bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas Sensitivity of In0.3Ga0.7As Surface QDs Coupled to Multilayer Buried QDs
Authors: Wang Guodong , Liu Zengguang , Wang Junjun , Yang Yingli , Liu Xiaolian , Zhang Xinran , Zhang Liwei , Cao Guohua 
Published: January 2020

AbstractA detailed analysis of the electrical response of In0.3Ga0.7As surface quantum dots (SQDs) coupled to 5-layer buried quantum dots (BQDs) is carried out as a function of ethanol and acetone concentration while temperature-dependent photoluminescence (PL) spectra are also analyzed. The coupling structure is grown by solid source molecular beam epitaxy. Carrier transport from BQDs to SQDs is confirmed by the temperature-dependent PL spectra. The importance of the surface states for the sensing application is once more highlighted. The results show that not only the exposure to the target gas but also the illumination affect the electrical response of the coupling sample strongly. In the ethanol atmosphere and under the illumination, the sheet resistance of the coupling structure decays by 50% while it remains nearly constant for the reference structure with only the 5-layer BQDs but not the SQDs. The strong dependence of the electrical response on the gas concentration makes SQDs very suitable for the development of integrated micrometer-sized gas sensor devices.
Epidemiology of TORCH Infections and Understanding the Serology in Their Diagnosis
Authors: Batra Priyam , Batra Megha , Singh Sarman 
Published: January 2020

AbstractTORCH, as coined by Nahmias et al. consists of Toxoplasmosis, other infections (includes, syphilis, HIV, Hepatitis viruses, varicella virus and Parvovirus B19), Rubella, Cytomegalovirus (CMV) and Herpes simplex virus. These infections are transmitted prenatally, perinatally, and postnatally through transplacental passage, contact with blood and vaginal secretions or from exposure to breast milk for CMV, HIV and HSV and infection generally manifests at birth, in infancy or in later years of life. The disease burden is maximum in low to middle-income countries. As treatment and prevention strategies are available for most of these infections, early recognition including prenatal serological screening are important. But routine full screening of ‘TORCH panel” is not recommended in low risk asymptomatic pregnant women. It is indicated in pregnancies with congenital infections, fetal hydrops, fetal brain lesions, unexplained IUGR, in pregnant women with non-vesicular rash or other signs and symptoms suggestive of systemic infections or in women with a history of contact with a person with such illness. The following article highlights the importance of serological tests for the diagnosis of TORCH infections.
Centrality and shortest path length measures for the functional analysis of urban drainage networks
Authors: Reyes-Silva Julian D. , Zischg Jonatan , Klinkhamer Christopher , Rao P. Suresh C. , Sitzenfrei Robert , Krebs Peter 
Published: January 2020

AbstractThe objective of this research is to evaluate whether complex dynamics of urban drainage networks (UDNs) can be expressed in terms of their structure, i.e. topological characteristics. The present study focuses on the application of topological measures for describing the transport and collection functions of UDNs, using eight subnetworks of the Dresden sewer network as study cases. All UDNs are considered as weighted directed graphs, where edge weights correspond to structural and hydraulic pipe characteristics which affect flow. Transport functions are evaluated in terms of travel time distributions (TTDs), under the hypothesis that frequency distributions of Single Destination Shortest Paths (SDSP) of nodes to the outlet had similar shapes than TTDs. Assessment of this hypothesis is done based on two-sample Kolmogorov-Smirnov tests and comparisons of statistical moments. Collection analysis, i.e. determination of flow paths, is done based on two approaches: (1) using Edge Betweenness Centrality (EBC), and (2) based on the number of SDSP going through an edge connecting a node to the outlet, referred as Paths. Hydrodynamic simulation results are used to validate the outcomes of graph analysis with actual flow behaviors. Results indicate that given an appropriate edge weighting factor, in this case Residence Time, SDSP has the potential to be used as an indicator for flow transport in UDNs. Moreover, both EBC and Paths values were highly correlated to average flows. The first approach, however, proved to be inadequate for estimating flows near the outlet but appropriate for identifying different paths in meshed systems, while the second approach lead to better results in branched networks. Further studies regarding the influence of UDNs layout are needed.
Using Gaia to measure the atmospheric dynamics in AGB stars
Authors: Chiavassa Andrea , Freytag Bernd , Schultheis Mathias 
Published: January 2020

AbstractWe use 3D radiative-hydrodynamics simulations of convection with CO5BOLD and the post-processing radiative transfer code Optim3D to compute intensity maps in the Gaia G band [325–1030 nm]. We calculate the intensity-weighted mean of all emitting points tiling the visible stellar surface (i.e., the photo-center) and evaluate its motion as a function of time. We show that the convection-related variability accounts for a substantial part to the Gaia DR2 parallax error of our sample of semiregular variables. Finally, we denote that Gaia parallax variations could be exploited quantitatively to extract stellar parameters using appropriate RHD simulations corresponding to the observed star.
The carbon star R Sculptoris sheds its skin
Authors: Wittkowski Markus 
Published: January 2020

AbstractWe describe near-IR H-band VLTI-PIONIER aperture synthesis images of the carbon AGB star R Sculptoris with an angular resolution of 2.5 mas. The data show a stellar disc of diameter ∼ 9 mas exhibiting a complex substructure including one dominant bright spot with a peak intensity of 40% to 60% above the average intensity. We interpret the complex structure as caused by giant convection cells, resulting in large-scale shock fronts, and their effects on clumpy molecule and dust formation seen against the photosphere at distances of 2–3 stellar radii. Moreover, we derive fundamental parameters of R Scl, which match evolutionary tracks of initial mass 1.5 ± 0.5 M⊙. Our visibility data are best fit by a dynamic model without a wind, which may point to problems with current wind models at low mass-loss rates.
Tomography of the red supergiant star μ Cep
Authors: Kravchenko K. , Chiavassa A. , Van Eck S. , Jorissen A. , Merle T. , Freytag B. 
Published: January 2020

AbstractA tomographic method, aiming at probing velocity fields at depth in stellar atmospheres, is applied to the red supergiant star μ Cep and to snapshots of 3D radiative-hydrodynamics simulation in order to constrain atmospheric motions and relate them to photometric variability.
Magnetic fields of AGB and post-AGB stars
Authors: Vlemmings Wouter 
Published: January 2020

AbstractThere is ample evidence for the presence of strong magnetic fields in the envelopes of (post-)Asymptotic Giant Branch (AGB) stars as well as supergiant stars. The origin and role of these fields are still unclear. This paper updates the current status of magnetic field observations around AGB and post-AGB stars, and describes their possible role during these stages of evolution. The discovery of magnetically aligned dust around a supergiant star is also highlighted. In our search for the origin of the magnetic fields, recent observations show the signatures of possible magnetic activity and rotation, indicating that the magnetic fields might be intrinsic to the AGB stars.
MAGRITTE: a new multidimensional accelerated general-purpose radiative transfer code
Authors: De Ceuster Frederik , Yates Jeremy , Boyle Peter , Decin Leen , Hetherington James 
Published: January 2020

AbstractMagritte is a new deterministic radiative transfer code. It is a ray-tracing code that computes the radiation field by solving the radiative transfer equation along a fixed set of rays for each grid cell. Its ray-tracing algorithm is independent of the type of input grid and thus can handle smoothed-particle hydrodynamics (SPH) particles, structured as well as unstructured grids. The radiative transfer solver is highly parallelized and optimized to have well scaling performance on several computer architectures. Magritte also contains separate dedicated modules for chemistry and thermal balance. These enable it to self-consistently model the interdependence between the radiation field and the local thermal and chemical states. The source code for Magritte will be made publically available at github.com/Magritte-code.
Central Stars of Planetary Nebulae in Galactic Open Clusters: Providing additional data for the White Dwarf Initial-to-Final-Mass Relation
Authors: Fragkou Vasiliki , Parker Quentin A. , Zijlstra Albert , Shaw Richard , Lykou Foteini 
Published: January 2020

AbstractAccurate (< 10%) distances of Galactic star clusters allow a precise estimation of the physical parameters of any physically associated Planetary Nebula (PN) and also that of its central star (CSPN) and its progenitor. The progenitor’s mass can be related to the PN’s chemical characteristics and, furthermore, provides additional data for the widely used white dwarf (WD) initial-to-final mass relation (IFMR) that is crucial for tracing the development of both carbon and nitrogen in entire galaxies. To date, there is only one PN (PHR1315- 6555) confirmed to be physically associated with a Galactic open cluster (ESO 96 -SC04) that has a turn-off mass ∼2Mʘ. Our deep HST photometry was used for the search of the CSPN of this currently unique PN. In this work, we present our results.
The dust production rate of carbon-rich stars in the Magellanic Clouds
Authors: Nanni Ambra , Groenewegen Martin A. T. , Aringer Bernhard , Marigo Paola , Rubele Stefano , Bressan Alessandro 
Published: January 2020

AbstractWe present our new investigation aimed to estimate the mass-loss and dust production rates of carbon-rich stars (C-stars) in the Magellanic Clouds (MCs). We compute dust growth and radiative transfer in circumstellar envelopes of C-stars for a grid of stellar parameters and for selected optical constants that simultaneously reproduce the main colour–colour diagrams in the infrared. We employ these grids of spectra to fit the spectral energy distribution of C-stars in the MCs. We find that our estimates can be significantly different from the other ones in the literature.
A Masing BAaDE’s Window
Authors: Sjouwerman Lorant O. , Pihlström Ylva M. , Trapp Adam C. , Stroh Michael C. , Quiroga-Nuñez Luis Henry , Lewis Megan O. , Michael Rich R. , Morris Mark R. , van Langevelde Huib Jan , Claussen Mark J ,   the BAaDE collaboration
Published: January 2020

AbstractWe report on the Bulge Asymmetries and Dynamic Evolution (BAaDE) survey which has observed 19 000 MSX color selected red giant stars for SiO maser emission at 43 GHz with the VLA and is in the process of observing 9 000 of these stars with ALMA at 86 GHz in the Southern sky. Our setup covers the main maser transitions, as well as those of isotopologues and selected lines of carbon-bearing species. Observations of this set of lines allow a far-reaching catalog of line-of-sight velocities in the dust-obscured regions where optical surveys cannot reach. Our preliminary detection rate is close to 70%, predicting a wealth of new information on the distribution of metal rich stars, their kinematics as function of location in the Galaxy, as well as the occurrence of lines and line ratios between the different transitions in combination with the spectral energy distribution from about 1 to 100 μm. Similar to the OH/IR stars, a clear kinematic signature between disk and bulge stars can be seen. Furthermore, the SiO J = →10 (v=3) line plays a prominent role in the derived maser properties.
MIKE High Resolution Spectroscopy of Raman-scattered O VI and C II Lines in the Symbiotic Nova RR Telescopii
Authors: Heo Jeong-Eun , Lee Hee-Won , Angeloni Rodolfo , Palma Tali , Di Mille Francesco 
Published: January 2020

AbstractWe present a high-resolution optical spectrum of the symbiotic nova RR Tel obtained with MIKE at Magellan-Clay telescope. RR Tel is a wide binary system of a hot white dwarf and a Mira with an orbital period of a few decades, where the white dwarf is accreting through gravitational capture of some fraction of material shed by the Mira. We find broad emission features at 6825, 7082, 7023, and 7053 Å, which are formed through Raman scattering of far-UV O VI ⋋⋋ 1032 and 1038 Å, C II ⋋⋋ 1036 and 1037 Å with atomic hydrogen. Raman O VI features exhibit clear double-peak profiles indicative of an accretion flow with a characteristic speed ∼ 30 km s−1, whereas the Raman C II features have a single Gaussian profile. We perform a profile analysis of the Raman O VI by assuming that O VI emission traces the accretion flow around the white dwarf with a fiducial scale of 1 AU. A comparison of the restored fluxes of C II ⋋⋋ 1036 and 1037 from Raman C II features with the observed C II ⋋ 1335 multiplet is consistent with the distance of RR Tel ∼ 2.6 kpc based on interstellar extinction of C II.
Rotating and magnetic stellar models of intermediate-mass stars up to the AGB
Authors: Mendes Luiz T. S. , Landin Natália R. , Ventura Paolo 
Published: January 2020

AbstractAiming at investigating the roles of rotation and magnetic fields on AGB stars, the rotating version of the ATON stellar evolution code is being extended in order to account for intermediate--mass stars and their later evolutionary stages. Here we report some preliminary results on the effects of rotation and of a large-scale magnetic field on the structure and evolution of 3 and 5 M⊙ stellar models from the pre-main sequence up to the AGB.
Calibrating TP-AGB stellar models and chemical yields through resolved stellar populations in the Small Magellanic Cloud
Authors: Pastorelli Giada , Marigo Paola , Girardi Léo ,   the STARKEY project team
Published: January 2020

AbstractMost of the physical processes driving the TP-AGB evolution are not yet fully understood and they need to be modelled with parameterised descriptions. We present the results of the on-going calibration of the TP-AGB phase based on a complete sample of AGB stars in the Small Magellanic Cloud (SAGE-SMC survey). We computed large grids of TP-AGB models with several combinations of third dredge-up and mass-loss prescriptions with the COLIBRI code. The SMC AGB population is modelled with the population synthesis code TRILEGAL according to the space-resolved star formation history derived with the deep photometry from the VISTA survey of the Magellanic Clouds. We put quantitative constraints on the efficiencies of the third dredge-up and mass loss by requiring the models to reproduce the star counts and the luminosity functions of the observed Oxygen-, Carbon-rich and extreme-AGB stars and we investigate the impact of the best-fitting prescriptions on the chemical yields.
Imaging the dust and the gas around Mira using ALMA and SPHERE/ZIMPOL
Authors: Khouri Theo , Vlemmings Wouter H. T. , Olofsson Hans , Ginski Christian , De Beck Elvire , Maercker Matthias , Ramstedt Sofia 
Published: January 2020

AbstractThe mass-loss mechanism of asymptotic giant branch stars has long been thought to rely on two processes: stellar pulsations and dust formation. The details of the mass-loss mechanism have remained elusive, however, because of the overall complexity of the dust formation process in the very dynamical pulsation-enhanced atmosphere. Recently, our understanding of AGB stars and the associated mass loss has evolved significantly, thanks both to new instruments which allow sensitive and high-angular-resolution observations and the development of models for the convective AGB envelopes and the dust formation process. ALMA and SPHERE/ZIMPOL on the VLT have been very important instruments in driving this advance in the last few years by providing high-angular resolution images in the sub-mm and visible wavelengths, respectively. I will present observations obtained using these instruments at the same epoch (2.5 weeks apart) of the AGB star Mira that resolve even the stellar disk. The ALMA data reveals the distribution and dynamics of the gas around the star, while the polarised light imaged using SPHERE shows the distribution of the dust grains expected to drive the outflows. Moreover, the observations show a central source surrounded by asymmetric distributions of gas and dust, with complementary structures seen in the two components. We model the observed CO v = 1, J = 3−2 line to determine the density, temperature and velocity of gas close to the star. This model is then used to estimate the abundance of AlO. Our results show that only a very small fraction of aluminium (≲0.1%) is locked in AlO molecules. We also calculate models to fit the observed polarised light based on the gas densities we find. The low level of visible-light polarisation detected using ZIMPOL implies that, at the time of the observations, aluminium atoms are either not efficiently depleted into dust or the aluminium-oxide grains are relatively small (≲0.02μm).
Separation of gas and dust in the winds of AGB stars
Authors: Mattsson Lars , Sandin Christer , Ventura Paolo 
Published: January 2020

AbstractWe present first results from a project aiming at a better understanding of how gas and dust interact in dust-driven winds from Asymptotic Giant Branch (AGB) stars. We are at the final stage of developing a new parallelised radiation-hydrodynamics (RHD) code for AGB-wind modelling including a new generalised implementation of drift. We also discuss first results from high-resolution box simulations of forced turbulence intended to give quantitative “3D corrections” to dust-driven winds from AGB stars. It is argued that modelling of dust-driven winds of AGB stars is a problem that may need to be treated in a less holistic way, where some parts of the problem are treated separately in detailed simulations and are parameterised back into a less detailed (1D spherically symmetric) model describing the entire picture.
Spectroscopic binaries among AGB stars from HERMES/Mercator: the case of V Hya
Authors: Jorissen Alain , Van Eck Sophie , Merle Thibault , Van Winckel Hans 
Published: January 2020

AbstractWe report on our search for spectroscopic binaries among a sample of AGB stars. Observations were carried out in the framework of the monitoring of radial velocities of (candidate) binary stars performed at the Mercator 1.2m telescope, using the HERMES spectrograph. We found evidence for duplicity in UV Cam, TU Tau, BL Ori, VZ Per, T Dra, and V Hya.
Near-Infrared Stellar Populations in the metal-poor, Dwarf irregular Galaxies Sextans A and Leo A
Authors: Jones Olivia C. , Maclay Matthew T. , Boyer Martha L. , Meixner Margaret , McDonald Iain 
Published: January 2020

AbstractWe present JHK observations of the metal-poor $$(\left[ {{\rm{Fe}}/{\rm{H}}} \right] < - 1.40)$$ dwarf-irregular galaxies, Leo A and Sextans A, obtained with the WIYN High-resolution Infrared Camera. Their near-IR stellar populations are characterized by using a combination of color-magnitude diagrams and by identifying long-period variable (LPV) stars. We detected red giant and asymptotic giant branch (AGB) stars, consistent with membership of the galaxy’s intermediate-age populations (2-8 Gyr old). We identify 32 dusty evolved stars in Leo A and 101 dusty stars in Sextans A, confirming that metal-poor stars can form substantial amounts of dust. We also find tentative evidence for oxygen-rich dust formation at low metallicity, contradicting previous models that suggest oxygen-rich dust production is inhibited in metal-poor environments. The majority of this dust is produced by a few very dusty evolved stars.
AGB stars and the cosmic dust cycle
Authors: Zhukovska Svitlana 
Published: January 2020

AbstractTheoretical and observational studies of dust condensed in outflows of AGB stars have substantially advanced the understanding of dust mixture from individual stars. This detailed information incorporated in models of the lifecycle of interstellar grains provides a flexible tool to study the contribution of AGB stars to the galactic dust budget. The role of these stars in dust production depends on the morphological type and age of galaxy. While AGB stars are sub-dominant dust sources in evolved systems as the Milky Way, the observed relation between the dust-to-gas ratio and metallicity suggests that the dust input in young dwarf galaxies with 7≲12+log(O/H)≲8 can be dominated by the AGB stars. In application to post-starburst and early-type galaxies, the models for stardust evolution in combination with modern infrared observations give insights in the origin of their high dust content and its implications for their evolutionary scenarios.
SWAG: Distribution and Kinematics of an Obscured AGB Population toward the Galactic Center
Authors: Ott Jürgen , Meier David S. , Ginsburg Adam , Yusef-Zadeh Farhad , Krieger Nico , Jäschke Cornelia 
Published: January 2020

AbstractOutflows from AGB stars enrich the Galactic environment with metals and inject mechanical energy into the ISM. Radio spectroscopy can recover both properties through observations of molecular lines. We present results from SWAG: “Survey of Water and Ammonia in the Galactic Center”. The survey covers the entire Central Molecular Zone (CMZ), the inner 3.35° × 0.9° (∼480 × 130 pc) of the Milky Way that contains 5 × 107 M⊙ of molecular gas. Although our survey primarily targets the CMZ, we observe across the entire sightline through the Milky Way. AGB stars are revealed by their signature of double peaked 22 GHz water maser lines. They are distinguished by their spectral signatures and their luminosities, which reach up to 10−7 L⊙. Higher luminosities are usually associated with Young Stellar Objects located in CMZ star forming regions. We detect a population of ∼600 new water masers that can likely be associated with AGB outflows.
Circumstellar molecular maser emission of AGB and post-AGB stars
Authors: Rudnitskij Georgij , Ashimbaeva Nuriya , Colom Pierre , Lekht Evgeny , Pashchenko Mikhail , Tolmachev Alexander 
Published: January 2020

AbstractResults of long-term studies of circumstellar molecular maser emission of late-type giant and supergiant variable stars are reported. In the 1.35-cm H2O line, the peak flux density correlates with the optical brightness lagging behind it by 0.3–0.4 P (P is the stellar period). “Superperiods” of 10 to 15 P are visible in several stars, demonstrated as high maxima in the visible light curve and associated flares in the H2O maser line. In the 18-cm OH lines, full polarization of the maser emission has been measured. Variable Zeeman patterns suggesting a changing magnetic field of a few milligauss have been detected.
Abundance Estimates in Carbon Star Envelopes
Authors: Massalkhi S. , Agúndez M. , Cernicharo J. 
Published: January 2020

AbstractThe synthesis of dust grains mostly takes place in the circumstellar envelopes (CSEs) of asymptotic giant branch (AGB) stars. What are the precursor seeds of condensation nuclei and how do these particles evolve toward the micrometer sized grains that populate the interstellar medium? These are key questions of the NANOCOSMOS project. In this study, we carried out an observational study to constrain what the main gas-phase precursors of dust in C-rich AGB stars are.