scholarly journals Red giant pulsations from the suspected symbiotic star StHA 169 detected in Kepler data

2014 ◽  
Vol 442 (1) ◽  
pp. 489-494 ◽  
Author(s):  
Gavin Ramsay ◽  
Pasi Hakala ◽  
Steve B. Howell
Keyword(s):  
Symbiotic Star ◽  
Red Giant ◽  
Giant Pulsations

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 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.

Relaxation Oscillations in Red-Giant Envelopes and the Symbiotic Stars

1973 ◽  
Vol 2 (4) ◽  
pp. 198-200 ◽  
Author(s):  
P. R. Wood
Keyword(s):  
Absorption Spectrum ◽  
Light Curves ◽  
Emission Lines ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Relaxation Oscillations ◽  
Cool Component ◽  
Cool Star ◽  
Red Giant ◽  
Eruptive Behaviour

The spectrum of a symbiotic star consists of an M-type absorption spectrum, a B-type shell spectrum and nebula emission lines, the relative contributions of these three components varying with time. The light curves of the symbiotic stars vary with a semi-regular period typically 200-800 days while larger eruptions occur on a timescale of ~ 3.5 years. Some suggestions which have been advanced to explain the combination spectrum, variability and eruptive behaviour of the symbiotic stars are: (a)the symbiotic stars are binaries consisting of a hot and cool component.(b)the symbiotic stars consist of a single hot star surrounded by a large optically thick envelope giving the appearance of a hot continuum with the absorption spectrum of a cool star superimposed on it.(c)the symbiotic stars are single stars surrounded by a shock wave heated chromosphere.Although some of the symbiotic stars are undoubtedly binaries (for example, T Coronae Borealis), observatienal evidence suggests that others may be explained by hypothesis (c) above. The calculations described below provide an explanation of the symbiotic stars in conjunction with hypothesis (c).

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 A Binary Model for the Symbiotic Star V 1329 Cygni

1980 ◽  
Vol 88 ◽  
pp. 547-547
Author(s):  
D. Chochol ◽  
J. Grygar ◽  
L. Hric
Keyword(s):  
Emission Line ◽  
Accretion Rate ◽  
Compact Star ◽  
Photometric Data ◽  
Symbiotic Star ◽  
Line Profiles ◽  
Polar Caps ◽  
Binary Model ◽  
Balmer Lines ◽  
Red Giant

This emission-line object was discovered by Kohoutek in 1969. Its light curve was subsequently reconstructed since 1891. Before 1964, the object fluctuated at around 15m, with occasional deep minima as deep as 2.3m. Its spectrum was late M. In 1964 the object brightened up to 14m and then it reached 11.5m in the middle of the year 1966. Since 1966 the object has been slowly decreasing in brightness. Stienon et al. (1974) suggested that the photometric behaviour prior to the outburst could be explained in terms of an eclipsing binary with a period of 960 days. This is now confirmed by the analysis of the post-outburst photometric data and independently by the investigation of the radial velocities of the emission-line component. We have derived the following spectroscopic elements: Period = 950.07d; γ = 37 ± 6 km/s; K1 = 62 ± 8 km/s; f(M) = 23 M⊙; aisin i = 1160 R⊙. We propose a binary model for the symbiotic object consisting of a bright red giant M5 II with a mass of 25 M⊙, and of a very hot compact star of 1 M⊙. Line profiles of the nebular lines as well as Balmer lines suggest the existence of ejected “polar caps” and an equatorial ring around the hot component, much like in novae. It seems that the hot component accretes the material from the giant via strong stellar wind. Changes in the accretion rate can cause the observed optical fluctuations. The major outburst in 1964-1966 was probably caused by a shell flash which also ionized the expanding nebula surrounding the hot component.

Isolating Red Giant Stars in M31's Elusive Outer Spheroid

1998 ◽  
Vol 116 (2) ◽  
pp. 707-722 ◽  
Author(s):  
David B. Reitzel ◽  
Puragra Guhathakurta ◽  
Andrew Gould
Keyword(s):  
Giant Stars ◽  
Red Giant Stars ◽  
Red Giant

scholarly journals Asteroseismology of luminous red giants with Kepler. II. Dependence of mass loss on pulsations and radiation

2020 ◽  
Author(s):  
Jie Yu ◽  
Saskia Hekker ◽  
Timothy R Bedding ◽  
Dennis Stello ◽  
Daniel Huber ◽  
...  
Keyword(s):  
Mass Loss ◽  
Mass Loss Rate ◽  
Asymptotic Giant Branch ◽  
Red Giants ◽  
Asymptotic Giant Branch Stars ◽  
Chemical Enrichment ◽  
Dust Mass ◽  
Red Giant ◽  
The Masses ◽  
Loss Rates

Abstract Mass loss by red giants is an important process to understand the final stages of stellar evolution and the chemical enrichment of the interstellar medium. Mass-loss rates are thought to be controlled by pulsation-enhanced dust-driven outflows. Here we investigate the relationships between mass loss, pulsations, and radiation, using 3213 luminous Kepler red giants and 135000 ASAS–SN semiregulars and Miras. Mass-loss rates are traced by infrared colours using 2MASS and WISE and by observed-to-model WISE fluxes, and are also estimated using dust mass-loss rates from literature assuming a typical gas-to-dust mass ratio of 400. To specify the pulsations, we extract the period and height of the highest peak in the power spectrum of oscillation. Absolute magnitudes are obtained from the 2MASS Ks band and the Gaia DR2 parallaxes. Our results follow. (i) Substantial mass loss sets in at pulsation periods above ∼60 and ∼100 days, corresponding to Asymptotic-Giant-Branch stars at the base of the period-luminosity sequences C′ and C. (ii) The mass-loss rate starts to rapidly increase in semiregulars for which the luminosity is just above the red-giant-branch tip and gradually plateaus to a level similar to that of Miras. (iii) The mass-loss rates in Miras do not depend on luminosity, consistent with pulsation-enhanced dust-driven winds. (iv) The accumulated mass loss on the Red Giant Branch consistent with asteroseismic predictions reduces the masses of red-clump stars by 6.3%, less than the typical uncertainty on their asteroseismic masses. Thus mass loss is currently not a limitation of stellar age estimates for galactic archaeology studies.

Subaru Hyper Suprime-Cam Survey for the Local Group Dwarf Galaxies: Ursa Minor

2018 ◽  
Vol 14 (S344) ◽  
pp. 94-95
Author(s):  
Yutaka Komiyama
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Structural Parameters ◽  
Deep Imaging ◽  
Ursa Minor ◽  
Red Giant

AbstractWe have carried out a wide and deep imaging survey for the Local Group dwarf spheroidal galaxy Ursa Minor (UMi) using Hyper Suprime-Cam (HSC). The data cover out beyond the nominal tidal radius down to ~25 mag in i band, which is ~2 mag below the main sequence turn-off point. The structural parameters of UMi are derived using red giant branch (RGB) stars and sub-giant branch (SGB) stars, and the tidal radius is suggested to be larger than those estimated by the previous studies. It is also found that the distribution of bluer RGB/SGB stars is more extended than that of redder RGB/SGB stars. The fraction of binary systems is estimated to be ~0.4 from the morphology of the main sequences.

scholarly journals Towards an Improved Model of the Galaxy

1998 ◽  
Vol 11 (1) ◽  
pp. 570-570
Author(s):  
Johan Holmberg ◽  
Lennart Lindegren ◽  
Chris Flynn
Keyword(s):  
Three Dimensional ◽  
Direct Determination ◽  
Galactic Structure ◽  
Open Clusters ◽  
Selection Effects ◽  
Observational Errors ◽  
Red Giant ◽  
Improved Model ◽  
First Time ◽  
Hr Diagram

We use the Hipparcos survey to derive an improved model of the local galactic structure. The availability of parallaxes for all the stars permits direct determination of stellar distributions, eliminating the basic indeterminacy of classical methods based on star counts. Hipparcos gives for the first time a truly three-dimensional view of the solar vicinity, and a complete, homogeneous and highly accurate set of magnitudes and colours. This means that new techniques can be applied in the treatment of the data which place strong constraints on a model that tries to describe the local Galactic structure. Here we investigate how well a static model of low complexitycan describe the Hipparcos observations. The interpretation of the Hipparcos data is complicated by various observational errors and selection effects that are hard to treat correctly. We do not try to correct the data, but instead use a model and subject this model to the same observational errors and selection effects. A model catalogue is created that can be compared with the observed catalogue directly in the observational domain, thereby eliminating the effects from various biases. Many features in the HR diagram are for the first time seen in field stars thanks to Hipparcos, such as the slanted red giant clump, previously seen in rich old open clusters such as Berkeley 18. This and other features ofthe observed HR diagram are well reproduced by the model thanks to the rather detailed modelling of the joint Mv/B — V distribution. Actually, separate distributions were derived for the three different components, disk, thick disk and halo, using the kinematic characteristics of the components to discriminate between them.

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