Black Holes Regions of space from which nothing, not even light, can escape because gravity is so strong. First postulated in 1783 by John Michell Term “black hole” coined in 1969 Observational evidence starting in 1970s We see the effects a black hole has on matter and radiation near it; we have not yet seen a black hole directly.

Journey to a Black Hole

Black Hole Structure Schwarzschild radius defines the event horizon R sch = 2GM/c 2 Singularity is “clothed” inside the event horizon Cosmic censorship prevails (you cannot see inside the event horizon) Schwarzschild BH

What is This? Diagram of the effect of gravity (gravitational potential well) near the black hole on the fabric of spacetime It is a 2-D depiction of a 3-D event

Types of Black Holes Primordial – can be any size, including very small (If <10 14 g, they would still exist) Stellar Mass – must be at least 3 solar masses (~10 34 g) Intermediate Mass – a few thousand to a few tens of thousands of solar masses; possibly the agglomeration of stellar mass holes Supermassive – millions to billions of solar masses; located in the centers of galaxies

The First “First” Black Hole Cygnus X-1 binary system Most likely mass is 16 (+/- 5) M o Mass determined by Doppler shift measurements of optical lines

NGC million light years away 1.2 billion M o black hole in a region the size of our Solar System Mass of disk is 100,000 M o Disk is 800 light years across

Supermassive Black Holes Rotating black hole in the center of a galaxy, which is emitting relativistic jets of material Emission is from just outside the event horizon

Active Galaxies Jets of fast moving particles and gamma-rays Disk of galaxy with supermassive blackhole in center Halo of gas, and dust Quasars, Blazars, Seyferts, AGN, ….etc, etc, etc

Radio & Optical Image of an AGN NGC 4261

Deep Image Black Holes Are Everywhere! Black holes in quasars QSO Galaxy Empty Black holes in“normal” galaxies Black holes in empty space Chandra deep field

Galactic Black Hole Zooms in to show the region surrounding the black hole in the center of a galaxy Accretion disk of gas swirls around black hole

Galactic Black Holes NGC 3377 & NGC 4486b are 2.7 arc-sec images NGC 3379 is 5.4 arc seconds Note double nucleus in central 0.5 arc- sec of NGC 4486b

Colliding BHs Spiral waveform can be calculated reliably Ringdown after merger tells you the mass Larger computers needed to predict the actual collision waveforms

Gamma-ray Bursts! Most powerful explosions in the Universe today - and one of the greatest mysteries of modern astrophysics “When you see a gamma-ray burst, a black hole is being born” – M. Livio

Gamma-ray Astronomy (The Short, Short Story…)

Sources of  -ray Emission Black holes Active Galaxies Pulsars Gamma-ray bursts Diffuse emission Supernovae Unidentified

GRBs: The Very Brief Version Humble Beginnings: A Bomb or Not a Bomb?  Vela Program A few hundred events, a few hundred theories Finally, science to the rescue  Compton Gamma Ray Observatory  BeppoSAX/ROTSE/HST/ (and a host of others)

Vela Program

CGRO

Gamma-Ray Bursts

Distribution of GRBs in the Sky

What BeppoSAX Saw

What HST Saw (Much Later)

Breakthrough!

Models for GRBs Hypernova Merging Neutron Stars

Come On…Let’s Vogue

What’s Next New Missions = Better Data Improved theory Serendipity

New Missions = Better Data Swift (2003)GLAST (2005) HETE II (launched 7 October 2000)INTEGRAL (2001) Swift

Imagine… we have detected a GRB! Our gamma-ray detector measures 5.27 x ergs/cm 2 Hey, Laura! What’s so impressive about that?!??!!!

Wrapping Up the Universe The light we measure decreases as a function of distance, We can find a galaxy’s distance if we can measure its velocity from its redshift, By measuring the distances of gamma-ray bursts from their redshifts, we can see how amazingly powerful these events are.

Remember the Falloff of Light What you detect = What was emitted 4  D 2

Remember Hubble’s Law v = H o * d H o is called the Hubble constant. It is generally believed to be around 65 km/sec/Mpc.

Remember the Doppler Shift  =    v c = z =

And Now for a Real Spectrum... This is an optical spectrum of a GRB from Keck, the world’s largest optical telescope. The locations of several Doppler shifted spectral lines are shown.

A Little Musical Interlude

A BIG Hint: From Redshift to Power Step-by-step power calculation: 1. Measure the redshift of three spectral lines 2. Take the average redshift, z 3. From this, calculate the velocity v=z*c 4. Using the Hubble Constant, get the distance d=v/H o 5. Convert distance in Mpc to distance in cm 6. Now, with the distance to the GRB, and the value measured at our detector, calculate power: P=4πd 2 *measured flux

1 Mpc ~ 3 x km L = 5.3 x ergs/cm 2 Needed Information

GRBs are the most in the Universe!