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. =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{deg}, {Delta}T=27K, f=28%, and l_3_=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 P_3_=44.6yr and P_4_=1.834yr and semi-amplitudes of K_3_=0.0100days and K_4_=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 M_3_=0.25M_{sun}_ and M_4_=0.90M_{sun}_. 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: ------------------------------------------------------------------------- RA (ICRS) DE Designation(s) (Period) ------------------------------------------------------------------------- 01 42 29.32 +44 45 42.4 EP Andromedae = GSC 02827-00017 (P=0.404108) ------------------------------------------------------------------------- File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- Byte-by-byte Description of file: table7.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- Byte-by-byte Description of file: refs.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 5 A5 --- Ref Reference identifier 7- 25 A19 --- BibCode Bibliographic code 27- 44 A18 --- Aut Author's name 46-179 A134 --- Com Comments -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 14-Apr-2014