The integration of the upgraded Recoil Filter Detector (RFD) with the EAGLE gamma-ray spectrometer at the Heavy Ion Laboratory, University of Warsaw, provides new opportunities for high-resolution in-beam spectroscopy. The modernization of the RFD aims to enhance performance under high-rate conditions by replacing traditional photomultiplier tubes with segmented silicon photomultiplier (SiPM) matrices and implementing a state-of-the-art FERS-5200 digital readout system. Dedicated Geant4 simulations of scintillation light distribution, induced by a 20 keV electron beam, demonstrate that individual SiPM elements operate independently, thereby improving the system’s counting-rate capability. These advancements will enable more accurate selection of evaporation residues, improved Doppler correction, and effective suppression of background contributions. The combined RFD–EAGLE-DIAMANT setup establishes a versatile experimental platform for exploring nuclear collective excitations, superdeformation, shape transitions, and the spectroscopy of heavy and exotic nuclei produced with very low cross sections.

The low-spin structure of the 206Tl nucleus was studied in the thermal neutron capture reaction 205Tl(n, gamma ) 206Tl at the Institut Laue-Langevin in Grenoble making use of the multidetector HPGe array Fission Product Prompt gamma -ray Spectrometer and gamma gamma -coincidence techniques. The information on discrete structures located below the neutron binding energy in 206Tl was extended: a total number of 99 gamma rays (75 new) were observed and 21 excited states (8 new) were located. The analysis of the angular correlations of gamma rays was used to extract information on transitions multipolarities, which helped with spin-parity assignments for the located levels. The obtained experimental results were compared to shell-model calculations involving one-proton-hole, oneneutron-hole excitations below the 208Pb core. The two-body nucleon-nucleon realistic interactions derived from CD-Bonn free nucleon-nucleon potential were used. Reasonable agreement is obtained for the excitation energies of the states which, according to calculations, have highly fragmented wave functions, particularly in the highenergy region where the density of levels increases. The observed discrepancies are interpreted as a consequence of the large uncertainties in the determination of the off-diagonal matrix elements of the realistic shell-model interaction, which are mainly responsible for the fragmentation of the wave functions.

We present the results of a search for gravitational-wave transients associated with core-collapse supernova SN 2023ixf, which was observed in the galaxy Messier 101 via optical emission on 2023 May 19, during the LIGO–Virgo–KAGRA 15th Engineering Run. We define a five-day on-source window during which an accompanying gravitational-wave signal may have occurred. No gravitational waves have been identified in data when at least two gravitational-wave observatories were operating, which covered ∼14% of this five-day window. We report the search detection efficiency for various possible gravitational-wave emission models. Considering the distance to M101 (6.7 Mpc), we derive constraints on the gravitational-wave emission mechanism of core-collapse supernovae across a broad frequency spectrum, ranging from 50 Hz to 2 kHz, where we assume the gravitational-wave emission occurred when coincident data are available in the on-source window. Considering an ellipsoid model for a rotating proto-neutron star, our search is sensitive to gravitational-wave energy 1 × 10 −4 M ⊙ c 2 and luminosity 2.6 × 10 −4 M ⊙ c 2 s −1 for a source emitting at 82 Hz. These constraints are around an order of magnitude more stringent than those obtained so far with gravitational-wave data. The constraint on the ellipticity of the proto-neutron star that is formed is as low as 1.08, at frequencies above 1200 Hz, surpassing past results.

The low-spin structures of the Pb-205 and Pb-207 isotopes, populated by thermal-neutron capture, have been studied by the gamma-ray coincidence technique with the FIPPS HPGe array at the Institut Laue-Langevin (Grenoble, France). Preliminary results of the data analysis provided information on the decay schemes of the capture states located at 6.7 MeV in both nuclei. The spins of several states in Pb-205 have been established owing to gamma gamma-angular correlations analysis.

The excited states of neutron-rich Fe isotopes have been studied through a multinucleon transfer reaction of a Zn-70 beam on a U-238 target. Unambiguous identification of prompt gamma rays belonging to each nucleus was performed by coincidence detection of the ions in a high-acceptance magnetic spectrometer. The observed spectra are compared with large-scale shell-model calculations in the fpgd model space.

We present Fermi Gamma-ray Burst Monitor (Fermi-GBM) and Swift Burst Alert Telescope (Swift-BAT) searches for gamma-ray/X-ray counterparts to gravitational wave (GW) candidate events identified during the third observing run of the Advanced LIGO and Advanced Virgo detectors. Using Fermi-GBM on-board triggers and sub-threshold gamma-ray burst (GRB) candidates found in the Fermi-GBM ground analyses, the Targeted Search and the Untargeted Search, we investigate whether there are any coincident GRBs associated with the GWs. We also search the Swift-BAT rate data around the GW times to determine whether a GRB counterpart is present. No counterparts are found. Using both the Fermi-GBM Targeted Search and the Swift-BAT search, we calculate flux upper limits and present joint upper limits on the gamma-ray luminosity of each GW. Given these limits, we constrain theoretical models for the emission of gamma-rays from binary black hole mergers.

In the present contribution, the experimental investigation of the possible occurrence of the shape coexistence phenomenon in the Se-83 (Z = 34 , N = 49) and Se-84 (Z = 34 , N = 50) isotopes is presented. The aim of the experiment was to identify excited states which may be associated with different deformed shapes, i.e., spherical, oblate, and prolate. The structure of both nuclei was studied by using gamma-ray spectroscopy techniques, and the states and transitions of interest were investigated in detail through lifetime measurements and correlations.

The properties of the 2(1)(+) and 2(2)(+) excited states in C-14 were studied in an experiment conducted at the Argonne National Laboratory. A Be-9(Li-6, p gamma) fusion-evaporation reaction and the GRETINA-ORRUBA setup were employed to populate states of C-14 and detect gamma-particle coincidence events. The precise determination of the 2(1)(+) level energy, complemented by the estimation of the gamma-ray branch of the 2(2)(+) near-threshold state, will serve as a benchmark to test the Shell Model Embedded in the Continuum calculations.

The B(E3) transition strengths in 90Zr and 91Zr isotopes were determined based on the half-life measurements of the first 3- and (11/2)- states, i.e., T1/2 = 7.8(16) ps and 500(16) ps, respectively. The plunger method and fast-timing techniques were employed. The B(E3) values of 16(3) and 20.5(7) W.u. for 90Zr and 91Zr were derived, pointing to a sizable octupole collectivity in both cases. The 90Zr value complements the systematics of the octupole strength in even-even Zr isotopic chain, revealing a smooth trend between A = 90 and 96, which is in agreement with the pattern of octupole strength predicted by quasiparticle random phase approximation calculations. In 91Zr, the hybrid configuration mixing model describes the (11/2)- low-energy strength in terms of a coupling of the unpaired neutron with the 3- octupole excitation of the 90Zr core, predicting a slight decrease of octupole strength which is in contrast with the experimental result. This suggests a more complex structure for the (11/2)- state in 91Zr than predicted by the weak-coupling limit.

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass $M>70$ $M_\odot$) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities $0 < e \leq 0.3$ at $0.33$ Gpc$^{-3}$ yr$^{-1}$ at 90\% confidence level.

The magnetar SGR 1935+2154 is the only known Galactic source of fast radio bursts (FRBs). FRBs from SGR 1935+2154 were first detected by the Canadian Hydrogen Intensity Mapping Experiment (CHIME)/FRB and the Survey for Transient Astronomical Radio Emission 2 in 2020 April, after the conclusion of the LIGO, Virgo, and KAGRA Collaborations' O3 observing run. Here, we analyze four periods of gravitational wave (GW) data from the GEO600 detector coincident with four periods of FRB activity detected by CHIME/FRB, as well as X-ray glitches and X-ray bursts detected by NICER and NuSTAR close to the time of one of the FRBs. We do not detect any significant GW emission from any of the events. Instead, using a short-duration GW search (for bursts <= 1 s) we derive 50% (90%) upper limits of 10(48) (10(49)) erg for GWs at 300 Hz and 10(49) (10(50)) erg at 2 kHz, and constrain the GW-to-radio energy ratio to <= 10(14)-10(16). We also derive upper limits from a long-duration search for bursts with durations between 1 and 10 s. These represent the strictest upper limits on concurrent GW emission from FRBs.

Magnetars are neutron stars with exceptionally strong dipole magnetic fields which are observed to display a range of x-ray flaring behavior, but the flaring mechanism is not well understood. The third observing run of Advanced LIGO and Virgo extended from April 1, 2019 to March 27, 2020, and contained x-ray flares from known magnetar SGR 1935+2154, as well as the newly-discovered magnetar, Swift J1818-1607. We search for gravitational waves coincident with these magnetar flares with minimally modeled, coherent searches which specifically target both short-duration gravitational waves produced by excited f-modes in the magnetar's core, as well as long-duration gravitational waves motivated by the Quasi-Periodic Oscillations observed in the tails of giant flares. In this paper, we report on the methods and sensitivity estimates of these searches, and the astrophysical implications.

The γ decay of the elusive narrow, near-threshold proton resonance in 11B was investigated at Laboratori Nazionali di Legnaro (INFN) in a particle-γ coincidence experiment, using the 6Li(6Li,pγ) fusion-evaporation reaction and the GALILEO-GALTRACE setup. No clear signature was found for a possible E1 decay to the 1/21−, first-excited state of 11B, predicted by the Shell Model Embedded in the Continuum (SMEC) with a branching of 0.98−69+167×10−3 with respect to the dominant particle-decaying modes. The statistical analysis of the γ-ray spectrum provided an average upper limit of 2.37×10−3 for this γ-ray branching, with a global significance of 5σ. On the other hand, by imposing a global confidence level of 3σ, a significant excess of counts was observed for E=γ9300(20) keV, corresponding to a resonance energy of 11429(20) keV (namely 200(20) keV above the proton separation energy of 11B) and a γ-ray branching of 1.12(35)×10−3. This result is compatible with the SMEC calculations, potentially supporting the existence of a near-threshold proton resonance in 11B.

This article is devoted to a review of decay properties of excited 0+ states in regions of the nuclear chart well known for shape coexistence phenomena. Even-even isotopes around the Z=20 (Ca), 28 (Ni), 50 (Sn), 82 (Pb) proton shell closures and along the Z=36 (Kr), Z=38 (Sr) and Z=40 (Zr) isotopic chains are mainly discussed. The aim is to identify examples of extreme shape coexistence, namely highly deformed structures, well localized in the Potential Energy Surface in the deformation space, which could lead to γ decays substantially hindered. This is in analogy to the 0+ fission shape isomers in the actinides region and to the superdeformed (SD) states at the decay-out spin in medium/heavy mass systems. In this survey, the Hindrance Factor (HF) of the E2 transitions de-exciting 0+ states or SD decay-out states is a primary quantity which is used to differentiate between types of shape coexistence. The 0+ states, examined with the help of the hindrance factor, reveal a multifaceted scenario of shape coexistence. A limited number of 0+ excitations (in the Ni, Sr, Zr and Cd regions) exhibit large HF values (>10), some of which are associated with the clear separation of coexisting wave functions, while in most cases the decay is not hindered, due to the mixing between different configurations. Comparisons with theory predictions based on various models are also presented, some of which shed light on the microscopic structure of the considered states and the origin of the observed hindrances. The impact of shape ensembles at finite temperature on the decay properties of highly-excited states (Giant Dipole Resonances) is also discussed. This research area offers a complementary approach for identifying regions where extreme shape coexistence phenomena may appear.

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for $U(1)_{B-L}$ gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the $U(1)_{B-L}$ gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM.

Gravitational lensing by massive objects along the line of sight to the source causes distortions to gravitational wave (GW) signals; such distortions may reveal information about fundamental physics, cosmology, and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO-Virgo network. We search for repeated signals from strong lensing by (1) performing targeted searches for subthreshold signals, (2) calculating the degree of overlap among the intrinsic parameters and sky location of pairs of signals, (3) comparing the similarities of the spectrograms among pairs of signals, and (4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by (1) frequency-independent phase shifts in strongly lensed images, and (2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the nondetection of GW lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects.