Astronomers discover new tidal tilt pulsator

Astronomers have discovered a new tidal pulsator star (TTP) by analyzing data from NASA’s Transiting Exoplanet Survey Satellite (TESS). The newly discovered pulsator star, named TIC 435850195, belongs to a rare class of pulsator stars known as triaxial TTPs. The discovery is detailed in a research paper published on the preprint server arXiv on September 5.

So-called TTPs are pulsating stars in tight binaries whose pulsation axis is tilted into the orbital plane due to a tidal bulge caused by the companion star. Generally, the pulsation axis of such systems coincides with the tidal bulge rather than the star’s rotation axis.

The TTP is a rare find, with only a handful of these pulsators having been discovered to date, and only one of them, known as TIC 184743498, exhibits pulsations along three different axes, making it a triaxial pulsator (TAP).

Now, a team of astronomers led by Rahul Jayaraman of the Massachusetts Institute of Technology (MIT) reports the discovery of another TAP: by conducting a visual survey of the light curves from TESS’s full-frame images, they found that the eclipsing binary TIC 435850195 is experiencing TAP behavior.

“Here we report the identification of the second triaxial pulsator discovered to date, with the reliable detection of 16 pulsating multiplets, 14 of which are dipole doublets separated by 2 νorbs,” the researchers write.

Overall, the study found that TIC 435850195 displays 14 dipole double pulsations, two single pulsations, and two triplet pulsations (one dipole and one quadrupole). The astronomers speculate that the triplet dipole modes may not be fully tilted by the tides, but the quadrupole modes are difficult to interpret with the currently available data.

After further investigation of the pulsations, the team concluded that the observed multiple events were indeed caused by tidal phenomena. They also ruled out the possibility that these multiple events were a function of the observational viewpoint of the system.

Regarding the parameters of TIC 435850195, the researchers found that it is composed of a slightly evolved primary star, Delta Scuti, and a K-type secondary star that still has a main sequence age of zero. The age of the system is estimated to be around 1 billion years and it is located about 1,750 light-years from Earth.

Summarizing their results, the authors noted that TIC 435850195 is rich in observed pulsation behavior, making the system a unique laboratory for thoroughly investigating the influence of the companion star’s gravitational field on the stellar pulsation.

Astronomers hope that future releases of TESS light curves will enable the detection of triaxial pulsations in even more types of stars.

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