HD 281229 reveals how a very young star rotates

Young star HD 281229, in the Perseus Molecular Cloud, shows a repeating pattern in its gravity-driven pulsations. The pattern makes it possible to probe the star’s interior and estimate how quickly its central regions rotate. It is the youngest star known with a detected and modelled pattern of this kind.

Star system: HD 281229 | Distance from the Sun: 988 light years

HD 281229 is the youngest star known to have a detected and modelled pattern of period spacings in its gravity-driven pulsations. These waves travel through a star’s interior, carrying clues about its structure and rotation. The pattern provides a way to study a star at a very early stage of its evolution.

The star’s brightness changes were measured using observations from NASA’s Transiting Exoplanet Survey Satellite, or TESS. The light measurements were analysed to identify pulsations, which are regular changes in brightness caused by waves inside a star. Researchers compared the timing between pulsations with models that account for rotation. They fitted two patterns, called dipole and quadrupole, which describe different shapes of pulsation.

The combined fit gives an estimated asymptotic period spacing of 4,776 ± 400 seconds. This value describes the underlying spacing between periods of gravity-driven pulsations. The analysis also estimates a rotation frequency of 1.317 ± 0.05 times per day near the star’s core. The result shows that these pulsations can provide useful measurements of the interior and rotation of very young stars.

The wider search examined 148 targets selected as members of the Perseus Molecular Cloud. It identified eight pressure-mode pulsators and two objects with possible gravity-mode pulsations. Pressure modes are waves restored by pressure, while gravity modes are shaped by buoyancy inside a star. The previously known pulsating star V705 Per was also analysed, bringing the total sample to 149 targets.

Key findings
HD 281229 is the youngest star known with a detected and modelled period-spacing pattern.
Fitting dipole and quadrupole patterns gives an asymptotic period spacing of 4,776 ± 400 seconds.
The estimated rotation frequency near the star’s core is 1.317 ± 0.05 times per day.
The search identified eight pressure-mode pulsators and two possible gravity-mode pulsators among 148 selected targets.

Scientific study

Asteroseismic properties of young pulsators in the Perseus Molecular Cloud. Discovery of period-spacing patterns in HD 281229 (external link)