LECTURE 16: X-RAY BINARIES AND What are MICROQUASARS X-ray binaries Substitute Lecturer: Paul Sell (XRBs)? Why are they called XRBs? Really energetic or hot processes produce lots of X-rays as material gets near the compact object! Neutron Stars What are the compact objects? The Bending of Spacetime Thank you Einstein! Black Holes Museum Coin Spin Gravity Well How big are black holes? • Particles closer in go faster: v1 > v2 • Black hole size = size of event horizon - event horizon = point at which even light cannot escape • What pulls the coin (particle) in and what keeps it out? - Balance kinetic vs. gravitational potential energy - (1/2)mc2 = GMm/r 2 • rS = 2GMBH / c v2 v1 • rS = Schwarzschild radius • Depends only on MBH! Difference in Black Hole Size 2 • rS = 2GMBH / c • Supermassive black holes in the centers of galaxies (previous lecture) - MBH ~ millions to billions times M⊙ (the mass of the Sun) - rS ~ millions to billions of km ~ the size of the inner solar system • Stellar mass black holes throughout galaxies (today) - MBH ~ M⊙ - rS ~ a few km ~ the size of a city - Very slightly smaller than a neutron star Where Do They Come From? Answer: Supernovae Real Supernova Simulation Movie Back to XRBs...How does gas get over to the compact object? • Wind - From hot, massive stars • Roche Lobe Overflow - From cooler, bloated stars How do we observe XRBs? Nearby Galaxy, M81 How do we observe XRBs? Timescale Nearby of movie: Galaxy, weeks M81 Size and Timescales of a BH/NS • How big is a BH or NS, which is a few times mass of the Sun? 2 - RS = 2GM / c ⇒ About the size of a city (few km) • v = d / t ⇒ t = d / v (d ~ 10-100 RS) - v ~ 0.01c ~ 3×103 km/s, d ~ 100 km (disk) ⇒ tmin ~ 0.03 s • How big is a BH millions of times the mass of the Sun? - v ~ 0.01c ~ 3×103 km/s, d ~ 108 km (disk) ⇒ tmin ~ 30000 s ~ 9 hr ➡ Can probe changes more easily with small BHs States of Activity in XRBs Redder, Bluer, Brighter Brighter Brightness Bluer, Fainter Redder, Fainter X-ray Color Microquasar: XRB with a very powerful jet Understanding Jets: Sonic Booms from the Ultimate Space-Based Rail Guns What is a Rail Gun? Transformers: Revenge of the Fallen A Real Rail Gun! • Up to Mach 8 (~6000 mi/h)! • Up to 32 megajoules! Rail Guns in Space: Jets from Black Holes and Neutron Stars • 600 million mph! (100,000x faster!) • 10^24 or 10000000000000000000000000000000000000 megajoules! (a trillion trillion times more powerful!) Jets Drive Shocks Shock: piled-up waves traveling faster than the speed of sound Example Shockwave: Russian Meteor Shock: waves traveling faster than the speed of sound Why so much later and unexpected? Light travels ~1 million times faster than sound, so people did not feel the shockwave until many minutes later! (like see lightning and hearing thunder later) SS433: XRB with Jets SS433: A Precessing Jet Another Microquasar: Cygnus X-1 Artist Impression Cygnus X-1 ~300,000 mi/h shockwave! ~20 lightyears Another Example Microquasar: Circinus X-1 20 40 Jet? -57:10:00 Dec (J2000) 20 40 Shocks 48 46 44 42 15:20:40 38 36 34 RA (J2000) Jets Blowing Bubble: Simulation Jets Blowing Bubble: SAX J1712 Summary • XRBs are a stellar-mass black hole or neutron star with a donor companion that is dumping gas onto it • The gas heats up as it approaches the black hole or neutron star and shines brightly in X-rays • Sometimes a very powerful jet is launched from the accretion disk that drives shockwaves at near the speed of light into space.