bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morally Permissible Risk Imposition and Liability to Defensive Harm
Authors: Burri Susanne 
Published: January 2020

AbstractThis paper examines whether an agent becomes liable to defensive harm by engaging in a morally permissible but foreseeably risk-imposing activity that subsequently threatens objectively unjustified harm. It first clarifies the notion of a foreseeably risk-imposing activity by proposing that an activity should count as foreseeably risk-imposing if an agent may morally permissibly perform it only if she abides by certain duties of care. Those who argue that engaging in such an activity can render an agent liable to defensive harm ground this liability in the luck egalitarian thought that we may justly hold individuals responsible for the consequences of their voluntary choices. Against this, I argue that a luck egalitarian commitment to holding people responsible cannot, by itself, ground liability to defensive harm. It can help ground such liability only against the backdrop of a distributively just society, and only if further considerations speak morally in favour of attaching certain well-defined costs to individuals’ risk-imposing choices. I conclude by suggesting that if an account of liability applies robustly across distributively just and unjust contexts alike, then what grounds an agent’s liability is plausibly not her responsibility for threatening objectively unjustified harm, but her culpability for doing so.
The role of shocks in the determination of empirical abundances for type-I PNe
Authors: Costa Roberto D. D. , Lago Paulo J. A. 
Published: January 2020

AbstractWe investigate, in the light of new diagnostic diagrams, the role of shocks in the ionization profile of type-I planetary nebulae, and their relation to the empirical derivation of chemical abundances. We apply our technique to two well-known type-I objects: NGC 2440 and NGC 6302. Our results indicate that shocks play a very important role in the spectra of both nebulae and, since the presence of shocks reinforces the flux of low ionization lines, this artificial reinforcement can lead to incorrect chemical abundances, when they are derived through Ionization Correction Factors, at least for type-I PNe.
The composition of Barium stars and the s-process in AGB stars
Authors: Cseh Borbála , Lugaro Maria , D’Orazi Valentina , de Castro Denise B. , Pereira Claudio B. , Karakas Amanda I. , Molnár László , Plachy Emese , Szabó Róbert , Pignatari Marco , Cristallo Sergio 
Published: January 2020

AbstractUsing abundances from the available largest, homogeneous sample of high resolution Barium (Ba) star spectra we calculated the ratios of different hs-like to ls-like elemental ratios and compared to different AGB nucleosynthesis models. The Ba star data show an incontestable increase of the hs-type/ls-type element ratio (for example, [Ce/Y]) with decreasing metallicity. This trend in the Ba star observations is predicted by low mass, non-rotating AGB models where 13C is the main neutron source and is in agreement with Kepler asteroseismology observations.
Circumstellar dust, IR spectroscopy, and mineralogy
Authors: Suh Kyung-Won 
Published: January 2020

AbstractWe review the mineralogy of circumstellar dust grains around AGB stars as investigated through infrared spectroscopic studies. The expanding envelopes of AGB stars are chemically fresh because of the strong binding force of CO molecules. O-rich dust grains (silicates and oxides) form in O-rich envelopes and C-rich dust grains (amorphous carbon and SiC) form in C-rich envelopes. Amorphous silicate grains can be crystallized by annealing processes in various environments of AGB stars. We also discuss dust mineralogy for objects that have undergone chemical transition processes.
Probing stellar evolution with S stars and Gaia
Authors: Shetye S. , Van Eck S. , Jorissen A. , Van Winckel H. , Siess L. , Goriely S. 
Published: January 2020

AbstractS-type stars are late-type giants enhanced with s-process elements originating either from nucleosynthesis during the Asymptotic Giant Branch (AGB) or from a pollution by a binary companion. The former are called intrinsic S stars, and the latter extrinsic S stars. The intrinsic S stars are on the AGB and have undergone third dredge-up events. The atmospheric parameters of S stars are more numerous than those of M-type giants (C/O ratio and s-process abundances affect the thermal structure and spectral synthesis), and hence they are more difficult to derive. These atmospheric parameters are also entangled within each other. Nevertheless, high-resolution spectroscopic data of S stars combined with the Gaia Data Release 2 (GDR2) parallaxes and with the MARCS model atmospheres for S-type stars were used to derive effective temperatures, surface gravities, and luminosities. These parameters not only allow to locate the intrinsic and extrinsic S stars in the Hertzsprung-Russell (HR) diagram but also allow the accurate abundance analysis of the s-process elements.
AGB star atmospheres modeling as feedback to stellar evolutionary and galaxy models
Authors: Rau Gioia , Wittkowski M. , Chiavassa A. , Carpenter K. , Nielsen K. , Airapetian V. S. 
Published: January 2020

AbstractThe chemical enrichment of the Universe is considerably affected by the contribution of cool evolved stars. We studied the O-rich star R Peg and the C-rich star V Oph, using respectively the VLTI/GRAVITY and VLTI/MIDI instruments. We interpret the data using grids of 1-D and 3-D dynamic model atmospheres.
The role of asymptotic giant branch stars in the chemical evolution of the Galaxy
Authors: Tautvaišienė G. , Viscasillas Vázquez C. , Bagdonas V. , Smiljanic R. , Drazdauskas A. , Mikolaitis Š. , Minkevičiėūtėė R. , Stonkutė E. 
Published: January 2020

AbstractAsymptotic giant branch stars play an important role in enriching galaxies by s-process elements. Recent studies have shown that their role in producing s-process elements in the Galactic disc was underestimated and should be reconsidered. Based on high-resolution spectra we have determined abundances of neutron-capture elements in a sample of 310 stars located in the field and open clusters and investigated elemental enrichment patterns according to their age and mean galactocentric distances.
WD+AGB star systems as the progenitors of type Ia supernovae
Authors: Wang Bo 
Published: January 2020

AbstractWD+AGB star systems have been suggested as an alternative way for producing type Ia supernovae (SNe Ia), known as the core-degenerate (CD) scenario. In the CD scenario, SNe Ia are produced at the final phase during the evolution of common-envelope through a merger between a carbon-oxygen (CO) WD and the CO core of an AGB secondary. However, the rates of SNe Ia from this scenario are still uncertain. In this work, I carried out a detailed investigation on the CD scenario based on a binary population synthesis approach. I found that the Galactic rates of SNe Ia from this scenario are not more than 20% of total SNe Ia due to more careful treatment of mass transfer, and that their delay times are in the range of ∼90 − 2500 Myr, mainly contributing to the observed SNe Ia with short and intermediate delay times.
The onset of mass loss in AGB stars
Authors: McDonald Iain 
Published: January 2020

AbstractThe factors controlling strong mass loss from evolved stars remain elusive, frustrating efforts to parameterise mass loss in models of evolved stars. We herein describe evidence we have collected to show that the mass-loss rate of stars is controlled by stellar pulsations, and that we are close to providing improved prescriptions for mass-loss rates from many kinds of evolved stars.
The Impact of Dust/Gas Ratios on Chromospheric Activity in Red Giant and Supergiant Stars
Authors: Carpenter Kenneth G. , Rau Gioia 
Published: January 2020

AbstractStencel et al. (1986) analyzed IUE spectra of a modest set of cool stars and found that they continue to produce chromospheres even in the presence of high dust levels in their outer atmospheres. This reversed the previous results of Jennings (1973) and Jennings & Dyck (1972). We describe an on-going extension of these studies to a sample of stars representing a broader range in dust/gas ratios, using archival IUE and archival and new HST data on both RGB and AGB stars. Surface fluxes in emission lines will be analyzed to assess the chromospheric activity and obscuration by dust in each star, as those fluxes will follow a different pattern for reduced activity (temperature/density dependent) vs. dust obscuration (wavelength dependent). Wind characteristics will be measured by modeling of wind-reversed chromospheric emission lines.
Signs of rotating equatorial density enhancements around SRb pulsators
Authors: Homan W. , Decin L. , Richards A. , Kervella P. 
Published: January 2020

AbstractWe observed the circumstellar environments (CSEs) of the semiregular AGB stars L2 Puppis, R Doradus and EP Aquarii with ALMA. (1) The molecular emission in the L2 Pup nebula reveals an edge-on rotating disk. (2) PV diagrams of the 28SiO emission in the inner CSE of R Dor expose a pattern pointing to an inclined rotating disk. (3) The CO emission in the CSE of EP Aqr reveals a nearly face-on equatorial density enhancement (EDE). The inner EDE strongly resembles theoretical wind-Roche-lobe-overflow models. The SiO emission points to a potential companion. The combination of (1), (2) and (3) suggests that a link may exist between the type of AGB pulsations and the morphological nature of the CSE.
Binary interaction along the RGB: The Barium Star perspective
Authors: Escorza A. , Siess L. , Karinkuzhi D. , Boffin H. M. J. , Jorissen A. , van Winckel H. 
Published: January 2020

AbstractBarium (Ba) stars form via mass-transfer in binary systems, and can subsequently interact with their white dwarf companion in a second stage of binary interaction. We used observations of main-sequence Ba systems as input for our evolutionary models, and try to reproduce the orbits of the Ba giants. We show that to explain short and sometimes eccentric orbits, additional interaction mechanisms are needed along the RGB.
Nucleosynthesis in stars: The Origin of the Heaviest Elements
Authors: Karakas Amanda I. 
Published: January 2020

AbstractThe chemical evolution of the Universe is governed by the nucleosynthesis contribution from stars, which in turn is determined primarily by the initial stellar mass. The heaviest elements are primarily produced through neutron capture nucleosynthesis. Two main neutron capture processes identified are the slow and rapid neutron capture processes (s and r processes, respectively). The sites of the r and s-process are discussed, along with recent progress and their associated uncertainties. This review is mostly focused on the s-process which occurs in low and intermediate-mass stars which have masses up to about 8 solar masses (M⊙). We also discuss the intermediate-neutron capture process (or i-process), which may occur in AGB stars, accreting white dwarfs, and massive stars. The contribution of the i-process to the chemical evolution of elements in galaxies is as yet uncertain.
To Be or Not to Be: EHB Stars and AGB Stars
Authors: Brown David A. 
Published: January 2020

AbstractThe formation of EHB stars is linked to the lives of AGB stars by indications that such EHB/sdB stars might form in globular clusters with multiple populations linked to AGB evolution. Observations of massive globular clusters, such as ω-Centauri (Bedin et al.2004, Piotto et al.2005) suggest that single EHB stars might form from He-enhanced progenitors (D’Antona et al.2005, D’Antona & Caloi 2008, Lee et al.2005) in environments enriched by AGB ejecta. The studies conducted by Han et al. (2002), Han et al. (2003), and Han et al. (2007) have been able to provide a strong case for the binary formation of EHB/sdB stars in the Galactic field, though binary formation channels in globular clusters is uncertain. Simulations presented here are an extension of the simulations of Han et al. (2002) and Han et al. (2003), for low metallicities to examine the binary EHB population in globular clusters.
Orbital properties of binary post-AGB stars
Authors: Oomen Glenn-Michael , Van Winckel Hans , Pols Onno 
Published: January 2020

AbstractWe present the results of a decade-long radial velocity monitoring campaign of post-AGB binaries. We derived the orbital elements of 33 post-AGB binaries. We find a companion mass distribution centred around 1.09 M⊙ with a very large spread. All the post-AGB binaries in our sample are expected to have filled their Roche lobes while at giant dimensions. Current binary evolution models are unable to explain the observed distribution of orbits.
Planetary Nebulae Detected in the AKARI Far-IR All-Sky Survey Maps
Authors: Ueta Toshiya , Szczerba Ryszard , Fullard Andrew G. , Takita Satoshi 
Published: January 2020

AbstractThe AKARI Far-IR All-Sky Survey (AFASS) maps produced by the AKARI Infrared Astronomical Satellite enabled us to probe the far-IR sky for objects having surface brightnesses greater than a few to a couple of dozen MJy sr−1. Recently, we have verified that, if AFASS-measured fluxes are properly corrected for using the aperture correction method based on the empirical point-spread-function templates derived directly from the AFASS maps, point-source photometry measured from the AFASS maps reproduces fluxes in the AKARI bright source catalogue (BSC). We have surveyed the far-IR sky in the AFASS for Galactic planetary nebulae (PNe) based on the University of Hong Kong/Australian Astronomical Observatory/Strasbourg Observatory Hα Planetary Nebula database (HASHPNDB), preliminarily yielding far-IR fluxes for roughly 1000 Galactic PNe including a few hundreds of PNe not listed in the AKARI/BSC.
Imaging Red Supergiants with VLT/SPHERE/ZIMPOL
Authors: Cannon E. , Montargès M. , Decin L. , de Koter A. 
Published: January 2020

AbstractUsing the VLT-SPHERE/ZIMPOL adaptive optics imaging polarimeter, images of a sample of nearby red supergiants (RSGs) were obtained in multiple filters. From these data, we obtain information on geometrical structures in the inner wind, the onset radius and spatial distribution of dust grains as well as dust properties such as grain size. As dust grains may play a role in initiating and/or driving the outflow, this could provide us with clues as to the wind driving mechanism.
Ammonia in C-rich stars
Authors: Etmański Bartosz , Schmidt Mirosław R. , Yung Bosco H. K. , Szczerba Ryszard 
Published: January 2020

AbstractHIFI instrument onboard the Herschel satellite provided an unprecedented number of detections of rotational transitions of ammonia in circumstellar envelopes of evolved stars including massive red supergiants, Asymptotic Giant Branch (AGB), and post-AGB stars. The chemistry of ammonia formation in the circumstellar envelopes of evolved stars is poorly understood. The mechanisms proposed for its formation are processes behind the shock front, photochemistry in the inner part of the clumpy envelope, and formation on dust grains. We present results of the non-local thermodynamical equilibrium (non-LTE) radiative transfer modeling of ammonia transitions, mainly of the ground-state rotational one NH3 JK = 10 – 00 at 572.5 GHz, in selected AGB stars, aiming at the quantitative estimation of the NH3 abundance. The model of ammonia includes IR radiative pumping via v2 = 1 vibrational band at 10 μm.
Variability in Post-AGB Stars: Pulsation in Proto-Planetary Nebulae
Authors: Hrivnak Bruce , Henson Gary , Van de Steene Griet , Van Winckel Hans , Hillwig Todd , Bremer Matthew 
Published: January 2020

AbstractWe have been intensely monitoring photometric variability in proto-planetary nebulae (PPNe) over the past 25 years and radial velocity variability over the past ten years. Pulsational variability has been obvious, in both the light and velocity, although the resulting curves are complex, with multiple periods and varying amplitudes. Observed periods range from 25 to 160 days, and the periods and amplitudes reveal evolutionary trends. We will present our observational results to date for approximately 30 PPNe, and discuss these results, including the search for period changes that might help constrain post-AGB evolutionary timescales.
Stacking analysis of HERITAGE data to statistically study far-IR dust emission from evolved stars
Authors: Dharmawardena Thavisha E. , Kemper Francisca , Srinivasan Sundar , Hony Sacha , Jones Olivia , Scicluna Peter 
Published: January 2020

AbstractWe aim to analyse the co-added Herschel images of various categories of evolved stars in the LMC and SMC from the Herschel HERITAGE survey in order to identify, in a statistical sense, a cool historic dust mass component emitted by these sources. The fluxes derived from the co-added stacks can then be compared with those predicted by the GRAMS model grid in order to refine the DPRs estimated for the SMC and LMC.
High angular resolution observations of AGB stars
Authors: Lagadec Eric 
Published: January 2020

AbstractMass loss of AGB stars is a key process for the late stages of evolution of low and intermediate mass stars and the chemical enrichment of galaxies. It is not fully understood yet, as it is the result of a complex combination of pulsation, convection, chemistry, shocks and dust formation.In this review I present what high angular resolution observations can teach us about this mass-loss process. Instruments such as SPHERE/VLT, Gravity and AMBER at the VLTI, and ALMA give us the possibility to map AGB stars from the optical to millimetre wavelengths with resolutions down to 1 milliarcsec. Moving from the surface of the star outwards, I present how high angular resolution observations can now produce images of the surface of the closest AGB stars and study convective motion at their surfaces, map their extended molecular atmospheres and the seeds for dust. The dust formation zone can also be mapped and its dust content characterized with mid-infrared interferometry, while ALMA can map the gas and its kinematics. I will conclude by showing how high angular resolution can help us study the impact of a companion on mass loss.
The star formation history of the M31 galaxy derived from Long-Period-Variable star counts
Authors: Torki Maryam , Javadi Atefeh , van Loon Jacco Th. , Safari Hossein 
Published: January 2020

AbstractThe determination of the star formation history is a key goal for understanding galaxies. In this regard, nearby galaxies in the Local Group offer us a complete suite of galactic environment that is perfect for studying the connection between stellar populations and galaxy evolution. In this paper, we present the star formation history of M31 using long period variable stars that are prime targets for studying the galaxy formation and evolution because of their evolutionary phase. In this method, at first, we convert the near-infrared K-band magnitude of evolved stars to mass and age and from this we reconstruct the star formation and evolution of the galaxy.
Constraining convection across the AGB with high-angular-resolution observations
Authors: Paladini Claudia , Baron Fabien , Jorissen A. , Le Bouquin J.-B. , Freytag B. , Van Eck S. , Wittkowski M. , Hron J. , Chiavassa A. , Berger J.-P. , Siopis C. , Mayer A. , Sadowski G. , Kravchenko K. , Shetye S. , Kerschbaum F. , Kluska J. , Ramstedt S. 
Published: January 2020

AbstractWe present very detailed images of the photosphere of an AGB star obtained with the PIONIER instrument, installed at the Very Large Telescope Interferometer (VLTI). The images show a well defined stellar disc populated by a few convective patterns. Thanks to the high precision of the observations we are able to derive the contrast and granulation horizontal scale of the convective pattern for the first time in a direct way. Such quantities are then compared with scaling relations between granule size, effective temperature, and surface gravity that are predicted by simulations of stellar surface convection.
Chemistry and binarity in the early Universe: what is the role of metal-poor AGB stars?
Authors: Arentsen Anke , Starkenburg Else , Shetrone Matthew D. , McConnachie Alan W. , Venn Kim A. , Depagne Éric 
Published: January 2020

AbstractCarbon-enhanced metal-poor stars are probes of the early universe, that teach us about metal-poor AGB stars and supernovae physics in the very first stars. We find a large fraction of CEMP-no stars with large absolute carbon abundance to be in binary systems. This may be an indication of binary interaction with ultra or extremely metal-poor AGB stars, curiously without enhancement in s-process elements.
Chemical enrichment of galaxies as the result of organic synthesis in evolved stars
Authors: Kwok Sun , Sadjadi SeyedAbdolreza , Zhang Yong 
Published: January 2020

AbstractInfrared spectroscopic observations have shown that complex organics with mixed aromatic-aliphatic structures are synthesized in large quantities during the late stages of stellar evolution. These organics are ejected into the interstellar medium and spread across the Galaxy. Due to the sturdy structures of these organic particles, they can survive through long journeys across the Galaxy under strong UV background and shock conditions. The implications that stellar organics were embedded in the primordial solar nebula is discussed.
TIGvival: High-resolution spectroscopic monitoring of LPV stars
Authors: Wolter Uwe , Engels Dieter , Aringer Bernhard , Freytag Bernd 
Published: January 2020

AbstractTIGvival is a spectroscopic monitoring program of long-period variables (LPV) using our robotic telescope TIGRE. Since 2013, we obtain low-noise, high-resolution spectra (R= 20 000) that cover the optical regime (3800 Å to 8800 Å). We are now continuously monitoring 7 LPVs with different periods and chemical properties. Our 350+ spectra evenly sample the target cycles, as far as ground-based observations allow. Analyzing the TIGvival spectra of Mira as a sample case, our measurements indicate that the strength of the TiO-absorption is phase-shifted with respect to the visual light curve.
KIC 5110739: A new Red Giant in NGC 6819
Authors: Jurua Edward , Trust Otto , Kampindi Felix 
Published: January 2020

AbstractThe Kepler Input Catalogue (KIC) misclassified a number of red giant stars as sub giants. This could have resulted from the large uncertainties in the KIC surface gravities. This resulted in 1523 stars which were recently classified as red giant stars. The cluster membership of the 1523 red giant stars was determined using age, distance modulus, and variation of colour magnitude with large frequency separation. We found that one star, KIC 5110739, is a member of NGC 6819.