AAS 200th meeting, Albuquerque, NM, June 2002
Session 46. Astrophysics in the Local Group
Display, Tuesday, June 4, 2002, 10:00am-6:30pm, SW Exhibit Hall

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[46.09] The Discovery of New Wolf-Rayet Star Candidates in the Starburst Galaxy IC10

S. B. Holmes, P. Massey (Lowell Observatory)

IC10 is a Local Group dwarf irregular galaxy described by Hubble (1936) as ``one of the most curious objects in the sky". Massey and Armandroff (1995) proposed that it is currently undergoing a starburst: despite its small size, it contains 15 spectroscopically confirmed Wolf-Rayet stars, which is a galaxy-averaged surface density that is as high as that found in young, massive OB associations. This is consistent with a comparison of the Halpha luminosity to HI mass or blue light luminosity (Hunter and Gallagher 1986, Hunter 1993), which suggests a star-formation rate comparable to that of NGC 1569, a classical starburst irregular. However, the relative number of WC-type and WN-type Wolf-Rayet stars is surprising high given the galaxy's low metallicity. Does this suggest a peculiar initial mass function or could some of the weaker-lined WN-type have been missed in earlier surveys? Here we present results of a deep Mosaic CCD search for Wolf-Rayet candidates in IC10 using narrow-band filters optimized for the detection of Wolf-Rayets. Our results have identified many new candidate Wolf-Rayets, and comparision with a neighboring ``control field" suggests that we have found a minimum of a dozen new Wolf-Rayet stars, and possibly as mandy as sixty. If spectroscopy confirms the majority of these, then the WC/WN ratio may well be normal, but the star-formation even higher than previously thought.

In addition, we have confirmed the candidacy of several stars proposed to be Wolf-Rayets by Royer et al (2001 A&A 366, L1) based their own interference filter imaging but never confirmed spectroscopically. The exception are their ``WC9" candidates; none of these were detected in our survey, causing us to question their surprising result that late-type WCs were to be found in such a low metallicity system. This work is being supported by the National Science Foundation under grant AST-0093060.

The author(s) of this abstract have provided an email address for comments about the abstract: massey@lowell.edu

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.