Orbital Modulation Research Articles

Investigating the Mini and Giant Radio Flare Episodes of Cygnus X-3

Abstract The microquasar Cygnus X-3 underwent a giant radio flare in 2017 April, reaching a maximum flux of ∼16.5 Jy at 8.5 GHz. We present results from a long monitoring campaign carried out with Medicina at 8.5, 18.6, and 24.1 GHz, parallel to the Metsähovi radio telescope at 37 GHz, from 2017 April 4 to 11. We observe a spectral steepening from to 0.5 (with ) within 6 hr of the epoch of the flare’s peak maximum, and rapid changes in the spectral slope in the following days during brief enhanced emission episodes while the general trend of the radio flux density indicated the decay of the giant flare. We further study the radio orbital modulation of Cyg X-3 emission associated with the 2017 giant flare and with six mini-flares observed in 1983, 1985, 1994, 1995, 2002, and 2016. The enhanced emission episodes observed during the decline of the giant flare at 8.5 GHz coincide with the orbital phase (orbital inferior conjunction). On the other hand, the light curves of the mini-flares observed at 15–22 GHz peak at , except for the 2016 light curve, which is shifted 0.5 w.r.t. the other ones. We attribute the apparent phase shift to the variable location of the emitting region along the bent jet. This might be explained by the different accretion states of the flaring episodes (the 2016 mini-flare occurred in the hypersoft X-ray state).

Evolution of the Quiescent Disk Surrounding a Superoutburst of the Dwarf Nova TW Virginis

Abstract In this paper, we investigate portions of the Kepler K2 Short Cadence light curve of the dwarf nova (DN) TW Vir at quiescence, using light-curve modeling. The light curve was separated into 24 sections, each with a data length of ∼0.93 days, comprising 4 sections before, and 20 after a superoutburst (SO). Due to morphological differences, the quiescent orbital modulation is classified into three types. Using a fixed disk radius and the two component stellar parameters, all 24 synthetic disk models from these sections show a consistent configuration, consisting of a disk and two hotspots: one at the vertical side of the edge of the disk and the other on the surface of the disk. Before the SO, the disk and a ringlike surface-hotspot are suddenly enhanced, triggering a precursor, and then the SO. At the end of the quiescent period following the SO and before the first normal outburst, the edge-hotspot becomes hotter, while the surface-hotspot switches into a “coolspot” with a coverage of nearly half of the disk’s surface. During quiescence, the surface-hotspot is always located at the outer part of the disk, with a constant radial width. A flat radial temperature distribution of the disk is found, and appears flatter when approaching the outburst. Like many U Gem-type DN with orbital periods of 3–5 hr, the mass transfer rate is significantly lower than the predictions of the standard/revised models of CV evolution.

Simulation modelling of autonomous navigation support for small satellite constellation

A small satellite system has many advantages related to its technical characteristics, production cycle and costs. At the same time, separate satellites are usually operating as a part of a ballistic-coupled constellation. The navigation and ballistic support tasks for the satellite group include calculation of satellite motion, of inter-satellite bases and prediction of the ballistic existence of the constellation. Currently, autonomous navigation support of the constellation is proved by onboard satellite navigation systems, the design cycle of which necessarily includes simulation of implemented algorithms. In the paper, the simulation model of small satellite navigation support is presented. The simulation procedure for the navigation support includes the following steps: formation the reference satellite constellation, estimation the current status of GPS and GLONASS systems orbital groupings, calculation the parameters of navigational satellite radio-visibility, solving the navigation problem according to global navigation satellite systems and inter-satellite navigation. The article also describes the procedure and results of modelling the process of the onboard navigation system functioning. Further development of the model associated with the software implementation of the small satellite disturbed orbital motion and modules for generating the radio frequency component of navigation and inter-satellite signals.

Toroidal modeling of runaway electron loss due to 3-D fields in DIII-D and COMPASS

The 3-D field induced relativistic runaway electron (RE) loss has been simulated for DIII-D and COMPASS plasmas, utilizing the MARS-F code incorporated with the recently developed and updated RE orbit module (REORBIT). Modeling shows effectively 100% loss of a post-disruption, high-current runaway beam in DIII-D due to the 1 kG level of magnetic field perturbation produced by a fast growing n = 1 resistive kink instability. This complete RE loss is shown to be independent of the particle energy or the initial location of particles in the configuration space. Applied resonant magnetic perturbation (RMP) fields from in-vessel coils are not effective for RE beam mitigation in DIII-D but do produce finite (>10%) RE loss in COMPASS post-disruption plasmas, consistent with experimental observations in the above two devices. The major reasons for this difference in RE control by RMP between these two devices are (i) the coil proximity to the RE beam and (ii) the effective coil current scaling vs the machine size and the toroidal magnetic field. In the modeling, the lost REs due to 3-D fields deposit onto the limiting surfaces of the devices. Distributions of the lost REs to the limiting surface show a poloidally peaked profile near the high-field-side in both DIII-D and COMPASS, covering about 100° poloidal angle. A higher perturbation field level and/or higher particle energy also result in REs being lost to the low-field-side of the limiting surface of these two devices, increasing the effective wetted area.

First in situ detection of the CN radical in comets and evidence for a distributed source

ABSTRACT Although the debate regarding the origin of the cyano (CN) radical in comets has been ongoing for many decades, it has yielded no definitive answer to date. CN could previously only be studied remotely, strongly hampering efforts to constrain its origin because of very limited spatial information. Thanks to the European Space Agency's Rosetta spacecraft, which orbited comet 67P/Churyumov–Gerasimenko for 2 yr, we can investigate, for the first time, CN around a comet at high spatial and temporal resolution. On board Rosetta's orbiter module, the high-resolution double-focusing mass spectrometer DFMS, part of the ROSINA instrument suite, analysed the neutral volatiles (including HCN and the CN radical) in the inner coma of the comet throughout that whole 2-yr phase and at variable cometocentric distances. From a thorough analysis of the full-mission data, the abundance of CN radicals in the cometary coma has been derived. Data from a close flyby event in 2015 February indicate a distributed origin for the CN radical in comet 67P/Churyumov–Gerasimenko.

Evidence for periodic accretion–ejection in LS I +61°303

ABSTRACT The stellar binary system LS I +61°303, composed of a compact object in an eccentric orbit around a B0 Ve star, emits from radio up to γ-ray energies. The orbital modulation of radio spectral index, X-ray, and GeV γ-ray data suggests the presence of two peaks. This two-peaked profile is in line with the accretion theory predicting two accretion–ejection events for LS I +61°303 along the 26.5 d orbit. However, the existing multiwavelength data are not simultaneous. In this paper, we report the results of a campaign covering radio, X-ray, and γ-ray observations of the system along one single orbit. Our results confirm the two predicted events along the orbit and in addition show that the positions of radio and γ-ray peaks are coincident with X-ray dips as expected for radio and γ-ray emitting ejections depleting the X-ray emitting accretion flow. We discuss future observing strategies for a systematic study of the accretion–ejection physical processes in LS I +61°303.

Charge-by-Charge Ion Pairing Preserves Fluorescence Emission

In this issue of Chem, Flood and co-workers demonstrate spatially and electronically isolated cationic dyes in crystalline charge-by-charge ion-pairing systems based on sandwiched [2 + 1]-type anion complexes of a π-electronic cyanostar macrocycle; these dyes exhibit fluorescent colors and intensities similar to those in solution.

An optical spectroscopic and polarimetric study of the microquasar binary system SS 433

Aims. Our aim is to study the mass transfer, accretion environment, and wind outflows in the SS 433 system, concentrating on the so-called stationary lines. Methods. We used archival high-resolution (X-shooter) and low-resolution (EMMI) optical spectra, new optical multi-filter polarimetry, and low-resolution optical spectra (Liverpool Telescope), spanning an interval of a decade and a broad range of precessional and orbital phases, to derive the dynamical properties of the system. Results. Using optical interstellar absorption lines and H I 21 cm profiles, we derive E(B − V) = 0.86 ± 0.10, with an upper limit of E(B − V) = 1.8 ± 0.1 based on optical Diffuse Interstellar Bands. We obtain revised values for the ultraviolet and U band polarizations and polarization angles (PA), based on a new calibrator star at nearly the same distance as SS 433 that corrects the published measurement and yields the same PA as the optical. The polarization wavelength dependence is consistent with optical-dominating electron scattering with a Rayleigh component in U and the UV filters. No significant phase modulation was found for PA while there is significant variability in the polarization level. We fortuitously caught a flare event; no polarization changes were observed but we confirm the previously reported associated emission line variations. Studying profile modulation of multiple lines of H I, He I, O I, Na I, Si II, Ca II, Fe II with precessional and orbital phase, we derive properties for the accretion disk and present evidence for a strong disk wind, extending published results. Using transition-dependent systemic velocities, we probe the velocity gradient of the wind, and demonstrate that it is also variable on timescales unrelated to the orbit. Using the rotational velocity, around 140 ± 20 km s−1, a redetermined mass ratio q = 0.37 ± 0.04, and masses MX = 4.2 ± 0.4 M⊙, MA = 11.3 ± 0.6 M⊙, the radius of the A star fills – or slightly overfills – its Roche surface. We devote particular attention to the O I 7772 Å and 8446 Å lines, finding that they show different but related orbital and precessional modulation and there is no evidence for a circumbinary component. The spectral line profile variability can, in general, be understood with an ionization stratified outflow predicted by thermal wind modeling, modulated by different lines of sight through the disk produced by its precession. The wind can also account for an extended equatorial structure detected at long wavelength.

Orbital period modulation in hot Jupiter systems

ABSTRACT We introduce a model for the orbital period modulation in systems with close-by giant planets based on a spin–orbit coupling that transfers angular momentum from the orbit to the rotation of the planet and vice versa. The coupling is produced by a permanent non-axisymmetric gravitational quadrupole moment assumed to be present in the solid core of the planet. We investigate two regimes of internal planetary rotation, that is, when the planet rotates rigidly and when the rotation of its deep interior is time-dependent as a consequence of a vacillating or intermittent convection in its outer shell. The model is applied to a sample of very hot Jupiters predicting maximum transit-time deviations from a constant-period ephemeris of approximately 50 s in the case of rigid rotation. The transit time variations of WASP-12, currently the only system showing evidence of a non-constant period, cannot be explained by assuming rigid rotation, but can be modelled in the time-dependent internal rotation regime, thus providing an alternative to their interpretation in terms of a tidal decay of the planet orbit.

Prediction of surface area size in orbital floor and medial orbital wall fractures based on topographical subregions

ObjectiveThis retrospective study evaluates the occurrence and frequency of different fracture patterns in a series of computed tomography (CT) scans in terms of the AOCMF Trauma Classification (TC) orbit module and correlates the assigned defects with measurements of the fracture area in order to get an approximate guideline for fracture size predictions on the basis of the classification. Material and methodsCT scans of patients with orbital floor fractures were evaluated using the AOCMFTC to determine the topographical subregions. The coding consisted of: W = orbital wall, 1 = anterior orbit, 2 = midorbit, i = inferior, m = medial. The 3-dimensional surface area size of the fractures was quantified by the “defect body” method (Brainlab, Munich, Germany). The fracture area size and its confidence and prediction interval within each topographical subregion was estimated by regression analysis. ResultsA total of 137 CT scans exhibited 145 orbital floor fractures, which were combined with 34 medial orbital wall fractures in 31 patients. The floor fractures – W1(i)2(i) (n = 86) and W1(i) (n = 19) were the most frequent patterns. Combined floor and medial wall fractures most frequently corresponded to the pattern W1 (im)2 (im) (n = 15) ahead of W1 (im) 2(i) (n = 10). The surface area size ranged from 0.11 cm2 to 6.09 cm2 for orbital floor and from 0.29 cm2 to 5.43 cm2 for medial wall fractures.The prediction values of the mean fracture area size within the subregions were computed as follows: W1(i) = 2.25 cm2, W2(i) = 1.64 cm2, W1(i)2(i) = 3.10 cm2, W1(m) = 1.36 cm2, W2(m) = 1.65 cm2, W1(m)2(m) = 2.98 cm2, W1 (im) = 3.35 cm2, W1 (im) 2(i) = 4.63 cm2, W1 (im)2(m) = 4.06 cm2 and W1 (im)2 (im) = 7.16 cm2. ConclusionThe AOCMFTC orbital module offers a suitable framework for topographical allocation of fracture patterns inside the infero-medial orbital cavity. The involvement of the subregions is of predictive value providing estimations of the mean 3-D fracture area size.

Orbital Modulation of Gamma Rays from PSR J2339-0533

Abstract We report on orbital modulation of the 100–600 MeV gamma-ray emission of the P B = 4.6 hr millisecond pulsar binary PSR J2339−0533 using 11 yr of Fermi Large Area Telescope data. The modulation has high significance (chance probability p ≈ 10−7), is approximately sinusoidal, peaks near pulsar superior conjunction, and is detected only in the low-energy 100–600 MeV band. The modulation is confined to the on-pulse interval, suggesting that the variation is in the 2.9 ms pulsed signal itself. This contrasts with the few other known systems exhibiting GeV orbital modulations, as these are unpulsed and generally associated with beamed emission from an intrabinary shock. The origin of the modulated pulsed signal is not yet clear, although we describe several scenarios, including Compton upscattering of photons from the heated companion. This would require high coherence in the striped pulsar wind.

Geometric resolution analysis of bistatic SAR with active orbital module

Geometric resolution analysis of bistatic SAR with active orbital module

Photometric Studies of the Intermediate Polar DO Dra in 2008 and 2019

An analysis is presented of photometric observations of the intermediate polar DO Dra obtained during an epoch of significant reduction in its outburst activity for different average brightnesses of the system: 13m.6-12m.8 (2008) and 14m.7-14m.3 (2019). The observations in 2008 were made in the Johnson BVR system and in 2019, in integrated light. For the first time in quasi-simultaneous observations in the BVR bands, orbital modulation of the brightness was recorded in the form of a two-humped curve in each band, presumably caused by ellipsoidality of the secondary component. For six nights in the BVR bands (2008) and one night in integrated light (2019), stable quasiperiodic oscillations around 0.02 days were observed. On the night of JD 2458575 (2019) an increase in the brightness by 0m.7 was observed over 3 min, followed by exponential decay. The flare lasted about an hour within the first half of which oscillations with a period of about 0.006 days and an amplitude of 0m.1 were observed that may be related either to the rotation period of the white dwarf or to the quasiperiodic oscillations. The nature of the flare is not yet clear and possible reasons for this effect are examined in this article.

Periodicity Search for Pulsar Binaries with TESS

Abstract Pulsar binaries, in particular redback systems, provide good sources to study the pulsar wind flow and its interaction with the companion stars. Fermi-LAT have proposed probable pulsar binary candidates in its catalogs. An orbital modulation search of binary candidates is an effective way to identify pulsar binary sources from the catalog. Transiting Exoplanet Survey Satellite (TESS) observes in survey mode for a large part of the sky and thus provides an excellent data set for the periodicity search of pulsar binary candidates by observing the flux variation, thought to mainly come from the stellar companion. Using TESS data we look for flux modulation of five pulsar binaries (or candidates) with reported orbital periods, including PSR J1023+0038, 3FGL J0523.3−2528, 3FGL J0212.1+5320, 3FGL J0744.1−2523, and PSR J1417−4402, demonstrating that TESS photometric data are very useful in identifying periodicities of redback-like systems. This method can be effective in searches for new pulsar binaries or similar binary systems in the future.

X-ray andγ-ray orbital variability from theγ-ray binary HESS J1832−093

Context.γ-ray binaries are systems composed of a massive star and a compact object whose interaction leads to particle acceleration up to relativistic energies. In the last fifteen years, a few binaries have been found to emit at high energies, but their number is still low. The TeV source HESS J1832−093 has been proposed as a binary candidate, although its nature is unclear. Neither a GeV counterpart nor a period was detected.Aims.The purpose of this work is to search for a GeV counterpart to understand the origin of the TeV signal detected by H.E.S.S. For an unambiguous identification of its binary nature, finding an orbital modulation is crucial.Methods.We analysed data spanning more than 10 years from theFermiLarge Area Telescope (Fermi-LAT), together withSwiftarchival observations taken between 2015 and 2018, using both the X-Ray Telescope and UV/Optical Telescope. We searched for periodicities in both X-ray and GeV bands.Results.We find a periodic modulation of ∼ 86 days in the X-ray source candidate counterpart XMMU J183245−0921539, together with indications ofγ-ray modulation with a compatible period in the GeV candidate counterpart 4FGL J1832.9−0913. Neither an optical nor a UV counterpart is found at the X-ray source location. The overall spectral energy distribution strongly resembles the knownγ-ray binary HESS J0632+057.Conclusions.Both the spectral energy distribution and the discovery of an orbital period allow the identification of the TeV source HESS J1832−093 as a new member of theγ-ray binary class.

GeV emission of gamma-ray binary with pulsar scenario

ABSTRACT We study GeV emission from gamma-ray binaries by assuming that the compact object is a young pulsar. We assume that the relativistic unshocked pulsar wind with a Lorentz factor of 104–5 can produce the GeV emission by the inverse-Compton scattering process in the dense soft-photon field of the companion star. The travel distance of the unshocked pulsar wind that moves toward the observer depends on the orbital phase of the pulsar. We discuss that the orbital modulation of the GeV emission is a result of combination of the effects of the travel distance of the unshocked pulsar wind and of the anisotropic soft-photon field of the companion star. In this paper, we study how the effect of the travel distance of the unshocked pulsar wind affects to the orbital modulation of GeV emission. We apply our scenario to two gamma-ray binaries, LMC P3 and 4FGL J1405.1−6119. We find that with the suggested system parameters of LMC P3, the observed amplitude of the orbital modulation and the peak width are more consistent with the model light curve by taking into account the effect of the travel distance. For LMC P3, we analyse the GeV spectrum with 8-yr Fermi-LAT data and discuss the broadband emission process in X-ray to TeV energy bands. We predict a possible system geometry for 4FGL J1405.1−6119 by fitting the GeV light curve.

FRB Periodicity: Mild Pulsars in Tight O/B-star Binaries

Abstract Periodicities observed in two fast radio burst (FRB) sources (16 days in FRB 180916.J0158+65 and 160 days in FRB 121102) are consistent with that of tight, stellar-mass binary systems. In the case of FRB 180916.J0158+65 the primary is an early OB-type star with the mass-loss rate yr−1, and the secondary is a neutron star. The observed periodicity is not intrinsic to the FRB’s source, but is due to the orbital phase-dependent modulation of the absorption conditions in the massive star’s wind. The observed relatively narrow FRB activity window implies that the primary’s wind dynamically dominates that of the pulsar, , where L sd is the pulsar spin-down, is the primary’s wind mass-loss rate, and v w is its velocity. The condition η ≤ 1 requires a mildly powerful pulsar with L sd ≲ 1037 erg s−1. The observations are consistent with magnetically powered radio emission originating in the magnetospheres of young, strongly magnetized neutron stars, the classical magnetars.

The long-term optical activity of the propellers AE Aquarii and AR Scorpii

Abstract This analysis of the long-term optical activity of the propellers AE Aqr and AR Sco uses data from the Catalina Real-time Transient Survey, DASCH, and AAVSO. The site and character of the emissions from the phenomena caused by the magnetic field of the white dwarf (WD) vary from system to system. The histogram of intensities of the ensemble of flares of AE Aqr suggests that the long-term activity consists of a large variety of the peak magnitudes of the flares, with the probability of their detection gradually decreasing with increasing intensity. Any increase of activity only leads to an increase of the number of blobs of the transferring matter. We also detected a season with a transient decrease or even a cessation of the mass outflow from the donor to the lobe of the WD. The very strong orbital modulation of AR Sco is most stable in the phases of the extrema of brightness for about a century; its minor changes suggest that the trailing side of the synchrotron-emitting region is more unstable than the leading side.

X-ray spectral and flux variability of the microquasar GRS 1758−258 on timescales from weeks to years

We present the spectral and timing evolution of the persistent black hole X-ray binary GRS 1758−258 based on almost 12 years of observations using theRossiX-ray Timing Explorer Proportional Counter Array. While the source was predominantly found in the hard state during this time, it entered the thermally dominated soft state seven times. In the soft state GRS 1758−258 shows a strong decline in flux above 3 keV rather than the pivoting flux around 10 keV more commonly shown by black hole transients. In its 3–20 keV hardness intensity diagram, GRS 1758−258 shows a hysteresis of hard and soft state fluxes typical for transient sources in outburst. The RXTE-PCA and RXTE-ASM long-term light curves do not show any orbital modulations in the range of 2–30 d. However, in the dynamic power spectra significant peaks drift between 18.47 and 18.04 d for the PCA data, while less significant signatures between 19 d and 20 d are seen for the ASM data as well as for theSwift/BAT data. We discuss different models for the hysteresis behavior during state transitions as well as possibilities for the origin of the long term variation in the context of a warped accretion disk.

A volcanic scenario for the Frasnian–Famennian major biotic crisis and other Late Devonian global changes: More answers than questions?

Abstract Although the prime causation of the Late Devonian Frasnian–Famennian (F–F) mass extinction remains conjectural, such destructive factors as the spread of anoxia and rapid upheavals in the runaway greenhouse climate are generally accepted in the Earth-bound multicausal scenario. In terms of prime triggers of these global changes, volcanism paroxysm coupled with the Eovariscan tectonism has been suspected for many years. However, the recent discovery of multiple anomalous mercury enrichments at the worldwide scale provides a reliable factual basis for proposing a volcanic–tectonic scenario for the stepwise F–F ecological catastrophe, specifically the Kellwasser (KW) Crisis. A focus is usually on the cataclysmic emplacement of the Viluy large igneous province (LIP) in eastern Siberia. However, the long-lasted effusive outpouring was likely episodically paired with amplified arc magmatism and hydrothermal activity, and the rapid climate oscillations and glacioustatic responses could in fact have been promoted by diverse feedbacks driven by volcanism and tectonics. The anti-greenhouse effect of expanding intertidal–estuarine and riparian woodlands during transient CO2-greenhouse spikes was another key feedback on Late Devonian land. An updated volcanic press-pulse model is proposed with reference to the recent timing of LIPs and arc magmatism and the revised date of 371.9 Ma for the F–F boundary. The global changes were initiated by the pre-KW effusive activity of LIPs, which caused extreme stress in the global carbonate ecosystem. Nevertheless, at least two decisive pulses of sill-type intrusions and/or kimberlite/carbonatite eruptions, in addition to flood basalt extrusions on the East European Platform, are thought to have eventually led to the end-Frasnian ecological catastrophe. These stimuli have been enhanced by effective orbital modulation. An attractive option is to apply the scenario to other Late Devonian global events, as evidences in particular by the Hg spikes that coincide with the end-Famennian Hangenberg Crisis.