[vsnet-alert 15756] new paper on Kepler observation of V344 Lyr and V1504 Cyg

[Taichi Kato]

   Here is our new paper.  A must read for those who are interested
in positive/negative superhumps.  This paper also describes 
the frequency variation of positive superhumps, which we tried to 
write as understandable as possible.

===

arXiv:1305.5877
Date: Sat, 25 May 2013 01:19:10 GMT   (1713kb)

Title: Study of Superoutbursts and Superhumps in SU UMa Stars by the Kepler
  Light Curves of V344 Lyrae and V1504 Cygni
Authors: Yoji Osaki (U. of Tokyo), Taichi Kato (Kyoto U.)
Categories: astro-ph.SR
Comments: 26 pages, 14 figures, accepted for publication in PASJ
\\
  We study the short cadence Kepler public light curves of SU UMa stars, V344
Lyr and V1504 Cyg extending for a period of well over two years by using power
spectral analysis. We have determined the orbital period of V344 Lyr to be
Porb=0.087903(1) d. We have reanalyzed the frequency variation of the negative
superhump in a complete supercycle of V1504 Cyg with additional data of the O-C
diagram, confirming its characteristic variation in accordance with the thermal
tidal instability model. We present a new two-dimensional period analysis based
on a new method least absolute shrinkage and selection operator (Lasso). The
new method gives very sharp peaks in the power spectra and it is very useful
for the study of frequency variation in cataclysmic variable stars. We have
analyzed simultaneous frequency variation of the positive and negative
superhumps. If appropriately converted, it is found that they vary in unison,
indicating that they represent the disk radius variation. We have studied the
frequency (or period) variations of the positive superhumps during
superoutbursts. These variations are understood in a qualitative way by a
combination of the disk radius variation and the variation of the pressure
effects during superoutburst. A sudden excitation of oscillation with a
frequency range near the negative superhump (which we call "impulsive negative
superhump") was observed in the descending branch of several outbursts of V344
Lyr. These events seem to occur just prior to the next superoutburst and to act
as a "lead" of the impending superoutburst.
\\ ( http://arxiv.org/abs/1305.5877 ,  1713kb)