Context.
Hydrodynamical simulations of planet-disk interactions suggest that planets may be responsible for a number of the substructures frequently observed in disks in both scattered light and dust ...thermal emission. Despite the ubiquity of these features, direct evidence of planets embedded in disks and of the specific interaction features like spiral arms within planetary gaps are still rare.
Aims.
In this study we discuss recent observational results in the context of hydrodynamical simulations in order to infer the properties of a putative embedded planet in the cavity of a transition disk.
Methods.
We imaged the transition disk SR 21 in
H
-band in scattered light with SPHERE/IRDIS and in thermal dust emission with ALMA band 3 (3 mm) observations at a spatial resolution of 0.1″. We combine these datasets with existing Band 9 (430
μ
m) and Band 7 (870
μ
m) ALMA continuum data.
Results.
The Band 3 continuum data reveals a large cavity and a bright ring peaking at 53 au strongly suggestive of dust trapping. The ring shows a pronounced azimuthal asymmetry, with a bright region in the northwest that we interpret as a dust overdensity. A similarly asymmetric ring is revealed at the same location in polarized scattered light, in addition to a set of bright spirals inside the millimeter cavity and a fainter spiral bridging the gap to the outer ring. These features are consistent with a number of previous hydrodynamical models of planet-disk interactions, and suggest the presence of a ∼1
M
Jup
planet at 44 au and PA = 11 deg. This makes SR21 the first disk showing spiral arms inside the millimeter cavity, and the first disk for which the location of a putative planet can be precisely inferred.
Conclusions.
The main features of SR 21 in both scattered light and thermal emission are consistent with hydrodynamical predictions of planet-disk interactions. With the location of a possible planet being well constrained by observations, it is an ideal candidate for follow-up observations to search for direct evidence of a planetary companion still embedded in its disk.
ABSTRACT
The Young Suns Exoplanet Survey consists of a homogeneous sample of 70 young, solar-mass stars located in the Lower Centaurus-Crux subgroup of the Scorpius-Centaurus association with an ...average age of 15 ± 3 Myr. We report the detection of a co-moving companion around the K3IV star TYC 8998-760-1 (2MASSJ13251211–6456207) that is located at a distance of 94.6 ± 0.3 pc using SPHERE/IRDIS on the VLT. Spectroscopic observations with VLT/X-SHOOTER constrain the mass of the star to $1.00\pm 0.02\, \mathrm{M}_{\odot }$ and an age of $16.7\pm 1.4\,$ Myr. The companion TYC 8998-760-1 b is detected at a projected separation of 1.71″, which implies a projected physical separation of 162 au. Photometric measurements ranging from Y to M band provide a mass estimate of $14\pm 3\, M_\mathrm{jup}$ by comparison to BT-Settl and AMES-dusty isochrones, corresponding to a mass ratio of q = 0.013 ± 0.003 with respect to the primary. We rule out additional companions to TYC 8998-760-1 that are more massive than $12\, M_\mathrm{jup}$ and farther than 12 au away from the host. Future polarimetric and spectroscopic observations of this system with ground and space based observatories will facilitate testing of formation and evolution scenarios shaping the architecture of the circumstellar environment around this ‘young Sun’.
Major histocompatibility complex (MHC) gene products control the repertoire of T cell responses that an individual may create against pathogens and foreign tissues. This text will review the current ...understanding of MHC genetics in nonhuman primates, with a focus on Mauritian-origin cynomolgus macaques (Macaca fascicularis) and Indian-origin rhesus macaques (Macaca mulatta). These closely related macaque species provide important experimental models for studies of infectious disease pathogenesis, vaccine development, and transplantation research. Recent advances resulting from the application of several cost effective, high-throughput approaches, with deep sequencing technologies have revolutionized our ability to perform MHC genotyping of large macaque cohorts. Pyrosequencing of cDNA amplicons with a Roche/454 GS Junior instrument, provides excellent resolution of MHC class I allelic variants with semi-quantitative estimates of relative levels of transcript abundance. Introduction of the Illumina MiSeq platform significantly increased the sample throughput, since the sample loading workflow is considerably less labor intensive, and each instrument run yields approximately 100-fold more sequence data. Extension of these sequencing methods from cDNA to genomic DNA amplicons further streamlines the experimental workflow and opened opportunities for retrospective MHC genotyping of banked DNA samples. To facilitate the reporting of MHC genotypes, and comparisons between groups of macaques, this text also introduces an intuitive series of abbreviated rhesus MHC haplotype designations based on a major Mamu-A or Mamu-B transcript characteristic for ancestral allele combinations. The authors believe that the use of MHC-defined macaques promises to improve the reproducibility, and predictability of results from pre-clinical studies for translation to humans.
The eucrites and diogenites are meteorites that probably originate from asteroid 4-Vesta. The upper part of the crust of this body is certainly composed of eucrites which are basaltic or gabbroic ...rocks. Diogenites are ultramafic cumulates whose relationships with eucritic lithologies are unknown. Here, we show that the orthopyroxenes of some diogenites display very deep negative Eu anomalies (Eu/Eu∗ close to 0.1 or lower). The contamination of the parental magmas of diogenites by melts derived by partial melting of the eucritic crust can satisfactorily explain the range of the Eu anomalies displayed by diogenites. Thus, these anomalies are the first firm indication that parental melts of diogenites have intruded the eucritic crust, and consequently are younger than eucrites.
The eucritic meteorites are basaltic rocks that originate from the upper part of the crust of some small bodies as exemplified possibly by asteroid 4-Vesta. A few eucrites appear to have been ...modified by different degrees of a late stage alteration process that caused significant variations in mineralogy. Three distinct alteration stages are identified: (1) Fe-enrichment along the cracks that cross cut the pyroxene crystals (“Fe-metasomatism”); secondary olivine and minute amounts of troilite are found only occasionally in cracks at this stage; (2) deposits of Fe-rich olivine (Fa
64-86) and minor amounts of troilite are frequent inside the cracks; sporadic secondary Ca-rich plagioclase (An
97-98) is associated with the fayalitic olivine; (3) at this stage, the Fe-enrichment of the pyroxene is accompanied by a marked Al-depletion; moreover, secondary Ca-rich plagioclase is more frequent and partly fills some cracks or rims of the primary plagioclase crystals. The composition of the secondary phases on one hand, the lack of incompatible trace element enrichment in the metasomatized pyroxenes on the other hand, rule out a silicate melt as the metasomatic agent. Although no hydrous phase has been yet identified in the studied samples, aqueous fluids are
plausible candidates for explaining the deposits of ferroan olivine and anorthitic plagioclase inside the fractures of the studied unequilibrated eucrites.
Context. Binarity is a widespread phenomenon around solar-type stars, including the host stars of transiting extrasolar planets. Aims. We performed a detailed study of six transiting planetary ...systems with relatively bright stars close enough to affect observations of these systems. These contaminants were characterised in a companion work. Methods. We used theoretical spectra to propagate the observed K-band light ratios into the optical passbands used to observe these systems. Light curves were analysed whilst taking the contaminating light and its uncertainty into account. We present and applied a method to correct the velocity amplitudes of the host stars for the presence of contaminating light. Results. We determined the physical properties of six systems (WASP-20, WASP-70, WASP-8, WASP-76, WASP-2, and WASP-131) whilst accounting for contaminating light. In the case of WASP-20, the measured physical properties are very different for the three scenarios considered: ignoring binarity, planet transits brighter star, and planet transits fainter star. In the other five cases, our results are very similar to those obtained when neglecting contaminating light. We used our results to determine the mean correction factors to planet radius, ⟨XR⟩, mass, ⟨XM⟩, and density, ⟨Xρ⟩, caused by nearby objects. We find ⟨XR⟩ = 1.009 ± 0.045, which is smaller than literature values because we were able to reject the possibility that the planet orbits the fainter star in all but one case. We find ⟨XM⟩ = 1.031 ± 0.019, which is larger than ⟨XR⟩ because of the strength of the effect of contaminating light on the radial velocity measurements of the host star. We find ⟨Xρ⟩ = 0.995 ± 0.046: the small size of this correction is due to two effects: the corrections on planet radius and mass partially cancel; and some nearby stars are close enough to contaminate the light curves of the system but not radial velocities of the host star. These corrections can be applied to samples of transiting hot Jupiters to statistically remove biases due to light contamination. Conclusions. We conclude that binarity of planet host stars is important for the small number of transiting hot Jupiters with a very bright and close nearby star, but it has only a small effect on population-level studies of these objects.
— We report on the major and trace element abundances of 18 diogenites, and O‐isotopes for 3 of them. Our analyses extend significantly the diogenite compositional range, both in respect of Mg‐rich ...(e.g., Meteorite Hills MET 00425, MgO = 31.5 wt%) and Mg‐poor varieties (e.g., Dhofar 700, MgO = 23 wt%). The wide ranges of siderophile and chalcophile element abundances are well explained by the presence of inhomogeneously distributed sulfide or metal grains within the analyzed chips. The behavior of incompatible elements in diogenites is more complex, as exemplified by the diversity of their REE patterns. Apart from a few diogenite samples that contain minute amounts of phosphate, and whose incompatible element abundances are unlike the orthopyroxene ones, the range of incompatible element abundances, and particularly the range of Dy/Yb ratios in diogenites is best explained by the diversity of their parental melts. We estimate that the FeO/MgO ratios of the diogenite parental melts range from about 1.4 to 3.5 and therefore largely overlap the values obtained for non‐cumulate eucrites. Our results rule out the often accepted view that all the diogenites formed from parental melts more primitive than eucrites during the crystallization of a magma ocean. Instead, they point to a more complex history, and suggest that diogenites were derived from liquids produced by the remelting of cumulates formed from the magma ocean.
Context. In recent years, our understanding of giant planet formation progressed substantially. There have even been detections of a few young protoplanet candidates still embedded in the ...circumstellar disks of their host stars. The exact physics that describes the accretion of material from the circumstellar disk onto the suspected circumplanetary disk and eventually onto the young, forming planet is still an open question. Aims. We seek to detect and quantify observables related to accretion processes occurring locally in circumstellar disks, which could be attributed to young forming planets. We focus on objects known to host protoplanet candidates and/or disk structures thought to be the result of interactions with planets. Methods. We analyzed observations of six young stars (age 3.5–10 Myr) and their surrounding environments with the SPHERE/ZIMPOL instrument on the Very Large Telescope (VLT) in the Hα filter (656 nm) and a nearby continuum filter (644.9 nm). We applied several point spread function (PSF) subtraction techniques to reach the highest possible contrast near the primary star, specifically investigating regions where forming companions were claimed or have been suggested based on observed disk morphology. Results. We redetect the known accreting M-star companion HD142527 B with the highest published signal to noise to date in both Hα and the continuum. We derive new astrometry ( r=62.8−2.7+2.1 $r{\,=\,}62.8^{+2.1}_{-2.7}$ r = 62.8−2.7+2.1 mas and PA=(98.7±1.8)° $\mathrm{PA}{\,=\,}(98.7{\,\pm\,}1.8)^{\circ}$PA = (98.7 ± 1.8)° ) and photometry (ΔN_Ha = 6.3−0.3+0.2 $6.3^{+0.2}_{-0.3}$6.3−0.3+0.2 mag, ΔB_Ha = 6.7 ± 0.2 mag and ΔCnt_Ha = 7.3−0.2+0.3 $7.3^{+0.3}_{-0.2}$7.3−0.2+0.3 mag) for the companion in agreement with previous studies, and estimate its mass accretion rate (Ṁ ≈ 1−2 × 10−10 M⊙yr−1). A faint point-like source around HD135344 B (SAO206462) is also investigated, but a second deeper observation is required to reveal its nature. No other companions are detected. In the framework of our assumptions we estimate detection limits at the locations of companion candidates around HD100546, HD169142, and MWC 758 and calculate that processes involving Hα fluxes larger than ~ 8 × 10−14–10−15 erg s−1 cm−2 (Ṁ > 10−10−10−12 M⊙yr−1) can be excluded. Furthermore, flux upper limits of ~10−14−10−15 erg s−1 cm−2 (Ṁ < 10−11–10−12 M⊙yr−1) are estimated within the gaps identified in the disks surrounding HD135344 B and TW Hya. The derived luminosity limits exclude Hα signatures at levels similar to those previously detected for the accreting planet candidate LkCa15 b.
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