Stellar Wind Accretion and Raman O VI Spectroscopy of the Symbiotic Star AG Draconis

2018 ◽  
Vol 14 (S343) ◽  
pp. 449-451
Author(s):  
Young-Min Lee ◽  
Jeong-Eun Heo ◽  
Hee-Won Lee ◽  
Ho-Gyu Lee ◽  
Rodolfo Angeloni ◽  
...  
Keyword(s):  
Loss Rate ◽  
Profile Analysis ◽  
Mass Loss Rate ◽  
Flux Ratio ◽  
Orbital Plane ◽  
Mass Transfer Process ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Accretion Flow ◽  
Best Fit

AbstractRaman scattered O VI features at 6825 Å and 7082 Å found in symbiotic stars are important spectroscopic tools to probe the mass transfer process. Adopting a Monte Carlo approach, we perform a profile analysis of Raman O VI features of the yellow SySt AG Draconis and make a comparison with the spectrum obtained with CFHT. It is assumed that the accretion flow is convergent on the entering side with enhanced O VI emission and the flux ratio F(1032)/F(1038)∼1, whereas on the opposite side the flow is divergent with low O VI emission and F(1032/F(1038)∼2. Our best fit to the spectrum is obtained from our model with a mass-loss rate of the giant ∼4 × 10−7 M⊙ yr−1. A slight red wing excess in the spectrum suggests the presence of bipolar neutral components receding in the directions perpendicular to the binary orbital plane with a speed ∼70km s−1

scholarly journals Wind morphology around cool evolved stars in binaries

2020 ◽  
Vol 637 ◽  
pp. A91 ◽  
Author(s):  
I. El Mellah ◽  
J. Bolte ◽  
L. Decin ◽  
W. Homan ◽  
R. Keppens
Keyword(s):  
Mass Loss ◽  
Adaptive Mesh Refinement ◽  
Loss Rate ◽  
Main Sequence ◽  
Mass Loss Rate ◽  
Large Fraction ◽  
Orbital Plane ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Evolved Stars

Context. The late evolutionary phase of low- and intermediate-mass stars is strongly constrained by their mass-loss rate, which is orders of magnitude higher than during the main sequence. The wind surrounding these cool expanded stars frequently shows nonspherical symmetry, which is thought to be due to an unseen companion orbiting the donor star. The imprints left in the outflow carry information about the companion and also the launching mechanism of these dust-driven winds. Aims. We study the morphology of the circumbinary envelope and identify the conditions of formation of a wind-captured disk around the companion. Long-term orbital changes induced by mass loss and mass transfer to the secondary are also investigated. We pay particular attention to oxygen-rich, that is slowly accelerating, outflows in order to look for systematic differences between the dynamics of the wind around carbon and oxygen-rich asymptotic giant branch (AGB) stars. Methods. We present a model based on a parametrized wind acceleration and a reduced number of dimensionless parameters to connect the wind morphology to the properties of the underlying binary system. Thanks to the high performance code MPI-AMRVAC, we ran an extensive set of 72 three-dimensional hydrodynamics simulations of a progressively accelerating wind propagating in the Roche potential of a mass-losing evolved star in orbit with a main sequence companion. The highly adaptive mesh refinement that we used, enabled us to resolve the flow structure both in the immediate vicinity of the secondary, where bow shocks, outflows, and wind-captured disks form, and up to 40 orbital separations, where spiral arms, arcs, and equatorial density enhancements develop. Results. When the companion is deeply engulfed in the wind, the lower terminal wind speeds and more progressive wind acceleration around oxygen-rich AGB stars make them more prone than carbon-rich AGB stars to display more disturbed outflows, a disk-like structure around the companion, and a wind concentrated in the orbital plane. In these configurations, a large fraction of the wind is captured by the companion, which leads to a significant shrinking of the orbit over the mass-loss timescale, if the donor star is at least a few times more massive than its companion. In the other cases, an increase of the orbital separation is to be expected, though at a rate lower than the mass-loss rate of the donor star. Provided the companion has a mass of at least a tenth of the mass of the donor star, it can compress the wind in the orbital plane up to large distances. Conclusions. The grid of models that we computed covers a wide scope of configurations: We vary the terminal wind speed relative to the orbital speed, the extension of the dust condensation region around the cool evolved star relative to the orbital separation, and the mass ratio, and we consider a carbon-rich and an oxygen-rich donor star. It provides a convenient frame of reference to interpret high-resolution maps of the outflows surrounding cool evolved stars.

scholarly journals The Role of Electron Scattering in Probing the Wind from the Hot Star in Symbiotic Binaries

2011 ◽  
Vol 7 (S282) ◽  
pp. 315-316
Author(s):  
Matej Sekeráš ◽  
Augustin Skopal
Keyword(s):  
Electron Scattering ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Empirical Relationship ◽  
Emission Measure ◽  
Emission Lines ◽  
Symbiotic Stars ◽  
Symbiotic Binaries ◽  
Scattering Contribution

AbstractWe modeled the broad wings of the OVI 1032,1038Å resonance lines and HeII 1640Å line in the spectra of some symbiotic stars by the electron-scattering process. We determined an empirical relationship between the emission measure of the symbiotic nebula and the electron optical depth. This allowed us to determine a contribution from the electron-scattering also to emission lines, which originate in a more extended, low density part of the nebula. For example, subtracting the electron-scattering contribution from the Hα line profile makes it possible to determine more precisely the mass loss rate via the wind from the hot star in symbiotic binaries.

scholarly journals Photoionization modelling of quiescence-phase spectra of novae and a symbiotic star

2020 ◽  
Vol 492 (2) ◽  
pp. 2326-2334 ◽  
Author(s):  
Anindita Mondal ◽  
Ramkrishna Das ◽  
G C Anupama ◽  
Soumen Mondal
Keyword(s):  
Physical Parameters ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Hydrogen Density ◽  
Elemental Abundances ◽  
Optical Region ◽  
Best Fitting ◽  
Best Fit ◽  
Absorption Features ◽  
Phase Spectra

ABSTRACT Using observed and published spectra in the optical region, we have studied a handful of novae and symbiotic stars that show novae-like variability in the quiescence phase. We present results for the novae T Coronae Borealis, GK Persei, RS Ophiuchi, V3890 Sagittarii and V745 Scorpii, and for a symbiotic star BX Monocerotis. Observations were carried out at the 2-m Himalayan Chandra Telescope (HCT). Generally, the spectra show prominent low-ionization emission features of hydrogen, helium, iron and oxygen and TiO absorption features resulting from the cool secondary component; T Coronae Borealis and GK Persei show higher ionization lines. We used the photoionization code cloudy to model these spectra. From the best-fitting models, we have estimated the physical parameters (e.g. temperature, luminosity and hydrogen density), the elemental abundances and other parameters related to the system. By matching the spectra of various giants with the absorption features and using the best fit, we have determined the types of secondaries and also their contribution to the spectra.

scholarly journals Z Andromedae: Quiescence and Activity

1988 ◽  
Vol 103 ◽  
pp. 181-186
Author(s):  
A. Cassatella ◽  
T. Fernandez-Castro ◽  
N. Oliversen
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
Flux Ratio ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Activity Phase ◽  
International Ultraviolet Explorer ◽  
History Of ◽  
Ubv Photometry ◽  
Principal Contributor

Z Andromedae, often considered as the prototype of symbiotic stars, experimented, after several years of quiescence, a small outburst in March-April 1984, followed by a larger one in September-October 1985. The imminence of a new activity phase was predicted by Viotti et al. (1982). Z And is, together with AG Draconis, the only symbiotic star observed both during quiescence and activity with the IUE satellite. The early photometric and spectroscopic history of Z And has been recently reviewed by Kenyon (1986).The behaviour of Z And in the ultraviolet during quiescence has been studied by Fernåndez-Castro et al. (1988), on the basis of data obtained by the International Ultraviolet Explorer from 1978 to 1982. In that period of time, the UV continuum and the emission line fluxes varied quasiperidically with a period of about two years, in phase with the Hα variability found by Altamore et al. (1979), with the UBV photometry by Belyakina (1985) and also in agreement with the ephemeris given by Kenyon and Webbink (1984). The electron density derived from Si III/C III] flux ratio, also varied in phase with the UV flux. In particular, a correlation was found between the electron density variations, and the UV continuum flux at 2900 A. This fact, together with the presence of a Balmer jump in emission, indicates that the principal contributor at those wavelengths is nebular emission, mainly free-bound transitions.

scholarly journals Light-curve analysis of KOI 2700b: the second extrasolar planet with a comet-like tail

2018 ◽  
Vol 611 ◽  
pp. A63 ◽  
Author(s):  
Z Garai
Keyword(s):  
Light Curve ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Orbital Plane ◽  
Light Curve Analysis ◽  
Orbital Inclination ◽  
Dust Density ◽  
Scientific Goal ◽  
Dust Tail ◽  
Parent Star

Context. The Kepler object KOI 2700b (KIC 8639908b) was discovered recently as the second exoplanet with a comet-like tail. It exhibits a distinctly asymmetric transit profile, likely indicative of the emission of dusty effluents and reminiscent of KIC 12557548b, the first exoplanet with a comet-like tail. Aim. The scientific goal of this work is to verify the disintegrating-planet scenario of KOI 2700b by modeling its light curve and to put constraints on various tail and planet properties, as was done in the case of KIC 12557548b. Methods. We obtained the phase-folded and binned transit light curve of KOI 2700b, which we subsequently iteratively modeled using the radiative-transfer code SHELLSPEC. We modeled the comet-like tail as part of a ring around the parent star and we also included the solid body of the planet in the model. During the modeling we applied selected species and dust particle sizes. Results. We confirmed the disintegrating-planet scenario of KOI 2700b. Furthermore, via modeling, we derived some interesting features of KOI 2700b and its comet-like tail. It turns out that the orbital plane of the planet and its tail are not edge-on, but the orbital inclination angle is from the interval [85.1, 88.6] deg. In comparison with KIC 12557548b, KOI 2700b exhibits a relatively low dust density decreasing in its tail. We also derived the dust density at the beginning of the ring and the highest optical depth through the tail in front of the star, based on a tail-model with a cross-section of 0.05 × 0.05 R⊙ at the beginning and 0.09 × 0.09 R⊙ at its end. Our results show that the dimension of the planet is Rp∕Rs ≤ 0.014 (Rp ≤ 0.871 R⊕, or ≤5551 km). We also estimated the mass-loss rate from KOI 2700b, and we obtained Ṁ values from the interval [5.05 × 107, 4.41 × 1015] g s−1. On the other hand, we could not draw any satisfactory conclusions about the typical grain size in the dust tail.

scholarly journals IRAS Observations of Symbiotic Stars

1989 ◽  
Vol 106 ◽  
pp. 391-400 ◽  
Author(s):  
M. Parthasarathy ◽  
H.C. Bhatt
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Planetary Nebulae ◽  
Evolutionary Stage ◽  
Symbiotic Stars ◽  
Late Type ◽  
Mira Variables ◽  
Show Evidence ◽  
The Masses

AbstractOf the 129 symbiotic stars in Allen's (1984) catalogue, 42 were found to be IRAS sources. Of these 42 IRAS sources, 22 are D-type (symbiotic Miras), 5 are D'-type (yellow symbiotics) and 15 are S-type. The separation of S, D and D’ types into three distinct groups is clearer in the log[fλ(25μm)/fλ(12μm)] versus (H-K) diagram. The IRAS fluxes of S-type symbiotics are consistent with that observed from normal M giants. This result suggests that mass-loss rate from most of the S-type symbiotics is similar to that from normal M giants. The IRAS data of D-type symbiotics shows evidence for the presence of dust envelopes. The masses of the dust envelopes (10-6 to 10-7 Mo) around Miras in D-type symbiotics are similar to that observed in field Mira variables. These results suggest that mass-loss rates in symbiotic Miras are similar to those from field Mira variables and also that the mass loss from symbiotic Miras is pulsationally driven similar to that found in field Mira variables by Whitelock, Pottasch and Feast (1987). Analysis of IRAS data of yellow symbiotics Ml-2, AS201, Cnl-1, Wray 157. and HD149427 suggests that they are young planetary nebulae containing a binary nucleus. Ml-2, AS201 and Cnl-1 show evidence for the presence of evolved hot companions. The evolutionary stage of the late type (F-G) companions is not clear.

scholarly journals Modelling spectra of MN112

2020 ◽  
Vol 496 (4) ◽  
pp. 5455-5462
Author(s):  
A Kostenkov ◽  
S Fabrika ◽  
O Sholukhova ◽  
A Sarkisyan ◽  
D Bizyaev
Keyword(s):  
Loss Rate ◽  
Spectroscopic Analysis ◽  
Mass Loss Rate ◽  
Chemical Abundances ◽  
Strong Emission ◽  
Non Local ◽  
Hydrogen Lines ◽  
Best Fit ◽  
Calar Alto ◽  
Luminous Blue Variable

ABSTRACT MN112 is a Galactic luminous blue variable (LBV) candidate with a circumstellar nebula. P Cygni was the first LBV discovered, and was recorded during major eruptions in the 17th century. The stars have similar spectra with strong emission hydrogen lines, He i, N ii, Si ii, and Fe iii lines. We present the results of spectroscopic analysis and modelling of MN112 spectra. We obtained the main stellar parameters and chemical abundances of MN112 and compared them with those of P Cygni. Atmosphere models were calculated using the non-local thermodynamic equilibrium radiative transfer code cmfgen. We have used spectra of MN112 obtained with the 3.5-m telescope at the Observatory of Calar Alto and 3.5-m ARC telescope at the Apache Point Observatory. P Cygni spectra were taken with the 6-m BTA telescope. We have found the best fit of the observed spectrum with the model at temperature $T_{\text{eff}}= 15\, 200$ K, clumping-corrected mass-loss rate $\dot{M}f^{-0.5}=5.74 \times 10^{-5}\, \mathrm{M}_{\odot }\text{yr}^{-1}$, filling factor f = 0.1, luminosity $L=5.77 \times 10^5\, \mathrm{L}_{\odot }$ for MN112. The ratio of helium to hydrogen He/H is 0.27 (by the number of atoms) with nitrogen overabundance (XN/X⊙ = 6.8) and an underabundance of carbon (XC/X⊙ < 0.1).

scholarly journals The X-Ray Evolution of the Symbiotic Star V407 Cyg During its 2010 Outburst

2012 ◽  
Vol 21 (1-2) ◽  
Author(s):  
K. Mukai ◽  
T. Nelson ◽  
L. Chomiuk ◽  
D. Donato ◽  
J. Sokoloski
Keyword(s):  
Mass Loss ◽  
Blast Wave ◽  
White Dwarf ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Symbiotic Star ◽  
X Ray ◽  
Binary Separation ◽  
Nova Outburst

AbstractWe present a summary of Swift and Suzaku X-ray observations of the 2010 nova outburst of the symbiotic star, V407 Cyg. the Suzaku spectrum obtained on day 30 indicates the presence of the supersoft component from the white dwarf surface, as well as optically thin component from the shock between the nova ejecta and the Mira wind. the Swift observations then allow us to track the evolution of both components from day 4 to day 150. Most notable is the sudden brightening of the optically thin component around day 20. We identify this as the time when the blast wave reached the immediate vicinity of the photosphere of the Mira. We have developed a simpe model of the blast wave - wind interaction that can reproduce the gross features of the X-ray evolution of V407 Cyg. If the model is correct, the binary separation is likely to be larger than previously suggested and the mass-loss rate of the Mira is likely to be relatively low.

scholarly journals DEATHSTAR: Nearby AGB stars with the Atacama Compact Array

2020 ◽  
Vol 640 ◽  
pp. A133 ◽  
Author(s):  
S. Ramstedt ◽  
W. H. T. Vlemmings ◽  
L. Doan ◽  
T. Danilovich ◽  
M. Lindqvist ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Minor Axis ◽  
Agb Stars ◽  
Radiative Transfer Modeling ◽  
Best Fit ◽  
Compact Array ◽  
Loss Rates

Context. This is the first publication from the DEATHSTAR project. The overall goal of the project is to reduce the uncertainties of the observational estimates of mass-loss rates from evolved stars on the Asymptotic Giant Branch (AGB). Aim. The aim in this first publication is to constrain the sizes of the 12CO emitting region from the circumstellar envelopes around 42 mostly southern AGB stars, of which 21 are M-type and 21 are C-type, using the Atacama Compact Array (ACA) at the Atacama Large Millimeter/submillimeter Array. The symmetry of the outflows is also investigated. Methods. Line emission from 12CO J = 2→1 and 3→2 from all of the sources were mapped using the ACA. In this initial analysis, the emission distribution was fit to a Gaussian distribution in the uv-plane. A detailed radiative transfer analysis will be presented in a future publication. The major and minor axis of the best-fit Gaussian at the line center velocity of the 12CO J = 2→1 emission gives a first indication of the size of the emitting region. Furthermore, the fitting results, such as the Gaussian major and minor axis, center position, and the goodness of fit across both lines, constrain the symmetry of the emission distribution. For a subsample of sources, the measured emission distribution is compared to predictions from previous best-fit radiative transfer modeling results. Results. We find that the CO envelope sizes are, in general, larger for C-type than for M-type AGB stars, which is as expected if the CO/H2 ratio is larger in C-type stars. Furthermore, the measurements show a relation between the measured (Gaussian) 12CO J = 2→1 size and circumstellar density that, while in broad agreement with photodissociation calculations, reveals large scatter and some systematic differences between the different stellar types. For lower mass-loss-rate irregular and semi-regular variables of both M- and C-type AGB stars, the 12CO J = 2→1 size appears to be independent of the ratio of the mass-loss rate to outflow velocity, which is a measure of circumstellar density. For the higher mass-loss-rate Mira stars, the 12CO J = 2→1 size clearly increases with circumstellar density, with larger sizes for the higher CO-abundance C-type stars. The M-type stars appear to be consistently smaller than predicted from photodissociation theory. The majority of the sources have CO envelope sizes that are consistent with a spherically symmetric, smooth outflow, at least on larger scales. For about a third of the sources, indications of strong asymmetries are detected. This is consistent with what was found in previous interferometric investigations of northern sources. Smaller scale asymmetries are found in a larger fraction of sources. Conclusions. These results for CO envelope radii and shapes can be used to constrain detailed radiative transfer modeling of the same stars so as to determine mass-loss rates that are independent of photodissociation models. For a large fraction of the sources, observations at higher spatial resolution will be necessary to deduce the nature and origin of the complex circumstellar dynamics revealed by our ACA observations.

scholarly journals CO envelope of the symbiotic star R Aquarii seen by ALMA

2018 ◽  
Vol 616 ◽  
pp. A61 ◽  
Author(s):  
S. Ramstedt ◽  
S. Mohamed ◽  
T. Olander ◽  
W. H. T. Vlemmings ◽  
T. Khouri ◽  
...  
Keyword(s):  
Mass Loss ◽  
Spatial Resolution ◽  
White Dwarf ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Line Emission ◽  
High Energy ◽  
Small Sample ◽  
Symbiotic Star ◽  
Binary Separation

The symbiotic star R Aqr is part of a small sample of binary AGB stars observed with the Atacama Large Millimeter/submillimeter Array (ALMA). The sample stars are: R Aqr, Mira, W Aql, and π1 Gru. The sample covers a range in binary separation and wind properties, where R Aqr is the source with the smallest separation. The R Aqr binary pair consists of an M-type AGB star and a white dwarf at a separation of 45 mas, equivalent to about 10 AU at 218 pc. The aim of the ALMA study is to investigate the dependence of the wind shaping on the binary separation and to provide constraints for hydrodynamical binary interaction models. R Aqr is particularly interesting as the source with the smallest separation and a complex circumstellar environment that is strongly affected by the interaction between the two stars and by the high-energy radiation resulting from this interaction and from the hot white dwarf companion. The CO(J = 3 →2) line emission has been observed with ALMA at ~0.5′′ spatial resolution. The CO envelope around the binary pair is marginally resolved, showing what appears to be a rather complex distribution. The outer radius of the CO emitting region is estimated from the data and found to be about a factor of 10 larger than previously thought. This implies an average mass-loss rate during the past ~100 yr of Ṁ ≈ 2×10−7 M⊙ yr−1, a factor of 45 less than previous estimates. The channel maps are presented and the molecular gas distribution is discussed and set into the context of what was previously known about the system from multiwavelength observations. Additional molecular line emission detected within the bandwidth covered by the ALMA observations is also presented. Because of the limited extent of the emission, firm conclusions about the dynamical evolution of the system will have to wait for higher spatial resolution observations. However, the data presented here support the assumption that the mass-loss rate from the Mira star strongly varies and is focused on the orbital plane.

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