Orbital Variations Research Articles

Determining the Nature of IC 10 X-2: A Comprehensive Study of the Optical/IR Emission from an Extragalactic BeHMXB

We present a comprehensive analysis of the optical and infrared (IR) properties of high-mass X-ray binary (HMXB) IC 10 X-2, classified as a supergiant HMXB and superfast X-ray transient by previous work. Our analysis of regular (daily and weekly) observations by both the Zwicky Transient Facility and Las Cumbres Observatory over a 5 yr period indicates both periodic flares and variations in the apparent magnitude and color with a period of ∼26.5 days—likely the orbital period of this binary system. The periodic flaring suggests the stellar companion is a Be star, with flares resulting from increased accretion onto the neutron star (NS) when it enters the stellar decretion disk. The periodic variations in the optical/IR brightness and color likely result from orbital variations in the hydrogen column density along the line of sight or a transient accretion disk around the NS. Lastly, the numerous short-duration episodes where IC 10 X-2 is significantly “redder” or “bluer” than normal likely result from clumps within this system—which can accrete onto the NS (causing IC 10 X-2 to appear bluer) or pass through the line of sight (causing IC 10 X-2 to appear redder). These results substantially increase our understanding of the evolution of this source, which is a significant source of ionizing photons in its host galaxy IC 10, a low-mass, metal-poor starburst galaxy similar in many respects to those thought to be common in the early Universe.

Orbital and suborbital temperature variability in the central Mediterranean across the Pliocene/Pleistocene transition.

A high-resolution record of central Mediterranean Sea Surface Temperatures (SSTs) based on the alkenone UK'37 index and planktic δ18O values for the surface-dweller G. ruber has been reconstructed across the Pliocene/Pleistocene transition at Monte San Nicola (Sicily), reference area for the GSSP (Global Boundary Stratotype Section and Point) of the Gelasian Stage. Spectral analyses indicate that the SST record is predominantly paced by a cyclicity in the ~47 kyr time domain, consistent with the obliquity driven glacial-interglacial variability that is expected to dominate in the interval of relevance. In addition, two suborbital periodicities in the ~5 kyr and ~8 kyr time domains provide a pervasive spectral signal that proves to be especially strong during the MIS (Marine Isotope Stage) 100 glacial, at the inception of the Northern Hemisphere Glaciation. This high frequency climatic instability, a prominent feature of the early Gelasian, might reflect episodic events of massive disruption of the Atlantic Meridional Overturning Circulation with increased production of cold, low-salinity water masses in the North Atlantic. Alternatively, it may be interpreted as the resonance (i.e., harmonics) of the low-latitude precessional forcing in mid-latitude regions. Although the driving mechanisms of these processes remain largely unconstrained, our study emphasizes the role of the central Mediterranean as the main reference for high-resolution paleoclimatic studies in the Neogene and the Quaternary.

Variations in orbital morphology, globe:orbit volume relation, and ophthalmological outcome in unicoronal synostosis.

Nonsyndromic unicoronal synostosis is associated with variability of severity in orbital morphology and ophthalmological manifestations. The relation between the two is not fully understood, nor how surgical treatment with fronto-orbital advancement and remodelling (FOAR) changes the relation. The aim of this study was to elucidate associations between ophthalmological manifestations and variations in orbital morphology and globe:orbit volume ratios preoperatively and at long-term follow-up after surgery. Twelve children referred to Uppsala Craniofacial Center who underwent computed tomography and standardized ophthalmological examinations regarding strabismus, spherical equivalent, astigmatism, anisometropia, and subnormal vision preoperatively and at 3 years of age were included. Orbits and globes were segmented. Principal component analysis elucidated morphological variation, and symmetry between orbital pairs was measured as the Dice similarity coefficient and globe:orbit volume ratios were calculated. The defined orbital shape variations were correlated with strabismus, refractive error, and subnormal vision. Different shape variations were associated with strabismus pre- and postoperatively and ipsi- and contralateral astigmatism. Greater improvement in orbital symmetry after surgery was associated with improvement in astigmatic anisometropia and new onset strabismus at follow-up. A small globe:orbit volume ratio was associated with preoperative strabismus, while the opposite was seen at follow-up. Different mechanisms seem to cause strabismus pre- and postoperatively, and FOAR might not sufficiently correct orbital morphology.

Geotechnologies applied in the monitoring of mealybug in the black pepper cultivation in the South of Bahia

The behavior of insect pests within the agricultural system represents a strategy for integrated pest management. The objective of this study was to evaluate the pattern of spatial and temporal distribution of mealybugs in black pepper crop with the use of applied geotechnologies. The study was conducted in an area of 26 hectares with black pepper cultivation, using a grid samples with 96 points. Notes were assigned according to the infestation of the mealybugs, with the presence, formation of colonies and/or dispersion in the plant. The data were grouped by season and submitted to the Lilliefors test at 5%. The ordinary kriging method was used for phytotechnical and orbital variables, and indicator kriging for infestation data. Drone images were used to calculate the aerial indexes and to obtain the leaf area of each plant. With satellite images, the vegetation index and surface temperature were obtained. Climatic data were associated with phytotechnical, spectral and monitoring variables, using principal component analysis, when it was found that cochineal infestation levels are directly associated with the summer season and with NDVI and GLI index with a correlation above of 0.90. It was observed that the insect presents random distribution. The spatial-temporal distribution of GLI and the maximum indices occur in the winter and spring seasons. From the probability of occurrence map, the spring and summer seasons presented more favorable conditions for the occurrence of mealybugs in the planting of black pepper.

Radial Metallicity Gradients for the Chemically Selected Galactic Thin Disc Main‐Sequence Stars

ABSTRACTWe present the radial metallicity gradients within the Galactic thin disc population through main‐sequence stars selected on the chemical plane using GALAH DR3 accompanied with Gaia DR3 astrometric data. The [Fe/H], [/Fe] and [Mg/H] radial gradients are estimated for guiding radius as , , dex kpc and for the traceback early orbital radius as , , dex kpc for 66,545 thin‐disc stars, respectively. Alteration of the chemical structure within the Galactic disc caused by the radial orbital variations complicates results for the radial metallicity gradient. The effect of radial orbital variations on the metallicity gradients as a function on time indicates the following results: (i) The presence of a gradient along the disc throughout the time for which the model provides similar prediction, (ii) the radial orbital variations becomes more pronounced with the age of the stellar population and (iii) the effect of radial orbital variations on the metallicity gradients is minimal. The effect of radial orbital variations is found to be at most 6% which does not statistically affect the radial gradient results. These findings contribute to a better understanding of the chemical evolution within the Galactic disc and provide an important basis for further research.

Long-term Dynamical Stability in the Outer Solar System. II. Detailed Secular Evolution of Four Large Regular and Resonant Trans-Neptunian Objects

The long-term evolution of the outer solar system is subject to the influence of the giant planets, however, perturbations from other massive bodies located in the region imprint secular signatures, which are discernible in long-term simulations. In this work, we performed an in-depth analysis of the evolution of massive objects Eris, 2015 KH162, Pluto, and 2010 EK139 (aka, Dziewanna), subject to perturbations from the giant planets and the 34 largest trans-Neptunian objects. We do this by analyzing 200, 1 Gyr long simulations with identical initial conditions, but requiring the numerical integrator to take different time steps for each realization. Despite the integrator’s robustness, each run’s results are surprisingly different, showing the limitations of individual realizations when studying the trans-Neptunian region due to its intrinsic chaotic nature. For each object, we find orbital variables with well-defined oscillations and limits, and others with surprisingly large variances and seemingly erratic behaviors. We found that 2015 KH162 is a nonresonant and very stable object that experiences only limited orbital excursions. Pluto is even more stable and we found a new underlying constraining mechanism for its orbit; 2010 EK139 is not well trapped in the 7:2 mean motion resonance in the long term and cannot be trapped simultaneously in von Zeipel–Lidov–Kozai resonance; and finally, we found that at present Eris’s longitude of perihelion is stationary, tightly librating around 190°, but unexpectedly loses its confinement, drifting away after 150 Myr, suggesting a missing element in our model.

An Orbital-attitude Coupled Control Framework for a Full-scale Flexible Electric Solar Wind Sail Spacecraft in Orbital Transformation Missions

In this work, a novel orbital-attitude coupled control framework is developed for the electric solar wind sail (E-sail) spacecraft, aiming to handle the orbital transformation and attitude maneuver simultaneously. In the framework, the desired attitude parameters and the slow-varying voltage component are provided by the orbital control strategy, while the current attitude parameters and the fast-varying voltage component are manipulated by the attitude control strategy to approach their desired values. The orbital-attitude coupled characteristics of the E-sail spacecraft, including the flexibility-induced coupling effect, are fully described by the referenced nodal coordinate formulation. Considering the input saturation conditions, the governing equation for the orbital control strategy is then derived, in which the in-plane and out-of-plane displacement and velocity errors are prescribed as the state variables to be eliminated. An integral sliding mode control (ISMC) scheme is proposed to improve the robustness against the unmeasurable disturbance term. A model predictive control (MPC) scheme is introduced to enhance the convergence efficiency, where a quadratic optimization is performed to plan the desired attitude parameters and voltage components within the prediction horizon. To evaluate the control performance in the orbital transformation and attitude maneuver missions on the displaced non-Keplerian orbit, a series of scenarios with complex initial conditions are simulated under different control schemes, including the ISMC-MPC compound scheme. The results show that the control strategy designed under the rigid-body assumptions may not be feasible for the flexible E-sail spacecraft, while the investigated control strategy realizes the accurate and efficient convergence of the orbital and attitude variables on both the rigid and flexible E-sail spacecraft with the tether deformation stabilized.

A photometric and spectroscopic study of eight semi-detached eclipsing binaries

Context. Semi-detached eclipsing binaries offer an exceptional opportunity to validate the evolutionary models of interacting binaries. This entails determining the absolute parameters and evaluating the evolutionary status of the binary components through simultaneous analysis of both light and radial velocity curves. The Transiting Exoplanet Survey Satellite (TESS) provides high-precision light curves, while the Large Sky Area Multi-Object Fibre Spectroscopic Telescope Medium-Resolution spectroscopic Survey (LAMOST MRS) offers multi-epoch observations. The combination of these data enhances the accuracy of deriving precise parameters for binary systems. Aims. The aim of this study is to estimate the absolute parameters of semi-detached binary components, offer potential explanations for their evolutionary status, and investigate long-term variations in orbital periods to explore their underlying causes. Methods. By cross-matching the eclipsing binary catalogue from TESS with that from LAMOST MRS, semi-detached eclipsing binaries with radial velocities spanning more than 0.3 phases were authenticated. The absolute parameters for these systems were determined by simultaneous modelling of light curves and radial velocities using the Wilson-Devinney programme. Additionally, the secular orbital variations were further analysed using O–C curves. Results. Eight semi-detached eclipsing binaries have been identified. Among them, seven contain primary stars situated within the main-sequence band, while their secondaries are all in evolved stages. This suggests that these systems likely originated as detached binaries and have undergone a reversal of the mass ratio. However, TIC 428257299 is an exception where the primary is Roche lobe-filling, and its secondary has experienced mass loss events. Additionally, TIC 8677671 and TIC 318217844 demonstrate secular cyclical variations in orbital periods. Specifically, for TIC 8677671, the cyclical change could result from magnetic activity or a third body that is likely to be compact, with a mass of at least 2.97 M⊙.

Orbital (Hydro)Climate Variability in the Ice-Free Early Eocene Arctic.

Early Eocene (∼56-48Ma) climates are useful to investigate polar climate dynamics in the absence of ice. We explore early Eocene orbital variability of Arctic climate using sediments recovered by the Arctic Coring Expedition (ACEX). High resolution records of lipid biomarkers (GDGTs; 2-kyr) and palynological assemblages (5-kyr) in the ∼4m interval below Eocene Thermal Maximum 2 (∼54Ma) show cyclic signals related to ∼20-kyr precession, ∼40-kyr obliquity, and ∼100-kyr eccentricity. Biomarkers indicate obliquity and precession variability representative of sea surface temperature (SST) variations up to ∼1.4 and ∼0.5°C, respectively. Peak SSTs coincide with an elevated supply of pollen and spores and increased marine productivity. This implies an orbital control on precipitation and terrestrial nutrient supply to the Arctic Basin. Assuming that SST maxima correspond to Arctic insolation maxima (precession minima/obliquity maxima), precipitation maxima also correspond to insolation maxima, implying regional hydrological processes as a forcing rather than variations in meridional water transport, contrasting Pleistocene Arctic hydrology. The relative amplitudes of precession and obliquity in the SST record match that of local insolation between spring and fall, corroborating a seasonal GDGT bias. The reconstructed complete orbital imprint refutes a bias to one end of the orbital variability. Eccentricity-related SST variability was ∼0.8°C, ∼2-3 times higher than synchronous variability in the deep ocean, and 3-4 times higher than similar variations in the tropics. This confirms eccentricity-forced global temperature variability and that this had pronounced polar amplification, despite the absence of ice-albedo feedbacks.

The isotopic composition of the French Illimani ice core in the Bolivian Andes supports the east-west South American precipitation dipole from the last deglaciation to the mid-Holocene

The age of the deepest part of the French Illimani ice core drilled in 1999 in Bolivia (16.63°S, 67.78°W) has been attributed to the Last Glacial Maximum (LGM). Major uncertainties remain on this initial dating, as it is based on the overall similarity in the isotopic composition of the ice between the Illimani and Huascarán (Peru, 9.11°S, 77.61°W) ice cores. Here, we use available measurements of atmospheric isotopic composition (δ18Oatm) over the last 5 m of the Illimani ice core to propose a revised dating. The age of the bottom of the Illimani ice core is now estimated at between 14.5 ka BP and 15.2 ka BP, covering a period from the end of the Heinrich stadial 1 to the mid-Holocene. Millennial and orbital variations of the isotopic composition of Illimani ice (δD) over this period are now consistent with records of the isotopic composition of speleothems (δ18O) located on the western pole of the east-west tropical South American precipitation dipole. We also discuss, for the first time for an Andean ice core, the continuously measured deuterium excess profile of the Illimani ice. The latter appears to be a promising new candidate for discussing vegetation changes that may have occurred in the Amazon basin during the last deglaciation.

New insight into the orbital parameters of the gamma-ray binary HESS J0632 + 057

ABSTRACT The gamma-ray binary HESS J0632 + 057 consists of a Be star and an undetected compact object in a $\sim$317 d orbit. The interpretation of the emission from this system is complicated by the lack of a clear orbital solution, as two different and incompatible orbital solutions were obtained by previous radial velocity studies of this source. In order to address this, we report on 24 new observations, covering $\sim$60 per cent of the orbit which we have undertaken with the Southern African Large Telescope (SALT). We obtained new radial velocity measurements by cross-correlating the narrower spectral features and fitting Voigt profiles to the wings of the Balmer emission lines. Additionally, we find an indication of orbital variability in the equivalent widths and V/R ratio of the Balmer lines. Using the combined data from this study, as well as archival data from the earlier radial velocity studies, we have derived updated orbital solutions. Using reported H $\alpha$ emission radial velocities – previously not considered for the orbital solution – along with the new SALT data, a solution is obtained where the brighter peak in the X-ray and gamma-ray light curves is closer to periastron. However, continuing sparse coverage in the data around the expected phases of periastron indicates that the orbital solution could be improved with further observation.

BSN: The First Photometric Study of 10 Contact Binary Systems from the Northern and Southern Hemispheres

Photometric observations were made with standard filters in four observatories for 10 contact binary systems. We analyzed the orbital period variations of the systems and found that six of them show long-term changes. The increase in the orbital period of the J07, N65, and PU Vir systems is caused by mass transfer, and the reduction in the orbital period of the J05, LO Psc, and N49 systems is caused by the combination of angular momentum loss and mass transfer. The first light-curve analysis was performed with the PHysics Of Eclipsing BinariEs Python code and Markov Chain Monte Carlo. We discussed the accuracy of photometric mass ratio estimates for contact binary systems with total and partial eclipses compared to spectroscopic results. We also compared our mass ratio findings to a recent method that estimates mass ratios from the light curve’s third derivative. Then, we also discussed this new mass ratio estimate method for photometric data. The systems’ positions were displayed in 18 empirical parameter relationships. According to the light-curve analysis and estimation of absolute parameters, systems BE Mus, J07, J08, N49, and N65 are A subtypes, and the others are W subtypes.

A Possible Explanation of W-type Phenomena in V694 Peg

Three sets of complete multicolor light curves of V694 Peg observed in 2013, 2015, and 2019 were presented and analyzed. Our photometric solutions show that this system was an A-type shallow contact binary in 2013 and 2015 while it converted to a W-type one in 2019. A large cool spot on the component of this binary could explain the conversion, implying the W-type phenomena may be caused by the magnetic activity of the components. We have collected available data on this binary and calculated 505 times of light minimum, which spans 17 yr. The orbital period investigation based on these timings shows there is a long-term period increase at a rate of dP/dt = 4.3(±0.3)×10−9 day yr−1 superposed on a periodic variation with a period of 11.81(±0.06) yr. The cyclic orbital variation may be the result of magnetic activity cycles or the existence of a third body. Until now, only eight transformed systems, including V694 Peg, have been reported. Compared with other converting contact systems between A-type and W-type, V694 Peg is recorded as the shortest-period one. All of these converting systems are late-type (later than F7) contact binaries with the O’Connell effect and show cyclic period variation, which indicates that magnetic activity may be the reason for the conversion between the two types of contact binaries. For investigating the nature of A-type and W-type phenomena, the discovery of more converting contact binaries is essential.

X-ray and optical observations of the millisecond pulsar binary PSR J1431–4715

We present the first X-ray observation of the energetic millisecond pulsar binary PSR J1431−4715, performed with XMM-Newton and complemented with fast optical multi-band photometry acquired with the ULTRACAM instrument at ESO-NTT. It is found as a faint X-ray source without a significant orbital modulation. This contrasts with the majority of systems that instead display substantial X-ray orbital variability. The X-ray spectrum is dominated by non-thermal emission and, due to the lack of orbital modulation, does not favour an origin in an intrabinary shock between the pulsar and companion star wind. While thermal emission from the neutron star polar cap cannot be excluded in the soft X-rays, the dominance of synchrotron emission favours an origin in the pulsar magnetosphere that we describe at both X-ray and gamma-ray energies with a synchro-curvature model. The optical multi-colour light curve folded at the 10.8 h orbital period is double-humped and dominated by ellipsoidal effects, but also affected by irradiation. The ULTRACAM light curves are fit with several models encompassing direct heating and a cold spot, or heat redistribution after irradiation either through convection or convection plus diffusion. Despite the inability to constrain the best irradiation models, the fits provide consistent system parameters, giving an orbital inclination of 59 ± 6° and a distance of 3.1 ± 0.3 kpc. The companion is found to be an F-type star, underfilling its Roche lobe (fRL = 73 ± 4%) with a mass of 0.20 ± 0.04 M⊙, confirming the redback status, but hotter than the majority of redbacks. The stellar dayside and nightside temperatures of 7500 K and 7400 K, respectively, indicate a weak irradiation effect on the companion, likely due to its high intrinsic luminosity. Although the pulsar mass cannot be precisely derived, a heavy (1.8−2.2 M⊙) neutron star is favoured.

Changes in the longitude polarization dependence of Jupiter's moon Io as evidence of the long-term variability of its volcanic activity

The aim of the work was to investigate the longitude (orbital) dependence of the polarization of Jupiter's moon Io and compare results of our study with what is reported in the literature. We used our published observations and supplemented them with new measurements carried out with the polarimeters mounted on the 2.6 m Shajn telescope of the Crimean Astrophysical Observatory and the 2 m telescope of the Peak Terskol Observatory in the UBVRI bands at phase angles between 10° and 12° in August 2023 – February 2024. We have determined that amplitude of the orbital polarization in the V band does not exceed ≈0.1 %. It is the deepest −0.17 ± 0.03 % at L ≈ 270° and the shallowest −0.07 ± 0.03 % near L ≈ 130°. These parameters differ markedly from that obtained by Zellner and Gradie (1975), which found that the orbital polarization variations from 0.4 to 0.5 % for α > 10°, and the negative branch is the deepest near L = 160° and the shallowest near L = 300°. These differences may be a consequence of changes in the reflective properties of the local areas of Io's surface due to long-term changes in Io's local or global volcanic activity.

Influence of Orbital Forcing on the Snowball Earth Deglaciation

AbstractNeoproterozoic snowball Earth events lasted for multiple million years, experiencing many orbital cycles. Here we investigate whether the deglaciation of these events would be triggered more easily at certain orbital configurations than others, by using an atmosphere‐land model that considers meltpond formation on land ice. Results show that the threshold concentration of atmospheric CO2 (pCO2) required for deglaciation can vary from 6 to 10 × 104 ppmv under different orbital forcings. The threshold pCO2 decreases with the equatorial maximum monthly insolation (EMMI), which is affected most by the eccentricity and secondarily by obliquity. Therefore, we conclude that the snowball Earth deglaciation likely occurred when the eccentricity was high and obliquity was low. Compared to previous estimate that used present‐day orbital configuration which has a minimal eccentricity, the duration of snowball Earth events would likely be much shorter when the influence of orbital variations are considered.

Tracking orbital and suborbital climate variability in the westernmost Mediterranean over the past 13,000 years: New insights from paleoperspectives on marine productivity responses

This study presents a comprehensive analysis of a sediment record from the Western Alboran Basin (core GP04PC), utilizing palynological and geochemical tools to investigate marine productivity responses to orbital and suborbital climate variability over the past 13,000 years. High productivity during the Younger Dryas humid phase (∼12.4–11.7 ka) and the Holocene humidity optimum (∼10.5–8.5 ka) was driven by increased local river discharges resulting from rapid mountain glaciers melting and enhanced regional precipitation. During the late Holocene, frequent flood events linked to negative North Atlantic Oscillation (NAO) incursions potentially led to multicentennial-scale productivity increases. The findings indicate that periods characterized by wet regional conditions and increased river run-off, influenced by orbital (e.g., insolation cycles) and suborbital factors (e.g., NAO and Atlantic Meridional Overturning Circulation changes), consistently enhanced marine productivity in the Western Alboran Basin. The study also reveals that the current high productivity and carbon export in the Western Alboran Basin are maintained by active upwelling and downwelling systems driven by a persistent positive NAO phase following the southward migration of the Intertropical Convergence Zone (ITCZ) that occurred around 6.5 ka. Furthermore, geochemical proxies support a strong detrital influence on trace metal concentrations, including barium (Ba), in deep Western Alboran sediments during the Holocene. This limits the use of Ba/Al ratios for accurately reconstructing productivity changes and highlights the importance of dinocyst analysis as a complementary tool for robust marine productivity reconstructions in this region. These observations provide valuable paleoperspectives on marine ecosystem responses to climate variability, contributing to the development of robust long-term productivity models essential for adapting to ongoing environmental changes in the region, and demonstrating the strong influence of North Atlantic climate and ocean dynamics on centennial-scale productivity oscillations in this region.

Constraining the overcontact phase in massive binary evolution. III. Period stability of known B+B and O+B overcontact systems

Binary systems play a crucial role in massive star evolution. Systems composed of B-type and O-type stars are of particular interest due to their potential to lead to very energetic phenomena or the merging of exotic compact objects. We aim to determine the orbital period variations of a sample of B+B and O+B massive overcontact binaries, with the primary objectives of characterizing the evolutionary timescales of these systems and addressing the existing discrepancy between observational data and theoretical predictions derived from population synthesis models. We used Period04 to analyze archival photometric data going back a century for a sample of seven binary systems to measure their orbital periods. We then determine the period variations using a linear fit. We find that the period variation timescales of five truly overcontact binary systems align with the nuclear timescale, in agreement with previous findings for more massive overcontact binaries. Additionally, we noticed a clear distinction between the five systems that had been unambiguously classified as overcontact systems and both SV Cen and VFTS 066, which seem to be evolving on thermal timescales and might be misclassified as overcontact systems. In the case of the five overcontact binaries, our results indicate a noticeable mismatch between the observational data and the theoretical predictions derived from population synthesis models. Furthermore, our results suggest that additional physical mechanisms must be investigated to compare the observed variations more thoroughly with theoretical predictions.

KM UMa: An Active Short-period Detached Eclipsing Binary in a Hierarchical Quadruple System

Abstract The first detailed photometric and spectroscopic analysis of the G-type eclipsing binary KM UMa is presented, which indicates that the system is a short-period detached eclipsing binary. The radial velocity curves were calculated using the cross-correlation function method based on Large Sky Area Multi-Object Fiber Spectroscopic Telescope, Sloan Digital Sky Survey, and our observations, which determined the mass ratio as q = 0.45 (±0.04). Based on the light curves from the Transiting Exoplanet Survey Satellite, other survey data, and our multiband observations, the positive and negative O’Connell effects have been detected evolving gradually and alternately over the last 20 yr, which can be explained by the presence of spots on the primary component. A superflare event was detected in the SuperWASP data on 2007 February 28, further indicating that KM UMa is a very active system. We calculated its energy to be 5 × 1034 erg by assuming it occurred on the primary star. Utilizing hundreds of medium-resolution spectra and one low-resolution spectrum, the equivalent width variations of the H α line were calculated, indicating the presence of a 5.21 (±0.67) yr magnetic activity cycle. The orbital period variations were analyzed using the O–C method, detecting a long-term decrease superimposed with a periodic variation. The amplitude of the cyclic variation is 0.01124 (±0.00004) day, with a period of 33.66 (±0.0012) yr, which exceeds the 5.21 yr activity cycle, suggesting that this is more likely attributable to the light travel time effect of a third body. Simultaneously, a visual companion has been detected based on the Gaia astrometric data, indicating that KM UMa is actually in a 2+1+1 hierarchical quadruple system.

VELOcities of CEpheids (VELOCE)

Classical Cepheids provide valuable insights into the evolution of stellar multiplicity among intermediate-mass stars. Here, we present a systematic investigation of single-lined spectroscopic binaries (SB1s) based on high-precision velocities measured by the VELOcities of CEpheids (VELOCE) project. We detected 76 (29%) SB1 systems among the 258 Milky Way Cepheids in the first VELOCE data release, 32 (43%) of which were not previously known to be SB1 systems. We determined 30 precise and three tentative orbital solutions, 18 (53%) of which are reported for the first time. This large set of Cepheid orbits provides a detailed view of the eccentricity e and orbital period Porb distribution among evolved intermediate-mass stars, ranging from e ∈ [0.0, 0.8] and Porb ∈ [240, 9000] d. The orbital motion on timescales exceeding the 11 yr VELOCE baseline was investigated using a template-fitting technique applied to literature data. Particularly interesting objects include (a) R Cru, the Cepheid with the shortest orbital period in the Milky Way (∼238 d); (b) ASAS J103158−5814.7, a short-period overtone Cepheid exhibiting time-dependent pulsation amplitudes as well as orbital motion; and (c) 17 triple systems with outer visual companions, among other interesting objects. Most VELOCE Cepheids (21/23) that exhibit evidence of a companion based on a Gaia proper motion anomaly are also spectroscopic binaries, whereas the remaining do not exhibit significant (> 3σ) orbital radial velocity variations. Gaia quality flags, notably the renormalized unit weight error (RUWE), do not allow Cepheid binaries to be identified reliably although statistically the average RUWE of SB1 Cepheids is slightly higher than that of non-SB1 Cepheids. A comparison with Gaia photometric amplitudes in G-, Bp, and Rp also does not allow one to identify spectroscopic binaries among the full VELOCE sample, indicating that the photometric amplitudes in this wavelength range are not sufficiently informative of companion stars.