The Collapse of the Wien Tail in the Coldest Brown Dwarf? Hubble Space Telescope Near-Infrared Photometry of WISE J085510.83-071442.5

We present Hubble Space Telescope (HST) near-infrared photometry of the coldest known brown dwarf, WISE J085510.83$-$071442.5 (WISE 0855$-$0714). WISE 0855$-$0714 was observed with the Wide Field Camera 3 (WFC3) aboard HST using the F105W, F125W, and F160W filters, which approximate the $Y$, $J$, and $H$ near-infrared bands. WISE 0855$-$0714 is undetected at F105W with a corresponding 2$\sigma$ magnitude limit of $\sim$26.9. We marginally detect WISE 0855$-$0714 in the F125W images (S/N $\sim$4), with a measured magnitude of 26.41 $\pm$ 0.27, more than a magnitude fainter than the $J-$band magnitude reported by Faherty and coworkers. WISE J0855$-$0714 is clearly detected in the F160W band, with a magnitude of 23.90 $\pm$ 0.02, the first secure detection of WISE 0855$-$0714 in the near-infrared. Based on these data, we find that WISE 0855$-$0714 has extremely red F105W$-$F125W and F125W$-$F160W colors relative to other known Y dwarfs. We find that when compared to the models of Saumon et al. and Morley et al., the F105W$-$F125W and F125W$-$F160W colors of WISE 0855$-$0714 cannot be accounted for simultaneously. These colors likely indicate that we are seeing the collapse of flux on the Wien tail for this extremely cold object.Comment: Accepted for publication in ApJ Letter

Sustainable Alternative Materials in Unbound Granular Layers of Pavement Structures

In Part 1 of this thesis, reclaimed cement concrete (commonly referred to as recycled concrete aggregate or RCA) and reclaimed asphalt pavement (RAP) are investigated as potential alternative construction materials for Granular B Type II subbase fill. Ontario Provincial Standard Specification (OPSS) 1010 currently allows the common use of processed reclaimed construction materials in a variety of road base, subbase and asphaltic concrete layers, with the notable exception of Granular B Type II, which at present may only include 100% crushed bedrock, talus, iron blast furnace slag or nickel slag. As more restrictions are placed on zoning and approvals for new natural aggregate extraction sites in Ontario, there is a need to better understand the performance of materials such as RCA and RAP as economically beneficial potential aggregate sources for granular base and subbase fill layers. An experimental program was created to assess and analyze the performance characteristics of a series of different subbase test mixtures incorporating RCA and/or RAP, either pure or blended with crushed bedrock, and the impact of the inclusion of these materials when compared to a conventional 100% crushed bedrock test mix meeting OPSS 1010 requirements for Granular B Type II. The performance characteristics to be assessed were field compactibility, gradations before and after field compaction, physical properties, standard and modified Proctor tests, California Bearing Ratio (CBR), permeability, resilient moduli and lightweight deflectometer (LWD) resilient moduli. Field testing programs conducted at Quarry 1 in Ottawa, Ontario and Quarry 2 in Burlington, Ontario indicate that the subbase test mixtures meeting OPSS Granular B Type II gradation requirements and incorporating different proportions of crushed rock, RCA and/or RAP exhibit similar field rolling compactibility relative to 100% crushed rock. Grain size analysis testing showed some aggregate breakdown in multiple test mixes, with only minimal increases in material passing the 75 µm sieve, which is crucial to preserving permeability and drainage characteristics. Tests using a lightweight deflectometer (LWD) were subject to substantial variability but indicated that mixes using elevated levels of RCA (50% and 100%) can potentially have lower in-situ moduli compared to the other blends tested. Laboratory tests indicate that high replacement levels of RCA can be used in subbase materials as a substitute for 100% crushed rock while maintaining good water permeability characteristics and similar or higher resilient moduli in blends incorporating RCA and/or RAP. CBR testing results were similar across all test blends incorporating crushed rock and RCA, but also indicated that the inclusion of 30% RAP can potentially reduce the bearing capacity of the granular material by approximately 30-40% in comparison to all other blends which do not contain RAP. Based on the overall results of this study, RCA and RAP appear to be capable of successfully substituting for natural aggregates in Granular B Type II in a range of compositional proportions. It is recommended that test sections should be completed on highway contracts with subbase mixture blends incorporating RCA and/or RAP in order to verify their performance in pavement structures in the field. In Part 2 of this thesis, foam glass lightweight aggregates (LWA) are investigated as a potential pavement engineering design alternative in order to mitigate roadway loading impacts upon underlying subgrade soils while promoting the sustainable and economical use of recycled waste glass. Foamyna Canada Inc. supplied the Centre for Pavement and Transportation Technology (CPATT) with two foam glass lightweight aggregate materials, designated in this thesis as LWA-A and LWA-B. Physical properties testing was carried out by CPATT, including grain size analysis, crushed particle content, flat and elongated particle content, Micro-Deval abrasion resistance, cyclic freezing-and-thawing resistance and resilient modulus testing procedures. These procedures were conducted in order to evaluate the LWA materials against locally applicable standards, namely Ontario Provincial Standard Specification document OPSS 1010 as currently used by the Ministry of Transportation of Ontario (MTO). The laboratory testing detailed in Part 2 indicates that both LWA-A and LWA-B have a very consistent and repeatable gradation with a high percentage of coarse aggregates. Both foam glass materials have very high crushed particle contents and very low flat and elongated particle contents. Micro-Deval abrasion resistance, freeze-and-thaw resistance and resilient moduli were also excellent for both materials, while relative density testing indicated LWA material specific gravity values which were substantially lower than that of water. However, it was found that the gradations of these two tested materials do not satisfy the existing requirements of OPSS 1010, which were developed for natural aggregates and, as currently constituted, may not be appropriately adapted to artificial lightweight aggregates. The coarse nature of the LWA materials would be highly beneficial to ensure the stability of the granular layers and prevent upward capillary water movement into other layers of the pavement structure. Pavement design calculations were carried out using the AASHTO 1993 empirical design procedure and found that utilizing foam glass LWA as a lightweight subgrade replacement fill material can result in substantially leaner pavement structures as compared to the use of conventional expanded polystyrene (EPS) geofoam blocks as an artificial subgrade. A life-cycle cost analysis (LCCA) procedure carried out on these pavement designs showed that the use of foam glass LWA as a lightweight fill material underlying pavement can result in overall cost savings of over 30 percent relative to pavement structures which are underlain by EPS geofoam. Overall, the two tested LWA materials showed excellent physical and mechanical characteristics, and would be suitable for use in pavement structures as innovative lightweight and environmentally friendly alternatives to natural aggregate materials

MAT-752: FIELD TESTING AND EVALUATION OF RECLAIMED MATERIALS AS AGGREGATE FOR OPSS GRANULAR B TYPE II

In urbanized regions of Ontario, the road construction industry faces a number of challenges due to the growing scarcity of locally-sourced natural aggregate materials and increased restrictions on the approval and development of new aggregate extraction sites. In an effort to maintain sustainable and economical sources of construction aggregates, companies are increasingly seeking to supplement or replace natural aggregates with available artificial materials such as crushed reclaimed concrete aggregate (RCA), and reclaimed asphalt pavement (RAP). Currently, Ontario Provincial Standard Specification (OPSS) 1010 permits the use of processed reclaimed construction materials in a variety of road base, subbase and asphaltic concrete layers, with the exception of Granular B Type II, which is a higher-performance subbase specification that solely allows primary materials produced from crushed bedrock. Consequently, there is a need to better understand the performance of reclaimed materials as alternative aggregates in Granular B Type II. This paper focuses on a field testing program carried out at two job sites in Ontario. This testing program assessed five different aggregate blends conforming to Granular B Type II gradation requirements which vary in composition from 100% natural crushed rock to 100% processed RCA. Test pads were constructed from each blended material to assess field compactibility using a nuclear density gauge and to determine the in-situ moduli of the compacted materials using a portable lightweight deflectometer (LWD). The field testing results indicate that RCA and RAP can be successfully utilized as aggregate materials in Granular B Type II subbase applications

HAZMAT VI: The Evolution of Extreme Ultraviolet Radiation Emitted from Early M Star

Quantifying the evolution of stellar extreme ultraviolet (EUV, 100 -- 1000 $\overset{\circ}{A}$) emission is critical for assessing the evolution of planetary atmospheres and the habitability of M dwarf systems. Previous studies from the HAbitable Zones and M dwarf Activity across Time (HAZMAT) program showed the far- and near-UV (FUV, NUV) emission from M stars at various stages of a stellar lifetime through photometric measurements from the Galaxy Evolution Explorer (GALEX). The results revealed increased levels of short-wavelength emission that remain elevated for hundreds of millions of years. The trend for EUV flux as a function of age could not be determined empirically because absorption by the interstellar medium prevents access to the EUV wavelengths for the vast majority of stars. In this paper, we model the evolution of EUV flux from early M stars to address this observational gap. We present synthetic spectra spanning EUV to infrared wavelengths of 0.4 $\pm$ 0.05 M$_{\odot}$ stars at five distinct ages between 10 and 5000 Myr, computed with the PHOENIX atmosphere code and guided by the GALEX photometry. We model a range of EUV fluxes spanning two orders of magnitude, consistent with the observed spread in X-ray, FUV, and NUV flux at each epoch. Our results show that the stellar EUV emission from young M stars is 100 times stronger than field age M stars, and decreases as t$^{-1}$ after remaining constant for a few hundred million years. This decline stems from changes in the chromospheric temperature structure, which steadily shifts outward with time. Our models reconstruct the full spectrally and temporally resolved history of an M star's UV radiation, including the unobservable EUV radiation, which drives planetary atmospheric escape, directly impacting a planet's potential for habitability.Comment: 23 pages, 15 figures, accepted to Ap

WISEA J114724.10-204021.3: A Free-Floating Planetary Mass Member of the TW Hya Association

We present WISEA J114724.10−204021.3, a young, low-mass, high probability member of the TW Hya association. WISEA J114724.10−204021.3 was discovered based on its red AllWISE color (W1−W2 = 0.63 mag) and extremely red 2MASS J−K_S color (> 2.64 mag), the latter of which is confirmed with near-infrared photometry from the VISTA Hemisphere Survey (J−K_S = 2.57±0.03). Follow-up near-infrared spectroscopy shows a spectral type of L7 ± 1 as well as several spectroscopic indicators of youth. These include a peaked H-band shape and a steeper K-band slope, traits typically attributed to low surface gravity. The sky position, proper motion, and distance estimates of WISEA J114724.10−204021.3 are all consistent with membership in the ∼10 Myr old TW Hya association. Using the age of the TW Hya association and evolutionary models, we estimate the mass of WISEA J114724.10−204021.3 to be 5−13 M_(Jup), making it one of the youngest and lowest mass free-floating objects yet discovered in the Solar neighborhood