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II/15       Photometric Measurements in the UBVr 20 System (Magnenat 1973)
Catalogue of Photometric Measurements in the UBVr 20 System
     Magnenat P.
    <CDS Internal Report No. 6 (1973)>
ADC_Keywords: Photometry, UBVr20 ; Colors


Description:
    In the  UBVr photometric system  defined by Sandage  and Smith (1963),
    (U-B)20,  (B-V)20, and (V-r)20 color indices  are given for stars from
    ten reference lists, along with  a  LID  coded  number,  V  magnitude,
    number  of observations  and reference.  A list  of weighted  means is
    included for stars appearing on more than one list. The reference list
    and an explanation of the  coded  numbering  system  are  included  in
    separate files.

Introduction:
    The UBVr system is defined by  Sandage  and  Smith  (1963).  The  then
    recent availability of photomultipliers with S20 cathodes sensitive to
    the wavelength range 3000 to  8000  A  suggested  that  the  customary
    tricolor  photometric system could be extended  to include a red point
    close to 6700 A. The V-r  color  index  can  be  employed  as  a  good
    indicator  of effective  temperature, thanks  to its  relatively small
    blanketing effect, compared to B-V.

    Sandage and Smith also tried to obtain  the  U,  B  and  V  colors  as
    closely  as possible to those of Johnson and Morgan's system. In 1960,
    64  standard stars of the UBV system (Johnson and Morgan 1953; Johnson
    and  Harris 1954) were measured. Comparison  of colors obtained in the
    natural  photometric system ubvr  20 with colors  from Johnson, Morgan
    and Harris give:

     B-V =   1.100(b-v)20 +   1.023
          ±0.004         ±/0.003

     U-B =   1.015(u-b)20 -   1.575
          ±0.003         ±0.006    (Sandage and Smith 1963)

    These  equations show  that the  UBVr 20  system is  close to  the UBV
    system without being identical.

    Means were calculated  for  stars  appearing  in  multiple  references
    according to the customary manner at  CDS,  based  on  the  number  of
    measures and the weight of each list. All ten lists were given weight 4.

See also:
    GCPD/69 : The General Catalogue of Photometric Data, maintained
              by Lausanne-Geneva


File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
obs.dat           80      418   Observations of UBVr 20 colors
mean.dat          80      366   Weighted means for stars in multiple lists
refs.dat          80       41   References to individual lists
codes.dat         80      169  *Definition of the coded numbering system

Notes on codes.dat:
   ampersands "&" in data files have been changed to "+"--------------------------------------------------------------------------------

Byte-by-byte Description of file: obs.dat mean.dat


Byte-by-byte Description of file: obs.dat mean.dat

   Bytes Format  Units   Label    Explanations

   1- 11  F11.8  ---     LID     *Coded number             (see codes.dat)
      12  A1     ---     rem     *Remark
  13- 18  F6.3   mag     U-B20   *? (U-B)20 index
  21- 26  F6.3   mag     B-V20   *? (B-V)20 index
  29- 34  F6.3   mag     V-r20    (V-r)20 index
      37  A1     ---     n_Nobs  *Remark about Nobs        (obs.dat only)
  38- 40  I3     ---     Nobs     ? Number of measurements (obs.dat only)
  43- 49  F7.3   mag     Vmag     ? V magnitude
  76- 80  I5     ---     ref      ? Reference number       (see refs.dat)

Note on LID:
   Defined in J.Cl. Mermilliod, CDS RISP 5 (see codes.dat)
Note on rem:
   D      = a multiple system
   1 or 2 = only one component of a binary was measured
Note on U-B20:

Note on B-V20:
   If either field is empty, that signifies that the star was not measured on
     the filters in question.
Note on n_Nobs:
   /     = N is unknown (1 is assumed)
   *     = N is a minimum number
   blank = N is exact


Byte-by-byte Description of file: refs.dat

   Bytes Format  Units   Label    Explanations

   2-  3  I2     ---     ref      ? Reference number
   6- 80  A75    ---     text     Reference (multiline)


Acknowledgement:
    The text of the introduction is taken from P. Magnenat [CDS],
    translated from French to English by J.A. Watko [SSDOO/ADC].

References:
   Sandage A. and Smith L.          =1963ApJ...137.1057S
   Johnson H.L. and Harris D.L.III. =1954ApJ...120..196J
   Johnson H.L. and Morgan W.W.     =1953ApJ...117..313J
   Mermilliod J.Cl., CDS RISP 5
(End)                                  Julie Anne Watko [SSDOO/ADC]  30-MAY-1996