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

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:

http://www.aavso.org/observing/charts/vsp/index.html?pickname=TT%20Ari


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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