Abstract

2MASS J16120668-3010270 (hereafter 2MJ1612) is a young M0 star that hosts a protoplanetary disk in the Upper Scorpius star-forming region. Recent Atacama Large Millimeter/submillimeter Array (ALMA) observations of 2MJ1612 show a mildly inclined disk (i = 37°) with a large dust-depleted gap (Rcav ? 0 . ? 4 or 53 au). We present high-contrast H? observations from MagAO-X on the 6.5 m Magellan telescope and new high-resolution submillimeter dust continuum observations with ALMA of 2MJ1612. On both 2025 April 13 and 16, we recovered a point source with H? excess with a signal-to-noise ratio ?5 within the disk gap in our MagAO-X angular and spectral differential images at a separation of 141.96 ± 2.10 mas (23.45 ± 0.29 au deprojected) from the star and a position angle ?????of 159 . ° 00 ± 0 . ° 55. Furthermore, this H? source is within close proximity to a K-band point source in the SPHERE/IRDIS observation taken on 2023 July 21. The astrometric offset between the K band and H? source can be explained by orbital motion of a bound companion. Thus, our observations can be best explained by the discovery of an accreting protoplanet, 2MJ1612 b, with an estimated mass of 4 MJup and a H? line flux ranging from (29.7 ± 7.5) × 10?16 erg s cm2 to (8.2 ± 3.4) × 10?16 erg s cm2. 2MJ1612 b is likely the third example of an accreting H? protoplanet responsible for carving the gap in its host disk, joining PDS 70 b and c. Further study is necessary to confirm and characterize this protoplanet candidate and to identify any additional protoplanets that may also play a role in shaping the gap. © 2025. The Author(s). Published by the American Astronomical Society.