the system must be very evolved, like Algol itself. However Marschall et al. (1990) reported that the system is a double-lined spectroscopic binary with nearly ...
A DETACHED BINARY SYSTEM V505 PERSEI ¨ OSMAN DEMIRCAN, SACIT OZDEMIR and MEHMET TANRIVER Ankara University Observatory, Science Faculty, Tando˘gan, Ankara, Turkey (Received 16 July, 1997; accepted 31 July, 1997)
Abstract. The UBV photometry of a detached F-type eclipsing binary V505 Persei is presented. The light curve solution by a simple spherical model combined with the radial velocity data from two high resolution spectra by Marschall et al. (1990) reveals that the system is formed with two identical 1:2M in the main sequence close to ZAMS in evolution. They should component stars of M 0:017). The isochrones with solar metallicity by Van denBerg have about solar metallicity (z (1985) yield an age of about (2:2 0:5) 109 yr for the system. The distance of the system should be about 60 pc.
1. Introduction The eclipsing binary nature of bright star SAO 023229 (BD + 39 0764 = HD 14384) was discovered recently, and designated DHK 11 in the discovery paper (Kaiser et al., 1990). The system was named later V505 Per in the 71st Name List of Variable Stars (Kozarovets et al., 1993). The eclipses of 0.55 mag depth and period of 2:d 111 were found but no secondary eclipses were reported by Kaiser et al. (1990), leaving open the question of whether the system contains a very shallow secondary minimum or identical primary and secondary minimum. In the first case the system must be very evolved, like Algol itself. However Marschall et al. (1990) reported that the system is a double-lined spectroscopic binary with nearly equal line strengths, indicating that the period is 4:d 222 and the primary and secondary minima are nearly equal in depths. The photoelectric observations by Williams et al. (1990) supported this conclusion. Thus, the components of the system should be very similar in mass, radius and luminosity. The light curves formed by the photoelectric observations indicate negligible ellipticity and reflection effects, and the orbit of the system appears to be circular. In order to understand the eclipse nature and physical properties of the system we included V505 Per in our observing program in 1990. 2. New Observations We observed V505 Per on 30 nights between September 1990 and February 1991, with a photometer attached to the 30 cm Maksutov telescope of the Ankara University Observatory. The photomultiplier in the photometer was an EMI 97890 QB. A total of 452 observations in each in B and V filters, and 362 observations in U filter were secured. Each observation comprised two measurements, in each filter, in Astrophysics and Space Science 250: 327–335, 1997. c 1997 Kluwer Academic Publishers. Printed in Belgium.
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Table I The log of the UBV observations of V505 Per Date
Filters
1990, Sept. 1 ” , Sept. 2 ” , Sept. 3 ” , Sept. 4 ” , Sept. 5 ” , Sept. 6 ” , Sept. 7 ” , Sept. 8 ” , Sept. 10 ” , Sept. 11 ” , Sept. 20 ” , Sept. 21 ” , Sept. 30 ” , Oct. 1 ” , Oct. 2 ” , Oct. 4 ” , Oct. 5 ” , Oct. 6 ” , Oct. 7 ” , Oct. 12 ” , Oct. 15 ” , Nov. 12 ” , Nov. 15 ” , Nov. 18 ” , Dec. 9 ” , Dec. 11 ” , Dec. 28 ” , Dec. 31 1991, Jan. 1 ” , Jan. 26
U; B; V ” ” ” ” ” ” ” ” ” ” ” ” ” ” ” ” ” ” ” ” ” ” ”
B; V ” ” ” ” ”
N
Observers
30 32 27 8 11 40 26 34 7 36 4 9 5 5 38 8 4 4 6 12 5 5 4 5 5 5 5 34 37 3
GK ZM ¨ SO BG BG BG ¨ FO ¨ SO ¨ SO BG BA ¨ FFO BA ZM BG BA ZM ZM ZM ¨ SO SS SS ZM ZM/ ZM AA ¨ SO BA GK ¨ FO
Number of observations in each filter.
ZM: Zekeriya M¨uyessero˘glu, SS: Selim O. ¨ Ferhat F. Ozeren, ¨ Selam, AA: Ayvur Akalm, FO: GK: G¨oksel Kahraman, FE: Fehmi Ekmekc¸i, HD: ¨ Sacit Ozdemir, ¨ H¨useyin D¨undar, SO: BG: Birol G¨urol, BA: Berahitdin Albayrak
the sequence comparison-variable-sky-variable-comparison. The comparison and check stars are BD + 54 0567 = SAO 023407 and BD + 54 0561 = 023389, respectively. The r.m.s. error of single observation, obtained from comparison minus check star observations, is 0.023, 0.026 and 0.075 mag in V , B and U filters, respectively. Differential observations, in the sense variable minus comparison,
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Table II New times of minima of V505 Per HD Min. time
0:0018 0:0063 0:0051 2448167:4708 0:0059 :4680 0:0044 :4692 0:0034 2448260:3561 0:0002 :3562 0:0004 2448146:3818 :3666 :3774
Filter
N
U B V
11 9 15
U B V
16 16 16
B V
24 24
Mean
e j c e j c e c
2448146:3753
0:0064
2448167:4693
0:0047
2448260:35615
0:0003
Figure 1. The light and color curves of V505 Per.
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Table III The mean values of the eclipse parameters of V505 Per
rp rs i Lp Ls up
0:09 0:01 0:08 0:01 88 0:5 0.59, 0.55 0.41, 0.45 0.68, 0.55
(in B and V , respectively) (in B and V , respectively) (in B and V respectively, adopted)
Figure 2. Theoretical light curves for the mean solution and the U , B and V observations in the primary eclipse.
were corrected for extinction and light time effect of the Earth’s motion. The log of the observations, which are available on request from the authors, is given in Table I. The light and color curves formed by our observations are shown in Figure 1. The primary minimum was observed three times during the observations. Three new minima times obtained by using the well known method of Kwee and
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Van Woerden (1956) are listed in Table II. In the phase calculations of the present observations we used the ephemeris derived by Williams et al. (1990): HJD Min I = 2447863.4858 + 4.222017E :0008 :000002 Figure 1 shows that there are gaps in our observations particularly during the secondary eclipse phases, although the primary eclipse phases are well covered. However, four observations in the ingress of the secondary eclipse supports the existence of deep secondary minimum (see Williams et al., 1990). Williams et al. (1990) observed nearly identical (differ by no more than 0:m 03) primary and secondary minima. Our observations also support the Williams et al.’s conclusion that the observations outside the eclipse phases are constant within the error of observations, so the ellipticity and reflection effects should be negligible. The depth of the primary minimum in our observations is about 0:m 59, 0:m 57 and 0:m 50 in the U , B and V filters, respectively, indicating a slightly hotter component is eclipsed during this minimum. Duration of the primary eclipse in our observations is about (0:051 0:002)P (5:17 0:20) hours which is about same as the value quoted by Williams et al. (1990).
3. Light Curve Solution The constancy of light outside eclipse phases shows that V505 Per is well-detached binary with negligible proximity effects. The component stars should be spherical with homogeneous light distribution over the surfaces. In this case the light curves are well presented by a spherical model and thus the normalised brightness measurement l( ) at any phase is given by l( ) = 1 L1 . Here, L1 stands for the fractional luminosity of the eclipsed component (L1 + L2 = 1), and L1 is the fractional loss of light due to eclipse. The spherical eclipse function can be effectively calculated by means of a new formulation (see Kopal and Demircan, 1978; and Demircan, 1978). Thus, a theoretical eclipse light curve is easily produced for a given set of eclipse parameters: the fractional radii r1;2 of the component stars, the inclination i of the orbital plane, the fractional luminosity L1 , and the limb darkening coefficient u1 of the eclipsed star. A comparison of the observational and theoretical light curves will lead to the readjustment of the eclipse parameters for a better agreement. A 2 -test is applied for this purpose. The eclipse parameters are assumed to be the final photometric solution when satisfactory agreement is reached between the observed and theoretical eclipse light curves. Five to ten fixed points in the eclipse phases, including mid-eclipse and external contact points, read on the free hand curves drawn among the observations were considered for the photometric solution of the eclipse parameters. As noted, the binary should be well detached unevolved algol system with nearly identical component stars in mass, radius and luminosity. In this case the primary minimum should be a
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Table IV The absolute dimensions of V505 Per Primary
M (M ) R(R ) L(L ) K (km/s) a(R ) Mb log g (cgs) log Te (K) aver: (cgs) (Mb ) system a(R ) = a1 + a2 Distance (pc)
1.23 1.31 2.74 88 7.4 3.6 4.30 3.813 0.775
Secondary 1.22 1.17 2.12 89 7.4 3.9 4.39 3.809 1.079 3:m 0 14.8 60
transit type: slightly more massive larger and hotter component is eclipsed during the primary minimum. It was found by Williams et al. (1990) that the system at maximum V = 6:m 37m and (B V ) = +0:43; the color is expected for an unreddened F5V star. The corresponding limb darkening coefficients u(B ) = 0:68 and u(V ) = 0:55 from Al-Naimiy (1978) of the hotter component were fixed for the solution of B and V light curves. The solution of the U light curve has not been attemped because of the larger scatter of the observations. The r1;2 = 0:1, i = 80 and L1 = 0:50 were adopted for the initial parameters and after about 20 iterations in each filter we reached the acceptable solutions. The parameters of the solutions are listed in Table III, and theoretical eclipse curves formed by these mean parameters are shown among the eclipse observations in Figure 2. The mean error in the fractional luminosities in Table III is about a few percent.
4. Absolute Dimensions Within the error of observations, the constancy of the colors (see Figure 1) in all phases indicates nearly equal surface fluxes (and thus temperatures) for the component stars. The mean error in (B V ) and (U B ) color measurements is about 0:m 03 and 0:m 04 respectively, which corresponds for an F5V spectral type star to an error of no more than about 60 K in temperature estimation. This figure should also be an upper limit for the temperature difference between the component stars. The difference in light levels of mid-eclipse phases in Williams et al.’s light curves reveals the surface flux ratio Jp =Js 1:03 which also corresponds to about 60 K temperature difference between the components. The temperature estimate for the primary component inferred from F5V spectral type gives T1 = 6500 60 K,
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Figure 3. Estimated positions of the components of V505 Per in the (M L) and (M The ZAMS and TAMS lines are for the solar composition from Van denBerg (1985).
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R) planes.
thus T2 should be of order 6440 60 K, where the error estimates are from the color curves. Two high resolution spectra of the system were observed and the radial velocities of the component stars at phases 0.08 and 0.717 were obtained by Marshall et al. (1990). Knowing that the conjunction time corresponds to mid-primary eclipse phase and the orbit is circular we estimated the amplitudes of radial velocity curves as 88 and 89 km/s with errors not more than a few km/s. Moreover the gamma velocity of the system turns out to be around zero. By combining our light curve solution with these radial velocity data we obtained the preliminary values for the absolute dimensions of V505 Per. They are listed in Table IV. The errors of the entries in Table IV are in the last figures. The total absolute magnitude of the
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Figure 4. Estimated positions of the components of V505 Per in the (T L) plane. The evolutionary tracks are for Z = 0:001 (dashed) and for Z = 0:020 (solid) from Van denBerg (1985).
system should be about 3:m 00 which corresponds to a total Mv of 3:m 02 with the estimated BC of 0:02. Considering that V = 6:m 87 outside eclipses, and a mean E (B V ) = 0:m 05, the distance of the system is estimated around 60 pc. 5. Evolutionary Status Due to very incomplete light and radial velocity curves, the resulting eclipse parameters in Table III and the absolute dimensions in Table IV should not be final. However they should define a first picture of the system. It is interesting to see in this picture that V505 Per is formed with two very identical components which should be normal main sequence stars. In order to understand the evolutionary status of the components of V505 Per, we plot the preliminary absolute dimensions from Table IV in the mass radius (M R), mass-luminosity (M L), and effective temperature-luminosity (T L) planes formed by the detached binaries and ZAMS
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and TAMS models by Van denBerg (1985). The theoretical evolutionary tracks and isochrones were also considered in the (T L) plane. It was seen in Figure 3 and Figure 4 that the components of V505 Per are unevolved main sequence stars which are close to ZAMS. Figure 4 shows that only the models with about solar metallicity (Z = 0:0169) could fit the component stars of V505 Per. The isochrones with solar metallicity yield an age of (2:2 0:5) 109 yr for the system. Finally, we think the system warrants further photometric and spectroscopic study, primarily through the potentially high accuracies of mass, radius and temperature values that can be achieved.
Acknowledgements We acknowledge the partial support by the Scientific and Technical Research Council of Turkey.
References Al-Naimiy, H.M.: 1978, Astrophys. Space Sci. 53, 181. Demircan, O.: 1978, PhD Thesis, The University of Manchester. Kaiser, D.H., Baldwin, M.E. and Williams, D.B.: 1990, Inf. Bull. Variable Stars 3442. Kopal, Z. and Demircan, O.: 1978, Astrophys. Space Sci. 55, 241. Kozarovets, E.V., Samus, N.N. and Goranskij, V.P.: 1993, Inf. Bull. Variable Stars 3840. Kwee, K.K. and Van Woerden, H.: 1956, Bull. Astron. Inst. Neth. 12, 327. Marschall, L.A., Stefanik, R.P., Nations, H.L. and Davis, R.J.: 1990, Inf. Bull. Variable Stars 3447. Van denBerg, D.A.: 1985, Astrophys. J. Suppl. 58, 711. Williams, D.B., Landis, H.J. and Pray, D.: 1990, Inf. Bull. Variable Stars 3479.
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