Contenuti
Immagini
Carica la tua immagine
DSS Images Other Images
Articoli relazionati
Two decades of optical photometry of short-period eclipsing RS CVn systems and other active chromosphere systems
I present BVRI photometry of short-period (P < 1d) eclipsing RS CVnbinary star systems collected between 1988 and 2009 at Mount LagunaObservatory. Most of the data are for ER Vul and WY Cnc, with lightcurves nearly every year during that time period. I also present lightcurves for at least several years for XY UMa, BH Vir, CG Cyg, RT And,and UV Psc. I have fewer light curves for SV Cam, UV Leo, 1E1919+0427,and GSC 2038-0293. In addition to the eclipsing short-period systems, Ialso include UBVRI data for two longer period noneclipsing RS CVn binarysystems: UZ Lib and DM UMa, as well as two active chromosphere singlestars: FK Com and HD 199178.
| Random forest automated supervised classification of Hipparcos periodic variable stars
We present an evaluation of the performance of an automatedclassification of the Hipparcos periodic variable stars into 26 types.The sub-sample with the most reliable variability types available in theliterature is used to train supervised algorithms to characterize thetype dependencies on a number of attributes. The most useful attributesevaluated with the random forest methodology include, in decreasingorder of importance, the period, the amplitude, the V-I colour index,the absolute magnitude, the residual around the folded light-curvemodel, the magnitude distribution skewness and the amplitude of thesecond harmonic of the Fourier series model relative to that of thefundamental frequency. Random forests and a multi-stage scheme involvingBayesian network and Gaussian mixture methods lead to statisticallyequivalent results. In standard 10-fold cross-validation (CV)experiments, the rate of correct classification is between 90 and 100per cent, depending on the variability type. The main mis-classificationcases, up to a rate of about 10 per cent, arise due to confusion betweenSPB and ACV blue variables and between eclipsing binaries, ellipsoidalvariables and other variability types. Our training set and thepredicted types for the other Hipparcos periodic stars are availableonline.
| Close Binaries with Infrared Excess: Destroyers of Worlds?
We present the results of a Spitzer photometric investigation into theIR excesses of close binary systems. In a sample of 10 objects, excessesin Infrared Array Camera and MIPS24 bands implying the presence of warmdust are found for 3. For two objects, we do not find excesses reportedin earlier IRAS studies. We discuss the results in the context of thescenario suggested by Rhee and co-workers, in which warm dust iscontinuously created by destructive collisions between planetary bodies.A simple numerical model for the steady-state distribution of dust inone IR excess system shows a central clearing of radius 0.22 AU causedby dynamical perturbations from the binary star. This is consistent withthe size of the central clearing derived from the Spitzer spectralenergy distribution. We conclude that close binaries could be efficient"destroyers of worlds" and lead to destabilization of the orbits oftheir planetary progeny by magnetically driven angular momentum loss andsecular shrinkage of the binary separation.
| The CCD photometric study of the newly identified RS CVn binary star DV Piscium
This paper presents new CCD BVRI light curves of the newly discovered RSCVn eclipsing binary star DV Psc. From the asymmetric light curvesoutside the eclipse, we find there are two depressions in the phaseranges 0.3-0.45 and 0.6-0.9, respectively. By analyzing thelight curves using the Wilson-Devinney program, the fourphotometric solutions of the system are obtained and the starspotparameters are also derived. It turns out that the case of two spotsbeing on the primary is most successful in reproducing the light curvedistortion of DV Psc. Moreover, analysis the longitudes of spotssuggests that there are two active longitude belts (one is about90°, the other is about 270°). At the same time, on 22 November2008, the first flare-like event was detected on DV Psc at phase 0.35whose duration was about 13.5 min. These findings reveal that DV Psc hasa high degree of magnetic activity.
| BAV-Results of Observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| A list of minima and maxima timings
The list contains minima of eclipsing and maxima of pulsating stars, itcontinues the list published in OEJV 0073.
| Starspot and flare activity of the dwarf system CM Dra
Not Available
| XID II: Statistical Cross-Association of ROSAT Bright Source Catalog X-ray Sources with 2MASS Point Source Catalog Near-Infrared Sources
The 18,806 ROSAT All Sky Survey Bright Source Catalog (RASS/BSC) X-raysources are quantitatively cross-associated with near-infrared (NIR)sources from the Two Micron All Sky Survey Point Source Catalog(2MASS/PSC). An association catalog is presented, listing the mostlikely counterpart for each RASS/BSC source, the probability Pid that the NIR source and X-ray source are uniquelyassociated, and the probability P no-id that none of the2MASS/PSC sources are associated with the X-ray source. The catalogincludes 3853 high quality (P id>0.98) X-ray-NIR matches,2280 medium quality (0.98 >= P id>0.9) matches, and4153 low quality (0.9 >= P id>0.5) matches. Of the highquality matches, 1418 are associations that are not listed in the SIMBADdatabase, and for which no high quality match with a USNO-A2 opticalsource was presented for the RASS/BSC source in previous work. Thepresent work offers a significant number of new associations withRASS/BSC objects that will require optical/NIR spectroscopy forclassification. For example, of the 6133 P id>0.92MASS/PSC counterparts presented in the association catalog, 2411 haveno classification listed in the SIMBAD database. These 2MASS/PSC sourceswill likely include scientifically useful examples of known sourceclasses of X-ray emitters (white dwarfs, coronally active stars, activegalactic nuclei), but may also contain previously unknown sourceclasses. It is determined that all coronally active stars in theRASS/BSC should have a counterpart in the 2MASS/PSC, and that the uniqueassociation of these RASS/BSC sources with their NIR counterparts thusis confusion limited.
| Photospheric and chromospheric activity in V405 Andromedae. An M dwarf binary with components on the two sides of the full convection limit
We investigate the fast-rotating (P_orb=P_rot=0.465d), active dwarfbinary V405 And (M0V+M5V) using photometric BV(RI)C andoptical spectroscopic data. The light variation is caused by thecombined effect of spottedness and binarity with a small eclipse. Weestimate the system parameters from the available light and radialvelocity curves. Three flare events occurred during the observations:two were found in the spectroscopic data and one was observedphotometrically in BV(RI)C colours. An interesting eruptivephenomenon emerged from the photometric measurements that can beinterpreted as a series of post-flare eruptions lasting for at least 3orbits (rotations) of the system, originating from trans-equatorialmagnetic loops, which connect the active regions in the two hemispheres.The two components of V405 And have masses well over and below thetheoretical limit of full convection. This rare property makes thebinary an ideal target for observing and testing models for stellardynamo action.
| Period Change and Possible Magnetic Braking in WY Cancri
In this paper, the orbital period change of the RS CVn-type binarysystem WY Cnc is analyzed through a detailed description of the O - Ccurve by a weighted least-squares method. It is found that the periodvariation is suffering a secular period decrease at a rate of dp/dt =-1.20 × 10-7 dy-1. Since WY Cnc is a typicaldetached binary system, and both components are late-type stars, thelong-term period decrease may be caused by angular momentum loss viamagnetic braking.
| BAV-Results of Observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| A catalogue of chromospherically active binary stars (third edition)
The catalogue of chromospherically active binaries (CABs) has beenrevised and updated. With 203 new identifications, the number of CABstars is increased to 409. The catalogue is available in electronicformat where each system has a number of lines (suborders) with a uniqueorder number. The columns contain data of limited numbers of selectedcross references, comments to explain peculiarities and the position ofthe binarity in case it belongs to a multiple system, classicalidentifications (RS Canum Venaticorum, BY Draconis), brightness andcolours, photometric and spectroscopic data, a description of emissionfeatures (CaII H and K, Hα, ultraviolet, infrared),X-ray luminosity, radio flux, physical quantities and orbitalinformation, where each basic entry is referenced so users can go to theoriginal sources.
| New absolute magnitude calibrations for detached binaries
Lutz-Kelker bias corrected absolute magnitude calibrations for thedetached binary systems with main-sequence components are presented. Theabsolute magnitudes of the calibrator stars were derived at intrinsiccolours of Johnson-Cousins and 2MASS (Two Micron All Sky Survey)photometric systems. As for the calibrator stars, 44 detached binarieswere selected from the Hipparcos catalogue, which have relative observedparallax errors smaller than 15% (σπ/π≤0.15).The calibration equations which provide the corrected absolute magnitudefor optical and near-infrared pass bands are valid for wide ranges ofcolours and absolute magnitudes: -0.18<(B-V)0<0.91,-1.6
| On the Period Variations of BH Virginis
In the present work, 17 new times of the light minimum for BHVir werederived from observations by Kjurkchieva etal. (2004, A&A, 424,993). Combining the new determined eclipse times with others compiledfrom the literature, the behavior of their O-C variation wasinvestigated. It has been found that the orbital period of BHVir showssome cyclic variations with three different periods: a long-periodvariation of 51.7years, and two short-period variations of 9.2years and11.8years, respectively. The mechanisms that could explain the periodchanges of the system are discussed.
| Long-term starspot activity of the eclipsing binaries BH Vir and WY Cnc
We present the results of multicolor photometry of the two spotted,short-period, late-type RS CVn stars BH Vir and WY Cnc. We have derivedthe parameters of the binaries’ components, and refined theirmasses, radii, and luminosities. A strong flare of WY Cnc was detectedfor the first time, and pre-flare variations of the star’sactivity studied. Our observations and published data spanning 40 yearsare analyzed using a zone starspot model. We demonstrate that the spotsare always concentrated near the equators and at intermediate latitudes,with maximum spotted areas as large as 29% for BH Vir and 21% for WYCnc. The temperature differences between spotted regions and the quietphotosphere were 2300 K (BH Vir) and 1800 K (WY Cnc). The detectedlong-term brightness variations of BH Vir suggest the existence of anactivity cycle with a probable period of 22 years. Both stars havestarspots concentrated at two active longitudes separated byapproximately half of the orbital period during all the studied seasons;these longitudes remained the same (0° and 184°) for BH Vir over40 years, whereas they migrated in the direction of the stellar rotationat a rate of 3.8°/yr for WY Cnc, suggesting a cycle of 47 years forthe migration of the active longitudes.
| B.R.N.O. Contributions #34
Not Available
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| CCD Times of Minima of Some Eclipsing Binaries from the SAVS Sky Survey
We present CCD observations of minima of 18 eclipsing binaries observedby SAVS sky survey in year 2004 - 2007.
| Photoelectric Minima of Some Eclipsing Binary Stars
We present 119 minima times of 47 eclipsing binaries.
| Dynamical evolution of active detached binaries on the logJo-logM diagram and contact binary formation
Orbital angular momentum (OAM, Jo), systemic mass (M) andorbital period (P) distributions of chromospherically active binaries(CAB) and W Ursae Majoris (W UMa) systems were investigated. Thediagrams of and logJo-logM were formed from 119 CAB and 102 WUMa stars. The logJo-logM diagram is found to be mostmeaningful in demonstrating dynamical evolution of binary star orbits. Aslightly curved borderline (contact border) separating the detached andthe contact systems was discovered on the logJo-logM diagram.Since the orbital size (a) and period (P) of binaries are determined bytheir current Jo, M and mass ratio, q, the rates of OAM loss(dlogJo/dt) and mass loss (dlogM/dt) are primary parametersto determine the direction and the speed of the dynamical evolution. Adetached system becomes a contact system if its own dynamical evolutionenables it to pass the contact border on the logJo-logMdiagram. The evolution of q for a mass-losing detached system is unknownunless the mass-loss rate for each component is known. Assuming q isconstant in the first approximation and using the mean decreasing ratesof Jo and M from the kinematical ages of CAB stars, it hasbeen predicted that 11, 23 and 39 per cent of current CAB stars wouldtransform to W UMa systems if their nuclear evolution permits them tolive 2, 4 and 6 Gyr, respectively.
| CCD Times of Minima of Selected Eclipsing Binaries
374 CCD minima observations of 187 eclipsing binaries are presented. Theobserved stars were chosen mainly from catalogue BRKA of observingprogramme of Variable Star Section of CAS.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Detection of a Large Flare in the RS CVn Star WY Cnc
We report detection of an optical flare in the RS CVn spotted star WYCnc. The flare duration is 64 min, the amplitude is 0.134 mag and theenergy is 1 * 10^35 erg in the B band. The WY Cnc spot activity beforeand during the flare is analyzed.
| Are the W Ursae Majoris-type systems EK Comae Berenices and UX Eridani surrounded by circumstellar matter?
The variations of the orbital periods of two nearly neglected W UMa-typeeclipsing binaries, EK Comae Berenices and UX Eridani, are presentedthrough a detailed analysis of the O C diagrams. It is found that theorbital period of EK Com is decreasing and the period of UX Eridani isincreasing, and several sudden jumps have occurred in the orbitalperiods of both binaries. We analyze the mechanism(s), which mightunderlie the changes of the orbital periods of both systems, and obtainsome new results. The long-term decrease of the orbital period of EKComae Berenices might be caused by the decrease of the orbital angularmomentum due to a magnetic stellar wind (MSW) or by mass transfer fromthe more massive to the less massive component. The secular increase inthe orbital period of UX Eridani might be caused by mass transfer fromthe less massive to the more massive star. The possible mechanisms,which underlie the sudden changes in the orbital periods of the closebinary systems are as the followings: (1) the variations of thestructure due to the variation of the magnetic field; (2) the rapid massexchange between the close binaries and their circumstellar matter.Finally, the evolutionary status of the systems EK Comae Berenices andUX Eridani is discussed.
| Mass loss and orbital period decrease in detached chromospherically active binaries
The secular evolution of the orbital angular momentum (OAM), thesystemic mass (M=M1+M2) and the orbital period of114 chromospherically active binaries (CABs) were investigated afterdetermining the kinematical ages of the subsamples which were setaccording to OAM bins. OAMs, systemic masses and orbital periods wereshown to be decreasing by the kinematical ages. The first-orderdecreasing rates of OAM, systemic mass and orbital period have beendetermined as per systemic OAM, per systemic mass and per orbitalperiod, respectively, from the kinematical ages. The ratio of d logJ/dlogM= 2.68, which were derived from the kinematics of the presentsample, implies that there must be a mechanism which amplifies theangular momentum loss (AML) times in comparison to isotropic AML ofhypothetical isotropic wind from the components. It has been shown thatsimple isotropic mass loss from the surface of a component or bothcomponents would increase the orbital period.
| A catalogue of eclipsing variables
A new catalogue of 6330 eclipsing variable stars is presented. Thecatalogue was developed from the General Catalogue of Variable Stars(GCVS) and its textual remarks by including recently publishedinformation about classification of 843 systems and making correspondingcorrections of GCVS data. The catalogue1 represents thelargest list of eclipsing binaries classified from observations.
| Times of Minima for Neglected Eclipsing Binaries in 2005
Times of minima obtained at Rolling Hills Observatory during 2005 for anumber of neglected eclipsing binaries are presented.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| Catalogue of the orbital elements, masses, and luminosities for short-periodic RS CVn-type eclipsing systems
New data on the orbital elements, masses, and luminosities werecollected for 31 pre-contact binary systems of short-periodic {RS}{CVn}-type. We treat the catalogued data statistically in order toaccurately define the properties and evolutionary status of each classsystem. The ages of pre-contact systems were estimated by the isochronemethod. Numerous comments and bibliographic references to the catalogueare also included.
|
Sottometti un nuovo articolo
Link relazionati
Sottometti un nuovo link
Membro dei seguenti gruppi:
|
Osservazione e dati astrometrici
| Costellazione: | Cancro |
| Ascensione retta: | 09h01m55.45s |
| Declinazione: | +26°41'22.7" |
| Magnitudine apparente: | 9.476 |
| Moto proprio RA: | -11.8 |
| Moto proprio Dec: | -49.4 |
| B-T magnitude: | 10.32 |
| V-T magnitude: | 9.546 |
Cataloghi e designazioni:
|
