arXiv subjects

Z. Henzl

Publications and source records attributed to Z. Henzl.

14 recordsLinked to original sources

arXiv2026

Six new doubly eclipsing quadruples in a 2+2 architecture

The study presents a confirmation of six quadruples with two sets of eclipses that have the 2+2 architecture. These so-called doubly eclipsing systems still present a quite rare group of stars. We collected all available photometric data and carried out a detailed analysis of them. In addition to the precise TESS photometry used to model the light curves for both inner eclipsing binaries, photometric survey data were also used, and more than 100 nights of our own dedicated observations were carried out. These were mainly used for the detection of the long-term evolution of orbital periods. Thanks to these data, we were able to derive the mutual orbits of the inner doubles via eclipse timing variations. The systems studied are: CzeV1254 (periods 0.715348 d + 0.362593 d, mutual period 15.6 yr); ASASSN-V J070838.27-171952.9 (4.300490 d + 3.767235 d, 4 yr); ASASSN-V J091951.17-593306.9 (2.668674 d + 14.342218 d, 0.95 yr); WISE J100820.07-731554.0 (0.368315 d + 7.945339 d, 3.8 yr); ASASSN-V J143536.01-721459.4 (7.353842 d + 6.368567 d, 27.4 yr); and Corot 310284765 (1.875418 d + 2.371126 d, 22.6 yr). Some of the binaries show significantly eccentric orbits. We also estimated their apsidal motion periods. With our six new systems, the number of confirmed orbits of 2+2 quadruples has been increased to 64 in total.

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arXiv2025

Three new 2+2 quadruple systems with changing inclination

We present a unique discovery of three new detected systems showing two different phenomena together. These are 2+2 quadruple stellar systems showing two eclipsing binaries as the inner pairs. And besides that, these systems were also found to exhibit the precession of the inner orbits causing the inclination changes manifesting themselves through the eclipse depth variations. We are not aware of any similar known system on the sky nowadays, hence our discovery is really unique. In particular these systems are: CzeV4315 = HD 228777 (periods 6.7391 d and 0.91932 d, inclination change of pair B of about 1.4deg/yr); ASASSN-V J075203.23-323102.7 = GDS_J0752031-323102 (8.86916 d + 2.6817 d, inclination change of pair B of about 1.03deg/yr, now only ellipsoidal variations); ASASSN-V J105824.33-611347.6 = TIC 465899856 (2.3304 d + 13.0033 d, inclination change of pair B, now undetectable). These systems provide us unique insight into the quadruple-star dynamics, including the orbit-orbit interaction, Kozai-Lidov cycles, and testing the stellar formation theories of these higher order multiples.

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arXiv2024

Eight new 2+2 doubly eclipsing quadruple systems detected

We studied eight new doubly eclipsing stellar systems. We found that they are all rare examples of quadruple systems of 2 + 2 architecture, where both inner pairs are eclipsing binaries. Until now, such a configuration had only been proven for dozens of systems on the whole sky. We enlarged this rare group of systems with four stars in the Small Magellanic Cloud (SMC) galaxy and four brighter stars on the northern sky. These analysed systems are the following: OGLE SMC-ECL-2339 (both eclipsing periods of 0.72884 days and 3.39576 days; mutual orbital period of 5.95 years); OGLE SMC-ECL-3075 (1.35890 d, 2.41587 d, 9.75 yr); OGLE SMC-ECL-4756 (0.91773 d, 2.06047 d, 4.34 yr); OGLE SMC-ECL-6093 (0.90193 d, 2.03033 d, 31.2 yr); GSC 01949-01700 (0.24058 d, 0.75834 d, 21.7 yr); ZTF J171602.61+273606.5 (0.36001 d, 4.51545 d, 19.5 yr); WISE J210935.8+390501 (0.33228 d, 3.51575 d, 1.9 yr); and V597 And (0.46770 d, 0.35250, 20.4 yr). These systems constitute a rare selection of W UMa stars among the doubly eclipsing quadruples. For all of the systems, new dedicated observations were obtained as well. V597 And is definitely the most interesting system for several reasons: (1) the system is the brightest in our sample; (2) it is a rare quintuple (2 + 2) + 1 system; and (3) it is also closest to the Sun. It yielded the predicted angular separation of the two components of 57 mas, which is probably within the detection limits for modern, high-angular-resolution techniques.

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arXiv2024

Periodic variable A-F spectral type stars in the southern TESS continuous viewing zone

We accurately identify and classify the variability of A-F stars in the southern continuous viewing zone of the TESS satellite. The brightness limit was set to 10 mag to ensure the utmost reliability of our results and allow for spectroscopic follow-up observations using small telescopes. We aim to compare our findings with existing catalogues of variable stars. The light curves from TESS and their Fourier transform were used to manually classify stars in our sample. Cross-matching with other catalogues was performed to identify contaminants and false positives. We have identified 1171 variable stars (51 % of the sample). Among these variable stars, 67 % have clear classifications, which includes $δ$ Sct and $γ$ Dor pulsating stars and their hybrids, rotationally variables, and eclipsing binaries. We have provided examples of the typical representatives of variable stars and discussed the ambiguous cases. We found 20 pairs of stars with the same frequencies and identified the correct source of the variations. Additionally, we found that the variations in 12 other stars are caused by the contamination with the light of faint nearby large-amplitude variable stars. To compare our sample with other variable star catalogues, we have defined two parameters reflecting the agreement in identification of variable stars and their classification. This comparison reveals intriguing disagreements in classification ranging from 52 % to 100 %. However, if we assume that stars without specific types are only marked as variable, then the agreement is relatively good, ranging from 57 % to 85 % (disagreement 15-43 %). We have demonstrated that the TESS classification is superior to the classification based on other photometric surveys. The classification of stellar variability is complex and requires careful consideration. Caution should be exercised when using catalogue classifications.

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arXiv2024

Six new eccentric eclipsing systems with a third body

We present the discovery of six new triple stellar system candidates composed of an inner eccentric-orbit eclipsing binary with an apsidal motion. These stars were studied using new, precise TESS light curves and a long-term collection of older photometric ground-based data. These data were used for the monitoring of ETVs (eclipse timing variations) and to detect the slow apsidal movements along with additional periodic signals. The systems analysed were ASASSN-V J012214.37+643943.3 (orbital period 2.01156 d, eccentricity 0.15, third body with 3.3 yr period); ASASSN-V J052227.78+345257.6 (2.42673 d, 0.35, 3.2 yr); ASASSN-V J203158.98+410731.4 (2.53109 d, 0.20, 2.7 yr); ASASSN-V J230945.10+605349.3 (2.08957 d, 0.18, 2.3 yr); ASASSN-V J231028.27+590841.8 (2.41767 d, 0.43, 4.9 yr); and NSV 14698 (3.30047 d, 0.147, 0.5 yr). In the system ASASSN-V J230945.10+605349.3, we detected a second eclipsing pair (per 2.99252 d) and found adequate ETV for the pair B, proving its 2+2 bound quadruple nature. All of these detected systems deserve special attention from long-term studies for their three-body dynamics since their outer orbital periods are not too long and because some dynamical effects should be detectable during the next decades. The system NSV 14698 especially seems to be the most interesting from the dynamical point of view due to it having the shortest outer period of the systems we studied, its fast apsidal motion, and its possible orbital changes during the whole 20th century.

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arXiv2023

Detection of seven 2+2 doubly eclipsing quadruple systems

In this work, we study a heterogeneous group of seven stellar systems for the first time. Despite their different distances or spectral types, all of them belong to a very rare group of quadruple systems of 2+2 architecture, where both of the inner pairs harbor eclipsing binaries. These systems are: ASASSN-V J102911.57-522413.6 (inner periods 0.57272, and 3.79027 days), V1037 Her (0.78758 and 5.80348 days), WISE J181904.2+241243 (0.36713 and 0.41942 days), V2894 Cyg (2.57434 and 1.30579 days), NSVS 5725040 (1.79368 and 0.76794 days), WISE J210230.8+610816 (1.84324 and 0.57159 days), and ZTF J220518.78+592642.1 (2.79572 and 3.34615 days). Their outer mutual periods are: 9.3, 25.4, 18.7, 27.5, 2.6, 2.2, and 14.0 yr, respectively. These outer periodicities were derived using longer time span of photometric observations of these systems and analysing their period changes of both inner pairs via ETVs (eclipse-timing variations). Most of these studied systems are detached, as evidenced by the proper modelling of their light curves. A few of them show significant eccentric orbits with apsidal motion (e.g. V2894 Cyg, and NSVS 5725040). Further spectroscopic follow-up observations would offer a better characterization of the component star's parameters (for e.g. NSVS 5725040), as well as a potential interferometric detection of the systems as real doubles on their mutual orbits (for e.g. V1037 Her). A rather interesting excess of systems close to a 3:2 mean motion resonance is seen only for early spectral-type stars with higher temperatures.

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arXiv2023

V994 Her: A Unique Triply Eclipsing Sextuple Star System

We report the discovery with $TESS$ of a third set of eclipses from V994 Herculis (TIC 424508303), previously only known as a doubly-eclipsing system. The key implication of this discovery and our analyses is that V994 Her is the second fully-characterized (2+2) + 2 sextuple system, in which all three binaries eclipse. In this work, we use a combination of ground-based observations and $TESS$ data to analyze the eclipses of binaries A and B in order to update the parameters of the inner quadruple's orbit (with a derived period of 1062 $\pm$ 2d). The eclipses of binary C that were detected in the $TESS$ data were also found in older ground-based observations, as well as in more recently obtained observations. The eclipse timing variations of all three pairs were studied in order to detect the mutual perturbations of their constituent stars, as well as those of the inner pairs in the (2+2) core. At the longest periods they arise from apsidal motion, which may help constraining parameters of the component stars' internal structure. We also discuss the relative proximity of the periods of binaries A and B to a 3:2 mean motion resonance. This work represents a step forward in the development of techniques to better understand and characterize multiple star systems, especially those with multiple eclipsing components.

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arXiv2022

TIC 452991707 and TIC 452991693 as a Candidate Sextuple System with Three Eclipsing Binaries

We present the discovery of a rare system detected in the TESS data showing three different eclipsing-like signals. TIC 452991707 and TIC 452991693 seem to be the second such system on the sky, whose two components separated about 16" are gravitationally bounded, or comprise a co-moving pair. The three periods detected from the TESS data are: PA=1.46155 d, PB=1.77418 d, and PC=1.03989 d, respectively. The A and B periods belong to TIC 452991707, while the C comes from the component TIC 452991693. The pair A shows the deepest eclipses, and its orbit is very slightly eccentric. The third period C has lowest amplitude (eclipsing or ellipsoidal nature), but originates from TIC 452991693, which is connected to A+B because both visual components share similar proper motion and distance. Long-term collection of data from older photometry from various surveys also shows that the two inner pairs A and B orbit around their barycenter. Its period is probably of a few years, but for a final derivation of its orbital parameters one needs more up-to-date data. Hence, we call for new observations of this amazing system.

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arXiv2022

Periodic variable A-F spectral type stars in the northern TESS continuous viewing zone

The goal of our study is to provide a reliable classification of variability of A-F stars brighter than 11 mag located in the northern TESS continuous viewing zone. We also aim at thorough discussion about issues in the classification related to the data characteristics and the issues arising from the similar light curve shape generated by different physical mechanisms. We used TESS long- and short-cadence photometric data and corresponding Fourier transform to classify the variability type of the stars. We present a clear and concise classification system that is demonstrated on many examples. We found clear signs of variability in 3025 of 5923 studied stars (51 %). For 1813 of these 3025 stars, we provide a classification. From the classified stars, 64.5 % are pulsating stars of GDOR and DSCT types and their hybrids. We realised that the long- and short-cadence PDCSAP data can differ significantly not only in amplitudes but also in the content of instrumental/data reduction artifacts making the long-cadence data less reliable. We identified a new group of stars showing stable light curves and characteristic frequency spectra pattern (8.5 % of the classified stars). According to the position in the Hertzsprung-Russell diagram, these stars are likely GDOR stars but are about 200 K cooler than GDORs on average and have smaller amplitudes and longer periods in average. We show that without spectroscopic observations, it can be impossible to unambiguously distinguish between ellipsoidal variability and rotational variability. We also apply our methodology to three previous studies and found significant discrepancies in the classification. We demonstrate how difficult the classification of variable A-F stars can be when using only photometric data.

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arXiv2022

Multiply eclipsing candidates from the TESS satellite

We present the catalogue of the TESS targets showing multiple eclipses. It means that in all of these stars we detected two sets of eclipses, for which their two distinctive periods can be derived. These multiple stellar systems can be either doubly eclipsing quadruples, or triple-star coplanar systems showing besides the inner eclipses also the eclipses on the outer orbit. In total, 116 systems were found as doubly eclipsing, while 25 stars were identified as triply eclipsing triples. Several confirmed blends of two close sources were not included into our analysis. All these systems were identified scanning the known eclipsing systems taken from VSX database checking their TESS light curves. The average period of the dominant pair A is 2.7 days in our sample, while for the second pair B the average period is 5.3 days. Several systems show evident ETV changes even from the short interval of the TESS data, indicating possible period changes and short mutual orbit. We also present an evidence that the system V0871 Cen is probably a septuple-star system of architecture (Aa-Ab)-B-C-D. Most of the presented systems are adequately bright and showing deep enough eclipses, hence we call for new ground-based observations for these extremely interesting multiples. Owing to this motivation our catalog contains besides the ephemerides for both pairs also their depths of eclipses and the light curve shapes as extracted from the TESS data. These new ground based observations would be very useful for further derivation of the mutual movement of both pairs on their orbit via detection of the ETVs of both pairs for example.

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arXiv2022

The first study of four doubly eclipsing systems

We present the discovery and the very first analysis of four stellar systems showing two periods of eclipses, that are the objects classified as doubly eclipsing systems. Some of them were proved to orbit each other thanks to their eclipse-timing-variations (ETVs) of both pairs, hence they really constitute rare quadruples with two eclipsing pairs. Some of them do not, as we are still waiting for more data to detect their mutual movement. Their light curves and period changes were analysed. All of them are detached and near-contact, but none of them contact; moreover, to our knowledge none of these stars can be considered as blend of two spatially unresolved close components on the sky. These systems are CzeV2647 (0.5723296 + 0.9637074 days), proved to orbit with 4.5-year periodicity; CzeV1645 (1.0944877 + 1.6594641 days), with a rather questionable detection of ETV; CzeV3436 (0.6836870 + 0.3833930 days); and, finally, OGLE SMC-ECL-1758 (0.9291925 + 3.7350826 days), proved to move on its 30-year orbit. Even more surprising is the fact that most of these systems show the ratio of their two orbital periods close to coupling near some resonant values of small integers, namely CzeV2647, with only 1% from 3:5 resonance, CzeV1645 1% from 2:3 resonance, and OGLE SMC-ECL-1758 with only 0.49% from 1:4 resonance. The nature of these near-resonant states still remains a mystery.

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arXiv2021

Hunt for extremely eccentric eclipsing binaries

We report the very first analysis of 27 eclipsing binary systems with high eccentricities that sometimes reach up to 0.8. The orbital periods for these systems range from 1.4 to 37 days, and the median of the sample is 10.3 days. Star CzeV3392 (= UCAC4 623 022784), for example, currently is the eclipsing system with the highest eccentricity (e = 0.22) of stars with a period shorter than 1.5 days. We analysed the light curves of all 27 systems and obtained the physical parameters of both components, such as relative radii, inclinations, or relative luminosities. The most important parameters appear to be the derived periods and eccentricities. They allow constructing the period-eccentricity diagram. This eccentricity distribution is used to study the tidal circularisation theories. Many systems have detected third-light contributions, which means that the Kozai-Lidov cycles might also be responsible for the high eccentricities in some of the binaries.

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arXiv2020

CzeV1731: The unique doubly eclipsing quadruple system

We report the discovery of the relatively bright (V = 10.5 mag), doubly eclipsing 2+2 quadruple system CzeV1731. This is the third known system of its kind, in which the masses are determined for all four stars and both the inner and outer orbits are characterized. The inner eclipsing binaries are well-detached systems moving on circular orbits: pair A with period PA = 4.10843 d and pair B with PB = 4.67552 d. The inner binaries contain very similar components (q = 1.0), making the whole system a so-called double twin. The stars in pair B have slightly larger luminosities and masses and pair A shows deeper eclipses. All four components are main-sequence stars of F/G spectral type. The mutual orbit of the two pairs around the system barycenter has a period of about 34 yr and an eccentricity of about 0.38. However, further observations are needed to reveal the overall architecture of the whole system, including the mutual inclinations of all orbits. This is a promising target for interferometry to detect the double at about 59 mas and dMbol < 1 mag. (The RV and ETV data available via CDS)

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arXiv2019

Doubly eclipsing systems

Aims: Our goal was to increase number of known doubly eclipsing systems such that the resulting dataset would allow to study them via statistical means, as well as prove that they constitute gravitationally bound 2+2 quadruple system. Methods: We analysed photometric data for eclipsing binaries provided by the OGLE survey in the LMC fields. We found a large number of new doubly eclipsing systems (our discoveries are 3x more numerous than previous studies). With a typical orbital period of days for the binaries, we sought eclipse time variations (ETVs) on the timescale of years. In the cases where we were able to detect the ETV period, the difference between the inner and outer periods in the quadruple system is large enough. This allows us to interpret ETVs primarily as the light-time effect, thus providing an interesting constraint on masses of the binaries. Results: In addition to significantly enlarging the database of known doubly eclipsing systems, we performed a thorough analysis of 72 cases. ETVs for 28 of them (39% of the studied cases) showed evidence of relative motion. We note OGLE BLG-ECL-145467 as the most interesting case; it is bright (I=12.6 mag), consists of two detached binaries with periods of about 3.3 d and 4.9 d (making it a candidate for a 3:2 resonant system), mutual period about 1538 d. Distribution of the orbital period ratio P_A/P_B of binaries in 2+2 quadruples shows statistically significant excess at 1 and 1.5. The former is likely a natural statistical preference in weakly interacting systems with periods within the same range. The latter is thought to be evidence of a capture in the 3:2 mean motion resonance of the two binaries. This sets important constraints on evolutionary channels in these systems. The total number of doubly eclipsing systems increased to 146, more than 90% of which are at low declinations on the southern sky.

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