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Astronomers have employed NASA's Transiting Exoplanet Survey Satellite (TESS) and the Very Large Telescope (VLT) to conduct a detailed study of a chemically peculiar star known as HD 72968. Results of the study, May 9 on the pre-print server arXiv, yield crucial insights into the properties of this star.

Chemically peculiar (CP) stars are those with unusual metal abundances, thus exhibiting strong or weak spectral lines for certain elements. Some of them are observed to have stronger magnetic fields and are hence known as magnetic chemically peculiar stars (mCPs).

However, the unusual chemical composition of the atmospheres of CP stars makes the determination of their fundamental parameters difficult. Knowing the properties of these objects is important to unveil their evolutionary states.

Located some 350.5 light years away, HD 72968 is an Alpha² Canum Venaticorum variable—a subtype of an mCP. The star has an orbital period of 11.3 days and its magnitude varies between 5.72 and 5.74 mag.

A team of astronomers led by Milton Macías Laz of the Valencian International University in Spain decided to take a closer look at HD 72968, hoping to shed more light on its properties and behavior. For this purpose, they used TESS and VLT's Ultraviolet and Visual Echelle Spectrograph (UVES) to perform a photometric and spectroscopic analysis of this star.

Based on the observations, the orbital period of HD 72968 was determined to be 11.307 days. Moreover, a sub-period of 2.7 days was identified, possibly related to the star's pulsations, which is approximately 76% shorter than the orbital period.

The observations revealed changes in the morphology of the light curve of HD 72968. Sudden drops in the star's brightness were observed, possibly related to some ejection of material caused by pulsation. Moreover, the observations show that after the second drop, a disturbance in the light curve is maintained, which seems to be a remnant of the star's second eclipse or material ejection from the star.

Furthermore, the astronomers were able to perform a chemical abundance study of HD 72968. They found spectral lines of such elements as chromium and strontium in the spectrum of the star.

When it comes to the parameters of HD 72968, the study found that it has an effective temperature of about 10,500 K and a rotational velocity of 8 km/s. The radius of HD 72968 was estimated to be 2.5 solar radii and the distance to the star was measured to be approximately 350.55 light years.

The authors of the paper note that further spectral studies of HD 72968 should be conducted in order to determine more properties of this star.

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