scholarly journals Steady Mass Loss Associated with Nova Outbursts

1984 ◽  
Vol 80 ◽  
pp. 295-298
Author(s):  
Mariko Kato
Keyword(s):  
Mass Loss ◽  
White Dwarfs ◽  
Nova Outbursts ◽  
Nova Outburst ◽  
Photospheric Radius

AbstractThe structure of optically thick mass-losing envelopes of white dwarfs are studied in relation to nova outbursts. A sequence of steady mass-loss solutions is constructed for a nova outburst from the maximum photospheric radius to the disappearance. Much of mass of the envelope will be blown out.

scholarly journals Numerical Modelling of the Classical Nova Outburst

1988 ◽  
Vol 108 ◽  
pp. 236-237
Author(s):  
G. Siegfried Kutter ◽  
Warren M. Sparks
Keyword(s):  
Numerical Modelling ◽  
White Dwarfs ◽  
Classical Nova ◽  
Accretion Rates ◽  
Nova Outbursts ◽  
Nova Outburst

AbstractWe describe a mechanism that promises to explain how classical nova outbursts take place on white dwarfs of 1 M⊙ or less and for accretion rates of 4 × 10−10 M⊙ yr−1 or greater.

scholarly journals The Hot Winds of Novae

1996 ◽  
Vol 152 ◽  
pp. 413-417
Author(s):  
Peter H. Hauschildt ◽  
S. Starrfield ◽  
E. Baron ◽  
F. Allard
Keyword(s):  
Velocity Field ◽  
Spectral Range ◽  
Density Profiles ◽  
Basic Model ◽  
Physical Effects ◽  
Nova Outbursts ◽  
Expanding Shells ◽  
Nova Outburst

We discuss the physical effects that are important for the formation of the late wind spectra of novae. Nova atmospheres are optically thick, rapidly expanding shells with almost flat density profiles, leading to geometrically very extended atmospheres. We show how the properties of nova spectra can be interpreted in terms of this basic model and discuss some important effects that influence the structure and the emitted spectrum of nova atmospheres, e.g., line blanketing, NLTE effects, and the velocity field. Most of the radiation from hot nova winds is emitted in the spectral range of the EUVE satellite. Therefore, we present predicted EUVE spectra for the later stages of nova outbursts. Observations of novae with EUVE could be used to test our models for the nova outburst.

scholarly journals Classical Novae in the Context of the Evolution of Cataclysmic Binaries

1990 ◽  
Vol 122 ◽  
pp. 313-324
Author(s):  
Hans Ritter
Keyword(s):  
Mass Transfer ◽  
White Dwarf ◽  
White Dwarfs ◽  
Mass Range ◽  
High Mass ◽  
Transfer Rates ◽  
Classical Novae ◽  
Secular Evolution ◽  
Cataclysmic Binaries ◽  
Nova Outbursts

AbstractIn this paper we explore to what extent the TNR model of nova outbursts and our current concepts of the formation and secular evolution of cataclysmic binaries are compatible. Specifically we address the following questions: 1) whether observational selection can explain the high white dwarf masses attributed to novae, 2) whether novae on white dwarfs in the mass range 0.6M⊙ ≲ M ≲ 0.9M⊙ can occur and how much they could contribute to the observed nova frequency, and 3) whether the high mass transfer rates imposed on the white dwarf in systems above the period gap can be accommodated by the TNR model of nova outbursts.

scholarly journals 29. Stellar Spectra

1970 ◽  
Vol 14 (1) ◽  
pp. 319-329
Author(s):  
M. W. Feast ◽  
Y. Fujita ◽  
M. K. V. Bappu ◽  
G. Herbig ◽  
L. Houziaux ◽  
...  
Keyword(s):  
Mass Loss ◽  
Working Group ◽  
White Dwarfs ◽  
Vice President ◽  
Stellar Atmospheres ◽  
High Dispersion ◽  
Stellar Rotation ◽  
Stellar Spectra ◽  
Working Groups ◽  
Main Activity

Material for this report was collected by the President, Vice-President and Members of the Organizing Committee. The President is, however, responsible for the form in which the report now appears. A number of special abbreviations in the references are explained in the report of Committee 27a. In addition, 3rd Harvard = 3rd Harvard-Smithsonian Conference on Stellar Atmospheres (1968). The field of Commission 29 overlaps particularly with those of 9, 27a, 36, 44 and 45 whose reports should be consulted. Since the last IAU meeting 29 has co-sponsored the following meetings: IAU Colloquium No. 4 on Stellar Rotation (Columbus, Ohio, September 1969); IAU Symposium No. 36, Ultraviolet Stellar Spectra and Related Ground-Based Observations (Lunteren, June, 1969); Second Trieste Colloquium, Mass Loss from Stars (September, 1968). We are also co-sponsoring IAU Symposium No. 42 on White Dwarfs to be held in Scotland (August, 1970). The thanks of the commission are due to their representatives on the organizing committees of these meetings. Reports from some working groups are appended. The working group with Commission 44 has not felt it necessary to submit a report (its main activity was the organization of Symposium No. 36). Miss Underhill (Chairman) recommends that the working group on Tracings of High Dispersion Stellar Spectra be dissolved.

scholarly journals On the Properties of Wolf-Rayet Stars and Their Mass Loss

1982 ◽  
Vol 99 ◽  
pp. 203-207
Author(s):  
N. Panagia ◽  
M. Felli
Keyword(s):  
Mass Loss ◽  
Multiple Scattering ◽  
Radiation Temperature ◽  
List Type ◽  
Type Number ◽  
Lyman Continuum ◽  
Stellar Radiation ◽  
Total Luminosity ◽  
Continuous Radiation ◽  
Photospheric Radius

From consideration of the observed properties of the envelopes produced by mass loss in WR stars we find that: a)The velocity at the optical photosphere is in the range 200–800 km sb)The effective photospheric radius for the continuous radiation capable to ionize helium twice (γ < 228 A) is typically 5 to 15 times the optical photospheric radius.c)The radiation temperature in the Lyman continuum (γ < 912 Å) is around 5 × 104K. Therefore, most of the stellar radiation is emitted in the far UV and the total luminosity is considerably higher than currently estimated.d)Multiple scattering (N ≃ 20) of radiation in the interval 228–504 Å can provide most of the momentum needed to accelerate the wind up to the observed terminal velocities.

Mass Loss and the Formation of White Dwarfs. II

1966 ◽  
Vol 145 ◽  
pp. 649 ◽  
Author(s):  
N. J. Woolf
Keyword(s):  
Mass Loss ◽  
White Dwarfs

scholarly journals White Dwarfs

1994 ◽  
Vol 146 ◽  
pp. 71-78
Author(s):  
Peter Thejll
Keyword(s):  
Mass Loss ◽  
White Dwarfs ◽  
Main Sequence ◽  
Asymptotic Giant Branch ◽  
List Type ◽  
Stellar Core ◽  
The Core ◽  
Long Time ◽  
Red Giant ◽  
Carbon Burning

It is the intention of this review to explain what white dwarfs are and why it is interesting to study them, and why the H+2molecule is of special interest.The evolution, from start to finish, of a star of mass less than about 2 solar masses (M⊙), can roughly be summarized as follows:–A cloud of gas contracts from the interstellar medium until hydrogen ignites at the center and amain sequence(MS) star forms. H is transformed to He and the MS phase continues until H is exhausted in the stellar core.–H continues burning in a shell outside the He core while the core contracts. He “ashes” are added to the core, and ared giantstar is formed as the envelope expands. The star evolves up the Red Giant Branch (RGB) (i.e. it becomes more and more luminous and the surface cools).–Towards the end of the RGB phase, mass-loss from the upper layers increases until helium to carbon burning in the core ignites suddenly under degenerate conditions – this is called theHelium Flash(HF). The HF terminates the RGB evolution, and therefore also the mass-loss and the growth of the stellar core.–The star readjusts its structure and the He-core burns steadily on thehorizontal branch(HB) (a phase of nearly-constant luminosity) until fuel is exhausted in the He-core.–Then the C/O core contracts anew and the expansion of the envelope, and the growth of the core, during He-shell burning, mimics RGB evolution but relatively little mass is added to the core this time.–The second ascent of the giant branch (the so-called Asymptotic Giant Branch, or AGB) continues with increased mass loss towards the end–Rapid detachment of a considerable fraction of the remaining envelope and the hot core takes place, sometimes observable as thePlanetary Nebulae(PN) phase.–The PN is dispersed as the core contracts to a white dwarf (WD).–The WD cools for a long time, as internal kinetic energy and latent heat is released.

scholarly journals Nova Outburst Due to Accretion of H-Rich Matter onto White Dwarfs

1979 ◽  
Vol 53 ◽  
pp. 290-293
Author(s):  
G. Siegfried Kutter ◽  
Warren M. Sparks
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Classical Novae ◽  
Secondary Star ◽  
Rich Material ◽  
Thermonuclear Runaway ◽  
Nova Outburst ◽  
Physical Realism ◽  
Degenerate Base

We assume that the outburst of classical novae is the result of transfer of H-rich material from a red secondary star to a He or C/O white dwarf and the development of a thermonuclear runaway in the e-degenerate “base of the accreted H-rich envelope. Based on these assumptions, we have investigated this problem in several stages of increasing theoretical complexity and physical realism.

scholarly journals On the Separations of Common Proper Motion Binaries Containing White Dwarfs

1989 ◽  
Vol 114 ◽  
pp. 454-457
Author(s):  
T.D. Oswalt ◽  
E.M. Sion
Keyword(s):  
Mass Loss ◽  
White Dwarf ◽  
Proper Motion ◽  
White Dwarfs ◽  
Main Sequence ◽  
Late Type ◽  
Class A ◽  
Color Class

Luyten [1,2] and Giclas et al. [3,4] list over 500 known common proper motion binaries (CPMBs) which, on the basis of proper motion and estimated colors, are expected to contain at least one white dwarf (WD) component, usually paired with a late type main sequence (MS) star. Preliminary assessments of the CPMBs suggest that nearly all are physical pairs [5,6]. In this paper we address the issue of whether significant orbital expansion has occurred as a consequence of the post-MS mass loss expected to accompany the formation of the WDs in CPMBs.Though the CPMB sample remains largely unobserved, a spectroscopic survey of over three dozen CPMBs by Oswalt [5] found that nearly all faint components of Luyten and Giclas color class “a-f” and “+1”, respectively, or bluer were a WD. This tendency was also evident in a smaller sample studied by Greenstein [7]. Conversely, nearly all CPMBs having two components of color class “g-k” and “+3” or redder were MS+MS pairs. With the caveat that such criteria discriminate against CPMBs containing cool (but rare) WDs, they nonetheless provide a crude means of obtaining statistically significant samples for the comparison of orbital separations: 209 highly probable WD+MS pairs and 109 MS+MS pairs.

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