Additional Radiation Source Research Articles

SN 2018gj: A Short Plateau Type II Supernova with Persistent Blueshifted Ha Emission

We present an extensive, panchromatic photometric (UV, optical, and near-IR) and low-resolution optical spectroscopic coverage of a Type IIP supernova SN 2018gj that occurred on the outskirts of the host galaxy NGC 6217. From the V-band light curve, we estimate the plateau length to be ∼ 70 ± 2 days, placing it among the very few well-sampled short plateau supernovae (SNe). With V-band peak absolute magnitude M V ≤ −17.0 ± 0.1 mag, it falls in the middle of the luminosity distribution of the Type II SNe. The color evolution is typical to other Type II SNe except for an early elbow-like feature in the evolution of V − R color owing to its early transition from the plateau to the nebular phase. Using the expanding photospheric method, we present an independent estimate of the distance to SN 2018gj. We report the spectral evolution to be typical of a Type II SNe. However, we see a persistent blueshift in emission lines until the late nebular phase, not ordinarily observed in Type II SNe. The amount of radioactive nickel (56Ni) yield in the explosion was estimated to be 0.026 ± 0.007 M ⊙. We infer from semianalytical modeling, nebular spectrum, and 1D hydrodynamical modeling that the probable progenitor was a red supergiant with a zero-age-main-sequence mass ≤13 M ⊙. In the simulated hydrodynamical model light curves, reproducing the early optical bolometric light curve required an additional radiation source, which could be the interaction with the proximal circumstellar matter.

RADIOPROTECTION SURVEILLANCE OF THE TJ-II OPERATION BY TLD.

The TJ-II stellarator presently in operation at the National Laboratory of Fusion is subject to radiological surveillance in compliance with the Spanish Nuclear Regulation. During its pulsed operation hard X-rays are emitted by the runaway electrons, and soft X-rays are generated by bremsstrahlung of thermalized electrons. Inside the experimental hall, the plasma heating systems and some active diagnostics are additional sources of radiation. Outside the experimental hall, some auxiliary systems, such as high-voltage power supplies, must be checked for radiological influence. In order to verify the adequate radiological classification of the different working areas, 15 dosemeters are distributed in radiologically controlled areas close to the machine, as well as in areas of public use in the TJ-II building. The integrated dose equivalent is analyzed to help establish the range of radiological influence of the stellarator. The results of the period 2015-20 are presented and analyzed.

Additional radiation sources in a treatment and control room of medical linear accelerators

Typical medical linear accelerators generating high-energy photon beams used in radiotherapy are a source of neutrons and induced radioactivity undesirable mainly in radiological protection of medical staff but also for treatment of patients. The main source of the secondary radiation are massive components of an accelerator head. The purpose of this work was to study additional sources of gamma rays and neutrons in the treatment and control rooms for the Elekta accelerator. Identification of radioisotopes induced in several examined objects used and stored in the treatment room, and measurements of the spectrum of gamma rays originated in the treatment room door or travelling through it were carried out using a gamma–ray spectroscopy technique with an HPGe detector. Additionally, identification of neutron field was performed in the control room. In total, five nuclear reactions and five radioisotopes Mn-56, Sb-122, Fe-59, Li-7 and Al-28 were identified basing on gamma rays from the radioactive decays in the 20 cm × 20 cm electron applicator enabling collimation of the therapeutic electron beam, a Wood’s alloy tray used as an additional shield against radiation, a special drawer for placing additional radiation shields, and a brick used to shield electronic modules of supporting equipment. Similarly, five nuclear reactions were also observed registering prompt gamma rays in the control room. The dominating nuclear reaction was the neutron capture. Moreover, the reactions induced by neutrons in the germanium crystal of the used HPGe detector confirmed the presence of neutrons in the control room.

Actual Trends in the Application of Rare-Earth Metals and Their Compounds in the Production of Magnetic and Luminescent Materials: A Review

Current trends in the application of rare-earth metals (REMs) in two major scientific and technological fields—the production of magnetic and luminescent materials—are considered. It is shown that it is REMs that endow these products with unique properties. The information on the content of the matrix and doping components and their influence on achieving the required characteristics of the most popular magnetic materials is systematized. The potential of new combinations of REMs for further progress in the production of magnetic materials for various purposes is described. Along with the traditional cobalt–samarium and neodymium–iron–boron compositions, new magnetic materials with increased hysteresis properties and better time–temperature stability are developed, and phases with variable valence, used as memory elements in information systems, are synthesized. In addition, the article also reviews and summarizes the results of studies in the creation of luminescent materials, which is another important area of application of REMs. Phosphors based on compounds of REMs are used in the production of high-pressure mercury lamps with improved characteristics, X-ray screens, high- and low-pressure fluorescent lamps, and screens for electrooptical converters. Narrow-band phosphors based on REM compounds are of interest for lamps used for growing plants, especially in areas with a cold climate, where growing plants year-round is possible only with the use of additional radiation sources. The trends in the synthesis of luminescent materials with varied REMs and their combinations are revealed. Emphasis is placed on the need to use chemically pure REM precursors in the synthesis of such materials. The prospects for the creation of nanophosphors, as well as the improvement of methods of synthesis and diagnostic techniques, are noted.

Lightweight obstacle detector based on scattered IR and Lock-In filtering

Obstacle detection in autonomous navigation involves the processing of the environment information obtained from sensors, such as LIDAR, radar, ultrasonic, magnetic and capacitive. Imaging techniques like stereoscopy, optical flux, and deep image, have been used for precise object detection but with a high computational cost. These sensors also have disadvantages like weight, its size or power consumption. The case of systems with lasers added like in LIDAR can be harmful to people. Ultrasonic sensors are safer for people but the signal to noise ratio decreases in outdoors. IR sensors are cheap and can be clustered to strength signal, however, additional sources of radiation can affect the measurement especially in outdoors. In this work, we propose an IR system with adequate spatial configuration and electronic filters to detect objects indoors and outdoors by means of scattered IR radiation centered at 940 nm. The developed sensor has the following specs: Front area dimensions is 5x5 cm that includes 10 IR LEDs at the center and a Si detector in each corner. The approximated detection volume is 17,000 cm3, considering a detection cone length of 300 cm and a solid angle of 30 degrees. Total system weight is 40 g. System was tested with four experiments to evaluate signal filtering, effect of object surface roughness, repeatability and working sensitivity region. This evaluation allowed to make a comparison with traditional Obstacle Detection System techniques, giving advantages in almost all parameters considered, allowing us to conclude that developed system can detect objects in indoors and outdoors, in a region suitable for aerial and surface vehicles or blind persons.

Mid-UV studies of the transitional millisecond pulsars XSS J12270−4859 and PSR J1023+0038 during their radio pulsar states★

We report mid-UV (MUV) observations taken with HST/WFC3, Swift/UVOT and GALEX/NUV of the transitional millisecond pulsars XSS J12270-4859 and PSR J1023+0038 during their radio pulsar states. Both systems were detected in our images and showed MUV variability. At similar orbital phases, the MUV luminosities of both pulsars are comparable. This suggests that the emission processes involved in both objects are similar. We estimated limits on the mass ratio, companion's temperature, inclination, and distance to XSS J12270-4859 by using a Markov Chain Monte Carlo algorithm to fit published folded optical light curves. Using the resulting parameters, we modeled MUV light curves in our HST filters. The resulting models failed to fit our MUV observations. Fixing the mass ratio of XSS J12270-4859 to the value reported in other studies, we obtained a distance of ~3.2 kpc. This is larger than the one derived from radio measurements (~1.4 kpc). Assuming a uniform prior for the mass ratio, the distance is similar to that from radio measurements. However, it requires an undermassive companion (~0.01 M_sun). We conclude that a direct heating model alone can not fully explain the observations in optical and MUV. Therefore, an additional radiation source is needed. The source could be an intrabinary shock which contributes to the MUV flux and likely to the optical one as well. During the radio pulsar state, the MUV orbital variations of PSR J1023+0038 detected with GALEX, suggests the presence of an asymmetric intrabinary shock.

A survey of eight hot Jupiters in secondary eclipse using WIRCam at CFHT.

We present near infrared high-precision photometry for eight transiting hot Jupiters observed during their predicted secondary eclipses. Our observations were carried out using the staring mode of the WIRCam instrument on the Canada-France-Hawaii Telescope (CFHT). We present the observing strategies and data reduction methods which delivered time series photometry with statistical photometric precision as low as 0.11%. We performed a Bayesian analysis to model the eclipse parameters and systematics simultaneously. The measured planet-to-star flux ratios allowed us to constrain the thermal emission from the day side of these hot Jupiters, as we derived the planet brightness temperatures. Our results combined with previously observed eclipses reveal an excess in the brightness temperatures relative to the blackbody prediction for the equilibrium temperatures of the planets for a wide range of heat redistribution factors. We find a trend that this excess appears to be larger for planets with lower equilibrium temperatures. This may imply some additional sources of radiation, such as reflected light from the host star and/or thermal emission from residual internal heat from the formation of the planet.

A novel system for commissioning brachytherapy applicators: example of a ring applicator

A novel system was developed to improve commissioning and quality assurance of brachytherapy applicators used in high dose rate (HDR). It employs an imaging panel to create reference images and to measure dwell times and dwell positions. As an example: two ring applicators of the same model were evaluated. An applicator was placed on the surface of an imaging panel and a HDR 192Ir source was positioned in an imaging channel above the panel to generate an image of the applicator, using the gamma photons of the brachytherapy source. The applicator projection image was overlaid with the images acquired by capturing the gamma photons emitted by the source dwelling inside the applicator. We verified 0.1, 0.2, 0.5 and 1.0 cm interdwell distances for different offsets, applicator inclinations and transfer tube curvatures. The data analysis was performed using in-house developed software capable of processing the data in real time, defining catheters and creating movies recording the irradiation procedure. One applicator showed up to 0.3 cm difference from the expected position for a specific dwell position. The problem appeared intermittently. The standard deviations of the remaining dwell positions (40 measurements) were less than 0.05 cm. The second ring applicator had a similar reproducibility with absolute coordinate differences from expected values ranging from −0.10 up to 0.18 cm. The curvature of the transfer tube can lead to differences larger than 0.1 cm whilst the inclination of the applicator showed a negligible effect. The proposed method allows the verification of all steps of the irradiation, providing accurate information about dwell positions and dwell times. It allows the verification of small interdwell positions (⩽0.1 cm) and reduces measurement time. In addition, no additional radiation source is necessary since the HDR 192Ir source is used to generate an image of the applicator.

Studying the mechanism of gamma quantum radiation in cosmic gamma-ray bursts using data from the Swift, CGRO, and FERMI spacecraft

Light curves of 115 bright gamma-ray bursts with known cosmological distances z from sources detected by the BAT telescope on board the Swift spacecraft in four energy channels are analyzed. An averaged curve describing the shift of the light curves is obtained that depends on the energy of the channels in the coordinate system associated with the source. The results are compared to similar detailed curves for individual gamma-ray bursts detected in a wider range of energies by the BATSE (CGRO) and GBM (FERMI) telescopes. The divergence of curves in the region of low energies for some gamma ray bursts indicates the existence of an additional radiation source.

Impact of ambient O2(a1Δg) on satellite-based laser remote sensing of O2columns using absorption lines in the 1.27 µm region

Determination of CO2 mixing ratio columns from space using Laser Absorption Spectroscopy (LAS) requires simultaneous measurements of CO2 number density columns and knowledge of the dry atmospheric surface pressure. One approach to determining the surface pressure is to make an LAS column measurement of O2 number density in the 7857.3–7921.7 cm−1 (1.27 µm) region of the O2(1Δ) state. A complicating factor in the LAS O2 measurement is the presence of a permanent but spatially variable natural source of airglow from the O2(1Δ) state. In addition, the laser radiation can induce stimulated emission from the ambient O2(1Δ) state and also cause stimulated absorption and emission from the ground state O2 molecules as the laser beam passes through the atmosphere. Finally, the upwelling surface-reflected solar radiation is an additional source of background radiation. The effects of these additional radiation sources on the LAS measurement of O2 are examined. The surface-reflected solar radiation produces the largest background at 3 orders of magnitude more intense than the laser backscatter signal, while the airglow is of the same order of magnitude as the laser backscatter. The stimulated emission from ambient O2(a1Δg) is found to be about the same order of magnitude as the laser radiation. These effects are evaluated under noon, twilight, and midnight conditions at midlatitudes, the equator, and the pole. The stimulated emission is in the same direction and in phase with the laser signal, its contamination of the LAS O2 measurement prevents a full sunlight determination of surface pressure.

Synthetic light curves of close binaries in a cool-disk model. The “hot line” and “hot spot” as visual indicators of interaction between the flow and disk

We present a “combined” model taking into account visual manifestations of the interaction between the gas flow and the accretion disk in a close binary system in the form of a “hot line” and a “hot spot.” The binary consists of a red dwarf that fills its Roche lobe and a compact spherical star (a white dwarf or neutron star) surrounded with a thick ellipsoidal accretion disk of a complex shape. The disk thickness is not large near the compact star but increases according to a parabolic law towards its outer edge. The oblique collision of the gaseous flow with matter of the cool, rotating disk, whose outer edge has a temperature <10 000 K, creates an extended region of enhanced energy release. In the combined model, this region is represented with a hot line that coincides with the optically opaque part of the flow and is located outside the disk, together with a hot spot at the outer surface of the disk, on the leeward side of the flow. The synthetic light curves for the combinedmodel and a hot-line model demonstrate that both models are able to fairly accurately reproduce the shapes of both classical and atypical light curves of cataclysmic variables in quiescence. Our determination of the parameters of the cataclysmic variable OY Car from an analysis of its light curves using the two models shows that the basic characteristics of the close binary, such as the component mass ratio q = M1/M2, orbital inclination i, effective temperatures of the red dwarf (T2) and white dwarf (T1), and orientation of the disk αe, remain the same within the errors. The parameters describing the size of the slightly elliptical disk and the radiation flux from the disk differ by several percent (∼ 2–8%). A more significant difference is detected in the parameters of the hot line, due to the different shape and alignment of the flow and the presence of an additional radiation source—the hot spot—on the disk.

Delayed recombination and standard rulers

Measurements of baryonic acoustic oscillations (BAOs) in galaxy surveys have been recognized as a powerful tool for constraining dark energy. However, this method relies on the knowledge of the size of the acoustic horizon at recombination derived from cosmic microwave background (CMB) anisotropy measurements. This estimate is typically derived assuming a standard recombination scheme; additional radiation sources can delay recombination altering the cosmic ionization history and the cosmological inferences drawn from CMB and BAO data. In this paper we quantify the effect of delayed recombination on the determination of dark energy parameters from future BAO surveys such as the Baryon Oscillation Spectroscopic Survey and the Wide-Field Multi-Object Spectrograph. We find the impact to be small but still not negligible. In particular, if recombination is nonstandard (to a level still allowed by CMB data), but this is ignored, future surveys may incorrectly suggest the presence of a redshift-dependent dark energy component. On the other hand, in the case of delayed recombination, adding to the analysis one extra parameter describing deviations from standard recombination does not significantly degrade the error bars on dark energy parameters and yields unbiased estimates. This is due to the CMB-BAO complementarity.

Cosmological constraints in the presence of ionizing and resonance radiation at recombination

With the recent measurement of full sky cosmic microwave background (CMB) polarization from WMAP, key cosmological degeneracies have been broken, allowing tighter constraints to be placed on cosmological parameters inferred assuming a standard recombination scenario. Here we consider the effect on cosmological constraints if additional ionizing and resonance radiation sources are present at recombination. We find that the new CMB data significantly improve the constraints on the additional radiation sources, with ${log}_{10}[{ϵ}_{\ensuremath{\alpha}}]&lt;\ensuremath{-}0.5$ and ${log}_{10}[{ϵ}_{i}]&lt;\ensuremath{-}2.4$ at 95% c.l. for resonance and ionizing sources, respectively. Including the generalized recombination scenario, however, we find that the constraints on the scalar spectral index ${n}_{s}$ are weakened to ${n}_{s}=0.98\ifmmode\pm\else\textpm\fi{}0.03$, with the ${n}_{s}=1$ case now well inside the 95% c.l. The relaxation of constraints on tensor modes, scale invariance, dark energy and neutrino masses are also discussed.

The Application of Reflected GPS Signals to Ocean Remote Sensing

The L-band broadcast signal from the Global Positioning System (GPS) reflected off of the sea surface is under study for use as a ocean, coastal, and wetlands remote sensing tool. The reflected signal from a given GPS satellite is cross-correlated with the pseudorandom noise code uniquely identifying that satellite. The shape of this cross-correlation, ordinarily a very sharp triangle when tracking a direct line of sight signal, becomes wider and smoother as the mean square slope of the reflecting surface increases. It is proposed that the surface wind speed can be determined by matching the recorded shape of this cross-correlation to that predicted by theoretical models as a function of wind speed and direction. The significance of these effects increases with altitude of the receiver. Experimental data have been collected using a specially modified GPS receiver on aircraft and on a balloon at altitudes of up to 25 km. These data compare favorably with predictions of analytical models and demonstrate the dependence of the waveform shape on surface wind speed and receiver altitude. The advantages that this measurement technique has over conventional scatterometers is the small size, low cost and simplicity of the receiver hardware, no requirement for a transmitter, and the ability to simultaneously collect data from usually 10 or more points (from a low earth-orbiting satellite). This number could be larger if the Russian Global Navigation Satellite System satellites are also considered as additional sources of radiation. Furthermore, the bistatic scattering geometry is complementary to the backscatter used by conventional scatterometers.

The Spectrum of TeV Gamma Rays from the Crab Nebula

The spectrum of gamma rays from the Crab Nebula has been measured in the energy range 500 GeV-8 TeV at the Whipple Observatory by the atmospheric Cerenkov technique. Two methods of analysis that were used to derive spectra, in order to reduce the chance of calibration errors, gave good agreement, as did analysis of observations made with changed equipment several years apart. It is concluded that stable and reliable energy spectra can now be made in the TeV range. The spectrum can be represented in this energy range by the power-law fit, J = (3.20 ± 0.17 ± 0.6) × 10-7 × (E/1 TeV)-2.49±0.06±0.04 m-2 s-1 TeV-1, or by the following form, which extends much better to the GeV domain: J=(3.25±0.14±0.6)×10−7E m-2 s-1 TeV-1 (E in TeV). The integral flux above 1 TeV is (2.1 ± 0.2 ± 0.3) × 10-7 m-2 s-1. Using the complete spectrum of the Crab Nebula, the spectrum of relativistic electrons is deduced, and the spectrum of the inverse Compton emission that they would generate is in good agreement with the observed gamma-ray flux from 1 GeV to many TeV, if the magnetic field in the region where these scattered photons originate (essentially the X-ray-emitting region, around 0.4 pc from the pulsar) is ~16 nT (160 μG), in reasonable agreement with the field deduced by Aharonian & Atoyan. If the same field strength were present throughout the nebula, there would be no clear need for an additional radiation source in the GeV domain such as has recently been suggested; the results give an indication that the magnetic field is well below the often-assumed equipartition strength (35-60 nT). Further accurate gamma-ray spectral measurements over the range from 1 GeV to tens of TeV have the potential to probe the growth in the magnetic field in the inner region of the nebula.