J/A+A/496/765 R light-curve of TT Ari (Kim+, 2009)
Nova-like cataclysmic variable TT Ari:
QPO behaviour coming back from positive superhumps.
Kim Y., Andronov I.L., Cha S.M., Chinarova L.L., Yoon J.N.
<Astron. Astrophys. 496, 765 (2009)>
=2009A&A...496..765K 2009A&A...496..765K
ADC_Keywords: Binaries, cataclysmic ; Photometry, CCD
Keywords: stars; novae: cataclysmic variables - stars: variables: general -
stars; binaries: general
Abstract:
We study the variability of the nova-like cataclysmic variable TT Ari,
on time-scales of between minutes and months. The observations in the
filter R were obtained at the 40-cm telescope of the Chungbuk National
University (Korea), 51 observational runs cover 226 hours.
In our analysis, we applied several methods: periodogram, wavelet, and
scalegram analysis. TT Ari remained in a "negative superhump" state
after its return from the "positive superhump" state, which lasted for
8 years. The ephemeris for 12 of the best pronounced minima is
Tmin=BJD 2453747.0700(47)+0.132322(53)E, where numbers in digits are
errors in units of the last digit. The phases of minima may reach 0.2,
which reflects the non-eclipse nature of these minima. The
quasi-periodic oscillations (QPO) are present with a mean "period" of
21.6min and mean semi-amplitude of 36mmag.This value is consistent
with the range 15-25min reported for previous "negative superhump"
states and does not support the hypothesis of secular decrease in the
QPO period. Either the period, or the semi-amplitude show significant
night-to-night variations. According to the position at the
two-parameter diagrams (i.e. diagrams of pairs of parameters: time,
mean brightness of the system, brightness of the source of QPO,
amplitude, and timescale of the QPOs), the interval of observations
was divided into 5 parts, showing different characteristics: 1) the
"pre-outburst" stage, 2) the "rise to outburst", 3) "top of the
outbursts", 4) "post- outburst QPO" state, and 5) "slow brightening".
The the QPO source was significantly brighter during the 10-day
outburst, than during the preceding interval. However, after the
outburst, the large brightness of the QPO source still existed for
about 30 days, producing the stage "4". The diagram for
mQPO({bar}{m}) exhibits two groups in the brightness range
10.6-10.8, which correspond to larger and smaller amplitudes of the
QPO. For the group "5" only, statistically significant correlations
were found, for which, with increasing mean brightness, the period,
amplitude, and brightness of the of QPO source also increase. The mean
brightness at the "negative superhump state" varies within 10.3-11.2,
so the system is brighter than at the "positive superhump" (11.3),
therefore the "negative superhump" phenomenon may be interpreted by a
larger accretion rate. The system is an excellent laboratory for
studying processes resulting in variations on timescales of between
seconds and decades and needs further monitoring at various states of
activity.
Description:
Table of R observations (HJD, magnitude) obtained at the 40cm
telescope of the CBNU observatory, Korea.
Objects:
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RA (2000) DE Designation(s)
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02 06 53.1 +15 17 42 TT Ari = V* TT Ari
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 20 14199 Photometric R observations of TT Ari
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See also:
J/A+A/265/77 : VBLUW Observations of TT Ari (Hollander+ 1992)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d HJD Heliocentric Julian date
15- 20 F6.3 mag Rmag R magnitude
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Acknowledgements:
Ivan Andronov, tt_ari(at)ukr.net
References:
Kopylova & Kopylov, 1998PAZh...24..573K 1998PAZh...24..573K, (1998AstL...24..491K 1998AstL...24..491K)
(End) Ivan Andronov [ONMU, Ukraine], Patricia Vannier [CDS] 02-Mar-2009