Abstracts of Interest
Selected by:
Adila Abdul Halim
Abstract: 2109.01674
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Title:Do cooling and heating functions actually exist?
Download PDFAbstract: Cooling and heating functions describe how radiative processes impact the thermal state of the gas as a function of its temperature and other physical properties. In a most general case they depend on the detailed distributions of level populations of numerous ionic species and on the radiation spectrum. Hence, these functions may vary on a very wide range of spatial and temporal scales. In this paper, we explore cooling and heating functions between $5\leq z \leq10$ in simulated galaxies from the Cosmic Reionization On Computers (CROC) project. We find that the actual cooling (heating) rates experienced by the gas at different temperatures in the simulations do not correspond to any single cooling (heating) function. Gas about $T \gtrsim 10^{4}$ K has sufficiently different combinations of density, metallicity, and photoionization rates than colder gas such that, if the hot gas were suddenly cooler, it would still cool and heat more efficiently than $T \lesssim 10^{4}$ K gas. In other words, the thermodynamics of the gas in the simulations cannot be described by a single set of a cooling plus a heating function that could be computed with common tools, such as Cloudy.
Abstract: 2109.01760
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Title:$Λ$CDM: Much more than we expected, but now less than what we want
Download PDFAbstract: The $\rm\Lambda$CDM cosmological model is remarkable: with just 6 parameters it describes the evolution of the Universe from a very early time when all structures were quantum fluctuations on subatomic scales to the present, and it is consistent with a wealth of high-precision data, both laboratory measurements and astronomical observations. However, the foundation of $\rm\Lambda$CDM involves physics beyond the standard model of particle physics: particle dark matter, dark energy and cosmic inflation. Until this `new physics' is clarified, $\rm\Lambda$CDM is at best incomplete and at worst a phenomenological construct that accommodates the data. I discuss the path forward, which involves both discovery and disruption, some grand challenges and finally the limits of scientific cosmology.
Abstract: 2109.01793
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Title:Morphological study of the nested planetary nebula Hubble 12
Download PDFAbstract: We present a visible-infrared imaging study of young planetary nebula (PN) Hubble 12 (Hb 12; PN G111.8-02.8) obtained with Hubble Space Telescope (HST) archival data and our own Canada-France-Hawaii Telescope (CFHT) measurements. Deep HST and CFHT observations of this nebula reveal three pairs of bipolar structures and an arc-shaped filament near the western waist of Hb 12. The existence of nested bipolar lobes together with the presence of H3 knots suggests that these structures originated from several mass-ejection events during the pre-PN phase. To understand the intrinsic structures of Hb 12, a three-dimensional model enabling the visualisation of this PN at various orientations was constructed. The modelling results show that Hb 12 may resemble other nested hourglass nebulae, such as Hen 2-320 and M 2-9, suggesting that this type of PN may be common and the morphologies of PNs are not so diverse as is shown by their visual appearances. The infrared spectra show that this PN has a mixed chemistry. We discuss the possible material that may cause the unidentified infrared emissions. The analyses of the infrared spectra and the spectral energy distribution suggest the existence of a cool companion in the nucleus of this object.
Abstract: 2109.01717
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Title:The third cosmological paradigm
Download PDFAbstract: I begin by briefly discussing the first two cosmological paradigms, the hot big-bang model and $\Lambda$CDM. In discussing the third paradigm, I focus on the issues it must address, what its aspirations should be, and how it might be initiated. I end with a brief history of my collaborations with Frank Wilczek.
Abstract: 2109.01853
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Title:Dark matter admixed neutron star as a possible compact component in the GW190814 merger event
Download PDFAbstract: We put constraints on the secondary component of GW190814 by analyzing the observational data of the event. The relativistic mean-field models are used to calculate the mass-radius profile and tidal deformability of the compact object, considering it as a massive neutron star with the presence of dark matter particles inside it. With the increase of dark matter percentage, the maximum mass, radius, and tidal deformability of the neutron star decreases. We observe that the predicted properties are well consistent with GW190814 observational data, suggesting the possibility of a dark matter admixed neutron star if the underlying nuclear equation of state is sufficiently stiff.
Abstract: 2109.01752
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Title:A transient radio source consistent with a merger-triggered core collapse supernova
Download PDFAbstract: A core-collapse supernova occurs when exothermic fusion ceases in the core of a massive star, typically due to exhaustion of nuclear fuel. Theory predicts that fusion could be interrupted earlier, by merging of the star with a compact binary companion. We report a luminous radio transient, VT J121001+495647, found in the Very Large Array Sky Survey. The radio emission is consistent with supernova ejecta colliding with a dense shell of material, potentially ejected by binary interaction in the centuries prior to explosion. We associate the supernova with an archival X-ray transient, which implies a relativistic jet was launched during the explosion. The combination of an early relativistic jet and late-time dense interaction is consistent with expectations for a merger-driven explosion.
Abstract: 2109.01759
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Title:Investigating possible unification of Seyfert galaxies and blazars in Fermi-LAT sample
Download PDFAbstract: Statistical analyses are invaluable methods used to understand intrinsic emission processes and the unification of extragalactic radio sources. In this paper, we collected radio, X-ray and {\gamma}-ray data of blazars from the Fermi-LAT and Seyfert galaxies from the INTEGRAL survey and investigated the relationship between the emission properties of Seyfert galaxies and blazar subclasses of flat-spectrum radio quasars (FSRQs) and BL Lac subclasses (BL Lacs). The results show from the average values that these objects follow a sequence that is indicative of probable Seyfert galaxies - BL Lacs - FSRQs unification. We discovered that Seyfert galaxies, BL Lacs and FSRQs share similar emission characteristics in X-ray luminosity (LX-ray), suggestive of the fundamental connection while the {\gamma}-ray and radio luminosities (L{\gamma}-ray and Lradio) of Seyfert galaxies are the least powerful, signifying an evolving structure. From the two-dimensional Kolmogorov-Smirnov test (K-S test), we found that Seyfert galaxies differ from the blazar subclasses in Lradio while there is no significant difference between them in LX-ray and L{\gamma}-ray which implies that high energy emissions in Seyfert galaxies and blazar subclasses may come from the same emission mechanism. Significant positive correlations exist between the high energy luminosities (X-ray and {\gamma}-ray bands) and the low energy component (radio) within the whole sample of blazars and Seyfert galaxies implying a form of connection between them. These results are not only consistent with the prediction of the unified scheme for blazars but also show that Seyfert galaxies have an evolutionary link with blazar subclasses.
Abstract: 2109.02446
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Title:On mass spectra of primordial black holes
Download PDFAbstract: Evidences for the primordial black holes (PBH) presence in the early Universe renew permanently. New limits on their mass spectrum challenge existing models of PBH formation. One of the known model is based on the closed walls collapse after the inflationary epoch. Its intrinsic feature is multiple production of small mass PBH which might contradict observations in the nearest future. We show that the mechanism of walls collapse can be applied to produce substantially different PBH mass spectra if one takes into account the classical motion of scalar fields together with their quantum fluctuations at the inflationary stage.
Abstract: 2109.02414
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Title:Levitating atmospheres around naked singularities
Download PDFAbstract: For a wide class of spherically symmetric naked singularities there is a sphere within which gravity is effectively repulsive. In such spacetimes accreting matter cannot reach the singularity and will instead form a levitating atmosphere, which is kept suspended by gravity alone. The density of the atmosphere has a maximum at a definite radius. In its qualitative properties the atmosphere is analogous to the recently discussed atmospheres that are supported by radiation pressure above luminous neutron stars, however for the levitating atmospheres around a naked singularity no radiation need be present.
Abstract: 2109.02488
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Title:Understanding the evolution of massive stars
Download PDFAbstract: To try to develop an intuitive understanding of why stars evolve in the way that they do, we compute sequences of snapshot stellar structure models. These models allow us to properly isolate the key internal properties that drive the evolution of stars in different phases. Our models can mimic the effects of a very wide range of physical processes including metallicity, internal mixing, binary interaction and mass loss. We focus on massive stars during the main sequence, the expansion across the HR diagram and core helium burning. With our novel approach, we isolate and quantify several important internal properties that set the surface properties at different evolutionary stages. For the main sequence, we find that models with the same mass and very similar surface properties can have different internal distributions of hydrogen and convective core masses. We discuss why stars expand after the main sequence and the fundamental reasons for why stars become red, blue or yellow supergiants. For the post-main sequence, we demonstrate that small changes in the abundance profile can have very large effects on the surface properties, discuss why stars with large envelope masses tend to be blue supergiants and study the cause of blue loops. We also show that massive stars with lower metallicity tend to be more compact for two reasons, lower CNO abundances in the burning regions and lower opacity in the envelope.
Abstract: 2109.02503
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Title:Investigating Deep Learning Methods for Obtaining Photometric Redshift Estimations from Images
Download PDFAbstract: Knowing the redshift of galaxies is one of the first requirements of many cosmological experiments, and as it's impossible to perform spectroscopy for every galaxy being observed, photometric redshift (photo-z) estimations are still of particular interest. Here, we investigate different deep learning methods for obtaining photo-z estimates directly from images, comparing these with traditional machine learning algorithms which make use of magnitudes retrieved through photometry. As well as testing a convolutional neural network (CNN) and inception-module CNN, we introduce a novel mixed-input model which allows for both images and magnitude data to be used in the same model as a way of further improving the estimated redshifts. We also perform benchmarking as a way of demonstrating the performance and scalability of the different algorithms. The data used in the study comes entirely from the Sloan Digital Sky Survey (SDSS) from which 1 million galaxies were used, each having 5-filter (ugriz) images with complete photometry and a spectroscopic redshift which was taken as the ground truth. The mixed-input inception CNN achieved a mean squared error (MSE)=0.009, which was a significant improvement (30%) over the traditional Random Forest (RF), and the model performed even better at lower redshifts achieving a MSE=0.0007 (a 50% improvement over the RF) in the range of z<0.3. This method could be hugely beneficial to upcoming surveys such as the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) which will require vast numbers of photo-z estimates produced as quickly and accurately as possible.
Abstract: 2109.02506
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Title:Studies of a muon-based mass sensitive parameter for the IceTop surface array
Download PDFAbstract: IceTop is the surface instrumentation of the IceCube Neutrino Observatory at the South Pole. It is designed to measure extensive air showers of cosmic rays in the primary energy range from PeV to EeV. Air showers induced by heavier primary particles develop earlier in the atmosphere and produce more muons observable at ground level than lighter cosmic rays with the same primary energy. Therefore, the fraction of muons to all charged particles measured by IceTop characterizes the mass of primary particles. This analysis seeks a muon-based mass sensitive parameter by using the charge signal distribution for each individual cosmic ray event. In this contribution we present the analysis method for the mass-sensitive parameter and our studies of its possible application to the measurement of cosmic ray mass composition with the IceTop surface array.
Abstract: 2109.02518
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Title:Results from the KASCADE-Grande Data Analysis
Download PDFAbstract: KASCADE-Grande and its original array of KASCADE were dedicated to measure individual air showers of cosmic rays with great detail in the primary energy range of 100 TeV up to 1 EeV. The experiment has significantly contributed to investigations of the energy spectrum and chemical composition of cosmic rays in the transition region from galactic to extragalactic origin of cosmic rays as well as to the further development of hadronic interaction models through validity tests using the multi-detector information from KASCADE-Grande. Though the data accumulation was completed in 2013, the data analysis is still continuing. Recently, we investigate the reliability of the new hadronic interactions model of the Sibyll version 2.3d with the combined data from KASCADE and KASCADE-Grande, and compare it to the predictions of different hadronic interaction models. In addition, we update the web-based platform of the KASCADE Cosmic Ray Data Centre (KCDC), where now full datasets from KASCADE and KASCADE-Grande and the corresponding Monte-Carlo simulated events are available.
Abstract: 2109.02524
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Title:Magnetic loading of magnetars' flares
Download PDFAbstract: Magnetars, the likely sources of Fast Radio Bursts (FRBs), produce both steady highly relativistic magnetized winds, and occasional ejection events. We demonstrate that the requirement of conservation of the magnetic flux dominates the overall dynamics of magnetic explosions. This is missed in conventional hydrodynamic models of the ejections as expanding shell with parametrically added magnetic field, as well as one-dimensional models of magnetic disturbances. Most of the initial free energy of an explosion is actually spent on stretching its own internal magnetic field, while doing minimal $pdV$ work against the surrounding. Magnetic explosions from magnetars come into force balance with the pre-flares wind close to the light cylinder. They are then advected quietly with the wind, or propagate as electromagnetic disturbances. No powerful shock waves are generated in the wind.
Abstract: 2109.02622
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Title:Jupiter as a Rotating Bipolytrope
Download PDFAbstract: Polytropes have long been used to model a wide variety of astrophysical objects. A bipolytrope (composite polytrope) may be used for bodies with a distinct core-envelope structure. In this short paper, I demonstrate that a rotating bipolytrope is a reasonable approximation for Jovian interior. Similar models may be used to probe rotating exoplanets to gain an intuitive understanding of their internal structure.
Abstract: 2109.02648
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Title:What powers the radio emission in TDE AT2019dsg: a long-lived jet or the disruption itself?
Download PDFAbstract: The tidal disruption event, AT2019dsg, was observed across a broad range of electromagnetic-wavelengths from radio to X-rays, and it was possibly accompanied by a high-energy neutrino. We study the nature of the radio-emitting outflow by analyzing the synchrotron self-absorbed spectra in terms of the equipartition model. We find that the time evolution of the outflow radius can be interpreted as either free expansion or deceleration. If the former, the outflow was launched $\simeq$ 40 days before the optical peak; if the latter, the launch was $\simeq$ 10 days after the optical peak. In addition, the energy in the radio-emitting region increases over time. This second conclusion is most naturally interpreted by a scenario resembling the earliest stage of a supernova remnant: as more and more material is swept up, it is heated by the forward shock at the expense of the outflow's kinetic energy. Energy injection from an accreting BH cannot be completely excluded, but the injection rate is very different from the fallback luminosity, requiring further physical explanation. If the neutrino association is real, the scale of energy injection needed is much greater than for the radio emission, suggesting that the detected neutrino did not arise from the radio emitting region.
Abstract: 2109.02651
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Title:The large-scale environment of thermonuclear and core-collapse supernovae
Download PDFAbstract: The new generation of wide-field time-domain surveys has made it feasible to study the clustering of supernova (SN) host galaxies in the large-scale structure (LSS) for the first time. We investigate the LSS environment of SN populations, using 106 dark matter density realisations with a resolution of $\sim$ 3.8 Mpc, constrained by the 2M++ galaxy survey. We limit our analysis to redshift $z<0.036$, using samples of 498 thermonuclear and 782 core-collapse SNe from the Zwicky Transient Facility's Bright Transient Survey and Census of the Local Universe catalogues. We detect clustering of SNe with high significance; the observed clustering of the two SNe populations is consistent with each other. Further, the clustering of SN hosts is consistent with that of the Sloan Digital Sky Survey (SDSS) Baryon Oscillation Spectroscopic Survey (BOSS) DR12 spectroscopic galaxy sample in the same redshift range. Using a tidal shear classifier, we classify the LSS into voids, sheets, filaments and knots. We find that both SNe and SDSS galaxies are predominantly found in sheets and filaments. SNe are significantly under-represented in voids and over-represented in knots compared to the volume fraction in these structures. This work opens the potential for using forthcoming wide-field deep SN surveys as a complementary LSS probe.
Abstract: 2109.02663
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Title:Asymmetric HI 21 cm lines of fast radio burst hosts: connection with galaxy interaction
Download PDFAbstract: Fast radio bursts (FRBs) are enigmatic transients with very short-duration radio emission. Their nature is still unknown and is widely debated. I provide the first analysis of atomic gas properties of FRB hosts to provide constraints on their nature. HI observations exist for NGC3252, the host of FRB 181030A, M81, the host of FRB 200120E, and the Milky Way, the host of FRB 200428. I report three observables: i) all three FRB hosts are interacting galaxies; ii) the HI spectra of both FRB hosts with such data available are highly asymmetric, several standard deviations above the general population of galaxies; iii) two FRB hosts have normal atomic gas properties and one is strongly deficient in atomic gas. This indicates that FRBs are connected with a recent enhancement of star formation due to interaction. This supports fast FRB channels, for example a massive star with a short delay time so that interaction signatures giving rise to the birth of the progenitor are still visible. Long gamma-ray burst (GRB) and broad-lined type Ic supernova (SN) hosts exhibit much more symmetric spectra, even though they were claimed to experience gas inflow from the intergalactic medium. The difference can be explained by the interactions experienced by FRB hosts being more disruptive than these gas inflow, or by the mass effect, with GRB/SN host at lower masses having less organized gas motions, so with HI lines closer to a symmetrical Gaussian. This also suggests that the emission mechanisms of FRBs and GRBs are likely different.
Abstract: 2109.02669
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Title:APOGEE-2 Discovery of a Large Population of Relatively High-Metallicity Globular Cluster Debris
Download PDFAbstract: We report the discovery of a new, chemically distinct population of relatively high-metallicity ([Fe/H] $> -0.7$) red giant stars with super-solar [N/Fe] ($\gtrsim +0.75$) identified within the bulge, disk, and halo of the Milky Way. This sample of stars was observed during the second phase of the Apache Point Observatory Galactic Evolution Experiment (APOGEE-2); the spectra of these stars are part of the seventeenth Data Release (DR 17) of the Sloan Digital Sky Survey. We hypothesize that this newly identified population was formed in a variety of progenitors, and are likely made up of either fully or partially destroyed metal-rich globular clusters, which we refer to as Globular Cluster Debris (GCD), identified by their unusual photospheric nitrogen abundances. It is likely that some of the GCD stars were probable members of the Gaia-Enceladus-Sausage accretion event, along with clusters formed in situ.
Abstract: 2109.03212
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Title:Binary Black Hole Merger Rates in AGN Disks versus Nuclear Star Clusters: Loud beats Quiet
Download PDFAbstract: Galactic nuclei are promising sites for stellar origin black hole (BH) mergers, as part of merger hierarchies in deep potential wells. We show that binary black hole (BBH) merger rates in active galactic nuclei (AGN) should always exceed merger rates in quiescent galactic nuclei (nuclear star clusters, NSCs) around supermassive BHs (SMBHs) without accretion disks. This is primarily due to average binary lifetimes in AGN that are significantly shorter than in NSCs. The lifetime difference comes from rapid hardening of BBHs in AGN, such that their semi-major axes are smaller than the hard-soft boundary of their parent NSC; this contrasts with the large average lifetime to merger for BBHs in NSCs around SMBHs, due to binary ionization mechanisms. Secondarily, merger rates in AGNs are enhanced by gas-driven binary formation mechanisms. Formation of new BHs in AGN disks are a minor contributor to the rate differences. With the gravitational wave detection of several BBHs with at least one progenitor in the upper mass gap, and signatures of dynamical formation channels in the $\chi_{\rm eff}$ distribution, we argue that AGN could contribute $\sim 25\%-80\%$ of the LIGO-Virgo measured rate of $\sim 24 \rm{Gpc}^{-3} \rm{yr}^{-1}$.
Abstract: 2109.03642
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Title:Nitrogen evolution in the halo, thick disc, thin disc and bulge of the Galaxy
Download PDFAbstract: We study the evolution of nitrogen in the Galactic halo, thick disc, thin disc and bulge by comparing detailed chemical evolution models with recent observations. The models used in this work have already been constrained to explain the abundance patterns of $\alpha$-elements and the metallicity distribution functions of halo, disc and bulge stars; here, we adopt them to investigate the origin and evolution of N in the different Galactic components. First, we consider different sets of yields and study the importance of the various channels proposed for N production. Secondly, we apply the reference models to study the evolution of both the Galactic discs and bulge. We conclude that: i) primary N produced by rotating massive stars is required to reproduce the plateau in log(N/O) and [N/Fe] ratios at low metallicity, as well as the secondary and primary production from low- and intermediate-mass stars to reproduce the data of the thin disc. ii) The parallel model can provide a good explanation of the evolution of N abundance in the thick and thin discs; we confirm that the thick disc has evolved much faster than the thin disc, in agreement with the results from the abundance patterns of other chemical elements. iii) Finally, we present new model predictions for N evolution in the Galactic bulge, and we show that the observations in bulge stars can be explained if massive stars rotate fast during the earliest phases of Galactic evolution, in agreement with findings from the abundance pattern of carbon.
Abstract: 2109.04032
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Title:Dark Age of Type II Supernova Remnants
Download PDFAbstract: Supernova remnants (SNRs) are important objects in terms of their connections with supernova (SN) explosion mechanism(s), progenitor stars, and cosmic-ray acceleration. Non-thermal emission from SNRs is an effective probe of the structure of their surrounding circumstellar media (CSM), which can in turn shed lights on mechanism and history of the elusive mass-loss of massive stars. In this work, we calculate the time evolution of broadband non-thermal emission from SNRs originating from Type II SNe embedded in a CSM environment linked to the mass loss history of the progenitor. Our results predict that Type II SNRs experience a prolonged period of weak radio and $\gamma$-ray emission if they run into a spatially extended bubble of low density and high temperature created by the stellar wind during main sequence. For a typical red supergiant progenitor evolved within an average interstellar medium (ISM), this "dark age" corresponds to a range of SNR ages spanning from ~1000 to 5000 yrs old. This result suggests that a majority of Type II SNRs are too faint to be detected, which may help explain why the number of known Galactic SNRs is significantly less than what we expect from the SN rate in our Galaxy.
Abstract: 2109.04388
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Title:The ubiquitous mechanism accelerating cosmic rays at all the energies
Download PDFAbstract: The mechanism accelerating cosmic rays in the Milky Way Galaxy and galaxy clusters is identified and described. The acceleration of cosmic rays is a purely electrostatic process which operates up to the maximum energies of $10^{23}$ eV in galaxy clusters. Galactic cosmic rays are accelerated in a pervasive electrostatic field active in the whole Galaxy except in restricted regions shielded by interstellar and stellar plasmas as, for instance, the region occupied by the solar system. It is proved that the energy spectrum of the cosmic radiation in the Milky Way Galaxy, in the region where the solar system resides, has a constant spectral index comprised between 2.64-2.68 and the maximum energies of Galactic protons are $3.0 \times 10^{19}$ eV. The agreement of these results with the experimental data is discussed in detail and underlined. The various physical processes that maintain the stability of the electrostatic structure in the Milky Way Galaxy are the same that generate the Galactic magnetic field. Accordingly, the intensity, orientation and direction of the Galactic magnetic field are evaluated. The results of the calculation are compared with the observational data, optical and mostly radio astronomy data. The accord of the intensity, orientation and direction of the observed magnetic field with calculation is excellent.
Abstract: 2109.04494
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Title:Erosion of Icy Interstellar Objects by Cosmic Rays and Implications for `Oumuamua
Download PDFAbstract: We study the destruction of icy interstellar objects by cosmic rays and gas collisions. Using the cosmic-ray flux measured in the local interstellar medium as well as inferred from gamma-ray observations at the different galactocentric radii, we find that cosmic-ray erosion is significant for interstellar objects made of common types of ices. Interestingly, cosmic-ray heating might destroy icy interstellar objects very efficiently such that the initial size of an N$_2$ fragment as suggested by Jackson & Desch (2021) to explain the composition of `Oumuamua should be at least 10 km in size in order to survive the journey of about 0.5 Gyr in the ISM and might be even larger if it originated from a region with an enhanced cosmic-ray flux. The erosion time due to cosmic-ray heating and gas collisions also allows us to set approximate limits on the initial size for other types of icy interstellar objects, e.g. composed of CO, CO$_2$, or CH$_4$. For a given initial size, we constrain the maximum distance to the birth site for interstellar objects with different speeds.
Abstract: 2109.04678
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Title:Decoding Morphological Evolution of Open Clusters
Download PDFAbstract: Base on {\it Gaia} Second Data Release and the combination of nonparametric bivariate density estimation with the least square ellipse fitting, we derive the shape parameters of the sample clusters. By analyzing the dislocation of the sample clusters, the dislocation $d$ is related to the X-axis pointing toward the Galactic center, Y-axis pointing in the direction of Galactic rotation, and the Z-axis (log(|H|/pc)) that is positive toward the Galactic north pole. This finding underlines the important role of the dislocation of clusters in tracking the external environment of the Milky Way. The orientation ($q_{pm}$) of the clusters with $e_{pm}$~$\geq$~0.4 presents an aggregate distribution in the range of -45$\degr$ to 45$\degr$, about 74\% of them. This probably suggests that these clusters tend to deform heavily in the direction of the Galactic plane. NGC~752 is in a slight stage of expansion in the two-dimensional space and will deform itself morphology along the direction perpendicular to the original stretching direction in the future if no other events occur. The relative degree of deformation of the sample clusters in the short-axis direction decreases as their ages increase. On average, the severely distorted sample clusters in each group account for about 26\%~$\pm$~9\%. This possibly implies a uniform external environment in the range of $|$H$|$~$\leq$~300~pc if the sample completeness of each group is not taken into account.
Abstract: 2109.04781
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Full Text: [ PostScript, PDF]
Title:SWEET-Cat 2.0: The Cat just got SWEETer; Higher quality spectra and precise parallaxes from GAIA eDR3
Download PDFAbstract: Aims. The catalog of Stars With ExoplanETs (SWEET-Cat) was originally introduced in 2013. Since then many more exoplanets have been confirmed, increasing significantly the number of host stars listed there. A crucial step toward a comprehensive understanding of these new worlds is the precise and homogeneous characterization of their host stars. Better spectroscopic stellar parameters along with new results from Gaia eDR3 provide updated and precise parameters for the discovered planets. A new version of the catalog, whose homogeneity in the derivation of the parameters is key to unraveling star-planet connections, is available to the community. Methods. We made use of high-resolution spectra for planet-host stars, either observed by our team or collected through public archives. The spectroscopic stellar parameters were derived for the spectra following the same homogeneous process using ARES and MOOG (ARES+MOOG) as for the previous SWEET-Cat releases. We re-derived parameters for the stars in the catalog using better quality spectra and/or using the most recent versions of the codes. Moreover, the new SWEET-Cat table can now be more easily combined with the planet properties listed both at the Extrasolar Planets Encyclopedia and at the NASA exoplanet archive to perform statistical analyses of exoplanets. We also made use of the recent GAIA eDR3 parallaxes and respective photometry to derive consistent and accurate surface gravity values for the host stars. Results. We increased the number of stars with homogeneous parameters by more than 40\% (from 645 to 928). We reviewed and updated the metallicity distributions of stars hosting planets with different mass regimes comparing the low-mass planets (< 30M$_{\oplus}$) with the high-mass planets. The new data strengthen previous results showing the possible trend in the metallicity-period-mass diagram for low-mass planets.
Abstract: 2109.04790
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Title:How can astrotourism serve the sustainable development goals? The Namibian example
Download PDFAbstract: Astrotourism brings new opportunities to generate sustainable socio-economic development, preserve cultural heritage, and inspire and educate the citizens of the globe. This form of tourism can involve many different activities, such as visiting observatories or travelling to remote areas to experience an evening under a pristine, dark night sky. Together, our UK-Namibian collaboration is working to develop and showcase astrotourism in Namibia, and to enhance the possibility for astrotourism worldwide.
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