Statistical properties of a sampleof serendipitous X-ray sources in

deep Swift GRB pointingsPaolo Giommi

ASI

Swift observationsarchive content as of June 2008

• 14,500 observations• 3,380 distinct pointings• ~300 sq deg of sky (< 1%)

Unique database of optical/UV X-ray simultaneous data

More than 300 GRB detected and followed up for several days/weeks with the X-ray Telescope

Swift XRT serendipitous sources in GRBs pointigs :the “perfect” serendipitous survey

Most X-ray sourcesare radio quiet QSOsOnly ~1 blazar/fieldexpected withradio flux > 10 mJy!

Energy spectral slope

235 deep (104-106 seconds) GRB exposures analyzed

~7,600 sources detected with off-axis < 10 arcminPositional uncertainty 3-5 arcsecs.

160 fields are at |bII| > 20 : ~5,600 sources156 radio/X-ray matches (blazar candidates)

Swift XRT serendipitous survey in GRB deep fields

The sample for this exercise5 fields in areas of the sky

covered by the Sloan Digital SkySurvey (SDSS)

240 X-ray sources

GRB 050416AGRB 050416BGRB 060908GRB 060904AGRB 050802

The sky coverage

www.asdc.asi.it/urbinoschool

Multiple Optical Counterparts(Likelihood Ratio)

- Photometric Redshifts calculation

55

X-ray/radio associations match 107 SDSS-DR6

objects(10 spectra)

Optical counterpartsOptical counterpartsin the SDSS-DR6in the SDSS-DR6

Turriziani et al. 2008, in preparation

Photometric redshiftdistributions