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
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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
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Compton Gamma-Ray
Observatory
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All Shapes and Sizes
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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
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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
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The Milky Way According
to COBE
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So...
• GRBs must be very close -- the Solar
System
• GRBs must be very far (distant galaxies)
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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!
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Where Do GRBS
Come From?
http://www.ibiblio.org/Dave/Dr-Fun/df9804/df980403.jpg
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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!
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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
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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
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GRBs Go Bump in the
Night
Expected from
GRB Alone
Expected from
SN Alone
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The Star Underneath
Interestingly, the spectra of the supernovae
underneath Long GRBs are missing both
Hydrogen and Helium.
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GRB
Hosts
Box Width
3.”75
Fruchter et al. 2006
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GOODS
cc SNe
Hosts
Box Width
7.”5
Fruchter et al. 2006
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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”
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Artist’s Conception of
GRB Environment
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You Are Here
Long GRBs like this
Not this
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Just When You
Thought You Were
Safe.....
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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.
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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”?
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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
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What Have We Found?
http://www.sciencecartoonsplus.com/gallery/astronomy/astron51_pretty-good-nova.gif
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If Confirmed
• Will conclusively show that short bursts
come from merging neutron stars
• Will explain much, and perhaps vast
majority, of heavy elements
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Merging Neutron Stars
Make Waves
http://www.youtube.com/watch?v=IZhNWh_lFuI
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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
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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
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The Nearest(?) SGRB
GRB 080905a 1.5 Billion light years away
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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
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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!
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