Recent Talks

We performed full Stokes spectropolarimetric observations of loop footpoints in the active region NOAA 13363 during a C-class flare with the GREGOR Infrared Spectrograph (GRIS) on 2023 July 16. The observed spectral region included the photospheric Si I 10 827 A and Ca I 10 839 A lines and the chromospheric He I 10 830 A triplet. Simultaneously, high-cadence and high-resolution imaging observations were carried out with the improved High-resolution Fast Imager (HiFI+) in the Ca II H line and TiO bands. The observations were conducted under excellent seeing conditions, as confirmed by the Fried-parameter measurements. Speckle-restored HiFI+ Ca II H images revealed thin flare-related filaments and diffuse haze-like emissions, further confirmed by background-subtracted solar activity maps (BaSAMs), which localized chromospheric variability near the sunspot. The He I triplet showed enhanced emission during the flare events and developed intense red- and blue-shifted components, with the decisive shift of 90 km/s, suggesting the significant energy release and plasma motion triggered by the flare. Simultaneously, a delayed increase in the Si I line wing intensity was observed approximately 6 minutes after the He I emission, suggesting that the upper photosphere experienced secondary heating, possibly due to thermal conduction rather than energetic particles. This time delay and spatial correlation support a scenario where dynamic flare processes influence chromospheric and upper photospheric layers. Our results demonstrate a temporal and spatial coupling between chromospheric and upper photospheric regions, and the time delay rules out direct heating by flare-accelerated electrons, so we propose thermal conduction or ionization effects as possible mechanisms.

Measurements of the 511 keV emission reveal the presence of a steady injection of positrons that is very concentrated around the Galactic centre, and whose origin remains unknown. While astrophysical sources do not easily fit the observed morphology and intensity of this excess, MeV dark matter has been proposed as a compelling explanation with interesting consequences. In this seminar, I will introduce the "positron puzzle" and discuss its correlation to other anomalous emissions at the Galactic centre, especially focusing on the observational consequences of the dark matter explanation of the 511 keV excess. Finally, I’ll show how these observations can be used to constrain the properties of asteroid-mass primordial black holes and beyond Standard Model particles, such as sterile neutrinos or axion-like particles.

El Spanish Space Solar Physics Consortium (S3CP) es un grupo formado por cinco instituciones españolas, entre ellas el Instituto de Astrofísica de Canarias (IAC), que desde 2002 trabajan conjuntamente para profundizar en el conocimiento de la física solar. En el marco de este consorcio se han desarrollado tres espectropolarímetros solares que han participado en misiones estratosféricas y espaciales como Sunrise I (IMaX), Sunrise II (IMaX), Solar Orbiter (PHI) y Sunrise III (TuMag). Actualmente, se está desarrollando un nuevo instrumento, Photospheric Magnetic Field Imager (PMI), que formará parte de la carga útil de la misión Vigil de la Agencia Espacial Europea (ESA).
Esta charla ofrecerá un repaso a la evolución de la instrumentación electrónica en estos proyectos, con especial énfasis en los desarrollos basados en FPGA, cada vez más utilizados en este ámbito por su versatilidad y capacidad de procesamiento. Estos dispositivos han sido clave como controladores de sensores CMOS en cámaras científicas, como capturadores de imágenes (“frame grabbers”) y como unidades de procesamiento de imagen y cálculo científico.

Matter ejection, in the form of either winds or jets, is ubiquitous in accreting X-ray binaries. Although it is clear that accretion and ejection are profoundly intertwined in these types of systems, the origin and the details of such an interconnection are yet to be unraveled. This is particularly true for systems where a low-magnetized neutron star (NS) accretes matter from a low-mass companion star (NS low-mass X-ray binaries, LMXBs). Indeed, unlike the case of accreting black holes, in NS LMXBs the already delicate interplay between accretion and ejection may be further complicated by the presence of, e.g., the NS magnetic field, the boundary layer and the emission from the NS surface. For instance, jets in NS LMXBs have been claimed to be more collimated than in BH LMXBs, their occurrence sometimes seems to be unrelated to the spectral state and their observed radio luminosity show a rather scattered distribution. X-ray winds on the other hand have been often detected in states where they were not expected, in particular in a class of NS LMXBs, the Accreting Millisecond X-ray Pulsars (AMXPs), where the channeling of the accretion flow along the magnetic field lines makes these systems visible as rapidly spinning X-ray pulsars. Finally, AMXPs typically drive more powerful jets than other (non-pulsating) NS LMXBs and their rapid orbital expansion can be explained by strong mass outflows. In this talk, I will review the emerging pattern of peculiar outflows in NS LMXBs, the possible implications for jet and wind-launching mechanisms in these systems and the key role that future multi-band observing campaigns will play in clarifying its physical origin.

Zoom link: https://rediris.zoom.us/j/97431924964?pwd=rpPDNaL2VrEKfs8TSZNyck8GbTnjnZ.1
Meeting ID: 974 3192 4964

Passcode: 078804

Youtube: https://youtube.com/live/ZO-hf7iNPRw?feature=share

Gamma rays are key when it comes to probing a wide range of astrophysical phenomena that provide a deeper understanding of the most energetic events in the universe, as well as topics such as dark matter searches from an indirect perspective or the Lorentz invariance. They can be detected through Imaging Atmospheric Cherenkov Telescopes (IACTs), which capture images of extensive air showers generated by gamma rays and cosmic rays when they interact with the atmosphere. One of the main challenges about this data is the reconstruction of the event's properties, i.e., estimating the direction of arrival, energy, and type (gamma ray, proton, electron, etc.) of the particles that triggered the shower. AI techniques, such as deep learning methods, have been demonstrated to be suitable for the reconstruction of these events since they are used to analyze and exploit loads of data for carrying out classification and characterization tasks.

The era of gravitational wave astronomy has dawned, allowing us not only to observe the universe but also to "listen" to it through gravitational waves. When a compact object ventures too close to a supermassive black hole, it becomes captured due to the emission of gravitational waves, eventually being swallowed whole as it crosses the event horizon. During this process, the system radiates energy, which can be viewed as a snapshot containing detailed information about the geometry of spacetime and the physical parameters of the system with extraordinary precision. Intriguingly, this information may also hold clues about the topology of spacetime, suggesting a potential link between geometry and topology in the strong-field regime of gravity. This phenomenon effectively maps the warped spacetime, serving as a unique probe of gravity in its most extreme regime. Thanks to these captures, we can now tackle fundamental questions: Do black holes truly exist? How do they accumulate their colossal mass over cosmic history? And what is the true nature of their event horizons? 

The first detection of an exoplanetary atmosphere dates back merely two decades and has undergone a veritable boom with a wide range of dedicated instrumentation. I will give a short overview of how we learn more about the composition of exoplanets and in consequence about the planet population and our place in it.  I will put a special emphasis on high-resolution spectroscopy and how we employ it now to observe the atmospheric dynamics in far-away worlds, such as churning jet-streams and powerful sub-to-antistellar flows. Looking to the future and the paradigm shift of the ELT-era, I will explore the implications of these technical advancements, with a particular focus on how we can leverage high-resolution spectroscopic data to decipher the complex interplay between dynamics and composition in these distant worlds in synergy with existing and upcoming space missions.

"DESI DR2 results: a hint for dynamical dark energy?" - José Ramón Bermejo Climent

“Euclid Q1 data release” - Marc Huertas Company

It is widely accepted that most galaxies undergo an active phase during their evolution. The impact of the energy released by active galactic nuclei (AGN) has been proposed as a key mechanism responsible for regulating star formation (SF) by influencing the interstellar medium (ISM) of the host galaxy. Dust, gas, and molecular components are key tracers of the interplay between the supermassive black hole (SMBH) and its host. The infrared (IR) regime hosts numerous spectral features, such as fine-structure lines, dust and ice features, organic molecules, hydrogen, and water, that act as sensitive barometers of the physical conditions in the ISM. These features are essential for tracing AGN feedback from the innermost regions (tens of pc) out to kiloparsec scales. With its unprecedented sensitivity and resolution, the James Webb Space Telescope (JWST) now enables detailed measurements of the gas flow cycle in AGN. Nearby AGN provide the additional advantages of high spatial resolution and strong signal-to-noise, allowing us to disentangle the key coupling mechanisms in their different phases. In this talk, we will present recent findings and ongoing work from the Galaxy Activity, Torus, and Outflow Survey (GATOS), with a focus on results from JWST and complementary observations such as ALMA and GTC.

Fast X-ray Transients (FXTs) are minute-to-hours long flashes of X-rays, first discovered serendipitously in X-ray satellite data (mainly Chandra and XMM-Newton). They are proven to be caused by energetic extra-galactic phenomena. Currently, Einstein Probe is revolutionizing the field by discovering many FXTs and, crucially, by their low-latency announcement thereof. These extra-galactic FXTs are ubiquitous: their density rate is several hundred per year per Mpc^3. FXTs have been proposed to arise from double neutron star mergers, tidal disruption events involving an intermediate-mass black hole and a white dwarf, and from off-axis or sub-luminous gamma-ray bursts. Brief extra-galactic FXTs also arise in supernova shock breakouts. Contemporaneous multi-wavelength detections possible only in the current Einstein Probe era show that FXTs originate from more than 1 progenitor. I will discuss the most recent findings and provide some (potential) science questions to be answered using FXT observations.