A Compact Multi-Planet System With A Significantly Misaligned Ultra Short Period Planet

• Published in: arXiv.org
• Main Authors: Rodriguez, Joseph E, Becker, Juliette C, Eastman, Jason D, Hadden, Sam, Vanderburg, Andrew, Khain, Tali, Quinn, Samuel N, Mayo, Andrew, Dressing, Courtney D, Schlieder, Joshua E, Ciardi, David R, Latham, David W, Rappaport, Saul, Adams, Fred C, Berlind, Perry, Bieryla, Allyson, Calkins, Michael L, Esquerdo, Gilbert A, Kristiansen, Martti H, Omohundro, Mark, Hans Martin Schwengeler, Stassun, Keivan G, Terentev, Ivan
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 29.10.2018
• Subjects: Extrasolar planets; Hubble Space Telescope; Inclination; Misalignment; Physics - Earth and Planetary Astrophysics; Physics - Solar and Stellar Astrophysics; Planet detection; Planetary systems; Planets; Space telescopes; Transit
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1806.08368

We report the discovery of a compact multi-planet system orbiting the relatively nearby (78pc) and bright (\(K=8.9\)) K-star, K2-266 (EPIC248435473). We identify up to six possible planets orbiting K2-266 with estimated periods of P\(_b\) = 0.66, P\(_{.02}\) = 6.1, P\(_c\) = 7.8, P\(_d\) = 14.7, P\(_e\) = 19.5, and P\(_{.06}\) = 56.7 days and radii of R\(_P\) = 3.3 R\(_{\oplus}\), 0.646 R\(_{\oplus}\), 0.705 R\(_{\oplus}\), 2.93 R\(_{\oplus}\), 2.73 R\(_{\oplus}\), and 0.90 R\(_{\oplus}\), respectively. We are able to confirm the planetary nature of two of these planets (d & e) from analyzing their transit timing variations (\(m_d= 8.9_{-3.8}^{+5.7} M_\oplus\) and \(m_e=14.3_{-5.0}^{+6.4} M_\oplus\)), confidently validate the planetary nature of two other planets (b & c), and classify the last two as planetary candidates (K2-266.02 & .06). From a simultaneous fit of all 6 possible planets, we find that K2-266 b's orbit has an inclination of 75.32\(^{\circ}\) while the other five planets have inclinations of 87-90\(^{\circ}\). This observed mutual misalignment may indicate that K2-266 b formed differently from the other planets in the system. The brightness of the host star and the relatively large size of the sub-Neptune sized planets d and e make them well-suited for atmospheric characterization efforts with facilities like the Hubble Space Telescope and upcoming James Webb Space Telescope. We also identify an 8.5-day transiting planet candidate orbiting EPIC248435395, a co-moving companion to K2-266.