Coordinates (11 columns)
 RA (D) [deg] SAS task
catcorr

Corrected Right Ascension of the detection in degrees (J2000) after
statistical correlation of the emldetect coordinates, RA_UNC and DEC_UNC, with the USNO B1.0, 2MASS or SDSS
(DR8) optical/IR source catalogues using the SAS task catcorr
(the process of correcting the coordinates is also referred to as field
rectification). In cases where
the crosscorrelation is determined to be unreliable, no correction is
applied and this value is therefore the same as RA_UNC (cf. Sec. 3XMMDR4 UG, Sec. 3.4).

DEC (D) [deg]SAS task
catcorr

Corrected Declination of the detection in degrees (J2000) after
statistical correlation of the emldetect coordinates, RA_UNC and DEC_UNC, with the USNO B1.0, 2MASS or SDSS
(DR8) optical/IR source catalogues using the SAS task catcorr
(the process of correcting the coordinates is also referred to as field
rectification). In cases where
the crosscorrelation is determined to be unreliable no correction is
applied and this value is therefore the same as DEC_UNC (cf. Sec. 3XMMDR4 UG, Sec. 3.4).

POSERR (E) [arcsec]

Total radial position uncertainty in arcseconds calculated by
combining the statistical error RADEC_ERR and the error arising from the field rectification process SYSERRCC as follows: POSERR = SQRT ( RADEC_ERR^2 + SYSERRCC^2 ). For a 2dimensional Gaussian error distribution, this radius reflects a 63% probability that the true source position lies within this radius of the measured position. The corresponding 68% confidence radius is 1.0714*POSERR.

LII (D) [deg]SAS task
catcorr

Galactic longitude of the detection in degrees corresponding to the
(corrected) coordinates RA and
DEC.

BII (D) [deg]SAS task
catcorr

Galactic latitude of the detection in degrees corresponding to the
(corrected) coordinates RA and
DEC.

RADEC_ERR (E) [arcsec]SAS task emldetect

RADEC_ERR (E) [arcsec] is a radial error on the position, computed as sqrt( ra_err^{2} + dec_err^{2}), in arcsecs, where ra_err and dec_err are the 1 σ uncertainties in the RA and DEC coordinates respectively. The ra_err and dec_err quantities are provided, in image pixel units, in the X_IMA_ERR and Y_IMA_ERR columns, respectively, in the P*OMSRLI*.FIT pipeline product file of each observation  they are not provided directly in the catalogue.

SYSERRCC (E) [arcsec]SAS tasks catcorr

The estimated error arising from the field rectification
process (in arcseconds). If the SAS task catcorr results in a
statistically reliable crosscorrelation with the USNO B1.0, 2MASS or
SDSS (DR8) optical/IR catalogues, SYSERRCC combines the 1 σ errors on the
translational shifts in the RA (rashift_error) and DEC (decshift_error)
directions, together with the rotational error component, derived from
from the catalogue that yields the 'best' solution, as follows:
SYSERRCC = SQRT ( rashift_error^{2} + decshift_error^{2} + (r * thetarot_error)^{2} )
where r is the radial offaxis angle of the detection from the spacecraft
boresight in arcsecs and thetarot_error is the 1 σ error on the rotational
correction (in radians). Where catcorr fails to obtain a
statistically reliable result,
SYSERRCC is 1.5 arcseconds (see Sec. 3XMMDR4 UG, Sec.
3.4 for details). Note that rashift_error, decshift_error and
thetarot_error are not provided separately in the catalogue.

REFCAT (I) SAS task catcorr

An integer code reflecting the absolute astrometric reference catalogue
which gave the statistically 'best' result for the field rectification
process (from which the corrections are taken). It is 1 for the
SDSS (DR9) catalogue, 2 for 2MASS and 3 for USNO B1.0. Where
catcorr fails to produce a reliable solution, REFCAT is a
negative number, indicating the cause of the failure.
The failure codes are 1 = Too few matches (< 10), 2 = poor fit
(goodness of fit parameter in catcorr < 5.0), 3 = error on
the field positional rectification correction is > 0.75 arcseconds)
(see Sec. 3XMMDR4 UG, Sec. 3.4). This column is new in 3XMMDR4..

POSCOROK (B) SAS task catcorr

Signifies whether catcorr obtained a statistically reliable
solution or not. This parameter is redundant in the sense that if
REFCAT is positive, then a
reliable solution was considered to have been found (see Sec. 3XMMDR4 UG, Sec. 3.4). This column is new in 3XMMDR4..

RA_UNC (D) [deg]SAS
task emldetect

Right Ascension of the detection in degrees (J2000) as determined by
the SAS task emldetect by fitting a detection
simultaneously in all cameras and energy bands.

DEC_UNC (D) [deg]SAS
task emldetect

Declination of the detection in degrees (J2000) as determined by the
SAS task emldetect by fitting a detection simultaneously in
all cameras and energy bands.