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- Grady, C., et al.
(författare)
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The outer disks of Herbig stars from the UV to NIR
- 2015
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Ingår i: Astrophysics and Space Science. - : Springer Science and Business Media LLC. - 0004-640X .- 1572-946X. ; 355:2, s. 253-266
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Forskningsöversikt (refereegranskat)abstract
- Spatially-resolved imaging of Herbig stars and related objects began with HST, but intensified with commissioning of high-contrast imagers on 8-m class telescopes. The bulk of the data taken from the ground have been polarized intensity imagery at H-band, with the majority of the sources observed as part of the Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS) survey. Sufficiently many systems have been imaged that we discuss disk properties in scattered, polarized light in terms of groups defined by the IR spectral energy distribution. We find novel phenomena in many of the disks, including spiral density waves, and discuss the disks in terms of clearing mechanisms. Some of the disks have sufficient data to map the dust and gas components, including water ice dissociation products.
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- Follette, Katherine B., et al.
(författare)
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SEEDS ADAPTIVE OPTICS IMAGING OF THE ASYMMETRIC TRANSITION DISK OPH IRS 48 IN SCATTERED LIGHT
- 2015
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 798:2
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Tidskriftsartikel (refereegranskat)abstract
- 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 similar to 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 mu m IRTF SpeX spectra of this object, which allow us to constrain the spectral class to A0 +/- 1 and measure a low mass accretion rate of 10(-8.5) M-circle dot yr(-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.
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- Lomax, Jamie R., et al.
(författare)
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CONSTRAINING THE MOVEMENT OF THE SPIRAL FEATURES AND THE LOCATIONS OF PLANETARY BODIES WITHIN THE AB AUR SYSTEM
- 2016
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 828:1
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Tidskriftsartikel (refereegranskat)abstract
- We present a new analysis of multi-epoch, H-band, scattered light images of the AB Aur system. We use a Monte Carlo radiative transfer code to simultaneously model the system's spectral energy distribution (SED) and H-band polarized intensity (PI) imagery. We find that a disk-dominated model, as opposed to one that is envelope-dominated, can plausibly reproduce AB Aur's SED and near-IR imagery. This is consistent with previous modeling attempts presented in the literature and supports the idea that at least a subset of AB Aur's spirals originate within the disk. In light of this, we also analyzed the movement of spiral structures in multi-epoch H-band total light and PI imagery of the disk. We detect no significant rotation or change in spatial location of the spiral structures in these data, which span a 5.8-year baseline. If such structures are caused by disk-planet interactions, the lack of observed rotation constrains the location of the orbit of planetary perturbers to be >47 au.
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| 7. |
- Rich, Evan A., et al.
(författare)
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The fundamental stellar parameters of FGK stars in the SEEDS survey Norman, OK 73071, USA
- 2017
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 472:2, s. 1736-1752
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Tidskriftsartikel (refereegranskat)abstract
- Large exoplanet surveys have successfully detected thousands of exoplanets to-date. Utilizing these detections and non-detections to constrain our understanding of the formation and evolution of planetary systems also requires a detailed understanding of the basic properties of their host stars. We have determined the basic stellar properties of F, K and G stars in the Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS) survey from Echelle spectra taken at the Apache Point Observatory's 3.5m telescope. Using ROBOSPECT to extract line equivalent widths and TemperatureGravity microtrubulentVelocity ITerations to calculate the fundamental parameters, we have computed T-eff, log(g), v(t), [Fe/H], chromospheric activity and the age for our sample. Our methodology was calibrated against previously published results for a portion of our sample. The distribution of [Fe/H] in our sample is consistent with that typical of the Solar neighbourhood. Additionally, we find the ages of most of our sample are < 500 Myr, but note that we cannot determine robust ages from significantly older stars via chromospheric activity age indicators. The futuremeta-analysis of the frequency ofwide stellar and sub-stellar companions imaged via the SEEDS survey will utilize our results to constrain the occurrence of detected comoving companions with the properties of their host stars.
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- Yamamoto, Suguru, et al.
(författare)
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Mineral and bone disorder management in hemodialysis patients : Comparing PTH control practices in Japan with Europe and North America: The Dialysis Outcomes and Practice Patterns Study (DOPPS) 11 Medical and Health Sciences 1103 Clinical Sciences
- 2018
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Ingår i: BMC Nephrology. - : Springer Science and Business Media LLC. - 1471-2369. ; 19:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: High-circulating level of parathyroid hormone (PTH) is associated with elevated mortality in dialysis patients. The Japanese Society for Dialysis Therapy guideline suggests a lower PTH target than other international guidelines; thus, PTH control may differ in Japan compared with other regions, and be associated with mortality. Methods: We analyzed data from hemodialysis patients with ≥3 measurements of PTH during the first 9 months after enrollment in the Dialysis Outcomes and Practice Patterns Study (DOPPS) phases 4-5 (2009-2015). PTH control was assessed by the mean, slope, and mean squared error (MSE) of all PTH measurements over the 9-month run-in period. Distribution of each PTH control was assessed by regions (Europe/Australia/New Zealand [Eur/ANZ], Japan and North America) and dialysis vintage. Mortality rates were compared across PTH control categories using Cox regression models. Results: Mean PTH was lower in Japan than in other regions across dialysis vintage categories. In patients with dialysis vintage < 90 days, PTH level was more likely to decline > 5% per month in Japan (48% of patients) versus Eur/ANZ (35%) and North America (35%). In patients with dialysis vintage > 1 year, Japanese patients maintained steady PTH, while patients in Eur/ANZ and North America were more likely to experience a PTH increase. Mean PTH was associated with mortality in the overall samples (highest mortality rate for PTH > 600 pg/mL, hazard ratio, 1.35; 95% confidence interval, 1.20 to 1.52 vs PTH 200-399 pg/mL), and the association was obvious in the prevalent patients (hazard ratio, 1.44; 95% confidence interval, 1.26 to 1.65). PTH slope and MSE did not show significant association with mortality in the overall sample as well as in subjects stratified both by region and dialysis vintage. Conclusion: PTH control in hemodialysis patients, as measured by keeping a stable PTH level over 9 months, was observed in Japan contrasted with other regions. High PTH mean, but not increased PTH slope and MSE, was associated with mortality especially in prevalent patients.
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