Alert Notice 408: Deep fading event in the cataclysmic variable TT Arietis

October 13, 2009

The VY Sculptoris-class cataclysmic variable TT Ari has begun its first large decline since its deep minimum of 1982-1985.  Observations of TT Ari are urgently requested.  The 1982-1985 event reached a minimum of m(vis)=15.5, where it remained for approximately 3.5 years. Observers are asked to closely follow TT Ari through its current decline, and to continue monitoring TT Ari if and when it reaches a stable minimum. All observations including visual estimates, CCD photometry, and CCD time-series are needed; visual positive and fainter-than estimates are both important.

The first hints of decline appeared in the AAVSO light curve in late September 2009, with a deep decline becoming clear by by 2009 Oct 03 (JD 2455108.4059; m(V) = 12.57, T. Gomez, Madrid, Spain).  The star has dropped rapidly, and currently stands at m(vis) = 14.2 on 2008 October 13.063 (JD 2455117.563; G. Poyner, Birmingham, England).

The event of 1982-1985 is the only recorded major fading in TT Ari, so the depth and duration of the current event cannot be predicted; it may reach its historic minimum of 15.5 and remain there for some time. Prior to the long-duration event, TT Ari declined to approximately 14.5 beginning in 1979; it had nearly recovered from this event before going into the deep minimum in early 1982.  Because of its unpredictable nature, continuous observations of TT Ari are urgently needed.

TT Ari is also known to exhibit rapid variability including quasiperiodic oscillations and negative superhumps.  Time series observations made throughout the decline and eventual minimum are urgently needed.  Please use exposure times that adequately balance signal-to-noise considerations with the need for short exposures; filters are not required.

TT Ari is located at the following (J2000) coordinates:

        RA: 02:06:53.10 , Dec: +15:17:42.0

Charts for TT Ari may be plotted with AAVSO VSP:

Please promptly submit all observations to the AAVSO with the name "TT ARI".

Clear skies, and good observing,

Matthew Templeton, AAVSO


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