Gemini/GMOS Transmission Spectroscopy of the Grazing Planet Candidate WD 1856+534 b

WD 1856+534 b is a Jupiter-sized, cool giant planet candidate transiting the white dwarf WD 1856+534. Here, we report an optical transmission spectrum of WD 1856+534 b obtained from ten transits using the Gemini Multi-Object Spectrograph. This system is challenging to observe due to the faintness of the host star and the short transit duration. Nevertheless, our phase-folded white light curve reached a precision of 0.12%. WD 1856+534 b provides a unique transit configuration compared to other known exoplanets: the planet is 8× larger than its star and occults over half of the stellar disk during mid-transit. Consequently, many standard modeling assumptions do not hold. We introduce the concept of a “limb darkening corrected, time-averaged transmission spectrum” and propose that this is more suitable than ( R p , λ / R s ) 2 for comparisons to atmospheric models for planets with grazing transits. We also present a modified radiative transfer prescription. Though the transmission spectrum shows no prominent absorption features, it is sufficiently precise to constrain the mass of WD 1856+534 b to be >0.84 M J (to 2σ confidence), assuming a clear atmosphere and a Jovian composition. High-altitude cloud decks can allow lower masses. WD 1856+534 b could have formed either as a result of common envelope evolution or migration under the Kozai–Lidov mechanism. Further studies of WD 1856+534 b, alongside new dedicated searches for substellar objects around white dwarfs, will shed further light on the mysteries of post-main-sequence planetary systems.

Deformation mechanism coherent migration of charges in thin film

We present new mechanism of the charge transport in thin films based on coherent migration of the deformation of the nanoclusters potential, which carries with it an electron. We represent correlation between deformation and charges as the distorton-inverson quasiparticle. This effect is based on the inversion of the potential energy of nanoclusters due to the Jahn-Teller effect in a nanocluster, when charges flow in a network of nanoclusters. The distorton-inverson is quasiparticle are consisted the distorton and electron or hole, this quasiparticle similar an inverson in the Watkins effect. A distorton is quasiparticle which appears itself in the effects of deformation of the potential of the nanocluster with not closed shell. This quasiparticle is similar a defecton in the Watkins effect. We are calculated transmission spectrum and dispersion properties this quasiparticle.

The influence of the surface density of oriented nickel networks on the conducting electrode’s optical transparency

This study is part of the work on the creation of a transparent conductive coating based on oriented nanonetwork and submicron nickel fibres. It is devoted to finding the optimal values of electrical conductivity and optical transparency of the developed coating. In this work, we study the transmission spectra of oriented nickel networks on a glass substrate in the UV, visible and near-IR regions at different amounts of deposited metal. An exciting feature of the coating was discovered: in the range of 950 nm and above, there is a "bend" of the transmission spectrum downward. This bend (increased absorption of radiation in the near-IR region) is observed only in the presence of nickel nanonetwork and is not typical for a pure submicron network.

Hollow Core Bragg Fiber-Based Sensor for Simultaneous Measurement of Curvature and Temperature

In this paper, the hollow core Bragg fiber (HCBF)-based sensor based on anti-resonant reflecting optical waveguide (ARROW) model is proposed and experimentally demonstrated for simultaneous measurement of curvature and temperature by simply sandwiching a segment of HCBF within two single-mode fibers (SMFs). The special construction of a four-bilayer Bragg structure provides a well-defined periodic interference envelope in the transmission spectrum for sensing external perturbations. Owing to different sensitivities of interference dips, the proposed HCBF-based sensor is capable of dual-parameter detection by monitoring the wavelength shift. The highest curvature sensitivity of the proposed sensor is measured to be 74.4 pm/m−1 in the range of 1.1859–2.9047 m−1 with the adjusted R square value of 0.9804. In the meanwhile, the best sensitivity of temperature sensing was detected to be 16.8 pm/°C with the linearity of 0.997 with temperature range varying from 25 to 55 °C. Furthermore, with the aid of the 2 × 2 matrix, the dual demodulation of curvature and temperature can be carried out to realize the simultaneous measurement of these two parameters. Besides dual-parameter sensing based on wavelength shift, the proposed sensor can also measure temperature-insensitive curvature by demodulating the intensity of resonant dips.

Long period fibre gratings inscribed by sinusoidal intensity modulated femtosecond laser

To the best of our knowledge, this is the first study to propose and verify a novel and simple direct inscription method for long-period fibre gratings (LPFGs) with an arbitrary grating period using a sinusoidal intensity modulated femtosecond laser. This method induces a sine refractive index (RI) modulation, which makes the LPFGs have no higher-order harmonic resonance that exists in the normal square-wave modulation method. This is beneficial for reducing the insertion loss of the LPFGs and optimising the transmission spectrum. Using this method, we also conveniently realise the inscription of superimposed, apodised, and chirped LPFGs. This work presents a simple but effective inscription scheme for various types of LPFGs using a femtosecond laser.

UV Absorption by Silicate Cloud Precursors in Ultra-hot Jupiter WASP-178b

Aerosols have been found to be nearly ubiquitous in substellar atmospheres. Evidence for the composition and conditions whereby these aerosols form remains limited (Cushing et al. 2006, Saumon & Marley 2008, Burningham 2021). Theoretical models and observations of muted spectral features suggest that silicate clouds play an important role in exoplanets between at least 950 and 2,100 K (Gao et al. 2020). However, some giant planets are thought to be hot enough to avoid condensation of even the most refractory elements (Lothringer et al. 2018, Kitzmann et al. 2018). Here, we present the near-UV transmission spectrum of an ultra-hot Jupiter WASP-178b (~2,450 K), that exhibits significant NUV absorption indicating the presence of gaseous refractory elements in the middle atmosphere. This short-wavelength absorption is among the largest spectral features ever observed in an exoplanet in terms of atmospheric scale heights. Bayesian retrievals indicate the broadband UV feature on WASP-178b is caused by refractory elements including silicon and magnesium bearing species, which are the precursors to condensate clouds at lower temperatures. Silicon in particular has not been detected in exoplanets before, but the presence of SiO in WASP-178b is consistent with theoretical expectation as the dominant Si-bearing species at high temperatures. These observations allow us to re-interpret previous observations of HAT-P-41b and WASP-121b to suggest that silicate cloud formation begins on exoplanets with equilibrium temperatures between 1,950 and 2,350 K.

Active narrowband filter based on 2.5D metasurface from Ge2Sb2Te5

We propose a new concept of an active narrowband filter based on a 2.5D metasurface from Ge2Sb2Te5 (GST). In this paper, we present a numerical calculation of the transmission spectrum from a structure of ellipsoids of revolution. For this 2.5D metasurface, modulation of narrow peaks in the IR range for s- and p-polarization is shown. A manufacturing technique using two-photon lithography and laser electrodispersion is proposed.

Simulation of the Transmission Spectrum of Long-Period Fiber Gratings Structures with a Propagating Acoustic Shock Front

In this paper, we investigate modification of transmission spectra of long-period fiber grating structures with an acoustic shock front propagating along the fiber. We simulate transmission through inhomogeneous long-period fiber gratings, π-shift and reflective π-shift gratings deformed by an acoustic shock front. Coupled mode equations describing interaction of co-propagating modes in a long-period fiber grating structures with inhomogeneous deformation are used for the simulation. Two types of apodization are considered for the grating modulation amplitude, such as uniform and raised-cosine. We demonstrate how the transmission spectrum is produced by interference between the core and cladding modes coupled at several parts of the gratings having different periods. For the π-shift long-period fiber grating having split spectral notch, the gap between the two dips becomes several times wider in the grating with the acoustic wave front than the gap in the unstrained grating. The behavior of reflective long-period fiber gratings depends on the magnitude of the phase shift near the reflective surface: an additional dip is formed in the 0-shift grating and the short-wavelength dip disappears in the π-shift grating.