Detection of 7Be ii in the Classical Nova V5669 Sgr (Nova Sagittarii 2015 No.3)

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).

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The CHANDRA data of the Classical Nova RR Pic (1925): A possible Magnetic Cataclysmic Variable Candidate

International Astronomical Union Colloquium ◽

10.1017/s0252921100002025 ◽

2004 ◽

Vol 190 ◽

pp. 172-173

Author(s):

Şölen Balman ◽

Aybuke Küpcü-Yoldaş

Keyword(s):

Spectral Analysis ◽

Count Rate ◽

Source Spectrum ◽

Cataclysmic Variable ◽

Photoelectric Absorption ◽

X Ray ◽

Classical Nova ◽

Show Evidence ◽

Partial Covering ◽

Two Temperature

AbstractDuring 25ksec of CHANDRA ACIS-S3 observations of the old nova RR Pic 1925 a count rate of 0.067±0.0017 c/s was detected. The results show evidence (spatial and spectral) for X-ray emission from the region around the prominent SW blob in the Hα images. Shell emission is detected with count rate ≥ (1.95±1.33)×10−3 c/s. The spectral analysis shows that the source spectrum can not be explained by a single or two temperature bremsstrahlung or VMEKAL models including photoelectric absorption, only models using powerlaw distribution of temperature fit the data well and indicate excess O, Al, Mg, S, and Si in the source spectrum. A soft excess in the CHANDRA data could be explained by a partial covering absorber model with covering fraction in a range 14-86 % consistent with characteristics of the Magnetic Cataclysmic Variable systems. The light curve shows significant orbital and other modulations.

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

International Astronomical Union Colloquium ◽

10.1017/s0252921100002049 ◽

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.

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Diffusion in Novae at High Accretion Rates

International Astronomical Union Colloquium ◽

10.1017/s0252921100068913 ◽

1990 ◽

Vol 122 ◽

pp. 394-396

Author(s):

Attay Kovetz ◽

Prialnik Dina

Keyword(s):

Numerical Models ◽

Variable Mass ◽

Apparent Discrepancy ◽

Full Understanding ◽

Transfer Rates ◽

Outstanding Problem ◽

Upper Limit ◽

Classical Nova ◽

Accretion Rates ◽

Diffusion Convection

The main outstanding problem in our full understanding of the classical nova mechanism is the apparent discrepancy between mass transfer rates (10−9 to 10−8M⊙/yr) inferred from observations (Patterson, 1984, Ap.J.Suppl.231, 789), and those required by numerical models in order to reproduce nova characteristics (10−11 to 10−9M⊙/yr). The low accretion rates are needed in order to obtain powerful runaways and high values of Z in the ejecta by the diffusion-convection mechanism. The discrepancy seems to have sharpened by the realization that accretional heating (Shaviv and Starrfield, 1987, Ap.J.321, L51) and angular momentum transfer (Sparks and Kutter, 1987, Ap.J.321, 394 and Kutter and Sparks, 1987, Ap.J.321, 386) tend to lower the theoretical upper limit for Ṁ to about 10−10M⊙/yr. On the other hand, scenarios invoking variable mass accretion rates — hibernation (Shara et al, 1986, Ap.J.311, 163) or ‘mild’ hibernation (Livio, Shankar and Truran, 1988, Ap.J.330, 264) — have shown that the high observed rates immediately prior and following outbursts can be reconciled with lower average accretion rates over the period between outbursts.

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