Changes in the red giant and dusty environment of the recurrent nova RS Ophiuchi following the 2006 eruption

Abstract

We present near-infrared spectroscopy of the recurrent nova RS Ophiuchi (RS Oph) obtained on several occasions after its latest outburst in 2006 February. The 1-5 μm spectra are dominated by the red giant, but the H I, He I and coronal lines present during the eruption are present in all our observations. From the fits of the computed infrared spectral energy distributions to the observed fluxes, we find T eff = 4200 ± 200 K for the red giant. The first overtone CO bands at 2.3 μm, formed in the atmosphere of the red giant, are variable. The spectra clearly exhibit an infrared excess due to dust emission longward of 5 μm; we estimate an effective temperature for the emitting dust shell of 500 K, and find that the dust emission is also variable, being beyond the limit of detection in 2007. Most likely, the secondary star in RS Oph is intrinsically variable.

The Supersoft X-Ray Phase of Nova Rs Ophiuchi 2006

“…Besides the X-ray observations, data on RS Oph were also collected in the radio (O'Brien et al 2006;Kantharia et al 2007;Eyres et al 2009), IR (Monnier et al 2006;Das et al 2006;Evans et al 2007aEvans et al , 2007bChesneau et al 2007;Lane et al 2007;Banerjee et al 2009;Rushton et al 2010;Brandi et al 2009), and optical bands (Hachisu et al 2006;Worters et al 2007;Bode et al 2007;Munari et al 2007;Brandi et al 2009). Hachisu et al (2007) discussed the temporal evolution of the RS Oph SSS X-ray light curve, but did not include any detailed consideration of the spectral characteristics or their evolution; nor did they include the effects of interstellar and (changing) circumstellar absorption on their conclusions.…”

First overtone CO bands in the giant component of RS Ophiuchi: the12C/13C ratio in 2008

“…This is consistent with that expected after the first dredge-up (Charbonnel 1994) and suggests that the RG in RS Oph has undergone the first dredge-up and has evolved beyond this evolutionary stage. In spectra shown by Rushton et al (2010), numerous emission lines are visible in the spectral regions around 1.0-1.8 μm. These form in material ejected in the 2006 eruption or in the shocked or ionized RG wind, in each case well away from the photosphere of the secondary.…”

“…The properties of the dust shell around RS Oph have been discussed by Evans et al (2007), van Loon (2008) and Woodward et al (2008). and Rushton et al (2010) have shown that the 2 μm spectral region of RS Oph is not affected by emission from the hot (∼500-600 K) dust known to currently envelop RS Oph, which is likely a permanent feature of the system. As this dust emission becomes prominent longwards of 3 μm, we are justified in carrying out our analysis for the dust-free case.…”

“…Dust is present in the RS Oph system (Evans et al 2007;van Loon 2008;Woodward et al 2008), emitting primarily at λ 10 μm. However Rushton et al (2010) have shown that there is also evidence for dust emission at shorter ( 5 μm) wavelengths and that emission by the dust envelope may be variable.…”

“…E-mail: yp@mao.kiev.ua showed that the secondary in RS Oph is an RG with T eff = 4100 ± 100 K and solar metallicity, but with a deficit of carbon and an overabundance of nitrogen with respect to solar. Rushton et al (2010) have modelled the spectral energy distribution (SED) of RS Oph in the near-IR (1-5 μm) and found that T eff is essentially constant over the period of 2006 August-2008 July. Nitrogen overabundance, and carbon underabundance, is typical of 'normal' RGs due to the conversion of C to N in the CN cycle of hydrogen burning and the subsequent dredge-up of the products on the red giant branch (RGB; Smith & Lambert 1985, 1986Smiljanic et al 2009).…”