Prompt optical observations of GRB 080330 and GRB 080413A

Background & Motivation

• Growing number of early optical afterglow observations– Collective study of temporal behavior– Panaitescu & Vestrand 2008: peak time and peak flux

correlation

• Growing number of prompt optical observations– Some show complicated behavior, GRB 08330 and GRB

080413a– Multiple components from both internal and external

shock?– Start from the better-understood afterglow part

2008 Mar. 30, 03:41:39.2

22.4 s after the burst (7.2 s after the GCN notice time)

Schaefer & Guver, GCN 7538

2008 Apr. 13, 02:54:39.7

20.4 s after the burst (6.7 s after the GCN notice time)

Rykoff & Rujopakarn, GCN 7593

2008 Mar. 30, 03:41:39.2

22.4 s after the burst (7.2 s after the GCN notice time)

Schaefer & Guver, GCN 7538

2008 Apr. 13, 02:54:39.7

20.4 s after the burst (6.7 s after the GCN notice time)

Rykoff & Rujopakarn, GCN 7593

2008 Mar. 30, 03:41:39.2

22.4 s after the burst (7.2 s after the GCN notice time)

Schaefer & Guver, GCN 7538

2008 Apr. 13, 02:54:39.7

20.4 s after the burst (6.7 s after the GCN notice time)

Rykoff & Rujopakarn, GCN 7593

GRB 080330

GRB 080330

GRB 080413a

GRB 080413a

Slowly decaying afterglow

• Structured flow viewed off-axis?

• Drowned by prompt emission in X-ray?

Panaitescu & Vestrand 2008

• Eγ,iso = 5.0 x 1051 erg

• γ = 2.5 +/-0.5

• tpeak ~ 150 s

• Γ0 ~ 200

(Sari & Piran 1999, Molinari et al. 2007)

• Can be classified as XRF(Sakamoto et al. 2008, Mao et al. 2008)

• Eγ,iso = 1.7 x 1053 erg• γ = 1.5 +/-0.1

• tpeak ~ 30 s• Γ0 ~ 600

Rising of afterglow

‘Prompt’ optical flash

Other ROTSE-III events

• Eγ,iso = 3.1 x 1051 erg• γ = 1.9 +/-0.1

• tpeak ~ 200 s• Γ0 ~ 150

• Eγ,iso = 4.2 x 1053 erg• γ = 1.1 +/-0.0

• tpeak ~ 40 s• Γ0 ~ 600

Rykoff 2008 in preparation

Summary

• ‘Prompt’ optical component – Need better sampling– Complicated by early afterglow– Better understanding of the afterglow phase will help

• Low Lorentz factor events– Delayed afterglow peak– Easier to observe the peak and shape of the early lightcurve

Next with ROTSE-III

• More interesting events from Swift (sub-threshold triggers)

• GLAST launched• ROTSE supernova verification project• Follow-up of IceCube neutrino doublet triggers

Thank you!

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