Dust Rings as a Footprint of Planet Formation in a Protoplanetary Disk

Relatively large dust grains (referred to as pebbles) accumulate at the outer edge of the gap induced by a planet in a protoplanetary disk, and a ring structure with a high dust-to-gas ratio can be formed. Such a ring has been thought to be located immediately outside the planetary orbit. We examined the evolution of the dust ring formed by a migrating planet, by performing two-fluid (gas and dust) hydrodynamic simulations. We found that the initial dust ring does not follow the migrating planet and remains at the initial location of the planet in cases with a low viscosity of α ∼ 10−4. The initial ring is gradually deformed by viscous diffusion, and a new ring is formed in the vicinity of the migrating planet, which develops from the trapping of the dust grains leaking from the initial ring. During this phase, two rings coexist outside the planetary orbit. This phase can continue over ∼1 Myr for a planet migrating from 100 au. After the initial ring disappears, only the later ring remains. This change in the ring morphology can provide clues as to when and where the planet was formed, and is the footprint of the planet. We also carried out simulations with a planet growing in mass. These simulations show more complex asymmetric structures in the dust rings. The observed asymmetric structures in the protoplanetary disks may be related to a migrating and growing planet.

Early science with SPIRou: near-infrared radial velocity and spectropolarimetry of the planet-hosting star HD 189733

SPIRou is the newest spectropolarimeter and high-precision velocimeter that has recently been installed at the Canada-France-Hawaii Telescope on Maunakea, Hawaii. It operates in the near-infrared and simultaneously covers the 0.98–2.35 μm domain at high spectral resolution. SPIRou is optimized for exoplanet search and characterization with the radial-velocity technique, and for polarization measurements in stellar lines and subsequent magnetic field studies. The host of the transiting hot Jupiter HD 189733 b has been observed during early science runs. We present the first near-infrared spectropolarimetric observations of the planet-hosting star as well as the stellar radial velocities as measured by SPIRou throughout the planetary orbit and two transit sequences. The planetary orbit and Rossiter-McLaughlin anomaly are both investigated and modeled. The orbital parameters and obliquity are all compatible with the values found in the optical. The obtained radial-velocity precision is compatible with about twice the photon-noise estimates for a K2 star under these conditions. The additional scatter around the orbit, of about 8 m s−1, agrees with previous results that showed that the activity-induced scatter is the dominant factor. We analyzed the polarimetric signal, Zeeman broadening, and chromospheric activity tracers such as the 1083nm HeI and the 1282nm Paβ lines to investigate stellar activity. First estimates of the average unsigned magnetic flux from the Zeeman broadening of the FeI lines give a magnetic flux of 290 ± 58 G, and the large-scale longitudinal field shows typical values of a few Gauss. These observations illustrate the potential of SPIRou for exoplanet characterization and magnetic and stellar activity studies.

Tuning in to the radio environment of HD189733b

The hot Jupiter HD189733b is expected to be a source of strong radio emission, due to its close proximity to its magnetically active host star. Here, we model the stellar wind of its host star, based on reconstructed surface stellar magnetic field maps. We use the local stellar wind properties at the planetary orbit obtained from our models to compute the expected radio emission from the planet. Our findings show that the planet emits with a peak flux density within the detection capabilities of LOFAR. However, due to absorption by the stellar wind itself, this emission may be attenuated significantly. We show that the best time to observe the system is when the planet is near primary transit of the host star, as the attenuation from the stellar wind is lowest in this region.

Semiotics Of Shape Of Block Notation As Icon Of Planetary Orbit

Block notation has a specific shape; however, its existence and the function of its shape are not recognized and are made to be intangible by its function as a symbol of tapping sound. In general, the basic shape of the block notation looks like an ellipse and is similar to the planetary orbit. Therefore, this present study focuses on the ellipse-shaped block notation as the icon of the planetary orbit.The phenomenological qualitative method was employed to interpret the meaning of the basic shape of the block notation as the icon of planetary orbit. The data were collected through guided interview and library research. The data were analyzed using the semiotic process, meaning that in the first phase the text was analyzed based on the shape structure and in the second phase the text was heuristically analyzed.The result of the study shows that the ellipse-shaped block notation is the planetary orbit whose function changes from the manifest function into the latent one, resulting from the function as the tapping sound value.Keywords: form, notation, icon, orbit, planet