J/A+A/544/A53 Long-term photometry and spectroscopy of EE Cep (Galan+, 2012)
International observational campaigns of the last two eclipses in EE Cephei:
2003 and 2008/9.
Galan C., Mikolajewski M., Tomov T., Graczyk D., Apostolovska G.,
Barzova I., Bellas-Velidis I., Bilkina B., Blake R.M., Bolton C.T.,
Bondar A., Brat L., Brozek T., Budzisz B., Cikala M., Csak B.,
Dapergolas A., Dimitrov D., Dobierski P., Drahus M., Drozdz M., Dvorak S.,
Elder L., Frackowiak S., Galazutdinov G., Gazeas K., Georgiev L., Gere B.,
Gozdziewski K., Grinin V.P., Gromadzki M., Hajduk M., Heras T.A.,
Hopkins J., Iliev I., Janowski J., Kocian R., Kolaczkowski Z., Kolev D.,
Kopacki G., Krzesinski J., Kucakova H., Kuligowska E., Kundera T.,
Kurpinska-Winiarska M., Kuzmicz A., Liakos A., Lister T.A., Maciejewski G.,
Majcher A., Majewska A., Marrese P.M., Michalska G., Migaszewski C.,
Miller I., Munari U., Musaev F., Myers G., Narwid A., Nemeth P.,
Niarchos P., Niemczura E., Ogloza W., Oegmen Y., Oksanen A., Osiwala J.,
Peneva S., Pigulski A., Popov V., Pych W., Pye J., Ragan E., Roukema B.F.,
Rozanski P.T., Semkov E., Siwak M., Staels B., Stateva I., Stempels H.C.,
Steslicki M., Swierczynski E., Szymanski T., Tomov N., Waniak W.,
Wiecek M., Winiarski M., Wychudzki P., Zajczyk A., Zola S., Zwitter T.
<Astron. Astrophys., 544, A53 (2012)>
=2012A&A...544A..53G 2012A&A...544A..53G
ADC_Keywords: Binaries, eclipsing ; Photometry, UBVRI
Keywords: binaries: eclipsing - circumstellar matter -
stars: emission-line, Be - planetary systems
Abstract:
EE Cep is an unusual long-period (5.6yr) eclipsing binary discovered
during the mid-twentieth century. It undergoes almost-grey eclipses
that vary in terms of both depth and duration at different epochs. The
system consists of a Be type star and a dark dusty disk around an
invisible companion. EE Cep together with the widely studied
epsilon Aur are the only two known cases of long-period eclipsing binaries
with a dark, dusty disk component responsible for periodic
obscurations.
Two observational campaigns were carried out during the eclipses of EE
Cep in 2003 and 2008/9 to verify whether the eclipsing body in the
system is indeed a dark disk and to understand the observed changes in
the depths and durations of the eclipses.
Multicolour photometric data and spectroscopic observations performed
at both low and high resolutions were collected with several dozen
instruments located in Europe and North America. We numerically
modelled the variations in brightness and colour during the eclipses.
We tested models with different disk structure, taking into
consideration the inhomogeneous surface brightness of the Be star. We
considered the possibility of disk precession.
The complete set of observational data collected during the last three
eclipses are made available to the astronomical community. The 2003
and 2008/9 eclipses of EE Cep were very shallow. The latter is the
shallowest among all observed. The very high quality photometric data
illustrate in detail the colour evolution during the eclipses for the
first time. Two blue maxima in the colour indices were detected during
these two eclipses, one before and one after the photometric minimum.
The first (stronger) blue maximum is simultaneous with a "bump" that
is very clear in all the UBV(RI)C light curves. A temporary increase
in the I-band brightness at the orbital phase ∼0.2 was observed after
each of the last three eclipses. Variations in the spectral line
profiles seem to be recurrent during each cycle. The NaI lines always
show at least three absorption components during the eclipse minimum
and strong absorption is superimposed on the Hα emission.
These observations confirm that the eclipsing object in EE Cep system
is indeed a dark, dusty disk around a low luminosity object. The
primary appears to be a rapidly rotating Be star that is strongly
darkened at the equator and brightened at the poles. Some of the
conclusions of this work require verification in future studies: (i) a
complex, possibly multi-ring structure of the disk in EE Cep; (ii) our
explanation of the "bump" observed during the last two eclipses in
terms of the different times of obscuration of the hot polar regions
of the Be star by the disk; and (iii) our suggested period of the disk
precession (∼11-12Porb) and predicted depth of about 2m for the
forthcoming eclipse in 2014.
Description:
We present a catalog of photometric and spectroscopic data collected
during and around of EE Cep eclipses in 1997, 2003 and 2008/9. The
photometric data were obtained with 25 different instruments, mainly
in Johnson-Cousins UBV(RI)C bands, and some small sets of the data
were obtained with narrow interference filters, placed on, or around
of H-alpha and H-beta lines. The photometry from the last two eclipses
have been compiled into the set of consistent photometric data in
UBV(RI)C bands, that has been used in the paper to modelling of the
eclipses in EE Cep system. The 100 of spectra released in this catalog
were obtained with 8 of different spectrographs at low, medium and
high resolutions (R in range ∼2000-48000). About half of them (54
spectra) cover narrow ranges of order 200 Angstroms with H-alpha,
H-beta lines or NaI dublet, and the second part (46 spectra) cover
longer ranges of wavelengths - several thousands of Angstroms in the
visual domain or in the near infrared.
Objects:
-------------------------------------------------
RA (2000) DE Designation(s)
-------------------------------------------------
22 09 22.76 +55 45 24.2 EE Cep = BD+55 2693
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
photom.dat 43 352 BV(RI)c photometry, EE Cep eclipse 2008/9,
Sonoita Res. Obs., 0.5m Cassegrain telescope
photom1.dat 38 1432 EE Cep eclipses differential photometry
(1 comparison star)
photom3.dat 44 1131 EE Cep eclipses differential photometry
(3 comparison stars)
notes.dat 80 244 Observation informations
tableb35.dat 129 352 *The mean points of the average UBV(RI)c light
curves obtained during and near the 2003 (E=9)
and 2008/9 (E=10) eclipses.
tableb36.dat 139 100 List of spectra obtained during and near of the
last three eclipses of EE Cep (from E=8 to E=10)
and names of the corresponding FITS files
sp/* . 74 FITS spectra
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Note on tableb35.dat: The compilation of photometric observations of all
observatories.
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Byte-by-byte Description of file: photom.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- ObsNo Observation code (B22 or B23), in notes.dat file
5- 7 A3 --- n_Date [HJD or JD]
9- 21 F13.5 d Date Julian date of observation (JD or HJD)
23- 28 F6.3 mag mag Magnitude in Band
30- 34 F5.3 mag dmag Differential magnitude in Band (1)
36- 39 F4.2 mag e_dmag ?=- rms uncertainty on dmag
42- 43 A2 --- Band [BVRcIc ] Observed band
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Note (1): Differential magnitudes in respect of BD+55 2690 comparison star.
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Byte-by-byte Description of file: photom1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- ObsNo Observation code, in notes.dat file
5- 7 A3 --- n_Date [HJD or JD]
9- 21 F13.5 d Date Julian date of observation (JD or HJD)
23- 28 F6.3 mag dmag Differential magnitude (1)
30- 34 F5.3 mag e_dmag ? rms uncertainty on dmag
(only for B1, B6 and B12)
36- 38 A3 --- Band [UBVRIci Hb Han Haw] Observed band (2)
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Note (1): Differential magnitudes in respect of BD+55 2690 comparison star,
except B16: GSC 3973 2150 comparison star
B21: BD+55 2691 comparison star
Note (2): Observed bands corresponds to :
U B V Rc Ic = Johnson-Cousins system
Hb = Hβ filter (FWHM∼100Å)
i = i filter (λmean=7420Å)
c = c filter (λmean=4804Å, FWHM∼100Å)
Haw = wide Hα filter (FWHM∼200Å)
Han = narrow Hα filter (FWHM∼30Å)
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Byte-by-byte Description of file: photom3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- ObsNo Observation code, in notes.dat file
5- 7 A3 --- n_Date [HJD or JD]
9- 21 F13.5 d Date Julian date of observation (JD or HJD)
22- 27 F6.3 mag dmaga ?=- Differential B-band photometry, v-a (1)
29- 34 F6.3 mag dmagb ?=- Differential B-band photometry, v-b (2)
36- 41 F6.3 mag dmagc Differential B-band photometry, v-c (3)
43- 44 A2 --- Band [UBV RcIc] Observed band
--------------------------------------------------------------------------------
Note (1): Differential magnitudes in respect of BD+55 2690 comparison star.
Note (2): Differential magnitudes in respect of GSC 3973-2150 comparison star.
Note (3): Differential magnitudes in respect of BD+55 2691 comparison star.
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Byte-by-byte Description of file: notes.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- ObsNo Observation code
5- 80 A76 --- Com Information on observation
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Byte-by-byte Description of file: tableb35.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.2 d JDU ? Julian date of observation for U band
12- 17 F6.3 mag Umag ?=- U-band photometry (1)
19- 23 F5.3 mag e_Umag ?=- rms uncertainty on Umag
25 I1 --- o_Umag ?=- The number of averaged photometric points
27- 36 F10.2 d JDB ? Julian date of observation for B band
38- 43 F6.3 mag Bmag ?=- B-band photometry (1)
45- 49 F5.3 mag e_Bmag ?=- rms uncertainty on Bmag
51 I1 --- o_Bmag ?=- The number of averaged photometric points
53- 62 F10.2 d JDV ? Julian date of observation for V band
64- 69 F6.3 mag Vmag ?=- V-band photometry (1)
71- 75 F5.3 mag e_Vmag ?=- rms uncertainty on Vmag
77 I1 --- o_Vmag ?=- The number of averaged photometric points
79- 88 F10.2 d JDRc ? Julian date of observation for Rc band
90- 95 F6.3 mag Rcmag ?=- Rc-band photometry (1)
97-101 F5.3 mag e_Rcmag ?=- rms uncertainty on Rcmag
103 I1 --- o_Rcmag ?=- The number of averaged photometric points
105-114 F10.2 d JDIc ? Julian date of observation for Ic band
116-121 F6.3 mag Icmag ?=- Ic-band photometry (1)
123-127 F5.3 mag e_Icmag ?=- rms uncertainty on Icmag
129 I1 --- o_Icmag ?=- The number of averaged photometric points
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Note (1): Magnitudes and the corresponding standard deviations are given.
Mean magnitudes were obtained by averaging the data (var-a): in the
case of the 2022 eclipse for Obs B2-B11 and in the case of the 2008/9
eclipse for Obs B12-B32. Finally, to obtain magnitudes in the standard
Johnson-Cousins photometric system, the comparison star (a=BD+55 2690)
magnitudes (according to Mikolajewski et al. (2003IBVS.5412....1M 2003IBVS.5412....1M.)
have been added.
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Byte-by-byte Description of file: tableb36.dat
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Bytes Format Units Label Explanations
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1- 10 A10 "YYYY-MM-DD" Obs.date Date of observation
12- 19 A8 "h:m:s" Obs.time Universal Time of observation
21- 32 F12.4 d HJD Heliocentric Julian date
34- 41 F8.5 --- Phase Phase according to Mikolajewski & Graczyk
(1999MNRAS.303..521M 1999MNRAS.303..521M) ephemeris
43- 44 I2 --- E Epoch number
46- 56 A11 --- ObsName Name of observatory
58- 91 A34 --- Inst Telescope and instrument
93-103 A11 --- lambda Spectral range
105-109 I5 --- R Resolving power
111-139 A29 --- FileName The name of FITS file in subdirectory sp,
spectra from Piwnice Observatory will be
added later
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Acknowledgements:
Cezary Galan, Cezary.Galan(at)astri.uni.torun.pl
(End) Patricia Vannier [CDS] 02-Oct-2012