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Alert Notice 146: Special multiwavelength monitoring of 0201+14 TT Arietis

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THE AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS
25 Birch Street, Cambridge, MA 02138 USA
BITNET: aavso@cfa8 SPAN: nssdca::cfa8::aavso
Tel. 617-354-0484 FAX 617-354-0665

AAVSO ALERT NOTICE 146 (July 19,1991)

SPECIAL MULTIWAVELENGTH MONITORING OF 0201+14 TT ARIETIS

The interesting cataclysmic variable 0201+14 TT Arietis will be the observing
target of multiwavelength monitoring starting 8:00 UT August 1 and continuing for
24 hours (!). This cataclysmic variable will be observed with the x-ray satellite
ROSAT and also possibly with coordinated observations with the Japanese x-ray
satellite Ginga and the ultraviolet satellite IUE.

We have been requested to monitor this star closely before the observing run, and
in particular during the 24 hours of the multiwavelength campaign. Observers with
photometers are urged to monitor TT Ari, with high speed photometry, if possible,
to detect the possible flares that have been recorded for this star.

It is essential for everyone monitoring this star to record the exact timing of
their observations. Visual observers should report the time to the minute (4
decimal places of the JD). Photometric observers should report the time to the
second (5 decimal places of the JD). Therefore, particularly those doing photometry
should have an accurate clock for timing their observations. Accurate timing is
essential because in the flaring activities of this star, an optical and x-ray
time lag of about 60 seconds has been detected in cross correlation, and it is
this aspect of TT Ari that is of particular interest during the multiwavelength
monitoring campaign.

Below I am enclosing the information (from Jensen et al., 1983, ApJ, 270, 211)
circulated by Dr. France Cordova, who is coordinating the multiwavelength campaign.

   "Optical Variability Time Scales for TT Ari

1. A roughly sinusoidal orbital modulation is detected on a time scale of about
12,000s (the variation in B magnitude was from 11.5 to 11.9 mag). I believe the
source is somewhat brighter now (V= ~10.7).

2. Persistent optical flickering occurs with an amplitude of ~ 0.2 mag on a time
scale of several minutes.

3. Transient optical oscillations occur with periods ~ 32s and ~ 12s.

4. An optical/X-ray time lag is detected in cross-correlations with a delay time
of 60 seconds."

Unfortunately, TT Ari is not very favorably placed at this time. On August 1, it
will be in the early morning sky and the Moon will be only 10 degrees away. Please
try to monitor this star closely, and inform us of its optical behavior, in
particular if there are any changes in brightness. This star has been in its
bright state at about visual magnitude 10.6 since 1985. Please use the enclosed
AAVSO finder chart in making your observations.

1247-28 EX HYDRAE

We have been informed by ROSAT astronomers that the x-ray satellite ROSAT detected
very high x-ray emission from 1247-28 EX Hydrae on July 17. Danie Overbeek from
South Africa informed us that the optical brightness of this star was at its
usual magnitude of 13.0 at 17 UT on July 17, and that the brightness had not
changed for about the past two months.

Observers are requested to use the enclosed AAVSO finder chart to keep a close
eye on EX Hya and to inform us of any changes in its brightness.

The Headquarters answering machine (617-354-Q484) is on nights and weekends for
your convenience.

My very sincere thanks for your efforts and valuable observations.

Good observing!

Janet A. Mattei
Director

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