Analysis Of Light Curves Research Articles

Accelerating Asteroidal Period and Pole Inversion from Multiple Lightcurves Using Parallel Differential Evolution and Cellinoid Shape Model

Determining asteroid properties provides valuable physical insights but inverting them from photometric lightcurves remains computationally intensive. This paper presents a new approach that combines a simplified Cellinoid shape model with the Parallel Differential Evolution (PDE) algorithm to accelerate inversion. The PDE algorithm is more efficient than the Differential Evolution algorithm, achieving an extraordinary speedup of 37.983 with 64 workers on multicore CPUs. The PDE algorithm accurately derives period and pole values from simulated data. The analysis of real asteroid lightcurves validates the method’s reliability: in comparison with results published elsewhere, the PDE algorithm accurately recovers the rotational periods and, given adequate viewing geometries, closely matches the pole orientations. The PDE approach converges to solutions within 20,000 iterations and under one hour, demonstrating its potential for large-scale data analysis. This work provides a promising new tool for unveiling asteroid physical properties by overcoming key computational bottlenecks.

Rotation of ZZ Ceti stars as seen by TESS

Context. Knowing the rotation rates and masses of white dwarf stars is an important step towards characterising the angular momentum transport mechanism in their progenitors, and coupling the cores of red giants to their envelopes. However, deriving these rotation rates is not an easy task. One can use the rotational broadening of spectral lines, but there is another way to gather reliable information on the stellar rotation periods of pulsators: through studying the splitting effect of rotation on oscillation frequencies. Aims. We aim to derive stellar rotation periods in the TESS sample for as many white dwarf pulsators as possible. Methods. We rely on light-curve analysis of the TESS observations, and search for closely spaced frequency multiplets that could be rotationally split pulsation modes. We work with triplet frequencies, even if one or two triplet components are only marginally detectable. We also utilise ground-based observations available from the literature in an attempt to confirm the presence of several triplets. Results. We successfully identified rotationally split multiplets and derived rotation rates for 14 stars. The fastest rotators we identified have rotation periods of 6.6–10.0 h. The majority of the pulsators rotate with periods of 11.9–47.5 h, while we derived 85.5 and 93.2 h periods for the slowest rotators. In addition to providing stellar mass estimations, our results confirm previous findings that larger-mass WDs rotate faster than their lower-mass counterparts. We determine the rotation periods of four stars for the first time.

Estimating the absolute parameters of W UMa-type binary stars using Gaia DR3 parallax

The accuracy of absolute parameters’ estimation in contact binary systems is important for investigating their evolution and solving some challenges. The Gaia DR3 parallax is one of the methods used for estimating the absolute parameters, in cases where photometric data is the only one that is available. The use of this method includes advantages and limitations that we have described and examined in this study. We selected 48 contact binary systems whose mass ratios were mostly obtained by spectroscopic data, in addition to a number of photometric studies. The target systems were suitable for AV and the Re-normalized Unit Weight Error (RUWE), and their absolute parameters were calculated based on Gaia DR3 parallax, observational information, orbital period, and light cure solution from the literature and catalogs. The outcomes of OO Aql differed significantly from those reported in the literature. Upon analyzing the system’s light curve with TESS data, we concluded that the stars’ temperatures were the reason for this difference, and utilizing Gaia DR3 parallax provided reasonable results. We displayed the target systems on the Hertzsprung–Russell (HR), q−Lratio, P−MV, and logMtot−logJ0 diagrams, and the systems are in good agreement with the theoretical fits. We showed that the estimation of absolute parameters with this method might be acceptable if Δa(R⊙) is less than ∼0.1(R⊙). There are open questions regarding the existence of l3 in the light curve analysis and its effect on the estimation of absolute parameters with this method.

OGLE-2017-BLG-0448Lb: A Low Mass–Ratio Wide-orbit Microlensing Planet?

The gravitational microlensing technique is most sensitive to planets in a Jupiter-like orbit and has detected more than 200 planets. However, only a few wide-orbit (s > 2) microlensing planets have been discovered, where s is the planet-to-host separation normalized to the angular Einstein ring radius, θ E. Here, we present the discovery and analysis of a strong candidate wide-orbit microlensing planet in the event OGLE-2017-BLG-0448. The whole light curve exhibits long-term residuals to the static binary-lens single-source model, so we investigate the residuals by adding the microlensing parallax, microlensing xallarap, an additional lens, or an additional source. For the first time, we observe a complex degeneracy between all four effects. The wide-orbit models with s ∼ 2.5 and a planet-to-host mass ratio of q ∼ 10−4 are significantly preferred, but we cannot rule out the close models with s ∼ 0.35 and q ∼ 10−3. A Bayesian analysis based on a Galactic model indicates that, despite the complicated degeneracy, the surviving wide-orbit models all contain a super-Earth-mass to Neptune-mass planet at a projected planet-host separation of ∼6 au and the surviving close-orbit models all consist of a Jovian-mass planet at ∼1 au. The host star is probably an M or K dwarf. We discuss the implications of this dimension-degeneracy disaster on microlensing light-curve analysis and its potential impact on statistical studies.

Lightcurve Analysis of a Sample of Asteroids and Comets Observed with the Isaac Newton Telescope

We present an analysis of six asteroids and one comet using data from the Wide Field Camera on the Isaac Newton Telescope, La Palma. As part of this work we developed a pipeline to reduce and absolutely calibrate photometry of inactive small bodies. For three of the objects, there was sufficient data to measure their rotation periods. We report rotation periods of (2.7774 ± 0.0004) hr and (3.121 ± 0.003) hr for main belt asteroids (7891) Fuchie and 1999 CP29 respectively, neither of which to our knowledge currently have a well-constrained rotation period. We also measure a rotation period for Jupiter-family comet 169P/NEAT of (8.37 ± 0.04) hr which is consistent with previous works. Colours in various filter combinations (Sloan r′ , g′ , i′ and RGO Z) were also determined, and for the six observed asteroids we present an approximate taxonomic classification.

The First Photometric Analysis of Two Low-mass-ratio Contact Binary Systems in TESS Survey

Low-mass-ratio (q) contact binary systems are progenitors of stellar mergers such as blue stragglers or fast-rotating FK Com stars. In this study, we present the first light curve analysis of two newly identified low mass-ratio contact binary systems, TIC 55007847 and TIC 63597006, that are identified from TESS. Both stars are classified as A-subtype contact binaries. We obtained the precise orbit periods for the two objects by using the O − C method, i.e., P = 0.6117108 day for TIC 55007847 and P = 0.7008995 day for TIC 63597006, and found an obvious periodic signal in the O − C curve of TIC 63597006. We suggest that the periodic signal comes from a third body. We further use the Markov chain Monte Carlo method with PHOEBE to derive the photometric solutions for the two binaries. The photometric solution for this object shows that the contribution of the third body is about 6%. Our analysis revealed that TIC 55007847 has an extremely low mass ratio of q = 0.08. By calculating the ratio of spin angular momentum to the orbital angular momentum J s/J o, we found that TIC 55007847 is very close to the instability threshold with J s/J o = 0.31, indicating that it may merge into a single, fast-rotating star in the future. For TIC 63597006, q = 0.14 and J s/J o = 0.15. This object is in a relatively stable evolutionary status at present.

Optical and soft X-ray light-curve analysis during the 2022 eruption of U Scorpii: Structural changes in the accretion disk

Abstract We present our optical photometric observations of the 2022 eruption of the recurrent nova U Scorpii (U Sco) using 49152 data points over 70 d following the optical peak. We have also analyzed its soft X-ray (0.3–1 keV) light curve by the Neil Gehrels Swift Observatory. During the 2022 eruption, the optical plateau stage started 13.8–15.0 d and ended 23.8–25.0 d after the optical peak. The soft X-ray stage started 14.6–15.3 d and ended 38.7–39.5 d after the optical peak. Both stages started later and had shorter durations, and the soft X-ray light curve peaked earlier and was less luminous compared to those during the U Sco 2010 eruption. These points suggest that there were differences in the envelope mass between the different cycles of the nova eruption. Furthermore, we have analyzed the optical eclipses during the 2022 eruption. The primary eclipse was first observed 10.4–11.6 d after the optical peak, earlier than the beginning of the optical plateau stage. This sequence of events can be explained by the receding ejecta photosphere associated with the expanding nova ejecta. We have determined the ingress and egress phases of the primary eclipses and estimated the outer radius of the optical light source centered at the white dwarf (WD). During the optical plateau stage, the source radius remained ∼1.2 times larger than the Roche volume radius of the primary WD, being close to the L1 point. When the optical plateau stage ended, the source radius drastically shrank to the tidal truncation radius within a few orbital periods. This previously unresolved phenomenon can be interpreted as a structural change in U Sco where the temporarily expanded accretion disk due to the nova wind returned to a steady state.

Attenuation of photosynthesis in nanosilver-treated Arabidopsis thaliana is inherently linked to the particulate nature of silver

Silver nanoparticles (AgNPs) are known to affect the physiology and morphology of plants in various ways, but the exact mechanism by which they interact with plant cells remains to be elucidated. An unresolved question of silver nanotoxicology is whether the interaction is triggered by the physical features of the particles, or by silver ions leached from their surface. In this study, we germinated and grew Arabidopsis thaliana seedlings in synthetic medium supplemented with sub-morbid concentrations (4 μg/mL) of AgNPs and silver nitrate (AgNO3). This treatment led to in planta accumulation of 106 μg/g and 97 μg/g of silver in the AgNO3- and AgNP-exposed seedlings, respectively. Despite the statistically indistinguishable silver accumulation, RNA sequencing data demonstrated distinct changes in the transcriptome of the AgNP-exposed, but not in the AgNO3-exposed plants. AgNP exposure induced changes in the expression of genes involved in immune response, cell wall organization, photosynthesis and cellular defense against reactive oxygen species. AgNO3 exposure, on the other hand, caused the differential expression of only two genes, neither of which belonged to any AgNP-enriched gene ontology categories. Moreover, AgNP exposure led to a 39% reduction (p < 0.001) in total chlorophyll concentration relative to untreated plants which was associated with a 56.9% and 56.2% drop (p < 0.05) in carbon assimilation rate at ambient and saturating light, respectively. Stomatal conductance was not significantly affected by AgNP exposure, and limitations to carbon assimilation, as determined through analysis of light and carbon dioxide (A/Ci) curves, were attributed to rates of electron transport, maximum carboxylation rates and triose phosphate use. AgNO3-exposure, on the other hand, did not lead to significant reduction either in chlorophyll concentration or in carbon assimilation rate. Given these data, we propose that the impact of AgNPs cannot be simply attributed to the presence of the metal in plants, but is innate to the particulate nature of nanosilver.

Owens Valley Radio Observatory monitoring of LS I +61°303 completes three cycles of the super-orbital modulation

Context. The high-mass X-ray binary LS I +61°303 is composed of a Be-type star and a compact object in an eccentric orbit. The emission from this source is variable and periodic across the electromagnetic spectrum, from radio to very high-energy γ rays. The orbital period has been determined as P1 ≈ 26.5 d, and the source also features a super-orbital period with a value of Plong ≈ 4.6 years. Long-term monitoring of the binary by the Owens Valley Radio Observatory (OVRO) at 15 GHz has now completed 13.8 years, which corresponds to three full cycles of the super-orbital period. This is exactly one long-term cycle more than in the previous publication about OVRO observations of this source. Aims. Our aim is to investigate the presence and the stability of periodic signals in the radio data and to test if they are in agreement with previous results. This will contribute to the understanding of the physical processes behind the non-thermal emission from this source. Methods. We performed a timing analysis of the OVRO radio light curve and made use of the generalized Lomb-Scargle periodogram. We also combined the OVRO data with the full archive of previous radio observations and computed the discrete autocorrelation function. Results. The most powerful features in the periodogram of the OVRO data are two peaks at P1 = 26.49 ± 0.05 d and P2 = 26.93 ± 0.05 d, which are well separated from each other and clearly stand out above the very low noise level. The previously detected long-term period is still present in these new radio data, and our measurement is Plong = 1698 ± 196 d. Dividing the OVRO data into three segments of equal length showed that the two periods, P1 and P2, are present in the periodogram of each of the consecutive long-term cycles. Our analysis of the full radio archive resulted in the detection of the same three periods, and the autocorrelation function showed a regular pattern, proving the continuity of the decades-spanning stability of the super-orbital modulation. In addition, we report a possible systematic modulation of the radio flux density with a timescale of approximately 40 years that has so far remained unnoticed. Conclusions. The physical model of a relativistic jet whose mass loading is modulated with the orbital period P1 and is precessing with the slightly larger period P2, giving rise to a beating with period Plong, had previously been able to reproduce the radio and gigaelectron volt emission from this source. The ongoing presence and the stability of the periodic signals imply that this model is still the most plausible explanation for the physical processes at work in this source.

TOI-6883.01: A Single-transit Planet Candidate Detected from TESS

A new candidate exoplanet, proposed in ExoFOP by authors, it was promoted from TIC 393818343 to TOI-6883.01 at coordinates R.A.(J2000)20:41:10.01 decl.(J2000) + 3:38:17.87 in the Delphinus constellation and its distance is (93.73 ± 0.35) pc from Earth. The target star is a Sun-type having G0 class according to Skiff spectral classification and it has photometric magnitude V(Johnson) = 9.5 mag. We analyzed the transit light curve using Transit Exoplanet Survey Satellite’s ExoMAST tool, and evaluated the Lightcurve Analysis Tool for Transiting Exoplanets-report by excluding false positives, studying the background, satellite and centroid motion, and analyzing the pixels in sector 55 to define the source goodness. The candidate exoplanet transit has a duration of TD = 3.957 hr, Depth = 0.1196% and mid-transit time occurs at TBJD = 2811.24. Only one event was observed, so the orbital period cannot be evaluated.

Light curve analysis and evolutionary status of four newly identified short-period eclipsing binaries

We present the physical and orbital parameters of four short-period eclipsing W UMa systems: ZTFJ000030.44+391106.9\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ZTFJ000030.44 +391106.9$$\\end{document} (referred to as S1), ZTFJ000817.08+402532.1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ZTFJ000817.08+402532.1$$\\end{document} (referred to as S2), ZTFJ002158.44+252934.04\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ZTFJ002158.44+252934.04$$\\end{document} (referred to as S3), and ZTFJ003357.62+415747.8\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ZTFJ003357.62+415747.8$$\\end{document} (referred to as S4). The absolute parameters and evolutionary status of these systems are determined, and new times of minima are calculated. Additionally, we present the 3D fill-out configuration for each system. The four Systems exhibit moderate contact W UMa binary with a fill-out factor of 49%, 38%, 28%, and 51%, respectively. Comparing the systems’ periods, we observed a proportional relationship, where shorter periods correspond to lower fill-out factors, and longer periods were associated with higher fill-out factors. Based on the derived surface temperatures and mass ratios of the components, all systems are classified as A-type W UMa binaries. The obtained parameters in addition to a list of previously published data are then utilized to derive an updated Mass-Luminosity relation (M-L) for both A and W-type eclipsing W UMa systems. A comparison with previously published relations reveals that the majority of the EW systems lie between 0.2 and 2 Msun on the M-L diagram. Moreover, we discuss the dynamical evolutionary aspects and evolutionary status of the four components, along with their positions on the Zero Age Main Sequence (ZAMS) and Terminal Age Main Sequence (TAMS).

TESS Hunt for Young and Maturing Exoplanets (THYME). XI. An Earth-sized Planet Orbiting a Nearby, Solar-like Host in the 400 Myr Ursa Major Moving Group

Young terrestrial worlds are critical test beds to constrain prevailing theories of planetary formation and evolution. We present the discovery of HD 63433 d—a nearby (22 pc), Earth-sized planet transiting a young Sun-like star (TOI-1726, HD 63433). HD 63433 d is the third planet detected in this multiplanet system. The kinematic, rotational, and abundance properties of the host star indicate that it belongs to the young (414 ± 23 Myr) Ursa Major moving group, whose membership we update using new data from the third data release of the Gaia mission and TESS. Our transit analysis of the TESS light curves indicates that HD 63433 d has a radius of 1.1 R ⊕ and closely orbits its host star with a period of 4.2 days. To date, HD 63433 d is the smallest confirmed exoplanet with an age less than 500 Myr, and the nearest young Earth-sized planet. Furthermore, the apparent brightness of the stellar host (V ≃ 6.9 mag) makes this transiting multiplanet system favorable to further investigations, including spectroscopic follow-up to probe the atmospheric loss in a young Earth-sized world.

Rotational Variability and Detection of Superflares in a Young Brown Dwarf by TESS

We present a comprehensive analysis of a Transiting Exoplanet Survey Satellite (TESS) high-quality light curve for a young brown dwarf, MHO 4 having spectral type M7.0, in the Taurus star-forming region. We investigate the rotation periods and characterize the brown dwarf’s dynamic atmosphere and surface features. Our light curve analysis of MHO 4 reveals a rotation period of approximately 2.224 days. Remarkably, MHO 4 exhibits two significant flaring events. Furthermore, we estimate the bolometric flare energies to be within the energy range of 1034 to 1035 erg, classifying them as superflares.

Rapid Optical Flares in the Blazar OJ 287 on Intraday Timescales with TESS

We have analyzed the optical light curves of the blazar OJ 287 obtained with the Transiting Exoplanet Survey Satellite over about 80 days from 2021 October 13 to December 31, with an unprecedented sampling of 2 minutes. Although significant variability has been found during the entire period, we have detected two exceptional flares with flux nearly doubling and then nearly tripling over 2 days in the middle of 2021 November. We went through the light-curve analysis using the excess variance, generalized Lomb–Scargle periodogram, and continuous autoregressive moving average methods and estimated the flux halving/doubling timescales. The most probable shortest variability timescale was found to be 0.38 days in the rising phase of the first flare. We briefly discuss some emission models for the variability in radio-loud active galactic nuclei that could be capable of producing such fast flares.

A Dual Perspective on Geostationary Satellite Monitoring Using DSLR RGB and sCMOS Sloan Filters

This paper outlines a multi-system approach for ground-based optical observations and the characterization of satellites in geostationary orbit. This multi-system approach is based on an in-depth analysis of the key factors to consider for light curve analysis of Earth’s orbiting satellites. Light curves have been observed in different spectral bands using two different systems. The first system is specialized for astronomical observations and consists of a telescope equipped with an sCMOS camera and Sloan photometric filters. In contrast, the second system is a more cost-effective solution designed for professional non-astronomical applications, incorporating DSLR cameras equipped with RGB channels associated with a Bayer mask and photographic lenses. This comparative analysis aims to highlight the differences and advantages provided by each system, stressing their respective performance characteristics. The observed light curves will be presented as a function of the phase angle, which depends on the relative positions of the observer, the object, and the Sun. This angle plays an important role in optimizing the visibility of Earth’s orbiting satellites. Finally, multiband observations of different satellites will be compared to seek an associated spectral signature, which may allow the identification of structurally similar objects through optical observations.

Light Curves and Period Analysis of Beta Lyrae Stars

We present the light-curve period analysis of 36 Beta Lyrae stars from the OMC Archive. We check the reference period of the sample by applying the phase dispersion minimization periodogram. From our research, we determine the orbital period of five stars in the sample. One of them is CP Psc, showing a prominent hump in the light curve before the deeper eclipse, and revealing a period of 0.6847936 day. Additionally, we improved the previously published orbital period for 27 stars. Within this sample, we discovered three stars with the O’Connell effect, and we identified a system with a second period known as II Per, with an orbital period of 0.4798512 day and a long period 9.2724776 days. The light curve of V 747 Cen can be reproduced with a dark spot of temperature about 70% its surroundings, which covers one of the poles of the more massive star.

Pre-selection of solar analogues with differential rotation signature

The light curve of a star allows studying the variation of its brightness over time, being suitable for determining rotation periods, detecting planets, studying binary systems and differential rotation. The light curve analysis can be performed with the autocorrelation function (ACF), a robust mathematical tool in the detection of the stellar rotation period, by finding patterns in the photometric data. In this work, a sample of stars from the CoRoT mission is analyzed. The analysis is carried out with the ACF to carry out a pre-selection of stars that show signs of rotational modulation, a determining characteristic for the study of differential rotation. 17 stars were selected by visual inspection of the curves and by the ACF function. It was found that three stars have an excellent profile of autocorrelation function and rotational modulation, three have a good profile and the remaining eleven have inappropriate profiles for the study of differential rotation. The photometric time series analyzes show that the autocorrelation function method is very suitable as a previous criterion for the selection of candidate stars for the study of differential rotation, when they present exponential decay of the oscillation peaks of the light curve.

Geometry of the LMC based on multiphase analysis of multiwavelength Cepheid light curves using OGLE-IV and Gaia DR3 data

ABSTRACT The period–luminosity (PL) relation of Cepheids in the Large Magellanic Cloud (LMC) plays a pivotal role in extragalactic distance measurement and the determination of the Hubble constant (H0). In this work, we probe the geometry of the LMC through a detailed study of multiphase PL relations of these Cepheids, leveraging data from the OGLE-IV and Gaia DR3 data bases. We analyse the light curves of a combined sample of ∼3300 fundamental (FU) and first overtone (FO) mode classical Cepheids. We obtain multiphase data with 50 phase points over a complete pulsation cycle from the OGLE (V, I) and Gaia (G, GBP, GRP) photometric bands. We determine the distance modulus and reddening values of individual Cepheids by fitting a simultaneous reddening law to the apparent distance modulus values. We calculate the LMC viewing angle parameters: the inclination angle (i) and position angle of line of nodes (θlon) by fitting a plane of the form z = f(x, y) to the three-dimensional distribution of Cepheids in Cartesian coordinates $(x, y, z)$. The values of LMC viewing angles from multiphase PL relations are found to be: i = 22.°87 ± 0.°43 (stat.) ± 0.°53 (syst.), θlon = 154.°76 ± 1.°16 (stat.) ± 1.°01 (syst.), respectively. The use of multiphase PL relations in multiple bands results in lower uncertainties for the LMC viewing angle parameters as compared to those derived from the mean-light PL relations. This shows that the use of multiphase PL relations with multiwavelength photometry significantly improves the precision of these measurements, allowing better constraints on the morphology and the structure of the LMC.

Rapid Evolution of the White Dwarf Pulsar AR Scorpii

Analysis of AR Sco optical light curves spanning 9 yr shows a secular change in the relative amplitudes of the beat pulse pairs generated by the two magnetic poles of its rotating white dwarf. Recent photometry now shows that the primary and secondary beat pulses have similar amplitudes, while in 2015 the primary pulse was approximately twice that of the secondary peak. The equalization in the beat pulse amplitudes is also seen in the linearly polarized flux. This rapid evolution is consistent with precession of the white dwarf spin axis. The observations imply that the pulse amplitudes cycle over a period of ≳40 yr but that the upper limit is currently poorly constrained. If precession is the mechanism driving the evolution, then over the next 10 yr the ratio of the beat pulse amplitudes will reach a maximum followed by a return to asymmetric beat pulses.

The enigmatic multiple star VV Ori

ABSTRACT New photometry, including TESS data, have been combined with recent spectroscopic observations of the Orion Ib pulsating triple-star system VV Ori. This yields a revised set of absolute parameters with increased precision. Two different programmes were utilized for the light-curve analysis, with results in predictably close agreement. The agreement promotes confidence in the analysis procedures. The spectra were analysed using the FDBinary programme. The main parameters are as follows: M1 = 11.56 ± 0.14 and M2 = 4.81 ± 0.06 (M⊙). We estimate an approximate mass of the wide companion as M3 = 2.0 ± 0.3 M⊙. Similarly, R1 = 5.11 ± 0.03, R2 = 2.51 ± 0.02, R3 = 1.8 ± 0.1 (R⊙); Te1 = 26600 ± 300, Te2 = 16250 ± 420, and Te3 = 10000 ± 1000 (K). The close binary’s orbital separation is a = 13.91 (R⊙); its age is 8 ± 2 (Myr) and its photometric distance is 396 ± 7 pc. The primary’s β Cep type oscillations support these properties and confirm our understanding of its evolutionary status. Examination of the well-defined λ6678 He i profiles reveals the primary to have a significantly low projected rotation: some 80 per cent of the synchronous value. This can be explained on the basis of the precession of an unaligned spin axis. This proposal can resolve also observed variations of the apparent inclination and address other longer term irregularities of the system reported in the literature. This topic invites further observations and follow-up theoretical study of the dynamics of this intriguing young multiple star.