2004ApJ...610L..29B

We have searched for the important radioactive isotope ²⁶Al in the nova-like source V4332 Sgr. Recent results from gamma-ray astronomy show that there is pervasive emission of the 1.809 MeV gamma-ray photon, arising from the decay of ²⁶Al to ²⁶Mg, from all over the Galactic plane. Although the sites from where this emission originates are not clearly established, novae are believed to be an important contributing source. In this context, V4332 Sgr presented a rare opportunity to observationally investigate whether novae or nova-like sources synthesize ²⁶Al and to what extent. Strong AlO bands in the near-IR have been reported in this object recently. As molecular bands of different isotopic compositions are readily resolved spectroscopically (e.g., ¹²CO and ¹³CO), it was thought that the components of AlO associated with ²⁶Al and stable ²⁷Al could be detected as separate bands. Our spectra indicate that there is no strong presence of ²⁶Al in V4332 Sgr. A reliable upper limit of 0.10 for the ²⁶Al/²⁷Al ratio is determined, which constitutes the first observational constraint for this ratio in a potential ²⁶Al-producing source. While V4332 Sgr is not a typical nova, its outburst amplitude and light-curve behavior bear close similarity to that of novae. Hence, although the results from V4332 Sgr cannot be directly extended to novae in general, the limit on the observed ²⁶Al/²⁷Al ratio could be a useful input in constraining rather uncertain nucleosynthesis models for the production of ²⁶Al in novae/nova-like sources. When we compare the observed ²⁶Al/²⁷Al ratio in V4332 Sgr with that expected in classical novae, it appears unlikely that the progenitor of V4332 Sgr is an oxygen-neon-magnesium white dwarf.