Description of Part I of the FK6 Catalogue
--------------------------------------------------------------------------------

Field 1:
FK6 No.
The FK6 number of the star is identical with its FK5 number. The numbering
system in the fundamental catalogues is historically grown and not
explained here.

Field 2:
HIP No.
Number of the star in the HIPPARCOS Catalogue (ESA 1997).
This numbering follows closely ordering by right ascension alpha
for the epoch J1991.25 (not J2000.0 !).

Field 3:
Name
The name of the star is given for an easier identification of the object by a
reader of the catalogue.

Fields 4-13:
The Fields 4-13 (and 67, 70) contain the FK6 results in the single-star (SI)
mode.

Field 4:
alpha (SI) 2000
The right ascension alpha of the star at epoch and equinox J2000.0 in
the ICRS/HIPPARCOS system for the SI mode of the FK6. alpha is given in the
printed catalogue in the conventional sexagesimal units of
hours, minutes of time, and seconds of time.
The machine-readable version of the FK6 gives alpha also in degrees and decimal
fractions of degrees. Below we use the notation alpha_* = alpha*cos(delta),
as it is done in the HIPPARCOS Catalogue.

Field 5:
delta (SI) 2000
The declination delta of the star at epoch and equinox J2000.0 in the
ICRS/HIPPARCOS system for the SI mode of the FK6. delta is given in the
printed catalogue in the conventional sexagesimal units of
degrees, minutes of arc, and seconds of arc.
The machine-readable version of the FK6 gives delta also in
degrees and decimal fractions of degrees.

Field 6:
mu_alpha (SI) 2000
The proper-motion component mu_alpha_* of the star in alpha_* at epoch and
equinox J2000.0 in the ICRS/HIPPARCOS system for the SI mode of the FK6.
Instead of the conventional way of presenting mu_alpha, the catalogue
gives mu_alpha_* = mu_alpha*cos(delta) in milliarcseconds (mas)/year.

Field 7:
mu_delta (SI) 2000
The proper-motion component mu_delta of the star in delta at epoch and
equinox J2000.0 in the ICRS/HIPPARCOS system for the SI mode of the FK6.
Units: mas/year.

Field 8:
T_alpha (SI)
Central epoch T_alpha in alpha of the star in the SI mode. The catalogue
gives T_alpha - 1900 in order to save printing space. Units: years.

Field 9:
epsilon_alpha (SI)
Mean error epsilon_alpha_* of alpha_* of the star at the central epoch T_alpha
(given in Field 8) in the SI mode. Units: mas.

Field 10:
epsilon_mu_alpha_* (SI)
Mean error epsilon_mu_alpha_* of mu_alpha_* of the star in the SI mode.
Units: mas/year.

Field 11:
T_delta (SI)
Central epoch T_delta in delta of the star in the SI mode. The catalogue
gives T_delta - 1900$ in order to save printing space. Units: years.

Field 12:
epsilon_delta (SI)
Mean error epsilon_delta of delta of the star at the central epoch T_delta
(given in Field 11) in the SI mode. Units: mas.

Field 13:
epsilon_mu_delta (SI)
Mean error epsilon_mu_delta of mu_delta of the star in the SI mode.
Units: mas/year.

Field 14:
p_res
'Resulting' parallax p_res of the star (see Section 12). This is either the
HIPPARCOS parallax or a photometric/spectroscopic parallax. Units: mas.

Field 15:
epsilon_p_res
Mean error epsilon_p_res of p_res. Units: mas.

Field 16:
K_p
Flag for the source of p_res:
  H = HIPPARCOS Catalogue (ESA 1997)
  P = Newly determined photometric/spectroscopic parallax

Field 17:
v_rad
Radial velocity v_rad of the star, used in calculating the foreshortening
effect. Units: km/s.

Field 18:
m_V
Apparent visual magnitude m_V of the star, taken from the HIPPARCOS Catalogue.

Field 19:
K_m
Flag for the variability of the brightness of the star, taken from the
HIPPARCOS Catalogue (HIP Field H6):
  blank = star not variable
      1 = star variable at the level of < 0.06 mag
      2 = star variable at the level of   0.06 - 0.6 mag
      3 = star variable at the level of > 0.6 mag

Field 20:
K_bin
Flag for the double-star nature of the object: K_bin = d1d2 = 10d1+d2
First digit d1:
The first digit d1 describes the information on the double-star nature based
on the proper-motion differences Delta_mu.
The method and the meaning of the corresponding test parameters F are
explained in Wielen et al.(1999a)
  1 = all values of F (F_FH, F_0H, F_0(GC)H, F_0F) are below 2.49
  2 = at least one value of F (F_FH, F_0H, F_0(GC)H, F_0F) is larger than 3.44
  3 = all other (intermediate) cases
Second digit d2:
The second digit d2 describes the information on the double-star nature based
on various other methods. If the data indicate various kinds of binarity, the
'astrometrically most disturbing' effect is given.
  1 = single star indicated
  2 = the star is a member of a visual binary (gravitationally bound system),
      or the object is resolved by speckle interferometry
  3 = the object is suspected to be a visual binary (mainly due to HIPPARCOS)
  4 = the star has at least one optical companion with a separation of rho<60"
  5 = the star has at least one optical companion, but all companions have
      a separation of rho >= 60"
  6 = astrometric binary (mainly the non-standard solutions O, G, V, X of HIP)
  7 = spectroscopic binary with a known orbit, or the star is an
      eclipsing binary
  8 = the radial velocity of the star is variable (indicating a
      spectroscopic binary), or the object shows a composite spectrum
      (indicating a double star)
  9 = the radial velocity of the star may be variable (possible indication
      for a spectroscopic binary), or the object may show a composite
      spectrum (possibly indicating a double star),
      or other weak indications of binarity,
      or the star has a (suspected) planetary companion

Field 21:
K_Delta_mu
Flag for the double-star nature of the object based on differences between
various proper motions (Wielen et al. 1999a):
     1 = single-star candidate
     2 = Delta_mu binary
 blank = uncertain (between 1 and 2),
         or the binary nature which is indicated by other data does
         not allow to classify the object as a single-star candidate

Field 22:
K_ae
Flag for 'astrometrically excellent stars' (see Section 5):
      3 = astrometrically excellent star with rank ***
      2 = astrometrically excellent star with rank **
      1 = astrometrically excellent star with rank *
  blank = star not classified as astrometrically excellent

Fields 23-40 :
General remarks:
In order to save printing space, we give for the other modes of the FK6, i.e.
the long-term prediction (LTP) and the short-term prediction (STP), and for HIP
(HIPPARCOS Catalogue) and FK5, not the full quantities, but only their
differences, Delta = other mode - SI mode, with respect to the single-star
(SI) mode of the FK6. These differences have to be added to the results of the
SI mode of the FK6 (Fields 4-7) in order to obtain the results of the other
modes. For right ascension, we give Delta_alpha_* instead of
Delta_alpha = Delta_alpha_*/cos(delta). For obtaining alpha, the formula
alpha(other mode) = alpha(SI mode) + Delta_alpha_*(other mode)/cos(delta)
should be used. The data given for the FK5 and for mu_0 are given in the
ICRS/HIPPARCOS system. Since the quantities for the SI mode and all the
differences Delta refer to the epoch and equinox J2000.0 in the
ICRS/HIPPARCOS system, this is then also the case for the full results of the
other modes.
The differences Delta are given for numerical and printing convenience only.
Therefore, the mean errors given in the FK6 Catalogue are not the errors of
these differences, but those of the full quantities in the other modes. The
mean errors given for the FK5 and for mu_0 include the mean errors of the
systematic differences between the FK5 system and the HIPPARCOS system.

Fields 23-26:
Delta_alpha_* 2000 [LTP, STP, HIP, FK5]
Difference Delta_alpha_* between alpha* in the other solutions (LTP, STP, HIP,
FK5) and alpha_* in the SI mode at epoch and equinox J2000.0. Units: mas.

Fields 27-30:
Delta_delta [LTP, STP, HIP, FK5]
Difference Delta_delta between delta in the other solutions (LTP, STP,
HIP, FK5) and delta in the SI mode at epoch and equinox J2000.0. Units: mas.

Fields 31-35:
Delta_mu_alpha_* [LTP, STP, HIP, FK5, mu_0]
Difference Delta_mu_alpha_* between mu_alpha_* in the other solutions (LTP, STP,
HIP, FK5, mu_0) and mu_alpha_* in the SI mode at epoch and equinox J2000.0.
Units: mas/year.

Fields 36-40:
Delta_mu_delta [LTP, STP, HIP, FK5, mu_0]
Difference Delta_mu_delta between mu_delta in the other solutions (LTP, STP,
HIP, FK5, mu_0) and mu_delta in the SI mode at epoch and equinox J2000.0.
Units: mas/year.

Fields 41-44:
T_alpha [LTP, STP, HIP, FK5]
Central epoch T_alpha in alpha of the star in the solutions LTP, STP, HIP, FK5.
The catalogue gives T - 1900. Units: years.

Fields 45-48:
epsilon_alpha_* [LTP, STP, HIP, FK5]
Mean error epsilon_alpha_* of alpha_* of the star at the central epoch T_alpha
in the solutions LTP, STP, HIP, FK5. Units: mas.

Fields 49-53:
epsilon_mu_alpha_* [LTP, STP, HIP, FK5, mu_0]
Mean error epsilon_mu_alpha_* of mu_alpha_* of the star in the solutions
LTP, STP, HIP, FK5, mu_0. Units: mas/year.

Fields 54-57:
T_delta [LTP, STP, HIP, FK5]
Central epoch T_delta in delta of the star in the solutions LTP, STP, HIP, FK5.
The catalogue gives T - 1900. Units: years.

Fields 58-61:
epsilon_delta [LTP, STP, HIP, FK5]
Mean error epsilon_delta of delta of the star at the central epoch T_delta
in the solutions LTP, STP, HIP, FK5. Units: mas.

Fields 62-66:
epsilon_mu_delta [LTP, STP, HIP, FK5, mu_0]
Mean error epsilon_mu_delta of mu_delta of the star in the solutions LTP, STP,
HIP, FK5, mu_0. Units: mas/year.

Field 67:
p [SI]
Parallax p_SI of the star derived in the SI mode of the FK6. Units: mas.

Field 68:
p [STP]
Parallax p_STP of the star derived in the STP mode of the FK6. Units: mas.

Field 69:
p [HIP]
Parallax p_H of the star given in the HIPPARCOS Catalogue (ESA 1997). Units:
mas.

Field 70:
epsilon_p [SI]
Mean error epsilon_p_SI of p_SI. Units: mas.

Field 71:
epsilon_p [STP]
Mean error epsilon_p_STP of p_STP. Units: mas.

Field 72:
epsilon_p [HIP]
Mean error epsilon_p_H of p_H. Units: mas.

Fields 73-80:
These fields list the systematic differences between the FK5 system and
ICRS/HIPPARCOS system (in the sense FK5 - HIP) for alpha_*, delta, mu_alpha_*,
mu_delta for the star under consideration at the epoch J1949.4 (see Section 6).
The differences have to be subtracted from the FK5 data at epoch J1949.4
in order to obtain the FK5 quantities at epoch J1949.4 in the HIPPARCOS
reference system. The systematic differences given include both the rotational
and regional systematic differences between the FK5 system and the HIPPARCOS
system. The mean errors of the systematic differences at epoch J1949.4 are
given in the Fields 77-80.

Field 73:
Delta_alpha_*_sys
Systematic difference Delta_alpha_sys in alpha_* between the FK5 system and the
HIPPARCOS system for the star under consideration at epoch J1949.4. Units: mas.

Field 74:
Delta_delta_sys
Systematic difference Delta_delta_sys in delta between the FK5 system and the
HIPPARCOS system for the star under consideration at epoch J1949.4. Units: mas.

Field 75:
Delta_mu_alpha_*_sys
Systematic difference Delta_mu_alpha_*_sys in mu_alpha_* between the FK5 system
and the HIPPARCOS system for the star under consideration at epoch J1949.4.
Units: mas/year.

Field 76:
Delta_mu_delta_sys
Systematic difference Delta_mu_delta_sys in mu_delta between the FK5 system
and the HIPPARCOS system for the star under consideration at epoch J1949.4.
Units: mas/year.

Field 77:
epsilon_alpha_*_sys
Mean error epsilon_alpha_*_sys of Delta_alpha_*_sys. Units: mas.

Field 78:
epsilon_delta_sys
Mean error epsilon_delta_sys of Delta_delta_sys. Units: mas.

Field 79:
epsilon_mu_alpha_*_sys
Mean error epsilon_mu_alpha_*_sys of Delta_mu_alpha_*_sys. Units: mas/year.

Field 80:
epsilon_mu_delta_sys
Mean error epsilon_mu_delta_sys of Delta_mu_delta_sys. Units: mas/year.

Field 81:
K_sys
Flag for the use of the star in determining the systematic differences between
the FK5 system and the HIPPARCOS system in position and proper motion:
      1 = used for positions and proper motions
  blank = not used

Fields 82-85
These fields contain the test parameters F for various proper-motion
differencs Delta_mu. The parameter F is defined by Eq.(23) of Wielen et
al. (1999a). It is essentially the ratio between the two-dimensional difference
Delta_mu and its mean error. Values of F > 3.44 indicate Delta_mu binaries.
If all the F values are below 2.49, the star may be classified as a
single-star candidate.

Field 82:
F_FH
F parameter based on the difference Delta_mu_FH = mu_F - mu_H between
the proper motions given by the FK5 and by HIPPARCOS.

Field 83:
F_0H
F parameter based on the difference Delta_mu_0H = mu_0 - mu_H between
the proper motion mu_0 (based on the stellar positions in the FK5 and in the
HIPPARCOS Catalogue) and the proper motion mu_H given by HIPPARCOS.

Field 84:
F_0(GC)H
F parameter based on the difference Delta_mu_0(GC)H = mu_0(GC) - mu_H between
the proper motion mu_0 (based on the stellar positions in the GC (Boss et al.
1937) and in the HIPPARCOS Catalogue) and the proper motion mu_H given by
HIPPARCOS.

Field 85:
F_0F
F parameter based on the difference Delta_mu_0F = mu_0 - mu_F between
the proper motion mu_0 (based on the stellar positions in the FK5 and in the
HIPPARCOS Catalogue) and the proper motion mu_F given by the FK5.

Field 86:
No. of note
The notes are numbered consecutively from 1) to 560) and are listed on the
pages 173 to 209. Explanations for the notes are given in Section 16 and on
page 173.

Updated: 17 November 1999