adsabs/SciX_UAT_keywords huggingface dataset:
Further Evidence for Significant Luminosity Evolution in Supernova Cosmology

Supernova (SN) cosmology is based on the assumption that the corrected luminosity of SNe Ia would not evolve with redshift. Recently, our age dating of stellar populations in early-type host galaxies (ETGs) from high-quality spectra has shown that this key assumption is most likely in error. It has been argued though that the age-Hubble residual (HR) correlation from ETGs is not confirmed from two independent age data sets measured from multiband optical photometry of host galaxies of all morphological types. Here we show, however, that one of the data sets is based on highly uncertain and inappropriate luminosity-weighted ages derived, in many cases, under serious template mismatch. The other data set employs more reliable mass-weighted ages, but the statistical analysis involved is affected by regression dilution bias, severely underestimating both the slope and significance of the age-HR correlation. Remarkably, when we apply regression analysis with a standard posterior sampling method to this data set comprising a large sample (N = 102) of host galaxies, very significant (>99.99%) correlation is obtained between the global population age and HR with the slope (-0.047 ± 0.011 mag Gyr-1) highly consistent with our previous spectroscopic result from ETGs. For the local age of the environment around the site of SNe, a similarly significant (>99.96%) correlation is obtained with a steeper slope (-0.057 ± 0.016 mag Gyr-1). Therefore, the SN luminosity evolution is strongly supported by the age dating based on multiband optical photometry and can be a serious systematic bias in SN cosmology.

Keywords: type ia supernovae; observational cosmology; dark energy
Long-period Radio Pulsars: Population Study in the Neutron Star and White Dwarf Rotating Dipole Scenarios

The nature of two recently discovered radio emitters with unusually long periods of 18 minutes (GLEAM-X J1627–52) and 21 minutes (GPM J1839–10) is highly debated. Their bright radio emission resembles that of radio magnetars, but their long periodicities and lack of detection at other wavelengths challenge the neutron star (NS) interpretation. In contrast, long rotational periods are common in white dwarfs (WDs) but, although predicted, dipolar radio emission from isolated magnetic WDs has never been unambiguously observed. In this work, we investigate these long-period objects as potential isolated NS or WD dipolar radio emitters and find that both scenarios pose significant challenges to our understanding of radio emission via pair production in dipolar magnetospheres. We also perform population-synthesis simulations based on dipolar spin-down in both pictures, assuming different initial-period distributions, masses, radii, beaming fractions, and magnetic field prescriptions, to assess their impact on the ultra-long pulsar population. In the NS scenario, we do not expect a large number of ultra-long-period pulsars under any physically motivated (or even extreme) assumptions for the period evolution. On the other hand, in the WD scenario, we can easily accommodate a large population of long-period radio emitters. However, no mechanism can easily explain the production of such bright coherent radio emission in either scenarios.

Keywords: radio sources; pulsars; neutron stars
Principal Component Analysis in the Modeling of Colors of Comae of Comets Hale-Bopp and Tabur

The temporal variability of the colors of comae of comets has been reported for some decades. The color indices B-R of comets Hale-Bopp and Tabur were estimated with a variation of the model of Kolokolova et al., according to geometrical, populational, and compositional parameters of cometary dust. A principal component analysis of five model parameters points that the variation of these color indices is usually associated with changes in population or geometric parameters, and their extremes with a compositional variation of the dust grains.

Keywords: small solar system bodies; coma dust; long period comets; broad band photometry
Scale Invariance in Gamma-Ray Flares of the Sun and 3C 454.3

Using the gamma-ray flare samples of the Sun and 3C 454.3 observed by the Fermi telescope, we investigate the statistical properties of sizes including fluence (energy), peak flux (luminosity), duration time, and waiting time in this work. We find that the cumulative distribution of the fluctuations of these sizes follow well the Tsallis q-Gaussian function. The obtained q values from q-Gaussian distribution remain stable around 2 without any significant change, implying that there is a scale invariance structure in gamma-ray flares of the Sun and 3C 454.3. This scale invariance characteristics of the Sun and 3C 454.3 indicated by q values are also comparable to those of earthquakes, soft gamma repeaters, fast radio burst (FRB 20121102), and X-ray flares of gamma-ray bursts. On top of that, we verify the relationship between q values and the power-law indices α from the size frequency distributions, which is expressed as q = (α + 2)/α. These statistical findings could be well explained within the physical framework of a self-organizing criticality system.

Keywords: gamma-rays; solar flares; quasars; astrostatistics
Distinguishing Dark Matter Cusps from Cores Using Globular Clusters

Globular clusters (GCs) provide valuable insight into the properties of their host galaxies' dark matter halos. Using N-body simulations incorporating semianalytic dynamical friction and GC-GC merger prescriptions, we study the evolution of GC radial distributions and mass functions in cuspy and cored dark matter halos. Modeling the dynamics of the GC-rich system in the dwarf galaxy UGC 7369, we find that friction-induced inspiral and subsequent mergers of massive GCs can naturally and robustly explain the mass segregation of the GCs and the existence of a nuclear star cluster (NSC). However, the multiple mergers required to form the NSC only take place when the dark matter halo is cuspy. In a cored halo, stalling of the dynamical friction within the core halts the inspiral of the GCs, and so the GC merger rate falls significantly, precluding the formation of an NSC. We therefore argue that the presence of an NSC requires a cusp in UGC 7369. More generally, we propose that the presence of an NSC and the corresponding alteration of the GC mass function due to mergers may be used as an indicator of a cuspy halo for galaxies in which we expect NSC formation to be merger dominated. These observables represent a simple, powerful complement to other inner halo density profile constraint techniques and should allow for straightforward extension to larger samples.

Keywords: galaxy dark matter halos; globular star clusters; dynamical friction; dwarf galaxies
As a Matter of State: The Role of Thermodynamics in Magnetohydrodynamic Turbulence

Turbulence simulations play a key role in advancing the general understanding of the physical properties of turbulence and in interpreting astrophysical observations of turbulent plasmas. For the sake of simplicity, however, turbulence simulations are often conducted in the isothermal limit. Given that the majority of astrophysical systems are not governed by isothermal dynamics, we aim to quantify the impact of thermodynamics on the physics of turbulence, through varying adiabatic index, γ, combined with a range of optically thin cooling functions. In this paper, we present a suite of ideal magnetohydrodynamics simulations of thermally balanced stationary turbulence in the subsonic, super-Alfvénic, high ${\beta }_{{\rm{p}}}$ (ratio of thermal to magnetic pressure) regime, where turbulent dissipation is balanced by two idealized cooling functions (approximating linear cooling and free-free emission) and examine the impact of the equation of state by considering cases that correspond to isothermal, monatomic, and diatomic gases. We find a strong anticorrelation between thermal and magnetic pressure independent of thermodynamics, whereas the strong anticorrelation between density and magnetic field found in the isothermal case weakens with increasing γ. Similarly, the linear relation between variations in density and thermal pressure with sonic Mach number becomes steeper with increasing γ. This suggests that there exists a degeneracy in these relations with respect to thermodynamics and Mach number in this regime, which is dominated by slow magnetosonic modes. These results have implications for attempts to infer (e.g.,) Mach numbers from (e.g.,) Faraday rotation measurements, without additional information regarding the thermodynamics of the plasma. However, our results suggest that this degeneracy can be broken by utilizing higher-order moments of observable distribution functions.

Keywords: magnetohydrodynamics; astrophysical fluid dynamics; plasma astrophysics; magnetohydrodynamical simulations; intracluster medium
Experimental Study of the Response of Sheared E × B Flow to Varying Ion-Neutral Collisions

Partially ionized plasma is a common occurrence in astrophysical and space environments. The emergence and development of plasma instabilities are significantly impacted by the inelastic collisions between the ions and neutrals in the partially ionized plasma, such as the charge exchange. In this study, the effect of the ion-neutral collisions on the sheared E × B flow was experimentally investigated. In the weak collision range, the shear-driven plasma instability, such as Kelvin-Helmholtz instability, was excited by the velocity-sheared flow. However, increasing ion-neutral collisions resulted in a decrease in the magnitude of the sheared E × B flow due to charge exchange-induced drag forces. Consequently, the Kelvin-Helmholtz instability is suppressed, and the Rayleigh-Taylor instability is triggered. The underlying mechanism was elucidated through experimental findings and numerical analysis. The result of this study proposes that a transition between the two modes occurred with increasing ion-neutral collision strength. It could be applied to the study of the solar chromosphere and prominence and planetary ionospheres, where plasma is partially ionized and the sheared E × B flow is often encountered.

Keywords: laboratory astrophysics; solar atmosphere; earth ionosphere; planetary ionospheres
A Massive Star Is Born: How Feedback from Stellar Winds, Radiation Pressure, and Collimated Outflows Limits Accretion onto Massive Stars

Massive protostars attain high luminosities as they are actively accreting and the radiation pressure exerted on the gas in the star's atmosphere may launch isotropic high-velocity winds. These winds will collide with the surrounding gas producing shock-heated (T ~ 107 K) tenuous gas that adiabatically expands and pushes on the dense gas that may otherwise be accreted. We present a suite of 3D radiation-magnetohydrodynamic simulations of the collapse of massive prestellar cores and include radiative feedback from the stellar and dust-reprocessed radiation fields, collimated outflows, and, for the first time, isotropic stellar winds to model how these processes affect the formation of massive stars. We find that winds are initially launched when the massive protostar is still accreting and its wind properties evolve as the protostar contracts to the main sequence. Wind feedback drives asymmetric adiabatic wind bubbles that have a bipolar morphology because the dense circumstellar material pinches the expansion of the hot shock-heated gas. We term this the "wind tunnel effect." If the core is magnetized, wind feedback is less efficient at driving adiabatic wind bubbles initially because magnetic tension delays their growth. We find that wind feedback eventually quenches accretion onto ~30 M ⊙ protostars that form from the collapse of the isolated cores simulated here. Hence, our results suggest that ≳30 M ⊙ stars likely require larger-scale dynamical inflows from their host cloud to overcome wind feedback. Additionally, we discuss the implications of observing adiabatic wind bubbles with Chandra while the massive protostars are still highly embedded.

Keywords: massive stars; star formation; stellar feedback; stellar winds; stellar wind bubbles
A Fully Time-dependent Ab Initio Cosmic-Ray Modulation Model Applied to Historical Cosmic-Ray Modulation

Cosmogenic nuclide records can in principle allow for the estimation of the behavior of the heliospheric magnetic field (HMF) in the distant past. This requires careful modeling of cosmic-ray transport in a manner that is as realistic as possible, taking into account as many of the factors affecting the transport of cosmic-rays (CRs) as possible. The present study presents a 3D time-dependent ab initio CR modulation code that utilizes as inputs simple theoretically and observationally motivated temporal profiles to model large-scale (such as the tilt angle) and small-scale (such as the magnetic variance) parameters relevant to CR transport. Galactic CR proton differential intensities computed using this model for the period 1977-2001 are in reasonable to good agreement with spacecraft observations, reproducing the major salient features of the observed CR intensity temporal profile. To investigate pre-space-age cosmic-ray modulation, and to test conclusions previously drawn regarding the relative importance of drift effects on said modulation, historic estimates of the past HMF presented by McCracken & Beer were used as inputs for the model. The resulting CR temporal intensity profile displays clear evidence of drift effects, with a sharp peak in intensities during the Dalton Minimum.

Keywords: heliosphere; cosmic rays; solar cycle
Flash Ionization Signatures in the Type Ibn Supernova SN 2019uo

We present photometric and spectroscopic observations of the type Ibn supernova (SN) 2019uo, the second ever SN Ibn with flash ionization (He II, C III, N III) features in its early spectra. SN 2019uo displays a rapid post-peak luminosity decline of 0.1 mag day-1 similar to most of the SNe Ibn, but is fainter ( ${M}_{\max }^{V}=-18.30\pm 0.24$ mag) than a typical SN Ibn and shows a color evolution that places it between SNe Ib and the most extreme SNe Ibn. SN 2019uo shows P-cygni He I features in the early spectra which gradually evolve and become emission dominated post peak. It also shows faster evolution in line velocities as compared to most other members of the type Ibn subclass. The bolometric light curve is fairly well described by a 56Ni + circumstellar interaction model.

Keywords: core-collapse supernovae; supernovae; ccd photometry; photometry; spectroscopy; astronomical techniques
A Constrained Dust Opacity for Models of Dense Clouds and Protostellar Envelopes

Radiative transfer models of dense clouds and protostellar envelopes rely on the availability of appropriate dust opacities, particularly as new JWST data become available. We present the model opacity known as KP5, which fits the (1–1000 μm) extinction curve measured for icy dust in dense molecular clouds by Spitzer and JCMT, and has been used by the community since 2009, but not previously published. The opacity law (absorption, scattering, and Henyey–Greenstein asymmetry parameter) includes H2O, CO, and CO2 ices, and has been shown to be well suited for models of embedded protostars.

Keywords: interstellar medium; circumstellar dust; ice spectroscopy; radiative transfer simulations; molecular clouds
INTEGRAL Discovery of a Burst with Associated Radio Emission from the Magnetar SGR 1935+2154

We report on International Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of the soft γ-ray repeater SGR 1935+2154 performed between 2020 April 28 and May 3. Several short bursts with fluence of $\sim {10}^{-7}\mbox{--}{10}^{-6}$ erg cm-2 were detected by the Imager on-board INTEGRAL (IBIS) instrument in the 20-200 keV range. The burst with the hardest spectrum, discovered and localized in real time by the INTEGRAL Burst Alert System, was spatially and temporally coincident with a short and very bright radio burst detected by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and Survey for Transient Astronomical Radio Emission 2 (STARE2) radio telescopes at 400-800 MHz and 1.4 GHz, respectively. Its lightcurve shows three narrow peaks separated by ∼29 ms time intervals, superimposed on a broad pulse lasting ∼0.6 s. The brightest peak had a delay of 6.5 ± 1.0 ms with respect to the 1.4 GHz radio pulse (that coincides with the second and brightest component seen at lower frequencies). The burst spectrum, an exponentially cutoff power law with photon index ${\rm{\Gamma }}={0.7}_{-0.2}^{+0.4}$ and peak energy ${E}_{p}=65\pm 5\,\mathrm{keV}$ , is harder than those of the bursts usually observed from this and other magnetars. By the analysis of an expanding dust-scattering ring seen in X-rays with the Neil Gehrels Swift Observatory X-ray Telescope (XRT) instrument, we derived a distance of ${4.4}_{-1.3}^{+2.8}$ kpc for SGR 1935+2154, independent of its possible association with the supernova remnant G57.2+0.8. At this distance, the burst 20-200 keV fluence of $(6.1\pm 0.3)\times {10}^{-7}$ erg cm-2 corresponds to an isotropic emitted energy of $\sim 1.4\times {10}^{39}$ erg. This is the first burst with a radio counterpart observed from a soft γ-ray repeater and it strongly supports models based on magnetars that have been proposed for extragalactic fast radio bursts.

Keywords: magnetars; soft gamma-ray repeaters; interstellar scattering; radio bursts
Energization of Charged Test Particles in Magnetohydrodynamic Fields: Waves versus Turbulence Picture

Direct numerical simulations of three-dimensional compressible magnetohydrodynamic (MHD) turbulence have been performed in order to study the relation between wave modes and coherent structures and the consequent energization of test particles. Moreover, the question of which is the main mechanism of this particle energization is rigorously discussed. In particular, using the same initial conditions, we analyzed the nonlinear and linear evolution of a turbulent state along with the case of randomized phases. Then, the behaviors of the linear and nonlinear simulations were compared through the study of the time evolution of particle kinetic energy and preferential concentration. Also, spatiotemporal spectra were used to identify the presence of wave modes and quantify the fraction of energy around the MHD modes in linear and nonlinear simulations. Finally, the variation of the correlation time of the external forcing is studied in detail along with the effect on the particle energization (and clustering) and the presence of wave modes. More specifically, particle energization tends to decrease when the fraction of linear energy increases, supporting the idea that energization by structures is the dominant mechanism for particle energization instead of resonance with wave modes as suggested by Fermi energization theory.

Keywords: hydrodynamical simulations; pickup ions; interplanetary turbulence
Where and How Does a Decay-index Profile Become Saddle-like?

The decay index of solar magnetic fields is known as an important parameter in regulating solar eruptions from the standpoint of the torus instability. In particular, a saddle-like profile of decay index, which hosts a local torus-stable regime at higher altitudes than where the decay index first exceeds the instability threshold, is found to be associated with some confined or two-step eruptions. To understand the occurrence of such a profile, we employed dipoles to emulate different kinds of photospheric flux distributions. Corroborated by observations of representative active regions, our major results are as follows: (1) in bipolar configurations the critical height increases away from the AR center along the polarity inversion line (PIL) and its average is roughly half of the centroid distance between opposite polarities; (2) in quadrupolar configurations saddle-like profiles appear above the PIL when the two dipoles oriented in the same direction are significantly more separated in this direction than in the perpendicular direction, and when the two dipoles are oriented differently or have unequal fluxes; and (3) saddle-like profiles in quadrupolar configurations are associated with magnetic skeletons such as a null point or a hyperbolic flux tube, and the role of such profiles in eruptions is anticipated to be double-edged if magnetic reconnection is involved.

Keywords: solar flares; solar coronal mass ejections; solar magnetic fields
Artificial Intelligence-Assisted Inversion (AIAI) of Synthetic Type Ia Supernova Spectra

We generate ∼100,000 model spectra of Type 1a supernovae (SNe Ia) to form a spectral library for the purpose of building an artificial intelligence-assisted inversion (AIAI) algorithm for theoretical models. As a first attempt, we restrict our studies to the time around B-band maximum and compute theoretical spectra with a broad spectral wavelength coverage from 2000 to 10000 Å using the code TARDIS. Based on the library of theoretically calculated spectra, we construct the AIAI algorithm with a multiresidual convolutional neural network to retrieve the contributions of different ionic species to the heavily blended spectral profiles of the theoretical spectra. The AIAI is found to be very powerful in distinguishing spectral patterns due to coupled atomic transitions and has the capacity to quantitatively measure the contributions from different ionic species. By applying the AIAI algorithm to a set of well-observed SN Ia spectra, we demonstrate that the model can yield powerful constraints on the chemical structures of these SNe Ia. Using the chemical structures deduced from AIAI, we successfully reconstructed the observed data, thus confirming the validity of the method. We show that the light-curve decline rate of SNe Ia is correlated with the amount of 56Ni above the photosphere in the ejecta. We detect a clear decrease of 56Ni mass with time that can be attributed to its radioactive decay. Our code and model spectra are available on the website https://github.com/GeronimoChen/AIAI-Supernova.

Keywords: type ia supernovae; convolutional neural networks
Molecular Clumps Disguising Their Star Formation Efficiency per Free-fall Time: What We Can Do Not to Be Fooled

The presence of a volume-density gradient in molecular clumps allows them to raise their star formation rate compared with what they would experience if their gas were uniform in density. This higher value for the star formation rate yields in turn a higher star formation efficiency per free-fall time that we measure. The measured star formation efficiency per free-fall time, ${\epsilon }_{\mathrm{ff},\mathrm{meas}}$ , of clumps is therefore plagued by a degeneracy, as two factors contribute to it: one is the density gradient of the clump gas, the other is the intrinsic star formation efficiency per free-fall time, ${\epsilon }_{\mathrm{ff},\mathrm{int}}$ , with which the clump would form stars should there be no gas-density gradient. This paper presents a method allowing one to recover the intrinsic efficiency of a centrally concentrated clump. It hinges on the relation between the surface densities in stars and gas measured locally from clump center to clump edge. Knowledge of the initial density profile of the clump gas is not required. A step-by-step description of the method is provided as a tool in hand for observers. Once ${\epsilon }_{\mathrm{ff},\mathrm{int}}$ has been estimated, it can be compared with its measured, clump-averaged, counterpart, ${\epsilon }_{\mathrm{ff},\mathrm{meas}}$ , to quantify the impact that the initial gas-density profile of a clump has had on its star formation history.

Keywords: star clusters; molecular clouds; star formation