Variable Stars

Among the 118218 stars measured by Hipparcos, 11597 were found to be (possibly) variable. Of these more than 8000 are new. If you want to find some background to understanding what variable stars are, and why they are important in astronomy, take a look here from the home page of the American Association of Variable Star Observers. Further information is also available from the Variable Star Network [external link] (VSNET ) web site.

Variables are broadly classified as follows (the star in brackets is a typical example for that class and is linked to the Hipparcos light curve for that star):

• pulsating variables
  • Cepheids (delta Cephei: HIP 110991)
  • RR Lyrae stars (RR Lyrae: HIP 95497)
  • RV Tauri stars (R Scuti: HIP 92202)
  • long-period/Mira variables (o Ceti (Mira): HIP 10826)
  • semiregular variables (Z Ursa Majoris: HIP 58225)
  • R Coronae Borealis stars (R Coronae Borealis: HIP 77442)
• eruptive variables
  • Gamma Cassiopeiae type stars (V960 Tau: HIP 26064)
  • Recurrent novae ( Nova CrB 1866 : HIP 78322)
  • Symbiotic stars (Z Andromedae: HIP 116287)
• eclipsing binary stars (beta Persei (Algol): HIP 14576)
• rotating stars (RS Canum Venaticorum: HIP 64293)

Two Annexes of the Hipparcos and Tycho Catalogues are dedicated specifically to variable stars.

• (Volume 11) The Hipparcos Variability Annex: Tables
  • Part 1: Periodic Variables (example page)
  • Part 2: Unsolved Variables (example page)

  Clicking on the highlighted text will bring up an example page from these tables of the Hipparcos Variability Annex in pdf format.

• (Volume 12) The Hipparcos Variability Annex: Light Curves
  • Part A: Folded light curves for periodic variables (examples)
  • Part B: AAVSO monitored stars (examples)
  • Part C: Unsolved variable stars (examples)

Clicking on the highlighted text will bring up 10 examples of the light curves from each of the different parts of the Variability Annex. The light curves are given in pdf format: you can examine them in greater detail; or you can experiment by trying to determine the periods of these variables yourself using the interactive software tool provided!