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Next: Source Count Rates Up: Effective Area Previous: Off-axis Effective Area

Long-term stability

  

It appears that the effective area has not varied significantly since launch. Observations of the sources HZ 43, Vega, A 2256, and N132D at several epochs yield non-varying count rates:

 

Source Date of observation Count rate (counts s tex2html_wrap_inline17397 )
A 2256* 1990 July 1 0.61 tex2html_wrap_inline17399 0.01
August 3, 1992 0.62 tex2html_wrap_inline17401 0.01
HZ 43 1990 July 2 12.3 tex2html_wrap_inline17403 0.2
1991 December 11 12.0 tex2html_wrap_inline17405 0.2
1992 June 9 11.91 tex2html_wrap_inline17407 0.04
Vega 1991 March 20 0.10 tex2html_wrap_inline17409 0.01
1992 March 21 0.11 tex2html_wrap_inline17411 0.01
1992 September 18 0.10 tex2html_wrap_inline17413 0.01
N132D 1990 July 3 4.41 tex2html_wrap_inline17415 0.13
1991 February 9 4.77 tex2html_wrap_inline17417 0.02
1992 September 18 4.89 tex2html_wrap_inline17419 0.06
1993 April 17 4.61 tex2html_wrap_inline17421 0.04
1994 January 10 4.51 tex2html_wrap_inline17423 0.04
1994 July 15 4.65 tex2html_wrap_inline17425 0.05
1995 February 11 4.54 tex2html_wrap_inline17427 0.04
1995 March 11 4.68 tex2html_wrap_inline17429 0.04
* The count rate for A 2256 is determined from the net emission
  within a 6' radius.
Table 5.4:  Stability of the HRI quantum efficiency

    


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Next: Source Count Rates Up: Effective Area Previous: Off-axis Effective Area

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