Standards for Astronomical Catalogues, Version 2.0
(February 2000)

3.3  Labels

Conventions used for some labels

Symbol Explanation Default Limits
RAh Part of the right ascension expressed in hours [0,24[ RAm Part of the right ascension expressed in minutes [0,60[ RAs Part of the right ascension expressed in seconds [0,60[ RAdeg Right ascension expressed in decimal degrees (Alternative: RAhms could be envisaged for a right ascension expressed in sexagesimal with no embedded blanks and leading zeroes, RAbhms for sexagesimal values with embedded blanks. Such extensions would however require special interpretation by FITS readers. ) [0,360[ RArad Right ascension expressed in radians [0,2π[ RAsec Right ascension expressed in seconds [0,86400[ DE- Sign of declination [+-] DEd Part of the declination expressed in degrees [0,90] DEm Part of the declination expressed in arc minutes [0,60[ DEs Part of the declination expressed in arc seconds [0,60[ DEdeg Declination expressed in decimal degrees (Alternative: DEdms could be envisaged for a declination expressed in sexagesimal with no embedded blanks and leading zeroes, DEbdms for sexagesimal values with embedded blanks; questions similar to the RAhms note have to be addressed. ) [–90,+90] DErad Declination expressed in radians [–π/2,+π/2] DEsec Declination expressed in arcsec [–324000,+324000] PosErr Position mean error >=0 dRA  dDE Difference in Right Ascension or Declination oRA  oDE Offset from a reference position in R.A. or Dec. ELON ecliptic longitude [0,360[ ELAT ecliptic latitude [–90,+90] GLON galactic longitude [0,360[ GLAT galactic latitude [–90,+90
Epoch Epoch — write Ep-1900 for a year with 1900 offset plx Parallax pmRA Proper motion in Right Ascension pmDE Proper motion in Declination pmX Proper motion along X direction
Seq a Sequential number used e.g. to number the objects Name the main name of an object or feature
Diam Diameter – or MajDiam and MinDiam >=0 Axis Half Diameter – also MajAxis and MinAxis >=0 PA Position Angle, normally North to East [0,360[ Rad Radius >=0 HRV Heliocentric Radial velocity RVel Radial velocity Sep Separation (anglular or linear) >=0 SpType Spectral type MType Morphological type Vmag Magnitude (apparent) in V filter VMag Absolute Magnitude in V filter Kmag Magnitude (apparent) in K filter ...
Sp+Index Spectral index (α in relation S(ν) = να) Sp-Index Spectral index (α in relation S(ν) = ν–α)
BibCode The 19-digit bibcode Text Free-format text like list of authors, titles...

Remember that a label is always a single word: it cannot contain any embedded blank or space. Other characters are in principle accepted, e.g. parentheses or other punctuation signs, with the following restrictions:

Some commonly used labels are presented in label. This table is not an exhaustive list of all possible column labels; it merely represents the standards adopted for the most common columns headings — like celestial coordinates, times and dates, and some of the most frequently found parameters. The VizieR service contains all definitions of all colums; these definitions are stored in the METAcol (field meta-data) table which can be queried like any of the tables accessible in VizieR. For instance, finding the columns having oscillator strength in their explanation can be found by entering the constraint *oscillator strength* (the * matches any number of characters) in the explain field of the METAcol

Some comments on the labels defined in label:

A parameter has frequently associated values, and we have adopted the rule of association with the one-letter-underscore prefix: if a column is obviously associated to another one — typically mean errors or uncertainty flags — we use one of the underscore prefixes listed in prefix.

Conventions used for label prefixes

Symbol Explanation Default Limits
a_label aperture used for parameter label >=0 B_label for a lower bound (minimal value) on parameter label b_label for an upper bound (maximal value) on parameter label D_label for a difference (Δ) on parameter label (e.g. (O-C) d_label for a number of degrees of freedom or for number of digits on parameter label >0 E_label mean error (upper limit) on parameter label >=0 e_label mean error (σ) on parameter label >=0 f_label flag on parameter label L_label Likelihood on parameter label l_label limit flag on parameter label [<>] m_label multiplicity index on parameter label to resolve ambiguities n_label note (remark) on parameter label o_label number of observations on parameter label >=0 q_label quality on parameter label r_label reference (source) for parameter label s_label dispersion (σ) on parameter label (the σ of a mean of N values is asymptotically equal to the dispersion divided by sqrt(N)) >=0 u_label uncertainty flag on parameter label [ :] w_label weight of parameter label >=0 x_label unit in which parameter label is expressed

Usual mathematical functions may be specified in the label, with parentheses or a dot; for instance, the logarithm of the effective temperature could be labelled log(Te) or log.Te.

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