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Eclipse timing variations (ETV) have been a successful tool for detecting circumbinary companions to eclipsing binaries (EB). While TESS and Kepler have been prolific for ETV searches, they sometimes can be limited by time and sky coverage which can be addressed by specialised ground-based ETV surveys. We present the initial results from the Solaris photometric survey which uses four 0.5m robotic telescopes in the southern hemisphere to look for circumbinary companions. We present the method of light curve extraction, detrending, and EB modelling using the observations from the Solaris network. Using these light curves we extract precise eclipse timing for 7 EB and look for companions using a Lomb-Scargle periodogram search. We find two possible periodic signals for the target GSC 08814-01026. With the system having strong activity, we check for the feasibility of orbital solutions at these two periods. We find that the 245 +/- 1 d period is due to an M-dwarf mass companion. This makes GSC 08814-01026 a candidate compact hierarchical triple system. The other periodic signal at 146 +/- 1 d is an artefact of stellar activity., Comment: 14 pages, 9 figures, Accepted for publication in MNRAS. This is a pre-copyedited, author-produced PDF of an article accepted for publication in MNRAS following peer review

We present results of the analysis of light and radial velocity (RV) curves of eight detached eclipsing binaries observed by the All-Sky Automated Survey, which we have followed up with high-resolution spectroscopy, and were later observed by the $Kepler$ satellite as part of the $K2$ mission. The RV measurements came from spectra obtained with OAO-188/HIDES, MPG-2.2m/FEROS, SMARTS 1.5m/CHIRON, Euler/CORALIE, ESO-3.6m/HARPS, and OHP-1.93/ELODIE instruments. The $K2$ time-series photometry was analyzed with the JKTEBOP code, with out-of-eclipse modulations of different origin taken into account. Individual component spectra were retrieved with the FD3 code, and analyzed with the code iSpec in order to determine effective temperatures and metallicities. Absolute values of masses, radii, and other stellar parameters are calculated, as well as ages, found through isochrone fitting. For five systems such analysis has been done for the first time. The presented sample consists of a variety of stars, from low-mass dwarfs, through G and F-type Main Sequence objects, to evolved active sub-giants, one of which is found to be crossing the Hertzsprung gap. One target may contain a $\gamma$ Dor-type pulsator, two more are parts of higher-order multiples, and spectra of their tertiaries were also retrieved and used to constrain the properties of these systems., Comment: This is a pre-copyedited, author-produced PDF of an article accepted for publication in MNRAS following peer review. 23 pages, 7 figures, 9 tables. Complete versions of some tables and figures will appear with the main article as supplementary material

We present the results of a spectroscopic campaign on eclipsing binaries with long orbital period (P = 20 - 75 d) carried out with the CHIRON spectrograph. Physical and orbital solutions for seven systems were derived from the V-band, and I-band ASAS, WASP, and TESS photometry, while radial velocities were calculated from high quality optical spectra using a two-dimensional cross-correlation technique. The atmospheric parameters of the stars have been determined from the separated spectra. Most of our targets are composed of evolved stars (sub-giants or red giants) but two systems show components in different phases of evolution and one possible merger. For four binaries the masses and radii of the components were obtained with precision better than 3%. These objects provide very valuable information on stellar evolution., Comment: 20 pages, 9 images, 5 tables. Accepted for publication in MNRAS

We present a new analysis of the multiple star V1200 Centauri based on the most recent observations for this system. We used the photometric observations from the Solaris network and the TESS telescope, combined with the new radial velocities from the CHIRON spectrograph and those published in the literature. We confirmed that V1200 Cen consists of a 2.5-day eclipsing binary orbited by a third body. We derived the parameters of the eclipsing components, which are $M_{Aa} = 1.393\pm0.018\,$M$_\odot$, $R_{Aa} = 1.407\pm0.014\,$R$_\odot$ and $T_{{\rm eff},Aa} = 6\,588\pm58\,$K for the primary, and $M_{Ab} = 0.863\,3\pm0.008\,1\,$M$_\odot$, $R_{Ab} = 1.154\pm0.014\,$R$_\odot$ and $T_{{\rm eff},Ab} = 4\,475\pm68\,$K for the secondary. Regarding the third body, we obtained significantly different results than previously published. The period of the outer orbit is found to be 180.4 days, implying a minimum mass $M_B = 0.871\pm0.020\,$M$_\odot$. Thus, we argue that V1200 Cen is a quadruple system with a secondary pair composed of two low-mass stars. Finally, we determined the ages of each eclipsing component using two evolution codes, namely MESA and CESTAM. We obtained ages of 16-18.5$\,$Myr and 5.5-7$\,$Myr for the primary and the secondary, respectively. In particular, the secondary appears larger and hotter than predicted at the age of the primary. We concluded that dynamical and tidal interactions occurring in multiples may alter the stellar properties and explain the apparent non-coevality of V1200 Centauri., Comment: Accepted for publication in MNRAS. 17 pages, 7 tables and 11 figures

We present the latest results of our spectroscopic observations and refined modelling of a sample of detached eclipsing binaries (DEBs), selected from the $Kepler$} Eclipsing Binary Catalog, that are also double-lined spectroscopic binaries (SB2). New high resolution spectra obtained with the HIDES spectrograph, attached to the 1.88-m telescope of the Okayama Astrophysical Observatory supplemented the previous observations, allowing to improve physical parameters of some systems, and characterize three previously omitted. All the obtained radial velocities (RVs) were combined with $Kepler$ photometry, in order to derive a full set of orbital and physical parameters. Ten out of eleven SB2s have their component spectra tomographically disentangled, and spectral analysis was performed with iSpec, in order to derive effective temperatures of components and metallicities of the systems. By comparing our results with theoretical models, we assess the age and evolutionary status of the studied objects. We find a good match to all but one systems. We have derived distances from thus determined parameters, and compare them with those from the $Gaia$ Data Release 2. For systems previously studied by other authors, our new results lead to better consistency between observations and models., Comment: 25 pages, 17 figures, 13 tables. To appear in MNRAS (production in progress). High-resolution light curve figures, and the entire Table B1 available in MNRAS

We present results of the combined photometric and spectroscopic analysis of three detached eclipsing binaries, which secondary components are not visible or very hard to identify in the optical spectra - ASAS J052743-0359.7, ASAS J065134-2211.5, and ASAS J073507-0905.7. The first one is a known visual binary ADS 4022, and we found that it is a quadruple system, composed of two spectroscopic binaries, one of which shows eclipses. None of the systems was previously recognized as a spectroscopic binary. We collected a number of high-resolution optical and IR spectra to calculate the radial velocities (RVs) and later combined them with MITSuME and ASAS photometry. The IR spectra were crucial for secure identification of the cooler components' lines. RV measurements were done with the TODCOR technique, and RV curves modelled with our own procedure V2FIT. Light curve modelling was performed with JKTEBOP and PHOEBE codes. Temperatures and metallicities of two systems were estimated from spectra. For the ADS 4022 system we also used the archival WDS data and new SOAR observations in order to derive the orbit of the visual pair for the first time. Ages were estimated by comparing our results with PARSEC isochrones. The eclipsing pair A052743 A ($P=5.27$ d) is composed of a 1.03(6) M$_\odot$, 1.03(2) R$_\odot$ primary and a 0.60(2) M$_\odot$, 0.59(2) R$_\odot$ secondary. The components of the $P=21.57$ d non-eclipsing pair B likely have masses in between the two eclipsing components, and both pairs are on a $\sim$188 yr orbit around their common centre of mass. The system A065134 ($P=8.22$ d) consists of a 0.956(12) M$_\odot$, 0.997(4) R$_\odot$ primary and a 0.674(5) M$_\odot$, 0.690(7) R$_\odot$ secondary. Finally, A073507 ($P=1.45$ d), which consists of a 1.452(34) M$_\odot$, 1.635(12) R$_\odot$ primary and a 0.808(13) M$_\odot$, 0.819(11) R$_\odot$ secondary, is likely a PMS system., Comment: 22 pages, 13 figures, 8 tables, accepted for publication in A&A, abstract modified for arXiv

We have obtained high-resolution spectra of four eclipsing binary systems (FM Leo, NN Del, V963 Cen and AI Phe) with the view to gaining insight into the relative orientation of their stellar spin axes and orbital axes. The so called Rossiter-McLaughlin (RM) effect, i.e. the fact that the broadening and the amount of blue- or redshift in the spectra during an eclipse depend on the tilt of the spin axis of the background star, has the potential of reconciling observations and theoretical models if such a tilt is found. We analyse the RM effect by disentangling the spectra, removing the front component and measuring the remaining, distorted lines with a broadening function (BF) obtained from single value decomposition (SVD), weighting by the intensity centre of the BF in the eclipse. All but one of our objects show no significant misalignment, suggesting that aligned systems are dominant. We provide stellar as well as orbital parameters for our systems. With five measured spin-orbit angles we significantly increase (from 9 to 14) the number of stars for which it has been measured. The spin-orbit angle $\beta$ calculated for AI Phe's secondary component shows a misalignment of 87$\pm$17 degrees. NN Del, with a large separation of components and a long dynamical timescale for circularisation and synchronisation, is an example of a close to primordial spin-orbit angle measurement., Comment: 30 pages, 15 figures

We present the design and commissioning of Project Solaris, a global network of autonomous observatories. Solaris is a Polish scientific undertaking aimed at the detection and characterization of circumbinary exoplanets and eclipsing binary stars. To accomplish this, a network of four fully autonomous observatories has been deployed in the Southern Hemisphere: Solaris-1 and Solaris-2 in the South African Astronomical Observatory in South Africa; Solaris-3 in Siding Spring Observatory in Australia; and Solaris-4 in Complejo Astronomico El Leoncito in Argentina. The four stations are nearly identical and are equipped with 0.5-m Ritchey-Cr\'etien (f/15) or Cassegrain (f/9, Solaris-3) optics and high-grade 2 K x 2 K CCD cameras with Johnson and Sloan filter sets. We present the design and implementation of low-level security; data logging and notification systems; weather monitoring components; all-sky vision system, surveillance system; and distributed temperature and humidity sensors. We describe dedicated grounding and lighting protection system design and robust fiber data transfer interfaces in electrically demanding conditions. We discuss the outcomes of our design, as well as the resulting software engineering requirements. We describe our system's engineering approach to achieve the required level of autonomy, the architecture of the custom high-level industry-grade software that has been designed and implemented specifically for the use of the network. We present the actual status of the project and first photometric results; these include data and models of already studied systems for benchmarking purposes (Wasp-4b, Wasp-64b, and Wasp-98b transits, PG 1663-018, an eclipsing binary with a pulsator) as well J024946-3825.6, an interesting low-mass binary system for which a complete model is provided for the first time.

We present the results of our analysis of KIC 4150611 (HD 181469) - an interesting, bright quintuple system that includes a hybrid $\delta$ Sct/$\gamma$ Dor pulsator. Four periods of eclipses - 94.2, 8.65, 1.52 and 1.43 d - have been observed by the Kepler satellite, and three point sources (A, B, and C) are seen in high angular resolution images. From spectroscopic observations made with the HIDES spectrograph attached to the 1.88-m telescope of the Okayama Astrophysical Observatory (OAO), for the first time we calculated radial velocities (RVs) of the component B - a pair of G-type stars - and combined them with Kepler photometry in order to obtain absolute physical parameters of this pair. We also managed to directly measure RVs of the pulsator, also for the first time. Additionally, we modelled the light curves of the 1.52 and 1.43-day pairs, and measured their eclipse timing variations (ETVs). We also performed relative astrometry and photometry of three sources seen on the images taken with the NIRC2 camera of the Keck II telescope. Finally, we compared our results with theoretical isochrones. The brightest component Aa is the hybrid pulsator, transited every 94.2 days by a pair of K/M-type stars (Ab1+Ab2), which themselves form a 1.52-day eclipsing binary. The components Ba and Bb are late G-type stars, forming another eclipsing pair with a 8.65 day period. Their masses and radii are $M_{Ba}=0.894\pm0.010$ M$_\odot$, $R_{Ba}=0.802\pm0.044$ R$_\odot$ for the primary, and $M_{Bb}=0.888\pm0.010$ M$_\odot$, $R_{Bb}=0.856\pm0.038$ R$_\odot$ for the secondary. The remaining period of 1.43 days is possibly related to a faint third star C, which itself is most likely a background object. The system's properties are well-represented by a 35 Myr isochrone. There are also hints of additional bodies in the system., Comment: 14 pages, 15 figures, 7 tables, to appear in A&A, abstract modified in order to fit the arXiv limit

We present the results of our spectroscopic observations of eight detached eclipsing binaries (DEBs), selected from the $Kepler$ Eclipsing Binary Catalog. Radial velocities (RVs) were calculated from high resolution spectra obtained with the HIDES pectrograph, attached to the 1.88-m telescope of the Okayama Astrophysical Observatory, and were used to characterize the targets in combination with the $Kepler$ light curves. For each binary we obtained a full set of orbital and physical parameters, reaching precision below 3% in masses and radii for 5 pairs. By comparing our results with theoretical models, we assess the distance, age and evolutionary status of the researched objects. We also study eclipse timing variations of selected objects, and identify a new system with a $\gamma$Dor pulsator. Two systems are triples, and show lines coming from three components. In one case the motion of the outer star and the perturbation in the RVs of the inner binary are clearly visible and periodical, which allows us to directly calculate the mass of the third star, and inclination of the outer orbit. In the second case we only see a clear motion of the tertiary, and investigate two scenarios: that it is a linear trend coming from the orbital motion around the inner binary, and that it is caused by a planetary mass companion. When possible, we also compare our results with the literature, and conclude that only by combining photometry with RVs it is possible to obtain correct physical parameters of both components of a DEB., Comment: Accepted by MNRAS, uncorrected proof. 23 pages, 19 figures, 9 tables (2 incomplete - will be published entirely with the electronic version in MNRAS)

We present spectroscopic and photometric solutions for three spotted systems with red giant components. Absolute physical and orbital parameters for these double-lined detached eclipsing binary stars are presented for the first time. These were derived from the V-, and I-band ASAS and WASP photometry, and new radial velocities calculated from high quality optical spectra we obtained with a wide range of spectrographs and using the two-dimensional cross-correlation technique (TODCOR). All of the investigated systems (ASAS J184949-1518.7, BQ Aqr, and V1207 Cen) show the differential evolutionary phase of their components consisting of a main sequence star or a subgiant and a red giant, and thus constitute very informative objects in terms of testing stellar evolution models. Additionally, the systems show significant chromospheric activity of both components. They can be also classified as classical RS CVn-type stars. Besides the standard analysis of radial velocities and photometry, we applied spectral disentangling to obtain separate spectra for both components of each analysed system which allowed for a more detailed spectroscopic study. We also compared the properties of red giant stars in binaries that show spots, with those that do not, and found that the activity phenomenon is substantially suppressed for stars with Rossby number higher than $\sim$1 and radii larger than $\sim$20 R$_\odot$., Comment: Published in MNRAS, 18 pages, 11 figures

We present results of our spectroscopic observations of nine detached eclipsing binaries (DEBs), selected from the $Kepler$ Eclipsing Binary Catalog, that only show one set of spectral lines. Radial velocities (RVs) were calculated from the high resolution spectra obtained with the HIDES instrument, attached to the 1.88-m telescope at the Okayama Astrophysical Observatory, and from the public APOGEE archive. In our sample we found five single-lined binaries, with one component dominating the spectrum. The orbital and light curve solutions were found for four of them, and compared with isochrones, in order to estimate absolute physical parameters and evolutionary status of the components. For the fifth case we only update the orbital parameters, and estimate the properties of the unseen star. Two other systems show orbital motion with a period known from the eclipse timing variations (ETVs). For these we obtained parameters of outer orbits, by translating the ETVs to RVs of the centre of mass of the eclipsing binary, and combining with the RVs of the outer star. Of the two remaining ones, one is most likely a blend of a faint background DEB with a bright foreground star, which lines we see in the spectra, and the last case is possibly a quadruple bearing a sub-stellar mass object. Where possible, we compare our results with literature, especially with results from asteroseismology. We also report possible detections of solar-like oscillations in our RVs., Comment: Accepted by MNRAS, uncorrected proof. 19 pages, 14 figures, 11 tables (3 incomplete - will be published entirely with the electronic version in MNRAS)

We evaluate a pre-production BACHES \'{e}chelle spectrograph in terms of its usefulness for radial velocity surveys of binary stars with small telescopes in a remote and autonomous. We use the Solaris-4 observatory located in Casleo, Argentina, that is part of a global network of autonomous observatories as the test-bed for the instrument. The setup is designed in such a way that spectroscopy and photometry can be carried out using the same telescope without the need to mechanically modify the imaging train. We observe single spectroscopic standard stars as well as binary stars up to 9.75 mag. We present results of mechanical tests of the instruments and spectroscopic observations carried out between Nov 26th and Dec 8th 2013. We conclude that BACHES is a very compact and capable spectrograph well suited for remote and autonomous operation. Coupled to a 0.5-m telescope it is capable of obtaining spectra of 10 mag targets with a SNR of 20 for 30-minute exposures. This is a very good result considering the price and size of the instrument. It brings new possibilities to the scientific community and opens a whole new range of research opportunities available to new and existing observatories., Comment: 11 pages, 16 figures, 2 tables, accepted for publication in MNRAS

Current precision in radial velocity (RV) measurements of binary stars reaches $\sim$2 ms$^{-1}$. This level of precision means that RV models have to take into account additional non-Keplerian effects such as tidal and rotational distortion of the components of a binary star, relativistic effects and orbital precession. We generate synthetic binaries using Yonsei-Yale stellar models. For typical representatives we investigate the impact of various orbital orientations and different non-Keplerian effects on the RV curves. To this end we simulate RV observations with an added white noise of different scale. Subsequently we try to reconstruct the input orbital parameters and their errors by fitting a model using a standard least-squares method. In particular we investigate the connection between the tidal distortion of the shape of the stars and the best-fit orbital eccentricity, the possibility of deriving orbital inclination of a non-eclipsing binary star by exploiting relativistic effects and the circumstances in which the orbital precession can be detected. We confirm that the method proposed by to obtain orbital inclination with use of the relativistic effect does work in favourable cases and that it can be used even for orbital configurations far from an edge-on orientation. We show that the RV variations imposed by tidally distorted stars can mimic non-zero eccentricity in some binaries. The scale of such an effect depends on the RV accuracy. Finally, we demonstrate that the apsidal precession can be easily detected with precision RVs. In particular we can detect orbital precession of $10^{-4}$ rad yr$^{-1}$, $10^{-3}$ rad yr$^{-1}$ for precision of RVs of 1 ms$^{-1}$ and 10 ms$^{-1}$ respectively., Comment: 10 pages, 8 figures

The Light-Time Effect (LTE) is observed whenever the distance between the observer and any kind of periodic event changes in time. The usual cause of this distance change is the reflex motion about the system's barycenter due to the gravitational influence of one or more additional bodies. We analyze 5032 eclipsing contact (EC) and detached (ED) binaries from the All Sky Automated Survey (ASAS) catalogue to detect variations in the times of eclipses which possible can be due to the LTE effect. To this end we use an approach known from the radio pulsar timing where a template radio pulse of a pulsar is used as a reference to measure the times of arrivals of the collected pulses. In our analysis as a template for a photometric time series from ASAS, we use a best-fitting trigonometric series representing the light curve of a given EC or ED. Subsequently, an O-C diagram is built by comparing the template light curve with light curves obtained from subsets of a given time series. Most of the variations we detected in O-Cs correspond to a linear period change. Three show evidence of more than one complete LTE-orbit. For these objects we obtained preliminary orbital solutions. Our results demonstrate that the timing analysis employed in radio pulsar timing can be effectively used to study large data sets from photometric surveys., Comment: 7 pages, 8 figures