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Refusing to Go Quietly: Gamma-Ray Bursts and Their Progenitors. Andy Fruchter STScI Hubble Science Briefing 5 Dec. 2013. What Are We Doing Here?. An introduction to Gamma-Ray Bursts (GRBs) Massive stars and the long bursts Short bursts and merging neutron star binaries

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refusing to go quietly gamma ray bursts and their progenitors
Refusing to Go Quietly:Gamma-Ray Bursts and Their Progenitors
  • Andy Fruchter
  • STScI
  • Hubble Science Briefing
  • 5 Dec. 2013
what are we doing here
What Are We Doing Here?
  • An introduction to Gamma-Ray Bursts (GRBs)
  • Massive stars and the long bursts
  • Short bursts and merging neutron star binaries
  • A new view on the universe

2

the vela satellites protecting the free world from illicit grbs
The Vela Satellites:Protecting the Free World from Illicit GRBs

Designed to detect nuclear tests (in violation of the test ban treaty), the Vela satellites discovered GRBs

3

slide6

Two Classes of GRBs

BATSE Band Energies:

1: 20 - 40 keV

2: 40 - 70 keV

3: 70 - 160 keV

4: 160 - 430 keV

Kouveliotou et al. 1993

6

slide7

Two Classes of GRBs

BATSE Band Energies:

1: 20 - 40 keV

2: 40 - 70 keV

3: 70 - 160 keV

4: 160 - 430 keV

Kouveliotou et al. 1993

7

slide10
So...
  • GRBs must be very close -- the Solar System
  • GRBs must be very far (distant galaxies)

10

slide11
But ...
  • If they are far out in the solar sytem, they must be produced by colliding balls of ice. Throwing snowballs may be more dangerous than we realized!
  • If they are very far, their energies may be stupendous....something like the rest mass of the sun being turned into gamma-rays!

11

where do grbs come from
Where Do GRBS Come From?

http://www.ibiblio.org/Dave/Dr-Fun/df9804/df980403.jpg

12

grb 990123
GRB 990123
  • One of the brightest GRBs observed
  • At its brightest, it was visible through a pair of binoculars
  • But the light from the burst travelled over 12 billion light years before hitting the binoculars!
  • Estimated energy in gamma rays of the burst = rest mass of the sun!

14

grb 9901231
GRB 990123

Fruchter et al.

1999

Now You See It

The transient has

faded by a factor

of two million since

peak in this first

HST image

15

grb 9901232
GRB 990123

Fruchter et al.

1999

Now You Don’t

16

a side view of a grb
A Side View of a GRB

300,000 light seconds

Regions of γ-ray

formation

Doomed Star

Internal Shocks?

Photosphere?

GRB Hitting

Interstellar Medium

Black Hole

17

grbs go bump in the night
GRBs Go Bump in the Night

Expected from

GRB Alone

Expected from

SN Alone

18

the star underneath
The Star Underneath

Interestingly, the spectra of the supernovae

underneath Long GRBs are missing both

Hydrogen and Helium.

19

slide20

GRB

Hosts

Box Width

3.”75

Fruchter et al. 2006

20

goods cc sne hosts
GOODS cc SNe Hosts

Box Width

7.”5

Fruchter et al. 2006

21

long grbs are not just like other supernovae
Long GRBs Are Not Just Like Other Supernovae
  • They like to be on the very brightest parts of their host galaxy (much more so than regular supernovae)
  • They like their hosts small -- probably to avoid “metals”

22

slide24

You Are Here

Long GRBs like this

Not this

24

slide26

A Short-Burst Host Mosaic

Images on the left were taken in the blue, on the right in the infrared

Short Bursts like all types of galaxies -- small to large, young to old.

26

so what causes short bursts
So What Causes Short Bursts?
  • Deep searches show no sign of supernovae, and Short GRBs do not greatly favor star-forming hosts, so massive stars are probably out.
  • Neutron star binaries can merge anywhere between 10 million years and a Hubble time, and are found in all types of galaxies.
  • But is there an observation that would be a “smoking gun”?

27

sgrb 130603b in black and white
SGRB 130603B in Black and White

0.6 µm = visible light

1.6 µm = infrared light

31

what have we found
What Have We Found?

http://www.sciencecartoonsplus.com/gallery/astronomy/astron51_pretty-good-nova.gif

32

if confirmed
If Confirmed
  • Will conclusively show that short bursts come from merging neutron stars
  • Will explain much, and perhaps vast majority, of heavy elements

33

slide34

Merging Neutron Stars Make Waves

http://www.youtube.com/watch?v=IZhNWh_lFuI

34

a future astronomical observatory
A Future AstronomicalObservatory

Advanced LIGO will be able to detect gravitational waves that

stretch the length of the arms by a fraction of the size of a proton

35

listening to neutron star mergers
Listening to Neutron Star Mergers

Figure: Caltech/Cornell/Cita Collaboration

Audio: Ben Farr, Northwestern U.

http://hubblesource.stsci.edu/services/events/telecons/media/listening_to_neutron_star_mergers.mp3

36

the nearest sgrb
The Nearest(?) SGRB

GRB 080905a 1.5 Billion light years away

37

we might not need a grb
We Might Not Need a GRB
  • A kilonova could act as a marker
  • Large new surveys instruments, such as LSST, could locate kilonovae
  • These may be our best way to find the first gravitational wave sources

38

the lesson
The Lesson
  • When there are two competing theories in science, often one is right and the other is wrong.
  • But in more interesting cases, they are both right.
  • Welcome to the progenitors of GRBs!

39

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