Rossiter-McLaughlin Effect Research Articles

Transits and starspots in the WASP-6 planetary system

We present updates to prism, a photometric transit-starspot model, and gemc, a hybrid optimization code combining MCMC and a genetic algorithm. We then present high-precision photometry of four transits in the WASP-6 planetary system, two of which contain a starspot anomaly. All four transits were modelled using prism and gemc, and the physical properties of the system calculated. We find the mass and radius of the host star to be 0.836 ± 0.063 M⊙ and 0.864 ± 0.024 R⊙, respectively. For the planet, we find a mass of 0.485 ± 0.027 MJup, a radius of 1.230 ± 0.035 RJup and a density of 0.244 ± 0.014 ρJup. These values are consistent with those found in the literature. In the likely hypothesis that the two spot anomalies are caused by the same starspot or starspot complex, we measure the stars rotation period and velocity to be 23.80 ± 0.15 d and 1.78 ± 0.20 km s−1, respectively, at a colatitude of 75.8°. We find that the sky-projected angle between the stellar spin axis and the planetary orbital axis is λ = 7.2° ± 3.7°, indicating axial alignment. Our results are consistent with and more precise than published spectroscopic measurements of the Rossiter–McLaughlin effect. These results suggest that WASP-6 b formed at a much greater distance from its host star and suffered orbital decay through tidal interactions with the protoplanetary disc.

High-precision multiband time series photometry of exoplanets Qatar-1b and TrES-5b

We present an analysis of the Qatar-1 and TrES-5 transiting exoplanetary systems, which contain Jupiter-like planets on short-period orbits around K-dwarf stars. Our data comprise a total of 20 transit light curves obtained using five medium-class telescopes, operated using the defocussing technique. The average precision we reach in all our data is $RMS_{Q} = 1.1$ mmag for Qatar-1 ($V = 12.8$) and $RMS_{T} = 1.0$ mmag for TrES-5 ($V = 13.7$). We use these data to refine the orbital ephemeris, photometric parameters, and measured physical properties of the two systems. One transit event for each object was observed simultaneously in three passbands ($gri$) using the BUSCA imager. The QES survey light curve of Qatar-1 has a clear sinusoidal variation on a period of $P_{\star} = 23.697 \pm 0.123$\,d, implying significant starspot activity. We searched for starspot crossing events in our light curves, but did not find clear evidence in any of the new datasets. The planet in the Qatar-1 system did not transit the active latitudes on the surfaces of its host star. Under the assumption that $P_{\star}$ corresponds to the rotation period of Qatar-1\,A, the rotational velocity of this star is very close to the $v \sin i_\star$ value found from observations of the Rossiter-McLaughlin effect. The low projected orbital obliquity found in this system thus implies a low absolute orbital obliquity, which is also a necessary condition for the transit chord of the planet to avoid active latitudes on the stellar surface.

Solar rotation inferred from radial velocities of the Sun-as-a-star during the 2012 May 21 eclipse

Abstract With the aim of examining how much information of solar rotation can be obtained purely spectroscopically by observing the Sun-as-a-star during the 2012 May 21 eclipse at Okayama Astrophysical Observatory, we studied the variation of radial velocities (Vr), which were derived by using the iodine-cell technique based on a set of 184 high-dispersion spectra consecutively obtained over a time span of ∼ 4 hr. The resulting Vr(t) was confirmed to show the characteristic variation (Rossiter–McLaughlin effect) caused by time-varying visibility of the solar disk. By comparing the observed Vr(t) curve with the theoretical ones [which were simulated with the latitude (ψ) dependent solar rotation law ωsidereal(ψ) = A + B sin 2ψ (degree d−1)] we found that the relation B ≃ −5.5A + 77 gives the best fit, though separate determinations of A and B were not possible. Since this relationship is consistent with the real values known for the Sun (A ≃ 14.5, B ≃ −2.8), we may state that our analysis yielded satisfactory results. This consequence may provide the prospect of getting useful information on stellar rotation of eclipsing binaries from radial-velocity studies during eclipse, if many spectra of sufficiently high time-resolution are available.

3D spin-orbit angle ofKepler-25and HAT-P-7

The number of discovered exoplanets now exceeds 1500, mostly due to the Kepler space instrument observations. Many of these planet orbit in less than a week around their host stars. This implies that the inward migration of those planets is a basic ingredient of successful theories of planet formation and evolution. Several mechanisms have been proposed to explain the observed periods, which lead to different orbit eccen- tricity and obliquity distributions. Here we summarise and discuss the results of obliqui- ties for two Kepler stars: HAT-P-7 and Kepler-25. These are interesting stellar systems as we could carry out a joint analysis using asteroseismology, transit lightcurve and the Rossiter-McLaughlin effect in order to measure the three dimensional obliquity.

WASP-94 A and B planets: hot-Jupiter cousins in a twin-star system

We report the discovery of two hot-Jupiter planets, each orbiting one of the stars of a wide binary system. WASP-94A (2MASS 20550794-3408079) is an F8 type star hosting a transiting planet with a radius of 1.72 +/- 0.06 R_Jup, a mass of 0.452 +/- 0.034 M_Jup, and an orbital period of 3.95 days. The Rossiter-McLaughlin effect is clearly detected, and the measured projected spin-orbit angle indicates that the planet occupies a retrograde orbit. WASP-94B (2MASS 20550915-3408078) is an F9 stellar companion at an angular separation of 15" (projected separation 2700 au), hosting a gas giant with a minimum mass of 0.618 +/- 0.028 M_Jup with a period of 2.008 days, detected by Doppler measurements. The orbital planes of the two planets are inclined relative to each other, indicating that at least one of them is inclined relative to the plane of the stellar binary. These hot Jupiters in a binary system bring new insights into the formation of close-in giant planets and the role of stellar multiplicity.

SOPHIE velocimetry ofKeplertransit candidates

In this paper we report a new transiting warm giant planet: KOI-1257 b. It was first detected in photometry as a planet-candidate by the ${\it Kepler}$ space telescope and then validated thanks to a radial velocity follow-up with the SOPHIE spectrograph. It orbits its host star with a period of 86.647661 d $\pm$ 3 s and a high eccentricity of 0.772 $\pm$ 0.045. The planet transits the main star of a metal-rich, relatively old binary system with stars of mass of 0.99 $\pm$ 0.05 Msun and 0.70 $ \pm $ 0.07 Msun for the primary and secondary, respectively. This binary system is constrained thanks to a self-consistent modelling of the ${\it Kepler}$ transit light curve, the SOPHIE radial velocities, line bisector and full-width half maximum (FWHM) variations, and the spectral energy distribution. However, future observations are needed to confirm it. The PASTIS fully-Bayesian software was used to validate the nature of the planet and to determine which star of the binary system is the transit host. By accounting for the dilution from the binary both in photometry and in radial velocity, we find that the planet has a mass of 1.45 $ \pm $ 0.35 Mjup, and a radius of 0.94 $ \pm $ 0.12 Rjup, and thus a bulk density of 2.1 $ \pm $ 1.2 g.cm$^{-3}$. The planet has an equilibrium temperature of 511 $\pm$ 50 K, making it one of the few known members of the warm-jupiter population. The HARPS-N spectrograph was also used to observe a transit of KOI-1257 b, simultaneously with a joint amateur and professional photometric follow-up, with the aim of constraining the orbital obliquity of the planet. However, the Rossiter-McLaughlin effect was not clearly detected, resulting in poor constraints on the orbital obliquity of the planet.

HOW TO DETERMINE AN EXOMOON'S SENSE OF ORBITAL MOTION

We present two methods to determine an exomoon's sense of orbital motion (SOM), one with respect to the planet's circumstellar orbit and one with respect to the planetary rotation. Our simulations show that the required measurements will be possible with the European Extremely Large Telescope (E-ELT). The first method relies on mutual planet-moon events during stellar transits. Eclipses with the moon passing behind (in front of) the planet will be late (early) with regard to the moon's mean orbital period due to the finite speed of light. This "transit timing dichotomy" (TTD) determines an exomoon's SOM with respect to the circumstellar motion. For the ten largest moons in the solar system, TTDs range between 2 and 12 s. The E-ELT will enable such measurements for Earth-sized moons around nearby stars. The second method measures distortions in the IR spectrum of the rotating giant planet when it is transited by its moon. This Rossiter-McLaughlin effect (RME) in the planetary spectrum reveals the angle between the planetary equator and the moon's circumplanetary orbital plane, and therefore unveils the moon's SOM with respect to the planet's rotation. A reasonably large moon transiting a directly imaged planet like beta Pic b causes an RME amplitude of almost 100 m/s, about twice the stellar RME amplitude of the transiting exoplanet HD209458b. Both new methods can be used to probe the origin of exomoons, that is, whether they are regular or irregular in nature.

Determination of three-dimensional spin–orbit angle with joint analysis of asteroseismology, transit lightcurve, and the Rossiter–McLaughlin effect: Cases of HAT-P-7 and Kepler-25

Abstract We develop a detailed methodology of determining three-dimensionally the angle between the stellar spin and the planetary orbit axis vectors, ψ, for transiting planetary systems. The determination of ψ requires the independent estimates of the inclination angles of the stellar spin axis and of the planetary orbital axis with respect to the line of sight, i⋆ and iorb, and the projection of the spin–orbit angle on to the plane of the sky, λ. These are mainly derived from asteroseismology, transit lightcurve, and the Rossiter–McLaughlin effect, respectively. The detailed joint analysis of those three datasets enables an accurate and precise determination of the numerous parameters characterizing the planetary system, in addition to ψ. We demonstrate the power of the joint analysis for the two specific systems HAT-P-7 and Kepler-25. HAT-P-7b is the first exoplanet suspected to be a retrograde (or polar) planet because of the significant misalignment λ ≈ 180°. Our joint analysis indicates i⋆ ≈ 30° and ψ ≈ 120°, suggesting that the planetary orbit is closer to polar rather than retrograde. Kepler-25 is one of the few multi-transiting planetary systems with measured λ, and hosts two short-period transiting planets and one outer non-transiting planet. The projected spin–orbit angle of the larger transiting planet, Kepler-25c, has been measured to be λ ≈ 0°, implying that the system is well aligned. With the help of the tight constraint from asteroseismology, however, we obtain $i_\star ={65{{^{\circ}_{.}}}4}^{+{10{{\kern.4pt.\vphantom{|}}^{\kern-2pt\circ}}6}}_{-{6{{\kern.4pt.\vphantom{|}}^{\kern-2pt\circ}}4}}$ and $\psi ={26{{^{\circ}_{.}}}9}^{+{7{{\kern.4pt.\vphantom{|}}^{\kern-2pt\circ}}0}}_{-{9{{\kern.4pt.\vphantom{|}}^{\kern-2pt\circ}}2}}$, and thus find that the system is actually mildly misaligned. This is the first detection of the spin–orbit misalignment for the multiple planetary system with a main-sequence host star, and points to mechanisms that tilt a stellar spin axis relative to its protoplanetary disk.

Asteroseismic inference on the spin-orbit misalignment and stellar parameters of HAT-P-7

The measurement of obliquities in star-planet systems is of great importance for the understanding of planet system formation and evolution. The bright and well studied HAT-P-7 system is intriguing as several Rossiter-McLaughlin (RM) measurements found a large projected obliquity in this system, but it was so far not possible to determine if the orbit is polar and/or retrograde. The goal of this study is to measure the stellar inclination and hereby the full 3D obliquity of the HAT-P-7 system instead of only the 2D projection as measured by the RM effect. In addition we provide an updated set of stellar parameters for the star. We use the full set of available observations from Kepler spanning Q0-Q17 to produce the power spectrum of HAT-P-7. We extract oscillation mode frequencies via an MCMC peak-bagging routine, and use the results from this to estimate the stellar inclination angle. Combining this with the projected obliquity from RM and the inclination of the orbital plane allows us to determine the stellar obliquity. We use asteroseismology to model the star from the extracted frequencies using two different approaches to the modelling where either the MESA or the GARSTEC stellar evolution codes are adopted. Using our updated asteroseismic modelling we find, i.a., the following stellar parameters for HAT-P-7: M=1.51{+0.04}{-0.05}Msun, $R=2.00{+0.01}{-0.02}Rsun, and age = 2.07{+0.28}{-0.23} Gyr. Our asteroseismic modelling offers a high precision on the stellar parameters, for instance is the uncertainty on age of the order ~11%. For the stellar inclination we estimate i_star<36.5 deg., which translates to an obliquity between 83 and 111 deg. We find that the planet HAT-P-7b is likely retrograde in its orbit, and that the orbit is close to being polar. The new parameters for the star gives an updated planetary density of 0.65+-0.03 g cm^{-3}, which is lower than previous estimates.

Determining stellar macroturbulence using asteroseismic rotational velocities from Kepler

The Rossiter-McLaughlin effect observed for transiting exoplanets often requires prior knowledge of the stellar projected equatorial rotational velocity. This is usually provided by measuring the broadening of spectral lines, however this method has uncertainties as lines are also broadened by velocity fields in the stellar photosphere known as macroturbulence. We have estimated accurate rotational velocity values from asteroseismic analyses of main sequence stars observed by Kepler. The rotational frequency splittings of the detected solar-like oscillations of these stars are determined largely by the near-surface rotation. These estimates have been used to infer the macroturbulence values for 28 Kepler stars. Out of this sample, 26 stars were used along with the Sun to obtain a new calibration between macroturbulence, effective temperature and surface gravity. The new calibration is valid for the temperature range 5200 to 6400 K and the gravity range 4.0 to 4.6 dex. A comparison is also provided with previous macroturbulence calibrations. As a result of this work, macroturbulence, and thus rotational velocity, can now be determined with confidence for stars that do not have asteroseismic data available. We present new spectroscopic rotational velocity values for the WASP planet host stars, using high resolution HARPS spectra.

ROSSITER-MCLAUGHLIN OBSERVATIONS OF 55 Cnc e

We present Rossiter-McLaughlin observations of the transiting super-Earth 55 Cnc e collected during six transit events between January 2012 and November 2013 with HARPS and HARPS-N. We detect no radial-velocity signal above 35 cm/s (3-sigma) and confine the stellar v sin i to 0.2 +/- 0.5 km/s. The star appears to be a very slow rotator, producing a very low amplitude Rossiter-McLaughlin effect. Given such a low amplitude, the Rossiter-McLaughlin effect of 55 Cnc e is undetected in our data, and any spin-orbit angle of the system remains possible. We also performed Doppler tomography and reach a similar conclusion. Our results offer a glimpse of the capacity of future instrumentation to study low amplitude Rossiter-McLaughlin effects produced by super-Earths.

A SPIN-ORBIT ALIGNMENT FOR THE HOT JUPITER HATS-3b

We have measured the alignment between the orbit of HATS-3b (a recently discovered, slightly inflated Hot Jupiter) and the spin-axis of its host star. Data were obtained using the CYCLOPS2 optical-fiber bundle and its simultaneous calibration system feeding the UCLES spectrograph on the Anglo-Australian Telescope. The sky-projected spin-orbit angle of $\lambda = 3\pm25^{\circ}$ was determined from spectroscopic measurements of Rossiter-McLaughlin effect. This is the first exoplanet discovered through the HATSouth transit survey to have its spin-orbit angle measured. Our results indicate that the orbital plane of HATS-3b is consistent with being aligned to the spin axis of its host star. The low obliquity of the HATS-3 system, which has a relatively hot mid F-type host star, agrees with the general trend observed for Hot Jupiter host stars with effective temperatures $>6250$K to have randomly distributed spin-orbit angles.

WASP-117b: a 10-day-period Saturn in an eccentric and misaligned orbit

We report the discovery of WASP-117b, the first planet with a period beyond 10 days found by the WASP survey. The planet has a mass of $M_p= 0.2755 \pm 0.0089 \, M_{J}$, a radius of $R_p= 1.021_{-0.065}^{+0.076}\, R_{J}$ and is in an eccentric ($ e= 0.302 \pm 0.023 $), $ 10.02165 \pm 0.00055 $~d orbit around a main-sequence F9 star. The host star's brightness (V=10.15 mag) makes WASP-117 a good target for follow-up observations, and with a periastron planetary equilibrium temperature of $T_{eq}= 1225_{-39}^{+36}$ K and a low planetary mean density ($\rho_p= 0.259_{-0.048}^{+0.054} \, \rho_{J}$) it is one of the best targets for transmission spectroscopy among planets with periods around 10 days. From a measurement of the Rossiter-McLaughlin effect, we infer a projected angle between the planetary orbit and stellar spin axes of $\beta = -44 \pm 11$ deg, and we further derive an orbital obliquity of $\psi = 69.6 ^{+4.7}_{-4.1}$ deg. Owing to the large orbital separation, tidal forces causing orbital circularization and realignment of the planetary orbit with the stellar plane are weak, having had little impact on the planetary orbit over the system lifetime. WASP-117b joins a small sample of transiting giant planets with well characterized orbits at periods above ~8 days.

The GAPS Programme with HARPS-N at TNG

The measurement of the Rossiter-McLaughlin effect for transiting exoplanets places constraints on the orientation of the orbital axis with respect to the stellar spin axis, which can shed light on the mechanisms shaping the orbital configuration of planetary systems. Here we present the interesting case of the Saturn-mass planet HAT-P-18b, which orbits one of the coolest stars for which the Rossiter-McLaughlin effect has been measured so far. We acquired a spectroscopic time-series, spanning a full transit, with the HARPS-N spectrograph mounted at the TNG telescope. The very precise radial velocity measurements delivered by the HARPS-N pipeline were used to measure the Rossiter-McLaughlin effect. Complementary new photometric observations of another full transit were also analysed to obtain an independent determination of the star and planet parameters. We find that HAT-P-18b lies on a counter-rotating orbit, the sky-projected angle between the stellar spin axis and the planet orbital axis being lambda=132 +/- 15 deg. By joint modelling of the radial velocity and photometric data we obtain new determinations of the star (M_star = 0.770 +/- 0.027 M_Sun; R_star= 0.717 +/- 0.026 R_Sun; Vsin(I_star) = 1.58 +/- 0.18 km/s) and planet (M_pl = 0.196 +/- 0.008 M_J; R_pl = 0.947 +/- 0.044 R_J) parameters. Our spectra provide for the host star an effective temperature T_eff = 4870 +/- 50 K, a surface gravity of log(g_star) = 4.57 +/- 0.07 cm/s, and an iron abundance of [Fe/H] = 0.10 +/- 0.06. HAT-P-18b is one of the few planets known to transit a star with T_eff < 6250 K on a retrograde orbit. Objects such as HAT-P-18b (low planet mass and/or relatively long orbital period) most likely have a weak tidal coupling with their parent stars, therefore their orbits preserve any original misalignment. As such, they are ideal targets to study the causes of orbital evolution in cool main-sequence stars.

THE BANANA PROJECT. V. MISALIGNED AND PRECESSING STELLAR ROTATION AXES IN CV VELORUM

As part of the BANANA project (Binaries Are Not Always Neatly Aligned), we have found that the eclipsing binary CV Velorum has misaligned rotation axes. Based on our analysis of the Rossiter-McLaughlin effect, we find sky-projected spin-orbit angles of $\beta_{\rm p} = -52\pm6^{\circ}$ and $\beta_{\rm s}= 3\pm7^{\circ}$ for the primary and secondary stars (B2.5V $+$ B2.5V, $P=6.9$ d). We combine this information with several measurements of changing projected stellar rotation speeds ($v \sin i_{\star}$) over the last $30$ years, leading to a model in which the primary star's obliquity is $\approx65^{\circ}$, and its spin axis precesses around the total angular momentum vector with a period of about $140$ years. The geometry of the secondary star is less clear, although a significant obliquity is also implicated by the observed time variations in the $v \sin i_{\star}$. By integrating the secular tidal evolution equations backward in time, we find that the system could have evolved from a state of even stronger misalignment similar to DI Herculis, a younger but otherwise comparable binary.

MEASUREMENTS OF STELLAR INCLINATIONS FORKEPLERPLANET CANDIDATES. II. CANDIDATE SPIN-ORBIT MISALIGNMENTS IN SINGLE- AND MULTIPLE-TRANSITING SYSTEMS

We present a test for spin-orbit alignment for the host stars of 25 candidate planetary systems detected by the {\it Kepler} spacecraft. The inclination angle of each star's rotation axis was estimated from its rotation period, rotational line broadening, and radius. The rotation periods were determined using the {\it Kepler} photometric time series. The rotational line broadening was determined from high-resolution optical spectra with Subaru/HDS. Those same spectra were used to determine the star's photospheric parameters (effective temperature, surface gravity, metallicity) which were then interpreted with stellar-evolutionary models to determine stellar radii. We combine the new sample with the 7 stars from our previous work on this subject, finding that the stars show a statistical tendency to have inclinations near 90$^\circ$, in alignment with the planetary orbits. Possible spin-orbit misalignments are seen in several systems, including three multiple-planet systems (KOI-304, 988, 2261). Ideally these systems should be scrutinized with complementary techniques---such as the Rossiter-McLaughlin effect, starspot-crossing anomalies or asteroseismology---but the measurements will be difficult owing to the relatively faint apparent magnitudes and small transit signals in these systems.

EXTREME ORBITAL EVOLUTION FROM HIERARCHICAL SECULAR COUPLING OF TWO GIANT PLANETS

Observations of exoplanets over the last two decades have revealed a new class of Jupiter-size planets with orbital periods of a few days, the so-called "hot Jupiters". Recent measurements using the Rossiter-McLaughlin effect have shown that many (~ 50%) of these planets are misaligned; furthermore, some (~ 15%) are even retrograde with respect to the stellar spin axis. Motivated by these observations, we explore the possibility of forming retrograde orbits in hierarchical triple configurations consisting of a star-planet inner pair with another giant planet, or brown dwarf, in a much wider orbit. Recently Naoz et al. (2011) showed that in such a system, the inner planet's orbit can flip back and forth from prograde to retrograde, and can also reach extremely high eccentricities. Here we map a significant part of the parameter space of dynamical outcomes for these systems. We derive strong constraints on the orbital configurations for the outer perturber that could lead to the formation of hot Jupiters with misaligned or retrograde orbits. We focus only on the secular evolution, neglecting other dynamical effects such as mean-motion resonances, as well as all dissipative forces. For example, with an inner Jupiter-like planet initially on a nearly circular orbit at 5 AU, we show that a misaligned hot Jupiter is likely to be formed in the presence of a more massive planetary companion (> 2 MJ) within 140 AU of the inner system, with mutual inclination 50 degrees and eccentricity above 0.25. This is in striking contrast to the test-particle approximation, where an almost perpendicular configuration can still cause large eccentricity excitations, but flips of an inner Jupiter-like planet are much less likely to occur. The constraints we derive can be used to guide future observations, and, in particular, searches for more distant companions in systems containing a hot Jupiter.

Probing the effect of gravitational microlensing on the measurements of the Rossiter-McLaughlin effect

In general, in the studies of transit light-curves and the Rossiter-McLaughlin (RM), the contribution of the planet's gravitational microlensing is neglected. Theoretical studies, have, however shown that the planet's microlensing can affect the transit light-curve and in some extreme cases cause the transit depth to vanish. In this letter, we present the results of our quantitative analysis of microlening on the RM effect. Results indicate that for massive planets in on long period orbits, the planet's microlensing will have considerable contribution to the star's RV measurements. We present the details of our study, and discuss our analysis and results.

HATS-3b: AN INFLATED HOT JUPITER TRANSITING AN F-TYPE STAR

We report the discovery by the HATSouth survey of HATS-3b, a transiting extrasolar planet orbiting a V=12.4 F-dwarf star. HATS-3b has a period of P = 3.5479d, mass of Mp = 1.07MJ, and radius of Rp = 1.38RJ. Given the radius of the planet, the brightness of the host star, and the stellar rotational velocity (vsini = 9.0km/s), this system will make an interesting target for future observations to measure the Rossiter-McLaughlin effect and determine its spin-orbit alignment. We detail the low/medium-resolution reconnaissance spectroscopy that we are now using to deal with large numbers of transiting planet candidates produced by the HATSouth survey. We show that this important step in discovering planets produces logg and Teff parameters at a precision suitable for efficient candidate vetting, as well as efficiently identifying stellar mass eclipsing binaries with radial velocity semi-amplitudes as low as 1 km/s.

KEPLER-63b: A GIANT PLANET IN A POLAR ORBIT AROUND A YOUNG SUN-LIKE STAR

We present the discovery and characterization of a giant planet orbiting the young Sun-like star Kepler-63 (KOI-63, $m_{\rm Kp} = 11.6$, $T_{\rm eff} = 5576$ K, $M_\star = 0.98\, M_\odot$). The planet transits every 9.43 days, with apparent depth variations and brightening anomalies caused by large starspots. The planet's radius is $6.1 \pm 0.2 R_{\earth}$, based on the transit light curve and the estimated stellar parameters. The planet's mass could not be measured with the existing radial-velocity data, due to the high level of stellar activity, but if we assume a circular orbit we can place a rough upper bound of $120 M_{\earth}$ (3$\sigma$). The host star has a high obliquity ($\psi$ = $104^{\circ}$), based on the Rossiter-McLaughlin effect and an analysis of starspot-crossing events. This result is valuable because almost all previous obliquity measurements are for stars with more massive planets and shorter-period orbits. In addition, the polar orbit of the planet combined with an analysis of spot-crossing events reveals a large and persistent polar starspot. Such spots have previously been inferred using Doppler tomography, and predicted in simulations of magnetic activity of young Sun-like stars.