Observations and light curve solutions of a selection of shallow-contact W UMa binaries

New Astronomy 62 (2018) 46–54

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Observations and light curve solutions of a selection of shallow-contact W UMa binaries

T

⁎

Diana P. Kjurkchieva ,a, Velimir A. Popova,b, Doroteya L. Vasilevaa, Nikola I. Petrovc a

Department of Physics and Astronomy, Shumen University, Shumen, Bulgaria IRIDA Observatory, Rozhen NAO, Bulgaria c Institute of Astronomy and NAO, Bulgarian Academy of Sciences, Sofia, Bulgaria b

A R T I C L E I N F O

A B S T R A C T

Keywords: Binaries Eclipsing binaries Close binaries Contact stars Fundamental parameters

Photometric observations in Sloan g′ and i′ bands of the W UMa binaries V0951 Per, CSS J062803.2+571604, CSS J222157.2+275308, CSS J075135.6+382028, V0338 Dra, NSVS 2256852, NSVS 4666412, V1355 Tau, NSVS 4808227, NSVS 4726498, CSS J075350.1+264830 and HL Lyn are presented. The light curve solutions revealed that these binaries have overcontact configurations with small fillout factors (within 0.1–0.2). Seven of them undergo total eclipses and their photometric mass ratios should be accepted with confidence. The temperature differences of the components of CSS J062803.2+571604 and NSVS 2256852 exceed 1100 K which is unusual for overcontact binaries. We suspect that NSVS 2256852 is a probable candidate for merger due to its small mass ratio of q = 0.16 and to the registered decreasing of the orbital period.

1. Introduction A remarkable feature of the low-temperature contact binaries is that the temperatures of their components are close to equal (typically to < 5%) while their masses may differ by a factor of 5 or more (Yakut and Eggleton, 2005). This means existence of effective heat transfer between the two components which photospheres are situated between the inner and outer Lagrangian equipotential surfaces. It is supposed that such short-period binaries, known as W UMa systems, result from the evolution of wide binaries by angular momentum and mass loss and/or tidal forces (Qian, 2003; Stepien, 2006; Ivanova, 2013) and that they ultimately evolve into single stars (Webbink, 1976; Rasio, 1995). Binnendijk (1970) introduced subdivision of contact binary stars in A and W sub-types based on the main criterion: for A-type binary the hotter component is the larger star; for W-type binary the hotter component is the smaller star. The last ones are recognized by the primary minima which are occultations (indicating that the small components are the hotter ones). Additional criteria for the W/A subclassification were found Rucinski (1973, 1974): (i) the A type systems are of earlier spectral type than the W type binaries which components are of G and K spectral type; (ii) the W-type binaries have shorter periods of 0.22 to 0.4 day (Smith, 1984); (iii) the mass ratios of A type are smaller than those of W type. The study of W UMa stars is essential for modern astrophysics

⁎

because they are probes for investigation of the processes of tidal interactions, mass loss and mass transfer, angular momentum loss, merging or fusion of the stars (Martin et al., 2011). According to the thermal relaxation oscillation (TRO) model each component of the W UMa stars is out of thermal equilibrium and oscillates around the inner Roche lobe (Lucy, 1976; Flannery, 1976; Robertson and Eggleton, 1977; Yakut and Eggleton, 2005). The binary spends a part of its present life in contact and the rest as a semi-detached binary, slowly evolving towards an extreme mass ratio system (Webbink, 1976). The alternative model (Stepien, 2004; 2006; 2009; 2011) assumes that each component is in thermal equilibrium and mass transfer occurs with the mass ratio reversal, similarly as in Algol-type binaries, following the Roche lobe overflow by the massive component. Besides the mechanism of energy transfer another important debatable problem of the W UMa stars is the W phenomenon (the hotter component is the smaller star). The study of the nature and evolution of W UMa stars requires a knowledge of their fundamental parameters. In this paper we present photometric observations and light curve solutions of twelve such systems. A goal of the investigation was determination of their parameters by light curve solutions of our data. The results can be used to improve the empirical relations of short-period W UMa-type systems. Table 1 presents the coordinates and available information for the light variability of the selected targets: V0951 Per, CSS J062803.2+571604, CSS J222157.2+275308, CSS J075135.6+382028, V0338 Dra, NSVS

Corresponding author. E-mail address: [email protected] (D.P. Kjurkchieva).

https://doi.org/10.1016/j.newast.2018.01.008 Received 6 December 2017; Received in revised form 11 January 2018; Accepted 16 January 2018 1384-1076/ © 2018 Elsevier B.V. All rights reserved.

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Table 1 Parameters of our targets from the VSX database. Target

RA

V0951 Per CSS J062803.2+571604 CSS J222157.2+275308 CSS J075135.6+382028 V0338 Dra NSVS 2256852 NSVS 4666412 V1355 Tau NSVS 4808227 NSVS 4726498 CSS J075350.1+264830 HL Lyn

04 06 22 07 15 05 07 05 08 07 07 07

Dec

10 28 21 51 49 32 18 02 24 52 53 47

36.31 03.28 57.26 35.65 11.14 55.08 38.88 06.82 03.60 36.20 50.14 50.30

+34 +57 +27 +38 +60 +54 +50 +24 +38 +38 +26 +41

02 16 53 20 38 19 47 27 31 35 48 05

58.1 04.0 08.0 28.8 02.9 25.0 54.1 39.7 19.2 13.8 30.4 21.8

Period [d]

mag

Ampl [mag]

0.27047879 0.322424 0.352348 0.352572 0.235149 0.34888808 0.28316697 0.24467 0.396217 0.31175 0.260686 0.292166

12.70 (R) 13.53 (CV) 15.72 (CV) 14.24 (CV) 13.3 (R1) 12.16 (R1) 13.73 (R1) 13.6 (V) 12.024 (R1) 13.65 (R1) 13.90 (CV) 13.37 (CV)

0.5 0.17 0.6 0.84 0.6 0.47 0.85 0.7 0.68 1.01 0.68 0.53

Table 2 Log of our photometric observations. Target

Date

V0951 Per

2015 2015 2015 2015 2014 2016 2016 2016 2016 2016 2016 2016 2016 2016 2016 2016 2016 2016 2016 2016 2016 2014 2014 2014 2016 2016 2014 2014 2014 2016 2016 2016 2016 2016 2014 2014 2016 2016 2016 2016 2016 2016 2016 2016 2017 2017 2016 2017

CSS J062803.2+571604 CSS J222157.2+275308

CSS J075135.6+382028

V0338 Dra

NSVS 2256852

NSVS 4666412

V1355 Tau

NSVS 4808227

NSVS 4726498

CSS J075350.1+264830

HL Lyn

Dec 15 Dec 18 Dec 19 Dec 20 Dec 24 Sep 22 Sep 23 Sep 24 Sep 27 Sep 29 Sep 30 Oct 1 Feb 9 Feb 15 Feb 28 Mar 6 Mar 17 Mar 18 Jul 7 Jul 8 Jul 9 Dec 12 Dec 13 Dec 18 Jan 28 Jan 29 Feb 3 Feb 6 Feb 7 No. 21 No. 22 No. 23 Mar 20 Mar 31 Apr 2 Apr 3 Feb 9 Feb 15 Feb 28 Mar 6 Mar 17 Mar 18 Dec 23 Dec 25 Jan 2 Jan 25 Jan 26 Jan 27

Exposure (g′, i′) [sec]

Number (g′, i′)

Mean error (g′, i′) [mag]

60, 120 60, 120 60, 120 60, 120 150, 150 120, 120 120, 120 120, 120 240, – 240, – –, 300 –, 300 180, 240 180, 240 180, 240 180, 240 180, 240 180, 240 150, 150 150, 150 150, 150 60, 90 60, 90 60, 90 180, 240 180, 240 180, 240 180, 240 180, 240 120, 150 120, 150 120, 150 90, 180 90, 180 90, 180 90, 180 180, 240 180, 240 180, 240 180, 240 180, 240 180, 240 150, 180 150, 180 150, 180 150, 150 150, 150 150, 150

139, 138 137, 136 77, 80 150, 150 114, 116 62, 58 79, 78 98, 94 57, – 108, – –, 87 –, 88 40, 40 63, 62 35, 34 35, 35 48, 48 59, 56 55, 55 25, 24 56, 55 142, 169 107, 122 146, 103 46, 46 18, 17 39, 38 68, 68 72, 72 73, 73 14, 14 84, 84 72, 72 71, 70 39, 38 70, 69 40, 40 63, 62 35, 34 36, 37 48, 48 59, 58 40, 40 58, 58 99, 99 48, 48 57, 57 102, 102

0.006, 0.005 0.007, 0.006 0.015, 0.010 0.007, 0.006 0.004, 0.008 0.033, 0.054 0.019, 0.039 0.031, 0.060 0.020, – 0.012, – –, 0.022 –, 0.022 0.007, 0.011 0.008, 0.013 0.010, 0.015 0.007, 0.013 0.010, 0.012 0.015, 0.017 0.005, 0.007 0.006, 0.008 0.006, 0.008 0.002, 0.004 0.002, 0.004 0.004, 0.005 0.005, 0.007 0.009, 0.009 0.006, 0.008 0.005, 0.006 0.005, 0.006 0.007, 0.008 0.007, 0.008 0.007, 0.008 0.004, 0.004 0.003, 0.004 0.006, 0.007 0.003, 0.004 0.005, 0.007 0.005, 0.007 0.006, 0.008 0.005, 0.009 0.007, 0.008 0.009, 0.009 0.007, 0.010 0.012, 0.017 0.007, 0.010 0.005, 0.010 0.009, 0.015 0.005, 0.009

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Table 3 Values of the fitted parameters. Star

T0

P

Ω

q

i

T2PH

V0951 Per CSS J062803.2+571604 CSS J222157.2+275308 CSS J075135.6+382028 V0338 Dra NSVS 2256852 NSVS 4666412 V1355 Tau NSVS 4808227 NSVS 4726498 CSS J075350.1+264830 HL Lyn

2457372.219220(88) 2457016.426883(399) 2457654.334683(117) 2457434.537818(145) 2457577.586477(95) 2457006.428722(121) 2457422.338250(182) 2457714.538030(109) 2457468.483974(196) 2457434.334605(120) 2457747.550252(144) 2457780.378047(86)

0.2704755(4) 0.3224327(5) 0.3523398(2) 0.3525725(4) 0.2351893(2) 0.3488812(2) 0.2831663(3) 0.2446698(2) 0.3962165(4) 0.3117609(3) 0.2606906(3) 0.2921654(3)

3.12(1) 3.515(2) 4.60(1) 3.38(1) 4.99(1) 2.117(3) 3.262(3) 2.766(6) 2.741(4) 5.97(1) 5.45(2) 2.824(2)

0.658(1) 0.893(3) 1.603(7) 0.82(1) 1.885(6) 0.1616(1) 0.752(1) 0.468(3) 0.455(2) 2.60(1) 2.22(1) 0.502(3)

76.56(4) 57.0(2) 74.3(1) 89.6(2) 88.2(1) 75.6(1) 70.08(6) 83.8(2) 89.5(1) 81.69(3) 86.42(6) 77.6(1)

4562(21) 4541(48) 4606(20) 5490(51) 4417(827) 5502(92) 4324(28) 4689(43) 5777(44) 4912(26) 4884(21) 5437(27)

3. Light curve solutions

Table 4 Parameters of the surface spots . Star

λ

α

CSS J062803.2+571604 CSS J222157.2+275308 CSS J075135.6+382028 V0338 Dra NSVS 2256852 NSVS 4666412 V1355 Tau NSVS 4808227 CSS J075350.1+264830

78(2) 100(2) 270(2) 310(2) 90(2) 270(2) 80(2) 270(2) 280(2)

17(1) 20(1) 18(1) 18(1) 8(0.5) 18(1) 12(1) 21(1) 22(1)

The IRIDA light curves of the targets were solved using the code (Prsa and Zwitter, 2005; Prsa, 2011; 2016). It is based on the Wilson–Devinney (WD) code (Wilson and Devinney, 1971; Wilson, 1979; 1993) but also provides a graphical user interface alongside other improvements, including updated filters as the Sloan filters used in our observations. We determined mean target temperatures Tm by their (g ′ − i′) colors at the light maxima and compilation of Covey (2007). The errors of Tm are up to ± 100 K due to the uncertainty of around 0.015 in (g ′ − i′) colors. The preliminary runs revealed that all targets are overcontact systems. Hence, we applied mode “Overcontact binary not in thermal contact” of the code. We adopted coefficients of gravity brightening g1 = g2 = 0.32 and reflection effect A1 = A2 = 0.5 appropriate for stars with convective equilibrium. The linear limb-darkening coefficients for each component and each color were updated according to the tables of Van Hamme (1993). Solar metallicity [M/H] = 0 was assumed in the absence of spectral line abundance determinations. To search for fit we fixed T1 = Tm and varied simultaneously the initial epoch T0, period P (around value from Table 1), secondary temperature T2 (around Tm), orbital inclination i, mass ratio q and potential Ω. The data in g′ and i′ bands were modelled simultaneously. The fit quality was estimated by the χ2 value. In order to reproduce the O’Connell effect of some light curves we used cool spots whose parameters (longitude λ, latitude β, angular size α and temperature factor κ) had to be adjusted. Due to the ambiguity of the solved multiparametric inverse problem we chose equatorial spots on the primary stellar components because they have the smallest size. Moreover, we fixed the temperature spot factor to the usual value of 0.9. After reaching the best fits we carried out also solutions for quadratic and logarithmic limb-darkening laws inserting two additional parameters. But they did not lead to better solutions. So, further we present the results corresponding to the linear limb-darkening law. Table 3 contains final values of the fitted stellar parameters: initial epoch T0; period P; mass ratio q; inclination i; potential Ω; secondary temperature T2PH . Table 4 gives the spot angular sizes and longitudes. The synthetic light curves corresponding to our solutions are shown in Figs. 1 and 2 as continuous lines while Fig. 3 exhibits the target 3D configurations. Although PHOEBE (as WD) works with potentials, it gives a possibility to calculate directly the relative radius ri = Ri / a of each component (Ri is linear radius and a is orbital separation). Moreover, PHOEBE yields as i of the two components output parameters bolometric magnitudes Mbol in conditional units (when radial velocity data are not available). But 2 1 − Mbol their difference Mbol determines the true luminosity ratio c = L2/ L1. Fillout factor f = [Ω − Ω(L1)]/[Ω(L2) − Ω(L1)] can be also PHOEBE

2256852, NSVS 4666412, V1355 Tau, NSVS 4808227, NSVS 4726498, CSS J075350.1+264830 and HL Lyn. All they have been classified as EW type binaries.

2. Observations The CCD photometric observations of the targets in Sloan g′ and i′ bands were carried out at Rozhen Observatory with the 30 cm Ritchey Chretien Astrograph (located into the IRIDA South dome) using CCD camera ATIK 4000M (2048 × 2048 pixels, 7.4 µm/pixel, field of view 35 × 35 arcmin). Information about our observations is presented in Table 2. The data were obtained during photometric nights with seeing within 1.1–1.9 arcsec. The standard procedure was used for the reduction of the photometric data (de-biasing, dark frame subtraction and flat-fielding) by software AIP4WIN2.0 (Berry and Burnell, 2006). The light variability of the targets was estimated with respect to nearby comparison (constant) stars in the observed field of each target (ensemble photometry). A check star served to determine the observational accuracy and to check constancy of the comparison stars. The CCD ensemble photometry permits calculations of the difference between the instrumental magnitude of the target and a comparison magnitude obtained from the mean of the intensities of the chosen comparison stars. The use of numerous comparison stars increases considerably the statistical accuracy of the comparison magnitude (Gilliland and Brown, 1988; Honeycutt, 1992). We performed the ensemble aperture photometry with the software VPHOT (https://www.aavso.org/vphot) using 6–12 comparison stars (Table 6 in Appendix) whose magnitudes were taken from the catalogue APASS DR9 (Henden, 2016). For transformation of the obtained instrumental magnitudes to standard ones we used the transformation coefficients of our equipment (Kjurkchieva et al., 2017). Our photometric data are available at www.irida-observatory.org/ Observations/IRIDA12stars.zip.

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CSS J062803.2+571604

V0951 Per 13.2

i'

12.8

Magnitude

Magnitude

12.4

g'

13.6

14.0

i'

13.4 14.0

g'

14.2

14.4

14.4

-0.6

-0.4

-0.2

0.0

0.2

0.4

14.6 -0.6

0.6

-0.4

-0.2

Phase

0.0

0.2

0.4

0.6

0.4

0.6

0.4

0.6

Phase

CSS J222157.2+275308

CSS J075135.6+382028

13.6

15.2

i'

14.0

i' Magnitude

Magnitude

15.6 16.0

g' 16.4

14.4 14.8

g'

15.2 16.8

15.6

17.2 -0.6

-0.4

-0.2

0.0

0.2

0.4

16.0 -0.6

0.6

-0.4

-0.2

Phase 12.5

0.2

Phase

NSVS 2256852

V0338 Dra

11.6

i'

13.0

0.0

i'

Magnitude

Magnitude

11.8 13.5 14.0

g' 14.5

12.0

g'

12.2 12.4

15.0

12.6 -0.6

-0.4

-0.2

0.0

0.2

0.4

-0.6

0.6

-0.4

-0.2

0.0

0.2

Phase

Phase

Fig. 1. Top of each panel: folded light curves of the first six targets and their fits; Bottom: corresponding residuals (shifted vertically by different amount to save space).

calculated from the output parameters Ω(L1) and Ω(L2) of PHOEBE solution. In order to obtain stellar temperatures T1 and T2 around the mean value Tm we used the formulae (Kjurkchieva and Vasileva, 2015):

T1 = Tm +

c ΔT , c+1

T2 = T1 − ΔT ,

Table 5 exhibits the calculated parameters: mean target temperature Tm; stellar temperatures T1, 2; relative stellar radii r1, 2 (volume values); fillout factor f. Their errors are determined from the uncertainties of output parameters used for their calculation.

(1)

4. Analysis of the results

(2) The main results from the light curve solutions of our data are as follows.

where c = L2 / L1 (luminosity ratio) and ΔT = Tm − T2PH were taken from the final PHOEBE fitting. 49

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12.8

V1355 Tau

13.2

i'

13.6

Magnitude

Magnitude

13.2

NSVS 4666412

14.0

g' 14.4

i'

14.4 14.8

g'

15.2 14.8

15.6 -0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

-0.6

-0.4

-0.2

Phase

0.0

0.2

0.4

0.6

0.2

0.4

0.6

0.2

0.4

0.6

Phase 12.8

NSVS 4808227

NSVS 4726498

11.7

13.2

i' Magnitude

Magnitude

12.0 12.3 12.6

g'

i'

13.6 14.0

g'

14.4

12.9

14.8 13.2

15.2 -0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

-0.6

-0.4

-0.2

Phase

13.2

Phase

CSS J075350.1+264830

HL Lyn 13.2

13.5

i'

i'

13.5

Magnitude

Magnitude

13.8 14.1 14.4 14.7

0.0

g'

13.8 14.1

g'

14.4

15.0

14.7 15.3 -0.6

-0.4

-0.2

0.0

0.2

0.4

15.0 -0.6

0.6

-0.4

Phase

-0.2

0.0

Phase Fig. 2. The same as in Fig. 1 for the last six targets.

(3) V0951 Per, CSS J062803.2+571604, CSS J222157.2+275308, NSVS 4666412, and HL Lyn reveal partial eclipses. The rest seven targets undergo total eclipses and their photometric mass ratios should be considered with confidence (Terrell and Wilson, 2005). (4) All targets have overcontact configurations (Fig. 3, Table 5) with small fillout factor 0.1–0.2. (5) The components of most targets differ in temperature by up to 300 K. However, the temperature differences of the components of NSVS 2256852 and CSS J062803.2+571604 exceed 1100 K

(1) We determined the initial epochs T0 of the all targets (Table 3). (2) The amplitudes of our light curves of V0951 Per (0.6 mag), V0338 Dra (0.7 mag), NSVS 2256852 (0.57 mag) and CSS J062803.2+571604 (0.21 mag) are bigger than previous determinations (Table 1). In contrast, the amplitudes of our light curves of CSS J222157.2+275308 (0.5 mag), CSS J075135.6+382028 (0.7 mag), NSVS 4666412 (0.5 mag), V1355 Tau (0.5 mag), CSS J075350.1+264830 (0.6 mag) and NSVS 4726498 (0.8 mag) are smaller than previously seen (Table 1).

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CSS J062803.2+571604

V0951 Per

CSS J222157.2+275308

CSS J075135.6+382028

V0338 Dra

NSVS 2256852

NSVS 4666412

V1355 Tau

NSVS 4808227

NSVS 4726498

CSS J075350.1+264830

HL Lyn

Fig. 3. 3D configurations of the targets.

Table 5 Calculated parameters. Star

Tm

T1

T2

r1

r2

f

V0951 Per CSS J062803.2+571604 CSS J222157.2+275308 CSS J075135.6+382028 V0338 Dra NSVS 2256852 NSVS 4666412 V1355 Tau NSVS 4808227 NSVS 4726498 CSS J075350.1+264830 HL Lyn

4720(100) 5700(100) 4763(100) 5560(100) 4417(100) 6700(100) 4557(100) 4800(100) 5883(100) 5212(100) 5125(100) 5600(100)

4778(122) 5992(169) 4819(121) 5591(152) 4417(927) 6804(227) 4645(130) 4835(144) 5922(145) 5286(128) 5276(122) 5652(128)

4620(121) 4834(148) 4661(120) 5521(151) 4417(927) 5606(192) 4412(128) 4724(143) 5816(144) 4986(126) 5035(121) 5489(127)

0.426(2) 0.401(2) 0.349(1) 0.411(2) 0.338(4) 0.547(4) 0.419(4) 0.459(4) 0.462(1) 0.312(4) 0.324(1) 0.455(1)

0.353(2) 0.391(2) 0.432(1) 0.376(2) 0.448(4) 0.243(4) 0.369(4) 0.327(4) 0.325(2) 0.477(4) 0.463(1) 0.335(1)

0.12(3) 0.118(4) 0.13(2) 0.15(2) 0.16(2) 0.17(3) 0.169(8) 0.17(2) 0.18(1) 0.18(2) 0.18(3) 0.186(6)

0.10

(Table 5) which is unexpected for overcontact binaries. (6) The light curve distortions of nine binaries were reproduced by cool spots (Table 4) which are appearances of magnetic activity of these late stars. (7) CSS J222157.2+275308, V0338 Dra, NSVS 4726498 and CSS J075350.1+264830 are of W subtype while the other targets are of A subtype. (8) NSVS 2256852 is an overcontact system (f = 0.167) with quite small mass ratio q = 0.16 (Table 3), close to the boundary value of W UMa binaries Rasio 1996). By time-series analysis we determined orbital periods of 0.348916 d, 0.3489058 d and 0.3488812 d correspondingly in 1999 (NSVS data), 2007 (SWASP data) and 2014 (our data). Moreover, from these data we determined twenty observed times of light minima (Table 7 in Appendix) by the software MINIMA (Nelson, 2007) and added the last eclipse time of NSVS 2256852 from early 2016 (Hubscher, 2017). Fig. 4exhibits the corresponding O–C diagram. Using the procedure of (Sterken, 2005) we calculated a period decrease of 2.36 × 10−7 d/yr from the quadratic fit of the O–C data of NSVS 2256852. This result as well as the small mass ratio implies future merger. Then, the big temperature difference of its components is even more surprising.

O-C = 0.0002 + 0.0000084*E - 0.0000000000394*E2

O-C [d]

0.05

0.00

-0.05

-8000

-4000

0

4000

8000

E Fig. 4. O–C diagram of NSVS 2256852: the values from the left to the right correspond to the minima from NSVS database, SWASP database, our observations and that of Hubscher (2017).

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5. Conclusions

Foundation of the Bulgarian Ministry of Education and Science as well as by project RD 02–102 of Shumen University. The authors are very grateful to the anonymous referee for the valuable recommendations and notes. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/ California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This research also has made use of the SIMBAD database, operated at CDS, Strasbourg, France, NASA Astrophysics Data System Abstract Service, the USNOFS Image and Catalogue Archive operated by the United States Naval Observatory, Flagstaff Station (http://www.nofs.navy.mil/ data/fchpix/) and the photometric software VPHOT operated by the AAVSO, Cambridge, Massachusetts.

Our observations and light curve solutions revealed that V0951 Per, CSS J062803.2+571604, CSS J222157.2+275308, CSS J075135.6+382028, V0338 Dra, NSVS 2256852, NSVS 4666412, V1355 Tau, NSVS 4808227, NSVS 4726498, CSS J075350.1+264830 and HL Lyn are shallow-contact configurations (with fillout factors 0.1–0.2). The components of the most targets are K stars and differ in temperature by up to 300 K excluding CSS J062803.2+571604 and NSVS 2256852 whose temperature differences exceed 1100 K. The last target might be suspected as a possible merger candidate due to the small mass ratio (q = 0.16) and decreasing period. It deserves future observations. Acknowledgements The research was supported partly by project DN08/20 of Scientific Appendix

Table 6 List of standard stars. Label

Star ID

RA

Target Chk C1 C2 C3 C4 C5 C6 C7 C8 C9 Target Chk C1 C2 C3 C4 C5 C6 C7 C8 Target Chk C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 Target Chk C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 Target

V0951 Per UCAC4 621-014711 UCAC4 621-014715 UCAC4 621-014679 UCAC4 621-014661 UCAC4 621-014692 UCAC4 621-014634 UCAC4 621-014659 UCAC4 621-014722 UCAC4 620-014265 UCAC4 620-014235 CSS J062803.2+571604 UCAC4-737–044764 UCAC4-737-044774 UCAC4-737-044766 UCAC4-737-044778 UCAC4-736-046930 UCAC4-736-046874 UCAC4-736-046859 UCAC4-736-046863 UCAC4-736-046818 CSS J222157.2+275308 UCAC4 591-134602 UCAC4 590-134319 UCAC4 590-134268 UCAC4 590-134302 UCAC4 591-134550 UCAC4 591-134590 UCAC4 591-134573 UCAC4 591-134594 UCAC4 591-134609 UCAC4 591-134625 UCAC4 590–134318 CSS J075135.6+382028 UCAC4 643–044185 UCAC4 643–044208 UCAC4 643–044212 UCAC4 643–044217 UCAC4 643–044225 UCAC4 643–044233 UCAC4 643–044248 UCAC4 643–044271 UCAC4 643–044218 UCAC4 643–044228 UCAC4 643–044235 UCAC4 643–044258 UCAC4 642–042689 V0338 Dra

04 04 04 04 04 04 04 04 04 04 04 06 06 06 06 06 06 06 06 06 06 22 22 22 22 22 22 22 22 22 22 22 22 07 07 07 07 07 07 07 07 07 07 07 07 07 07 15

Dec 10 10 10 10 10 10 10 10 11 10 10 28 27 27 27 27 27 26 26 26 25 21 21 21 21 21 21 21 21 21 21 21 21 51 51 51 51 51 52 52 52 53 51 52 52 52 52 49

36.31 57.12 59.12 43.54 35.38 48.54 24.78 34.42 03.34 40.54 27.60 03.28 28.22 41.41 30.58 48.83 53.71 46.16 33.14 36.42 48.21 57.26 47.14 58.53 27.93 48.22 15.51 38.84 31.08 41.55 51.23 59.90 57.52 35.65 20.51 47.59 49.87 54.27 03.85 15.03 40.64 09.97 54.46 07.68 19.56 55.66 04.30 11.14

+34 +34 +34 +34 +34 +34 +34 +34 +34 +33 +33 +57 +57 +57 +57 +57 +57 +57 +57 +57 +57 +27 +28 +27 +27 +27 +28 +28 +28 +28 +28 +28 +27 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +60

52

g′ 02 04 09 10 11 04 01 00 03 57 56 16 14 16 16 18 11 11 04 02 08 53 05 57 58 59 04 05 07 08 08 05 55 20 34 35 35 32 32 31 32 31 29 27 25 24 21 38

58.1 43.53 28.92 39.44 16.00 24.18 48.82 46.05 29.75 49.05 34.85 04.0 51.82 07.39 07.12 39.37 14.10 30.66 49.70 51.35 54.91 08.0 28.21 39.13 29.23 26.26 13.34 26.42 20.65 12.48 03.18 28.35 26.19 28.8 24.58 55.44 24.70 17.07 23.81 48.84 08.27 21.83 44.02 03.01 59.02 46.13 25.15 02.9

13.39 13.957 11.968 13.606 12.908 13.296 12.999 12.325 12.695 12.045 12.681 13.96 13.912 14.768 14.517 13.565 13.344 13.964 13.514 14.111 13.787 15.91 14.360 13.700 14.206 13.982 13.539 13.229 13.213 13.318 13.773 13.329 13.479 14.43 14.121 14.120 14.660 14.572 14.709 13.911 14.134 13.671 14.346 13.635 14.447 14.096 14.479 13.93

i′ 12.28 13.062 11.129 11.693 11.972 12.533 12.655 11.016 10.854 11.523 12.811 13.17 12.355 14.029 13.872 13.001 12.349 13.318 12.656 13.185 12.977 15.20 13.201 13.190 13.301 13.359 12.884 12.297 12.615 12.713 13.106 12.661 12.254 13.73 13.686 13.657 13.681 13.818 14.018 13.311 13.686 13.366 13.859 13.310 13.755 13.712 13.864 12.67 (continued on next page)

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D.P. Kjurkchieva et al.

Table 6 (continued) Label

Star ID

RA

Chk C1 C2 C3 C4 C5 C6 C7 C8 C9 Target Chk C1 C2 C3 C4 C5 C6 C7 C8 Target Chk C1 C2 C3 C4 C5 C6 Target Chk C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 Target Chk C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 Target Chk C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 Target Chk C1 C2 C3 C4 C5 C6 C7

UCAC4 754–049579 UCAC4 754–049594 UCAC4 754–049576 UCAC4 754–049603 UCAC4 754–049580 UCAC4 754–049596 UCAC4 753–051433 UCAC4 753–051430 UCAC4 753–051448 UCAC4 753–051464 NSVS 2256852 UCAC4-722-039658 UCAC4-723-040392 UCAC4-723-040308 UCAC4-723-040286 UCAC4-722-039641 UCAC4-722-039683 UCAC4-722-039653 UCAC4-722-039701 UCAC4-722-039763 NSVS 4666412 UCAC4 705–045055 UCAC4 704–044503 UCAC4 704–044543 UCAC4 704–044539 UCAC4 705–045015 UCAC4 705–045065 UCAC4 704–044484 V1355 Tau UCAC4 572–013841 UCAC4 574–013186 UCAC4 574–013127 UCAC4 573–013880 UCAC4 573–013795 UCAC4 573–013848 UCAC4 573–013817 UCAC4 573–013815 UCAC4 572–013772 UCAC4 572–013860 UCAC4 572–013808 NSVS 4808227 UCAC4 644–044904 UCAC4 644–044928 UCAC4 644–044943 UCAC4 644–044929 UCAC4 643–045329 UCAC4 643–045380 UCAC4 643–045349 UCAC4 643–045340 UCAC4 643–045337 UCAC4 642–043916 UCAC4 642–043907 NSVS 4726498 UCAC4 643–044185 UCAC4 643–044208 UCAC4 643–044212 UCAC4 643–044217 UCAC4 643–044225 UCAC4 643–044233 UCAC4 643–044248 UCAC4 643–044271 UCAC4 643–044218 UCAC4 643–044228 UCAC4 643–044235 UCAC4 643–044258 UCAC4 642–042689 CSS J075350.1+264830 UCAC4 585–040865 UCAC4 585–040922 UCAC4 585–040893 UCAC4 585–040902 UCAC4 585–040935 UCAC4 584–040561 UCAC4 584–040525 UCAC4 584–040482

15 15 15 15 15 15 15 15 15 15 05 05 05 05 05 05 05 05 05 05 07 07 07 07 07 07 07 07 05 05 05 05 05 05 05 05 05 05 05 05 08 08 08 08 08 08 08 08 08 08 08 08 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07

Dec 48 49 48 50 48 49 48 48 48 50 32 32 33 32 32 32 32 32 32 33 18 18 18 19 19 18 19 18 02 02 02 01 02 01 02 01 01 01 02 01 24 23 24 24 24 23 25 24 23 23 24 24 52 51 51 51 51 52 52 52 53 51 52 52 52 52 53 53 54 54 54 54 54 53 53

44.05 39.47 42.80 28.34 51.30 43.97 09.41 00.99 57.08 13.74 55.08 18.95 44.09 49.83 34.76 09.46 35.51 14.28 47.44 30.05 38.88 53.59 43.01 41.02 38.17 00.28 05.66 13.70 06.82 18.23 17.24 44.37 19.58 33.75 00.81 45.36 44.91 40.60 27.29 58.53 03.60 40.79 21.24 43.75 22.77 10.93 00.58 04.57 44.45 30.64 52.45 33.41 36.20 20.51s 47.59 49.87 54.27 03.85 15.03 40.64 09.97 54.46 07.68 19.56 55.66 04.30 50.14 35.00 17.53 00.08 05.58 28.95 30.72 57.01 13.24

+60 +60 +60 +60 +60 +60 +60 +60 +60 +60 +54 +54 +54 +54 +54 +54 +54 +54 +54 +54 +50 +50 +50 +50 +50 +50 +50 +50 +24 +24 +24 +24 +24 +24 +24 +24 +24 +24 +24 +24 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +38 +26 +26 +26 +26 +26 +26 +26 +26 +26

53

g′ 36 47 45 47 46 43 34 26 27 27 19 20 27 27 28 18 23 23 18 16 47 49 45 42 46 52 53 38 27 23 37 36 34 30 29 28 25 21 23 18 31 38 42 39 38 33 27 26 25 25 19 18 35 34 35 35 32 32 31 32 31 29 27 25 24 21 48 54 53 53 50 51 44 40 39

08.51 43.23 39.38 06.47 42.67 43.40 24.00 37.02 01.19 31.31 25.0 31.50 24.99 51.75 19.45 25.38 18.63 15.49 17.53 09.87 54.1 30.10 03.92 56.07 54.09 25.05 59.35 22.77 39.7 58.27 31.86 30.01 15.81 36.27 34.30 01.78 10.12 28.06 10.95 22.74 19.2 10.34 29.60 07.05 34.19 49.87 24.34 04.22 03.83 03.00 06.41 36.07 13.8 24.58 55.44 24.70 17.07 23.81 48.84 08.27 21.83 44.02 03.01 59.02 46.13 25.15 30.4 33.48 48.65 20.97 51.63 24.22 26.49 05.26 44.50

15.439 13.127 13.395 12.633 14.494 14.197 14.011 12.748 12.878 12.761 12.04 13.004 12.349 14.259 13.339 12.189 12.495 12.971 13.576 13.416 13.98 14.492 13.902 13.529 14.138 13.113 12.989 13.689 13.99 14.282 14.285 13.192 14.400 12.999 13.285 14.085 13.638 13.194 12.806 13.366 12.24 13.292 13.580 13.496 12.870 13.366 13.091 13.583 13.753 13.468 13.857 13.475 13.86 14.121 14.120 14.660 14.572 14.709 13.911 14.134 13.671 14.346 13.635 14.447 14.096 14.479 14.23 13.816 14.496 14.100 13.940 13.966 13.452 14.495 13.047

i′ 12.355 12.499 12.935 12.191 13.550 13.597 13.293 12.189 12.053 11.602 11.59 12.268 11.492 13.452 12.687 11.770 11.809 12.422 12.720 11.341 12.92 14.200 13.004 12.832 13.742 12.523 12.572 12.650 13.24 13.179 12.852 11.810 13.136 12.282 12.651 12.647 12.507 12.728 12.197 12.594 11.64 12.308 13.165 12.812 12.269 12.806 12.469 13.189 13.241 13.015 13.026 12.291 12.96 13.686 13.657 13.681 13.818 14.018 13.311 13.686 13.366 13.859 13.310 13.755 13.712 13.864 13.38 13.087 13.679 13.499 13.345 12.755 12.492 13.579 12.509 (continued on next page)

New Astronomy 62 (2018) 46–54

D.P. Kjurkchieva et al.

Table 6 (continued) Label

Star ID

C8 Target Chk C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11

UCAC4 HL Lyn UCAC4 UCAC4 UCAC4 UCAC4 UCAC4 UCAC4 UCAC4 UCAC4 UCAC4 UCAC4 UCAC4 UCAC4

RA 585–040832

07 07 07 07 07 07 07 07 07 07 07 07 07 07

656–048861 656–048893 657–049203 657–049169 657–049164 656–048870 656–048866 656–048824 656–048825 656–048853 656–048873 655–049352

Dec 53 47 47 48 48 47 47 48 48 46 46 47 48 48

04.18 50.29 54.52 40.79 04.21 30.13 21.32 09.08 02.83 48.87 51.58 42.74 10.46 43.63

+26 +41 +41 +41 +41 +41 +41 +41 +41 +41 +41 +41 +41 +40

48 05 02 11 16 15 15 09 07 03 00 01 04 58

58.85 21.77 19.96 19.75 06.89 51.35 50.80 05.13 53.27 30.69 59.80 22.40 07.73 53.19

g′

i′

13.976 13.88 13.648 13.304 11.838 12.289 13.194 13.225 13.141 13.398 13.622 13.269 13.210 12.854

13.207 13.12 13.034 12.868 11.479 11.144 12.621 12.648 12.767 12.789 13.272 12.706 12.722 12.437

Table 7 Times of minima of NSVS 2256852. Source

Type

Observed

E

Calculated

O-C

NSVS SWASP SWASP SWASP SWASP SWASP SWASP SWASP SWASP SWASP SWASP SWASP SWASP SWASP SWASP SWASP SWASP our our our Hubscher

MinI MinII MinII MinI MinII MinII MinI MinI MinI MinI MinII MinI MinI MinI MinI MinII MinII MinII MinII MinI MinI

2451273.06975 2454372.65378 2454373.69892 2454383.64308 2454387.65523 2454394.63309 2454397.59863 2454398.64753 2454405.62468 2454406.67132 2454409.63674 2454419.58155 2454420.62911 2454427.60508 2454436.68146 2454437.55072 2454438.59669 2457005.55840 2457006.25560 2457006.42967 2457385.3482

-8915 -31.5 -28.5 0 11.5 31.5 40 43 63 66 74.5 103 106 126 152 154.5 157.5 7514.5 7516.5 7517 8603

2451273.14787 2454372.65255 2454373.69926 2454383.64308 2454387.65550 2454394.63361 2454397.59931 2454398.64603 2454405.62415 2454406.67086 2454409.63656 2454419.58038 2454420.62709 2454427.60521 2454436.67676 2454437.54903 2454438.59574 2457005.49571 2457006.19353 2457006.36798 2457385.27968

-0.07813 0.00123 -0.00034 0.00000 -0.00027 -0.00052 -0.00068 0.00150 0.00053 0.00046 0.00018 0.00117 0.00202 -0.00013 0.00470 0.00169 0.00095 0.06269 0.06207 0.06169 0.06852

Prsa, A., et al., 2016. ApJS 227, 29. Qian, S.-B., 2003. MNRAS 342, 1260. Rasio, F., 1995. ApJ 444L, 41. Robertson, J.A., Eggleton, P.P., 1977. MNRAS 179, 359. Rucinski, S., 1973. AcA 23, 79. Rucinski, S., 1974. AcA 24, 119. Smith, R.C., 1984. QJRAS 25, 405. Stepien, K., 2004. IAUS 219, 967. Stepien, K., 2006. AcA 56, 199. Stepien, K., 2009. MNRAS 397, 857. Stepien, K., 2011. AcA 61, 139. Sterken, C., 2005. ASPC 335, 3. Terrell, D., Wilson, R., 2005. ApSpSci 296, 221. Van Hamme, W., 1993. AJ 106, 2096. Webbink, R.F., 1976. ApJ 209, 829. Wilson, R., Devinney, E., 1971. ApJ 166, 605. Wilson, R., 1979. ApJ 234, 1054. Wilson, R., 1993. ASPC 38, 91. Yakut, K., Eggleton, P., 2005. ApJ 629, 1055.

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