Extending the sample of core-collapse supernovae for searches of axion-like-particle induced gamma-ray bursts with the Fermi LAT

During a core-collapse supernova (SN), axion-like particles (ALPs) could be produced through the Primakoff process and subsequently convert into gamma rays in the magnetic field of the Milky Way. Using a sample of well studied extragalactic SNe at optical wavelengths, we estimate the time of the core collapse and search for a coincident gamma-ray burst with the Fermi Large Area Telescope (LAT). Under the assumption that at least one SN was contained within the LAT field of view, we exclude photon-ALP couplings within a factor of $\sim$5 of previous limits from SN1987A. With the increasing number of SNe observed with optical surveys, our results demonstrate the potential to probe ALP dark matter with combined optical and gamma-ray observations. We also provide preliminary results for the estimation of explosion times of 15 close-by SNe observed recently with ZTF. Our findings show that the explosion time can be estimated within one day (statistical uncertainty only) making them promising targets for a follow-up LAT analysis.Comment: Proceedings of the 37th International Cosmic Ray Conference (ICRC 2021

Search for Axionlike-Particle-Induced Prompt Gamma-Ray Emission from Extragalactic Core-Collapse Supernovae with the Fermi Large Area Telescope

During a core-collapse supernova (SN), axionlike particles (ALPs) could be produced through the Primakoff process and subsequently convert into $\gamma$ rays in the magnetic field of the Milky Way. We do not find evidence for such a $\gamma$-ray burst in observations of extragalactic SNe with the Fermi Large Area Telescope (LAT). The SN explosion times are estimated from optical light curves and we find a probability of about $\sim$90% that the LAT observed at least one SN at the time of the core collapse. Under the assumption that at least one SN was contained within the LAT field of view, we exclude photon-ALP couplings $\gtrsim 2.6\times10^{-11}$GeV$^{-1}$ for ALP masses $m_a \lesssim 3\times 10^{-10}$ eV, within a factor of $\sim 5$ of previous limits from SN1987A.Comment: Published in Physical Review Letters. Includes Supplemental Material. 8+18 pages. Updated version fixes bug that overestimated the ALP flux. Constraints and conclusions have been updated (erratum is published). Version fixes typos in ArXiv versio

Toxicity of Food Supplements as An Adjuvant for COVID-19 Treatment or Prevention

Commercially available food supplements, especially vitamins and minerals,are be-coming increasingly popular in the era of COVID-19 pandemic. Sales of food sup-plements increased dynamicallybecause of the belief that they could be more effec-tive than conventional antiviral or corticosteroid drugs as well as missing the specific medical therapy for preventing or treating this disease.The greatest interest is asso-ciated with immune-related nutrients and antioxidant agents, including vitamin C, vitamin D, vitamin E, selenium(Se),and zinc(Zn). These are currently under clini-cal investigation for possible application in the prevention and management of COVID-19. This review summarizes postulated mechanisms of commonly used sup-plements suggested reducingthe duration and severity of viral infections by improv-ing immune response. Their toxicity in thecontext of potential adverse effects is also discussed. Whether these molecules and theamount could hurt patients with COVID-19 are research questions worth evaluating. Considering both efficacy and safety, evidence supporting larger intakes of specific nutrients with immune-boost-ing and/or antioxidant properties needs further research. Until relevant responses are provided, age and gender related tolerable upper intake levels for vitamins and min-erals should be considered to avoid weight gainingas an additional risk factor of developing complications during the disease course, besidesthe risk of inappropriate doses associated with toxicity.Herein, high-quality information respecting specific nutrients proposed to have positive effect against COVID-19 is disseminated and certain research gaps are addressed, requiring the research on the health effects of supplements to be tightly correlated to age, nutritional status, wellbeing and partic-ular to existing co-morbidities

Black holes, gravitational waves and fundamental physics: a roadmap

The grand challenges of contemporary fundamental physics—dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem—all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on 'Black holes, Gravitational waves and Fundamental Physics'

Analisi e caratterizzazione degli effetti sistematici di tipo termico sui dati di PLANCK - LFI

The cosmic microwave background radiation discovered by Penzias and Wilson in 1965, is considered one of the most important experimental evidences in favour of the Hot Big Bang standard cosmological model. This radiation provides an image of the Universe when it was about 380,000 years old and has a blackbody spectral distribution at temperature T=2.725±0.002 K, index of thermodynamic equilibrium with the mater in epoch when it was released. The cosmic background radiation presents anisotropies at level of 10 5 which provide valuable information about the origin and the evolution of the Universe. After the discovery of background radiation, tens of experiments have been performed to measure this radiation and its anisotropies. In 1992 the COBE satellite revolutionized cosmology by detecting temperature anisotropies for the first time. Launched on May 14, 2009, Planck is a European Space Agency mission designed to measure the CMB anisotropies with an accuracy set by fundamental astrophysical limits. To do this, Planck is imaging the whole sky with an unprecedented combination of sensitivity ( ΔT/T~2*10^-6), angular resolution (to 5’), and 9 frequency coverage (30 857 GHz). To reach these ambitious requirements, Planck uses an active cryogenic thermal system which cools the instruments to 0.1 K. The high sensitivity of the instrument and the cryogenic system makes the thermal systematic effects study of crucial importance to the scientific success. The thesis is divided into six chapters: 1. Chapter 1 explains the properties of the cosmic background radiation and its anisotropies2. Chapter 2 presents a short overview of the various experiments dedicated to the study of cosmic background radiation3. Chapter 3 describes the Planck mission, its instruments and its goals, in particular the Low Frequency Instrument (LFI) and its thermal structureChapter 4 discusses the analysis of the LFI thermal stability. This work was carried out in the Physics department at the University of Trieste, at the LFI Data Processing Centre located at INAF (Instituto Nazionale di AstroFisica) - OATS (Astronomical Observatory of Trieste)Chapter 5 presents the results of this analysisin Chapter 6 conclusions are drawn and proposals for future work are discussed.La radiazione cosmica di fondo nelle microonde scoperta nel 1965 da Penzias e Wilson, `e considerata una delle piu` importanti prove sperimentali a favore del modello cosmologico standard noto come Big Bang caldo. Questa radiazione, fornisce un’immagine dell’Universo quando aveva circa 380.000 anni ed ha una distribuzione spettrale di corpo nero alla temperatura T = 2.725±0.002 K, indice dell’equilibrio termodinamico con la materia nell’epoca quando `e stata rilasciata. La radiazione cosmica di fondo presenta anisotropie a livello di 10 5 che forniscono delle informazioni preziose riguardo l’origine e l’evoluzione dell’Universo. Dopo la scoperta della radiazione di fondo, sono stati condotti decine di esperimenti per misurare la radiazione e le sue anisotropie. Nel 1992, il satellite COBE ha rivoluzionato la cosmologia rilevando queste anisotropie per la prima volta. Lanciata il 14 maggio 2009, Planck `e una missione dell’Agenzia Spaziale Europea progettata per misurare le anisotropie della radiazione cosmica di fondo con una precisione senza precedenti. Planck osserva tutto il cielo con sensibilita` ΔT/T~2*10^-6, risoluzione angolare fino a 5’ e copertura in 9 bande di frequenza da 30 a 857 GHz. Per raggiungere questi ambiziosi requisiti, Planck utilizza un sistema criogenico che ra↵redda gli strumenti fino a 0.1 K. L’elevata sensibilita` dello strumento e il complesso sistema criogenico rende lo studio degli e↵etti termici sistematici (argomento principale di questa tesi) di importanza fondamentale per il successo scientifico della missione. La tesi si articola in sei capitoli: 1. nel Capitolo 1 si presentano le proprietà della radiazione cosmica di fondo e le sue anisotropie2. nel Capitolo 2 si fa una breve panoramica dei vari esperimenti dedicati allo studio della radiazione cosmica di fondo3. nel Capitolo 3 si descrive la missione Planck, i suoi strumenti ed i suoi scopi, in particolare lo strumento di bassa frequenza (Low Frequency Instrument, LFI) e la sua struttura termicanel Capitolo 4 si descrive l’analisi dei dati sulla stabilità termica dello strumento LFI di Planck. Il lavoro `e stato e↵ettuato presso il dipartimento di fisica dell’Università di Trieste e presso il Data Processing Centre di LFI situato presso INAF (Instituto Nazionale di AstroFisica) - OATS (Osservatorio Astronomico di Trieste). nel Capitolo 5 si presentano i risultati di questa analisinel Capitolo 6 si traggono le conclusioni e si mostrano le proposte per il futuro proseguimento del lavoro

Prospects for lensed supernovae behind galaxy clusters with the James Webb Space Telescope

Galaxies, and clusters of galaxies, can act as gravitational lenses and magnify the light of objects behind them. The effect enables observations of very distant supernovae, that otherwise would be too faint to be detected by existing telescopes, and allows studies of the frequency and properties of these rare phenomena when the universe was young. Under the right circumstances, multiple images of the lensed supernovae can be observed, and due to the variable nature of the objects, the difference between the arrival times of the images can be measured. Since the images have taken different paths through space before reaching us, the time-differences are sensitive to the expansion rate of the universe. One class of supernovae, Type Ia, are of particular interest to detect. Their well known brightness can be used to determine the magnification, which can be used to understand the lensing systems. I will also report our discovery of the first resolved multiply-imaged gravitationally lensed supernova Type Ia. I will also show the expectations of search campaigns that can be conducted with future facilities, such as the James Webb Space Telescope (JWST) or the Wide-Field Infrared Survey Telescope (WFIRST)

Strongly Lensed Supernovae in Well-Studied Galaxy Clusters with the Vera C. Rubin Observatory

Strong lensing by galaxy clusters can be used to significantly expand the survey reach, thus allowing observation of magnified high-redshift supernovae that otherwise would remain undetected. Strong lensing can also provide multiple images of the galaxies that lie behind the clusters. Detection of strongly lensed Type Ia supernovae (SNe Ia) is especially useful because of their standardizable brightness, as they can be used to improve either cluster lensing models or independent measurements of cosmological parameters. The cosmological parameter, the Hubble constant, is of particular interest given the discrepancy regarding its value from measurements with different approaches. Here, we explore the feasibility of the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) of detecting strongly lensed SNe in the field of five galaxy clusters (Abell 1689 and Hubble Frontier Fields clusters) that have well-studied lensing models. Considering the 88 systems composed of 268 individual multiple images in the five cluster fields, we find that the LSST will be sensitive to SNe Ia (SNe IIP) exploding in 41 (23) galaxy images. The range of redshift of these galaxies is between 1.01 < z < 3.05. During its 10 years of operation, LSST is expected to detect 0.2 ± 0.1 SN Ia and 0.9 ± 0.3 core collapse SNe. However, as LSST will observe many more massive galaxy clusters, it is likely that the expectations are higher. We stress the importance of having an additional observing program for photometric and spectroscopic follow-up of the strongly lensed SNe detected by LSST

The rise and fall of the iron-strong nuclear transient PS16dtm

Context. Thanks to the advent of large-scale optical surveys, a diverse set of flares from the nuclear regions of galaxies has recently been discovered. These include the disruption of stars by supermassive black holes at the centers of galaxies – nuclear transients known as tidal disruption events (TDEs). Active galactic nuclei (AGN) can show extreme changes in the brightness and emission line intensities, often referred to as changing-look AGN (CLAGN). Given the physical and observational similarities, the interpretation and distinction of nuclear transients as CLAGN or TDEs remains difficult. One of the obstacles of making progress in the field is the lack of well-sampled data of long-lived nuclear outbursts in AGN. Aims. Here, we study PS16dtm, a nuclear transient in a Narrow Line Seyfert 1 (NLSy1) galaxy, which has been proposed to be a TDE candidate. Our aim is to study the spectroscopic and photometric properties of PS16dtm, in order to better understand the outbursts originating in NLSy1 galaxies. Methods. Our extensive multiwavelength follow-up that spans around 2000 days includes photometry and spectroscopy in the UV/optical, as well as mid-infrared (MIR) and X-ray observations. Furthermore, we improved an existing semiempirical model in order to reproduce the spectra and study the evolution of the spectral lines. Results. The UV/optical light curve shows a double peak at ∼50 and ∼100 days after the first detection, and it declines and flattens afterward, reaching preoutburst levels after 2000 days of monitoring. The MIR light curve rises almost simultaneously with the optical, but unlike the UV/optical which is approaching the preoutburst levels in the last epochs of our observations, the MIR emission is still rising at the time of writing. The optical spectra show broad Balmer features and the strongest broad Fe II emission ever detected in a nuclear transient. This broad Fe II emission was not present in the archival preoutburst spectrum and almost completely disappeared +1868 days after the outburst. We found that the majority of the flux of the broad Balmer and Fe II lines is produced by photoionization. We detect only weak X-ray emission in the 0.5−8 keV band at the location of PS16dtm, at +848, +1130, and +1429 days past the outburst. This means that the X-ray emission continues to be lower by at least an order of magnitude, compared to archival, preoutburst measurements. Conclusions. We confirm that the observed properties of PS16dtm are difficult to reconcile with normal AGN variability. The TDE scenario continues to be a plausible explanation for the observed properties, even though PS16dtm shows differences compared to TDE in quiescent galaxies. We suggest that this event is part of a growing sample of TDEs that show broad Balmer line profiles and Fe II complexes. We argue that the extreme variability seen in the AGN host due to PS16dtm may have easily been misclassified as a CLAGN, especially if the rising part of the light curve had been missed. This implies that some changing look episodes in AGN may be triggered by TDEs. Imaging and spectroscopic data of AGN with good sampling are needed to enable testing of possible physical mechanisms behind the extreme variability in AGN