Obs op: khi Cyg S6-class variable extra bright maximum

The following is note from visnet (worth reposting) on khi Cyg - an
irregular long-period (~408 day) S-class variable that is currently
nearing a 200 year maximum near mag. 3.9. When you look up at Cygnus
around midnight, you may notice a third star between eta and beta Cyg
that is normally not there. It is khi Cyg.

khi Cyg is on the AAVSO Easy Variables observing list. If you are
unfamiliar (as I am) with long period variables, this may be a good
place to start.

Burnham's _Celestial Handbook_ has a good entry on khi Cyg (Vol. II, p.
762-768). khi Cyg is also list item Kaler 21 in Kaler's _100 Greatest
Stars_. Kaler also has a brief description of khi Cyg on his variable
stars website:
http://www.astro.uiuc.edu/~kaler/sow/chicyg.html

An AAVSO finder charts are available at (enter as chi Cyg):
http://www.aavso.org/cgi-bin/searchc...name=CHI%20CYG
http://www.aavso.org/cgi-bin/shrinkw...G/CHICYG-A.GIF

An AAVSO light curve (recommend 1200 days) can be generated at (enter
as chi Cyg):
http://www.aavso.org/data/lcg/

Better look now. In about 170 days, khi Cyg will be mag 12!

- Canopus56

-----Original Message-----
From: vsnet-alert-bounces@...
[mailto:vsnet-alert-bounces@...] On
Behalf Of Taichi Kato
Sent: 25 July 2006 01:03
To: ;
vsnet-alert@...;
;
vsnet-campaign@...
Subject: [vsnet-alert 8957] exceptionally bright maximum of chi Cyg

(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)

canopus56 wrote:
The following is note from visnet (worth reposting) on khi Cyg - an
irregular long-period (~408 day) S-class variable that is currently
nearing a 200 year maximum near mag. 3.9. When you look up at Cygnus
around midnight, you may notice a third star between eta and beta Cyg
that is normally not there. It is khi Cyg.

I "discovered" this star a couple of weeks ago. Looked up and noticed
that there was an extra naked-eye star in Cygnus, between Beta and
Gamma, where usually there is just one, Eta (it's very light-polluted
where I live). For a few moments I thought maybe a nova or supernova
had erupted, but then I vaguely remembered that there was a bright
long-period variable in that general area, which was confirmed by
looking in my star atlas.

Last night it was clearly brighter than Eta Cygni by 0.2 or 0.3
magnitudes, and Eta is 3.8 (I think) on the AAVSO charts, so I'd put it
at 3.5 or 3.6.

"canopus56" wrote in message
ups.com...

The following is note from visnet (worth reposting) on khi Cyg - an
irregular long-period (~408 day) S-class variable that is currently
nearing a 200 year maximum near mag. 3.9. When you look up at Cygnus
around midnight, you may notice a third star between eta and beta Cyg
that is normally not there. It is khi Cyg.

khi Cyg is on the AAVSO Easy Variables observing list. If you are
unfamiliar (as I am) with long period variables, this may be a good
place to start.
[snip]

Sorry to nitpick on this, but do you mean "chi" Cygni? Or perhaps "phi"
Cygni?

Not being absolutely certain about the English names of the Greek letters
even after 9 years in the States, I checked Wiki:

http://en.wikipedia.org/wiki/Greek_alphabet

and I see no "khi" letter.

- Canopus56
--
Ioannis

Indeed, this is "chi" Cygni that is being talked about. As of last
night and based on many intercomparisons with magnitude labled stars in
the AAVSO Atlas, intended for use in comparing with chi when it is
especially bright, the star was at magnitude 3.8 . This would make the
current maximum of this long period (not irregular) variable the
brightest in 148 years.

JBortle

"Ioannis" wrote in message
news:1154390692.897172@athnrd02...
Sorry to nitpick on this, but do you mean "chi" Cygni?

Your'r not nitpicking. I tend to use the CDS Simbad designations:

http://simbad.u-strasbg.fr/guide/chA.htx

chi = khi
xi = ksi

- Canopus56

In article 1154390692.897172@athnrd02,
"Ioannis" wrote:

"canopus56" wrote in message
ups.com...

The following is note from visnet (worth reposting) on khi Cyg [...]

Snip

Sorry to nitpick on this, but do you mean "chi" Cygni? Or perhaps "phi"
Cygni?

Not being absolutely certain about the English names of the Greek letters
even after 9 years in the States, I checked Wiki:

http://en.wikipedia.org/wiki/Greek_alphabet

and I see no "khi" letter.

The Greek letter _chi_ (which looks like our X) was originally an
aspirated K (_kappa_), and this sound is often transliterated as "kh".
We use the spelling with C because it's the traditional Latin style of
transliterating Greek, but for most other languages we use the version
with a K instead: "Kharkov", "khaki", "khan", "Khalid", &c. (Cf.
"chaos", "chasm", "architect", &c.) Anyway, while the spelling "khi" is
uncommon, it's an accurate transliteration, and indeed has the advantage
that readers won't be tempted to pronounce it like the initial and final
sounds in "church".

--
Odysseus