目录
图像
上传图像
DSS Images Other Images
相关文章
CH Cygni in 2004 – II: Nebular spectrum features
We report in a series on the spectra of CH Cygni obtained in October2004 in this paper. The spectra showed emission lines of H I, [O I], [OIII], [N II], [Ne III] and Fe II: most of them became stronger thanthose obtained in April 2004. In order to retrieve the intrinsicemission profile, we removed the underlying M-type spectrum and telluriclines of O2 from the spectra. Then, we deconvoluted theresulting Hα and [O III] profiles into several Gaussian functions.Radial velocities of all lines observed in October 2004 were measured.Results are compared with those in April 2004, and are discussed by wayof an accretion disk and a circumstellar model.
| Silicates in D-Type Symbiotic Stars: An Infrared Space Observatory Overview
We investigate the IR spectral features of a sample of D-type symbioticstars in order to constrain the emitting properties of coupled dust-gasparticles across the whole system. In particular, by analyzingunexploited ISO Short Wavelength Spectrometer data, deriving the basicobservational parameters of dust bands, and comparing them with respectto those observed in other astronomical sources, we try to highlight theeffect of environment on grain chemistry and physics. We find strongamorphous silicate emission bands at ~10 and ~18 μm in a largefraction of the sample. The analysis of the ~10 μm band, along with adirect comparison with several astronomical sources, reveals thatsilicate dust in symbiotic stars shows features between thecharacteristic circumstellar environments and the interstellar medium.This indicates an increasing reprocessing of grains in relation tospecific symbiotic behavior of the objects. A correlation between thecentral wavelengths of the ~10 and ~18 μm dust bands is found. Bymodeling IR spectral lines we also investigate dust grain conditionswithin the shocked nebulae. Both the unusual depletion values and thehigh sputtering efficiency might be explained by the formation of SiOmolecules, which are known to be a very reliable shock tracer. Weconclude that the signature of dust chemical disturbance due tosymbiotic activity should be looked for in the outer, circumbinary,expanding shells where the environmental conditions for grain processingmight be achieved. Symbiotic stars are thus attractive targets for newmid-IR and millimeter observations.
| CH Cygni X-Ray Jet Activity and Multicomponent Structures
In this paper we report detection of multiple component structures in aChandra X-ray image obtained in 2001 March of the nearby symbioticinteracting binary system CH Cyg. These components include a compactcentral source, an arclike structure or a loop extending to 1.5" (400AU) from the central source associated with the 1997 jet activity, andpossibly a newly formed jet extending to ~150 AU from the centralsource. The structures are also visible in VLA and HST images obtainedclose in time to the Chandra observations. The emission from the loop isconsistent with optically thin thermal X-ray emission originating from ashock resulting from interaction of the jet ejecta with the densecircumbinary material. The emission from the central source originateswithin <50 AU region, and is likely associated with the accretiondisk around the white dwarf. CH Cyg is only the second symbiotic systemwith jet activity detected at X-ray wavelengths, and the Chandra highangular resolution image, combined with the VLA and HST images, providesthe closest view of the region of jet formation and interaction with thecircumbinary material in a symbiotic binary.
| Discovery of Rapid Hard X-Ray Variability and New Jet Activity in the Symbiotic Binary R Aquarii
Two Chandra observations of the R Aqr symbiotic binary system taken 3.3yr apart show dramatic changes in the X-ray morphology and spectralcharacteristics in the inner 500 AU of this system. The morphology ofthe soft X-ray emission has evolved from a nearly circular regioncentered on the binary system to an hourglass shape that indicates theformation of a new southwest jet. Synchrotron radiation from the new jetin contemporaneous VLA radio spectra implies the physical conditions inthe early stages of jet development are different from those in the moreextended outer thermal jets known to exist for decades in this system.The central binary source has two X-ray spectral components in each ofthe two epochs, a soft component and a highly absorbed hard componentcharacterized by T~108 K if fit with a thermal plasma model.The spectrum hardened considerably between 2000.7 and 2004.0, primarilydue to increased flux above 5 keV, suggesting a change in the accretionactivity of the white dwarf on a timescale of a few years or less.Point-source Fe K emission is detected at the position of the centralbinary system in both observations. While the earlier observation showsevidence of only a single emission peak near Fe Kα at 6.4 keV, thelater observation shows a more complex emission structure between 6 and7 keV. Finally, we have discovered a modulation in the hard X-ray fluxwith a period of 1734 s at a 95% confidence level in the 2004observation only. The modulation potentially arises from standing shocksin an accretion column, and we have explored the possibility that thewhite dwarf in R Aqr is analogous to the magnetic white dwarfs inIntermediate Polars.
| Infrared Spectroscopy of Symbiotic Stars. V. First Orbits for Three S-Type Systems: Henize 2-173, CL Scorpii, and AS 270
Infrared radial velocities have been used to compute first orbits of theM giants in three southern S-type symbiotic systems. Of the three, Hen2-173 has the longest orbital period, 911 days, and also has anoncircular orbit with an eccentricity of 0.21. The large value of itsmass function suggests that Hen 2-173 may be an eclipsing system. For CLSco our spectroscopic orbital period of 626 days is essentiallyidentical to the previously determined light variability period of 625days, and we have adopted the latter. AS 270 has an orbital period ofsimilar length, 671 days, and both CL Sco and AS 270 have circularorbits. Only CL Sco has been extensively investigated previously, and wecompare our results with the conclusions of Kenyon & Webbink. Wealso have examined the period-eccentricity relation for 30 S-typesymbiotics. Circular orbits are found for 81% of the systems withorbital periods up to 800 days, while they occur for only 22% withperiods greater than 800 days. This distribution is quite unlike thatfor G and K giants; rather, it is similar to that for barium stars,another type of mass-transfer binary, which also consists of a late-typegiant and a white dwarf companion.
| Summary of the Conference
After showing how ideas about the nature of symbiotic binaries and theirrelation with other classes of objects, also examined at this meeting,have become more precise, personally selected highlights of theconference are mentioned. A few lessons for the future are drawn.
| Ch Cygni on the Background of Heterogeneity of Symbiotic Stars
With its cool component as a semiregular M6--M7 III variable of solarchemical composition, CH Cygni fits well into the classification schemesof symbiotic stars (S- and D-type). On the other hand, its activitybehavior is different from most of the other symbiotic stars. Wedescribe some aspects of recent spectroscopic variability of CH Cyg. Anattempt is made to explain most of the peculiarities of CH Cyg as aconsequence of extremely long orbital period ( ˜ 5300 d) for anS-type symbiotic star.
| V407 CYG as a Member of a New Subclass of Symbiotic Stars
We analyze the results of new multicolor UBVRIJHKLM photometricobservations of the symbiotic Mira V407 Cyg, obtained on return toquiescence from its 1998 outburst.
| Chemical Composition and Spectroscopic Variability of CH CYG
We discuss some details of abundance analysis of the cool component ofthe symbiotic system CH Cyg. The depth variation of absorption lines isshown to correlate with the light curve in the infrared M passband.
| Symbiotic Stars: Continually Embarrassing Binaries
This paper aims at presenting the state-of-the-art in understanding ofsymbiotic binaries. In particular, we discuss their basic parameters,the mechanisms of mass loss and accretion and the role of theseprocesses in the observed activity of symbiotic systems.
| A new interpretation of the remarkable X-ray spectrum of the symbiotic star CH Cyg
We have re-analysed the ASCA X-ray spectrum of the bright symbiotic starCH Cyg, which exhibits apparently distinct hard and soft X-raycomponents. Our analysis demonstrates that the soft X-ray emission canbe interpreted as scattering of the hard X-ray component in aphotoionized medium surrounding the white dwarf. This is in contrast toprevious analyses in which the soft X-ray emission was fitted separatelyand assumed to arise independently of the hard X-ray component. We notethe striking similarity between the X-ray spectra of CH Cyg and Seyfert2 galaxies, which are also believed to exhibit scattering in aphotoionized medium.
| A Radio Study of the Seyfert Galaxy Markarian 6: Implications for Seyfert Life Cycles
We have carried out an extensive radio study with the Very Large Arrayon the Seyfert 1.5 galaxy Mrk 6 and imaged a spectacular radio structurein the source. The radio emission occurs on three different spatialscales: ~7.5 kpc bubbles, ~1.5 kpc bubbles lying nearly orthogonal tothem, and a ~1 kpc radio jet lying orthogonal to the kiloparsec-scalebubble. To explain the complex morphology, we first consider a scenarioin which the radio structures are the result of superwinds ejected by anuclear starburst. However, recent Spitzer observations of Mrk 6 providean upper limit to the star formation rate (SFR) of ~5.5Msolar yr-1, an estimate much lower than the SFRof ~33 Msolar yr-1 derived assuming that thebubbles are a result of starburst winds energized by supernovaexplosions. Thus, a starburst alone cannot meet the energy requirementsfor the creation of the bubbles in Mrk 6. We then present anenergetically plausible model wherein the bubbles are a result of energydeposited by the kiloparsec-scale jet as it plows into the interstellarmedium. Finally, we consider a model in which the complex radiostructure is a result of an episodically powered precessing jet thatchanges its orientation. This model is the most attractive as it cannaturally explain the complex radio morphology and is consistent withthe energetics, the spectral index, and the polarization structure.Radio emission in this scenario is a short-lived phenomenon in thelifetime of a Seyfert galaxy, which results from an accretion event.
| UBV(RI)C photometric sequences for symbiotic stars. III
We present accurate UBV(RI)C photometric sequences andastrometric positions for a final set of 41 symbiotic stars. In asimilar manner to the 40 targets of Papers I and II, these sequencesextend over wide brightness and color ranges and are suited to coveringboth quiescence and outburst phases. They are intended to assist boththe CCD photometric monitoring of current variability and exploitationof old photographic plates from historical archives.
| Broad Hα wings from the optically thin stellar wind of the hot components in symbiotic binaries
Aims.To model broad Hα wings observed in symbiotic binaries by anoptically thin, bipolar stellar wind from their hot components as analternative to that considering the Raman scattering of Lyβ photonson atomic hydrogen. Methods: .Profile-fitting analysis. Comparisonof the observed broad Hα wings and their luminosity with thosepredicted by the model. Results: .Synthetic Hα profiles fitexcellently the observed wings for | Δ v | 200 kms-1 in our sample of 10 symbiotic stars during the quiescentas well as active phases. The wing profile formed in the stellar windcan be approximated by a function f(Δ v) ∝ Δv-2, which is of the same type as that arising from the Ramanscattering. Therefore it is not possible to distinguish between thesetwo processes only by modeling the line profile. Some observationalcharacteristics of the Hα-emission, its relationship with theemission measure of the symbiotic nebula and a steep radio spectrum at1.4-15 GHz suggest the ionized stellar wind from the hot component to bethe dominant source contributing to the Hα wings during activephases. The model corresponding mass-loss rates from the hot componentsare of a few × 10-8 Mȯ yr-1and of a few × (10-7 - 10-6)Mȯ yr-1 during quiescent and active phases,respectively.
| ChaMPlane Discovery of Candidate Symbiotic Binaries in Baade's and Stanek's Windows
We have searched the OGLE-II archive for candidate counterparts of X-raysources detected in two low-extinction windows included in our Galacticbulge Chandra-HST survey. We find that a significant number-that is, inexcess of the expected level of random associations-can be matched withprobable M giants. Their X-ray properties can be understood if thesesources are symbiotic binaries in which the X-rays are typically, eitherdirectly or indirectly, the result of a white dwarf accreting from thewind of a cool giant. Optical and near-infrared properties of selectedsources are consistent with a symbiotic nature, although none of thespectra collected for eight out of 13 candidate counterparts show thehigh-ionization nebular emission lines observed for many symbiotics. Thehard X-ray emission for several sources (power-law photon indices-1.5<~Γ<~1.5) suggests that our sample includes systemssimilar to the symbiotics recently detected with INTEGRAL and Swift.
| Resolving the Dusty Circumstellar Structure of the Enigmatic Symbiotic Star CH Cygni with the MMT Adaptive Optics System
We imaged the symbiotic star CH Cyg and two PSF calibration stars usingthe unique 6.5 m MMT deformable secondary adaptive optics system. Ourhigh-resolution (FWHM = 0.3"), very high Strehl (98%+/-2%), mid-infrared(9.8 and 11.7 μm) images of CH Cyg allow us to probe finer lengthscales than ever before for this object. CH Cyg is significantlyextended compared to our unresolved PSF calibration stars (μ UMa andα Her) at 9.8 and 11.7 μm. We estimated the size of theextension by convolving a number of simple Gaussian models with the μUMa PSF and determining which model provided the best fit to the data.Adopting the Hipparcos distance for this object of 270 pc, we found anearly Gaussian extension with a FWHM at 9.8 μm of ~40.5+/-2.7 AU(0.15"+/-0.01") and a FWHM at 11.7 μm of 45.9+/-2.7 AU(0.17"+/-0.01"). After subtracting out the Gaussian component of theemission (convolved with our PSF), we found a faint ~ 0.7" asymmetricextension, which peaks in flux ~0.5" north of the stars. This extensionis roughly coincident with the northern knotlike feature seen in HSTWFPC2 images obtained in 1999.The results presented here made use of the of MMT Observatory, afacility jointly operated by the University of Arizona and theSmithsonian Institution.
| The nature of ultraviolet spectra of AG Pegasi and other symbiotic stars: locations, origins, and excitation mechanisms of emission lines
A detailed study of ultraviolet spectra of the symbiotic star AG Peg hasbeen undertaken to derive the atomic excitation mechanisms and origin offormation for the lines common in symbiotic systems. More than 600emission lines are observed in spectra from {IUE}, {HST} and {FUSE} ofwhich 585 are identified. Population mechanisms and origin of formationare given for a majority of those lines. Based on the understanding ofthe AG Peg spectra {IUE} data of 19 additional symbiotic stars areinvestigated and differences and similarities of their spectra arediscussed. Fe II fluorescence lines pumped by strong emission linesbetween 1000 and 2000 Å are observed in 13 of these systems. Someof the symbiotic systems belonging to the subclass symbiotic novae havemore than 100 Fe II fluorescence lines in the ultraviolet wavelengthregion. Forbidden lines are detected for 13 of the stars, mostly fromhighly-ionized spectra such as Ar V, Ne V and Mg V. Further, [Mg VI] and[Mg VII] lines are observed in a symbiotic star (AG Dra) for the firsttime. Five of the symbiotic stars have broad white-dwarf wind profiles({FWHM} > 400 km s-1) for a few lines in their spectra.The stars with no such broad lines can be divided into two similarlysized groups, one where all lines have FWHM less than 70 kms-1 and the other where one, a few or all of the broad({FWHM} > 400 km s-1) lines of AG Peg have an enhancedbroad wing (110-140 km s-1).
| Hydrodynamical simulations of the jet in the symbiotic star MWC 560. II. Simulations beyond density balance
Context: .In the first paper of this series, we presented hydrodynamicalsimulations with radiative cooling of jet models with parametersrepresentative of the symbiotic system MWC 560. These were jetsimulations of a pulsed, initially underdense jet in a high-densityambient medium. They were stopped when the jet reached a length of 50AU. There, however, a transition of the initially underdense jet towardsan overdense jet should occur, which should result in changedkinematics. A few minor differences between the models and theobservations were thought to be solved by a model with an increased jetdensity during the pulses which was calculated only with purelyhydrodynamical means in the former paper. Aims: .Therefore, wedescribe two hydrodynamical simulations with cooling beyond this densitybalance, one with the same parameters as model i in Paper I (now calledmodel i´), which was presented there with and without cooling, andthe second with higher gas densities in the jet pulses (modeliv´). Methods: .Hydrodynamical simulations, with a furtherapproximated cooling treatment compared to Paper I, were used to be ableto enlarge the computational domain. Results: .The transitioncauses changes in the expansion of the cocoon and therefore themorphology of the jet, e.g. a larger radial width of the jet knots. Weinvestigate the radiation properties of the jets, the bremsstrahlung andoptical emissivities, integrated emission maps, and synthetic absorptionline profiles. Conclusions: .The conclusion that the high observedvelocities in CH Cygni, R Aquarii, and MWC 560 favor the models withcooling is unchanged by the transition. The observed parallel featuresin R Aquarii can be produced by the internal knots or by a variabledense radiative shell of shocked ambient medium. The absorption lineprofiles show that the real parameters in MWC 560 are closer to modeliv´ than to model i´.
| X-ray luminosity function of faint point sources in the Milky Way
We assessed the contribution to the X-ray (above 2 keV) luminosity ofthe Milky Way by different classes of low-mass binary systems and singlestars. We began by using the RXTE Slew Survey of the sky at|b|>10° to construct an X-ray luminosity function (XLF) of nearbyX-ray sources in the range 1030 ergs-1
| The high resolution spectra of symbiotic star CH Cygni in 2004
High resolution spectra of the symbiotic star CH Cygni secured at theBohyunsan Astronomy Observatory (BOAO) in April 2004 are discussed. Inthis phase, while CH Cygni was in quiescence photometrically, H I lineshad complicate emission and absorption components, while [O III] lineshad emission components and Na I D lines had absorption components. Wemeasured radial velocities for emission and absorption components ofthese lines. The lines were also de-convoluted and fitted withmulti-Gaussian functions to study a relationship between line shapes andgeometrical arrangements of the line source. Results are discussed interms of an accretion disk model and a gaseous envelope surrounding thesystem.
| Searching for Flickering Variability in Several Symbiotic Stars and Related Objects: BX Mon, V471 Per, RS Oph, V627 Cas, CI Cam, V886 Her, Z And, T CrB, MWC 560, V407 Cyg
UBVRI photometric observations of 10 symbiotic stars and related objectsobtained in the period 2002-2003 are presented. Analyzing differentiallight curves we found rapid light variations with timescales of tens ofminutes and significant amplitudes in the well-known flickers MWC 560,RS Oph, V407 Cyg and T CrB. MWC 560 and V407 Cyg demonstrate quasiperiodic oscillations (QPO) with similar amplitudes and timescales. Flickering and unusual flare in V627 Cas as well as some indications offlickering presence in BX Mon are detected. The existence of 29 minoscillations in Z And with an amplitude approx 0.02 mag in the U-band isconfirmed. Only one symbiotic star, V471 Per, and both non symbiotic, CICam and V886 Her, seem to be constant on flickering timescales. Nevertheless, small night to night changes in the brightness of V886 Herwere observed as well.
| Eccentricity generation in hierarchical triple systems: the planetary regime
In previous papers, we developed a technique for estimating the innereccentricity in hierarchical triple systems, with the inner orbit beinginitially circular. We considered systems with well-separated componentsand different initial setups (e.g., coplanar and non-coplanar orbits).However, the systems we examined had comparable masses. In the presentpaper, the validity of some of the formulae derived previously is testedby numerically integrating the full equations of motion for systems withsmaller mass ratios (from 10-3 to 103, i.e.systems with Jupiter-sized bodies). There is also discussion aboutHD217107 and its planetary companions.
| An abundance analysis of the symbiotic star CH Cygni
The photospheric abundances for the cool component of the symbiotic starwere calculated for the first time using high-resolution near-infraredspectra and the method of of standard LTE analysis and atmosphericmodels. The iron abundance for CH Cyg was found to besolar, [Fe/H] = 0.0 ± 0.19. The atmospheric parameters (T_eff =3100 K, log g = 0.0 (cgs), ξt = 2.2 km s-1) andmetallicity for CH Cyg are found to be approximately equal to those fornearby field M7 giants. The calculated [C/H] = -0.15, [N/H] = +0.16,[O/H] = -0.07, and the isotopic ratios of 12C/13Cand 16O/17O are close to the mean values forsingle M giants that have experienced the first dredge-up. A reasonableexplanation for the absence of barium star-like chemical peculiaritiesseems to be the high metallicity of CH Cyg. The emission line techniquewas explored for estimating CNO ratios in the wind of the giant.
| Nonradial pulsations of the hot component of the symbiotic star CH Cyg during its active phase
We observed the symbiotic star CH Cyg with the 70 cm telescope of theCrimean Astrophysical Observatory in 1982, during its active phase, whenit was brighter than 6m in the V band. We simultaneously detected thecontinuum brightness at wavelengths of 3737, 5092, and 5500 Å witha time resolution of 20 s. We present light curves for these wavelengthsfor four nights between July 13 and August 22, demonstrating thecharacter of the star’s rapid variations. Variousfrequency-analysis methods were applied to the data series at 3737 and5092 Å, where the light from the hot component made an appreciablecontribution. For both series, we find some 20 similar frequenciescorresponding to periods ranging from 150 to 6000 s. Our estimates ofthe significance of the identified frequencies indicate that thesignificance level exceeds 3 σ in all cases, and is even higher inmost cases. For many of the oscillations, the amplitudes varied on timescales shorter than one day. Multiperiodicity and variable oscillationamplitudes are characteristic of nonradial pulsations. We conclude thatnonradial oscillations typical of a white dwarf’s g modes wereexcited during the symbiotic star’s state of highest activity.
| Pulsation of the late-type star in symbiotic systems
Pulsation has been detected spectroscopically in the late-type star inboth D- and S-type symbiotic binaries. Time-series radial velocitiesreveal Mira stellar pulsation in the late-type star in D-typesymbiotics. Orbital motion has too long a period to be detected withcurrent time series. For the S-type systems time series of radialvelocities are typically dominated by orbital motion but in some systems``long-secondary period'' stellar pulsation is present.
| Aus der Sektion Kataklysmische Sterne Juli - November 2006.
Not Available
| Visuelle Beobachtungen von BG Dra.
Not Available
| Emission line variability of RS Ophiuchi*
We report that the Hα emission line of RS Oph was stronglyvariable during our 2004 observations on a time-scale of one month. Theline consisted of both a double-peaked central narrow component [fullwidth at half-maximum (FWHM) ~ 220 kms-1] and a stronglyvariable broad one (FWHM > 2000 kms-1). The base of theHα line was very broad, with full width at zero intensity ~4600kms-1 on all spectra from 1986 to 2004. The variability ofthe broad component extends from -2000 to +2000 kms-1. Mostprobably this is due either to blobs ejected from the white dwarf (witha typical blob mass estimated to be ~10-10Msolar)or to a variable accretion disc wind. We also detected variability ofthe HeIIλ4686 line on a time-scale shorter than 1 d. The possibleorigin is discussed.
| Disentangling the composite continuum of symbiotic binaries. I. S-type systems
We describe a method of disentangling the composite, 0.12-5 μmcontinuum of symbiotic binaries. The observed SED is determined by theIUE/HST archival spectra and flux-points corresponding to the opticalUBVRI and infrared JHKLM photometric measurements. The modeled SED isgiven by superposition of fluxes from the cool giant, hot stellar sourceand nebula including the effect of the Rayleigh scattering process andconsidering influence of the iron curtain absorptions. We applied thismethod to 21 S-type symbiotic stars during quiescence, activity andeclipses. We isolated four main components of radiation and determinedtheir properties. (i) Stellar radiation from the giant corresponds to aunique luminosity class - normal giants. Characteristic luminosities are1600 ± 200 and 290 ± 30 Lȯ for red andyellow giants, respectively in our sample of objects. (ii) Hot objectradiation during quiescence consists of the nebular and stellarcomponent. The former radiates at a mean electron temperature of 19 000K and its amount of emission suggests a mass-loss rate from giants viathe wind at dot MW = a few × 10-7Mȯ yr-1. Radiation of the latter conformswell with that of a black-body photosphere at a characteristictemperature of 105 000 K. The corresponding effective radii are a factorof 10 larger than those of white dwarfs, which thus precludes observingthe accretor's surface. Extreme cases of AX Per and V443 Her, for whichthe hot star temperature from the fit is not capable of producing thenebular emission, signal a disk-like structure of the hot stellar sourceeven during quiescence. (iii) Hot object radiation during activityconsists of three components - the stellar and the low- andhigh-temperature nebular radiation. The stellar radiation satisfies thatof a black-body photosphere at a low characteristic temperature of 22000 K (we call it the 1st type of outbursts) or at a very highcharacteristic temperature of ≈165 000 K (2nd type of outbursts). Allthe active objects with a high orbital inclination show features of the1st-type of outbursts (here Z And, AE Ara, CD-43circ14304, TXCVn, BF Cyg, CH Cyg, CI Cyg, AR Pav, AX Per), while AG Dra representsthe 2nd-type. The presence of a two-temperature type of UV spectrum andan enlargement of effective radii of the stellar source by a factor of 10 with respect to the quiescent values during the 1st-type of outburstsuggest an expansion of an optically thick medium at the orbital planein the form of a disk. The low-temperature nebula radiates at a meanelectron temperature of 14 000 K and is subject to eclipses, while thehigh-temperature nebula, which is seen during eclipses as the onlycomponent, is characterized by Te > 30 000 K. Radiativeand geometric properties of the main sources of radiation allowed us toreconstruct a basic structure of the hot object during the 1st-type ofoutburst. There is an edge-on disk around the accretor. Its outer flaredrim represents a warm pseudophotosphere of the hot stellar source, whoseradiation is Rayleigh attenuated and affected by the iron curtainabsorptions in the neutral gas concentrated at the orbital plane. Thelow-temperature nebula is placed just above/below the disk with aconcentration at its edge as to be subject to eclipses and to“see” well the central ionizing source. High above/below theorbital plane, there is a hot nebular emitting region.
| Bipolar jet growth and decline in Hen 3-1341: a direct link to fast wind and outburst evolution*
We report on and investigate the evolution and disappearance in thesymbiotic star Hen 3-1341 of collimated bipolar jets, which take theform of symmetrically displaced components of emission lines. Frommodelling of the emission-line spectrum it turns out that the accretingwhite dwarf (WD) in quiescence has TWD~ 1.2 ×105 K and RWD~ 0.14 Rsolar, for aluminosity of 3.8 × 103 Lsolar, and it isstably burning hydrogen on the surface at a rate of , feeding ionizingphotons to a radiation bounded circumstellar nebula extending for ~17au. The WD underwent a multimaxima outburst lasting from 1998 to 2004during which its H-burning envelope reacted to a probable small increasein the mass accretion by expanding and cooling to Teff~ 1× 104 K and R~ 20 Rsolar, mimicking anA-type giant that radiated a total of ~6 × 1044 erg, atan average rate of ~1 × 103 Lsolar. Bipolarjets developed at the time of outburst maximum and their strengthdeclined in parallel with the demise of the fast wind from the inflatedWD, finally disappearing when the wind stopped halfway to quiescence,marking a 1:1 correspondence between jets presence and feeding action ofthe fast wind. The total mass in the jets was Mjet~ 2.5× 10-7 Msolar for a kinetic energy ofEkinjet~ 1.7 × 1042(sini)-1 erg, corresponding to ~0.3(sini)-1 percent of the energy radiated during the whole outburst. We suggest thatthe spectroscopic search for jets in symbiotic stars could pay higherdividends if focused on the outburst phases characterized by maximumwind intensity.
|
提交文章
相关链接
提交链接
下列团体成员
|
观测天体数据
目录:
|
