The afterglow and host galaxy of GRB 090205:

evidence for a Ly-α emitter at z = 4.65

Paolo D’Avanzo (INAF-Osservatorio Astronomico di Brera);

in collaboration with:

GRB 090205

0.5-10 keV

15-350 keV

T90 = 8.8 ± 1.8 s

No UVOT detection @ t-t0 = 92 s

Perri et al. 2009, GCN 8884Evans et al. 2009, GCN 8885Perri & Stratta, 2009, GCN 8891

Perri et al. 2009, GCN 8884Landsman & Perri, 2009, GCN 8893

Perri et al. 2009, GCN 8884Cummings et al. 2009, GCN 8886

GRB 090205

RAB ~ 22.3; IAB ~ 20.8(D’Avanzo et al. 2009;, GCN 8887)

F(t) t -α ; α ~ 1.4

t-t0 ~ 7 h

GRB 090205

z =4.65(Thoene et al. 2009, GCN 8889; Fugazza et al. 2009, GCN 8892)

RAB ~ 22.3; IAB ~ 20.8(D’Avanzo et al. 2009;, GCN 8887)

F(t) t -α ; α ~ 1.4

t-t0 ~ 7 h

GRB 090205 afterglowtb,1 tb,2

α1

ГX,1

α2

ГX,2

α3

ГX,3

F(t) t -α

α1 ~ 1.4; α2 ~ -1.7; α3 ~ 1.2;

Time resolved X-ray spectroscopy: absorbed power-law withГX,1~ ГX,2~ ГX,3~ 2.0Galactic NH ~ 8 x 1020 cm-2 (no evidence for intrinsic absorbtion; NH < 3.5 x 1022 cm-2)

X-ray and optical AG explained within the standard FS model with νc,νm < νopt and νX

X-ray “brightnening” possibly due to energy injection into the FS by the engine

complex X-ray AG: brightening at ~T0+1000s and flaring

activity

GRB 090205: classification

Ch1 = 15-25 keVCh2 = 25-50 keVCh3 = 50-100 keVCh4 = 100-350 keV

Eγ,iso = (7.86 ± 1.21)x 1051 ergEp,i = 192 ± 85 keV

Lag(Ch2-Ch1): -15 +/- 867 ms Lag(Ch3-Ch2): 648 +/- 1336 ms Lag(Ch3-Ch1): 705 +/- 1326 ms

T90,rf = 1.6s

GRB 090205: classification

Ch1 = 15-25 keVCh2 = 25-50 keVCh3 = 50-100 keVCh4 = 100-350 keV

Eγ,iso = (7.86 ± 1.21)x 1051 ergEp,i = 192 ± 85 keV

Lag(Ch2-Ch1): -15 +/- 867 ms Lag(Ch3-Ch2): 648 +/- 1336 ms Lag(Ch3-Ch1): 705 +/- 1326 ms

Consistent with the

Ep,i - Eγ,iso

correlation (Amati et al.

2008)

GRB 090205

T90,rf = 1.6s

(Antonelli et al. 2009)

GRB 090205: evidence for a LAE (I)

GRB 090205: evidence for a LAE (I)

Lyman-α emission line

GRB 090205: evidence for a LAE (II)

0.4” offset with respect to the continuum(3 kpc @ z=4.65)

The same offset is found in imaging framesLy-α emission from the host galaxy

Farthest GRB host galaxy spectroscopically confirmed

Lyman-α emission line

GRB 090205 host galaxy

LLy-α ~ 0.6-0.7 L*

SFR ~ 4.2 MSun/yrZ ≥ 0.27 ZSun

τ < 150 MyrM* < 150 MSun

GRB 090205: conclusions

• optical afterglow and host galaxy discovery; redshift determination

• complex X-ray AG: brightening at ~T0+1000s and flaring activity

•rest frame short duration (1.6s), but likely long, of massive stellar collapse origin

• the host galaxy is a LAE @ z = 4.65• SFR ~ 4.2 MSun/yr• young stellar population (< 150 Myr) • high metallicity (Z ≥ 0.27 ZSun) • farthest GRB HG spectroscopically confirmed

• GRBs as one of the most effective way, complementary to surveys, to study the high-z Universe

D’Avanzo et al., A&A submitted