Refusing to Go Quietly: GRBs and Their Progenitors

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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
• A new view on the universe
2
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
Compton Gamma-Ray
Observatory
4
All Shapes and Sizes
5
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
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
8
The Milky Way According
to COBE
9
So...
• GRBs must be very close -- the Solar
System
• GRBs must be very far (distant galaxies)
10
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?
http://www.ibiblio.org/Dave/Dr-Fun/df9804/df980403.jpg
12
13
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 990123
Fruchter et al.
1999
The transient has
faded by a factor
of two million since
peak in this first
HST image
QuickTime™ and a
GIF decompressor
are needed to see this picture.
Now You
See It
15
GRB 990123
Fruchter et al.
1999
QuickTime™ and a
GIF decompressor
are needed to see this picture.
Now You
Don’t
16
A Side View of a GRB
300,000 light seconds
Regions of γ-ray
formation
Doomed Star
Black Hole
Internal Shocks?
Photosphere?
GRB Hitting
Interstellar Medium
17
GRBs Go Bump in the
Night
Expected from
GRB Alone
Expected from
SN Alone
18
The Star Underneath
Interestingly, the spectra of the supernovae
underneath Long GRBs are missing both
Hydrogen and Helium.
19
GRB
Hosts
Box Width
3.”75
Fruchter et al. 2006
20
GOODS
cc SNe
Hosts
Box Width
7.”5
Fruchter et al. 2006
21
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
Artist’s Conception of
GRB Environment
23
You Are Here
Long GRBs like this
Not this
24
Just When You
Thought You Were
Safe.....
25
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?
• 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
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Environment of
GRB 130603B
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SGRB 130603B
in Black and White
0.6 µm = visible light
1.6 µm = infrared light
31
What Have We Found?
http://www.sciencecartoonsplus.com/gallery/astronomy/astron51_pretty-good-nova.gif
32
If Confirmed
• Will conclusively show that short bursts
come from merging neutron stars
• Will explain much, and perhaps vast
majority, of heavy elements
33
Merging Neutron Stars
Make Waves
http://www.youtube.com/watch?v=IZhNWh_lFuI
34
A Future Astronomical
Observatory
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
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
GRB 080905a 1.5 Billion light years away
37
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
• 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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