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Dwarf Nova (dwarf + nova)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

Dwarf nova oscillations and quasi-periodic oscillations in cataclysmic variables , VII.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009
OY Carinae, oscillations in dwarf novae in quiescence
ABSTRACT We have observed dwarf nova oscillations (DNOs) in OY Car during outburst, down through decline and beyond; its behaviour is similar to what we have previously seen in VW Hyi, making it only the second dwarf nova to have DNOs late in outburst that continue well into quiescence. There are also occasional examples of DNOs in deep quiescence, well away from outburst , they have properties similar to those during outburst, indicating similar physical causes and structures. We discuss the occurrence of DNOs in other dwarf novae and conclude that DNOs during quiescence are more common than often supposed and exhibit properties similar to those seen in outburst. [source]

VW Hyi: optical spectroscopy and Doppler tomography

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006
Amanda J. Smith
ABSTRACT We present high-quality optical spectroscopy of the SU UMa-subtype dwarf nova, VW Hyi taken while the system was in quiescence. An S-wave is executed by the emission cores of the hydrogen Balmer lines and by the emission lines of He i, Ca ii, Fe ii and He ii. Using Doppler tomography, we show it originates in the accretion stream,disc impact region. The He ii emission is strongly phase-dependent, suggesting it originates exclusively within a hot cavity at the initial impact. We map the ionization structure of the stream,disc interaction region. One possible interpretation of this is that the Balmer hotspot lies downstream of the He ii hotspot in the outer accretion disc, with the He i and Ca ii hotspots at intermediate locations between the two. This suggests that Balmer emission is suppressed until material has cooled somewhat downstream of the impact site and is able to recombine. We favour a phase offset of 0.15 ± 0.04 between the photometric ephemeris and inferior conjunction of the mass donor. The white dwarf contributes significantly to the optical continuum, with broad Balmer absorption and narrow Mg ii ,4481 absorption clearly apparent. This latter feature yields the gravitational redshift: vgrav= 38 ± 21 km s ,1, so M1= 0.71+0.18,0.26 M,. This implies M2= 0.11 ± 0.03 M, and hence the donor is not a brown dwarf. A prominent Balmer jump is also observed. We note that the previously accepted system parameters for both VW Hyi and WX Hyi incorporate an algebraic error, and we provide a recalculated M1(q) plane for WX Hyi. [source]

Mirror eclipses in the cataclysmic variable IP Peg

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2001
S.P. Littlefair
We present time resolved K -band infrared spectra of the dwarf nova (DN) IP Peg in early quiescence. The Brackett , and He i (,2.0581) lines in our data show hitherto unseen behaviour, which we term a mirror eclipse, and interpret as an eclipse of the secondary star by an optically thin accretion disc. Mirror eclipses are a direct probe of the structure and physical conditions of accretion discs. For example, on assuming the relevant level populations to be in local thermal equilibrium, we constrain the temperature and density of the optically thin material, causing the mirror eclipse in IP Peg to be and respectively. In order to match our data, we find that at least the outermost 20 per cent of the disc (in radius) must be entirely optically thin. Implications for time-dependent disc models are examined. [source]

Dwarf nova oscillations and quasi-periodic oscillations in cataclysmic variables , VII.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009
OY Carinae, oscillations in dwarf novae in quiescence
ABSTRACT We have observed dwarf nova oscillations (DNOs) in OY Car during outburst, down through decline and beyond; its behaviour is similar to what we have previously seen in VW Hyi, making it only the second dwarf nova to have DNOs late in outburst that continue well into quiescence. There are also occasional examples of DNOs in deep quiescence, well away from outburst , they have properties similar to those during outburst, indicating similar physical causes and structures. We discuss the occurrence of DNOs in other dwarf novae and conclude that DNOs during quiescence are more common than often supposed and exhibit properties similar to those seen in outburst. [source]

New Stars and telescopes: Nova research in the last four centuries

ASTRONOMISCHE NACHRICHTEN, Issue 6 2009
H.W. Duerbeck
Abstract This article gives a brief overview of 400 years of research in the field of novae and related stars. Important objects, first applications of various observing techniques, and early ideas of the interpretation of phenomena are listed. Also, the historical evolution of the classification of novae and related stars (supernovae, dwarf novae), as well as their use as distance indicators is discussed (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]