DOCSLIB.ORG

Neutron Stars in Binary Systems G

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Neutron Stars in Binary Systems G Neutron Stars in Binary Systems G. Borner, Munich (Max-Planck Institute for Physics and Astrophysics) The discovery of a 58 keV line fea­ sources, and sources showing irre­ already been established that they are ture in the spectrum of the X-ray gular fluctuations (as e.g. Cyg X-1 on members of a binary system (several source HerX-1 by J. TrÜmper and his a timescale of milliseconds) appear are listed in Table 1), i.e. they are in colleagues from Tubingen & Garching less exotic than the flare-like objects, orbit around an optical companion. (Germany) in 1976 '), as reported in which appear, reach a peak lumino­ As long as there is no evidence to Europhysics News, 8 (1977) 5, is the sity, and then fade away as if they the contrary, we may live happily with latest exciting news from the rapidly had never been. But most peculiar are the assumption that all other galactic expanding field of X-ray astronomy. the burst-like sources, which emit X-ray sources are also binary systems Cosmic X-rays are completely absor­ their X-rays in short term bursts of a with mass flow, and we may wait bed by the earth's atmosphere, and few seconds duration, with no appa­ confidently for further candidates to therefore the observing instruments rent periodicity involved. The theorists Table 1. have to be placed in the outer layers do not hesitate, however, to invoke Most of the energy is liberated or outside the atmosphere. Up to equally exotic images, when they try deep inside the gravitational well, i.e. 1970, balloon and rocket flights had to explain the observations. Although on the stellar surface, if the compact led to the discovery of about 30 X-ray we are far from understanding these object is a neutron star, or within a sources. But then, in December 1970, X-ray stars completely, we have lear­ few Schwarzschild radii, if the object NASA launched the Uhuru satellite ned quite a bit during the past years. is a black hole. In both cases, for 1 which was devoted entirely to X-ray Some general, fairly obvious, but not solar mass objects, distances are astronomy. This was the big step necessarily compelling conclusions $$ 106 cm. A proton in free fall on to forward, because within less than 2 (there is always a more complicated a 1 Mo object would have a kinetic years, Uhuru had found about 100 fairy tale with the same outcome) can energy of 100 MeV at such a dis­ galactic and about 50 extragalactic be drawn immediately from the data : tance. If one thermally radiates away X-ray sources. About 90 % of these The rapid variability on timescales the energy in X-rays of a few keV, i.e. galactic sources apparently constitu­ of seconds or milliseconds (cf. Table at temperatures of 7 $$ 107 to 3x107 K, ted a new class of stellar objects 1) suggests that a compact object from areas with such typical dimen­ with an X-ray luminosity exceeding (white dwarf, neutron star, black hole) sions, one finds luminosities of 1036 - the sun's total luminosity by a factor is involved. The energy source for the 1038 erg/s. 5 of 10 . This was substantiated by X-rays comes from gas which accre­ This is in good agreement with the satellite observations in later years. tes in the deep gravitational well of observations. Talking only of black The new satellites also revealed the compact object, flowing over from holes and neutron stars is, of course, new types of galactic X-ray stars, so a companion star, which is not com­ unfair to the white dwarfs, which can that now one knows of a large variety pact. This view is supported by the also satisfy the constraints imposed of types, of which regular pulsating fact that for 10 X-ray sources, it has by the data. But accretion on white Table 1 Source Short term variability Long term variability Optical candidate Distance Luminosity (2-10 keV) (kpc) (1036 erg) HerX-1 1.24 s pulsations X-ray eclipses (1.7d) HZ Her ; 2-6 1 -10 (6 kpc) (3U1653 + 35) 35d modulation 1.7d binary long-term on-off Cen X-3 4.84 pulsations X-ray eclipses (2.1 d) double ellipsoidal 6-9 10-30 (9) (3U1118-60) extended lows light variation Ob star Cyg X-1 Irreg. var. in times slow transition HDE 226868 2.5 3-10 var (3U1956 + 35) of milliseconds between 2 distinct 5.6d binary spectral states Vela X-1 283 s pulsations flares, eclipse HD 77581 2 10 (3U0900-40) (282.8913 ± 0.0004) (8.95d) SMCX-1 0.71 s pulsation X-ray eclipses, 3.9d SK 160 60 30 - 300 (3U0115-73) extended lows 13 mag. ScoX-1 Irreg. var. min slow (~ 10 min-h) ScoX-1, blue 1 -2 10 (3U1617-15) flares 0.787d period A0620-00 none appears in outbursts optical 1 100 lasting $$ 1 year Identification (1967 & 1975) no period determined tures of the X-ray source (in Fig. 1, therefore that HerX-1 is a neutron star. a schematic drawing of the gas flow It also establishes that neutron stars is presented). Table 1 (ref. 2) con­ really have the large magnetic fields tains several regularly pulsating X-ray expected for them from theoretical sources, with pulse periods in the considerations of stellar collapse, and range of 1.24 s (HerX-1) - 283 s (Vela from the slowing down of the pulsars X-1). The time-keeping mechanism is by the emission of electromagnetic probably rotation of the compact ob­ dipole radiation. Meanwhile a second ject, which means rotation of a neu­ experiment by Trümper ef al. has tron star at least for the fast rotators. confirmed the results of the first mea­ The observed pulses must be produ­ surements, and other observers have ced by an asymmetry in the infall also obtained evidence for a line fea­ of matter, and the obvious way to ture in the spectrum of HerX-1. achieve this is to have inclined to the The large value of 5. 108 T also in­ axis of rotation, a stellar magnetic dicates that the line emission is a field, which guides the matter down, quantum effect. In strong magnetic such that only certain hot spots on fields, the motion of the electron per­ the surface accrete. As these hot pendicular to the field is quantized, spots move through our field of vision, similar to the quantization of the elec­ we see X-ray pulses. tron orbits in an atom. The energy difference between two adjacent or­ Fig. 1. — Schematic drawing of accretion bits or levels is $$ωB_ where ωB = from a stellar wind and Roche Lobe Measurement of the Magnetic Field overflow with disk accretion. of a Neutron Star B B What information do we gain from eBlmc is the classical gyration fre­ dwarfs produces keV X-rays only, if observations on the physics of the quency. A spin reversal of the elec­ the infall is radial ; the observed accretion process close to a neutron trons has the same energy difference period changes are very difficult to star ? The spectrum of the radiation 2π h ωB. So there are two excited explain, and strong magnetic fields, emerges from a complicated and in­ states with the same energy diffe­ as measured by Trümper 1), cannot tricate interaction of many distinct rence with respect to a ground state : be supported by white dwarfs. With features, such as hot plasmas accele­ a higher orbit quantum number, or a accretion on to neutron stars or black rated by a strong gravitational field, different spin direction of the electron holes, about 10% of the rest mass guided by a rotating magnetic field, on the same orbit. Transitions into the energy of the infalling gas is conver­ finally hitting a neutron star surface ground state from the first excited ted into X-rays. Thus the accretion of very high density. There are so state in this system of Landau levels rates do not have to be very large : many parameters unknown, that a produce the observed line. The emis­ 8 10 sion of higher harmonics should also 10- Mo/a to 10- Mo/a is sufficient quantitative picture of the accretion to give the powers observed. process is not available, one only be possible. There is, indeed, an indication of an enhancement in the These or larger mass-transfer rates knows that it must be quite compli­ observed spectrum around 110 keV, can easily occur in close binary sys­ cated. where one would expect the second tems. Three different mechanisms There are great hopes, however, for harmonic to occur. may be important : an improvement of the theoretical i) A massive companion expanding situation, due to the measurement by Fig. 2. — Measurement of J. Trümper et across the critical equipotential the group of J. Trümper. They have al1) showing the spectrum of the HerX-1 surface between the two stars observed the regularly pulsating pulses and of OSO-8 (Aug. 75) showing the total spectrum. — Roche lobe overflow — could source HerX-1 for about 4 hours in a transfer mass at a rate of 10-6 balloon flight from Palestine/Texas on 3 Mo/a to 10- Mo/a. May 3, 1976. The spectrum for the ii) A stellar wind, I.e. an atmosphere pulsed flux they have obtained is streaming radially outwards, as shown in Fig. 2. There is strong evi­ expected from Ob or Be stars, can dence of a spectral line feature at 58 ± have a magnitude of 10-6 Mo/a.
Load more

Recommended publications
  • The Star Newsletter
    THE HOT STAR NEWSLETTER ? An electronic publication dedicated to A, B, O, Of, LBV and Wolf-Rayet stars and related phenomena in galaxies ? No. 70 2002 July-August http://www.astro.ugto.mx/∼eenens/hot/ editor: Philippe Eenens http://www.star.ucl.ac.uk/∼hsn/index.html [email protected] ftp://saturn.sron.nl/pub/karelh/uploads/wrbib/ Contents of this newsletter Call for Data . 1 Abstracts of 12 accepted papers . 2 Abstracts of 2 submitted papers . 10 Abstracts of 6 proceedings papers . 11 Jobs .......................................................................13 Meetings ...................................................................14 Call for Data The multiplicity of 9 Sgr G. Rauw and H. Sana Institut d’Astrophysique, Universit´ede Li`ege,All´eedu 6 Aoˆut, BˆatB5c, B-4000 Li`ege(Sart Tilman), Belgium e-mail: [email protected], [email protected] The non-thermal radio emission observed for a number of O and WR stars implies the presence of a small population of relativistic electrons in the winds of these objects. Electrons could be accelerated to relativistic velocities either in the shock region of a colliding wind binary (Eichler & Usov 1993, ApJ 402, 271) or in the shocks due to intrinsic wind instabilities of a single star (Chen & White 1994, Ap&SS 221, 259). Dougherty & Williams (2000, MNRAS 319, 1005) pointed out that 7 out of 9 WR stars with non-thermal radio emission are in fact binary systems. This result clearly supports the colliding wind scenario. In the present issue of the Hot Star Newsletter, we announce the results of a multi-wavelength campaign on the O4 V star 9 Sgr (= HD 164794; see the abstract by Rauw et al.).
    [Show full text]
  • SXP 1062, a Young Be X-Ray Binary Pulsar with Long Spin Period⋆
    A&A 537, L1 (2012) Astronomy DOI: 10.1051/0004-6361/201118369 & c ESO 2012 Astrophysics Letter to the Editor SXP 1062, a young Be X-ray binary pulsar with long spin period Implications for the neutron star birth spin F. Haberl1, R. Sturm1, M. D. Filipovic´2,W.Pietsch1, and E. J. Crawford2 1 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany e-mail: [email protected] 2 University of Western Sydney, Locked Bag 1797, Penrith South DC, NSW1797, Australia Received 31 October 2011 / Accepted 1 December 2011 ABSTRACT Context. The Small Magellanic Cloud (SMC) is ideally suited to investigating the recent star formation history from X-ray source population studies. It harbours a large number of Be/X-ray binaries (Be stars with an accreting neutron star as companion), and the supernova remnants can be easily resolved with imaging X-ray instruments. Aims. We search for new supernova remnants in the SMC and in particular for composite remnants with a central X-ray source. Methods. We study the morphology of newly found candidate supernova remnants using radio, optical and X-ray images and inves- tigate their X-ray spectra. Results. Here we report on the discovery of the new supernova remnant around the recently discovered Be/X-ray binary pulsar CXO J012745.97−733256.5 = SXP 1062 in radio and X-ray images. The Be/X-ray binary system is found near the centre of the supernova remnant, which is located at the outer edge of the eastern wing of the SMC. The remnant is oxygen-rich, indicating that it developed from a type Ib event.
    [Show full text]
  • Origin and Binary Evolution of Millisecond Pulsars
    Origin and binary evolution of millisecond pulsars Francesca D’Antona and Marco Tailo Abstract We summarize the channels formation of neutron stars (NS) in single or binary evolution and the classic recycling scenario by which mass accretion by a donor companion accelerates old NS to millisecond pulsars (MSP). We consider the possible explanations and requirements for the high frequency of the MSP population in Globular Clusters. Basics of binary evolution are given, and the key concepts of systemic angular momentum losses are first discussed in the framework of the secular evolution of Cataclysmic Binaries. MSP binaries with compact companions represent end-points of previous evolution. In the class of systems characterized by short orbital period %orb and low companion mass we may instead be catching the recycling phase ‘in the act’. These systems are in fact either MSP, or low mass X–ray binaries (LMXB), some of which accreting X–ray MSP (AMXP), or even ‘transitional’ systems from the accreting to the radio MSP stage. The donor structure is affected by irradiation due to X–rays from the accreting NS, or by the high fraction of MSP rotational energy loss emitted in the W rays range of the energy spectrum. X– ray irradiation leads to cyclic LMXB stages, causing super–Eddington mass transfer rates during the first phases of the companion evolution, and, possibly coupled with the angular momentum carried away by the non–accreted matter, helps to explain ¤ the high positive %orb’s of some LMXB systems and account for the (apparently) different birthrates of LMXB and MSP. Irradiation by the MSP may be able to drive the donor to a stage in which either radio-ejection (in the redbacks) or mass loss due to the companion expansion, and ‘evaporation’ may govern the evolution to the black widow stage and to the final disruption of the companion.
    [Show full text]
  • Gravity Tests with Radio Pulsars
    universe Review Gravity Tests with Radio Pulsars Norbert Wex 1,* and Michael Kramer 1,2 1 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany; [email protected] 2 Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK * Correspondence: [email protected] Received: 19 August 2020; Accepted: 17 September 2020; Published: 22 September 2020 Abstract: The discovery of the first binary pulsar in 1974 has opened up a completely new field of experimental gravity. In numerous important ways, pulsars have taken precision gravity tests quantitatively and qualitatively beyond the weak-field slow-motion regime of the Solar System. Apart from the first verification of the existence of gravitational waves, binary pulsars for the first time gave us the possibility to study the dynamics of strongly self-gravitating bodies with high precision. To date there are several radio pulsars known which can be utilized for precision tests of gravity. Depending on their orbital properties and the nature of their companion, these pulsars probe various different predictions of general relativity and its alternatives in the mildly relativistic strong-field regime. In many aspects, pulsar tests are complementary to other present and upcoming gravity experiments, like gravitational-wave observatories or the Event Horizon Telescope. This review gives an introduction to gravity tests with radio pulsars and its theoretical foundations, highlights some of the most important results, and gives a brief outlook into the future of this important field of experimental gravity. Keywords: gravity; general relativity; pulsars 1.
    [Show full text]
  • Stellar Mass Black Holes Maximum Mass of a Neutron Star Is Unknown, but Is Probably in the Range 2 - 3 Msun
    Stellar mass black holes Maximum mass of a neutron star is unknown, but is probably in the range 2 - 3 Msun. No known source of pressure can support a stellar remnant with a higher mass - collapse to a black hole appears to be inevitable. Strong observational evidence for black holes in two mass ranges: Stellar mass black holes: MBH = 5 - 100 Msun • produced from the collapse of very massive stars • lower mass examples could be produced from the merger of two neutron stars 6 9 Supermassive black holes: MBH = 10 - 10 Msun • present in the nuclei of most galaxies • formation mechanism unknown ASTR 3730: Fall 2003 Other types of black hole could exist too: 3 Intermediate mass black holes: MBH ~ 10 Msun • evidence for the existence of these from very luminous X-ray sources in external galaxies (L >> LEdd for a stellar mass black hole). • `more likely than not’ to exist, but still debatable Primordial black holes • formed in the early Universe • not ruled out, but there is no observational evidence and best guess is that conditions in the early Universe did not favor formation. ASTR 3730: Fall 2003 Basic properties of black holes Black holes are solutions to Einstein’s equations of General Relativity. Numerous theorems have been proved about them, including, most importantly: The `No-hair’ theorem A stationary black hole is uniquely characterized by its: • Mass M Conserved • Angular momentum J quantities • Charge Q Remarkable result: Black holes completely `forget’ how they were made - from stellar collapse, merger of two existing black holes etc etc… Only applies at late times.
    [Show full text]
  • Stellar Evolution
    AccessScience from McGraw-Hill Education Page 1 of 19 www.accessscience.com Stellar evolution Contributed by: James B. Kaler Publication year: 2014 The large-scale, systematic, and irreversible changes over time of the structure and composition of a star. Types of stars Dozens of different types of stars populate the Milky Way Galaxy. The most common are main-sequence dwarfs like the Sun that fuse hydrogen into helium within their cores (the core of the Sun occupies about half its mass). Dwarfs run the full gamut of stellar masses, from perhaps as much as 200 solar masses (200 M,⊙) down to the minimum of 0.075 solar mass (beneath which the full proton-proton chain does not operate). They occupy the spectral sequence from class O (maximum effective temperature nearly 50,000 K or 90,000◦F, maximum luminosity 5 × 10,6 solar), through classes B, A, F, G, K, and M, to the new class L (2400 K or 3860◦F and under, typical luminosity below 10,−4 solar). Within the main sequence, they break into two broad groups, those under 1.3 solar masses (class F5), whose luminosities derive from the proton-proton chain, and higher-mass stars that are supported principally by the carbon cycle. Below the end of the main sequence (masses less than 0.075 M,⊙) lie the brown dwarfs that occupy half of class L and all of class T (the latter under 1400 K or 2060◦F). These shine both from gravitational energy and from fusion of their natural deuterium. Their low-mass limit is unknown.
    [Show full text]
  • 10. Binary Pulsars to Test General Relativity
    10. Binary Pulsars to test General Relativity 10.1. Binary pulsars are rare systems. After the discovery of the first pulsar in 1968 by Hewish and Bell the search and study of pulsars quickly became a new and growing research field taken up by nearly all large radioastronomy observatories. By 1972 already seven dozen pulsars were known, all discovered by examining strip-chart records which were soon replaced by computerized searches. It was obvious that pulsars are very precise clocks with extremely stable periods and −13 −19 slowdown rates of the order of t&P ≈ 10 −10 . If a pulsar is accompanied by an equally compact companion, a white dwarf, a neutron star or a black hole (at a distance approximately Moon-Earth) such a system would offer an ideal laboratory to study effects in strong gravitational fields and to test General Relativity under strong field conditions. Today nearly 2000 pulsars are known in our galaxy, only about 4 % are in binary systems and most of those are ms-pulsars with a low mass companion. Mass and momentum transfer from the companion lead to a reloading of the pulsar. Such systems will further evolve into low mass X-ray binary systems (LMXB) with a fast spinning ms-pulsar (t P ≈ 1−10 ms ), see also lect. 09. Binary pulsars with high mass companions (main sequence stars or neutron stars) are found to have eccentric orbits (0,15 < e < 0,90). If the mass of the companion is large enough to finally lead to a core supernova explosion a second NS will be born.
    [Show full text]
  • Exploring Pulsar-Black Hole Binaries Using the Next
    EXPLORING PULSAR{BLACK HOLE BINARIES USING THE NEXT GENERATION OF RADIO TELESCOPES A thesis submitted to the University of Manchester for the degree of Doctor of Philosophy in the Faculty of Engineering and Physical Sciences 2012 By Kuo Liu Jodrell Bank Centre for Astrophysics School of Physics and Astronomy Contents Contents 2 List of Figures 8 List of Tables 11 Abstract 13 Declaration 15 Copyright 17 The author 19 Publications 21 Acknowledgements 23 1 Introduction 25 1.1 Pulsars . 26 1.2 Dipole model . 27 1.2.1 Spin evolution and braking index . 28 1.2.2 Characteristic age . 30 1.2.3 Magnetic ¯eld strength . 30 1.3 Population and the P -P_ diagram . 31 1.4 Propagation through the ISM . 32 2 1.4.1 Dispersion delay . 32 1.4.2 Scattering and scintillation . 34 1.5 Binary systems . 35 1.6 Rotational stability . 39 1.7 Celestial laboratory in relativity test . 41 1.7.1 Double neutron star binaries . 41 1.7.2 Neutron star-white dwarf binaries . 42 1.7.3 Neutron star-black hole binaries . 44 1.8 Searching for binary pulsars . 44 1.8.1 Constant acceleration search . 44 1.8.2 Phase modulation search . 46 1.8.3 Additional tools . 46 1.9 Thesis structure . 47 2 Pulsar Timing analysis 49 2.1 Introduction . 49 2.2 Instrumentation . 50 2.3 TOA measurement . 53 2.3.1 Algorithm . 54 2.3.2 Limitation . 55 2.4 Interpreting TOAs . 58 2.4.1 Time standard . 59 2.4.2 Timing model . 60 2.4.3 Binary correction .
    [Show full text]
  • General Relativity with Double Pulsars
    SLAC Summer Institute on Particle Physics (SSI04), Aug. 2-13, 2004 General Relativity with Double Pulsars M. Kramer Jodrell Bank Observatory, The University of Manchester, Jodrell Bank, Macclesfield SK11 9DL, UK A new era in fundamental physics began with the discovery of pulsars 1967, the discovery of the first binary pulsar in 1974 and the first millisecond pulsar in 1982. Ever since, pulsars have been used as precise cosmic clocks, taking us beyond the weak-field regime of the solar-system in the study of theories of gravity. Their contribution is crucial as no test can be considered to be complete without probing the strong-field realm of gravitational physics by finding and timing pulsars. This is particularly highlighted by the discovery of the first double pulsar system. This first ever double pulsar, discovered by our team 18 months ago, consists of two pulsars, one with period of only 22 ms and the other with a period of 2.8 sec. This binary system with a period of only 2.4-hr provides a truly unique laboratory for relativistic gravitational physics. 1. Introduction Rarely had the formulation of a single theory changed our view of the Universe so dramatically as Einstein's theory of general relativity (GR). Immediately after its publication, scientists were considering ways of testing GR to experimentally verify the revolutionary different effects that were predicted as deviations from Newton's theory of gravity which had ruled supreme for about three hundred years. Already during World War I., British scientists were planning two expeditions to test GR by observing a predicted bending of light around the Sun during a total solar eclipse to be observed in 1919 in Brazil and Africa.
    [Show full text]
  • Formation of Double Neutron Stars, Millisecond Pulsars and Double Black Holes
    Formation of Double Neutron Stars, Millisecond pulsars and Double Black Holes Edward P.J. van den Heuvel Anton Pannekoek Institute of Astronomy, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands, and Kavli Institute for Theoretical Physics, University of California Santa Barbara, CA 93106-4030, USA Abstract The 1982 model for the formation of Hulse-Taylor binary radio pulsar PSR B1913+16 is described, which since has become the “standard model” for the formation of the double neutron stars, confirmed by the 2003 discovery of the double pulsar system PSR J0737-3039AB. A brief overview is given of the present status of our knowledge of the double neutron stars, of which 15 systems are presently known. The binary-recycling model for the formation of millisecond pulsars is described, as put forward independently by Alpar et al. (1982), Radhakrishnan and Srinivasan (1982), and Fabian et al. (1983). This now is the “standard model” for the formation of these objects, confirmed by the discovery in 1998 of the accreting millisecond X-ray pulsars. It is noticed that the formation process of close double black holes has analogies to that of close double neutron stars, extended to binaries with larger initial component masses, although there are also considerable differences in the physics of the binary evolution at these larger masses. 1. Introduction The X-ray binaries were discovered in 1972 (Schreier et al. 1972) and the first binary radio pulsar was discovered in 1974: the Hulse-Taylor pulsar PSR B1913+16, in a very eccentric binary system (e=0.617) with a very short orbital period (7h45 minutes; Hulse and Taylor 1975).
    [Show full text]
  • Measuring the Masses of Neutron Stars
    Reports from Observers Measuring the Masses of Neutron Stars Lex Kaper1 Arjen van der Meer1 Marten van Kerkwijk Ed van den Heuvel1 Visualisation: B. Pounds 1 Astronomical Institute “Anton Panne- koek” and Centre for High Energy Astrophysics, University of Amsterdam, the Netherlands Department of Astronomy and Astro- physics, University of Toronto, Canada Until a few years ago the common un- derstanding was that neutron stars, the compact remnants of massive stars, have a canonical mass of about 1.4 MA. Recent observations with VLT/UVES support the view that the neutron stars in high-mass X-ray binaries display a relatively large spread in mass, ranging from the theoretical lower mass limit Figure 1: Artist’s impression of a high-mass X-ray of 1 MA up to over 2 MA. Such a mass ter of such a high density. As bosons do distribution provides important informa- not contribute to the fermi pressure1, their binary hosting a massive OB-type star and a compact X-ray source, a neutron star or a black tion on the formation mechanism of presence will tend to ‘soften’ the EOS. hole. neutron stars (i.e. the supernovae), and For a soft EOS, the maximum neutron star on the (unknown) behaviour of matter at mass will be low (~ 1.5 MA); for a high- 1807 with a mass of .1 ± 0. MA (Nice et supranuclear densities. er mass, the object would collapse into al. 005). These results favour a stiff EOS. a black hole. More than 100 candidate equations of state are proposed, but only A neutron star cannot be more massive The compact remnants of massive stars one EOS can be the correct one.
    [Show full text]
  • Astronomical Tests of General Relativity
    Astronomical Tests of General Relativity A thesis for the award of Doctor of Philosophy Keith John TRESCHMAN BSc, DipEd, BEdSt, BA, MEd, MSc 2015 i Abstract This thesis is an in depth investigation of the history of the acceptance of Einstein’s Theory of General Relativity by scientists and by the public through the media. It emphasises the key role that Australia played in that acceptance and in the verification of General Relativity. This contribution came from the 1922 total solar eclipse across the continent as well as the discovery in 2003 at Parkes Radio Telescope of the first, and to this date only, pair of pulsars in mutual orbit. This system provides a unique opportunity to plumb the theory in a much stronger gravitational field regime than previously. This historical scrutiny provides an insight into scientific revolutions in general. The examination of this particular development may then act as a template for the study of other scientific revolutions. One of the key findings is that the Theory of General Relativity was prematurely accepted. The main argument of the thesis is for 1928 being the year when sufficient evidence existed for scientists to begin accepting the theory based on gravitational deflection of light instead of the commonly accepted date of 1919. Emphasis is given to the explorations of the 1922 eclipse parties in Australia and the activities of the eight groups measuring light deflection at this eclipse. This work is gathered together here for the first time. The upshot is that it was 1928 before the results were published in full and a conclusion could be drawn.
    [Show full text]