About 467 light-years away, a stellar system designated TIC 197757000 is performing a cosmic dance—two stars orbiting each other every 2.2 days.

Now, a team of scientists has unveiled the secrets of this system using data from NASA's TESS space telescope alongside ground-based observations. They confirm that the binary is tidally synchronized, offering fresh insights into how tidal locking shapes pulsations in close binaries.

Led by Ph.D. student Shahidin Yaqup and his supervisor Prof. Ali Esamdin at the Xinjiang Astronomical Observatory (XAO) of the Chinese Academy of Sciences (CAS), the research was published in the journal Research in Astronomy and Astrophysics.

According to the researchers, what makes this binary stand out is that one of its components is a δ Scuti pulsating star—a class of stars that rhythmically "beat" with periods of just a few hours. When such a pulsator resides in a close binary, the gravitational pull from its companion can dramatically reshape its pulsation behavior.

The researchers first used spectroscopy to measure the primary's temperature, then performed orbital fitting using high-precision TESS and multi-band ground photometry to constrain the masses and radii of the binary stars. The derived key physical parameters are as follows: the primary has Teff ≈ 7782 K and M = 1.78 solar masses, while the secondary has Teff ≈ 4409 K and M = 0.98 solar masses.

The team also measured a large frequency separation of 33.45 μHz. This separation acts as a unique pulsation fingerprint for the star, allowing researchers to calculate the stellar mean density and providing evidence for investigating the star's internal structure. The mean density derived from the large frequency separation shows remarkable agreement with the value computed via the binary star model parameters, which validates the reliability of the binary model analysis.

Three lines of evidence—the short orbital period, ellipsoidal distortions in the light curve, and the presence of orbital harmonics in the pulsation signals—all converge on a single conclusion: TIC 197757000 is a tidally synchronized system.

The researchers said this work not only provides a valuable benchmark for stellar interior studies but also opens a new window into how tidal locking influences the pulsation behavior of stars in close binaries.