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

We present the discoveries of KELT-25 b (TIC 65412605, TOI-626.01) and KELT-26 b (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 Transiting Exoplanet Survey Satellite (TESS) photometry. KELT-25 b is on a 4.40 day orbit around the V = 9.66 star CD-24 5016 ( ${T}_{\mathrm{eff}}={8280}_{-180}^{+440}$ K, M_⋆ = ${2.18}_{-0.11}^{+0.12}$ M_⊙), while KELT-26 b is on a 3.34 day orbit around the V = 9.95 star HD 134004 ( ${T}_{\mathrm{eff}}$ = ${8640}_{-240}^{+500}$ K, M_⋆ = ${1.93}_{-0.16}^{+0.14}$ M_⊙), which is likely an Am star. We have confirmed the substellar 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 = ${1.64}_{-0.043}^{+0.039}$ R_J and a 3σ upper limit on the companion's mass of ∼64 M_J. For KELT-26 b, we infer a planetary mass and radius of M_P = ${1.41}_{-0.51}^{+0.43}$ ${M}_{{\rm{J}}}$ and R_P = ${1.94}_{-0.058}^{+0.060}$ R_J. From Doppler tomographic observations, we find KELT-26 b 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-25 b appears to be in a well-aligned, prograde orbit, and the system is likely a member of the cluster Theia 449. ^* This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.