Refusing to Go Quietly: GRBs 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? • 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

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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! 11

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! 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

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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 24

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”? 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

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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 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

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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! 39