Photometric Study of KR Aurigae during the High State in 2001

Abstract

We photometrically observed the VY Scl-type cataclysmic variable KR Aurigae after its final rise from the fading episode in 2000-2001. Time-resolved observation revealed that the light curve is dominated by persistent short-term variation with time-scales of minutes to tens of minutes. On some nights, quasiperiodic variations with periods of 10-15 min were observed. No coherent variation was detected. The power spectral density of the variation has a power law component (f −1.63 ). The temporal properties of the short-term variations in KR Aur present additional support for the possibility that flickering in CVs may be better understood as a result of self-organized critical state as in black-hole candidates. The light curve lacks "superhump"-type signals, which are relatively frequently seen in VY Scl-type systems and which are suggested to arise from tidal instability of the accretion disk induced by changing mass-transfer rates. The present observation suggests a borderline of superhump excitation in VY Scl-type stars between mass ratios q=0.43 (MV Lyr) and q=0.60 (KR Aur).

A flickering study of nova-like systems KR Aur and UU Aqr

“…KR Aur is a nova‐like system of VY Scl type. Its flickering activity was studied by Kato, Ishioka & Uemura (2002) during a high state. The authors used 17 observations, with a mean coverage of 9000‐s and 50‐s time resolution, to calculate the power density spectra (PDS).…”

“… 1 –Shafter (1983), 2 –Kato et al (2002), 3 –Baptista, Steiner & Cieslinski (1994), 4 –Baptista & Bortoletto (2008). …”

XMM–Newton observation of MV Lyr and the sandwiched model confirmation

“…Shahbaz et al 2010, Mushotzky et al 2011), a broken power law (two power law components) with a single break frequency in between (see e.g. Kato et al 2002, Baptista & Bortoletto 2008 or a multicomponent PDS with several characteristic break frequencies (see e.g. Sunyaev & Revnivtsev 2000, Dobrotka et al 2014.…”

Detection of superhumps in the VY Scl-type nova-like variable KR Aur

“…Singh et al (1993) detected large‐amplitude quasi‐periodic oscillations (QPOs) in this star, with periods in the range 500–800 s. There were also indications of a modulation with a period of about 4 h. This modulation might represent the orbital period or might be a type of superhump. However, Kato, Ishoka & Uemura (2002) conducted photometric observations of KR Aur and found no modulation with such a period. We decided to clarify whether a photometric signal near the orbital period is present in KR Aur, and the first observational night clearly showed such a modulation.…”