Stellar Dynamics: Rotation, Convection, and Magnetic Fields
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Hydrodynamical Simulations of Convection-Related Stellar Micro-Variability II
A&A 506, 167–173 (2009) Astronomy DOI: 10.1051/0004-6361/200911930 & c ESO 2009 Astrophysics The CoRoT space mission: early results Special feature Hydrodynamical simulations of convection-related stellar micro-variability II. The enigmatic granulation background of the CoRoT target HD 49933 H.-G. Ludwig1,, R. Samadi2,M.Steffen3, T. Appourchaux4 ,F.Baudin4, K. Belkacem5, P. Boumier2, M.-J. Goupil2, and E. Michel2 1 GEPI, Observatoire de Paris, CNRS, Univ. Paris 7, 92195 Meudon Cedex, France e-mail: [email protected] 2 LESIA, Observatoire de Paris, CNRS (UMR 8109), Univ. Paris 6, Univ. Paris 7, 92195 Meudon Cedex, France 3 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany 4 Institut d’Astrophysique Spatiale, Univ. Paris 11, CNRS (UMR 8617), 91405 Orsay, France 5 Institut d’Astrophysique et de Géophysique de l’Université de Liège, Allée du 6 Août 17, 4000 Liège, Belgium Received 23 February 2009 / Accepted 17 April 2009 ABSTRACT Context. Local-box hydrodynamical model atmospheres provide statistical information about a star’s emergent radiation field which allows one to predict the level of its granulation-related micro-variability. Space-based photometry is now sufficiently accurate to test model predictions. Aims. We aim to model the photometric granulation background of HD 49933 as well as the Sun, and compare the predictions to the measurements obtained by the CoRoT and SOHO satellite missions. Methods. We construct hydrodynamical model atmospheres representing HD 49933 and the Sun, and use a previously developed scaling technique to obtain the observable disk-integrated brightness fluctuations. We further performed exploratory magneto- hydrodynamical simulations to gauge the impact of small scale magnetic fields on the synthetic light-curves. -
R-Process Elements from Magnetorotational Hypernovae
r-Process elements from magnetorotational hypernovae D. Yong1,2*, C. Kobayashi3,2, G. S. Da Costa1,2, M. S. Bessell1, A. Chiti4, A. Frebel4, K. Lind5, A. D. Mackey1,2, T. Nordlander1,2, M. Asplund6, A. R. Casey7,2, A. F. Marino8, S. J. Murphy9,1 & B. P. Schmidt1 1Research School of Astronomy & Astrophysics, Australian National University, Canberra, ACT 2611, Australia 2ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia 3Centre for Astrophysics Research, Department of Physics, Astronomy and Mathematics, University of Hertfordshire, Hatfield, AL10 9AB, UK 4Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 5Department of Astronomy, Stockholm University, AlbaNova University Center, 106 91 Stockholm, Sweden 6Max Planck Institute for Astrophysics, Karl-Schwarzschild-Str. 1, D-85741 Garching, Germany 7School of Physics and Astronomy, Monash University, VIC 3800, Australia 8Istituto NaZionale di Astrofisica - Osservatorio Astronomico di Arcetri, Largo Enrico Fermi, 5, 50125, Firenze, Italy 9School of Science, The University of New South Wales, Canberra, ACT 2600, Australia Neutron-star mergers were recently confirmed as sites of rapid-neutron-capture (r-process) nucleosynthesis1–3. However, in Galactic chemical evolution models, neutron-star mergers alone cannot reproduce the observed element abundance patterns of extremely metal-poor stars, which indicates the existence of other sites of r-process nucleosynthesis4–6. These sites may be investigated by studying the element abundance patterns of chemically primitive stars in the halo of the Milky Way, because these objects retain the nucleosynthetic signatures of the earliest generation of stars7–13. -
Stellar Dynamics and Stellar Phenomena Near a Massive Black Hole
Stellar Dynamics and Stellar Phenomena Near A Massive Black Hole Tal Alexander Department of Particle Physics and Astrophysics, Weizmann Institute of Science, 234 Herzl St, Rehovot, Israel 76100; email: [email protected] | Author's original version. To appear in Annual Review of Astronomy and Astrophysics. See final published version in ARA&A website: www.annualreviews.org/doi/10.1146/annurev-astro-091916-055306 Annu. Rev. Astron. Astrophys. 2017. Keywords 55:1{41 massive black holes, stellar kinematics, stellar dynamics, Galactic This article's doi: Center 10.1146/((please add article doi)) Copyright c 2017 by Annual Reviews. Abstract All rights reserved Most galactic nuclei harbor a massive black hole (MBH), whose birth and evolution are closely linked to those of its host galaxy. The unique conditions near the MBH: high velocity and density in the steep po- tential of a massive singular relativistic object, lead to unusual modes of stellar birth, evolution, dynamics and death. A complex network of dynamical mechanisms, operating on multiple timescales, deflect stars arXiv:1701.04762v1 [astro-ph.GA] 17 Jan 2017 to orbits that intercept the MBH. Such close encounters lead to ener- getic interactions with observable signatures and consequences for the evolution of the MBH and its stellar environment. Galactic nuclei are astrophysical laboratories that test and challenge our understanding of MBH formation, strong gravity, stellar dynamics, and stellar physics. I review from a theoretical perspective the wide range of stellar phe- nomena that occur near MBHs, focusing on the role of stellar dynamics near an isolated MBH in a relaxed stellar cusp. -
PSR J1740-3052: a Pulsar with a Massive Companion
Haverford College Haverford Scholarship Faculty Publications Physics 2001 PSR J1740-3052: a Pulsar with a Massive Companion I. H. Stairs R. N. Manchester A. G. Lyne V. M. Kaspi Fronefield Crawford Haverford College, [email protected] Follow this and additional works at: https://scholarship.haverford.edu/physics_facpubs Repository Citation "PSR J1740-3052: a Pulsar with a Massive Companion" I. H. Stairs, R. N. Manchester, A. G. Lyne, V. M. Kaspi, F. Camilo, J. F. Bell, N. D'Amico, M. Kramer, F. Crawford, D. J. Morris, A. Possenti, N. P. F. McKay, S. L. Lumsden, L. E. Tacconi-Garman, R. D. Cannon, N. C. Hambly, & P. R. Wood, Monthly Notices of the Royal Astronomical Society, 325, 979 (2001). This Journal Article is brought to you for free and open access by the Physics at Haverford Scholarship. It has been accepted for inclusion in Faculty Publications by an authorized administrator of Haverford Scholarship. For more information, please contact [email protected]. Mon. Not. R. Astron. Soc. 325, 979–988 (2001) PSR J174023052: a pulsar with a massive companion I. H. Stairs,1,2P R. N. Manchester,3 A. G. Lyne,1 V. M. Kaspi,4† F. Camilo,5 J. F. Bell,3 N. D’Amico,6,7 M. Kramer,1 F. Crawford,8‡ D. J. Morris,1 A. Possenti,6 N. P. F. McKay,1 S. L. Lumsden,9 L. E. Tacconi-Garman,10 R. D. Cannon,11 N. C. Hambly12 and P. R. Wood13 1University of Manchester, Jodrell Bank Observatory, Macclesfield, Cheshire SK11 9DL 2National Radio Astronomy Observatory, PO Box 2, Green Bank, WV 24944, USA 3Australia Telescope National Facility, CSIRO, PO Box 76, Epping, NSW 1710, Australia 4Physics Department, McGill University, 3600 University Street, Montreal, Quebec, H3A 2T8, Canada 5Columbia Astrophysics Laboratory, Columbia University, 550 W. -
Rotation and Mixing in Binary Stars
ROTATION AND MIXING IN BINARY STARS Gloria Koenigsberger2 and Edmundo Moreno1 Abstract. Rotation in massive stars plays a key role in the transport of nuclear-processed elements to the stellar surface. Although a large fraction of massive stars are binaries, most current models rely on the assumption that their mixing efficiency is the same as in single stars. This assumption neglects the perturbing effect of the binary companion. In this poster we examine the manner in which the rotation structure of an asynchronous binary star is affected by the presence of a companion. We use the TIDES code (Moreno & Koenigsberger 1999; 2017; Moreno et al. 2011) to solve for the spatielly-resolved velocity of several concentric shells in a star that is tidally perturbed by its companion and focus on the azimuthal component of the velocity field, v'(r; θ; '). The code includes gravitational, centrifugal, Coriolis, gas pressure and viscous forces. The input parameters for the example in this poster are: stellar d masses m1 = 30M , m2 = 20M , equilibrium radius R1 = 6:44R , eccentricity e = 0:1, orbital period P = 6 , 2 rotation velocity vrot = 0, kinematical viscosity ν = 5:56 cm =s, shell thickness ∆R = 0:06R1. The binary interaction produces time-dependent shearing flows in both the polar and in the radial directions which, we speculate, may lead to a more efficient transport of angular momentum and nuclear processed material in binaries than in their single-star analogues. Key unresolved issues concern the value that is adopted for the viscosity, the inner radius to which tidal forces are effective, and the interplay between tidal flows and convection. -
Communications in Asteroseismology
Communications in Asteroseismology Volume 156 November/December, 2008 Communications in Asteroseismology Editor-in-Chief: Michel Breger, [email protected] Editorial Assistant: Daniela Klotz, [email protected] Layout & Production Manager: Paul Beck, [email protected] Language Editor: Natalie Sas, [email protected] Institut f¨ur Astronomie der Universit¨at Wien T¨urkenschanzstraße 17, A - 1180 Wien, Austria http://www.univie.ac.at/tops/CoAst/ [email protected] Editorial Board: Conny Aerts, Gerald Handler, Don Kurtz, Jaymie Matthews, Ennio Poretti Cover Illustration The Milky Way behind the dome of the 40-inch telescope at the Siding Spring Observatory, Australia. Data from this telescope is used in a paper by Handler & Shobbrook in this issue (see page 18). (Photo kindly provided by R. R. Shobbrook) British Library Cataloguing in Publication data. A Catalogue record for this book is available from the British Library. All rights reserved ISBN 978-3-7001-6539-2 ISSN 1021-2043 Copyright c 2008 by Austrian Academy of Sciences Vienna Austrian Academy of Sciences Press A-1011 Wien, Postfach 471, Postgasse 7/4 Tel. +43-1-515 81/DW 3402-3406, +43-1-512 9050 Fax +43-1-515 81/DW 3400 http://verlag.oeaw.ac.at, e-mail: [email protected] Comm. in Asteroseismology Vol. 156, 2008 Introductory Remarks The summer of 2008 was a densely packed season with a number of excellent astero- seismological conferences. CoAst will publish the proceedings of the Wroclaw, Liege and Vienna (JENAM) meetings. In fact, the proceedings of the HELAS Wroclaw conference is mailed to you together with this regular issue. -
Incidence of Stellar Rotation on the Explosion Mechanism of Massive
Supernova 1987A:30 years later - Cosmic Rays and Nuclei from Supernovae and their aftermaths Proceedings IAU Symposium No. 331, 2017 A. Marcowith, M. Renaud, G. Dubner, A. Ray c International Astronomical Union 2017 &A.Bykov,eds. doi:10.1017/S1743921317004471 Incidence of stellar rotation on the explosion mechanism of massive stars R´emi Kazeroni,1,2 J´erˆome Guilet1 and Thierry Foglizzo2 1 Max-Planck-Institut f¨ur Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching, Germany email: [email protected] 2 Laboratoire AIM, CEA/DRF-CNRS-Universit´eParisDiderot, IRFU/D´epartement d’Astrophysique, CEA-Saclay, F-91191, France Abstract. Hydrodynamical instabilities may either spin-up or down the pulsar formed in the collapse of a rotating massive star. Using numerical simulations of an idealized setup, we investi- gate the impact of progenitor rotation on the shock dynamics. The amplitude of the spiral mode of the Standing Accretion Shock Instability (SASI) increases with rotation only if the shock to the neutron star radii ratio is large enough. At large rotation rates, a corotation instability, also known as low-T/W, develops and leads to a more vigorous spiral mode. We estimate the range of stellar rotation rates for which pulsars are spun up or down by SASI. In the presence of a corotation instability, the spin-down efficiency is less than 30%. Given observational data, these results suggest that rapid progenitor rotation might not play a significant hydrodynamical role in the majority of core-collapse supernovae. Keywords. hydrodynamics, instabilities, shock waves, stars: neutron, stars: rotation, super- novae: general 1. -
Effects of Stellar Rotation on Star Formation Rates and Comparison to Core-Collapse Supernova Rates
The Astrophysical Journal, 769:113 (12pp), 2013 June 1 doi:10.1088/0004-637X/769/2/113 C 2013. The American Astronomical Society. All rights reserved. Printed in the U.S.A. EFFECTS OF STELLAR ROTATION ON STAR FORMATION RATES AND COMPARISON TO CORE-COLLAPSE SUPERNOVA RATES Shunsaku Horiuchi1,2, John F. Beacom2,3,4, Matt S. Bothwell5,6, and Todd A. Thompson3,4 1 Center for Cosmology, University of California Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697, USA; [email protected] 2 Center for Cosmology and Astro-Particle Physics, The Ohio State University, 191 West Woodruff Avenue, Columbus, OH 43210, USA 3 Department of Physics, The Ohio State University, 191 West Woodruff Avenue, Columbus, OH 43210, USA 4 Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA 5 Steward Observatory, University of Arizona, Tucson, AZ 85721, USA 6 Cavendish Laboratory, University of Cambridge, 19 J.J. Thomson Avenue, Cambridge CB3 0HE, UK Received 2013 February 1; accepted 2013 March 28; published 2013 May 13 ABSTRACT We investigate star formation rate (SFR) calibrations in light of recent developments in the modeling of stellar rotation. Using new published non-rotating and rotating stellar tracks, we study the integrated properties of synthetic stellar populations and find that the UV to SFR calibration for the rotating stellar population is 30% smaller than for the non-rotating stellar population, and 40% smaller for the Hα to SFR calibration. These reductions translate to smaller SFR estimates made from observed UV and Hα luminosities. Using the UV and Hα fluxes of a sample −1 of ∼300 local galaxies, we derive a total (i.e., sky-coverage corrected) SFR within 11 Mpc of 120–170 M yr −1 and 80–130 M yr for the non-rotating and rotating estimators, respectively. -
Differential Rotation in Sun-Like Stars from Surface Variability and Asteroseismology
Differential rotation in Sun-like stars from surface variability and asteroseismology Dissertation zur Erlangung des mathematisch-naturwissenschaftlichen Doktorgrades “Doctor rerum naturalium” der Georg-August-Universität Göttingen im Promotionsprogramm PROPHYS der Georg-August University School of Science (GAUSS) vorgelegt von Martin Bo Nielsen aus Aarhus, Dänemark Göttingen, 2016 Betreuungsausschuss Prof. Dr. Laurent Gizon Institut für Astrophysik, Georg-August-Universität Göttingen Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany Dr. Hannah Schunker Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany Prof. Dr. Ansgar Reiners Institut für Astrophysik, Georg-August-Universität, Göttingen, Germany Mitglieder der Prüfungskommision Referent: Prof. Dr. Laurent Gizon Institut für Astrophysik, Georg-August-Universität Göttingen Max-Planck-Institut für Sonnensystemforschung, Göttingen Korreferent: Prof. Dr. Stefan Dreizler Institut für Astrophysik, Georg-August-Universität, Göttingen 2. Korreferent: Prof. Dr. William Chaplin School of Physics and Astronomy, University of Birmingham Weitere Mitglieder der Prüfungskommission: Prof. Dr. Jens Niemeyer Institut für Astrophysik, Georg-August-Universität, Göttingen PD. Dr. Olga Shishkina Max Planck Institute for Dynamics and Self-Organization Prof. Dr. Ansgar Reiners Institut für Astrophysik, Georg-August-Universität, Göttingen Prof. Dr. Andreas Tilgner Institut für Geophysik, Georg-August-Universität, Göttingen Tag der mündlichen Prüfung: 3 Contents 1 Introduction 11 1.1 Evolution of stellar rotation rates . 11 1.1.1 Rotation on the pre-main-sequence . 11 1.1.2 Main-sequence rotation . 13 1.1.2.1 Solar rotation . 15 1.1.3 Differential rotation in other stars . 17 1.1.3.1 Latitudinal differential rotation . 17 1.1.3.2 Radial differential rotation . 18 1.2 Measuring stellar rotation with Kepler ................... 19 1.2.1 Kepler photometry . -
Star-Planet Interactions I
A&A 591, A45 (2016) Astronomy DOI: 10.1051/0004-6361/201528044 & c ESO 2016 Astrophysics Star-planet interactions I. Stellar rotation and planetary orbits Giovanni Privitera1; 2, Georges Meynet1, Patrick Eggenberger1, Aline A. Vidotto1; 3, Eva Villaver4, and Michele Bianda2 1 Geneva Observatory, University of Geneva, Maillettes 51, 1290 Sauverny, Switzerland e-mail: [email protected] 2 Istituto Ricerche Solari Locarno, via Patocchi, 6605 Locarno-Monti, Switzerland 3 School of Physics, Trinity College Dublin, Dublin-2, Ireland 4 Department of Theoretical Physics, Universidad Autonoma de Madrid, Modulo 8, 28049 Madrid, Spain Received 25 December 2015 / Accepted 16 April 2016 ABSTRACT Context. As a star evolves, planet orbits change over time owing to tidal interactions, stellar mass losses, friction and gravitational drag forces, mass accretion, and evaporation on/by the planet. Stellar rotation modifies the structure of the star and therefore the way these different processes occur. Changes in orbits, subsequently, have an impact on the rotation of the star. Aims. Models that account in a consistent way for these interactions between the orbital evolution of the planet and the evolution of the rotation of the star are still missing. The present work is a first attempt to fill this gap. Methods. We compute the evolution of stellar models including a comprehensive treatment of rotational effects, together with the evolution of planetary orbits, so that the exchanges of angular momentum between the star and the planetary orbit are treated in a self-consistent way. The evolution of the rotation of the star accounts for the angular momentum exchange with the planet and also follows the effects of the internal transport of angular momentum and chemicals. -
Arxiv:1202.1422V2 [Astro-Ph.SR] 17 Feb 2012 Dtdb .Bgi,M Eei,E Ihl&C Moutou C
Transiting planets, vibrating stars & their connection nd Proceedings of the 2 CoRoT symposium (14 - 17 June 2011, Marseille) Edited by A. Baglin, M. Deleuil, E. Michel & C. Moutou Some CoRoT highlights - A grip on stellar physics and beyond E. Michel1, A. Baglin1 and the CoRoT Team 1 LESIA, Observatoire de Paris, CNRS UMR 8109, Univ. Pierre et Marie Curie, Univ. Paris Diderot, pl. J. Janssen, 92195 Meudon, France [[email protected]] Abstract. About 2 years ago, back in 2009, the first CoRoT Symposium was the occasion to present and discuss unprecedented data revealing the behaviour of stars at the micro- magnitude level. Since then, the observations have been going on, the target sample has enriched and the work of analysis of these data keeps producing first rank results. These analyses are providing the material to address open questions of stellar structure and evolution and to test the so many physical processes at work in stars. Based on this material, an increasing number of interpretation studies is being published, addressing various key aspects: the extension of mixed cores, the structure of near surface convective zones, magnetic activity, mass loss, ... Definitive conclusions will require cross-comparison of results on a larger ground (still being built), but it is already possible at the time of this Second CoRoT Symposium, to show how the various existing results take place in a general framework and contribute to complete our initial scientific objectives. A few results already reveal the potential interest in considering stars and planets globally, as it is stressed in several talks at this symposium. -
Three-Dimensional Numerical Simulations of the Pulsar Magnetosphere: Preliminary Results
A&A 496, 495–502 (2009) Astronomy DOI: 10.1051/0004-6361:200810281 & c ESO 2009 Astrophysics Three-dimensional numerical simulations of the pulsar magnetosphere: preliminary results C. Kalapotharakos and I. Contopoulos Research Center for Astronomy, Academy of Athens, 4 Soranou Efessiou Str., Athens 11527, Greece e-mail: [email protected];[email protected] Received 29 May 2008 / Accepted 14 November 2008 ABSTRACT We investigate the three-dimensional structure of the pulsar magnetosphere through time-dependent numerical simulations of a mag- netic dipole that is set in rotation. We developed our own Eulerian finite difference time domain numerical solver of force-free electrodynamics and implemented the technique of non-reflecting and absorbing outer boundaries. This allows us to run our simu- lations for many stellar rotations, and thus claim with confidence that we have reached a steady state. A quasi-stationary corotating pattern is established, in agreement with previous numerical solutions. We discuss the prospects of our code for future high-resolution investigations of dissipation, particle acceleration, and temporal variability. Key words. pulsars: general – stars: magnetic fields 1. Introduction ±θ above and below the rotation equator (θ being the inclina- tion angle between the rotation and magnetic axes) and has an In the 40 years following the discovery of pulsars, significant undulating shape of a spiral form with radial wavelength equal progress has been made towards understanding the pulsar phe- to 2π times the light cylinder distance rlc ≡ c/Ω∗,whereΩ∗ is nomenon (e.g. Michel 1991; Bassa et al. 2008). We know that the angular velocity of rotation of the central neutron star (e.g.