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Refusing to Go Quietly:Refusing to Go Quietly:Gamma-Ray Bursts Gamma-Ray Bursts
and Their Progenitorsand Their Progenitors
Andy FruchterAndy FruchterSTScISTScI
Hubble Science BriefingHubble Science Briefing5 Dec. 20135 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
22
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
33
Compton Gamma-Ray Observatory
44
All Shapes and Sizes
55
BATSE Band Energies:
1: 20 - 40 keV2: 40 - 70 keV
3: 70 - 160 keV4: 160 - 430 keV
Two Classes of GRBs
Kouveliotou et al. 1993 66
BATSE Band Energies:
1: 20 - 40 keV2: 40 - 70 keV
3: 70 - 160 keV4: 160 - 430 keV
Two Classes of GRBs
Kouveliotou et al. 1993 77
88
The Milky Way According to COBE
99
So...
• GRBs must be very close -- the Solar System
• GRBs must be very far (distant galaxies)
1010
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!
1111
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!
1414
GRB 990123
Fruchter et al. 1999
QuickTime™ and aGIF decompressor
are needed to see this picture. Now You See
It
The transient hasfaded by a factor
of two million sincepeak in this first
HST image
1515
GRB 990123
QuickTime™ and aGIF decompressor
are needed to see this picture. Now You
Don’t
Fruchter et al. 1999
1616
A Side View of a GRB
Doomed Star
Black Hole
Regions of γ-ray formation
GRB Hitting Interstellar Medium
300,000 light seconds
Internal Shocks?Photosphere?
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GRBs Go Bump in the Night
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Expected fromGRB Alone
Expected fromSN Alone
The Star Underneath
Interestingly, the spectra of the supernovaeunderneath Long GRBs are missing both
Hydrogen and Helium. 1919
GRBHosts
Box Width3.”75
Fruchter et al. 20062020
GOODS cc SNe Hosts
Box Width7.”5
Fruchter et al. 2006
2121
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”
2222
Artist’s Conception Artist’s Conception of GRB Environmentof GRB Environment
2323
Long GRBs like this
Not this
You Are Here
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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
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0.6 µm = visible light 1.6 µm = infrared light
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
3333
Merging Neutron Stars Make Waves
http://www.youtube.com/watch?v=IZhNWh_lFuI
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A Future AstronomicalObservatory
Advanced LIGO will be able to detect gravitational waves thatstretch 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 CollaborationAudio: Ben Farr, Northwestern U.
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http://hubblesource.stsci.edu/services/events/telecons/media/listening_to_neutron_star_mergers.mp3
The Nearest(?) SGRB
GRB 080905a 1.5 Billion light years away 3737
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
3838
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!
3939