Dr. Rabus, Markus

2021, Dr. Rabus, Markus, Scarsdale, Nicholas, Murphy, Joseph, Batalha, Natalie, Crossfield, Ian, Dressing, Courtney, Fulton, Benjamin, Howard, Andrew, Huber, Daniel, Isaacson, Howard, Kane, Stephen, Petigura, Erik, Robertson, Paul, Roy, Arpita, Weiss, Lauren, Beard, Corey, Behmard, Aida, Chontos, Ashley, Christiansen, Jessie, Ciardi, David, Claytor, Zachary, Collins, Karen, Collins, Kevin, Dai, Fei, Dalba, Paul, Dragomir, Diana, Fetherolf, Tara, Fukui, Akihiko, Giacalone, Steven, Gonzales, Erica, Hill, Michelle, Hirsch, Lea, Jensen, Eric, Kosiarek, Molly, de Leon, Jerome, Lubin, Jack, Lund, Michael, Luque, Rafael, Mayo, Andrew, Močnik, Teo, Mori, Mayuko, Narita, Norio, Nowak, Grzegorz, Pallé, Enric, Rosenthal, Lee, Rubenzahl, Ryan, Schlieder, Joshua, Shporer, Avi, Stassun, Keivan, Twicken, Joe, Wang, Gavin, Yahalomi, Daniel, Jenkins, Jon, Latham, David, Ricker, George, Seager, S., Vanderspek, Roland, Winn, Joshua

We present the discovery of two nearly identically sized sub-Neptune transiting planets orbiting HD 63935, a bright (V = 8.6 mag), Sun-like (Teff = 5560 K) star at 49 pc. TESS identified the first planet, HD 63935 b (TOI509.01), in Sectors 7 and 34. We identified the second signal (HD 63935 c) in Keck High Resolution Echelle Spectrometer and Lick Automated Planet Finder radial velocity data as part of our follow-up campaign. It was subsequently confirmed with TESS photometry in Sector 34 as TOI-509.02. Our analysis of the photometric and radial velocity data yielded a robust detection of both planets with periods of 9.0600 ± 0.007 and 21.40 ± 0.0019 days, radii of 2.99 ± 0.14 and 2.90 ± 0.13 R⊕, and masses of 10.8 ± 1.8 and 11.1 ± 2.4 M⊕. We calculated densities for planets b and c consistent with a few percent of the planet mass in hydrogen/helium envelopes. We also describe our survey’s efforts to choose the best targets for James Webb Space Telescope atmospheric followup. These efforts suggest that HD 63935 b has the most clearly visible atmosphere of its class. It is the best target for transmission spectroscopy (ranked by the transmission spectroscopy metric, a proxy for atmospheric observability) in the so far uncharacterized parameter space comprising sub-Neptune-sized (2.6 R⊕ < Rp < 4 R⊕), moderately irradiated (100 F⊕ < Fp < 1000 F⊕) planets around G stars. Planet c is also a viable target for transmission spectroscopy, and given the indistinguishable masses and radii of the two planets, the system serves as a natural laboratory for examining the processes that shape the evolution of sub-Neptune planets.