57 research outputs found
An Orbital Stability Study of the Proposed Companions of SW Lyncis
We have investigated the dynamical stability of the proposed companions
orbiting the Algol type short-period eclipsing binary SW Lyncis (Kim et al.
2010). The two candidate companions are of stellar to sub-stellar nature, and
were inferred from timing measurements of the system's primary and secondary
eclipses. We applied well-tested numerical techniques to accurately integrate
the orbits of the two companions and to test for chaotic dynamical behaviour.
We carried out the stability analysis within a systematic parameter survey
varying both the geometries and orientation of the orbits of the companions, as
well as their masses. In all our numerical integrations we found that the
proposed SW Lyn multi-body system is highly unstable on time-scales on the
order of 1000 years. Our results cast doubt on the interpretation that the
timing variations are caused by two companions. This work demonstrates that a
straightforward dynamical analysis can help to test whether a best-fit
companion-based model is a physically viable explanation for measured eclipse
timing variations. We conclude that dynamical considerations reveal that the
propsed SW Lyncis multi-body system most likely does not exist or the
companions have significantly different orbital properties as conjectured in
Kim et al. (2010).Comment: 9 pages, 6 figures, 2 tables. Submitted to and accepted by JASS --
Journal for Astronomy and Space Sciences (using JKAS LaTeX style file
The Dynamical History of Chariklo and its Rings
Chariklo is the only small Solar system body confirmed to have rings. Given
the instability of its orbit, the presence of rings is surprising, and their
origin remains poorly understood. In this work, we study the dynamical history
of the Chariklo system by integrating almost 36,000 Chariklo clones backwards
in time for one Gyr under the influence of the Sun and the four giant planets.
By recording all close encounters between the clones and planets, we
investigate the likelihood that Chariklo's rings could have survived since its
capture to the Centaur population. Our results reveal that Chariklo's orbit
occupies a region of stable chaos, resulting in its orbit being marginally more
stable than those of the other Centaurs. Despite this, we find that it was most
likely captured to the Centaur population within the last 20 Myr, and that its
orbital evolution has been continually punctuated by regular close encounters
with the giant planets. The great majority (> 99%) of those encounters within
one Hill radius of the planet have only a small effect on the rings. We
conclude that close encounters with giant planets have not had a significant
effect on the ring structure. Encounters within the Roche limit of the giant
planets are rare, making ring creation through tidal disruption unlikely
Photometric defocus observations of transiting extrasolar planets
We have carried out photometric follow-up observations of bright transiting
extrasolar planets using the CbNUOJ 0.6m telescope. We have tested the
possibility of obtaining high photometric precision by applying the telescope
defocus technique allowing the use of several hundred seconds in exposure time
for a single measurement. We demonstrate that this technique is capable of
obtaining a root-mean-square scatter of order sub-millimagnitude over several
hours for a V 10 host star typical for transiting planets detected from
ground-based survey facilities. We compare our results with transit
observations with the telescope operated in in-focus mode. High photometric
precision is obtained due to the collection of a larger amount of photons
resulting in a higher signal compared to other random and systematic noise
sources. Accurate telescope tracking is likely to further contribute to
lowering systematic noise by probing the same pixels on the CCD. Furthermore, a
longer exposure time helps reducing the effect of scintillation noise which
otherwise has a significant effect for small-aperture telescopes operated in
in-focus mode. Finally we present the results of modelling four light-curves
for which a root-mean-square scatter of 0.70 to 2.3 milli-magnitudes have been
achieved.Comment: 12 pages, 11 figures, 5 tables. Submitted to Journal of Astronomy and
Space Sciences (JASS
Measuring the severity of close encounters between ringed small bodies and planets
Rings have recently been discovered around the trans-Neptunian object (TNO) 136108 Haumea and the Centaur 10199 Chariklo. Rings are also suspected around the Centaur 2060 Chiron. As planetary close encounters with ringed small bodies can affect ring longevity, we previously
measured the severity of such encounters of Chariklo and Chiron using the minimum encounter distance, dmin. The value of dmin that separates noticeable encounters from non-noticeable encounters we called the ‘ring limit’, R. R was then approximated as 10 tidal disruption distances, 10Rtd. In this work, we seek to find analytical expressions for R that fully account for the effects of the planet mass, small body mass, ms, ring orbital radius, r, and velocity at
infinity, v∞, for fictitious ringed Centaurs using ranges 2 × 1020 kg ≤ms≤ 1 Pluto mass and 25 000 ≤r ≤ 100 000 km. To accomplish this, we use numerical integration to simulate close encounters between each giant planet and ringed Centaurs in the three-body planar problem. The results show that R has a lower bound of approximately 1.8Rtd. We compare analytical and experimental R values for a fictitious Haumea, Chariklo, and Chiron with r= 50 000 km.
The agreement is excellent for Haumea, but weaker for Chariklo and Chiron. The agreement is best for Jupiter and Saturn. The ring limits of the real Haumea, Chariklo, and Chiron are <4Rtd. Experimental R values for the fictitious bodies make better approximations for the R values of the real bodies than does 10Rtd. Analytical values make good first approximations
Kepler-413b: a slightly misaligned, Neptune-size transiting circumbinary planet
We report the discovery of a transiting, Rp = 4.347+/-0.099REarth,
circumbinary planet (CBP) orbiting the Kepler K+M Eclipsing Binary (EB) system
KIC 12351927 (Kepler-413) every ~66 days on an eccentric orbit with ap =
0.355+/-0.002AU, ep = 0.118+/-0.002. The two stars, with MA =
0.820+/-0.015MSun, RA = 0.776+/-0.009RSun and MB = 0.542+/-0.008MSun, RB =
0.484+/-0.024RSun respectively revolve around each other every
10.11615+/-0.00001 days on a nearly circular (eEB = 0.037+/-0.002) orbit. The
orbital plane of the EB is slightly inclined to the line of sight (iEB =
87.33+/-0.06 degrees) while that of the planet is inclined by ~2.5 degrees to
the binary plane at the reference epoch. Orbital precession with a period of
~11 years causes the inclination of the latter to the sky plane to continuously
change. As a result, the planet often fails to transit the primary star at
inferior conjunction, causing stretches of hundreds of days with no transits
(corresponding to multiple planetary orbital periods). We predict that the next
transit will not occur until 2020. The orbital configuration of the system
places the planet slightly closer to its host stars than the inner edge of the
extended habitable zone. Additionally, the orbital configuration of the system
is such that the CBP may experience Cassini-States dynamics under the influence
of the EB, in which the planet's obliquity precesses with a rate comparable to
its orbital precession. Depending on the angular precession frequency of the
CBP, it could potentially undergo obliquity fluctuations of dozens of degrees
(and complex seasonal cycles) on precession timescales.Comment: 48 pages, 13 figure
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