Binaries3

HOW TO DETECT A BLACK HOLE: 

HOW TO DETECT A BLACK HOLE Effects on matter/light outside the horizon gravitational attraction of other bodies “dark star” with mass distinguish from normal star, white dwarf, neutron star Accretion (swallowing) of gas gas heated by compression/turbulence in strong gravity field X-rays but need a source of gas accretion from interstellar matter insignificant mass transfer in binaries to the rescue

CAN WE IMAGE BLACK HOLES?: 

CAN WE IMAGE BLACK HOLES?

CAN WE IMAGE BLACK HOLES?: 

CAN WE IMAGE BLACK HOLES? HUBBLE: read newspaper @ 1 mile Optical/UV telescope in space Falls short by 100,000 VLBA: read newspaper in Philly Transcontinental radio telescope Falls short by 1,000 MAXIM: Read newspaper on moon X-ray interferometer in space Can do it! Ready for launch (?) 2020-2030 …NOT YET, BUT SOMEDAY…?

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MAXIM = Micro- arcsecond X-ray Imaging Mission

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HOW TO DETECT BLACK HOLES 1. Mass of “compact “ companion in close binary system (stellar remnants only) X-ray binary (artist’s impression)

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HOW TO DETECT BLACK HOLES 2. Orbital motion of stars or gas clouds (supermassive holes) M87 disk

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HOW TO DETECT BLACK HOLES 3. Random motions of stars in galaxy’s nucleus (supermassive holes) Globular cluster M3 (similar appearance to a galactic nucleus)

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Gas almost never falls directly into a black hole Too much “swirl” (angular momentum) …

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Too much “swirl” (angular momentum) … …makes it more like a whirlpool Gas almost never falls directly into a black hole

ACCRETION DISK: 

ACCRETION DISK Like a flattened whirlpool Gas must give up angular momentum to go down the drain VISCOSITY (~FRICTION)

ACCRETION DISKS ALLOW US to PROBE the HORIZON: 

ACCRETION DISKS ALLOW US to PROBE the HORIZON GRAVITY MOTION HEAT RADIATION (X-rays, UV…) Energy flows from one form to another... matter swirling inward friction

ENERGY FLOW IN ACCRETION DISK: 

ENERGY FLOW IN ACCRETION DISK GRAVITATIONAL POTENTIAL ENERGY KINETIC ENERGY HEAT RADIATION Energy flows from one form to another... falling matter compression/turbulence particle collisions, etc.

EVOLUTION OF CLOSE BINARIES: 

EVOLUTION OF CLOSE BINARIES “Algol Paradox” and its resolution Roche lobe = “sphere” of influence actually teardrop shaped Matter flows across Lagrange point Too much angular momentum ACCRETION DISK

ALGOLS CAN EVOLVE INTO X-RAY BINARIES: 

ALGOLS CAN EVOLVE INTO X-RAY BINARIES Crucial that mass ratio flips otherwise stars can fly apart Compact star either NS or BH depends on mass of precursor Two modes of mass transfer stellar wind: star smaller than Roche lobe “Roche lobe overflow”: star swells to fill Roche lobe

BINARY MASS FUNCTION depends on...: 

BINARY MASS FUNCTION depends on... Orbit period: easy Doppler shift of normal star: easy Mass of normal star: hard Orbit inclination: hard 0.1 10 1 100 Log Mass (solar units)

NEUTRON STAR VS. BLACK HOLE: …how to tell: 

NEUTRON STAR VS. BLACK HOLE: …how to tell BH if: mass (reliable) distinctive spectrum (unreliable ????) NS if: pulsing (X-ray pulsar) evidence of nuclear explosions on surface (X-ray burster)

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X-ray pulsar (accretion) X-ray burster (thermonuclear)