We present high-contrast observations of 68 young stellar objects (YSOs) that have been explored as part of the Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS) survey on the Subaru ...telescope. Our targets are very young (<10 Myr) stars, which often harbor protoplanetary disks where planets may be forming. We achieve a typical contrast of ∼10−4-10−5.5 at an angular distance of 1″ from the central star, corresponding to typical mass sensitivities (assuming hot-start evolutionary models) of ∼10 MJ at 70 au and ∼6 MJ at 140 au. We detected a new stellar companion to HIP 79462 and confirmed the substellar objects GQ Lup b and ROXs 42B b. An additional six companion candidates await follow-up observations to check for common proper motion. Our SEEDS YSO observations probe the population of planets and brown dwarfs at the very youngest ages; these may be compared to the results of surveys targeting somewhat older stars. Our sample and the associated observational results will help enable detailed statistical analyses of giant planet formation.
We present H-band polarized scattered light imagery and JHK high-contrast spectroscopy of the protoplanetary disk around HD 163296 observed with the High-Contrast Coronographic Imager for Adaptive ...Optics (HiCIAO) and Subaru Coronagraphic Extreme Adaptive Optics (SCExAO)/Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) instruments at Subaru Observatory. The polarimetric imagery resolve a broken ring structure surrounding HD 163296 that peaks at a distance along the major axis of 0 65 (66 au) and extends out to 0 98 (100 au) along the major axis. Our 2011 H-band data exhibit clear axisymmetry, with the NW and SE side of the disk exhibiting similar intensities. Our data are clearly different from 2016 epoch H-band observations of the Very Large Telescope (VLT)/Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE), which found a strong 2.7× asymmetry between the NW and SE side of the disk. Collectively, these results indicate the presence of time-variable, non-azimuthally symmetric illumination of the outer disk. While our SCExAO/CHARIS data are sensitive enough to recover the planet candidate identified from NIRC2 in the thermal infrared (IR), we fail to detect an object with JHK brightness nominally consistent with this object. This suggests that the candidate is either fainter in JHK bands than model predictions, possibly due to extinction from the disk or atmospheric dust/clouds, or that it is an artifact of the data set/data processing, such as a residual speckle or partially subtracted disk feature. Assuming standard hot-start evolutionary models and a system age of 5 Myr, we set new, direct mass limits for the inner (outer) Atacama Large Millimeter/submillimeter Array (ALMA)-predicted protoplanet candidate along the major (minor) disk axis of of 1.5 (2) MJ.
Abstract
Bottom-up emission inventories can provide valuable information for understanding emission status and are needed as input datasets to drive chemical transport models. However, this type of ...inventory has the disadvantage of taking several years to be compiled because it relies on a statistical dataset. Top-down approaches use satellite data as a constraint and overcome this disadvantage. We have developed an immediate inversion system to estimate anthropogenic NO
x
emissions with NO
2
column density constrained by satellite observations. The proposed method allows quick emission updates and considers model and observation errors by applying linear unbiased optimum estimations. We used this inversion system to estimate the variation of anthropogenic NO
x
emissions from China and India from 2005 to 2016. On the one hand, NO
x
emissions from China increased, reaching a peak in 2011 with 29.5 Tg yr
−1
, and subsequently decreased to 25.2 Tg yr
−1
in 2016. On the other hand, NO
x
emissions from India showed a continuous increase from 2005 to 2016, reaching 13.9 Tg yr
−1
in 2016. These opposing trends from 2011 to 2016 were −0.83 and +0.76 Tg yr
−1
over China and India, respectively, and correspond to strictly regulated and unregulated future scenarios. Assuming these trends continue after 2016, we expect NO
x
emissions from China and India will be similar in 2023, with India becoming the world’s largest NO
x
emissions source in 2024.
We analyze the kinematic histories of stars within 30 pc of the Sun, for which three-dimensional spatial coordinates and three-dimensional velocity vectors are available. From this sample, we extract ...members of stellar kinematic groups (SKGs) in the following manner. First, we consider in the three-dimensional velocity space centered on the local standard of rest, a sphere with a radius of 8 km s--1 centered on the mean velocity vector of a particular SKG. Around each SKG velocity center, we have found a significant excess of stars compared to background field stars. For each candidate, in the three-dimensional spatial coordinate space, its trajectory is traced back in time by the age of the relevant SKG to obtain the estimated distance from the SKG center at the time of the SKG's birth by the epicyclic approximation and harmonic vertical motion. It often happens that a star is a candidate member of multiple SKGs. Then we rank the candidacy to multiple SKGs based on the smallness of distance separations. In this manner, we have kinematically selected 238 candidates. We further impose at least one of the following qualitative criteria for being a member: spectral type A or B, variability, or EUV and X-ray emission. We have finally selected 137 candidate members of SKGs out of a sample of 966 stars.
We present the first resolved near-infrared imagery of the transition disk Oph IRS 48 (WLY 2-48), which was recently observed with ALMA to have a strongly asymmetric submillimeter flux distribution. ...H-band polarized intensity images show a ~60 AU radius scattered light cavity with two pronounced arcs of emission, one from northeast to southeast and one smaller, fainter, and more distant arc in the northwest. K-band scattered light imagery reveals a similar morphology, but with a clear third arc along the southwestern rim of the disk cavity. This arc meets the northwestern arc at nearly a right angle, revealing the presence of a spiral arm or local surface brightness deficit in the disk, and explaining the east-west brightness asymmetry in the H-band data. We also present 0.8-5.4 mum IRTF SpeX spectra of this object, which allow us to constrain the spectral class to A0 + or - 1 and measure a low mass accretion rate of 10 super(-8.5) Mmiddot in circle yr super(-1), both consistent with previous estimates. We investigate a variety of reddening laws in order to fit the multiwavelength spectral energy distribution of Oph IRS 48 and find a best fit consistent with a younger, higher luminosity star than previous estimates.
Bottom-up emission inventories can provide valuable information for understanding emission status and are needed as input datasets to drive chemical transport models. However, this type of inventory ...has the disadvantage of taking several years to be compiled because it relies on a statistical dataset. Top-down approaches use satellite data as a constraint and overcome this disadvantage. We have developed an immediate inversion system to estimate anthropogenic NOx emissions with NO2 column density constrained by satellite observations. The proposed method allows quick emission updates and considers model and observation errors by applying linear unbiased optimum estimations. We used this inversion system to estimate the variation of anthropogenic NOx emissions from China and India from 2005 to 2016. On the one hand, NOx emissions from China increased, reaching a peak in 2011 with 29.5 Tg yr−1, and subsequently decreased to 25.2 Tg yr−1 in 2016. On the other hand, NOx emissions from India showed a continuous increase from 2005 to 2016, reaching 13.9 Tg yr−1 in 2016. These opposing trends from 2011 to 2016 were −0.83 and +0.76 Tg yr−1 over China and India, respectively, and correspond to strictly regulated and unregulated future scenarios. Assuming these trends continue after 2016, we expect NOx emissions from China and India will be similar in 2023, with India becoming the world's largest NOx emissions source in 2024.
We report the first independent, second epoch (re-)detection of a directly imaged protoplanet candidate. Using L' high-contrast imaging of HD 100546 taken with the Near-Infrared Coronagraph and ...Imager on Gemini South, we recover "HD 100546 b" with a position and brightness consistent with the original Very Large Telescope/NAos-COnica detection from Quanz et al., although data obtained after 2013 will be required to decisively demonstrate common proper motion. HD 100546 b may be spatially resolved, up to asymptotically = 12-13 AU in diameter, and is embedded in a finger of thermal IR-bright, polarized emission extending inward to at least 0."3. Standard hot-start models imply a mass of asymptotically =15 M sub(J). However, if HD 100546 b is newly formed or made visible by a circumplanetary disk, both of which are plausible, its mass is significantly lower (e.g., 1-7 M sub(J)). Additionally, we discover a thermal IR-bright disk feature, possibly a spiral density wave, at roughly the same angular separation as HD 100546 b but 90degrees away. Our interpretation of this feature as a spiral arm is not decisive, but modeling analyses using spiral density wave theory implies a wave launching point exterior to asymptotically =0."45 embedded within the visible disk structure: plausibly evidence for a second, hitherto unseen, wide-separation planet. With one confirmed protoplanet candidate and evidence for one to two others, HD 100546 is an important evolutionary precursor to intermediate-mass stars with multiple super-Jovian planets at moderate/wide separations like HR 8799.
The total OH reactivity of the secondary products formed from the OH-initiated oxidation of toluene, p-xylene, and 1,3,5-trimethylbenzene was directly measured in the presence of NOx using a ...laboratory environmental chamber in order to investigate unidentified reactive species in urban air. The total OH reactivity was also calculated from the concentrations of the reactants and products, which were monitored by Fourier-transform infrared spectroscopy. The difference between the measured and calculated OH reactivity, the so-called missing OH reactivity, comprised 58–81% of the total OH reactivity of the secondary products. These results suggest that the secondary products formed from the oxidation of aromatic hydrocarbons may be important candidates in accounting for the missing OH reactivity in the analyses of urban environments. The Master Chemical Mechanism (MCM) calculations were performed to predict the temporal variation in the total OH reactivity for the oxidation of aromatic hydrocarbons. The MCM calculations successfully reproduced the observed total OH reactivity when the particle and semi-volatile product concentrations were negligibly low. The MCM calculations were used to identify the missing secondary products. The results suggest that important components of the missing OH reactivity are unsaturated multifunctional products such as unsaturated dicarbonyls, unsaturated epoxydicarbonyls, and furanones.
Display omitted
•The total OH reactivity was measured for oxidation of aromatic hydrocarbons.•The “missing” OH reactivity comprised 58–81% of the product OH reactivity.•The “missing” OH reactivity results from unsaturated multifunctional products.
We present near-infrared coronagraphic imaging polarimetry of RY Tau. The scattered light in the circumstellar environment was imaged at the H band at a high resolution (~(0".05) for the first time, ...using Subaru/HiCIAO. The observed polarized intensity (PI) distribution shows a butterfly-like distribution of bright emission with an angular scale similar to the disk observed at millimeter wavelengths. This distribution is offset toward the blueshifted jet, indicating the presence of a geometrically thick disk or a remnant envelope, and therefore the earliest stage of the Class II evolutionary phase. We perform comparisons between the observed PI distribution and disk models with (1) full radiative transfer code, using the spectral energy distribution (SED) to constrain the disk parameters; and (2) monochromatic simulations of scattered light which explore a wide range of parameters space to constrain the disk and dust parameters. We show that these models cannot consistently explain the observed PI distribution, SED, and the viewing angle inferred by millimeter interferometry. We suggest that the scattered light in the near-infrared is associated with an optically thin and geometrically thick layer above the disk surface, with the surface responsible for the infrared SED. Half of the scattered light and thermal radiation in this layer illuminates the disk surface, and this process may significantly affect the thermal structure of the disk.
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