rgsxsrc

rgsxsrc: XMM/RGS extended source analysis

Convolution model for the analysis of moderately-extended (~ arcmin) sources, developed by Andy Rasmussen of the Columbia University XMM/Newton RGS instrument team. The code convolves the spectral model with an angular structure function for a given extended source. The structure function is taken directly from an image (e.g., XMM/Newton EPIC, Chandra ACIS etc) where the user provides RA and Dec (2000) coordinates for the source, position angle of the spacecraft, and an aperture size suitable for the source in order to characterize the convolution function. The model resulting from the convolution is then used with the standard RGS point source spectral response to fit data.

The user is required to have used the XSPEC command xset prior to defining the spectral model, e.g.:

XSPEC12>xset rgs_xsource_file <filename>

This command points XSPEC to an external file containing the attitude and aperture information. A typical file must look like this:

RGS_XSOURCE_IMAGE

RGS_XSOURCE_BORESIGHT

RGS_XSOURCE_EXTRACTION

For example :

RGS_XSOURCE_IMAGE

/local/data/mymachine/myusername/MOS1.FIT

RGS_XSOURCE_BORESIGHT

05:25:02.9 -69:38:30 339.760974

RGS_XSOURCE_EXTRACTION

1.8

The RA and Dec of the center of the source can be determined by the user from the image or taken from the headers of the source spectrum. The position angle can be found in the image headers.

The file is reread on each iteration so editing the file during an XSPEC session will cause these parameters to be changed. The only model parameter is

par1	the order of the spectrum (this number is always negative)

N.B. The interpretation of results using this model is not trivial. The method assumes that the spatial distributions of the continuum and all lines are identical to the broad band image. This is unlikely to be the case. Resulting line velocities and profiles should be treated with appropriate caution.

Contact the US XMM_Newton GOF for help. xmmhelp@athena.gsfc.nasa.gov.