[vsnet-alert 8957] exceptionally bright maximum of chi Cyg

[Taichi Kato]

(past records from [vsnet-lpv 92] by Eric Broens)

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

  YYYYMMDD(UT)   mag  observer
  20060701.948    65  (Gary Poyner)
  20060702.926    61  (Marian Legutko)
  20060703.851    62  (Guenther Krisch)
  20060704.855    61  (Guenther Krisch)
  20060708.531    56  (Atsuko Takahashi)
  20060709.931    52  (Gary Poyner)
  20060710.560    51  (Atsuko Takahashi)
  20060710.849    51  (Guenther Krisch)
  20060711.594    50  (Yutaka Maeda)
  20060711.960    48  (Georg Comello)
  20060712.656    50  (Yutaka Maeda)
  20060713.508    49  (Yutaka Maeda)
  20060713.951    48  (Gary Poyner)
  20060714.560    46  (Hiroyuki Someya)
  20060714.603    45  (Takuichiro Onishi)
  20060714.631    48  (Kenji Nakai)
  20060714.849    47  (Guenther Krisch)
  20060715.608    48  (Yutaka Maeda)
  20060715.641    48  (Ryosuke Naito)
  20060715.642    47  (Yukiko Tsuchiyama)
  20060717.914    43  (Gary Poyner)
  20060718.010    42  (Georg Comello)
  20060718.889    44  (Marian Legutko)
  20060719.853    42  (Guenther Krisch)
  20060720.547    42  (Atsuko Takahashi)
  20060720.893    39  (Marian Legutko)
  20060720.931    42  (Jose Ripero)
  20060721.910    40  (Maciej Reszelski)
  20060722.548    42  (Atsuko Takahashi)
  20060722.981    44  (J. Toone)
  20060723.555    38  (Atsuko Takahashi)
  20060723.881    38  (Marian Legutko)
  20060724.656    39  (Yutaka Maeda)