No Arabic abstract
We report the discovery of a sextuply-eclipsing sextuple star system from TESS data, TIC 168789840, also known as TYC 7037-89-1, the first known sextuple system consisting of three eclipsing binaries. The target was observed in Sectors 4 and 5 during Cycle 1, with lightcurves extracted from TESS Full Frame Image data. It was also previously observed by the WASP survey and ASAS-SN. The system consists of three gravitationally-bound eclipsing binaries in a hierarchical structure of an inner quadruple system with an outer binary subsystem. Follow-up observations from several different observatories were conducted as a means of determining additional parameters. The system was resolved by speckle interferometry with a 0.42 separation between the inner quadruple and outer binary, inferring an estimated outer period of ~2 kyr. It was determined that the fainter of the two resolved components is an 8.217 day eclipsing binary, which orbits the inner quadruple that contains two eclipsing binaries with periods of 1.570 days and 1.306 days. MCMC analysis of the stellar parameters has shown that the three binaries of TIC 168789840 are triplets, as each binary is quite similar to the others in terms of mass, radius, and Teff. As a consequence of its rare composition, structure, and orientation, this object can provide important new insight into the formation, dynamics, and evolution of multiple star systems. Future observations could reveal if the intermediate and outer orbital planes are all aligned with the planes of the three inner eclipsing binaries.
We report the discovery of a compact, coplanar, quadruply-lined, eclipsing quadruple star system from TESS data, TIC 454140642, also known as TYC 0074-01254-1. The target was first detected in Sector 5 with 30-min cadence in Full-Frame Images and then observed in Sector 32 with 2-min cadence. The light curve exhibits two sets of primary and secondary eclipses with periods of PA = 13.624 days (binary A) and PB = 10.393 days (binary B). Analysis of archival and follow-up data shows clear eclipse-timing variations and divergent radial velocities, indicating dynamical interactions between the two binaries and confirming that they form a gravitationally-bound quadruple system with a 2+2 hierarchy. The Aa+Ab binary, Ba+Bb binary, and A-B system are aligned with respect to each other within a fraction of a degree: the respective mutual orbital inclinations are 0.25 degrees (A vs B), 0.37 degrees (A vs A-B), and 0.47 degrees (B vs A-B). The A-B system has an orbital period of 432 days - the second shortest amongst confirmed quadruple systems - and an orbital eccentricity of 0.3.
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 days, and the presence of a third star in an outer eccentric orbit of 121.872 day period was found from two sets of third-body eclipses and from eclipse timing variations. The latter exhibit signatures of strong 3rd-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 lightcurves (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 $M_odot$ and radius 0.88 $R_odot$. The third star is just 9% more massive and 18% 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$^circ$ and 0.2$^circ$ of 90$^circ$, respectively. The mutual inclination angle is $lesssim 1/4^circ$. All of these results were obtained without radial velocity observations.
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 unstudied, circular eclipsing binary with a period of 4.781 days with a tertiary component in a wider, circular orbit of 235.55 days 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 $M_odot$ and radii of 1.40 and 1.31 $R_odot$. The third, less massive star has a mass of 0.75 $M_odot$ and radius of 0.70 $R_odot$. The low mutual inclination and eccentricities of the orbits show that the system is highly coplanar and surprisingly circular.
We present a quintuple star system that contains two eclipsing binaries. The unusual architecture includes two stellar images separated by 11 on the sky: EPIC 212651213 and EPIC 212651234. The more easterly image (212651213) actually hosts both eclipsing binaries which are resolved within that image at 0.09, while the westerly image (212651234) appears to be single in adaptive optics (AO), speckle imaging, and radial velocity (RV) studies. The A binary is circular with a 5.1-day period, while the B binary is eccentric with a 13.1-day period. The gamma velocities of the A and B binaries are different by ~10 km/s. That, coupled with their resolved projected separation of 0.09, indicates that the orbital period and separation of the C binary (consisting of A orbiting B) are ~65 years and ~25 AU, respectively, under the simplifying assumption of a circular orbit. Motion within the C orbit should be discernible via future RV, AO, and speckle imaging studies within a couple of years. The C system (i.e., 212651213) has a radial velocity and proper motion that differ from that of 212651234 by only ~1.4 km/s and ~3 mas/yr. This set of similar space velocities in 3 dimensions strongly implies that these two objects are also physically bound, making this at least a quintuple star system.
We report the discovery of the third tidally tilted pulsator, TIC 63328020. Observations with the TESS satellite reveal binary eclipses with an orbital period of 1.1057 d, and $delta$ Scuti-type pulsations with a mode frequency of 21.09533 d$^{-1}$. This pulsation exhibits a septuplet of orbital sidelobes as well as a harmonic quintuplet. Using the oblique pulsator model, the primary oscillation is identified as a sectoral dipole mode with $l = 1, |m| = 1$. We find the pulsating star to have $M_1 simeq 2.5, {rm M}_odot$, $R_1 simeq 3 , {rm R}_odot$, and $T_{rm eff,1} simeq 8000$ K, while the secondary has $M_2 simeq 1.1 , {rm M}_odot$, $R_2 simeq 2 , {rm R}_odot$, and $T_{rm eff,2} simeq 5600$ K. Both stars appear to be close to filling their respective Roche lobes. The properties of this binary as well as the tidally tilted pulsations differ from the previous two tidally tilted pulsators, HD74423 and CO Cam, in important ways. We also study the prior history of this system with binary evolution models and conclude that extensive mass transfer has occurred from the current secondary to the primary.