Constraining Heavy Axionlike Particles by Energy Deposition in Globular Cluster Stars.

Heavy axionlike particles (ALPs) with masses up to a few 100 keV and coupled with photons can be efficiently produced in stellar plasmas. We present a new "ballistic" recipe that covers both the energy-loss and energy-transfer regimes, and we perform the first dedicated simulation of Globular Cluster stars including the ALP energy transfer. This argument allows us to constrain ALPs with m_{a}≲0.4 MeV and g_{aγ}≃10^{-5} GeV^{-1}, probing a section of the ALP parameter space informally known as the "cosmological triangle". This region is particularly interesting since it has been excluded only using standard cosmological arguments that can be evaded in nonstandard scenarios.

Enhanced Supernova Axion Emission and Its Implications.

We calculate the axion emission rate from reactions involving thermal pions in matter encountered in supernovae and neutron star mergers, identify unique spectral features, and explore their implications for astrophysics and particle physics. We find that it is about 2-5 times larger than nucleon-nucleon bremsstrahlung, which in past studies was considered to be the dominant process. The axion spectrum is also found be much harder. Together, the larger rates and higher axion energies imply a stronger bound on the mass of the QCD axion and better prospects for direct detection in a large underground neutrino detector from a nearby galactic supernova.

Axionlike Particles from Hypernovae.

It was recently pointed out that very energetic subclasses of supernovae (SNe), like hypernovae and superluminous SNe, might host ultrastrong magnetic fields in their core. Such fields may catalyze the production of feebly interacting particles, changing the predicted emission rates. Here we consider the case of axionlike particles (ALPs) and show that the predicted large scale magnetic fields in the core contribute significantly to the ALP production, via a coherent conversion of thermal photons. Using recent state-of-the-art supernova (SN) simulations, including magnetohydrodynamics, we find that, if ALPs have masses m_{a}∼O(10) MeV, their emissivity in such rare but exciting conditions via magnetic conversions would be over 2 orders of magnitude larger than previously estimated. Moreover, the radiative decay of these massive ALPs would lead to a peculiar delay in the arrival times of the daughter photons. Therefore, high-statistics gamma-ray satellites can potentially discover MeV ALPs in an unprobed region of the parameter space and shed light on the magnetohydrodynamical nature of the SN explosion.

Constraints on Axionlike Particles from a Hard X-Ray Observation of Betelgeuse.

We use the first observation of Betelgeuse in hard x rays to perform a novel search for axionlike particles (ALPs). Betelgeuse is not expected to be a standard source of x rays, but light ALPs produced in the stellar core could be converted back into photons in the Galactic magnetic field, producing a detectable flux that peaks in the hard x-ray band (E_{γ}>10 keV). Using a 50 ks observation of Betelgeuse by the NuSTAR satellite telescope, we find no significant excess of events above the expected background. Using models of the regular Galactic magnetic field in the direction of Betelgeuse, we set a 95% C.L. upper limit on the ALP-photon coupling of g_{aγ}<(0.5-1.8)×10^{-11} GeV^{-1} (depending on magnetic field model) for ALP masses m_{a}<(5.5-3.5)×10^{-11} eV.

Solar Axions Cannot Explain the XENON1T Excess.

We argue that the interpretation in terms of solar axions of the recent XENON1T excess is not tenable when confronted with astrophysical observations of stellar evolution. We discuss the reasons why the emission of a flux of solar axions sufficiently intense to explain the anomalous data would radically alter the distribution of certain type of stars in the color-magnitude diagram in the first place and would also clash with a certain number of other astrophysical observables. Quantitatively, the significance of the discrepancy ranges from 3.3σ for the rate of period change of pulsating white dwarfs and exceeds 19σ for the R parameter and for M_{I,TRGB}.

Integrated system of phytodepuration and water reclamation: A comparative evaluation of four municipal wastewater treatment plants.

In dry regions, water resources have become increasingly limited, and the use of alternative sources is considered one of the main strategies in sustainable water management. A highly viable alternative to commonly used water resources is treated municipal wastewater, which could strongly benefit from advanced and low-cost techniques for depuration, such as the integrated system of phytodepuration (ISP). The current manuscript investigates four Italian case studies with different sizes and characteristics. The raw wastewaters and final effluents were sampled on a monthly basis over a period of up to five years, allowing the quantification of the ISP performances. The results obtained show that the investigated plants are characterized by an average efficiency value of approximately 83% for chemical oxygen demand removal, 84% for biochemical oxygen demand, 89% for total nitrogen, 91% for total phosphorus, and 85% for total suspended solids. Moreover, for three of the case studies, the ISP final effluent is suitable for irrigation, and in the fourth case study, the final effluent can be released in surface water.

Integrated System of Phytodepuration for Agroindustrial Wastewater: Three Different Case Studies.

The effluents deriving from agricultural industries are sources of wastewater sensibly different from common civil wastewater treatment plants effluents, because they are characterized by significant amounts of nutrients and organic load. Agricultural industries require considerable water volumes for processing the farm products, in doing so generating huge volumes of wastewater, with high concentration of chemical oxygen demand (COD), nitrogen (N) and phosphorus (P). Advanced and low cost techniques for water depuration are required in such circumstances, as the use of Integrated System of Phytodepuration (ISP). In the present work, three different case studies (a dairy, a pig feedlot and a vinegar industry) are investigated: the performances of the ISPs were evaluated analyzing raw wastewaters and final effluents over a period ranging from 2 to 4 years. The results obtained show that the designed ISPs are characterized by a mean efficiency value higher than 85% for COD removal, 73% for N and 85% for P. Moreover, for the pig feedlot the ISP final effluent is characterized by a quality level not only suited for the release into surface waters but also for irrigation, while for the other two case studies is possible to release the final effluent in surface water.

The Integrated System of Phytodepuration of Sile River Natural Park.

The water conservation topic is likely to become increasingly important and alternative water resources employment should be considered as one possible response to the challenges of fresh water demand and environmental protection; among alternative water sources, municipal wastewaters represent one of the most profitable source but in order to reuse them they need adequate and advanced depuration techniques, such as the use of Integrated System of Phytodepuration (ISP). Across a 3-year sampling period, the performances of an ISP within the Natural Park of the Sile River in the Northern Italy were evaluated, analyzing raw wastewater and final effluent characteristics according to the recommendations of European and Italian legislation. The investigated ISP represents one of the first attempts designed in Italy to improve the efficiency of an existing wastewater treatment plant, able to serve 8000 equivalent inhabitants. The results obtained during the 3 years of analysis show that the designed ISP is characterized by a general efficiency value higher than 87% for TSS removal, 79% for TN, 91% for BOD5 and 86% for COD; moreover the ISP final effluent is characterized by a quality not only suited for release into surface waters but also for irrigation.

Revisiting the bound on axion-photon coupling from globular clusters.

We derive a strong bound on the axion-photon coupling g(aγ) from the analysis of a sample of 39 Galactic Globular Clusters. As recognized long ago, the R parameter, i.e., the number ratio of stars in horizontal over red giant branch of old stellar clusters, would be reduced by the axion production from photon conversions occurring in stellar cores. In this regard, we have compared the measured R with state-of-the-art stellar models obtained under different assumptions for g(aγ). We show that the estimated value of g(aγ) substantially depends on the adopted He mass fraction Y, an effect often neglected in previous investigations. Taking as a benchmark for our study the most recent determinations of the He abundance in H ii regions with O/H in the same range of the Galactic Globular Clusters, we obtain an upper bound g(aγ)<0.66×10(-10) GeV(-1) at 95% confidence level. This result significantly improves the constraints from previous analyses and is currently the strongest limit on the axion-photon coupling in a wide mass range.

Constraining the axion-photon coupling with massive stars.

We point out that stars in the mass window ~8-12M([circumpunct]) can serve as sensitive probes of the axion-photon interaction, g(Aγγ). Specifically, for these stars axion energy losses from the helium-burning core would shorten and eventually eliminate the blue loop phase of the evolution. This would contradict observational data, since the blue loops are required, e.g., to account for the existence of Cepheid stars. Using the MESA stellar evolution code, modified to include the extra cooling, we conservatively find g(Aγγ)

Probing the axion-nucleon coupling with the next generation of axion helioscopes.

A finite axion-nucleon coupling, nearly unavoidable for QCD axions, leads to the production of axions via the thermal excitation and subsequent de-excitation of 57 Fe isotopes in the sun. We revise the solar bound on this flux adopting the up to date emission rate, and investigate the sensitivity of the proposed International Axion Observatory IAXO and its intermediate stage BabyIAXO to detect these axions. We compare different realistic experimental options and discuss the model dependence of the signal. Already BabyIAXO has sensitivity far beyond previous solar axion searches via the nucleon coupling and IAXO can improve on this by more than an order of magnitude.