UBVRI Photometric Analysis of the Solar-Type Eclipsing Binary TYC 3034-299-1

Abstract

TYC 3034-0299-1 (CV_n) is a magnetically active, contact binary, ROTSE variable. UBVR_cI_c light curves are presented along with a period study and a simultaneous UBVRI light curve solution. Our light curves show eclipse amplitudes of 0.72 and 0.62 mags (V) in the primary and secondary eclipses. Modeled results include a dark spot region, found at longitude 51°, a 24% Roche lobe fill-out, and a mass ratio of 0.48. A total eclipse is found to occur in the secondary eclipse making TYC 3034-0299-1 a W-type (less massive star is hotter) W UMa variable.

1. History

TYC 3034-299-1 [𝛼(2000)=14h05m09.043s, 𝛿(2000)=+38^∘54^′19.26^] was discovered by ROTSE I [1]. It was reported in IBVS no. 5699 [2]. Observations were taken by Diethelm [3]. He gives the following ephemeris:HJD𝑇_minI=2453382.6919+0.395010𝑑∗𝐸.(1) TYC 3034-299-1 was listed in the catalog of 1022 bright contact binary stars by Geske et al. [4] lists a period of 0.395013d, 𝑉_max=11.462 V mag, and amplitude = 0.585 V mag. In addition, two times of minimum light were determined by BBSAG observers given in IBVS no. 5781 [3]. Also, two eclipse timings were recently observed by Nelson [5, 6].

2. Finding Chart

Our comparison star (𝐶) was GSC 3034 0404 [𝛼(2000)=14h05m21.4758s, 𝛿(2000)=+38^∘48^′35.436^]. The check star (𝐾) was GSC 3034 0497 [𝛼(2000)=14h05m13.8544s, 𝛿(2000)=+38^∘57^′24.156^]. We include a finding chart of these stars including the variable (𝑉) in Figure 1.

Figure 1 

Finding chart, TYC 3034-299-1 variable (𝑉), comparison (𝐶) and check (𝐾).

3. Observations

This system was observed as a part of our student/professional collaborative studies of interacting binaries from data taken from the national undergraduate research observatory (NURO). The observations were taken by RGS and NB. Reduction and analyses were jointly completed by RGS and AJ. The present 2010 UBVRI light curves were taken with the Lowell 0.81-m reflector in Flagstaff on May 10 and May 11 with CRYOTIGER cooled (−100°C) 2048X2048 NASACAM and standard UBVRI Besell filters. The individual observations included 216 in the U-filter, 230 in B, 232 in V, 243 in R, and 239 in I. The standard error of a single observation was 1% in U, V, and R and I an 1.2% in B (Table 1).

Table 1 

4. Period Determination

The following timings of minimum light were calculated using parabola fits from our present observations (PO). They were determined in each of UBVRI and averaged. They include (with standard errors) HJD I = 2455326.72754±0.00024,2455327.713303±0.00025; HJD II = 2455326.92427±0.00068,2455327.91256±0.00060. We also obtained the following timings of minimum light from parabola fits to the data of Blattler, 2006: HJD I = 2453382.6915, 2453445.4980, 2453502.3800, 2453515.4154, 2453517.3907; HJD II = 2453463.4719, 2453515.607. From these and Bob Nelson’s timings, an improved ephemeris below was calculated from all the available eclipse timings: J.D.HelMinI=+2405.359352060.9827404±±00.0.00000050016𝑑∗𝐸.(2) The O-C residuals are shown, graphically, in Figure 2 and tabled residualsare tabulated in Table 2.

Table 2 

Times of minimum light, TYC 3034-299-1.

Figure 2 

O-C residuals from (2).

Observations taken over some 5000 orbits (5.3 years) seem to show a constant period. A quadratic ephemeris was calculated, but the negative quadratic term was not significant. Further observations are needed to determine any trends that indicate changes in period.

5. Standard Magnitudes

Observations of over a dozen Landolt standard stars along with the variable, comparison, and check stars throughout the evening of May 11 allowed us to calculate principal and transformation coefficients in BVR and I. Comparing these to Kron-Cousins calibrations, we found the results given in Table 3 [7] with the standard errors given in parentheses. From these calculations, we found a temperature of 6600 K (type F6V) for our primary star used for our synthetic light curve modeling.

Table 3 

Standard magnitudes of the variable, comparison and check stars.

6. Light Curves

The light curves were folded ΔU, ΔB, ΔV, ΔR, ΔI, Δ(U-B), Δ(B-V), and Δ(R-I) color curves using (2). They are given in Figures 3(a), 3(b), and 3(c). All bands give high precision, high amplitude 𝑊 UMa light curves with an obvious O’Connell effect due to spot activity. The curves reveal a time of constant light in the secondary minima indicating total eclipses. This usually indicates that the system is a 𝑊-type 𝑊 UMa binary system. The amplitudes are rather deep for a contact binary, ranging from 0.85 mag in U to 0.66 in I. The O’Connell effect ranges from 67 mmag to 36 mmag from U to I, respectively, revealing substantial magnetic activity.

(a)

(b)

(c)

Figure 3 

(a) U, B delta magnitude and color magnitudes versus phase plots in the sense of V-C. (b) B, V delta magnitude and color magnitudes versus phase plots in the sense of V-C. (c) R, I delta magnitude and color magnitudes versus phase plots in the sense of V-C.

7. Synthetic Light Curve Solutions

The U, B, V, R, and I curves were premodeled with Binary Maker 2.0 [8] fits in all filter bands. The parameters were then averaged and input into a 5-color simultaneous light curve calculation using the Wilson Code [9–12]. Adjusted parameters were those with parentheses in Table 4.

Table 4 

Synthetic curve parameters, TYC 3034-299-1.

The solution was computed in Mode 3, the contact mode. Convective parameters, 𝑔=0.32,𝐴=0.5, were used. Our first solution,𝑞=0.52, gave a sum of square residuals equal to 8.33 (goodness of fit parameter). This fit the out of eclipse shoulders well but did not match the eclipse at phase 0.50. Due to the brevity of the total eclipse, the modeling procedure does not produce unambiguous results (many solutions may be possible). Consequently, we performed a 𝑞-search over the interval from 𝑞=0.3 to 0.8. The residuals minimized at 𝑞∼0.45 (see Figure 4). Additional iterations were run from the minimized 𝑞 with the mass ratio allowed to adjust to our final solution. Our final solution is a 𝑊-type 𝑊 UMa binary, as noted from the light curve appearance. The solution is seen overlaying the normalized flux curves shown in Figures 5(a), 5(b), and 5(c). The complete solutions are given as Table 4. Two phases of the Roche-lobe model of the binary for the dark spot solution are shown in Figures 6(a) and 6(b). Phase 0.0 shows the total eclipse.

Figure 4 

Determination of best fitting mass ratio.

(a)

(b)

(c)

Figure 5 

(a) U, B synthetic light curve solutions overlaying the normalized flux curves. (b) B, V synthetic light curve solutions overlaying the normalized flux curves. (c) R, I synthetic light curve solutions overlaying the normalized flux curves.

(a)

(b)

Figure 6 

(a) Roche lobe surfaces from our UBVRI solution, phase 0.76. (b) Roche lobe surfaces from our UBVRI solution, phase 0.00.

8. Discussion

TYC 3034-299-1 is a mid-F type magnetically active contact binary. The solution gives a eclipse duration of ~7 minutes. The firm 24% fillout and the nearly identical temperatures of the two stars show that the system has nearly reached thermal contact. After this point is reached, we would suspect that over long periods the mass ratio would become more extreme. This is caused by torques provided by stellar winds leaving the star along stiff magnetic field lines [13] rotating synchronously with the gravitationally coupled binary.

Acknowledgments

The authors wish to thank Lowell Observatory for their allocation of observing time, and the American Astronomical Society and the Arizona Space Grant for travel support for this observing run.