We report the discovery of a spatially resolved clumpy ejecta structure in the reverse-shocked ejecta of SNR 0509–67.5, revealed through multiple faint and broad forbidden coronal emission lines in deep MUSE observations. We also identify two new broad coronal emission lines not reported before in this remnant, [Fe xi] 7894 Å and [Fe x] 6374.5 Å, which extend the set of previously reported [Fe xv] 7059.59 Å, [Fe xiv] 5302.86Å, [Fe ix] 8236.55 Å, [Ca xv] 5695Å, and [S xii] 7611.0 Å. Near-continuous ionisation states of Fe allow us to follow the ionisation progression behind the reverse shock. We use a 1D analytical model to evolve Fe charge states following reverse shock interaction to compare with observations, indicating the need for preshock clumping or over-density in order to reproduce the observed surface brightness of the [Fe xiv] line. Additionally, we report the spatially resolved distribution of ejecta clumps and show that reverse-shock interaction drives their compression and fragmentation. We also find a clear trend of decreasing velocity width with increasing Fe ionisation state, from the broadest [Fe ix] emission to the narrowest [Fe xv], with intermediate-ionisation species ([Fe x], [Fe xi], [Fe xiv]) showing intermediate widths. Finally, we compare our observations to a dynamically driven double-degenerate double detonation (D6) 3D remnant model at similar Fe and S ionisation states and conclude that the observed clumps are predominantly due to Rayleigh–Taylor instabilities.

AM CVn stars are ultra-compact semi-detached binaries consisting of a white dwarf primary and a hydrogen-depleted secondary. In this paper, we present spectroscopic and photometric results of 15 transient sources pre-classified as AM CVn candidates. Our analysis confirms 9 systems of the type AM CVn, 3 hydrogen-rich cataclysmic variables (accreting white dwarfs with near-main-sequence stars for donors), and 3 systems that could be evolved cataclysmic variables. Eight of the AM CVn stars are analysed spectroscopically for the first time, which increases the number of spectroscopically confirmed AM CVns by about 10%. TESS data revealed the orbital period of the AM CVn star ASASSN-20pv to be $P_{\mathrm{orb}}=27.282\,\mathrm{min}$, which helps to constrain the possible values of its mass ratio. TESS also helped to determine the superhump periods of one AM CVn star (ASASSN-19ct, $P_{\mathrm{sh}}=30.94\,\mathrm{min}$) and two cataclysmic variables we classify as WZ Sge stars ($P_{\mathrm{sh}}=90.77\,\mathrm{min}$ for ZTF18aaaasnn and $P_{\mathrm{sh}}=91.6\,\mathrm{min}$ for ASASSN-15na). We identified very different abundances in the spectra of the AM CVns binaries ASASSN-15kf and ASASSN-20pv (both $P_{\mathrm{orb}}\sim 27.5$ min), suggesting different type of donors. Six of the studied AM CVns are X-ray sources, which helped to determine their mass accretion rates. Photometry shows that the duration of all the superoutbursts detected in the AM CVns is consistent with expectations from the disc instability model. Finally, we provide refined criteria for the identification of new systems using all-sky surveys such as LSST.

In this talk, I discuss what we learn from the spectra of the extremes in solar and stellar flares. I will start with an introduction to the production of the highest energy particles in solar flares, which are one of the major sources of radiated energy in flares. I will then transition to surprises about energetic stellar flares from recent NUV spectra from the Hubble Space Telescope. I discuss a unique property of hydrogen lines that can help to connect the action in the reconnection region to the conditions in the brightest chromospheric sources in solar flares.

This project presents a spectroscopic study of the eclipsing binary star BUL-SC16 335, aiming to determine its physical properties and dynamical behavior. First, we review the different types of binary systems and the experimental methods used for their detection, as well as the processes applied to obtain the spectral lines of BUL-SC16 335. The analyzed data, recorded at La Silla Astronomical Observatory (Chile) by Alfred Tillich in October 2008, include more than 35 observations. These were reduced using several packages and tasks of the IRAF software, while also considering the instrumental effects of CCD cameras and the spectroscopic techniques applied in observational astronomy. Subsequently, specific scripts were implemented for the efficient determination of radial velocity and Julian date. Finally, the use of gnuplot allowed us to construct the radial velocity curve of BUL-SC16 335, contributing to the characterization of its eclipsing nature.

The extended Main Sequence Turn-off (eMSTO) in the open cluster NGC 2355 is investigated using precise astrometry and photometry from Gaia DR3 and spectroscopic data from the Gaia-ESO Survey. We find a clear positive correlation between the rotational velocity ($v \sin i$) and color of eMSTO stars, supporting the role of stellar rotation and gravity darkening in causing the observed color spread. Contrary to predictions from binary tidal-locking scenarios, spatial distribution analysis reveals that fast-rotating stars are preferentially concentrated in the cluster’s central regions. This finding provides the observational evidence favoring star-disk interactions during the pre-main-sequence phase, rather than tidal locking in binaries, as the primary mechanism responsible for the origin of rotational spread in eMSTO stars.

The Gaia mission and its follow-up observations have discovered BH binaries without mass transfer, hereafter called “astrometric BH binaries”. We examine if these astrometric BH binaries hide “astrometric BBH triples” consisting of inner binary BH (BBH) and visible stars. We find that open clusters can form astrometric BBH triples at a high rate (10 % of astrometric BH binaries) in low metallicity environments. About 30 % of these astrometric BBH triples can be identified from astrometric BH binaries by high-precision radial-velocity observations. Eventually, there is one detectable astrometric BBH triples in about 40 astrometric BH binaries. Since it is predicted that several 10 astrometric BH binaries will be discovered in Gaia Data Release 4 era, our results strongly motivate survey for astrometric BBH triples in the next few years.

Current and future surveys rely on machine learning classification to obtain large and complete samples of transients. Many of these algorithms are restricted by training samples that contain a limited number of spectroscopically confirmed events. Here, we present the first real-time application of Active Learning to optimise spectroscopic follow-up with the goal of improving training sets of early type Ia supernovae (SNe Ia) classifiers. Using a photometric classifier for early SN Ia, we apply an Active Learning strategy for follow-up optimisation using the real-time Fink broker processing of the ZTF public stream. We perform follow-up observations at the ANU 2.3m telescope in Australia and obtain 92 spectroscopic classified events that are incorporated in our training set. We show that our follow-up strategy yields a training set that, with 25% less spectra, improves classification metrics when compared to publicly reported spectra. Our strategy selects in average fainter events and, not only supernovae types, but also microlensing events and flaring stars which are usually not incorporated on training sets. Our results confirm the effectiveness of active learning strategies to construct optimal training samples for astronomical classifiers. With the Rubin Observatory LSST soon online, we propose improvements to obtain earlier candidates and optimise follow-up. This work paves the way to the deployment of real-time AL follow-up strategies in the era of large surveys.

Circular dichroism (CD) spectroscopy is a widely utilized technique for studying the structures of chiral molecules, including nucleic acids. It is particularly valued for its ability to quickly probe structural changes in these biomolecules. Despite its potential, the prediction of nucleic acid structures by CD has been challenging due to insufficient families’ reference spectral data. This study introduces a robust method for defining CD spectra families of nucleic acid structures. We developed an iterative workflow that accurately classifies spectra for nucleic acid structures in solution. Our approach demonstrates high robustness and accuracy in assigning CD spectra to specific nucleic acid folds, facilitating advancements in nucleic acid structure analysis. The algorithm we developed identifies structural classes based on reference spectra, aiding in the assignment of unknown spectra. This method paves the way for creating a comprehensive list of reference spectra for various nucleic acid structures, like those already available for proteins.

Satellite constellation interference occurs across astronomical disciplines. We touch on the challenges for existing regulatory frameworks in radio astronomy, and present examples of interference from radio and γ-ray astronomy to optical and spectroscopic interference in ground-based and space-borne facilities. In particular, we discuss the impact of artificial satellites on the Hubble Space Telescope (HST), the High Energy Stereoscopic System (H.E.S.S.), an Imaging Atmospheric Cherenkov Telescope array, as well as possible mitigation strategies for the European Southern Observatory 4-metre Multi-Object Spectrograph Telescope (ESO 4MOST). Furthermore, we shed light on how ground-based optical telescopes such as the Oukaimeden Observatory contribute to IAU Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (IAU CPS) efforts that quantify satellite brightness.

This study focuses on the impact of satellite trails on spectroscopic observations in the visible and near-infrared, which represent a large fraction of the observing time on large professional telescopes. We simulate the number of observations affected using an hypothetical large set of low Earth orbit satellite constellations. We evaluate the effect of this contamination on various spectrographs. We also measure the contamination on actual data from the ESO archive for a set of representative objects, after adding a scaled solar analogue spectrum to represent the satellite.

Even with a satellite population much larger than today’s, the fraction of contaminated spectra will remain low, essentially thanks to the typically small field of view of these instruments. Furthermore, high-resolution spectrographs, and medium-resolution ones on smaller telescopes, are essentially blind to satellites. However, for a range of instruments the contamination will be at a level comparable to that of the science signal, making its identification difficult, and potentially affecting the astrophysical measurements derived from the data.

The parallel and synergistic developments of atomic resolution structural information, new spectroscopic methods, their underpinning formalism, and the application of sophisticated theoretical methods have led to a step function change in our understanding of photosynthetic light harvesting, the process by which photosynthetic organisms collect solar energy and supply it to their reaction centers to initiate the chemistry of photosynthesis. The new spectroscopic methods, in particular multidimensional spectroscopies, have enabled a transition from recording rates of processes to focusing on mechanism. We discuss two ultrafast spectroscopies – two-dimensional electronic spectroscopy and two-dimensional electronic-vibrational spectroscopy – and illustrate their development through the lens of photosynthetic light harvesting. Both spectroscopies provide enhanced spectral resolution and, in different ways, reveal pathways of energy flow and coherent oscillations which relate to the quantum mechanical mixing of, for example, electronic excitations (excitons) and nuclear motions. The new types of information present in these spectra provoked the application of sophisticated quantum dynamical theories to describe the temporal evolution of the spectra and provide new questions for experimental investigation. While multidimensional spectroscopies have applications in many other areas of science, we feel that the investigation of photosynthetic light harvesting has had the largest influence on the development of spectroscopic and theoretical methods for the study of quantum dynamics in biology, hence the focus of this review. We conclude with key questions for the next decade of this review.

The nature of the complexes in aqueous solutions of Cu(II) and Ni(II) with diethylenetriamine (dien) and tetraethylenepentamine tetren) is pH-dependent. At M(II):dien = 2 and M(II):tetren = 1, the main complexes are [M(dien H)2(H2O)2]4+ and [M(tetren H)(H2O)2]3+. In excess ligand (pH = 10.30), the majority species are [M(dien)2]2+ and [M(tetren)(H2O)]2+, and considerable amounts of monoprotonated amines are adsorbed. The surface of hectorite prefers the tetragonally distorted complexes in all cases studied. The complexes readily lose their axially coordinated water molecules to form planar complexes on the interlamellar surface. The planar Ni(II)-complexes are diamagnetic, showing that the surface is a very weak axial ligand. The divalent complexes [M(dien)2]2+ and [M(tetren)(H2O]2+ can also be partially transformed to the corresponding planar forms on the surface, especially in the case of [Cu(dien)2]2+. The driving forces are thought to be the acid nature of the clay-adsorbed water and the gain in crystal field stabilization energy of the transition metal ions.