DOCSLIB.ORG

Magnetically Accreting Isolated Old Neutron Stars Robert E

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Magnetically Accreting Isolated Old Neutron Stars Robert E THE ASTROPHYSICAL JOURNAL, 553:796È800, 2001 June 1 ( 2001. The American Astronomical Society. All rights reserved. Printed in U.S.A. MAGNETICALLY ACCRETING ISOLATED OLD NEUTRON STARS ROBERT E. RUTLEDGE Space Radiation Laboratory, MS 220-47, California Institute of Technology, Pasadena, CA 91125; rutledge=srl.caltech.edu; and Institute for Theoretical Physics, Kohn Hall, University of California, Santa Barbara, CA 93106 Received 2000 December 13; accepted 2001 February 2 ABSTRACT Previous work on the emission from isolated old neutron stars (IONSs) accreting from the interstellar medium (ISM) has focused on gravitational captureÈi.e., Bondi accretion. We propose a new class of sources that accrete via magnetic interaction with the ISM. While for the Bondi mechanism the accre- tion rateM0 decreases with increasing neutron star velocity, in magnetic accretors (MAGACs) Bondi P ~3 P 1@3 M0 MAGAC increases with increasing neutron star velocity(M0 Bondi v vs.M0 MAGAC v ). MAGACs will be produced among high-velocity(Z100 km s~1), high magnetic Ðeld (B [ 1014 G) radio pulsarsÈthe ““ magnetars ÏÏÈafter they have evolved Ðrst through magnetic dipole spin-down, followed by a ““ propeller ÏÏ phase (during which the object sheds angular momentum on a timescale[1010 yr). The properties of MAGACs may be summarized thus: dipole magnetic Ðelds ofB Z 1014 G; minimum velocities relative to the ISM of 25È100 km s~1 or higher, depending on B, well below the median in the observed radio pulsar population; spin periods of greater than days to years; accretion luminosities of 28 31 ~1 \ 10 È10 ergs s ; and e†ective temperatureskTeff 0.3È2.5 keV if they accrete onto the magnetic polar cap. We Ðnd no examples of MAGACs among previously observed source classes (anomalous X-ray pulsars, soft gamma-ray repeaters, or known IONs). However, MAGACs may be more prevalent in Ñux-limited X-ray catalogs than their gravitationally accreting counterparts. Subject headings: pulsars: general È stars: magnetic Ðelds È stars: neutron È X-rays: stars 1. INTRODUCTION Bondi accretion rate decreases with the NS velocity, while in MAGACs, the accretion rate increases with increasing Accretion onto isolated old neutron stars (IONSs) velocity: through the spherical Bondi accretion mode (Bondi & \ 2 Hoyle 1944; Bondi 1952) has been investigated as a means M0 MAGAC nRM vo , (2) to produce a population of neutron stars detectable in the \ 2 2 1@6 ROSAT All-Sky Survey (RASS; Treves & Colpi 1991; Blaes whereRM [k /(4nov )] is the size scale for the magne- & Madau 1993; Madau & Blaes 1994; Zane et al. 1995; tosphere of a nonrotating NS with the magnetic energy density from the NSÏs magnetic moment k, equal to the ram Popov et al. 2000). The estimated number of these sources P 1@3 in the RASS was initially high (D103È104). However, as pressure of the WIM. This yieldsM0 MAGAC v . So, for a observations of higher mean velocities in the radio pulsar given magnetic Ðeld strength, Bondi accretion dominates at population (Lorimer, Bailes, & Harrison 1997; Hansen & low velocities, while magnetic accretion dominates at high Phinney 1997; Cordes & Cherno† 1998 and references velocities. therein) were considered, the predicted number of detect- The evolutionary scenario of magnetically accreting NSs able IONSs accreting from the interstellar medium (ISM) has been outlined by Harding & Leventhal (Harding & decreased dramatically (D102È103). This is because the Leventhal 1992, hereafter HL92). HL92 found that magne- Bondi accretion rate is a strong function of the neutron star tized NSs Ðrst spin down via dipole radiation, followed by a (NS) velocity through the ISM:1 longer spin-down period via the propeller e†ect. They restricted their attention to sources with surface magnetic \ 2 ~3 M0 Bondi 4n(GMNS) ov , (1) Ðelds[1013 G and found that they are unable to accrete where o is the local mass density of the ISM. Bondi- onto the compact object, as the propeller spin-down time is accreting IONSs are expected to have X-ray luminosities longer than the age of the universe. A similar line of argu- D1031 ergs s~1 and e†ective temperatureskT [ 200 eV, ment is followed in the review by Treves et al. (2000) in the eff context of Bondi-accreting IONSs. This limitation does not both dependent upon the accretion rate. 14 There will be a di†erent accretion mode, however, when apply to NSs with magnetic ÐeldsZ10 G: an NS with magnetic Ðeld B \ 1015 G and velocity v \ 300 km s~1 the NS magnetic Ðeld dominates over the gravitational Ðeld ] 9 in attracting accretion from the ISM. In this mode, the spins down in D4 10 yr. warm ionized medium (WIM) attaches to the NS magnetic On the other hand, this same evolutionary scenario has been used to argue for magnetic Ðeld decay in the IONSs Ðeld at the magnetosphere, accreting directly onto the NS [ surface. These magnetically accreting isolated old neutron RX J0720.4 3125 (Wang 1997; Konenkov & Popov 1997) stars (MAGACs, pronounceable ““ magics ÏÏ) contrast with and in NSs in general (see Livio, Xu, & Frank 1998; Colpi IONSs, which accrete through the Bondi mode, in that the et al. 1998). We suggest, instead, that high magnetic Ðeld IONSs have not been discovered because strong magnetic 1 \ 2] 2 1@2 Ðeld sources accreting from the ISM are spectrally harder Herev (V Cs ) , the geometric sum of the spatial velocity of the NS and the sound speed in the accreted medium. The sound speed of (as we Ðnd below) than Bondi accretors and have been the ISM is low (D10 km s~1) compared with spatial velocities relevant to selected against by observers, or confused with background ~1 the present work(v Z 100 km s ), so we assumev ? Cs throughout. active galactic nuclei. 796 MAGACs 797 45 2 Moreover, since HL92Ïs work, observations have whereI45 is the moment of inertia in units of 10 gcm. revealed NSs with considerably stronger magnetic Ðelds This is a short timescale, compared with the life of the NS. 15 than considered by HL92, in the range of 10 GÈthe After reaching this period, the light cylinder is at RM ; magnetars. Pulse timing of soft gamma-ray repeaters however, the NS still cannot accrete (or accretes in- (Kouveliotou et al. 1998, 1999) conÐrms their existence as efficiently) as a result of the ““ propeller e†ect ÏÏ (Illarionov & proposed in earlier theoretical work (Thompson & Duncan Sunyaev 1975), in which matter is spun away by the magne- 1993; Duncan & Thompson 1992). Circumstantial evidence tosphere, which is outside the Keplerian orbit in corotation suggests that anomalous X-ray pulsars have similarly with the neutron star (the corotation radius). This matter is strong B-Ðelds (Thompson & Duncan 1996; Vasisht & Got- ejected from the system, carrying angular momentum with thelf 1997; Heyl & Hernquist 1997), and precision pulsar- it and spinning down the NS until the corotation radius timing evidence also implies magnetic Ðelds in excess of reachesRM, at which point the NS will have a spin period of 14 10 G (Kaspi, Chakrabarty, & Steinberger 1999), conÐrm- \ ] 6 1@2 ~1@2 ~1@4 ~1@2 ing less precise, multiepoch timing solutions that nonethe- PP 3.9 10 k33 v7 n~1 MNS s . (6) less led to a magnetar interpretation (Gotthelf, Vasisht, & This spin period is substantially longer (by 3 orders of Dotani 1999). Static solutions for NSs have been proposed magnitude) than any spin period yet observed from an NS. for surface Ðelds up to D1018 G (Bocquet et al. 1995; The propeller spin-down timescale, when the accretion rate Cardall, Prakash, & Lattimer 2001), although no objects is dominated by magnetospheric accretion, is with magnetic Ðelds as high as this have yet been observed. \ ] 10 ~4@3 ~5@3 ~1@3 Thus, with theoretical and observational motivation, we qP 2.3 10 I45 k33 v7 n~1 yr (7) reconsider the scenario of HL92, but with particular atten- (Illarionov & Sunyaev 1975; Davies, Fabian, & Pringle tion paid to NSs with magnetic Ðelds above 1013 G. 1979). TheqP timescale dominates the evolutionary time In ° 2, we describe the model for this population, follow- between NS birth and emergence of the NS as a magnetic ing the scenario of HL92. In 3, we summarize the proper- ° accretor. It is comparable to the age of the Galaxy ([1010 ties of MAGACs, discuss observational ramiÐcations, and yr) for velocities already observed among the NS popu- conclude. lation, but only for high magnetic Ðeld sources(Z1015 G). MODEL This makes magnetic accretors with the right combination 2. of magnetic Ðeld and velocity observable. 2.1. Evolutionary Model Following spin-down via the propeller, matter is accreted We assume that the neutron star is born with a velocity onto the polar cap of the NS. The maximum accretion rate v \ v 107 cm s~1 relative to the ISM and a magnetic onto the compact object is 7 \ 33 3 momentk k33 10 G cm , which corresponds to a dipole M0 \ nR2 vo \ 9.6 ] 107k2@3 v1@3 n2@3 gs~1 . (8) Ðeld strength at the NS surface (10 km) of 1015 G MAGAC M 33 7 ~1 (appropriate for magnetars; Thompson & Duncan 1993; (HL92). This is an upper limit to the mass accretion rate Duncan & Thompson 1992). The spin period is initially onto the NS surface and could be potentially much lower short (P > 10 s). We assume that the magnetic Ðeld does not (see ° 2.2). Moreover, the Bondi and MAGAC accretion decay. We assume a compact object mass M \ M 1.4 M rates are simply related to the magnetospheric and Bondi \ 6 NS _ and radiusR RNS 10 cm. We assume the NS travels radius: through a spatially uniform proton density n \ 0.1n ~3 p ~1 M0 R 2 cm in the WIM (Boulares & Cox 1990; Ferriere 1998a, MAGAC \ A M B .
Load more

Recommended publications
  • Supernovae Sparked by Dark Matter in White Dwarfs
    Supernovae Sparked By Dark Matter in White Dwarfs Javier F. Acevedog and Joseph Bramanteg;y gThe Arthur B. McDonald Canadian Astroparticle Physics Research Institute, Department of Physics, Engineering Physics, and Astronomy, Queen's University, Kingston, Ontario, K7L 2S8, Canada yPerimeter Institute for Theoretical Physics, Waterloo, Ontario, N2L 2Y5, Canada November 27, 2019 Abstract It was recently demonstrated that asymmetric dark matter can ignite supernovae by collecting and collapsing inside lone sub-Chandrasekhar mass white dwarfs, and that this may be the cause of Type Ia supernovae. A ball of asymmetric dark matter accumulated inside a white dwarf and collapsing under its own weight, sheds enough gravitational potential energy through scattering with nuclei, to spark the fusion reactions that precede a Type Ia supernova explosion. In this article we elaborate on this mechanism and use it to place new bounds on interactions between nucleons 6 16 and asymmetric dark matter for masses mX = 10 − 10 GeV. Interestingly, we find that for dark matter more massive than 1011 GeV, Type Ia supernova ignition can proceed through the Hawking evaporation of a small black hole formed by the collapsed dark matter. We also identify how a cold white dwarf's Coulomb crystal structure substantially suppresses dark matter-nuclear scattering at low momentum transfers, which is crucial for calculating the time it takes dark matter to form a black hole. Higgs and vector portal dark matter models that ignite Type Ia supernovae are explored. arXiv:1904.11993v3 [hep-ph] 26 Nov 2019 Contents 1 Introduction 2 2 Dark matter capture, thermalization and collapse in white dwarfs 4 2.1 Dark matter capture .
    [Show full text]
  • Arxiv:2101.12220V2 [Astro-Ph.HE]
    Neutron Stars Harboring a Primordial Black Hole: Maximum Survival Time Thomas W. Baumgarte1 and Stuart L. Shapiro2, 3 1Department of Physics and Astronomy, Bowdoin College, Brunswick, Maine 04011 2Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 3Department of Astronomy and NCSA, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 We explore in general relativity the survival time of neutron stars that host an endoparasitic, possibly primordial, black hole at their center. Corresponding to the minimum steady-state Bondi accretion rate for adiabatic flow that we found earlier for stiff nuclear equations of state (EOSs), we derive analytically the maximum survival time after which the entire star will be consumed by the black hole. We also show that this maximum survival time depends only weakly on the stiffness for polytropic EOSs with Γ ≥ 5/3, so that this survival time assumes a nearly universal value that depends on the initial black hole mass alone. Establishing such a value is important for constraining −16 −10 the contribution of primordial black holes in the mass range 10 M⊙ . M . 10 M⊙ to the dark-matter content of the Universe. Primordial black holes (PBHs) that may have formed the spherical, steady-state, Bondi accretion formula, in the early Universe (see, e.g., [1, 2]) have long been con- M 2ρ sidered candidates for contributing to, if not accounting M˙ =4πλ 0 (1) for, the mysterious and elusive dark matter (see, e.g., [3], a3 as well as [4] for a recent review). Constraints on the PBH contribution to the dark matter have been estab- for adiabatic flow ([18]; see also [19] for a textbook treat- lished by a number of different observations.
    [Show full text]
  • Lecture Notes in Astrophysical Fluid Dynamics
    Lecture Notes in Astrophysical Fluid Dynamics Mattia Sormani November 19, 2017 1 Contents 1 Hydrodynamics6 1.1 Introductory remarks..........................6 1.2 The state of a fluid...........................6 1.3 The continuity equation........................7 1.4 The Euler equation, or F = ma ....................8 1.5 The choice of the equation of state.................. 10 1.6 Manipulating the fluid equations................... 14 1.6.1 Writing the equations in different coordinate systems.... 14 1.6.2 Indecent indices......................... 16 1.6.3 Tables of unit vectors and their derivatives.......... 17 1.7 Conservation of energy......................... 18 1.8 Conservation of momentum...................... 21 1.9 Lagrangian vs Eulerian view...................... 21 1.10 Vorticity................................. 22 1.10.1 The vorticity equation..................... 23 1.10.2 Kelvin circulation theorem................... 24 1.11 Steady flow: the Bernoulli's equation................. 26 1.12 Rotating frames............................. 27 1.13 Viscosity and thermal conduction................... 28 1.14 The Reynolds number......................... 33 1.15 Adding radiative heating and cooling................. 35 1.16 Summary................................ 36 1.17 Problems................................. 37 2 Magnetohydrodynamics 38 2.1 Basic equations............................. 38 2.2 Magnetic tension............................ 44 2.3 Magnetic flux freezing......................... 45 2.4 Magnetic field amplification.....................
    [Show full text]
  • Numerical Hydrodynamics in General Relativity
    Numerical hydrodynamics in general relativity Jos´eA. Font Departamento de Astronom´ıay Astrof´ısica Edificio de Investigaci´on “Jeroni Mu˜noz” Universidad de Valencia Dr. Moliner 50 E-46100 Burjassot (Valencia), Spain Abstract The current status of numerical solutions for the equations of ideal general rel- ativistic hydrodynamics is reviewed. With respect to an earlier version of the article the present update provides additional information on numerical schemes and extends the discussion of astrophysical simulations in general relativistic hy- drodynamics. Different formulations of the equations are presented, with special mention of conservative and hyperbolic formulations well-adapted to advanced numerical methods. A large sample of available numerical schemes is discussed, paying particular attention to solution procedures based on schemes exploiting the characteristic structure of the equations through linearized Riemann solvers. A comprehensive summary of astrophysical simulations in strong gravitational fields is presented. These include gravitational collapse, accretion onto black holes and hydrodynamical evolutions of neutron stars. The material contained in these sections highlights the numerical challenges of various representative simulations. It also follows, to some extent, the chronological development of the field, concerning advances on the formulation of the gravitational field and arXiv:gr-qc/0003101v2 12 May 2003 hydrodynamic equations and the numerical methodology designed to solve them. 1 Introduction The description
    [Show full text]
  • Bondi-Hoyle Accretion
    A Review of Bondi–Hoyle–Lyttleton Accretion Richard Edgar a aStockholms observatorium, AlbaNova universitetscentrum, SE-106 91, Stockholm, Sweden Abstract If a point mass moves through a uniform gas cloud, at what rate does it accrete ma- terial? This is the question studied by Bondi, Hoyle and Lyttleton. This paper draws together the work performed in this area since the problem was first studied. Time has shown that, despite the simplifications made, Bondi, Hoyle and Lyttleton made quite accurate predictions for the accretion rate. Bondi–Hoyle–Lyttleton accretion has found application in many fields of astronomy, and these are also discussed. Key words: accretion PACS: 95.30.Lz, 97.10.Gz, 98.35.Mp, 98.62.Mw 1 Introduction arXiv:astro-ph/0406166v2 21 Jun 2004 In its purest form, Bondi–Hoyle–Lyttleton accretion concerns the supersonic motion of a point mass through a gas cloud. The cloud is assumed to be free of self-gravity, and to be uniform at infinity. Gravity focuses material behind the point mass, which can then accrete some of the gas. This problem has found applications in many areas of astronomy, and this paper is an attempt to address the lack of a general review of the subject. I start with a short summary of the original work of Bondi, Hoyle and Lyt- tleton, followed by a discussion of the numerical simulations performed. Some issues in Bondi–Hoyle–Lyttleton accretion are discussed, before a brief sum- mary of the fields in which the geometry has proved useful. Email address: [email protected] (Richard Edgar).
    [Show full text]
  • Accretion Processes on a Black Hole Sandip K
    Contents Abstract ........................................... ............. 4 1: Introduction ..................................... .............. 5 1.1 Some General Issues Related to Black Hole Astrophysics . .................. 7 1.1.1 Formation of Black Holes ......................... ....................... 7 1.1.2 Fueling Active Galactic Nuclei . ........................ 9 1.1.3 Evolution of Galactic Centers .................... ....................... 12 1.1.4 Black Holes in Galactic Halos? .................... ..................... 13 1.1.5 Some Signatures of Black Holes .................... ..................... 14 1.2 Difference between Motions around a Newtonian Star and a BlackHole ... 16 1.3 Basics of Pseudo-Newtonian Geometries . .................... 21 1.4 Remarks About Units and Dimensions . .................. 23 2: Spherical Accretion ............................... ............ 24 2.1 Bondi Accretion on a Newtonian Star .................. ................... 25 2.1.1 Basic Equations ................................ ........................ 25 2.1.2 Phase Space Behaviour of the Bondi Flow . ................. 28 2.2 Bondi Flow on a Black Hole ........................... ................... 30 2.2.1 In Schwarzschild Geometry ....................... ....................... 30 2.2.2 In pseudo-Newtonian Geometry .................... ..................... 31 2.3 Bondi Flow with Simple Radiative Transfer . ................... 32 2.4 Bondi Flow with General Radiative Transfer . ................... 32 2.4.1 Single Temperature Solutions
    [Show full text]
  • Brian David Metzger
    Curriculum Vitae, Updated 10/20 Brian David Metzger Columbia University Email: [email protected] Department of Physics Web: http://www.columbia.edu/∼bdm2129 909 Pupin Hall, MC 5217 Phone: (212) 854-9702 New York, NY 10027 Fax: (212) 854-3379 ACADEMIC POSITIONS 07/20− Full Professor of Physics, Columbia University 07/19−07/20 Visiting Scholar, Simons Flatiron Institute 01/17−07/20 Associate Professor of Physics, Columbia University 01/13−01/17 Assistant Professor of Physics, Columbia University 09/12−12/12 Lyman Spitzer Jr. Fellow, Princeton University 09/09−12/12 NASA Einstein Fellow, Princeton University EDUCATION 08/03−05/09 University of California at Berkeley M.A. & Ph.D. in Physics (Thesis Adviser: Prof. Eliot Quataert) Dissertation: \Theoretical Models of Gamma-Ray Burst Central Engines" 08/99−05/03 The University of Iowa B.S. in Physics, Astronomy, & Mathematics (Highest Distinction) SELECT HONORS, FELLOWSHIPS and AWARDS 2020 Blavatnik National Laureate in Natural Sciences & Engineering 2020 Simons Investigator in Mathematics and Theoretical Physics 2019 Simons Fellow in Mathematics and Theoretical Physics 2019 2020 Decadal Survey in Astronomy & Astrophysics, Program Panelist 2019 Salpeter Honorary Lecturer, Cornell 2019 Bruno Rossi Prize, American Astronomical Society 2018,19,20 Blavatnik National Awards for Young Scientists, Finalist 2019 New Horizons Breakthrough Prize in Physics 2018 Charles and Thomas Lauritsen Honorary Lecture, Caltech 2016 Scialog Fellow, Research Science Corporation 2014 Alfred P. Sloan Research Fellowship 2009−12 NASA Einstein Fellowship, Princeton 2009 Dissertation Prize, AAS High Energy Astrophysics Division 2009 NASA Hubble Fellowship 2009 Lyman Spitzer Jr. Fellowship, Princeton 2009 Mary Elizabeth Uhl Prize, UC Berkeley Astronomy 2005−08 NASA Graduate Student Research Fellowship 2003 James A.
    [Show full text]
  • Arxiv:2002.12778V2 [Astro-Ph.CO] 9 May 2021 8
    CONSTRAINTS ON PRIMORDIAL BLACK HOLES Bernard Carr,1, 2, ∗ Kazunori Kohri,3, 4, 5, y Yuuiti Sendouda,6, z and Jun'ichi Yokoyama2, 5, 7, 8, x 1School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS, UK 2Research Center for the Early Universe (RESCEU), Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan 3KEK Theory Center, IPNS, KEK, Tsukuba, Ibaraki 305-0801, Japan 4The Graduate University for Advanced Studies (SOKENDAI), Tsukuba, Ibaraki 305-0801, Japan 5Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo, Kashiwa, Chiba 277-8568, Japan 6Graduate School of Science and Technology, Hirosaki University, Hirosaki, Aomori 036-8561, Japan 7Department of Physics, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan 8Trans-scale Quantum Science Institute, The University of Tokyo, Tokyo 113-0033, Japan (Dated: Tuesday 11th May, 2021, 00:43) We update the constraints on the fraction of the Universe that may have gone into primordial black holes (PBHs) over the mass range 10−5{1050 g. Those smaller than ∼ 1015 g would have evaporated by now due to Hawking radiation, so their abundance at formation is constrained by the effects of evaporated particles on big bang nucleosynthesis, the cosmic microwave background (CMB), the Galactic and extragalactic γ-ray and cosmic ray backgrounds and the possible generation of stable Planck mass relics. PBHs larger than ∼ 1015 g are subject to a variety of constraints associated with gravitational lensing, dynamical effects, influence on large-scale structure, accretion and gravitational waves.
    [Show full text]
  • Accretion Onto Black Holes from Large Scales Regulated by Radiative Feedback
    Abstract Title of Dissertation: Accretion onto Black Holes from Large Scales Regulated by Radiative Feedback KwangHo Park, Doctor of Philosophy, 2012 Dissertation directed by: Professor Massimo Ricotti Department of Astronomy This thesis focuses on radiation-regulated gas accretion onto black holes (BHs) from galactic scales emphasizing the role of thermal and radiation pressure in lim- iting gas supply to the BH. Assuming quasi-spherical symmetry, we explore how the gas accretion depends on free parameters such as radiative efficiency, BH mass, ambient gas density/temperature, and the spectral index of the radiation. Our nu- merical simulations show an oscillatory behavior of the accretion rate, and thus the luminosity from the BH. We present a model for the feedback loop and provide analytical relationships for the average/maximum accretion rate and the period of the accretion bursts. The thermal structure inside the Str¨omgrensphere is a key factor for the regulation process, while with increasing ambient gas density and mass of BHs, eventually the accretion rate becomes limited by radiation pressure. The period of the luminosity bursts is proportional to the average size of the ionized hot bubble, but we discover that there are two distinct modes of oscillations with very different duty cycles, and that are governed by different depletion processes of the gas inside the ionized bubble. We also study how angular momentum of the gas affects the accretion process. In the second part of the thesis, we study the growth rate and luminosity of BHs in motion with respect to their surrounding medium. We run a large set of two-dimensional axis-symmetric simulations to explore a large parameter space of initial conditions and formulate an analytical model for the accretion.
    [Show full text]
  • Turning Points in the Evolution of Isolated Neutron Stars' Magnetic
    Turning Points in the Evolution of Isolated Neutron Stars’ Magnetic Fields U. Geppert Departament de F´ısica Aplicada, Univeritat d’ Alacant, ap. Correus 99, 03080 Alacant, Spain, [email protected] Summary. During the life of isolated neutron stars (NSs) their magnetic field passes through a variety of evolutionary phases. Depending on its strength and structure and on the physical state of the NS (e.g. cooling, rotation), the field looks qualitatively and quantitatively different after each of these phases. Three of them, the phase of MHD instabilities immediately after NS’s birth, the phase of fallback which may take place hours to months after NS’s birth, and the phase when strong temperature gradients may drive thermoelectric instabilities, are concentrated in a period lasting from the end of the proto–NS phase until 100, perhaps 1000 years, when the NS has become almost isothermal. The further evolution of the magnetic field proceeds in general inconspicuous since the star is in isolation. However, as soon as the product of Larmor frequency and electron relaxation time, the so–called mag- netization parameter (ωB τ), locally and/or temporally considerably exceeds unity, phases, also unstable ones, of dramatic changes of the field structure and magnitude can appear. An overview is given about that field evolution phases, the outcome of which makes a qualitative decision regarding the further evolution of the magnetic field and its host NS. 1 Introduction The energy of the magnetic fields of neutron stars (NSs) is even for magne- tar field strengths (∼ 1015 G) negligible in comparison with the gravitational energy of even the least massive NSs.
    [Show full text]
  • A Review of Bondi–Hoyle–Lyttleton Accretion
    New Astronomy Reviews 48 (2004) 843–859 www.elsevier.com/locate/newastrev A review of Bondi–Hoyle–Lyttleton accretion Richard Edgar * Stockholms Observatorium, AlbaNova Universitetscentrum, SE-106 91 Stockholm, Sweden Accepted 1 June 2004 Available online 2 July 2004 Abstract If a point mass moves through a uniform gas cloud, at what rate does it accrete material? This is the question studied by Bondi, Hoyle and Lyttleton. This paper draws together the work performed in this area since the problem was first studied. Time has shown that, despite the simplifications made, Bondi, Hoyle and Lyttleton made quite accurate predictions for the accretion rate. Bondi–Hoyle–Lyttleton accretion has found application in many fields of astronomy, and these are also discussed. Ó 2004 Elsevier B.V. All rights reserved. PACS: 95.30.Lz; 97.10.Gz; 98.35.Mp; 98.62.Mw Keyword: Accretion Contents 1. Introduction..................................................... 844 2. Basics.......................................................... 844 2.1. The analysis of Hoyle and Lyttleton . 844 2.2. Analytic solution. 845 2.3. The analysis of Bondi and Hoyle . 846 2.4. Connection to Bondi accretion . 849 3. Numericalsimulations.............................................. 849 3.1. Summary . 849 3.2. Examples in the literature . 850 4. Issues in Bondi–Hoyle–Lyttleton flow . 852 * Tel.: +46-8-5537-8552; fax: +46-8-5537-8510. E-mail address: [email protected] (R. Edgar). 1387-6473/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.newar.2004.06.001 844 R. Edgar / New Astronomy Reviews 48 (2004) 843–859 4.1. The drag force . 852 4.2.
    [Show full text]
  • Arxiv:2108.08982V1 [Astro-Ph.HE] 20 Aug 2021 Luminosities Than the Non-Repeating Ones
    Draft version August 23, 2021 Typeset using LATEX default style in AASTeX63 Reconciling the 16.35-day period of FRB 20180916B with jet precession Hao-Yan Chen,1 Wei-Min Gu,1 Mouyuan Sun,1 Tong Liu,1 and Tuan Yi1 1Department of Astronomy, Xiamen University, Xiamen, Fujian 361005, P. R. China (Received XXX; Revised YYY; Accepted ZZZ) Submitted to ApJ ABSTRACT A repeating fast radio burst (FRB), FRB 20180916B (hereafter FRB 180916), was reported to have a 16.35-day period. This period might be related to a precession period. In this paper, we investigate two precession models to explain the periodic activity of FRB 180916. In both models, the radio emission of FRB 180916 is produced by a precessing jet. For the first disk-driven jet precession model, −8 an extremely low viscous parameter (i.e., the dimensionless viscosity parameter α . 10 ) is required to explain the precession of FRB 180916, which implies its implausibility. For the second tidal force- driven jet precession model, we consider a compact binary consists of a neutron star/black hole and a white dwarf; the white dwarf fills its Roche lobe and mass transfer occurs. Due to the misalignment between the disk and orbital plane, the tidal force of the white dwarf can drive jet precession. We show that the relevant precession periods are several days to hundreds of days, depending on the specific accretion rates and component masses. The duration of FRB 180916 generation in the binary with extremely high accretion rate will be several thousand years. Keywords: Compact binary stars (283)|Jets (870)|Stellar accretion disks (1579)|White dwarf stars (1799)|Radio transient sources (2008) 1.
    [Show full text]