This utility searches for the desired source (by name or coordinates) for data from the HEASARC Data Archive. If usable images are found in the archive, a cropped image of desired radius is displayed centered on the object of interest (along with the corresponding exposure map region, if possible).

In order to run quickly, source "detection" is simply taking the position of the brightest pixel of the smoothed image (the original image is used in flux and significance calculations). At the moment the spectrum is hard-coded to be a power-law with a photon index of 1.8, but with the Galactic column to the source. The detection probability is also the confidence limit used in computing upper-limits. A long-term light curve is produced if more than 2 detections are found, with an assumed minimum flux error of 20% (i.e., dominated by systematic error). If an exposure map is found in the archive, it is used in computing the count rates. Otherwise, if a background image is found it is converted into an exposure "mask" in which all points with a bgd. level > 50% of the maximum are set to the exposure time.

Note: ASCA support is experimental at the moment but should be good enough for proposal purposes.

This is a simplified version of the full XAssist system which will handle "details" properly such as detecting serendipitious sources (and excluding them from background regions), deriving fluxes using the spectrum of each source, etc.

Please be patient after hitting submit. The speed of the results is dependant on the current speed of the HEASARC http and ftp sites and how many images there are for each search target. It may take a few moments for the results to be displayed. If you continuously get no results even after waiting a considerable time, please send an email to help@xassist.org with detailed information on the problem.