TT Ari: "Intermediate-High" Luminosity State Transition and Now Back

ATel #698; J. N. Yoon (CBNU), I. L. Andronov (ONU), Y. Kim (CBNU),S. M. Cha(CBNU)
on 20 Jan 2006; 01:10 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Kim, Yonggi (ykkim153@chungbuk.ac.kr)

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Abstract. We report on the presently continuing "outburst-like" event in TT Ari with an amplitude of 0.9m (R) and characteristic timescales dt/dm=15.87(11)days/mag (rise at JD 2453704-715) and dt/dm=4.95(7)days/mag (fall at HJD 2453721-724). TT Ari has been recently found to be out of the "positive superhump" state, which lasted from 1997 (Skillman et al. , 1998, ApJ, 503 L67; Andronov et al., 1999, AJ, 117, 574) to at least 2004 (Andronov, Ostrova & Burwitz 2004, VSNET-Campaign 1555, http://uavso.pochta.ru/TTAri ), by Andronov, Gazeas & Niarchos (2005, VSNET-Campaign 1630, http://uavso.pochta.ru/TTAri2005 ). The light curve was dominated by quasi-periodic oscillation with a characteristic semi-amplitude ~0.045 mag (VR) (Andronov et al., IBVS 5664). After that, the brightening of TT Ari was reported by Maehara [vsnet-alert 8771]. Here we present a brief report on the "outburst-like" behaviour of TT Ari. It is based on 22 nights of the CCD observations obtained at the 40-cm telescope of the University Observatory, Chungbuk National University, Cheongju, Korea. From October 25 to December 19, 2005, alltogether 6106 data point have been obtained using the R filter with a time resolution 34-70 sec. Detailed study of variability at three detected time-scales will be presented elsewhere after finishing the observational campaign "TT Ari-2005". The long-term light curve based on our observations, is presented at http://uavso.pochta.ru/TT2005R.gif The table of nightly sample mean values of time , magnitude and its accuracy estimate sigma are presented in the following table: -2400000 sigma 53669.16608 10.9975 0.0073 53684.13588 11.1667 0.0033 53685.06281 11.1341 0.0042 53686.14215 11.1767 0.0028 53687.08587 11.1435 0.0031 53692.06316 11.1194 0.0021 53693.09523 11.1228 0.0026 53694.12418 11.1418 0.0029 53695.12250 11.1039 0.0028 53697.03612 11.1090 0.0028 53699.07330 11.0404 0.0028 53701.07125 11.0932 0.0075 53704.21028 10.9180 0.0044 53705.15261 10.8413 0.0035 53707.12664 10.7678 0.0031 53707.90587 10.7859 0.0106 53713.08494 10.4350 0.0040 53715.10349 10.2661 0.0036 53718.95241 10.4005 0.0113 53720.18131 10.3689 0.0082 53722.05972 10.3352 0.0031 53724.10434 10.6694 0.0039 To this table, one nightly mean in the filter V may be added in the same format: -2400000 sigma 53683.22808 11.4050 0.0057 The light curve may be splitted into at least 4 parts: approximate standstills in the intervals HJD 2453684-701 ("intermediately faint state" = 11.123(1)) , HJD 2453713-722 ("bright state" = 10.341(3)) , nearly linear rise HJD 2453704-715 (the slope dt/dm=15.87(11)) , and fall HJD 2453721,724 (the slope dt/dm=4.95(7), but two recent nights only) The maximum amplitude of this outburst-like event is 0.9 mag (R).