Remarkable Changes in the Near-Infrared Spectrum of the Nova-like Variable V4332 Sagittarii

Abstract

We report on recent near-IR observations of V4332 Sgr -the nova-like variable that erupted in 1994. Its rapid, post-outburst evolution to a cool M type giant/supergiant, soon after its outburst, had showed that it was an unusual object differing from other eruptive variables like classical/symbiotic novae or born-again AGB stars. The present study of V4332 Sgr was motivated by the keen interest in the recent eruption of V838 Mon -an object with a spectacular light-echo and which, along with V4332 Sgr, is believed to belong to a new class of objects (we propose they may be called "quasi-novae"). Our observations show new developments in the evolution of V4332 Sgr. The most striking feature is the detection of several molecular bands of AlO -a rarely seen molecule

L and M Band Infrared Studies of V4332 Sagittarii: Detection of the Water Ice Absorption Band at 3.05 μm and the CO Fundamental Band in Emission

“…The 5 4 # 10 L , outburst luminosity of V4332 Sgr is difficult to estimate, as the distance d to the object is very uncertain. Using an estimate of pc (Martini et al 1999), we have shown that the star d p 300 has a quiescent luminosity of (Banerjee et al 2003). A 0.3 L , 9.5 mag brightening at outburst would yield an outburst luminosity of ∼ .…”

“…A considerable change in the spectral energy distribution (SED) of the object was seen between Two Micron All Sky Survey (2MASS) data of 1998 and observations in 2003 indicating the formation of a dust shell between these two epochs (Banerjee et al 2003). A better estimate of the epoch when the dust actually formed is discussed here.…”

“…These are all young objects observationally known to possess CSDs. Furthermore, all the gaseous components of V4332 Sgr are seen in emission, i.e., the K i/Na i, CO, AlO, and TiO lines (Banerjee & Ashok 2004;Banerjee et al 2003). These species are at a low temperature (200 K for AlO; a low excitation temperature is also implied for the K i/Na i lines, which need only ∼1.5-2 eV for excitation).…”

“…Recent infrared studies of V4332 Sgr have detected several bands of AlO at a low rotational temperature of 200-300 K (Banerjee et al 2003). A considerable change in the spectral energy distribution (SED) of the object was seen between Two Micron All Sky Survey (2MASS) data of 1998 and observations in 2003 indicating the formation of a dust shell between these two epochs (Banerjee et al 2003).…”

Rotational spectroscopy of AlO

“…The mineralogical dust condensation sequence and processes involved are issues of considerable interest to astronomers. The AlO radical also received considerable attention after the strong detection of several A → X bands in the near-infrared (1-2.5 microns) in the eruptive variables V4332 Sgr and V838 Mon (Banerjee et al 2003;Evans et al 2003). Other IR detections of AlO include IRAS 08182-6000 and IRAS 18530+0817 (Walker et al 1997).…”