Deuterium limits measured in spectra of HD 32115 and 21 Peg

Star system: HD 32115 | Distance from the Sun: 160 light years

Deuterium is a heavier version of hydrogen that is typically destroyed by nuclear fusion in the interiors of stars. Because of this, it is not expected to appear in the light emitted from a star's surface, or photosphere. However, early-type stars, which include B, A, and F-type categories, have outer layers that mix slowly. This property might allow recently accreted material containing deuterium to survive long enough to be detected in spectral observations.

The research explored the ability to detect deuterium in these stars by creating synthetic spectral models. These models focused on the Balmer lines, which are specific sets of light wavelengths emitted by hydrogen atoms. A statistical method known as Markov Chain Monte Carlo was used to analyze how varying the quality of data—specifically the signal-to-noise ratio—and the physical properties of the stars, such as temperature and rotation speed, affect the chances of identifying deuterium.

This analytical framework was then applied to real-world data from two stars: the A9-type star HD 32115 and the B9.5-type star 21 Peg. The investigation determined the upper limits of deuterium abundance for these objects. By establishing these constraints, the study suggests that detecting deuterium in future observations could act as a new method for tracking the intake of planetary material falling onto stars.

Key findings
- Deuterium abundance upper limit for HD 32115 established at D/H < -5.5 dex.
- Deuterium abundance upper limit for 21 Peg established at D/H < -4.9 dex.
- Detection sensitivity for deuterium improves significantly with higher signal-to-noise ratios.
- Stellar temperature and rotational velocity are critical factors in the ability to detect deuterium.
- Observation of deuterium on star surfaces offers a potential way to study fallen proto-planetary or exo-planetary material.

Scientific study

Detectability of deuterium in spectra of early-type stars (external link)