AG Dra a Symbiotic Star with an Uncommon Cool Component

Friedjung, M.

doi:10.1007/978-94-009-2969-2_35

Cited by 2 publications

(1 citation statement)

References 16 publications

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“…SYMBIOTIC SYSTEMS Symbiotic systems are wide binaries consisting of a red giant star and a WD (cf Kenyon 1986, Friedjung 1988, Mikolajewska & Kenyon 1992, Viotti et al 1996. This is the second obvious class of binary systems in which high mass-transfer rates towards WDs can be achieved such that nuclear burning in the surface layers can be ignited.…”

Section: Which Companions Are Able To Provide the Right Accretion Ratmentioning

confidence: 99%

Luminous Supersoft X-Ray Sources

Kahabka

Heuvel

1997

Annu. Rev. Astron. Astrophys.

327

262

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Luminous supersoft X-ray sources were discovered with the Einstein observatory and have been established as an important new class of X-ray binaries on the basis of observations with the Roentgen Satellite (ROSAT). They have extremely soft spectra (equivalent blackbody temperatures of ∼15-80 eV) and are highly luminous (bolometric luminosities of 10 36 -10 38 erg s −1 ). Correcting for the heavy extinction of soft X rays by interstellar neutral hydrogen, their numbers in the disks of ordinary spiral galaxies like our own and M31 are estimated to be of the order of 10 3 . Their observed characteristics are consistent with those of white dwarfs, which are steadily or cyclically burning hydrogen-rich matter accreted onto the surface at a rate of order 10 −7 M year −1 . The required high accretion rates can be supplied by mass transfer on a thermal time scale (10 6 -10 7 years) from close companion stars that are more massive than the white dwarf accretor, typically 1.3-2.5 M . Steady burning can also occur in a post-nova stage, but for shorter time scales, and it has been observed in a few classical novae and symbiotic novae. A few supersoft sources have been found to be recurrent transients. They are possibly connected with very massive white dwarfs accreting at high rates. Luminous supersoft sources may make a considerable contribution to the Type Ia supernova rate in spiral and irregular galaxies.

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Section: Which Companions Are Able To Provide the Right Accretion Ratmentioning

confidence: 99%

Luminous Supersoft X-Ray Sources

Kahabka

Heuvel

1997

Annu. Rev. Astron. Astrophys.

327

262

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UV and X-ray monitoring of AG draconis during the 1994/1995 outbursts

Greiner

Bickert

Luthardt

et al.

Lecture Notes in Physics

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Abstract. The recent 1994-1995 active phase of AG Draconis has given us for the first time the opportunity to follow the full X-ray behaviour of a symbiotic star during two successive outbursts and to compare with its quiescence X-ray emission. With ROSAT observations we have discovered a remarkable decrease of the X-ray flux during both optical maxima, followed by a gradual recovering to the pre-outburst flux. In the UV the events were characterized by a large increase of the emission line and continuum fluxes, comparable to the behaviour of AG Dra during the 1980-81 active phase. The anticorrelation of X-ray/UV flux and optical brightness evolution is shown to very likely be due to a temperature decrease of the hot component. Such a temperature decrease could be produced by an increased mass transfer to the burning compact object, causing it to slowly expand to about twice its original size.

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AG Dra a Symbiotic Star with an Uncommon Cool Component

Cited by 2 publications

References 16 publications

Luminous Supersoft X-Ray Sources

Luminous Supersoft X-Ray Sources

UV and X-ray monitoring of AG draconis during the 1994/1995 outbursts

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