GRB050502B optical and X-ray light curves

Paulo Afonso

Working with:

Jochen Greiner, Elena Pian, Aybüke Yoldaş

- with the collaboration of Daniele Malesani, Stefano Covino, Thomas Krühler

Schloss Ringberg meeting

21-2-2008

Paulo Afonso - Schloss Ringberg, 21-2-2008

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Bright x-ray flares are superposed on underlying power-law decay (solid line). Possible jet break at ~ 1 day (100 000 sec) postburst. From Burrows et alia, 2005

Paulo Afonso - Schloss Ringberg, 21-2-2008

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Conspicuous characteristics

• X-Ray flare has ~ same energy (~9x10-7 erg/cm2, 0.3-10 keV) as the prompt emission observed by BAT (~8x10-7 erg/cm2, 15-350 keV). This was never observed before!

• Early fainter afterglow than other XRT-detected, but rapid brightening several minutes later

• Bumpiness continues at late-time, before decaying back to preflare fluxes (Burrows et al, 2005)

Paulo Afonso - Schloss Ringberg, 21-2-2008

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Explanations/models

• Continued activity in the internal engine is required – not associated with the afterglow external shock, because:

• Rise and decay times of flare are very fast

• The afterglow started already before the flare (same time decay index before and after flare)

• Later bumpiness not so easy to explain: maybe internal engine & afterglow shock together (Falcone et al., 2006)

Paulo Afonso - Schloss Ringberg, 21-2-2008

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But things are more complex: flares, plateaus, chromatic breaks. (Figure from Panaitescu, 2007)

Paulo Afonso - Schloss Ringberg, 21-2-2008

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Work in progress: reduce data again, for better optical photometry

Preliminary light curve:

Data points from TNG and ANU.

Note steep decay at t~ 1 day in the I-Band.

Time correlation with end of 2nd X-ray flare?

Paulo Afonso - Schloss Ringberg, 21-2-2008

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Final science image

(combining 2 images)

TNG 1for I band.

Problems:bad pixels,

fringing effects

Paulo Afonso - Schloss Ringberg, 21-2-2008

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TNG 3 final science

image for I band.

Glare: due to problem in

automatic flat

procedure.

Paulo Afonso - Schloss Ringberg, 21-2-2008

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TNG 1 Vs. TNG 3 – fringes “disappear” because of higher number of combined science images. Normally a higher number is

required for successful removal of fringes. We are looking for more data in archives of TNG right now.

Paulo Afonso - Schloss Ringberg, 21-2-2008

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TNG2 I band – fringes removed with just 2 individual images

Paulo Afonso - Schloss Ringberg, 21-2-2008

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TNG3 I band – even with many individual images, removal of fringing seems now more effective

Paulo Afonso - Schloss Ringberg, 21-2-2008

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TNG2 I band without fringes: very first crude

photometry – not so bad!

In this image:

22.33 +/- 0.27

former image:

22.10 +/- 0.16

Paulo Afonso - Schloss Ringberg, 21-2-2008

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Next steps – ongoing work:

• Fringe effects removal/reduction on TNG1

• Photometry of TNG3 – very faint object!!?

• Photometry of TNG2 R band

• Use of further TNG archive images to make better fringe patterns