The origins of fast X-ray transients (FXTs), which are bursts of soft X-ray photons (~0.3-10 keV), have so far been amongst the most elusive of transients. Their origins in binary neutron star mergers which lead to the formation of a millisecond pulsars whose rapid spin down power the bursts; tidal disruption events (TDE) involving white dwarfs disrupted by intermediate-mass black holes; shock...
XRISM, launched in September 2023, offers unprecedented capability in resolving the Fe K band. We use a deep 430 ks observation with XRISM/Resolve to investigate the AGN environment of NGC 3783 and model the structure through Fe Kα emission lines. I will present our latest results on both the narrow Fe Kα line and the relativistic broad iron line.
Our preliminary findings suggest that the...
The recent very-high-energy (VHE; >100GeV) spectra of the afterglow emission of three gamma-ray bursts (GRBs) shake the current understanding of the underlying physics of a relativistic shock, formed at the impact surface from a plasma outflow crashing at almost the speed of light into its surrounding. I will show the limitations of established modeling and discuss new scenarios including...
Fast X-ray transients (FXTs) are extragalactic flashes of X-rays, lasting from seconds to hours, whose nature remains largely unknown. Several progenitor mechanisms have been proposed to explain their origin, for instance, neutron star mergers, tidal disruption events involving a white dwarf and an intermediate-mass black hole, supernova shock break-out, and gamma-ray burst cocoon-like/jet...
Construction of low frequency component (50 - 350 MHz) of the Square Kilometre Array has started in Australia. With an immensely dense core of almost 60 thousand antennas within a square kilometer, the telescope provides a unique opportunity to study cosmic rays in the energy range between 10$^{15}$ and 10$^{18}$ eV. High resolution observations and new analysis strategies will provide more...
The Radio Detector (RD) at the Pierre Auger Observatory is a new large-scale instrument designed to measure the highest-energy cosmic rays. It consists of 1660 radio antennas spread across 3000 km², detecting the radio emission from extensive air showers in the 30–80 MHz range. By combining these measurements with data from water-Cherenkov detectors, we can determine both the energy and...
The Radar Echo Telescope for Cosmic Rays (RET-CR) is a prototype experiment for the future neutrino detector, the Radar Echo Telescope for Neutrinos (RET-N). It is deployed at Summit Station in Greenland, with an entire data-taking run conducted in the summer of 2024.
RET-CR explores the possibility of the long-term goal for RET-N, hence advancing neutrino astronomy with new detection...
Cataclysmic variables, accreting white dwarfs in binaries, can zoom into and out of view of our telescopes in a matter of days or weeks, first brightening then fading, only to repeat this later the same year. This timescale of variability is a sign of the dwarf nova, a class of cataclysmic variable. The dwarf nova outburst is a change in the accretion disc of these systems, which not only...
In the last few years, a new class of mysterious periodic radio transients has been discovered, with periods far exceeding those seen on pulsars. These long-period transients (LPTs) produce bright, often strongly polarised emission in pulses that last less than a minute and repeat on a timescale of minutes to hours. The origins of LPTs are largely unknown still, with proposed progenitor...
Fast Radio Bursts (FRBs) are millisecond-duration radio transients that serve as unique probes of extragalactic matter. We report on the discovery and localization of two FRBs piercing the Andromeda Galaxy (M31) by the realfast fast transient detection system at the Very Large Array. Their unique sightlines allow constraints on M31’s electron density distribution. We localized FRB 20230930A...
Most Sun-like stars host planets. Once these stars run out of fuel in the core, they will go through a short red giant phase and end their life as a white dwarf. It is unknown what happens the planetary systems around these stars: does the red giant engulf them, ejected, or are entirely new planets born?
In my talk, I will present the results of a systematic search of Zwicky Transient...
Post-asymptotic giant branch (post-AGB) stars have recently lost their envelopes and are contracting to higher effective temperatures, while maintaining constant luminosity, to become white dwarfs. About half of the optically bright post-AGB stars are found to exhibit near-infrared excesses in their spectral energy distributions, interpreted as hot dusty discs around the objects, and are...
Before the launch of Gaia, eccentricity in wide evolved binaries (with periods of ~10²–10⁴ days) was considered an oddity, as only a few small samples were known. These observations have revealed that many of these systems are eccentric, with the range of observed eccentricities increasing with orbital period. Notably, the maximum observed eccentricities also rise as the orbital period grows....
