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 Recurrent Novae: What Do We Know about Them?

2011 ◽  
Vol 7 (S281) ◽  
pp. 154-161 ◽  
Author(s):  
G. C. Anupama
Keyword(s):  
White Dwarf ◽  
Binary Systems ◽  
Accretion Rate ◽  
Cataclysmic Variables ◽  
Type Ia Supernovae ◽  
Type Ia ◽  
Ia Supernovae ◽  
Nova Outbursts ◽  
Nova Outburst

AbstractRecurrent novae (RNe) belong to the group of cataclysmic variables that exhibit nova outbursts at intervals on the order of decades. They are rare, with 10 Galactic RNe known to date. Two are known in the LMC, while there are a few suspected RNe in M31. Nova outburst models require a high accretion rate on a massive white dwarf to explain the recurring nova outbursts, making this class of objects one of the most likely progenitor binary systems of Type Ia supernovae. The observational properties of the known Galactic recurrent novae are presented here, together with some discussion on the recent outbursts of RS Ophiuchi (2006), U Scorpii (2010), and T Pyxidis (2011).

scholarly journals Complex long-term activity of the post-nova X Serpentis

2018 ◽  
Vol 614 ◽  
pp. A141 ◽  
Author(s):  
V. Šimon
Keyword(s):  
Accretion Disk ◽  
Mass Transfer Rate ◽  
Complex Activity ◽  
Viscous Instability ◽  
Classical Nova ◽  
The Individual ◽  
Instability Regime ◽  
Nova Outbursts ◽  
Nova Outburst

Aims. X Ser is a cataclysmic variable (CV) which erupted as a classical nova in 1903. In this work we use over 100 years of photometry to characterize the long-term light curve of X Ser, with the aim of interpreting the post-nova activity in X Ser in the context of behaviors in other old novae. Methods. This analysis of its long-term optical activity uses the data from the Digital Access to a Sky Century @ Harvard (DASCH), AAVSO, and Catalina Real-time Transient Survey databases, supplemented by the data of other authors. Results. We show that X Ser displays a strong complex activity with the characteristics of various CV types after the return to quiescence from its classical nova outburst. Both nova-like and dwarf nova (DN) features are present. The decaying branches of the individual post-nova outbursts display large mutual similarities and obey the Bailey law for outbursts of DNe. These outbursts of X Ser constitute a uniform group (inside-out outbursts), and their decaying branches can be explained by propagation of cooling front through the accretion disk. In the interpretation, X Ser rapidly transitioned to a thermal-viscous instability regime of the disk, initially only intermittently. The occurrence of the DN outbursts shortly after the end of the nova outburst suggests that the mass transfer rate into the disk was usually not sufficiently high to prevent a thermal-viscous instability of this post-nova. The very long orbital period, and hence large accretion disk of X Ser can contribute to this.

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 Dwarf Nova Outbursts and Superoutbursts

1996 ◽  
Vol 158 ◽  
pp. 45-46
Author(s):  
J. Smak
Keyword(s):  
Accretion Disks ◽  
Time Scale ◽  
Strong Dependence ◽  
Light Curves ◽  
Instability Wave ◽  
Dwarf Nova ◽  
Rate Of Decline ◽  
Nova Outbursts ◽  
Nova Outburst ◽  
Insight Into

Dwarf nova outbursts provide an almost unique opportunity of getting an insight into the nature of viscosity in accretion disks or, within the α- disk approach, of putting some constraints on α. In particular, the strong dependence of the viscous time-scale on viscosity itself permits us to estimate a almost directly from the observed time-scales. In the case of the hot branch of the ∑ — Te relation, the most reliable estimates (αhot) are based on the rate of decline following the dwarf nova outburst. From a comparison with model light curves calculated with different αs one gets: αhot ≈ 0.2(e.g. Smak 1984b). An independent, but much cruder, estimate can be obtained from the widths of normal outbursts, by assuming that the duration of an outburst represents the travel time of an instability wave across the disk. The result is similar: αhot ≈ 0.2 (Gicger 1987).

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 Ion dynamics driven by a strongly nonlinear plasma wake

2021 ◽  
Author(s):  
Vadim Khudiakov ◽  
Konstantin V Lotov ◽  
Mike Downer
Keyword(s):  
Ion Dynamics ◽  
Density Peak ◽  
Density Profiles ◽  
Ion Density ◽  
Strongly Nonlinear ◽  
Plasma Wakefield Accelerators ◽  
Ion Acoustic Solitons ◽  
Physical Effects ◽  
Bubble Regime ◽  
Plasma Wakefield

Abstract In plasma wakefield accelerators, the wave excited in the plasma eventually breaks and leaves behind slowly changing fields and currents that perturb the ion density background. We study this process numerically using the example of a FACET experiment where the wave is excited by an electron bunch in the bubble regime in a radially bounded plasma. Four physical effects underlie the dynamics of ions: (1) attraction of ions toward the axis by the fields of the driver and the wave, resulting in formation of a density peak, (2) generation of ion-acoustic solitons following the decay of the density peak, (3) positive plasma charging after wave breaking, leading to acceleration of some ions in the radial direction, and (4) plasma pinching by the current generated during the wavebreaking. Interplay of these effects result in formation of various radial density profiles, which are difficult to produce in any other way.

A method for recovering stratospheric minor species densities from the Odin/OSIRIS scattered-sunlight measurements

2002 ◽  
Vol 80 (4) ◽  
pp. 395-408 ◽  
Author(s):  
I C McDade ◽  
K Strong ◽  
C S Haley ◽  
J Stegman ◽  
D P Murtagh ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Least Squares ◽  
Absorption Spectroscopy ◽  
Spectral Range ◽  
Local Density ◽  
Species Density ◽  
Optical Absorption Spectroscopy ◽  
Spectroscopy Technique ◽  
Density Profiles ◽  
Infrared Imager

A method for recovering minor species density profiles in the stratosphere from observations made with the OSIRIS (optical spectrograph and infrared imager system) instrument on the Odin satellite is described. The OSIRIS instrument measures limb radiances of scattered sunlight over the spectral range 2800 to 8000 Å, for tangent heights ranging from 10 to 100 km. We describe how the limb spectra may be processed using the DOAS (differential optical absorption spectroscopy) technique to derive apparent column densities for the minor atmospheric constituents O3, NO2, OClO, and BrO. We also show how these column densities, measured over a range of tangent heights, may be inverted using an iterative least-squares technique to determine the local density profiles. The procedures are illustrated using simulated limb radiances generated with a realistic OSIRIS instrument model. PACS Nos.: 42.68Mj, 94.10Dy

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 Spectrometer-Based Magnetographs

1993 ◽  
Vol 141 ◽  
pp. 156-165
Author(s):  
Harrison P. Jones
Keyword(s):  
Fourier Transform ◽  
Velocity Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Spectral Range ◽  
Equivalent Width ◽  
Active Regions ◽  
Continuum Intensity ◽  
Array Detectors ◽  
Line Depth

AbstractThe techniques and instrumentation for inferring magnetic fields using a spectrometer or spectrograph rather than a narrowband filter are reviewed. With array detectors and/or Fourier transform spectroscopy, the polarimetric data is acquired over the relevant spectral range strictly simultaneously with no possibility of spatial misregistration. Several recent examples of spectrometer-based magnetographs are discussed and compared, and new observations from the NASA/NSO Spectromagnetograph of magnetic flux, velocity field, continuum intensity, equivalent width, and line depth in active regions and the whole sun are shown.

scholarly journals Nova Outbursts Due to Accretion from Rotating H-Rich Disks onto White Dwarfs

1979 ◽  
Vol 53 ◽  
pp. 294-296
Author(s):  
Warren M. Sparks ◽  
G. Siegfried Kutter
Keyword(s):  
Angular Momentum ◽  
White Dwarf ◽  
Shear Instability ◽  
Marginal Stability ◽  
Solar Composition ◽  
Third Stage ◽  
Rich Material ◽  
Nova Outbursts ◽  
Work Done ◽  
Nova Outburst

In this paper we discuss the third stage of our research on the nova outburst as described in the preceeding paper (Kutter and Sparks, page 290), i.e. we accrete hydrogen-rich material (normal solar composition) with Keplerian velocity onto a helium white dwarf at a rate of 10-8 M⊙/yr. When material with high angular momentum from a circumstellar disk is accreted onto a white dwarf with negligible angular momentum, a tremendous shear instability is created, and hydrogen-rich material is mixed with helium-rich material of the white dwarf on a scale that is short compared to the accretion time scale. Following Kippenhahn and Thomas (1978), we assume that in the mixing region marginal stability is established. Mathematically this is expressed by setting the Richardson number (the ratio of the work done against buoyancy to the kinetic energy of the turbulence) equal to ¼.

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