The Geometry and Ionization Structure of the Wind in the Eclipsing Nova-like Variables RW Tri and UX UMa

The UV spectra of nova-like variables are dominated by emission from the accretion disk, modified by scattering in a wind emanating from the disk. Here we model the spectra of RW Tri and UX UMa, the only two eclipsing nova-likes which have been observed with the Hubble Space Telescope in the far-ultraviolet, in an attempt to constrain the geometry and the ionization structure of their winds. Using our Monte Carlo radiative transfer code we computed spectra for simply-parameterized axisymmetric biconical outflow models and were able to find plausible models for both systems. These reproduce the primary UV resonance lines - N V, Si IV, and C IV - in the observed spectra in and out of eclipse. The distribution of these ions in the wind models is similar in both cases as is the extent of the primary scattering regions in which these lines are formed. The inferred mass loss rates are 6% to 8% of the mass accretion rates for the systems. We discuss the implication of our point models for our understanding of accretion disk winds in cataclysmic variables.Comment: 13 pages, 15 figures and 4 tables. Published in Ap

Spectral modeling of type II supernovae. I. Dilution factors

We present substantial extensions to the Monte Carlo radiative transfer code TARDIS to perform spectral synthesis for type II supernovae. By incorporating a non-LTE ionization and excitation treatment for hydrogen, a full account of free-free and bound-free processes, a self-consistent determination of the thermal state and by improving the handling of relativistic effects, the improved code version includes the necessary physics to perform spectral synthesis for type II supernovae to high precision as required for the reliable inference of supernova properties. We demonstrate the capabilities of the extended version of TARDIS by calculating synthetic spectra for the prototypical type II supernova SN1999em and by deriving a new and independent set of dilution factors for the expanding photosphere method. We have investigated in detail the dependence of the dilution factors on photospheric properties and, for the first time, on changes in metallicity. We also compare our results with two previously published sets of dilution factors by Eastman et al. (1996) and by Dessart & Hillier (2005), and discuss the potential sources of the discrepancies between studies.Comment: 16 pages, 12 figures, 2 tables, accepted for publication in A&

Early light curves for Type Ia supernova explosion models

Upcoming high-cadence transient survey programmes will produce a wealth of observational data for Type Ia supernovae. These data sets will contain numerous events detected very early in their evolution, shortly after explosion. Here, we present synthetic light curves, calculated with the radiation hydrodynamical approach Stella for a number of different explosion models, specifically focusing on these first few days after explosion. We show that overall the early light curve evolution is similar for most of the investigated models. Characteristic imprints are induced by radioactive material located close to the surface. However, these are very similar to the signatures expected from ejecta-CSM or ejecta-companion interaction. Apart from the pure deflagration explosion models, none of our synthetic light curves exhibit the commonly assumed power-law rise. We demonstrate that this can lead to substantial errors in the determination of the time of explosion. In summary, we illustrate with our calculations that even with very early data an identification of specific explosion scenarios is challenging, if only photometric observations are available.Comment: 15 pages, 14 figures, 3 tables, accepted for publication in MNRA

Self-consistent modelling of line-driven hot-star winds with Monte Carlo radiation hydrodynamics

Radiative pressure exerted by line interactions is a prominent driver of outflows in astrophysical systems, being at work in the outflows emerging from hot stars or from the accretion discs of cataclysmic variables, massive young stars and active galactic nuclei. In this work, a new radiation hydrodynamical approach to model line-driven hot-star winds is presented. By coupling a Monte Carlo radiative transfer scheme with a finite-volume fluid dynamical method, line-driven mass outflows may be modelled self-consistently, benefiting from the advantages of Monte Carlo techniques in treating multi-line effects, such as multiple scatterings, and in dealing with arbitrary multidimensional configurations. In this work, we introduce our approach in detail by highlighting the key numerical techniques and verifying their operation in a number of simplified applications, specifically in a series of self-consistent, one-dimensional, Sobolev-type, hot-star wind calculations. The utility and accuracy of our approach is demonstrated by comparing the obtained results with the predictions of various formulations of the so-called CAK theory and by confronting the calculations with modern sophisticated techniques of predicting the wind structure. Using these calculations, we also point out some useful diagnostic capabilities our approach provides. Finally we discuss some of the current limitations of our method, some possible extensions and potential future applications.Comment: 15 pages, 8 figures; accepted for publication in MNRA

A voz do usuário: métodos para processos participativos de projeto em arquitetura e urbanismo

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Arquitetura e Urbanismo, Florianópolis, 2016.É senso comum a premissa de que a arquitetura é comprometida com as necessidades das pessoas. Por esta razão, é necessário que o arquiteto conheça bem tais necessidades. A diversidade humana e os múltiplos fatores a serem considerados em um projeto de arquitetura e urbanismo, torna a atividade projetual bastante complexa, requerendo uma formação ampla, que inclui domínios artísticos, sociais e técnicos, visando a solução de problemas multifacetados. Paradoxalmente, este amplo espectro de conhecimento muitas vezes distancia os arquitetos das pessoas ditas não técnicas, pois cria uma lente própria pela qual os projetistas vêem o mundo e se torna obstáculo para a identificação das reais demandas dos usuários. Esta pesquisa visa diminuir o hiato entre os projetos produzidos pelos arquitetos e as pessoas que se apropriarão dos lugares construídos por meio destes projetos. Para tal, sondou vários temas, dos quais pode-se destacar: processo de projeto, projeto centrado no usuário, participação em projetos de arquitetura e urbanismo e métodos participativos de projeto. O processo desta investigação qualitativa foi iterativo e lançou mão de uma abordagem híbrida, com princípios da pesquisa exploratória e da Design Science, onde a construção do conhecimento partiu dos temas estudados, da experiência de profissionais e da reflexão integrativa. Assim, por meio de revisões bibliográficas, entrevistas com arquitetos projetistas e/ou professores de projeto e pelo estudo da própria ação projetual, foram aclarados os meandros existentes em processos projetuais de arquitetura e urbanismo. Foi possível compreender as interações projetista-usuário, as situações e os estágios projetuais e definir as variadas modalidades de projeto centrado no usuário. Ao analisar 10 pesquisas sobre o tema, identificou-se os problemas recorrentes em projetos participativos de arquitetura e urbanismo ocorridos no Brasil. Com subsídios teórico-práticos, delimitou-se o fenômeno participação no âmbito desta pesquisa. Por uma revisão bibliográfica específica associada às experiências projetuais dos arquitetos entrevistados e da pesquisadora, foram investigados 137 métodos participativos de projeto. Destes, foram indicados os mais apropriados para a ideação projetual em arquitetura e urbanismo. Além disso, os estudos de caso em processos participativos de projeto conduzidos pela pesquisadora, permitiram o teste de 15 métodos, em diferentes situações projetuais. Com este lastro teórico e experiencial, visando apoiar a escolha de meios que confiram voz aos usuários na ideação da arquitetura e do urbanismo, foram elaborados os critérios e realizadas a seleção e a classificação de 40 métodos participativos. Não se pretendeu oferecer novas verdades, mas visibilidadeao fato de que é possível e desejável, em qualquer situação projetual, a parceria entre o conhecimento do arquiteto e o saber vivencial dos usuários. A expectativa deste trabalho repousa no potencial que o estudo e a classificação propostos têm no apoio à escolha e à aplicação de métodos participativos de projeto, favorecendo uma produção arquitetônica mais fiel ao atendimento das necessidades e expectativas das pessoas.Abstract : It is common sense the premise that architecture is committed to the needs of people. For this reason, it is necessary for the architect to know these needs very well. The human diversity and the multiple factors to be considered in a project of architecture and urbanism, makes the project activity quite complex, requiring a broad formation that includes artistic, social and technical domains, aiming at the solution of multifaceted problems. Paradoxically, this broad spectrum of knowledge often distances architects from non-technical people, because it creates a lens of its own by which designers see the world and becomes an obstacle to identifying the real demands of users. This research aims to reduce the gap between the projects produced by the architects and the people who will own the places built through these projects. In order to do so, it has probed several themes, such as: project process, user centered project, participation in architecture and urbanism projects, and participatory project methods. The process of this qualitative research was interactive and it adopted a hybrid approach, with principles of exploratory research and Design Science, where the construction of knowledge started from the themes studied, the experience of professionals and the integrative reflection. Thus, by means of bibliographical revisions, interviews with architects and / or design teachers and by the study of the own design action, the meanders existing in architectural and urbanistic design processes were clarified. It was possible to understand the user-designer interactions, the situations and the design stages and to define the various modalities of user-centered design. When analyzing ten researches on the theme, we identified the recurrent problems in participative projects of architecture and urbanism occurred in Brazil. With theoretical-practical subsidies, the participation phenomenon within the scope of this research was delimited. Through a specific bibliographic review associated with the project experiences of the interviewed architects and the researcher, 137 participatory design methods were investigated. Of these, the most appropriate ones were indicated for the projective ideation in architecture and urbanism. In addition, the case studies in participatory design processes conducted by the researcher allowed the testing of 15 methods, in different design situations. With this theoretical and experiential support, in order to support the choice of means that give voice to users in the ideation ofarchitecture and urbanism, the criteria and the selection and classification of 40 participative methods were elaborated. It was not intended to offer new truths, but visibility to the fact that it is possible and desirable, in any projectual situation, the partnership between the architect's knowledge and the users' experiential knowledge. The expectation of this work rests on the potential that the study and the classification proposed have in support to the choice and the application of participative methods of project, favoring an architectural production more faithful to the attendance of the needs and expectations of the people

Loss of Protein Stability and Function Caused by P228L Variation in NADPH-Cytochrome P450 Reductase Linked to Lower Testosterone Levels.

Cytochrome P450 oxidoreductase (POR) is the redox partner of steroid and drug-metabolising cytochromes P450 located in the endoplasmic reticulum. Mutations in POR cause a broad range of metabolic disorders. The POR variant rs17853284 (P228L), identified by genome sequencing, has been linked to lower testosterone levels and reduced P450 activities. We expressed the POR wild type and the P228L variant in bacteria, purified the proteins, and performed protein stability and catalytic functional studies. Variant P228L affected the stability of the protein as evidenced by lower unfolding temperatures and higher sensitivity to urea denaturation. A significant decline in the rate of electron transfer to cytochrome c and thiazolyl blue tetrazolium (MTT) was observed with POR P228L, while activities of CYP3A4 were reduced by 25% and activities of CYP3A5 and CYP2C9 were reduced by more than 40% compared with WT POR. The 17,20 lyase activity of CYP17A1, responsible for the production of the main androgen precursor dehydroepiandrosterone, was reduced to 27% of WT in the presence of the P228L variant of POR. Based on in silico and in vitro studies, we predict that the change of proline to leucine may change the rigidity of the protein, causing conformational changes in POR, leading to altered electron transfer to redox partners. A single amino acid change can affect protein stability and cause a severe reduction in POR activity. Molecular characterisation of individual POR mutations is crucial for a better understanding of the impact on different redox partners of POR

The supernova impostor PSN J09132750+7627410 and its progenitor

We report the results of our follow-up campaign of the supernova impostor PSN J09132750+7627410, based on optical data covering $\sim250\,\rm{d}$. From the beginning, the transient shows prominent narrow Balmer lines with P-Cygni profiles, with a blue-shifted absorption component becoming more prominent with time. Along the $\sim3\,\rm{months}$ of the spectroscopic monitoring, broad components are never detected in the hydrogen lines, suggesting that these features are produced in slowly expanding material. The transient reaches an absolute magnitude $M_r=-13.60\pm0.19\,\rm{mag}$ at maximum, a typical luminosity for supernova impostors. Amateur astronomers provided $\sim4\,\rm{years}$ of archival observations of the host galaxy, NGC 2748. The detection of the quiescent progenitor star in archival images obtained with the Hubble Space Telescope suggests it to be an $18-20$\msun white-yellow supergiant.Comment: 7 pages, 4 figures, supplemental material available in the source file. Accepted for publication on Astrophysical Journal Letter

Strongly lensed SNe Ia in the era of LSST: observing cadence for lens discoveries and time-delay measurements

The upcoming Large Synoptic Survey Telescope (LSST) will detect many strongly lensed Type Ia supernovae (LSNe Ia) for time-delay cosmography. This will provide an independent and direct way for measuring the Hubble constant $H_0$, which is necessary to address the current $4.4 \sigma$ tension in $H_0$ between the local distance ladder and the early Universe measurements. We present a detailed analysis of different observing strategies for the LSST, and quantify their impact on time-delay measurement between multiple images of LSNe Ia. For this, we produced microlensed mock-LSST light curves for which we estimated the time delay between different images. We find that using only LSST data for time-delay cosmography is not ideal. Instead, we advocate using LSST as a discovery machine for LSNe Ia, enabling time delay measurements from follow-up observations from other instruments in order to increase the number of systems by a factor of 2 to 16 depending on the observing strategy. Furthermore, we find that LSST observing strategies, which provide a good sampling frequency (the mean inter-night gap is around two days) and high cumulative season length (ten seasons with a season length of around 170 days per season), are favored. Rolling cadences subdivide the survey and focus on different parts in different years; these observing strategies trade the number of seasons for better sampling frequency. In our investigation, this leads to half the number of systems in comparison to the best observing strategy. Therefore rolling cadences are disfavored because the gain from the increased sampling frequency cannot compensate for the shortened cumulative season length. We anticipate that the sample of lensed SNe Ia from our preferred LSST cadence strategies with rapid follow-up observations would yield an independent percent-level constraint on $H_0$.Comment: 25 pages, 22 figures; accepted for publication in A&

Wind-accretion disks in wide binaries, second generation protoplanetary disks and accretion onto white dwarfs

Mass transfer from an evolved donor star to its binary companion is a standard feature of stellar evolution in binaries. In wide binaries, the companion star captures some of the mass ejected in a wind by the primary star. The captured material forms an accretion disk. Here, we study the evolution of wind-accretion disks, using a numerical approach which allows us to follow the long term evolution. For a broad range of initial conditions, we derive the radial density and temperature profiles of the disk. In most cases, wind-accretion leads to long-lived stable disks over the lifetime of the AGB donor star. The disks have masses of a few times 10^{-5}-10^{-3} M_sun, with surface density and temperature profiles that follow broken power-laws. The total mass in the disk scales approximately linearly with the viscosity parameter used. Roughly 50% to 80% of the mass falling into the disk accretes onto the central star; the rest flows out through the outer edge of the disk into the stellar wind of the primary. For systems with large accretion rates, the secondary accretes as much as 0.1 M_sun. When the secondary is a white dwarf, accretion naturally leads to nova and supernova eruptions. For all types of secondary star, the surface density and temperature profiles of massive disks resemble structures observed in protoplanetary disks, suggesting that coordinated observational programs might improve our understanding of uncertain disk physics.Comment: ApJ, in press. Some discussion on thermal instabilities, and different viscosities adde

Massive stars exploding in a He-rich circumstellar medium - VIII. PSN J07285387+3349106, a highly reddened supernova Ibn

We present spectroscopic and photometric observations for the Type Ibn supernova (SN) dubbed PSN J07285387+3349106. Using data provided by amateur astronomers, we monitored the photometric rise of the SN to maximum light, occurred on 2015 February 18.8 UT (JD(max,V) = 2457072.0 +- 0.8). PSN J07285387+3349106 exploded in the inner region of an infrared luminous galaxy, and is the most reddened SN Ibn discovered so far. We apply multiple methods to derive the total reddening to the SN, and determine a total colour excess E(B-V)(tot) = 0.99 +- 0.48 mag. Accounting for the reddening correction, which is affected by a large uncertainty, we estimate a peak absolute magnitude of M(V) = -20.30 +- 1.50. The spectra are dominated by continuum emission at early phases, and He I lines with narrow P-Cygni profiles are detected. We also identify weak Fe III and N II features. All these lines show an absorption component which is blue-shifted by about 900-1000 km/s. The spectra also show relatively broad He I line wings with low contrast, which extend to above 3000 km/s. From about 2 weeks past maximum, broad lines of O I, Mg II and the Ca II near-infrared triplet are identified. The composition and the expansion velocity of the circumstellar material, and the presence of He I and alpha-elements in the SN ejecta indicate that PSN J07285387+3349106 was produced by the core-collapse of a stripped-envelope star. We suggest that the precursor was WNE-type Wolf-Rayet star in its dense, He-rich circumstellar cocoon.Comment: 12 pages, 7 figures, 2 tables. Accepted for publication in MNRA