scholarly journals Two new nova shells associated with V4362 Sagittarii and DO Aquilae

2020 ◽  
Vol 499 (2) ◽  
pp. 2959-2976
Author(s):  
E J Harvey ◽  
M P Redman ◽  
P Boumis ◽  
S Akras ◽  
K Fitzgerald ◽  
...  
Keyword(s):  
White Dwarf ◽  
Supernova Remnants ◽  
Preliminary Investigation ◽  
Central Component ◽  
Distance Measurements ◽  
Ionization Structure ◽  
Classical Nova ◽  
Nova Shells ◽  
Sgr A ◽  
Field Unit

ABSTRACT A classical nova is an eruption on the surface of a white dwarf in an accreting binary system. The material ejected from the white dwarf surface generally forms an axisymmetric shell. The shaping mechanisms of nova shells are probes of the processes that take place at energy scales between planetary nebulae and supernova remnants. We report on the discovery of nova shells surrounding the post-nova systems V4362 Sagittarii (1994) and more limited observations of DO Aquilae (1925). Distance measurements of $0.5\substack{+1.4 \\ -0.2}$ kpc for V4362 Sgr and 6.7 ± 3.5 kpc for DO Aql are found based on the expansion parallax method. The growth rates are measured to be 0.07 arcsec yr−1 for DO Aql and 0.32 arcsec yr−1 for V4362 Sgr. A preliminary investigation into the ionization structure of the nova shell associated with V4362 Sgr is presented. The observed ionization structure of nova shells depends strongly on their morphology and the orientation of the central component towards the observer. X-ray, IR, and UV observations as well as optical integral field unit spectroscopy are required to better understand these interesting objects.

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 Galactic Center threads as nuclear magnetohydrodynamic waves

2020 ◽  
Vol 72 (2) ◽  
Author(s):  
Yoshiaki Sofue
Keyword(s):  
Magnetic Field ◽  
Supernova Remnants ◽  
Galactic Center ◽  
Mhd Waves ◽  
Fast Mode ◽  
Magnetohydrodynamic Waves ◽  
Compression Waves ◽  
Sgr A ◽  
The Waves ◽  
The Magnetic Field

Abstract Propagation of fast-mode magnetohydrodynamic (MHD) compression waves is traced in the Galactic Center with a poloidal magnetic cylinder. MHD waves ejected from the nucleus are reflected and guided along the magnetic field, exhibiting vertically stretched fronts. The radio threads and non-thermal filaments are explained as due to tangential views of the waves driven by sporadic activity in Sgr A$^*$, or by multiple supernovae. In the latter case, the threads could be extremely deformed relics of old supernova remnants exploded in the nucleus.

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 Near-Synchronous Polar Candidate V4633 Sgr (Nova Sagittarii 1998)

2004 ◽  
Vol 190 ◽  
pp. 176-177
Author(s):  
Y. Lipkin ◽  
E. M. Leibowitz
Keyword(s):  
Angular Momentum ◽  
Momentum Transfer ◽  
White Dwarf ◽  
Moment Of Inertia ◽  
The Other ◽  
Angular Momentum Transfer ◽  
Classical Nova ◽  
Order Of Magnitude ◽  
Photometric Monitoring ◽  
The Moment

AbstractThe classical nova V4633 Sgr (1998) exhibits two photometric periodicities. The shorter period (P1=3.01 hr) is stable, while the other one, longer by ~2.5%, has decreased monotonically since shortly after the nova eruption, with Ṗ2 ≈ –10−6 (Lipkin et al. 2001).Here we report on results of photometric monitoring of the star in 2001 and 2002. During our observations, the longer period decreased more, and in 2002 it was only 1.8% longer than P1 The decrease rate (Ṗ2) in 2001-2002 was an order of magnitude smaller than in 1998-2000.These new results support the Near-Synchronous Polar classification which was suggested for V4633 Sgr (Lipkin et al. 2001). In this model, the longer period of V4633 Sgr is the spin of the white dwarf, and its variation since 1998 reflects changes in the moment of inertia of the white dwarf, and angular momentum transfer in the system following the nova eruption.

scholarly journals Rapid Oscillations in DQ Her and UX Uma

1979 ◽  
Vol 53 ◽  
pp. 518-518
Author(s):  
Jacobus A. Petterson
Keyword(s):  
Phase Shift ◽  
Inclination Angle ◽  
Phase Stability ◽  
White Dwarf ◽  
Front Side ◽  
Classical Nova ◽  
Nonradial Pulsation ◽  
Color Emission ◽  
Better Than ◽  
Related Phase

Although the novalike variable UX UMa strongly resembles the classical nova DQ Her in color, emission spectrum, and optical lightcurve, the properties of the rapid oscillations in both systems are quite different. The oscillations differ in period, amplitude, and phase stability, but most remarkably they differ in the characteristics of the “eclipse related phase shift.” The phase shift in DQ Her is explainable by partial obscuration of the disk during eclipse, together with the idea that the oscillating light does not reach us directly from the white dwarf, but is reflected by the disk. It comes from a rotating UV beam originating near the white dwarf surface, which is reflected better by the backside of the disk than by the front side. We show that the phase shift in UX UMa is explainable by the same model, viewed at a different inclination angle i, if it is assumed that at this value of i reflection from the frontside of the disk is better than from the backside. There may be different ways to accomplish this preference. The results suggest that no retrograde rotation of the white dwarf (or retrogradely rotating nonradial pulsation) is needed to explain UX UMa’s eclipse related phase shift. These phase shifts provide a new (and quite accurate) way to determine a system’s inclination angle. Specific predictions are made for the behaviour of amplitude and phase of the oscillations in other eclipsing systems.

scholarly journals Nova GK Persei – A Miniature Supernova Remnant?

1988 ◽  
Vol 101 ◽  
pp. 47-50
Author(s):  
E.R. Seaquist ◽  
D.A. Frail ◽  
M.F. Bode ◽  
J.A. Roberts ◽  
D.C.B. Whittet ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Synchrotron Radiation ◽  
Strong Evidence ◽  
White Dwarf ◽  
Planetary Nebula ◽  
Supernova Remnants ◽  
Supernova Remnant ◽  
Optical Images ◽  
Ambient Gas ◽  
The Magnetic Field

AbstractWe present radio and optical images of the shell-like remnant of the 1901 outburst of Nova GK Persei. The behaviour of this object is remarkably similar to supernova remnants. The synchrotron radiation-emitting shell is polarized with the magnetic field oriented radially, as in young SNR’s. This similarity plus extensive data we have acquired on the expansion and the interstellar environment of GK Per indicate that the nova shell is colliding with ambient gas whose density is substantially higher than the ISM.Furthermore, there is strong evidence that the ambient gas is circumstellar rather than interstellar, and that this material is the shell of an ancient planetary nebula associated with the white dwarf companion of GK Per.

The white dwarf mass distribution in classical nova systems

1991 ◽  
Vol 376 ◽  
pp. 177 ◽  
Author(s):  
Hans Ritter ◽  
Michael Politano ◽  
Mario Livio ◽  
Ronald F. Webbink
Keyword(s):  
Mass Distribution ◽  
White Dwarf ◽  
Classical Nova

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.

An Extremely Massive White Dwarf of the Symbiotic Classical Nova V407 Cyg as Suggested by the RS Oph and U SCO Models

2012 ◽  
Vol 21 (1-2) ◽  
Author(s):  
I. Hachisu ◽  
M. Kato
Keyword(s):  
Light Curve ◽  
White Dwarf ◽  
Early Phase ◽  
Symbiotic Star ◽  
X Ray ◽  
Classical Nova ◽  
Optical Light Curve ◽  
Nova Outburst

AbstractWe have analyzed the optical light curve of the symbiotic star V407 Cyg that underwent a classical nova outburst in 2010 March. Being guided by a supersoft X-ray phase observed during days 20-40 after the nova outburst, we are able to reproduce the light curve during a very early phase of the nova outburst. Our model consists of an outbursting white dwarf and an extended equatorial disk. An extremely massive white dwarf of 1.35-1.37 M

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