The input image

The image is expected to be a typical, square, photon count image, that is, a FITS file containing an NxN array of integer numbers.

The image is expected be sparse, i.e., with a majority of pixels being empty, as what a typical X-ray image is like. The performance of EXSdetect in case of very dense image (with a very long exposure time) is not under well control.

Attention should be make to reprojected images, in which one count from one pixel may be redistributed into a few neighboring pixels during the reprojection, resulting in float pixel values. If you want to use combined image from different observations, please combine the event files and make an image from the combined event file rather than combine the images, so as to avoid image reprojection and guarentee integer values in the image.


-e, --expmap expmapfile(required)

Input exposure map file.

-b, --bkg Bkg value or Bkg region (optional) default=None

Set the "Bkg" parameter.

If Bkg==None (default) the default background measurement method will be applied. If it fails in some special cases, the background can be set manually in the following two ways.

1. If a value is given, the background is assumed to be uniform and the value is taken as the average background flux. Multiplying this flux by the exposure map gives rise to the background map.

2. If a region file is given, the average background is calculated from the user specified regions of the input image, taking account of the exposure map if given.

Background region file definition

If a ds9 region file is given, it must contain only some circles, and must be saved in "image" coordinate system. If circles marked as background are found, they are taken as background regions. Or else the circles are regarded as source regions, and the source-free region is defined as background sampling region.

If a fits image file is given, the filled (>0) pixels are taken as the source regions and the empty (=0) pixels background.

-i, --instrument SWIFT / CHANDRA (optional)

Now only "SWIFT" is supported.

By default, it reads the TELESCOP key from the image header.

-o, --outfile string (optional)

Set the output file name, which by default is is "exs_src"

See EXSdetect Output for details.

-p, --pixelsize Pixel Size in arcsec (optional)

By default, it is calculated using the CDELT1 and CDELT2 keys from the image header. The image is assumed to be a square, that is, abs(CDELT1)==abs(CDELT2).

--coreradius Core Radius in pixels (optional)

The default core radius is 5 pixel sizes. All the parameters associated with source classification were optimized on the basis of this parameter. So do not change it until you want to run simulations to reset all the associated parameters.

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Last modified: December 2013

Ha ha~, you know where the web page style is stolen from, if you are a X-ray astronomer. I like the "CIAO" website a lot. Grazie, CIAO. I acknowledge the Chandra X-ray Center (CXC) for their excellent work.

Teng Liu Email: lewtonstein@gmail.com