2025ApJ...995L...4E

We present the OASIS survey program discovery of a substellar companion orbiting the young A1V star HIP 71618, detected using precision astrometry from Gaia and Hipparcos and high-contrast imaging with SCExAO/CHARIS and Keck/NIRC2. Atmospheric modeling favors a spectral type of M5-M8 and a temperature of ∼2700 ± 100 K. Dynamical modeling constrains HIP 71618 B's mass to be ${60}_{-21}^{+27}$M_Jup or ${65}_{-29}^{+54}$M_Jup, depending on the adopted companion mass prior. It has a nearly-edge-on 11 au orbit with high eccentricity. HIP 71618 B will be located within the Roman Coronagraph's dark-hole region during the instrument's technological demonstration phase. A high-signal-to-noise-ratio detection of HIP 71618 B at 575 nm would demonstrate a 5σ contrast of 10^–7 or better. The system is also located within or very close to the Roman Coronagraph's Continuous Viewing Zone-near multiple candidate reference stars for dark-hole digging-and its primary is bright (V ≈ 5). The suitability of HIP 71618 as a potential Roman Coronagraph target for demonstrating the instrument's core requirement (TTR5) should motivate the timely deep vetting of candidate reference stars.