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V348 and and V572 Per: Bright Triple Systems with Eccentric Eclipsing Binaries

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V348 and and V572 Per: Bright Triple Systems with Eccentric Eclipsing Binaries Draft version August 15, 2019 Preprint typeset using LATEX style emulateapj v. 12/16/11 V348 AND, AND V572 PER: BRIGHT TRIPLE SYSTEMS WITH ECCENTRIC ECLIPSING BINARIES P. Zasche1,R.Uhlarˇ2, P.Svoboda3, J. Jurysekˇ 4,D.Korcˇakov´ a´1,M.Wolf1, M. Sˇlechta5,L.Kotkova´5 1 Astronomical Institute, Charles University, Faculty of Mathematics and Physics, CZ-180 00, Praha 8, V Holeˇsoviˇck´ach 2, Czech Republic, 2 Private Observatory, Pohoˇr´ı71, CZ-254 01 J´ılov´eu Prahy, Czech Republic 3 Private Observatory, V´ypustky 5, CZ-614 00, Brno, Czech Republic 4 Institute of Physics, The Czech Academy of Sciences, Na Slovance 1999/2, CZ-182 21, Praha, Czech Republic 5 Astronomical Institute, The Czech Academy of Sciences, CZ-251 65, Ondˇrejov, Czech Republic (Dated: Received 2019 April 2; revised 2019 June 3; accepted 2019 June 25; published 2019 August 2) Draft version August 15, 2019 ABSTRACT The eclipsing binaries are still important objects for our understanding of the Universe. Especially these ones located within the more complex multiple systems can help us solving the problem of their origin and sub- sequent evolution of these higher-order multiples. Photometry and spectroscopy spanning over more than 25 years were used for the first complete analysis of the two bright triple systems, namely V348 And and V572 Per. The light curves in photometric filters were combined together with the radial velocities and analysed simulta- neously, yielding the precise physical parameters of the eclipsing components of these multiple systems. The system V348 And consists of two eclipsing components with its orbital period of about 27.7 days. The system is a very detached one, and both eclipses are rather narrow, lasting only about 0.016 of its period. The visual orbit of the wide pair has the period of about 87 years. All three components of the system are probably of B8-9 spectral type, and the parallax of the system was slightly shifted to the value of 2.92 mas. On the other hand, the system V572 Per shows apsidal motion of its inner orbit, the orbital period being of about 1.2 days, while the apsidal motion of about 48 years. The components are of A and F spectral types, while the motion with the third component around a common barycenter is only negligible. According to our modelling, this system is not a member of open cluster Alpha Persei. Subject headings: stars: binaries: eclipsing – stars: binaries: visual – stars: binaries: spectroscopic – stars: fundamental parameters – stars: individual: V348 And, V572 Per – open clusters and asso- ciations: individual: Alpha Persei Cluster 1. INTRODUCTION ticular system and derive its parameters. The importance of The eclipsing binaries still represent the most general dedicated studies of particular systems with higher hierarchies method how to derive the stellar masses, radii and luminosi- was presented e.g. in the updated version of the Multiple Star ties most precisely. The fruitful combination of the obser- Catalog MSC, Tokovinin (2018). This is the main aim of the vational techniques like photometry and spectroscopy is still present paper, to bring new results on two new multiple sys- being used also for deriving the temperatures, surface gravi- tems never studied before. And moreover, both these systems ties or limb darkening, but also to compute the distances to are bright enough for subsequent follow-up observations. these systems. Due to this reason, we have focused our effort on two sys- On the other hand, studying the binaries as parts of the tems for which their light curves (hereafter LC) and radial higher order multiple systems can bring us new important re- velocity curves were not studied yet (namely V348 And, and sults connected with the stellar origin and evolution. We can V572 Per). Besides the inner eclipsing pair, both these sys- ask – how many multiple systems are there within the stellar tems also contain the distant third component detected via in- population? What is the multiplicity fraction of the field stars, terferometry with its rather long orbital period. Moreover, arXiv:1908.04975v1 [astro-ph.SR] 14 Aug 2019 and is this number still the same? Or is it somehow evolving both these stars show the eccentric orbits. in time and the multiplicity fraction can be tracked as different 2. THE ANALYSIS between PopI and PopIII stars? Is the mass ratio, period ratio, Whole our analysis is using a classical combination of the or eccentricity ratio the same for the low mass as well as for photometry and spectroscopy into one joint approach. If we the high mass stars? What is the role of the Kozai cycles (see combine these methods, we can obtain the physical parame- ff e.g. Eggleton & Kiseleva-Eggleton 2001)? Can the e ects ters of both eclipsing components as well as the parameters like synchronization or circularization predicted by the tidal of their mutual orbit. As a consequence, having the complete theories (Zahn 2008) be traced in particular systems via de- information about their masses, inclinations, periods, etc. we riving their orbital and physical parameters? These and many can also fill in still quite incomplete statistics of the multiple other still open questions play a crucial role in our theories (triple and quadruple) systems. All of these distributions of of stellar formation and evolution, see e.g. Tokovinin (2008), orbital and physical parameters are being used for discussions Halbwachs et al. (2003), or Tokovinin (2014). And of course, about the origin and subsequent evolution of such multiples the models can be tested and verified only when using the (Tokovinin 2008 and Tokovinin 2014). real data, which can be obtained only via studying the par- All of our new spectroscopic observations were secured in the Ondˇrejov observatory in Czech Republic, using the 2- [email protected]ff.cuni.cz meter telescope. The classical slit spectrograph has its res- 2 Zasche et al. olution R ∼ 12500. The individual exposure times were cho- its brightness and northern declination, its detailed analysis is sen according to the quality of the particular night, typically still missing. The star was classified as an eclipsing binary 800–3600 seconds. All the spectrograms were reduced in based on the Hipparcos data (Perryman & ESA 1997), hav- a standard way, the wavelength calibration was made via a ing the supposed orbital period of about 5.5 days. However, ThAr comparison spectra obtained before and after the stellar according to our observations obtained during 2007–2008 we ones. The flatfields were taken in the beginning and end of found there no evidence of eclipse. Hence, we prematurely the night and their averages were then used for the reduction. stated that the star was incorrectly classified as an eclipsing bi- After then, the radial velocities (hereafter RV) were derived nary, see our previous paper on this star in Zasche & Svoboda with the program SPEFO (Horn et al. 1996, or Skodaˇ 1996), (2008). on several absorption lines in the measured spectral region According to our new findings presented in this paper, we around Hα (usually Fe, Ca, or Si lines), with using the zero found that the star is eclipsing, but with much longer orbital point correction via measuring the telluric lines. period. Moreover, the star is also known as a visual binary, ′′ Owing to relatively high brightness of these stars, only having the distant component of about 0.1 away from the rather small telescopes were used for the photometric obser- primary. However, its orbital period is still rather uncer- vations. The system V348 And was observed (by PS) with tain (see below). The parallax of the system was derived as only the 34-mm refractor at his private observatory in Brno, 3.02 mas (van Leeuwen 2007), while more recently by GAIA Czech Republic, using the SBIG ST-7 CCD camera. The sec- (Gaia Collaboration et al. 2018) as 2.16 mas. ond star V572 Per was monitored with the similar instrument After several years of observations, there was detected a at the private observatory (by RU) in J´ılov´eu Prahy, Czech photometric decrease, indicating that the star is really an Republic, using a G2-0402 CCD camera. All the measure- eclipsing one. And finally after many other nights of ob- ments were reduced in a standard way using the programme servations we found out that its period is much longer than C-MUNIPACK1 which is based on aperture photometry and previously assumed, being of about 27.7 days. However, uses the standard DAOPHOT procedures (Tody 1993). The these eclipses are very narrow (lasting about only 0.016 of photometric data were obtained during the time span 2007– the phase, which is of about 10.4 hours), but relatively deep, 2018. Nevertheless, some of the older data were only used for of about 0.14 mag in R filter. the minima times derivation. All of these data were secured in The combined analysis of LC+RV provides us an insight the Johnson-Cousins photometric system (Bessell 1990), par- into basic physical parameters of both components. System is ticularly the system V348 And was observed in BVR, while composed of two very similar stars. Primary and secondary the system V572 Per in BVRI filters. components are both of B9V spectral type. The results of Both photometric and spectroscopic observations were our analysis are given in Table 1, while the plots of the RV studied in the standard approach. Hence, the program curve as well as the light curves are given in Fig. 1. The PHOEBE (Prˇsa & Zwitter 2005), which is using the classical third componentis even more luminous than the eclipsing pair Wilson-Devinney algorithm (Wilson & Devinney (1971) and itself, and according to the spectra its spectral type should its later modifications) was used for the analysis.
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