We present a high-resolution spectroscopic study of the ultracompact neutron-star LMXB 4U 1916–053 (Porb ≈ 50 min), a prototypical dipping system in which recurrent intensity drops are produced by variable absorption in disk-associated plasma. Using new XRISM/Resolve observations together with simultaneous XMM-Newton data, we investigate the structure, ionization state, and kinematics of the...
Pebble accretion is widely considered a key, and probably necessary, ingredient for rapid planet formation. However, most studies still rely on simplified gas prescriptions or assume a single particle size. In this work, we revisit pebble accretion using a multifluid hydrodynamical model that evolves the gas and multiple pebble species self-consistently. This allows us to move beyond static...
In this talk, I will present a real-time transient detection pipeline in the image plane for LOFAR data. This pipeline creates short duration snapshot images (seconds to a minute) and searches for transient sources in the differences between consecutive images. Upon detection of a transient candidate that passes our filters, buffered LOFAR station data will be dumped for offline analysis....
Local scaling relations of disc galaxies contain key information on the different physical processes that regulate their formation and evolution. While these relations are well established at z=0, their physical origin and evolution across cosmic time remain poorly constrained.
We present a new and unique radially resolved semi-analytic model for the evolution of star-forming disc galaxies,...
The BlackGEM telescope array has been in regular operation for over a year now. It has been actively following up on gravitational wave alerts from LIGO-Virgo-KAGRA, as well as high-energy alerts from SWIFT and other telescopes. Additionally, BlackGEM has been utilized for the Local Transient Survey to regularly monitor the nearby universe, and it has conducted deep observations of the...
High-energy neutrinos act as cosmic messengers, pointing back towards sources in the
universe. These particles have an extremely low flux, so radio techniques can help us to
probe large volumes and thus increase detection rates. The Radar Echo Telescope (RET)
aims to detect neutrinos by reflecting radio signals from the ionized trail left behind by
the cascade. This is done in ice, as it...
Fast X-ray transients (FXTs) are singular bright bursts of X-rays. The Einstein Probe (EP) satellite, launched in 2024, is revolutionising the field thanks to its timely discoveries and precise localizations of the events. These newly discovered FXTs have a strong connection with gamma-ray bursts (GRBs), which comes from the emission of a relativistic jet pointing towards us.
It seems that...
The Ionised interstellar medium (IISM) is a major source of unmodelled noise in Pulsar Timing Array (PTA) data. Spatial effects like scattering and scintillation lead to short-term diffractive and long-term refractive noise. These overlaid with variations in electron density further complicate and bias PTA noise models - directly impacting sensitivity to low-frequency gravitational waves....
We rarely have images of individual stars before they end their lives as supernovae. This makes the study of supernova, or more generally astrophysical transient environments invaluable for constraining their stellar progenitors. Much effort has been invested in studying the large populations of low redshift supernovae that have been uncovered in recent years, along with populations of...
Before the Gaia mission, eccentricity in wide, evolved binaries (with periods of ~10²–10⁴ days) was considered an oddity, as only a few small samples were known. Recent observations, however, reveal that eccentricity is widespread in these systems, with both the range and the maximum values of observed eccentricities increasing with orbital period. This pattern—consistent across diverse...
Gas-giant exoplanets are expected to generate low-frequency radio emission (< 40 MHz) via the cyclotron maser mechanism. Detecting this emission is likely the only viable way to measure exoplanets’ magnetic field and space-weather conditions. Despite many attempts, there has not been a confirmed detection of an exoplanet in the radio band. I will present results from our ongoing search for...
The energy region around the "knee" of the cosmic-ray spectrum marks a transition where changes in the observed spectral shape and composition indicate a shift in the underlying physical processes of the sources of Galactic cosmic rays. In this work, cosmic-ray transport around this energy is simulated with CRPropa, using the JF12 Galactic magnetic field model with both large-scale and...
The GUSTO mission aims to unravel the life cycle of interstellar gas in the Milky Way and Large Magellanic Cloud (LMC), tracing the formation and destruction of star-forming clouds, probing the dynamics of the Galactic Center, and exploring the interplay between star formation, stellar feedback, and the structure of the interstellar medium. By mapping [CII] and [NII] emission, GUSTO provides...
Thermonuclear X-ray bursts are observed from weakly magnetized neutron stars in low-mass X-ray binaries (LMXBs). In these systems, accreted material such as hydrogen and/or helium from a donor star undergoes unstable thermonuclear burning on the NS’s surface. These bursts typically show a fast rise for a few seconds, followed by an exponential decay for tens of seconds. Thermonuclear bursts...
Millisecond pulsars are among the most precise clocks in the Universe. The triple system PSR J0337+1715, composed of a neutron star and two white dwarfs, is a unique gravitational laboratory, that enables excellent tests of the Strong Equivalence Principle (SEP). With microsecond-level timing precision, even tiny deviations from theoretical models become detectable. However, recent analyses...
The molecular composition of exoplanetary atmospheres can be heavily influenced by non-equilibrium and photochemistry. Determining this composition can thus be very computationally demanding, with conventional ODE-solving strategies often taking hours to converge. This makes incorporation into retrieval algorithms difficult. As such, we investigate the application of machine learning for...
The physical state of a star is primarily determined by its initial mass and chemical composition, while other factors (e.g. rotation, magnetic fields, companion) play a secondary role. Precise stellar masses are therefore fundamental for constraining stellar structure and evolution (SSE), particularly for rapidly evolving stars more massive than ~1.2 solar masses (i.e. OBAF-type stars)....
Massive star formation is thought to occur within the Galactic disk, so the presence of massive stars at a Galactic height of more than a kiloparsec is unexpected given their short lifetime. Using the Alma Luminous Star (ALS) III catalogue (Pantaleoni González et al. 2025) and Gaia DR3 data, we determined the scale height of Galactic OB candidate stars (64±4 pc) and identified 90 luminous...
High PeV to EeV cosmic rays can be used to probe extreme environments in the universe like supernovae and AGN. When these cosmic rays hit the Earth's atmosphere they generate large cascades of secondary particles called "airshowers". The evolution of these airshowers is still not completely understood, with current efforts to resolve it focusing on beamforming with radio arrays like LOFAR....
The discovery of gravitational waves (GWs) has revolutionized our understanding of the Universe, providing a unique observational window into cosmic phenomena. Active Galactic Nuclei (AGN) are promising sites for the formation of binary black holes (BHs).
In this scenario, the so-called AGN channel, BHs from the galactic nucleus gradually align with the AGN accretion disk, forming a dynamic...
Type-I X-ray bursts in neutron star (NS) low mass X-ray binaries are highly energetic events with the power to dynamically change the accretion flow. Studying such dynamical effects is a powerful new method that could shed light on accretion disk physics, coronae and the origin of relativistic jets. Correctly modelling time resolved X-ray spectra during these bursts allows for measurements of...
Circumbinary planets (CBPs), planets orbiting binary star systems, offer unique insights into planet formation. However, they are challenging to detect using traditional methods. While photometric surveys such as Kepler and TESS have led to the discovery of around a dozen transiting CBPs, the majority of these systems lack precise mass measurements due to limitations of transit-based methods....
Conventional coronagraph architectures struggle to reach the theoretical limit of exoplanet detection when the exoplanet is close to the star, particularly when the telescope has a complex aperture or when the star itself is partially resolved. Coronagraphy or nulling using spatial mode-sorting is capable of reaching the theoretical limit, but the optimal solution has so far only been...
The Milky Way is expected to contain many ultra-compact binaries (UCBs) with orbital periods on the order of hours. Due to the relatively high wavelengths of these signals these are not detectable by ground-based gravitational wave (GW) detectors, but will be in the range of the future Laser Interferometer Space Antenna (LISA). LISA will be used to construct a catalog of the different UCB...
High contrast imaging from the ground requires extremely sensitive wavefront sensing to correct the effects of the atmosphere. While the information limits of a wavefront sensor are well known, a practical, robust design that saturates these limits remains elusive. Furthermore, previous work often ignores the effects of amplitude aberrations (scintillation) when considering the fundamental...
We are currently at the dawn of a new era in multi-messenger astrophysics. Imaging air-Cherenkov telescopes such as MAGIC, H.E.S.S., and VERITAS have already detected around 90 active galactic nuclei (AGN) at TeV energies, while neutrino observatories like IceCube and KM3NeT have identified several high-energy neutrinos likely associated with AGN. A key open question remains: where in the jet,...
Radio waves emitted by pulsars experience a frequency-dependence propagation effect caused by free elections in the ionized interstellar medium (IISM), parameterized by the dispersion measure (DM). Temporal variations in the DM of pulsars provide a powerful probe of the density fluctuations of the free electrons in the ionized interstellar medium. These variations provide insight into the...
The Near-Ultraviolet eXplorer (NUX) is a proposed ground-based observatory that will operate at 300-350 nm to survey fast, hot transient sources. At the moment, its scientific and technical feasibility is being tested with a prototype system called Proto-NUX. The main purpose of Proto-NUX is to find the atmospheric throughput and variability in the 300-350 nm band, and to determine the...
Fast radio bursts (FRBs) are transient radio events of extragalactic origin whose sources remain uncertain. As their signals propagate over cosmological distances, they are modified by a range of propagation effects along the line of sight, including dispersion from free electrons and frequency-dependent scattering due to multipath propagation. Isolating the propagation effects local to the...
By harnessing the unique capabilities afforded by optical interferometry, VLTI/GRAVITY+ has recently become a powerful new tool for the direct detection and characterisation of exoplanets. Its extreme astrometric precision allows us to accurately constrain orbital geometries and dynamical masses just as its direct K-band spectra permit peering into the atmospheres of these objects. On top of...
Ram-pressure stripping (RPS) is an environmental process that transforms galaxies as they travel at high velocity through the hot gas in clusters and groups by removing their interstellar medium, forming one-sided tails. With radio continuum observations, we can detect the non-thermal component, i.e. the cosmic ray electrons and magnetic fields, in the stripped tails. Since the process of...
In 2020 the sustainability committee of the Dutch Astronomy Council published an inventory of CO2 impact of astronomy in 2019. In the strategic plan for astronomy 2021-2030 a significant reduction of the CO2 impact was announced. We present an update on the CO2 emissions of Dutch astronomy, in particular related to air travel and discuss this in the context of the announced CO2 reductions.
55 Cnc e is the first rocky exoplanet for which strong evidence of a thick, volatile atmosphere exists (Hu+2024). The atmosphere of this hot super Earth shows sub-weekly variability in emission (Demory+2016, Meier-Valdez+2023, Patel+2024). Among the multiple suggested scenarios is an outgassing – cloud formation cycle driving this variability. We investigate, whether lava worlds could host...
Planet formation is an important topic, but how planets are forming in protoplanetary disks is still not fully understood. Silicate monomers (um-sized) are present in the disk and may attach to each-other to form fluffy, porous aggregates, which may then further progress into more solid pebbles, into planetesimals or protoplanets through a variety of proposed pathways. The material properties...
Just over a decade ago the first X-ray pulsations were discovered in an Ultraluminous X-ray source (ULX), revolutionizing our understanding of these systems. The detection of pulsations showed at least some ULXs offer us ideal laboratories to study the most extreme manifestation of accretion onto neutron stars (NSs), even if the number of NS-ULXs within the ULX population remains uncertain....
Mass transfer from a thermally pulsing (TP) asymptotic giant branch (AGB) star is a common phase in the evolution of low- and intermediate-mass binary systems. When carbon and s-process-enriched material is transferred from the TP-AGB star to a relatively unevolved companion, the accretor can become a barium- or carbon-enriched star. Observationally, such systems are found in binaries with...
Black hole low-mass X-ray binaries (BH LMXBs) are transient sources which spend most of their lifetime in quiescent states. Once or twice a year they are characterised by bright outbursts that last for days to months, during which accretion flow, compact jets and discrete ejecta undergo significant evolution. These relatively short outburst timescales make BH LMXBs ideal natural laboratories...
Surface Brightness Fluctuations (SBF) provide redshift-independent galaxy distances and probe stellar populations through pixel-to-pixel brightness variations. With the high resolution Euclid data it is now possible to use this method to determine distances of dwarf galaxies in the whole Local Universe up to 50 Mpc.
In this work, Euclid data is used to measure SBF magnitudes and colors for...
Mass transfer is arguably one of the most important aspects in the evolution of binary stars, with the majority of binaries having at least one episode of mass transfer during their lifetime. Yet its efficiency — the fraction of the transferred mass that is accreted — remains plagued by uncertainties, despite dictating the outcomes of mass transfer and predicted populations of stripped-star...
Fast radio bursts (FRBs) are millisecond-duration radio transients of extragalactic origin whose progenitors and emission mechanism(s) remain mysterious. Of the ~4000 FRBs discovered to date, only ~100 repeat, raising the question of whether repeating and apparently non-repeating FRBs arise from the same underlying population.
I present recent milliarcsecond localisations of FRBs that...
Each stars is expected to have a planetary systems, and most stars end up as a white dwarf. The evolution of a star into a white dwarf has a significant impact on the planetary system. With large sky surveys, we are now starting to see signs of the (disruption of) planetary systems around white dwarfs. This includes enrichment of the white dwarf atmosphere by planet material, engulfment of...
The Dutch Research Council (NWO) is one of the most important science funding bodies in the Netherlands and realises quality and innovation in science. Each year, NWO invests almost 1 billion euros in curiosity-driven research, research related to societal challenges and research infrastructure.
Are you wondering what kind of different funding instruments are available at NWO? How they are...
It is well known that dense environments like clusters play a role in galaxy evolution, showing an increase in quenched galaxies with an increase in density. However, the exact mechanisms involved in quenching these galaxies are not well understood, and there is also evidence indicating that some galaxies experience preprocessing before falling into the cluster. To investigate this, I present...
