System Parameters of the Transiting Extrasolar Planet HD 209458b

Abstract

We derive improved system parameters for the HD 209458 system using a model that simultaneously fits both photometric transit and radial velocity observations. The photometry consists of previous Hubble Space Telescope STIS and FGS observations, The radial velocities were derived from Keck HIRES observations. The model properly treats the orbital dynamics of the system and thus yields robust and physically self-consistent solutions. Our set of system parameters agrees with previously published results, although with improved accuracy. For example, applying robust limits on the stellar mass of 0.93-1.20 M , we find 1:26R J < R planet < 1:42R J and 0:59M J < M planet < 0:70M J . We can reduce the uncertainty of these estimates by including a stellar mass-radius relation constraint, yielding R planet ¼ 1:35 AE 0:07 ð Þ R J and M planet ¼ 0:66 AE 0:04 ð Þ M J . Our results verify that the planetary radius is 10%-20% larger than predicted by irradiated planet evolution models, confirming the need for an additional mechanism to slow the evolutionary contraction of the planet. A revised ephemeris is derived, T 0 ¼ 2; 452; 854:82545 þ 3:52474554E ( HJD), which now contains an uncertainty in the period of 0.016 s and should facilitate future searches for planetary satellites and other bodies in the HD 209458 system. Subject headingg s: planetary systems -stars: individual ( HD 209458)

Transit Photometry of the Core‐dominated Planet HD 149026b

“…We list these values in Table 3 and plot the ''observed minus calculated'' (O À C ) residuals in Figure 4. The typical timing precision is 2 minutes, which is comparable to results from other groundbased photometry (for a tabulation of O À C for other transitingplanet systems, see Charbonneau et al [2005] for TrES-1, and Wittenmyer et al [2005] for HD 209458). We find no evidence for deviations from the predictions of a constant orbital period.…”

“…Of all the previously known transiting systems, only HD 209458 (Charbonneau et al 2000;Henry et al 2000) and TrES-1 (Alonso et al 2004;Sozzetti et al 2004) have parent stars brighter than V ¼ 12, and therefore only they are amenable to a number of fascinating measurements requiring a very high signal-to-noise ratio. Among these studies are (1) the search for satellites and rings ( Brown et al 2001), (2) the search for period variations due to additional companions ( Wittenmyer et al 2005), (3) the detection of (or upper limits on) atmospheric absorption features in transmission Brown et al 2002;Deming et al 2005a), (4) the characterization of the exosphere ( Bundy & Marcy 2000;Moutou et al 2001Moutou et al , 2003Vidal-Madjar et al 2003Winn et al 2004;Narita et al 2005), (5) the measurement of the angle between the sky-projected orbit normal and stellar rotation axis (Queloz et al 2000;Winn et al 2005), (6) the search for spectroscopic features near the times of secondary eclipse (Richardson et al 2003a(Richardson et al , 2003b, and (7) the direct detection of thermal emission from the planet (Charbonneau et al 2005;Deming et al 2005b). Charbonneau (2004) reviewed these techniques and related investigations.…”

Transit Spectroscopy of the Extrasolar Planet HD 209458b: The Search for Water

“…They binned their result in ten spectrophotometric bandpasses and made simultaneous fits to the planet's radius, the stellar limb darkening, and the inclination. By using a multi-wavelength fit, they broke the degeneracy between radius and inclination and obtained a mass of 1.320 ± 0.025 M J , which is a factor of two more precise than, but in agreement with, previous work (Wittenmyer et al, 2005, Richardson et al, 2005.…”

Measurement of the Spin-Orbit Alignment in the Exoplanetary System HD 189733

“…HD 189733 is the third exoplanetary system (and the third hot Jupiter) for which it has been possible to measure l. The first system was HD 209458, for which (Winn l p Ϫ4Њ .4 ‫ע‬ 1Њ .4 et al 2005; see also Wittenmyer et al 2005, who modeled the RM effect but required ). The second system was HD l p 0 149026 (Wolf et al 2007), for which .…”

“…Observations of the exoplanetary RM effect have been reported for HD 209458 (Bundy & Marcy 2000;Queloz et al 2000;Winn et al 2005;Wittenmyer et al 2005) and HD 149026 (Wolf et al 2007). Here we report observations of the RM effect for HD 189733.…”