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Articles publicats en revistes (Física Quàntica i Astrofísica)

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    Time-resolved solvation of alkali ions in superfluid helium nanodroplets: Theoretical simulationof a pump–probe study
    (American Institute of Physics (AIP), 2025-10-11) García-Alfonso, Ernesto; Barranco Gómez, Manuel; Pi Pericay, Martí; Halberstadt, Nadine
    The solvation process of an alkali ion (Na+, K+, Rb+, and Cs+) inside a superfluid 4He2000 nanodroplet is investigated theoretically using liquid 4He time-dependent density functional theory at zero temperature. We simulate both steps of the pump–probe experiment conducted on Na+ [Albrechtsen et al., Nature 623, 319 (2023)], where the alkali atom residing at the droplet surface is ionized by the pump pulse and its solvation is probed by ionizing a central xenon atom and detecting the expulsed Na+Hen ions. Our results confirm the Poissonian model for the binding of the first five He atoms for the lighter Na+ and K+ alkalis, with a rate in good agreement with the more recent experimental results on Na+ [Albrechtsen et al., J. Chem. Phys. 162, 174309 (2025)]. For the probe step, we show that the ion takes several picoseconds to get out of the droplet. During this rather long time, the solvation structure around it is very hot and far from equilibrium, and it can gain or lose more He atoms. Surprisingly, analyzing the Na+ solvation structure energy reveals that it is not stable by itself during the first few picoseconds of the solvation process. After that, energy relaxation follows a Newton behavior, as found experimentally, but with a longer time delay, 5.0 ≤ t0 ≤ 6.5 ps vs 0.23 ± 0.06 ps, and characteristic time, 7.3 ≤ τ ≤ 16.5 ps vs 2.6 ± 0.4 ps. We conclude that the first instants of the solvation process are highly turbulent and that the solvation structure is stabilized only by the surrounding helium “solvent.”
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    Characterizing the Multiple Protostellar System VLA 1623-2417 with JWST, ALMA, and VLA: Outflow Origins, Dust Growth, and an Unsettled Disk
    (Institute of Physics (IOP), 2025-03) Forbrich, Jan; Girart, Josep M.; Hoare, Melvin G.; Hernández Garnica, Ricardo; Jiménez-Serra, Izaskun; Loinard, Laurent; Ordóñez-Toro, Jazmín; Podio, Linda; Radley, Isaac C.; Busquet Rico, Gemma; Ilee, John D.; Liu, Hauyu Baobab; Pineda, Jaime E.; Pontoppidan, Klaus M.; Macías, Enrique; Maureira, María José; Bianchi, Eleonora; Bourke, Tyler L.; Codella, Claudio
    Utilizing the James Webb Space Telescope (JWST), the Atacama Large Millimeter/submillimeter Array (ALMA), and the Very Large Array (VLA), we present high angular resolution (0 06–0 42), multiwavelength (4 μm–3 cm) observations of the VLA 1623-2417 protostellar system to characterize the origin, morphology and, properties of the continuum emission. JWST observations at 4.4 μm reveal outflow cavities for VLA 1623 A and, for the first time, VLA 1623 B, as well as scattered light from the upper layers of the VLA 1623 W disk. We model the millimeter-centimeter spectral energy distributions to quantify the relative contributions of dust and ionized gas emission, calculate dust masses, and use spectral index maps to determine where optical depth hinders this analysis. In general, all objects appear to be optically thick down to ∼90 GHz, show evidence for significant amounts (tens to hundreds of M⊕) of large (>1 mm) dust grains, and are dominated by ionized gas emission for frequencies ≲15 GHz. In addition, we find evidence of unsettled millimeter dust in the inclined disk of VLA 1623 B possibly attributed to instabilities within the circumstellar disk, adding to the growing catalog of unsettled Class 0/I disks. Our results represent some of the highest-resolution observations possible with current instrumentation, particularly in the case of the VLA. However, our interpretation is still limited at low frequencies (≲22 GHz) and thus motivates the need for next-generation interferometers operating at centimeter wavelengths.
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    ALMA-IMF: XIX. C18O (J = 2─1): Measurements of turbulence in 15 massive protoclusters
    (EDP Sciences, 2025-10) Busquet Rico, Gemma; Braine, J.; Liu, H.-L.; Csengeri, T.; Gusdorf, A.; Fernández-López, Manuel; Cunningham, N.; Bronfman, L.; Bonfand, Mélisse; Koley, Atanu; Stutz, Amelia; Louvet, F.; Motte, Frédérique; Ginsburg, A.; Galván-Madrid, Roberto; Álvarez-Gutiérrez, Rodrigo H.; Sanhueza, Patricio; Baug, T.; Sandoval-Garrido, N.; Salinas, J.
    ALMA-IMF is a Large Program of the Atacama Large Millimeter/submillimeter Array (ALMA) that aims to determine the origin of the core mass function (CMF) of 15 massive Galactic protoclusters (~1.0─25.0 × 103 M⊙ within ~2.5 × 2.5 pc2) located toward the Galactic plane. In addition, the objective of the program is to obtain a thorough understanding of their physical and kinematic properties. Here we study the turbulence in these protoclusters with the C18O (2─1) emission line using the sonic Mach number analysis (Ms) and the size-linewidth relation. The probability distribution functions (PDFs) for Ms show a similar pattern, exhibiting no clear trend associated with evolutionary stage, peaking in the range between 4 and 7, and then extending to ~25. Such values of Ms indicate that the turbulence in the density regime traced by the C18O line inside the protoclusters is supersonic in nature. In addition, we compared the non-thermal velocity dispersions (σnth,C18O) obtained from the C18O (2─1) line with the non-thermal line widths (σnth, DCN) of the cores obtained from the DCN (3─2) line. We observed that, on average, the non-thermal linewidth in cores is half that of the gas surrounding them. This suggests that turbulence diminishes at smaller scales or dissipates at the periphery of the cores. Furthermore, we examined the size-linewidth relation for the structures we extracted from the position-position-velocity C18O (2─1) line emission cube with the dendrogram algorithm. The power-law index (p) obtained from the size-linewidth relation is between 0.41 and 0.64, steeper than the Kolmogorov law of turbulence, as expected for compressible media. In conclusion, this work is one of the first to carry out a statistical study of turbulence for embedded massive protoclusters.
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    ALMA-IMF: XVIII. The assembly of a star cluster: Dense N2H+ (1─0) kinematics in the massive G351.77 protocluster
    (EDP Sciences, 2025-04) Koley, Atanu; Sanhueza, Patricio; Bernal-Mesina, G.; Braine, J.; Bronfman, L.; Busquet Rico, Gemma; Csengeri, T.; Di Francesco, James; Fernández-López, Manuel; Garcia, Pablo; Sandoval-Garrido, Nicolás A.; Stutz, Amelia; Álvarez-Gutiérrez, Rodrigo H.; Galván-Madrid, Roberto; Motte, Frédérique; Ginsburg, A.; Cunningham, N.; Reyes-Reyes, S.; Redaelli, E.; Bonfand, Mélisse; Gusdorf, A.; Salinas, J.; Liu, H.-L.
    ALMA-IMF observed 15 massive protoclusters capturing multiple spectral lines and the continuum emission. Here, we focus on the massive protocluster G351.77 (~2500 M⊙, estimated from single-dish continuum observations) located at 2 kpc. We trace the dense gas emission and kinematics with N2H+ (1–0) at ~4 kau resolution. We estimate an N2H+ relative abundance of ~(1.66 ± 0.46) × 10−10. We decompose the N2H+ emission into up to two velocity components, highlighting the kinematic complexity in the dense gas. By examining the position-velocity (PV) and position-position-velocity (PPV) diagrams on small scales, we observe clear inflow signatures (V-shapes) associated with 1.3 mm cores. The most prominent V-shape has a mass inflow rate of ~13.45 × 10−4 M⊙ yr−1 and a short timescale of ~11.42 kyr. We also observe V-shapes without associated cores. This suggests both that cores or centers of accretion exist below the 1.3 mm detection limit, and that the V-shapes may be viable tracers of very early accretion and star formation on ~4 kau scales. The large-scale PV diagram shows that the protocluster is separated into two principal velocity structures separate by ~2 km s−1. Combined with smaller-scale DCN and H2CO emission in the center, we propose a scenario of larger-scale slow contraction with rotation in the center based on simple toy models. This scenario is consistent with previous lines of evidence, and leads to the new suggestion of outside-in evolution of the protocluster as it collapses. The gas depletion times implied by the V-shapes are short (~0.3 Myr), requiring either very fast cluster formation, and/or continuous mass feeding of the protocluster. The latter is possible via the Mother Filament that G351.77 is forming out of. The remarkable similarities in the properties of G351.77 and the recently published work in G353.41 indicate that many of the physical conditions inferred via the ALMA-IMF N2H+ observations may be generic to protoclusters.
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    Erosion of a dense molecular core by a strong outflow from a massive protostar
    (EDP Sciences, 2025-03) López-Vázquez, Jesús Alejandro; Fernández-López, Manuel; Girart, Josep Miquel; Curiel, Salvador; Estalella, Robert; Busquet Rico, Gemma; Zapata, Luis; Lee, Chin-Fei; Galván-Madrid, Roberto
    Context. Molecular outflows from massive protostars can impact the interstellar medium in different ways, adding turbulence on different spatial scales, dragging material at supersonic velocities, producing shocks and heating, and physically impinging onto dense structures that may be harboring other protostars. Aims. We aim to quantify the impact of the outflow associated with the high-mass protostar GGD 27-MM2(E) on its parent envelope and how this outflow affects its environment. Methods. We present Atacama Large Millimeter/submillimeter Array Band 3 observations of N2H+ (1–0) and CH3CN (5–4), as well as Band 7 observations of the H2CO molecular line emissions from the protostellar system GGD 27-MM2(E). Through position–velocity diagrams along and across the outflow axis, we studied the kinematics and structure of the outflow. We also fit extracted spectra of the CH3CN emission to obtain the physical conditions of the gas. We use the results to discuss the impact of the outflow on its surroundings. Results. We find that N2H+ emission traces a dense molecular cloud surrounding GGD 27-MM2(E). We estimate that the mass of this cloud is ~13.3–26.5 M⊙. The molecular cloud contains an internal cavity aligned with the H2CO-traced molecular outflow. The outflow, also traced by CH3CN, shows evidence of a collision with a molecular core (MC), as indicated by the distinctive increases in the distinct physical properties of the gas such as the excitation temperature, column density, line width, and velocity. This collision results in an X-shaped structure in the northern part of the outflow around the position of the MC, which produces spray-shocked material downstream in the north of MC, as observed in position–velocity diagrams both along and across the outflow axis. The outflow has a mass of 1.7–2.1 M⊙, a momentum of 7.8–10.1 M⊙ km s‑1, a kinetic energy of 5.0–6.6×1044 erg, and a mass-loss rate of 4.9–6.0×10‑4 M⊙ yr‑1. Conclusions. The molecular outflow from GGD 27-MM2(E) significantly perturbs and erodes its parent cloud, compressing the gas of sources such as the MC and ALMA 12. The feedback from this powerful protostellar outflow helps maintain the turbulence in the surrounding area.
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    The SOFIA Massive (SOMA) star formation Q-band follow-up: II. Hydrogen recombination lines towards high-mass protostars
    (EDP Sciences, 2025-10) Gaches, Brandt A. L.; Saberi, Maryam; Das, Ankan; Gorai, Prasanta; Taniguchi, Kotomi; Tan, Jonathan C.; Gómez-Garrido, Miguel; Rosero, Viviana; Jiménez-Serra, Izaskun; Zhang, Yichen; Cosentino, Giuliana; Law, Chi-Yan; Fedriani, Rubén; Busquet Rico, Gemma
    Context. Hydrogen recombination lines (HRLs) are valuable diagnostics of the physical conditions in ionized regions surrounding high-mass stars. Understanding these lines, including broadening mechanisms and intensity trends, can provide insights into HII region densities, temperatures, and kinematics. Aims. This study aims to investigate the physical properties of ionized gas around massive protostars by analysing the HRLs (Hα and Hβ) in the Q band. Methods. We carried out observations using the Yebes 40m radio telescope in the Q band (30.5─50 GHz) towards six high-mass protostars selected from the SOMA Survey (G45.12+0.13, G45.47+0.05, G28.20−0.05, G35.20−0.74, G19.08−0.29, and G31.28+0.06). The observed line profiles were analysed to assess broadening mechanisms, and electron densities and temperatures were derived. The results were compared with available Q-band data from the TianMa 65-m Radio Telescope (TMRT) that have been reported in the literature, and ALMA Band 1 (35─50 GHz) Science Verification observations towards Orion KL, analysed in this study. Results. A total of eight Hα (n = 51 to 58) and ten Hβ (n = 64 to 73) lines were detected towards G45.12+0.13, G45.47+0.05, and G28.20−0.05; there were no detections in other sources. We derived electron densities of ~1−5 × 106 cm−3 and temperatures of 8000─10 000 K for the sources. However, for Orion KL, we obtained an electron density one order of magnitude lower, while its temperature was found to be more similar. Interestingly, G45.12 and G28.20 show an increasing intensity trend with frequency for both Hα and Hβ transitions, contrary to the decreasing trend observed in Orion KL. Conclusions. The line widths of the detected HRLs indicate contributions from both thermal and dynamical broadening, suggesting the presence of high-temperature ionized gas that is likely kinematically broadened (e.g. due to turbulence, outflows, rapid rotation, or stellar winds). Pressure broadening caused by electron density may also have a minor effect. We discuss different scenarios to explain the measured line widths of the HRLs. The contrasting intensity trends between the sources may reflect variations in local physical conditions or radiative transfer effects, highlighting the need for further investigation through higher-resolution observations and detailed modelling.
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    Evidence for Jet/Outflow Shocks Heating the Environment around the Class I Protostellar Source Elias 29: FAUST XXI
    (Institute of Physics (IOP), 2025-02) Oya, Yoko; Saiga, Eri; Miotello, Anna; Koutoulaki, Maria; Johnstone, Doug; Ceccarelli, Cecilia; Chandler, Claire J.; Codella, Claudio; Sakai, Nami; Bianchi, Eleonora; Bouvier, Mathilde; Charnley, Steven; Busquet Rico, Gemma; et al.
    We have observed the late Class I protostellar source Elias 29 at a spatial resolution of 70 au with the Atacama Large Millimeter/submillimeter Array as part of the FAUST Large Program. We focus on the line emission of SO, while that of 34SO, C18O, CS, SiO, H13CO+, and DCO+ are used supplementarily. The spatial distribution of the SO rotational temperature (Trot(SO)) is evaluated by using the intensity ratio of its two rotational excitation lines. Besides in the vicinity of the protostar, two hot spots are found at a distance of 500 au from the protostar; Trot(SO) locally rises to 53 K at the interaction point of the outflow and the southern ridge, and 72 K within the southeastern outflow probably due to a jet-driven bow shock. However, the SiO emission is not detected at these hot spots. It is likely that active gas accretion through the disk-like structure and onto the protostar still continues even at this evolved protostellar stage, at least sporadically, considering the outflow/jet activities and the possible infall motion previously reported. Interestingly, Trot(SO) is as high as 20–30 K even within the quiescent part of the southern ridge apart from the protostar by 500–1000 au without clear kinematic indication of current outflow/jet interactions. Such a warm condition is also supported by the low deuterium fractionation ratio of HCO+ estimated by using the H13CO+ and DCO+ lines. The B-type star HD147889 ∼0.5 pc away from Elias 29, previously suggested as a heating source for this region, is likely responsible for the warm condition of Elias 29.
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    Predictors of long-term survival in patients with a first episode of acute heart failure
    (Polskie Towarzystwo Kardiologiczne) Repullo, Daniel; Fuentes, Lidia; Anaya Bustos, Sara; Miñana, Gemma; Llorens Soriano, Pere; Miró i Andreu, Òscar; Romero-Carrete, Carlos Jose; Alquézar Arbé, Aitor; Nuñez, Julio; Gil Espinosa, Victor; Jacob, Javier; Aguirre, Alfons; Villarejo Jimenez, Ana; Borja-Cano, Maria; de la Espriella, Rafael; Santas, Enrique; Sánchez Marcos, Carolina
    Introduction: Acute heart failure (AHF) represents a critical event in heart failure progression, but data on long-term outcomes after first hospitalization remain scarce. The aim is to describe long-term survival and evaluate its predictors after the first episode of AHF. Material and methods: Patients from five Spanish hospitals with a confirmed first diagnosis of AHF were categorized based on survival (≥5 or <5 years). Thirteen independent variables were identified. Mortality was assessed using Kaplan-Meier curves after up to 10 years of follow-up. Adjusted odds ratios (OR) with 95% confidence intervals (CI) for mortality were calculated. Additionally, adjusted survival probabilities according to patient age and left ventricular ejection fraction (LVEF) were obtained using restricted cubic splines. Results: A total of 1986 patients were included, with a median age 76 years (range: 68-82), 50% women, and 57% with preserved LVEF. Five-year mortality was 52%. Adjusted analysis showed that age (OR, 0.470 per 10-year increment; 95% CI, 0.421-0.525), New York Heart Association class III-IV vs. I (OR, 0.476; 95% CI, 0.341-0.666) and II vs. I (OR, 0.780; 95% CI, 0.627-0.969), chronic kidney disease (OR, 0.609; 95% CI, 0.452-0.820), coronary artery disease (OR, 0.657; 95% CI, 0.523-0.824), diabetes mellitus (OR, 0.658; 95% CI, 0.534-0.811), and male sex (OR, 0.774; 95% CI, 0.625-0.958) were associated with death within 5 years. LVEF at inclusion was not related to 5-year survival. Conclusions: Survival after a first AHF episode is poor, with age, New York Heart Association class, kidney function, coronary artery disease, diabetes, and sex being key predictors of long-term mortality.
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    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.
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    Probing the detectability of electromagnetic signatures from Galactic isolated black holes
    (EDP Sciences, 2025-08) Martinez, Javier Rodrigo; Bosch i Ramon, Valentí; Vieyro, Florencia; del Palacio, Santiago
    Context. A large number of isolated stellar-mass black holes (IBHs) are expected to populate the Galaxy. However, only one has been confirmed by the analysis of a microlensing event, and no confirmed emission detection from an IBH has been reported so far. Aims. We analysed the detectability of electromagnetic signatures from IBHs moving in the Galaxy. Methods. We considered accretion from the interstellar medium onto an IBH and assumed the formation of an outflow. We then semi-analytically modelled the accretion process and the interaction of the outflow with the surrounding medium on large scales, including mechanical feedback on the accretion process. Furthermore, we also (semi-)analytically calculated the emission from three different regions: the accretion region, the thermal and the non-thermal radiation from the outflow-medium interaction structure, and the non-thermal emission of relativistic particles that diffuse in the surrounding medium. Results. Our results show that multi-wavelength emission associated with Galactic IBHs can be detected in systems moving through a very dense medium such as the core of a molecular cloud. In particular, thermal emission from accretion could be observed in the mid-infrared and in hard X-rays with current and forthcoming observatories. Thermal and non-thermal emission from the outflowmedium shock could also be detected in the radio and millimetre ranges. Moreover, detection of the emission from particles diffusing in a dense medium could be feasible in γ-rays. Applying our model to the IBH associated with the gravitational microlensing event MOA-2011-BLG-191/OGLE-2011-BLG-0462, we inferred that radio and infrared detection of the IBH is plausible. Also, we derived that IBHs could be modest Galactic cosmic ray contributors, potentially reaching a ∼1% contribution at E >~ 1 PeV. Finally, by extending our model to primordial black holes, we conclude that efficient leptonic acceleration in their outflow-medium interactions would rule them out as a major dark matter component.
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    Ionization cross section of the Cu shell by electron impact from the threshold to 90 keV, determined on the basis of diagram lines, satellite lines, and the radiative Auger effect
    (American Physical Society, 2025) Barros, Suelen F.; Dardengo, Kai L.; Maidana, Nora L.; Mangiarotti, Alessio; Vanin, Vito R.; Fernández Varea, José María
    The Cu ionization cross section by electron impact has been measured in the energy range from the -shell threshold to 90keV. To this end, a thin Cu film deposited on a thin C backing has been employed. The x rays emitted by the target have been detected by two silicon drift detectors placed at front and back angles with respect to the direction of the incident beam, which allowed us to better assess the peak fit procedure of the multiplet. A careful analysis of the Cu x-ray spectra generated by electron bombardment has been conducted, including not only the diagram lines but also the satellite lines and the counts that come from the radiative Auger effect. This enabled us to obtain the ⁢ and ⁢ x-ray production cross sections with relative uncertainties of the order of 5%, and the -shell ionization cross section with a precision around 7.5%. We show that, in most cases, the ionization cross sections reported according to current practice cannot be compared with the available theoretical calculations because the latter do not account for multiple-ionization effects. Our results agree with the distorted-wave Born approximation only when the x-ray counts from satellite lines, which amount to about 20% of the total, are excluded.
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    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.
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    Burst or Bust: ISAAC at Antu Sets New Standards with Lunar Occultations
    (European Southern Observatory, 2006-12) Richichi, Andrea; Fors Aldrich, Octavi; Mason, Elena; Stegmeier, Jörg
    Imagine a car as fast as a Ferrari, and as cheap as a Trabi. Sounds crazy? Maybe it is, but when it comes to high angular resolution in astronomy there is something that comes close to the miracle: lunar occultations. As the Moon moves over a background star, the phenomenon of diffraction causes tenuous, quick fringes to appear in the stellar light just before it vanishes. The fringes carry valuable information on the size of the source, on scales much smaller than possible with even a perfect, extremely large telescope. Paranal is now superbly equipped to perform this kind of observation, and for that matter all sorts of high-speed near-IR photometry. And the results are impressive. Find out more about the ISAAC burst mode, which is now officially supported from Period 79.
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    The Beauty of Speed
    (European Southern Observatory, 2009-03) Richichi, Andrea; Barbieri, Cesare; Fors Aldrich, Octavi; Mason, Elena; Naletto, Giampiero
    The burst mode of ISAAC has been used systematically to record lunar occultations with high time resolution, producing several unique new results that remain unattainable by any other technique. This is not the only possible choice of instrument for high time resolution, and fast time modes of one kind or another have been implemented on several other ESO instruments. We provide a brief overview of the present capabilities and summarise some scientific results. We speculate about the future of high temporal resolution applications, presenting the trail-blazing instrument Iqueye that recently completed its first technical run at La Silla.
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    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.
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    Improved π0,η,η′ transition form factors in resonancechiral theory and their aHLbL μ contribution
    (Springer Verlag, 2024-12-27) Estrada, Emilio J.; Gonzàlez-Solís, Sergi; Guevara, Adolfo; Roig, Pablo
    Working with Resonance Chiral Theory, within the two resonance multiplets saturation scheme, we satisfy leading (and some subleading) chiral and asymptotic QCD constraints and accurately fit simultaneously the π0,η,η′transition form factors, for single and double virtuality. In the latter case, we supplement the few available measurements with lattice data to ensure a faithful description. Mainly due to the new results for the doubly virtual case, we improve over existing descriptions for the η and η′. Our evaluationof the corresponding pole contributions to the hadronic light-by-light piece of the muon g−2 read: aπ0-pole µ=(61.9 ±0.6+2.4−1.5)×10−11, aη-poleµ=(15.2 ±0.5+1.1−0.8)×10−11 and aη′-poleµ=(14.2 ±0.7+1.4−0.9)×10−11, for a total of aπ0+η+η′-poleµ= (91.3 ±1.0+3.0−1.9)×10−11, where the first and second errors are the statistical and systematic uncertainties, respectively.
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    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.
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    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.
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    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.
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    Prospects for γ-ray observations of the Perseus galaxy cluster with the Cherenkov Telescope Array
    (Institute of Physics (IOP), 2024-10-01) The CTA Consortium; Aguasca Cabot, Arnau; Bordas Coma, Pol; Paredes i Poy, Josep Maria; Ribó Gomis, Marc; Sanuy Charles, Andreu
    Galaxy clusters are expected to be both dark matter (DM) reservoirs and storage rooms for the cosmic-ray protons (CRp) that accumulate along the cluster's formation history. Accordingly, they are excellent targets to search for signals of DM annihilation and decay at γ-ray energies and are predicted to be sources of large-scale γ-ray emission due to hadronic interactions in the intracluster medium (ICM). In this paper, we estimate the sensitivity of the Cherenkov Telescope Array (CTA) to detect diffuse γ-ray emission from the Perseus galaxy cluster. We first perform a detailed spatial and spectral modelling of the expected signal for both the DM and the CRp components. For each case, we compute the expected CTA sensitivity accounting for the CTA instrument response functions. The CTA observing strategy of the Perseus cluster is also discussed. In the absence of a diffuse signal (non-detection), CTA should constrain the CRp to thermal energy ratio X 500 within the characteristic radius R 500 down to about X 500 < 3 × 10-3, for a spatial CRp distribution that follows the thermal gas and a CRp spectral index αCRp = 2.3. Under the optimistic assumption of a pure hadronic origin of the Perseus radio mini-halo and depending on the assumed magnetic field profile, CTA should measure αCRp down to about ΔαCRp ≃ 0.1 and the CRp spatial distribution with 10% precision, respectively. Regarding DM, CTA should improve the current ground-based γ-ray DM limits from clusters observations on the velocity-averaged annihilation cross-section by a factor of up to ∼ 5, depending on the modelling of DM halo substructure. In the case of decay of DM particles, CTA will explore a new region of the parameter space, reaching models with τ χ > 1027 s for DM masses above 1 TeV. These constraints will provide unprecedented sensitivity to the physics of both CRp acceleration and transport at cluster scale and to TeV DM particle models, especially in the decay scenario.