KELT-25b and KELT-26b: A Hot Jupiter and a Substellar Companion Transiting Young A-stars Observed by TESS

We present the discoveries of KELT-25b (TIC 65412605, TOI-626.01) and KELT-26b (TIC 160708862, TOI-1337.01), two transiting companions orbiting relatively bright, early A-stars. The transit signals were initially detected by the KELT survey, and subsequently confirmed by TESS photometry. KELT-25b is on a 4.40-day orbit around the V = 9.66 star CD-24 5016 (T_(eff) = 8280⁺⁴⁴⁰₋₁₈₀K, M⋆ = 2.18^(+0.12)_(−0.11) M⊙), while KELT-26b is on a 3.34-day orbit around the V = 9.95 star HD 134004 (T_(eff) =8640⁺⁵⁰⁰₋₂₄₀ K, M⋆ = 1.93^(+0.14)_(−0.16) M⊙), which is likely an Am star. We have confirmed the sub-stellar nature of both companions through detailed characterization of each system using ground-based and TESS photometry, radial velocity measurements, Doppler Tomography, and high-resolution imaging. For KELT-25, we determine a companion radius of R_P = 1.64^(+0.039)_(−0.043) R_J, and a 3-sigma upper limit on the companion's mass of ∼64 M_J. For KELT-26b, we infer a planetary mass and radius of M_P = 1.41^(+0.43)_(−0.51) M_J and R_P = 1.940^(+0.060)_(−0.058) R_J. From Doppler Tomographic observations, we find KELT-26b to reside in a highly misaligned orbit. This conclusion is weakly corroborated by a subtle asymmetry in the transit light curve from the TESS data. KELT-25b appears to be in a well-aligned, prograde orbit, and the system is likely a member of a cluster or moving group.