Astrophysical properties of a luminous Wolf-rayet type object in the core of the extragalactic HII region IC 132 from an analysis of its lambda lambda 1200-6000 A spectrum.

Abstract

We discuss the λλ1200-6000 Å spectrum of the ionizing source of the extragalactic H II region IC 132 in M33. The optical spectrum shows a broad λ4686 Å emission: the UV data from lUE show emission lines of N V, N IV, N III, C IV and He II. The WR features suggest an early WN classification with equivalent widths about a factor of 2 weaker than in galactic WR stars of that type.

If the object is a single star, the data are consistent with the central source of IC 132 having a temperature of 40000 ± 5000 K and M_Bol = -11.6. This would make it the brightest star in the galaxy M33, with a mass larger than lOOM_sun.

Alternatively, we show that the data are equally well represented by a multiple system, consisting of three components (04 V + 09.5 I + WN4). In either of these two cases, our result confirms that the most luminous hot stars of a spiral or irregular galaxy are likely to be found in the cores of its giant H II regions and in many cases show WR features in their spectra.