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Characterising planetary systems with SPIRou: Questions about the magnetic cycle of 55 Cnc A and two new planets around B
No full textOne of the first exoplanet hosts, discovered about thirty years ago, the star 55 Cnc has been continuously observed ever since. It is now known to host at least five planets with orbital periods ranging from 17 hours to 15 years. It is also one of the most extreme metal-rich stars in the neighbourhood, and it has a low-mass secondary star. In this article, we present data obtained at the Canada-France-Hawai’i Telescope with the SPIRou spectropolarimeter on both components of the 55 Cnc stellar system. We revisit the long-period radial-velocity signals of 55 Cnc A, with a focus on the role of the magnetic cycle, and propose the existence of a sixth planet candidate, whose period falls close to that of the magnetic cycle, or half of it. The other massive outer planet has a revised period of 13.15 years and a minimum mass of 3.8 MJup. Although some uncertainty remains about these outer planets, the characterisation of the four inner planets is very robust through the combination of many different datasets, and all signals are consistent in the near-infrared (nIR) and optical domains. In addition, the magnetic topology of the solar-type primary component of the system was observed by SPIRou at the minimum of its activity cycle, characterised by an amplitude ten times smaller than observed that during its maximum in 2017. For the low-mass component 55 Cnc B, we report the discovery of two exoplanets in the system, with a period of 6.799 ± 0.0014 and 33.75 ± 0.04 days and a minimum mass of 3.5 ± 0.8 and 5.3 ± 1.4 M⊕, respectively. The secondary magnetic field is very weak, and the current dataset does not allow its precise characterisation, setting an upper limit of 10 G. The system 55 Cnc stands out as the sixth binary system with planetary systems around both components and the first one with non-equal-mass stellar components
Publisher Erratum: A gravity-based mounting approach for large-scale cryogenic calorimeter arrays
No full textSearch for imprints of isovector–scalar mesons and kaon condensation in binary neutron star inspiral gravitational waves
No full textGravitational wave signals emitted during the binary neutron star inspiral phase offer a promising avenue for probing stellar internal composition. Isovector–scalar mesons and kaon condensation are thought to play pivotal roles in characterizing asymmetric nuclear matter and constraining the dense nuclear equation of state. This study explores whether their potential effects in neutron stars can be identified from inspiral gravitational wave frequencies, retarded times and orbital phases. Our analysis reveals the isovector–scalar meson accelerates the inspiral process, leading to shorter retarded times and lower maximum gravitational wave frequencies compared to standard binary neutron star systems, while binary systems influenced by kaon condensation exhibit even shorter inspiral retarded times and lower gravitational wave frequencies than those influenced solely by isovector–scalar mesons. Quantitatively, the incorporation of kaon condensation leads to a reduction of approximately 200 Hz in the maximum inspiral gravitational wave frequency, and the variations in retarded times across different kaon potentials reach approximately five milliseconds, whereas the corresponding variations induced by isovector–scalar mesons are around one millisecond. Combined with observable mass–radius relationships and tidal deformabilities, our findings strongly suggest that inspiral gravitational wave signals could serve as a strategic probe for identifying potential isovector–scalar and kaon mesons
Impact of nonlinear electrodynamics on particle motion around a charged black hole with matter coupling
No full textWe study the dynamics of particles near a charged back hole (BH) in the f(R, T) theory of gravity coupled with nonlinear electrodynamics and analyze how the parameters of the BH affect the motion of test particles. We discuss the stability of the circular orbits by employing the effective potential technique. We derive the mathematical expressions for the particle energy and its angular momentum as a function of the BH parameters and study them graphically. We also study the innermost stable circular orbits and the effective force acting on the test particles. The epicyclic oscillations of test particles are examined, and the analytical expressions for the radial frequency, the vertical frequency, and the orbital frequency are obtained. We also discuss the frequency of the periastron precession of particles. We show that the BH parameters have a significant impact on the particle dynamics. We observe that the effective potential increases with increasing charge and angular momentum, and the orbits are more unstable compared with the smaller values of these parameters: as the BH charge or the particle’s angular momentum increases, the particle experiences a greater effective force. However, it is not affected by the BH parameters a and b. We investigate the emission energy as a thermodynamic property of the BH and discuss the evaporation aspects of the BH
Probing the chronology protection conjecture via scalar quasiresonance
No full textHawking’s Chronology Protection Conjecture (CPC) proposes that the laws of physics prevent the formation of time machine. In his original argument, fields near a would-be chronology horizon undergo repeated blueshifts, signaling the onset of instabilities. In this work, we obtain an exact analytical solution of the Klein–Gordon equation for a relativistic scalar field in a spherically symmetric Morris–Thorne traversable wormhole. By polynomializing the radial equation and analyzing the Klein–Gordon current, we find that the resulting radiation modes generically possess complex eigenfrequencies: unstable modes grow in time and propagate inward toward the throat, while stable modes decay and flow outward. This directional instability prevents stationary configuration required to support time machine constructions, providing a dynamical obstruction consistent with Hawking’s Chronology Protection Conjecture
Static spherical vacuum solution to bumblebee gravity with time-like VEVs
No full textThe static spherical vacuum solution in a bumblebee gravity model where the bumblebee field has a one-component time-like vacuum expectation value is studied. We show that in general curved space-time solutions are not allowed and only the Minkowski space-time exists. However, it is surprising that two non-trivial solutions can be obtained so long as a unique condition for the vacuum expectation , where , is satisfied. One of the solutions contains a naked singularity, while the other exhibits features analogous to a confining potential. We argue that naturally these solutions are not stable since quantum corrections would invalidate the likely numerical coincidence, unless there are some unknown fine-tuning mechanisms preventing any deviation from this condition. Nevertheless, the naked singularities and the photon sphere of these novel but peculiar solutions are discussed, and we show that the extremal Reissner-Nordström solution is a limit of one of our solutions
Thermodynamic topology of Einstein–Maxwell-dilaton theories
No full textWe present a systematic investigation of the thermodynamic topology for a broad class of asymptotically charged Anti-de Sitter (AdS) black holes in Einstein–Maxwell-Dilaton (EMD) theories, examining how scalar coupling parameters and spacetime dimensions influence black hole thermodynamics. Employing a topological approach that utilizes the torsion number of vector fields constructed from the generalized free energy, we characterize black hole states as topological defects within the thermodynamic parameter space. Through analytical solutions spanning dimensions and including the Gubser–Rocha model, we demonstrate that variations in the dilaton coupling constant particularly near its critical value induce transitions between distinct thermodynamic topological phases. Our analysis reveals that certain black hole solutions constitute a novel class designated as characterized by a torsion number that corresponds to a unique stability structure. We establish that Gubser–Rocha models belong to this topological classification. These results significantly expand the existing classification framework while reinforcing thermodynamic topology as a robust analytical tool for probing the universal properties of black holes in both gravitational and holographic contexts. The findings provide new insights into the relationship between microscopic couplings and macroscopic thermodynamic behavior in extended gravity theories
Topological Mod(A)Max AdS black holes
No full textIn this work, we construct new classes of topological black hole solutions in anti-de Sitter (AdS) spacetime using a novel model of nonlinear electrodynamics called Modification Maxwell (ModMax) and Modification phantom or Modification anti-Maxwell (ModAMax). We then evaluate the thermodynamic quantities and verify the first law of thermodynamics. Our study examines how the parameters of the ModMax and ModAMax fields, as well as the topological constant, affect the black hole solutions, thermodynamic quantities, and local and global thermal stabilities. Furthermore, within the framework of extended phase space thermodynamics, we analyze the Joule–Thomson expansion process and determine the inversion curves. This analysis reveals that the ModMax and ModAMax parameters significantly alter the cooling and heating behavior of these AdS black holes, depending on their topology. Finally, by treating these topological Mod(A)Max AdS black holes as heat engines, we assess their efficiencies, demonstrating that the parameters of nonlinear electrodynamics and horizon topology play crucial roles in enhancing or suppressing the system’s thermodynamic performance
Tighter constraints on the atmosphere of GJ 436 b from combined high-resolution CARMENES and CRIRES
No full textContext. Transmission spectra of Neptune-sized exoplanets are frequently observed to be featureless at low-to-mid resolutions from space; whereas high-altitude clouds can mute spectral features, high atmospheric metallicities can also result in compressed envelopes, where low scale heights may also yield undetectable signatures.
Aims. We aim to study the atmospheric properties of the warm Neptune GJ 436 b by combining a set of five transit events observed with the CARMENES spectrograph with one transit from CRIRES+ so as to provide the most constrained results possible at high resolution.
Methods. We removed telluric and stellar signals from the data using SysRe
Cancer Immunotherapy: From Immune Surveillance to Clinical Applications
No full textCancer immunotherapy is an important means of treating cancer by clearing malignant cells through the immune system. Unlike chemotherapy or radiation therapy that directly targets tumors, immunotherapy enhances immune recognition and memory, thus having higher specificity and the possibility of lasting remission. The immune surveillance theory provided the foundation for this method, which was later refined into an immune editing model. Tumors utilize these processes through immune checkpoint signaling, inhibitory cell recruitment, metabolic competition, and the formation of an immunosuppressive microenvironment, which presents significant challenges for treatment. The advancement of medical technology has not only driven the development of immune checkpoint inhibitors (ICIs), but also demonstrated their significant efficacy - drugs such as anti-CTLA-4 and anti-PD-1/PD-L1 antibodies have produced meaningful results in melanoma, lung cancer, and other cancers. Significant progress has been made in cell therapy for hematological cancers, with tumor infiltrating lymphocytes (TIL) and chimeric antigen receptor (CAR) T cells demonstrating considerable effectiveness. Cancer vaccines are used to induce targeted adaptive responses. Immune modulators can enhance innate immune activation and strengthen checkpoint blockade