# Gas phase SiO in the circumstellar environment of the recurrent nova T Coronae Borealis

## TL;DR

This study reports the detection of SiO gas in the environment of the recurrent nova T Coronae Borealis, revealing details about its composition, temperature, and potential for future observations of maser emission and high-energy phenomena.

## Contribution

First detection of gas-phase SiO in T CrB's environment, with analysis of its properties and implications for nova eruptions and stellar wind interactions.

## Key findings

- SiO column density ~2.8x10^17 /cm2
- Red giant's 12C/13C ratio <9, best ~5
- No evidence of dust in the environment

## Abstract

We report the discovery of the diatomic molecule SiO in the gas phase in the environment of the recurrent nova T Coronae Borealis. While some of the SiO is photospheric, a substantial portion must arise in the wind from the red giant component of T CrB. A simple fit to the SiO feature, assuming local thermodynamic equilibrium, suggests a SiO column density of 2.8x10^17 /cm2 and temperature ~1000K; the SiO column density is similar to that present in the winds of field red giants. A search for SiO maser emission is encouraged both before and after the next anticipated eruption. We find that the 12C/13C ratio in the red giant is <9, with a best fit value of ~5, a factor ~18 times lower than the solar value of 89. We find no convincing evidence for the presence of dust in the environment of T CrB, which we attribute to the destructive effects on nucleation sites of hard X-ray emission. When the next eruption of T CrB occurs, the ejected material will shock the wind, producing X-ray and coronal line emission, as is the case for the recurrent nova RS Oph. T CrB is also a good candidate for very high energy gamma-ray emission, as first observed during the 2010 outburst of V407 Cyg. We include in the paper a wide variety of infrared spectroscopic and photometric data.