Photon Luminosity Research Articles

Thermal evolution and axion emission properties of strongly magnetized neutron stars

Emission properties of compact astrophysical objects such as Neutron stars (NSs) are associated with crucial astronomical observables. In the current work, we obtain the mass, pressure profiles of the non-rotating NSs using the modified Tolman Oppenheimer Volkoff (TOV) system of equations in the presence of intense magnetic field. We obtain the profiles by using a specific distance-dependent magnetic field in the modified TOV equations. We employ three different equations of states (EoS) to solve the TOV equations by assuming the core of NSs comprises a hadronic matter. Employing the above profiles, we determine the cooling rates of spherically symmetric NSs as a function of time with and without including the magnetic field using the NSCool code. We have also determined the cooling rates as a function of radius for three different NSs. Furthermore, we determine the luminosity of neutrinos, axions, and photons emitting from the NSs in the presence and absence of a magnetic field for an axion mass 16 meV and three different EoS. Our comparative study indicates that the cooling rate and luminosities of neutrinos, axions, and photons change significantly due to the impact of the strong magnetic field. We also find that due to the magnetic field, the axion mass bound increases slightly compared to without a magnetic field.

Hot bubbles of planetary nebulae with hydrogen-deficient winds. III. Formation and evolution in comparison with hydrogen-rich bubbles

We seek to understand the evolution of Wolf-Rayet central stars by comparing the diffuse X-ray emission from their wind-blown bubbles with that from their hydrogen-rich counterparts with predictions from hydrodynamical models. We simulate the dynamical evolution of heat-conducting wind-blown bubbles using our 1D radiation-hydrodynamics code NEBEL/CORONA . We use a post-AGB-model of 0.595 but allow for variations of its evolutionary timescale and wind power. We follow the evolution of the circumstellar structures for different post-AGB wind prescriptions: for O-type central stars and for Wolf-Rayet central stars where the wind is hydrogen-poor, more dense, and slower. We use the CHIANTI software to compute the X-ray properties of bubble models along the evolutionary paths. We explicitly allow for non-equilibrium ionisation of key chemical elements. A sample of 12 planetary nebulae with diffuse X-ray emission ---seven harbouring an O-type and five a Wolf-Rayet nucleus--- is used to test the bubble models. The properties of most hydrogen-rich bubbles (X-ray temperature, X-ray luminosity, size) and their central stars (photon and wind luminosity) are fairly well represented by bubble models of our 0.595 AGB remnant. The bubble evolution of Wolf-Rayet objects is different, thanks to the high radiation cooling of their carbon- and oxygen-rich winds. The bubble formation is delayed, and the early evolution is dominated by condensation instead of evaporation. Eventually, evaporation begins and leads to chemically stratified bubbles. The bubbles of the youngest Wolf-Rayet objects appear chemically uniform, and their X-ray properties can be explained by faster-evolving nuclei. The bubbles of the evolved Wolf-rayet objects have excessively low characteristic temperatures that cannot be explained by our modelling. The formation of nebulae with O-type nuclei follows mainly a single path, but the formation pathways leading to the Wolf-Rayet-type objects appear diverse. Bubbles with a pure Wolf-Rayet composition can exist for some time after their formation despite the presence of heat conduction.

Exclusive production of Tcc− in hadron-hadron ultraperipheral collisions

Understanding the production mechanisms and utilizing them as probes to investigate the structure of exotic states represent some of the most actively studied research areas in particle physics. In this study, we present a theoretical analysis of the charmed meson Tcc− in the γp→D+Tcc−Λc+ and γγ→D+Tcc−D*0 reactions, considering Tcc+ as a DD* molecule. The differential cross section and total cross section for the photoproduction of Tcc− in the γp→D+Tcc−Λc+ and γγ→D+Tcc−D*0 reactions are presented for nucleus-nucleus (nucleon-nucleon) ultraperipheral collisions at HL-LHC and RHIC, respectively. Taking into account the integrated luminosity per typical run and the luminosity of photons from the nucleus (nucleon), we observe a significant event count for Tcc− production in p−p ultraperipheral collisions at HL-LHC. Published by the American Physical Society 2024

Magnetar hard X-ray emission from axion-like particle conversion

We explore the possibility that axion-like-particles (ALPs), which would be produced in the core of magnetars and would then convert in the magnetosphere into photons, can explain magnetar hard X-ray spectra. We remark that this scenario would also provide answers to some questions related to magnetar heating. Indeed, considering that magnetars have: 1) hard X-ray spectra that are difficult to explain with known mechanisms; 2) large photon luminosities that force high core temperatures; 3) high core temperatures that imply large neutrino emissivities; 4) and large neutrino emissivities that lead to small magnetar lifetimes in contradiction to observations — explaining the hard X-ray spectra with ALPs could decrease the core temperatures and thus the neutrino emissivities, allowing for longer magnetar lifetimes as expected from observations. In this work, we initiate the study of this scenario for three magnetars with extreme luminosities, and conclude that the general idea is likely worth investigating in more detail.

Probing dark gauge boson with observations from neutron stars

We present an investigation on the production of light dark gauge bosons by the nucleon bremsstrahlung processes in the core of neutron stars. The dark vector is assumed to be a $U(1{)}_{B\ensuremath{-}L}$ gauge boson with a mass much below keV. We calculate the emission rate of the dark vector produced by the nucleon bremsstrahlung in the degenerate nuclear matter. In addition, we take into account the photon-dark vector conversion for the photon luminosity observed at infinity. Combining with the observation of J1856 surface luminosity, we find that a recently discovered excess of J1856 hard x-ray emission in the 2--8 keV energy range by X-ray Multi-Mirror Mission-Newton and Chandra x-ray telescopes could be consistently explained by a dark vector with gauge coupling ${e}^{\ensuremath{'}}=5.56\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$, mixing angle $ϵ=1.29\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}$, and mass ${m}_{{\ensuremath{\gamma}}^{\ensuremath{'}}}\ensuremath{\lesssim}{10}^{\ensuremath{-}5}\text{ }\text{ }\mathrm{eV}$. We also show that the mixing angle $ϵ>7.97\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}$ for ${m}_{{\ensuremath{\gamma}}^{\ensuremath{'}}}\ensuremath{\lesssim}3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}\text{ }\text{ }\mathrm{eV}$ and the gauge coupling ${e}^{\ensuremath{'}}>4.13\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}$ for ${m}_{{\ensuremath{\gamma}}^{\ensuremath{'}}}\ensuremath{\lesssim}1\text{ }\text{ }\mathrm{keV}$ have been excluded at 95% confidence level by the J1856 surface luminosity observation. Our best-fit dark vector model satisfies the current limits on hard x-ray intensities from the Swift and INTEGRAL hard x-ray surveys. Future hard x-ray experiments such as the Nuclear Spectroscopic Telescope Array may give a further test on our model.

Study of timing and spectral properties of the X-ray pulsar 1A 0535+262 during the giant outburst in 2020 November–December

ABSTRACT We made a detailed study of the timing and spectral properties of the X-ray pulsar 1A 0535+262 during the recent giant outburst in 2020 November and December. The flux of the pulsar reached a record value of ∼12.5 Crab as observed by Swift/BAT (15–50 keV) and the corresponding mass accretion rate was ∼6.67 × 1017 g s−1 near the peak of the outburst. There was a transition from the subcritical to the supercritical accretion regime which allows exploring different properties of the source in the supercritical regime. A q-like feature was detected in the hardness–intensity diagram during the outburst. We observed high variability and strong energy dependence of pulse profiles during the outburst. Cyclotron Resonant Scattering Feature (CRSF) was detected at ∼44 keV from the NuSTAR energy spectrum in the subcritical regime and the corresponding magnetic field was B ≃ 4.9 × 1012 G. The energy of the CRSF was shifted towards lower energy in the supercritical regime. The luminosity dependence of the CRSF was studied and during the supercritical regime, a negative correlation was observed between the line energy and luminosity. The critical luminosity was ∼6 × 1037erg s−1 above which a state transition occurred. A reversal of correlation between the photon index and luminosity was observed near the critical luminosity. The NuSTAR spectra can be described by a composite model with two continuum components, a blackbody emission, cut-off power law, and a discrete component to account for the iron emission line at 6.4 keV. An additional cyclotron absorption feature was included in the model.

Differentiating short gamma-ray bursts progenitors through multi-MeV neutrinos

With the arrival of future neutrino detectors, a new window is opening to study high-energy astrophysical sources with the help of neutrinos. This work focuses on those neutrinos produced by thermal processes within the progenitors of short gamma-ray bursts (sGRBs), a black hole-neutron star (BH-NS), or a neutron star-neutron star (NS-NS) configuration. Several numerical simulations show that whereas the remnant of the BH-NS merger preserves the magnetic field of the single neutron star (∼1012G), the magnetic field strength of the post-merger central remnant of NS-NS binary system could be amplified by several orders of magnitude, reaching values of ∼(1015−1016) G. Considering the strength of the magnetic field and the opacity created by the baryon-loaded winds ejected in each case, we study the neutrino oscillation and propagation in both scenarios to discriminate between the sGRBs progenitors. We found that it is more feasible to detect neutrinos from BH-NS mergers than those originated from NS-NS since in the second case, the neutrinos cannot go through the medium highly opaque and leave the source freely. In particular, 20 MeV-neutrinos created during an NS-NS merger can hardly leave the progenitor when they propagate with half-opening angles greater than ∼62∘. Finally, we estimate the number of events expected on the future Hyper-Kamiokande detector, finding that it is indeed possible to detect around 20 neutrinos from a burst with a typical photon luminosity of ∼8×1051 erg s−1 located at 40 Mpc.

Dipole radiation and beyond from axion stars in electromagnetic fields

We investigate the production of photons from coherently oscillating, spatially localized clumps of axionic fields (oscillons and axion stars) in the presence of external electromagnetic fields. We delineate different qualitative behaviour of the photon luminosity in terms of an effective dimensionless coupling parameter constructed out of the axion-photon coupling, and field amplitude, oscillation frequency and radius of the axion star. For small values of this dimensionless coupling, we provide a general analytic formula for the dipole radiation field and the photon luminosity per solid angle, including a strong dependence on the radius of the configuration. For moderate to large coupling, we report on a non-monotonic behavior of the luminosity with the coupling strength in the presence of external magnetic fields. After an initial rise in luminosity with the coupling strength, we see a suppression (by an order of magnitude or more compared to the dipole radiation approximation) at moderately large coupling. At sufficiently large coupling, we find a transition to a regime of exponential growth of the luminosity due to parametric resonance. We carry out 3+1 dimensional lattice simulations of axion electrodynamics, at small and large coupling, including non-perturbative effects of parametric resonance as well as backreaction effects when necessary. We also discuss medium (plasma) effects that lead to resonant axion to photon conversion, relevance of the coherence of the soliton, and implications of our results in astrophysical and cosmological settings.

The Carina Nebula and Gum 31 Molecular Complex. III. The Distribution of the 1–3 GHz Radio Continuum across the Whole Nebula

Abstract We report the most detailed 1–3 GHz radio continuum emission map of the nearest region of massive-star formation, the Carina Nebula. As part of a large program with the Australia Telescope Compact Array, we have covered ∼12 deg2, achieving an angular resolution of ∼16″, representing the largest and most complete map of the radio continuum to date. Our continuum map shows a spectacular and complex distribution of emission across the nebula, with multiple structures such as filaments, shells, and fronts across a wide range of size scales. The ionization fronts have advanced far into the southern and northern region of the Galactic plane, as fronts are clearly detected at distances of ∼80 pc from the stellar clusters in the center. We estimated an ionization photon luminosity Q H = (7. 8 ± 0.8) × 1050 s−1, which corresponds to ∼85% of the total value obtained from stellar population studies. Thus, approximately 15% of the ionizing flux has escaped from the nebula into the diffuse Galactic interstellar medium. Comparison between radio continuum and the hydrogen atomic and molecular gas maps offers a clear view of the bipolar outflow driven by the energy released by the massive stellar clusters that also affects the fraction of molecular gas across the nebula. Comparison between 8 μm and 70 μm emission maps and the radio continuum reveals how the hot gas permeates through the molecular cloud; shapes the material into features such as pillars, small shells, and arc-like structures; and ultimately escapes.

Stromlo Stellar Tracks: Non-solar-scaled Abundances for Massive Stars

Abstract We present the Stromlo Stellar Tracks, a set of stellar evolutionary tracks, computed by modifying the Modules for Experiments in Stellar Astrophysics (MESA) 1D stellar evolution package, to fit the Galactic Concordance abundances for hot (T > 8000 K) massive (≥10 M ⊙) main-sequence (MS) stars. Until now, all stellar evolution tracks have been computed at solar, scaled-solar, or α-element-enhanced abundances, and none of these models correctly represent the Galactic Concordance abundances at different metallicities. This paper is the first implementation of Galactic Concordance abundances to the stellar evolution models. The Stromlo tracks cover massive stars (10 ≤ M/M ⊙ ≤ 300) with varying rotations (v/v crit = 0.0, 0.2, 0.4) and a finely sampled grid of metallicities (−2.0 ≤ [Z/H] ≤ +0.5; Δ[Z/H] = 0.1) evolved from the pre-main sequence to the end of 12C burning. We find that the implementation of Galactic Concordance abundances is critical for the evolution of MS, massive hot stars in order to estimate accurate stellar outputs (L, T eff, g), which, in turn, have a significant impact on determining the ionizing photon luminosity budgets. We additionally support prior findings of the importance that rotation plays on the evolution of massive stars and their ionizing budget. The evolutionary tracks for our Galactic Concordance abundance scaling provide a more empirically motivated approach than simple uniform abundance scaling with metallicity for the analysis of H ii regions and have considerable implications for determining nebular emission lines and metallicity. Therefore, it is important to refine existing stellar evolutionary models for comprehensive high-redshift extragalactic studies. The Stromlo tracks are available to the astronomical community.

The ultraluminous X-ray source bubble in NGC 5585

ABSTRACT Some ultraluminous X-ray sources (ULXs) are surrounded by collisionally ionized bubbles, larger and more energetic than supernova remnants: they are evidence of the powerful outflows associated with super-Eddington X-ray sources. We illustrate the most recent addition to this class: a huge (350 pc × 220 pc in diameter) bubble around a ULX in NGC 5585. We modelled the X-ray properties of the ULX (a broadened-disc source with LX ≈ 2–4 × 1039 erg s−1) from Chandra and XMM–Newton, and identified its likely optical counterpart in Hubble Space Telescope images. We used the Large Binocular Telescope to study the optical emission from the ionized bubble. We show that the line emission spectrum is indicative of collisional ionization. We refine the method for inferring the shock velocity from the width of the optical lines. We derive an average shock velocity ≈125 km s−1, which corresponds to a dynamical age of ∼600 000 yr for the bubble, and an average mechanical power Pw ∼ 1040 erg s−1; thus, the mechanical power is a few times higher than the current photon luminosity. With Very Large Array observations, we discovered and resolved a powerful radio bubble with the same size as the optical bubble, and a 1.4-GHz luminosity ∼1035 erg s−1, at the upper end of the luminosity range for this type of source. We explain why ULX bubbles tend to become more radio luminous as they expand while radio supernova remnants tend to fade.

Super Star Clusters in the Central Starburst of NGC 4945

Abstract The nearby (3.8 Mpc) galaxy NGC 4945 hosts a nuclear starburst and Seyfert type 2 active galactic nucleus (AGN). We use the Atacama Large Millimeter/submillimeter Array (ALMA) to image the 93 GHz (3.2 mm) free–free continuum and hydrogen recombination line emission (H40α and H42α) at 2.2 pc (0.″12) resolution. Our observations reveal 27 bright, compact sources with FWHM sizes of 1.4–4.0 pc, which we identify as candidate super star clusters. Recombination line emission, tracing the ionizing photon rate of the candidate clusters, is detected in 15 sources, six of which have a significant synchrotron component to the 93 GHz continuum. Adopting an age of ∼5 Myr, the stellar masses implied by the ionizing photon luminosities are (M ⋆/M⊙) ≈ 4.7–6.1. We fit a slope to the cluster mass distribution and find β = −1.8 ± 0.4. The gas masses associated with these clusters, derived from the dust continuum at 350 GHz, are typically an order of magnitude lower than the stellar mass. These candidate clusters appear to have already converted a large fraction of their dense natal material into stars and, given their small freefall times of ∼0.05 Myr, are surviving an early volatile phase. We identify a pointlike source in 93 GHz continuum emission that is presumed to be the AGN. We do not detect recombination line emission from the AGN and place an upper limit on the ionizing photons that leak into the starburst region of Q 0 < 1052 s−1.

Comprehensive Analysis of Magnetospheric Gaps around Kerr Black Holes Using 1D GRPIC Simulations

Abstract Spark gaps are likely the source of plasma in active black hole (BH) magnetospheres. In this paper, we present results of 1D general relativistic particle-in-cell simulations of a starved BH magnetosphere with a realistic treatment of inverse-Compton scattering and pair production, for a broad range of conditions, run times longer than in previous studies, and different setups. We find that following the initial discharge, the system undergoes gradual evolution over prolonged time until either restoring the vacuum state or reaching a state of quasiperiodic oscillations, depending on the spectral shape and luminosity of the ambient radiation field. The oscillations occur near the null charge surface in cases where the global magnetospheric current is in the direction defined by the product of the asymptotic Goldreich–Julian charge density and the radial velocity, while they occur near the boundary of the simulation box when it is the opposite direction (return current). Their amplitude and the resultant luminosity of TeV photons emitted from the gap depend sensitively on the conditions; for the cases studied here the ratio of TeV luminosity to the Blandford–Znajek power ranges from 10−5 to 10−2, suggesting that strong flares may be generated by moderate changes in disk emission. We also examined the dependence of the solution on the initial number of particles per cell (PPC) and found convergence for PPC of about 50 for the cases examined. At lower PPC values the pair multiplicity is found to be artificially high, affecting the solution considerably.

A roadmap to hadronic supercriticalities: a comprehensive study of the parameter space for high-energy astrophysical sources

ABSTRACT Hadronic supercriticalities are radiative instabilities that appear when large amounts of energy are stored in relativistic protons. When the proton energy density exceeds some critical value, a runaway process is initiated resulting in the explosive transfer of the proton energy into electron–positron pairs and radiation. The runaway also leads to an increase of the radiative efficiency, namely the ratio of the photon luminosity to the injected proton luminosity. We perform a comprehensive study of the parameter space by investigating the onset of hadronic supercriticalities for a wide range of source parameters (i.e. magnetic field strengths of 1 G−100 kG and radii of 1011−1016 cm) and maximum proton Lorentz factors (103−109). We show that supercriticalities are possible for the whole range of source parameters related to compact astrophysical sources, like gamma-ray bursts and cores and jets of active galactic nuclei. We also provide an in-depth look at the physical mechanisms of hadronic supercriticalities and show that magnetized relativistic plasmas are excellent examples of non-linear dynamical systems in high-energy astrophysics.

Hard X-ray properties of radio-selected blazars

Context. Hard X-ray properties of beamed active galactic nuclei have been published in the 105-month Swift/BAT catalog, but there have not been any studies carried out so far on a well-defined, radio-selected sample of low-peaked blazars in the hard X-ray band. Aims. Using the statistically complete MOJAVE-1 sample, we aim to determine the hard X-ray properties of radio-selected blazars, including the enigmatic group of gamma-ray-faint blazars. Additionally, we aim to determine the contribution of radio-selected low-peaked blazars to the diffuse cosmic X-ray background (CXB). Methods. We determined photon indices, fluxes, and luminosities in the range of 20 keV–100 keV of the X-ray spectra of blazars and other extragalactic jets from the MOJAVE-1 sample, derived from the 105-month Swift/BAT survey. We calculated log N–log S distributions and determined the luminosity functions. Results. The majority of the MOJAVE-1 blazars are found to be hard X-ray emitters albeit many at low count rates. The log N–log S distribution for the hard X-ray emission of radio-selected blazars is clearly non-Euclidean, in contrast to the radio flux density distribution. Approximately 0.2% of the CXB in the 20 keV–100 keV band can be resolved into MOJAVE-1 blazars. Conclusions. The peculiar log N–log S distribution disparity might be attributed to different evolutionary paths in the X-ray and radio bands, as tested by luminosity-function modeling. X-ray variability can be ruled out as the dominant contributor. Low-peaked blazars constitute an intrinsically different source population in terms of CXB contribution compared to similar studies of X-ray-selected blazars. The hard X-ray flux and spectral index can serve as a good proxy for the gamma-ray detection probability of individual sources. Future observations combining deep X-ray survey, for example, with eROSITA, and targeted gamma-ray observations with CTA can benefit strongly from the tight connection between these high-energy bands for the different blazar sub-classes.

WWγ production at hadron colliders with NLO QCD+EW corrections and parton shower effects

production in proton–proton collision provides a window to the mechanism of electroweak symmetry breaking and a direct accessment to triple and quartic gauge couplings. Precision study of gauge boson self-interactions may also provide evidence of existence of new physics beyond the standard model. In this paper, we study the production at the LHC and future higher energy proton–proton colliders at the QCD+EW NLO including parton shower effects. We find that the contributions from the photon-induced (i.e. qγ- and γγ-initiated) channels are non-negligible since the photon luminosity can be enhanced significantly with the increment of colliding energy, and the large real jet emission QCD and EW corrections can be depressed sufficiently by applying the jet veto event selection scheme. Moreover, we also investigate the theoretical errors arising from the PDF uncertainty and the factorization/renormalization scale dependence.

On Stellar Evolution in a Neutrino Hertzsprung–Russell Diagram

Abstract We explore the evolution of a select grid of solar metallicity stellar models from their pre-main-sequence phase to near their final fates in a neutrino Hertzsprung–Russell diagram, where the neutrino luminosity replaces the traditional photon luminosity. Using a calibrated MESA solar model for the solar neutrino luminosity ( · × 1031 erg s−1) as a normalization, we identify ≃0.3 MeV electron neutrino emission from helium burning during the helium flash (peak , flux (10 pc/d)2 cm−2 s−1 for a star located at a distance of d parsec, timescale ≃3 days) and the thermal pulse (peak , flux × 107 (10 pc/d)2 cm−2 s−1, timescale ≃0.1 yr) phases of evolution in low-mass stars as potential probes for stellar neutrino astronomy. We also delineate the contribution of neutrinos from nuclear reactions and thermal processes to the total neutrino loss along the stellar tracks in a neutrino Hertzsprung–Russell diagram. We find, broadly but with exceptions, that neutrinos from nuclear reactions dominate whenever hydrogen and helium burn, and that neutrinos from thermal processes dominate otherwise.

Exploring the prominent channel: Charged Higgs pair production in supersymmetric two-parameter non-universal Higgs model

In this study, the charged Higgs pair production is calculated in the context of the supersymmetry at a γγ-collider. The channel is explored in Two-parameter Non-Universal Higgs Model where the model provides relatively light neutral and charged Higgs bosons. The computation is extended to one loop-level, and the divergence arising in the loop-diagrams are cured with the radiative photon correction. The production rate of the charged Higgs pair reaches up to σˆUULO+NLO=121fb at sˆ=635GeV. The analysis of the cross-section is also given varying the parameters mA and tan⁡β. The total convoluted cross-section with the photon luminosity in an e+e− machine is calculated as a function of the center-of-mass energy up to 1TeV, and it gets up to 42fb at s=900GeV depending on the polarization of the initial electron and laser photon.

A pulsar’s shocking power

Accretion onto neutron stars can generate photon luminosities well in excess of the Eddington limit. Now it has been shown that it can also produce outflows with similar mechanical power, requiring a rethink of the interaction between accretion flows and neutron star magnetospheres.

Photon--Photon Scattering in the Resonance Region at Midrapidity at the LHC

A study is presented to extend the measurements of photon-photon scattering in ultra-peripheral Pb-Pb collisions at the LHC into the mass region of the pseudoscalar resonances $\eta$ and $\eta'$. The elementary photon-photon scattering cross section is presented. The cross section for photon-photon scattering in Pb-Pb is derived by convoluting the elementary photon-photon cross section with the Pb-Pb photon luminosity. The main background to two-photon final states, arising from double $\pi^{0}$ production with two of the four decay photons escaping detection, is examined, and possible kinematical conditions are discussed to optimize the signal-to-background ratio for such measurements at mid-rapidity.