Daisuke YONETOKU (Kanazawa Univ.) T. Murakami (Kanazawa Univ.),R. Tsutsui, T. Nakamura (Kyoto Univ.),K. Takahashi (Nagoya Univ.)

The Spectral Ep–Lp and Ep–Eiso Relations:

The Origin of Dispersion and Its Improvement

yonetoku@astro.s.kanazawa-u.ac.jp

GRB Cosmology Project

102 known redshift samples with ( Ep, 1 sec peak flux, fluence ).Lp is calculated by 1 sec peak flux in the obs. frame.

νFν

∝ Eα

∝ Eβ

ピークエネルギー (Ep)

Briggs et al. 2000

■ Application for the GRB Cosmology■ Investigate the characteristic of GRB itself

Introduction

C.C. = 0.890d.o.f. = 100

Tully-Fisher Relation (Rotation–Luminosity)

Type Ia Supernovae

HR diagram

Cepheid Variable(Period–Luminosity)

parallaxredshift

z = 1.755

Cosmic Distance Ladder (Distance Indicators) When we measure the energy density of D-E and D-M,

we need “distance” and “redshift” relation.

Just after the Big B

ang (CM

B)

L ≡ 4πdL2 F

　 Gamma-Ray Bursts 　 　z = 8.2 !

z = 1.755

Calibrated Epeak-Luminosity relation52 GRBs （ z<1.755 ）

Epeak(1+z) [keV]

Pea

k Lu

min

osity

[1051

erg

/sec

]

Lp = 5.93 x 1047 [ Epeak (1+z) ]1.85

5.93 x 1047 [ Epeak (1+z) ]1.85

4πFdL 2 =

Redshift

Lum

inos

ity D

ista

nce

(cm

)10

2610

2710

2810

29

0.01 0.1 1 10

Type Ia SNe New!GRB

CalibratedGRB

Hubble Diagram ( 1.8 < z < 8.2)■ GRB data (z < 1.755)■ GRB data (1.755 < z < 8.2)＋ Type Ia SNe

(Ωm, ΩΛ) = (1, 0)

(0.3, 0.7)

(0, 1)

z = 8.2

ΩΛ

Cosmological Parameters (1.8 < z < 8.2 )D

ark

Ene

rgy

: ΩΛ

Matter : Ωm

( 0.24±0.10 , 0.76±0.10)(Ωm, ΩΛ) =

First Measurement of DM & DEin the early universe of z > 2.

Tsutsui, DY + (2009)

( flat universe )

Poster-094Tsutsui et al.

Origin of Data Dispersions

Peak Flux Redshift

We classified 102 GRB events into 3 groups,according to the bolometric peak flux and the redshift.

We found a redshift evolution in the Ep-Lp relation in 2 s significance, but there is no peak flux dependence.

Ep-Lp Ep-LpBrightMiddleDim

High-zMiddle-zLow-z

We systematically overestimate the peak luminosityfor higher redshift GRBs.

Rel

ativ

e P

eak

Flux

in O

bs. F

ram

e

Time Scale of Peak Flux (sec)

64msec512msec

1024msec

Redshift Evolution ?

1sec@ z=0

1sec@ z=1

1sec@ z=2

Original Ep – Lp

58 GRBs Konus & Swift

~ 3 sec

31 Konus data

2088 msec ~ 3 sec

Redefinition of the peak luminosity ( Lp,GRB )

We searched the best time scalefor the peak luminosity in the GRB frame.

Time Scale of Peak Luminosity in GRB Frame (sec)

Cor

rela

tion

Coe

ffici

ent

Lp = 1048.70 [ Ep(1+z) ]1.46

Deviation : σsys = 0.213

1sec Peak Luminosity ( measured in Obs. frame )

Cor. Coef = 0.890

Ep (1+z) [keV]

Pea

k Lu

min

osity

[erg

/sec

]

Lp = 1048.18 [ Ep(1+z) ]1.53

Deviation : σsys = 0.180

3sec Peak Luminosity (measured in GRB frame )

Cor. Coef = 0.921

Ep (1+z) [keV]

Pea

k Lu

min

osity

[erg

/sec

]

Fluence Redshift

Ep-Eiso Ep-Eiso

We found a fluence dependence in the Ep-Eiso relation in 2 s significance, but there is no redshift evolution.

Similar analysis for the Ep – Eiso relation.

BrightMiddleDim

High-zMiddle-zLow-z

■ We measured the cosmological parameters,

1.755 < z < 8.2( 0.24±0.10 , 0.76±0.10 )(Ωm, ΩΛ) =

■ We succeeded in extending the cosmic distance ladder toward z=8.2 with the Ep – Lp relation.

Redshift evolution

Peak Flux/Fluence Dependence

Ep – Lp Yes (2s C.L.) NoEp – Eiso No Yes (2s C.L.)

■ Possible origins of data dispersion

■ Using the NEW definition of “Lp,GRB (~ 3sec in GRB frame)”, we succeeded in canceling the redshift evolution, and in improving the Ep – Lp relation.

Summary