GRBTheory and observations

Useful reviews:Waxman astro-ph/0103186Ghisellini astro-ph/0111584Piran astro-ph/0405503Meszaros astro-ph/0605208Gehrels 2009 ariv:0909.1531Useful links:http://qso.lanl.gov/~clf/papers (Chris Fryer lectures)

GRBs most luminous objects in the Universe!!

• Sun Luminosity L~4 1033 erg/s• Supernova L~1051 erg/s• Galaxies with nuclei L~1048 erg/s

• GRB luminosity L~1052 erg/s

GRB light curves

GRBs: flashes of 0.1 MeV gamma rays that last 1-100 s

• Isotropy in the skyIsotropy in the sky

• Duration: Duration: TT9090 0.2 s short 0.2 s short

20 s long20 s long

• Flux: Flux: f f = 10= 10-4 -4 -10-10-7 -7 erg/cmerg/cm22 s s

• Rate Rate R R 300/yr BATSE and 100/yr Swift 300/yr BATSE and 100/yr Swift

-ray observations summary

• Variability: Variability: Most show Most show t ~ 64 mst ~ 64 msSome Some t ~ 1 mst ~ 1 ms

GRB

3 July 1969: first detection of a GRB by Vela 5A

Vela Satellites• 105 km Orbits• Launched in

pairs – launched 1963-1965

• Operated until 1979

• All satellites allowed for some localization.

First Detected Gamma-Ray Burst

Vela Satellites - Results• 73 Bursts in Gamma-Rays

over 10 years• Not from the Earth (not

weapons tests) and not in the plane of solar system

Ray Klebasadel

Gamma-Ray Bursts in the Solar System

• Lightning in the Earth’s atmosphere (High Altitude)

• Relativistic Iron Dust Grains

• Magnetic Reconnection in the Heliopause

Red Sprite Lightning

Gamma-Ray Bursts in the Milky Way

• Accretion Onto White Dwarfs

• Accretion onto neutron stars I) From binary companion II) Comets

• Neutron Star Quakes• Magnetic Reconnection

X-ray Novae

Galactic Gamma-Ray Bursts: Soft Gamma-Ray Repeaters

One Class of GRBsIs definitely Galactic:Soft gamma-ray Repeaters (SGRs)

Characteristics:1) Repeat Flashes2) Photon Energy Distribution lowerEnergy than otherGRBs (hard x-rays)

X-ray map of N49 SN remnant. The whiteBox shows location of the March 5th event

Models for SGRs

• Accretion I) Binary Companion - no companion seen II) SN Fallback – Too long after explosion

• Magnetic Fields ~1015 G Fields

-“Magnetars”

Extragalactic Models• Large distances

means large energy requirement (1051erg)

• Event rate rare (10-

6-10-5 per year in an L* galaxy) – Object can be exotic

Cosmological Models

• Collapsing WDs• Stars Accreting on

AGN• White Holes• Cosmic Strings• Black Hole Accretion

Disks I) Binary Mergers II) Collapsing Stars

Black-Hole Accretion Disk (BHAD) Models

Binary merger orCollapse of rotatingStar producesRapidly accretingDisk (>0.1 solar Mass per second!) Around black hole.

Massive Star CollapseCollapsar Model – Collapse of a Rotating Massive Star into a Black Hole

Stan Woosley

Main Predictions: Beamed Explosion, Accompanying supernova-like explosion

BATSE - Burst And Transient Spectrometer Experiment

BATSE Module

BATSE Consists oftwo NaI(TI) Scintillation Detectors: Large Area Detector (LAD) For sensitivity and the Spectroscopy Detector (SD) for energy coverage

8 Detectors Almost Full Sky Coverage Few Degree Resolution 20-600keV

Galactic Models

BATSE Results – IsotropyCosmological Models Favored!

Gamma-Ray Burst Lightcurves

GRB Lightcurves haveA broad range of Characteristics

Fast Rise Exponential Decay“FREDs”

GRB970508

GRB990316

Gamma-Ray Burst Durations

Two Populations: Short – 0.03-3s Long – 3-1000sPossible third Population 1-10s

Gamma-Ray Burst Duration vs. Energy Spectrum

BATSE - Summary

• GRBs are Isotropic – The beginning of the end for Galactic Models, but persistent theorists move the Galactic Models to the Halo

• GRBs come in all shapes and sizes but two obvious subgroups exist - I) Short, Hard Bursts II) Long, Soft Bursts

BeppoSAXItalian-Dutch Satellite Launch: April 30, 1996Goal: Positional Accuracy <5 arc minutes

Honoring Giuseppe Occhialini

High Pressure Gas ScintillationProportional Counter

WFC – 40o x 40o, 2-28keV

BeppoSAX Instruments

• Xenon Gas Scintillator

• Energy Range: .1-1keV (1-10keV)

• ~1 arc minute resolution

• Goal – Localize Object

• HPGSPC - High Pressure Xenon/He Gas

• PDS Phoswitch - NaI(Tl), CsI(Na) Scintillators

• 4-120keV (15-300keV)• Goal – Broad Energy

resolution in X-ray narrow field

LECS/MECS HPGSPC PDS

BeppoSAX: I GRB sono sorgenti a distanze cosmologiche!

Costa+ 1997 BeppoSAX

Van Paradijs+ 1997 WHT

Pedichini+ 1997 Campo imperatore

GRB 970228 – host galaxy observed?

This blob, a peculiarGalaxy to be sure, Is in the same positionAs the Burst!

Could it have been theGRBs host?

The galaxy has a Redshift of 0.695.

GRB 970508 – Optical Counterpart

BeppoSAXX-ray LocalizationAllowed a The OpticalTransient toBe detected While still on The rise.

OT allowedSpectral Measurement!

GRB970508 – Absorption Lines: z=0.835

Fe IIFe II

Mg IIMg II I

Optical Emission

Absorption

Metzger et al. 1997 flux

Wavelength

Wavelength

flux

Host Galaxy Detected for GRB970508

Z=0.835

Wavelength

flux

Radio Twinkling can also be used to estimate the GRB distance: consistent with z=0.835

Just as the Earth’sAtmosphere Causes light To scatterCausing pointSources to“twinkle”, the Interstellar Medium causesRadio emissionTo twinkle. WhenThe burst gets Large enough,Like planets, the Twinkling stops.

ISM Scattering

T=0, pointSource

Twinkle,Twinkle Observer

Always SeesPart of Burst

T=t, r=c tWhere c is speed of light

Waxman, Kulkarni, & Frail 1997

A crash Course in A crash Course in ScintillationsScintillations

Scintillations determine the size of the source in a Scintillations determine the size of the source in a model independent way. The size (~10model independent way. The size (~101717cm) is in a cm) is in a perfect agreement with the prediction of the perfect agreement with the prediction of the Fireball model.Fireball model.

GRB971214 @z=3.42

GRB NH and AV

HETE2Fregate: 6-400 keV GRB triggers and low res. Spectra

WXM 2-25 keV, medium energy resolution and 10arcmin localization

SXC 0.5-10 keV, good energy resolution and 1arcmin localization

Swift: a new era for GRB studiedBurst Alert Telescope (BAT) - 32,000 CdZnTe detectors - 2 sr field of view

X-Ray Telescope (XRT) - CCD spectroscopy - Arcsec GRB positions

UV-Optical Telescope (UVOT) - Sub-arcsec position - 22 mag sensitivity

Spacecraft slews XRT & UVOT to GRB in <100 s

Swift GRBs

XRFShortGRB

XRF

ShortGRB

XRF

XRFXRF

XRF

XRF

ShortGRB

XRF

ShortGRB

ShortGRB

ShortGRB

ShortGRBXRF

XRFXRF

ShortGRB Short

GRB

Swift localizes short GRBs

• elliptical hosts• low SF rates• offset positions• redshifts z ~ 0.2>> inconsistent with collapsar model>> supportive of NS-NS model

BATXRT XRT

Chandra

Il GRB piu’ lontano, quello piu’ brillante e quello piu’ energetico

QuickTime™ e undecompressore Animation

sono necessari per visualizzare quest'immagine.

GRB080319B

GRB080913

GRB080916C Fermi -rays

3 GRB @ z>6

Subaru Spectroscopy

GRB050904 Ly break in the IR J=17.6 at 3.5 hours

Observational Constraints on the Central Engine

• Host Galaxies• GRB Environments• Prompt Emission• Bumps in the Afterglow (SN?) • Energetics and Beaming• Using GRBs as Cosmological Probes

I: Host Galaxies

The fading optical afterglow of GRB 990123as seen by HST on Days 16, 59 and 380 after the burst.

Accurate positionsAllowed AstronomersTo watch the burstsFade, and then Study their HostGalaxy!

Host Galaxy

Optical Afterglow

PropertiesOf HostGalaxies

I) Like Many Star-formingGalaxiesAt thatObservedredshift

Holland 2001

II) Star-formation rates high, but consistentWith star forming galaxies.

Location, Location, Location(In addition to detecting hosts, we can determine where

a burst occurs with respect to the host.

GRB hosts

• GRBs trace brightest regions in hosts

• Hosts are sub-luminous irregular galaxies

Concentrated in regions of most massive stars

Restricted to low metallicity galaxies

If we takeThese Positions At face Value, We can Determine The DistributionOf bursts With respectTo the half-Light radiusOf hostGalaxies!

This Will ConstrainThe models!

Distribution Follows StellarDistribution

GRB Hosts Exhibit Larger Mg line Equivalent Widths Than QSO absorbers: Higher Density?

Fiore 2000Salamanca et al.2002Savaglio, Fall & Fiore 2003

Results from low resolution spectroscopy

Savaglio, Fall & Fiore 2003

High dust depletion

High dust content

Denser clouds

2) Metallicity depends on galaxy mass

Savaglio et al. 2008 Berger et al. 2006

Star-formation rate in GRB hosts

Savaglio+ 2008

What we’ve learned from GRB Hosts!

• Hosts of long GRBs are star-forming galaxies

• GRBs trace the stellar distribution (in distance from galaxy center)

• GRBs occur in dense environments (star forming regions?)

Using GRBs as Cosmological Probes

Gamma-Ray Bursts are observed at extremely high redshifts and can be used to study the early universe.

• Star Formation History• Beacons to direct large telescopes to study

nascent galaxies• Studies of intervening material between us and

GRB – akin to quasar absorption studies

METAL ABUNDANCES IN HIGH z GALAXIES

GRB explosion site

Circumburstenvironment

To Earth

Host gasfar away

Redshift DistributionOf GRBsWith knownRedshifts(2002)

RedshiftsAs high as5 observed!

Lloyd-Ronning et al. 2002

Solid squares Denote burstsWith observedRedshifts.Open squaresDenotePositions usingA Luminosity-Variability Relation.(Fenimore & Ramirez-Ruiz2000).Dashed line Artifact of Luminosity Cut-off in FR-RSample.

Lloyd-Ronning, Fryer, & Ramirez-Ruiz 2002

Redshift distributions

Redshift (z)

Pre-SwiftSwift

GalaxiesQuasarsGRBs

10

12

13

8Dist

a nce

(Bi

lli o

n L i

ght

Yea r

s )

0 1 2 4 10

High resolution spectroscopy: GRB021004

FORS1 R~1000 CIV CIV z=2.296 z=2.328

UVES R=40000

z=2.296 z=2.328

GRB050730 UVES spectrum

GRBs show higher gas densities and metallicities,And have significantly lower [(Si,Fe,Cr)/Zn] ratios,Implying a higher dust content: Star Formation Region

GRB locations within galaxies

History of metal enrichment

Savaglio+2003 Prochaska+ 2003

050730

030323

000926

050820

050401060206

050904

GRB host galaxy metallicities

However… metallicity depends on: 1)Impact factor2)Galaxy mass3)Star-formation rate4)Etc….

1) Metallicity depend on impact factor

GRB021004

VariabilityGRB060418 z=1.49VLT/UVES Vreeswijk et al. 2007

Intervening absorbersLy forest: deviation from what is already known from quasar forests. ``Proximity effect'' should be much reduced for GRBs. An accurate determination of dn/dz at high z has strong implications for investigations of the re-ionization epoch, since the optical depth due to Ly line blanketing is evaluated by extrapolating the Ly dn/dz measured at lower-z.MgII and CIV absorbers: Incidence of MgII absorbers ~4 times higher than along QSO sight-lines. Incidence of CIV absorbers similar… WHY???

Dust composition/evolutionthe case of GRB 050904 @z=6.3

Large X-ray absorption and UV dust extinction

Haislip WFCAM-UKIRT ~0.5 days, Ly corr. = 3.02Tagliaferri FORS-VLT ~1 day, Ly corr. = 1.27Haislip GMOS-Gemini ~3 days, Ly corr. = 2.38

GRB 050904 z=6.3Stratta et al 2007

QSO@6.2 extinction curve0.5 day A3000=0.89+\-0.161 day A3000=1.33+\-0.293 days A3000=0.46+\-0.28

NH~1023 cm-2

AV/NH~50 times lower than Galactic!!

@z~6 no dust from AGB stars. Only sources are CCSNe (and AGNs)

Much less dust and much smaller AV/NH

GRB Environments II: Studying the environment using radio

and optical observation of GRBs

• Density profiles are different for different environments: massive stars will be enveloped by a wind profile.

• These different density profiles produce different radio, optical emission.

The Density Profile from Winds

ISM density is constantThe ShockRadiusDependsOn theDensityProfile!

RadioAnd OpticalLight CurvesAre a FunctionOf this Radius!

For ManyGamma-Ray Bursts,Wind-sweptEnvironmentsBest fit the Data (radioAnd R-bandData best Diagnostics!

Li & Chevalier 2003

Roger Chevalier

GRB021004

On the Surface,It appears we Can constrainThe environments,But, beware,There still remainMany free Parameters in These calculations!

The connection between SNe and GRBs

Afterglow and GRB Energetics IV:

• As we learned yesterday, afterglows allowed us to calculate redshifts.

• Assuming a cosmology, we can then get distances.

• Assuming isotropic explosions, we can estimate the GRB energies! These energies range over many orders of magnitude.

GRB Redshift IsotropicEnergy

GRB970228 0.695 5x1051

GRB970508 0.835 8x1051

GRB970828 0.958 NA

GRB971214 3.418 3x1053

GRB980326 1? 3x1051

GRB980329 2 or 3-5 NA

GRB980425 0.0085 1048

GRB980613 1.096 NA

GRB980703 0.966 1x1053

GRB990123 1.600 3x1054

GRB Redshifts (2000)

GRB Redshift IsotropicEnergy

GRB990308 >1.2? NA

GRB990506 1.3 NA

GRB990510 1.619 3x1053

GRB990705 0.86 NA

GRB990712 0.430 NA

GRB991208 0.706 1.3x1053

GRB991216 1.02 6.7x1053

GRB000131 4.5 1054

GRB000418 1.118 5x1052

GRB000926 2.066 2.6x1053

Afterglow and GRB Energetics

• As we learned yesterday, afterglows allowed us to calculate redshifts.

• Assuming a cosmology, we can then get distances.

• Assuming isotropic explosions, we can estimate the GRB energies! These energies range over many orders of magnitude.

• But are GRBs isotropic?

Jet Signatures

3/8break

8/1

iso,

o

1 t

En

⎥⎦⎤

⎢⎣⎡

+⎥⎥⎦⎤

⎢⎢⎣⎡

∝zb

ηθ

GRB 010222

Stan

ek e

t al.

(200

1)

/2)cos1(f

E)cos1(E2

b

iso,

bb

b

θθ

θ

≈−=

−=

Piran, Science, 08 Feb 2002

Energy and Beaming Corrections

• The dispersion in isotropic GRG energies results from a variation in the opening (or viewing) angle

• The mean opening angle is about 4 degrees (i.e. fb-1 ~ 500 )

• Geometry-corrected energies are narrowly clustered (1=2x)

Frail et al. (2001)

assumed)cm 0.1n(for

erg 105 E 3-

o

50

=

×=

15 events with z and t_jet

Energy and Beaming (Continued)

• Improved analysis• Larger sample• Used measured densities• Error propagation

• Geometrically corrected gamma-ray energy …

• Increase is due to using real density values

• 1 of 0.35 dex (2.2x)

Bloom, Frail & Kulkarni (2003)

erg 101.3 E 51×=

24 events with z and t_jet

Outliers

Summary of GRB Energetics• Gamma-ray bursts and

their afterglows have (roughly) standard energies

• Robust result using several complementary methods

E gamma-rays

Ek X-rays

Ek BB modeling

Ek Calorimetryerg 10E

erg 10E51

k

51

≈

≈

5.0E/E

erg 10 fewE EE

shock

51kshock

≈≡

×≈+≈

η

SN/GRB connection!GRBs have SN-like outbursts. But these bursts are beamed, and we won’t see all

explosions as a GRB. What do we make of the SN/GRB connection:I) All GRBs produce SNe?II) All SNe are GRBs (only those observed along the jet

axis are GRBs)?

Are either of these true?

Ambitious Theorists – New SN Mechanism

• Collapsar Theorists argue I) is true, but not II)

• Others argue that all supernovae have jets (e.g. asymmetries in SN1987A) and the standard SN engine is wrong!

• SN-like is NOT SN

What fraction of SNe are GRBs?

The GRB community tends to not talk to the SN community. Hence this problem has lingered for a long time. The simple fact is that the SN-like spectra and lightcurves are quite different than true SNe.

But let’s assume we don’t know this, how else can we tell? - Radio!

A Complete Radio Catalog• 5 yr period (1997-2001)• BeppoSAX, IPN, RXTE and

HETE satellites• 75 GRBs searched for radio

AGs• searches at 5 and 8.5 GHz• frequencies 0.8-650 GHz• 1521 flux density

measurements (or limits)• 2002-2003 data on Web

Frail, Kulkarni, Berger and Wieringa AJ May 2003http://www.aoc.nrao.edu/~dfrail/grb_public.shtml

Cumulative Flux Density Distribution

• Max radio flux 2 mJy• 19 detections

– mean=315+/-82 uJy• 44 GRB in total

– mean = 186+/-40 uJy• 50% of all bursts are brighter

than 110 uJy• Radio afterglow observations

are severely sensitivity limited!

Complete sample of 44 GRBs with 8.5 GHz measurements made between 5 and 10 days post-burst

50 %

Spectral Radio Luminosity

Complete sample of 18 GRBs with redshifts and 8.5 GHz measurements made between 5 and 10 days post-burst

1-1- 27

1-1-31

12L

Hz s erg 102 SN1993JHz s erg 10

F )1(Fd4L

×=≈

∝+= −−

men

twηerez

bn

bnn

nπ

! 102FF 8

RR

×≈nn

Fireball Calorimetry • Long-lived radio

afterglow makes a transition to NR expansion– no geometric uncertainties – can employ robust Sedov

formulation for dynamics– compare with equipartition

Most energy estimates require knowledge of the geometry of the outflow

– radius and cross check with ISS-derived radius

• Limited by small numbers

Frail, Waxman & Kulkarni (2000)

3-o

50o

cm 1nerg 105 E

≈×≈

How Common are Engine-Powered SNe?

VLA/ATCA survey of 34 Type Ib/c SNe to detect off-axis GRBs via radio emission

Berger PhD

• Most nearby SNe Ib/c do not have relativistic ejecta• Two distinct populations• Ek(GRB)<<1 foe (hydo

collapse)• <10% are 1998bw-like