Active Binary Systems Research Articles

Simultaneous Photometric and Spectroscopic Analysis of V505 Lacertae, a Photospherically and Chromospherically Active Contact Binary Star

New BVR photometric and high-resolution spectroscopic observations of V505 Lac are presented with Transiting Exoplanet Survey Satellite (TESS) photometric data. The orbital period has experienced a secular decrease during the past 16 yr. A clear anticorrelation in the primary and secondary eclipse timing variation (PSETV) obtained from the TESS data is also identified. A double-lined radial velocity (RV) curve is secured, and the effective temperatures of the less- and more-massive stars (Stars 1 and 2, respectively) are measured. Using a spectral subtraction technique, excess emissions are detected in the time-series Ca ii H and K and Hα lines for Star 2. Simultaneous analysis of the light and RV curves using the Wilson–Devinney (WD) code reveals that V505 Lac is a photospherically and chromospherically active W-subtype contact binary system. The component-star masses and radii are determined to an accuracy of approximately 1%. The WD spot model is individually applied to 221 light curves segmented from the TESS data so as to derive the spot parameters of a cool spot on Star 2. The combined variations in both longitude and colatitude among the spot parameters appear to be strongly associated with those of both the anticorrelation in the PSETV and the O’Connell effect in the TESS light curves. Robust negative linear relationships between the PSETV anticorrelation size and the O’Connell effect magnitude are found for the first time. Mass–radius, mass–luminosity, and mass ratio–mass diagrams of contact binaries, along with the mass ratio frequency distribution, are presented in an attempt to elucidate the evolutionary characteristics of these systems.

Prominence detection and chromosphere feature on the prototype RS CVn of active binary systems

ABSTRACT We present a study of high-resolution spectra of RS Canum Venaticorum (RS CVn), a prototype of active binary systems. Our data were obtained from 1998 to 2017 using different telescopes. We analyse the chromospheric activity indicators $\rm{Ca~{\small II}}$ IRT, Hα, $\rm{Na~{\small I}}$ D1, D2 doublet, $\rm{He~{\small I}}$ D3, and Hβ using a spectral subtraction technique. The chromospheric emission stems mainly from the K2 IV primary star, while the F5 V secondary star only shows weak emission features in a few of our spectra. We find excess absorption features in the subtracted Hα lines and other activity indicators from spectra taken near primary eclipse, which we ascribe to prominence-like material associated with the primary star. We estimate size limits of these tentative prominences based on the geometry of the binary system, and investigate the physical properties of the strongest prominence. An optical flare, characterized by $\rm{He~{\small I}}$ D3 line emission, together with stronger emission in other activity lines, was detected. The flare energy is roughly comparable to strong flares observed on other RS CVn-type stars. The chromospherically active longitudes of RS CVn most frequently appear near the two quadratures of the system and display changes between observing runs, which indicates an ongoing evolution of its active regions.

The nature of the X-ray sources constituting the 6.7 keV Galactic ridge emission

We reanalyze the deep Chandra X-ray observations near the Galactic center and show that reliable identifications of X-ray sources can be obtained with the Gaia EDR3 data to investigate which types of stellar sources are responsible for the X-ray emission observed from the Galactic ridge (GRXE). In the central 3 arcmin region 318 X-ray sources are detected, about one-third of which can be identified with objects listed in Gaia EDR3; however, only 22 objects have parallaxes and colors and can be placed into a color-magnitude diagram and thus be identified as coronal X-ray emitters. A rather large fraction of the X-ray sources cannot be identified with Gaia EDR3 entries, and we discuss the optical brightnesses of these sources. We analyze the counting events obtained in the 6.7 keV iron line spectral region and show that they are mainly caused by background events; however, 237 events can be associated with the detected X-ray sources, and we carry out an intensity measurement of the whole iron line complex. Our analysis shows that the mean energy of this iron line complex is located at a wavelength of ≈1.87 Å, where a variety of emission lines of iron ions in ionization stages FeXXIII–FeXXV are located; another line at 7.0 keV is only marginally detected, while the fluorescent 6.4 keV neutral iron line is clearly not seen. We demonstrate that only a few of the detected X-ray sources are responsible for the bulk of the observed iron line emission. We discuss to what extent coronal emission can be held responsible and demonstrate that M dwarfs and active binary systems like RS CVn systems do not significantly contribute to the observed emission; instead, it appears that the Galactic ridge emission is produced by optically fainter sources. Among the known population of cataclysmic variables, polars and dwarf novae appear to be the most promising candidates as main contributors to the GRXE.

New periodograms separating orbital radial velocities and spectral shape variation

We present new periodograms that are effective in distinguishing Doppler shift from spectral shape variability in astronomical spectra. These periodograms, building upon the concept of partial distance correlation, separate the periodic radial velocity modulation induced by orbital motion from that induced by stellar activity. These tools can be used to explore large spectroscopic databases in search of targets in which spectral shape variations obscure the orbital motion; such systems include active planet-hosting stars or binary systems with an intrinsically variable component. We provide a detailed prescription for calculating the periodograms, demonstrate their performance via simulations and real-life case studies, and provide a public Python implementation.

Observationally Constraining the Starspot Properties of Magnetically Active M67 Sub-subgiant S1063

Abstract Our understanding of the impact of magnetic activity on stellar evolution continues to unfold. This impact is seen in sub-subgiant stars, defined to be stars that sit below the subgiant branch and red of the main sequence in a cluster color–magnitude diagram. Here we focus on S1063, a prototypical sub-subgiant in open cluster M67. We use a novel technique combining a two-temperature spectral decomposition and light-curve analysis to constrain starspot properties over a multiyear time frame. Using a high-resolution near-infrared IGRINS spectrum and photometric data from K2 and ASAS-SN, we find a projected spot filling factor of 32% ± 7% with a spot temperature of 4000 ± 200 K. This value anchors the variability seen in the light curve, indicating the spot filling factor of S1063 ranged from 20% to 45% over a four-year time period with an average spot filling factor of 30%. These values are generally lower than those determined from photometric model comparisons but still indicate that S1063, and likely other sub-subgiants, are magnetically active spotted stars. We find observational and theoretical comparisons of spotted stars are nuanced due to the projected spot coverage impacting estimates of the surface-averaged effective temperature. The starspot properties found here are similar to those found in RS CVn systems, supporting classifying sub-subgiants as another type of active giant star binary system. This technique opens the possibility of characterizing the surface conditions of many more spotted stars than previous methods, allowing for larger future studies to test theoretical models of magnetically active stars.

HL Dra: an active Algol-like binary system with a pulsating component star and a cool third body

ABSTRACT HL Draconis (HL Dra) is an oscillating eclipsing binary with an orbital period of 0.944276 d. By analysing the light curves observed with the Transiting Exoplanet Survey Satellite (TESS), it has been detected that HL Dra is an Algol-like binary system with a mass ratio of 0.361, where the radius filling factor (=r/RL) of the primary and secondary component is $87\, {{\ \rm per\ cent}}$ and $98\, {{\ \rm per\ cent}}$, respectively. The secondary component is almost filling its critical Roche lobe, but not entirely. The absolute parameters of the component are estimated in this paper. Both the variable O’Connell effect and the existence of superflares indicate that the secondary should have strong magnetic activities. It is discovered that the O − C curve shows a sinusoidal variation with a period of 129.88 yr. This cyclic change might be caused by the effects of the light travel time as a result of the presence of a cool red dwarf third body. The correlations between the changes of the O − C diagrams and the variable O’Connell effect during TESS observations might be caused by the magnetic activity of the secondary (i.e. the Applegate mechanism). After removal of the binary model, a total of 252 pulsation frequencies are detected from the high-precision photometric data of TESS, including 28 multiplets of tidally split frequencies. We identify two radial modes, 21 non-radial p-modes and three non-radial f-modes from the possible independent frequencies. All of these features reveal that HL Dra is a very interesting system for further investigations of binary formation and evolution, and for tidal interactions on stellar pulsations and on magnetic activities.

Inhomogeneous activity enhances density phase separation in active model B

ABSTRACT We study the binary phase separation in active model B, on a two-dimensional substrate with inhomogeneous activity. Activity was introduced with a maximum value at the center of the box and spread as a Bivariate-Gaussian distribution as we move away from the center. The system was studied for three different intensities of the distribution. Toward the boundary of the box, activity is zero or the model is similar to the passive model B. We start from the random homogeneous distribution of density of particles, and the system evolves toward a structured distribution of density. With time, density starts to phase separate with maximum density at the center of the box and decreases as we move away from the center of the box. The width of the density profile at the center increases as a power law exponent remains close between 2/3 and 3/4 up to some moderate time and then decays to zero in the steady state. Hence, our result shows the response of density in an active binary system with respect to the patterned substrate. It can be used to design devices useful for the trapping and segregation of active particles.

NEW SPECTRAL ANALYSIS RESULTS WITHIN THE SCOPE OF EXTENDED MATTER RESEARCH IN THE AR LACERTAE ACTIVE BINARY SYSTEM

Within the scope of extended matter research, we present new spectral analysis results of an active binary system, AR Lac. The low and high resolution spectra of this system, were taken during the period 2013-2016. The evaluation of low dispersion spectra together with the B, V, Rc, Ic and WISE photometric data showed that AR Lac has an excess radiation in the W2 band. In addition, the spectral energy distribution and the minima depth ratios of the light curves of this active binary system were studied to examine the flux contributions of the components of the system depending on wavelengths and on orbital phase. Furthermore, high resolution spectral analysis showed evidence of prominence-like structures and a possible extended matter around the cooler component of AR Lac.

A New Magnetically Active Binary System Discovered in Yunnan-Hong Kong Wide Field Survey

We present a newly discovered magnetically active binary system detected by Yunnan-Hong Kong wide field survey, with an orbital period of 0.60286 days. Two color photometry for the system was performed using the 1m Cassegrain telescope of Yunnan Observatories with its CCD (Charge-Coupled Device) camera. In the observed light curves, there are clearly different light maxima existed in the out-of-eclipse regions. We made spectroscopic observations for the binary system using the 2.4m telescope and YFOSC (Yunnan Faint Object Spectrograph and Camera) of Lijiang station of Yunnan Observatories, China. The radial velocity curve was derived for primary star of the binary system. The primary star exhibited strong chromospheric activity, which confirms that the distortion of the light curves results from the starspot activity on the primary star. Through analyzing the light curves and RV (Radial Velocity) curve mentioned above by means of the W-D (Wilson-Devinney) code, orbital parameters and starspot configuration of the binary system are obtained. Finally, we have discussed the properties of the binary system, and given the prospects on the future work.

Catalytic upgrading of ethanol to butanol over a binary catalytic system of FeNiOx and LiOH

Catalytic conversion of ethanol to butanol is vital to bridge the gap between huge amounts of ethanol production, the limited blending ratio of ethanol in gasoline, and the outstanding performance of butanol. In this work, a highly active binary catalytic system of FeNiOx and LiOH was developed for upgrading of ethanol to butanol. After 24 h reaction at 493 K, the selectivity to butanol reached 71% with >90% high carbon alcohols at 28% ethanol conversion, which was comparable to the performance of some noble metal homogeneous catalysts.

A survey of extended matter around chromospherically active binary systems

AbstractWe present an analysis of colour excess(CE)observations for 13 chromospherically active binary systems, together with 27 inactive reference stars of similar spectral types and luminosity classes of the components of these 13 binaries. We used the observations which were made by Johnson-Cousins${BVR}_{c}\mathrm{I}_{c}$,2MASS, andWISEphotometric systems. Our new photometric${BVR}_{c}\mathrm{I}_{c}$observations were obtained by means of 1 m telescope at TÜBİTAK National Observatory and 40 cm telescope at Ankara University Kreiken Observatory. To check the existence of extended matter around an active binary component(s) of these 13 binary systems, we examined theCEvalues at around primary/secondary minima and outside eclipses. The comparison of theseCEs, obtained relative to those of reference stars of the same${(B-V)_\circ}$colours, especially during primary minima with those of secondary minima and outside eclipses, showed that these systems have greater excess radiation in primary minima than in both secondary minima and outside eclipses. We observed that the colour excesses, in general, most likely arise from the extended matter around the cooler component of a binary system. The comparison ofCEvalues also showed that the extended matter of some of these systems was most likely covered or affected both of their components. Since no observational data were obtained during primary minimum ofRW UMa, by excluding this binary system, an examination of the locations of cool and active components of the remaining 12 systems of this study on Hertzsprung-Russell diagram, together with corresponding evolutionary tracks, showed that most of the active binary systems have an extended matter not only caused from stellar activity but also more likely caused from evolutionary processes.

Reflection of radiation from an atmosphere with a chaotic magnetic field

We consider a semi-infinite turbulent atmosphere with a chaotic magnetic field. We assume that the ratio of the cyclotron frequency to the radiation frequency is small. In this case the Faraday rotation influences only the radiation polarization. The magnetic-field fluctuations are assumed to be isotropic and of Gaussian type. We present the solution of two problems – the reflection of non-polarized radiation with normal incidence to the surface and the reflection of non-polarized radiation from a point source above the surface. The latter occurs when the observed radiation escapes from the part of the jet where most of the radiation (at the relevant wavelength) arises. In this case the polarization degree depends on the level of magnetic-field fluctuations, the wavelength λ and the aperture Θ of the point source, which is determined by the height of the source and the radius of the optically thick part of an accretion disc. The calculations show that the chaotic Faraday rotations very strongly diminish the polarization degree of the emerging radiation compared to the non-magnetized atmosphere. The calculations of the intensity distribution and polarization degree can be used to estimate the level of magnetic-field fluctuations in the accretion discs in active galactic nuclei and binary systems.

Aromatic guanidines as highly active binary catalytic systems for the fixation of CO2 into cyclic carbonates under mild conditions

The formation of hydrogen bonding causes a considerable decrease in the reaction temperature and CO2 pressure used in this process.

Close-by planets and flares in their host stars

Context. The interaction between the magnetic fields of late-type stars and their close-by planets may produce stellar flares as observed in active binary systems. However, in spite of several claims, conclusive evidence is still lacking. Aim. We estimate the magnetic energy available in the interaction using analytical models to provide an upper bound to the expected flare energy. Methods. We investigated three different mechanisms leading to magnetic energy release. The first two can release an energy up to (0.2–1.2) B02R3/μ, where B0 is the surface field of the star, R its radius, and μ the magnetic permeability of the plasma. These two mechanisms operate in young active stars whose coronae have closed magnetic field lines up to the distance of their close-by planets that can trigger the energy release. The third mechanism operates in weakly or moderately active stars with a coronal field with predominantly open field lines at the distance of their planets. The released energy is of the order of (0.002–0.1) B02R3/μ and depends on the ratio of the planetary to the stellar fields, thus allowing an indirect measurement of the former when the latter is known. Results. We compute the released energy for various separations of the planet and various stellar parameters finding the conditions for the operation of the proposed mechanisms. An application to eight selected systems is presented. Conclusions. The computed energies and dissipation timescales are in agreement with flare observations in the eccentric system HD 17156 and in the circular systems HD 189733 and HD 179949. This kind of star–planet interaction can be unambiguously identified by the higher flaring frequency expected close to periastron in eccentric systems.

Seismic inference of 57 stars using full-lengthKeplerdata sets

We present stellar properties (mass, age, radius, distances) of 57 stars from a seismic inference using full-length data sets from Kepler. These stars comprise active stars, planet-hosts, solar-analogs, and binary systems. We validate the distances derived from the astrometric Gaia-Tycho solution. Ensemble analysis of the stellar properties reveals a trend of mixing-length parameter with the surface gravity and effective temperature. We derive a linear relationship with the seismic quantity $\langle r_{02} \rangle$ to estimate the stellar age. Finally, we define the stellar regimes where the Kjeldsen et al (2008) empirical surface correction for 1D model frequencies is valid.

Overview of MAGIC results

MAGIC is a system of two 17-m diameter Cherenkov telescopes, located at the Observatorio del Roque de los Muchachos, in the Canary island La Palma (Spain). MAGIC performs astronomical observations of gamma-ray sources in the energy range between 50 GeV and 10 TeV. The first MAGIC telescope has been operating since 2004, and in 2009 the system was completed with the second one. During 2011 and 2012 the electronics for the readout system were fully upgraded, and the camera of the first telescope replaced. After that, no major hardware interventions are foreseen in the next years, and the experiment has undertaken a final period of steady astronomical observations.MAGIC studies particle acceleration in the most violent cosmic environments, such as active galactic nuclei, gamma-ray bursts, pulsars, supernova remnants or binary systems. In addition, it addresses some fundamental questions of Physics, such as the origin of Galactic cosmic rays and the nature of dark matter. Moreover, by observing the gamma-ray emission from sources at cosmological distances, we measure the intensity and evolution of the extragalactic background radiation, and perform tests of Lorentz Invariance.In this paper I present the status and some of the latest results of the MAGIC gamma-ray telescopes.

Aluminium salabza complexes for fixation of CO2 to organic carbonates.

A highly stable and easy to synthesize aluminium complex bearing a flexible N2O2-donor salabza ligand (N,N'-bis(salicylene)-2-aminobenzylamine) in combination with tetrabutylammonium bromide forms an active binary catalytic system for the cycloaddition of CO2 to epoxides (TOFs 120-3434 h(-1)) under mild conditions (10 bar, 80 °C) and low catalyst loadings (0.05-0.2 mol%). Kinetic experiments have shown that the cycloaddition of CO2 to styrene oxide catalyzed by 1/TBAB is first order in 1, TBAB, CO2 and epoxide. A reaction mechanism is proposed based on these observations. Fe(iii) and Co(iii) related complexes are less active catalysts for this reaction.

Doppler imaging of the double‐lined active binary V824 Ara

AbstractWe introduce an iterative spectral disentangling technique combined with Doppler imaging in order to recover surface temperature maps for both components of double‐lined active binary systems. Our method provides an opportunity to separate spectra of the active components while minimizing the unwanted disturbances on the given line profile from the other component. The efficiency of the method is demonstrated on real data of the double‐lined RS CVn‐type binary V824 Ara. The resulting Doppler images reveal cool spots on the polar regions as well as low‐latitude features on both of the stars. Moreover, both components have hot spots, that are facing each other. This may indicate interconnection between the stellar magnetic fields. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Highly active and selective binary catalyst system for the coupling reaction of CO2 and hydrous epoxides

Although most of the zinc-containing catalysts show excellent catalytic activity for the coupling reaction of carbon dioxide (CO2) with epoxides, generally, trace amounts of water in the reaction systems could cause a significant decrease of the catalytic activity. In this work, a nanoporous zinc-cobalt double metal cyanide complex (Zn–CoIII DMCC) with high surface area was synthesized via a modified hydrothermal process using tri-block copolymer EO20PO70EO20 (P123) as the template. When cetyltrimethylammonium bromide (CTAB) was used as the co-catalyst, the Zn–CoIII DMCC/CTAB binary catalyst system could effectively catalyze the coupling reaction of CO2 with hydrous propylene oxide (PO), producing propylene carbonate (PC) with nearly 100% productivity and 100% selectivity. This binary catalyst system could also catalyze the coupling reaction of other commercial epoxides and CO2 without using any solvents with nearly 100% productivity and 100% selectivity. With such new catalyst system, hundreds of ppm water in the reaction system will no longer be the matter.

DRAFTS: A DEEP, RAPID ARCHIVAL FLARE TRANSIENT SEARCH IN THE GALACTIC BULGE

We utilize the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS) HST/ACS dataset for a Deep Rapid Archival Flare Transient Search (DRAFTS) to constrain the flare rate toward the older stellar population in the Galactic bulge. During 7 days of monitoring 229,293 stars brighter than V=29.5, we find evidence for flaring activity in 105 stars between V=20 and V=28. We divided the sample into non-variable stars and variable stars whose light curves contain large-scale variability. The flare rate on variable stars is \sim 700 times that of non-variable stars, with a significant correlation between the amount of underlying stellar variability and peak flare amplitude. The flare energy loss rates are generally higher than those of nearby well-studied single dMe flare stars. The distribution of proper motions is consistent with the flaring stars being at the distance and age of the Galactic bulge. If they are single dwarfs, they span a range of \approx 1.0 - 0.25M\odot. A majority of the flaring stars exhibit periodic photometric modulations with P <3d. If these are tidally locked magnetically active binary systems, their fraction in the bulge is enhanced by a factor of \sim20 compared to the local value. These stars may be useful for placing constraints on the angular momentum evolution of cool close binary stars. Our results expand the type of stars studied for flares in the optical band, and suggest that future sensitive optical time-domain studies will have to contend with a larger sample of flaring stars than the M dwarf flare stars usually considered.