Refusing to Go Quietly: Gamma-Ray Bursts and Their Progenitors Andy Fruchter STScI Hubble Science Briefing 5 Dec. 2013.

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

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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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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

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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

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

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GRB 990123

QuickTime™ and aGIF decompressor

are needed to see this picture. Now You

Don’t

Fruchter et al. 1999

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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

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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 Artist’s Conception of GRB Environmentof GRB Environment

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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

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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

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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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