Using the FFOREST high-resolution fiber-optic spectrograph installed at the 6-m BTA SAO RAS telescope, variations in the radial velocities were measured for the Main Sequence star TOI1408 of the spectral type F and the presence of an exoplanet was confirmed. Analysis of the spectroscopic data obtained with the BTA together with photometric estimates of the TESS orbital telescope suggests that a so-called grazing transit is observed, in which a planet covers its parent star with only part of its visible disk. Therefore, the exact radius of the planet TOI-1408.01 remains uncertain with a lower limit about ~1 R_Jup, which is significantly higher than the photometric estimate according to the TESS data. We also estimated the planet's mass as 1.69 ± 0.20 M_Jup and the orbital period ~4.425 days which makes this object a typical hot Jupiter, but with an unusually high orbital eccentricity of 0.259 ± 0.026! Based on the results of our modeling, it can be assumed that the planet will likely be subject to intense rounding of its orbit with high tidal eccentricity. An alternative is the possible presence of other invisible companions of the star TOI1408 that still have to be discovered.

Fig. 1. Doppler measurements from the FFOREST spectrograph with the orbital curve of the best model, the phases corresponding to the transit are marked with a gray rectangle.

Fig. 2. The photometric data from the TESS orbital telescope, an average curve is drawn through each of the 96 observed transits.

Published:
Galazutdinov G. A., Baluev R. V., Valyavin G., Aitov V., Gadelshin D., Valeev A., Sendzikas E., Sokov E., Mitiani G., Burlakova T., Yakunin I., Antonyuk K. A., Vlasyuk V., Romanyuk I., Rzaev A., Yushkin M., Ivanova A., Tavrov A., Korablev O., “Doppler confirmation of TESS planet candidate TOI1408.01: grazing transit and likely eccentric orbit”, Monthly Notices of the Royal Astronomical Society: Letters, 2023
DOI: 10.1093/mnrasl/slad127