25s detection of the Sy1 galaxy NGC3516 The Palermo BAT survey project Application to a sample of SDSS LINERs V. La Parola, A.Segreto, G. Cusumano, V. Mangano, P. Romano (INAF-IASFPa) Introduction. The Burst Alert Telescope (BAT) onboard Swift is a highly sensitive, large FOV instrument designed to provide critical GRB triggers and 4-arcmin positions. It is a coded aperture imaging instrument with a 1.4 steradian field-of-view (half coded, in the keV energy range). While waiting for new GRBs, it continuously collects spectral and imaging information in hard X-rays and accumulates data in “survey” mode covering a fraction between 50 and 80% of the sky every day. The data are immediately made available to the scientific community in the public Swift data archive. The project We are exploiting the BAT survey data through a systematic search for new hard X-ray sources. To this aim, we have developed the BatImager, a dedicated software, completely independent from the official one, to process the BAT survey data. The code The BatImager provides mosaic reconstruction of the observed sky using appropriate data selection; identification and fine localization of hard X-ray sources after accurate modelling of the non-uniform background distribution and correction of the instrumental systematics; cross correlation with hard X-ray catalogs; subtraction of the detected sources from the skymap and further detection process on the “cleaned” mosaic. This last step allows the detection of faint sources, ensuring a highly efficient correction for the contamination of bright sources in the field of view. A complete description of the software and its performance will be presented in Segreto et al. 2008, in preparation. The code has been fully tested and run over the first 2.5 years of the BAT survey data in five energy bands (15–30 keV, 15–70 keV, 30–70 keV, 70–150 keV, 15–150 keV), retaining the value of 4.8 as significance threshold for source detection. This run resulted in the detection of 350 sources that can be identified with objects found in the most recent INTEGRAL catalogue (Bird et al. 2007, ApJS, 170, 175) and in the BAT catalogues compiled by Tueller et al.(2007, arXiv: ) and Ajello et al (2007, arXiv: ), plus several unidentified sources, for which XRT follow up observation are already planned. An example of application We have applied the BatImager to the first 2.5 years of the BAT survey data, optimizing the run for a complete sample of 43 SDSS/LLAGN that have been already accepted as fill-in targets for Swift-XRT (in the keV band). The aim is to have a database of X-ray detection and/or upper limits for the optically selected sample. While the X-ray analysis is still ongoing, we have searched for these sources in the BAT survey archive, assessing the upper limit to their emission in the keV band in the flux range x erg s -1 cm -2. This is an extreme case that demonstrates how our method can be easily applied to any sample of sources. As a comparison, we show the image of the nearby Sy1 galaxy NGC 3515, detected at 25  One of the mosaics at three different zoom levels, showing the position of two sources in the sample. Bat survey view of the Galactic center Contact: Left: Percentage of sky covered as a function of the limiting flux. Right: 5  sensitivity as a function of the exposure Map of the total 2.5 yrs effective exposure over the whole sky. The Galactic Center and Anticenter and the Ecliptic plane are under- exposed due to pointing constraint. Distribution of the SDSS targets over the sky (aitoff rojection, equatorial coordinates),superimposed on the 5  limiting flux (mCrab) after 2.5 yrs.