A Superjupiter/Small Brown Dwarf in a 10 AU Orbit Around its Host Star

A companion on the planet/brown dwarf mass boundary on a wide orbit discovered by gravitational microlensing

Authors:

Poleski et al

Abstract:
We present the discovery of a substellar companion to the primary host lens in the microlensing event MOA-2012-BLG-006. The companion-to-host mass ratio is 0.016, corresponding to a companion mass of ≈8 MJup(M∗/0.5M⊙). Thus, the companion is either a high-mass giant planet or a low-mass brown dwarf, depending on the mass of the primary M∗. The companion signal was separated from the peak of the primary event by a time that was as much as four times longer than the event timescale. We therefore infer a relatively large projected separation of the companion from its host of ≈10 a.u.(M∗/0.5M⊙)1/2 for a wide range (3-7 kpc) of host star distances from the Earth. We also challenge a previous claim of a planetary companion to the lens star in microlensing event OGLE-2002-BLG-045.

OGLE-2013-BLG-1761Lb: A SuperJupiter Orbiting a M/K Dwarf Star

OGLE-2013-BLG-1761Lb: A Massive Planet around an M/K Dwarf 

Authors:
Hirao et al

Abstract:
We report the discovery and the analysis of the planetary microlensing event, OGLE-2013-BLG-1761. There are some degenerate solutions in this event because the planetary anomaly is only sparsely sampled. However, the detailed light-curve analysis ruled out all stellar binary models and shows the lens to be a planetary system. There is the so-called close/wide degeneracy in the solutions with the planet/host mass ratio of q ~ (7.0 ± 2.0) × 10−3 and q ~ (8.1 ± 2.6) × 10−3 with the projected separation in Einstein radius units of s = 0.95 (close) and s = 1.18 (wide), respectively. The microlens parallax effect is not detected, but the finite source effect is detected. Our Bayesian analysis indicates that the lens system is located ${D}_{{\rm{L}}}={6.9}_{-1.2}^{+1.0}\,\mathrm{kpc}$ away from us and the host star is an M/K dwarf with a mass of ${\text{}}{M}_{{\rm{L}}}={0.33}_{-0.19}^{+0.32}\,{\text{}}{M}_{\odot }$ orbited by a super-Jupiter mass planet with a mass of ${\text{}}{m}_{{\rm{P}}}={2.7}_{-1.5}^{+2.5}\,{M}_{\mathrm{Jup}}$ at the projected separation of ${a}_{\perp }={1.8}_{-0.5}^{+0.5}\,\mathrm{au}$. The preference of the large lens distance in the Bayesian analysis is due to the relatively large observed source star radius. The distance and other physical parameters may be constrained by the future high-resolution imaging by large ground telescopes or HST. If the estimated lens distance is correct, then this planet provides another sample for testing the claimed deficit of planets in the Galactic bulge.

Three Polar Stars Found to Have Exoplanets

Search for Exoplanets around Northern Circumpolar Stars- II. The Detection of Radial Velocity Variations in M Giant Stars HD 36384, HD 52030, and HD 208742 

Authors:

Lee et al

Abstract: 

We present the detection of long-period RV variations in HD 36384, HD 52030, and HD 208742 by using the high-resolution, fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) for the precise radial velocity (RV) survey of about 200 northern circumpolar stars. Analyses of RV data, chromospheric activity indicators, and bisector variations spanning about five years suggest that the RV variations are compatible with planet or brown dwarf companions in Keplerian motion. However, HD 36384 shows photometric variations with a period very close to that of RV variations as well as amplitude variations in the weighted wavelet Z-transform (WWZ) analysis, which argues that the RV variations in HD~36384 are from the stellar pulsations. Assuming that the companion hypothesis is correct, HD~52030 hosts a companion with minimum mass 13.3 M_Jup$ orbiting in 484 days at a distance of 1.2 AU. HD~208742 hosts a companion of 14.0 M_Jup at 1.5 AU with a period of 602 days. All stars are located at the asymptotic giant branch (AGB) stage on the H-R diagram after undergone the helium flash and left the giant clump.With stellar radii of 53.0 R_Sun and 57.2 R_Sun for HD 52030 and HD 208742, respectively, these stars may be the largest yet, in terms of stellar radius, found to host sub-stellar companions. However, given possible RV amplitude variations and the fact that these are highly evolved stars the planet hypothesis is not yet certain.

GJ 676Ab is a Super Jupiter

The mass of planet GJ676A b from ground-based astrometry: A planetary system with two mature gas giants suitable for direct imaging

Authors:

Sahlmann et al

Abstract:

GJ676A is an M0 dwarf hosting both gas-giant and super-Earth-type planets discovered with radial-velocity measurements. Using FORS2/VLT, we obtained position measurements of the star in the plane of the sky that tightly constrain its astrometric reflex motion caused by the super-Jupiter planet `b` in a 1052-day orbit. This allows us to determine the mass of this planet to Mb=6.7+1.8−1.5MJ, which is ∼40 \% higher than the minimum mass inferred from the radial-velocity orbit. Using new HARPS radial-velocity measurements, we improve upon the orbital parameters of the inner low-mass planets `d` and `e` and we determine the orbital period of the outer giant planet `c` to Pc=7340 days under the assumption of a circular orbit. The preliminary minimum mass of planet `c` is Mcsini=6.8MJ with an upper limit of ∼39MJ that we set using NACO/VLT high-contrast imaging. We also determine precise parallaxes and relative proper motions for both GJ676A and its wide M3 companion GJ676B. Despite the probably mature age of the system, the masses and projected separations (∼0.1" -- 0.4") of planets `b` and `c` make them promising targets for direct imaging with future instruments in space and on extremely large telescopes. In particular, we estimate that GJ676A b and GJ676A c are promising targets for directly detecting their reflected light with the WFIRST space mission. Our study demonstrates the synergy of radial-velocity and astrometric surveys that is necessary to identify the best targets for such a mission.

HD 219828 System has a hot Neptune & Super Jupiter

An extreme planetary system around HD 219828

Authors:

Santos et al

Abstract:

Context.

With about 2000 extrasolar planets confirmed, the results show that planetary systems have a whole range of unexpected properties. This wide diversity provides fundamental clues to the processes of planet formation and evolution.

Aims.

We present a full investigation of the HD 219828 system, a bright metal-rich star for which a hot Neptune has previously been detected.

Methods.

We used a set of HARPS, SOPHIE, and ELODIE radial velocities to search for the existence of orbiting companions to HD 219828. The spectra were used to characterise the star and its chemical abundances, as well as to check for spurious, activity induced signals. A dynamical analysis is also performed to study the stability of the system and to constrain the orbital parameters and planet masses.

Results.

We announce the discovery of a long period (P = 13.1 yr) massive (m sini = 15.1 MJup) companion (HD 219828 c) in a very eccentric orbit (e = 0.81). The same data confirms the existence of a hot Neptune, HD 219828 b, with a minimum mass of 21 M⊕ and a period of 3.83 days. The dynamical analysis shows that the system is stable, and that the equilibrium eccentricity of planet b is close to zero.

Conclusions.

The HD 219828 system is extreme and unique in several aspects. First, ammong all known exoplanet systems it presents an unusually high mass ratio. We also show that systems like HD 219828, with a hot Neptune and a long-period massive companion are more frequent than similar systems with a hot Jupiter instead. This suggests that the formation of hot Neptunes follows a different path than the formation of their hot jovian counterparts. The high mass, long period, and eccentricity of HD 219828 c also make it a good target for Gaia astrometry as well as a potential target for atmospheric characterisation, using direct imaging or high-resolution spectroscopy. Astrometric observations will allow us to derive its real mass and orbital configuration. If a transit of HD 219828 b is detected, we will be able to fully characterise the system, including the relative orbital inclinations. With a clearly known mass, HD 219828 c may become a benchmark object for the range in between giant planets and brown dwarfs.

HD 219828: An extreme planetary system with One long-period super Jupiter to a hot-neptune host star

An extreme planetary system around HD219828. One long-period super Jupiter to a hot-neptune host star

Authors:

Santos et al

Abstract:

With about 2000 extrasolar planets confirmed, the results show that planetary systems have a whole range of unexpected properties. We present a full investigation of the HD219828 system, a bright metal-rich star for which a hot neptune has previously been detected. We used a set of HARPS, SOPHIE, and ELODIE radial velocities to search for the existence of orbiting companions to HD219828. A dynamical analysis is also performed to study the stability of the system and to constrain the orbital parameters and planet masses. We announce the discovery of a long period (P=13.1years) massive (msini=15.1MJup) companion (HD219828c) in a very eccentric orbit (e=0.81). The same data confirms the existence of a hot-neptune, HD219828b, with a minimum mass of 21 MEarth and a period of 3.83days. The dynamical analysis shows that the system is stable. The HD219828 system is extreme and unique in several aspects. First, among all known exoplanet systems it presents an unusually high mass ratio. We also show that systems like HD219828, with a hot neptune and a long-period massive companion are more frequent than similar systems with a hot jupiter instead. This suggests that the formation of hot neptunes follows a different path than the formation of their hot jovian counterparts. The high mass, long period, and eccentricity of HD219828c also make it a good target for Gaia astrometry as well as a potential target for atmospheric characterisation, using direct imaging or high-resolution spectroscopy. Astrometric observations will allow us to derive its real mass and orbital configuration. If a transit of HD219828b is detected, we will be able to fully characterise the system, including the relative orbital inclinations. With a clearly known mass, HD219828c may become a benchmark object for the range in between giant planets and brown dwarfs.

κ Andromedae Hosts a 22 Jupiter Mass SuperJupiter

The Age of the Directly-Imaged Planet Host Star κ Andromedae Determined From Interferometric Observations

Authors:

Jones et al

Abstract:

κ Andromedae, an early type star that hosts a directly imaged low mass companion, is expected to be oblate due to its rapid rotational velocity (vsini = ∼162 km s−1). We observed the star with the CHARA Array's optical beam combiner, PAVO, measuring its size at multiple orientations and determining its oblateness. The interferometric measurements, combined with photometry and this vsini value are used to constrain an oblate star model that yields the fundamental properties of the star and finds a rotation speed that is ∼85\% of the critical rate and a low inclination of ∼30∘. Three modeled properties (the average radius, bolometric luminosity, and equatorial velocity) are compared to MESA evolution models to determine an age and mass for the star. In doing so, we determine an age for the system of 47+27−40 Myr. Based on this age and previous measurements of the companion's temperature, the BHAC15 evolution models imply a mass for the companion of 22+8−9 MJ.

Stability of Multi Exoplanetary Systems With Very High Mass Worlds

Orbital Stability of Multi-Planet Systems: Behavior at High Masses

Authors:

Morrison et al

Abstract:

In the coming years, high contrast imaging surveys are expected to reveal the characteristics of the population of wide-orbit, massive, exoplanets. To date, a handful of wide planetary mass companions are known, but only one such multi-planet system has been discovered: HR8799. For low mass planetary systems, multi-planet interactions play an important role in setting system architecture. In this paper, we explore the stability of these high mass, multi-planet systems. While empirical relationships exist that predict how system stability scales with planet spacing at low masses, we show that extrapolating to super-Jupiter masses can lead to up to an order of magnitude overestimate of stability for massive, tightly packed systems. We show that at both low and high planet masses, overlapping mean motion resonances trigger chaotic orbital evolution, which leads to system instability. We attribute some of the difference in behavior as a function of mass to the increasing importance of second order resonances at high planet-star mass ratios. We use our tailored high mass planet results to estimate the maximum number of planets that might reside in double component debris disk systems, whose gaps may indicate the presence of massive bodies.

SAO 206462/HD 135344B Appears to Have a SuperJupiter Orbiting at 100 to 120 AU

PLANETARY SIGNATURES IN THE SAO 206462 (HD 135344B) DISK: A SPIRAL ARM PASSING THROUGH VORTEX?

Authors:

Bae et al

Abstract:

The disk surrounding SAO 206462, an 8 Myr old Herbig Ae star, has recently been reported to exhibit spiral arms, an asymmetric dust continuum, and a dust-depleted inner cavity. By carrying out two-dimensional, two-fluid hydrodynamic calculations, we find that a planetary-mass companion located at the outer disk could be responsible for these observed structures. In this model, the planet excites primary and secondary arms interior to its orbit. It also carves a gap and generates a local pressure bump at the inner gap edge where a vortex forms through Rossby wave instability. The vortex traps radially drifting dust particles, forming a dust-depleted cavity in the inner disk. We propose that the vortex is responsible for the brightest southwestern peak seen in infrared scattered light and sub-millimeter dust continuum emission. In particular, it is possible that the scattered light is boosted as one of the spiral arms passes through the high density vortex region, although the vortex alone may be able to explain the peak. We suggest that a planetary companion with a mass of 10–15 ${M}_{J}$ is orbiting SAO 206462 at 100–120 au. Monitoring of the brightest peak over the next few years will help reveal its origin because the spiral arms and vortex will show distinguishable displacement.

A Super-Jupiter Microlens Planet

A Super-Jupiter Microlens Planet Characterized by High-Cadence KMTNet Microlensing Survey Observations

Authors:

Shin et al

Abstract:

We report the characterization of a massive planet m_p=4.4 +- 1.6 M_jup orbiting an M dwarf host M=0.37 +- 0.14 M_sun at a distance of 0.6 +- 0.3 kpc toward the Galactic bulge, with planet host projected separation a_perp ~ 1.2 AU. The characterization was made possible by the wide-field (4 deg^2) high cadence (6/hr) monitoring of the Korea Microlensing Telescope Network (KMTNet), which had two of its three telescopes in commissioning operations at the time of the planetary anomaly. The source crossing time, t_* ~ 16 min, is among the shortest ever published. The high-cadence, wide-field observations that are the hallmark of KMTNet are the only way to routinely capture such short crossings. High-cadence resolution of short caustic crossings will preferentially lead to mass and distance measurements for the lens. This is because the short crossing time typically implies a nearby lens, which enables the measurement of additional effects (bright lens and/or microlens parallax). When combined with the measured crossing time, these effects can yield complete solutions.

Is 2MASS J21265040-8140293 Really TYC 9486-927-1b or TYC 9486-927-1B? The Widest Separation SuperJupiter or L Class Brown Dwarf Known

A nearby young M dwarf with a wide, possibly planetary-mass companion

Authors:

Deacon et al

Abstract:

We present the identification of two previously known young objects in the solar neighbourhood as a likely very wide binary. TYC 9486-927-1, an active, rapidly rotating early-M dwarf, and 2MASS J21265040-8140293, a low-gravity L3 dwarf previously identified as candidate members of the ∼45 Myr old Tucana Horologium association (TucHor). An updated proper motion measurement of the L3 secondary, and a detailed analysis of the pair's kinematics in the context of known nearby, young stars, reveals that they share common proper motion and are likely bound. New observations and analyses reveal the primary exhibits Li 6708~\AA~absorption consistent with M dwarfs younger than TucHor but older than the ∼10 Myr TW Hydra association yielding an age range of 10-45 Myr. A revised kinematic analysis suggests the space motions and positions of the pair are closer to, but not entirely in agreement with, the ∼24 Myr old β Pictoris moving group. This revised 10-45 Myr age range yields a mass range of 11.6--15 MJ for the secondary. It is thus likely 2MASS J21265040-8140293short is the widest orbit planetary mass object known (greater than 4500AU) and its estimated mass, age, spectral type, and Teff are similar to the well-studied planet β Pictoris b. Because of their extreme separation and youth, this low-mass pair provide an interesting case study for very wide binary formation and evolution.

KIC 7177553: a Quadruple System of two Close Binaries With a Superjupiter

KIC 7177553: a quadruple system of two close binaries

Authors:

Lehmann et al

Abstract:

KIC 7177553 was observed by the Kepler satellite to be an eclipsing eccentric binary star system with an 18-day orbital period. Recently, an eclipse timing study of the Kepler binaries has revealed eclipse timing variations in this object with an amplitude of about 100 sec, and an outer period of 529 days. The implied mass of the third body is that of a superJupiter, but below the mass of a brown dwarf. We therefore embarked on a radial velocity study of this binary to determine its system configuration and to check the hypothesis that it hosts a giant planet. From the radial velocity measurements, it became immediately obvious that the same Kepler target contains another eccentric binary, this one with a 16.5-day orbital period. Direct imaging using adaptive optics reveals that the two binaries are separated by 0.4 arcsec (about 167 AU), and have nearly the same magnitude (to within 2%). The close angular proximity of the two binaries, and very similar Gamma velocities, strongly suggest that KIC 7177553 is one of the rare SB4 systems consisting of two eccentric binaries where at least one system is eclipsing. Both systems consist of slowly rotating, non-evolved, solar-like stars of comparable masses. From the orbital separation and the small difference in Gamma velocity, we infer that the period of the outer orbit most likely lies in the range 1000 to 3000 years. New images taken over the next few years, as well as the high-precision astrometry of the Gaia satellite mission, will allow us to set much narrower constraints on the system geometry. Finally, we note that the observed eclipse timing variations in the Kepler data cannot be produced by the second binary. Further spectroscopic observations on a longer time scale will be required to prove the existence of the massive planet.

Two Super-Jupiters in a 3:5 Resonance Orbiting the Giant Star HD 33844

The Pan-Pacific Planet Search. IV. Two super-Jupiters in a 3:5 resonance orbiting the giant star HD33844

Authors:

Wittenmyer et al

Abstract:

We report the discovery of two giant planets orbiting the K giant HD 33844 based on radial velocity data from three independent campaigns. The planets move on nearly circular orbits with semimajor axes ab=1.60±0.02 AU and ac=2.24±0.05 AU, and have minimum masses (m sin i) of Mb=1.96±0.12 Mjup and Mc=1.76±0.18 Mjup. Detailed N-body dynamical simulations show that the two planets remain on stable orbits for more than 106 years for low eccentricities, and are most likely trapped in a mutual 3:5 mean-motion resonance.

Hubble Directly Images Cloudy Super Jupiter's Rotation as it Orbits a Brown Dwarf

Astronomers using NASA's Hubble Space Telescope have measured the rotation rate of an extreme exoplanet by observing the varied brightness in its atmosphere. This is the first measurement of the rotation of a massive exoplanet using direct imaging.

"The result is very exciting," said Daniel Apai of the University of Arizona in Tucson, leader of the Hubble investigation. "It gives us a unique technique to explore the atmospheres of exoplanets and to measure their rotation rates."

The planet, called 2M1207b, is about four times more massive than Jupiter and is dubbed a "super-Jupiter." It is a companion to a failed star known as a brown dwarf, orbiting the object at a distance of 5 billion miles. By contrast, Jupiter is approximately 500 million miles from the sun. The brown dwarf is known as 2M1207. The system resides 170 light-years away from Earth.

link.  2nd link.

paper here.

HD 100546b is a SuperJovian and HD 100546c is a SuperJovian at 13 AU

Resolving the HD 100546 Protoplanetary System with the Gemini Planet Imager: Evidence for Multiple Forming, Accreting Planets

Authors:

Currie et al

Abstract:

We report Gemini Planet Imager H band high-contrast imaging/integral field spectroscopy and polarimetry of the HD 100546, a 10 Myr-old early-type star recently confirmed to host a thermal infrared bright (super)jovian protoplanet at wide separation, HD 100546 b. We resolve the inner disk cavity in polarized light, recover the thermal-infrared (IR) bright arm, and identify one additional spiral arm. We easily recover HD 100546 b and show that much of its emission originates an unresolved, point source. HD 100546 b likely has extremely red infrared colors compared to field brown dwarfs, qualitatively similar to young cloudy superjovian planets, however, these colors may instead indicate that HD 100546 b is still accreting material from a circumplanetary disk. Additionally, we identify a second point source-like peak at rproj ∼ 13 AU, located just interior to or at inner disk wall consistent with being a 10--20 MJ candidate second protoplanet-- "HD 100546 c" -- and lying within a weakly polarized region of the disk but along an extension of the thermal IR bright spiral arm. Alternatively, it is equally plausible that this feature is a weakly polarized but locally bright region of the inner disk wall. Astrometric monitoring of this feature over the next 2 years and emission line measurements could confirm its status as a protoplanet, rotating disk hot spot that is possibly a signpost of a protoplanet, or a stationary emission source from within the disk.

Determining the Composition of Pulsar Orbiting Super Jupiters With Radio Line Spectroscopy

Inferring the composition of super-Jupiter mass companions of pulsars with radio line spectroscopy

Authors:

Ray et al

Abstract:

We propose using radio line spectroscopy to detect molecular absorption lines (such as OH at 1.6-1.7 GHz) before and after the total eclipse of black widow (BW) and other short orbital period binary pulsars with low mass companions. The companion in such a binary may be ablated away by energetic particles and high energy radiation produced by the pulsar wind. The observations will probe the eclipsing wind being ablated by the pulsar and constrain the nature of the companion and its surroundings. Maser emission from the interstellar medium stimulated by a pulsar beam might also be detected from the intrabinary medium. The short temporal resolution allowed by the millisecond pulsars can probe this medium with the high angular resolution of the pulsar beam.

Hot Jupiters Predicted to Have Distant, Massive Cosystem Exoplanets

HOT JUPITERS FROM COPLANAR HIGH-ECCENTRICITY MIGRATION

Author:

Petrovich

Abstract:

We study the possibility that hot Jupiters (HJs) are formed through the secular gravitational interactions between two planets in eccentric orbits with relatively low mutual inclinations ($\lesssim 20{}^\circ $) and friction due to tides raised on the planet by the host star. We term this migration mechanism Coplanar High-eccentricity Migration (CHEM) because, like disk migration, it allows for migration to occur on the same plane in which the planets formed. CHEM can operate from the following typical initial configurations: (i) the inner planet in a circular orbit and the outer planet with an eccentricity $\gtrsim 0.67$ for ${{m}_{{\rm in}}}/{{m}_{{\rm out}}}{{({{a}_{{\rm in}}}/{{a}_{{\rm out}}})}^{1/2}}\lesssim 0.3$; (ii) two eccentric ($\gtrsim 0.5$) orbits for ${{m}_{{\rm in}}}/{{m}_{{\rm out}}}{{({{a}_{{\rm in}}}/{{a}_{{\rm out}}})}^{1/2}}\lesssim 0.16$. A population synthesis study of hierarchical systems of two giant planets using the observed eccentricity distribution of giant planets shows that CHEM produces HJs with low stellar obliquities ($\lesssim 30{}^\circ $), with a semi-major axis distribution that matches the observations, and at a rate that can account for their observed occurrence. A different mechanism is needed to create large obliquity HJs, either a different migration channel or a mechanism that tilts the star or the protoplanetary disk. CHEM predicts that HJs should have distant ($a\gtrsim 5$ AU) and massive (most likely ~1–3 times more massive than the HJ) companions with relatively low mutual inclinations ($\lesssim 20{}^\circ $) and moderately high eccentricities ($e\sim 0.2-0.5$).

Update: Forming Giant Moons Around SuperJovian Exoplanets

Water ice lines and the formation of giant moons around super-Jovian planets

Authors:

Heller et al

Abstract:

Most of the exoplanets with known masses at Earth-like distances to Sun-like stars are heavier than Jupiter, which raises the question of whether such planets are accompanied by detectable, possibly habitable moons. Here we simulate the accretion disks around super-Jovian planets and find that giant moons with masses similar to Mars can form. Our results suggest that the Galilean moons formed during the final stages of accretion onto Jupiter, when the circumjovian disk was sufficiently cool. But in contrast to other studies, with our assumptions, we show that Jupiter was still feeding from the circumsolar disk and that its principal moons cannot have formed after the complete photoevaporation of the circumsolar nebula. To counteract the steady loss of moons into the planet due to type I migration, we propose that the water ice line around Jupiter and super-Jovian exoplanets acted as a migration trap for moons. Heat transitions, however, cross the disk during the gap opening within 10^4 yr, which makes them inefficient as moon traps. This indicates a fundamental difference between planet and moon formation. We find that icy moons larger than the smallest known exoplanet can form at about 15 - 30 Jupiter radii around super-Jovian planets. Their size implies detectability by the Kepler and PLATO space telescopes as well as by the European Extremely Large Telescope.

Original.

LkCa 15b is Between 6 and 15 Jupiter Masses

Spectro-astrometry of LkCa 15 with X-Shooter: Searching for emission from LkCa 15b

Authors:

Whelan et al

Abstract:

Planet formation is one explanation for the partial clearing of dust observed in the disks of some T Tauri stars. Indeed studies using state-of-the-art high angular resolution techniques have very recently begun to observe planetary companions in these so-called transitional disks. The goal of this work is to use spectra of the transitional disk object LkCa 15 obtained with X-Shooter on the Very Large Telescope to investigate the possibility of using spectro-astrometry to detect planetary companions to T Tauri stars. It is argued that an accreting planet should contribute to the total emission of accretion tracers such as Hα and therefore planetary companions could be detected with spectro-astrometry in the same way as it has been used to detect stellar companions to young stars. A probable planetary-mass companion was recently detected in the disk of LkCa 15. Therefore, it is an ideal target for this pilot study. We studied several key accretion lines in the wavelength range 300 nm to 2.2 μm with spectro-astrometry. While no spectro-astrometric signal is measured for any emission lines the accuracy achieved in the technique is used to place an upper limit on the contribution of the planet to the flux of the Hα, Paγ, and Paβ lines. The derived upper limits on the flux allows an upper limit of the mass accretion rate, log(M˙acc) = -8.9 to -9.3 for the mass of the companion between 6 MJup and 15 MJup, respectively, to be estimated (with some assumptions).

What Does it Take to Form a Mars Mass Icy ExoMoon Around Super Jovians?

Conditions for water ice lines and Mars-mass exomoons around accreting super-Jovian planets at 1 - 20 AU from Sun-like stars

Authors:

Heller et al

Abstract:

Exomoon detections might be feasible with NASA's Kepler or ESA's upcoming PLATO mission or the ground-based E-ELT. To use observational resources most efficiently we need to know where the largest, most easily detected moons can form. We explore the possibility of large exomoons by following the movement of water (H2O) ice lines in the accretion disks around young super-Jovian planets. We want to know how different heating sources in those disks affect the H2O ice lines. We simulate 2D rotationally symmetric accretion disks in hydrostatic equilibrium around super-Jovian exoplanets. The energy terms in our semi-analytical model -- (1) viscous heating, (2) planetary illumination, (3) accretional heating, and (4) stellar illumination -- are fed by precomputed planet evolution tracks. We consider planets accreting 1 to 12 Jupiter masses at distances between 1 and 20 AU to a Sun-like star. Accretion disks around Jupiter-mass planets closer than ~4.5 AU to Sun-like stars do not feature H2O ice lines, but the most massive super-Jovians can form icy satellites as close as ~3 AU to Sun-like stars. Super-Jovian planets forming beyond ~5 AU can host Mars-mass moons. We study a broad range of disk parameters for planets at 5.2 AU and find that the H2O ice lines are universally between ~15 and 30 Jupiter radii when the last generation of moons is forming. If the abundant population of super-Jovian planets at ~1 AU formed in situ, then they should lack giant icy moons because their disks did not host H2O ice in the final stages of accretion. In the more likely case that these planets migrated to their current locations from beyond a few AU, they might be orbited by large, H2O-rich moons. In this case, Mars-mass ocean moons might be common in the stellar habitable zones. Future exomoon searches can provide powerful constraints on the formation and migration history of giant exoplanets.