Table 3

Shift and separation of RASS X-ray and optical positions (from RBS and SDSS cross-correlation catalogues) in ecliptic latitude β in arcsec depending on ecliptic longitude (i.e. scan direction).

RASS-2 RASS-3 Rounding error RASS-3.1 Comment
(1RXS) re-correction (2RXS) (reference)

RBS 0.894 ± 0.418 0.861 ± 3.401 0.630 ± 0.984 0.573 ± 0.539 only point-like  (Schwope et al. 2000)
SDSS 0.615 ± 0.551 0.663 ± 3.136 0.430 ± 0.734 0.630 ± 0.327 only northern sky  (Agüeros et al. 2009)

Notes. The table is described in Sect. 4.5.2. For the RASS-2 column, for instance, the value of 0.894 is the mean 1RXS-RBS distance in arcsec. The value of 0.418 refers to the systematic separation between the 1RXS and RBS optical positions in arcsec depending on scan direction. The same holds for columns RASS-3 and RASS-3.1. The large separation of more than 3 arcsec for RASS-3 arises because only one of two compensating errors present in RASS-2 had been corrected. Applying an a posteriori rounding error re-correction (attitude time shift) reduces the separation significantly. We have applied an additional correction to minimise the the X-ray – optical offsets (column RASS-3.1, as in 2RXS, and new public event files).

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