arXiv subjects

Brett C. Addison

Publications and source records attributed to Brett C. Addison.

21 records · Page 2Linked to original sources

arXiv2017

Transiting Exoplanet Monitoring Project (TEMP). III. On the Relocation of the Kepler-9~b Transit

The Kepler-9 system harbors three known transiting planets. The system holds significant interest for several reasons. First, the outer two planets exhibit a period ratio that is close to a 2:1 orbital commensurability, with attendant dynamical consequences. Second, both planets lie in the planetary mass "desert" that is generally associated with the rapid gas agglomeration phase of the core accretion process. Third, there exist attractive prospects for accurately measuring both the sky-projected stellar spin-orbit angles as well as the mutual orbital inclination between the planets in the system. Following the original \textit{Kepler} detection announcement in 2010, the initially reported orbital ephemerides for Kepler-9~b and c have degraded significantly, due to the limited time base-line of observations on which the discovery of the system rested. Here, we report new ground-based photometric observations and extensive dynamical modeling of the system. These efforts allow us to photometrically recover the transit of Kepler-9~b, and thereby greatly improve the predictions for upcoming transit mid-times. Accurate ephemerides of this system are important in order to confidently schedule follow-up observations of this system, for both in-transit Doppler measurements as well as for atmospheric transmission spectra taken during transit.

astro-ph.EP↗

arXiv2017

Spin-Orbit Misalignments of Three Jovian Planets via Doppler Tomography

We present measurements of the spin-orbit misalignments of the hot Jupiters HAT-P-41 b and WASP-79 b, and the aligned warm Jupiter Kepler-448 b. We obtained these measurements with Doppler tomography, where we spectroscopically resolve the line profile perturbation during the transit due to the Rossiter-McLaughlin effect. We analyze time series spectra obtained during portions of five transits of HAT-P-41 b, and find a value of the spin-orbit misalignment of $λ= -22.1_{-6.0}^{+0.8 \circ}$. We reanalyze the radial velocity Rossiter-McLaughlin data on WASP-79 b obtained by Addison et al. (2013) using Doppler tomographic methodology. We measure $λ=-99.1_{-3.9}^{+4.1\circ}$, consistent with but more precise than the value found by Addison et al. (2013). For Kepler-448 b we perform a joint fit to the Kepler light curve, Doppler tomographic data, and a radial velocity dataset from Lillo-Box et al. (2015). We find an approximately aligned orbit ($λ=-7.1^{+4.2 \circ}_{-2.8}$), in modest disagreement with the value found by Bourrier et al. (2015). Through analysis of the Kepler light curve we measure a stellar rotation period of $P_{\mathrm{rot}}=1.27 \pm 0.11$ days, and use this to argue that the full three-dimensional spin-orbit misalignment is small, $ψ\sim0^{\circ}$.

astro-ph.EP↗

arXiv2014

Planets in Spin-Orbit Misalignment and the Search for Stellar Companions

The discovery of giant planets orbiting close to their host stars was one of the most unexpected results of early exoplanetary science. Astronomers have since found that a significant fraction of these 'Hot Jupiters' move on orbits substantially misaligned with the rotation axis of their host star. We recently reported the measurement of the spin-orbit misalignment for WASP-79b by using data from the 3.9 m Anglo-Australian Telescope. Contemporary models of planetary formation produce planets on nearly coplanar orbits with respect to their host star's equator. We discuss the mechanisms which could drive planets into spin-orbit misalignment. The most commonly proposed being the Kozai mechanism, which requires the presence of a distant, massive companion to the star-planet system. We therefore describe a volume-limited direct-imaging survey of Hot Jupiter systems with measured spin-orbit angles, to search for the presence of stellar companions and test the Kozai hypothesis.

astro-ph.EP↗