scholarly journals Shaping of Nova Shells by Binary Motion

1996 ◽  
Vol 158 ◽  
pp. 313-314
Author(s):  
H. M. Lloyd ◽  
T. J. O’Brien ◽  
M. F. Bode
Keyword(s):  
Binary System ◽  
Optical Emission ◽  
Spherical Shells ◽  
Classical Novae ◽  
Common Features ◽  
Hydrodynamic Calculations ◽  
Nova Shells

AbstractSeveral years after outburst, extended optical emission can be seen around many classical novae. Common features include shells, polar ‘blobs’, equatorial rings and, at least in the case of DQ Her (1934), tropical rings above and below the ‘equator’. We present hydrodynamic calculations of the dynamical effects of the underlying binary system on the material ejected during outburst, and show that many of the features observed in the optical remnants of novae can be reproduced. Polar blobs, banded shells and spherical shells can all be obtained in the model, depending on the speed class of the nova.

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 What Determines the Speed Cuss of a Nova?

1979 ◽  
Vol 53 ◽  
pp. 521-521
Author(s):  
M.M. Shara ◽  
D. Prialnik ◽  
G. Shaviv
Keyword(s):  
Binary System ◽  
White Dwarf ◽  
Accretion Rate ◽  
List Type ◽  
Type Number ◽  
Hydrodynamic Models ◽  
Nova Shells ◽  
Stellar Emission

Recent theoretical hydrodynamic models show that novae of different speed class can be obtained by varying the CNO enrichment and envelope mass. Recent observations of old nova shells, uncontaminated by disc or stellar emission, indicate that various degrees of CNO enrichment are found in slow novae. Using Prialnik et al’s (1978) finding that the “shut-off” mechanism of novae is fuel exhaustion, i.e. expulsion of most of the hydrogen-rich envelope by means of an optically thick wind, we propose the following unified picture for novae: 1) CNO enrichment and envelope mass Menvel together determine the speed class of a nova.2) is determined by the accretion mechanism and convective efficiency on the white dwarf surface.3) Menvel is determined by the nature of the binary system and by envel the accretion rate ṁ.4) Fast novae tend to have larger and smaller Menvel than slow novae, but CNO-rich slow novae and CNO-poor fast novae are permitted with certain envelope masses. We present below a qualitative diagram of the Menvel, - plane.

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 X-ray observations of the nova shell IPHASX J210204.7+471015*

2021 ◽  
Author(s):  
J A Toalá ◽  
G Rubio ◽  
E Santamaría ◽  
M A Guerrero ◽  
S Estrada-Dorado ◽  
...  
Keyword(s):  
Time Series ◽  
Binary System ◽  
Binary Star ◽  
Optical Observations ◽  
X Ray ◽  
Imaging Camera ◽  
Nova Shells ◽  
Intermediate Polars ◽  
Time Series Analyses ◽  
Nova Shell

Abstract We present the analysis of XMM-Newton European Photon Imaging Camera (EPIC) observations of the nova shell IPHASX J210204.7+471015. We detect X-ray emission from the progenitor binary star with properties that resemble those of underluminous intermediate polars such as DQ Her: an X-ray-emitting plasma with temperature of TX = (6.4 ± 3.1) × 106 K, a non-thermal X-ray component, and an estimated X-ray luminosity of LX = 1030 erg s−1. Time series analyses unveil the presence of two periods, the dominant with a period of 2.9 ± 0.2 hr, which might be attributed to the spin of the white dwarf, and a secondary of 4.5 ± 0.6 hr that is in line with the orbital period of the binary system derived from optical observations. We do not detect extended X-ray emission as in other nova shells probably due to its relatively old age (130–170 yr) or to its asymmetric disrupted morphology which is suggestive of explosion scenarios different to the symmetric ones assumed in available numerical simulations of nova explosions.

scholarly journals Internal shocks from variable outflows in classical novae

2019 ◽  
Vol 491 (3) ◽  
pp. 4232-4246 ◽  
Author(s):  
Elad Steinberg ◽  
Brian D Metzger
Keyword(s):  
Gamma Ray ◽  
Optical Emission ◽  
Spectral Lines ◽  
One Dimensional ◽  
Classical Novae ◽  
Internal Shock ◽  
Forward Shock ◽  
The Common ◽  
Hydrodynamical Simulations

ABSTRACT We present one-dimensional hydrodynamical simulations including radiative losses, of internal shocks in the outflows from classical novae, to explore the role of shocks in powering multiwavelength emission from radio to gamma-ray wavelengths. Observations support a picture in which the initial phases of some novae generate a slow, equatorially focused outflow (directly from the outer Lagrange point, or from a circumbinary disc), which then transitions to, or is overtaken by, a faster more isotropic outflow from the white dwarf which collides and shocks the slower flow, powering gamma-ray and optical emission through reprocessing by the ejecta. However, the common occurrence of multiple peaks in nova light curves suggests that the outflow’s acceleration need not be monotonic, but instead can involve successive transitions between ‘fast’ and ‘slow’ modes. Such a time-fluctuating outflow velocity naturally can reproduce several observed properties of nova, such as correlated gamma-ray and optical flares, expansion of the photosphere coincident with (though lagging slightly) the peak flare luminosity, and complex time evolution of spectral lines (including accelerating, decelerating, and merging velocity components). While the shocks are still deeply embedded during the gamma-ray emission, the onset of ∼keV X-ray and ∼10 GHz radio synchrotron emission is typically delayed until the forward shock of the outermost monolithic shell (created by merger of multiple internal shock-generated shells) reaches a sufficiently low column through the dense external medium generated by the earliest phase of the outburst.

scholarly journals On the Binary Nature of the Slow Nova, RR Telescopii

1974 ◽  
Vol 59 ◽  
pp. 123-124
Author(s):  
B. L. Webster
Keyword(s):  
Binary System ◽  
Energy Distribution ◽  
Wavelength Range ◽  
Mass Exchange ◽  
Orbital Period ◽  
Optical Spectrum ◽  
Classical Novae ◽  
Cool Star ◽  
Current Mass ◽  
Orbital Periods

Those novae known to be binaries generally have orbital periods of the order of hours, exceptions being the atypical recurrent novae T CrB and RS Oph, which have giant companions and probably much longer periods. Since the orbital period in a semi-detached system relates to the mechanism of current mass exchange and also to the extent to which the primary evolved before mass exchange took place at an earlier stage, it is of interest to see if any classical novae are in more widely separated systems.This communication concerns the star RR Telescopii, which has all the characteristics of a slow nova – a range in amplitude greater than seven magnitudes, a spectral type at maximum of F, and a decline through a nebular stage of increasing ionization level (e.g. Thackeray, 1955). RR Tel was seen as a variable before outburst, but little is known about this variable apart from its period of 387 days, although doubts have been expressed about its being a red variable (Payne-Gaposchkin, 1957). Dr Thackeray has Radcliffe spectrograms of RR Tel from soon after maximum to the present. On some of the more recent of these, bands of TiO have become visible, presumably as the hot star has faded, and Dr Thackeray and I interpret these as meaning that the original variable is still there and is an M giant. Thus RR Tel is in a binary system containing a giant M star and a hot companion and such a system cannot have an orbital period of hours like the classical novae mentioned above.In 1972, Dr Glass and I examined RR Tel in the infrared between 1.2 and 20 µ. The energy distribution does not resemble the cool star that might be expected, but is exactly like that of free-free radiation over the whole wavelength range. The puzzle is that the infrared is two orders of magnitude stronger than we would predict from the optical spectrum for free-free radiation.

scholarly journals Constraining Models of Classical Nova Outbursts with the Murchison Meteorite

2003 ◽  
Vol 20 (4) ◽  
pp. 351-355 ◽  
Author(s):  
Jordi José ◽  
Margarita Hernanz ◽  
Sachiko Amari ◽  
Ernst Zinner
Keyword(s):  
Interstellar Medium ◽  
Light Curves ◽  
Infrared Observations ◽  
Isotopic Signatures ◽  
Classical Novae ◽  
Murchison Meteorite ◽  
Classical Nova ◽  
Hydrodynamic Calculations ◽  
Nova Outbursts ◽  
Expanding Shells

AbstractInfrared observations of nova light curves reveal that classical novae form grains in the expanding shells, ejected into the interstellar medium as a consequence of a violent outburst. Such grains contain nucleo-synthetic fingerprints of the nova explosion. In this paper, we analyse different isotopic signatures expected to be present in nova grains on the basis of detailed hydrodynamic calculations of CO and ONe novae and compare them with recent determinations of presolar nova grains from the Acfer 094 and Murchison meteorites.

scholarly journals Hydrodynamic efficiency of illumination by ion beams

1990 ◽  
Vol 8 (3) ◽  
pp. 409-419 ◽  
Author(s):  
M. M. Basko
Keyword(s):  
Energy Deposition ◽  
Charged Particles ◽  
Ion Beams ◽  
The Other ◽  
Spherical Shells ◽  
Hydrodynamic Efficiency ◽  
Bulk Motion ◽  
Self Similar Solution ◽  
Hydrodynamic Calculations ◽  
Self Similar

The hydrodynamic efficiency of conversion of the energy of fast charged particles into the kinetic energy of the bulk motion of plane-parallel shells is investigated in the framework of two simple models–one based on the stepwise density profile and the other employing a self-similar solution. The analytical estimates obtained are substantiated with ID hydrodynamic calculations. In case of spherical shells, the three key dimensionless parameters determining the values of the hydrodynamic efficiency are pointed out; the dependence of the hydrodynamic efficiency on these parameters has been explored numerically. The effects of a nonuniform energy deposition (increasing by the end of the fast particle ranges) and of a nonuniform absorber composition are also discussed.

scholarly journals Exploring the role of X-ray reprocessing and irradiation in the anomalous bright optical outbursts of A0538−66

2019 ◽  
Vol 624 ◽  
pp. A9 ◽  
Author(s):  
L. Ducci ◽  
S. Mereghetti ◽  
K. Hryniewicz ◽  
A. Santangelo ◽  
P. Romano
Keyword(s):  
Neutron Star ◽  
Binary System ◽  
Optical Emission ◽  
X Ray ◽  
Orbital Parameters ◽  
Uv Emission ◽  
Radial Density Distribution ◽  
Spherical Cloud ◽  
Gas Cloud ◽  
X Ray Binaries

Context. In 1981, the Be/X-ray binary A0538−66 showed outbursts characterized by high peak luminosities in the X-ray (Lx ≈ 1039 erg s−1) and optical (Lopt ≈ 3 × 1038 erg s−1) bands. The bright optical outbursts were qualitatively explained as X-ray reprocessing in a gas cloud surrounding the binary system. Aims. Since then, further important information about the properties of A0538−66 have been obtained, and sophisticated photoionization codes have been developed to calculate the radiation emerging from a gas nebula illuminated by a central X-ray source. In the light of the new information and tools available, we considered it was worth studying again the enhanced optical emission displayed by A0538−66 to understand the mechanisms responsible for these unique events among the class of Be/X-ray binaries. Methods. We performed about 105 simulations of a gas envelope surrounding the binary system photoionized by an X-ray source. We assumed for the shape of the gas cloud either a sphere or a circumstellar disc observed edge-on. We studied the effects of varying the main properties of the envelope (shape, density, slope of the power law density profile, size) and the influence of different input X-ray spectra and X-ray luminosity on the optical/UV emission emerging from the photoionized cloud. We determined the properties of the cloud and the input X-ray emission by comparing the computed spectra with the IUE spectrum and photometric UBV measurements obtained during the outburst of 29 April 1981. We also explored the role played by the X-ray heating of the surface of the donor star and the accretion disc irradiated by the X-ray emission of the neutron star. Results. We found that reprocessing in a spherical cloud with a shallow radial density distribution and size of about 3 × 1012 cm can reproduce the optical/UV emission observed on 29 April 1981. To our knowledge, this configuration has never been observed either in A0538−66 during other epochs or in other Be/X-ray binaries. We found, contrary to the case of most other Be/X-ray binaries, that the optical/UV radiation produced by the X-ray heating of the surface of the donor star irradiated by the neutron star is non-negligible, due to the particular orbital parameters of this system that bring the neutron star very close to its companion.

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