Variations In Degree Of Polarization Research Articles

Limiting the accretion disc light in two mass transferring hot subdwarf binaries

ABSTRACT We report the results from follow-up observations of two Roche-lobe filling hot subdwarf binaries with white dwarf companions predicted to have accretion discs. ZTF J213056.71+442046.5 (ZTF J2130) with a 39-min period and ZTF J205515.98+465106.5 (ZTF J2055) with a 56-min period were both discovered as subdwarf binaries with light curves that could only be explained well by including an accretion disc in their models. We performed a detailed high-resolution spectral analysis, using Keck/ESI to search for possible accretion features for both objects. We also employed polarimetric analysis using the Nordic Optical Telescope (NOT) for ZTF J2130. We did not find any signatures of an accretion disc in either object, and placed upper limits on the flux contribution and variation in degree of polarization due to the disc. Owing to the short 39-min period and availability of photometric data over 6 yr for ZTF J2130, we conducted an extensive O − C timing analysis in an attempt to look for orbital decay due to gravitational wave radiation. No such decay was detected conclusively, and a few more years of data paired with precise and consistent timing measurements were deemed necessary to constrain $\dot{P}$ observationally.

Retrieval of marine inorganic particle concentrations in turbid waters using polarization signals

ABSTRACT The polarization properties of water-leaving radiance (L w) contains rich information about hydrosols, which has great potential to improve the retrieval accuracy of oceanic constituents. However, current ocean colour inversion algorithms are only based on the water-leaving radiation intensity, and the polarization properties have been ignored. Here, based on the radiative transfer simulations, the possibility of retrieving suspended particulate matter in turbid waters based on the polarization properties was investigated. The results showed that the degree of polarization (DOP) of the upward radiation just beneath the water surface has significant angular and spectral variations with respect to the observational geometries, inorganic particle concentrations, solar zenith angles and aerosol optical thicknesses (AOTs). The directional variations in DOP along with viewing zenith angles are typically characterized by a double peak feature with a maximum of 0.5 in the principal plane. In addition, the DOP in the visible bands is highly sensitive to inorganic particle concentrations. The DOP gradually decreases from 412 nm to 555 nm and increases with wavelengths beyond 555 nm, particularly for wavelengths larger than 620 nm. An empirical relationship between the DOP at 670 nm and the inorganic particle concentration was established for different viewing geometries with determination coefficient (R 2) up to 0.9996. Overall, our simulation results indicate that the polarization property of underwater upward radiance has great potential for suspended particulate matter retrieval in coastal waters.

Optical spectroscopic and polarization properties of 2011 outburst of the recurrent nova T Pyxidis

Aims. We aim to study the spectroscopic and ionized structural evolution of T Pyx during its 2011 outburst, and also study the variation in degree of polarization during its early phase. Methods. Optical spectroscopic data of this system obtained from day 1.28–2415.62 since discovery, and optical, broadband imaging polarimetric observations obtained from day 1.36–29.33 during the early phases of the outburst were used in the study. The physical conditions and the geometry of the ionized structure of the nova ejecta was modelled for a few epochs using the photo-ionization code, CLOUDY in 1D and pyCloudy in 3D. Results. The spectral evolution of the nova ejecta during its 2011 outburst is similar to that of the previous outbursts. The variation in the line profiles is seen very clearly in the early stages due to good coverage during this period. The line profiles vary from P Cygni (narrower, deeper, and sharper) to emission profiles that are broader and structured, which later become narrower and sharper in the late post-outburst phase. The average ejected mass is estimated to be 7.03 × 10−6 M⊙. The ionized structure of the ejecta is found to be a bipolar conical structure with equatorial rings, with a low inclination angle of 14.75 ° ±0.65°.

Multi-frequency Variability Study of Ton 599 during the High Activity of 2017

Abstract In this work, I have presented a multi-frequency variability and correlation study of the blazar Ton 599, which was observed for the first time in the flaring state at the end of 2017. Data from Fermi-LAT, Swift-XRT/UVOT, Steward observatory, and Owens Valley Radio Observatory(OVRO) (15 GHz) are used and it is found that the source is more variable in γ-rays and optical/UV than in X-rays and radio. Large variations in degree of polarization and position angle are observed during the flaring period. Maximum flux during the γ-ray flare is found to be 12.63 × 10−7 at MJD 58057.5 from the 1 day bin light curve, which is the highest flux ever achieved by this source. It is further found that all the peaks of the flare are very symmetric, which suggests the cooling time of electrons is much smaller than the light-crossing time. Using 1 day as a fast variability time, the size of the γ-ray emission region is estimated as 1.88 × 1016 cm. Two 42 GeV of photons are detected during the flare, which puts a constraint on the location of the emission region, and it is found that the γ-ray emitting blob is located at the outer edge or outside the broad-line region. The trend of increasing fractional variability toward higher energies is also seen. Strong correlations were seen between γ-ray, optical/UV, X-ray, and radio (15 GHz) emission. A small time lag between γ-rays and the optical/UV suggests their emission to be co-spatial, while the lag of 27 days between γ-rays and OVRO (15 GHz) suggests two different emission zones separated by a distance of ∼5 pc.

Assessment of magneto-optic Faraday effect-based drift on interferometric single-mode fiber optic gyroscope (IFOG) as a function of variable degree of polarization (DOP)

In this study, a novel interferometric fiber optic gyroscope (IFOG), which has a different depolarizer structure, is designed in TUBITAK UME (National Metrology Institute of Turkey) to experimentally and relatively evaluate the effect of the degree of polarization on the Faraday effect-based drift of the light waves injected into both arms of a Sagnac interferometer. In order to observe whether or not any change occurs in the Faraday-based drift, depending on the variations in degree of polarization (DOP), a triple structure-depolarizer IFOG possessing adjustable DOP is firstly designed and prototyped. The minimum DOP achieved with triple structure-depolarizers is typically 0.15% for both clockwise (CW) and counterclockwise (CCW) light waves at both arms of the Sagnac interferometer. The experimental evaluations about the drift are given for DOP changes extending from 78.00% to 0.15% together with two main and different theoretical approaches in the literature. According to the experimental evaluations given herein, it is experimentally proved that the Faraday-based drift does not change depending on DOP values of both CW and CCW light waves injected into the single-mode (SM) sensing coil and it is impossible to state a concept of a depolarized IFOG by considering the polarization state at the entrance arms of the SM sensing coil.

SIMULTANEOUS PHOTOMETRIC AND POLARIMETRIC OBSERVATIONS OF ASTEROID 3 JUNO

Simultaneous photometric and polarimetric observations of asteroid 3 Juno have been carried out with a low-resolution spectropolarimeter HBS at Okayama Astrophysical Observatory from 2000 August 4 to 8. The amplitude of the light curve was 0.14 mag with almost the same brightness maxima and 0.10 mag different minima. Polarimetric data showed one maximum and minimum in the absolute values of polarization degree |Pr |, and the difference attained 0.149% in the V band. The minimum of |Pr | appeared around the second minimum of the light curve, which means that a bright area exists on the surface of 3 Juno. We found that the values of |Pr | tend to increase 0.1%-0.2% with wavelength, and this result is consistent with the general tendency of S-type asteroids. In addition, we might find that the increase rate of |Pr | is steeper in wavelengths longer than 7000 A. From the variation of polarization degree with the rotation of 3 Juno, we estimated the albedo of the bright area with a simple model and obtained a range of 0.19-0.41.

What causes the variation of polarization degree across the emission spectrum of proteins?

A gradual decrease in fluorescence polarization across the emission spectrum on increase in wavelength has been recorded for a number of proteins and also for tryptophan, N-acetyltryptophan and glycyltryptophan. Various factors responsible for this dependence have been analyzed. It is shown that if the emission originates from both the 1La and 1Lb states, the position and form of the fluorescence spectrum polarization components as well as the slope of the dependence of the degree of polarization upon emission wavelength must always vary with the excitation wavelength. However, this condition, although necessary, is not enough to prove the participation of 1Lb in emission. The dependence of the form of the emission polarization spectrum upon excitation wavelength obtained for some proteins is explained by tyrosine residues contributing to the emission. Consequently, there are no reasons for assuming that the 1Lb oscillator participates in emission. It has been observed that for individual emitting centres, the slope of the dependence of the degree of polarization upon emission wavelength is determined by alteration of the vibrational substates, between which the transition with radiation takes place. The heterogeneity in the microenvironment properties of separate tryptophan residues in multitryptophan proteins and the existence, under certain conditions, of a correlation between the radiative lifetime of the emitting centre (determining the degree of the emission polarization) and the completeness of the microenvironment orientational relaxation (determining the emitted quantum of energy) can also affect the slope of this dependence.