Spectral and photometric observations of TT Ari. III.

Abstract

The nova-like cataclysmic variable (CV) TT Ari was detected in its second deep minimum inNovember 2009. Study of its evolutionary phase is very important for research on the nature of CVs in the VY Scl group. During this phase the spectral energy distribution of the star changed rapidly. The emission lines of elements with high excitation, such as HeII λ4686 and NIII/CIII, as well as broad absorption in the hydrogen Balmer series, originating in the photosphere of the white dwarf or in the lower layers of an accretion disk, vanished. The average ratio of the intensities of the Balmer series emission lines in the normal state and in the deep low state can be explained in terms of a simple photoionization-recombination model. At the same time, the intensity ratios of the triplet-singlet levels of neutral helium, HeIλ5876/ HeIλ6678, differ greatly in the normal state of the star and in its deep minimum. In the deep minimum, the star's spectrum contains only a very faint trace of the G band at a wavelength λ4300Å, together with flarelike events with amplitudes up to 0 2 m . m ≈ Δ or greater. These and some other observed characteristicsindicate that during the deep minimum it is mainly emission from the secondary companion of the binary system, which is probably a T Tau star of an early K spectral class, that is observed.

Nova-Like Cataclysmic Variables in the Infrared

“…Cowley et al (1975) subsequently confirmed it as a CV through time-resolved spectroscopic observations. TT Ari is notable for displaying a wide range of variability on short timescales (e.g., Smak & St epień 1969;Mardirossian et al 1980), bright and faint state transitions (i.e., VY Scl behavior-see Appendix A.9; e.g., Gänsicke et al 1999;Kraicheva et al 1999;Melikian et al 2010), and both positive and negative superhumps (at different times). Emission line P Cygni profiles have been observed in its UV and optical spectra, likely indicative of an outflowing accretion disk wind (Melikian & Karapetian 2004;Hutchings & Cowley 2007).…”

TT Arietis: 40 yr of photometry

“…The first one was treated in some detail by Shafter et al (1985) and later by Gänsicke et al (1999), while Hutchings & Cote (1985) presented some complementary observations. To my knowledge, the only paper discussing observations of the 2009 -2011 low state was published by Melikian et al (2010). Apart from some time resolved light curves observed by Shafter et al (1985) not much detailed photometry performed in this state has been studied.…”

“…14, individual flares are heavily structured. Melikian et al (2010) have already drawn attention to this flaring activity of TT Ari during the low state. However, their limited amount of data did not permit a more thorough characterization of this behaviour.…”

“…The 1979 -1985 low state was covered by Shafter et al (1985), Hutchings & Cote (1985), and Gänsicke et al (1999). The only detailed paper dedicated to the 2009 -2011 low state was published by Melikian et al (2010). The low state photometry of Shafter et al (1985) reveals flickering, indicating residual mass transfer even during the lowest observed brightness, while Melikian et al (2010) report strong flares superposed on a baseline level of about the same magnitude.…”

Novalike Cataclysmic Variables in the Infrared

“…Cowley et al (1975) subsequently confirmed it as a CV through time-resolved spectroscopic observations. TT Ari is notable for displaying a wide range of variability on short timescales (e.g., Smak & Stȩpień 1969;Mardirossian et al 1980), bright and faint state transitions (i.e., VY Scl behaviorsee Section A.9; e.g., Gänsicke et al 1999;Kraicheva et al 1999;Melikian et al 2010), and both positive and negative superhumps (at different times). Emission line P Cygni profiles have been observed in its UV and optical spectra, likely indicative of an outflowing accretion disk wind (Melikian & Karapetian 2004;Hutchings & Cowley 2007).…”