Discovery in IC10 of the farthest known symbiotic star

We report the discovery of the first known symbiotic star in IC10, a starburst galaxy belonging to the Local Group, at a distance of ~750 kpc. The symbiotic star was identified during a survey of emission-line objects. It shines at V = 24.62 +/- 0.04,V - R_C = 2.77 +/- 0.05 and R_C - I_C = 2.39 +/- 0.02, and suffers from E_{B- V} = 0.85 +/- 0.05 reddening. The spectrum of the cool component well matches that of solar neighbourhood M8III giants. The observed emission lines belong to Balmer series, [SII], [NII] and [OIII]. They suggest a low electronic density, negligible optical depth effects and 35000 < T_eff < 90000 K for the ionizing source. The spectrum of the new symbiotic star in IC10 is an almost perfect copy of that of Hen 2-147, a well-known Galactic symbiotic star and Mira.

Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership. We also retrieved UBVRI images of the `Survey of Local Group Galaxies Currently Forming Stars', Massey et al. (2007).

E-mail: denise@ov.ufrj.br