Astron. Astrophys. 362, 711-714 (2000)

1. Introduction

In recent years it has become clear that young neutron stars do not necessarily manifest themselves as radio pulsars. Instead a large variety of unresolved objects associated with supernova remnants are thought to be the stellar remnants of the explosion (see Helfand 1998for a review). Examples are the point-like sources recently discovered in Cas A (Tananbaum 1999) and Puppis A (Petre et al. 1996), the enigmatic variable source in RCW 103 (Gotthelf et al. 1999), and a handful of relatively slow rotating X-ray pulsars called "anomalous X-ray pulsars" or AXPs (see Mereghetti 1998for a review).

Here we report on our analysis of an unresolved X-ray source in the supernova remnant RCW 86 (G315.4-2.3, MSH 14-63 ). We discovered it during our work on the X-ray properties of the remnant (Vink et al. 1997, Bocchino et al. 2000). The source qualifies as the possible stellar remnant associated with RCW 86, but the presence of a possible optical counterpart and long term source variability make this identification, as we will show, uncertain.

RCW 86 is the candidate remnant of the supernova AD 185 (Clark & Stephenson 1977, Strom 1994), but the interpretation of the Chinese records is ambiguous (Chin & Huang 1994). The large extent of the remnant (40´) can only be reconciled with an explosion as recent as AD 185, if its distance does not exceed 1 kpc too much. However, Rosado et al. (1996) have pointed out that the kinematic distance towards RCW 86 seems to be higher, namely  kpc. In that case RCW 86 may be physically associated with an OB association (Westerlund 1969). The presence of a stellar remnant in RCW 86 would establish the nature of the supernova as a core collapse supernova (Type II or Ib/c), and therefore a connection with the OB association would be more likely.

© European Southern Observatory (ESO) 2000

Online publication: October 24, 2000
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