DOCSLIB.ORG

Astrophysics on the Velocity of the Vela Pulsar

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Astrophysics on the Velocity of the Vela Pulsar A&A 369, 174–177 (2001) Astronomy DOI: 10.1051/0004-6361:20010104 & c ESO 2001 Astrophysics On the velocity of the Vela pulsar V. Gvaramadze1,2,3,? 1 Abastumani Astrophysical Observatory, Georgian Academy of Sciences, A. Kazbegi ave. 2-a, Tbilisi 380060, Georgia 2 Sternberg State Astronomical Institute, Universitetskij Prospect 13, Moscow 119899, Russia 3 Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, PO Box 586, 34100 Trieste, Italy Received 10 May 2000 / Accepted 14 December 2000 Abstract. It is shown that if the shell of the Vela supernova remnant is responsible for nearly all the scattering of the Vela pulsar, then the scintillation and proper motion velocities of the pulsar can only be reconciled with each other in the case of nonzero transverse velocity of the scattering material. A possible origin of large-scale transverse motions in the shell of the Vela supernova remnant is discussed. Key words. pulsars: individual: Vela – ISM: individual objects: Vela supernova remnant – scattering 1. Introduction Aschenbach et al. 1995; Bocchino et al. 1999; Cha et al. 1999; Cha & Sembach 2000)1. One of the arguments (pro- The Vela pulsar is one of the best studied radio pulsars posed by Ogelman¨ et al. 1989 and repeated by Oberlack and was the first one found to be associated with the su- et al. 1994; Cha et al. 1999) was based on the compari- pernova remnant (SNR) (Large et al. 1968). In spite of its son of the Vela pulsar transverse velocity (inferred from relative proximity to the Earth, there is still no consensus the new estimate of the pulsar proper motion by Ogelman¨ on the value of its (transverse) velocity, which is connected et al. 1989) with the scintillation velocity (reported by with the yet unsolved problem of the distance to the Vela Cordes 1986). It is known that proper motion velocities of pulsar/Vela SNR. The first attempt to estimate the pulsar pulsars show significant correlation with pulsar velocities velocity was made by Bignami & Caraveo (1988), whose inferred from interstellar scintillation measurements (e.g. optical measurments gave an upper limit on the pulsar Lyne & Smith 1982; Gupta 1995). Therefore, assuming proper motion (<60 mas yr−1). However, even the max- that the scintillation velocity V isa“true”valueofthe imum admissible value of the pulsar proper motion was iss pulsar transverse velocity, Ogelman¨ et al. (1989) suggested found to be too low to explain the pulsar offset from the −1 that Viss =53 5kms (Cordes 1986) could be recon- apparent geometrical centre of the Vela SNR, which ques- − ciled with the proper motion µ ' 38 8masyr 1 if the tions the pulsar/SNR association. Later, it was recognized distance to the Vela pulsar (and the Vela SNR) is about (e.g. Seward 1990; Aschenbach et al. 1995) that the real 290 80 pc. The distance reduction might be even more extent of the Vela SNR is much larger than was accepted dramatic if one takes the recent high-precision estimate of in early studies, so now there can be no doubt that the − the Vela pulsar proper motion (52 3masyr 1) obtained Vela pulsar and the Vela SNR are the remnants of the by De Luca et al. (2000; see also Nasuti et al. 1997). same supernova explosion. However, this association has The situation with the distance to the Vela SNR was caused some problems in estimating the pulsar velocity. “improved” after Gupta et al. (1994) showed that the Wallerstein & Silk (1971) questioned for the first scintillation velocity calculation formula used by Cordes time the “canonical” value of the distance to the (1986) underestimates V by factor of 3. The revised Vela SNR of 500 pc given by Milne (1968; see also iss value of the scintillation velocity of the Vela pulsar of Taylor et al. 1993) and suggested that this distance − 152 km s 1 better corresponds to the proper motion veloc- should be reduced to some smaller value (' 250 pc). − ity of 123 km s 1 (for the distance to the pulsar of 500 pc Since that time many additional arguments in support of this suggestion have been put forward (Ogelman¨ et al. 1 1989; Oberlack et al. 1994; Jenkins & Wallerstein 1995; We critically analysed these arguments (Gvaramadze 2000a,b) and came to the conclusion that ? Address for correspondence: Krasin str. 19, ap. 81, Moscow there are no weighty reasons to revise the “canonical” distance 123056, Russia; e-mail: [email protected] of 500 pc. Article published by EDP Sciences and available at http://www.aanda.org or http://dx.doi.org/10.1051/0004-6361:20010104 V. Gvaramadze,: On the velocity of the Vela pulsar 175 and µ =52masyr−1). However, the real situation is a bit more complicated. It should be noted that the calculations of Gupta (1995) were based on the assumptions that the scatter- ing material is concentrated in a thin screen and that the screen is placed midway between the observer and the pulsar. Although the first assumption is realistic, the second one is not suitable in the case of the Vela pulsar. Indeed, it is believed that the scattering irreg- ularities responsible for the enhanced scattering of the Vela pulsar (Backer 1974) are localized in a thin screen rather than uniformly distributed along our line of sight to the pulsar (Backer 1974; Lee & Jokipii 1976, see also Williamson 1974), and that the scattering screen resides close to the pulsar and could be associated with the shell of the Vela SNR (Desai et al. 1992; Taylor & Cordes 1993; Gwinn et al. 1993, see however Gwinn et al. 1997, 2000 and cf. Cordes & Rickett 1998). The asymmetrical loca- tion of the screen implies (see Sect. 2) that the actual value of the scintillation velocity should be considerably larger Fig. 1. The 843 MHz image of the central part of the Vela SNR than that given by Gupta (1995) and that the scintillation (adopted from Bock et al. 1998). Position of the Vela pulsar velocity is not equal to the proper motion velocity. is indicated by a cross. The arrow shows the direction of the In this paper, we show that if the scattering of the pulsar proper motion velocity (Bailes et al. 1989). North is up, Vela pulsar indeed occurs in the shell of the Vela SNR east at left. The horizontal bar is 1◦ long then the scintillation velocity could be reconciled with the pulsar proper motion velocity only if the scatterer has a observer’s reference frame, the scintillation velocity is con- nonzero transverse velocity. A possible origin of large-scale nected with the pulsar proper motion velocity transverse motions in the Vela SNR’s shell is discussed. −1 Vpm =4.74µDkpc km s , (2) −1 2. Scintillation and proper motion velocities where µ is measured in mas yr , by the following rela- tionship (cf. Gupta et al. 1994; Cordes & Rickett 1998): The scintillation velocity for an asymmetrically placed h 2 2 − thin scattering screen is (Gupta et al. 1994; Gupta 1995): Viss = x Vpm 2x(1 + x)VpmVscr,k i1/2 1/2 2 2 2 2 4 (νd,MHzDkpcx) −1 +(1 + x) Vscr,k +(1+x) Vscr,⊥ , (3) Viss =3.85 10 km s , (1) fGHztd where Vscr,k and Vscr,⊥ are the components of the trans- where νd,MHz and td are the scintillation bandwidth and verse velocity of the screen, correspondingly, parallel and the time-scale measured respectively in MHz and sec- perpendicular to the vector of the pulsar proper motion onds, Dkpc is the distance from observer to pulsar in kpc, velocity. In (3) we neglected small contributions from x = Do/Dp, Do and Dp are the distances from observer to the differential Galactic rotation and the Earth’s orbital screen and from screen to pulsar, fGHz is the frequency of motion around the Sun. If Vscr = 0, one has Vpm = −1 observation in units of GHz. For νd,MHz =0.001, td =5.6, Viss/x ' 38 km s (Dkpc =0.5), i.e. about 3 times smaller fGHz = 1 (Cordes 1986), Dkpc =0.5, and assuming that than that from Eq. (2). These velocity estimates could −1 x = 1, one finds for the Vela pulsar that Viss = 152 km s be reconciled only if the distance to the Vela pulsar is −1 (Gupta 1995). As we mentioned in Sect. 1, Desai et al. Dkpc =0.05(x/15.7) , which is too small to be likely. (1992) showed that the scattering screen is close to the The pulsar, however, could be placed at its “canonical” pulsar. Assuming that D = 500 pc, they found that distance if Vscr =0.6 Do/D ' 0.81, and that this value could be increased up to Figure 1 shows the 843 MHz image (Bock et al. 1998) 0.96 if 5% of the scattering of the Vela pulsar is due to the of the central part of the Vela SNR, known as the ra- effect of the Gum Nebula. The latter value of Do/D is ex- dio source Vela X (Milne 1968). A considerable fraction pected if the scattering material is mainly concentrated in of the radio emission from Vela X originates in filamen- the shell of the Vela SNR of angular diameter of 5◦ (the fig- tary structures, one of which crosses the Vela pulsar po- ure accepted in early studies of the Vela SNR). Assuming sition. This filament (or rather its part to the south of that the Vela SNR’s shell is indeed the main scatterer of the pulsar) is known as a radio counterpart of the Vela the Vela pulsar and using the currently adopted angular X-ray “jet” discovered by Markwardt & Ogelman¨ (1995).
Load more

Recommended publications
  • Neutron Stars
    Chandra X-Ray Observatory X-Ray Astronomy Field Guide Neutron Stars Ordinary matter, or the stuff we and everything around us is made of, consists largely of empty space. Even a rock is mostly empty space. This is because matter is made of atoms. An atom is a cloud of electrons orbiting around a nucleus composed of protons and neutrons. The nucleus contains more than 99.9 percent of the mass of an atom, yet it has a diameter of only 1/100,000 that of the electron cloud. The electrons themselves take up little space, but the pattern of their orbit defines the size of the atom, which is therefore 99.9999999999999% Chandra Image of Vela Pulsar open space! (NASA/PSU/G.Pavlov et al. What we perceive as painfully solid when we bump against a rock is really a hurly-burly of electrons moving through empty space so fast that we can't see—or feel—the emptiness. What would matter look like if it weren't empty, if we could crush the electron cloud down to the size of the nucleus? Suppose we could generate a force strong enough to crush all the emptiness out of a rock roughly the size of a football stadium. The rock would be squeezed down to the size of a grain of sand and would still weigh 4 million tons! Such extreme forces occur in nature when the central part of a massive star collapses to form a neutron star. The atoms are crushed completely, and the electrons are jammed inside the protons to form a star composed almost entirely of neutrons.
    [Show full text]
  • II Publications, Presentations
    II Publications, Presentations 1. Refereed Publications Izumi, K., Kotake, K., Nakamura, K., Nishida, E., Obuchi, Y., Ohishi, N., Okada, N., Suzuki, R., Takahashi, R., Torii, Abadie, J., et al. including Hayama, K., Kawamura, S.: 2010, Y., Ueda, A., Yamazaki, T.: 2010, DECIGO and DECIGO Search for Gravitational-wave Inspiral Signals Associated with pathfinder, Class. Quantum Grav., 27, 084010. Short Gamma-ray Bursts During LIGO's Fifth and Virgo's First Aoki, K.: 2010, Broad Balmer-Line Absorption in SDSS Science Run, ApJ, 715, 1453-1461. J172341.10+555340.5, PASJ, 62, 1333. Abadie, J., et al. including Hayama, K., Kawamura, S.: 2010, All- Aoki, K., Oyabu, S., Dunn, J. P., Arav, N., Edmonds, D., Korista sky search for gravitational-wave bursts in the first joint LIGO- K. T., Matsuhara, H., Toba, Y.: 2011, Outflow in Overlooked GEO-Virgo run, Phys. Rev. D, 81, 102001. Luminous Quasar: Subaru Observations of AKARI J1757+5907, Abadie, J., et al. including Hayama, K., Kawamura, S.: 2010, PASJ, 63, S457. Search for gravitational waves from compact binary coalescence Aoki, W., Beers, T. C., Honda, S., Carollo, D.: 2010, Extreme in LIGO and Virgo data from S5 and VSR1, Phys. Rev. D, 82, Enhancements of r-process Elements in the Cool Metal-poor 102001. Main-sequence Star SDSS J2357-0052, ApJ, 723, L201-L206. Abadie, J., et al. including Hayama, K., Kawamura, S.: 2010, Arai, A., et al. including Yamashita, T., Okita, K., Yanagisawa, TOPICAL REVIEW: Predictions for the rates of compact K.: 2010, Optical and Near-Infrared Photometry of Nova V2362 binary coalescences observable by ground-based gravitational- Cyg: Rebrightening Event and Dust Formation, PASJ, 62, wave detectors, Class.
    [Show full text]
  • Optical Observations of Pulsars: the ESO Contribution R.P
    Figure 3: The normalised spectral energy distribution of 3 galaxies. From left to right we show a regular Ly-break galaxy (Fig. 2c), the “spiral” galaxy (Fig. 2d), and the very red galaxy from Figure 2e. The red continuum feature of the last two galaxies can be due to the Balmer/4000 Angstrom break or due to dust. Only one of these would be selected by the regular Ly-break selection technique, as the others are too faint in the optical (rest-frame UV). Acknowledgement References van Dokkum, P. G., Franx, M., Fabricant, D., Kelson, D., Illingworth, G. D., 2000, sub- Dickinson, M., et al, 1999, preprint, as- It is a pleasure to thank the staff at mitted to ApJ. troph/9908083. Steidel, C. C., Giavalisco, M., Pettini, M., ESO who contributed to the construc- Gioia, I., and Luppino, G. A., 1994, ApJS, tion and operation of the VLT and Dickinson, M., Adelberger, K. L., 1996, 94, 583. ApJL, 462, L17. ISAAC. This project has only been van Dokkum, P. G., Franx, M., Fabricant, D., Williams, R. E., et al, 2000, in prepara- possible because of their enormous ef- Kelson, D., Illingworth, G. D., 1999, ApJL, tion. forts. 520, L95. Optical Observations of Pulsars: the ESO Contribution R.P. MIGNANI1, P.A. CARAVEO 2 and G.F. BIGNAMI3 1ST-ECF, [email protected]; 2IFC-CNR, [email protected]; 3ASI [email protected] Introduction matic gamma-rays source Geminga, and ESO telescopes gave to the not yet recognised as an X/gamma-ray European astronomers the chance to Our knowledge of the optical emis- pulsar, was proposed.
    [Show full text]
  • 16Th HEAD Meeting Session Table of Contents
    16th HEAD Meeting Sun Valley, Idaho – August, 2017 Meeting Abstracts Session Table of Contents 99 – Public Talk - Revealing the Hidden, High Energy Sun, 204 – Mid-Career Prize Talk - X-ray Winds from Black Rachel Osten Holes, Jon Miller 100 – Solar/Stellar Compact I 205 – ISM & Galaxies 101 – AGN in Dwarf Galaxies 206 – First Results from NICER: X-ray Astrophysics from 102 – High-Energy and Multiwavelength Polarimetry: the International Space Station Current Status and New Frontiers 300 – Black Holes Across the Mass Spectrum 103 – Missions & Instruments Poster Session 301 – The Future of Spectral-Timing of Compact Objects 104 – First Results from NICER: X-ray Astrophysics from 302 – Synergies with the Millihertz Gravitational Wave the International Space Station Poster Session Universe 105 – Galaxy Clusters and Cosmology Poster Session 303 – Dissertation Prize Talk - Stellar Death by Black 106 – AGN Poster Session Hole: How Tidal Disruption Events Unveil the High 107 – ISM & Galaxies Poster Session Energy Universe, Eric Coughlin 108 – Stellar Compact Poster Session 304 – Missions & Instruments 109 – Black Holes, Neutron Stars and ULX Sources Poster 305 – SNR/GRB/Gravitational Waves Session 306 – Cosmic Ray Feedback: From Supernova Remnants 110 – Supernovae and Particle Acceleration Poster Session to Galaxy Clusters 111 – Electromagnetic & Gravitational Transients Poster 307 – Diagnosing Astrophysics of Collisional Plasmas - A Session Joint HEAD/LAD Session 112 – Physics of Hot Plasmas Poster Session 400 – Solar/Stellar Compact II 113
    [Show full text]
  • The SAI Catalog of Supernovae and Radial Distributions of Supernovae
    Astronomy Letters, Vol. 30, No. 11, 2004, pp. 729–736. Translated from Pis’ma v Astronomicheski˘ı Zhurnal, Vol. 30, No. 11, 2004, pp. 803–811. Original Russian Text Copyright c 2004 by Tsvetkov, Pavlyuk, Bartunov. TheSAICatalogofSupernovaeandRadialDistributions of Supernovae of Various Types in Galaxies D. Yu. Tsvetkov*, N.N.Pavlyuk**,andO.S.Bartunov*** Sternberg Astronomical Institute, Universitetski ˘ı pr. 13, Moscow, 119992 Russia Received May 18, 2004 Abstract—We describe the Sternberg Astronomical Institute (SAI)catalog of supernovae. We show that the radial distributions of type-Ia, type-Ibc, and type-II supernovae differ in the central parts of spiral galaxies and are similar in their outer regions, while the radial distribution of type-Ia supernovae in elliptical galaxies differs from that in spiral and lenticular galaxies. We give a list of the supernovae that are farthest from the galactic centers, estimate their relative explosion rate, and discuss their possible origins. c 2004MAIK “Nauka/Interperiodica”. Key words: astronomical catalogs, supernovae, observations, radial distributions of supernovae. INTRODUCTION be found on the Internet. The most complete data are contained in the list of SNe maintained by the Cen- In recent years, interest in studying supernovae (SNe)has increased signi ficantly. Among other rea- tral Bureau of Astronomical Telegrams (http://cfa- sons, this is because SNe Ia are used as “standard www.harvard.edu/cfa/ps/lists/Supernovae.html)and candles” for constructing distance scales and for cos- the electronic version of the Asiago catalog mological studies, and because SNe Ibc may be re- (http://web.pd.astro.it/supern). lated to gamma ray bursts.
    [Show full text]
  • FY13 High-Level Deliverables
    National Optical Astronomy Observatory Fiscal Year Annual Report for FY 2013 (1 October 2012 – 30 September 2013) Submitted to the National Science Foundation Pursuant to Cooperative Support Agreement No. AST-0950945 13 December 2013 Revised 18 September 2014 Contents NOAO MISSION PROFILE .................................................................................................... 1 1 EXECUTIVE SUMMARY ................................................................................................ 2 2 NOAO ACCOMPLISHMENTS ....................................................................................... 4 2.1 Achievements ..................................................................................................... 4 2.2 Status of Vision and Goals ................................................................................. 5 2.2.1 Status of FY13 High-Level Deliverables ............................................ 5 2.2.2 FY13 Planned vs. Actual Spending and Revenues .............................. 8 2.3 Challenges and Their Impacts ............................................................................ 9 3 SCIENTIFIC ACTIVITIES AND FINDINGS .............................................................. 11 3.1 Cerro Tololo Inter-American Observatory ....................................................... 11 3.2 Kitt Peak National Observatory ....................................................................... 14 3.3 Gemini Observatory ........................................................................................
    [Show full text]
  • The Radio Spectral Index of the Vela Supernova Remnant
    A&A 372, 636–643 (2001) Astronomy DOI: 10.1051/0004-6361:20010509 & c ESO 2001 Astrophysics The radio spectral index of the Vela supernova remnant H. Alvarez1, J. Aparici1,J.May1,andP.Reich2 1 Departamento de Astronom´ıa, Universidad de Chile, Casilla 36-D, Santiago, Chile 2 Max-Planck-Institut f¨ur Radioastronomie, Auf dem H¨ugel 69, 53121 Bonn, Germany Received 25 October 2000 / Accepted 9 March 2001 Abstract. We have calculated the integrated flux densities of the different components of the Vela SNR between 30 and 8400 MHz. The calculations were done using the original brightness temperature maps found in the literature, a uniform criterion to select the background temperature, and a unique method to compute the integrated flux density. We have succeeded in obtaining separately, and for the first time, the spectrum of Vela Y and Vela Z. The index of the flux density spectrum of Vela X,VelaY and Vela Z are −0.39, −0.70 and −0.81, respectively. We also present a map of brightness temperature spectral index over the region, between 408 and 2417 MHz. This shows a circular structure in which the spectrum steepens from the centre (Vela X) towards the periphery (Vela Y and Vela Z). X-ray observations show also a circular structure. We compare our spectral indices with those previously published. Key words. ISM: supernova remnants – ISM: Vela X – radio continuum: ISM 1. Introduction between the indices of X and YZ(α ∼−0.35) so that the whole Vela SNR belongs to the shell type. Weiler et al., Radio continuum maps of the Vela SNR area show a com- on the other hand, sustain that YZ has a spectrum con- plex structure.
    [Show full text]
  • Astronomy Magazine 2011 Index Subject Index
    Astronomy Magazine 2011 Index Subject Index A AAVSO (American Association of Variable Star Observers), 6:18, 44–47, 7:58, 10:11 Abell 35 (Sharpless 2-313) (planetary nebula), 10:70 Abell 85 (supernova remnant), 8:70 Abell 1656 (Coma galaxy cluster), 11:56 Abell 1689 (galaxy cluster), 3:23 Abell 2218 (galaxy cluster), 11:68 Abell 2744 (Pandora's Cluster) (galaxy cluster), 10:20 Abell catalog planetary nebulae, 6:50–53 Acheron Fossae (feature on Mars), 11:36 Adirondack Astronomy Retreat, 5:16 Adobe Photoshop software, 6:64 AKATSUKI orbiter, 4:19 AL (Astronomical League), 7:17, 8:50–51 albedo, 8:12 Alexhelios (moon of 216 Kleopatra), 6:18 Altair (star), 9:15 amateur astronomy change in construction of portable telescopes, 1:70–73 discovery of asteroids, 12:56–60 ten tips for, 1:68–69 American Association of Variable Star Observers (AAVSO), 6:18, 44–47, 7:58, 10:11 American Astronomical Society decadal survey recommendations, 7:16 Lancelot M. Berkeley-New York Community Trust Prize for Meritorious Work in Astronomy, 3:19 Andromeda Galaxy (M31) image of, 11:26 stellar disks, 6:19 Antarctica, astronomical research in, 10:44–48 Antennae galaxies (NGC 4038 and NGC 4039), 11:32, 56 antimatter, 8:24–29 Antu Telescope, 11:37 APM 08279+5255 (quasar), 11:18 arcminutes, 10:51 arcseconds, 10:51 Arp 147 (galaxy pair), 6:19 Arp 188 (Tadpole Galaxy), 11:30 Arp 273 (galaxy pair), 11:65 Arp 299 (NGC 3690) (galaxy pair), 10:55–57 ARTEMIS spacecraft, 11:17 asteroid belt, origin of, 8:55 asteroids See also names of specific asteroids amateur discovery of, 12:62–63
    [Show full text]
  • Liverpool Telescope 2: a New Robotic Facility for Rapid Transient Follow-Up
    Noname manuscript No. (will be inserted by the editor) Liverpool Telescope 2: a new robotic facility for rapid transient follow-up C.M. Copperwheat · I.A. Steele · R.M. Barnsley · S.D. Bates · D. Bersier · M.F. Bode · D. Carter · N.R. Clay · C.A. Collins · M.J. Darnley · C.J. Davis · C.M. Gutierrez · D.J. Harman · P.A. James · J.H. Knapen · S. Kobayashi · J.M. Marchant · P.A. Mazzali · C.J. Mottram · C.G. Mundell · A. Newsam · A. Oscoz · E. Palle · A. Piascik · R. Rebolo · R.J. Smith Received: date / Accepted: date Abstract The Liverpool Telescope is one of the world’s premier facilities for time domain astronomy. The time domain landscape is set to radically change in the coming decade, with synoptic all-sky surveys such as LSST providing huge numbers of transient detections on a nightly basis; transient detections across the electromagnetic spectrum from other major facilities such as SVOM, SKA and CTA; and the era of ‘multi-messenger astronomy’, wherein astro- physical events are detected via non-electromagnetic means, such as neutrino or gravitational wave emission. We describe here our plans for the Liverpool Telescope 2: a new robotic telescope designed to capitalise on this new era of time domain astronomy. LT2 will be a 4-metre class facility co-located with the Liverpool Telescope at the Observatorio del Roque de Los Muchachos on the Canary island of La Palma. The telescope will be designed for extremely C.M. Copperwheat · I.A. Steele · R.M. Barnsley · S.D. Bates · D. Bersier · M.F. Bode · D.
    [Show full text]
  • Supernova Remnants: the X-Ray Perspective
    Astron Astrophys Rev (2012) 20:49 DOI 10.1007/s00159-011-0049-1 Supernova remnants: the X-ray perspective Jacco Vink Published online: 8 December 2011 © The Author(s) 2011. This article is published with open access at Springerlink.com Abstract Supernova remnants are beautiful astronomical objects that are also of high scientific interest, because they provide insights into supernova explosion mecha- nisms, and because they are the likely sources of Galactic cosmic rays. X-ray obser- vations are an important means to study these objects. And in particular the advances made in X-ray imaging spectroscopy over the last two decades has greatly increased our knowledge about supernova remnants. It has made it possible to map the prod- ucts of fresh nucleosynthesis, and resulted in the identification of regions near shock fronts that emit X-ray synchrotron radiation. Since X-ray synchrotron radiation re- quires 10–100 TeV electrons, which lose their energies rapidly, the study of X-ray synchrotron radiation has revealed those regions where active and rapid particle ac- celeration is taking place. In this text all the relevant aspects of X-ray emission from supernova remnants are reviewed and put into the context of supernova explosion properties and the physics and evolution of supernova remnants. The first half of this review has a more tutorial style and discusses the basics of supernova remnant physics and X-ray spectroscopy of the hot plasmas they contain. This includes hydrodynamics, shock heating, thermal conduction, radiation processes, non-equilibrium ionization, He-like ion triplet lines, and cosmic ray acceleration. The second half offers a review of the advances made in field of X-ray spectroscopy of supernova remnants during the last 15 year.
    [Show full text]
  • Neutron Star
    Explosive end of a star (masses M > 8 M⊙ ) Death of massive stars M > 8 M⊙ nuclear reactions stop at Fe ⟹ contraction continues to T = 1010 K (e− degenerate gas cannot support the star for core mass Mcore > 1.4 M⊙ ) ⟹ Fe photo-disintegration (production of α particles, neutrons, protons) ⟹ energy absorbed, contraction goes faster, density grows to point when: e− + p → n + νe ⟹ e− are removed support of e− degenerate gas drops ⟹ collapse continues 12 17 3 T = 10 K, core density 3×10 kg / m ⟹ neutron degeneracy pressure ⟹ collapse suddenly stops ⟹ matter falling inward at high high speed matter bounces when core reached ⟹ shock front outwards ⟹ STAR EXPLODES (SUPERNOVA) ⟹ STAR EXPLODES (SUPERNOVA) Not clear what happens, some or all of the following processes: • Shock wave blows apart outer layer, mainly light elements • Shock wave heats gas to T = 1010 K ⟹ explosive nuclear reactions ⟹ fusion produce Fe-peak elements ⟹ outer layer blown apart • Enormous amount of neutrinos formed. Most escape without interaction, some lift off mass in outer layer External envelope falling inwards at speed up to v ~ 70,000 km/s Bounce backward when core reached → Shock front outward Star destroyed by explosion Stellar explosion = supernova (computer simulation) Video: https://www.youtube.com/watch?v=xVk48Nyd4zY Final result of core collapse: neutron star Supernova remnant: Crab Nebula Distance: 6500 light years Explosion seen in 1054 Size of the bubble: ~ 10 pc Final result of core collapse: neutron star Supernova remnant: Crab Nebula Distance: 6500 light
    [Show full text]
  • Pulsar Wind Nebulae in Evolved Supernova Remnants John M
    THE ASTROPHYSICAL JOURNAL, 563:806È815, 2001 December 20 V ( 2001. The American Astronomical Society. All rights reserved. Printed in U.S.A. PULSAR WIND NEBULAE IN EVOLVED SUPERNOVA REMNANTS JOHN M. BLONDIN Department of Physics, North Carolina State University, Raleigh, NC 27695 ROGER A. CHEVALIER Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903 AND DARGAN M. FRIERSON Department of Mathematics, Princeton University, Princeton, NJ 08544 Received 2001 July 4; accepted 2001 August 27 ABSTRACT For pulsars similar to the one in the Crab Nebula, most of the energy input to the surrounding wind nebula occurs on a timescale[103 yr; during this time, the nebula expands into freely expanding super- nova ejecta. On a timescale D104 yr, the interaction of the supernova with the surrounding medium drives a reverse shock front toward the center of the remnant, where it crushes the pulsar wind nebula (PWN). We have carried out one- and two-dimensional, two-Ñuid simulations of the crushing and reex- pansion phases of a PWN. We show that (1) these phases are subject to Rayleigh-Taylor instabilities that result in the mixing of thermal and nonthermal Ñuids, and (2) asymmetries in the surrounding inter- stellar medium give rise to asymmetries in the position of the PWN relative to the pulsar and explosion site. These e†ects are expected to be observable in the radio emission from evolved PWN because of the long lifetimes of radio-emitting electrons. The scenario can explain the chaotic and asymmetric appear- ance of the Vela X PWN relative to the Vela pulsar without recourse to a directed Ñow from the vicinity of the pulsar.
    [Show full text]