The TESS mission was designed to find transiting planets around bright, nearby stars. Here we present the detection and mass measurement of a small, short period (\(\sim 4\) day) transiting planet aroundthe bright (V = 7.9), solar-type star HD 86226 (TOI-652, TIC 22221375), previously known to host along-period (\(\sim 1600\) day) giant planet. HD 86226 c (TOI-652.01) has a radius of \(2.16\pm0.08\) \(R_\oplus\) and a mass of \(7.25^{+1.19}_{-1.12}\) \(M_\oplus\) based on archival and new radial velocity data. We also update the parameters of the longer-period, not-known-to-transit planet, and find it to be less eccentric and less massive than previously reported. The density of the transiting planet is \(3.97\) \(g\) \(cm^{-3}\), which is low enough to suggest that the planet has at least a small volatile envelope, but the mass fractions of rock, iron, and water are not well constrained. Given the host star brightness, planet period, and location of the planet near both the “radius gap” and the “hot Neptune desert”, HD 86226 c is an interesting candidate for transmission spectroscopy to further refine its composition.
Authors: Johanna Teske, Matías R. Díaz, Rafael Luque, Teo Močnik, Julia V. Seidel, Jon Fernández Otegi, Fabo Feng, James S. Jenkins, Enric Pallè, Damien Sègransan, Stèphane Udry, Karen A. Collins, Jason D. Eastman, George R. Ricker,Roland Vanderspek, David W. Latham, Sara Seager, Joshua N. Winn, Jon M. Jenkins, David. R. Anderson, Thomas Barclay, François Bouchy, Jennifer A. Burt, R. Paul Butler, Douglas A. Caldwell, Kevin I. Collins, Jeffrey D. Crane, Caroline Dorn, Erin Flowers, Jonas Haldemann, Ravit Helled, Coel Hellier, Eric L. N. Jensen, Stephen R. Kane, Nicholas Law, Jack J. Lissauer, Andrew W. Mann, Maxime Marmier, Louise Dyregaard Nielsen, Mark E. Rose, Stephen A. Shectman, Avi Shporer, Guillermo Torres, Sharon X. Wang, Angie Wolfgang, Ian Wong and Carl Ziegler