Hi Eric,
I would not discount the possibility that the background subtraction at low
energy is the cause for the high fitted value for NH. You could examine the
ROSAT all-sky survey maps of the diffuse X-ray background in your target
direction with those in the directions that make up the background data-set
that you are using. The survey maps are available from
http://www.xray.mpe.mpg.de/rosat/survey/sxrb/12/ass.html
I have found that the -110C and -120C data-sets for the S3 chip were
unsuitable for background subtraction for a particular direction in which I
was interested because they sampled brighter parts of the sky than the
direction of interest.
========
Michael Juda mjuda@cfa.harvard.edu
Harvard-Smithsonian Center for Astrophysics phone: 617-495-7062
60 Garden Street, MS 70 fax: 617-495-7356
Cambridge, MA 02138 OCC phone: 617-496-7065
Cell phone: 617-721-4365
Pager: 1-877-702-4186 or 7024186@archwireless.net
http://hea-www.harvard.edu/~juda/HomePage.html
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