Novae

Novae are close binary star systems with a hot white dwarf and a cool main sequence companion. The strong gravity from the compact white dwarf star pulls matter away from the outer layers of the main sequence star. Eventually, the material accumulated on the surface of the white dwarf will undergo explosive nuclear burning in a flash that causes the system to brighten tremendously, by a factor of a thousand to a million (7 to 15 magnitudes) over the course of a day, or in some cases more slowly, over many months. After an outburst, the system fades more slowly. The timing of the flashes is not predictable. There are several different classes of nova, which are also called cataclysmic variables.

T Pyxidis

We have sonified data of the recurrent nova T Pyxidis, a binary star system about sixteen thousand light years from Earth. In quiescence, its magnitude is about 15.5, but during eruptions observed in 1890, 1902, 1920, 1944, 1966 and 2011, T Pyx has become as bright as magnitude 7. The photometric observations capture an eruption and its dimming, and the spectrum was taken 2 days after the discovery of the 2011 eruption.

Below is a sonified video of some observations of TPyx from February of 2011 to April of 2013, including 239 observations of TPyx. Each beat of time represents 3 days of time on Earth. The video scans over time (x-axis) and modulates pitch based on magnitude (y-axis). Lower pitch represents dimmer magnitudes. The baseline magnitude of about 15.5 is heard at the beginning of the video, interrupted by a powerful explosion that brings the magnitude to about 7. Then, the brightness undergoes a parabolic dimming for the following two years until it reaches its original quiescence.

Next, the observed spectrum of the nova TPyx is shown below as a sonified video. This video scans across a plot of brightness measured in flux or intensity of light (y axis) versus wavelength (x axis), moving from blue to red wavelengths from 3800 to 7200 angstroms. TPyx is hot, so the baseline of its spectrum is highest at shorter wavelengths towards the beginning of the video. Its spectrum is punctuated by huge hydrogen emission lines, and the largest peak can be heard clearly at 6562 Angstroms.

The spectrum of T Pyxidis was provided by the FAST Spectral Archive. The light curve is an optical v-band from AAVSO.