Constraining the Properties of Dark Energy Using GRBs

D. Q. Lamb (U. Chicago)

High-Energy Transient Explorer Swift

Department of Astronomy, Nanjing University Nanjing, China, 27 July 2006

The Long and Short of It

Hurley (1991); Lamb, Graziani, and Smith (2003); Kouveliotou et al. (1993)

Short GRBs

Long GRBs

GRB 050709: Accurate LocalizationGRB 050709: Accurate Localization

HETE-2 IPC error circle on Chandra image, showing X-ray afterglow

HST image showing optical afterglow and host galaxy w. Chandra X-ray error circle

Images courtesy of D. Fox

Movie of HST ImagesMovie of HST Images

Movie courtesy of D. Fox

GRB 050709: “Solid Gold” EventGRB 050709: “Solid Gold” Event

Some observational “firsts”: First observation of optical afterglow of short GRB First secure identification of host galaxy First secure measurement of distance to short GRB First determination of where in host galaxy burst occurred

Implications Burst occurred in dwarf irregular galaxy undergoing some

star formation Energy and luminosity of this short GRB is ~ 103 times smaller than for long GRBs No supernova down to very faint limits (R > 27) Properties of long, soft bump imply burst occurred in low-

density environment Prompt emission is jet-like

GRB 050724: Also a “Gold Plated” BurstGRB 050724: Also a “Gold Plated” Burst

Berger et al. (2005)

Swift XRT detection of X-ray afterglow led to discovery of optical afterglow and host galaxy

Kulkarni & Cameron

Red elliptical galaxyz = 0.258L =1.6 L*

SFR < 0.03 M yr-1

GRB 050724: Host GalaxyGRB 050724: Host Galaxy

Evidence That Short GRBs Come Evidence That Short GRBs Come from Mergers of Compact Objectsfrom Mergers of Compact Objects

Short GRBs come from outskirts of star-forming galaxies or from elliptical galaxies – unlike long GRBs which all come from brightest star-forming regions in their host galaxies

No supernova component seen in optical afterglow down to very faint limits – unlike long GRBs for which such components are seen for all bursts with z < 0.5

Luminosity L and isotropic-equivalent energy Eiso

factor 100-1000 smaller than for long GRBs Ambient densities of some short GRBs very low, as

expected if they lie in outskirts of their host galaxy

– these properties are exactly those expected if short GRBs come from mergers of compact objects

Binary Coalescence

1

Collapsar

Magnetar

1

1 1 1

Energy Density Host Offset No SNe

1

1 0 00

0

1

0 0

1

Progenitor ScorecardProgenitor Scorecard

Slide courtesy of D. Frail

Short GRBs Emit Short GRBs Emit Strong Gravitational WavesStrong Gravitational Waves

Slide courtesy of D. Frail

Short GRBs as Standard SirensShort GRBs as Standard Sirens

Detection of gravitational waves gives absolute luminosity distance dGRB to short GRB

This plus distance dCMB to surface of last scattering of CMB means that accurate determination of H0 = cz/dGRB provides strong constraint on dark energy

To see this, consider a flat univers (i.e., a CMB prior) and a constant w; then ΩDE = 1 – ΩM, and only parameters are h, ΩM, and w

CMB provides 2 (dCMB, ΩMh2); short GRBs provide h

Constraints are not degraded by gravitational lensing, as those from Type Ia SNe and long GRBs

K.Thorne / NSF Review Figure courtesy of D. Fox

Detectability of Gravitational Waves Detectability of Gravitational Waves from Short GRBsfrom Short GRBs

Detection of Short GRB gives tmerger, (RA,Dec), andinclination angle i of binary relative to plane of the sky, which increases sensitivity of LIGO y factor ~ 3

Determination of DDetermination of D

Dalal, Holz, Hughes, and Jain (2006); DQL et al. (2006)

Uncertainties in Uncertainties in ww and and hh

Dalal, Holz, Hughes, and Jain (2006); DQL et al. (2006)

Only 200 short GRBs can give accuracy of 0.006 in hand 0.03 in w!

Constraints on Constraints on ww for Different Jet Opening Anglesfor Different Jet Opening Angles

Dalal, Holz, Hughes, and Jain (2006); DQL et al. (2006)

θjet < 20o Isotropic emission

The Long and Short of It

Hurley (1991); Lamb, Graziani, and Smith (2003); Kouveliotou et al. (1993)

Short GRBs

Long GRBs

Schematic Picture of GRB Jets

Peter Meszaros

GRBs Come From Narrow Jets

Frail et al. (1999)

Bulk motion of jet is v = 0.999 c, so special relativistic beaming is dramatic Optical light decreases when jet slows down and we begin to see beyond edge of jet

Type Ia-SN—Like Relation Type Ia-SN—Like Relation Exists Between E Exists Between Eγγ and and

EEpeakpeak

Epeak

Eγ

Ghirlanda et al. (2004)

Empirical Relation Exists Empirical Relation Exists Between Between EEpeakpeak--EEisoiso--ttbreakbreak

Liang and Zhang (2005); Ghirlanda et al. (2006)

Hubble Diagram for Type Ia SNe and GRBsHubble Diagram for Type Ia SNe and GRBs

Before “standard candle” calibration

After “standard candle” calibration

GRB Hubble DiagramGRB Hubble Diagram

Xu, Dai, and Liang (2005)

GRB Constraints on Dark EnergyGRB Constraints on Dark Energy

Xu, Dai, and Liang (2005)

Definition of Emission Duration TDefinition of Emission Duration Temem

Reichart, Lamb, Fenimore, Ramirez-Ruiz, Cline, and Hurley (2001)

Comparison of TComparison of Temem and T and T9090

Donaghy, Graziani, and DQL (2006)

Tem,50 (Tem,90) values are similar to T50 (T90) values Tem is robust to energy range and choice of f Tem can more easily be transformed to burst rest frame

Comparison of Ghirlanda et al. (2004) and Firmani et al. (2006) Relations

Firmani et al. (2006)

Constraints on ΩConstraints on ΩMM and Ω and ΩDEDE

Firmani et al. (2006)

SNe Ia

SNe Ia + GRBs

Constraints on Dark Energy Constraints on Dark Energy EOS Parameters EOS Parameters ww00 and and ww11

Firmani et al. (2006)

SNe Ia

SNe Ia

SNe Ia + GRBs

SNe Ia + GRBs

Spectra of Gamma-Ray BurstsSpectra of Gamma-Ray Bursts

GRB SpectrumPeaks in Gamma - Rays

XRF Spectrum Peaks in X-Rays

Epeak

Epeak

XRFs Satisfy Firmani et al. (2006) RelationXRFs Satisfy Firmani et al. (2006) Relation

DQL et al. (2006)

Low-z GRBs Are Vital to Constraining Low-z GRBs Are Vital to Constraining Properties of Dark EnergyProperties of Dark Energy

Ghirlanda et al. (2005)Ghirlanda et al. (2005)

Mostly GRBs w. z > 1 GRBs w. z > 1 + XRFs w. z < 0.5

GRB Dark Energy GRB Dark Energy Mission Concept StudyMission Concept Study

ConclusionsConclusions

Short GRBs can be used as “standard sirens” to constrain properties of dark energy

Long GRBs can be used as “standard candles” to constrain properties of dark energy

With Firmani et al. (2006) relation, need only satellite that can detect prompt emission

In former case, need efficient detection and accurate localization of short GRBs

In latter case, need efficient detection and accurate localization of long GRBs, plus broad energy response in order to determine Eobs

peak and Liso

Important open question is “What is the size of systematic errors?”