We present new results on how the presence of stellar companions affects disk evolution based on a study of the 5-11 Myr old Upper Scorpius OB Association. Of the 50 G0-M3 Upper Sco members with ...disks in our sample, only seven host a stellar companion within 2″ and brighter than K = 15, compared to 35 of 75 members without disks. This matches a trend seen in the 1-2 Myr old Taurus region, where systems with a stellar companion within 40 au have a lower fraction of infrared-identified disks than those without such companions, indicating shorter disk lifetimes in close multiple systems. However, the fractions of disk systems with a stellar companion within 40 au match in Upper Sco and Taurus. Additionally, we see no difference in the millimeter brightnesses of disks in Upper Sco systems with and without companions, in contrast to Taurus where systems with a companion within 300 au are significantly fainter than wider and single systems. These results suggest that the effects of stellar companions on disk lifetimes occur within the first 1-2 Myr of disk evolution, after which companions play little further role. By contrast, disks around single stars lose the millimeter-sized dust grains in their outer regions between ages of 1-2 Myr and 5-11 Myr. The end result of small dust disk sizes and faint millimeter luminosities is the same whether the disk has been truncated by a companion or has evolved through internal processes.
Abstract
We present the complete sample of protoplanetary disks from the Gemini- Large Imaging with the Gemini Planet Imager Herbig/T Tauri Survey, which observed bright Herbig Ae/Be stars and T ...Tauri stars in near-infrared polarized light to search for signatures of disk evolution and ongoing planet formation. The 44 targets were chosen based on their near- and mid-infrared colors, with roughly equal numbers of transitional, pre-transitional, and full disks. Our approach explicitly did not favor well-known, “famous” disks or those observed by the Atacama Large Millimeter/submillimeter Array, resulting in a less-biased sample suitable to probe the major stages of disk evolution during planet formation. Our optimized data reduction allowed polarized flux as low as 0.002% of the stellar light to be detected, and we report polarized scattered light around 80% of our targets. We detected point-like companions for 47% of the targets, including three brown dwarfs (two confirmed, one new), and a new super-Jupiter-mass candidate around V1295 Aql. We searched for correlations between the polarized flux and system parameters, finding a few clear trends: the presence of a companion drastically reduces the polarized flux levels, far-IR excess correlates with polarized flux for nonbinary systems, and systems hosting disks with ring structures have stellar masses <3 M
⊙
. Our sample also included four hot, dusty “FS CMa” systems, and we detected large-scale ( >100 au) scattered light around each, signs of extreme youth for these enigmatic systems. Science-ready images are publicly available through multiple distribution channels using a new FITS file standard that has been jointly developed with members of the Very Large Telescope Spectro-polarimetric High-contrast Exoplanet Research team.
We report the discovery of an extremely red planetary-mass companion to 2MASS J22362452+4751425, a approximate0.6 M sub(middot in circle) late-K dwarf likely belonging to the ~120 Myr AB Doradus ...moving group. 2M2236+4751 b was identified in multi-epoch NIRC2 adaptive optics imaging at Keck Observatory at a separation of 3".7, or 230 + or - 20 AU in projection at the kinematic distance of 63 + or - 5 pc to its host star. Assuming membership in the AB Dor group, as suggested from its kinematics, the inferred mass of 2M2236+4751 b is 11-14 M sub(Jup). Follow-up Keck/OSIRIS K-band spectroscopy of the companion reveals strong CO absorption similar to other faint red L dwarfs and lacks signs of methane absorption, despite having an effective temperature of approximate900-1200 K. With a (J-K) sub(MKO) color of 2.69 + or - 0.12 mag, the near-infrared slope of 2M2236+4751 b is redder than all of the HR 8799 planets and instead resembles the approximate23 Myr isolated planetary-mass object PSO J318.5-22, implying that similarly thick photospheric clouds can persist in the atmospheres of giant planets at ages beyond 100 Myr. In near-infrared color-magnitude diagrams, 2M2236+4751 b is located at the tip of the red L dwarf sequence and appears to define the "elbow" of the AB Dor substellar isochrone separating low-gravity L dwarfs from the cooler young T dwarf track. 2M2236+4751 b is the reddest substellar companion to a star and will be a valuable benchmark to study the shared atmospheric properties of young low-mass brown dwarfs and extrasolar giant planets.
ABSTRACT Surveys of nearby field stars indicate that stellar binaries are common, yet little is known about the effects that these companions may have on planet formation and evolution. The Friends ...of Hot Jupiters project uses three complementary techniques to search for stellar companions to known planet-hosting stars: radial velocity monitoring, adaptive optics imaging, and near-infrared spectroscopy. In this paper, we examine high-resolution K band infrared spectra of fifty stars hosting gas giant planets on short-period orbits. We use spectral fitting to search for blended lines due to the presence of cool stellar companions in the spectra of our target stars, where we are sensitive to companions with temperatures between 3500 and 5000 K and projected separations less than 100 AU in most systems. We identify eight systems with candidate low-mass companions, including one companion that was independently detected in our AO imaging survey. For systems with radial velocity accelerations, a spectroscopic non-detection rules out scenarios involving a stellar companion in a high inclination orbit. We use these data to place an upper limit on the stellar binary fraction at small projected separations, and show that the observed population of candidate companions is consistent with that of field stars and also with the population of wide-separation companions detected in our previous AO survey. We find no evidence that spectroscopic stellar companions are preferentially located in systems with short-period gas giant planets on eccentric and/or misaligned orbits.
ABSTRACT We present the first scattered light detections of the HD 106906 debris disk using the Gemini/Gemini Planet Imager in the infrared and Hubble Space Telescope (HST)/Advanced Camera for ...Surveys in the optical. HD 106906 is a 13 Myr old F5V star in the Sco-Cen association, with a previously detected planet-mass candidate HD 106906b projected 650 AU from the host star. Our observations reveal a near edge-on debris disk that has a central cleared region with radius ∼50 AU, and an outer extent >500 AU. The HST data show that the outer regions are highly asymmetric, resembling the "needle" morphology seen for the HD 15115 debris disk. The planet candidate is oriented ∼21° away from the position angle of the primary's debris disk, strongly suggesting non-coplanarity with the system. We hypothesize that HD 106906b could be dynamically involved in the perturbation of the primary's disk, and investigate whether or not there is evidence for a circumplanetary dust disk or cloud that is either primordial or captured from the primary. We show that both the existing optical properties and near-infrared colors of HD 106906b are weakly consistent with this possibility, motivating future work to test for the observational signatures of dust surrounding the planet.
Abstract
High angular resolution observations of young stellar objects are required to study the inner astronomical units of protoplanetary disks in which the majority of planets form. As they ...evolve, gaps open up in the inner disk regions and the disks are fully dispersed within ∼10 Myr. MWC 614 is a pretransitional object with a ∼10 au radius gap. We present a set of high angular resolution observations of this object including SPHERE/ZIMPOL polarimetric and coronagraphic images in the visible, Keck/NIRC2 near-infrared (NIR) aperture masking observations, and Very Large Telescope Interferometer (AMBER, MIDI, and PIONIER) and Center for High Angular Resolution Astronomy (CLASSIC and CLIMB) long-baseline interferometry at infrared wavelengths. We find that all the observations are compatible with an inclined disk (
i
∼ 55° at a position angle of ∼20°–30°). The mid-infrared data set confirms that the disk inner rim is at 12.3 ± 0.4 au from the central star. We determined an upper mass limit of 0.34
M
⊙
for a companion inside the cavity. Within the cavity, the NIR emission, usually associated with the dust sublimation region, is unusually extended (∼10 au, 30 times larger than the theoretical sublimation radius) and indicates a high dust temperature (
T
∼ 1800 K). As a possible result of companion-induced dust segregation, quantum heated dust grains could explain the extended NIR emission with this high temperature. Our observations confirm the peculiar state of this object where the inner disk has already been accreted onto the star, exposing small particles inside the cavity to direct stellar radiation.
The companion to the G0V star HR7672 directly imaged by Liu et al. has moved measurably along its orbit since the discovery epoch, making it possible to determine its dynamical properties. Originally ...targeted with adaptive optics because it showed a long-term radial velocity (RV) acceleration (trend), we have monitored this star with precise Doppler measurements and have now established a 24 year time baseline. The RV variations show significant curvature (change in the acceleration) including an inflection point. We have also obtained a recent image of HR7672B with NIRC2 at Keck. The astrometry also shows curvature. In this paper, we use jointly fitted Doppler and astrometric models to calculate the three-dimensional orbit and dynamical mass of the companion. The mass of the host star is determined using a direct radius measurement from CHARA interferometry in combination with high-resolution spectroscopic modeling. We find that HR7672B has a highly eccentric, e = 0.50 super(+0.01) sub(-0.01) near edge-on, i = 97.3 super(+0.4) sub(-0.5) deg, orbit with semimajor axis, a = 18.3 super(+0.4) sub(-0.5)AU. The mass of the companion is m = 68.7 super(+2.4) sub(-3.1) MJ. HR7672B thus resides near the substellar boundary, just below the hydrogen-fusing limit. These measurements of the companion mass are independent of its brightness and spectrum and establish HR7672B as a rare and precious "benchmark" brown dwarf with a well-determined mass, age, and metallicity essential for testing theoretical evolutionary models and synthetic spectral models. Indeed, we find that such models under-predict its luminosity by a factor of approximately 2. HR 7672B is presently the only L, T, or Y dwarf known to produce an RV trend around a solar-type star.
At present, the principal limitation on the resolution and contrast of astronomical imaging instruments comes from aberrations in the optical path, which may be imposed by the Earth's turbulent ...atmosphere or by variations in the alignment and shape of the telescope optics. These errors can be corrected physically, with active and adaptive optics, and in post-processing of the resulting image. A recently developed adaptive optics post-processing technique, called kernel-phase interferometry, uses linear combinations of phases that are self-calibrating with respect to small errors, with the goal of constructing observables that are robust against the residual optical aberrations in otherwise well-corrected imaging systems. Here, we present a direct comparison between kernel phase and the more established competing techniques, aperture masking interferometry, point spread function (PSF) fitting and bispectral analysis. We resolve the α Ophiuchi binary system near periastron, using the Palomar 200-Inch Telescope. This is the first case in which kernel phase has been used with a full aperture to resolve a system close to the diffraction limit with ground-based extreme adaptive optics observations. Excellent agreement in astrometric quantities is found between kernel phase and masking, and kernel phase significantly outperforms PSF fitting and bispectral analysis, demonstrating its viability as an alternative to conventional non-redundant masking under appropriate conditions.
A reassessment of ground‐based observations confirms to better than a 98% confidence level that the Galileo probe entered a 5‐μm hot spot, a region of unusual clarity and dryness, some 900±300 km ...north of its southern boundary. Cloud conditions at that point were similar to those in the center of this region, some 600 km further north. At the time of the probe entry, the region was evolving to a slightly larger size and even thinner cloud conditions, as evidenced by its rapidly brightening appearance at 4.78 μm. The low reflectivity of the region in red light is highly anticorrelated with 4.78‐μm thermal emission, but this correlation breaks down in the blue. In general, the reflectivity of most hot spots is remarkably uniform, although the 4.78‐μm thermal emission is highly variable. A cloud structure most consistent with both the observed reflected sunlight and thermal emission properties consists of two layers: (1) a cloud layer above the 450‐mbar level extending up to the 150‐mbar level that probably consists of submicron sized particles and (2) a tropospheric cloud that is probably below the 1‐bar level, possibly ammonia hydrosulfide, with low optical thickness in the infrared. A population of particles larger than ∼3 μm, clearly present at the NH3 ice cloud level outside hot spots, is absent inside them. The NH3 gas abundance near 300–400 mbar pressure does not appear to be unusually depleted in hot spots. Zonal structures in the tropospheric temperature field near the probe entry site were not correlated with the location of 5‐μm hot spots but moved at speeds closer to the internal rotation rate of the planet. The properties of the tropospheric thermal waves at the probe entry latitude show little correlation to the properties of the 5‐μm hot spot waves. Temperatures at the probe entry site derived from remote sensing are warmer than the Atmospheric Structure Instrument (ASI) experiment results near the tropopause, probably because the low‐temperature ASI features are confined to regions smaller than the ∼6000‐km resolution characteristic of the remote sensing.
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