55 CANCRI: STELLAR ASTROPHYSICAL PARAMETERS, A PLANET IN THE HABITABLE ZONE, AND IMPLICATIONS FOR THE RADIUS OF A TRANSITING SUPER-EARTH
/ Authors
K. V. Braun, T. Boyajian, T. A. Brummelaar, S. Kane, G. Belle, D. Ciardi, S. Raymond, M. López-Morales, H. Mcalister, G. Schaefer
and 16 more authors
S. Ridgway, L. Sturmann, J. Sturmann, R. White, N. Turner, C. Farrington, P. J. G. N. E. S. I. Caltech, U. GeorgiaState, Hubble Fellow, Eso, CSIC-IEEC, Chará, Noao, CarnegieDTM, U. Bordeaux, L. Bordeaux
/ Abstract
The bright star 55 Cancri is known to host five planets, including a transiting super-Earth. The study presented here yields directly determined values for 55 Cnc's stellar astrophysical parameters based on improved interferometry: R = 0.943 ± 0.010 R☉, TEFF = 5196 ± 24 K. We use isochrone fitting to determine 55 Cnc's age to be 10.2 ± 2.5 Gyr, implying a stellar mass of 0.905 ± 0.015 M☉. Our analysis of the location and extent of the system's habitable zone (HZ; 0.67–1.32 AU) shows that planet f, with period ∼260 days and Msin i = 0.155 MJupiter, spends the majority of the duration of its elliptical orbit in the circumstellar HZ. Though planet f is too massive to harbor liquid water on any planetary surface, we elaborate on the potential of alternative low-mass objects in planet f's vicinity: a large moon and a low-mass planet on a dynamically stable orbit within the HZ. Finally, our direct value for 55 Cancri's stellar radius allows for a model-independent calculation of the physical diameter of the transiting super-Earth 55 Cnc e (∼2.05 ± 0.15 R⊕), which, depending on the planetary mass assumed, implies a bulk density of 0.76 ρ⊕ or 1.07 ρ⊕.
Journal: The Astrophysical Journal