Photometric investigation of the contact binary GU Orionis with high metallicity

Zhou, Xiao; Qian, Shengbang; Boonrucksar, Soonthornthum; Poshyachinda, Saran; Zhu, Li-Ying; Liu, Nian-Ping; Sarotsakulchai, Thawicharat; Fang, Xiao-Hui

doi:10.1093/pasj/psy084

Abstract

GU Ori was observed with the 1 m telescope at Yunnan Observatories in 2005. To determine its physical properties, the Wilson–Devinney program was used. The results reveal that GU Ori is a W-subtype shallow contact binary with a more massive but cooler second star. The masses of its two component stars are estimated to be M₁ = 0.45 M_⊙, M₂ = 1.05 M_⊙. The O’Connell effect was reported to be negative on the light curves observed in 2005. However, it changed to a positive one on the light curves observed from 2011 to 2012. The mean surface temperatures of star 2 (T₂) determined by the two sets of light curves were different, which may result from stellar activity. The O − C diagram shows that the period of GU Ori is decreasing at a rate of dP/dt = −6.24 × 10⁻⁸d yr⁻¹, which may be caused by mass transfer from star 2 to star 1 with a rate of |${dM_{2}}/{dt}= - 2.98\times {10^{-8}}\, M_{\odot }$| yr⁻¹. GU Ori is a contact binary with quite high metallicity.

1 Introduction

In the Universe, over 60% of stars are in binary or multiple systems. However, only a very small fraction (nearly 0.2%) of them have eclipses that can be observed from Earth (Guinan 2004). Eclipsing binaries are ideal targets for determining absolute parameters of stars when light curves and radial velocity curves are combined. The evolution of close binaries is more complex than that of single stars, since the evolution of the components will be highly affected by each other. Qian et al. (2018) divide the W UMa-type contact binaries into three groups: (1) long-period massive EWs with the same metallicities with lower log g than those of EAs with the same orbital period; (2) short-period less-massive EWs that have lower metallicities and higher log g; (3) EWs have higher metallicities that may be contaminated by the material from the evolution of compact companion objects. In the present work we focus on the contact binary GU Ori with high metallicity ([Fe/H] = 0.31). It belongs to the class of extreme Populaton I stars and is located in the spiral arm of the Milky Way galaxy. Qian et al. (2018) assumed that they may be contaminated by material from nearby compact objects. Many contact binaries are found to be accompanied by tertiary components (Zhou et al. 2015, 2016a, 2016b). Tokovinin (2018) updated the catalog of multiple stars. It is supposed that the tertiary component may accelerate the orbital evolution of the host binary through the Kozai mechanism (Kozai 1962; Fabrycky & Tremaine 2007) and shorten the pre-contact timescale of close binaries.

GU Ori was listed in the General Catalog of Variable Stars (GCVS; Samus et al. 2017) as an Algol-type variable star. Samolyk (1985) determined its period to be 0.470681 d and concluded that the period of GU Ori is not constant. However, it is listed as a W UMa-type contact binary in the International Variable Star Index (VSX; Watson et al. 2006), with photometric magnitude range from 12.5 to 13.3 mag in the V band, and a period of 0.4706769 d. Yang et al. (2017) claimed its spectral type to be G0V and published V and R_c light curve solutions. The spectrum of GU Ori was obtained on 2014 January 3 by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST; Su et al. 2012; Cui et al. 2012; Zhao et al. 2012; Luo et al. 2012, 2015; Deng et al. 2012), which determined its spectral type to be G1, effective temperature to be 6050 K, and metallicity ([Fe/H]) to be 0.31. In the present work the light curves and period variations of GU Ori are investigated to understand the theory of formation for contact binaries with high metallicity.

2 Photometric observations

GU Ori was observed on 2005 February 6 and 9 with the 1.0 m reflecting telescope at Yunnan Observatories, Chinese Academy of Sciences; the B, V, and R_c filters (Johnson–Cousins filter system) were used. The 1 m telescope has a field of view of about 6.5 arcmin². The exposure time was 140 s for all images. A total of 79 images in the B band, 78 images in the V band, and 77 images in the R_c band were obtained. One of the observational images is displayed in figure 1.

Fig. 1.

Observational image of GU Ori from 2005 February 6.

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All of the observational images were reduced with IRAF. UCAC4 514-020704 and UCAC4 515-021077 were chosen as the comparison star (C) and the check star (Ch), respectively. Differential aperture photometry method was applied to calculate light variations of GU Ori. GU Ori (V), UCAC4 514-020704 (C), and UCAC4 515-021077 (Ch) are marked in figure 1; their coordinates and V-band magnitudes are listed in table 1.

Table 1.

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Coordinates and V-band magnitudes.

Target	α_J2000.0	δ_J2000.0	V _mag
GU Ori	\|$06^{\rm h}10^{\rm m}04{^{\rm s}_{.}}621$\|	+12°\|$49^{\prime }46{^{\prime\prime}_{.}}63$\|	12.657
UCAC4 514-020704	\|$06^{\rm h}10^{\rm m}02{^{\rm s}_{.}}468$\|	+12°\|$47^{\prime }52{^{\prime\prime}_{.}}02$\|	12.953
UCAC4 515-021077	\|$06^{\rm h}10^{\rm m}08{^{\rm s}_{.}}639$\|	+12°\|$49^{\prime }47{^{\prime\prime}_{.}}32$\|	14.283

Target	α_J2000.0	δ_J2000.0	V _mag
GU Ori	\|$06^{\rm h}10^{\rm m}04{^{\rm s}_{.}}621$\|	+12°\|$49^{\prime }46{^{\prime\prime}_{.}}63$\|	12.657
UCAC4 514-020704	\|$06^{\rm h}10^{\rm m}02{^{\rm s}_{.}}468$\|	+12°\|$47^{\prime }52{^{\prime\prime}_{.}}02$\|	12.953
UCAC4 515-021077	\|$06^{\rm h}10^{\rm m}08{^{\rm s}_{.}}639$\|	+12°\|$49^{\prime }47{^{\prime\prime}_{.}}32$\|	14.283

Table 1.

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Coordinates and V-band magnitudes.

Target	α_J2000.0	δ_J2000.0	V _mag
GU Ori	\|$06^{\rm h}10^{\rm m}04{^{\rm s}_{.}}621$\|	+12°\|$49^{\prime }46{^{\prime\prime}_{.}}63$\|	12.657
UCAC4 514-020704	\|$06^{\rm h}10^{\rm m}02{^{\rm s}_{.}}468$\|	+12°\|$47^{\prime }52{^{\prime\prime}_{.}}02$\|	12.953
UCAC4 515-021077	\|$06^{\rm h}10^{\rm m}08{^{\rm s}_{.}}639$\|	+12°\|$49^{\prime }47{^{\prime\prime}_{.}}32$\|	14.283

Target	α_J2000.0	δ_J2000.0	V _mag
GU Ori	\|$06^{\rm h}10^{\rm m}04{^{\rm s}_{.}}621$\|	+12°\|$49^{\prime }46{^{\prime\prime}_{.}}63$\|	12.657
UCAC4 514-020704	\|$06^{\rm h}10^{\rm m}02{^{\rm s}_{.}}468$\|	+12°\|$47^{\prime }52{^{\prime\prime}_{.}}02$\|	12.953
UCAC4 515-021077	\|$06^{\rm h}10^{\rm m}08{^{\rm s}_{.}}639$\|	+12°\|$49^{\prime }47{^{\prime\prime}_{.}}32$\|	14.283

Two times of minimum light were determined, and the averaged values are listed in table 2. The first two columns are the observational times of minimum light and their errors. The lower-case “p” and “s” refer to the primary minimum and the secondary one. The filters used during the observations are listed in the fourth column.

Table 2.

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New CCD times of minimum light.

JD (Hel.)	Error (d)	p/s	Filter	Telescope*
2453408.1405	±0.0003	s	BVR_C	1 m
2453411.2031	±0.0003	p	BVR_C	1 m

*1 m denotes the 1 m reflecting telescope at Yunnan Observatories, Chinese Academy of Sciences.

Table 2.

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New CCD times of minimum light.

JD (Hel.)	Error (d)	p/s	Filter	Telescope*
2453408.1405	±0.0003	s	BVR_C	1 m
2453411.2031	±0.0003	p	BVR_C	1 m

*1 m denotes the 1 m reflecting telescope at Yunnan Observatories, Chinese Academy of Sciences.

Based on the primary minimum listed in table 2 and the period given out by VSX, the phases were calculated with the ephemeris:

\begin{equation} \mathrm{Min.I(HJD)} =2453411.2031(3)+0{^{\rm d}_{.}}4706769\times {E}. \end{equation}

(1)

The light variations are displayed in figure 2. The blue, green, and red colors refer to the light curves in the B, V, and R_c bands, respectively. V − C means the magnitude difference between the variable star and the comparison star. The light curve of V − C is shifted by 0.3 mag downward in the B band and 0.3 mag upward in the R_c band. C − Ch means the magnitude difference between the comparison star and the check star. The light curves of C − Ch are shifted by 0.7 mag, −0.2 mag, and −0.8 mag in the B, V, and R_c bands, respectively. As displayed in figure 2, the light curve of C − Ch in the B band has much larger scatter than those in the V and R_c bands. The check star, UCAC4 515-021077 (Ch), is much fainter than GU Ori (V) and the comparison star, UCAC4 514-020704 (C). The radiant flux in the V and R_c bands is much stronger than that in the B band for a late-type star.

Fig. 2.

The solid and open circles refer to data observed on 2005 February 6 and 9, respectively. (Color online)

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3 Orbital period investigation

Mass transfer and a tertiary component are quite common in contact binary systems, and cause the periods of contact binaries to change. The O − C method is usually used to detect the period variations. The photometric observation GU Ori has a long history and many times of minimum light have been published. They are listed in table 3.

Table 3.

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Available times of light minima for GU Ori.*

JD (Hel.) (2400000+)	p/s	Method	E	(O − C)	Error	Ref.^†	JD (Hel.) (2400000+)	p/s	Method	E	(O − C)	Error	Ref.^†
14718.2600	p	pg	−30993	−0.0278		(1)	50888.3750	p	ccd	45853	0.0583	0.0024	(4)
25235.4710	s	pg	−8648.5	0.0293		(1)	50897.3183	p	ccd	45872	0.0586	0.0003	(5)
25272.3660	p	pg	−8570	−0.0243		(1)	50904.3750	p	ccd	45887	0.0551	0.0005	(6)
25329.3450	p	pg	−8449	0.0022		(1)	51144.1871	s	ccd	46396.5	0.0547		(2)
25502.5960	p	pg	−8081	0.0422		(1)	51144.8938	p	ccd	46398	0.0554		(2)
25622.4070	s	pg	−7826.5	0.0647		(1)	51165.3671	s	ccd	46441.5	0.0540	0.0002	(6)
25643.3730	p	pg	−7782	0.0853		(1)	51165.6013	p	ccd	46442	0.0529	0.0003	(6)
25649.4570	p	pg	−7769	0.0505		(1)	51176.4278	p	ccd	46465	0.0537	0.0003	(6)
25651.3800	p	pg	−7765	0.0907		(1)	51225.3767	p	ccd	46569	0.0516	0.0002	(6)
25652.2920	p	pg	−7763	0.0614		(1)	51241.3810	p	ccd	46603	0.0528	0.0020	(7)
25671.3550	s	pg	−7722.5	0.0618		(1)	51481.4266	p	ccd	47113	0.0505	0.0009	(7)
25672.3280	s	pg	−7720.5	0.0934		(1)	51488.7227	s	ccd	47128.5	0.0511		(2)
26633.6250	p	pg	−5678	0.0224		(1)	51543.5568	p	ccd	47245	0.0507	0.0023	(7)
28127.5250	p	pg	−2504	−0.0223		(1)	51544.7311	s	ccd	47247.5	0.0483		(2)
29306.3400	s	pg	0.5	−0.0303		(1)	51568.2640	s	ccd	47297.5	0.0471	0.0001	(8)
30079.2300	s	pg	1642.5	−0.0002		(1)	51568.4986	p	ccd	47298	0.0464	0.0007	(8)
30705.5380	p	pg	2973	0.0654		(1)	51571.3231	p	ccd	47304	0.0468	0.0006	(8)
33570.5810	p	pg	9060	0.0671		(1)	51571.5555	s	ccd	47304.5	0.0438	0.0035	(8)
33922.6290	p	pg	9808	0.0449		(1)	51586.6216	s	ccd	47336.5	0.0481		(2)
35757.6260	s	pg	13706.5	0.0882		(1)	51592.2700	s	ccd	47348.5	0.0483	0.0023	(9)
36114.6240	p	pg	14465	0.0739		(1)	51602.6253	s	ccd	47370.5	0.0486		(2)
36163.5630	p	pg	14569	0.0619		(1)	51620.2764	p	ccd	47408	0.0491	0.0024	(9)
36607.4080	p	pg	15512	0.0538		(1)	51626.3930	p	ccd	47421	0.0469	0.0039	(10)
37588.6110	s	pg	17596.5	0.1202		(1)	51799.6057	p	ccd	47789	0.0486	0.0022	(10)
39531.3370	p	pg	21724	0.1062		(1)	51881.7348	s	ccd	47963.5	0.0437		(2)
39876.3610	p	pg	22457	0.1203		(1)	51898.4460	p	ccd	47999	0.0457	0.0016	(9)
43112.7290	p	pg	29333	0.0789		(1)	51912.5648	p	ccd	48029	0.0440		(2)
43933.3740	s	pg	31076.5	0.0898		(1)	51923.3900	p	ccd	48052	0.0435	0.0021	(9)
44171.5150	s	pg	31582.5	0.0657		(1)	51924.3332	p	ccd	48054	0.0454	0.0026	(11)
44254.3890	s	pg	31758.5	0.0997		(1)	51956.3386	p	ccd	48122	0.0444	0.0025	(9)
44256.4810	p	pg	31763	0.0736		(1)	52209.5612	p	ccd	48660	0.0401		(9)
44985.3470	s	pg	33311.5	0.0886		(1)	52279.4571	s	ccd	48808.5	0.0397	0.0005	(8)
45676.5290	p	pg	34780	0.0740		(1)	52312.6396	p	ccd	48879	0.0391		(2)
46005.5320	p	pg	35479	0.0703		(1)	52321.3465	s	ccd	48897.5	0.0384	0.0034	(9)
46036.3790	s	pg	35544.5	0.0877		(1)	52337.5850	p	ccd	48932	0.0384		(2)
46114.2760	p	pg	35710	0.0868		(1)	52609.8730	s	ccd	49510.5	0.0368		(2)
46321.6040	s	pg	36150.5	0.0794		(1)	52610.8135	s	ccd	49512.5	0.0360		(2)
46466.3390	p	pg	36458	0.0796		(1)	52619.5214	p	ccd	49531	0.0363	0.0004	(12)
46707.6010	s	pg	36970.5	0.1171		(1)	52625.8747	s	ccd	49544.5	0.0354		(2)
46746.6460	s	pg	37053.5	0.0955		(1)	52662.5902	s	ccd	49622.5	0.0377		(2)
46768.5030	p	pg	37100	0.0658		(1)	52669.6486	s	ccd	49637.5	0.0358		(2)
50120.2312	p	ccd	44221	0.0675	0.0025	(3)	52672.4735	s	ccd	49643.5	0.0366	0.0014	(11)
50138.3520	s	ccd	44259.5	0.0670	0.0031	(3)	52683.2987	s	ccd	49666.5	0.0362	0.0039	(11)
50139.2915	s	ccd	44261.5	0.0652	0.0020	(3)	52683.3004	s	ccd	49666.5	0.0379	0.0063	(11)
50147.2955	s	ccd	44278.5	0.0676	0.0035	(3)	52694.3591	p	ccd	49690	0.0355	0.0042	(11)
50163.2988	s	ccd	44312.5	0.0677	0.0021	(3)	52694.3596	p	ccd	49690	0.0360	0.0042	(11)
50773.5269	p	ccd	45609	0.0566	0.0014	(3)	52695.3015	p	ccd	49692	0.0366	0.0030	(11)
50839.4256	p	ccd	45749	0.0598	0.0021	(4)	52695.3022	p	ccd	49692	0.0373	0.0044	(11)
50863.4275	p	ccd	45800	0.0569	0.0003	(5)	52701.6544	s	ccd	49705.5	0.0353		(2)
50865.3103	p	ccd	45804	0.0570	0.0005	(5)	52723.3060	s	ccd	49751.5	0.0355	0.0034	(11)
52981.4722	p	ccd	50300	0.0326	0.0001	(13)	54845.3560	p	ccd	54260	0.0157	0.0005	(24)
52983.3553	p	ccd	50304	0.0330	0.0029	(11)	54846.0629	s	ccd	54261.5	0.0166		(2)
52983.3557	p	ccd	50304	0.0334	0.0029	(11)	54877.5967	s	ccd	54328.5	0.0147		(2)
52983.3561	p	ccd	50304	0.0338	0.0028	(11)	54888.6566	p	ccd	54352	0.0135	0.0004	(25)
52983.5916	s	ccd	50304.5	0.0339	0.0029	(11)	54890.7736	s	ccd	54356.5	0.0125	0.0004	(25)
52983.5918	s	ccd	50304.5	0.0341	0.0030	(11)	54905.6039	p	ccd	54388	0.0163		(1)
52983.5933	s	ccd	50304.5	0.0356	0.0029	(11)	55114.8208	s	ccd	54832.5	0.0150		(2)
53035.6009	p	ccd	50415	0.0329		(1)	55156.7104	s	ccd	54921.5	0.0139		(2)
53047.1311	s	ccd	50439.5	0.0314	0.0002	(14)	55181.4210	p	ccd	54974	0.0137		(1)
53314.9481	s	ccd	51008.5	0.0303		(1)	55206.6022	s	ccd	55027.5	0.0135		(2)
53323.8904	s	ccd	51027.5	0.0297		(1)	55210.6022	p	ccd	55036	0.0127		(2)
53368.6039	s	ccd	51122.5	0.0284		(1)	55253.6686	s	ccd	55127.5	0.0116		(2)
53408.1405	s	ccd	51206.5	0.0277	0.0003	(16)	55262.6120	s	ccd	55146.5	0.0121		(1)
53409.3196	p	ccd	51209	0.0301	0.0004	(17)	55263.5537	s	ccd	55148.5	0.0124		(1)
53411.2031	p	ccd	51213	0.0308	0.0003	(16)	55566.6698	s	ccd	55792.5	0.0093		(1)
53413.7883	s	ccd	51218.5	0.0273		(1)	55575.6091	s	ccd	55811.5	0.0057	0.0005	(26)
53435.6774	p	ccd	51265	0.0297		(1)	55577.9661	s	ccd	55816.5	0.0093	0.0003	(25)
53445.3257	s	ccd	51285.5	0.0290	0.0002	(17)	55581.9680	p	ccd	55825	0.0104	0.0004	(25)
53674.5457	s	ccd	51772.5	0.0269	0.0005	(17)	55631.6244	s	ccd	55930.5	0.0098		(1)
53717.3759	s	ccd	51863.5	0.0250	0.0001	(18)	55896.8518	p	ccd	56494	0.0079	0.0004	(27)
53735.7347	s	ccd	51902.5	0.0272		(1)	55920.1498	s	ccd	56543.5	0.0071	0.0003	(25)
53763.7384	p	ccd	51962	0.0253		(1)	55921.7978	p	ccd	56547	0.0078		(2)
54061.9119	s	ccd	52595.5	0.0218		(1)	55958.9822	p	ccd	56626	0.0083	0.0002	(25)
54091.3295	p	ccd	52658	0.0217	0.0016	(19)	55964.6295	p	ccd	56638	0.0074		(2)
54091.5641	s	ccd	52658.5	0.0210	0.0025	(19)	55981.3356	s	ccd	56673.5	0.0043		(2)
54105.6856	s	ccd	52688.5	0.0220		(1)	56217.8539	p	ccd	57176	0.0049		(2)
54107.5678	s	ccd	52692.5	0.0215		(1)	56221.8535	s	ccd	57184.5	0.0037		(2)
54107.8033	p	ccd	52693	0.0217		(1)	56256.9186	p	ccd	57259	0.0030	0.0003	(28)
54143.1051	p	ccd	52768	0.0223		(1)	56256.9207	p	ccd	57259	0.0051		(2)
54165.6978	p	ccd	52816	0.0223		(1)	56272.9166	p	ccd	57293	−0.0022	0.0017	(25)
54179.5823	s	ccd	52845.5	0.0217		(1)	56272.9218	p	ccd	57293	0.0030		(1)
54185.7023	s	ccd	52858.5	0.0228		(1)	56309.6355	p	ccd	57371	0.0034		(1)
54380.5621	s	ccd	53272.5	0.0203	0.0002	(20)	56325.6381	p	ccd	57405	0.0029		(1)
54476.3446	p	ccd	53476	0.0190	0.0019	(21)	56592.9812	p	ccd	57973	−0.0014		(25)
54476.5794	s	ccd	53476.5	0.0184	0.0010	(21)	56592.9843	p	ccd	57973	0.0017	0.0002	(1)
54496.5837	p	ccd	53519	0.0187		(1)	56715.5916	s	ccd	58233.5	−0.0037	0.0001	(25)
54500.3478	p	ccd	53527	0.0174	0.0005	(21)	56715.5940	s	ccd	58233.5	−0.0013		(1)
54505.2898	s	ccd	53537.5	0.0172	0.0005	(22)	56956.8175	p	ccd	58746	−0.0023		(1)
54520.5873	p	ccd	53570	0.0176		(1)	57316.8890	p	ccd	59511	−0.0025		(1)
54526.7072	p	ccd	53583	0.0186		(1)	57320.8881	s	ccd	59519.5	−0.0042		(1)
54800.8748	s	ccd	54165.5	0.0139	0.0004	(23)	57375.7239	p	ccd	59636	−0.0029		(1)

JD (Hel.) (2400000+)	p/s	Method	E	(O − C)	Error	Ref.^†	JD (Hel.) (2400000+)	p/s	Method	E	(O − C)	Error	Ref.^†
14718.2600	p	pg	−30993	−0.0278		(1)	50888.3750	p	ccd	45853	0.0583	0.0024	(4)
25235.4710	s	pg	−8648.5	0.0293		(1)	50897.3183	p	ccd	45872	0.0586	0.0003	(5)
25272.3660	p	pg	−8570	−0.0243		(1)	50904.3750	p	ccd	45887	0.0551	0.0005	(6)
25329.3450	p	pg	−8449	0.0022		(1)	51144.1871	s	ccd	46396.5	0.0547		(2)
25502.5960	p	pg	−8081	0.0422		(1)	51144.8938	p	ccd	46398	0.0554		(2)
25622.4070	s	pg	−7826.5	0.0647		(1)	51165.3671	s	ccd	46441.5	0.0540	0.0002	(6)
25643.3730	p	pg	−7782	0.0853		(1)	51165.6013	p	ccd	46442	0.0529	0.0003	(6)
25649.4570	p	pg	−7769	0.0505		(1)	51176.4278	p	ccd	46465	0.0537	0.0003	(6)
25651.3800	p	pg	−7765	0.0907		(1)	51225.3767	p	ccd	46569	0.0516	0.0002	(6)
25652.2920	p	pg	−7763	0.0614		(1)	51241.3810	p	ccd	46603	0.0528	0.0020	(7)
25671.3550	s	pg	−7722.5	0.0618		(1)	51481.4266	p	ccd	47113	0.0505	0.0009	(7)
25672.3280	s	pg	−7720.5	0.0934		(1)	51488.7227	s	ccd	47128.5	0.0511		(2)
26633.6250	p	pg	−5678	0.0224		(1)	51543.5568	p	ccd	47245	0.0507	0.0023	(7)
28127.5250	p	pg	−2504	−0.0223		(1)	51544.7311	s	ccd	47247.5	0.0483		(2)
29306.3400	s	pg	0.5	−0.0303		(1)	51568.2640	s	ccd	47297.5	0.0471	0.0001	(8)
30079.2300	s	pg	1642.5	−0.0002		(1)	51568.4986	p	ccd	47298	0.0464	0.0007	(8)
30705.5380	p	pg	2973	0.0654		(1)	51571.3231	p	ccd	47304	0.0468	0.0006	(8)
33570.5810	p	pg	9060	0.0671		(1)	51571.5555	s	ccd	47304.5	0.0438	0.0035	(8)
33922.6290	p	pg	9808	0.0449		(1)	51586.6216	s	ccd	47336.5	0.0481		(2)
35757.6260	s	pg	13706.5	0.0882		(1)	51592.2700	s	ccd	47348.5	0.0483	0.0023	(9)
36114.6240	p	pg	14465	0.0739		(1)	51602.6253	s	ccd	47370.5	0.0486		(2)
36163.5630	p	pg	14569	0.0619		(1)	51620.2764	p	ccd	47408	0.0491	0.0024	(9)
36607.4080	p	pg	15512	0.0538		(1)	51626.3930	p	ccd	47421	0.0469	0.0039	(10)
37588.6110	s	pg	17596.5	0.1202		(1)	51799.6057	p	ccd	47789	0.0486	0.0022	(10)
39531.3370	p	pg	21724	0.1062		(1)	51881.7348	s	ccd	47963.5	0.0437		(2)
39876.3610	p	pg	22457	0.1203		(1)	51898.4460	p	ccd	47999	0.0457	0.0016	(9)
43112.7290	p	pg	29333	0.0789		(1)	51912.5648	p	ccd	48029	0.0440		(2)
43933.3740	s	pg	31076.5	0.0898		(1)	51923.3900	p	ccd	48052	0.0435	0.0021	(9)
44171.5150	s	pg	31582.5	0.0657		(1)	51924.3332	p	ccd	48054	0.0454	0.0026	(11)
44254.3890	s	pg	31758.5	0.0997		(1)	51956.3386	p	ccd	48122	0.0444	0.0025	(9)
44256.4810	p	pg	31763	0.0736		(1)	52209.5612	p	ccd	48660	0.0401		(9)
44985.3470	s	pg	33311.5	0.0886		(1)	52279.4571	s	ccd	48808.5	0.0397	0.0005	(8)
45676.5290	p	pg	34780	0.0740		(1)	52312.6396	p	ccd	48879	0.0391		(2)
46005.5320	p	pg	35479	0.0703		(1)	52321.3465	s	ccd	48897.5	0.0384	0.0034	(9)
46036.3790	s	pg	35544.5	0.0877		(1)	52337.5850	p	ccd	48932	0.0384		(2)
46114.2760	p	pg	35710	0.0868		(1)	52609.8730	s	ccd	49510.5	0.0368		(2)
46321.6040	s	pg	36150.5	0.0794		(1)	52610.8135	s	ccd	49512.5	0.0360		(2)
46466.3390	p	pg	36458	0.0796		(1)	52619.5214	p	ccd	49531	0.0363	0.0004	(12)
46707.6010	s	pg	36970.5	0.1171		(1)	52625.8747	s	ccd	49544.5	0.0354		(2)
46746.6460	s	pg	37053.5	0.0955		(1)	52662.5902	s	ccd	49622.5	0.0377		(2)
46768.5030	p	pg	37100	0.0658		(1)	52669.6486	s	ccd	49637.5	0.0358		(2)
50120.2312	p	ccd	44221	0.0675	0.0025	(3)	52672.4735	s	ccd	49643.5	0.0366	0.0014	(11)
50138.3520	s	ccd	44259.5	0.0670	0.0031	(3)	52683.2987	s	ccd	49666.5	0.0362	0.0039	(11)
50139.2915	s	ccd	44261.5	0.0652	0.0020	(3)	52683.3004	s	ccd	49666.5	0.0379	0.0063	(11)
50147.2955	s	ccd	44278.5	0.0676	0.0035	(3)	52694.3591	p	ccd	49690	0.0355	0.0042	(11)
50163.2988	s	ccd	44312.5	0.0677	0.0021	(3)	52694.3596	p	ccd	49690	0.0360	0.0042	(11)
50773.5269	p	ccd	45609	0.0566	0.0014	(3)	52695.3015	p	ccd	49692	0.0366	0.0030	(11)
50839.4256	p	ccd	45749	0.0598	0.0021	(4)	52695.3022	p	ccd	49692	0.0373	0.0044	(11)
50863.4275	p	ccd	45800	0.0569	0.0003	(5)	52701.6544	s	ccd	49705.5	0.0353		(2)
50865.3103	p	ccd	45804	0.0570	0.0005	(5)	52723.3060	s	ccd	49751.5	0.0355	0.0034	(11)
52981.4722	p	ccd	50300	0.0326	0.0001	(13)	54845.3560	p	ccd	54260	0.0157	0.0005	(24)
52983.3553	p	ccd	50304	0.0330	0.0029	(11)	54846.0629	s	ccd	54261.5	0.0166		(2)
52983.3557	p	ccd	50304	0.0334	0.0029	(11)	54877.5967	s	ccd	54328.5	0.0147		(2)
52983.3561	p	ccd	50304	0.0338	0.0028	(11)	54888.6566	p	ccd	54352	0.0135	0.0004	(25)
52983.5916	s	ccd	50304.5	0.0339	0.0029	(11)	54890.7736	s	ccd	54356.5	0.0125	0.0004	(25)
52983.5918	s	ccd	50304.5	0.0341	0.0030	(11)	54905.6039	p	ccd	54388	0.0163		(1)
52983.5933	s	ccd	50304.5	0.0356	0.0029	(11)	55114.8208	s	ccd	54832.5	0.0150		(2)
53035.6009	p	ccd	50415	0.0329		(1)	55156.7104	s	ccd	54921.5	0.0139		(2)
53047.1311	s	ccd	50439.5	0.0314	0.0002	(14)	55181.4210	p	ccd	54974	0.0137		(1)
53314.9481	s	ccd	51008.5	0.0303		(1)	55206.6022	s	ccd	55027.5	0.0135		(2)
53323.8904	s	ccd	51027.5	0.0297		(1)	55210.6022	p	ccd	55036	0.0127		(2)
53368.6039	s	ccd	51122.5	0.0284		(1)	55253.6686	s	ccd	55127.5	0.0116		(2)
53408.1405	s	ccd	51206.5	0.0277	0.0003	(16)	55262.6120	s	ccd	55146.5	0.0121		(1)
53409.3196	p	ccd	51209	0.0301	0.0004	(17)	55263.5537	s	ccd	55148.5	0.0124		(1)
53411.2031	p	ccd	51213	0.0308	0.0003	(16)	55566.6698	s	ccd	55792.5	0.0093		(1)
53413.7883	s	ccd	51218.5	0.0273		(1)	55575.6091	s	ccd	55811.5	0.0057	0.0005	(26)
53435.6774	p	ccd	51265	0.0297		(1)	55577.9661	s	ccd	55816.5	0.0093	0.0003	(25)
53445.3257	s	ccd	51285.5	0.0290	0.0002	(17)	55581.9680	p	ccd	55825	0.0104	0.0004	(25)
53674.5457	s	ccd	51772.5	0.0269	0.0005	(17)	55631.6244	s	ccd	55930.5	0.0098		(1)
53717.3759	s	ccd	51863.5	0.0250	0.0001	(18)	55896.8518	p	ccd	56494	0.0079	0.0004	(27)
53735.7347	s	ccd	51902.5	0.0272		(1)	55920.1498	s	ccd	56543.5	0.0071	0.0003	(25)
53763.7384	p	ccd	51962	0.0253		(1)	55921.7978	p	ccd	56547	0.0078		(2)
54061.9119	s	ccd	52595.5	0.0218		(1)	55958.9822	p	ccd	56626	0.0083	0.0002	(25)
54091.3295	p	ccd	52658	0.0217	0.0016	(19)	55964.6295	p	ccd	56638	0.0074		(2)
54091.5641	s	ccd	52658.5	0.0210	0.0025	(19)	55981.3356	s	ccd	56673.5	0.0043		(2)
54105.6856	s	ccd	52688.5	0.0220		(1)	56217.8539	p	ccd	57176	0.0049		(2)
54107.5678	s	ccd	52692.5	0.0215		(1)	56221.8535	s	ccd	57184.5	0.0037		(2)
54107.8033	p	ccd	52693	0.0217		(1)	56256.9186	p	ccd	57259	0.0030	0.0003	(28)
54143.1051	p	ccd	52768	0.0223		(1)	56256.9207	p	ccd	57259	0.0051		(2)
54165.6978	p	ccd	52816	0.0223		(1)	56272.9166	p	ccd	57293	−0.0022	0.0017	(25)
54179.5823	s	ccd	52845.5	0.0217		(1)	56272.9218	p	ccd	57293	0.0030		(1)
54185.7023	s	ccd	52858.5	0.0228		(1)	56309.6355	p	ccd	57371	0.0034		(1)
54380.5621	s	ccd	53272.5	0.0203	0.0002	(20)	56325.6381	p	ccd	57405	0.0029		(1)
54476.3446	p	ccd	53476	0.0190	0.0019	(21)	56592.9812	p	ccd	57973	−0.0014		(25)
54476.5794	s	ccd	53476.5	0.0184	0.0010	(21)	56592.9843	p	ccd	57973	0.0017	0.0002	(1)
54496.5837	p	ccd	53519	0.0187		(1)	56715.5916	s	ccd	58233.5	−0.0037	0.0001	(25)
54500.3478	p	ccd	53527	0.0174	0.0005	(21)	56715.5940	s	ccd	58233.5	−0.0013		(1)
54505.2898	s	ccd	53537.5	0.0172	0.0005	(22)	56956.8175	p	ccd	58746	−0.0023		(1)
54520.5873	p	ccd	53570	0.0176		(1)	57316.8890	p	ccd	59511	−0.0025		(1)
54526.7072	p	ccd	53583	0.0186		(1)	57320.8881	s	ccd	59519.5	−0.0042		(1)
54800.8748	s	ccd	54165.5	0.0139	0.0004	(23)	57375.7239	p	ccd	59636	−0.0029		(1)

*Column 1: Heliocentric Julian date of observed minimum (HJD − 2400000). Column 2: Identification of primary (p) or secondary (s) minimum. Column 3: Method used to determined the time of light minimum— pg means observed by photograph; CCD refers to charge-coupled device. Column 4: Cycle numbers from the initial epoch. Column 5: The (O − C) values calculated from equation (2). Column 6: Observational error. Column 7: Reference for the time of light minimum.

^†Reference: (1) The O − C gateway; (2) BAV 〈http://www.bav-astro.eu/〉; (3) Safar and Zejda (2000a); (4) Safar and Zejda (2000b); (5) Agerer, Dahm, and Hubscher (1999); (6) Agerer, Dahm, and Hubscher (2001); (7) Safar and Zejda (2002); (8) Agerer and Hubscher (2002); (9) Brát, Zejda, and Svoboda (2007); (10) Zejda (2002); (11) Zejda (2004); (12) Agerer and Hubscher (2003); (13) Kotkova and Wolf (2006); (14) Krajci (2005); (15) Locher (2005); (16) this paper; (17) Zejda, Mikulasek, and Wolf (2006); (18) Hubscher, Paschke, and Walter (2006); (19) Hubscher and Walter (2007); (20) Borkovits et al. (2008); (21) Hubscher, Steinbach, and Walter (2009); (22) Diethelm (2008); (23) Diethelm (2009); (24) Hubscher et al. (2010); (25) Yang et al. (2017); (26) Diethelm (2011); (27) Diethelm (2012); (28) Diethelm (2013).

Table 3.

Open in new tab

Available times of light minima for GU Ori.*

JD (Hel.) (2400000+)	p/s	Method	E	(O − C)	Error	Ref.^†	JD (Hel.) (2400000+)	p/s	Method	E	(O − C)	Error	Ref.^†
14718.2600	p	pg	−30993	−0.0278		(1)	50888.3750	p	ccd	45853	0.0583	0.0024	(4)
25235.4710	s	pg	−8648.5	0.0293		(1)	50897.3183	p	ccd	45872	0.0586	0.0003	(5)
25272.3660	p	pg	−8570	−0.0243		(1)	50904.3750	p	ccd	45887	0.0551	0.0005	(6)
25329.3450	p	pg	−8449	0.0022		(1)	51144.1871	s	ccd	46396.5	0.0547		(2)
25502.5960	p	pg	−8081	0.0422		(1)	51144.8938	p	ccd	46398	0.0554		(2)
25622.4070	s	pg	−7826.5	0.0647		(1)	51165.3671	s	ccd	46441.5	0.0540	0.0002	(6)
25643.3730	p	pg	−7782	0.0853		(1)	51165.6013	p	ccd	46442	0.0529	0.0003	(6)
25649.4570	p	pg	−7769	0.0505		(1)	51176.4278	p	ccd	46465	0.0537	0.0003	(6)
25651.3800	p	pg	−7765	0.0907		(1)	51225.3767	p	ccd	46569	0.0516	0.0002	(6)
25652.2920	p	pg	−7763	0.0614		(1)	51241.3810	p	ccd	46603	0.0528	0.0020	(7)
25671.3550	s	pg	−7722.5	0.0618		(1)	51481.4266	p	ccd	47113	0.0505	0.0009	(7)
25672.3280	s	pg	−7720.5	0.0934		(1)	51488.7227	s	ccd	47128.5	0.0511		(2)
26633.6250	p	pg	−5678	0.0224		(1)	51543.5568	p	ccd	47245	0.0507	0.0023	(7)
28127.5250	p	pg	−2504	−0.0223		(1)	51544.7311	s	ccd	47247.5	0.0483		(2)
29306.3400	s	pg	0.5	−0.0303		(1)	51568.2640	s	ccd	47297.5	0.0471	0.0001	(8)
30079.2300	s	pg	1642.5	−0.0002		(1)	51568.4986	p	ccd	47298	0.0464	0.0007	(8)
30705.5380	p	pg	2973	0.0654		(1)	51571.3231	p	ccd	47304	0.0468	0.0006	(8)
33570.5810	p	pg	9060	0.0671		(1)	51571.5555	s	ccd	47304.5	0.0438	0.0035	(8)
33922.6290	p	pg	9808	0.0449		(1)	51586.6216	s	ccd	47336.5	0.0481		(2)
35757.6260	s	pg	13706.5	0.0882		(1)	51592.2700	s	ccd	47348.5	0.0483	0.0023	(9)
36114.6240	p	pg	14465	0.0739		(1)	51602.6253	s	ccd	47370.5	0.0486		(2)
36163.5630	p	pg	14569	0.0619		(1)	51620.2764	p	ccd	47408	0.0491	0.0024	(9)
36607.4080	p	pg	15512	0.0538		(1)	51626.3930	p	ccd	47421	0.0469	0.0039	(10)
37588.6110	s	pg	17596.5	0.1202		(1)	51799.6057	p	ccd	47789	0.0486	0.0022	(10)
39531.3370	p	pg	21724	0.1062		(1)	51881.7348	s	ccd	47963.5	0.0437		(2)
39876.3610	p	pg	22457	0.1203		(1)	51898.4460	p	ccd	47999	0.0457	0.0016	(9)
43112.7290	p	pg	29333	0.0789		(1)	51912.5648	p	ccd	48029	0.0440		(2)
43933.3740	s	pg	31076.5	0.0898		(1)	51923.3900	p	ccd	48052	0.0435	0.0021	(9)
44171.5150	s	pg	31582.5	0.0657		(1)	51924.3332	p	ccd	48054	0.0454	0.0026	(11)
44254.3890	s	pg	31758.5	0.0997		(1)	51956.3386	p	ccd	48122	0.0444	0.0025	(9)
44256.4810	p	pg	31763	0.0736		(1)	52209.5612	p	ccd	48660	0.0401		(9)
44985.3470	s	pg	33311.5	0.0886		(1)	52279.4571	s	ccd	48808.5	0.0397	0.0005	(8)
45676.5290	p	pg	34780	0.0740		(1)	52312.6396	p	ccd	48879	0.0391		(2)
46005.5320	p	pg	35479	0.0703		(1)	52321.3465	s	ccd	48897.5	0.0384	0.0034	(9)
46036.3790	s	pg	35544.5	0.0877		(1)	52337.5850	p	ccd	48932	0.0384		(2)
46114.2760	p	pg	35710	0.0868		(1)	52609.8730	s	ccd	49510.5	0.0368		(2)
46321.6040	s	pg	36150.5	0.0794		(1)	52610.8135	s	ccd	49512.5	0.0360		(2)
46466.3390	p	pg	36458	0.0796		(1)	52619.5214	p	ccd	49531	0.0363	0.0004	(12)
46707.6010	s	pg	36970.5	0.1171		(1)	52625.8747	s	ccd	49544.5	0.0354		(2)
46746.6460	s	pg	37053.5	0.0955		(1)	52662.5902	s	ccd	49622.5	0.0377		(2)
46768.5030	p	pg	37100	0.0658		(1)	52669.6486	s	ccd	49637.5	0.0358		(2)
50120.2312	p	ccd	44221	0.0675	0.0025	(3)	52672.4735	s	ccd	49643.5	0.0366	0.0014	(11)
50138.3520	s	ccd	44259.5	0.0670	0.0031	(3)	52683.2987	s	ccd	49666.5	0.0362	0.0039	(11)
50139.2915	s	ccd	44261.5	0.0652	0.0020	(3)	52683.3004	s	ccd	49666.5	0.0379	0.0063	(11)
50147.2955	s	ccd	44278.5	0.0676	0.0035	(3)	52694.3591	p	ccd	49690	0.0355	0.0042	(11)
50163.2988	s	ccd	44312.5	0.0677	0.0021	(3)	52694.3596	p	ccd	49690	0.0360	0.0042	(11)
50773.5269	p	ccd	45609	0.0566	0.0014	(3)	52695.3015	p	ccd	49692	0.0366	0.0030	(11)
50839.4256	p	ccd	45749	0.0598	0.0021	(4)	52695.3022	p	ccd	49692	0.0373	0.0044	(11)
50863.4275	p	ccd	45800	0.0569	0.0003	(5)	52701.6544	s	ccd	49705.5	0.0353		(2)
50865.3103	p	ccd	45804	0.0570	0.0005	(5)	52723.3060	s	ccd	49751.5	0.0355	0.0034	(11)
52981.4722	p	ccd	50300	0.0326	0.0001	(13)	54845.3560	p	ccd	54260	0.0157	0.0005	(24)
52983.3553	p	ccd	50304	0.0330	0.0029	(11)	54846.0629	s	ccd	54261.5	0.0166		(2)
52983.3557	p	ccd	50304	0.0334	0.0029	(11)	54877.5967	s	ccd	54328.5	0.0147		(2)
52983.3561	p	ccd	50304	0.0338	0.0028	(11)	54888.6566	p	ccd	54352	0.0135	0.0004	(25)
52983.5916	s	ccd	50304.5	0.0339	0.0029	(11)	54890.7736	s	ccd	54356.5	0.0125	0.0004	(25)
52983.5918	s	ccd	50304.5	0.0341	0.0030	(11)	54905.6039	p	ccd	54388	0.0163		(1)
52983.5933	s	ccd	50304.5	0.0356	0.0029	(11)	55114.8208	s	ccd	54832.5	0.0150		(2)
53035.6009	p	ccd	50415	0.0329		(1)	55156.7104	s	ccd	54921.5	0.0139		(2)
53047.1311	s	ccd	50439.5	0.0314	0.0002	(14)	55181.4210	p	ccd	54974	0.0137		(1)
53314.9481	s	ccd	51008.5	0.0303		(1)	55206.6022	s	ccd	55027.5	0.0135		(2)
53323.8904	s	ccd	51027.5	0.0297		(1)	55210.6022	p	ccd	55036	0.0127		(2)
53368.6039	s	ccd	51122.5	0.0284		(1)	55253.6686	s	ccd	55127.5	0.0116		(2)
53408.1405	s	ccd	51206.5	0.0277	0.0003	(16)	55262.6120	s	ccd	55146.5	0.0121		(1)
53409.3196	p	ccd	51209	0.0301	0.0004	(17)	55263.5537	s	ccd	55148.5	0.0124		(1)
53411.2031	p	ccd	51213	0.0308	0.0003	(16)	55566.6698	s	ccd	55792.5	0.0093		(1)
53413.7883	s	ccd	51218.5	0.0273		(1)	55575.6091	s	ccd	55811.5	0.0057	0.0005	(26)
53435.6774	p	ccd	51265	0.0297		(1)	55577.9661	s	ccd	55816.5	0.0093	0.0003	(25)
53445.3257	s	ccd	51285.5	0.0290	0.0002	(17)	55581.9680	p	ccd	55825	0.0104	0.0004	(25)
53674.5457	s	ccd	51772.5	0.0269	0.0005	(17)	55631.6244	s	ccd	55930.5	0.0098		(1)
53717.3759	s	ccd	51863.5	0.0250	0.0001	(18)	55896.8518	p	ccd	56494	0.0079	0.0004	(27)
53735.7347	s	ccd	51902.5	0.0272		(1)	55920.1498	s	ccd	56543.5	0.0071	0.0003	(25)
53763.7384	p	ccd	51962	0.0253		(1)	55921.7978	p	ccd	56547	0.0078		(2)
54061.9119	s	ccd	52595.5	0.0218		(1)	55958.9822	p	ccd	56626	0.0083	0.0002	(25)
54091.3295	p	ccd	52658	0.0217	0.0016	(19)	55964.6295	p	ccd	56638	0.0074		(2)
54091.5641	s	ccd	52658.5	0.0210	0.0025	(19)	55981.3356	s	ccd	56673.5	0.0043		(2)
54105.6856	s	ccd	52688.5	0.0220		(1)	56217.8539	p	ccd	57176	0.0049		(2)
54107.5678	s	ccd	52692.5	0.0215		(1)	56221.8535	s	ccd	57184.5	0.0037		(2)
54107.8033	p	ccd	52693	0.0217		(1)	56256.9186	p	ccd	57259	0.0030	0.0003	(28)
54143.1051	p	ccd	52768	0.0223		(1)	56256.9207	p	ccd	57259	0.0051		(2)
54165.6978	p	ccd	52816	0.0223		(1)	56272.9166	p	ccd	57293	−0.0022	0.0017	(25)
54179.5823	s	ccd	52845.5	0.0217		(1)	56272.9218	p	ccd	57293	0.0030		(1)
54185.7023	s	ccd	52858.5	0.0228		(1)	56309.6355	p	ccd	57371	0.0034		(1)
54380.5621	s	ccd	53272.5	0.0203	0.0002	(20)	56325.6381	p	ccd	57405	0.0029		(1)
54476.3446	p	ccd	53476	0.0190	0.0019	(21)	56592.9812	p	ccd	57973	−0.0014		(25)
54476.5794	s	ccd	53476.5	0.0184	0.0010	(21)	56592.9843	p	ccd	57973	0.0017	0.0002	(1)
54496.5837	p	ccd	53519	0.0187		(1)	56715.5916	s	ccd	58233.5	−0.0037	0.0001	(25)
54500.3478	p	ccd	53527	0.0174	0.0005	(21)	56715.5940	s	ccd	58233.5	−0.0013		(1)
54505.2898	s	ccd	53537.5	0.0172	0.0005	(22)	56956.8175	p	ccd	58746	−0.0023		(1)
54520.5873	p	ccd	53570	0.0176		(1)	57316.8890	p	ccd	59511	−0.0025		(1)
54526.7072	p	ccd	53583	0.0186		(1)	57320.8881	s	ccd	59519.5	−0.0042		(1)
54800.8748	s	ccd	54165.5	0.0139	0.0004	(23)	57375.7239	p	ccd	59636	−0.0029		(1)

JD (Hel.) (2400000+)	p/s	Method	E	(O − C)	Error	Ref.^†	JD (Hel.) (2400000+)	p/s	Method	E	(O − C)	Error	Ref.^†
14718.2600	p	pg	−30993	−0.0278		(1)	50888.3750	p	ccd	45853	0.0583	0.0024	(4)
25235.4710	s	pg	−8648.5	0.0293		(1)	50897.3183	p	ccd	45872	0.0586	0.0003	(5)
25272.3660	p	pg	−8570	−0.0243		(1)	50904.3750	p	ccd	45887	0.0551	0.0005	(6)
25329.3450	p	pg	−8449	0.0022		(1)	51144.1871	s	ccd	46396.5	0.0547		(2)
25502.5960	p	pg	−8081	0.0422		(1)	51144.8938	p	ccd	46398	0.0554		(2)
25622.4070	s	pg	−7826.5	0.0647		(1)	51165.3671	s	ccd	46441.5	0.0540	0.0002	(6)
25643.3730	p	pg	−7782	0.0853		(1)	51165.6013	p	ccd	46442	0.0529	0.0003	(6)
25649.4570	p	pg	−7769	0.0505		(1)	51176.4278	p	ccd	46465	0.0537	0.0003	(6)
25651.3800	p	pg	−7765	0.0907		(1)	51225.3767	p	ccd	46569	0.0516	0.0002	(6)
25652.2920	p	pg	−7763	0.0614		(1)	51241.3810	p	ccd	46603	0.0528	0.0020	(7)
25671.3550	s	pg	−7722.5	0.0618		(1)	51481.4266	p	ccd	47113	0.0505	0.0009	(7)
25672.3280	s	pg	−7720.5	0.0934		(1)	51488.7227	s	ccd	47128.5	0.0511		(2)
26633.6250	p	pg	−5678	0.0224		(1)	51543.5568	p	ccd	47245	0.0507	0.0023	(7)
28127.5250	p	pg	−2504	−0.0223		(1)	51544.7311	s	ccd	47247.5	0.0483		(2)
29306.3400	s	pg	0.5	−0.0303		(1)	51568.2640	s	ccd	47297.5	0.0471	0.0001	(8)
30079.2300	s	pg	1642.5	−0.0002		(1)	51568.4986	p	ccd	47298	0.0464	0.0007	(8)
30705.5380	p	pg	2973	0.0654		(1)	51571.3231	p	ccd	47304	0.0468	0.0006	(8)
33570.5810	p	pg	9060	0.0671		(1)	51571.5555	s	ccd	47304.5	0.0438	0.0035	(8)
33922.6290	p	pg	9808	0.0449		(1)	51586.6216	s	ccd	47336.5	0.0481		(2)
35757.6260	s	pg	13706.5	0.0882		(1)	51592.2700	s	ccd	47348.5	0.0483	0.0023	(9)
36114.6240	p	pg	14465	0.0739		(1)	51602.6253	s	ccd	47370.5	0.0486		(2)
36163.5630	p	pg	14569	0.0619		(1)	51620.2764	p	ccd	47408	0.0491	0.0024	(9)
36607.4080	p	pg	15512	0.0538		(1)	51626.3930	p	ccd	47421	0.0469	0.0039	(10)
37588.6110	s	pg	17596.5	0.1202		(1)	51799.6057	p	ccd	47789	0.0486	0.0022	(10)
39531.3370	p	pg	21724	0.1062		(1)	51881.7348	s	ccd	47963.5	0.0437		(2)
39876.3610	p	pg	22457	0.1203		(1)	51898.4460	p	ccd	47999	0.0457	0.0016	(9)
43112.7290	p	pg	29333	0.0789		(1)	51912.5648	p	ccd	48029	0.0440		(2)
43933.3740	s	pg	31076.5	0.0898		(1)	51923.3900	p	ccd	48052	0.0435	0.0021	(9)
44171.5150	s	pg	31582.5	0.0657		(1)	51924.3332	p	ccd	48054	0.0454	0.0026	(11)
44254.3890	s	pg	31758.5	0.0997		(1)	51956.3386	p	ccd	48122	0.0444	0.0025	(9)
44256.4810	p	pg	31763	0.0736		(1)	52209.5612	p	ccd	48660	0.0401		(9)
44985.3470	s	pg	33311.5	0.0886		(1)	52279.4571	s	ccd	48808.5	0.0397	0.0005	(8)
45676.5290	p	pg	34780	0.0740		(1)	52312.6396	p	ccd	48879	0.0391		(2)
46005.5320	p	pg	35479	0.0703		(1)	52321.3465	s	ccd	48897.5	0.0384	0.0034	(9)
46036.3790	s	pg	35544.5	0.0877		(1)	52337.5850	p	ccd	48932	0.0384		(2)
46114.2760	p	pg	35710	0.0868		(1)	52609.8730	s	ccd	49510.5	0.0368		(2)
46321.6040	s	pg	36150.5	0.0794		(1)	52610.8135	s	ccd	49512.5	0.0360		(2)
46466.3390	p	pg	36458	0.0796		(1)	52619.5214	p	ccd	49531	0.0363	0.0004	(12)
46707.6010	s	pg	36970.5	0.1171		(1)	52625.8747	s	ccd	49544.5	0.0354		(2)
46746.6460	s	pg	37053.5	0.0955		(1)	52662.5902	s	ccd	49622.5	0.0377		(2)
46768.5030	p	pg	37100	0.0658		(1)	52669.6486	s	ccd	49637.5	0.0358		(2)
50120.2312	p	ccd	44221	0.0675	0.0025	(3)	52672.4735	s	ccd	49643.5	0.0366	0.0014	(11)
50138.3520	s	ccd	44259.5	0.0670	0.0031	(3)	52683.2987	s	ccd	49666.5	0.0362	0.0039	(11)
50139.2915	s	ccd	44261.5	0.0652	0.0020	(3)	52683.3004	s	ccd	49666.5	0.0379	0.0063	(11)
50147.2955	s	ccd	44278.5	0.0676	0.0035	(3)	52694.3591	p	ccd	49690	0.0355	0.0042	(11)
50163.2988	s	ccd	44312.5	0.0677	0.0021	(3)	52694.3596	p	ccd	49690	0.0360	0.0042	(11)
50773.5269	p	ccd	45609	0.0566	0.0014	(3)	52695.3015	p	ccd	49692	0.0366	0.0030	(11)
50839.4256	p	ccd	45749	0.0598	0.0021	(4)	52695.3022	p	ccd	49692	0.0373	0.0044	(11)
50863.4275	p	ccd	45800	0.0569	0.0003	(5)	52701.6544	s	ccd	49705.5	0.0353		(2)
50865.3103	p	ccd	45804	0.0570	0.0005	(5)	52723.3060	s	ccd	49751.5	0.0355	0.0034	(11)
52981.4722	p	ccd	50300	0.0326	0.0001	(13)	54845.3560	p	ccd	54260	0.0157	0.0005	(24)
52983.3553	p	ccd	50304	0.0330	0.0029	(11)	54846.0629	s	ccd	54261.5	0.0166		(2)
52983.3557	p	ccd	50304	0.0334	0.0029	(11)	54877.5967	s	ccd	54328.5	0.0147		(2)
52983.3561	p	ccd	50304	0.0338	0.0028	(11)	54888.6566	p	ccd	54352	0.0135	0.0004	(25)
52983.5916	s	ccd	50304.5	0.0339	0.0029	(11)	54890.7736	s	ccd	54356.5	0.0125	0.0004	(25)
52983.5918	s	ccd	50304.5	0.0341	0.0030	(11)	54905.6039	p	ccd	54388	0.0163		(1)
52983.5933	s	ccd	50304.5	0.0356	0.0029	(11)	55114.8208	s	ccd	54832.5	0.0150		(2)
53035.6009	p	ccd	50415	0.0329		(1)	55156.7104	s	ccd	54921.5	0.0139		(2)
53047.1311	s	ccd	50439.5	0.0314	0.0002	(14)	55181.4210	p	ccd	54974	0.0137		(1)
53314.9481	s	ccd	51008.5	0.0303		(1)	55206.6022	s	ccd	55027.5	0.0135		(2)
53323.8904	s	ccd	51027.5	0.0297		(1)	55210.6022	p	ccd	55036	0.0127		(2)
53368.6039	s	ccd	51122.5	0.0284		(1)	55253.6686	s	ccd	55127.5	0.0116		(2)
53408.1405	s	ccd	51206.5	0.0277	0.0003	(16)	55262.6120	s	ccd	55146.5	0.0121		(1)
53409.3196	p	ccd	51209	0.0301	0.0004	(17)	55263.5537	s	ccd	55148.5	0.0124		(1)
53411.2031	p	ccd	51213	0.0308	0.0003	(16)	55566.6698	s	ccd	55792.5	0.0093		(1)
53413.7883	s	ccd	51218.5	0.0273		(1)	55575.6091	s	ccd	55811.5	0.0057	0.0005	(26)
53435.6774	p	ccd	51265	0.0297		(1)	55577.9661	s	ccd	55816.5	0.0093	0.0003	(25)
53445.3257	s	ccd	51285.5	0.0290	0.0002	(17)	55581.9680	p	ccd	55825	0.0104	0.0004	(25)
53674.5457	s	ccd	51772.5	0.0269	0.0005	(17)	55631.6244	s	ccd	55930.5	0.0098		(1)
53717.3759	s	ccd	51863.5	0.0250	0.0001	(18)	55896.8518	p	ccd	56494	0.0079	0.0004	(27)
53735.7347	s	ccd	51902.5	0.0272		(1)	55920.1498	s	ccd	56543.5	0.0071	0.0003	(25)
53763.7384	p	ccd	51962	0.0253		(1)	55921.7978	p	ccd	56547	0.0078		(2)
54061.9119	s	ccd	52595.5	0.0218		(1)	55958.9822	p	ccd	56626	0.0083	0.0002	(25)
54091.3295	p	ccd	52658	0.0217	0.0016	(19)	55964.6295	p	ccd	56638	0.0074		(2)
54091.5641	s	ccd	52658.5	0.0210	0.0025	(19)	55981.3356	s	ccd	56673.5	0.0043		(2)
54105.6856	s	ccd	52688.5	0.0220		(1)	56217.8539	p	ccd	57176	0.0049		(2)
54107.5678	s	ccd	52692.5	0.0215		(1)	56221.8535	s	ccd	57184.5	0.0037		(2)
54107.8033	p	ccd	52693	0.0217		(1)	56256.9186	p	ccd	57259	0.0030	0.0003	(28)
54143.1051	p	ccd	52768	0.0223		(1)	56256.9207	p	ccd	57259	0.0051		(2)
54165.6978	p	ccd	52816	0.0223		(1)	56272.9166	p	ccd	57293	−0.0022	0.0017	(25)
54179.5823	s	ccd	52845.5	0.0217		(1)	56272.9218	p	ccd	57293	0.0030		(1)
54185.7023	s	ccd	52858.5	0.0228		(1)	56309.6355	p	ccd	57371	0.0034		(1)
54380.5621	s	ccd	53272.5	0.0203	0.0002	(20)	56325.6381	p	ccd	57405	0.0029		(1)
54476.3446	p	ccd	53476	0.0190	0.0019	(21)	56592.9812	p	ccd	57973	−0.0014		(25)
54476.5794	s	ccd	53476.5	0.0184	0.0010	(21)	56592.9843	p	ccd	57973	0.0017	0.0002	(1)
54496.5837	p	ccd	53519	0.0187		(1)	56715.5916	s	ccd	58233.5	−0.0037	0.0001	(25)
54500.3478	p	ccd	53527	0.0174	0.0005	(21)	56715.5940	s	ccd	58233.5	−0.0013		(1)
54505.2898	s	ccd	53537.5	0.0172	0.0005	(22)	56956.8175	p	ccd	58746	−0.0023		(1)
54520.5873	p	ccd	53570	0.0176		(1)	57316.8890	p	ccd	59511	−0.0025		(1)
54526.7072	p	ccd	53583	0.0186		(1)	57320.8881	s	ccd	59519.5	−0.0042		(1)
54800.8748	s	ccd	54165.5	0.0139	0.0004	(23)	57375.7239	p	ccd	59636	−0.0029		(1)

*Column 1: Heliocentric Julian date of observed minimum (HJD − 2400000). Column 2: Identification of primary (p) or secondary (s) minimum. Column 3: Method used to determined the time of light minimum— pg means observed by photograph; CCD refers to charge-coupled device. Column 4: Cycle numbers from the initial epoch. Column 5: The (O − C) values calculated from equation (2). Column 6: Observational error. Column 7: Reference for the time of light minimum.

^†Reference: (1) The O − C gateway; (2) BAV 〈http://www.bav-astro.eu/〉; (3) Safar and Zejda (2000a); (4) Safar and Zejda (2000b); (5) Agerer, Dahm, and Hubscher (1999); (6) Agerer, Dahm, and Hubscher (2001); (7) Safar and Zejda (2002); (8) Agerer and Hubscher (2002); (9) Brát, Zejda, and Svoboda (2007); (10) Zejda (2002); (11) Zejda (2004); (12) Agerer and Hubscher (2003); (13) Kotkova and Wolf (2006); (14) Krajci (2005); (15) Locher (2005); (16) this paper; (17) Zejda, Mikulasek, and Wolf (2006); (18) Hubscher, Paschke, and Walter (2006); (19) Hubscher and Walter (2007); (20) Borkovits et al. (2008); (21) Hubscher, Steinbach, and Walter (2009); (22) Diethelm (2008); (23) Diethelm (2009); (24) Hubscher et al. (2010); (25) Yang et al. (2017); (26) Diethelm (2011); (27) Diethelm (2012); (28) Diethelm (2013).

The O − C gateway¹ is a database that collects times of minima of eclipsing binaries, and includes GU Ori. The initial epoch and period published in the O − C gateway are used:

\begin{equation} \mathrm{Min.I(HJD)} = 2429306.135+0.^{\!\!\!\rm d}470682\times {E}. \end{equation}

(2)

As shown in figure 3, the period of GU Ori is not constant. According to the result calculated by Yang et al. (2017), the parabola goes upward when only CCD (charge-coupled device) data are used. However, the parabola goes downward when pg (photographic) data are considered. The only reasonable explanation is that a cyclic variation exists. Therefore, a long-term increase (or decrease) and periodic variations are superposed on the linear ephemeris,

\begin{equation} O - C = \Delta T_0 + \Delta P_0\times E +\frac{1}{2} \frac{dP}{dE}\times E^2 + \tau , \end{equation}

(3)

where ΔT₀ and ΔP₀ are corrections to the initial epoch and period, the quadratic term refers to secular variation, and τ is the periodic variation. The periodic term is explained in detail by Irwin (1952). We assume a circular orbit in the present work.

Fig. 3.

The open and solid circles represent times of light minimum observed by pg and CCD, respectively. In the upper panel, the blue line refers to the parabolic variation. The fit residuals are displayed at the bottom. (Color online)

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Based on the least-squares method, the new ephemeris is determined as

\begin{eqnarray} \mathrm{Min. I} &=& 2429306.19455(\pm 0.00006)\nonumber\\ && +\, 0.470683791(\pm 0.000000003)\times {E} \nonumber \\ && -\, 4.0226(\pm 0.0069)\times {10^{-11}}\times {E^{2}} \nonumber \\ && +\, 0.02744(\pm 0.00004)\sin [0{^{\circ}_{.}}00662(\pm 0{^{\circ}_{.}}00005)\nonumber\\ && \times \, {E}+238{^{\circ}_{.}}25(\pm 0{^{\circ}_{.}}08)] \end{eqnarray}

(4)

According to the new ephemeris, the period of GU Ori is decreasing continuously at a rate of dP/dt = −6.24 × 10⁻⁸ d yr⁻¹, and a cyclic change is revealed.

4 Analysis of light curves

To model the light curves of GU Ori and determine its physical properties, the Wilson–Devinney program (Van Hamme & Wilson 2007; Wilson 2012) was used. Since GU Ori has EW-type light curves, Mode 3 for contact binaries with both component stars filling their Roche lobe was applied. According to the spectral information obtained by LAMOST, the mean surface temperature of the star eclipsed at the primary minimum was set to be T₁ = 6050 K. The gravity-darkening coefficients, the bolometric albedo coefficients, and the limb-darkening coefficients were adopted accordingly (Lucy 1967; Ruciński 1969; Van Hamme 1993).

First, the q-search method was used to determine the initial mass ratio of GU Ori, in which q was set from 0.02 to 9. The step was 0.02 while q ranges from 0.02 to 1, and 0.05 when q ranges from 1 to 9. The results are plotted in the left part of figure 4, and show two minima at q = 0.44 and q = 2.40. Then the initial mass ratio of q = 2.40 was adopted and set as a free parameter. The final values of all the adjustable parameters are listed in the second column of table 4. The corresponding theoretical light curves based on the determined parameters and the fitting results are displayed in figure 5.

Fig. 4.

The q-search diagram. Left panel: q-search results based on the data of the 1 m telescope at Yunnan Observations, Chinese Academy of Sciences. Right panel: q-search results based on the data published by Yang et al. (2017).

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Fig. 5.

The solid circles are the B-, V-, and R_c-band light curves obtained by the 1 m telescope at Yunnan Observations, Chinese Academy of Sciences. The colored lines are the theoretical light curves. The colored crosses in the lower part are the residuals. (Color online)

Open in new tab Download slide

Table 4.

Open in new tab

Photometric solutions of GU Ori.

Parameters	1 m data	Yang et al. (2017)
T ₁ (K)	6050(fixed)	6050(fixed)
q (M₂/M₁)	2.32(±0.05)	2.35(±0.06)
i (°)	83.3(±0.4)	83.7(±0.5)
Ω_in	5.68	5.68
Ω_out	5.08	5.08
Ω₁ = Ω₂	5.59(±0.07)	5.58(±0.09)
T ₂ (K)	6021(±68)	5846(±16)
ΔT (K)	29	204
T ₂/T₁	0.995(±0.011)	0.966(±0.003)
L ₁/(L₁ + L₂) (B)	0.326(±0.009)	—
L ₁/(L₁ + L₂) (V)	0.325(±0.012)	0.354(±0.001)
L ₁/(L₁ + L₂) (R_c)	0.324(±0.006)	0.349(±0.001)
r ₁ (pole)	0.297(±0.003)	0.301(±0.003)
r ₁ (side)	0.311(±0.004)	0.315(±0.003)
r ₁ (back)	0.350(±0.006)	0.358(±0.004)
r ₂ (pole)	0.434(±0.007)	0.439(±0.009)
r ₂ (side)	0.465(±0.009)	0.471(±0.012)
r ₂ (back)	0.495(±0.013)	0.502(±0.017)
f	17.7 %( ±11.2%)	26.5 %( ±14.8%)
Spot 1
θ (°)	142.2(±3.3)	7.3(±3.4)
ψ (°)	33.6(±9.0)	275.4(±8.8)
r (rad)	0.67(±0.05)	0.67(±0.15)
T_f	0.82(fixed)	0.82(fixed)
Spot 2
θ (°)	36.8(±5.9)	—
ψ (°)	188.1(±4.0)	—
r (rad)	0.54(±0.14)	—
T_f	0.81(fixed)	—
Σω(O − C)²	0.000967	0.001486

Parameters	1 m data	Yang et al. (2017)
T ₁ (K)	6050(fixed)	6050(fixed)
q (M₂/M₁)	2.32(±0.05)	2.35(±0.06)
i (°)	83.3(±0.4)	83.7(±0.5)
Ω_in	5.68	5.68
Ω_out	5.08	5.08
Ω₁ = Ω₂	5.59(±0.07)	5.58(±0.09)
T ₂ (K)	6021(±68)	5846(±16)
ΔT (K)	29	204
T ₂/T₁	0.995(±0.011)	0.966(±0.003)
L ₁/(L₁ + L₂) (B)	0.326(±0.009)	—
L ₁/(L₁ + L₂) (V)	0.325(±0.012)	0.354(±0.001)
L ₁/(L₁ + L₂) (R_c)	0.324(±0.006)	0.349(±0.001)
r ₁ (pole)	0.297(±0.003)	0.301(±0.003)
r ₁ (side)	0.311(±0.004)	0.315(±0.003)
r ₁ (back)	0.350(±0.006)	0.358(±0.004)
r ₂ (pole)	0.434(±0.007)	0.439(±0.009)
r ₂ (side)	0.465(±0.009)	0.471(±0.012)
r ₂ (back)	0.495(±0.013)	0.502(±0.017)
f	17.7 %( ±11.2%)	26.5 %( ±14.8%)
Spot 1
θ (°)	142.2(±3.3)	7.3(±3.4)
ψ (°)	33.6(±9.0)	275.4(±8.8)
r (rad)	0.67(±0.05)	0.67(±0.15)
T_f	0.82(fixed)	0.82(fixed)
Spot 2
θ (°)	36.8(±5.9)	—
ψ (°)	188.1(±4.0)	—
r (rad)	0.54(±0.14)	—
T_f	0.81(fixed)	—
Σω(O − C)²	0.000967	0.001486

Table 4.

Open in new tab

Photometric solutions of GU Ori.

Parameters	1 m data	Yang et al. (2017)
T ₁ (K)	6050(fixed)	6050(fixed)
q (M₂/M₁)	2.32(±0.05)	2.35(±0.06)
i (°)	83.3(±0.4)	83.7(±0.5)
Ω_in	5.68	5.68
Ω_out	5.08	5.08
Ω₁ = Ω₂	5.59(±0.07)	5.58(±0.09)
T ₂ (K)	6021(±68)	5846(±16)
ΔT (K)	29	204
T ₂/T₁	0.995(±0.011)	0.966(±0.003)
L ₁/(L₁ + L₂) (B)	0.326(±0.009)	—
L ₁/(L₁ + L₂) (V)	0.325(±0.012)	0.354(±0.001)
L ₁/(L₁ + L₂) (R_c)	0.324(±0.006)	0.349(±0.001)
r ₁ (pole)	0.297(±0.003)	0.301(±0.003)
r ₁ (side)	0.311(±0.004)	0.315(±0.003)
r ₁ (back)	0.350(±0.006)	0.358(±0.004)
r ₂ (pole)	0.434(±0.007)	0.439(±0.009)
r ₂ (side)	0.465(±0.009)	0.471(±0.012)
r ₂ (back)	0.495(±0.013)	0.502(±0.017)
f	17.7 %( ±11.2%)	26.5 %( ±14.8%)
Spot 1
θ (°)	142.2(±3.3)	7.3(±3.4)
ψ (°)	33.6(±9.0)	275.4(±8.8)
r (rad)	0.67(±0.05)	0.67(±0.15)
T_f	0.82(fixed)	0.82(fixed)
Spot 2
θ (°)	36.8(±5.9)	—
ψ (°)	188.1(±4.0)	—
r (rad)	0.54(±0.14)	—
T_f	0.81(fixed)	—
Σω(O − C)²	0.000967	0.001486

Parameters	1 m data	Yang et al. (2017)
T ₁ (K)	6050(fixed)	6050(fixed)
q (M₂/M₁)	2.32(±0.05)	2.35(±0.06)
i (°)	83.3(±0.4)	83.7(±0.5)
Ω_in	5.68	5.68
Ω_out	5.08	5.08
Ω₁ = Ω₂	5.59(±0.07)	5.58(±0.09)
T ₂ (K)	6021(±68)	5846(±16)
ΔT (K)	29	204
T ₂/T₁	0.995(±0.011)	0.966(±0.003)
L ₁/(L₁ + L₂) (B)	0.326(±0.009)	—
L ₁/(L₁ + L₂) (V)	0.325(±0.012)	0.354(±0.001)
L ₁/(L₁ + L₂) (R_c)	0.324(±0.006)	0.349(±0.001)
r ₁ (pole)	0.297(±0.003)	0.301(±0.003)
r ₁ (side)	0.311(±0.004)	0.315(±0.003)
r ₁ (back)	0.350(±0.006)	0.358(±0.004)
r ₂ (pole)	0.434(±0.007)	0.439(±0.009)
r ₂ (side)	0.465(±0.009)	0.471(±0.012)
r ₂ (back)	0.495(±0.013)	0.502(±0.017)
f	17.7 %( ±11.2%)	26.5 %( ±14.8%)
Spot 1
θ (°)	142.2(±3.3)	7.3(±3.4)
ψ (°)	33.6(±9.0)	275.4(±8.8)
r (rad)	0.67(±0.05)	0.67(±0.15)
T_f	0.82(fixed)	0.82(fixed)
Spot 2
θ (°)	36.8(±5.9)	—
ψ (°)	188.1(±4.0)	—
r (rad)	0.54(±0.14)	—
T_f	0.81(fixed)	—
Σω(O − C)²	0.000967	0.001486

Yang et al. (2017) also published the light curve solutions for GU Ori. They obtained the minimum at q = 0.45 when the q-search method was applied. Using the data published by them, we produced the q-search diagram displayed in the right panel of figure 4. Two minima at q = 0.44 and q = 2.35 are visible, which is consistent with the result determined using the light curve data observed by the 1 m telescope at Yunnan Observations, Chinese Academy of Sciences. The sulution is listed in the third column of table 4. The light curve fits are shown in figure 6. We usually get two minima when the q-search method is applied, and the two q values are inverses. The deeper minimum is usually chosen. The two ambiguity solutions correspond to A or W configuration and produce the same mass, radius, and luminosity for the two components. However, the temperature and star eclipsed at the primary minimum are different. For q = 0.44, the massive star is mistaken as the star eclipsed at the primary minimum and the temperature of the massive star is higher. In fact, it is a W-subtype system so that the less massive but hotter star is the star eclipsed at the primary minimum.

Fig. 6.

The solid circles are the V- and R_c-band light curves published by Yang et al. (2017). The green and red lines are the theoretical light curves. The colored crosses in the lower part are the residuals. (Color online)

Open in new tab Download slide

5 Discussions and conclusions

In the present work, two sets of light curves of GU Ori are analyzed with the Wilson–Devinney program, and its basic physical parameters are determined. GU Ori is a totally eclipsing binary, and the parameters determined have very high confidence (Terrell & Wilson 2005). The mass ratio and orbital inclination calculated from the two sets of light curves are almost the same, which means that the two separated observations produce consistent results. The fill-out factor determined here is a little higher than that determined by Yang et al. (2017), which may be caused by mass transfer from star 2 to star 1. In 2005, the temperature difference between the two stars was only 29 K. However, the difference has become quite large (204 K) several years later. Since GU Ori is a solar-type contact binary, spots are common on its component stars. The spots’ parameters are listed in table 4. The stellar activities may result in the changes of the determined mean surface temperature of the secondary star (T₂). The average temperature of star 2 is 5934(42) K, and the mass of star 2 is estimated to be 1.05 M_⊙ (Cox 2000). Then, the absolute parameters of the two component stars were calculated and are listed in table 5. The orbital semi-major axis is 2.92 R_⊙.

Table 5.

Open in new tab

Absolute elements of the primary and secondary stars in GU Ori.

Parameters	Star 1	Star 2
M	0.45 M_⊙	1.05 M_⊙
R	0.95 R_⊙	1.3 R_⊙
L	1.09 L_⊙	2.10 L_⊙

Table 5.

Open in new tab

Absolute elements of the primary and secondary stars in GU Ori.

Parameters	Star 1	Star 2
M	0.45 M_⊙	1.05 M_⊙
R	0.95 R_⊙	1.3 R_⊙
L	1.09 L_⊙	2.10 L_⊙

The O’Connell effect appears in late-type contact binaries commonly. It is suggested that it is closely related to magnetic activity of the component stars (Wang et al. 2015; Zhou et al. 2016c), circumstellar material around the binary system (Liu & Yang 2003), or mass transfer between the component stars (Shaw et al. 1990). For GU Ori, a negative O’Connell effect was reported for the light curves obtained in 2005, in which the light maxima after the secondary minima (Max II) were brighter than the light maxima at phase 0.25 (Max I). The differences between the two light maxima (Max I − Max II) are 0.037 mag in the B band, 0.033 mag in the V band, and 0.030 mag in the R_c band. However, the O’Connell effect changed to a positive one with Max I − Max II of −0.026 mag in the V band and −0.022 mag in the R_c band for the light curves obtained by Yang et al. (2017). The O’Connell effect on GU Ori may be related to stellar activities (Zhou et al. 2016d).

The period investigation of Yang et al. (2017) showed that the period of GU Ori was increasing at a rate of dP/dt = +1.45 × 10⁻⁷ d yr⁻¹. However, only times of light minima observed by the CCD method were used in their work. In our O − C diagram, times of light minima obtained by the photographic method are also used. Although the pg data do not have as high accuracy as the CCD data, they do show a downward tendency, while the variation tendency is upward when only CCD data are used. Therefore, the pg data are very important when the period variation of GU Ori is investigated since they will give a quite different result, as show in figure 3. The mass transfer from the more massive star to the smaller one is supposed to explain the long-term period decrease (dP/dt = −6.24 × 10⁻⁸ d yr⁻¹), with its rate being |${dM_{2}}/{dt}= - 2.98\times {10^{-8}}\, M_{\odot }$| yr⁻¹. Also, a cyclic period change is revealed, which may be caused by the light-travel-time effect of a tertiary component.

W UMa-type contact binary stars may evolve from short-period detached binaries, over quite a long pre-contact evolution timescale (Stȩpień 2006, 2011; Yıldız & Doğan 2013; Yıldız 2014). Nuclear and angular momentum evolution play very important roles during the evolution stage from detached to contact status (Hilditch et al. 1988). Thus, most research work has focused on the two evolutionary mechanisms. Nowadays, LAMOST have obtained atmosphere parameters for thousands of contact binaries, which attract our research interest. The statistical research shows that the atmosphere parameters of contact binaries may also give us some important information on their formation and evolution. The high metallicity is a key factor in selecting a group of binary systems, in which GU Ori is a sample. Qian et al. (2018) pointed out that a contact binary with high metallicity may be contaminated by a compact object during its evolution lifetime. In the case of UX Eri ([Fe/H] = 0.45), the mass of the tertiary is estimated to be less than 0.56 M_⊙ (Qian et al. 2007). The tertiary component may have shortened its pre-contact evolution time (Qian et al. 2013). GU Ori is also a contact binary with quite high metallicity ([Fe/H] = 0.31). Its formation and evolution may be different from that of UX Eri. The cyclic period change implies that there may be a tertiary component orbiting GU Ori. However, third light is not detected in the light curves. The information is insufficient to estimate the parameters of the tertiary component, and more evidence is needed to confirm whether GU Ori is really contaminated by a tertiary component. The present work is just the beginning, and more and more contact binaries with high metallicity will be investigated carefully in the future, which will shed new light on the research of contact binaries.

Acknowledgements

We thank the referee for valuable comments that have improved the quality of the present work. This work is partly supported by the Chinese Natural Science Foundation (Grant Nos. 11703080 and 11703082) and the Yunnan Natural Science Foundation (No. 2018FB006). Guoshoujing Telescope (the Large Sky Area Multi-Object Fiber Spectroscopic Telescope LAMOST) is a National Major Scientific Project built by the Chinese Academy of Sciences. Funding for the project has been provided by the National Development and Reform Commission. LAMOST is operated and managed by the National Astronomical Observatories, Chinese Academy of Sciences. This work is part of the research activities at the National Astronomical Research Institute of Thailand (Public Organization).

Footnotes

1

〈http://var2.astro.cz/ocgate/〉

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Article Contents

Photometric investigation of the contact binary GU Orionis with high metallicity

Abstract

1 Introduction

2 Photometric observations

3 Orbital period investigation

4 Analysis of light curves

5 Discussions and conclusions

Acknowledgements

Footnotes

References

Citations

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Article Contents

Photometric investigation of the contact binary GU Orionis with high metallicity

Abstract

1 Introduction

2 Photometric observations

3 Orbital period investigation

4 Analysis of light curves

5 Discussions and conclusions

Acknowledgements

Footnotes

References

Citations

Views

Altmetric

Email alerts

Astrophysics Data System

Citing articles via

Latest

Most Read

Most Cited

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