Astrophysical Models Research Articles

Energy levels, oscillator strengths, transition probabilities and lifetimes of the O-like Cl X ion

Energy levels, lifetimes, oscillator strengths and transition probabilities for the multicharged oxygen like Cl X ion have been calculated with the configuration expansion: 2s22p4, 2p6, 2s22p33p, 2s2p5, 2s22p33s, 2s22p34s, 2s22p33d, 2s22p34d, 2s2p43s and 2s2p44s. We used two methods in the calculations: the Hartree–Fock pseudo-relativistic approach and the Thomas–Fermi–Dirac–Amaldi potential approach using the Cowan and the AUTOSTRUCTURE atomic structure codes respectively. Results have been compared with available experimental data from the National Institute of Standards and Technology Atomic Spectra Database (NIST-ASD) and with results from other available calculations.There is a great lack of atomic structure data of Cl X and obtained new data will be important for physics applications and astrophysical modeling.

Astrophysical and relativistic modeling of the recoiling black hole candidate in quasar 3C 186

The compact object in quasar 3C 186 is one of the most promising recoiling black hole candidates, exhibiting both an astrometric displacement between the quasar and the host galaxy as well as a spectroscopic shift between broad and narrow lines. 3C 186 also presents a radio jet that, when projected onto the plane of the sky, appears to be perpendicular to the quasar-galaxy displacement. Assuming a gravitational-wave kick is indeed responsible for the properties of 3C 186 and using state-of-the-art relativistic modeling, we show that current observations allow for exquisite modeling of the recoiling black hole. Most notably, we find that the kick velocity and the black hole spin are almost collinear with the line of sight and the two former vectors appear perpendicular to each other only because of a strong projection effect. The targeted configuration requires substantial fine-tuning: while there is a region in the black hole binary parameter space that is compatible with 3C 186, the observed system appears to be a rare occurrence. Using archival radio observations, we explored different strategies that could potentially confirm or rule out our interpretation. In particular, we developed two observational tests that rely on the brightness ratio between the approaching and receding jet as well as the asymmetry of the jet lobes. While the available radio data provide loose constraints, deeper observations have the unique potential of unveiling the nature of 3C 186.

The Dynamics and Gravitational-wave Signal of a Binary Flying Closely by a Kerr Supermassive Black Hole

Recent astrophysical models predict that stellar-mass binary black holes (BBHs) could form and coalesce within a few gravitational radii of a supermassive black hole (SMBH). Detecting the gravitational waves (GWs) from such systems requires numerical tools that can track the dynamics of the binaries while capturing all the essential relativistic effects. This work develops upon our earlier study of a BBH moving along a circular orbit in the equatorial plane of a Kerr SMBH. Here we modify the numerical method to simulate a BBH falling toward the SMBH along a parabolic orbit of arbitrary inclination with respect to the equator. By tracking the evolution in a frame freely falling alongside the binary, we find that the eccentricity of the BBH is more easily excited than it is in the previous equatorial case, and that the cause is the asymmetry of the tidal tensor imposed on the binary when the binary moves out of the equatorial plane. Since the eccentricity reaches maximum around the same time as the BBH becomes the closest to the SMBH, multiband GW bursts could be produced that are simultaneously detectable by space- and ground-based detectors. We show that the effective spin parameters of such GW events also undergo significant variation due to the rapid reorientation of the inner BBHs during their interaction with SMBHs. These results demonstrate the richness of three-body dynamics in the region of strong gravity, and highlight the necessity of building new numerical tools to simulate such systems.

Quick recipes for gravitational-wave selection effects

Accurate modeling of selection effects is a key ingredient to the success of gravitational-wave astronomy. The detection probability plays a crucial role in both statistical population studies, where it enters the hierarchical Bayesian likelihood, and astrophysical modeling, where it is used to convert predictions from population-synthesis codes into observable distributions. We review the most commonly used approximations, extend them, and present some recipes for a straightforward implementation. These include a closed-form expression capturing both multiple detectors and noise realizations written in terms of the so-called Marcum Q-function and a ready-to-use mapping between signal-to-noise ratio (SNR) thresholds and false-alarm rates from state-of-the-art detection pipelines. The bias introduced by approximating the matched filter SNR with the optimal SNR is not symmetric: sources that are nominally below threshold are more likely to be detected than sources above threshold are to be missed. Using both analytical considerations and software injections in detection pipelines, we confirm that including noise realizations when estimating the selection function introduces an average variation of a few %. This effect is most relevant for large catalogs and specific subpopulations of sources at the edge of detectability (e.g. high redshifts).

Constraints on dark matter and astrophysics from tomographic γ -ray cross-correlations

We study the cross-correlation between maps of the unresolved γ-ray background constructed from the 12-year data release of the Large-Area Telescope, and the overdensity of galaxies in the redshift range z≲0.4 as measured by the 2MASS photometric redshift survey and the WISE-SuperCOSMOS photometric survey. A signal is detected at the 8−10σ level, which we interpret in terms of both astrophysical γ-ray sources, and weakly interacting massive particles (WIMP) dark matter decay and annihilation. The sensitivity achieved allows us to characterise the energy and redshift dependence of the signal, and we show that the latter is incompatible with a pure dark matter origin. We thus use our measurement to place an upper bound on the WIMP decay rate and the annihilation cross section, finding constraints that are competitive with those found in other analyses. Our analysis is based on the extraction of clean model-independent observables that can then be used to constrain arbitrary astrophysical and particle physics models. In this sense we produce measurements of the γ-ray emissivity as a function of redshift and rest-frame energy ϵ, and of a quantity F(ϵ) encapsulating all WIMP parameters relevant for dark matter decay or annihilation. We make these measurements, together with a full account of their statistical uncertainties, publicly available. Published by the American Physical Society 2024

Mass-redshift dependency of supermassive black hole binaries for the gravitational wave background

ABSTRACT Studying how the black hole (BH)–(galaxy) bulge mass relation evolves with redshift provides valuable insights into the co-evolution of supermassive black holes and their host galaxies. However, obtaining accurate measurement of BH masses is challenging due to the bias towards the most massive and luminous galaxies. Instead, we focus on the BH and bulge masses as they vary with redshift using the EAGLE, Illustris, TNG100, TNG300, Horizon-AGN, and SIMBA large-scale cosmological simulations. We use an analytical astrophysical model with galaxy stellar mass function, pair fraction, merger time-scale and BH–bulge mass relation extended to include redshift evolution. The model can predict the intensity of the gravitational wave background (GWB) produced by a population of supermassive black hole binary (SMBHB) as a function of the frequency. This allows us to compare the predictions of this model with the constraints of pulsar timing array observations. Here, we employ Bayesian analysis for the parameter inference. We find that all six simulations are consistent $\le 3.5\sigma$ with a range of simulated GWB spectra. By fixing the BH–bulge mass parameters to the simulations we analyse the changes in the constraints on the other astrophysical parameters. Furthermore, we also examine the variation in SMBHB merger rate with mass and redshift between these large-scale simulations.

New dark matter analysis of milky way dwarf satellite galaxies with madhatv2

We obtain bounds on dark matter annihilation using 14 years of publicly available Fermi-LAT data from a set of 54 dwarf spheroidal galaxies, using spectral information from 16 energy bins. We perform this analysis using our updated and publicly available code , which can be used to test a variety of models for dark matter particle physics and astrophysics in an accessible manner. In particular, we note that including Carina III in the analysis strengthens constraints on s-wave annihilation into two-body Standard Model final states by a factor of ∼3 but broadens the error on the constraint due to the large uncertainty of its J-factor. Our findings illustrate the importance of verifying if Carina III is in fact a dwarf spheroidal galaxy and measuring more precisely its J-factor. More generally, they highlight the significance of forthcoming discoveries of nearby ultrafaint dwarfs for dark matter indirect detection. Published by the American Physical Society 2024

Ionization of sulfur clusters, S[formula omitted] (n = 2−8) by electron collisions

This article reports the electron scattering ionization cross sections for S2, S3, S4, S5, S6, S7, and S8 target molecules essential to many fields like radiation chemistry, atmospheric, astrophysical, and astrochemical modeling. The theoretical approach utilizes a complex scattering potential ionization contribution method. The computation is carried from the ionization threshold of the target molecule to 5000 eV to investigate the entire energy range, which is significant to the ionization process of the molecules. A simple additivity rule is applied to study complex and non-spherical cases. Further, screening correction is implemented within the molecular system to reduce the overestimation in cross section values due to the overlapping charge density. A high correlation was obtained for the maximum ionization cross section value and the square root of the ratio of polarizability to the target molecule’s ionization energy, indicating the present method’s accuracy. Besides the Astro modeling applications, the cross section values also find utility in industrial plasma, sulfur lamps, lithium-sulfur batteries, and mass spectrometry.

Safety First: Stability and Dissipation of Line-tied Force-free Flux Tubes in Magnetized Coronae

Magnetized plasma columns and extended magnetic structures with both footpoints anchored to a surface layer are an important building block of astrophysical dissipation models. Current loops shining in X-rays during the growth of plasma instabilities are observed in the corona of the Sun and are expected to exist in highly magnetized neutron star magnetospheres and accretion disk coronae. For varying twist and system sizes, we investigate the stability of line-tied force-free flux tubes and the dissipation of twist energy during instabilities using linear analysis and time-dependent force-free electrodynamics simulations. Kink modes (m = 1) and efficient magnetic energy dissipation develop for plasma safety factors q ≲ 1, where q is the inverse of the number of magnetic field line windings per column length. Higher-order fluting modes (m > 1) can distort equilibrium flux tubes for q > 1 but induce significantly less dissipation. In our analysis, the characteristic pitch μ˜0 of flux-tube field lines determines the growth rate ( ∝μ˜03 ) and minimum wavelength of the kink instability ( ∝μ˜0−1 ). We use these scalings to determine a minimum flux tube length for the growth of the kink instability for any given μ˜0 . By drawing analogies to idealized magnetar magnetospheres with varying regimes of boundary shearing rates, we discuss the expected impact of the pitch-dependent growth rates for magnetospheric dissipation in magnetar conditions.

Investigating the Soft X-Ray Spectra of Solar Flare Onsets

In this study, we present the analysis of six solar flare events that occurred in 2022, using new data from the third-generation Miniature X-Ray Solar Spectrometer, also known as the Dual-zone Aperture X-ray Solar Spectrometer (DAXSS). The primary focus of this study is on the flare’s onset phase, which is characterized by elevated soft X-ray emissions even before the flare’s impulsive phase. We analyze the temporal evolution of plasma temperature, emission measure, and elemental abundance factors during the flare onset phase by fitting the DAXSS spectra with the Astrophysical Plasma Emission Code model. The model fitting results indicate that the flaring plasma is already at a high temperature (10–15 MK) during the onset period. The temperature rises during the onset phase, followed by a decrease and subsequent increase during the impulsive phase. Elemental abundance factors show a trend of falling below preflare values during the onset phase, with some recovery before the impulsive phase. During the impulsive phase, the abundance factors decrease from elevated coronal values to about photospheric values. We also analyze images from the 193 Å channel of the Atmospheric Imaging Assembly (AIA), highlighting the formation or brightening of coronal loop structures during the onset phase. Two distinct onset loop configurations are observed, which are referred to as one-loop and two-loop onsets. Both DAXSS and AIA observations indicate that the flare onset phase exhibits hot coronal plasma properties similar to those of the impulsive phase, suggesting that the onset phase may act as a preconditioning effect for some flares.

Fundamental physics studies in time domain and multi-messenger astronomy

The era of ime domain and multi-messenger astronomy is not only leading to the development of a much broader set of detectors and instruments for astrophysical observations, but is also providing the means for astronomy to tie directly to cutting-edge studies in physics. In this manner, fundamental physics (theory and experiment) coupled with a strong theoretical understanding of astrophysical phenomena (guided by high-performance computing simulations) can tie directly to the amazing new observations in astronomy. This paper discusses how physics, astrophysical models, and observations can not only help astronomy probe fundamental physics but guide the needs for next-generation astrophysical missions.

Physical properties and maximum allowable mass-radius relation of complexity-free compact stellar objects within modified gravity formalism* *The authors MKJ and SKM acknowledge that this work is carried out under TRC Project (BFP/RGP/CBS/22/014). This study is also supported via funding from Prince Sattam bin Abdulaziz University project number (PSAU/2024/R/1445). The authors are thankful to the Deanship of Graduate Studies and Scientific

This paper investigates the physical properties and predicted radii of compact stars generated by the Tolman-IV complexity-free model within the background of modified gravity theory, particularly the -gravity theory, under complexity formalism for a spherically symmetric spacetime proposed by L. Herrera [Phys Rev D 97: 044010, 2018]. By solving the resulting set of differential equations, we obtain the explicit forms of the energy-momentum (EM) tensor components, including the density, radial pressure, and tangential pressure. The influence of the parameter χ on various physical properties of the star is thoroughly investigated. The model undergoes a series of rigorous tests to determine its physical relevance. The findings indicate that the model exhibits regularity, stability, and a surface with vanishing pressure. The boundary of this surface is determined by carefully selecting the parameter space. The complexity method employed in gravity offers an interesting approach for developing astrophysical models that are consistent with observable events as demonstrated by recent experiments. In this regard, we use observational data from the GW190814 event, detected by the LIGO and Virgo observatories, to investigate the validity of the Tolman-IV model in gravity. The analysis includes comparing the model's predictions with the observed characteristics of the compact object involved in the merger. In addition, data from two-millisecond pulsars, PSR J1614-2230 and PSR J0952-0607, are incorporated to further constrain the theoretical theories. However, we present a diagram depicting the relationship between the total mass and radius of the compact object candidates for different values of χ.

DIAmante TESS AutoRegressive Planet Search (DTARPS). II. Hundreds of New TESS Candidate Exoplanets

The DIAmante TESS AutoRegressive Planet Search for the southern ecliptic hemisphere (DTARPS-S) project seeks to identify photometric transiting planets from 976,814 southern hemisphere stars observed in Year 1 of the TESS mission. This paper follows the methodology developed by Melton et al. (Paper I) using light curves extracted and preprocessed by the DIAmante project. Paper I emerged with a list of 7377 light curves with statistical properties characteristic of transiting planets but dominated by false alarms and false positives. Here a multistage vetting procedure is applied including: centroid motion and crowding metrics, false alarm and false positive reduction, photometric binary elimination, and ephemeris match removal. The vetting produces a catalog of 462 DTARPS-S candidates across the southern ecliptic hemisphere and 310 objects in a spatially incomplete Galactic plane list. 58% were not previously identified as transiting systems. Candidates are flagged for possible blending from nearby stars based on Zwicky Transient Facility data and for possible radial velocity variations based on Gaia satellite data. Orbital periods and planetary radii are refined using astrophysical modeling; the resulting parameters closely match published values for confirmed planets. The DTARPS-S population and astrophysical properties are discussed in Paper III.

The lunar 40Ar/36Ar antiquity indicator in the presence of a lunar paleomagnetosphere

The ratio of 40Ar/36Ar trapped within lunar grains, commonly known as the lunar antiquity indicator, is an important semi-empirical method for dating the time at which lunar samples were exposed to the solar wind. The behavior of the antiquity indicator is governed by the relative implantation fluxes of solar wind-derived 36Ar ions and indigenously sourced lunar exospheric 40Ar ions. Previous explanations for the behavior of the antiquity indicator have assumed constancy in both the solar wind ion precipitation and exospheric ion recycling fluxes; however, the presence of a lunar paleomagnetosphere likely invalidates these assumptions. Furthermore, most astrophysical models of stellar evolution suggest that the solar wind flux should have been significantly higher in the past, which would also affect the behavior of the antiquity indicator. Here, we use numerical simulations to explore the behavior of solar wind 36Ar ions and lunar exospheric 40Ar ions in the presence of lunar paleomagnetic fields of varying strengths. We find that paleomagnetic fields suppress the solar wind 36Ar flux by up to an order-of-magnitude while slightly enhancing the recycling flux of lunar exospheric 40Ar ions. We also find that at an epoch of ∼2 Gya, the suppression of solar wind 36Ar access to the lunar surface by a lunar paleomagnetosphere is−somewhat fortuitously−nearly equally balanced by the expected increase in the upstream solar wind flux. These counterbalancing effects suggest that the lunar paleomagnetosphere played a critical role in preserving the correlation between the antiquity indicator and the radioactive decay profile of indigenous lunar 40K. Thus, a key implication of these findings is that the accuracy of the 40Ar/36Ar indicator for any lunar sample may be strongly influenced by the poorly constrained history of the lunar magnetic field.

Beyond the Background: Gravitational-wave Anisotropy and Continuous Waves from Supermassive Black Hole Binaries

Pulsar timing arrays have found evidence for a low-frequency gravitational-wave background (GWB). Assuming that the GWB is produced by supermassive black hole binaries (SMBHBs), the next gravitational-wave (GW) signals astronomers anticipate are continuous waves (CWs) from single SMBHBs and their associated GWB anisotropy. The prospects for detecting CWs and anisotropy are highly dependent on the astrophysics of SMBHB populations. Thus, information from single sources can break degeneracies in astrophysical models and place much more stringent constraints than the GWB alone. We simulate and evolve SMBHB populations, model their GWs, and calculate their anisotropy and detectability. We investigate how varying components of our semianalytic model, including the galaxy stellar mass function, the SMBH–host galaxy relation (M BH–M bulge), and the binary evolution prescription, impact the expected detections. The CW occurrence rate is greatest for few total binaries, high SMBHB masses, large scatter in M BH–M bulge, and long hardening times. The occurrence rate depends most on the binary evolution parameters, implying that CWs offer a novel avenue to probe binary evolution. The most detectable CW sources are in the lowest frequency bin for a 16.03 yr PTA, have masses from ∼109 to 1010 M ⊙, and are ∼1 Gpc away. The level of anisotropy increases with frequency, with the angular power spectrum over multipole modes ℓ varying in low-frequency C ℓ>0/C 0 from ∼5 × 10−3 to ∼2 × 10−1, depending on the model; typical values are near current upper limits. Observing this anisotropy would support SMBHB models for the GWB over cosmological models, which tend to be isotropic.

Ultra-refractory metal assemblages in calcium-aluminum-rich inclusions: Probes of the inner solar protoplanetary disk

Calcium-aluminum-rich inclusions (CAIs) are the first formed solids in our solar system. Information regarding their formation and alteration is imprinted within their crystal structures, and so analysis of CAIs can provide insight into the early stages of solar system formation. Here we report on micrometer-sized metal grains that occur inside of fluffy type A (FTA) CAIs in the NWA 8323 and Leoville CV3 chondrites. Transmission electron microscopy (TEM) shows that the ultra-refractory metal assemblages contain subhedral grains of crystalline alloys of Pt, Os, Ir, Ru, Fe, Ni, and Mo, with minor amounts of oxides and silicates inclusions. These assemblages occur in melilite and are surrounded by or adjacent to spinel and perovskite. TEM analysis shows that the majority of the alloys present in the assemblages are significantly enriched in Pt-group elements, with compositions of 75 wt % Pt in some Fe-Ni-Pt grains, and >90 wt % Pt-group elements in Os-Ir-Ru grains. Electron diffraction shows that the alloys occur predominantly in a hexagonal (HCP) structure, with a minority of the grains exhibiting cubic (FCC) and tetragonal lattices. To support these findings, we present a thermodynamic model for the formation of hexagonal (HCP) and cubic (BCC and FCC) ultra-refractory alloys. We use an Fe-Os-Ir ternary system to approximate the various compositions and crystal structures observed in the metal grains. Modeling results indicate a condensation temperature for the alloys as high as 1831 K (HCP, 10−4 bar), placing them well above those predicted for the major CAI phases that surround them. Based on the spatial relationships of the refractory metal grains to their host CAIs, our thermodynamic predictions, and prevailing astrophysical models of the solar protoplanetary disk, the data imply that the grains could have formed inward of the regions where CAI materials condensed. We hypothesize that the refractory metal grains were transported radially outward to the part of the disk where CAIs formed and provided a nucleation site for the condensation of CAI phases such as melilite, hibonite, perovskite, and spinel.

Spectra of phosphorus ions for astrophysical modeling: P I–P XV

Phosphorus (P), a basic element of life, has been a least studied element due to its poor presence in astrophysical spectra. However, search for the P lines has increased considerably with discoveries of exoplanets and are being detected by high resolution and sophisticated astronomical observatories, e.g., James Webb Space Telescope (JWST). JWST may provide a clue for life with detection of P in its infrared (IR) region. Identification of the element and analysis of the observed spectra will require high accuracy data for atomic processes that produces lines and their predicted features. The present study focuses on these needs and reports systematically regions of wavelengths, from X-ray to IR, that show prominent lines by the 15 individual ionization stages of phosphorus, P I–P XV for the first time. We present large amount of relevant atomic data for energies, transition parameters, and lifetimes obtained in relativistic Breit–Pauli approximation using the R-matrix method and atomic structure program SUPERSTRUCTURE. Our spectral features for the 15 ions, P I–P XV, predict strengths of lines in various wavelength regions. They show dominance of P I and P II in the IR region and other ions in the ultraviolet and optical regions often stretching to IR in the continuum. For determination of accuracy, we have made extensive comparisons of our atomic data with available experimental and theoretical values. Based on these, our results and features are expected to provide precise plasma diagnostics and astrophysical modeling.

Collision induced molecular rotation of SiC4–He for astrophysical implications

ABSTRACT To probe the physical conditions in molecular clouds, observations of the rotational transitions of a molecular system are very important. Thus, accurate modelling of the emission spectra of silicon carbides requires the calculation of collision rate coefficients for its systems. We determine here, the collisional rate coefficients for the excitation of SiC4 by He using a new potential energy surface. The state-to-state rate coefficients between the lower levels (j ≤ 28) are calculated using the coupled-channel and coupled-state methods for temperatures ranging from 5 to 300 K. Finally, we model the excitation of the SiC4 radical in cold molecular clouds and star-forming regions using a radiative transfer model. For this purpose, the new rate coefficients are used to estimate the molecular abundances in interstellar clouds. Therefore, we recommend the use of this new data set in any astrophysical model of SiC4 radical excitation.

Asymetrical shape of C–He lines in the ultraviolet

ABSTRACT We present the first theoretical line profile calculations of the ultraviolet spectral lines of carbon perturbed by helium using a semiclassical collision approach and high-quality ab initio potentials and electronic transition dipole moments. The temperature range is from 5000 to 8000 K. These results are important for astrophysical modelling of spectra in atmospheres of white dwarf stars showing atomic carbon in an helium atmosphere. Beyond the conventional symmetrical Lorentzian core at low He density, these lines exhibit a blue asymmetric behaviour. This blue asymmetry is a consequence of low maxima in the corresponding C–He potential energy difference curves at short internuclear distances. The collisional profiles are carefully examined and their perturber density dependence allow to understand the various line shapes of the observed carbon spectral lines in helium-rich white dwarf photosphere where the He perturber densities reach several 1021 cm−3.

Spontaneous Stochasticity Amplifies Even Thermal Noise to the Largest Scales of Turbulence in a Few Eddy Turnover Times.

How predictable are turbulent flows? Here, we use theoretical estimates and shell model simulations to argue that Eulerian spontaneous stochasticity, a manifestation of the nonuniqueness of the solutions to the Euler equation that is conjectured to occur in Navier-Stokes turbulence at high Reynolds numbers, leads to universal statistics at finite times, not just at infinite time as for standard chaos. These universal statistics are predictable, even though individual flow realizations are not. Any small-scale noise vanishing slowly enough with increasing Reynolds number can trigger spontaneous stochasticity, and here we show that thermal noise alone, in the absence of any larger disturbances, would suffice. If confirmed for Navier-Stokes turbulence, our findings would imply that intrinsic stochasticity of turbulent fluid motions at all scales can be triggered even by unavoidable molecular noise, with implications for modeling in engineering, climate, astrophysics, and cosmology.