The general theory of relativity is our most accurate description of gravitation
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The general theory of relativity is our most accurate description of gravitation. Published by Einstein in 1915, this is a theory of gravity A massive object causes space to curve and time to slow down These effects manifest themselves as a gravitational force

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The general theory of relativity is our most accurate description of gravitation

  • Published by Einstein in 1915, this is a theory of gravity

  • A massive object causes space to curve and time to slow down

  • These effects manifest themselves as a gravitational force

  • These distortions of space and time are most noticeable in the vicinity of large masses or compact objects


The general theory of relativity also predicts the existence of

gravitational waves, which are ripples in the overall geometry of

space and time produced by moving masses

Gravitational waves have been detected indirectly, and specialized

antennas are under construction to make direct measurement

of the gravitational waves from cosmic cataclysms



Supermassive black holes exist at the centers of of most galaxies

  • These are detected by observing the motions of material around the black hole




Black holes evaporate spacetime, or even some other universe?


Black Holes have no Hair spacetime, or even some other universe?

Properties of a black hole:

- Mass

- Spin (angular momentum)

- Charge (tends to be zero)


Black Holes can have impact on their environments spacetime, or even some other universe?


Do Black Holes Really Exist? Good Candidate: Cygnus X-1 spacetime, or even some other universe?

- Binary system: 30 MSun star with unseen companion.

- Binary orbit => companion > 7 MSun.

- X-rays => million degree gas falling into black hole.


An early gamma ray-burst spacetime, or even some other universe?

Vela satellite


A Gamma Ray Burst Sampler spacetime, or even some other universe?


Great debate: 1967-1997 spacetime, or even some other universe?


Bepposax satellite
Bepposax Satellite spacetime, or even some other universe?

GRBM:

40-600 keV

WFC: 2-30

keV

NFI: 2-10

keV


X ray afterglow from grb 971214
X-Ray Afterglow from GRB 971214 spacetime, or even some other universe?

t=6.5 hrs

t=12.5 hrs

t=54 hrs


Optical afterglow from grb 971214
Optical Afterglow from GRB 971214 spacetime, or even some other universe?

Keck

Images

2 days

2 months

Host

HST Image


Optical afterglow from grb 080319b
Optical Afterglow from GRB 080319b spacetime, or even some other universe?

Swift Image

Light Curve

Naked-eye visible for ~30 sec. Distance = 7.5 billion ly


Uh-oh spacetime, or even some other universe?


GRB Host spacetime, or even some other universe?

Galaxies

Bloom et al. 2002


Radio light curves from long grbs
Radio Light Curves from long GRBs spacetime, or even some other universe?


GRB 970508 spacetime, or even some other universe?

  • First VLBI detection of a GRB Afterglow

  • absolute position to < 1 mas

  • Size < 10^19 cm (3 lt years)

  • Distance > 10000 lt years

Taylor et al 1997


GRB Expansion spacetime, or even some other universe?

Relativistic Expansion v ~ 0.96c

E ~ 10^53 ergs

(isotropic equivalent)

R ~ (E/n)^1/8

Taylor et al 2004

Pihlstrom et al 2007


The evidence long grbs

Peak toward low end of gamma-ray, complex gamma-ray light curves

Often have bright afterglows

Evidence for a relativistic explosion

Energy required of ~ 1053 ergs (isotropic)

Associated with regions of star formation in distant galaxies (out to edge of observable universe)

Sometimes obscured by dust

Plus …

The Evidence (long GRBs)




Final States of a Star curves

1. White Dwarf

If initial star mass < 8 MSun or so

2. Neutron Star

If initial mass > 8 MSun and < 25 MSun

3. Black Hole

If initial mass > 25 MSun

No Event + PN

Supernova + ejecta

GRB + Supernova + ejecta


Clicker question

Clicker Question: curves

What is the remnant left over from a GRB?

A: a white dwarf + expanding shell

B: a neutron star + expanding shell

C: a black hole + expanding shell

D: no remnant, just the expanding shell


Clicker question1

Clicker Question: curves

Where do most GRBs occur:

A: in globular clusters

B: in star forming regions

C: in old open clusters

D: in the Oort cloud


Clicker question2

Clicker Question: curves

What was the subject of the great debate about GRBs that went on for ~30 years?

A: If they were produced by Supernovae or colliding stars.

B: If they were galactic or extragalactic in origin.

C: If they were of terrestrial or extraterrestrial in origin?

D: If a nearby GRB killed off the dinosaurs.


NS-NS binary curves

Massive star

Coalescence versus Collapse


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