Improved Attitude Correction and Pileup Estimation for Suzaku Data

 

We present here two routines: aeattcor.sl and pile_estimate.sl, designed to aid in the analysis of Suzaku data. Both are scripts written in S-lang and are designed to be run on the command line using ISIS, the Interactive Spectral Analysis System, as a driver. Both utilize a number of S-Lang Modules Packages. For all intents and purposes, the scripts behave similar to typical Unix command line tools.

Attitude Correction with aeattcor.sl:

As documented by

   "Restoring the Suzaku Source Position Accuracy and Point-Spread Function",
   Y. Uchiyama, Y. Maeda, M. Ebara, R. Fujimoto, Y. Ishisaki, M. Ishida,
   R. Iizuka, M. Ushio, H. Inoue, S. Okada, H. Mori, and M. Ozaki,
   2008  PASJ, 60, p. 35
thermal flexing of the Suzaku spacecraft leads to slow wobbling of the optical axis, and hence blurring of the image. Current Suzaku tools partially correct this effect by adjusting the spacecraft attitude file (based upon details of the spacecraft orbit, temperature, etc.). aeattcor.sl further improves this correction for bright sources by using their detected image to create a new attitude file. Applying this attitude file via the FTOOLS xiscoord command leads to sharper PSF images, as shown below. A more detailed description of aeattcor.sl is presented here.

PSF
Left: Standard Suzaku correction. Right: aeattcor.sl correction.

Pileup Estimation with pile_estimate.sl:

Pileup occurs in CCD detectors when two or more photons fall on the same pixel during the same frame, and therefore are read as a single higher energy photon or are discarded as a bad event. pile_estimate.sl is designed to be run after aeattcor.sl. It will create a smoothed, discretized image for a given Suzaku chip. Rather than display count rates, the image will show an estimated, minimum pileup fraction for user specified levels. It then allows the user to create a region file that excludes the most piled areas, and then estimates the effective pileup fraction of the remaining events. An image is shown below, and a more detailed description is presented here.


PILEUP
The estimated pileup fraction in a Suzaku image.


This page was last updated Apr 26, 2010 by Michael Nowak. To comment on it or the material presented here, send email to mnowak@space.mit.edu.
Valid HTML 4.01! Made with JED. Viewable With Any Browser.