Nova Systems Research Articles

The nature of the recurrent novae

view Abstract Citations (185) References (179) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Nature of the Recurrent Novae Webbink, Ronald F. ; Livio, Mario ; Truran, James W. ; Orio, Marina Abstract The basic properties of individual recurrent nova systems are reviewed, and the mechanisms of their outbursts are studied. Some general properties associated with accretion events and thermonuclear runaway models are briefly examined, and detailed models for the recurrent novae T CrB, RS Oph, T Pyx, U Sco, and V1017 Sgr and the possible recurrent novae WZ Sge, V616 Mon, VY Aqr, RZ Leo, V1195 Oph, and V529 Ori are discussed. The results suggest that the outbursts of U Sco and T Pyx are caused by thermonuclear runaways on the surface of massive white dwarfs, while the outbursts of T CrB and RS Oph are very probably accretion events, initiated by a burst of mass transferred from a giant companion onto a main sequence star. V1017 Sgr fails the model criteria for a recurrent nova, being more properly considered a symbiotic star. V1195 Oph, RZ Leo, VY Aqr, and WZ Sge are assigned to the class of dwarf novae. No evidence is found that V529 Ori has recurred. Publication: The Astrophysical Journal Pub Date: March 1987 DOI: 10.1086/165095 Bibcode: 1987ApJ...314..653W Keywords: Binary Stars; Novae; Stellar Physics; Main Sequence Stars; Nuclear Fusion; Red Giant Stars; Stellar Mass Accretion; Symbiotic Stars; Astrophysics; NUCLEOSYNTHESIS; STARS: BINARIES; STARS: NOVAE full text sources ADS | data products SIMBAD (12)

Possible rôle of the white dwarf in grain formation in CV systems

Zhilyaev & Zubko described white dwarf model atmospheres in which carbon might condense. Whittaker2 presented a version of the phase diagram for carbon on which there is a region where carbyne is thermodynamically favoured over graphite. Because the ratio of cross-section to mass is much higher for a thin cylinder, a carbyne cylinder has a much better chance of being blown out of a white dwarf atmosphere by radiation pressure. However even for small grains, gravity overcomes radiation pressure for cylinders, as it does for spherical grains. In the case of a non-polar cataclysmic variable (CV) system, the white dwarf is surrounded by an accretion disk and the luminosity of the disk may provide sufficient additional radiation pressure to drive a grain out of the system. If a grain can initially be transported out of the white dwarf atmosphere there may be several CV systems in which the combined radiation pressure of the disk and white dwarf can blow grains out of the system. For small grains and white dwarf masses ≳ 0.5 Mo radiation pressure can overcome gravity. These remarks also apply to grains that originate in the cooler regions of the disk, where the density may be high enough to sustain grain formation. Thus some non-polar CV systems may possess circumstellar dust shells, whose composition may reflect the nature of the white dwarf or secondary. For cases in which grains originate in the disk any circumstellar dust may be transient, as the mass transfer varies. Furthermore, in classical nova systems, this process may provide grain precursors, on which larger grains might grow during a noya outburst. A more complete discussion may be found in Albinson & Evans.

On the frequency of occurrence of oxygen-neon-magnesium white dwarfs in classical nova systems

view Abstract Citations (191) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Frequency of Occurrence of Oxygen-Neon-Magnesium White Dwarfs in Classical Nova Systems Truran, J. W. ; Livio, M. Abstract The question of the expected frequency of occurrence of oxygen-neon-magnesium (ONeMg) degenerate dwarfs in classical nova systems is examined. Heavy-element abundance enrichments observed in nova ejecta are reviewed, and possible interpretations of their origins are discussed. It is concluded that these abundance enrichments imply the presence of ONeMg white dwarfs, and it is estimated that they might be expected to account for a significant fraction of the observed outbursts. Particular attention is given to providing a realistic estimate of the magnitude of the selection effect which operates to insure the occurrence of a significant population of ONeMg white dwarfs in these systems. The implications of these findings are reviewed, and possible complicating factors are discussed. Publication: The Astrophysical Journal Pub Date: September 1986 DOI: 10.1086/164544 Bibcode: 1986ApJ...308..721T Keywords: Magnesium; Neon; Novae; Oxygen; Stellar Composition; White Dwarf Stars; Frequency Distribution; Stellar Mass Ejection; Astrophysics; STARS: ABUNDANCES; STARS: NOVAE; STARS: WHITE DWARFS full text sources ADS | data products SIMBAD (13)

The decline and fall of classical novae

We address questions concerning the evolution of classical nova systems through outburst and the time scale for the return to their preoutburst state. Observations indicate that evolution on a purely nuclear burning time scale is not sufficient. We call attention to the sequence of events involving common envelope evolution which naturally occurs following thermonuclear runaways in the accreted hydrogen shells on the white dwarf components of these close binary systems. We estimate that a significant fraction of the envelope may be lost as a result of dynamical friction during a relatively short-lived common envelope phase which is experienced by most classical nova systems. The residual hydrogen-rich envelope matter may be consumed by nuclear burning or wind-driven mass loss or both on time scales compatible with observations of nova systems. As mass is consumed, the photospheric radius decreases and consequently the photospheric temperature rises. The associated hardening of the radiation from novae causes them progressively to become UV, EUV, and ultimately soft X-ray sources. Estimates of the fluxes during these late stages are provided and shown to be compatible with their being detected with EXOSAT or equivalent X-ray facilities. Such detection would provide strong confirmation of theoretical models for the classicalmore » novae. We also point out that infrared emission from X-ray heated grains may be detectable during the soft X-ray phase.« less

A possible observational constraint on the production of lithium by galactic novae

Recent computations (D'Antona and Mazzitelli, 1982), together with the general scheme of evolution of cataclysmic binaries (CBs), lead to conclude that the secondaries in those CBs having periods shorter than ∼4.5 hr have a large3He content in the envelope, ranging from 10−4 (P=4.5 hr) to >2×10−3 (P=3 hr) in mass fraction, if the nova systems have an age of some billion years. The consequence on the frequency of novae outbursts is shortly examined. If lithium is produced by galactic novae, the7Li content of old disk stars should be very close to the Population II content.

On the overstability of axisymmetric oscillations in thin accretion disks

view Abstract Citations (92) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the overstability of axisymmetric oscillations in thin accretion disks Blumenthal, G. R. ; Lin, D. N. C. ; Yang, L. T. Abstract The stability of geometrically thin and optically thick and thin accretion disks to axisymmetric perturbations is examined. It is shown that the standard alpha-disk models admit not only classical thermal and viscous instabilities, which are generally associated with regions where electron scattering and radiation pressure are dominant, but also radial pulsational instabilities. A general dispersion relationship is derived, and the eigenvectors' response to local axisymmetric perturbations is examined. These general results are applied for various choices of viscosity, opacity, and equation of state. The results indicate that there are pulsationally overstable regions, which are otherwise thermally and viscously stable. The underlaying physical origin and the implications of these instabilities are discussed. Finally, it is speculated that quasi-periodic oscillation found in dwarf nova systems may be a manifestation of these pulsation overstabilities. Publication: The Astrophysical Journal Pub Date: December 1984 DOI: 10.1086/162736 Bibcode: 1984ApJ...287..774B Keywords: Accretion Disks; Dwarf Novae; Motion Stability; Optical Thickness; Stellar Mass Accretion; Stellar Oscillations; Axisymmetric Bodies; Differential Equations; Electron Scattering; High Reynolds Number; Laminar Flow; Perturbation Theory; Steady State; Astrophysics full text sources ADS |

On the evolution of accretion disc flow in cataclysmic variables - I. The prospect of a limit cycle in dwarf nova systems

We present the basic physics of a mechanism which explains dwarf nova outbursts as accretion disc instabilities. Briefly put, the strong and oppositely directed temperature dependences of opacity in hydrogen ionization regions drive a thermal instability which modulates mass transfer throughout the disc. We also show that the conventional thin disc treatment breaks down in cool regions, where the surface boundary condition dominates the structure. One major purpose of the paper is to modify the conventional treatment, to produce analytical approximations for many of the relationships of interest. When these results are applied to a schematic local treatment of disc flows, the prospect of a thermal limit cycle is revealed. Finally, these results will be particularly useful for time-dependent treatments of global accretion disc flow.

CNO abundances and the strengths of nova outbursts and hydrogen flashes on accreting white dwarfs

view Abstract Citations (140) References (85) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS CNO abundances and the strengths of nova outbursts and hydrogen flashes on accreting white dwarfs. MacDonald, J. Abstract Simple theories of the accretion phase and expansion phase of hydrogen shell flashes on accreting white dwarfs are used to find the conditions under which classical novae occur. Particular attention is paid to the possibility that the CNO abundances in the accreted envelope are greatly enhanced relative to the Sun. It is shown that such an enhancement is necessary for fast novae, yet slow novae, such as DQ Her, can still occur with large CNO enhancements. An analysis of the observed properties of nova ejecta indicates that the white dwarfs in nova systems have masses in the range 1.02-1.18 Msun. It is found that in some novae, including RR Pic, CP Lac, and V603 Aql, the accretion rate deduced from the optical luminosity in quiescence is too high to allow accretion of sufficient envelope material to get the strong hydrogen flash needed for the nova outburst. Some possible resolutions of this problem are discussed. We also find it unlikely that recurrent novae are thermonuclear runaways on accreting white dwarfs. Publication: The Astrophysical Journal Pub Date: April 1983 DOI: 10.1086/160911 Bibcode: 1983ApJ...267..732M Keywords: Abundance; Novae; Stellar Mass Accretion; Stellar Models; White Dwarf Stars; Carbon; Nitrogen Atoms; Nuclear Fusion; Oxygen Atoms; Stellar Envelopes; Astrophysics full text sources ADS | data products SIMBAD (9)

The Formation of Optical CNO Emission Lines in Cataclysmic Variables

ABSTRACTSpectroscopic observations of CNO emission lines are presented for old nova systems, and possible excitation processes for the lines are considered. The Bowen fluorescence mechanism cannot generally be responsible for the strength of N III λ4640 because of the weakness of 0 III λ3429. Other CNO lines are observed which indicate that all of the lines are excited by resonance fluorescence of UV continuum radiation. Several nonfluorescent excited lines of carbon are also present in old novae, probably formed by recombination processes. The available data for the optical CNO lines suggest that non-solar CNO enhancements exist in quiescent novae, indicating that some of the binary systems may be evolved.

An X-ray model for the nebula of nova DQ Herculis 1934

view Abstract Citations (65) References (46) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An X-ray model for the nebula of nova DQ HER 1934. Ferland, G. J. ; Truran, J. W. Abstract A model for the nebula of DQ Her is presented which is built upon the assumption that the power is provided by an X-ray source. The X-ray and UV energy spectra recently calculated by Kylafis and Lamb for the case of spherical accretion onto degenerate dwarfs are modified to take account of the geometry of the system. The influence of a low frequency cutoff is considered: the column density we find to be consistent with our model falls nicely in the range inferred for nova systems by recent observations of Cordova, Mason, and Nelson. The effects of the radiation field upon the envelope ejected in the 1934 outburst were determined with a photoionization program which includes all X-ray heating and ionization processes known to be important (Compton recoil by both bound and free electrons, the Auger effects, and secondary ionization by suprathermal electrons). Our calculations show that many observed features of the nebula follow as a very natural consequence of this model. Specifically, the nebula is expected to be very cool, ∼300 K, and to show extremely strong recombination lines of ionized carbon, nitrogen, and oxygen, as previously reported by Williams et al. Time variations of the inferred nebular composition are to be expected, as the reestablishment of accretion flows, formation of a disk, and the ensuing emergence of an X-ray flux must follow upon the turnoff of the underlying white-dwarf nova remnant. Scrutiny of the spectroscopic data for DQ Her suggests that this turnoff occurred in the late 1940s, and that the nebula cooled rapidly in this stage. The relevance of our results to studies of other nova nebular remnants is briefly examined. Publication: The Astrophysical Journal Pub Date: March 1981 DOI: 10.1086/158773 Bibcode: 1981ApJ...244.1022F Keywords: Astronomical Models; Dwarf Stars; Nebulae; Novae; X Ray Sources; X Ray Spectra; Emission Spectra; Line Spectra; Photoionization; Stellar Mass Accretion; Ultraviolet Astronomy; Ultraviolet Spectra; Astrophysics full text sources ADS | data products SIMBAD (2)

Comments on the evolution and origin of cataclysmic binaries

Some aspects of the observational data on cataclysmic binaries are discussed and some possible correlations between type of behaviour and binary period are noted. A gap between 2 and 3 hours in the histogram of binary periods is estimated to be real. A numerical procedure for following the evolution of Roche-lobe-fiUing stars using simplified equations is described. This procedure Is applied to white/red dwarf binaries for a variety of initial conditions, and of mass loss and angular momentum loss mechanisms. The results of these calculations, in which we ignore the short timescale behaviour of the systems, are classified into four modes of evolution: normal, nuclear evolution dominated, angular momentum loss dominated and hydrodynamical. The results are discussed in connection with cataclysmic binaries. The clustering in period below 2 hours is Interpreted in terms of evolution following the hydrodynamical mode, and it is suggested that such systems contain low mass white dwarfs as well as low mass secondaries. These may be the most common type of cataclysmic binary. A possible explanation of the clustering of classical novae systems to binary periods of 3 to 5 hours is mentioned, and evolutionary scenarios for cataclysmic binaries are outlined. We suggest, following Ritter and Webbink, that the short period systems (≲ 2 hrs) arise mainly from late Case B mass transfer in the original binary (original primary mass 1.5 to 3M ⊙ ) and the longer period systems arise mainly from Case C mass transfer. Full text to be published in Monthly Notices of the Royal Astronomical Society.

He3 as the Recurrent Nova Trigger Mechanism

Observations of recurrent novae (Warner 1976) imply the presence of a red giant (RG) in most, if not all, cases. Giant secondaries in nova systems are otherwise known or suspected only in the peculiar slow novae RR Tel and RT Ser. Bath and Shaviv (1978) showed quantitatively that only a red giant can transfer enough hydrogen-rich mass (~10-5M⊙) to a white dwarf (WD) companion rapidly enough (in ∽30 years) to yield a recurrent nova.

Comments on the Evolution and Origin of cataclysmic Binaries

AbstractSome aspects of the observational data on cataclysmic binaries are discussed and some possible correlations between type of behaviour and binary period are noted. A gap between 2 and 3 hours in the histogram of binary periods is estimated to be real. A numerical procedure for following the evolution of Roche-lobe-fiUing stars using simplified equations is described. This procedure Is applied to white/red dwarf binaries for a variety of initial conditions, and of mass loss and angular momentum loss mechanisms. The results of these calculations, in which we ignore the short timescale behaviour of the systems, are classified into four modes of evolution: normal, nuclear evolution dominated, angular momentum loss dominated and hydrodynamical. The results are discussed in connection with cataclysmic binaries. The clustering in period below 2 hours is Interpreted in terms of evolution following the hydrodynamical mode, and it is suggested that such systems contain low mass white dwarfs as well as low mass secondaries. These may be the most common type of cataclysmic binary. A possible explanation of the clustering of classical novae systems to binary periods of 3 to 5 hours is mentioned, and evolutionary scenarios for cataclysmic binaries are outlined. We suggest, following Ritter and Webbink, that the short period systems (≲ 2 hrs) arise mainly from late Case B mass transfer in the original binary (original primary mass 1.5 to 3M⊙) and the longer period systems arise mainly from Case C mass transfer.Full text to be published in Monthly Notices of the Royal Astronomical Society.

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

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.

The origin of the emission lines shown by RW Tauri and other binary systems

It is proposed that the observed double-component emission lines originate from the triangular Lagrangian points, L4 and L5, of the restricted three-body problem. The light curves of many close binary systems show absorption dips at ±60° of the primary (and sometimes also the secondary) minimum, indicating appreciable accumulation of matter at these points. The orbital velocity of L4 and L5 is derived as a function of period and the masses of the component stars. This equation is an independent relationship for determining the two stellar masses. It also reproduces Struve's empirical finding ofV3∝P−1. The observed emission line velocity is consistently higher than the calculated orbital velocity of L4 and L5. This is due to the serious erosion of the low velocity sides of the emission components by the stellar and shell absorption lines. There are observational evidences which indicate the intermittent high velocity radial ejection of matter to be a mode of mass loss from the secondary. And the energy of mass motion from this ejection is sufficient, and may be responsible, for heating the gas at L4 and L5. The ionizing radiation emitted by the primary of the Algol systems is many orders of magnitude below that required by the observed strength of the emission lines. Some related discussion is also given to nova and dwarf nova systems.