Wide Separation Planets in Time (WISPIT): Discovery of a Gap H<i>α</i> Protoplanet WISPIT 2b with MagAO-X

Abstract Excellent (&lt;25 mas) H α images of the star TYC 5709-354-1 led to the discovery of a rare H α protoplanet. This star was discovered by the WISPIT survey to have a large multi-ring transitional disk, and is hereafter WISPIT 2. Our H α images of 2025 April 13 and 16 discovered an accreting (H α in emission) protoplanet: WISPIT 2b ( r = 309.43 ± 1.56 mas; (∼54 au deprojected), PA = 242 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mtext>°</mml:mtext> </mml:mrow> </mml:mover> </mml:math> 21 ± 0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mtext>°</mml:mtext> </mml:mrow> </mml:mover> </mml:math> 41) likely clearing a dust-free gap between the two brightest dust rings in the transitional disk. Our signal-to-noise ratio of 12.5 detection gave an H α ASDI contrast of (6.5 ± 0.5) × 10 −4 and an H α line flux of (1.29 ± 0.28) × 10 −15 erg s −1 cm −2 . We also present L ′ photometry from LBT/LMIRcam of the planet ( L ′ = 15.30 ± 0.05 mag), which, when coupled with an age of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>5</mml:mn> <mml:mo>.</mml:mo> <mml:msubsup> <mml:mn>1</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> <mml:mo>.</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>2</mml:mn> <mml:mo>.</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> Myr, yields a planet mass estimate of 5.3 ± 1.0 M jup from the DUSTY evolutionary models. WISPIT 2b is accreting at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>2</mml:mn> <mml:mo>.</mml:mo> <mml:msubsup> <mml:mn>25</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0</mml:mn> <mml:mo>.</mml:mo> <mml:mn>17</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>3</mml:mn> <mml:mo>.</mml:mo> <mml:mn>75</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> × 10 −12 M Sun yr −1 . WISPIT 2b is very similar to the other H α protoplanets in terms of mass, age, flux, and accretion rate. The inclination of the system ( i = 44°) is also, surprisingly, very similar to the other known H α protoplanet systems, which all cluster from 37° ≤ i ≤ 52°. We argue this clustering has only a ∼1.0% (2.6 σ ) probability of occurring randomly, and so we speculate that magnetospherical accretion might have a preferred inclination range (∼37°–52°) for the direct (cloud free, low extinction) line of sight to the H α line formation/shock region. We also find at 110 mas (∼15 au deprojected) a close companion candidate (CC1) that may be consistent with an inner dusty 9 ± 4 M jup planet.