William C.; Keating, Brian G.; Kovac, John M; Kuo, Chao-lin; Lange, Andrew E.; Leitch, Erik M.; Mason, Peter V.; Nguyen, Hien T.; Ponthieu, Nicolas; Pryke, Clement L.; Richter, Steffen; Rocha, Graca M.; Takahashi, Yuki D.; Yoon, Ki Won (2017-08-04)
      We present a method of cross-calibrating the polarization angle of a polarimeter using Bicep Galactic observations. Bicep was a ground based experiment using an array of 49 pairs of polarization sensitive bolometers observing ...

    • Absolute Properties of the Low-Mass Eclipsing Binary CM Draconis 

      Morales, Juan Carlos; Ribas, Ignasi; Jordi, Carme; Torres, Guillermo; Gallardo, Jose; Guinan, Edward F.; Charbonneau, David; Wolf, Marek; Latham, David W.; Anglada-Escude, Guillem; Bradstreet, David H.; Everett, Mark E.; O'Donovan, Francis T.; Mandushev, Georgi; Mathieu, Robert D. (Institute of Physics, 2009)
      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 ...

    • Absorption in X-ray spectra of high-redshift quasars 

      Elvis, Martin S.; Fiore, Fabrizio; Wilkes, Belinda Jane; McDowell, Jonathan Christopher; Bechtold, Jill (IOP Publishing, 1994)
      We present evidence that X-ray absorption is common in high-redshift quasars. We have studied six high-redshift (z approximately 3) quasars with the ROSAT Position Sensitive Proportional Counter (PSPC) of which four are ...

    • Accelerations of Water Masers in NGC 4258 

      Bragg, Ann E.; Greenhill, Lincoln Jared; Moran, James M.; Henkel, Christian (IOP Publishing, 2000)
      The water masers in NGC4258 delineate the structure and dynamics of a sub-parsec-diameter accretion disk around a supermassive black hole. VLBA observations provide precise information about the positions in the plane of ...

    • Accurate galactic N(H) values towards quasars and AGN 

      Elvis, Martin; Wilkes, Belinda Jane; Lockman, Felix J. (IOP Publishing, 1989)
      Integrated Galactic 21-cm column densities toward about 174 quasars and AGN are presented. The data are corrected for stray radiation, using the technique of Lockman et al. (1986). Because of the 21-arcmin beam size of the ...

    • Active Galactic Nucleus and Starburst Classification from Spitzer Mid‐Infrared Spectra for High‐Redshift SWIRE Sources 

      Weedman, D.; Polletta, M.; Lonsdale, C. J.; Wilkes, Belinda Jane; Siana, B.; Houck, John; Surace, J.; Shupe, D.; Farrah, D.; Smith, H. E. (IOP Publishing, 2006)
      Spectra have been obtained with the Infrared Spectrograph (IRS) on the Spitzer Space Telescope for 20 sources in the Lockman Hole field of the SWIRE survey. The sample is divided between sources with indicators of an ...

    • An Activity-Rotation Relationship and Kinematic Analysis of Nearby Mid-to-Late-Type M Dwarfs 

      West, Andrew A.; Weisenburger, Kolby L.; Irwin, Jonathan; Berta-Thompson, Zachory K.; Charbonneau, David; Dittmann, Jason Adam; Pineda, J. Sebastian (IOP Publishing, 2015)
      Using spectroscopic observations and photometric light curves of 238 nearby M dwarfs from the MEarth exoplanet transit survey, we examine the relationships between magnetic activity (quantified by Hα emission), rotation ...

    • The ADS All-Sky Survey 

      Pepe, Alberto; Goodman, Alyssa; Muench, August A. (Astronomical Society of the Pacific, 2012)
      The ADS All-Sky Survey (ADSASS) is an ongoing effort aimed at turning the NASA Astrophysics Data System (ADS), widely known for its unrivaled value as a literature resource for astronomers, into a data resource. The ADS ...

    • Advection-dominated accretion and the black hole event horizon 

      Narayan, Ramesh; McClintock, Jeffrey E. (Elsevier BV, 2008)
      As the luminosity of an accreting black hole drops to a few percent of Eddington, the spectrum switches from the familiar soft state to a hard state that is well-described by a distended and tenuous advection-dominated ...