Planet Formation in Binaries - Planetary Exploration and Science: Recent Results and Advances - page 329

Table 13.3 Estimates of the boundaries of the binary HZ calculated using Eq. ( 13.2 )forthemax-
imum and minimum amount of flux received by the planet from the secondary star corresponding
to the closest and farthest distances between the two bodies
Estimates of narrow HZ (AU) Estimates of empirical HZ (AU)

With secondary Without secondary With secondary Without secondary

Host star Inner Outer Inner Outer Inner Outer Inner Outer

Ǜ Cen A
(Max)

1.197 2.068 1.195 2.056 0.925 2.194 0.924 2.179

Ǜ Cen A (Min) 1.195 2.057 1.195 2.056 0.924 2.181 0.924 2.179

Ǜ Cen B
(Max)

0.712 1.259 0.708 1.238 0.544 1.340 0.542 1.315

Ǜ Cen B (Min) 0.708 1.241 0.708 1.238 0.543 1.317 0.542 1.315

HD 196885
A(Max)

1.454 2.477 1.454 2.475 1.137 2.622 1.137 2.620

HD 196885
A(Min)

1.454 2.475 1.454 2.475 1.137 2.620 1.137 2.620

HD 196885
B(Max)

0.260 0.491 0.258 0.481 0.198 0.529 0.197 0.516

HD 196885
B(Min)

0.258 0.483 0.258 0.481 0.197 0.518 0.197 0.516

the estimated limits of the binary HZ by a noticeable amount. This is primarily due
to the high luminosity of Ǜ Cen A and the relatively large eccentricity of the binary
which brings the two stars as close as 11.3 AU from one another (and as such
making planet formation very difficult around Ǜ Cen A).
Given the eccentricity of the Ǜ Cen binary .e Bin D 0:518/, both narrow and
nominal HZs for Ǜ Cen A and B are stable. The stability limit around the primary
G2V star is at 2.768 AU. This limit is slightly exterior to the outer boundary of
the star's narrow and empirical HZs. Although the latter suggests that the HZ of Ǜ
Cen A is dynamically stable, the close proximity of this region to the stability limit
may have strong consequences on the actual formation of an Earth-like planet in
this region (see, e.g. Thebault et al. 2008 , Eggl et al. 2012 ).

13.8.2 Habitable Zone of HD 196885

HD 196885 is a close main-sequence S-type binary system with a semimajor axis
of 21 AU and eccentricity of 0.42 (Chauvin et al. 2011 ). The primary of this system
(HD 169885 A) is an F8V star with a T Star of 6,340 K, mass of 1.33M Sun and
luminosity of 2.4L Sun . The secondary star (HD 196885 B) is an M1V dwarf with
amassof0:45M Sun . Using the mass-luminosity relation L M 3:5 where L and
M are in solar units, the luminosity of this star is approximately 0:06L Sun ,andwe
consider its effective temperature to be T Star D 3;700K. The primary of HD 196885
hosts a Jovian-type planet suggesting that the mass ratio and orbital elements of this