scholarly journals Theoretically Inferred Masses of the White Dwarf Components of Common Nova Systems

1979 ◽  
Vol 53 ◽  
pp. 469-473
Author(s):  
James W. Truran
Keyword(s):  
Boundary Conditions ◽  
White Dwarf ◽  
Cataclysmic Variables ◽  
Theoretical Models ◽  
Origin And Evolution ◽  
Classical Novae ◽  
The Subject ◽  
Increasing Knowledge ◽  
Thermonuclear Runaway

Questions concerning the origin and evolution of cataclysmic variables continue to be the subject of considerable inquiry and debate. Significant boundary conditions upon theoretical models may be imposed by our increasing knowledge of the characteristics of specific systems. It is the purpose of this contribution to argue that, within the framework of the thermonuclear runaway model, the classical novae are most reasonably interpreted as systems characterized by relatively massive white dwarf components.

scholarly journals Two-dimensional simulations of mixing in classical novae: The effect of white dwarf composition and mass

2018 ◽  
Vol 619 ◽  
pp. A121 ◽  
Author(s):  
Jordi Casanova ◽  
Jordi José ◽  
Steven N. Shore
Keyword(s):  
White Dwarf ◽  
Binary Systems ◽  
Main Sequence ◽  
Chemical Species ◽  
Two Dimensions ◽  
Classical Novae ◽  
Nova Shells ◽  
Solar Abundances ◽  
Low Mass ◽  
Thermonuclear Runaway

Context. Classical novae are explosive phenomena that take place in stellar binary systems. They are powered by mass transfer from a low-mass main sequence star onto either a CO or ONe white dwarf. The material accumulates for 104–105 yr until ignition under degenerate conditions, resulting in a thermonuclear runaway. The nuclear energy released produces peak temperatures of ∼0.1–0.4 GK. During these events, 10−7−10−3 M⊙ enriched in intermediate-mass elements, with respect to solar abundances, are ejected into the interstellar medium. However, the origin of the large metallicity enhancements and the inhomogeneous distribution of chemical species observed in high-resolution spectra of ejected nova shells is not fully understood. Aims. Recent multidimensional simulations have demonstrated that Kelvin-Helmholtz instabilities that operate at the core-envelope interface can naturally produce self-enrichment of the accreted envelope with material from the underlying white dwarf at levels that agree with observations. However, such multidimensional simulations have been performed for a small number of cases and much of the parameter space remains unexplored. Methods. We investigated the dredge-up, driven by Kelvin-Helmholtz instabilities, for white dwarf masses in the range 0.8–1.25 M⊙ and different core compositions, that is, CO-rich and ONe-rich substrates. We present a set of five numerical simulations performed in two dimensions aimed at analyzing the possible impact of the white dwarf mass, and composition, on the metallicity enhancement and explosion characteristics. Results. At the time we stop the simulations, we observe greater mixing (∼30% higher when measured in the same conditions) and more energetic outbursts for ONe-rich substrates than for CO-rich substrates and more massive white dwarfs.

scholarly journals Classical Novae – Before and After Outburst

1988 ◽  
Vol 108 ◽  
pp. 226-231
Author(s):  
Mario Livio
Keyword(s):  
White Dwarf ◽  
Main Sequence ◽  
Orbital Parameters ◽  
Classical Novae ◽  
Classical Nova ◽  
Before And After ◽  
Low Mass ◽  
Orbital Periods ◽  
Thermonuclear Runaway ◽  
Nova Outburst

Classical nova (CN) and dwarf nova (DN) systems have the same binary components (a low-mass main sequence star and a white dwarf) and the same orbital periods. An important question that therefore arises is: are these systems really different ? (and if so, what is the fundamental difference ?) or, are these the same systems, metamorphosing from one class to the other ?The first thing to note in this respect is that the white dwarfs in DN systems are believed to accrete continuously (both at quiescence and during eruptions). At the same time, both analytic (e.g. Fujimoto 1982) and numerical calculations show, that when sufficient mass accumulates on the white dwarf, a thermonuclear runaway (TNR) is obtained and a nova outburst ensues (see e.g. reviews by Gallagher and Starrfield 1978, Truran 1982). It is thus only natural, to ask the question, is the fact that we have not seen a DN undergo a CN outburst (in about 50 years of almost complete coverage) consistent with observations of DN systems ? In an attempt to answer this question, we have calculated the probability for a nova outburst not to occur (in 50 years) in 86 DN systems (for which at least some of the orbital parameters are known).

scholarly journals The Ejecta of Classical Novae

2001 ◽  
Vol 205 ◽  
pp. 260-263
Author(s):  
T.J. O'Brien ◽  
R.J. Davis ◽  
M.F. Bode ◽  
S. P. S. Eyres ◽  
J.M. Porter
Keyword(s):  
Coherent Structures ◽  
White Dwarf ◽  
Binary Stars ◽  
Hubble Space Telescope ◽  
Classical Novae ◽  
Common Envelope ◽  
Physical Mechanisms ◽  
The Common ◽  
Thermonuclear Runaway ◽  
Prolate Ellipsoidal

Classical novae are interacting binary stars in which a thermonuclear runaway in material accreted onto a white dwarf from a companion red dwarf results in the ejection of around 10−4M⊙ at hundreds to thousands of kilometres per second. Recent Hubble Space Telescope and MERLIN imaging of the expanding ejecta from several classical novae are presented. In general the ejecta are clumpy but often display coherent structures, most notably equatorial rings of enhanced emission encircling prolate ellipsoidal shells. Physical mechanisms (including the common envelope phase and anisotropic irradiation of the shell) which may result in the generation of these structures are discussed.

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.

A comparison of optical and X-ray novae

1979 ◽  
Vol 366 (1726) ◽  
pp. 357-365
Keyword(s):  
Binary System ◽  
White Dwarf ◽  
Theoretical Models ◽  
Dwarf Novae ◽  
X Ray ◽  
Classical Novae ◽  
Binary Structure ◽  
Nuclear Burning ◽  
Similarities And Differences

The similarities and differences between optical novae and transient X-ray novae are discussed. Both classes almost certainly require a semi­-detached binary structure. Present theoretical models of classical novae account for the outburst in terms of a nuclear burning runaway in the accreted material on the white dwarf within a semi-detached binary system. In the case of the dwarf novae and the transient X-ray sources, unstable accretion events are the generally accepted model. Mechanisms that could generate unstable accretion events are described.

scholarly journals Multiple Time Scales in Cataclysmic Variables: Observations Vs. Mathematical Models

1998 ◽  
Vol 11 (1) ◽  
pp. 375-375
Author(s):  
I.L. Andronov
Keyword(s):  
White Dwarf ◽  
Cataclysmic Variables ◽  
Theoretical Models ◽  
Magnetic Activity ◽  
Multiple Time Scales ◽  
State Transitions ◽  
Multiple Time ◽  
Intermediate Polars ◽  
Magnetic Cataclysmic Variables ◽  
The Magnetic Field

Theoretical models and observational evidence for various processes in magnetic cataclysmic variables are briefly reviewed. Among them: modulation of the accretion rate by the magnetic field of the white dwarf; excitation of the orientation change of the magnetic axis of the white dwarf with respect to the secondary; structure of the accretion column and its instability; mass and angular momentum transfer; magnetic activity of the secondary; high/low luminosity state transitions; QPO’s, ”shot noise” and ”red noise” in polars, intermediate polars and nova-like objects.

scholarly journals Rotation and Cataclysmic Variables

2004 ◽  
Vol 215 ◽  
pp. 551-560 ◽  
Author(s):  
Sumner Starrfield ◽  
Edward M. Sion ◽  
Paula Szkody
Keyword(s):  
Angular Momentum ◽  
Accretion Disk ◽  
White Dwarf ◽  
White Dwarfs ◽  
Binary Star ◽  
Center Of Mass ◽  
Cataclysmic Variables ◽  
Lagrangian Point ◽  
The Past ◽  
The Subject

Cataclysmic Variables are binary star systems and so are closely connected to the subject of this meeting. The stars revolve around the center of mass of the system. The gas lost by the secondary through the inner Lagrangian point enters the Roche lobe of the white dwarf with the angular momentum of the L1 point and, therefore, forms an accretion disk which rotates around the white dwarf. The gas must lose angular momentum to fall onto the white dwarf, and the white dwarf itself must rotate as it accretes infalling material and angular momentum and is gradually spun up. We will review what is known about these phenomena, and emphasize the new results about the white dwarfs that have been learned in the past few years.

scholarly journals Search for 7Be in the outbursts of four recent novae

2020 ◽  
Vol 492 (4) ◽  
pp. 4975-4985 ◽  
Author(s):  
P Molaro ◽  
L Izzo ◽  
P Bonifacio ◽  
M Hernanz ◽  
P Selvelli ◽  
...  
Keyword(s):  
Milky Way ◽  
Theoretical Models ◽  
Small Mass ◽  
Core Material ◽  
Echelle Spectrograph ◽  
Classical Novae ◽  
The Core ◽  
A Value ◽  
Order Of Magnitude ◽  
Thermonuclear Runaway

ABSTRACT Following the recent detection of 7Be ii in the outburst spectra of classical novae, we report the search for this isotope in the outbursts of four recent bright novae by means of high-resolution Ultraviolet and Visual Echelle Spectrograph (UVES) observations. The 7Be ii λλ313.0583, 313.1228 nm doublet resonance lines are detected in the high-velocity components of Nova Mus 2018 and ASASSN-18fv during outbursts. However, 7Be ii is not detected in ASASSN-17hx and possibly not in Nova Cir 2018, which shows that 7Be is not always ejected in the thermonuclear runaway. Taking into account the 7Be decay, we find X(7Be)/X(H) ≈ 1.5 × 10−5 and 2.2 × 10−5 in Nova Mus 2018 and ASASSN-18fv, respectively. A value of 7Be/H ≈ 2 × 10−5 is found in five out of the seven extant measurements, and it can be considered as a typical 7Be yield for novae. However, this value is almost one order of magnitude larger than predicted by current theoretical models. We argue that the variety of high 7Be/H abundances could be the result of a higher than solar content of 3He in the donor star. The cases with 7Be not detected might be related to the small mass of the white dwarf (WD) or to relatively little mixing with the core material of the WD. The 7Be/H, or 7Li/H, abundance is ≈ 4 dex above meteoritic abundance, thus confirming the novae as the main sources of 7Li in the Milky Way.

scholarly journals Infrared and sub-mm observations of cataclysmic variables

2009 ◽  
Vol 5 (H15) ◽  
pp. 553-554
Author(s):  
A. Evans
Keyword(s):  
Main Sequence ◽  
Cataclysmic Variables ◽  
Accretion Disc ◽  
Lagrangian Point ◽  
Primary Star ◽  
Cool Component ◽  
Classical Novae ◽  
Compact Component ◽  
Thermonuclear Runaway ◽  
The Magnetic Field

Although cataclysmic variables (CVs) come in a wide variety of shapes and sizes, the essential ingredients are a compact primary star and a Roche-lobe-filling secondary. In most cases the cool component is a main sequence dwarf, and the compact component a white dwarf (WD). Material from the cool component flows through the inner Lagrangian point via an accretion disc onto the surface of the WD; the flow near the WD is significantly affected by the strength of the magnetic field the WD may have (see Warner for a review of CVs). CVs are characterised by regular eruptions, ranging in energetics and frequency from ‘dwarf novae’, in which eruptions of amplitude ~3-4 mag in the visual occur every few days to weeks, to classical novae (CNe) in which the eruption is explosive, due to thermonuclear runaway (TNR) in material accreted on the surface of the WD (see Bode & Evans for a review of CNe).

scholarly journals Symbiotic Binary Stars

1992 ◽  
Vol 151 ◽  
pp. 137-146
Author(s):  
Scott J. Kenyon
Keyword(s):  
White Dwarf ◽  
Binary Stars ◽  
Main Sequence ◽  
Cataclysmic Variables ◽  
Symbiotic Stars ◽  
Paper Briefly ◽  
Primary Star ◽  
Classical Novae ◽  
Long Period ◽  
Red Giant

This paper briefly reviews the physical properties of symbiotic stars: long-period interacting binaries composed of a red giant primary star and a hot companion. Two types of binaries produce symbiotic optical spectra: semi-detached systems with a main sequence secondary and detached systems with a white dwarf secondary. Semi-detached symbiotics resemble cataclysmic variables and Algol binaries, but on a much larger scale, and undergo dwarf nova-like eruptions. Wind accretion powers detached systems; occasional thermonuclear runaways produce symbiotic novae - distant cousins of classical novae.

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