Gamma-Ray Bursts as Gamma-Ray Bursts as Cosmological ProbesCosmological Probes

Robert J. NemiroffRobert J. Nemiroff

Gamma-Ray Bursts as Gamma-Ray Bursts as Cosmological ProbesCosmological Probes

Gamma ray bursts (GRBs), the most powerful explosions known in Gamma ray bursts (GRBs), the most powerful explosions known in the universe, are telling us about the universe itself. These the universe, are telling us about the universe itself. These enigmatic explosions are useful probes because they are so rapidly enigmatic explosions are useful probes because they are so rapidly transient and because they can be seen further out into the universe transient and because they can be seen further out into the universe than any other transient phenomenon. The lack of a gravitational than any other transient phenomenon. The lack of a gravitational lensing signature, for example, limits the abundance of potential lensing signature, for example, limits the abundance of potential lenses, and hence the composition, of the universe. The high lenses, and hence the composition, of the universe. The high redshift of many GRBs allows a unique probe of the density of star redshift of many GRBs allows a unique probe of the density of star formation rate during first few billion years of the universe. The formation rate during first few billion years of the universe. The quest to find a standard candle for GRBs, which could be used to quest to find a standard candle for GRBs, which could be used to confirm and calibrate the geometry of the universe, will be reviewed, confirm and calibrate the geometry of the universe, will be reviewed, along with the recent results. Analyses of GRB light curves allow a along with the recent results. Analyses of GRB light curves allow a probe of the light path for effects of quantum gravity, limits on the probe of the light path for effects of quantum gravity, limits on the energy dependence of the speed of light, and even intelligent life.energy dependence of the speed of light, and even intelligent life.

Talk Outline: GRBs and CosmologyTalk Outline: GRBs and Cosmology

Discovery of GRBsDiscovery of GRBs

What and where are GRBs?What and where are GRBs?

How can GRBs tell us about the universe?How can GRBs tell us about the universe?

Gamma-Ray Burst: A Milestone ExplosionAstronomy Picture of the Day: 2000 July 2

Credit: R. Klebesadel, I. Strong & R. Olson (LANL), Vela Project

The first gamma-Ray burst modelAppeared beforeThe Vela resultsWere published!

By 1992, over 100 models Existed!

Despite this Number, the Currently favoredModel is not on This list!

Table: Nemiroff, R. J. 1991, Comments on Astrophysics

On the 75th anniversary of the great debate between Curtis and ShapleyOn the Scale of the Universe, Bohdan Paczynski (left) and Donald Lamb (right) debated The Distance Scale to Gamma Ray Bursts in the sameAuditorium. Martin Rees (center) moderated. (Photo: Jerry Bonnell)

Credit: G. Fishman et al., BATSE, CGRO, NASA

BATSE GRB Final Sky Map: Astronomy Picture of the Day 2000 June 28

S 1

00

- 3

00

ke

V /

S 5

0 -

1

00

ke

V

90 % Width ( sec )

Soft

Hard

Two Duration Classes of GRBsTwo Duration Classes of GRBs

Gamma-Ray Burst DurationsGamma-Ray Burst Durations

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

A GRB 000301C SymphonyCredit: Andrew Fruchter (STScI) et al., STIS, HST, NASAAstronomy Picture of the Day 2000 March 14

Explanation: Telescopic instruments in Earth and space are still tracking a tremendous explosion that occurred across the universe. A nearly unprecedented symphony of international observations began abruptly on March 1 when Earth-orbiting RXTE, Sun-orbiting Ulysses, and asteroid-orbiting NEAR all detected a 10-second burst of high-frequency gamma radiation. Within 48 hours astronomers using the 2.5-meter Nordic Optical Telescope chimed in with the observation of a middle-frequency optical counterpart that was soon confirmed with the 3.5-meter Calar Alto Telescope in Spain. By the next day the explosion was picked up in low-frequency radio waves by the by the European IRAM 30-meter dish in Spain, and then by the VLA telescopes in the US. The Japanese 8-meter Subaru Telescope interrupted a maiden engineering test to trumpet in infrared observations. Major telescopes across the globe soon began playing along as GRB 000301C came into view, detailing unusual behavior. The Hubble Space Telescope captured the above image and was the first to obtain an accurate distance to the explosion, placing it near redshift 2, most of the way across the visible universe. The Keck II Telescope in Hawaii quickly confirmed and refined the redshift. Still, no one is sure what type of explosion this was. The symphony is not over - oddly no host galaxy appears near the position of this explosion. Will one appear as the din of the loud fireball fades?

Image Credit: S. Kulkarni, J. Bloom, P. Price, Caltech - NRAO GRB Collaboration

Gamma-Ray Burst, Supernova Bump: Astronomy Picture of the Day 2002 May 17

A Slow ExplosionAstronomy Picture of the Day: 2003 March 25

Credit: Y. Grosdidier (U. Montreal) et al., WFPC2, HST, NASA

Short Gamma-Ray Busts LocalizedAstronomy Picture of the Day: 2005 October 17

Illustration Credit : Dana Berry, NASA

On the Origin of Gold: Astronomy Picture of the Day: 2005 May 15

Credit & Copyright: Visualization: Ralf Kaehler (ZIB) & Tom Abel (Penn. State)Simulation: Tom Abel (Penn. State), Greg Bryan (Oxford) & Mike Norman (UCSD)

Zooming in on the First Stars Astronomy Picture of the Day 2003 June 10

RelationsRelations

Lag-Luminosity (Norris et al.): Lag-Luminosity (Norris et al.): L L -1.15-1.15

Variability-Luminosity (Fenimore & Ramirez-Ruiz, Variability-Luminosity (Fenimore & Ramirez-Ruiz, Reichart et al.):Reichart et al.): L L V V3.33.3

AtteiaAtteia NN/E/Eptpt/√T/√T9090 f(z) f(z)

Amati: Amati: EEptpt E Eisoiso1/21/2

Ghirlanda:Ghirlanda: EEptpt EE0.70.7

Yonetoku:Yonetoku: EEptpt L L1/21/2

From Nemiroff & Tilvi 2005, in preparation: E_peak corrected for redshiftStill appears to be a function of redshift.

Some Burst TerminologySome Burst Terminology

Ep is E of peak of E2N(E)f

Peak of lightcurve

Spectrum may be from lightcurve peak or entire burst (“fluence spectrum”)

Integrate spectrum for bolometric flux or fluence

Integrate over entire burst for total energy

Spiky-ness can be quantified

But GRBs at low BATSE peak fluxes do look similar.But GRBs at low BATSE peak fluxes do look similar.

Fraction of long-lag bursts increases Fraction of long-lag bursts increases approaching BATSE threshold.approaching BATSE threshold.

Long-lag bursts:- lags > 0.5s- tend to be dim- simple, few pulses (Stern, Poutanen & Svensson 1999)

- wide pulses- softer spectrum

A Main Sequence “HR Diagram for Gamma-Ray Bursts”

L53 ≈ 1.1 (lag/0.01 s)-1.15

Updated from Norris, Marani, Bonnell (2000). Woosley & MacFadyen (1999), Ioka & Nakamura (2001), others predicted subclass of numerous, nearby GRBs: low luminosity, soft-spectrum, long-lag.See Sazonov et al. (2004) for subluminous GRB 031203. See GCN 3484 (redshift, lag for GRB 050525).

970228

000131

991216

031203

Beamed Burst EmissionBeamed Burst Emission

External shock—origin of afterglow

Internal shocks—origin of burst

Central Engine

Break in lightcurve resulting from jet’s finite width; modeling gives

Possible Central Engine Possible Central Engine Unified ModelUnified Model

SN IISN II MMprogprog > 10 M > 10 Moo NSNS

Long GRB & SNIcLong GRB & SNIc MMprogprog> 20 M> 20 Moo NS + SN fallback to BHNS + SN fallback to BH

Dark CollapseDark Collapse MMprogprog > 40 M > 40 Moo BH direct, no SNBH direct, no SN

Long GRBLong GRB MMprogprog > 40 M > 40 Moo + some spin + some spin BH + GRBBH + GRB

Short GRBShort GRB NS+NS merger ???NS+NS merger ???

From Gehrels, N., 2004, GSFC presentation

Credit: Nemiroff et al. 2001, PRL 86, 580

Millilensing Candidate GRB: BATSE Trigger 5457

Limits on Universe abundance of Compact Objects: Entire BATSE Sample

Credit: Nemiroff et al. 2001, PRL 86, 580

• GRB pulse structure at GeV energies + Gigaparsec distances may constrain EQuantum Gravity ~1019GeV

• Amelino-Camelia et al. (1998) predict energy-dependent dispersion:

v c{1 - Ephoton/EQG)}

• t = (1 GeV/EQG)(1 Gpc/c) ~ 10 ms

• LAT could look for the predicted energy- and distance-dependent effects.

Lorentz Invariance Violation: Bounds on the energy dependence of the speed of light can constrain the effective energy scale for quantum gravity effects.

GRB as SETI MarkersGRB as SETI Markers

Search for ET signals in direction of GRBs Search for ET signals in direction of GRBs just after GRBjust after GRB

Send an ET-like signal in the opposite Send an ET-like signal in the opposite direction of a GRB, just after a GRBdirection of a GRB, just after a GRB

Identifies unique angles and times on the skyIdentifies unique angles and times on the sky

Might be found serendipitously by ETs Might be found serendipitously by ETs studying GRBsstudying GRBs

See: Corbet, R. H. D. 1999, PASP, 111, 881:See: Corbet, R. H. D. 1999, PASP, 111, 881:

X-Ray Rings Expand from a Gamma Ray Burst Astronomy Picture of the Day 2004 January 30

Credit: S. Vaughan, R. Willingale (U. Leicester) et al., XMM, ESA