7 research outputs found
Eclipse Timing Variation Analyses of Eccentric Binaries with Close Tertiaries in the Kepler field
We report eclipse timing variation analyses of 26 compact hierarchical triple
stars comprised of an eccentric eclipsing ('inner') binary and a relatively
close tertiary component found in the {\em Kepler} field. We simultaneously fit
the primary and secondary curves of each system for the light-travel time
effect (LTTE), as well as dynamical perturbations caused by the tertiary on
different timescales. For the first time, we include those contributions of
three-body interactions which originate from the eccentric nature of the inner
binary. These effects manifest themselves both on the period of the triple
system, , and on the longer "apse-node" timescale. We demonstrate that
consideration of the dynamically forced rapid apsidal motion yields an
efficient and independent tool for the determination of the binary orbit's
eccentricity and orientation, as well as the 3D configuration of the triple.
Modeling the forced apsidal motion also helps to resolve the degeneracy between
the shapes of the LTTE and the dynamical delay terms on the timescale,
due to the strong dependence of the apsidal motion period on the triple's mass
ratio. This can lead to the independent determination of the binary and
tertiary masses without the need for independent radial velocity measurements.
Through the use of our analytic method for fitting curves we have
obtained robust solutions for system parameters for the ten most ideal triples
of our sample, and only somewhat less robust, but yet acceptable, fits for the
remaining systems. Finally we study the results of our 26 system parameter fits
via a set of distributions of various physically important parameters,
including mutual inclination angle, and mass and period ratios.Comment: 83 pages, including 32 pages (26 tables) of tabulated Times of Minima
data for the analysed 26 systems; submitted to MNRAS (revised version
Tidally Induced Oscillations and Orbital Decay in Compact Triple-Star Systems
We investigate the nature of tidal effects in compact triple-star systems.
The hierarchical structure of a triple system produces tidal forcing at high
frequencies unobtainable in binary systems, allowing for the tidal excitation
of high frequency p-modes in the stellar components. The tidal forcing exists
even for circular, aligned, and synchronized systems. We calculate the
magnitude and frequencies of three-body tidal forcing on the central primary
star for circular and coplanar orbits, and we estimate the amplitude of the
tidally excited oscillation modes. We also calculate the secular orbital
changes induced by the tidally excited modes, and show that they can cause
significant orbital decay. During certain phases of stellar evolution, the
tidal dissipation may be greatly enhanced by resonance locking. We then compare
our theory to observations of HD 181068, which is a hierarchical triply
eclipsing star system in the Kepler field of view. The observed oscillation
frequencies in HD 181068 can be naturally explained by three-body tidal
effects. We then compare the observed oscillation amplitudes and phases in HD
181068 to our predictions, finding mostly good agreement. Finally, we discuss
the past and future evolution of compact triple systems like HD 181068.Comment: 19 pages, 8 figures, published in MNRA
TIC 184743498: The First Tri-Axial Stellar Pulsator
We have discovered a Scuti pulsator in a tight binary (P = 1.053 d)
with nine pulsation modes whose frequencies are between 38 and 56 d.
Each of these modes exhibits amplitude modulations and -rad phase shifts
twice per orbital cycle. Five of these modes exhibit amplitude and phase shifts
that are readily explained by dipole pulsations along an axis that is aligned
with the binary's tidal axis. The novelty of the system lies in the remaining
four pulsation modes, which we show are dipole pulsations along an axis that is
perpendicular to both the tidal axis and the binary's orbital angular momentum
axis. There are additionally two pulsation modes whose amplitudes and phases do
not change significantly with orbital phase; they are explained as dipole modes
along an axis aligned with the orbital/rotation axis. Hence, we propose that
TIC 184743498 is a tri-axial pulsator, the first of its kind.Comment: Submitted to MNRAS, 12 figures, 4 table
101 Eclipsing Quadruple Star Candidates Discovered in TESS Full Frame Images
We present our second catalog of quadruple star candidates, containing 101
systems discovered in TESS Full-Frame Image data. The targets were initially
detected as eclipsing binary stars with the help of supervised machine learning
methods applied to sectors Sectors 1 through 54. A dedicated team of citizen
scientists subsequently identified through visual inspection two sets of
eclipses following two different periods. All 101 systems presented here pass
comprehensive photocenter motion tests confirming that both sets of eclipses
originate from the target star. Some of the systems exhibit prominent eclipse
time variations suggesting dynamical interactions between the two component
binary stars. One target is an eclipsing quintuple candidate with a (2+1)+2
hierarchical configuration, such that the (2+1) subsystem produces eclipses on
the triple orbit as well. Another has recently been confirmed as the second
shortest period quadruple reported to date. This catalog provides ephemerides,
eclipse depths and durations, sample statistics, and highlights potentially
interesting targets for future studies.Comment: 38 pages, 21 figures, 2 tables. Table with targets available online
at MNRA
TIC 168789840: A Sextuply-Eclipsing Sextuple Star System
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
TIC 184743498: The first tri-axial stellar pulsator
We have discovered a δ Scuti pulsator in a tight binary (P = 1.053 d) with nine pulsation modes whose frequencies are between 38 and 56 d−1. Each of these modes exhibits amplitude modulations and π-rad phase shifts twice per orbital cycle. Five of these modes exhibit amplitude and phase shifts that are readily explained by dipole pulsations along an axis that is aligned with the binary’s tidal axis. The novelty of the system lies in the remaining four pulsation modes, which we show are dipole pulsations along an axis that is perpendicular to both the tidal axis and the binary’s orbital angular momentum axis. There are additionally two pulsation modes whose amplitudes and phases do not change significantly with orbital phase; they are explained as dipole modes along an axis aligned with the orbital/rotation axis. Hence, we propose that TIC 184743498 is a tri-axial pulsator, the first of its kind
97 Eclipsing Quadruple Star Candidates Discovered in TESS Full Frame Images
We present a catalog of 97 uniformly-vetted candidates for quadruple star
systems. The candidates were identified in TESS Full Frame Image data from
Sectors 1 through 42 through a combination of machine learning techniques and
visual examination, with major contributions from a dedicated group of citizen
scientists. All targets exhibit two sets of eclipses with two different
periods, both of which pass photocenter tests confirming that the eclipses are
on-target. This catalog outlines the statistical properties of the sample,
nearly doubles the number of known multiply-eclipsing quadruple systems, and
provides the basis for detailed future studies of individual systems. Several
important discoveries have already resulted from this effort, including the
first sextuply-eclipsing sextuple stellar system and the first transiting
circumbinary planet detected from one sector of TESS data.Comment: 56 pages, 27 figures, 4 table