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55 CANCRI: STELLAR ASTROPHYSICAL PARAMETERS, A PLANET IN THE HABITABLE ZONE, AND IMPLICATIONS FOR THE RADIUS OF A TRANSITING SUPER-EARTH

2011; IOP Publishing; Volume: 740; Issue: 1 Linguagem: Inglês

10.1088/0004-637x/740/1/49

1538-4357

Kaspar von Braun, S. Boyajian Tabetha, Theo A. ten Brummelaar, Stephen R. Kane, Gerald van Belle, David R. Ciardi, Sean N. Raymond, Mercedes López‐Morales, Harold A. McAlister, Gail Schaefer, Stephen T. Ridgway, L. Sturmann, J. Sturmann, R. J. White, N. H. Turner, C. Farrington, P. J. Goldfinger,

Astrophysics and Star Formation Studies

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: $R=0.943 \pm 0.010 R_{\odot}$, $T_{\rm EFF} = 5196 \pm 24$ K. We use isochrone fitting to determine 55 Cnc's age to be 10.2 $\pm$ 2.5 Gyr, implying a stellar mass of $0.905 \pm 0.015 M_{\odot}$. Our analysis of the location and extent of the system's habitable zone (0.67--1.32 AU) shows that planet f, with period $\sim$ 260 days and $M \sin i = 0.155 M_{Jupiter}$, spends the majority of the duration of its elliptical orbit in the circumstellar habitable zone. 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 habitable zone. 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 ($\sim 2.05 \pm 0.15 R_{\earth}$), which, depending on the planetary mass assumed, implies a bulk density of 0.76 $\rho_{\earth}$ or 1.07 $\rho_{\earth}$.