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Special Notice #172: Observing campaign on TT Ari

AAVSO Special Notice #172

Observing campaign on TT Ari
October 20, 2009

The AAVSO requests intensive time-series observations of TT Ari during the current fading episode to fully record its behavior during minimum. TT Ari has entered its first faint state since the event of 1982-1985. However, it is exhibiting very high-amplitude (~1 magnitude) periodic oscillations with a period of 0.371 days.  This period is of unknown origin; it is significantly longer than the orbital period of 0.137551 days, and is longer than the pulsation periods of white dwarf stars. Continuous photometry of TT Ari will show whether this long period remains coherent.

All observations of TT Ari are encouraged including visual observations. Observers with the capability of performing calibrated multicolor time-series photometry are especially needed; such observations may provide additional physical information about the object that is varying (the primary, the secondary, or the accretion disk).  For observers with multiple filters, the suggested priority order is V, Rc, Ic, and B.

There is no fixed duration for this campaign, since we do not know the origin of the periodic variability, or when TT Ari will return to its novalike state.  There have only been two well-observed fading events in TT Ari: the 1982-1985 event, and a shorter event in 1979-1980, and neither have extensive time-series data.  Observers are encouraged to add TT Ari to their long-term observing programs if possible, and to make time-series observations when TT Ari is well-placed.

This campaign is being conducted at AAVSO Headquarters by Matthew Templeton and Arne Henden.

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

Please submit all observations to the AAVSO as "TT ARI".

This AAVSO Special Notice was prepared by M. Templeton.
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