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Item type: Item , Crystal-field effects on dipole moments and static first hyperpolarizability in noncentrosymmetric ionic organic crystals(2026) Leão, Salviano de Araújo; Jesus, Augusto César de; Castro, Marcos Antônio de; Fonseca, Tertius Lima daUnderstanding how crystal fields modify local nonlinear optical responses is essential for the rational design of acentric ionic organic crystals. Here, we investigate a structurally diverse set of noncentrosymmetric push−pull ionic crystals, including classical stilbazolium benchmarks and 6MNEP-related GUR/GUS crystals identified by their CCDC refcodes, to evaluate how electrostatic embedding affects the dipole moment and total static first hyperpolarizability (βtot) of asymmetric units. A selfconsistent electrostatic-embedding approach combined with density functional theory (DFT) and time-dependent-DFT (TDDFT) calculations was used to compare isolated and in-crystal ionpair responses within a consistent local-descriptor framework. The results show that the crystal field does not act as a uniform amplifier or suppressor of βtot. Instead, its effect depends on the local electrostatic environment, ion-pair organization, and tensor-component balance. Classical stilbazolium salts generally retain large embedded hyperpolarizabilities, with DAPSH, DSTMS, DSCHS, and DSNS-1 among the most responsive systems. In contrast, most 6MNEP-related GUR/GUS crystals show substantial attenuation of βtot upon embedding, while DSCHS, DSNS-1, and the structurally related MBST salt display enhanced embedded responses relative to their isolated counterparts. These results indicate that favorable local crystal-field alignment and contact patterns can reinforce, rather than suppress, the molecular response in selected cases. Overall, explicit crystal embedding provides a useful comparative strategy for analyzing how ion-pair composition and lattice organization modulate local dipolar and hyperpolarizability descriptors in ionic organic Organic nonlinear optical (NLO) crystalsItem type: Item , H.E.S.S. observations of composite Seyfert–starburst galaxies(2026) Acharyya, Atreya; Aharonian, Felix; Achkar, Halim El; Backes, Michael; Martins, Victor Barbosa; Batzofin, Rowan; Becherini, Yvonne; Berge, David; Boettcher, Markus; Boisson, CatherineContext. Composite galaxies that contain both Seyfert and starburst components may produce very high-energy (VHE; >100 GeV) γ-ray emission at a wide range of spatial scales, from a few Schwarzschild radii of a supermassive black hole (SMBH; RS = 10−6 pc for MSMBH = 107 M ) to dimensions of kiloparsec-size jet-driven outflows. In addition to supernova remnants, various sources have been suggested to explain data collected on composite galaxies, including multi-messenger neutrino and ultra-high-energy cosmic-ray data. Aims. The closest composite Seyfert–starburst galaxies (NGC 1068, the Circinus galaxy, and NGC 4945) are observed with the High Energy Stereoscopic System (H.E.S.S.) to provide constraints on cosmic-ray populations in these systems. Methods. Data obtained in H.E.S.S. observations have been analyzed to search for VHE γ-ray counterparts to the GeV γ-ray signals detected with Fermi-LAT and for potential spectral components in the VHE range. Results. No significant signals have been found in these H.E.S.S. data. Upper limits on the VHE γ-ray fluxes were applied to constrain theoretical models involving different spectral components.Item type: Item , Chasing gamma-ray signals from binary neutron star coalescences with the cherenkov telescope array: prospects and observing strategies(2026) Abe, Shotaro; Abhir, J.; Abhishek, A.; Acero, F.; Acharyya, Atreya; Adam, R.; Aguasca-Cabot, A.; Agudo, I.; Albanese, I.; Alfaro, J.; Martins, Victor BarbosaThe detection of gravitational waves (GWs) from a binary neutron star (BNS) merger by Advanced LIGO and Advanced Virgo (GW170817), together with its electromagnetic counterpart, the short gamma-ray burst GRB 170817A, heralded the birth of multimessenger astronomy. The detection of TeV emission from GRBs motivates follow-up observations with the Cherenkov Telescope Array Observatory (CTAO), which is ideal for detecting such signals due to its unprecedented sensitivity, rapid response, and wide-field survey capabilities. The aim of this work is to evaluate GeV–TeV GW follow-up strategies for CTAO using a multistep simulation pipeline and to estimate the expected rate of joint GW–GRB detections during observing run O5. Using a simulated sample of BNS systems with corresponding GW detections, gamma-ray emission is simulated through phenomenological prescriptions based on the observed population of short GRBs, including off-axis jet scenarios. CTAO observations are simulated to account for instrument response, sky tiling strategies, integration times, and varying observing conditions. Strategies with variable and constant integration times are investigated. We find that, via an optimized follow-up strategy, about 5% of simulated GW-associated short GRBs produce GeV–TeV radiation detectable by CTAO. Detectability is strongly influenced by the jet opening angle and viewing angle, suggesting that even rough estimates of the viewing angle in GW alerts could enhance targeting. This framework motivates future follow-ups of GW-detectable events, including neutron star–black hole mergers, and further supports the development of advanced strategies incorporating galaxy distributions and synergies with future detectors such as the Einstein Telescope.Item type: Item , Solvent polarity as a selective modulator of the first hyperpolarizability in para-substituted azo-carbazole dyes(2026) Ferreira, Murilo Benedito Martins; Georg, Herbert de Castro; Castro, Marcos Antônio de; Fonseca, Tertius Lima daAzo−carbazole monolithic dyes are promising candidates for photonic and optoelectronic applications due to their tunable push−pull character and strong nonlinear optical response. Here, we present a systematic density functional theory (DFT)/time-dependent DFT investigation of seven para-substituted azo−carbazoles (AmACzE, MACzE, HACzE, FACzE, AACzE, CACzE, and NACzE), aimed at elucidating how solvent polarity modulates the first hyperpolarizability (βHRS) using longrange corrected hybrid functionals combined with a polarizable continuum model. Our results demonstrate that solvent polarity does not act as a universal enhancer of nonlinear response, but rather as a selective amplifier whose efficiency is governed by the intrinsic charge-transfer capability of the chromophore. Electron-withdrawing substituents (F, COCH3, CN, and NO2) establish a well-defined push−pull axis, leading to large ground-toexcited-state dipole moment variation (Δμ) and high βHRS values, reaching up to 115 × 10−30 esu for NACzE in water. In contrast, donor-substituted derivatives (NH2, OCH3, and OH) exhibit enhanced local polarization but a limited Δμ, indicating a predominantly localized excited-state character, even in highly polar environments. By correlating βHRS with Δμ within a two-state framework, this work establishes Δμ as a quantitative descriptor controlling both the magnitude and the solvent sensitivity of the nonlinear response. These findings provide clear design guidelines for azo−carbazole-based NLO materials, demonstrating that efficient second-order response arises from the synergistic combination of strong acceptor substitution and polar environments, while also defining the intrinsic limits of solvent-induced enhancementItem type: Item , Science with a large field-of-view polarization survey: the Large Array Survey Telescope Polarization Node (LAST-P)(2026) Martins, Victor Barbosa; Jordana-Mitjans, Núria; Garrappa, Simone; Franckowiak, Anna; Ofek, Eran; Ben-Ami, Sagi; Borowska-Naguszewska, Jowita; Ramazani, Vandad Fallah; Konno, Ruslan; Küsters, Daniel; Parsons, Robert DanielOptical polarimetry provides information on the geometry of the emitting region, the magnetic field configuration and the properties of dust in astrophysical sources. Current state-of-the-art instruments typically have a small field of view (FoV), which poses a challenge for conducting wide surveys. We propose the construction of the Large Array Survey Telescope Polarization Node (LAST-P), a wide-field array of optical polarimeters. LAST-P is designed for high-cadence (≲1 day) polarization monitoring of numerous astrophysical transients, such as the early phases of gamma-ray bursts, supernovae, and novae. Furthermore, LAST-P will facilitate the creation of extensive polarization catalogs for X-ray binaries and white dwarfs, alongside a large FoV study of the interstellar medium. In survey mode, LAST-P will cover a FoV of 88.8 deg2. With a 15 ×1 minutes exposure, the instrument will be capable of measuring polarization of sources as faint as Gaia Bp-magnitude ∼20.9. The precision on the linear polarization degree will reach 0.7%, 1.5%, and 3.5% for sources with magnitudes 17, 18, and 19, respectively, for a seeing of 2.7, air mass of about 1 for observations in dark locations. We propose three distinct non-simultaneous survey strategies, among them an active galactic nuclei (AGN) strategy for long-term monitoring of ∼200 AGN with <1 day cadence. In this paper, we present the predicted sensitivity of the instrument and outline the various science cases it is designed to explore.