Kavli Affiliate: Gregory J. Herczeg
| First 5 Authors: Jialin Li, Jialin Li, , ,
| Summary:
2MASS J16120668-3010270 (hereafter 2MJ1612) is a young M0 star that hosts a
protoplanetary disk in the Upper Scorpious star-forming region. Recent ALMA
observations of 2MJ1612 show a mildly inclined disk ($i$=37$^circ$) with a
large dust-depleted gap (R$_textcavapprox$0.4" or 53 au). We present
high-contrast H$alpha$ observations from MagAO-X on the 6.5m Magellan
Telescope and new high resolution sub-mm dust continuum observations with ALMA
of 2MJ1612. On both 2025 April 13 and 16, we recovered a point source with
H$alpha$ excess with SNR $gtrsim$5 within the disk gap in our MagAO-X Angular
and Spectral Differential (ASDI) images at a separation of 141.96$pm$2.10 mas
(23.45$pm$0.29 au deprojected) from the star and position angle (PA)=
159.00$pm$0.55$^circ$. Furthermore, this H$alpha$ source is within close
proximity to a K band point source in SPHERE/IRDIS observation taken on 2023
July 21 citepsphere2025sub. The astrometric offset between the K band and
H$alpha$ 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$M_textJup$ and H$alpha$
line flux ranging from (29.7 $pm$7.5)$times$10$^-16$ ergs/s/cm$^2$ to
(8.2$pm$3.4)$times$10$^-16$ ergs/s/cm$^2$. 2MJ1612 b is likely the third
example of an accreting H$alpha$ protoplanet responsible for carving the gap
in its host disk, joining PDS 70b 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.
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