A radio jet associated with the symbiotic star CH Cygni

1986 ◽  
Vol 64 (4) ◽  
pp. 520-522 ◽  
Author(s):  
E. R. Seaquist ◽  
A. R. Taylor
Keyword(s):  
Electron Density ◽  
White Dwarf ◽  
Transverse Velocity ◽  
Stellar Object ◽  
Symbiotic Star ◽  
Ionized Gas ◽  
Radio Outburst ◽  
Supercritical Accretion ◽  
End To End ◽  
Red Giant

We present observations that show that the symbiotic star CH Cygni recently underwent a strong radio outburst that produced a radio-emitting thermal jet. The jet is two-sided and is expanding lengthwise at an observed rate (end to end) of 1 arcsec/year, corresponding to a transverse velocity of 1100 km∙s−1 in each direction. The electron density on January 22, 1985 exceeded 2 × 106 cm−3, and the mass of the (ionized) gas exceeded [Formula: see text]. The emergence of the jet coincided with a decline in the visual luminosity of [Formula: see text].The data are consistent with a jet produced by supercritical accretion in a binary containing a red giant and a [Formula: see text] white dwarf. The discovery of a jet in such a system provides confirming evidence of the role played by accretion in determining the optical and radio properties of this system. It is also the first expanding jet found to be associated with an evolved stellar object.

scholarly journals Accreting Double Shell Source Degenerate Stars

1979 ◽  
Vol 53 ◽  
pp. 530-530 ◽  
Author(s):  
Edward M. Sion
Keyword(s):  
Energy Source ◽  
Steady State ◽  
White Dwarf ◽  
Nuclear Reactions ◽  
Variable Stars ◽  
Symbiotic Star ◽  
Additional Energy ◽  
Source Models ◽  
Red Giant ◽  
Thermonuclear Runaway

Ultraviolet photometry from the OAO-2 satellite supports the white dwarf thermonuclear runaway model for the symbiotic star AG Peg (Gallagher et al. 1979). Massive white dwarfs (M>1.1M⊙) burning hydrogen in a steady state with accretion (Sion et al. 1979) undergo either repetitive hydrogen shell flashes (Ṁ ≲1.03×10-7M⊙/yr), burn hydrogen stably in a steady state with accretion (1.03≲Ṁ≲2.7×10-7M⊙/yr) or evolve into a red giant structure (Ṁ≳2.7×10-7M⊙/yr). The nuclear reactions do not “shut off” between outbursts and mass is not ejected. If these models represent the behavior of the hot component of symbotic variable stars, the high luminosities and masses lead to the possibility that helium shell burning should be important as an additional energy source. The behavior of double shell burning near the surface of a white dwarf of any luminosity has not been explored (Webbink et al. 1978); Models have been constructed to represent such stars having (1) M=1M⊙, Ṁ=1.25×10-7M⊙/yr (L=104L⊙), log Te=5.70 and log R=8.965 and (2) M=1M⊙, Ṁ=1.26×10-8 M⊙/yr (L=103L⊙), log Te=5.52 and log R=8.85. Evolutionary sequences using these initial double shell source models are being constructed.

scholarly journals The Ionization of Novae Ejecta

1990 ◽  
Vol 122 ◽  
pp. 215-227
Author(s):  
R.E. Williams
Keyword(s):  
Emission Line ◽  
White Dwarf ◽  
Line Spectrum ◽  
Ionized Gas ◽  
Grain Formation ◽  
Emission Line Spectrum ◽  
Pass Through

AbstractNovae ejecta pass through four distinct phases of evolution of the emission-line spectrum, caused by different ionization characteristics of the shell. These include a neutral (I), an auroral (II), a coronal (III), and a nebular (IV) phase. Photoionization from the contracting photosphere of the hot white dwarf is the source of the ionization, including the highly ionized coronal phase. Changing emission line ratios in certain novae that develop dust are caused by condensation of grains from the gas, and can be used to determine the composition of the dust. In V1370 Aql, substantial silicate grain formation appears to have taken place, probably within the ionized gas.

scholarly journals The most massive white dwarfs in the solar neighbourhood

2021 ◽  
Vol 503 (4) ◽  
pp. 5397-5408
Author(s):  
Mukremin Kilic ◽  
P Bergeron ◽  
Simon Blouin ◽  
A Bédard
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Transverse Velocity ◽  
Maximum Mass ◽  
Model Calculations ◽  
Rapid Rotation ◽  
Rotation Rates ◽  
Binary Mergers ◽  
Chandrasekhar Limit

ABSTRACT We present an analysis of the most massive white dwarf candidates in the Montreal White Dwarf Database 100 pc sample. We identify 25 objects that would be more massive than $1.3\, {\rm M}_{\odot }$ if they had pure H atmospheres and CO cores, including two outliers with unusually high photometric mass estimates near the Chandrasekhar limit. We provide follow-up spectroscopy of these two white dwarfs and show that they are indeed significantly below this limit. We expand our model calculations for CO core white dwarfs up to M = 1.334 M⊙, which corresponds to the high-density limit of our equation-of-state tables, ρ = 109 g cm−3. We find many objects close to this maximum mass of our CO core models. A significant fraction of ultramassive white dwarfs are predicted to form through binary mergers. Merger populations can reveal themselves through their kinematics, magnetism, or rapid rotation rates. We identify four outliers in transverse velocity, four likely magnetic white dwarfs (one of which is also an outlier in transverse velocity), and one with rapid rotation, indicating that at least 8 of the 25 ultramassive white dwarfs in our sample are likely merger products.

scholarly journals Rapid Mass Accretion in the Symbiotic Star AG Dra

1987 ◽  
Vol 93 ◽  
pp. 759-762
Author(s):  
T. Iijima
Keyword(s):  
White Dwarf ◽  
Accretion Rate ◽  
Symbiotic Star ◽  
Mass Accretion Rate ◽  
Accretion Process ◽  
Rapid Mass

AbstractThe mass accretion process onto the hot component of AG Dra and its explosive phenomena are discussed. The hot component seems to be a massive white dwarf (M > 1 M⊙). The mass accretion rate is estimated to be about 10−7M⊙/year. Many properties of the explosive phenomena agree with those of mild hydrogen flashes expected from this rapid mass accretion.

scholarly journals Helium Shell-Flashes in Accreting White Dwarfs

1979 ◽  
Vol 53 ◽  
pp. 285-289 ◽  
Author(s):  
M. Y. Fujimoto ◽  
D. Sugimoto
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Giant Stars ◽  
Deep Interior ◽  
Constant Rate ◽  
Red Giant Stars ◽  
Red Giant

When gas is accreted onto a carbon-oxygen white dwarf, a hydrogen shell-flash is triggered. Recently such phenomena are studied by many authors in relation to nova explosions and rekindling of white dwarfs. Unless all of the accreted gas is ejected by the process of the nova, a helium zone is formed as a result of hydrogen shell-burning. As the hydrogen shell-flashes recur many times, the helium zone grows gradually in mass. Then the helium shell-flash will be ignited as in the deep interior of ordinary red giant stars. We have investigated such process, simulating it by helium accretion at a constant rate. In the present paper we show that the helium shell-flashes result in a variety of strengths depending upon situations.

scholarly journals Symbiotic Stars as Possible Progenitors of SNe Ia: Binary Parameters and Overall Outlook

2011 ◽  
Vol 7 (S281) ◽  
pp. 162-165 ◽  
Author(s):  
J. Mikołajewska
Keyword(s):  
White Dwarf ◽  
Physical Characteristics ◽  
Type Ia Supernovae ◽  
Symbiotic Stars ◽  
Type Ia ◽  
Red Giant ◽  
Ia Supernovae

AbstractSymbiotic stars are interacting binaries in which the first-formed white dwarf accretes and burns material from a red giant companion. This paper aims at presenting physical characteristics of these objects and discussing their possible link with progenitors of Type Ia supernovae.

Supernova: The Result of the Death Spiral of a White Dwarf into a Red Giant

1974 ◽  
Vol 188 ◽  
pp. 149 ◽  
Author(s):  
W. M. Sparks ◽  
T. P. Stecher
Keyword(s):  
White Dwarf ◽  
Death Spiral ◽  
Red Giant

scholarly journals UV and optical spectroscopy of CH Cygni in 1980–86

1987 ◽  
Vol 122 ◽  
pp. 487-489 ◽  
Author(s):  
J. Mikołajewska ◽  
M. Mikołajewski ◽  
R. Biernikowicz ◽  
P.L. Selvelli ◽  
Z. Turło
Keyword(s):  
Emission Line ◽  
Optical Spectroscopy ◽  
Active Phase ◽  
Emission Lines ◽  
Symbiotic Star ◽  
Uv Spectrum ◽  
Brightness Level ◽  
Radio Outburst ◽  
Large Continuum

CH Cyg is a binary (P∼5750 days) consisting of a normal M6-7 giant and an unseen companion. During active phase its spectrum is similar to that of a symbiotic star - the strong B-A continuum and numerous low-excitation emission lines dominate the visual and UV spectrum. The last outburst, started in 1977, is conspicuous by the highest brightness level observed since monitoring begun in 1935. In mid 1984, a drop in brightness was accompanied by large continuum and emission line changes and correlated with a radio outburst and two expanding jets appearance (Taylor et al. 1985).

scholarly journals Asymmetric distributions of H2O and SiO masers towards V627 Cas

2020 ◽  
Vol 495 (1) ◽  
pp. 1284-1290 ◽  
Author(s):  
Haneul Yang ◽  
Se-Hyung Cho ◽  
Youngjoo Yun ◽  
Dong-Hwan Yoon ◽  
Dong-Jin Kim ◽  
...  
Keyword(s):  
Red Giants ◽  
Symbiotic Star ◽  
Physical Size ◽  
Typical Size ◽  
North West ◽  
The North ◽  
Ring Radius ◽  
Asymmetric Distributions ◽  
Red Giant ◽  
Expected Position

ABSTRACT We performed simultaneous observations of the $\rm H_2O$ 61,6 − 52,3 (22.235080 GHz) and SiO v = 1, 2, J = 1 → 0, SiO v = 1, J = 2 → 1, 3 → 2 (43.122080, 42.820587, 86.243442, and 129.363359 GHz) masers towards the suspected D-type symbiotic star, V627 Cas, using the Korean VLBI Network. Here, we present astrometrically registered maps of the $\rm H_2O$ and SiO v = 1, 2, J = 1 → 0, SiO v = 1, J = 2 → 1 masers for five epochs from January 2016 to June 2018. Distributions of the SiO maser spots do not show clear ring-like structures, and those of the $\rm H_2O$ maser are biased towards the north–north-west to west with respect to the SiO maser features according to observational epochs. These asymmetric distributions of $\rm H_2O$ and SiO masers are discussed based on two scenarios of a bipolar outflow and the presence of the hot companion, a white dwarf, in V627 Cas. We carried out ring fitting of SiO v = 1, and v = 2 masers and estimated the expected position of the cool red giant. The ring radii of the SiO v = 1 maser are slightly larger than those of the SiO v = 2 maser, as previously known. Our assumption for the physical size of the SiO maser ring of V627 Cas to be the typical size of a SiO maser ring radius (∼4 au) of red giants yields the distance of V627 Cas to be ∼1 kpc.

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