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Astron. Astrophys. 342, 839-853 (1999)
2. The data
Two pointed X-ray observations of the North and North-East rim of
the Vela supernova remnant have been carried out with the Position
Sensitive Proportional Counter on-board ROSAT (Trümper
1983). Table 1 summarizes the relevant information about the two
sequences (RP200133 and RP500015). RP200133 (PI Sciortino) has been
already studied in Paper I and in Paper II, while the public
archive sequence RP500015 (PI Kahn) has been chosen to extend the
coverage of the Vela outer shell in our spatially resolved spectral
analysis. We recall that the PSPC has a circular field of view of
diameter, and its spatial resolution
is FWHM on axis and
FWHM at
off-axis, while the spectral
resolution is at 1 keV. Fig. 1 shows
the ROSAT All-Sky Survey observation of the Vela SNR, with the
position of the two sequences over-imposed. In order to remove high
background time intervals from the X-ray observation, we have run the
optimized time-screening algorithm of Bocchino et al. (1998) on both
sequences: in Table 1 we report the screened and unscreened
exposure times. The exposure maps have been recomputed according to
the procedure of Snowden et al. (1994). The spatial grid used for
spatially resolved spectral analysis consists of sectors and
rings (Fig. 2), and was introduced in Paper II for
RP200133. In particular, the outermost ring corresponds to the
radius circle introduced by
Aschenbach (1993, also reproduced in Fig. 1), which encloses the Vela
SNR diffuse emission.
![[TABLE]](img15.gif)
Table 1. The RP200133 and RP500015 PSPC sequences
Notes:
a We report the exposure time before and after the application of the time screening algorithm of Bocchino et al. (1998).
b Number of counts in the whole field of view.
![[FIGURE]](img18.gif) |
Fig. 1. The Vela SNR in the ROSAT 0.1-2.4 keV All-Sky Survey. Small circles mark the position of the PSPC sequences RP200133 and RP500015, whereas the large radius circle encloses the Vela SNR diffuse emission (adapted from Aschenbach 1993).
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![[FIGURE]](img24.gif) |
Fig. 2a and b. Spatial distribution of 0.2-2.0 keV surface brightness of RP200133 (left panel ) and RP500015 (right panel ) PSPC sequences. 1.0 and 4.0 cnt s- 1 arcmin-2 contours which marks the background, diffuse emission and clumps regions defined in Sect. 3.1 are overlaid. Grayscale is linear from 0 to 8.0 cnt s- 1 arcmin-2. North is up and East is on the left.
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© European Southern Observatory (ESO) 1999
Online publication: February 23, 1999
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