bluuebunny/crossref_metadata_2025_split huggingface dataset:
Constraining the orbit of the planet-hosting binary τ Boötis
Authors: Justesen A. B. , Albrecht S. 
Published: April 2019

Context. The formation of planets in compact or highly eccentric binaries and the migration of hot Jupiters are two outstanding problems in planet formation. Detailed characterisation of known systems is important for informing and testing models. The hot Jupiter τ Boo Ab orbits the primary star in the long-period (P ≳ 1000 yr), highly eccentric (e ~ 0.9) double star system τ Boötis. Due to the long orbital period, the orbit of the stellar binary is poorly constrained.
Aims. Here we aim to constrain the orbit of the stellar binary τ Boo AB in order to investigate the formation and migration history of the system. The mutual orbital inclination of the stellar companion and the hot Jupiter has important implications for planet migration. The binary eccentricity and periastron distance are important for understanding the conditions under which τ Boo Ab formed.
Methods. We combine more than 150 yr of astrometric data with twenty-five years of high-precision radial velocities. The combination of sky-projected and line-of-sight measurements places tight constraints on the orbital inclination, eccentricity, and periastron distance of τ Boo AB.
Results. We determine the orbit of τ Boo B and find an orbital inclination of 47.2−3.7+2.7°, a periastron distance of 28.3−3.0+2.3 au, and an eccentricity of 0.87−0.03+0.04. We find that the orbital inclinations of τ Boo Ab and τ Boo B, as well as the stellar spin-axis of τ Boo A coincide at ~45°, a result consistent with the assumption of a well-aligned, coplanar system.
Conclusions. The likely aligned, coplanar configuration suggests planetary migration within a well-aligned protoplanetary disc. Due to the high eccentricity and small periastron distance of τ Boo B, the protoplanetary disc was tidally truncated at ≈6 au. We suggest that τ Boo Ab formed near the edge of the truncated disc and migrated inwards with high eccentricity due to spiral waves generated by the stellar companion.
Advanced aspects of Galactic habitability
Authors: Đošović Vladimir , Vukotić Branislav , Ćirković Milan M. 
Published: April 2019

Context. Astrobiological evolution of the Milky Way (or the shape of its “astrobiological landscape”) has emerged as a key research topic in recent years. In order to build precise, quantitative models of the Galactic habitability, we need to account for two opposing tendencies of life and intelligence in the most general context: the tendency to spread to all available ecological niches (conventionally dubbed “colonization”) and the tendency to succumb to various types of existential catastrophes (“catastrophism”). These evolutionary tendencies have become objects of study in fields such as ecology, macroevolution, risk analysis, and futures studies, though a serious astrobiological treatment has so far been lacking.Aims. Our aim is to numerically investigate the dynamics of opposed processes of expansion (panspermia, colonization) and extinction (catastrophic mechanisms) of life in the Galaxy.Methods. We employed a new type of numerical simulation based on 1D probabilistic cellular automaton with very high temporal resolution, in order to study astrobiological dynamics.Results. While the largest part of the examined parameter space shows very low habitability values, as expected, the remaining part has some observationally appealing features that imply, among other things, a reduction in the amount of fine-tuning necessary for resolving the Fermi paradox.Conclusions. Advanced aspects of Galactic habitability are amenable to precision studies using massive parallel computer simulations. There are regions of the parameter space that correspond to a quasi-stationary state satisfying observable constraints and possessing viable SETI targets.
Hard and bright gamma-ray emission at the base of the Fermi bubbles
Authors: Herold L. , Malyshev D. 
Published: April 2019

Context. The Fermi bubbles (FBs) are large gamma-ray emitting lobes extending up to 55° in latitude above and below the Galactic center (GC). Although the FBs were discovered eight years ago, their origin and the nature of the gamma-ray emission are still unresolved. Understanding the properties of the FBs near the Galactic plane may provide a clue to their origin. Previous analyses of the gamma-ray emission at the base of the FBs, what remains after subtraction of Galactic foregrounds, have shown an increased intensity compared to the FBs at high latitudes, a hard power-law spectrum without evidence of a cutoff up to approximately 1 TeV, and a displacement of the emission to negative longitudes relative to the GC.
Aims. We analyze nine years of Fermi Large Area Telescope data in order to study in more detail than the previous analyses the gamma-ray emission at the base of the FBs, especially at energies above 10 GeV.
Methods. We used a template analysis method to model the observed gamma-ray data and calculate the residual emission after subtraction of the expected foreground and background emission components. Since there are large uncertainties in the determination of the Galactic gamma-ray emission toward the GC, we used several methods to derive Galactic gamma-ray diffuse emission and the contribution from point sources to estimate the uncertainties in the emission at the base of the FBs.
Results. We confirm that the gamma-ray emission at the base of the FBs is well described by a simple power law up to 1 TeV energies. The 95% confidence lower limit on the cutoff energy is about 500 GeV. It has larger intensity than the FBs emission at high latitudes and is shifted to the west (negative longitudes) from the GC. If the emission at the base of the FBs is indeed connected to the high-latitude FBs, then the shift of the emission to negative longitudes disfavors models in which the FBs are created by the supermassive black hole at the GC. We find that the gamma-ray spectrum can be explained either by gamma rays produced in hadronic interactions or by leptonic inverse Compton scattering. In the hadronic scenario, the emission at the base of the FBs can be explained either by several hundred supernova remnants (SNRs) near the GC or by about ten SNRs at a distance of ~1 kpc. In the leptonic scenario, the necessary number of SNRs that can produce the required density of CR electrons is a factor of a few larger than in the hadronic scenario.
Background modelling for γ-ray spectroscopy with INTEGRAL/SPI
Authors: Siegert Thomas , Diehl Roland , Weinberger Christoph , Pleintinger Moritz M. M. , Greiner Jochen , Zhang Xiaoling 
Published: April 2019

Context. The coded-mask spectrometer-telescope SPI on board the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) records photons in the energy range between 20 and 8000 keV. A robust and versatile method for modelling the dominating instrumental background radiation is difficult to establish for such a telescope in the rapidly changing space environment.
Aims. In a previous paper we presented our spectral parameter database, developed from long-term monitoring of the SPI germanium detectors, that characterises the instrument response and background behaviour. Our aim is to build a self-consistent and broadly applicable background model for typical science cases of INTEGRAL/SPI based on this database.
Methods. The general analysis method for SPI relies on distinguishing between illumination patterns on the 19-element germanium detector array from background and sky in a maximum-likelihood framework. We illustrate how the complete set of measurements, even including the exposures of the sources of interest, can be used to define a background model. The observation strategy of INTEGRAL makes it possible to determine individual background components, originating from continuum and γ-ray line emission. We apply our method to different science cases, including point-like, diffuse, continuum, and line emission, and evaluate the adequacy in each case.
Results. From likelihood values and the number of fitted parameters, we determine how strong the impact of the unknown background variability is. We find that the number of fitted parameters, i.e. how often the background has to be re-normalised, depends on the emission type (diffuse with many observations over a large sky region, or point-like with concentrated exposure around one source), the spectral energy range, and bandwidth. A unique timescale, valid for all analysis issues, is not applicable for INTEGRAL/SPI, but must and can be inferred from the chosen data set.
Conclusions. We conclude that our background modelling method can be used in a wide variety of INTEGRAL/SPI science cases, and provides nearly systematics-free and robust results.
Correlation of the rate of Type Ia supernovae with the parent galaxy properties: Light and shadows
Authors: Greggio L. , Cappellaro E. 
Published: April 2019

Context. The identification of the progenitors of Type Ia supernovae (SNIa) is extremely important in several astrophysical contexts, ranging from stellar evolution in close binary systems to evaluating cosmological parameters. Determining the distribution of the delay times (DTD) of SNIa progenitors can shed light on their nature. The DTD can be constrained by analysing the correlation between the SNIa rate and those properties of the parent galaxy which trace the average age of their stellar populations.
Aims. We investigate the diagnostic capabilities of this correlation by examining its systematics with the various parameters at play: simple stellar population models, the adopted description for the star formation history (SFH) in galaxies, and the way in which the masses of the galaxies are evaluated.
Methods. We computed models for the diagnostic correlations for a variety of input ingredients and for a few astrophysically motivated DTD laws appropriate for a wide range of possibilities for the SNIa progenitors. The models are compared to the results of three independent observational surveys.
Results. The scaling of the SNIa rate with the properties of the parent galaxy is sensitive to all input ingredients mentioned above. This is a severe limitation on the possibility to discriminate alternative DTDs. In addition, current surveys show some discrepancies for the reddest and bluest galaxies, likely because of limited statistics and the inhomogeneity of the observations. For galaxies with intermediate colours the rates are in agreement, leading to a robust determination of the productivity of SNIa from stellar populations of ≃0.8 events per 1000 M⊙.
Conclusions. Large stastistics of SNIa events along with accurate measurements of the SFH in the galaxies are required to derive firm constraints on the DTD. The LSST will achieve these results by providing a homogeneous, unbiased, and vast database on both SNIa and galaxies.
Influence of general-relativity effects, dynamical tides, and collisions on planet–planet scattering close to the star
Authors: Marzari F. , Nagasawa M. 
Published: April 2019

Context.Planet–planet (P–P) scattering is an efficient and robust dynamical mechanism for producing eccentric exoplanets. Coupled to tidal interactions with the central star, this phenomenon can also explain close-in giant planets on circularized and potentially misaligned orbits.Aims.We explore scattering events occurring close to the star and test if they can reproduce the main features of the observed orbital distribution of giant exoplanets on tight orbits.Methods.In our modeling we exploited a numerical integration code based on the Hermite algorithm and including the effects of general relativity, dynamical tides, and two-body collisions.Results.We find that P–P scattering events occurring in systems with three giant planets initially moving on circular orbits close to their star produce a population of planets similar to that presently observed, including eccentric and misaligned close-in planets. The contribution of tides and general relativity is relevant in determining the final outcome of the chaotic phase.Conclusions.Even if two-body collisions dominate the chaotic evolution of three planets in crossing orbits close to their star, the final distribution shows a significant number of planets on eccentric orbits. The highly misaligned close-in giant planets are instead produced by systems where the initial semimajor axis of the inner planet was around 0.2 au or beyond.
Small iron meteoroids
Authors: Čapek David , Koten Pavel , Borovička Jiří , Vojáček Vlastimil , Spurný Pavel , Štork Rostislav 
Published: April 2019

Context.A significant fraction of small meteors are produced by iron meteoroids. Their origin and the interaction with the atmosphere have not been well explained up to now.Aims.The goals of the study are to observe faint, slow, low altitude meteors, to identify candidates for iron meteoroids among them, to model their ablation and light curves, and to determine their properties.Methods.Double station video observations were used for the determination of atmospheric trajectories, heliocentric orbits, light curves, and spectra of meteors. Meteors with iron spectra or of suspected iron composition based on beginning heights and light curves were modeled. The immediate removal of liquid iron from the surface as a cloud of droplets with Nukiyama–Tanasawa size distribution and their subsequent vaporization was assumed as the main ablation process on the basis of our previous work. The numerical model has only five parameters: meteoroid initial velocityv∞, zenith distancez, initial massm∞, mean drop sizeDdr, and luminous efficiencyτ. The theoretical light curves were compared with the observed ones.Results.The model is able to explain the majority of the selected light curves, and meteoroid parameters that are not directly observable –m∞,Ddr, andτ– are determined. Unlike in most meteor studies, the mass and luminous efficiency are determined independently. Luminous efficiency ranges from 0.08 to 5.8%; it weakly decreases with increasing initial meteoroid mass. No simple dependency on initial velocity was found. The mean size of iron drops depends on the meteoroid velocity. Slower meteoroids can produce drops with a wide range of mean sizes, whereas faster ones are better matched with larger drops with a smaller dispersion of sizes.
Hot exozodiacal dust: an exocometary origin?
Authors: Sezestre É. , Augereau J.-C. , Thébault P. 
Published: April 2019

Context. Near- and mid-infrared interferometric observations have revealed populations of hot and warm dust grains populating the inner regions of extrasolar planetary systems. These are known as exozodiacal dust clouds, or exozodis, reflecting the similarity with the solar system’s zodiacal cloud. Radiative transfer models have constrained the dust to be dominated by tiny submicron-sized, carbon-rich grains that are accumulated very close to the sublimation radius. The origin of this dust is an unsolved issue.
Aims. We explore two exozodiacal dust production mechanisms, first re-investigating the Poynting-Robertson drag pile-up scenario, and then elaborating on the less explored but promising exocometary dust delivery scenario.
Methods. We developed a new, versatile numerical model that calculates the dust dynamics, with non-orbit-averaged equations for the grains close to the star. The model includes dust sublimation and incorporates a radiative transfer code for direct comparison to the observations. We consider in this study four stellar types, three dust compositions, and we assume a parent belt at 50 au.
Results. In the case of the Poynting-Robertson drag pile-up scenario, we find that it is impossible to produce long-lived submicron-sized grains close to the star. The inward drifting grains fill in the region between the parent belt and the sublimation distance, producing an unrealistically strong mid-infrared excess compared to the near-infrared excess. The dust pile-up at the sublimation radius is by far insufficient to boost the near-IR flux of the exozodi to the point where it dominates over the mid-infrared excess. In the case of the exocometary dust delivery scenario, we find that a narrow ring can form close to the sublimation zone, populated with large grains from several tens to several hundreds of micrometers in radius. Although not perfect, this scenario provides a better match to the observations, especially if the grains are carbon-rich. We also find that the number of active exocomets required to sustain the observed dust level is reasonable.
Conclusions. We conclude that the hot exozodiacal dust detected by near-infrared interferometry is unlikely to result from inward grain migration by Poynting-Robertson drag from a distant parent belt, but could instead have an exocometary origin.
Constraining non-linear dynamo models using quasi-biennial oscillations from sunspot area data
Authors: Inceoglu F. , Simoniello R. , Arlt R. , Rempel M. 
Published: April 2019

Context. Solar magnetic activity exhibits variations with periods between 1.5 and 4 years, the so-called quasi-biennial oscillations (QBOs), in addition to the well-known 11-year Schwabe cycles. Solar dynamo is thought to be the mechanism responsible for the generation of QBOs.
Aims. In this work, we analyse sunspot areas to investigate the spatial and temporal behaviour of the QBO signal and study the physical mechanisms responsible using simulations from fully non-linear mean-field flux-transport dynamos.
Methods. We investigated the behaviour of the QBOs in the sunspot area data for the full disk, and the northern and southern hemispheres, using wavelet and Fourier analyses. We also ran solar dynamos with two different approaches to generating a poloidal field from an existing toroidal field, namely Babcock–Leighton and turbulent α mechanisms. We then studied the simulated magnetic field strengths as well as meridional circulation and differential rotation rates using the same methods.
Results. The results from the sunspot areas show that the QBOs are present in the full disk and hemispheric sunspot areas. These QBOs show slightly different spatial and temporal behaviours, indicating slightly decoupled solar hemispheres. The QBO signal is generally intermittent and in-phase with the sunspot area data, surfacing when the solar activity is at its maximum. The results from the BL-dynamos show that they are neither capable of generating the slightly decoupled behaviour of solar hemispheres nor can they generate QBO-like signals. The turbulent α-dynamos on the other hand generated decoupled hemispheres and some QBO-like shorter cycles.
Conclusions. In conclusion, our simulations show that the turbulent α-dynamos with the Lorentz force seem more efficient in generating the observed temporal and spatial behaviour of the QBO signal compared with the BL-dynamos.
The CORALIE survey for southern extrasolar planets
Authors: Rickman E. L. , Ségransan D. , Marmier M. , Udry S. , Bouchy F. , Lovis C. , Mayor M. , Pepe F. , Queloz D. , Santos N. C. , Allart R. , Bonvin V. , Bratschi P. , Cersullo F. , Chazelas B. , Choplin A. , Conod U. , Deline A. , Delisle J.-B. , Dos Santos L. A. , Figueira P. , Giles H. A. C. , Girard M. , Lavie B. , Martin D. , Motalebi F. , Nielsen L. D. , Osborn H. , Ottoni G. , Raimbault M. , Rey J. , Roger T. , Seidel J. V. , Stalport M. , Suárez Mascareño A. , Triaud A. , Turner O. , Weber L. , Wyttenbach A. 
Published: April 2019

Context. Since 1998, a planet-search around main sequence stars within 50 pc in the southern hemisphere has been underway with the CORALIE spectrograph at La Silla Observatory.
Aims. With an observing time span of more than 20 yr, the CORALIE survey is able to detect long-term trends in data with masses and separations large enough to select ideal targets for direct imaging. Detecting these giant companion candidates will allow us to start bridging the gap between radial-velocity-detected exoplanets and directly imaged planets and brown dwarfs.
Methods. Long-term precise Doppler measurements with the CORALIE spectrograph reveal radial-velocity signatures of massive planetary companions and brown dwarfs on long-period orbits.
Results. In this paper, we report the discovery of new companions orbiting HD 181234, HD 13724, HD 25015, HD 92987 and HD 50499. We also report updated orbital parameters for HD 50499b, HD 92788b and HD 98649b. In addition, we confirm the recent detection of HD 92788c. The newly reported companions span a period range of 15.6–40.4 yr and a mass domain of 2.93–26.77 MJup, the latter of which straddles the nominal boundary between planets and brown dwarfs.
Conclusions. We report the detection of five new companions and updated parameters of four known extrasolar planets. We identify at least some of these companions to be promising candidates for imaging and further characterisation.
CIELO-RGS: a catalog of soft X-ray ionized emission lines
Authors: Mao Junjie , Kaastra Jelle S. , Guainazzi Matteo , González-Riestra Rosario , Santos-Lleó Maria , Kretschmar Peter , Grinberg Victoria , Kalfountzou Eleni , Ibarra Aitor , Matzeu Gabi , Parker Michael , Rodríguez-Pascual Pedro 
Published: April 2019

Context.High-resolution X-ray spectroscopy has advanced our understanding of the hot Universe by revealing physical properties like kinematics, temperature, and abundances of the astrophysical plasmas. Despite technical and scientific achievements, the lack of scientific products at a level higher than count spectra is hampering complete scientific exploitation of high-quality data. This paper introduces the Catalog of Ionized Emission Lines Observed by the Reflection Grating Spectrometer (CIELO-RGS) onboard theXMM-Newtonspace observatory.Aims.The CIELO-RGS catalog aims to facilitate the exploitation of emission features in the public RGS spectra archive. In particular, we aim to analyze the relationship between X-ray spectral diagnostics parameters and measurements at other wavelengths. This paper focuses on the methodology of catalog generation, describing the automated line-detection algorithm.Methods.A moderate sample (∼2400 observations) of high-quality RGS spectra available atXMM-NewtonScience Archive is used as our starting point. A list of potential emission lines is selected based on a multi-scale peak-detection algorithm in a uniform and automated way without prior assumption on the underlying astrophysical model. The candidate line list is validated via spectral fitting with simple continuum and line profile models. We also compare the catalog content with published literature results on a small number of exemplary sources.Results.We generate a catalog of emission lines (1.2 × 104) detected in ∼1600 observations toward stars, X-ray binaries, supernovae remnants, active galactic nuclei, and groups and clusters of galaxies. For each line, we report the observed wavelength, broadening, energy and photon flux, equivalent width, and so on.