[vsnet-campaign-dn 6578] Large amplitude variations of TT Ari

[Ivan Andronov]

Large amplitude variations of TT Ari

In an addition to our report (N.Virnina, [vsnet-chat 7501] TT Ari: Large Variations).
based on the observations at the telescope: Ritchey-Chretien 16" + SBIG STL-6303
(Exposure: 120 s)
we have obtained more observations at the same night at the same observatory using:
Telescope: AP-180 + SBIG STL-11000
Filter: Rc (clear), which is wider, but close to R-band:
Rc-R=-0.04(+-0.011)+0.083(+-0.024)*(V-R)
Exposure: 180s
Tzec Maun observatory, USA


The brightness was calibrated using the main comparison star "N" (Goetz 1987, IBVS 2823) with V=14.633, R=14.231 (A.Henden, ftp://ftp.aavso.org/public/calib/ttaribvri.dat).
The composite light curve from two telescopes in the R filter and "clear", is shown at the attached figure.

The range of the brightness variations is 14.89-16.29, i.e. 1.3 mag with a sharp descending branch lasting 0.008d=11.5 minutes, while the ascending branch seems to be 3 times longer. The best fit period using a cosine approximation is 0.098d=221 min is comparable to the length of the run. So this value can be a lower estimate for a possible period of the nightly variations. 

The complete data set from the two telescopes is below. (1) in the table and filled blue circles in the figure mark observations at Ritchey-Chretien 16"

HJD 24..... mag (R) comment
55171.55511 15.1878 1
55171.56033 15.2582 1
55171.56377 15.3285
55171.56413 15.4599 1
55171.56641 15.6535
55171.56790 15.8846 1
55171.56907 15.8798
55171.57173 16.0095
55171.57182 16.0584 1
55171.57439 16.1178
55171.57564 15.9984 1
55171.57704 15.9530
55171.57973 15.9783 1
55171.57980 15.9898
55171.58247 16.1228
55171.58350 16.1681 1
55171.58513 16.0582
55171.58727 16.2923 1
55171.58779 16.0356
55171.59044 16.1768
55171.59313 16.2066
55171.59578 16.0382
55171.59841 16.2128
55171.60115 16.0521
55171.60390 15.7713
55171.60750 15.7253
55171.61101 15.7177
55171.61374 15.8516
55171.61643 15.7021
55171.61910 15.3422
55171.62178 15.2415
55171.62445 15.4577
55171.62712 15.1905
55171.62978 14.8896
55171.63246 15.0573
55171.63513 15.2573


With best regards,
Virnina Natalia,
Odessa (ONMU,ONU), Ukraine


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