Confirmation of a Sub-Saturn-size Transiting Exoplanet Orbiting a G Dwarf: TOI-1194 b and a Very Low Mass Companion Star: TOI-1251 B from TESS

We report the confirmation of a sub-Saturn-size exoplanet, TOI-1194 b with a mass about 0.456(-0.051)(+0.055) MJ, and a very low mass companion star with a mass of about 96.5 +/- 1.5 M-J, TOI-1251 B. Exoplanet candidates provided by the Transiting Exoplanet Survey Satellite (TESS) are suitable for further follow-up observations by ground-based telescopes with small and medium apertures. The analysis is performed based on data from several telescopes worldwide, including telescopes in the Sino-German multiband photometric campaign, which aimed at confirming TESS Objects of Interest (TOIs) using ground-based small-aperture and medium-aperture telescopes, especially for long-period targets. TOI-1194 b is confirmed based on the consistent periodic transits depths from the multiband photometric data. We measure an orbital period of 2.310644 +/- 0.000001 d, and radius is 0.767(-0.041 )(+0.045)RJ, and amplitude of RV curve is 69.4(-7.3)(+7.9) m/s(-1). TOI-1251 B is confirmed based on the multiband photometric and high-resolution spectroscopic data, whose orbiting period is 5.963054(-0.000001)(+0.000002) d, the radius is 0.947(-0.033)(+0.035) RJ, and amplitude of RV curve is 9849(-40 )(+42)m/s(-1).