J/AJ/147/42 V light curves of EP Cep, ES Cep, and V369 Cep (Zhu+, 2014)
Three close binaries in different evolutionary stages in the old open cluster
NGC 188.
Zhu L.Y., Qian S.B., Soonthornthum B., Liu L., He J.J., Liu N.P.,
Zhao E.G., Zhang J., Wang J.J.
<Astron. J., 147, 42 (2014)>
=2014AJ....147...42Z 2014AJ....147...42Z (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Binaries, eclipsing ; Photometry, UBV ;
Photometry, CCD
Keywords: binaries: close - binaries: eclipsing - stars: evolution -
stars: individual (EP Cep,ES Cep,V369 Cep)
Abstract:
NGC 188 is a good laboratory for studying the formation and evolution
of W UMa type contact binaries due to its rich populations of them. We
present a detailed photometric study of three short-period close
binaries, EP Cep, ES Cep, and V369 Cep, in the old open cluster NGC
188 based on our two-set photometric observations. We discovered that
both EP Cep and ES Cep are shallow-contact binaries with continuously
decreasing periods. The difference is in their mass ratios. EP Cep has
an extremely low-mass ratio, q=0.15, while ES Cep has a relatively
high-mass ratio, q=0.69, indicating that they lie in different
evolutionary stages. ES Cep is likely a newly formed contact binary
via a Case A mass transfer, while EP Cep is an evolved system and may
be on the oscillations caused by the combined effect of the thermal
relaxation oscillation and the variable angular momentum loss. For
another system, V369 Cep, we found that it is a primary-filling
near-contact binary. Both the semidetached configuration and the
continuous decrease in the orbital period indicate that it is
undergoing a mass transfer from the primary component to the secondary
one. This conclusion is in agreement with the excess luminosity seen
in the light curves on the ingress of the secondary minimum produced
by the impact of the mass transfer. All of the results suggest that
V369 Cep is evolving into contact, and a shallow-contact high-mass
ratio system similar to ES Cep will be formed. Then, it will evolve
into a low-mass ratio contact binary just like EP Cep, and finally
merge into a rapidly rotating single star.
Description:
With the 85cm reflecting telescope at Xinglong Station of the National
Astronomical Observatories (NAO), we acquired V-band observations of
the NGC 188 field on three nights (2009 November 18 and 2010 December
25 and 30). A 1024*1024 PI CCD camera and a standard Johnson-Cousins
multicolor filter system were used.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 43 3 Positions and periods
table1.dat 29 595 V-band CCD observations of EP Cep, ES Cep, and
V369 Cep in the old open cluster NGC 188
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See also:
B/gcvs : General Catalogue of Variable Stars (Samus+ 2007-2012)
B/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-2013)
II/185 : NGC 188 photographic UBV photom. star catalog (Frolov, 1990)
J/AJ/144/37 : BVRI photometry of the eclipsing binary BS Vul (Zhu+, 2012)
J/AJ/137/5086 : NGC 188 V12 VI light curves (Meibom+, 2009)
J/AJ/133/1409 : u'g'r'i'z' photometry in NGC 188 (Fornal+, 2007)
J/AJ/131/1565 : UBVI photometry of Berkeley 17 and NGC 188 (Krusberg+, 2006)
J/A+A/438/291 : X-ray sources in NGC 188 (Gondoin+, 2005)
J/PASP/116/1012 : A star catalog for the open cluster NGC 188 (Stetson+, 2004)
J/AJ/126/2922 : Astrometry and membership in NGC 188 (Platais+, 2003)
J/A+A/390/961 : VI photometry in NGC 188 (Andreuzzi+, 2002)
J/AJ/124/601 : Absolute positions & proper motions in NGC188 (Platais+ 2002)
J/AJ/118/2894 : UBVRI CCD photometry in NGC 188 (Sarajedini+, 1999)
Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Star name
10- 11 I2 h RAh Hour of Right Ascension (J2000) (1)
13- 14 I2 min RAm Minute of Right Ascension (J2000) (1)
16- 20 F5.2 s RAs Second of Right Ascension (J2000) (1)
22 A1 --- DE- Sign of the Declination (J2000) (1)
23- 24 I2 deg DEd Degree of Declination (J2000) (1)
26- 27 I2 arcmin DEm Arcminute of Declination (J2000) (1)
29- 32 F4.1 arcsec DEs Arcsecond of Declination (J2000) (1)
34- 43 F10.8 d Per Period
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Note (1): From SIMBAD database (http://simbad.u-strasbg.fr/simbad/).
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Star name (EP Cep, ES Cep, V369 Cep)
10- 23 F14.6 d HJD Heliocentric Julian Date
25- 29 F5.3 mag DVmag Differential Johnson V band magnitude
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 04-Sep-2014