bluuebunny/crossref_metadata_2025_split huggingface dataset:
AGB population as probes of galaxy structure and evolution
Authors: Javadi Atefeh , van Loon Jacco Th. 
Published: January 2020

AbstractThe evolution of galaxies is driven by the birth and death of stars. AGB stars are at the end points of their evolution and therefore their luminosities directly reflect their birth mass; this enables us to reconstruct the star formation history. These cool stars also produce dust grains that play an important role in the temperature regulation of the interstellar medium (ISM), chemistry, and the formation of planets. These stars can be resolved in all of the nearby galaxies. Therefore, the Local Group of galaxies offers us a superb near-field cosmology site. Here we can reconstruct the formation histories, and probe the structure and dynamics, of spiral galaxies, of the many dwarf satellite galaxies surrounding the Milky Way and Andromeda, and of isolated dwarf galaxies. It also offers a variety of environments in which to study the detailed processes of galaxy evolution through studying the mass-loss mechanism and dust production by cool evolved stars. In this paper, I will first review our recent efforts to identify mass-losing Asymptotic Giant Branch (AGB) stars and red supergiants (RSGs) in Local Group galaxies and to correlate spatial distributions of the AGB stars of different mass with galactic structures. Then, I will outline our methodology to reconstruct the star formation histories using variable pulsating AGB stars and RSGs and present the results for rates of mass–loss and dust production by pulsating AGB stars and their analysis in terms of stellar evolution and galaxy evolution.
A systematic survey of grain growth in discs around post-AGB binaries with PACS and SPIRE photometry
Authors: Dsilva K. , Van Winckel H. , Kluska J. 
Published: January 2020

AbstractPost-AGB stars are the final stage of evolution of low-intermediate mass stars (M < 8 Mʘ). Those in binary systems have stable circumbinary discs. Using data from Herschel (PACS/SPIRE), we extend the SEDs of 50 galactic post-AGB binary systems to sub-millimetre wavelengths and use the slope of the SED as a diagnostic tool to probe the presence of large grains. Using a Monte Carlo radiative transfer code (MCMax), we create a large grid of models to quantify the observed spectral indices, and use the presence of large grains in the disc as a proxy for evolution.
AGB Stars: Remaining Problems
Authors: Lattanzio John 
Published: January 2020

AbstractI present a subjective list of what I think are the most serious problems in the modelling of AGB stars. Because AGB stars represent the last phase of stellar evolution, they suffer from the accumulation of the effects of uncertainties in all the earlier phases. The complexity of AGB evolution adds further uncertainties specific to the evolutionary behaviour of those stars. Most of the problems are associated with mixing, specifically the boundaries of mixed regions. The nature of the “extra-mixing” remains a mystery, let alone how to model it reliably. Other problems are briefly mentioned and I finish with some hopes of making progress in the future.
Carbon and oxygen isotopes in AGB stars. From the cores of AGB stars to presolar dust
Authors: Lebzelter Thomas , Hinkle Kenneth , Straniero Oscar 
Published: January 2020

AbstractIsotopic ratios are a powerful tool for gaining insights into stellar evolution and nucleosynthesis. The isotopic ratios of the key elements carbon and oxygen are perfectly suited to investigate the pristine composition of red giants, the conditions in their interiors, and the mixing in their extended atmospheres. Of course the dust ejected from red giants in their final evolution also contains isotopically tagged material. This red giant dust is present in the solar system as presolar dust grains. We have measured isotopic ratios of carbon and oxygen in spectra from a large sample of AGB stars including both Miras and semiregular variables. We show how the derived ratios compare with expectations from stellar models and with measurements in presolar grains. Comparison of isotopes that are affected by different types of nucleosynthesis provides insights into galactic evolution.
GK Car and GZ Nor: Two low-luminous, depleted RV Tauri stars
Authors: Gezer I. , Van Winckel H. , Manick R. , Kamath D. 
Published: January 2020

AbstractRV Tauri stars are luminous population II Cepheids which show a characteristic light curve of alternating deep and shallow minima. There are 126 RV Tauri variables in our Galaxy. Using WISE [3.4]-[4.6], [12]-[22] diagram we show that Galactic RV Tauri stars show three main types of IR properties in their SEDs; disc-type, non-IR and uncertain, which does not show a clear characteristic in the SED. We also show that there is a strong correlation between disc-type SED and binarity (Gezer et al. 2015). RV Tauri stars were linked to post AGB stars in early studies (Jura 1986), however, recent studies show that their evolutionary nature is more complex than previously thought (Kamath & Van Winckel 2014, and Manick et al. 2018). In this study, we intentionally selected two RV Tauri stars, GK Car (disc-type) and GZ Nor (uncertain), with different IR characteristics to compare their chemical and photometric properties.
Infrared light curves of dusty & metal-poor AGB stars
Authors: Goldman Steven R. , Boyer Martha ,   the DUSTiNGS team
Published: January 2020

AbstractThe effects of metallicity on both the dust production and mass loss of evolved stars have consequences for stellar masses, stellar lifetimes, progenitors of core-collapse SNe, and the origin of dust in the ISM. With the DUST in Nearby Galaxies with Spitzer (DUSTiNGS) survey, we have discovered samples of dusty evolved AGB stars out to the edge of the Local Group with metallicities down to 0.6% solar. This makes them the nearest analogs of AGB stars in high-redshift galaxies. We present new infrared light curves of the dustiest AGB stars in 10 galaxies from the DUSTiNGS survey and show how the infrared Period-Luminosity (PL) relation is affected by dust and metallicity. These results have implications for the efficiency of AGB dust production at high-redshift and for the use of the Mira PL relation as a distance indicator.
A DARWIN C-star model grid with new dust opacities
Authors: Eriksson Kjell , Höfner Susanne , Aringer Bernhard 
Published: January 2020

AbstractWe have improved the treatment of dust opacity from the small-particle limit approximation to size-dependent which leads to models with smaller grains, lower dust-to-gas ratios, but about the same mass-loss rates and outflow velocities. The K-magnitudes get brighter, whereas the V-magnitudes can be either brighter or dimmer depending on the wind properties.
Evolutionary timescales from the AGB to the CSPNe phase
Authors: Miller Bertolami Marcelo M. 
Published: January 2020

AbstractThe transition from the asymptotic giant branch (AGB) to the final white dwarf (WD) stage is arguably the least understood phase in the evolution of single low- and intermediate-mass stars (0.8 ≲MZAMS/M⊙≲ 8…10). Here we briefly review the progress in the last 50 years of the modeling of stars during the post-AGB phase. We show that although the main features, like the extreme mass dependency of post-AGB timescales were already present in the earliest post-AGB models, the quantitative values of the computed post-AGB timescales changed every time new physics was included in the modeling of post-AGB stars and their progenitors. Then we discuss the predictions and uncertainties of the latest available models regarding the evolutionary timescales of post-AGB stars.
Looking for new water-fountain stars
Authors: Uscanga L. , Gómez J. F. , Yung B. H. K. , Imai H. , Rizzo J. R. , Suárez O. , Miranda L. F. , Trinidad M. A. , Anglada G. , Torrelles J. M. 
Published: January 2020

AbstractWe carried out simultaneous observations of H2O and OH masers, and radio continuum at 1.3 cm with the Karl G. Jansky Very Large Array (VLA) towards 4 water-fountain candidates. Water fountains (WFs) are evolved stars, in the AGB and post-AGB phase, with collimated jets traced by high-velocity H2O masers. Up to now, only 15 sources have been confirmed as WFs through interferometric observations. We are interested in the discovery and study of new WFs. A higher number of these sources is important to understand their properties as a group, because they may represent one of the first manifestations of collimated mass-loss in evolved stars. These observations will provide information about the role of magnetic fields in the launching of jets in WFs. Our aim is to ascertain the WF nature of these candidates, and investigate the spatial distribution of the H2O and OH masers.
The Nearby Evolved Stars Survey: Project description and initial results
Authors: Scicluna Peter 
Published: January 2020

AbstractThe Nearby Evolved Stars Survey aims to observe over 400 evolved stars within 2 kpc, to determine why, and how much, our Galaxy cares about AGB stars. This contribution presents a brief introduction to the survey and data. NESS is an open project. Anyone is welcome to get involved and we aim to make as much data and code available to the community as possible.
On the nature and mass loss of Bulge OH/IR stars
Authors: Blommaert Joris A. D. L. , Groenewegen Martin A. T. , Justtanont Kay , Decin L. 
Published: January 2020

AbstractWe report on the successful search for CO (2-1) and (3-2) emission associated with OH/IR stars in the Galactic Bulge. We observed a sample of eight extremely red AGB stars with the APEX telescope and detected seven. The sources were selected at sufficient high Galactic latitude to avoid interference by interstellar CO, which hampered previous studies of inner galaxy stars. We also collected photometric data and Spitzer IRS spectroscopy to construct the SEDs, which were analysed through radiative transfer modelling. We derived variability periods of our stars from the VVV and WISE surveys. Through dynamical modelling we then retrieve the total mass loss rates (MLR) and the gas-to-dust ratios. The luminosities range between approximately 4,000 and 5,500 L⊙ and periods are below 700 days. The total MLR ranges between 10−5 and 10−4 M⊙ yr−1. The results are presented in Blommaert et al. 2018 and summarized below.
A step further on the physical, kinematic and excitation properties of PNe
Authors: Rocha Gonçalves Denise , Akras Stavros 
Published: January 2020

AbstractPNe are known to be photoionized objects. However they also have low-ionization structures (LIS) with different excitation behavior. We are only now starting to answer why most LIS have lower electron densities than the PN shells hosting them, and whether or not their intense emission in low-ionization lines is the key to their main excitation mechanism. Can LIS line ratios, chemical abundances and kinematics enlight the interplay between the different excitation and formation processes in PNe? Based on the spectra of five PNe with LIS and using new diagnostic diagrams from shock models, we demonstrate that LIS’s main excitation is due to shocks, whereas the other components are mainly photoionized. We propose new diagnostic diagrams involving a few emission lines ([N II], [O III], [S II]) and fshocks/f*, where fshocks and f* are the ionization photon fluxes due to the shocks and to the central star ionizing continuum, respectively.
Dust Structure Around Asymptotic Giant Branch Stars
Authors: Upadhyay Devendra Raj , Khanal Lochan , Hamal Priyanka , Aryal Binil 
Published: January 2020

AbstractThis paper presents mass, temperature profile, and the variation of Planck’s function in different regions around asymptotic giant branch (AGB) stars. The physics of the interstellar medium (ISM) is extremely complex because the medium is very inhomogeneous and is made of regions with fairly diverse physical conditions. We studied the dust environment such as flux, temperature, mass, and inclination angle of the cavity structure around C-rich asymptotic giant branch stars in 60 μm and 100 μm wavelengths band using Infrared Astronomical Survey. We observed the data of AGB stars named IRAS 01142+6306 and IRAS 04369+4501. Flexible image transport system image was downloaded from Sky View Observatory; we obtained the surrounding flux density using software Aladin v2.5. The average dust color temperature and mass are found to be 25.08 K, 23.20 K and 4.73 × ;1026 kg (0.00024 M⊙), 2.58 × 1028 kg (0.013 M⊙), respectively. The dust color temperature ranges from 18.76 K ± 3.16 K to 33.21K ± K and 22.84 K ± 0.18 K to 24.48 K ± 0.63 K. The isolated cavity like structure around the AGB stars has an extension of 45.67 pc × 17.02 pc and 42.25 pc × 17.76 pc, respectively. The core region is found to be edge-on having an inclination angle of 79.46° and 73.99°, respectively.
Near IR and visual polarimetry of the Planetary Nebula M2-9
Authors: Navarro Silvana G. , Serrano Omar , Luna Abraham , Devaraj Rangaswami , Corral Luis J. , Ramírez Vélez Julio , Hiriart David 
Published: January 2020

AbstractBipolar and more complex morphologies observed in planetary nebulae have been explained by two principal hypotheses: by the existence of a companion producing a circumstellar disk, by the effects of a magnetic field, or by a combination of both. The polarimetric analysis of these objects could give information about the presence of dust grains aligned with any preferential direction, due to a magnetic field or to the action of radiative torques (RAT). We performed polarimetric observations of some planetary nebulae in order to detect linear polarization and (in the best scenario) to detect the signature of an accretion disk in these objects. We observed in the visual region with POLIMA at the San Pedro Mártir observatory, and with POLICAN the NIR polarimeter in the Guillermo Haro observatory. We present the result of these observations in one of these objects: the PN M2-9.
ALMA spectrum of the extreme OH/IR star OH 26.5+0.6
Authors: Justtanont K. , Muller S. , Barlow M. J. , Engels D. , García-Hernández D. A. , Groenewegen M. A. T. , Matsuura M. , Olofsson H. , Teyssier D. , Marti-Vidal I. , Khouri T. , Van de Sande M. , Homan W. , Danilovich T. , de Koter A. , Decin L. , Waters L. B. F. M. , Stancliffe R. , Vlemmings W. , Royer P. , Kerschbaum F. , Paladini C. , Blommaert J. , de Nutte R. 
Published: January 2020

AbstractWe present ALMA band 7 data of the extreme OH/IR star, OH 26.5+0.6. In addition to lines of CO and its isotopologues, the circumstellar envelope also exhibits a number of emission lines due to metal-containing molecules, e.g., NaCl and KCl. A lack of C18O is expected, but a non-detection of C17O is puzzling given the strengths of H217O in Herschel spectra of the star. However, a line associated with Si17O is detected. We also report a tentative detection of a gas-phase emission line of MgS. The ALMA spectrum of this object reveals intriguing features which may be used to investigate chemical processes and dust formation during a high mass-loss phase.
SMA Spectral Line Survey of the Proto-Planetary Nebula CRL 618
Authors: Patel Nimesh A. , Gottlieb Carl , Young Ken , Kaminski Tomasz , McCarthy Michael , Menten Karl , Lee Chin-Fei , Gupta Harshal 
Published: January 2020

AbstractCarbon-rich Asymptotic Giant Branch (AGB) stars are major sources of gas and dust in the interstellar medium. During the brief (∼1000 yr) period in the evolution from AGB to the Planetary Nebula (PN) stage, the molecular composition evolves from mainly diatomic and small polyatomic species to more complex molecules. Using the Submillimeter Array (SMA), we have carried out a spectral line survey of CRL 618, covering a frequency range of 281.9 to 359.4 GHz. More than 1000 lines were detected in the ∼60 GHz range, most of them assigned to HC3N and c-C3H2, and their isotopologues. About 200 lines are unassigned. Lines of CO, HCO+, and CS show the fast outflow wings, while the majority of line emission arises from a compact region of ∼1” diameter. We have analyzed the lines of HC3N, c-C3H2, CH3CN, and their isotopologues with rotation temperature diagrams.
Fine Three‐Dimensional VHF Lightning Mapping Using Waveform Cross‐Correlation TOA Method
Authors: Liu Bo , Shi Lihua , Qiu Shi , Liu Hengyi , Dong Wansheng , Li Yun , Sun Zheng 
Published: January 2020

AbstractWaveform cross‐correlation approach was first applied to three‐dimensional very high frequency (VHF) lightning mapping. A Hilbert transform of the original waveform and a three‐step cross‐correlation parsing process were employed to compute the time differences with a small 10‐μs time window for the final time‐of‐arrival (TOA) positioning. The lightning channel continuity was significantly improved, and its fine structure, including the K process, was clearly distinguished with speeds of up to 1.1 × 107 m/s. The two overlapped K processes indicate the high location accuracy of the time‐of‐arrival, based on the waveform correlation method. The median (mean) values of the positioning precision with the proposed method were evaluated by duplicate located sources and estimated as σx = 20 m (26 m), σy = 19 m (28 m), and σz = 54 m (67 m).
Is the Regional Precipitation Predictable in Decadal Scale? A Possible Approach for the Decadal Prediction of the Summer Precipitation Over North China
Authors: Huang Yanyan , Wang Huijun 
Published: January 2020

AbstractA skillful decadal precipitation (DP) prediction is beneficial for infrastructure implementation, water management, and sustainable development, which currently face many challenges. In this study, a new increment method is applied to the decadal prediction of summer precipitation during 1961–2014 over North China, which has suffered water resource scarcity and increased droughts in recent decades. There are three steps in the increment method. First, the DP over North China is obtained by applying a 5‐year running mean. Second, the 3‐year decadal increment (DI) of the DP (DP at the current year minus the DP at the 3 years before, DI_DP) is predicted by a statistical model with the leading 3‐year DI of sea surface temperature anomalies over the North Atlantic and the leading 4‐year DI of the sea ice concentration over the East Siberian Sea. Third, the well‐predicted DI_DP is added to the observed DP at 3 years ago to obtain the final DP prediction. With realistic DP prediction, including correct regime shifts, the increment method provides a promising and valuable approach to decadal climate prediction.
Magnetic Properties of Asteroid (162173) Ryugu
Authors: Hercik David , Auster Hans‐Ulrich , Constantinescu Dragos , Blum Jürgen , Fornaçon Karl‐Heinz , Fujimoto Masaki , Gebauer Kathrin , Grundmann Jan‐Thimo , Güttler Carsten , Hillenmaier Olaf , Ho Tra‐Mi , Hördt Andreas , Krause Christian , Kührt Ekkehard , Lorda Laurence , Matsuoka Ayako , Motschmann Uwe , Moussi‐Soffys Aurélie , Richter Ingo , Sasaki Kaname , Scholten Frank , Stoll Bernd , Weiss Benjamin P. , Wolff Friederike , Glassmeier Karl‐Heinz 
Published: January 2020

AbstractObservations of the magnetization state of asteroids indicate diverse properties. Values between 1.9
10
Am
/kg (Eros) and 10
Am
/kg (Braille) have been reported. A more detailed understanding of asteroidal magnetic properties allows far‐reaching conclusions of the magnetization mechanism as well as the strength of the magnetic field of the solar system regions the asteroid formed in. The Hayabusa2 mission with its lander Mobile Asteroid Surface Scout is equipped with a magnetometer experiment, MasMag. MasMag is a state‐of‐the‐art three‐axis fluxgate magnetometer, successfully operated also on Philae, the Rosetta mission lander. MasMag has enabled, after Eros for the second time ever, to determine the magnetic field of an asteroid during descent and on‐surface operations. The new observations show that Ryugu, a low‐albedo C‐type asteroid, has no detectable global magnetization, and any local magnetization is either small (
Am
/kg) or on very small (subcentimeter) scales. This implies, for example, that energetic solar wind particles could reach and alter the surface unimpeded by strong asteroidal magnetic fields, such as minimagnetospheres in case of the Moon.
New Constraints on Thermal and Dielectric Properties of Lunar Regolith from LRO Diviner and CE‐2 Microwave Radiometer
Authors: Feng Jianqing , Siegler Matthew A. , Hayne Paul O. 
Published: January 2020

AbstractWe derive a new constraint on the thermal and dielectric properties of the lunar regolith layer by reconciling data from the Lunar Reconnaissance Orbiter (LRO) Diviner infrared radiometer and Chang'E‐2 (CE‐2) microwave radiometer (MRM). The bolometric Bond albedo of the lunar surface, which characterizes the ability of the lunar surface to reflect visible radiation, is a function of incidence angle. We determined the Bond albedo by using the Lunar Orbiter Laser Altimeter 1,064‐nm normal albedo and the surface temperature at noon as a function of latitude. The results suggest a modification to existing regolith thermal conductivity models based on a fit to the diurnal variation of Diviner data. Based on the thermal model, a 1‐D radiative transfer and dielectric properties model is developed to fit MRM data for the global Moon. With a new dielectric loss tangent equation for highland regolith applied, our model matches MRM data well at 19.35 and 37 GHz, which are generally accepted to be well calibrated. A global map of loss tangent of the Moon at these frequencies is also obtained by fitting the diurnal amplitude of microwave brightness temperature (TB) of each location on the Moon. We find that the loss tangent of highlands regolith has a slight frequency dependence and is larger than previous studies. We also identify a large discrepancy between our theoretical model and TB obtained by CE‐2 MRM at low frequencies, which is attributed to issues caused by contamination on calibration horn.
Planktic Foraminiferal Test Size and Weight Response to the Late Pliocene Environment
Authors: Todd C. L. , Schmidt D. N. , Robinson M. M. , De Schepper S. 
Published: January 2020

AbstractAtmospheric carbon dioxide (pCO2atm) is impacting the ocean and marine organisms directly via changes in carbonate chemistry and indirectly via a range of changes in physical parameters most dominantly temperature. To assess potential impacts of climate change on carbonate production in the open ocean, we measured size and weight of planktic foraminifers during the late Pliocene atpCO2atmconcentrations comparable to today and global temperatures 2 to 3 °C warmer. Size of all foraminifers was measured at Atlantic Ocean Deep Sea Drilling Project (DSDP) Site 610, Ocean Drilling Program (ODP) Site 999, and Integrated Ocean Drilling Program (IODP) Site U1313. Test size was smaller during the Pliocene than in modern assemblages under the same environmental conditions. During the cold marine isotope stage (MIS) M2, size increased at Site 999, potentially linked to intensified stratification of the surface ocean in response to the closure of the Central American Seaway. At Site U1313, test size tracks the warming throughout the late Pliocene. Size‐normalized weight (SNW) ofGlobigerina bulloidesat Site U1313 decreased during warmer temperature intervals. SNW ofGlobigerinoides ruber(white) at Site 999 displays high‐frequency variability not correlated to temperature. Yet during the glacial period within MIS M2, test weight was higher during higher temperatures. Our results support studies in the modern ocean, which challenge the view that carbonate chemistry is the primary driver for calcification. To better understand processes driving changes in SNW, computer tomography was used to quantify calcite to volume ratios. During interglacial periods, lower calcite volume but higher test volume suggests less suitable conditions for calcification. As this signal is not evident in SNW, subtle changes in calcification might not be observed by the weight‐based method.