NSVS_254037 Light Curve

Researchers: Kyle Koeller

Observations suggest that NSVS 254037 is an eclipsing variable star of W Ursae Majoris type. This star is located at α=00:28:28.0 δ=+78:57:42.7 and has the following alternate stellar designations: TYC 4500-730-1, NSVS 254037, [TNK2005] 3, GSC 04500-00730, 1RXS J002827.8+785750, 2MASS J00282798+7857426, [GGM2006] 254036, Gaia DR1 564727829363764992, and Gaia DR2 564727833661817472.  Star field with the target star and comparison stars used in ensemble differential photometry are shown in Figure 1.

Figure 1: Star field with ensemble stars used for differential photometry marked. The eclipsing variable star NSVS 254037 is marked by the green target (T1). All ensemble stars are marked by the red apertures and designated the labels C2-C15. If a B band magnitude is known, it is given with each comparison. Field-scale is given on the left side of the image. Image is a representative image taken with the BSUO 20-inch telescope.

(J2000.0) Magnitudes
Comparison Catalog α δ B V Rc
C2 TYC 4500-2008-1 00:29:47.83 +78:58:08.11 11.76 ± 0.08 11.37 ± 0.37
C3 TYC 4500-1763-1 00:30:09.30 +79:01:24.79 11.91 ± 0.10 11.44 ± 0.10
C4 TYC 4500-1584-1 00:30:59.97 +78:53:15.69 13.03 ± 0.33 11.63 ± 0.14
C5 TYC 4500-1418-1 00:27:18.16 +79:00:36.10 12.43 ± 0.20 11.79 ± 0.15
C6 TYC 4500-1942-1 00:28:22.20 +78:48:12.02 10.85 ± 0.04 10.46 ± 0.04
C7 TYC 4500-1677-1 00:31:38.99 +78:47:36.78 12.91 ± 0.25 12.46 ± 0.19
C8 TYC 4500-1776-1 00:32:41.02 +78:52:01.75 12.53 ± 0.20 12.04 ± 0.16
C9 IRAS 00294+7847 00:32:46.58 +79:04:44.67 12.00 ± 0.20 9.99 ± 0.03
C10 IRAS 00287+7849 00:32:02.12 +79:06:14.25 12.89 ± 0.32 11.17 ± 0.09
C11 TYC 4500-1985-1 00:25:09.65 +78:50:43.57 10.90 ± 0.06 9.77 ± 0.03
C12 TYC 4500-2049-1 00:24:45.94 +78:53:35.34 11.40 ± 0.08 10.29 ± 0.04
C13 TYC 4500-848-1 00:26:11.59 +78:50:23.51 12.23 ± 0.17 11.42 ± 0.10
C14 TYC 4500-1545-1 00:28:40.89 +79:09:37.26 11.73 ± 0.08 11.16 ± 0.07
C15 TYC 4500-1789-1 00:25:39.42 +78:58:23.23 14.42 ± 0.85 11.62 ± 0.17

Table 1: List of comparison stars used in differential ensemble photometry analysis. First column gives the comparison designation. Columns 2 & 3 give the Right Ascension (α) and Declination (δ) of the comparison in J2000.0. Columns 3-6 report measured Johnson B (B), Johnson V (V) and Cousins R (Rc) band magnitudes. Magnitudes are used to calibrate the magnitudes of the target star. Calibrated magnitudes are used to determine magnitudes in the Johnson-Cousins system.
We have observed this star with the Ball State University Observatory (BSUO) 20-inch (0.6-m) telescope in the B, V, and Rc bandpasses. All stellar photometry is performed by the AstroImageJ (AIJ) software package. All photometry is performed with similar ensemble stars. If a calibrated magnitude for a comparison star is known, then it is used by AIJ to calibrate the magnitude for the target star. Folded light curves are shown for B, V, and Rc in Figure 2.
NSVS 896797 Color Light CurveFigure 2: Folded color light curve for NSVS 254037. All photometry is differential ensemble photometry performed by the AstroImageJ (AIJ) software package. Top panel shows folded V-band curve. Bottom panel shows folded (B-V) color curve. All magnitudes are calibrated by the known magnitudes of the ensemble stars. Error bars are not shown for clarity.

Observed Minus Calculated (O-C) Time of Minimum Analysis

Times of minimum light were determined for the nights observed, and are given in the following table along with Observed minus calculated (O-C) times of minimum. All reported errors are 1σ error bars.

[HJD] [days]
Time of Minimum Error Eclipse (O-C) Error
2458403.58736 ±0.00028 primary 0.000 ±0.00028
2458403.74592 ±0.00018 secondary -0.00018 ±0.00033
2458408.66613 ±0.00029 primary -0.00089 ±0.00040
2458408.82456 ±0.00030 secondary -0.00012 ±0.00041
2458410.57069 ±0.00022 primary -0.00012 ±0.00035
2458410.72911 ±0.00028 secondary -0.00015 ±0.00040

Table 2: Heliocentric Julian dates [HJD] for times of minimum (first column) are reported along with 1σ error bars (second column). All times of minimum light are first determined for each filter (B, V, and R) light curve, and are determined by the method described by Kwee & van Woorden (1976). Similar times of minimum for differing filter light curves are averaged together and reported in column Times of Minimum. Eclipses are designated by primary for the primary eclipse and secondary for the secondary eclipse in the Eclipse column (third/middle column). Values of (O-C) (fourth column) are given in units of days along with 1σ errors (fifth column).

Figure 3: Observed time of minimum minus calculated time of minimum (O-C) plot with best-fit linear linear line (solid line) versus epoch number (E). Error bars are 1σ error bars assuming the period of the system is known with out errors. All O-C values are given in units of days and are determined by the linear ephemeris given in equation (1). Best-fit linear line is determined by an unweighted linear least squares analysis. Slope of best-fit line represents a negligible correction to the ephemeris given in equation (1).

Best fitting Wilson-Devinney (WD) Models

All modeling is performed using the PHysics Of Eclipsing BinariEs (PHOEBE) (v0.31a) software package. PHOEBE is a graphical user interface (gui) to the WD code that is used to model binary stars. Figure 4 shows the best fit WD model with a single star spot. Figure 5 shows a graphical representation of the stellar surface.

Figure 4: Best-fit WD model fit with spots (red solid curve) to the folded light curve for differential B, V, and RC (from left to right) band magnitudes (top panel). The bottom panel shows the residuals from the best-fit WD model (red solid curve).

Figure 5: Stellar models showing best-fit stellar models for the light curves shown in Figure 4. Orbital phases (Φ) for each panel are included with each panel. The model includes two stellar spot with one spot on each stellar component and are apparent at orbital phases 0.25 and 0.5.

Derived System Parameters

Below is Table 3, which lists parameters and their values derived in the analysis of this system via the methods discussed above. Note that the ns subscript represents values/errors without spots (“no spots”), and the subscript s denotes values/errors with spots. See the table caption for more details and/or clarification.

No Spots Spots
(1) (2) (3) (4) (5) (6)
Parameter Symbol [unit] Value Error Value Error
Period P [days] 0.3175 0.0015
Epoch T0 [HJD] 2458403.58763 0.00028
Inclination i [deg] 67.765316 0.26 67.813308 0.26
Surface Temp. Teff,1 [K] 6409 44 6409 44
Teff,2 [K] 6064 44 6035 44
Surface Potential Ω1,2 [-] 3.893036 0.11 3.672063 0.11
Mass Ratio q [-] 0.987 0.04 0.987 0.04
Stellar Mass M1 [M] 1.371 0.025 1.371 0.025
M2 [M] 1.353 0.028 1.353 0.028
Semi-major Axis a [R] 2.735 0.081 2.735 0.081
Luminosity [L1/(L1+L2]B 2.533281 0.007 2.707191 0.007
[L1/(L1+L2]V 4.370816 0.009 4.670039 0.009
[L1/(L1+L2]RC 1.815237 0.023 1.938516 0.023
Limb Darkening xbol,1,2 0.64218 0.64218
ybol,1,2 0.23570 0.23570
xB,1,2 0.809331 0.809331
yB,1,2 0.231508 0.231508
xV,1,2 0.716875 0.716875
yV,1,2 0.275911 0.275911
xRC,1,2 0.624225 0.624225
yRC,1,2 0.280503 0.280503
Spot Colatitude 130
Spot Longitude 300
Spot Radius 5.0
Temp Factor 2.0

Table 3: System parameters of NSVS 254037.  Column (1) gives the name of the parameter, (2) gives the parameter symbol and [units], (3) and (4) give the parameter value and error, respectively, without spots (ns), while (5) and (6) give the parameter value and error with spots (s). Some values aren’t dependent on spots and remain constant regardless, so the second instance is marked with a quotation mark (“). Any blanks in the table denote data which is, as of the last edit, unknown and/or unavailable.
These values were calculated using the equations in Harmanec (1988). These equations assume our star(s) are main sequence, which is suspect. We only include the values as crude estimates, as spectral and radial velocity data will be required to obtain more certain values.


Parameter Filter 1 Error Filter 2 Error Filter 3 Error
a1 −0.01769 ±0.00029 -0.01497 ±0.00024 −0.01428 ±0.0016
a2 −0.14912 ±0.00064 −0.14238 ±0.00068 −0.1405 ±0.00125
a4 −0.02487 ±0.0003 -0.01497 ±0.00033 −0.02319 ±0.00143
a2(0.125-a2) −0.14912 ±0.00064 −0.14238 ±0.00068 −0.1405 ±0.00125
2b1 0.00598 ±0.00046 0.00481 ±0.00055 0.00356 ±0.000314
∆IFT 0.00646 ±0.00141 0.00462 ±0.00177 0.00415 ±0.00784
∆Iave 0.00911 ±0.00049 0.00969 ±0.00047 0.0058 ±0.00148
OER 1.0138 ±0.00151 1.01268 ±0.00205 1.00894 ±0.01198
LCA 0.00456 ±0.00141 0.00351 ±0.00151 0.00531 ±0.00458

Table 4: Calculated O’Connell effect quanitites. The given filters are Johnson B (Filter 1), Johnson V (Filter 2), and Cousins
RC (Filter 3) with parameters an being specific Fourier fits. Paramters 2b1, IFT , and Iave are quantifying parameters in
terms of the difference in maxima of the light curve peaks (Figure 2). OER is the ratio of area under the light curve between
φ = 0.0 and φ = 0.5. The LCA measures deviance from symmetry of the two halves of the light curve as seen in Figure 2.

Presentations

Contact Information

All members of the Variable Star Research group are enthusiastic researchers with a passion for the work performed by the group. We are always happy to discuss any research projects and are always looking for like-minded and enthusiastic collaborators. For more information regarding any of the aforementioned research activities or the research activities of the Variable Star Research Group, please do not hesitate to contact Robert Berrington.