Is there any way I can tell from Hipparcos catalog which stars are Binary/Multiple Stars and which are Variable stars?


2 Answers 2


Yes. If you have the Hipparcos data from ftp (http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=I/239&-to=3), you will have several data files.

In hip_main.dat you have a field MultFlag at position 347 that indicates whether the star is a double or multiple star:

Note on MultFlag: indicates that further details are given in the Double
     and Multiple Systems Annex:
     C : solutions for the components
     G : acceleration or higher order terms
     O : orbital solutions
     V : variability-induced movers (apparent motion arises from variability)
     X : stochastic solution (probably astrometric binaries with short period)

To determine whether the star is a double or multiple star system, look in one of the files for double star solutions. For instance in h_dm_com.dat there is a field at bytes 24-25 that gives the number of components (2 for double and >2 for multiple stars).

24- 25  I2     ---     Ncomp    Number of components in this solution   (DCM2)

The Hipparcos number identifying the star can be found in bytes 43-48.

Of course this only works for multiple stars with orbital solutions.

For variability, three fields are provided in the main Hipparcos file:

314-320  F7.2  d       Period    ? Variability period (days)              (H51)
     322  A1    ---     HvarType *[CDMPRU]? variability type               (H52)
     324  A1    ---     moreVar  *[12] Additional data about variability   (H53)

with two notes (NB. if HvarType is C then the star is constant, i.e. not variable!):

Note on HvarType: Hipparcos-defined type of variability (a blank entry
     signifies that the entry could not be classified as variable or constant):
     C : no variability detected ("constant")
     D : duplicity-induced variability
     M : possibly micro-variable (amplitude < 0.03mag)
     P : periodic variable
     R : V-I colour index was revised due to variability analysis
     U : unsolved variable which does not fall in the other categories
Note on moreVar: more data about periodic variability are provided

There are two additional files on variability: hip_va_1.dat and hip_va_2.dat, which provide information such as variable type (GCVS) and max and min magnitude and also the variable star name. You can find a description of the variable type in the General Catalogue of Variable Stars (GCVS) in the file vartype.txt if you download the GCVS at http://cdsarc.u-strasbg.fr/viz-bin/Cat?B/gcvs

  • $\begingroup$ Meant to add Variable stars as well, is that available from hipparcos? $\endgroup$ Commented Apr 17, 2015 at 12:51
  • $\begingroup$ What is meant by Orbital Solutions? $\endgroup$ Commented Apr 17, 2015 at 13:03
  • $\begingroup$ Yes on variable stars, see my edit of the answer. $\endgroup$
    – Dieudonné
    Commented Apr 17, 2015 at 13:06
  • $\begingroup$ Orbital solutions are used to calculate the orbit of one star in the binary with respect to the other star. They can be found in the file 'hip_dm_o.dat'. $\endgroup$
    – Dieudonné
    Commented Apr 17, 2015 at 13:09

The logic for double/multiple systems in Hipparcos is fairly complex.

Some good documentation is here (large PDF) and here.

Just looking at the MultFlag may not be enough. If I understand it correctly, some double/multiple stars, sharing the same CCDM identifier (field H55), appear as separate entries in Hipparcos. Many would want to consider all such entries sharing the same CCDM as belonging to the same system.

The CCDM id comes from a separate catalog of double/multiple stars. (It also comes from Hipparcos itself, which created new CCDM ids as part of its processing.)


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .