Articles publicats en revistes (Institut de Ciències del Cosmos (ICCUB))

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Enhancing the detection of low-energy M dwarf flares: wavelet-based denoising of CHEOPS data
(EDP Sciences, 2024-12-24) Poyatos, Julien; Fors Aldrich, Octavi; Gómez Cama, José María; Ribas Canudas, Ignasi
Stellar flares are powerful bursts of electromagnetic radiation triggered by magnetic reconnection in the chromosphere of stars, occurring frequently and intensely on active M dwarfs. While missions like TESS and Kepler have studied regular and super-flares, their detection of flares with energies below 10^30 erg remains incomplete. Extending flare studies to include these low-energy events could enhance flare formation models and provide insight into their impacts on exoplanetary atmospheres. This study investigates CHEOPS's capacity to detect low-energy flares in M dwarf light curves. Using CHEOPS's high photometric precision and observing cadence, along with a tailored wavelet-based denoising algorithm, we aim to improve detection completeness and refine flare statistics for low-energy events. We conducted a flare injection and recovery process to optimise denoising parameters, applied it to CHEOPS light curves to maximise detection rates, and used a flare breakdown algorithm to analyse complex structures. Our analysis recovered 349 flares with energies ranging from 2.2×10^26 to 8.1×10^30 erg across 63 M dwarfs, with ∼40% exhibiting complex, multi-peaked structures. The denoising algorithm improved flare recovery by ∼34%, though it marginally extended the lower boundary of detectable energies. For the full sample, the power-law index α was 1.92±0.07, but a log-normal distribution fit better, suggesting multiple flare formation scenarios. While CHEOPS's observing mode is not ideal for large-scale surveys, it captures weaker flares than TESS or Kepler, expanding the observed energy range. Wavelet-based denoising enhances low-energy event recovery, enabling exploration of the micro-flaring regime. Expanding low-energy flare observations could refine flare generation models and improve the understanding of their role in star-planet interactions.
The production of orbitally modulated UHE photons in LS 5039
(EDP Sciences, 2025-08) Bosch i Ramon, Valentí; Khangulyan, Dmitry
Conntext. Gamma-ray binaries present emission that is variable and can reach ultra-high energies. The processes behind the acceleration of the particles that produce this very energetic radiation are yet to be understood. Aims. We probe the properties of the particle accelerator and the ultra-high-energy photon emitter in the gamma-ray binary LS 5039. Methods. From the properties of the binary system and the ultra-high-energy radiation detected by HAWC, we used analytical tools to investigate how these properties constrain the emission and acceleration regions, namely the role of synchrotron losses, particle confinement, and the accelerated particle spectrum, and propose an acceleration scenario that can relax the derived constraints. Results. The modest target densities for hadronic processes and the overall gamma-ray orbital variability favor inverse Compton scattering of ultraviolet photons from the massive companion star by highly relativistic electrons. The acceleration of the highest energy electrons implies a constraint on synchrotron cooling in the acceleration region, which can set an upper limit on its magnetic field. Moreover, the detected variability requires very strong particle confinement in both the acceleration and emission regions, which sets a lower limit on their magnetic fields that is barely consistent with the synchrotron cooling constraint from acceleration. Synchrotron losses may be higher in the emitting region if it is separated from the accelerator, but this requires a very hard particle injection spectrum. An accelerator based on an ultrarelativistic magnetized outflow can alleviate these requirements. Conclusions. A scenario for LS 5039 of the kind proposed by Derishev and collaborators, in which an ultrarelativistic magnetized outflow accelerates leptons injected within the outflow by γγ absorption, provides a viable mechanism to accelerate very energetic electrons. This mechanism relaxes the acceleration and confinement requirements by reducing the impact of synchrotron cooling, and can generate the required particle spectrum.
C60 fullerene as an on-demand single photon source at room temperature
(American Chemical Society, 2025-10-03) Lahoz Sanz, Raul; Lozano Martín, Lidia; Brú Cortés, Adrià; Hernández Márquez, Sergi; Duocastella, Martí; Gómez Cama, José María; Juliá-Díaz, Bruno
Single photon sources are fundamental for applications in quantum computing, secure communication, and sensing, as they enable the generation of individual photons and ensure strict control over photon number statistics. However, current single photon sources can be limited by a lack of robustness, difficulty of integration into existing optical or electronic devices, and high cost. In this study, we present the use of off-the-shelf C60 fullerene molecules embedded in polystyrene as room-temperature reliable single-photon emitters. As our results demonstrate, these molecules exhibit on-demand single-photon emission, with short fluorescence lifetimes and, consequently, high emission rates. The wide availability and ease of preparation and manipulation of fullerenes as single photon sources can pave the way for the development of practical, economic and scalable quantum photonic technologies.
Using clustering for disperse objects fields segmentation in MIRADAS instrument
(Society of Photo-Optical Instrumentation Engineers (SPIE), 2018-07-06) Sabater, Josep; Torres Álvarez, Santiago; Garzón López, Francisco; Gómez Cama, José María
Mid-resolution InfRAreD Astronomical Spectrograph (MIRADAS) is a near-infrared multi-object spectrograph for Gran Telescopio Canarias (GTC). It has 12 deployable Integral Field Units (IFU) based on probe arms with pick-off mirrors, each of which can observe a different user-defined sky object. MIRADAS can work with target sets where their components are spread over such a wide area so that all of them do not fit in the field-of-view of the instrument. Therefore, data sets of that kind require, prior to capturing them, some arrangement that groups its elements in different subsets where the distance between the two most remote elements is inferior to the field-of-view diameter. This field segmentation is achieved using a hierarchical clustering technique. Our method relies on determining mutual nearest-neighbors, which will be merged if they show a given degree of similarity known beforehand. Moreover, we also compute a geometric center for these clusters, information to be delivered to the telescope’s pointing process. This step is formulated as the minimum bounding disk problem, which founds the center of the smallest radius circle enclosing all points of a cluster. Finally, we consider several real science cases and analyze the performance of the proposed solution.
Gaia's Cepheids and RR Lyrae stars and luminosity calibrations based on Tycho-Gaia Astrometric Solution
(EDP Sciences, 2017-09-08) Clementini, Gisella; Eyer, Laurent; Muraveva, Tatiana; Garofalo, A.; Ripepi, Vincenzo; Marconi, Marcella; Sarro, Luis M.; Palmer, Max; Luri Carrascoso, Xavier; Molinaro, Roberto; Rimoldini, Lorenzo; Szabados, Laszlo; Anderson, Richard I.; Musella, Ilaria
Gaia Data Release 1 contains parallaxes for more than 700 Galactic Cepheids and RR Lyrae stars, computed as part of the Tycho-Gaia Astrometric Solution (TGAS). We have used TGAS parallaxes, along with literature (V, I, J, Ks, W1) photometry and spectroscopy, to calibrate the zero point of the period-luminosity and period-Wesenheit relations of classical and type II Cepheids, and the near-infrared period-luminosity, period-luminosity-metallicity and optical luminosity-metallicity relations of RR Lyrae stars. In this contribution we briefly summarise results obtained by fitting these basic relations adopting different techniques that operate either in parallax or distance (absolute magnitude) space
Spectroscopic age estimates for APOGEE red-giant stars: Precise spatial and kinematic trends with age in the Galactic disc
(EDP Sciences, 2023-10) Anders, Friedrich; Gispert, P.; Ratcliffe, Bridget; Chiappini, C.; Minchev, I.; Nepal, Samir; Queiroz, A. B. A.; Amarante, João Antônio Silveira do; Antoja Castelltort, M. Teresa; Casali, Giada; Casamiquela, L.; Khalatyan, A.; Miglio, A.; Perottoni, Helio; Schultheis, M.
Over the last few years, many studies have found an empirical relationship between the abundance of a star and its age. Here we estimate spectroscopic stellar ages for 178 825 red-giant stars observed by the APOGEE survey with a median statistical uncertainty of 17%. To this end, we use the supervised machine learning technique XGBoost, trained on a high-quality dataset of 3060 redgiant and red-clump stars with asteroseismic ages observed by both APOGEE and Kepler. After verifying the obtained age estimates with independent catalogues, we investigate some of the classical chemical, positional, and kinematic relationships of the stars as a function of their age. We find a very clear imprint of the outer-disc flare in the age maps and confirm the recently found split in the local age-metallicity relation. We present new and precise measurements of the Galactic radial metallicity gradient in small age bins between 0.5 and 12 Gyr, confirming a steeper metallicity gradient for ∼2−5 Gyr old populations and a subsequent flattening for older populations mostly produced by radial migration. In addition, we analyse the dispersion about the abundance gradient as a function of age. We find a clear power-law trend (with an exponent β ≈ 0.15) for this relation, indicating a relatively smooth radial migration history in the Galactic disc over the past 7−9 Gyr. Departures from this power law may possibly be related to the Gaia Enceladus merger and passages of the Sagittarius dSph galaxy. Finally, we confirm previous measurements showing a steepening in the agevelocity dispersion relation at around ∼9 Gyr, but now extending it over a large extent of the Galactic disc (5 kpc < RGal < 13 kpc). To establish whether this steepening is the imprint of a Galactic merger event, however, detailed forward modelling work of our data is necessary. Our catalogue of precise stellar ages and the source code to create it are publicly available.
Superfluid rings as quantum pendulums
(American Physical Society, 2024-07-31) Muñoz Mateo, Antonio; Astrakharchik, Grigory E.; Juliá-Díaz, Bruno
A nondispersive quantum pendulum is presented. The proposed setup consists of an ultracold atomic cloud, featuring attractive interatomic interactions, loaded into a tilted ring potential. The classical and quantum domains are switched on by tuned interactions, and the classical dynamical stabilization of unstable states, i.e., à la Kapitza, is shown to be driven by quantum phase imprinting. One potential application of this system as a gravimeter is discussed.
Anomalous quantum transport in fractal lattices
(Springer Nature, 2024-08-02) Rojo Francàs, Abel; Pansari, Priyanshu; Bhattacharya, Utso; Juliá-Díaz, Bruno; Grass, Tobias
Fractal lattices are self-similar structures with repeated patterns on different scales. Quantum transport through such structures is subtle due to the possible co-existence of localized and extended states. Here, we study the dynamical properties of two fractal lattices, the Sierpiński gasket and the Sierpiński carpet. While the gasket exhibits sub-diffusive behavior, sub-ballistic transport occurs in the carpet. We show that the different dynamical behavior is in line with qualitative differences of the systems’ spectral properties. Specifically, in contrast to the Sierpiński carpet, the Sierpiński gasket exhibits an inverse power-law behavior of the level spacing distribution. As a possible technological application, we discuss a memory effect in the Sierpiński gasket which allows to read off the phase information of an initial state from the spatial distribution after long evolution times. We also show that interpolating between fractal and regular lattices allows for flexible tuning between different transport regimes.
New high-sensitivity, milliarcsecond resolution results from routine observations of lunar occultations at the ESO VLT
(EDP Sciences, 2010-11-04) Richichi, A.; Fors Aldrich, Octavi; Chen, W. -P.; Mason, E.
Context. Lunar occultations (LO) are a very efficient and powerful technique that achieves the best combination of high angular resolution and sensitivity possible today at near-infrared wavelengths. Given that the events are fixed in time, that the sources are occulted randomly, and that the telescope use is minimal, the technique is very well suited for service mode observations.Aims: We have established a program of routine LO observations at the VLT observatory, especially designed to take advantage of short breaks available in-between other programs. We have used the ISAAC instrument in burst mode, capable of producing continuous read-outs at millisecond rates on a suitable subwindow. Given the random nature of the source selection, our aim has been primarily the investigation of a large number of stellar sources at the highest angular resolution in order to detect new binaries. Serendipitous results such as resolved sources and detection of circumstellar components were also anticipated.Methods: We have recorded the signal from background stars for a few seconds, around the predicted time of occultation by the Moon's dark limb. At millisecond time resolution, a characteristic diffraction pattern can be observed. Patterns for two or more sources superimpose linearly, and this property is used for the detection of binary stars. The detailed analysis of the diffraction fringes can be used to measure specific properties such as the stellar angular size and the presence of extended light sources such as a circumstellar shell.Results: We present a list of 191 stars for which LO data could be recorded and analyzed. Results include the detection of 16 binary and 2 triple stars, all but one of which were previously unknown. The projected angular separations are as small as 4 milliarcsec and magnitude differences as high as Δ K = 5.8 mag. Additionally we derive accurate angular diameters for 2 stars and resolve circumstellar emission around another one, also all for the first time. We have established upper limits on the angular size of 177 stars, mostly in the 1 to 5 mas range, and we plan to include them in a future list of sources well suited for the calibration of interferometers.Conclusions: We confirm the performance of the technique already established in our previous work. LO at an 8 m-class telescope can achieve an angular resolution close to 0farcs001 with a sensitivity K ≈ 12 mag.
Lunar occultations of 184 stellar sources in two crowded regions toward the Galactic bulge
(EDP Sciences, 2011-08-01) Richichi, A.; Chen, W. P.; Fors Aldrich, Octavi; Wang, P. F.
Context. Lunar occultations (LO) provide a unique combination of high angular resolution and sensitivity at near-infrared wavelenghts. At the ESO Very Large Telescope, it is possible to achieve about 1 milliarcsecond (mas) resolution and detect sources as faint as K ≈ 12 mag.Aims: We have taken advantage of a passage of the Moon over two crowded and reddened regions in the direction of the inner part of the Galactic bulge to obtain a high number of occultation light curves over two half nights. Our goal was to detect and characterize new binary systems, and to investigate highly extincted and relatively unknown infrared sources in search of circumstellar shells and similar peculiarities. Our target list included a significant number of very late-type stars, but the majority of the sources was without spectral classification.Methods: An LO event requires the sampling of the light curve at millisecond rates to permit a detailed study of the diffraction fringes. For this, we used the so-called burst mode of the ISAAC instrument at the Melipal telescope. Our observing efficiency was ultimately limited by overheads for telescope pointing and data storage to about one event every three minutes.Results: We could record useful light curves for 184 sources. Of these, 24 were found to be binaries or multiples, all previously unknown. The projected separations are as small as 7.5 mas, and the magnitude differences as high as ΔK = 6.5 mag. Additionally we could also establish for the first time the resolved nature of at least two more stars, along with an indication of circumstellar emission. We were also able to put upper limits on the angular size of about 165 unresolved stars, an information that combined with previous and future observations will be very helpful in establishing a list of reliable calibrators for long baseline interferometers.Conclusions: Many of the newly detected companions are beyond the present capabilities of other high angular resolution techniques, but some could be followed up by long baseline interferometry or adaptive optics. From estimates of the stellar density we conclude that statistically the influence of chance alignments appears to be negligible. We infer that most cases are probably giant-dwarf pairs.
Optimization of the Pixel Design for Large Gamma Cameras Based on Silicon Photomultipliers
(MDPI, 2024-09-19) Wunderlich, Carolin; Paoletti, Riccardo; Guberman, Daniel
Most single-photon emission computed tomography (SPECT) scanners employ a gamma camera with a large scintillator crystal and 50–100 large photomultiplier tubes (PMTs). In the past, we proposed that the weight, size and cost of a scanner could be reduced by replacing the PMTs with large-area silicon photomultiplier (SiPM) pixels in which commercial SiPMs are summed to reduce the number of readout channels. We studied the feasibility of that solution with a small homemade camera, but the question on how it could be implemented in a large camera remained open. In this work, we try to answer this question by performing Geant4 simulations of a full-body SPECT camera. We studied how the pixel size, shape and noise could affect its energy and spatial resolution. Our results suggest that it would be possible to obtain an intrinsic spatial resolution of a few mm FWHM and an energy resolution at 140 keV close to 10%, even if using pixels more than 20 times larger than standard commercial SiPMs of 6 × 6 mm2. We have also found that if SiPMs are distributed following a honeycomb structure, the spatial resolution is significantly better than if using square pixels distributed in a square grid.
Strong interaction physics at the luminosity frontier with 22 GeV electrons at Jefferson Lab
(Società Italiana di Fisica & Springer Verlag, 2024-09-04) Gonzàlez-Solís, Sergi; Mathieu, Vincent; Perry, Robert J.
The purpose of this document is to outline the developing scientific case for pursuing an energy upgrade to 22 GeV of the Continuous Electron Beam Accelerator Facility (CEBAF) at the Thomas Jefferson National Accelerator Facility (TJNAF, or JLab). This document was developed with input from a series of workshops held in the period between March 2022 and April 2023 that were organized by the JLab user community and staff with guidance from JLab management (see Sec. 10). The scientific case for the 22 GeV energy upgrade leverages existing or already planned Hall equipment and world-wide uniqueness of CEBAF high-luminosity operations.CEBAF delivers the world’s highest intensity and high-est precision multi-GeV electron beams and has been do so for more than 25 years. In Fall 2017, with the completion of the 12 GeV upgrade and the start of the 12 GeV science program, a new era at the Laboratory began. The 12 GeV era is now well underway, with many important experimental results already published, and an exciting portfolio Program Advisory Committee approved experiments plannedfor at least the next 8–10 years [1]. At the same time, the CEBAF community is looking toward its future and the science that could be obtained through a future cost-effective upgrade to 22 GeV. The great potential to upgrade CEBAF to higher energies opens a rich and unique experimental nuclear physics program that combines illustrious history with an exciting future, extending the life of the facility well into the 2030s and beyond.JLab at 22 GeV will provide unique, world-leading science with high-precision, high-luminosity experiments elucidating the properties of quantum chromodynamics (QCD) in the valence regime (x ≥ 0.1). JLab at 22 GeV also enables researchers to probe the transition to a region of sea dominance, with access to hadrons of larger mass and different structures. With a fixed-target program at the “luminosity frontier”, large acceptance detection systems, as well as high-precision spectrometers, CEBAF will continue to offer unique opportunities to shed light on the nature of QCD and the emergence of hadron structure for decades to come. In fact, CEBAF today, and with an energy upgrade, will continue to operate with several orders of magnitude higher luminosity than what is planned at the Electron-Ion Collider (EIC). CEBAF’s current and envisioned capabilities enable exciting scientific opportunities that complement the EIC operational reach, thus giving scientists the full suite of tools necessary to comprehensively understand how QCD builds hadronic matter.The physics program laid out in this document spans a broad range of exciting initiatives that focus on a common theme, namely, investigations that explore different facets of the nonperturbative dynamics that manifest in hadron structure and probe the richness of these strongly interacting systems. The central themes of this program are reviewed in Sect. 2 - Introduction. The main components of the research program are highlighted in Sects. 3 through 8, followed by Sect. 9, which provides a brief overview of the 22 GeV CEBAF energy-doubling concept. These sections outline the key measurements in different areas of experimental studies possible at a 22 GeV CEBAF accelerator in the existing JLab experimental end stations. They provide details on the key physics outcomes and unique aspects of the programs not possible at other existing or planned facilities.
Introducing tools to test Higgs boson interactions via WW scattering. II. the coupled-channel formalism and scalar resonances
(American Physical Society, 2023) Asiáin, Iñigo; Espriu, D. (Domènec); Mescia, F. (Federico)
In this work, we explore in detail the presence of scalar resonances in the ⁢ fusion process in the context of the LHC experiments working in the theoretical framework provided by Higgs effective field theories (HEFTs). While the phenomenology of vector resonances is reasonably understood in the framework of Weinberg sum-rules and unitarization studies, scalar resonances are a lot less constrained and, more importantly, do depend on HEFT low-energy effective couplings different from the ones of vector resonances that are difficult to constrain experimentally. More specifically, unitarization techniques combined with the requirement of causality allows us to set nontrivial bounds on Higgs self-interactions. This is due to the need for considering coupled channels in the scalar case along the unitarization process. As a byproduct, we can gain some relevant information on the Higgs sector from ⁢ → ⁢ elastic processes without needing to consider two-Higgs production.
Limits on dark matter compact objects implied by supermagnified stars in lensing clusters
(Royal Astronomical Society, 2024-12-17) Vall Müller, Claudi; Miralda Escudé, Jordi
Supermagnified stars are gravitationally lensed individual stars that are located close to a caustic of a lensing galaxy cluster, and have their flux magnified by a large enough factor (typically ⁠) to make them detectable with present telescopes. The maximum magnification is limited by microlensing caused by intracluster stars or other compact objects, which create a network of corrugated critical lines with an angular width proportional to the surface density of microlenses. We consider a set of nine cases of supermagnified stars reported in the literature, and derive an upper limit on the surface density of compact objects, such as primordial black holes, that might be present as a fraction of the dark matter in addition to known intracluster stars. Any such additional compact objects would widen the corrugated critical line network and therefore the width of the distribution of supermagnified stars around the modelled critical lines of the lens. We find that any compact objects, including primordial black holes, with masses above (below which the microcaustics are closer together than the typical angular size of supermagnified stars) cannot account for more than per cent of the dark matter.
Gravitational duals from equations of state
(Springer Verlag, 2024-07-10) Bea, Yago; Jiménez, Raúl (Jiménez Tellado); Mateos, David (Mateos Solé); Shuheng, Liu; Protopapas, Pavlos; Tarancón Álvarez, Pedro; Tejerina Pérez, Pablo
Holography relates gravitational theories in five dimensions to four-dimensionalquantum field theories in flat space. Under this map, the equation of state of the field theoryis encoded in the black hole solutions of the gravitational theory. Solving the five-dimensionalEinstein’s equations to determine the equation of state is an algorithmic, direct problem.Determining the gravitational theory that gives rise to a prescribed equation of state is amuch more challenging, inverse problem. We present a novel approach to solve this problembased on physics-informed neural networks. The resulting algorithm is not only data-drivenbut also informed by the physics of the Einstein’s equations. We successfully apply it totheories with crossovers, first- and second-order phase transitions
Two waves of massive stars running away from the young cluster R136
(Nature Publishing Group, 2024-10-24) Stoop, Mitchel; Koter, Alex de; Kaper, Lex; Brands, Sarah; Portegies Zwart, Simon; Sana, Hugues; Stoppa, Fiorenzo; Gieles, Mark; Mahy, Laurent; Shenar ,Tomer; Guo, Difeng; Nelemans, Gijs; Rieder, Steven
Massive stars are predominantly born in stellar associations or clusters [1]. The irradiation fields, stellar winds, and supernovae strongly impact their local environment. In the first few million years of a cluster’s life, massive stars are dynamically1arXiv:2410.06255v1 [astro-ph.SR] 8 Oct 2024 rejected running away from the cluster at high speed [2]. However, the production rate of dynamically ejected runaways is poorly constrained. Here we report on a sample of 55 massive runaway stars ejected from the young cluster R136in the Large Magellanic Cloud. Astrometric analysis with Gaia [3–5] reveals two channels of dynamically ejected runaways. The first channel ejects massive stars in all directions and is consistent with dynamical interactions during and after the birth of R136. The second channel launches stars in a preferred direction and may be related to a cluster interaction. We find that 23-33% of the most luminous stars initially born in R136 are runaways. Model predictions [2, 6, 7] have significantly underestimated the dynamical escape fraction of massive stars. Consequently, their role in shaping and heating the interstellar and galactic medium,along with their role in driving galactic outflows, is far more important than previously thought.
Euclid: Validation of the MontePython forecasting tools
(EDP Sciences, 2024-02-08) Euclid Collaboration; Schöneberg, Nils
Context. The Euclid mission of the European Space Agency will perform a survey of weak lensing cosmic shear and galaxy clustering in order to constrain cosmological models and fundamental physics. Aims. We expand and adjust the mock Euclid likelihoods of the MontePython software in order to match the exact recipes used in previous Euclid Fisher matrix forecasts for several probes: weak lensing cosmic shear, photometric galaxy clustering, the crosscorrelation between the latter observables, and spectroscopic galaxy clustering. We also establish which precision settings are required when running the Einstein–Boltzmann solvers CLASS and CAMB in the context of Euclid. Methods. For the minimal cosmological model, extended to include dynamical dark energy, we perform Fisher matrix forecasts based directly on a numerical evaluation of second derivatives of the likelihood with respect to model parameters. We compare our results with those of previously validated Fisher codes using an independent method based on first derivatives of the Euclid observables. Results. We show that such MontePython forecasts agree very well with previous Fisher forecasts published by the Euclid Collaboration, and also, with new forecasts produced by the CosmicFish code, now interfaced directly with the two Einstein–Boltzmann solvers CAMB and CLASS. Moreover, to establish the validity of the Gaussian approximation, we show that the Fisher matrix marginal error contours coincide with the credible regions obtained when running Monte Carlo Markov chains with MontePython while using the exact same mock likelihoods. Conclusions. The new Euclid forecast pipelines presented here are ready for use with additional cosmological parameters, in order to explore extended cosmological models.
Euclid: Searching for pair-instability supernovae with the Deep Survey
(EDP Sciences, 2022) Moriya, T.J.; Inserra, C.; Courbin, Frédéric; Euclid Collaboration
Pair-instability supernovae are theorized supernovae that have not yet been observationally confirmed. They are predicted to exist in low-metallicity environments. Because overall metallicity becomes lower at higher redshifts, deep near-infrared transient surveys probing high-redshift supernovae are suitable to discover pair-instability supernovae. The Euclid satellite, which is planned launch in 2023, has a near-infrared wide-field instrument that is suitable for a high-redshift supernova survey. The Euclid Deep Survey is planned to make regular observations of three Euclid Deep Fields (40 deg2 in total) spanning Euclid’s six-year primary mission period. While the observations of the Euclid Deep Fields are not frequent, we show that the predicted long duration of pair-instability supernovae would allow us to search for high-redshift pair-instability supernovae with the Euclid Deep Survey. Based on the current observational plan of the Euclid mission, we conduct survey simulations in order to estimate the expected numbers of pair-instability supernova discoveries. We find that up to several hundred pair-instability supernovae at z . 3.5 can be discovered within the Euclid Deep Survey. We also show that pair-instability supernova candidates can be efficiently identified by their duration and color, which can be determined with the current Euclid Deep Survey plan. We conclude that the Euclid mission can lead to the first confirmation of pair-instability supernovae if their event rates are as high as those predicted by recent theoretical studies. We also update the expected numbers of superluminous supernova discoveries in the Euclid Deep Survey based on the latest observational plan.
TDCOSMO: IX. Systematic comparison between lens modelling software programs: Time-delay prediction for WGD 2038-4008
(EDP Sciences, 2022) Courbin, Frédéric
The importance of alternative methods for measuring the Hubble constant, such as time-delay cosmography, is highlighted by the recent Hubble tension. It is paramount to thoroughly investigate and rule out systematic biases in all measurement methods before we can accept new physics as the source of this tension. In this study, we perform a check for systematic biases in the lens modelling procedure of time-delay cosmography by comparing independent and blind time-delay predictions of the system WGD 2038−4008 from two teams using two different software programs: glee and lenstronomy. The predicted time delays from the two teams incorporate the stellar kinematics of the deflector and the external convergence from line-of-sight structures. The un-blinded timedelay predictions from the two teams agree within 1.2σ, implying that once the time delay is measured the inferred Hubble constant will also be mutually consistent. However, there is a ∼4σ discrepancy between the power-law model slope and external shear, which is a significant discrepancy at the level of lens models before the stellar kinematics and the external convergence are incorporated. We identify the difference in the reconstructed point spread function (PSF) to be the source of this discrepancy. When the same reconstructed PSF was used by both teams, we achieved excellent agreement, within ∼0.6σ, indicating that potential systematics stemming from source reconstruction algorithms and investigator choices are well under control. We recommend that future studies supersample the PSF as needed and marginalize over multiple algorithms or realizations for the PSF reconstruction to mitigate the systematics associated with the PSF. A future study will measure the time delays of the system WGD 2038−4008 and infer the Hubble constant based on our mass models.
Final state rescattering effects in axio-hadronic η and η' decays
(Springer Verlag, 2024-07-30) Alves, Daniele S.M.; Gonzàlez-Solís, Sergi
It has been long-understood that final state rescattering effects provide O(1) corrections to hadronic meson decays rates, such as η →πππ and η′→ηππ. Hence, one would expect that such effects would be just as important in axio-hadronic η and η′decays, such as η(′) →ππa, where a is an axion or axion-like particle (ALP). And indeed they are, as we show in this paper by using the treatment of dispersion relations to include the effects of strong final state interactions in several axio-hadronic processes, namely, η(′) →π0π0a, η(′) →π+π−a, and η′→ηπ0a. We also compute the perturbative, leading order decay rates for multiple ALP emission, such as in η(′) →π0aa, η′ →ηaa and η(′) →aaa, and briefly discuss the expected corrections from strong interactions and the processes that must be considered for an accurate rate estimation of these multi-ALP decay channels.

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