[vsnet-j 1993] chi Cyg historically bright maxima

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

chi Cyg historically bright maxima

　過去の明るい極大は以下の通りだそうです。もしかすると今回の極大は近代的な
　観測が始まってからの記録的なところに行くかも知れません。

＃もし記録更新したらミラが１等星になるのに匹敵するぐらいの大事件なのかも。

＃さすがに超新星爆発はしないと思いますが (^^;

Subject: [vsnet-lpv 92] Re: chi Cyg bright historical maximum

The 3.3-mag maximum was recorded at the end of 1847 (JDmax=2396014.8) and
was observed by Argelander,
Heis and Schmidt. Other maxima brighter than magnitude 4 are listed below
(maxima reaching magnitude 4 are more common).
I selected these maxima based on a visual inspection of the historical
lightcurve of chi Cygni dating back to the date
of discovery by Gottfried Kirch in 1686 up to 1998. The dates of the maxima
are taken from [3].
I guess the historical 3.3 maxima is based on the brightest estimate. By
visual inspection of the lightcurve I rather judge the mean maximum
magnitude as magnitude 3.5. There is no sign of a maximum of magnitude 2.3
in the data.
It is striking that these bright maxima only occur in the "ancient"
observations. I compared the magnitudes of the comparison stars as they are
listed in the references mentioned below and they cannot account for this.
Maxima brighter than magnitude 4.5 occurred about 12 times in the period
1900-1998.

JDmax         mag.        Observers
2342812.9    >3.8?        Gottfried Kirch
2395205.6     3.8         Argelander, Heis, Schmidt
2396014.8     3.5 (3.3)   Argelander, Heis, Schmidt
2399680.7     3.6         Argelander, Heis, Schmidt, Winnecke
2402161.6     3.9         Heis, Schmidt

Many amateurs did and still do a fabulous job observing this "well-known"
stars.
Thanks to them the long term behaviour is logged excellent and unknown
features are revealed.
Did you know that chi Cygni has increased its period by about 1 day each
century?


References:
[1] Long-term visual magnitude estimates of the Mira variable chi Cygni I.
1686--1900
    C. Sterken, E. Broens, 1998, Journal of Astronomical Data 4

[2] Long-term visual magnitude estimates of the Mira variable chi Cygni II.
1900--1998
    E. Broens, C. Sterken, D. McAdam, M. Watanabe, 1998, Journal of
Astronomical Data 4

[3] On the period history of Chi Cygni
    C. Sterken, E. Broens, C. Koen, 1999, A&A 342, 167-172


Best Regards,
Eric

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VVS Werkgroep Veranderlijke Sterren

Eric Broens
Wateringstraat 143
B-2400 Mol
BELGIUM

e-mail: Eric.Broens@advalvas.be
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