Abstract
We present further Spitzer Space Telescope observations of the recurrent nova RS Ophiuchi, obtained over the period 208-430 days after the 2006 eruption. The later Spitzer IRS data show that the line emission and free-free continuum emission reported earlier is declining, revealing incontrovertible evidence for the presence of silicate emission features at 9.7 and 18 μm. We conclude that the silicate dust survives the hard radiation impulse and shock blast wave from the eruption. The existence of the extant dust may have significant implications for understanding the propagation of shocks through the red giant wind and likely wind geometry.
Highlights
RS Oph is a recurrent nova (RN) that erupted in 1898, 1933, 1958, 1967, and 1985 (Wallerstein 2008)
On the assumption that the silicate dust we see in the Spitzer spectrum arises in the red giant (RG) wind, we conclude that the RG in the RS Oph system cannot be carbon-rich; this is consistent with the presence of TiO bands in the optical (Blair et al 1983), and the presence of deep O i absorption combined with no carbon absorption in the X-ray range (Ness et al 2007)
Our continuing Spitzer observations of RS Oph will enable us to examine the effects of irradiation on the dust, and of the re-formation of dust as the circumbinary environment is reestablished by RG wind infill
Summary
RS Oph is a recurrent nova (RN) that erupted in 1898, 1933, 1958, 1967, and 1985 (Wallerstein 2008) It consists of a semidetached binary (orbital period 455.7 days) comprising a Roche-lobe-filling red giant (M2 III) and a massive (տ1.2 M,) white dwarf (WD; Fekel et al 2000). The 1985 eruption was, for the first time, the subject of a multiwavelength observational campaign, from the radio to the X-ray (Bode 1987). Infrared (IR) observations (Das et al 2006; Evans et al 2007a, 2007b) showed evidence for the shock, seen at radio (Eyres et al 2007; O’Brien et al 2006) and X-ray (Bode et al 2006; Sokoloski et al 2006; Ness et al 2007; Osborne et al 2007) wavelengths, as the ejecta interacted with the RG wind. We present here further IR observations conducted as part of a long-duration synoptic campaign, obtained later in the outburst with the Spitzer Infrared Spectrometer (IRS; Houck et al 2004)
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