GRB
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Transcript of GRB
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 sky
• Duration: T90 0.2 s short
20 s long
• Flux: f = 10-4 -10-7 erg/cm2 s• Rate R 300/yr BATSE and 100/yr Swift
-ray observations summary
• Variability: Most show t ~ 64 msSome t ~ 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 Scintillations
Scintillations determine the size of the source in a model independent way. The size (~1017cm) is in a perfect agreement with the prediction of the 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
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
Þ Concentrated in regions of most massive stars
Þ 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
8
Dis
tanc
e (B
illi o
n L i
ght Y
ears
)
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
[email protected] 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 NAGRB971214 3.418 3x1053
GRB980326 1? 3x1051
GRB980329 2 or 3-5 NAGRB980425 0.0085 1048
GRB980613 1.096 NAGRB980703 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 NAGRB990712 0.430 NAGRB991208 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
GRB 010222
Stan
ek e
t al.
(200
1)
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)
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)
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-raysEk X-raysEk BB modelingEk Calorimetry
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
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)
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