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Negreiros Lecture II
General Relativity and Neutron Stars - II Rodrigo Negreiros – UFF - Brazil Outline • Compact Stars • Spherically Symmetric • Rotating Compact Stars • Magnetized Compact Stars References for this lecture Compact Stars • Relativistic stars with inner structure • We need to solve Einstein’s equation for the interior as well as the exterior Compact Stars - Spherical • We begin by writing the following metric • Which leads to the following components of the Riemman curvature tensor Compact Stars - Spherical • The Ricci tensor components are calculated as • Ricci scalar is given by Compact Stars - Spherical • Now we can calculate Einstein’s equation as 휇 • Where we used a perfect fluid as sources ( 푇휈 = 푑푖푎푔(휖, 푃, 푃, 푃)) Compact Stars - Spherical • Einstein’s equation define the space-time curvature • We must also enforce energy-momentum conservation • This implies that • Where the four velocity is given by • After some algebra we get Compact Stars - Spherical • Making use of Euler’s equation we get • Thus • Which we can rewrite as Compact Stars - Spherical • Now we introduce • Which allow us to integrate one of Einstein’s equation, leading to • After some shuffling of Einstein’s equation we can write Summary so far... Metric Energy-Momentum Tensor Einstein’s equation Tolmann-Oppenheimer-Volkoff eq. Relativistic Hydrostatic Equilibrium Mass continuity Stellar structure calculation Microscopic Ewuation of State Macroscopic Composition Structure Recapitulando … “Feed” with diferente microscopic models Microscopic Ewuation of State Macroscopic Composition Structure Compare predicted properties with Observed data. Rotating Compact Stars • During its evolution, compact stars may acquire high rotational frequencies (possibly up to 500 hz) • Rotation breaks spherical symmetry, increasing the degrees of freedom. -
Accretion Flows in Nonmagnetic White Dwarf Binaries As Observed in X-Rays
Accretion Flows in Nonmagnetic White Dwarf Binaries as Observed in X-rays Şölen Balmana,< aKadir Has University, Faculty of Engineering and Natural Sciences, Cibali 34083, Istanbul, Turkey ARTICLEINFO ABSTRACT Keywords: Cataclysmic Variables (CVs) are compact binaries with white dwarf (WD) primaries. CVs and other cataclysmic variables - accretion, accre- accreting WD binaries (AWBs) are useful laboratories for studying accretion flows, gas dynamics, tion disks - thermal emission - non-thermal outflows, transient outbursts, and explosive nuclear burning under different astrophysical plasma con- emission - white dwarfs - X-rays: bina- ditions. They have been studied over decades and are important for population studies of galactic ries X-ray sources. Recent space- and ground-based high resolution spectral and timing studies, along with recent surveys indicate that we still have observational and theoretical complexities yet to an- swer. I review accretion in nonmagnetic AWBs in the light of X-ray observations. I present X-ray diagnostics of accretion in dwarf novae and the disk outbursts, the nova-like systems, and the state of the research on the disk winds and outflows in the nonmagnetic CVs together with comparisons and relations to classical and recurrent nova systems, AM CVns and Symbiotic systems. I discuss how the advective hot accretion flows (ADAF-like) in the inner regions of accretion disks (merged with boundary layer zones) in nonmagnetic CVs explain most of the discrepancies and complexities that have been encountered in the X-ray observations. I stress how flickering variability studies from optical to X-rays can be probes to determine accretion history and disk structure together with how the temporal and spectral variability of CVs are related to that of LMXBs and AGNs. -
1983Apj. . .273. .280K the Astrophysical Journal, 273:280-288, 1983 October 1 © 1983. the American Astronomical Society. All Ri
.280K .273. The Astrophysical Journal, 273:280-288, 1983 October 1 . © 1983. The American Astronomical Society. All rights reserved. Printed in U.S.A. 1983ApJ. THE OUTBURSTS OF SYMBIOTIC NOVAE1 Scott J. Kenyon and James W. Truran Department of Astronomy, University of Illinois Received 1982 December 21 ; accepted 1983 March 9 ABSTRACT We discuss possible conditions under which thermonuclear burning episodes in the hydrogen-rich envelopes of accreting white dwarfs give rise to outbursts similar in nature to those observed in the symbiotic stars AG Peg, RT Ser, RR Tel, AS 239, V1016 Cyg, V1329 Cyg, and HM Sge. In principle, thermonuclear runaways involving low-luminosity white dwarfs accreting matter at low rates produce configurations that evolve into A-F supergiants at maximum visual light and which resemble the outbursts of RR Tel, RT Ser, and AG Peg. Very weak, nondegenerate hydrogen 8 -1 shell flashes on white dwarfs accreting matter at high rates (M > 10" M0 yr ) do not produce cool supergiants at maximum, and may explain the outbursts in V1016 Cyg, V1329 Cyg, and HM Sge. The low accretion rates demanded for systems developing strong hydrogen shell flashes on low-luminosity white dwarfs are not compatible with observations of “normal” quiescent symbiotic stars. The extremely slow outbursts of symbiotic novae appear to be typical of accreting white dwarfs in wide binaries, which suggests that the outbursts of classical novae may be accelerated by the interaction of the expanding white dwarf envelope with its close binary companion. Subject headings: stars: accretion — stars: combination spectra — stars: novae — stars: white dwarfs I. -
Black Hole Formation the Collapse of Compact Stellar Objects to Black Holes
Utrecht University Institute of Theoretical Physics Black Hole Formation The Collapse of Compact Stellar Objects to Black Holes Author: Michiel Bouwhuis [email protected] Supervisor: Dr. Tomislav Prokopec [email protected] February 17, 2009 Theoretical Physics Colloquium Abstract This paper attemps to prove the existence of black holes by combining obser- vational evidence with theoretical findings. First, basic properties of black holes are explained. Then black hole formation is studied. The relativistic hydrostatic equations are derived. For white dwarfs the equation of state and the Chandrasekhar limit M = 1:43M are worked out. An upper bound of M = 3:6M for the mass of any compact object is determined. These results are compared with observational evidence to prove that black holes exist. Contents 1 Introduction 3 2 Black Holes Basics 5 2.1 The Schwarzschild Metric . 5 2.2 Black Holes . 6 2.3 Eddington-Finkelstein Coordinates . 7 2.4 Types of Black Holes . 9 3 Stellar Collapse and Black Hole Formation 11 3.1 Introduction . 11 3.2 Collapse of Dust . 11 3.3 Gravitational Balance . 15 3.4 Equations of Structure . 15 3.5 White Dwarfs . 18 3.6 Neutron Stars . 23 4 Astronomical Black Holes 26 4.1 Stellar-Mass Black Holes . 26 4.2 Supermassive Black Holes . 27 5 Discussion 29 5.1 Black hole alternatives . 29 5.2 Conclusion . 29 2 Chapter 1 Introduction The idea of a object so heavy that even light cannot escape its gravitational well is very old. It was first considered by British amateur astronomer John Michell in 1783. -
Physics of Compact Stars
Physics of Compact Stars • Crab nebula: Supernova 1054 • Pulsars: rotating neutron stars • Death of a massive star • Pulsars: lab’s of many-particle physics • Equation of state and star structure • Phase diagram of nuclear matter • Rotation and accretion • Cooling of neutron stars • Neutrinos and gamma-ray bursts • Outlook: particle astrophysics David Blaschke - IFT, University of Wroclaw - Winter Semester 2007/08 1 Example: Crab nebula and Supernova 1054 1054 Chinese Astronomers observe ’Guest-Star’ in the vicinity of constellation Taurus – 6times brighter than Venus, red-white light – 1 Month visible during the day, 1 Jahr at evenings – Luminosity ≈ 400 Million Suns – Distance d ∼ 7.000 Lightyears (ly) (when d ≤ 50 ly Life on earth would be extingished) 1731 BEVIS: Telescope observation of the SN remnants 1758 MESSIER: Catalogue of nebulae and star clusters 1844 ROSSE: Name ’Crab nebula’ because of tentacle structure 1939 DUNCAN: extrapolates back the nebula expansion −! Explosion of a point source 766 years ago 1942 BAADE: Star in the nebula center could be related to its origin 1948 Crab nebula one of the brightest radio sources in the sky CHANDRA (BLAU) + HUBBLE (ROT) 1968 BAADE’s star identified as pulsar 2 Pulsars: Rotating Neutron stars 1967 Jocelyne BELL discovers (Nobel prize 1974 for HEWISH) pulsating radio frequency source (pulse in- terval: 1.34 sec; pulse duration: 0.01 sec) Today more than 1700 of such sources are known in the milky way ) PULSARS Pulse frequency extremely stable: ∆T=T ≈ 1 sec/1 million years 1968 Explanation -
Cygnus X-3 and the Case for Simultaneous Multifrequency
by France Anne-Dominic Cordova lthough the visible radiation of Cygnus A X-3 is absorbed in a dusty spiral arm of our gal- axy, its radiation in other spectral regions is observed to be extraordinary. In a recent effort to better understand the causes of that radiation, a group of astrophysicists, including the author, carried 39 Cygnus X-3 out an unprecedented experiment. For two days in October 1985 they directed toward the source a variety of instru- ments, located in the United States, Europe, and space, hoping to observe, for the first time simultaneously, its emissions 9 18 Gamma Rays at frequencies ranging from 10 to 10 Radiation hertz. The battery of detectors included a very-long-baseline interferometer consist- ing of six radio telescopes scattered across the United States and Europe; the Na- tional Radio Astronomy Observatory’s Very Large Array in New Mexico; Caltech’s millimeter-wavelength inter- ferometer at the Owens Valley Radio Ob- servatory in California; NASA’s 3-meter infrared telescope on Mauna Kea in Ha- waii; and the x-ray monitor aboard the European Space Agency’s EXOSAT, a sat- ellite in a highly elliptical, nearly polar orbit, whose apogee is halfway between the earth and the moon. In addition, gamma- Wavelength (m) ray detectors on Mount Hopkins in Ari- zona, on the rim of Haleakala Crater in Fig. 1. The energy flux at the earth due to electromagnetic radiation from Cygnus X-3 as a Hawaii, and near Leeds, England, covered function of the frequency and, equivalently, energy and wavelength of the radiation. -
Massive Close Binaries
Publishedintheyear2001,ASSLseries‘TheInfluenceofBinariesonStellarPopulationStudies’, ed. D. Vanbeveren, Kluwer Academic Publishers: Dordrecht. MASSIVE CLOSE BINARIES Dany Vanbeveren Astrophysical Institute, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium [email protected] keywords: Massive Stars, stellar winds, populations Abstract The evolution of massive stars in general, massive close binaries in particular depend on processes where, despite many efforts, the physics are still uncertain. Here we discuss the effects of stellar wind as function of metallicity during different evolutionary phases and the effects of rotation and we highlight the importance for population (number) synthesis. Models are proposed for the X-ray binaries with a black hole component. We then present an overall scheme for a massive star PNS code. This code, in combination with an appropriate set of single star and close binary evolutionary computations predicts the O-type star and Wolf-Rayet star population, the population of double compact star binaries and the supernova rates, in regions where star formation is continuous in time. 1. INTRODUCTION Population number synthesis (PNS) of massive stars relies on the evolution of massive stars and, therefore, uncertainties in stellar evolution imply uncertainties in PNS. The mass transfer and the accretion process during Roche lobe overflow (RLOF) in a binary, the merger process and common envelope evolution have been discussed frequently in the past by many authors (for extended reviews see e.g. van den Heuvel, 1993, Vanbeveren et al., 1998a, b). In the present paper we will focus on the effects of stellar wind mass loss during the various phases of stellar evolution and the effect of the metallicity Z. -
Fermi-Gst: a New View of the Gamma-Ray
FERMI-GST: A NEW VIEW OF THE γ-RAY SKY S. CHATY on behalf of the Fermi-LAT collaboration Laboratoire AIM (UMR 7158 CEA/DSM-CNRS-Universit´eParis Diderot), Irfu/Service d’Astrophysique, CEA-Saclay, FR-91191 Gif-sur-Yvette Cedex, France, e-mail: [email protected] The Large Area Telescope on the Fermi γ-ray Space Telescope (FGST, ex-GLAST) provides unprecedented sensitivity for all-sky monitoring of γ-ray activity. It is an adequate telescope to detect transient sources, since the observatory scans the entire sky every three hours and allows a general search for flaring activity on daily timescale. This search is conducted automatically as part of the ground processing of the data and allows a fast response –less than a day– to transient events. Follow-up observations in X-rays, optical, and radio are then performed to attempt to identify the origin of the emission and probe the possible existence of new transient γ-ray sources in the Galaxy. Since its launch on 11th June 2008, Fermi-LAT has detected nearly 1500 γ-ray sources, nearly half of them being extragalactic. After a brief census of detected celestial objects, we report here on the LAT results focusing on Galactic transient binary systems. The Fermi-LAT has detected 2 γ-ray binaries, a microquasar and an unexpected new type of γ-ray source: a symbiotic nova. 1 Introduction There has been two firmly established classes of variable sources in the high-energy γ-ray sky: blazars and γ-ray bursts (GRBs). The Energetic γ-Ray Experiment Telescope (EGRET) on the Compton Γ-Ray Observatory discovered a population of variable γ-ray blazars above 100 MeV 7. -
The Symbiotic Stars 79
6 The Symbiotic Stars ULISSE MUNARI 6.1 Symbiotic Stars: Binaries accreting from a Red Giant When Merrill and Humason (1932) discovered CI Cyg and AX Per, the first known sym- biotic stars (hereafter SySts), they were puzzled (in line with the wisdom of the time, not easily contemplating stellar binarity) by the co-existence in the ’same’ star of features be- longing to distant cornersof the HR diagram: the TiO bands typical of the coolest M giants, the HeII 4686 A˚ seen only in the hottest O-type stars, and an emission line spectrum match- ing that of planetary nebulae (hereafter PN). All these features stands out prominently in the spectrum of CI Cyg shown in Figure 6.1 together with its light-curve displaying a large assortment of different types of variability, with the spectral appearance changing in pace (a brighter state usually comes with bluer colors and a lower ionization). A great incentive to the study of SySts was provided in the 1980ies by the first confer- ence (Friedjung and Viotti, 1982) and monograph(Kenyon, 1986) devoted entirely to them, the first catalog and spectral atlas of known SySts by Allen (1984), and the first simple ge- ometrical modeling of their ionization front (Seaquist et al., 1984). Allen offered a clean classification criterium for SySts: a binary star, combining a red giant (RG) and a compan- ion hot enough to sustain HeII (or higher ionization) emission lines. The spectral atlas by Munari and Zwitter (2002), shows how the majorityof SySts meeting this criterium display in their spectra emission lines of at least the NeV, OVI or FeVII ionization stages, requiring a minimum photo-ionization temperature of 130,000 K (Murset and Nussbaumer, 1994). -
ASTR 1120-001 Midterm 2 Phil Armitage, Bruce Ferguson
ASTR 1120-001 Midterm 2 Phil Armitage, Bruce Ferguson SECOND MID-TERM EXAM MARCH 21st 2006: Closed books and notes, 1 hour. Please PRINT your name and student ID on the places provided on the scan sheet. ENCODE your student number also on the scan sheet. Questions 1-10 are TRUE / FALSE, 1 point each. Mark (a) True, (b) False on scan sheet, using a number 2 pencil. 1. The speed of light depends upon the velocity of the light source relative to the observer. FALSE 2. A clock moving at high speed relative to an observer appears to run slow. TRUE 3. The General Theory of Relativity includes the effects of gravity. TRUE 4. An accelerating observer feels heavier in exactly the same way as if the strength of gravity had increased. TRUE 5. Neutron stars and black holes are compact objects which have event horizons. FALSE 6. Radiation that escapes to large distances from very near the event horizon is shifted to higher energies. FALSE 7. Supermassive black holes are commonly found in the spiral arms of galaxies such as the Milky Way. FALSE 8. The center of the Milky Way is hard to observe in visible radiation due to obscuration by intervening gas and dust. TRUE 9. Hawking radiation is only observed for supermassive black holes. FALSE 10. The Sun will eventually explode as a supernova, leaving behind a stellar mass black hole. FALSE Questions 11-50 are MULTIPLE CHOICE, 1 point each. Mark scan sheet with letter of the BEST answer, using a number 2 pencil. -
Variable Star
Variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) fluctuates. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as either: Intrinsic variables, whose luminosity actually changes; for example, because the star periodically swells and shrinks. Extrinsic variables, whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth; for example, because the star has an orbiting companion that sometimes Trifid Nebula contains Cepheid variable stars eclipses it. Many, possibly most, stars have at least some variation in luminosity: the energy output of our Sun, for example, varies by about 0.1% over an 11-year solar cycle.[1] Contents Discovery Detecting variability Variable star observations Interpretation of observations Nomenclature Classification Intrinsic variable stars Pulsating variable stars Eruptive variable stars Cataclysmic or explosive variable stars Extrinsic variable stars Rotating variable stars Eclipsing binaries Planetary transits See also References External links Discovery An ancient Egyptian calendar of lucky and unlucky days composed some 3,200 years ago may be the oldest preserved historical document of the discovery of a variable star, the eclipsing binary Algol.[2][3][4] Of the modern astronomers, the first variable star was identified in 1638 when Johannes Holwarda noticed that Omicron Ceti (later named Mira) pulsated in a cycle taking 11 months; the star had previously been described as a nova by David Fabricius in 1596. This discovery, combined with supernovae observed in 1572 and 1604, proved that the starry sky was not eternally invariable as Aristotle and other ancient philosophers had taught. -
International Astronomical Union Commission G1 BIBLIOGRAPHY
International Astronomical Union Commission G1 BIBLIOGRAPHY OF CLOSE BINARIES No. 103 Editor-in-Chief: W. Van Hamme Editors: H. Drechsel D.R. Faulkner P.G. Niarchos D. Nogami R.G. Samec C.D. Scarfe C.A. Tout M. Wolf M. Zejda Material published by September 15, 2016 BCB issues are available at the following URLs: http://ad.usno.navy.mil/wds/bsl/G1_bcb_page.html, http://www.konkoly.hu/IAUC42/bcb.html, http://www.sternwarte.uni-erlangen.de/pub/bcb, or http://faculty.fiu.edu/~vanhamme/IAU-BCB/. The bibliographical entries for Individual Stars and Collections of Data, as well as a few General entries, are categorized according to the following coding scheme. Data from archives or databases, or previously published, are identified with an asterisk. The observation codes in the first four groups may be followed by one of the following wavelength codes. g. γ-ray. i. infrared. m. microwave. o. optical r. radio u. ultraviolet x. x-ray 1. Photometric data a. CCD b. Photoelectric c. Photographic d. Visual 2. Spectroscopic data a. Radial velocities b. Spectral classification c. Line identification d. Spectrophotometry 3. Polarimetry a. Broad-band b. Spectropolarimetry 4. Astrometry a. Positions and proper motions b. Relative positions only c. Interferometry 5. Derived results a. Times of minima b. New or improved ephemeris, period variations c. Parameters derivable from light curves d. Elements derivable from velocity curves e. Absolute dimensions, masses f. Apsidal motion and structure constants g. Physical properties of stellar atmospheres h. Chemical abundances i. Accretion disks and accretion phenomena j. Mass loss and mass exchange k.