We present a photometric study of the poorly investigated eclipsing binary KOI 6832 using 1459.49 d of long cadence Kepler observations. The Wilson–Devinney light curve solution favours a detached configuration composed of two cool late type components. With T1=4573 K fixed, the adopted solution gives T2=4501 K, q=0.92, i=87.47°, and mean fractional radii of 〈r1〉=0.0374 and 〈r2〉=0.0464. The calibration dependent absolute parameters are M1=0.71M⊙, M2=0.66M⊙, R1=0.61R⊙, and R2=0.76R⊙, although radial velocities are required for dynamical values. The secondary eclipse occurs near phase 0.49; after adopting ΔE=0.49, no significant timing variation requiring apsidal motion or a light time effect is detected. The eclipse cleaned light curve shows a dominant modulation at ν1=0.1355d−1, corresponding to Prot=7.3805 d, different from Porb=6.490663 d and consistent with asynchronous or latitude dependent spot modulation. We detect 59 flares, with N1=0.001684h−1 and N2=9.190×10−6. The OPEA model gives a Plateau value of 1.724 ± 0.1739 and a half time of 6853.42 s. We conclude that KOI 6832 is a magnetically active detached binary showing flare activity, spot modulation, and non-synchronous surface rotation.
We investigate photon motion, black-hole shadows, weak gravitational lensing, and image magnification for a charged static black hole in bumblebee gravity immersed in dispersive plasma environments. The bumblebee field introduces spontaneous Lorentz-symmetry breaking through the dimensionless parameter L, while the electric charge is characterized by Q/M. Photon propagation is treated with the Hamiltonian formalism for a cold non-magnetized plasma. A homogeneous plasma and a non-uniform power-law profile are used in the photon-sphere and shadow analyses, while homogeneous and singular-isothermal-sphere (SIS) plasmas are considered in the weak-lensing analysis We first determine the allowed black-hole domain from the horizon condition and then compute the photon-sphere radius, optical shadow radius, EHT-compatible angular shadow size, weak deflection angle, and magnification observables. The results show that increasing the charge-to-mass ratio decreases the photon-sphere and shadow radii and suppresses the weak deflection angle, while the Lorentz-violating parameter produces a milder but systematic reduction of these observables through its coupling to the charge sector. Plasma dispersion shifts the photon sphere outward but reduces the apparent shadow radius; in contrast, its effect on weak lensing depends on the plasma profile, enhancing the homogeneous-plasma deflection while slightly suppressing the SIS-plasma deflection. We further confront the theoretical shadow with the Event Horizon Telescope measurements of M87* and Sgr A*. The EHT angular diameters, θM87∗=42±3μas and θSgr A∗=48.7±7μas, translate into exclusion regions in the (L,Q/M) parameter space and show that charge, Lorentz violation, and plasma dispersion are strongly degenerate in shadow-based tests. These results demonstrate that simultaneous use of shadow constraints, weak deflection, and magnification can provide complementary probes of Lorentz-violating charged black-hole spacetimes in realistic plasma environments.
Rotating regular black holes (BHs) share a signature: their effective source obeys the null and weak energy conditions everywhere and breaks the dominant one only inside a compact core. We ask whether an algebraically non-local deformation reproduces that pattern. The charged Dunkl metric function of Baddis et al. extended by a Letelier cloud of strings, is rotated with the Azreg-Aïnou modified Newman–Janis algorithm, and we read the matter content off the Einstein tensor so that the analysis rests on the ordinary field equations rather than on the Dunkl-modified operators that motivate the seed. The effective mass function splits into three powers of r, carrying the string deficit, the Dunkl-renormalized mass and the Coulomb term. Conservation follows from the contracted Bianchi identity, and symbolic and numerical checks confirm the curvature invariants and every stress–energy component. The pattern is not reproduced. The strong energy condition fails on the whole scanned domain and the null, weak and dominant conditions over most of it, so the source is phantom-like rather than regular. A horizon survives up to a ceiling on the string density, with no closed timelike curves outside it. Event Horizon Telescope diameters bound both deformation parameters, and a precession fit to twin oscillations returns a Dunkl parameter near 0.3 in three X-ray binaries.
There are several reports on the rotational behavior of different kinds of solar features. However, a direct comparison of the rotation rates of disk-integrated bright and dark coronal features over the same observing interval has received little attention. Here, we compare the temporal variability of the rotation rates of disk-integrated bright features (BFs) and dark features (DFs) of the solar corona. For this, we applied flux modulation (FM) method on the solar full disk (SFD) images at 21.1 nm wavelength taken by the SDO/AIA space mission between 2011 and 2025 covering the descending phase of Solar Cycle 24, its minimum, and the ascending and maximum phases of Solar Cycle 25. Here, we find that temporal variation of rotation rates of BFs and DFs largely follow the trend of solar activity cycle from 2011 to 2025. We noticed that every year, BFs have slightly higher rotation rate than DFs. The difference is relatively small during the descending phase and minimum of Cycle 24 but increases substantially during the ascending and maximum phases of Cycle 25, reaching its highest value in 2024. Notably, the variation of this difference also follow the same temporal variation as solar activity from 2011 to 2025. The observed differences in the rotation rates of BFs and DFs appears to arise from the differential rotation of the solar corona, since most BFs are concentrated at mid-latitudes where the rotation is intrinsically faster. Furthermore, these results demonstrate that disk-integrated intensity measurements give a significant approach for studying the temporal evolution of solar rotation and its connection with the solar activity cycle.
The heaviest known pulsars (≃2.08M⊙) require a stiff dense-matter equation of state (EOS); the three-nucleon force supplies the stiffening and dominates the uncertainty where the maximum mass is set. We organise the EOS by connectedness, as a graded sum of connected n-body cumulants Λn, with the relativistic mean field as its leading two-body truncation and the maximum-mass stiffening carried by the three-body cumulant Λ3. In neutron matter the Pauli closure of Hebeler and Schwenk fixes Λ3 by two-body data — by the pion–nucleon couplings at N2LO, with no three-body constant entering through N3LO — and the assembly, with a single three-body regulator constant, reproduces ab initio quantum Monte Carlo to 7%–15% up to 2n0. We build the star from this engine with no input from observation: the cumulant EOS is computed to 10n0, taken to β-equilibrium with empirical symmetric matter (symmetry energy 38 MeV, slope 59 MeV, the latter consistent with ab initio values) and solved for the stellar structure. It is causal, crosses cs2=1/3 at 3.5n0 and gives Mmax=1.92 (1.86–1.98)M⊙ with R1.4=11.8 km and Λ1.4=286; closed conformally at 2n0 it gives a floor of 1.91M⊙, robust to closure violations and higher-order forces at the 0.03M⊙ level. Reaching 2.08M⊙ requires a super-conformal stiffening immediately above 2n0. A Bayesian analysis of a flexible, perturbative-QCD-consistent extension against NICER, GW170817 and the radio masses gives a peak sound speed of 0.80 (90%: 0.50–1.00), super-conformal with probability 1.00, and Mmax=2.28 (2.08–2.59)M⊙: the data require the stiffening but do not pin it.
