Wide Separation Planets In Time (WISPIT): Discovery of a Gap H$\hat{I}\pm$ Protoplanet WISPIT 2b with MagAO-X

Abstract

Excellent (<25 mas) H${}_{\hat{I}}\pm$ images of the star TYC 5709-354-1 led to the discovery of a rare H${}_{\hat{I}}\pm$ protoplanet. This star was discovered by the WISPIT survey to have a large multi-ring transitional disk, and is hereafter WISPIT 2. Our H${}_{\hat{I}}\pm$ images of 2025, April 13 and April 16 discovered an accreting (H${}_{\hat{I}}\pm$ in emission) protoplanet: WISPIT 2b (r=309.43$\pm$1.56 mas; (~54 au deprojected), PA=242.21$\pm$0.41 degrees) likely clearing a dust-free gap between the two brightest dust rings in the transitional disk. Our SNR=12.5 detection gave an H${}_{\hat{I}}\pm$ ASDI contrast of (6.5$\pm$0.5)x10${}^{-4}$ and a H${}_{\hat{I}}\pm$ line flux of (1.29$\pm$0.28)x10${}^{-15}$ erg/s/cm${}^2$. We also present L' photometry from LBT/LMIRcam of the planet (L'=15.30$\pm$0.05 mag) which, when coupled with an age of 5.1${}_{-1.3}^{+2.4}$ Myr, yields a planet mass estimate of 5.3$\pm$1.0 Mjup from the DUSTY evolutionary models. WISPIT 2b is accreting at 2.25${}_{+3.75}^{-0.17}$x10${}^{-12}$ Msun/yr. WISPIT 2b is very similar to the other H${}_{\hat{I}}\pm$ protoplanets in terms of mass, age, flux, and accretion rate. The inclination of the system ($i$=44 degrees) is also, surprisingly, very similar to the other known H$\hat{I}\pm$ protoplanet systems which all cluster from 37$\le i\le$52 degrees. We argue this clustering has only a ~1.0% (2.6 sigma) probability of occurring randomly, and so we speculate that magnetospherical accretion might have a preferred inclination range (~37-52 degrees) for the direct (cloud free, low extinction) line of sight to the H-alpha line formation/shock region. We also find at 110mas (~15au deprojected) a close companion candidate (CC1) which may be consistent with an inner dusty 9$\pm$4 Mjup planet.

33 pages, 7 figures, Accepted for publication in ApJ Letters