We present new 1-1.25 µm (z and J band) Subaru/IRCS and 2 µm (K band) VLT/NaCo data for HR 8799 and a rereduction of the 3-5 µm MMT/Clio data first presented by Hinz et al. (2010). Our VLT/NaCo data yields a detection of a fourth planet at a projected separation of ∼ 15 AU -"HR 8799e". We also report new, albeit weak detections of HR 8799b at 1.03 µm and 3.3 µm. Empirical comparisons to field brown dwarfs show that at least HR 8799b and HR8799c, and possibly HR 8799d, have near-to-mid IR colors/magnitudes significantly discrepant from the L/T dwarf sequence. Standard cloud deck atmosphere models appropriate for brown dwarfs provide only (marginally) statistically meaningful fits to HR 8799b and c for unphysically small radii. Models with thicker cloud layers not present in brown dwarfs reproduce the planets' SEDs far more accurately and without the need for rescaling the planets' radii. Our preliminary modeling suggests that HR 8799b has log(g) = 4-4.5, T ef f = 900K, while HR 8799c, d, and (by inference) e have log(g) = 4-4.5, T ef f = 1000-1200K. Combining results from planet evolution models and new dynamical stability limits implies that the masses of HR 8799b, c, d, and e are 6-7 M J , 7-10 M J , 7-10 M J and 7-10 M J . "Patchy" cloud prescriptions may provide even better fits to the data and may lower the estimated surface gravities and masses. Finally, contrary to some recent claims, forming the HR 8799 planets by core accretion is still plausible, although such systems are likely rare.

We present a new method to constrain the grain size in protoplanetary disks with polarization observations at millimeter wavelengths. If dust grains are grown to the size comparable to the wavelengths, the dust grains are expected to have a large scattering opacity and thus the continuum emission is expected to be polarized due to self-scattering. We perform 3D radiative transfer calculations to estimate the polarization degree for the protoplanetary disks having radial Gaussian-like dust surface density distributions, which have been recently discovered. The maximum grain size is set to be 100 µm and the observing wavelength to be 870 µm. We find that the polarization degree is as high as 2.5% with a subarcsec spatial resolution, which is likely to be detected with near-future ALMA observations. The emission is polarized due to scattering of anisotropic continuum emission. The map of the polarization degree shows a double peaked distribution and the polarization vectors are in the radial direction in the inner ring and in the azimuthal direction in the outer ring. We also find the wavelength dependence of the polarization degree: the polarization degree is the highest if dust grains have a maximum size of a max ∼ λ/2π, where λ is the observing wavelength. Hence, multi-wave and spatially resolved polarization observations toward protoplanetary disks enable us to put a constraint on the grain size. The constraint on the grain size from polarization observations is independent of or may be even stronger than that from the opacity index.

We report on the properties of pre-main-sequence objects in the Taurus molecular clouds as observed in 7 mid-and far-infrared bands with the Spitzer Space Telescope. There are 215 previously-identified members of the Taurus star-forming region in our ∼44 square degree map; these members exhibit a range of Spitzer colors that we take to define young stars still surrounded by circumstellar dust (noting that ∼20% of the bonafide Taurus members exhibit no detectable dust excesses). We looked for new objects in the survey field with similar Spitzer properties, aided -2by extensive optical, X-ray, and ultraviolet imaging, and found 148 candidate new members of Taurus. We have obtained follow-up spectroscopy for about half the candidate sample, thus far confirming 34 new members, 3 probable new members, and 10 possible new members, an increase of 15-20% in Taurus members. Of the objects for which we have spectroscopy, 7 are now confirmed extragalactic objects, and one is a background Be star. The remaining 93 candidate objects await additional analysis and/or data to be confirmed or rejected as Taurus members. Most of the new members are Class II M stars and are located along the same cloud filaments as the previously-identified Taurus members. Among non-members with Spitzer colors similar to young, dusty stars are evolved Be stars, planetary nebulae, carbon stars, galaxies, and AGN.Subject headings: stars: formation -stars: circumstellar matter -stars: pre-main sequenceinfrared: starswhere m is the reported magnitude (and F ν the flux density) for a given object, Z = 18.259, 17.204, and 14.837, and f = 1.94×10 −16 , 4.76×10 −16 , and 5.71×10 −15 ergs cm −2 s −1Å−1 counts −1 sec for U , UVW1, and UVW2 (respectively). In the equation, λ is in units ofÅ, and c is 3×10 18Å s −1 The effective wavelengths are 0.344, 0.291, and 0.212 µm for U , UVW1, and UVW2. There are ∼1600 objects with XMM-Newton OM flux densities in our catalog (0.2% of the entire catalog).We note that many of the X-ray detected XEST sources are likely background galaxies (see Güdel et al. 2007) and that XEST included regions not covered by our map, such as L1551.The XEST team assembled a catalog of supporting data from the literature, such as optical photometric measurements, for all of the previously-identified Taurus members (see §3.1.1 below); we have included these photometric points in our database, converting Johnson magnitudes to flux densities using zero-points available in the literature (e.g., Cox 2001 and references therein).The SEDs presented in this paper use all of these supporting data where available (except for the X-ray fluxes), and are presented as λF λ in cgs units (erg s −1 cm −2 ), against λ in microns.2 In SDSS, a "maggy" is the ratio of the flux density of the object to a standard flux density. The Sloan magnitudes are AB magnitudes, as opposed to Vega magnitudes. In the AB system, a flat spectrum object with 3631 Jy at each band should have every magnitude equal to zero, and all maggies equal to one. Flux densities returned by th...

We present high-resolution, H-band, imaging observations, collected with Subaru/HiCIAO, of the scattered light from the transitional disk around SAO 206462 (HD 135344B). Although previous submm imagery suggested the existence of the dust-depleted cavity at r ≤ 46 AU, our observations reveal the presence of scattered light components as close as 0. ′′ 2 (∼ 28 AU) from the star. Moreover, we have discovered two small-scale spiral structures lying within 0. ′′ 5 (∼ 70 AU). We present models for the spiral structures using the spiral density wave theory, and derive a disk aspect ratio of h ∼ 0.1, which is consistent with previous sub-mm observations. This model can potentially give estimates of the temperature and rotation profiles of the disk based on dynamical processes, independently from sub-mm observations. It also predicts the evolution of the spiral structures, which can be observable on timescales of 10-20 years, providing conclusive tests of the model. While we cannot uniquely identify the origin of these spirals, planets embedded in the disk may be capable of exciting the observed morphology. Assuming that this is the case, we can make predictions on the locations and, possibly, the masses of the unseen planets. Such planets may be detected by future multi-wavelengths observations.

Context. Debris discs are a consequence of the planet formation process and constitute the fingerprints of planetesimal systems. Their solar system counterparts are the asteroid and Edgeworth-Kuiper belts. Aims. The DUNES survey aims at detecting extra-solar analogues to the Edgeworth-Kuiper belt around solar-type stars, putting in this way the solar system into context. The survey allows us to address some questions related to the prevalence and properties of planetesimal systems. Methods. We used Herschel/PACS to observe a sample of nearby FGK stars. Data at 100 and 160 μm were obtained, complemented in some cases with observations at 70 μm, and at 250, 350 and 500 μm using SPIRE. The observing strategy was to integrate as deep as possible at 100 μm to detect the stellar photosphere. Results. Debris discs have been detected at a fractional luminosity level down to several times that of the Edgeworth-Kuiper belt. The incidence rate of discs around the DUNES stars is increased from a rate of ∼12.1% ± 5% before Herschel to ∼20.2% ± 2%. A significant fraction (∼52%) of the discs are resolved, which represents an enormous step ahead from the previously known resolved discs. Some stars are associated with faint far-IR excesses attributed to a new class of cold discs. Although it cannot be excluded that these excesses are produced by coincidental alignment of background galaxies, statistical arguments suggest that at least some of them are true debris discs. Some discs display peculiar SEDs with spectral indexes in the 70-160 μm range steeper than the Rayleigh-Jeans one. An analysis of the debris disc parameters suggests that a decrease might exist of the mean black body radius from the F-type to the K-type stars. In addition, a weak trend is suggested for a correlation of disc sizes and an anticorrelation of disc temperatures with the stellar age.

We present a near-infrared image of the Herbig Ae star AB Aur obtained with the Coronagraphic Imager with Adaptive Optics mounted on the Subaru Telescope. The image shows a circumstellar emission extending out to a radius of AU, with a double spiral structure detected at AU. The surface brightness r p 580 r p 200-450 decreases as , steeper than the radial profile of the optical emission possibly affected by the scattered Ϫ3.0‫1.0ע‬ r light from the envelope surrounding AB Aur. This result, together with the size of the infrared emission similar to that of the 13 CO ( ) disk, suggests that the spiral structure is indeed associated with the circumstellar J p 1-0 disk but is not part of the extended envelope. We identified four major spiral arms, which are trailing if the brighter southeastern part of the disk is the near side. The weak gravitational instability, maintained for millions of years by continuous mass supply from the envelope, might explain the presence of the spiral structure at the relatively late phase of the pre-main-sequence period.

We present Subaru/IRCS J band data for Fomalhaut and a (re)reduction of archival [2004][2005][2006] HST/ACS data first presented by Kalas et al. (2008). We confirm the existence of a candidate exoplanet, Fomalhaut b, in both the 2004 and 2006 F606W data sets at a high signal-to-noise. Additionally, we confirm the detection at F814W and present a new detection in F435W. Fomalhaut b's space motion may be consistent with it being in an apsidally-aligned, non debris ring-crossing orbit, although new astrometry is required for firmer conclusions. We cannot confirm that Fomalhaut b exhibits 0.7-0.8 mag variability cited as evidence for planet accretion or a semi-transient dust cloud. The new, combined optical SED and IR upper limits confirm that emission identifying Fomalhaut b originates from starlight scattered by small dust, but this dust is most likely associated with a massive body. The Subaru and IRAC/4.5 µm upper limits imply M < 2 M J , still consistent with the range of Fomalhaut b masses needed to sculpt the disk. Fomalhaut b is very plausibly "a planet identified from direct imaging" even if current images of it do not, strictly speaking, show thermal emission from a directly imaged planet.

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