The X-ray Universe Sarah Bank Presented July 22, 2004.

The X-ray The X-ray UniverseUniverse

Sarah BankSarah Bank

Presented July 22, 2004Presented July 22, 2004

OverviewOverview

X-ray Production MechanismsX-ray Production Mechanisms The Sun (in brief)The Sun (in brief) The Main FeaturesThe Main Features Supernovae (SNe), Supernova Supernovae (SNe), Supernova

Remnants (SNRs), and SuperbubblesRemnants (SNRs), and Superbubbles Active Galactic NulceiActive Galactic Nulcei

X-ray SourcesX-ray Sources

The three main sources of The three main sources of astrophysical x-raysastrophysical x-rays

Thermal - bremsstrahlung and line Thermal - bremsstrahlung and line emissionemission

Synchrotron radiation from Synchrotron radiation from relativistic electronsrelativistic electrons

Inverse Compton ScatteringInverse Compton Scattering

Thermal BremsstrahlungThermal Bremsstrahlung

Thermal bremsstrahlung or free-free Thermal bremsstrahlung or free-free emission occurs when an eemission occurs when an e-- is is accelerated due to the strong electrical accelerated due to the strong electrical attraction of a positive ion in a plasma.attraction of a positive ion in a plasma.

TemperatureTemperatures above 10s above 1055 K K are are necessary.necessary.

http://imagine.gsfc.nasa.gov/docs/science/how_l2/xray_generation.html

Line EmissionLine Emission Heavy elements, not fully ionized, Heavy elements, not fully ionized,

can have inner electrons collisionally can have inner electrons collisionally excited to higher energy levels. excited to higher energy levels. Upon decay they emit an X-ray.Upon decay they emit an X-ray.

http://csep10.phys.utk.edu/astr162/lect/light/bohr.html

Synchrotron/Relativistic Synchrotron/Relativistic ee--

Charged particles in a magnetic field are Charged particles in a magnetic field are accelerated around field lines releasing accelerated around field lines releasing radiation.radiation.

If the particle is relativistic the radiation If the particle is relativistic the radiation undergoes ‘beaming’ and the maximum undergoes ‘beaming’ and the maximum EEphotonphoton is then proportional to the field is then proportional to the field strength and inversely proportional to the strength and inversely proportional to the particle’s momentum.particle’s momentum.

http://imagine.gsfc.nasa.gov/docs/science/how_l2/xray_generation.html

Inverse Compton Inverse Compton ScatteringScattering

A relativistic eA relativistic e-- colliding with a colliding with a low energy low energy photon can photon can impart energy impart energy resulting in an X-resulting in an X-ray.ray.

Seen in SNe and Seen in SNe and AGN.AGN.

http://venables.asu.edu/quant/proj/compton.html

The SunThe Sun Turbulence in the convection zone Turbulence in the convection zone

amplifies magnetic fields to create loops amplifies magnetic fields to create loops conducting electric currents, thus conducting electric currents, thus heating the solar corona to X-ray heating the solar corona to X-ray temperatures.temperatures.

Solar Photosphere ≈ 6000K

Solar Corona ≈ 106 K

Charles & Seward, Exploring the X-ray Universe. Cambridge U. Press, Great Britain©1995

Solar Flare/LoopSolar Flare/Loop

The Main The Main FeaturesFeatures

The 1/4 The 1/4 keVkeV

(McCammon,D. et al. (Sept. 2002) ApJ. v.576, no.1,pt.1 p.290-300)

The 3/4 The 3/4 keVkeV

(McCammon,D. et al. (Sept. 2002) ApJ. v.576, no.1,pt.1 p.290-300)

The FeaturesThe Features The Lockman Hole: a region where absorbing The Lockman Hole: a region where absorbing

material, HI and dust, are sparsematerial, HI and dust, are sparse Draco Cloud: enhanced soft X-ray region due Draco Cloud: enhanced soft X-ray region due

to a molecular cloud falling into the plane of to a molecular cloud falling into the plane of the Galaxythe Galaxy

Cygnus Superbubble/Loop: nearby Cygnus Superbubble/Loop: nearby superbubble from the explosion of many Sne, superbubble from the explosion of many Sne, 14 times the size (at 400 pc in diameter) of 14 times the size (at 400 pc in diameter) of the Cynus Loop, a 20,000 year old SNR the Cynus Loop, a 20,000 year old SNR emitting thermal bremsstrahlung as soft x-emitting thermal bremsstrahlung as soft x-rays.rays.

North Polar Spur (NPS)/Loop 1: The NPS is a North Polar Spur (NPS)/Loop 1: The NPS is a bright region of the Loop 1 superbubble, a bright region of the Loop 1 superbubble, a well-known radio feature.well-known radio feature.

More FeaturesMore Features The Virgo Cluster: the cluster of galaxies at The Virgo Cluster: the cluster of galaxies at

the center of the local superclusterthe center of the local supercluster Galactic Bulge: not well understood, but Galactic Bulge: not well understood, but

definitely consists of some component definitely consists of some component beyond the NPSbeyond the NPS

LMC: a nearby dwarf irregular galaxyLMC: a nearby dwarf irregular galaxy Vela/Puppis SNRs: Vela SNR ~ 1,500 ly Vela/Puppis SNRs: Vela SNR ~ 1,500 ly

away, 11,000 y old and 230 ly in diameter; away, 11,000 y old and 230 ly in diameter; whereas Puppis, superimposed on the Vela whereas Puppis, superimposed on the Vela remnant is ~4 times farther away, but the remnant is ~4 times farther away, but the brightest X-ray source between 0.5 and 1 brightest X-ray source between 0.5 and 1 keVkeV

Vela and Vela and PuppisPuppis

http://heasarc.gsfc.nasa.gov/docs/rosat/gallery/snr_velapup.html

More FeaturesMore Features

Eridanus Enhancement: from the Orion Eridanus Enhancement: from the Orion superbubble, ~1200 ly across, being superbubble, ~1200 ly across, being energized by stars in the Orion OB1 energized by stars in the Orion OB1 associationassociation

Monogem Ring: a SNR in a low density Monogem Ring: a SNR in a low density region of the Galaxy, thus evolved into region of the Galaxy, thus evolved into a low surface-brightness remnanta low surface-brightness remnant

The Crab: a SNR recorded in 1054 and The Crab: a SNR recorded in 1054 and now observed to contain a 33 ms pulsarnow observed to contain a 33 ms pulsar

Supernova RemnantsSupernova Remnants Type 1: mass transfer onto a white dwarf from a Type 1: mass transfer onto a white dwarf from a

binary companion resulting in accretion beyond the binary companion resulting in accretion beyond the Chandrasekhar limit.Chandrasekhar limit.

Type 2: core collapse of a massive star (~10 MType 2: core collapse of a massive star (~10 Msolarsolar) ) that has formed an iron core.that has formed an iron core.

Most profuse X-ray emission during phases 1 & 2.Most profuse X-ray emission during phases 1 & 2. Thermal x-rays via line emission or bremsstrahlung.Thermal x-rays via line emission or bremsstrahlung.

Charles & Seward, Exploring the X-ray Universe. Cambridge U. Press, Great Britain©1995

SuperbubblesSuperbubbles SN - Star Formation - SNe - SuperbubbleSN - Star Formation - SNe - Superbubble Not created by a single “super-supernova,” Not created by a single “super-supernova,”

but by many such events over time.but by many such events over time. Dynamite vs. Digger analogyDynamite vs. Digger analogy

Charles & Seward, Exploring the X-ray Universe. Cambridge U. Press, Great Britain©1995

Active Galactic NucleiActive Galactic Nuclei The super massive The super massive

Black Holes (BHs) at Black Holes (BHs) at the centers of the centers of galaxies, actively galaxies, actively accrete gas from the accrete gas from the ISM, cannibalized ISM, cannibalized galaxies, nearby galaxies, nearby stars.stars.

An accretion disk An accretion disk forms, heating the forms, heating the material, as well as material, as well as jets of relativistic jets of relativistic matter at the poles of matter at the poles of the MBH.the MBH.

http://www.seds.org/hst/ngc4261.html