J/AJ/149/194 Differential BVR light curves of DK Cyg (Lee+, 2015)
The physical nature and orbital behavior of the eclipsing system DK Cygni.
Lee J.W., Youn J.-H., Park J.-H., Wolf M.
<Astron. J., 149, 194 (2015)>
=2015AJ....149..194L 2015AJ....149..194L
ADC_Keywords: Binaries, eclipsing ; Photometry, UBVRI ; Photometry, CCD
Keywords: binaries: close - binaries: eclipsing -
stars: individual: DK Cyg - starspot
Abstract:
New CCD photometry is presented for the hot overcontact binary DK Cyg
together with reasonable explanations for the light and period
variations. Historical light and velocity curves from 1962 to 2012
were simultaneously analyzed with the Wilson-Devinney (W-D) synthesis
code. The brightness disturbances were satisfactorily modeled by
applying a magnetic cool spot on the primary star. Based on 261 times
of minimum light that include 116 new timings and span more than 87
years, a period study reveals that the orbital period has varied due
to a periodic oscillation superimposed on an upward parabola. The
period and semi-amplitude of the modulation are about 78.1years and
0.0037days, respectively. This detail is interpreted as a
light-travel-time effect due to a circumbinary companion with a
minimum mass of M3=0.065M☉, within the theoretical limit of
∼0.07M☉ for a brown dwarf star. The observed period increase at
a fractional rate of +2.74x10-10 is in excellent agreement with that
calculated from our W-D synthesis. Mass transfer from the secondary to
the primary component is mainly responsible for the secular period
change. We examined the evolutionary status of the DK Cyg system from
the absolute dimensions.
Description:
We carried out CCD photometry of DK Cyg on nine nights from 2012
September 20 through October 21 in order to obtain new multiband light
curves. The observations were taken with a PIXIS: 2048B CCD camera and
a BVR filter set attached to the 61 cm reflector at Sobaeksan Optical
Astronomy Observatory (SOAO) in Korea.
Objects:
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RA (ICRS) DE Designation(s) (Period)
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21 35 02.67 +34 35 45.4 V* DK Cyg = HIP 106574 (P=0.4706906)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 65 1478 CCD photometric observations of DK Cyg observed
at Sobaeksan Optical Astronomy Observatory (SOAO)
table6.dat 57 234 Observed photoelectric and CCD times of minimum
light for DK Cyg
refs.dat 110 58 References
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See also:
B/gcvs : General Catalogue of Variable Stars (Samus+ 2007-2013)
J/AJ/145/100 : Differential BVR light curves of EP And (Lee+, 2013)
J/A+A/289/137 : DK Cygni light curve (Awadalla, 1994)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d HJD-B Heliocentric Julian Date of B band observation
15- 21 F7.4 mag DBmag Differential B band magnitude (1)
23- 35 F13.5 d HJD-V ? Heliocentric Julian Date of V band observation
37- 43 F7.4 mag DVmag ? Differential V band magnitude (1)
45- 57 F13.5 d HJD-R ? Heliocentric Julian Date of R band observation
59- 65 F7.4 mag DRmag ? Differential R band magnitude (1)
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Note (1): TYC 2712-1372-1 was chosen as a comparison star.
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 11 F11.5 d HJD Heliocentric Julian Date (HJD-2400000)
13- 23 F11.5 d HJED Heliocentric Julian Ephemeris Date in the
Terrestrial Time (TT) scale (HJED-2400000)
25- 31 F7.5 d e_HJD ? Error in HJD
33- 39 F7.1 --- E [-4753/39989] Epoch (cycle)
41- 48 F8.5 d O-C [-0.005/0.004] The (O-C) residual
50- 51 A2 --- Min Minimum type (I or II)
53- 57 A5 --- Ref Reference; in refs.dat file
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Ref Reference identifier
7- 25 A19 --- BibCode Bibliographic code
27- 51 A25 --- Aut Author's name
53-110 A58 --- Com Comments
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 11-Jun-2015