Тема: Цефеида в затменной системе

[kirx]

Вот не поскромничаю и напишу в этом разделе о результате, к которому имею некоторую причасность.

В созвездии Орла обнаружена Цефеида (TYC 1031 01262 1), входящая в затменную систему. Это первый пример такого объекта в Галактике. Находка открывает массу возможностей в изучении самих пульсаций, влияния на это близкой звезды-компаньона и независимой (от оценок расстояний до скоплений и неточных HIPPARCOS'овских парралаксов классических Цефеид) калибровки зависимости период-светимость (а значит и шкалы расстояний во Вселенной).
Но это всё в перспективе, пока радует сам факт открытия.

С наблюдательной точки зрения объект выглядит как цефеида 12й величины с неглубокими провалами на кривой блеска. Период пульсаций - 4.1523 суток, орбитальный период - 51.38. Кроме того, свёрнутая с цефеидным периодом кривая получается лохматой из-за наличия эллипсоидальной переменности у одного (а вероятнее - у обоих) компонент системы. Некруглая цефеида... 

Для дальнейших исследований нужны будут спектры и хорошая многоцветна фотометрия...

Препринт тута: http://arxiv.org/abs/0705.0605

Абстракт воспроизведу.

TYC 1031 01262 1: The First Known Galactic Eclipsing Binary with a Type II Cepheid Component
S.V. Antipin, K.V. Sokolovsky, T.I. Ignatieva
We present the discovery and CCD observations of the first eclipsing binary with a Type II Cepheid component in our Galaxy. The pulsation and orbital periods are found to be 4.1523 and 51.38 days, respectively, i.e. this variable is a system with the shortest orbital period among known Cepheid binaries. Pulsations dominate the brightness variations. The eclipses are assumed to be partial. The EB-subtype eclipsing light curve permits to believe that the binary's components are non-spherical.

Такие дела. 

[ctac]

 Молодец Кирилл!

 Опубликуй тут эфемериды затмений и пульсаций + амплитуды. А то я с КПК из КрАО. Видать разменемся буквально в сутки-двое
 Вчера наблюдал на АЗТ-8, сегодня с широким полем (3.5х2.5 гр) с ПЗС.

 Стас

[kirx]

Сорри за задержку. Не сразу увидел пост...

Элементы пульсаций: Max = HJD 2453196.529 + 4.1523 х E
элементы затмений:   Min = HJD 2453571.36 + 51.38 х E

[kirx]

AAVSO'шники стартуют наблюдательную компанию по этой звёздочке! 

AAVSO Alert Notice 351

Campaign for a New Eclipsing Cepheid
June 8, 2007

Name:
TYC 1031 01262 1
ASAS 182611+1212.6
1821+12B   (Harvard Designation)
ASAS182612    (AAVSO name)

Discovered by:
Pojmanski, G., Pilecki, B., Szczygiel, D. 2005, AcA 55, 275
and
Antipin, S.V., Sokolovsky, K. V. and Ignatieva, T. I.
2007, astro-ph/0705.0605

Position (from Sonoita Research Observatory, UCAC2):
18:26:11.50 +12:12:35.0  (+/- 100mas)

Description:
Pojmanski et al. discovered this cepheid several years
ago in the course of the ASAS survey.  Antipin and
collaborators independently discovered the variable
on Moscow archive plates.  It can also be found
in the NSVS (Wozniak et al. 2004, AJ 127, 2436).
Russ Robb gives it a spectral classification of
F8I, and it is considered a type II cepheid.

The light curve looks like a typical cepheid with
period 4.1523 days.  However, scatter in the light
curve was reminiscent of multiperiodic behavior, and
so Antipin began CCD observations in 2004.  After three
years, it was apparent that the system was exhibiting
eclipses with period 51.38 days.  This is the first known
galactic eclipsing binary cepheid (there are three known
examples in the LMC, discovered by the MACHO collaboration;
see Alcock et al., 2002, ApJ 573, 338).

ASAS182612 is a bright (11th mag), easy target with a good
reference frame.  The amplitude of the cepheid pulsation is
about 0.5mag, difficult for visual observers, so this
campaign is primarily for CCD and PEP observers.  The primary
eclipse is about 0.3mag deep, and a secondary eclipse is
suspected with perhaps 0.2mag depth.  However, the light
curve is not well studied, and high-precision, multicolor
photometry over several eclipse cycles would be extremely
beneficial in understanding this system.

Towards that end, we are starting a campaign on ASAS182612.
You can obtain a finding chart at
http://www.aavso.org/observing/charts/vsp
(enter ASAS182612 for its name, or use the coordinates)
with suitable comparison stars marked.  If you are going
to use a single comparison star along with a check star,
we recommend using:
ID       RA(J2000) DEC           V     B-V    V-Rc   Rc-Ic  V-Ic
comp  18:26:09.44 +12:17:37.2  11.914  0.748  0.444  0.432  0.876
check 18:26:23.68 +12:15:47.2  10.892  0.665  0.383  0.358  0.738

Multiple filters are best for modelling this system.  Try to
obtain S/N=100 or better on every image.  With a 4-day period,
time resolution of one hour is adequate, so you can take your
time in cycling through your filters.  If you know your transformation
coefficients, be sure to apply them.  Upload your data using
the name ASAS182612 (or equivalently, 1821+12B).  If you don't
want to do time series, then try to get one multifilter dataset
every evening.

For those of you capable of calculating ephemerides, the
pulsational maximum occurred on HJD 2453196.529 with a
period of 4.1523 days; the eclipse primary minimum occurred
on HJD 2453571.36 with a period of 51.38 days.  The next
primary eclipse will occur around July 9, but these eclipses
are several days wide.

Note: KU Her, a relatively unstudied semiregular variable, is only
5arcmin west of this cepheid.  At coordinates:
18:25:52.78  +12:12:49.0 J2000
it has a mean magnitude of about 11.3 and a period from
ASAS of about 74.5 days.  The color is about (B-V) = 1.7,
so quite a bit redder than the cepheid.  You should be
able to get the two comparison stars, the cepheid and
the SR all in the same field of view.  If so, then report
both stars.  The Harvard Designation for KU Her is
1821+12A and its AAVSO name is KU Her.  Thanks to
Greg Crawford for pointing out this added bonus!

This campaign will be coordinated by Arne Henden,
Doug Welch and Dirk Terrell.

-------------------------------------------
SUBMIT OBSERVATIONS TO THE AAVSO

Information on submitting observations to the AAVSO may be found at:

http://www.aavso.org/observing/submit/

ALERT NOTICE ARCHIVE AND SUBSCRIPTION INFORMATION

An Alert Notice archive is available at the following URL:
http://www.aavso.org/publications/alerts/

Subscribing and Unsubscribing may be done at the following URL:
http://www.aavso.org/publications/email/

[ctac]

Интерес - это Успех!
 Поздравляю, Кирилл!