Jae Woo Lee, Jae-Hyuck Youn, Seung-Lee Kim, Chung-Uk Lee, Tobias Cornelius Hinse
We present new photometric data of the transiting planet HAT-P-12b observed
in 2011. Our three transit curves are modelled using the JKTEBOP code and
adopting the quadratic limb-darkening law. Including our measurements, 18
transit times spanning about 4.2 yr were used to determine the improved
ephemeris with a transit epoch of 2,454,187.85560$\pm$0.00011 BJD and an
orbital period of 3.21305961$\pm$0.00000035 d. The physical properties of the
star-planet system are computed using empirical calibrations from eclipsing
binary stars and stellar evolutionary models, combined with both our transit
parameters and previously-known spectroscopic results. We found that the
absolute dimensions of the host star are $M_{\rm A}$=0.73$\pm$0.02 M$_\odot$,
$R_{\rm A}$=0.70$\pm$0.01 R$_\odot$, log $g_{\rm A}$=4.61$\pm$0.02, $\rho_{\rm
A}$=2.10$\pm$0.09 $\rho_{\odot}$, and $L_{\rm A}$=0.21$\pm$0.01 L$_\odot$. The
planetary companion has $M_{\rm b}$=0.21$\pm$0.01 M$_{\rm Jup}$, $R_{\rm
b}$=0.94$\pm$0.01 R$_{\rm Jup}$, log $g_{\rm b}$=2.77$\pm$0.02, $\rho_{\rm
b}$=0.24$\pm$0.01 $\rho_{\rm Jup}$, and $T_{\rm eq}$=960$\pm$14 K. Our results
agree well with standard models of irradiated gas giants with a core mass of
11.3 M$_{\oplus}$.
View original:
http://arxiv.org/abs/1201.6419
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