The M33 varjable star population revealed by Spitzer

Kristen B McQuinn, Chick E Woodward, S. P. Willner, E. F. Polomski, Robert D Gehrz, Roberta M Humphreys, Jacco Th Van Loon, M. L.N. Ashby, K. Eicher, G. G. Fazio

Research output: Contribution to journalArticlepeer-review

52 Scopus citations


We analyze five epochs of Spitzer Space Telescope Infrared Array Camera (IRAC) observations of the nearby spiral galaxy M33. Each epoch covered nearly a square degree at 3.6,4.5, and 8.0 μm. The point-source catalog from the full data set contains 37,650 stars. The stars have luminosities characteristic of the asymptotic giant branch and can be separated into oxygen-rich and carbon-rich populations by their [3.6] - [4.5] colors. The [3.6] - [8.0] colors indicate that over 80% of the stars detected at 8.0 μm have dust shells. Photometric comparison of epochs using conservative criteria yields a catalog of 2923 variable stars. These variables are most likely long-period variables amid an evolved stellar population. At least one-third of the identified carbon stars are variable.

Original languageEnglish (US)
Pages (from-to)850-861
Number of pages12
JournalAstrophysical Journal
Issue number2 I
StatePublished - Aug 1 2007


  • Galaxies: individual (M33)
  • Galaxies: stellar content
  • Infrared: stars
  • Stars: AGB and post-AGB
  • Stars: Variables: other

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