DOCSLIB.ORG

Theoretical Studies of the Tidal Disruption of Stars

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Theoretical Studies of the Tidal Disruption of Stars Snacktime for Hungry Black Holes: Theoretical Studies of the Tidal Disruption of Stars by Linda Elisabeth Strubbe A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Astrophysics in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Eliot Quataert, Chair Professor Joshua Bloom Professor Steven Boggs Fall 2011 Snacktime for Hungry Black Holes: Theoretical Studies of the Tidal Disruption of Stars Copyright 2011 by Linda Elisabeth Strubbe 1 Abstract Snacktime for Hungry Black Holes: Theoretical Studies of the Tidal Disruption of Stars by Linda Elisabeth Strubbe Doctor of Philosophy in Astrophysics University of California, Berkeley Professor Eliot Quataert, Chair A star that wanders too close to the massive black hole (BH) in the center of a galaxy is headed for trouble: within a distance r r (M /M )1/3 (where r and M are the star’s T ∼ ⋆ BH ⋆ ⋆ ⋆ radius and mass, and MBH is the BH’s mass), the BH’s tidal gravity overcomes the binding gravity of the star, and the star is shredded into a stream of stellar debris. Studying this process of tidal disruption has the potential to give us insights into how central BHs and their surrounding stellar population grow and evolve. Motivated by new and upcoming rapid- cadence optical transient surveys, which should detect and allow study of tidal disruption events (TDEs) in unprecedented detail, I make theoretical predictions of the observable properties of these events to aid in their detection, identification, and interpretation. I find that stellar debris falling towards the BH is likely driven off again by radiation pressure at early times when the feeding rate is super-Eddington: this outflow has a large photosphere 43 44 1 and relatively cool temperature, producing a luminous ( 10 few 10 erg s− ) transient event at optical wavelengths. I predict that new transient∼ surveys− × such as the Palomar Transient Factory are likely to find tens to hundreds of these events. I further predict the spectroscopic signature of super-Eddington outflows—broad, blueshifted absorption lines in the ultraviolet—which should help confirm and teach us more about TDE candidates. Finding that the observable appearance of TDEs depends not only on BH mass but on pericenter radius of the star’s last fateful orbit, I derive a theoretical expression for the disruption rate as a function of pericenter and apply it to the galaxy NGC 4467 using real observational data, laying the groundwork for more extensive studies in the future. Finally, I also present my work on the debris disk surrounding the star AU Mic, in which I propose an explanation for the physical processes of dust dynamics that give rise to the observed disk profile. i For Mummy and Papa, who taught me to wonder about Nature, and who encourage me at every step. And for David, the best brother in the Universe. ii Contents List of Figures v List of Tables vii Acknowledgments viii 1 Introduction 1 1.1 Overview: for non-scientists and scientists . .......... 1 1.2 Astrophysicalcontext. ... 4 1.2.1 The presence and masses of central black holes . ...... 5 1.2.2 Theorbitsofstarsingalacticnuclei. ..... 6 1.2.3 Thegrowthofblackholes ........................ 8 1.3 Previousstudies................................. 11 1.3.1 Stellar dynamical studies . .. 12 1.3.2 Predicted observational appearance . ..... 15 1.3.3 Observations of tidal disruption candidates . ........ 17 1.4 Summaryofchapters ............................... 20 2 Optical Signatures of Tidally Disrupted Stars 23 2.1 Introduction.................................... 24 2.2 TheInitiallyBoundMaterial. .... 25 2.2.1 Super-EddingtonOutflows . 26 2.2.2 TheAccretionDisk............................ 28 2.3 TheEquatorialUnboundMaterial. .... 30 2.4 PredictedEmission ............................... 33 2.4.1 Super-EddingtonOutflows . 33 2.4.2 Disk and Photoionized Unbound Debris . ... 34 2.5 PredictedRates.................................. 39 2.5.1 DiskandPhotoionizedMaterial . .. 40 2.5.2 Current Observational Constraints . .... 41 2.5.3 Super-EddingtonOutflows . 43 2.6 Discussion..................................... 46 Contents iii 2.6.1 Super-EddingtonOutflows . 48 2.6.2 The Accretion Disk, Photoionized Gas, & Broad EmissionLines . 50 2.6.3 ObservationalConsiderations . ... 51 2.6.4 Astrophysical Applications . ... 52 3 Spectroscopic Signatures of the Tidal Disruption of Stars 54 3.1 Introduction.................................... 55 3.2 Super-EddingtonOutflows . .. 56 3.2.1 SummaryofBasicProperties . 56 3.2.2 The Applicability of Thermal Equilibrium . ..... 58 3.2.3 SpectroscopicCalculations . ... 60 3.3 PredictedSpectra................................ 64 3.3.1 Implications of an X-ray Power-law . ... 68 3.4 Supernova Rates in Galactic Nuclei . ..... 71 3.5 Discussion..................................... 74 3.5.1 ObservationalProspects . 75 3.5.2 Optically-selected candidates . ..... 78 4 Tidal Disruption Rate as a Function of Pericenter 79 4.1 Introduction.................................... 80 4.2 Tidaldisruptionratebasics . .... 81 4.3 Fokker-Planckformalism . ... 84 4.3.1 The distribution function and coordinate systems . ........ 84 4.3.2 Deriving the Fokker-Planck equation for (E, R; r)space........ 87 4.3.3 Diffusioncoefficients ........................... 89 4.3.4 The Fokker-Planck equation, continued . ..... 92 4.3.5 The distribution function outside the tidal disruptionzone ...... 93 4.3.6 The distribution function inside the tidal disruptionzone....... 94 4.3.7 Flowratesinphasespace ........................ 96 4.3.8 Calculating f(Rlc) ............................ 97 4.4 Tidal disruption rate as a function of pericenter . .......... 99 4.4.1 Keplerian potential with power-law density profile . ......... 101 4.4.2 Thenon-Keplerianpotential . 103 4.5 Results:NGC4467................................ 109 4.5.1 Implications for optical transient surveys . ........ 110 4.6 Discussion & directions for future work . ....... 111 5 Dust Dynamics, Surface Brightness Profiles, and Thermal Spectra of De- bris Disks: The Case of AU Mic 116 5.1 Introduction.................................... 117 5.2 Preliminaries ................................... 118 5.2.1 StellarProperties . .. .. 119 Contents iv 5.2.2 CollisionTimes .............................. 119 5.2.3 Blow-out by Stellar Wind and Radiation Pressure . ...... 120 5.2.4 Corpuscular and Poynting-Robertson Drag . ..... 122 5.3 Theory....................................... 123 5.3.1 Equilibrium Size Distribution . 124 5.3.2 Physical Implications of Optical Depth Profiles . ....... 129 5.3.3 Unbound Grains (β 1/2)........................ 133 ≥ 5.3.4 Unequilibrated Grains (sblow <s<sage) ................ 134 5.4 MonteCarloModelling............................. 135 5.4.1 Procedure ................................. 135 5.4.2 Products of the Monte Carlo Calculation . .... 137 5.4.3 Results................................... 138 5.5 SummaryandDirectionsforFutureWork . .... 140 6 Epilogue: Recent observational work 148 6.1 PTF10iya ..................................... 148 6.2 Swift1644+57................................... 152 Bibliography 153 v List of Figures 2.1 Spatialdiagramofthestellardebris. ......... 30 2.2 Predicted spectral energy distributions for super-Eddingtonoutflows . 31 2.3 Predicted optical light curves . ....... 32 2.4 Peak luminosities of the super-Eddington outflows . ............ 35 2.5 Predicted spectral energy distributions for the accretion disk & unbound debris 37 2.6 Predicted ultraviolet to near-infrared spectra for the accretion disk & unbound debris ......................................... 38 2.7 Predicted evolution of emission line strengths . ............ 38 2.8 Duration of maximum luminosity during the late-time accretion disk phase . 42 2.9 Predicted detection rates as a function of black hole mass for a survey like Pan- STARRS 3π ...................................... 43 2.10 Predicted detection rates as a function of pericenter distance for a survey like Pan-STARRS 3π ................................... 44 2.11 Duration of peak luminosity during the early super-Eddington outflow phase . 45 2.12 Predicted detection rates for emission from super-Eddington outflows by a survey like Pan-STARRS 3π ................................. 46 2.13 Predicted detection rates for emission from super-Eddington outflows for various opticaltransientsurveys . ... 47 3.1 Predicted spectra for our three fiducial tidal disruption flares at several different timesafterdisruption.. .. .. .. 65 3.2 Predicted spectra varying the mass-loss rate in the outflow, focusing on the wave- length region 1000 2000 A.............................˚ 66 − 3.3 Predicted spectra showing the effects of varying the mass-loss rate and outflow speedinthesuper-Eddingtonwind . ... 69 3.4 Predicted spectra including the presence of an X-ray power-lawtail . 70 3.5 Rates of supernovae close to the galactic nucleus . ............ 72 4.1 Normalized tidal disruption rate as a function of pericenter distance at various energies ........................................ 100 4.2 Tidal disruption rate as a function of pericenter distance at various energies inside theradiusofinfluence ................................ 103 List of Figures vi 4.3 Ratio q and distribution function f calculatedforNGC4467 . 109 4.4 Predicted tidal disruption rate as a function of pericenter distance for the galaxy NGC4467....................................... 110 4.5 Predicted optical detection rate incorporating dγ/d ln rp result .
Load more

Recommended publications
  • Radio Afterglow of the Jetted Tidal Disruption Event Swift J1644+57 B.D
    EPJ Web of Conferences 39, 04001 (2012) DOI: 10.1051/epjconf/20123904001 c Owned by the authors, published by EDP Sciences, 2012 Radio afterglow of the jetted tidal disruption event Swift J1644+57 B.D. Metzger1,a, D. Giannios1, and P. Mimica2 1 Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544, USA 2 Departmento de Astronomia y Astrofisica, University de Valencia, 46100 Burjassot, Spain Abstract. The recent transient event Swift J1644+57 has been interpreted as resulting from a relativistic outflow, powered by the accretion of a tidally disrupted star onto a supermassive black hole. This discovery of a new class of relativistic transients opens new windows into the study of tidal disruption events (TDEs) and offers a unique probe of the physics of relativistic jet formation and the conditions in the centers of distant quiescent galaxies. Unlike the rapidly-varying γ/X-ray emission from Swift J1644+57, the radio emission varies more slowly and is well modeled as synchrotron radiation from the shock interaction between the jet and the gaseous circumnuclear medium (CNM). Early after the onset of the jet, a reverse shock propagates through and decelerates the ejecta released during the first few days of activity, while at much later times the outflow approaches the self-similar evolution of Blandford and McKee. The point at which the reverse shock entirely crosses the earliest ejecta is clearly observed as an achromatic break in the radio light curve at t ≈ 10 days. The flux and break frequencies of the afterglow constrain the properties of the jet and the CNM, including providing robust evidence for a narrowly collimated jet.
    [Show full text]
  • Correction: Corrigendum: the Superluminous Transient ASASSN
    LETTERS PUBLISHED: 12 DECEMBER 2016 | VOLUME: 1 | ARTICLE NUMBER: 0002 The superluminous transient ASASSN-15lh as a tidal disruption event from a Kerr black hole G. Leloudas1,​2*, M. Fraser3, N. C. Stone4, S. van Velzen5, P. G. Jonker6,​7, I. Arcavi8,​9, C. Fremling10, J. R. Maund11, S. J. Smartt12, T. Krühler13, J. C. A. Miller-Jones14, P. M. Vreeswijk1, A. Gal-Yam1, P. A. Mazzali15,​16, A. De Cia17, D. A. Howell8,​18, C. Inserra12, F. Patat17, A. de Ugarte Postigo2,​19, O. Yaron1, C. Ashall15, I. Bar1, H. Campbell3,​20, T.-W. Chen13, M. Childress21, N. Elias-Rosa22, J. Harmanen23, G. Hosseinzadeh8,​18, J. Johansson1, T. Kangas23, E. Kankare12, S. Kim24, H. Kuncarayakti25,​26, J. Lyman27, M. R. Magee12, K. Maguire12, D. Malesani2, S. Mattila3,​23,​28, C. V. McCully8,​18, M. Nicholl29, S. Prentice15, C. Romero-Cañizales24,​25, S. Schulze24,​25, K. W. Smith12, J. Sollerman10, M. Sullivan21, B. E. Tucker30,​31, S. Valenti32, J. C. Wheeler33 and D. R. Young12 8 12,13 When a star passes within the tidal radius of a supermassive has a mass >10 M⊙ , a star with the same mass as the Sun black hole, it will be torn apart1. For a star with the mass of the could be disrupted outside the event horizon if the black hole 8 14 Sun (M⊙) and a non-spinning black hole with a mass <10 M⊙, were spinning rapidly . The rapid spin and high black hole the tidal radius lies outside the black hole event horizon2 and mass can explain the high luminosity of this event.
    [Show full text]
  • Distribuição De Matéria De Sistemas Estelares Esferoidais: Propriedades Dinâmicas, Intrínsecas E Observáveis
    Universidade Federal do Rio Grande - FURG Instituto de Matemática, Estatística e Física - IMEF Grupo de Astrofísica Teórica e Computacional - GATC Distribuição de Matéria de Sistemas Estelares Esferoidais: Propriedades Dinâmicas, Intrínsecas e Observáveis. Graciana Brum João Rio GrandeRS, 7 de novembro de 2013 Universidade Federal do Rio Grande - FURG Instituto de Matemática, Estatística e Física - IMEF Grupo de Astrofísica Teórica e Computacional - GATC Distribuição de Matéria de Sistemas Estelares Esferoidais: Propriedades Dinâmicas, Intrínsecas e Observáveis. Discente: Graciana Brum João Orientador: Prof. Dr. Fabricio Ferrari Trabalho de Conclusão de Curso apresentado ao curso de Física Bacharelado da Universidade Federal do Rio Grande como requisito parcial para obtenção do tíitulo de bacharel em Física. Rio Grande RS, 7 de novembro de 2013 Sumário 1 Introdução. 4 1.1 Galáxias..........................................5 1.1.1 Galáxias Espirais.................................6 1.1.2 Galáxias Espirais Barradas............................6 1.1.3 Galáxias Irregulares................................7 1.1.4 Galáxias Elípticas.................................7 1.2 Pers de Brilho......................................7 1.3 Fotometria e Massa....................................9 1.3.1 Relação Massa-Luminosidade........................... 11 1.3.2 Distribuição de Brilho supercial......................... 11 1.4 Dinâmica de Galáxias................................... 11 2 Teoria Potencial 13 2.1 Propriedades Dinâmicas, Intrínsecas e Observáveis..................
    [Show full text]
  • In-System'' Fission-Events: an Insight Into Puzzles of Exoplanets and Stars?
    universe Review “In-System” Fission-Events: An Insight into Puzzles of Exoplanets and Stars? Elizabeth P. Tito 1,* and Vadim I. Pavlov 2,* 1 Scientific Advisory Group, Pasadena, CA 91125, USA 2 Faculté des Sciences et Technologies, Université de Lille, F-59000 Lille, France * Correspondence: [email protected] (E.P.T.); [email protected] (V.I.P.) Abstract: In expansion of our recent proposal that the solar system’s evolution occurred in two stages—during the first stage, the gaseous giants formed (via disk instability), and, during the second stage (caused by an encounter with a particular stellar-object leading to “in-system” fission- driven nucleogenesis), the terrestrial planets formed (via accretion)—we emphasize here that the mechanism of formation of such stellar-objects is generally universal and therefore encounters of such objects with stellar-systems may have occurred elsewhere across galaxies. If so, their aftereffects may perhaps be observed as puzzling features in the spectra of individual stars (such as idiosyncratic chemical enrichments) and/or in the structures of exoplanetary systems (such as unusually high planet densities or short orbital periods). This paper reviews and reinterprets astronomical data within the “fission-events framework”. Classification of stellar systems as “pristine” or “impacted” is offered. Keywords: exoplanets; stellar chemical compositions; nuclear fission; origin and evolution Citation: Tito, E.P.; Pavlov, V.I. “In-System” Fission-Events: An 1. Introduction Insight into Puzzles of Exoplanets As facilities and techniques for astronomical observations and analyses continue to and Stars?. Universe 2021, 7, 118. expand and gain in resolution power, their results provide increasingly detailed information https://doi.org/10.3390/universe about stellar systems, in particular, about the chemical compositions of stellar atmospheres 7050118 and structures of exoplanets.
    [Show full text]
  • Experimental Evidence of Black Holes Andreas Müller
    Experimental Evidence of Black Holes Andreas Müller∗ Max–Planck–Institut für extraterrestrische Physik, p.o. box 1312, D–85741 Garching, Germany E-mail: [email protected] Classical black holes are solutions of the field equations of General Relativity. Many astronomi- cal observations suggest that black holes really exist in nature. However, an unambiguous proof for their existence is still lacking. Neither event horizon nor intrinsic curvature singularity have been observed by means of astronomical techniques. This paper introduces to particular features of black holes. Then, we give a synopsis on current astronomical techniques to detect black holes. Further methods are outlined that will become important in the near future. For the first time, the zoo of black hole detection techniques is completely presented and classified into kinematical, spectro–relativistic, accretive, eruptive, ob- scurative, aberrative, temporal, and gravitational–wave induced verification methods. Principal and technical obstacles avoid undoubtfully proving black hole existence. We critically discuss alternatives to the black hole. However, classical rotating Kerr black holes are still the best theo- retical model to explain astronomical observations. arXiv:astro-ph/0701228v1 9 Jan 2007 School on Particle Physics, Gravity and Cosmology 21 August - 2 September 2006 Dubrovnik, Croatia ∗Speaker. c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. http://pos.sissa.it/ Experimental Evidence of Black Holes Andreas Müller 1. Introduction Black holes (BHs) are the most compact objects known in the Universe. They are the most efficient gravitational lens, a lens that captures even light. Albert Einstein’s General Relativity (GR) is a powerful theory to describe BHs mathematically.
    [Show full text]
  • Tidal Disruption Events in Active Galactic Nuclei
    The Astrophysical Journal, 881:113 (14pp), 2019 August 20 https://doi.org/10.3847/1538-4357/ab2b40 © 2019. The American Astronomical Society. All rights reserved. Tidal Disruption Events in Active Galactic Nuclei Chi-Ho Chan1,2 , Tsvi Piran1 , Julian H. Krolik3 , and Dekel Saban1 1 Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem 91904, Israel 2 School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel 3 Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA Received 2019 April 27; revised 2019 June 18; accepted 2019 June 18; published 2019 August 20 Abstract A fraction of tidal disruption events (TDEs) occur in active galactic nuclei (AGNs) whose black holes possess accretion disks; these TDEs can be confused with common AGN flares. The disruption itself is unaffected by the disk, but the evolution of the bound debris stream is modified by its collision with the disk when it returns to pericenter. The outcome of the collision is largely determined by the ratio of the stream mass current to the azimuthal mass current of the disk rotating underneath the stream footprint, which in turns depends on the mass and luminosity of the AGN. To characterize TDEs in AGNs, we simulated a suite of stream–disk collisions with various mass current ratios. The collision excites shocks in the disk, leading to inflow and energy dissipation orders of magnitude above Eddington; however, much of the radiation is trapped in the inflow and advected into the black hole, so the actual bolometric luminosity may be closer to Eddington. The emergent spectrum may not be thermal, TDE-like, or AGN-like.
    [Show full text]
  • Revealing Hidden Substructures in the $ M {BH} $-$\Sigma $ Diagram
    Draft version November 14, 2019 A Typeset using L TEX twocolumn style in AASTeX63 Revealing Hidden Substructures in the MBH –σ Diagram, and Refining the Bend in the L–σ Relation Nandini Sahu,1,2 Alister W. Graham2 And Benjamin L. Davis2 — 1OzGrav-Swinburne, Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, VIC 3122, Australia 2Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, VIC 3122, Australia (Accepted 2019 October 22, by The Astrophysical Journal) ABSTRACT Using 145 early- and late-type galaxies (ETGs and LTGs) with directly-measured super-massive black hole masses, MBH , we build upon our previous discoveries that: (i) LTGs, most of which have been 2.16±0.32 alleged to contain a pseudobulge, follow the relation MBH ∝ M∗,sph ; and (ii) the ETG relation 1.27±0.07 1.9±0.2 MBH ∝ M∗,sph is an artifact of ETGs with/without disks following parallel MBH ∝ M∗,sph relations which are offset by an order of magnitude in the MBH -direction. Here, we searched for substructure in the MBH –(central velocity dispersion, σ) diagram using our recently published, multi- component, galaxy decompositions; investigating divisions based on the presence of a depleted stellar core (major dry-merger), a disk (minor wet/dry-merger, gas accretion), or a bar (evolved unstable 5.75±0.34 disk). The S´ersic and core-S´ersic galaxies define two distinct relations: MBH ∝ σ and MBH ∝ 8.64±1.10 σ , with ∆rms|BH = 0.55 and 0.46 dex, respectively. We also report on the consistency with the slopes and bends in the galaxy luminosity (L)–σ relation due to S´ersic and core-S´ersic ETGs, and LTGs which all have S´ersic light-profiles.
    [Show full text]
  • Probing Quiescent Massive Black Holes: Insights from Tidal Disruption Events
    Probing Quiescent Massive Black Holes: Insights from Tidal Disruption Events A Whitepaper Submitted to the Decadal Survey Committee Authors Suvi Gezari (Johns Hopkins, Hubble Fellow), Linda Strubbe, Joshua S. Bloom (UC Berkeley), J. E. Grindlay, Alicia Soderberg, Martin Elvis (Harvard/CfA), Paolo Coppi (Yale), Andrew Lawrence (Edinburgh), Zeljko Ivezic (University of Washington), David Merritt (RIT), Stefanie Komossa (MPG), Jules Halpern (Columbia), and Michael Eracleous (Pennsylvania State) Science Frontier Panels: Galaxies Across Cosmic Time (GCT) Projects/Programs Emphasized: 1. The Energetic X-ray Imaging Survey Telescope (EXIST); http://exist.gsfc.nasa.gov 2. The Wide-Field X-ray Telescope (WFXT); http://wfxt.pha.jhu.edu 3. Panoramic Survey Telescope & Rapid Response System (Pan-STARRS); http://pan-starrs.ifa.hawaii.edu/public/ 4. The Large Synoptic Survey Telescope (LSST); http://lsst.org 5. The Synoptic All-Sky Infrared Survey (SASIR); http://sasir.org Key Questions: 1. What is the assembly history of massive black holes in the uni- verse? 2. Is there a population of intermediate mass black holes that are the primordial seeds of supermassive black holes? 3. How can we increase our understanding of the physics of accre- tion onto black holes? 4. Can we localize sources of gravitational waves from the de- tection of tidal disruption events around massive black holes and recoiling binary black hole mergers? 1 Introduction Dynamical studies of nearby galaxies suggest that most if not all galaxies with a bulge component host a central supermassive black hole (SMBH), and that the bulge and BH masses are tightly correlated [1, 2, 3, 4, 5, 6]. This is referred to as the MBH−σ∗ relation, where the velocity dispersion (σ∗) of bulge stars is a proxy of the bulge mass.
    [Show full text]
  • VERGINE (Virgo) Aspetto, Posizione, Composizione
    VERGINE (virgo) Aspetto, posizione, composizione. Questa nota costellazione è la seconda più grande. Al suo interno gli antichi di Roma identificavano Astrea, la divinità della giustizia, a cui veniva associata la vicina costellazione della bilancia. La costellazione zodiacale viene attraversata dal Sole durante il 23 settembre. Al suo interno troviamo un interessante ammasso di galassie, questi si estendono fino ala Coma Berenices. Questo ammasso dista circa 65 milioni di a.l. e ospita fino a 3000 galassie. alfa Virginis (Spica), mag. 1.0, è una stella bianco-azzurra distante 260 a.l. È una binaria a eclissi che varia di circo 1/10 di magnitudine con un periodo di 4 giorni. beta Vir, mag. 3.6, una stella gialla distante 33 a.l. gamma Vir (Porrima), distante 36 a.l., è una celebre stella doppia. Nel suo insieme appare come una stella di mag. 2.8, ma con un piccolo telescopio sono visibili le due componenti bianco-gialle, entrambe di mag. 3.6, che orbitano l’una intorno all’altra con un periodo di 172 anni. Attualmente si stanno avvicinando; intorno al 2000 per separarle ci vorrà un telescopio da 75 mm; intorno al 2008 saranno troppo vicine per poter essere separate con un telescopio per dilettanti. delta Vir, mag. 3.4, è una gigante rossa distante 180 a.l. epsilon Vir (Vindemiatrix), mag. 2.8, è una gigante gialla distante 100 a.l. theta Vir, distante 140 a.l., è una stella doppia, visibile con un piccolo telescopio, con componenti bianco-azzurre di mag. 4.4 e 8.6.
    [Show full text]
  • Download This Article in PDF Format
    A&A 439, 487–496 (2005) Astronomy DOI: 10.1051/0004-6361:20042529 & c ESO 2005 Astrophysics Are radio galaxies and quiescent galaxies different? Results from the analysis of HST brightness profiles, H. R. de Ruiter1,2,P.Parma2, A. Capetti3,R.Fanti4,2, R. Morganti5, and L. Santantonio6 1 INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy 2 INAF – Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy 3 INAF – Osservatorio Astronomico di Torino, Strada Osservatorio 25, 10025 Pino Torinese, Italy 4 Istituto di Fisica, Università degli Studi di Bologna, via Irnerio 46, 40126 Bologna, Italy 5 Netherlands Foundation for Research in Astronomy, Postbus 2, 7990 AA, Dwingeloo, The Netherlands 6 Università degli Studi di Torino, via Giuria 1, 10125 Torino, Italy Received 14 December 2004 / Accepted 12 April 2005 Abstract. We present a study of the optical brightness profiles of early type galaxies, using a number of samples of radio galax- ies and optically selected elliptical galaxies. For the radio galaxy samples – B2 of Fanaroff-Riley type I and 3C of Fanaroff-Riley type II – we determined a number of parameters that describe a “Nuker-law” profile, which were compared with those already known for the optically selected objects. We find that radio active galaxies are always of the “core” type (i.e. an inner Nuker law slope γ<0.3). However, there are core-type galaxies which harbor no significant radio source and which are indistinguishable from the radio active galaxies. We do not find any radio detected galaxy with a power law profile (γ>0.5).
    [Show full text]
  • 7.5 X 11.5.Threelines.P65
    Cambridge University Press 978-0-521-19267-5 - Observing and Cataloguing Nebulae and Star Clusters: From Herschel to Dreyer’s New General Catalogue Wolfgang Steinicke Index More information Name index The dates of birth and death, if available, for all 545 people (astronomers, telescope makers etc.) listed here are given. The data are mainly taken from the standard work Biographischer Index der Astronomie (Dick, Brüggenthies 2005). Some information has been added by the author (this especially concerns living twentieth-century astronomers). Members of the families of Dreyer, Lord Rosse and other astronomers (as mentioned in the text) are not listed. For obituaries see the references; compare also the compilations presented by Newcomb–Engelmann (Kempf 1911), Mädler (1873), Bode (1813) and Rudolf Wolf (1890). Markings: bold = portrait; underline = short biography. Abbe, Cleveland (1838–1916), 222–23, As-Sufi, Abd-al-Rahman (903–986), 164, 183, 229, 256, 271, 295, 338–42, 466 15–16, 167, 441–42, 446, 449–50, 455, 344, 346, 348, 360, 364, 367, 369, 393, Abell, George Ogden (1927–1983), 47, 475, 516 395, 395, 396–404, 406, 410, 415, 248 Austin, Edward P. (1843–1906), 6, 82, 423–24, 436, 441, 446, 448, 450, 455, Abbott, Francis Preserved (1799–1883), 335, 337, 446, 450 458–59, 461–63, 470, 477, 481, 483, 517–19 Auwers, Georg Friedrich Julius Arthur v. 505–11, 513–14, 517, 520, 526, 533, Abney, William (1843–1920), 360 (1838–1915), 7, 10, 12, 14–15, 26–27, 540–42, 548–61 Adams, John Couch (1819–1892), 122, 47, 50–51, 61, 65, 68–69, 88, 92–93,
    [Show full text]
  • Making a Sky Atlas
    Appendix A Making a Sky Atlas Although a number of very advanced sky atlases are now available in print, none is likely to be ideal for any given task. Published atlases will probably have too few or too many guide stars, too few or too many deep-sky objects plotted in them, wrong- size charts, etc. I found that with MegaStar I could design and make, specifically for my survey, a “just right” personalized atlas. My atlas consists of 108 charts, each about twenty square degrees in size, with guide stars down to magnitude 8.9. I used only the northernmost 78 charts, since I observed the sky only down to –35°. On the charts I plotted only the objects I wanted to observe. In addition I made enlargements of small, overcrowded areas (“quad charts”) as well as separate large-scale charts for the Virgo Galaxy Cluster, the latter with guide stars down to magnitude 11.4. I put the charts in plastic sheet protectors in a three-ring binder, taking them out and plac- ing them on my telescope mount’s clipboard as needed. To find an object I would use the 35 mm finder (except in the Virgo Cluster, where I used the 60 mm as the finder) to point the ensemble of telescopes at the indicated spot among the guide stars. If the object was not seen in the 35 mm, as it usually was not, I would then look in the larger telescopes. If the object was not immediately visible even in the primary telescope – a not uncommon occur- rence due to inexact initial pointing – I would then scan around for it.
    [Show full text]