Optical Flux Research Articles

Multiple-wavelength Correlation and Variation Study for 3C 279 at Various Timescales

The study on variation phenomena of blazars can shed light on the jet activity and structures. We collect nearly ten years γ-ray, X-ray, optical, and radio light curves of the target 3C 279, and use the local cross-correlation function to perform the correlation analysis among them. Based on lags among different wavelengths, we obtain that the optical as well as the X-ray emitting regions are and pc away from the jet base, and are upstream of the radio core region. The optical and γ-ray emitting regions are not completely co-spatial. We select several periods to study various variation phenomena at long-term, short-term, and very-short-term timescales. We find a redder when brighter trend of the optical color index at the quiescent state and a bluer when brighter trend at the active state. We also find a softer when brighter trend of the γ-ray at low luminosity and a possible harder when brighter trend at high luminosity. The correlation between the optical polarization and fluxes is complex. We find an anticorrelation for one long-term flare, and positive correlations for two short-term flares. The stack of the multiple optical components can explain the anticorrelation, while the appearance of a dominating component can explain the positive correlations. The disk plus many jet components scenario can explain the complex optical variation behaviors for 3C 279. As a remarkable intermediate synchrotron peaked blazar target, 3C 279 play an important role to understand the classification and transition between the low synchrotron peaked and high synchrotron peaked subclass of blazars, since its variation phenomena shows the indication of connection between these two categories.

Revisiting X-Ray-bright Optically Normal Galaxies with the Chandra Source Catalog

X-ray bright optically normal galaxies (XBONGs) are galaxies with X-ray luminosities consistent with those of active galactic nuclei (AGNs) but no evidence of AGN optical emission lines. Crossmatching the Chandra Source Catalog version 2 with the Sloan Digital Sky Survey sample of spectroscopically classified galaxies, we have identified 817 XBONG candidates with L X > 1042 erg s−1 and X-ray to optical flux ratio F XO > 0.1. Comparisons with Wide-field Infrared Survey Explorer colors and near-IR, optical, UV, and radio luminosities show that the loci of XBONGs are in-between those of control samples of normal galaxies and quasars and are consistent with low-luminosity quasars. We find that 43% of the XBONG sample have X-ray colors suggesting N H > 1022 cm−2, double the fraction in the QSO sample, suggesting that a large fraction of XBONG are highly obscured AGNs. However, ∼50% of the XBONGs are not obscured and have X-ray colors harder than those of normal galaxies. Some of these XBONGs have spatially extended X-ray emission. These characteristics suggest that they may be unidentified galaxy groups and clusters. Using the X-ray luminosity functions of QSOs, galaxies, groups and clusters, we estimate the approximate fraction of extended XBONGs to be <20%. We also assess the approximate fraction of XBONGs whose AGN signatures are diluted by stellar light of host galaxies to be ∼30%, based on their redshift and deviation from the extrapolation of the QSO L X–L r relation.

Optical and near-UV spectroscopic properties of low-redshift jetted quasars in the main sequence context

ABSTRACT This paper presents new optical and near-UV spectra of 11 extremely powerful jetted quasars, with radio to optical flux density ratio &amp;gt;103, which concomitantly cover the low-ionization emission of Mg iiλ2800 and hβ as well as the Fe ii blends in the redshift range 0.35 ≲ z ≲ 1. We aim to quantify broad emission line differences between radio-loud (RL) and radio-quiet (RQ) quasars by using the 4D eigenvector 1 parameter space and its main sequence (MS) and to check the effect of powerful radio ejection on the low-ionization broad emission lines. The hβ and Mg iiλ2800 emission lines were measured by using non-linear multicomponent fittings as well as by analysing their full profile. We found that broad emission lines show large redward asymmetry both in hβ and Mg iiλ2800. The location of our RL sources in a UV plane looks similar to the optical one, with weak Fe iiUV emission and broad Mg iiλ2800. We supplement the 11 sources with large samples from previous work to gain some general inferences. We found that, compared to RQ, our extreme RL quasars show larger median hβ full width at half maximum (FWHM), weaker Fe ii emission, larger MBH, lower Lbol/LEdd, and a restricted bf space occupation in the optical and UV MS planes. The differences are more elusive when the comparison is carried out by restricting the RQ population to the region of the MS occupied by RL sources, albeit an unbiased comparison matching MBH and Lbol/LEdd suggests that the most powerful RL quasars show the highest redward asymmetries in hβ.

The Vanishing of the Primary Emission Region in PKS 1510–089

In 2021 July, PKS 1510−089 exhibited a significant flux drop in the high-energy γ-ray (by a factor 10) and optical (by a factor 5) bands and remained in this low state throughout 2022. Similarly, the optical polarization in the source vanished, resulting in the optical spectrum being fully explained through the steady flux of the accretion disk and the broad-line region. Unlike the aforementioned bands, the very-high-energy γ-ray and X-ray fluxes did not exhibit a significant flux drop from year to year. This suggests that the steady-state very-high-energy γ-ray and X-ray fluxes originate from a different emission region than the vanished parts of the high-energy γ-ray and optical jet fluxes. The latter component has disappeared through either a swing of the jet away from the line of sight or a significant drop in the photon production efficiency of the jet close to the black hole. Either change could become visible in high-resolution radio images.

A Multiwavelength Light-curve Analysis of the Classical Nova YZ Ret: An Extension of the Universal Decline Law to the Nebular Phase

YZ Ret is the first X-ray flash detected classical nova, and is also observed in optical, X-ray, and gamma-ray. We propose a comprehensive model that explains the observational properties. The white dwarf mass is determined to be ∼1.33 M ☉, which reproduces the multiwavelength light curves of YZ Ret, from optical, X-ray, to gamma-ray. We show that a shock is naturally generated far outside the photosphere because winds collide with themselves. The derived lifetime of the shock explains some of the temporal variations of emission lines. The shocked shell significantly contributes to the optical flux in the nebular phase. The decline trend of shell emission in the nebular phase is close to ∝t −1.75 and the same as the universal decline law of classical novae, where t is the time from the outburst.

A novel design to optimize the optical performances of parabolic trough collector using Taguchi, ANOVA and grey relational analysis methods

Parabolic trough collectors (PTC) are the most widely used in the world's highest capacity solar power plants. This paper presents a novel design for a PTC that employs Monte Carlo Ray-Trace (MCRT) method to predict the solar flux distribution on the absorber tube surface. The optical modeling results are in good agreement with previous findings in the literature. Taguchi and ANOVA analysis methods are applied to simultaneously investigate multiple control parameters, and determine their contribution rates. Furthermore, the multi-objective optimization of optical efficiency and solar flux uniformity is achieved using the Grey Relational Analysis (GRA) method. The proposed design achieved an optical efficiency of 83.01% and a heat flux uniformity of 92.24%, demonstrating its effectiveness in balancing optical efficiency and heat flux uniformity. The innovative design can be insightful for future development in the concentrated solar energy field.

The nature of the X-ray sources in dwarf galaxies in nearby clusters from the KIWICS

ABSTRACT We present a deep search for and analysis of X-ray sources in a sample of dwarf galaxies (Mr &amp;lt; −15.5 mag) located within twelve galaxy clusters from the Kapteyn IAC WHT Enhanced Area Velocity Explores Isaac Newton Telescope Cluster Survey of photometric observations in the r and g using the Wide Field Camera at the 2.5-m Isaac Newton telescope. We first investigated the optical data, identified 2720 dwarf galaxies in all fields and determined their characteristics; namely, their colours, effective radii, and stellar masses. We then searched the Chandra data archive for X-ray counterparts of optically detected dwarf galaxies. We found a total of 20 X-ray emitting dwarf galaxies, with X-ray flux ranging from 1.7 × 10−15 to 4.1 × 10−14 erg cm−2 s−1 and X-ray luminosities varying from 2 × 1039 to 5.4 × 1041 erg s−1. Our results indicate that the X-ray luminosity of the sources in our sample is larger than the Eddington luminosity limit for a typical neutron star, even at the lowest observed levels. This leads us to conclude that the sources emitting X-rays in our sample are likely black holes. Additionally, we have employed a scaling relation between black hole and stellar mass to estimate the masses of the black holes in our sample, and have determined a range of black hole masses from 4.6 × 104 to 1.5 × 106 M⊙. Finally, we find a trend between X-ray to optical flux ratio and X-ray flux. We discuss the implications of our findings and highlight the importance of X-ray observations in studying the properties of dwarf galaxies.

Clockwise evolution in the hardness–intensity diagram of the black hole X-ray binary Swift J1910.2−0546

ABSTRACT We present a detailed study of optical data from the 2012 outburst of the candidate black hole X-ray binary Swift J1910.2−0546 using the Faulkes Telescope and Las Cumbres Observatory (LCO). We analyse the peculiar spectral state changes of Swift J1910.2−0546 in different energy bands, and characterize how the optical and UV emission correlates with the unusual spectral state evolution. Using various diagnostic tools like the optical/X-ray correlation and spectral energy distributions, we disentangle the different emission processes contributing towards the optical flux of the system. When Swift J1910.2−0546 transitions to the pure hard state, we find significant optical brightening of the source along with a dramatic change in the optical colour due to the onset of a jet during the spectral state transition. For the rest of the spectral states, the optical/UV emission is mostly dominated by an X-ray irradiated disc. From our high cadence optical study, we have discovered a putative modulation. Assuming that this modulation arises from a superhump, we suggest Swift J1910.2−0546 to have an orbital period of 2.25–2.47 h, which would make it the shortest orbital period black hole X-ray binary known to date. Finally, from the state transition luminosity of the source, we find that the distance to the source is likely to be ∼4.5–20.8 kpc, which is also supported by the comparative position of the source in the global optical/X-ray correlation of a large sample of black hole and neutron star X-ray binaries.

Combined X-ray and optical analysis to probe the origin of the plateau emission in γ-ray burst afterglows

A large fraction of γ-ray bursts (GRBs) show a plateau phase during the X-ray afterglow emission, which has a physical origin that is still debated. In this work, we select a sample of 30 GRBs with simultaneous X-ray and optical data during and after the plateau phase. Through a time-resolved spectral analysis of the X-ray plateaus, we test the consistency of the unabsorbed optical fluxes with those obtained via X-ray-to-optical spectral extrapolation by assuming a synchrotron spectrum. By combining X-ray with optical data, we find that 63% (19/30) of GRBs are compatible with a single synchrotron spectrum, thus suggesting that both the optical and X-ray radiations are produced from a single emitting region. For these GRBs, we derive the temporal evolution of the break frequency, and we compare it with the expectations predicted by several models. For 11 of the 30 GRBs, the optical emission is above the predicted range of values extrapolated from the X-rays in at least one temporal bin of the light curve. These 11 GRBs may not be explained with a single-zone emission, indicating the necessity of invoking two co-operating processes in order to explain the broad-band spectral behaviour. We discuss our findings in the framework of different scenarios that are invoked to explain the plateau feature, including the energy injection from a spinning-down magnetar and the high latitude emission from a structured jet.

EXPERIMENTAL EVALUATION OF THE HOMOGENEITY OF THE OUTPUT STREAMS OF OPTICAL RADIATION OF A RECTANGULAR SHAPE FOR VARIOUS VERSIONS OF THE OUTPUT SECTIONS OF THE LIGHT GUIDE NOZZLES FOR MEDICAL LASER EQUIPMENT

The article presents the results of a study of the homogeneity of rectangular optical radiation fluxes for different versions of the initial sections of the light guide nozzles. When conducting a significant part of laser exposure in medicine, pathological areas of biological tissue or their projections located on the surface of the body are covered with light spots with contours, as a rule, in the form of flat geometric shapes.&#x0D; The variability of the implementation of light spots in shape (circle, square, rectangle, triangle, rhombus, etc.) and linear dimensions of the cross section allows you to select the shape and size of the light spot, covering a specific pathological surface with minimal capture of intact tissues. At the same time, regardless of the shape and linear dimensions, the light spots should be as uniform as possible. To date, of particular interest is the provision of optical uniformity of rectangular light spots.&#x0D; Firstly, similar forms of spots are widely used under the influence of laser medicine. Secondly, in the original optical stages of laser equipment and the light guides connected to them, first of all, optical fibers of a cylindrical shape with a rounded cross section of the optical flow at the output are used. The purpose of this work is to optimize the parameters of light guide nozzles of medical laser equipment with rectangular output optical radiation fluxes by evaluating the uniformity of the power density distribution for various options for the output sections of the nozzles. In the work, optical flows at the output of three versions of the distal sections of light guides were studied. The light guides were formed by optical fibers, including the use of microlenses at the output ends, and were apertured by channel optical waveguides in the form of rectangular parallelepipeds.&#x0D; The experimental results obtained at the stage of physical modeling show the promise of using spherical micro-optical elements at the initial ends of optical fibers in combination with rectangular apertures in the form of channel optical waves to obtain rectangular light spots with a high level of optical homogeneity.

CMOS AlN and ScAlN Pyroelectric Detectors with Optical Enhancement for Detection of CO2 and CH4 Gases

AbstractGas sensors are useful for monitoring of greenhouse gases. As the move toward complementary metal‐oxide‐semiconductor (CMOS) compatible pyroelectric room temperature detectors is gaining traction due to its scalability to 8‐in./12‐in. wafer area and integrable with CMOS electronics, CMOS compatible aluminum nitride (AlN)‐ and scandium aluminum nitride (ScAlN)‐based pyroelectric detectors are developed for sensing of CO2and CH4gases, which are two of the greenhouse gases that contribute significantly to global warming. Leveraging gas absorption at respective mid‐infrared (IR) wavelengths, CO2 and CH4 gases are detected at various concentrations with fast response time ≈1 s. A compound parabolic collector (CPC) is designed and integrated into the gas sensor to enhance the optical flux received by the detector, which demonstrates ≈10× signal improvement in its presence. Further factors such as the effect of sensing area reduction and response to random gas concentrations are also tested on AlN‐ and ScAlN‐based pyroelectric detectors respectively to observe the gas sensing behaviors of both detectors. The results obtained provide further understanding of the behavior of CMOS AlN‐ and ScAlN‐based pyroelectric detectors as IR gas sensors, which can potentially inspire new design and design selection for various gas sensing applications.

GRB 221009A afterglow from a shallow angular structured jet

ABSTRACT Exceptionally bright gamma-ray burst (GRB) afterglows can reveal the angular structure of their jets. GRB jets appear to have a narrow core (of half-opening angle θc), beyond which their kinetic energy drops as a power-law with angle θ from the jet’s symmetry axis, $E_{\mathrm{ k},\rm iso}(\theta)\propto [1+(\theta /\theta _\mathrm{ c})^2]^{-a/2}$. The power-law index a reflects the amount of mixing between the shocked jet and confining medium, which depends on the jet’s initial magnetization. Weakly magnetized jets undergo significant mixing, leading to shallow (a ≲ 2) angular profiles. We use the exquisite multiwaveband afterglow observations of GRB 221009A to constrain the jet angular structure using a dynamical model that accounts for both the forward and reverse shocks, for a power-law external density profile, next ∝ R−k. Both the forward shock emission, that dominates the optical and X-ray flux, and the reverse shock emission, that produces the radio afterglow, require a jet with a narrow core (θc ≈ 0.021) and a shallow angular structure (a ≈ 0.8) expanding into a stellar wind (k ≈ 2). Moreover, these data appear to favour a small fraction (ξe ≈ 10−2) of shock heated electrons forming a power-law energy distribution in both shocks.

Varstrometry selected radio-loud candidates of dual and off-nucleus quasars at sub-kpc scales

ABSTRACT Dual super massive black holes (SMBHs) at sub-kpc to kpc scales, the product of galaxy mergers, are progenitors of eventually coalescing binary SMBHs. If both or one of the dual SMBHs are accreting, they may appear as dual AGNs or off-nucleus AGNs. Studying such systems is essential to learn the dynamical evolution of binary SMBHs as well as the process of galaxy merging. Recently a novel astrometry-based method named varstrometry has been put forward to search for dual SMBHs at high redshift, as the unsynchronized flux variability of dual AGNs (or off-nucleus AGNs) will cause astrometric jitters detectable by Gaia without spatially resolving them. Based on Gaia varstrometry, we select a rare sample of five radio loud quasars with clear Gaia astrometric jitters. With e-MERLIN observations, we have revealed a single compact radio source for each of them. Remarkably all but one exhibit clear Gaia-radio offsets of ∼9–60 mas. The observed Gaia jitters appear consistent with the expected values. These detected Gaia-radio offsets suggest these candidate dual SMBHs may have projected separations as small as ∼0.01–0.1 arcsec (∼0.1 kpc, depending on the optical flux ratio of two SMBHs). Meanwhile, this work highlights the remarkably high efficiency of Gaia varstrometry selection of jittering sources.

Comparative optical performance investigation of Cross Compound Parabolic Concentrators designed with the elimination of multiple reflections principle

This paper evaluates low-profile solar concentrators with low-material consumption that improve the optical performance of Crossed-Compound-Parabolic-Concentrators (CCPCs) by using Eliminating-Multiple-Reflections (EMR). Three CCPC designs, LEMR, HEMR, and hybrid, were analysed using Monte-Carlo ray tracing, with optical efficiency and light flux uniformity as primary metrics. The LEMR and HEMR CCPCs achieved almost 88% average optical efficiency at the outlet aperture within the half acceptance angle. At the BCP, the LEMR CCPC attained an average efficiency of 85.7%, while the HEMR CCPC achieved an average efficiency of 85%. The hybrid CCPC achieved an average optical efficiency of 80% and 86% when the incidence angle was varied in the XY and YZ planes. The results showed that the non-uniformity of the light flux at the BCP remained low compared to the outlet aperture with changes in the incidence angle. A material consumption analysis revealed that the LEMR CCPC has the lowest material consumption as compared to the HMR and hybrid CCPCs and has a more uniform irradiance flux at the BCP. The LEMR CCPC has a relatively lower acceptance angle than the HEMR CCPC, making it suitable for a tracking system with a higher concentration ratio. The HEMR CCPC, on the other hand, can be used as a stationary concentrator due to its larger acceptance angle with a lower concentration ratio and can be applied in rooftops and building-integrated photovoltaics. Similarly, the hybrid CCPC has two different ranges of acceptance angles, making it advantageous for use in rooftops and building-integrated photovoltaics with seasonal tracking.

Early excess emission in Type Ia supernovae from the interaction between supernova ejecta and their circumstellar wind

ABSTRACT The effects of the interaction between Type Ia supernova ejecta and their circumstellar wind on the photometric properties of Type Ia supernovae are investigated. We assume that a hydrogen-rich, dense, and extended circumstellar matter (CSM) is formed by the steady mass-loss of their progenitor systems. The CSM density is assumed to be proportional to r−2. When the mass-loss rate is above 10−4 M⊙ yr−1 with a wind velocity of 100 km s−1, CSM interaction results in an early flux excess in optical light curves within 4 d of explosion. In these cases, the optical colour quickly evolves to the blue. The ultraviolet flux below 3000 Å is found to have a persistent flux excess compared to Type Ia supernovae as long as CSM interaction continues. Type Ia supernovae with progenitor mass-loss rates between 10−4 and 10−3 M⊙ yr−1 may not have a CSM that is dense enough to affect spectra to make them Type Ia CSM, but they may still result in Type Ia supernovae with an early optical flux excess. Because they have a persistent ultraviolet flux excess, ultraviolet light curves around the luminosity peak would be significantly different from those with a low-density CSM.

Correlation between Emission-line Luminosity and Gamma-Ray Dominance in the Blazar 3C 279

Despite numerous studies, the origin of the γ-ray emission from blazars is still debated, in particular whether it is produced by leptonic or hadronic processes. In this study, we are testing the leptonic scenario for the flat-spectrum radio quasar 3C 279, assuming that the γ-ray emission is generated by inverse Compton scattering of external target photons from the broad-line region (IC-BLR scenario). For this purpose we use a 10 yr data set of the source consisting of the optical spectroscopy data from the Steward Observatory blazar monitoring program and Fermi Large Area Telescope γ-ray data. We search for a possible correlation between the Compton dominance and the emission-line luminosity using the discrete correlation function analysis. As a result, we find no significant correlation between these two quantities at any time lag value, while the emission-line luminosity displays a moderate correlation with the γ-ray flux at a zero time lag. We also reveal that the optical synchrotron continuum flux shows a pronounced correlation with the γ-ray flux, and therefore we interpret these results within the leptonic IC-BLR scenario where the variations in Compton dominance are primarily induced by changes in the magnetic field, rather than in the emission-line luminosity.

Optical and near-infrared spectroscopy of the black hole transient 4U 1543–47 during its 2021 ultra-luminous state

We present simultaneous optical and near-infrared spectra obtained during the 2021 outburst of the black hole transient 4U 1543–47. The X-ray hardness-intensity diagram and the comparison with similar systems reveal a luminous outburst, probably reaching the Eddington luminosity, as well as a long-lasting excursion to the so-called ultra-luminous state. VLT/X-shooter spectra were taken in two epochs 14 days apart during the early and brightest part of the outburst, while the source was in this ultra-luminous accretion state. The data show strong H and He I emission lines, as well as high-excitation He II and O III transitions. Most lines are single-peaked in both spectra, except for the O III lines that exhibit evident double-peaked profiles during the second epoch. The Balmer lines are embedded in broad absorption wings that we believe are mainly produced by the contribution of the A2V donor to the optical flux, which we estimate to be in the range of 11–14% in the r band during our observations. Although no conspicuous outflow features are found, we observe some wind-related line profiles, particularly in the near-infrared. Such lines include broad emission line wings and skewed red profiles, suggesting the presence of a cold (i.e., low ionisation) outflow with similar observational properties to those found in other low-inclination black hole transients.

Intra-night optical flux and polarization variability of BL Lacertae during its 2020–2021 high state

ABSTRACT In this work, we report the presence of rapid intra-night optical variations in both flux and polarization of the blazar BL Lacertae during its unprecedented 2020–2021 high state of brightness. The object showed significant flux variability and some colour changes, but no firmly detectable time delays between the optical bands. The linear polarization was also highly variable in both polarization degree and angle (electric vector polarization angle). The object was observed from several observatories throughout the world, covering a total of almost 300 h during 66 nights. Based on our results, we suggest that the changing Doppler factor of an ensemble of independent emitting regions, travelling along a curved jet that at some point happens to be closely aligned with the line of sight, can successfully reproduce our observations during this outburst. This is one of the most extensive variability studies of the optical polarization of a blazar on intra-night time-scales.

External Inverse-compton and Proton Synchrotron Emission from the Reverse Shock as the Origin of VHE Gamma Rays from the Hyper-bright GRB 221009A

The detection of the hyper-bright gamma-ray burst (GRB) 221009A enables us to explore the nature of the GRB emission and the origin of very high-energy gamma rays. We analyze the Fermi Large Area Telescope (Fermi-LAT) data of this burst and investigate the GeV–TeV emission in the framework of the external reverse-shock model. We show that the early ∼1–10 GeV emission can be explained by the external inverse-Compton mechanism via upscattering MeV gamma rays by electrons accelerated at the reverse shock, in addition to the synchrotron self-Compton component. The predicted early optical flux could have been brighter than that of the naked-eye GRB 080319B. We also show that proton synchrotron emission from accelerated ultrahigh-energy cosmic rays (UHECRs) is detectable and could potentially explain ≳TeV photons detected by LHAASO or constrain the UHECR acceleration mechanism. Our model suggests that the detection of photons with energies up to ∼18 TeV is possible for reasonable models of the extragalactic background light without invoking new physics and predicts anticorrelations between MeV photons and TeV photons, which can be tested with the LHAASO data.

New optical recursional spherical ferromagnetic flux for optical sonic microscale

In this paper, we construct optical spherical recursion flux for optical spherical [Formula: see text]-magnetic curve with optical normalized microscale by sonic magnetic crystal. Also, we design optical spherical magnetic normalized density of optical spherical [Formula: see text]-magnetic curve. Then, we illustrate new version of optical spherical recursional flux of optical spherical [Formula: see text]-magnetic curve. Moreover, we characterize total magnetical normalized density with optical ferromagnetic model for optical spherical [Formula: see text]-magnetic curve. The obtained spherical recursion flux and optical graphical representations visualize geometry of sonic magnetic crystal media.