0.8–13 Micron Spectroscopy of V838 Monocerotis and a Model for Its Emission

Abstract

We report on the results of a number of infrared spectra (0.8-2.5, 2.1-4.6, and 3-14 m) of V838 Monocerotis, taken from a short time after discovery in 2002 January to about 14 months later, in early 2003. The spectrum evolved dramatically, changing from a quasi-photospheric stellar spectrum with weak atomic emission lines (some with P Cygni profiles) to one showing a wide range of deep absorption features indicative of a cool, extended atmosphere with a circumstellar dust shell. The early spectra showed lines of s-process elements, such as Sr ii and Ba i. The later spectra showed absorption by gaseous H 2 O, CO, AlO, TiO, SiO, SO 2 , OH, VO, and SH, as well as a complex of emission near 10 m reminiscent of silicate emission, with a central absorbing feature at 10:3 m. Thus, V838 Mon appears to be oxygen-rich. A simple, spherically symmetric model of the system involving a central star with a two-component expanding circumstellar shell is presented that is able to explain the major molecular features and spectral energy distribution in the object's late stages. The derived shell mass and distance are 0.04 M and 9.2 kpc, respectively.

An Extended Grid of Nova Models. Iii. Very Luminous, Red Novae

“…(2007)) to have physical properties inconsistent with all of the nova models in Paper I. While thermonuclear-powered nova eruptions can explain the luminosities of these objects, their massive and very cool ejecta seem totally different from those of other novae (Mould et al (1990), Bond et al (2003), Munari et al (2002), Banerjee & Ashok (2002), Kimeswenger et al (2002), Soker & Tylenda (2003), Kipper, Klochkova, & Annuk (2004), Lynch et al (2004)). Does the nova model fail for these objects?…”

On the properties of dust and gas in the environs of V838 Monocerotis

“…The spectrum has been evolving dynamically and in terms of composition from the first to the most recent observations. The response of the star to the outburst seems to have been to develop an expanding photosphere and a multi-component circumstellar shell (Lynch et al 2004;Geballe et al 2007;Tylenda et al 2009), this material flowing out and some falling back. The velocities are generally from some tens to 200 km s −1 , and temperatures range from about 2000 K in the photosphere, to a few 100 K in the extended circumstellar region some 200−300 AU out.…”

“…The CO energy diagram shows two discrete components: a cold component with a peak of the line intensity at the upper state energy E up < 55 K (lower than J = 4−3), and a warm component with a rising trend with increasing E up . Our working hypothesis is that the cold component is associated with ISM gas -although it is also possible that it arises from a cold shell (à la Lynch et al 2004) -while the warm component is associated with the circumstellar envelope/environment (i.e. arising out of the outflow triggered by the stellar impact).…”

“…We note here that in the RADEX calculations, the escape probability used is that for a slab/cylinder morphology. Lynch et al (2004) suggests a model of a hollow sphere, and this model is one we wish to follow as much as possible in our calculations. The typical optical depth of the CO lines for V838 Mon as estimated by the RADEX modelling of the Herschel spectra is 3.…”

“…Lynch et al 2004;Rushton et al 2005). This includes the detection of CO rotational-vibration bands at near-infrared wavelengths (Lynch et al 2004) and rotational transition at millimetre wavelengths (Kaminski et al 2007), and rotational-vibration bands of SiO (Lynch et al 2004), as well as SiO masers (Deguchi et al 2005). We will compare some of these past observations with our molecular line analysis.…”