Refusing to Go Quietly: GRBs and Their Progenitors

January 9, 2018 | Author: Anonymous | Category: Science, Astronomy
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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


Compton Gamma-Ray Observatory


All Shapes and Sizes


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


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



The Milky Way According to COBE



• GRBs must be very close -- the Solar System

• GRBs must be very far (distant galaxies)


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?



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


GRB 990123

Fruchter et al. 1999 QuickTime™ and a GIF decompressor are needed to see this picture.

Now You Don’t


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


GRBs Go Bump in the Night

Expected from GRB Alone

Expected from SN Alone


The Star Underneath

Interestingly, the spectra of the supernovae underneath Long GRBs are missing both Hydrogen and Helium.


GRB Hosts

Box Width 3.”75

Fruchter et al. 2006


GOODS cc SNe Hosts Box Width 7.”5

Fruchter et al. 2006


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”


Artist’s Conception of GRB Environment


You Are Here

Long GRBs like this Not this 24

Just When You Thought You Were Safe.....


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.


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



Environment of GRB 130603B


SGRB 130603B in Black and White

0.6 µm = visible light 1.6 µm = infrared light 31

What Have We Found?


If Confirmed

• Will conclusively show that short bursts come from merging neutron stars

• Will explain much, and perhaps vast majority, of heavy elements


Merging Neutron Stars Make Waves


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.


The Nearest(?) SGRB

GRB 080905a 1.5 Billion light years away


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


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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