[Aavso-photometry] Intensive photometry of TU Cas

[Richard Miles]

At Arne's suggestion 2 nights ago on the AAVSO chatroom, I carried out 
simultaneous V- and I-filter photometry of this double-period Cepheid over a 
6-hr interval.

Have now uploaded the reduced data thereby increasing the size of the AAVSO 
data archive on this star by one-third.

I was fortunate to catch the star as it approached and passed through 
minimum.  There are some real interesting features on the V lightcurve, 
which are entirely absent in the I-band indicative of changes in the blue 
region of the spectrum.

For instance at 2453692.35, there is a gradual decline in brightness of 0.10 
mag over the course of 3 minutes followed by a similar return to normal 
brightness.

However, what's really cool is the interval from 2453692.48 to 2453692.50 
when the star undergoes some sort of oscillation resulting in very rapid 
drops in brightness in V magnitude on a 1-minute timescale having a typical 
amplitude of 0.2 mag!  The most extreme oscillation involved a drop of about 
0.3 mag over a minute or so, followed by a return to the normal brightness 
level in less than 20 seconds.  Now that's what I call a variable star!

I should point out that there is a nice write up on this star, which has a 
very long history and is the current  Variable Star of the Season, on the 
AAVSO website at:

http://www.aavso.org/vstar/vsots/

It's a very informative account prepared by Kerri Malatesta, AAVSO Technical 
Assistant, and make good reading.

Enjoy,
Richard Miles (MXL)