arXiv subjects

K. G. Hełminiak

Publications and source records attributed to K. G. Hełminiak.

At least 19 recordsLinked to original sources

arXiv2026

Plato benchmark stars I. The initial benchmark sample

The ESA PLATO mission aims to detect and characterise Earth-size exoplanets orbiting bright, late-type stars using high-precision photometry and asteroseismology. Precise stellar parameters of host stars are essential for exoplanet characterisation and model benchmarking. This work defines the PLATO benchmark stars (PBS) catalogue, a comprehensive sample of well-characterised stars designed to support all mission phases. We compiled data from eclipsing and spectroscopic binaries, interferometry, asteroseismology, and large spectroscopic and photometric surveys. Fundamental and atmospheric stellar properties (mass, radius, luminosity, age, effective temperature, surface gravity, density, and limb darkening) were assigned quality levels (B1, B2, B3) reflecting their degree of model dependence. Homogenized ancillary parameters (including Gaia DR3 bias-corrected parallaxes, metallicities, bolometric fluxes, extinction, rotation periods, and X-ray fluxes for M dwarfs) are also provided. The PBS catalogue contains 1090 FGKM main-sequence and subgiant stars, divided into three quality tiers based on model-independent (B1) parameters: gold (15 stars with B1 mass, radius, and luminosity), silver (195 with B1 mass and radius), and bronze (416 with at least one B1 property). The remaining stars feature well-characterised model-dependent (B2) or empirical (B3) properties. About 40% of the sample lies within the PLATO fields of view (285 in LOPN1 and 143 in LOPS2). The PBS sample represents the largest catalogue of benchmark stars assembled to date, providing a key resource for validating automated pipelines, testing evolutionary models, and cross-survey calibration. The catalogue is available online at https://astro.ulb.ac.be/pbs and will be updated regularly.

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arXiv2026

Ariel stellar characterisation IV. Fundamental parameters of 18 hot stars in the Ariel mission candidate sample

The characterisation of exoplanetary systems depends on the accurate determination of host star parameters. The Ariel mission will probe the atmospheres of a statistically significant sample of exoplanets, and so requires a precise characterisation of the stellar properties well before its launch in 2029. The homogeneous determination of stellar parameters for Ariel will enable both the optimisation of the final target list and set roots for a reliable interpretation of the formation and evolution of planetary systems. Such a homogeneous characterisation has thus far only been carried out for the cool (\teff\ $\lesssim 7000\,$K) host stars among the Ariel target candidates. We present a uniform determination of fundamental stellar parameters for 18 hot stars in the Tier 1 candidate list of the Ariel mission candidate sample. We adopted an iterative spectro-trigonometric approach optimised for high-temperature stars. High-resolution spectra were analysed using the \textsc{zeeman} code with $χ^2$ minimisation, combining model fits to metal and Balmer lines. Surface gravity was refined using photometry-based radii and masses from stellar evolutionary tracks. We derived effective temperatures, surface gravities, projected rotational velocities, microturbulent velocities, overall metallicities, iron abundances, stellar masses, and radii for our sample of $18$ hot stars. Our results were validated against a set of benchmark stars previously presented in the literature. The derived parameters provide an internally consistent basis for studying the link between stellar properties and planetary characteristics in intermediate-mass stars. Building on our previous work on FGK host stars, we show that correlations between stellar mass, metallicity, and planetary radii also extend to early-type stars, and stellar properties influence the architecture of multi-planet systems.

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arXiv2026

RX Gru: a short-period pre-main-sequence eclipsing binary with a distant circumbinary companion

We report the discovery of a new short-period pre-main-sequence eclipsing binary, RX Gru, orbited by a distant circumbinary companion. We characterized the system by analysing the photometric observations from the Solaris network, the Transiting Exoplanet Survey Satellite, and the Super Wide Angle Search for Planets survey, combined with the radial velocities from four high-resolution spectrographs: HARPS, FEROS, CHIRON, and HRS. We derived the parameters of the eclipsing components, which are $M_{\rm Aa} = 1.004^{+0.027}_{-0.026}\,$M$_\odot$, $R_{\rm Aa} = 1.007\pm0.021\,$R$_\odot$, and $T_{\rm eff,Aa} = 5379\pm289\,$K for the primary, and $M_{\rm Ab} = 0.985^{+0.024}_{-0.025}\,$M$_\odot$, $R_{\rm Ab} = 1.024\pm0.023\,$R$_\odot$, and $T_{\rm eff,Ab} = 5322\pm278\,$K for the secondary. We determined the age of the system from the observed parameters using two evolution codes, MESA and Cesam2k20. We obtained an age of $\sim$28$\,$Myr, placing the two stars at the very end of the pre-main-sequence phase. We also derived the minimum mass and orbital period of the tertiary companion, which are found to be $M_{\rm B} = 89.0\pm3.5\,$M$_{\rm Jup}$ and $P_{\rm AB} = 23.79 ^{+0.10 }_{-0.25}\,$yr, respectively. We conclude that RX Gru consists of a tight inner binary composed of two twin components and an outer low-mass companion (a massive brown dwarf or a very low-mass star) in a relatively wide orbit, and we suggest that the system was formed via the dynamical unfolding mechanism coupled with the shared accretion of the circumbinary material by the binary components.

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arXiv2026

V446 Cephei: a $β$ Cep pulsator in a multiple system

$β$ Cep stars in eclipsing binary (EB) systems give us an opportunity to put observational constraints on their structure and stellar parameters. We present a comprehensive analysis of the $β$ Cep star in the EB V446 Cep, using \textit{TESS} photometry and HERMES spectra. We calculate the stellar and orbital parameters using light curve modelling and spectral disentangling. The EB has an orbital period of $3.808567 \pm 0.000012$ d and a mass ratio of $0.1550 \pm 0.0012$. We find the $β$ Cep star to have a mass of $10.68 \pm 0.06$ $\mathrm{M_{\odot}}$, a radius of $5.864 \pm 0.033$ $\mathrm{R}_{\odot}$, and a $T_{\rm eff}$ of $24220 \pm 180$ K. The secondary has a mass of $1.657 \pm 0.017$ $\mathrm{M_{\odot}}$, a radius of $1.530 \pm 0.014$ $\mathrm{R}_{\odot}$, and a $T_{\rm eff}$ of $9080 \pm 390$ K. We also extract the abundances of C, N, O, Mg, and Si for the $β$ Cep star, which are found to be consistent with galactic OB binaries. We identified 21 distinct pulsation frequencies, with the dominant mode at 10.24324 d$^{-1}$, which corresponds to a near-harmonic of the system's orbital frequency. The two stars in the EB have asynchronous rotation, with both stars rotating faster than the orbital frequency. We detect a companion to the EB using eclipse timing variations and period changes of the dominant pulsation frequency. We calculate the minimum mass of this tertiary companion to be $4.11 \pm 0.32$ $\mathrm{M_{\odot}}$ which is on an orbit of 2303$\pm$69 d around the EB. Using spectral energy distributions and MIST isochrones, we conclude that V446 Cep is either a co-evolving hierarchical 2+2 quadruple or a triple system where the third body is a compact object.

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arXiv2025

A comprehensive study of $δ$ Scuti-type pulsators in eclipsing binaries: oscillating eclipsing Algols

Eclipsing double-lined spectroscopic binaries hosting $δ$ Scuti-type pulsators offer a unique laboratory for simultaneously constraining stellar geometry and interior structure. In this study, we present a comprehensive analysis of five oscillating eclipsing Algol binaries. By combining high-precision, short-cadence TESS photometry with multi-epoch high-resolution spectroscopy, we derive precise stellar and orbital parameters. Frequency power spectra were obtained using residuals from binary modelling. We further investigate the evolutionary history of these systems using a grid of MESA binary evolution simulations. Our analysis suggests that the systems must have undergone either case A or case B mass transfer, with the primary components repositioned in the Hertzsprung-Russell diagram and now pulsating in the $δ$ Scuti regime, while the cooler secondaries are underluminous and inflated, filling their Roche lobes. This study contributes to the growing catalog of well-characterised oEA systems and our understanding of the effects of mass-transfer on the fate of these short-period binaries.

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arXiv2024

Comprehensive study of five candidate delta Scuti-type pulsators in detached eclipsing binaries

Pulsating stars in eclipsing binaries (EBs) provide an excellent opportunity to obtain precise, model-independent stellar parameters for studying oscillations in detail. One common class of pulsators in these EBs exhibits delta Scuti-type oscillations. Characterising these pulsators using the precise parameters obtained from EB modelling enhances our understanding of such stars and strengthens asteroseismic studies. We conducted a comprehensive photometric and spectroscopic analysis of candidate pulsators in detached EBs to expand the sample of systems with accurately determined absolute parameters. We performed radial velocity and light curve modelling to estimate the absolute stellar parameters, along with detailed spectroscopic modelling to obtain global metallicity and temperatures. Frequency power spectra were derived from the residuals of binary modelling. Isochrones were used to determine the stars' ages, which were then compared to theoretically obtained values. We present a detailed analysis of four candidate delta Scuti-type pulsators in EBs and update the light curve analysis of the previously studied system TIC 308953703. The masses and radii of the components are constrained with high accuracy, aiding in age estimation. We perform a Fourier analysis of the observed oscillations and explore their origin. For TIC 81702112, we report tidal effects causing amplitude variation in the oscillation frequencies over the orbital phase.

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arXiv2024

Spectroscopy of Eclipsing Compact Hierarchical Triples I

Eclipsing Compact Hierarchical Triples (ECHTs) are systems with the tertiary star orbiting an eclipsing binary (EB) in an orbit of fewer than 1000 days. In a CHT, all three stars exist in a space less than 5 AU in separation. A low-mass CHT is an interesting case to understand multiple star and planet formation at such small scales. In this study, we combine spectroscopy and photometry to estimate the orbital, stellar and atmospheric parameters of stars in a sample of CHTs. Using the complete set of parameters we aim to constrain the metallicity and age of the systems. We use time-series spectroscopy to obtain radial velocities (RVs) and disentangled spectra. Using RV modelling, EB light curve modelling, and spectral analysis, we estimated the metallicities and temperatures. Using isochrone fitting, we constrain the ages of the system. We then combine observations of masses, outer eccentricities (e_2), orbital periods and age estimates of the systems from the literature. We compare the distributions of e_2, and tertiary mass ratio, q_3 = M_3/(M_1+M_2), for three different metallicity ranges and two ranges of age. We estimate masses, radii, temperatures, metallicities and age of 12 stars in 4 CHTs. The CHT CD-32 6459 shows signs of von Zeipel-Lidov-Kozai oscillations while CD-62 1257 can evolve to form a triple common envelope. The rest of the CHTs are old and have an M-dwarf tertiary. We find that the q_3 distribution for CHTs with sub-solar metallicity has a uniform distribution but the systems with solar and above-solar metallicity peak between 0.5 and 1. When dividing them according to their ages, we found the q_3 of old systems around 0.5. The eccentricity e_2 favours a value around 0.3 irrespective of metallicity or age. The distributions are biased by the lack of observations and observing methods and therefore call for more observations of low-mass CHT.

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arXiv2024

Discovery of a hot post-AGB star in Galactic globular cluster E3

We report a new hot post-asymptotic giant branch (PAGB) star in the Galactic globular cluster (GC) E3, which is one of the first of the identified PAGB stars in a GC to show a binary signature. The star stands out as the brightest source in E3 in the \mbox{\em Astrosat}/UVIT images. We confirmed its membership with the cluster E3 using Gaia DR3 kinematics and parallax measurements. We supplemented the photometric observations with radial velocities (RVs) from high-resolution spectroscopic observations at two epochs and with ground- and space-based photometric observations from 0.13 $μ$m to 22 $μ$m. We find that the RVs vary over $\sim$6 \kms\ between the two epochs. This is an indication of the star being in a binary orbit. A simulation of possible binary systems with the observed RVs suggests a binary period of either 39.12 days or 17.83 days with mass ratio q$\geq$1.0. The [Fe/H] derived using the high-resolution spectra is $\sim -$0.7 dex, which closely matches the cluster metallicity. The spectroscopic and photometric measurements suggest \Teff\ and $\log g$ of the star as 17\,500$\pm$1\,000~K and 2.37$\pm$0.20~dex, respectively. Various PAGB evolutionary tracks on the Hertzsprung--Russell (H-R) diagram suggest a current mass of the star in the range 0.51$-$0.55 \Msun. The star is enriched with C and O abundances, showing similar CNO abundances compared to the other PAGB stars in GCs with the evidence of the third dredge-up on the AGB phase.

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arXiv2023

Solaris photometric survey: Search for circumbinary companions using eclipse timing variations

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.

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arXiv2023

Detached Eclipsing Binaries in Compact Hierarchical Triples: Triple-lined systems BD+44 2258 and KIC 06525196

Compact Hierarchical Triples (CHT) are systems with the tertiary star orbiting the inner binary in an orbit shorter than 1000 days. CHT with an eclipsing binary as its inner binary can help us extract a multitude of information about all three stars in the system. In this study, we use independent observational techniques to estimate the orbital, stellar, and atmospheric parameters of two triple-lined CHT: BD+442258 and KIC06525196. We find that the masses of stars in BD+442258 are $1.011\pm0.029 M_{\odot}$, $0.941\pm0.033 M_{\odot}$, and $0.907\pm0.065 M_{\odot}$ while in KIC06525196 the estimated masses are $1.0351\pm0.0055 M_{\odot}$, $0.9712\pm0.0039 M_{\odot}$, and $0.777\pm0.012 M_{\odot}$. Using spectral disentangling, we obtained individual spectra of all the stars and combined them with light curve modeling to obtain radii, metallicities, and temperatures. Using stellar evolution models from MESA, we constrain the log(age) of BD+442258 to be 9.89 and 9.49 for KIC06525196. Two stars in BD+442258 are found to be sub-giants while all three stars in KIC06525196 are main-sequence stars. We constrain the mutual inclinations to certain angles for BD+442258 and KIC06525196 using numerical integration. Integrating with tidal interaction schemes and stellar evolution models, we find that KIC06525196 is a stable system. But the inner binary of BD+442258 merges within 550 Myrs. The time of this merger is affected by the orientation of the tertiary, even rushing the collapse by 100 Myrs when the mutual inclination is close to 90 degrees.

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arXiv2023

Comprehensive spectroscopic and photometric study of pulsating eclipsing binary star AI Hya

The pulsating eclipsing binaries are remarkable systems that provide an opportunity to probe the stellar interior and to determine the fundamental stellar parameters precisely. Especially the detached eclipsing binary systems with (a) pulsating component(s) are significant objects to understand the nature of the oscillations since the binary effects in these systems are negligible. Recent studies based on space data have shown that the pulsation mechanisms of some oscillating stars are not completely understood. Hence, comprehensive studies of a number of pulsating stars within detached eclipsing binaries are important. In this study, we present a detailed analysis of the pulsating detached eclipsing binary system AI Hya which was studied by two independent groups with different methods. We carried out a spectroscopic survey to estimate the orbital parameters via radial velocity measurements and the atmospheric parameters of each binary component using the composite and/or disentangled spectra. We found that the more luminous component of the system is a massive, cool and chemically normal star while the hotter binary component is a slightly metal-rich object. The fundamental parameters of AI Hya were determined by the analysis of binary variations and subsequently used in the evolutionary modelling. Consequently, we obtained the age of the system as 850 $\pm$ 20 Myr and found that both binary components are situated in the Delta Scuti instability strip. The frequency analysis revealed pulsation frequencies between the 5.5 - 13.0 d$^{-1}$ and we tried to estimate which binary component is the pulsating one. However, it turned out that those frequencies could originate from both binary components.

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arXiv2021

Orbital and physical parameters of eclipsing binaries from the ASAS catalogue -- XII. A sample of systems with $K2$ photometry

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 $γ$ 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.

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arXiv2020

Orbital and physical parameters of eclipsing binaries from the ASAS catalogue -- XI. CHIRON investigation of long-period binaries

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.

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arXiv2020

Analysis of eclipsing binaries in multiple stellar systems: the case of V1200 Centauri

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.

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arXiv2020

The TESS light curve of AI Phoenicis

Accurate masses and radii for normal stars derived from observations of detached eclipsing binary stars are of fundamental importance for testing stellar models and may be useful for calibrating free parameters in these model if the masses and radii are sufficiently precise and accurate. We aim to measure precise masses and radii for the stars in the bright eclipsing binary AI Phe, and to quantify the level of systematic error in these estimates. We use several different methods to model the TESS light curve of AI Phe combined with spectroscopic orbits from multiple sources to estimate precisely the stellar masses and radii together with robust error estimates. We find that the agreement between different methods for the light curve analysis is very good but some methods underestimate the errors on the model parameters. The semi-amplitudes of the spectroscopic orbits derived from spectra obtained with modern echelle spectrographs are consistent to within 0.1%. The masses of the stars in AI Phe are $M_1 = 1.1938 \pm 0.0008 M_{\odot}$ and $M_2 = 1.2438 \pm 0.0008M_{\odot}$, and the radii are $R_1 = 1.8050 \pm 0.0022 R_{\odot}$ and $R_2 = 2.9332 \pm 0.0023 R_{\odot}$. We conclude that it is possible to measure accurate masses and radii for stars in bright eclipsing binary stars to a precision of 0.2% or better using photometry from TESS and spectroscopy obtained with modern echelle spectrographs. We provide recommendations for publishing masses and radii of eclipsing binary stars at this level of precision.

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arXiv2019

HIDES spectroscopy of bright detached eclipsing binaries from the $Kepler$ field - III. Spectral analysis, updated parameters, and new systems

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.

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arXiv2018

Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue - X. Three high-contrast systems with secondaries detected with IR spectroscopy

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.

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arXiv2018

Tracking the spin axes orbital alignment in selected binary systems - Torun Rossiter-McLaughlin effect survey

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 $β$ 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.

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