J/AJ/145/100 Differential BVR light curves of EP And (Lee+, 2013)
The eclipsing system EP Andromedae and its circumbinary companions.
Lee J.W., Hinse T.C., Park J.-H.
<Astron. J., 145, 100 (2013)>
=2013AJ....145..100L 2013AJ....145..100L
ADC_Keywords: Binaries, eclipsing ; Photometry, UBVRI ; Photometry, CCD
Keywords: binaries: close - binaries: eclipsing - stars: individual: EP And -
starspots
Abstract:
We present new long-term CCD photometry for EP And acquired during the
period 2007-2012. The light curves display total eclipses at primary
minima and season-to-season light variability. Our synthesis for all
available light curves indicates that the eclipsing pair is a W-type
overcontact binary with parameters of q=2.578, i=83.3°,
ΔT=27K, f=28%, and l3=2%-3%. The asymmetric light curves in
2007 were satisfactorily modeled by a cool spot on either of the
eclipsing components from a magnetic dynamo. Including our 95 timing
measurements, a total of 414 times of minimum light spanning about
82yr was used for a period study. A detailed analysis of the eclipse
timing diagram revealed that the orbital period of EP And has varied
as a combination of an upward-opening parabola and two periodic
variations, with cycle lengths of P3=44.6yr and P4=1.834yr and
semi-amplitudes of K3=0.0100days and K4=0.0039days, respectively.
The observed period increase at a fractional rate of +1.39*10-10 is
in excellent agreement with that calculated from the W-D code and can
be plausibly explained by some combination of mass transfer from the
primary to the secondary star and angular momentum loss due to
magnetic braking. The most reasonable explanation for both cycles is a
pair of light-travel-time effects driven by the possible existence of
a third and fourth component with projected masses of
M3=0.25M☉ and M4=0.90M☉. The more massive companion
could be revealed using high-resolution spectroscopic data extending
over the course of a few years and could also be a binary itself. It
is possible that the circumbinary objects may have played an important
role in the formation and evolution of the eclipsing pair, which would
cause it to have a short initial orbital period and thus evolve into
an overcontact configuration by angular momentum loss.
Description:
New CCD photometric observations of EP And were obtained on 2007 Oct
26-Nov 24 (SITe 2K CCD camera), 2008 Sep 30-Nov 4 (SITe 2K CCD
camera), 2009 Feb 8 (SITe 2K CCD camera), 2009 Sep 17-Nov 21 (FLI
IMG4301E 2K CCD camera), 2010 Nov 29 (FLI IMG4301E 2K CCD camera),
2011 Sep 22-Oct 18 (PIXIS: 2048B CCD camera), and 2012 Sep 25-Oct 19
(PIXIS: 2048B CCD camera) using CCD cameras and a BVR filter set
attached to the 61cm reflector at Sobaeksan Optical Astronomy
Observatory (SOAO) in Korea. The observations of the first two seasons
(2007 and 2008) were carried out to secure complete multiband light
curves (Table2) and the others to collect additional eclipse timings
(Table7).
Objects:
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RA (ICRS) DE Designation(s) (Period)
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01 42 29.32 +44 45 42.4 EP Andromedae = GSC 02827-00017 (P=0.404108)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 59 1012 CCD photometric data of EP And in 2007 and 2008
table7.dat 57 140 Observed photo-electric and CCD times of
minimum light for EP And
refs.dat 179 33 References
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See also:
B/gcvs : General Catalogue of Variable Stars (Samus+ 2007-2013)
V/119 : Catalogue of field contact binary stars (Pribulla+, 2003)
V/124 : Approximate elements of eclipsing binaries (Svechnikov+, 1990)
J/AJ/143/99 : Photometry of W UMa eclipsing binaries (Terrell+, 2012)
J/AJ/143/34 : SZ Her BVRI light curves (Lee+, 2012)
J/AJ/142/12 : WZ Cyg BVRI light curves (Lee+, 2011)
J/AJ/138/466 : NSVS variables automated classification (Hoffman+, 2009)
J/PASP/121/104 : BVRI differential photometry of GW Gem (Lee+, 2009)
J/AJ/138/478 : AR Boo differential BVR photometry (Lee+, 2009)
J/AJ/137/3181 : HW Vir differential VR light curves (Lee+, 2009)
J/MNRAS/379/1665 : XX Cep BVRI light curves (Lee+, 2007)
J/AJ/131/2986 : Multiplicity of contact binaries (Pribulla+, 2006)
J/A+A/446/785 : Catalogue of eclipsing variables (Malkov+, 2006)
J/AJ/131/621 : Catalog of 1022 bright contact binary stars (Gettel+, 2006)
http://www.aavso.org/ : AAVSO database
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d HDJ-B ? Heliocentric Julian Date of B band observation
15- 19 F5.3 mag DBmag [0.208/0.906]? Differential B band magnitude
21- 33 F13.5 d HDJ-V Heliocentric Julian Date of V band observation
35- 39 F5.3 mag DVmag [0.177/0.848] Differential V band magnitude
41- 53 F13.5 d HDJ-R ? Heliocentric Julian Date of R band observation
55- 59 F5.3 mag DRmag [0.148/0.809]? Differential R band magnitude
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Byte-by-byte Description of file: table7.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 --- Epoch [6392/33608.5] Epoch (number of cycles)
41- 48 F8.5 d O-C Timing residual from the full ephemeris
50- 51 A2 --- Min Type of minimum (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- 44 A18 --- Aut Author's name
46-179 A134 --- Com Comments
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 14-Apr-2014