Journal articles: 'Binary stars; Eclipse mapping'

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Cameron, A. C. "Eclipse mapping of late-type close binary stars." Monthly Notices of the Royal Astronomical Society 287, no. 3 (May 21, 1997): 556–66. http://dx.doi.org/10.1093/mnras/287.3.556.

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Nuspl, J., and I. B. Bíró. "Eclipse Mapping of Non-Radial Pulsation in Binary Stars." International Astronomical Union Colloquium 185 (2002): 100–101. http://dx.doi.org/10.1017/s0252921100015669.

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AbstractWe review a slightly modified method of eclipse mapping, applicable to mode identification in eclipsing binaries containing a pulsating component. The observed light curve is used by the procedure without removing from it the badly determined eclipsing part.

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Kaitchuck, Ronald H. "How Does One Detect An Accretion Disk?" Symposium - International Astronomical Union 151 (1992): 175–83. http://dx.doi.org/10.1017/s007418090012217x.

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The history of the first detection of an accretion disk in a interacting binary system is presented. The nature of transient and permanent disks in Algol-type binaries is discussed as are the problems associated with the interpretation of emission line profiles from the disks in cataclysmic variable stars. The new technique of eclipse mapping from continuum photometry is reviewed. Some results of Doppler tomography of emission lines are presented.

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Latković, Olivera, and Attila Cséki. "Modeling non-radial oscillations on components of close binaries." Proceedings of the International Astronomical Union 9, S301 (August 2013): 447–48. http://dx.doi.org/10.1017/s1743921313014981.

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AbstractWe developed an advanced binary system model that includes stellar oscillations on one or both stars, with the goal of mode identification by fitting of the photometric light curves. The oscillations are modeled as perturbations of the local surface temperature and the local gravitational potential. In the case of tidally distorted stars, it is assumed that the pulsation axis coincides with the direction connecting the centers of the components rather than with the rotation axis. The mode identification method, originally devised by B. Bíró, is similar to eclipse mapping in that it utilizes the amplitude, phase and frequency modulation of oscillations during the eclipse; but the identification is achieved by grid-fitting of the observed light curve rather than by image reconstruction. The proposed model and the mode identification method have so far been tested on synthetic data with encouraging results.

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Lehmann, H., V. Tsymbal, F. Pertermann, A. Tkachenko, D. E. Mkrtichian, and N. A-thano. "Spectroscopic time-series analysis of R Canis Majoris." Astronomy & Astrophysics 615 (July 2018): A131. http://dx.doi.org/10.1051/0004-6361/201629914.

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R Canis Majoris is the prototype of a small group of Algol-type stars showing short orbital periods and low mass ratios. A previous detection of short-term oscillations in its light curve has not yet been confirmed. We investigate a new time series of high-resolution spectra with the aim to derive improved stellar and system parameters, to search for the possible impact of a third component in the observed spectra, to look for indications of activity in the Algol system, and to search for short-term variations in radial velocities. We disentangled the composite spectra into the spectra of the binary components. Then we analysed the resulting high signal-to-noise spectra of both stars. Using a newly developed program code based on an improved method of least-squares deconvolution, we were able to determine the radial velocities of both components also during primary eclipse. This allowed us to develop a better model of the system including the Rossiter–McLaughlin effect and to derive improved orbital parameters. Combining the results with those from spectrum analysis, we obtain accurate stellar and system parameters. We further deduce at least one oscillation frequency of 21.38 c d−1. It could be detected during primary eclipses only and confirms a previous photometric finding. Results point to an amplitude amplification of non-radial pulsation modes due to the eclipse mapping effect. The presence of a He I line in the spectra indicates mass transfer in the R CMa system. Calculations of its Roche geometry give evidence that the cool secondary component may fill its Roche lobe. No evidence of a third body in the system could be found in the observed spectra.

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Horne, Keith. "Tomography of Accretion Flows in Binary Stars and Active Galactic Nuclei." International Astronomical Union Colloquium 163 (1997): 14–26. http://dx.doi.org/10.1017/s0252921100042469.

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AbstractAstrotomography resolves accretion flows with micro-arcsecond angular resolution. Eclipses by a binary companion star slice up a disk surface, giving monochromatic maps of the disk, or spectra from any region of its surface. Doppler tomography maps emission-line regions from the changing velocity profile as the binary rotates, revealing radial and azimuthal structure, gas streams, irradiated companion stars, magnetic flows, and slingshot prominences. Echo mapping exploits time delays between the hard radiation from near the compact object at the focus of the flow, and softer emission generated by irradiation of regions farther out. The maximum entropy techniques for fitting intensity maps to data are currently being extended by incorporating local physics and mapping physical parameters such as temperature, density, surface density, and velocity dispersion.

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Lehmann, Holger, David Mkrtichian, and Andrew Tkachenko. "Spectroscopic eclipse mapping of oEA stars." Journal of Physics: Conference Series 118 (October 1, 2008): 012062. http://dx.doi.org/10.1088/1742-6596/118/1/012062.

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Rutten, René G. M. "Eclipse mapping and related techniques." Symposium - International Astronomical Union 176 (1996): 69–84. http://dx.doi.org/10.1017/s007418090008311x.

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Eclipse mapping is a technique to deduce spatial structure on very small angular scales in eclipsing cataclysmic variable stars (CVs). By analysing the eclipse light curve, information is obtained on the brightness structure of the accretion disk and of the compact mass-accreting object in these systems. This information would otherwise be well beyond the resolving power of any optical telescope. Since the development of the eclipse mapping technique by K. Horne, about one decade ago, it has now become an important tool in the study of CVs. Originally eclipse mapping was employed to construct brightness maps of accretion disks in broad spectral bands. Recently, maps of much higher spectral resolution have become available from which optical and UV spectra have been reconstructed in spatial detail across accretion disks. Such information is very important for our understanding of the physics of the accretion process.In this paper I will describe the eclipse mapping technique and review recent results. In conjunction, I will briefly highlight other techniques related to the mapping of surface structure in CVs.

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Schmitt, J. H. M. M. "Eclipse mapping at X-ray wavelengths." Symposium - International Astronomical Union 176 (1996): 85–94. http://dx.doi.org/10.1017/s0074180900083121.

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Stellar coronae cannot be spatially resolved, and yet stellar coronae are likely to exhibit a similar amount of structure as the solar corona. Currently, the only way to infer structure from spatially unresolved data is to look for rotational modulation of the X-ray emission or eclipses in the case of binary systems. I will discuss some of the observations obtained and critically review the methods used to infer structure from these data. Particular emphasis will be placed on the ill-conditioned nature of the inversion problem, that makes it next to impossible to infer the possibly three-dimensional structure of stellar coronae.

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von Boetticher, Alexander, Amaury H. M. J. Triaud, Didier Queloz, Sam Gill, Pierre F. L. Maxted, Yaseen Almleaky, David R. Anderson, et al. "The EBLM Project." Astronomy & Astrophysics 625 (May 2019): A150. http://dx.doi.org/10.1051/0004-6361/201834539.

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Measurements of the physical properties of stars at the lower end of the main sequence are scarce. In this context we report masses, radii and surface gravities of ten very-low-mass stars in eclipsing binary systems, with orbital periods of the order of several days. The objects probe the stellar mass-radius relation in the fully convective regime, M⋆ ≲ 0.35 M⊙, down to the hydrogen burning mass-limit, MHB ∼ 0.07 M⊙. The stars were detected by the WASP survey for transiting extra-solar planets, as low-mass, eclipsing companions orbiting more massive, F- and G-type host stars. We use eclipse observations of the host stars, performed with the TRAPPIST, Leonhard Euler and SPECULOOS telescopes, and radial velocities of the host stars obtained with the CORALIE spectrograph, to determine the physical properties of the low-mass companions. Surface gravities of the low-mass companions are derived from the eclipse and orbital parameters of each system. Spectroscopic measurements of the host star effective temperature and metallicity are used to infer the host star mass and age from stellar evolution models for solar-type stars. Masses and radii of the low-mass companions are then derived from the eclipse and orbital parameters of the binary systems. The objects are compared to stellar evolution models for low-mass stars, to test for an effect of the stellar metallicity and orbital period on the radius of low-mass stars in close binary systems. Measurements are found to be in good agreement with stellar evolution models; a systematic inflation of the radius of low-mass stars with respect to model predictions is limited to 1.6 ± 1.2%, in the fully convective low-mass regime. The sample of ten objects indicates a scaling of the radius of low-mass stars with the host star metallicity. No correlation between stellar radii and the orbital periods of the binary systems is determined. A combined analysis with thirteen comparable objects from the literature is consistent with this result.

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Watson, C. A., and V. S. Dhillon. "The effect of star-spots on eclipse timings of binary stars." Monthly Notices of the Royal Astronomical Society 351, no. 1 (June 2004): 110–16. http://dx.doi.org/10.1111/j.1365-2966.2004.07763.x.

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Royer, Pierre, Gregor Rauw, Jean Manfroid, Eric Gosset, and Jean-Marie Vreux. "Narrow-band photometry of the eclipsing WN7+O binary WR 22." Symposium - International Astronomical Union 193 (1999): 94–95. http://dx.doi.org/10.1017/s0074180900205111.

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In the present paper, we discuss photometric observations of the February 1996 eclipse of the very massive WR+O binary WR 22. Our data were obtained with a set of narrow-band filters, specially designed for the study of WR stars.

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Shevchenko, Ivan I. "Habitable worlds of merging stars." International Journal of Astrobiology 19, no. 6 (October 6, 2020): 500–504. http://dx.doi.org/10.1017/s1473550420000282.

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AbstractIt is shown that W UMa-type and SX Phe-type stellar populations are both perfectly and uniquely suited for maintaining hyper-effective biopolymer chain reactions (BCR) on their planets once the planet is in the stellar habitable zone. W UMa-type stars are known to be contact binaries, and SX Phe-type stars are presumably post-binaries, i.e., products of stellar mergers. In case of the contact binaries, the eclipse-driven periodic heating/cooling of planetary surfaces has period-amplitude parameters that perfectly satisfy stringent conditions for maintaining BCR-like reactions. In case of the post-binaries, the stars pulsate with periods and amplitudes also perfectly suited for maintaining the reactions. Therefore, the ‘W UMa – SX Phe’ metamorphosis (from a contact binary to a post-binary, via the merger) seems to provide a potential biosystem reboot on planets in these systems.

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Polzin, E. J., R. P. Breton, B. Bhattacharyya, D. Scholte, C. Sobey, and B. W. Stappers. "Study of spider pulsar binary eclipses and discovery of an eclipse mechanism transition." Monthly Notices of the Royal Astronomical Society 494, no. 2 (March 3, 2020): 2948–68. http://dx.doi.org/10.1093/mnras/staa596.

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ABSTRACT We present a comparative study of the low-frequency eclipses of spider (compact and irradiating binary) PSRs B1957+20 and J1816+4510. Combining these data with those of three other eclipsing systems we study the frequency dependence of the eclipse duration. PSRs B1957+20 and J1816+4510 have similar orbital properties, but the companions to the pulsars have masses that differ by an order of magnitude. A dedicated campaign to simultaneously observe the pulsed and imaged continuum flux densities throughout the eclipses reveals many similarities between the excess material within the two binaries, irrespective of the companion star properties. The observations show that the pulsar fluxes are removed from the line of sight throughout the main body of the eclipses. For PSR J1816 + 4510, we present the first direct evidence of an eclipse mechanism that transitions from one that removes the pulsar flux from the line of sight to one that merely smears out pulsations, and claim that this is a consequence of scattering in a tail of material flowing behind the companion. Inferred mass-loss rates from the companion stars are found to be $\dot{M}_{\text{C}} \sim 10^{-12}$ and $\sim 2 \times 10^{-13}\,\mathrm{M}_\odot$ yr−1 for PSR B1957+20 and PSR J1816 + 4510, respectively; seemingly too low to evaporate the stars within Hubble time. Measurements of eclipse durations over a wide range of radio frequencies show a significant dependence of eclipse duration on frequency for all pulsars, with wider eclipses at lower frequencies. These results provide a marked improvement in the observational constraints available for theoretical studies of the eclipse mechanisms.

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Nasiroglu, Ilham, Krzysztof Goździewski, Aga Słowikowska, Krzysztof Krzeszowski, Michal Żejmo, Staszek Zola, and Huseyin Er. "Searching for planets around eclipsing binary stars using timing method: NSVS 14256825." Proceedings of the International Astronomical Union 12, S330 (April 2017): 405–6. http://dx.doi.org/10.1017/s1743921317005658.

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AbstractWe present four new mid eclipse times and an updated O-C diagram of the short period eclipsing binary NSVS14256825. The new data follow the (O-C) trend and its model proposed in Nasiroglu et al. (2017). The (O-C) diagram shows quasi-periodic variations that can be explained with the presence of a brown-dwarf in a quasi-circular circumbinary orbit.

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Balona, L. A., and J. Cuypers. "An Extraordinary Early-Type Eclipsing Binary." International Astronomical Union Colloquium 139 (1993): 188. http://dx.doi.org/10.1017/s0252921100117270.

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HR 2680 (B5V) was used as a comparison star in a multi-site (ESO & SAAO) campaign organised in 1988 to observe Be stars. We found that the star is an eclipsing binary with a period of 8.1 days. The eclipse is partial with a depth of 0.18 mag. Radial velocity observations confirmed the period.A light variation with an amplitude of as much as 0.03 mag was seen outside the eclipse (Fig. 1). This variation can be interpreted as two oscillations with approximate periods of 1.19 and 1.28 days. Further photometric observations were obtained in 1989, 1990 and 1991 at SAAO. The multiperiodicity was confirmed, but the periods were not constant from season to season.We suspect that the star is a pulsator of the 53 Per class of line-profile variables. Being an eclipsing binary, this unique system is of potentially great importance as a test bed for stellar dynamics and nonradial pulsations.

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Welsh, William F., and J. H. Wood. "Eclipse Mapping the Flickering in HT Cas." International Astronomical Union Colloquium 151 (1995): 300–301. http://dx.doi.org/10.1017/s0252921100035259.

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Flickering is a well-known, though poorly understood, signature of accretion in cataclysmic variables. HT Cas is an excellent system in which to study flickering because its well determined characteristics allow a calibration of the experimental system (see Horne et al. 1991).Patterson (1981) argues that the flickering in HT Cas originates from regions very near the white dwarf. In U Gem, the flickering appears to be associated with the bright spot (Warner & Nather 1971). In RW Tri, the flickering occurs throughout the disk but is centrally concentrated (Horne & Stiening 1985); the same holds true for V2051 Oph (Warner & Cropper 1983).HT Cas is a 16m.4 eclipsing dwarf nova with a binary period of 106 min and an inclination of ∼ 81°. The entire eclipse last about 15 min with the white dwarf totally eclipsed for ∼ 5 min. The mass ratio is 0.15 with the white dwarf having mass ∼ 0.6M⊙ (Horne et al. 1991).We obtained 20 eclipses of HT Cas between 1982 and 1991 in U, B and V at Mt. Palomar and also McDonald Observatory with 0.5 – 2 sec integrations. These data were folded on the ephemeris given by Horne et al. (1991) and corrected for the 30 sec drift in the phasing as noted by Wood et al. (1995).

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Borkovits, T., S. A. Rappaport, T. Hajdu, P. F. L. Maxted, A. Pál, E. Forgács-Dajka, P. Klagyivik, and T. Mitnyan. "TICs 167692429 and 220397947: the first compact hierarchical triple stars discovered with TESS." Monthly Notices of the Royal Astronomical Society 493, no. 4 (February 18, 2020): 5005–23. http://dx.doi.org/10.1093/mnras/staa495.

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ABSTRACT We report the discovery and complex analyses of the first two compact hierarchical triple star systems discovered with TESS in or near its southern continuous viewing zone during Year 1. Both TICs 167692429 and 220397947 were previously unknown eclipsing binaries, and the presence of a third companion star was inferred from eclipse timing variations exhibiting signatures of strong third-body perturbations and, in the first system, also from eclipse depth variations. We carried out comprehensive analyses, including the simultaneous photodynamical modelling of TESS and archival ground-based WASP light curves, as well as eclipse timing variation curves. Also, for the first time, we included in the simultaneous fits multiple star spectral energy distribution data and theoretical PARSEC stellar isochrones, taking into account Gaia DR2 parallaxes and catalogued metallicities. We find that both systems have twin F-star binaries and a lower mass tertiary star. In the TIC 167692429 system, the inner binary is moderately inclined (imut = 27°) with respect to the outer orbit, and the binary versus outer (triple) orbital periods are 10.3 versus 331 d, respectively. The mutually inclined orbits cause a driven precession of the binary orbital plane that leads to the disappearance of binary eclipses for long intervals. In the case of TIC 220397947, the two orbital planes are more nearly aligned and the inner versus outer orbital periods are 3.5 and 77 d, respectively. In the absence of radial velocity observations, we were unable to calculate highly accurate masses and ages for the two systems. According to stellar isochrones TIC 167692429 might be either a pre-main sequence (MS) or an older post-MS system. In the case of TIC 220397947, our solution prefers a young pre-MS scenario.

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Rodriguez, Joseph E., Joshua Pepper, and Keivan G. Stassun. "First Results from the Disk Eclipse Search with KELT (DESK) Survey." Proceedings of the International Astronomical Union 10, S314 (November 2015): 167–70. http://dx.doi.org/10.1017/s1743921315005931.

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AbstractUsing time-series photometry from the Kilodegree Extremely Little Telescope (KELT) exoplanet survey, we are looking for eclipses of stars by their protoplanetary disks, specifically in young stellar associations. To date, we have discovered two previously unknown, large dimming events around the young stars RW Aurigae and V409 Tau. We attribute the dimming of RW Aurigae to an occultation by its tidally disrupted disk, with the disruption perhaps resulting from a recent flyby of its binary companion. Even with the dynamical environment of RW Aurigae, the distorted disk material remains very compact and presumably capable of forming planets. This system also shows that strong binary interactions with disks can also influence planet and core composition by stirring up and mixing materials during planet formation. We interpret the dimming of V409 Tau to be due to a feature, possibly a warp or perturbation, lying at least 10 AU from the host star in its nearly edge-on circumstellar disk.

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Hilditch, R. W., A. C. Cameron, G. Hill, S. A. Bell, and T. J. Harries. "Spectroscopy and eclipse-mapping of the mass-exchanging binary star V361 Lyr." Monthly Notices of the Royal Astronomical Society 291, no. 4 (November 11, 1997): 749–62. http://dx.doi.org/10.1093/mnras/291.4.749.

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Reed, M. D., B. J. Brondel, and S. D. Kawaler. "Pulsating Stars in Close Binaries. I. Investigations of Eclipse Mapping and Oblique Pulsations." Astrophysical Journal 634, no. 1 (November 20, 2005): 602–15. http://dx.doi.org/10.1086/491666.

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Gies, D. R. "O and B-star surface mapping." Symposium - International Astronomical Union 176 (1996): 121–28. http://dx.doi.org/10.1017/s0074180900083157.

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The massive O and B-type stars will be among the first targets of the new generation of long baseline optical interferometers (such as the CHARA Array, a 400-m diameter distributed array of five 1-m telescopes). Many of these objects are binary stars for which joint astrometric and spectroscopic observations will provide masses and distances (e.g., 15 Mon; Gies et al. 1993), but there is also great interest in resolving disks of single stars. Early interferometric observations have already resolved the flattened circumstellar disks around some Be stars (Quirrenbach et al. 1994).

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Krzesinski, J., A. Blokesz, M. Siwak, and G. Stachowski. "The quest for planets around subdwarfs and white dwarfs from Kepler space telescope fields." Astronomy & Astrophysics 642 (October 2020): A105. http://dx.doi.org/10.1051/0004-6361/202038121.

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Context. In this study, we independently test the presence of an exoplanet around the binary KIC 9472174, which is composed of a red dwarf and a pulsating type B subdwarf. We also present the results of our search for Jupiter-mass objects orbiting near to the eclipsing binary KIC 7975824, which is composed of a white dwarf and type B subdwarf, and the pulsating white dwarf KIC 8626021. Aims. The goal is to test analytical techniques and prepare the ground for a larger search for possible substellar survivors on tight orbits around post-common envelope binaries and stars at the end of their evolution, that is, extended horizontal branch stars and white dwarfs. We, therefore, mainly focus on substellar bodies orbiting these stars within the range of the host’s former red-giant or asymptotic-giant phase envelopes. Due to the methods we use, the quest is restricted to single-pulsating type B subdwarf and white dwarf stars and short-period eclipsing binaries containing a white dwarf or a subdwarf component. Methods. Our methods rely on the detection of exoplanetary signals hidden in photometric time series data from the Kepler space telescope, and they are based on natural clocks within the data itself, such as stellar pulsations and eclipse times. The light curves are analyzed using Fourier transforms, time-delays, and eclipse timing variations. Results. Based on the three objects studied in this paper, we demonstrate that these methods can be used to detect giant exoplanets orbiting around pulsating white dwarf or type B subdwarf stars as well as short-period binary systems, at distances which fall within the range of the former red-giant envelope of a single star or the common envelope of a binary. Using our analysis techniques, we reject the existence of a Jupiter-mass exoplanet around the binary KIC 9472174 at the distance and orbital period previously suggested in the literature. We also found that the eclipse timing variations observed in the binary might depend on the reduction and processing of the Kepler data. The other two objects analyzed in this work do not have Jupiter mass exoplanets orbiting within 0.7–1.4 AU from them, or larger-mass objects on closer orbits (the given mass limits are minimum masses). Conclusions. Depending on the detection threshold of the time-delay method and the inclination of the exoplanet orbit toward the observer, data from the primary Kepler mission allows for the detection of bodies with a minimum of ~1 Jupiter-mass orbiting these stars at ~1 AU, while data from the K2 mission extends the detection of objects with a minimum mass of ~7 Jupiter-mass on ~0.1 AU orbits. The exoplanet mass and orbital distance limits depend on the length of the available photometric time series.

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Pan, Tony, and Abraham Loeb. "Identifying stars of mass >150 M⊙ from their eclipse by a binary companion." Monthly Notices of the Royal Astronomical Society: Letters 425, no. 1 (July 25, 2012): L91—L95. http://dx.doi.org/10.1111/j.1745-3933.2012.01308.x.

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Jorissen, A., J. Manfroid, and C. Sterken. "HD 46407: The First Eclipsing-Binary Barium Star." Symposium - International Astronomical Union 151 (1992): 411–14. http://dx.doi.org/10.1017/s0074180900122600.

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A long-term, high-accuracy, differential uvby monitoring of a sample of 19 barium stars revealed that HD 46407, a well known barium star with an orbital period of 458 d, is an eclipsing binary. The eclipse (of the companion by the barium star) was most clearly seen in November 1988, when a dip of 0.02 mag (in y) having a FWHM of about 10 d was recorded in the lightcurve. Confirmation of the eclipsing nature of HD 46407 was also obtained in February 1985 and in February 1990. A shallow secondary eclipse (extending over about 50% of the orbital period) seems to be present as well. The b – y index is marginally variable, while v – b color variations are correlated with the y variations, in the sense that the system appears redder when it is fainter. We suggest that these variations originate in the scattering of the red-giant light by dust particles trapped (in a wide ring or shell?) around the (compact) companion. The eclipsed light would then be the light of the red giant backscattered by the dust around the companion.

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Zhu, L. Y., S. B. Qian, E. G. Zhao, E. Fernández Lajús, and Z. T. Han. "Close-In Substellar Companions and the Formation of sdB-Type Close Binary Stars." Acta Polytechnica CTU Proceedings 2, no. 1 (February 23, 2015): 183–87. http://dx.doi.org/10.14311/app.2015.02.0183.

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The sdB-type close binaries are believed to have experienced a common-envelope phase and may evolve into cataclysmic binaries (CVs). About 10% of all known sdB binaries are eclipsing binaries consisting of very hot subdwarf primaries and low-mass companions with short orbital periods. The eclipse profiles of these systems are very narrow and deep, which benefits the determination of high precise eclipsing times and makes the detection of small and close-in tertiary bodies possible. Since 2006 we have monitored some sdB-type eclipsing binaries to search for the close-in substellar companions by analyzing the light travel time effect. Here some progresses of the program are reviewed and the formation of sdB-type binary is discussed.

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Li, M. C. A., N. J. Rattenbury, I. A. Bond, T. Sumi, D. P. Bennett, N. Koshimoto, F. Abe, et al. "The first eclipsing binary catalogue from the MOA-II data base." Monthly Notices of the Royal Astronomical Society 470, no. 1 (May 23, 2017): 539–50. http://dx.doi.org/10.1093/mnras/stx1280.

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Abstract We present the first catalogue of eclipsing binaries in two MOA (Microlensing Observations in Astrophysics) fields towards the Galactic bulge, in which over 8000 candidates, mostly contact and semidetached binaries of periods <1 d, were identified. In this paper, the light curves of a small number of interesting candidates, including eccentric binaries, binaries with noteworthy phase modulations and eclipsing RS Canum Venaticorum type stars, are shown as examples. In addition, we identified three triple object candidates by detecting the light-travel-time effect in their eclipse time variation curves.

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Kochukhov, O., C. Johnston, J. Labadie-Bartz, S. Shetye, T. A. Ryabchikova, A. Tkachenko, and M. E. Shultz. "V772 Cas: an ellipsoidal HgMn star in an eclipsing binary." Monthly Notices of the Royal Astronomical Society 500, no. 2 (November 10, 2020): 2577–89. http://dx.doi.org/10.1093/mnras/staa3472.

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ABSTRACT The late B-type star V772 Cas (HD 10260) was previously suspected to be a rare example of a magnetic chemically peculiar star in an eclipsing binary system. Photometric observations of this star obtained by the TESS satellite show clear eclipses with a period of 5.0137 d accompanied by a significant out-of-eclipse variation with the same period. High-resolution spectroscopy reveals V772 Cas to be an SB1 system, with the primary component rotating about a factor two slower than the orbital period and showing chemical peculiarities typical of non-magnetic HgMn chemically peculiar stars. This is only the third eclipsing HgMn star known and, owing to its brightness, is one of the very few eclipsing binaries with chemically peculiar components accessible to detailed follow-up studies. Taking advantage of the photometric and spectroscopic observations available for V772 Cas, we performed modelling of this system with the phoebe code. This analysis provided fundamental parameters of the components and demonstrated that the out-of-eclipse brightness variation is explained by the ellipsoidal shape of the evolved, asynchronously rotating primary. This is the first HgMn star for which such variability has been definitively identified.

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Swayne, Matthew I., Pierre F. L. Maxted, Vedad Kunovac Hodžić, and Amaury H. M. J. Triaud. "The TESS light curve of the eccentric eclipsing binary 1SWASP J011351.29+314909.7 – no evidence for a very hot M-dwarf companion." Monthly Notices of the Royal Astronomical Society: Letters 498, no. 1 (July 10, 2020): L15—L19. http://dx.doi.org/10.1093/mnrasl/slaa122.

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ABSTRACT A 2014 study of the eclipsing binary star 1SWASPJ011351.29+314909.7 (J0113+31) reported an unexpectedly high effective temperature for the M-dwarf companion to the 0.95-M⊙ primary star. The effective temperature inferred from the secondary eclipse depth was ∼600 K higher than the value predicted from stellar models. Such an anomalous result questions our understanding of low-mass stars and might indicate a significant uncertainty when inferring properties of exoplanets orbiting them. We seek to measure the effective temperature of the M-dwarf companion using the light curve of J0113+31 recently observed by the Transiting Exoplanet Survey Satellite (TESS). We use the pycheops modelling software to fit a combined transit and eclipse model to the TESS light curve. To calculate the secondary effective temperature, we compare the best-fitting eclipse depth to the predicted eclipse depths from theoretical stellar models. We determined the effective temperature of the M dwarf to be Teff,2 = 3208 ± 43 K, assuming log g2 = 5, [Fe/H] = −0.4, and no alpha-element enhancement. Varying these assumptions changes Teff,2 by less than 100 K. These results do not support a large anomaly between observed and theoretical low-mass star temperatures.

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Reed, Phillip A. "The Effects of Eccentric Accretion Structures on the Light Curves of Interacting Algol-type Binary Stars." Proceedings of the International Astronomical Union 7, S282 (July 2011): 325–26. http://dx.doi.org/10.1017/s1743921311027736.

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AbstractThe light curves of many Algol-type binary stars are complicated with strange variations. Secular variations are due to the transient nature of the accretion structure, while the phase-dependent features, such as outside-of-eclipse dips, are likely geometrical effects of the accretion structure eclipsing the primary star. Presented here is a model of the ultraviolet light curve of R Arae that explains these variations through the combination of an eccentric accretion structure and the system's orbital inclination.The orbital period of R Ara is 4.4 days, which is too long to allow for direct impact of the mass transfer stream onto the primary star, but not long enough for a stable accretion disk to form. Such intermediate-period Algols are good candidates in which to find transient and eccentric accretion structures. Other examples of interacting Algols that exhibit outside-of-eclipse dips in their light curves include RV Oph (Porb.=3.7 days) and Y Psc (Porb.=3.9 days).In order to more accurately model eccentric accretion structures with synthetic light curves, especially at visible (and longer) wavelengths, more work must be done to account for emission by the parts of the accretion structure that are not in the line of sight to the primary star. The model presented here accounts only for the eclipsing regions of the accretion structure.

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Wang, Jiaxin, Jianning Fu, Hubiao Niu, Yang Pan, Chunqian Li, Weikai Zong, and Yonghui Hou. "KIC 5359678: a detached eclipsing binary with starspots." Monthly Notices of the Royal Astronomical Society 504, no. 3 (April 29, 2021): 4302–11. http://dx.doi.org/10.1093/mnras/stab1219.

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ABSTRACT We study the detached eclipsing binary, KIC 5359678, with starspot modulation using the high-quality Kepler photometry and LAMOST spectroscopy. The phoebe model, optimal for this binary, reveals that this system is a circular detached binary, composed of two F-type main-sequence stars. The masses and radii of the primary and the secondary are M1 = 1.31 ± 0.05 M⊙, R1 = 1.52 ± 0.04 R⊙, M2 = 1.12 ± 0.04 M⊙, and R2 = 1.05 ± 0.06 R⊙, respectively. The age of this binary is estimated to be about 2 Gyr, a value much longer than the synchronization time-scale of 17.8 Myr. The residuals of light curves show quasi-sinusoidal signals, which could be induced by starspots. We apply autocorrelation function analysis on the out-of-eclipse residuals and find that the spot with rotational period close to the orbital period, while, the decay time-scale of starspots is longer than that on the single stars with the same temperature, period range, and rms scatter. A two-starspot model is adopted to fit the signals with two-dip pattern, whose result shows that the longitude decreases with time.

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Garcia, Michael R., and Scott J. Kenyon. "Orbital Radial Velocity Curves of Symbiotic Stars." International Astronomical Union Colloquium 103 (1988): 27–32. http://dx.doi.org/10.1017/s0252921100103094.

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AbstractFor the past 6 years we have been measuring the radial velocity of the M-giant component of Symbiotics Stars with high dispersion echelle spectrographs. Because these velocities are based on the absorption line spectrum of the M-star, very reliable orbital radial velocity curves can be constructed. The orbital solutions derived from these velocity curves allow the approximate size of the binary to be determined, and also provide insight into the origin of the photometric variations seen in these stars. For most of the stars, the photometric variations are due to eclipse or reflection effects (two notable exceptions are Z And and RW Hya). Stars which may be near to filling their Roche lobes are TX CVn, Z And, EG And, UV Aur, and CI Cyg. Stars which do not appear to fill their Roche lobes are AG Dra, RW Hya, and AG Peg.

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Mitnyan, T., T. Borkovits, S. A. Rappaport, A. Pál, and P. F. L. Maxted. "TIC 278825952: a triply eclipsing hierarchical triple system with the most intrinsically circular outer orbit." Monthly Notices of the Royal Astronomical Society 498, no. 4 (September 11, 2020): 6034–43. http://dx.doi.org/10.1093/mnras/staa2762.

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ABSTRACT We report the discovery of a compact triply eclipsing triple star system in the southern continuous viewing zone of the TESS space telescope. TIC 278825952 is a previously known, but unstudied circular eclipsing binary with a period of 4.781 d with a tertiary component in a wider, circular orbit of 235.55-d period that was found from three sets of third-body eclipses and from light travel-time effect dominated eclipse timing variations. We performed a joint photodynamical analysis of the eclipse timing variation curves, photometric data, and the spectral energy distribution, coupled with the use of PARSEC stellar isochrones. We find that the inner binary consists of slightly evolved, near twin stars of masses of 1.12 and 1.09 M⊙ and radii of 1.40 and 1.31 R⊙. The third, less massive star has a mass of 0.75 M⊙ and radius of 0.70 R⊙. The low mutual inclination and eccentricities of the orbits show that the system is highly coplanar and surprisingly circular.

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Borkovits, T., S. A. Rappaport, P. F. L. Maxted, I. Terentev, M. Omohundro, R. Gagliano, T. Jacobs, et al. "BG Ind: the nearest doubly eclipsing, compact hierarchical quadruple system." Monthly Notices of the Royal Astronomical Society 503, no. 3 (March 4, 2021): 3759–74. http://dx.doi.org/10.1093/mnras/stab621.

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ABSTRACT BG Ind is a well-studied, bright, nearby binary consisting of a pair of F stars in a 1.46-d orbit. We have discovered in the TESS light curve for TIC 229804573 (aka BG Ind), a second eclipsing binary in the system with a 0.53-d period. Our subsequent analyses of the recent TESS and archival ground-based photometric and radial velocity (RV) data reveal that the two binaries are gravitationally bound in a 721-d period, moderately eccentric orbit. We present the results of a joint spectro-photodynamical analysis of the eclipse timing variation curves of both binaries based on TESS and ground-based archival data, the TESS light curve, archival RV data, and the spectral energy distribution, coupled with the use of PARSEC stellar isochrones. We confirm prior studies of BG Ind that found that the brighter binary A consists of slightly evolved F-type stars with refined masses of 1.32 and 1.43 M⊙, and radii of 1.59 and 2.34R⊙. The previously unknown binary B has two less massive stars of 0.69 and 0.64 M⊙ and radii of 0.64 and 0.61R⊙. Based on a number of different arguments that we discuss, we conclude that the three orbital planes are likely aligned to within 17○.

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Kim, C. H., J. M. Kreiner, B. Zakrzewski, W. Ogłoza, H. W. Kim, and M. J. Jeong. "A Comprehensive Catalog of Galactic Eclipsing Binary Stars with Eccentric Orbits Based on Eclipse Timing Diagrams." Astrophysical Journal Supplement Series 235, no. 2 (April 19, 2018): 41. http://dx.doi.org/10.3847/1538-4365/aab7ef.

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IJspeert, L. W., A. Tkachenko, C. Johnston, S. Garcia, J. De Ridder, T. Van Reeth, and C. Aerts. "An all-sky sample of intermediate- to high-mass OBA-type eclipsing binaries observed by TESS." Astronomy & Astrophysics 652 (August 2021): A120. http://dx.doi.org/10.1051/0004-6361/202141489.

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Context. Intermediate- to high-mass stars are the least numerous types of stars, and they are less well understood than their more numerous low-mass counterparts in terms of their internal physical processes. Modelling the photometric variability of a large sample of main-sequence intermediate- to high-mass stars in eclipsing binary systems will help to improve the models for such stars. Aims. Our goal is to compose a homogeneously compiled sample of main-sequence intermediate- to high-mass OBA-type dwarfs in eclipsing binary systems from TESS photometry. We search for binaries with and without pulsations and determine their approximate ephemerides. Methods. Our selection starts from a catalogue of dwarfs with colours corresponding to those of OBA-type dwarfs in the TESS Input Catalog. We develop a new automated method aimed at detecting eclipsing binaries in the presence of a strong pulsational and/or rotational signal relative to the eclipse depths and apply it to publicly available 30-min cadence TESS light curves. Results. Using targets with TESS magnitudes below 15 and cuts in the 2MASS magnitude bands of J − H < 0.045 and J − K < 0.06 as the most stringent criteria, we arrive at a total of 189 981 intermediate- to high-mass candidates, 91 193 of which have light curves from at least one of two data reduction pipelines. The eclipsing binary detection and subsequent manual check for false positives resulted in 3155 unique OBA-type eclipsing binary candidates. Conclusions. Our sample of eclipsing binary stars in the intermediate- to high-mass regime allows for future binary (and asteroseismic) modelling with the aim to better understand the internal physical processes in this hot part of the main sequence.

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Kochukhov, O., J. Labadie-Bartz, V. Khalack, and M. E. Shultz. "New eclipsing binaries with mercury–manganese stars." Monthly Notices of the Royal Astronomical Society: Letters 506, no. 1 (June 17, 2021): L40—L44. http://dx.doi.org/10.1093/mnrasl/slab066.

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ABSTRACT Eclipsing binary stars are rare and extremely valuable astrophysical laboratories that make possible precise determination of fundamental stellar parameters. Investigation of early-type chemically peculiar stars in eclipsing binaries provides important information for understanding the origin and evolutionary context of their anomalous surface chemistry. In this study, we discuss observations of eclipse variability in six mercury–manganese (HgMn) stars monitored by the Transiting Exoplanet Survey Satellite (TESS) satellite. These discoveries double the number of known eclipsing HgMn stars and yield several interesting objects requiring further study. In particular, we confirm eclipses in HD 72208, thereby establishing this object as the longest-period eclipsing HgMn star. Among five other eclipsing binaries, reported here for the first time, HD 36892 and HD 53004 stand out as eccentric systems showing heartbeat variability in addition to eclipses. The latter object has the highest eccentricity among eclipsing HgMn stars and also exhibits tidally induced oscillations. Finally, we find evidence that HD 55776 may be orbited by a white dwarf companion.

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Bennett, Philip D., Graham M. Harper, Alexander Brown, and Jeffrey L. Linsky. "NLTE Radiative Transfer in the Extended Atmospheres and Winds of Cool Stars." Symposium - International Astronomical Union 210 (2003): 93–105. http://dx.doi.org/10.1017/s0074180900133285.

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The mechanism responsible for driving the ubiquitous winds of cool giant and supergiant stars remains to be established. To this end, we are constructing semi-empirical models of the extended outer atmospheres (‘chromospheres’) and winds of selected red supergiants. These models are constrained by analyses of the UV line spectra of single stars, and of red supergiants in binaries that eclipse their main-sequence companions: the ζ Aur and VV Cep stars. These detached binaries are well-separated, with no evidence of mass transfer. The C II] 2325 Å line profiles of the binaries are similar to those of comparable single stars, suggesting that the chromospheres remain relatively unperturbed by binarity. However, it is unclear how much binarity disturbs the wind: binary observations suggest a gradual acceleration (β ∼ 3), but line profile analyses of single red supergiants imply a rapid acceleration (β < 1). To date, we have obtained extensive series of HST/GHRS and STIS observations of three eclipsing red supergiant binaries: ζ Aur, HR 2554 and VV Cep. In this paper, we focus on ζ Aur, and present observations and modelling results for this eclipsing binary.

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Iglesias-Marzoa, Ramón, María J. Arévalo, Mercedes López-Morales, Guillermo Torres, Carlos Lázaro, and Jeffrey L. Coughlin. "Absolute dimensions of the low-mass eclipsing binary system NSVS 10653195." Astronomy & Astrophysics 627 (July 2019): A153. http://dx.doi.org/10.1051/0004-6361/201935516.

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Context. Low-mass stars in eclipsing binary systems show radii larger and effective temperatures lower than theoretical stellar models predict for isolated stars with the same masses. Eclipsing binaries with low-mass components are hard to find due to their low luminosity. As a consequence, the analysis of the known low-mass eclipsing systems is key to understand this behavior. Aims. We aim to investigate the mass–radius relation for low-mass stars and the cause of the deviation of the observed radii in low-mass detached eclipsing binary stars (LMDEB) from theoretical stellar models. Methods. We developed a physical model of the LMDEB system NSVS 10653195 to accurately measure the masses and radii of the components. We obtained several high-resolution spectra in order to fit a spectroscopic orbit. Standardized absolute photometry was obtained to measure reliable color indices and to measure the mean Teff of the system in out-of-eclipse phases. We observed and analyzed optical VRI and infrared JK band differential light-curves which were fitted using PHOEBE. A Markov chain Monte-Carlo (MCMC) simulation near the solution found provides robust uncertainties for the fitted parameters. Results. NSVS 10653195 is a detached eclipsing binary composed of two similar stars with masses of M1 = 0.6402 ± 0.0052 M⊙ and M2 = 0.6511 ± 0.0052 M⊙ and radii of R1 = 0.687+0.017−0.024 R⊙ and R2 = 0.672+0.018−0.022 R⊙. Spectral types were estimated to be K6V and K7V. These stars rotate in a circular orbit with an orbital inclination of i = 86.22 ± 0.61 degrees and a period of P = 0.5607222(2) d. The distance to the system is estimated to be d = 135.2+7.6−7.9 pc, in excellent agreement with the value from Gaia. If solar metallicity were assumed, the age of the system would be older than log (age) ∼ 8 based on the Mbol–log Teff diagram. Conclusions. NSVS 10653195 is composed of two oversized and active K stars. While their radii is above model predictions their Teff are in better agreement with models.

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Hartman, N., R. S. Polidan, A. D. Welty, R. Wade, P. B. Etzel, and F. C. Bruhweiler. "The Unusual Short Period Binary V342 Aquilae; Does it Break the Evolutionary Theory Mold?" Highlights of Astronomy 11, no. 1 (1998): 372. http://dx.doi.org/10.1017/s1539299600021225.

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Analysis of the eclipsing (period=3.39 days) binary V342 Aquilae at visible wavelengths reveals that the system is heavily enshrouded with gas, masking the identity of the underlying stars. In the ultraviolet V342 Aquilae shows six times more attenuation at phases outside of eclipse than most Algols. It is likely, then, that V342 Aquilae is the most enshrouded short period Algol system known. Our ultraviolet spectra show very pronounced Fe II absorption lines arising from ground and metastable levels, indicating an extensive circumstellar gas envelope. The strength of this absorption shows both an orbital and a cycle-to-cycle variability. The eclipse spectra display very strong emission from lines such as C II, Si IV, and C IV, with a striking similarity to the interacting binary TT Hydrae (B9.5V+K0III). We have deduced that the system consists of a late B star with a late GIII-IV companion and a mass ratio on the order of 0.5. A detailed descriptionof the observations, as well as deduced geometrical and physical properties of the system are presented. The apparent conflict of these observations with presently understood theory of binary evolution will be discussed.

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Linnell, Albert P. "W Ursae Majoris Star Models: Observational Constraints." International Astronomical Union Colloquium 108 (1988): 213–14. http://dx.doi.org/10.1017/s0252921100093842.

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W Ursae Majoris stars can be understood as contact binary stars with a common envelope (Lucy 1968). They subdivide into two types: The A-type are earlier inspectral class than about F5, are believed to have radiative envelopes, and associate primary (deeper) eclipse minimum with transit eclipse. The W-type have spectral classes later than F5, are believed to have convectlve envelopes, and associate primary minimum with occultation eclipse. Controversy has surrounded the explanation of W-type light curves.Four distinct models have been introduced to describe the envelopes or photospheres of W UMa stars. (1) The Rucinski hot secondary model directly explains W-type light curves on a postulational basis. Since 70%-90% of the emitted radiation from the secondary (less massive) component is believed to reach the secondary via circulation currents from the primary, there is an apparent thermodynamic mystery why the secondary should be hotter. (2) The Lucy Thermal Relaxation Oscillation (TRO) model argues that the secondary component is perpetually out of thermal equilibrium and that the components are in contact only during part of a given TRO cycle. During contact the photosphere is supposed to be barotropic. In this case primary minimum always associates with transit eclipse, in disagreement with observation for W-type systems. (3) The Shu et al. thermal discontinuity (DSC) model also argues for a barotropic photosphere but differs from Lucy on the gravity brightening exponent. The changes are insufficient to produce W-type light curves, (4) Webbink (1977), and, separately, Nariai (1976), argue for a baroclinic envelope. If the baroclinicity extends to the photosphere there is a possibility that W-type l i g h t curves could be explained. In particular, the Webbink scenario produces a hot secondary.

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Saito, R. K., and R. Baptista. "Spectral mapping of V348 Puppis: spiral arms in the period gap★." Monthly Notices of the Royal Astronomical Society 457, no. 1 (January 19, 2016): 198–211. http://dx.doi.org/10.1093/mnras/stv3007.

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Abstract We report the analysis of Hubble Space Telescope (HST) UV–optical spectroscopy of the nova-like variable V348 Puppis with eclipse mapping techniques. We measured the eclipse width at disc centre and determined a lower limit on the mass ratio of q > 0.3, with a tight relation between q and the binary inclination i. For 0.31 ≤ q ≤ 0.6, we have 79$_{.}^{\circ}$5 ≤ i ≤ 88$_{.}^{\circ}$2. Simulations with 3D eclipse mapping give no support to the suggestion of self-shielding of the accretion disc of V348 Pup, indicating a geometrically thin disc. Eclipse maps reveal two structures in the accretion disc interpreted as tidally induced spiral arms, which account for 50–60 per cent of the disc flux in the continuum. The uneclipsed component accounts for 30–50 per cent of the light, indicating that a significant fraction of the light comes from a vertically extended disc chromosphere + wind. Its spectrum can be fitted by an isothermal slab of gas with temperature T = 9600 K and column density Σ ∼1010 g cm−2, corresponding to optically thick thermal emission. Superhumps had faded by the epoch of the HST observations; the disc shrank in size while the disc wind flux increased with respect to observations when superhumps were present. This may be explained if the disc wind outflow is the dominant source of angular momentum loss from the accretion disc. Previously observed accretion disc radii of V348 Pup and of two other binaries with large discs are used to derive an empirical expression for the maximum possible disc radius, which implies that superhumps may be found in systems with up to q ≃ 0.7.

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Neff, James E. "Chromospheric emission line mapping." Symposium - International Astronomical Union 176 (1996): 113–20. http://dx.doi.org/10.1017/s0074180900083145.

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Throughout its eighteen years of operation, the International Ultraviolet Explorer has afforded us the opportunity to make many new discoveries regarding the nature of the outer atmospheres of magnetically active, late-type stars. High-resolution spectra obtained continuously throughout the rotational cycle of rapidly-rotating stars have been used to map the spatial structure of the magnetic active regions in stellar chromospheres. The RS CVn-type binary system AR Lacertae has been observed intensively at 3 epochs, with additional observations with less complete phase coverage was obtained at 4 other epochs. Taken together, we are able to probe the evolution of atmospheric structure of AR Lac over a 13-year timeline. I briefly review techniques of chromospheric emission line mapping, and I summarize the IUE results for AR Lac, V711 Tau, EI Eri, V1794 Cyg, and TY Pyx. I conclude with a description of chromospheric imaging programs (present and future) that make use of the Hubble Space Telescope.

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McLaughlin, Kenneth W., and Janak Panthi. "Synchronous Rotation in the Eclipsing Binary 68 Herculis Inferred from Doppler Shifts in its Spectrum and Light Curve Modeling." Journal of the Iowa Academy of Science 121, no. 1-4 (January 1, 2014): 5–15. http://dx.doi.org/10.17833/121-02.1.

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Our differential photometry of the eclipsing binary 68 Herculis through V- and R-filters shows periodic minima consistent with a previously established period. As a function of its orbital motion, we report spectra over a limited wavelength range encompassing H-alpha 656.3 nm and helium 667.8 nm lines. Doppler shifts of both stars were resolved in H-alpha, while only the more massive star rendered the helium line with Doppler shifts that agree with the radial velocity we derive for it from the H-alpha profile. Sinusoidal curve-fits to the orbital dependence of the radial velocities imply circular orbits for both components, with amplitudes indicating a mass ratio for the two stars in agreement with published values. A subtle Doppler shift associated with stellar rotation is evident in the radial velocity of the primary component as its eclipse commences; modeling indicates this rotation is synchronous with the orbital revolution, an expected tidal effect of near-contact binary systems.

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Conroy, Kyle E., Andrej Prša, Keivan G. Stassun, Jerome A. Orosz, Daniel C. Fabrycky, and William F. Welsh. "KEPLERECLIPSING BINARY STARS. IV. PRECISE ECLIPSE TIMES FOR CLOSE BINARIES AND IDENTIFICATION OF CANDIDATE THREE-BODY SYSTEMS." Astronomical Journal 147, no. 2 (January 14, 2014): 45. http://dx.doi.org/10.1088/0004-6256/147/2/45.

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Borkovits, T., S. A. Rappaport, T. G. Tan, R. Gagliano, T. Jacobs, X. Huang, T. Mitnyan, et al. "The compact triply eclipsing triple star TIC 209409435 discovered with TESS." Monthly Notices of the Royal Astronomical Society 496, no. 4 (June 24, 2020): 4624–36. http://dx.doi.org/10.1093/mnras/staa1817.

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ABSTRACT We report the discovery in TESS Sectors 3 and 4 of a compact triply eclipsing triple star system. TIC 209409435 is a previously unknown eclipsing binary with a period of 5.717 d, and the presence of a third star in an outer eccentric orbit of 121.872-d period was found from two sets of third-body eclipses and from eclipse timing variations. The latter exhibits signatures of strong third-body perturbations. After the discovery, we obtained follow-up ground-based photometric observations of several binary eclipses as well as another of the third-body eclipses. We carried out comprehensive analyses, including the simultaneous photodynamical modelling of TESS and ground-based light curves (including both archival WASP data, and our own follow-up measurements), as well as eclipse timing variation curves. Also, we have included in the simultaneous fits multiple star spectral energy distribution data and theoretical PARSEC stellar isochrones. We find that the inner binary consists of near twin stars of mass 0.90 M⊙ and radius 0.88 R⊙. The third star is just 9 per cent more massive and 18 per cent larger in radius. The inner binary has a rather small eccentricity, while the outer orbit has e = 0.40. The inner binary and outer orbit have inclination angles within 0.1° and 0.2° of 90°, respectively. The mutual inclination angle is ≲1/4°. All of these results were obtained without radial velocity observations.

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Getley, A. K., B. Carter, R. King, and S. O’Toole. "Stability of planetary, single M dwarf, and binary star companions to Kepler detached eclipsing binaries and a possible five-body system." Monthly Notices of the Royal Astronomical Society 498, no. 3 (August 21, 2020): 4356–64. http://dx.doi.org/10.1093/mnras/staa2532.

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ABSTRACT In this study, we identify 11 Kepler systems (KIC 5255552, 5653126, 5731312, 7670617, 7821010, 8023317, 10268809, 10296163, 11519226, 11558882, and 12356914) with a flip-flop effect in the eclipse timing variations O − C diagrams of the systems, report on what these systems have in common and whether these systems are dynamically stable. These systems have previously reported high eccentric binary stars with highly eccentric third bodies/outer companions. We find that all of the additional bodies in the system are dynamically stable for the configurations previously reported and are therefore likely to exist as described. We also provide additional evidence of KIC 5255552 being a quadruple star system composed of an eclipsing binary pair and non-eclipsing binary pair with the possibility of a fifth body in the system. With the advent of the NASA’s Transiting Exoplanet Survey Satellite (TESS) exoplanet survey, its precision photometric monitoring offers an opportunity to help confirm more local eclipsing binary star companions, including planets.

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Carmo, A., C. E. Ferreira Lopes, A. Papageorgiou, F. J. Jablonski, C. V. Rodrigues, A. J. Drake, N. J. G. Cross, and M. Catelan. "Recovering variable stars in large surveys: EAup Algol-type class in the Catalina Survey." Monthly Notices of the Royal Astronomical Society 498, no. 2 (August 20, 2020): 2833–44. http://dx.doi.org/10.1093/mnras/staa2518.

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ABSTRACT The discovery and characterization of Algol eclipsing binaries (EAs) provide an opportunity to contribute for a better picture of the structure and evolution of low-mass stars. However, the cadence of most current photometric surveys hinders the detection of EAs since the separation between observations is usually larger than the eclipse(s) duration and hence few measurements are found at the eclipses. Even when those objects are detected as variable, their periods can be missed if an appropriate oversampling factor is not used in the search tools. In this paper, we apply this approach to find the periods of stars catalogued in the Catalina Real-Time Transient Survey (CRTS) as EAs having unknown period (EAup). As a result, the periods of ${\sim} 56{\rm {per \, cent}}$ of them were determined. Eight objects were identified as low-mass binary systems and modelled with the Wilson & Devinney synthesis code combined with a Markov chain Monte Carlo optimization procedure. The computed masses and radii are in agreement with theoretical models and show no evidence of inflated radii. This paper is the first of a series aiming to identify suspected binary systems in large surveys.

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Mimica, P., and K. Pavlovski. "Reconstruction of an Accretion Disk Image in AU Mon from CoRoT Photometry." Proceedings of the International Astronomical Union 7, S282 (July 2011): 63–64. http://dx.doi.org/10.1017/s1743921311026901.

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AbstractThe long-period binary system AU Mon was photometrically observed on-board the CoRoT satellite in a continuous run of almost 60 days long which has covered almost 5 complete cycles. Unprecedented sub milimag precision of CoRoT photometry reveals all complexity of its light variations in this, still active mass-transfer binary system. We present images of an accretion disk reconstructed by eclipse mapping, and an optimization of intensity distribution along disk surface. Time resolution and accurate CoRoT photometric measurements allow precise location of spatial distribution of ‘hot’ spots on the disk, and tracing temporal changes in their activity. Clumpy disk structure is similar to those we detected early for another W Serpentis binary W Cru (Pavlovski, Burki & Mimica, 2006, A&A, 454, 855).

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Valio, Adriana. "Study of stellar activity through transit mapping of starspots." Proceedings of the International Astronomical Union 6, S273 (August 2010): 96–103. http://dx.doi.org/10.1017/s1743921311015079.

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AbstractDuring the eclipse of a planet, spots and other features on the surface of the host star may be occulted. This will cause small variations in the light curve of the star. Detailed studies of these variations during planetary transits provide a wealth of information about the starspots properties such as size, position, temperature (i.e. intensity), and magnetic field. If observation of multiple transits is available, the spots lifetime can be estimated. Moreover it may also be possible to determine the stellar rotation and whether differential rotation is present. Here, the study is performed using a method that simulates the passage of a planet (dark disk) in front of a star with multiple spots of different sizes, intensities, and positions on its surface. The data variations in the light curve of the star are fit using this method, yielding the starspots properties. Results are presented for solar-like stars, such as the active star CoRoT-2a.

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Journal articles on the topic 'Binary stars; Eclipse mapping'

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