* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download The Main Features of the X
Fine-tuned Universe wikipedia , lookup
Non-standard cosmology wikipedia , lookup
Timeline of astronomy wikipedia , lookup
History of supernova observation wikipedia , lookup
Gamma-ray burst wikipedia , lookup
Hubble Deep Field wikipedia , lookup
Physical cosmology wikipedia , lookup
High-velocity cloud wikipedia , lookup
H II region wikipedia , lookup
Advanced Composition Explorer wikipedia , lookup
Structure formation wikipedia , lookup
History of gamma-ray burst research wikipedia , lookup
Future of an expanding universe wikipedia , lookup
Star formation wikipedia , lookup
Astronomical spectroscopy wikipedia , lookup
X-ray astronomy wikipedia , lookup
History of X-ray astronomy wikipedia , lookup
The X-ray Universe Sarah Bank Presented July 22, 2004 Overview X-ray Production Mechanisms The Sun (in brief) The Main Features Supernovae (SNe), Supernova Remnants (SNRs), and Superbubbles Active Galactic Nulcei X-ray Sources The three main sources of astrophysical x-rays Thermal - bremsstrahlung and line emission Synchrotron radiation from relativistic electrons Inverse Compton Scattering Thermal Bremsstrahlung Thermal bremsstrahlung or free-free emission occurs when an e- is accelerated due to the strong electrical attraction of a positive ion in a plasma. Temperatures above 105 K are necessary. http://imagine.gsfc.nasa.gov/docs/science/how_l2/xray_generation.html Line Emission Heavy elements, not fully ionized, can have inner electrons collisionally excited to higher energy levels. Upon decay they emit an X-ray. http://csep10.phys.utk.edu/astr162/lect/light/bohr.html Synchrotron/Relativistic e Charged particles in a magnetic field are accelerated around field lines releasing radiation. If the particle is relativistic the radiation undergoes ‘beaming’ and the maximum Ephoton is then proportional to the field strength and inversely proportional to the particle’s momentum. http://imagine.gsfc.nasa.gov/docs/science/how_l2/xray_generation.html Inverse Compton Scattering A relativistic ecolliding with a low energy photon can impart energy resulting in an Xray. Seen in SNe and AGN. http://venables.asu.edu/quant/proj/compton.html The Sun Turbulence in the convection zone amplifies magnetic fields to create loops conducting electric currents, thus heating the solar corona to X-ray temperatures. Solar Photosphere ≈ 6000K Solar Corona ≈ 106 K Charles & Seward, Exploring the X-ray Universe. Cambridge U. Press, Great Britain©1995 Solar Flare/Loop The Main Features The 1/4 keV (McCammon,D. et al. (Sept. 2002) ApJ. v.576, no.1,pt.1 p.290-300) The 3/4 keV (McCammon,D. et al. (Sept. 2002) ApJ. v.576, no.1,pt.1 p.290-300) The Features The Lockman Hole: a region where absorbing material, HI and dust, are sparse Draco Cloud: enhanced soft X-ray region due to a molecular cloud falling into the plane of the Galaxy Cygnus Superbubble/Loop: nearby superbubble from the explosion of many Sne, 14 times the size (at 400 pc in diameter) of the Cynus Loop, a 20,000 year old SNR emitting thermal bremsstrahlung as soft x-rays. North Polar Spur (NPS)/Loop 1: The NPS is a bright region of the Loop 1 superbubble, a wellknown radio feature. More Features The Virgo Cluster: the cluster of galaxies at the center of the local supercluster Galactic Bulge: not well understood, but definitely consists of some component beyond the NPS LMC: a nearby dwarf irregular galaxy Vela/Puppis SNRs: Vela SNR ~ 1,500 ly away, 11,000 y old and 230 ly in diameter; whereas Puppis, superimposed on the Vela remnant is ~4 times farther away, but the brightest X-ray source between 0.5 and 1 keV Vela and Puppis http://heasarc.gsfc.nasa.gov/docs/rosat/gallery/snr_velapup.html More Features Eridanus Enhancement: from the Orion superbubble, ~1200 ly across, being energized by stars in the Orion OB1 association Monogem Ring: a SNR in a low density region of the Galaxy, thus evolved into a low surface-brightness remnant The Crab: a SNR recorded in 1054 and now observed to contain a 33 ms pulsar Supernova Remnants Type 1: mass transfer onto a white dwarf from a binary companion resulting in accretion beyond the Chandrasekhar limit. Type 2: core collapse of a massive star (~10 Msolar) that has formed an iron core. Most profuse X-ray emission during phases 1 & 2. Thermal x-rays via line emission or bremsstrahlung. Charles & Seward, Exploring the X-ray Universe. Cambridge U. Press, Great Britain©1995 Superbubbles SN - Star Formation - SNe - Superbubble Not created by a single “super-supernova,” but by many such events over time. Dynamite vs. Digger analogy Charles & Seward, Exploring the X-ray Universe. Cambridge U. Press, Great Britain©1995 Active Galactic Nuclei http://www.seds.org/hst/ngc4261.html The super massive Black Holes (BHs) at the centers of galaxies, actively accrete gas from the ISM, cannibalized galaxies, nearby stars. An accretion disk forms, heating the material, as well as jets of relativistic matter at the poles of the MBH.