Ariel Majcher Gamma-ray bursts and GRB080319B XXIVth IEEE-SPIE Joint Symposium on Photonics, Web Engineering, Electronics for Astronomy and High Energy Physics Experiments Wilga, May

Outline Introduction to gamma-ray bursts GRB080319B observations and model “Pi of the Sky” GRB observations

Gamma-ray Bursts short (0.1 – 100 s) impulses of gamma radiation point sources discovered in 1967 by Vela satellites the most powerful phenomena in the Universe energy of burst reaching ergs (over years of current sunshine) isotropic distribution on the sky 2 – 3 bursts a day, 1/3 registered by satellites nearly 50% have optical counterparts recent models: long burst (longer than 2 s) – massive star dying in hypernova explosion, short burst (the rest) – collision of compact objects in double systems

Gamma- Ray Bursts BATSE instrument on board satellite CGRO in years 1991 – 2000 discovered and measured 2704 GRB observations of optical counterparts (Beppo – SAX in 1997) and redshifts measurements confirmed extragalactic origin currently most distant GRB (GRB090426) is z = 8.2 (13.6 billion light years)

Fireball model Γ ~ 100 JET OPENING ANGLE ~ a few degrees Synchrotron radiation and SSC

Methods of observations (reaction on GCN alerts) INTEGRAL FERMI SWIFT RAPTOR ROTSE TAROT PROMPT

Optical counterpart of GRB observations Gamma-Ray bursts Coordinates Network information about burst and his position is passed from satellites to telescopes on Earth (time of reaction: second to minutes) there are only a few bursts for which optical and gamma observations were made simultaneously What should be improve? time of reactions (no one knows when and where next burst will occur) time resolution

Search for prompt optical emission GRB fortunately in ROTSE FoV GRB optical observations triggered by precursor GRB080319B observations triggered by GRB080319A

A naked-eye burst GRB080319B

On 5:42:45 UT first burst GRB A occured on position:  = 13 h 45 m 25 s  = +44 o 04'22'' “Pi of the Sky” cameras swung to this burst.

A naked-eye burst GRB080319B On 5:42:45 UT first burst GRB A occured on position:  = 13 h 45 m 25 s  = +44 o 04'22'' “Pi of the Sky” cameras swung to this burst.

A naked-eye burst GRB080319B On 5:42:45 UT first burst GRB A occured on position:  = 13 h 45 m 25 s  = +44 o 04'22'' “Pi of the Sky” cameras swung to this burst. On 6:12:49 UT second burst GRB B occured on position:  = 14 h 31 m 42 s  = +36 o 18'10'' It was so close to first burst, that it fitted in “Pi of the Sky” field of view.

A naked-eye burst GRB080319B found automatically by on-line algorithm for optical flashes search maximum brightness 5.3 mag (visible to naked eye) the brightest ever observed GRB in optical and X range redshift (7.5 billion light years) unprecedented coverage of light curve published in Nature 11 Sep 455 No. 7210

prompt optical and γ-ray emission starts and ends at the same moments Optical (TORTORA) and γ-ray peaks are correlated

Mechanisms of radiation production optical emission from synchrotron radiation γ-ray from synchrotron self-compton expected: significant second order synchrotron self-compton GeV component, but could not be observed by AGILE due to Earth occultation (GLAST / FERMI not yet on the orbit). THIS COULD CARRY MOST OF THE ENERGY!

Unprecedented coverage of light curve

Huge Lorentz factor Γ ~ 10 3 Two – jets model was fitted It can happen in other GRBs, but narrow jet aims to the Earth very rarely

Broadband observations: 11.5 orders of magnitude in wavelength, 8 orders in flux, 6 orders in time... 0 < T<50s prompt emission internal shocks in narrow jet 50s < T< 800s reverse shock of wide jet T > 800s external forward shock of wide jet on ISM

GRB080319B summary long GRB (T 90 ~ 57 s) redshift (distance 7.5 billion light years) optically and in X-ray brightest object ever discovered also intrinsically brightest ever optical object total energy E , iso ~1.3x ergs in 20 keV – 7 MeV (among highest) jet corrected energy ~4x10 50 ergs (moderate) Why it was so bright? unusually huge Lorentz factor Γ ~ 10 3 narrow jet pointing toward the Earth (probability ~ = one over 1 – 3 years)

What can we learn from GRB080319B? features observed in GRB080319B were observed in other bursts, but separately maybe 2-jets structure is a common feature, but in most cases we see only wider jet; this could explain for example chromatic breaks (optical and X-ray) if GRB080319B was observed slighty off-axis it would be very similar to other bursts

2 + 2 inside FoV, limits before / during / after GRB080319B (GCN 7439): < 11. m 5 / max ~5. m 3 / GRB (GCN 6437): < 12. m 2 / < 12. m 6 / < 12. m 5 GRB (GCN 3240): < 11. m 5 / < 11. m 0 / < 11. m 5 GRB040825A (GCN 2677): < 10. m 0 / < 12. m 0 / < 9. m 5 “Pi of the sky” GRB observations (without FERMI's alerts) GRBs observed since June 2004 to July 2005 and since June 2006 until now outside FoV, 10 GCN published GRB (GCN 8707): < 12. m 5 GRB (GCN 8063): < 12. m 5 GRB (GCN 5891): < 14. m 0 GRB (GCN 5346): < 12. m 5 GRB (GCN 5241): < 13. m 4 GRB (GCN 3526): < 12. m 5 GRB (GCN 3146): < 11. m 0 GRB (GCN 2970): < 12. m 0 GRB (GCN 2862): < 11. m 5 GRB (GCN 2725): < 13. m clouds or apparatus off daytime or below horizon

Thank you for your attention