224 research outputs found
KOI-142, the King of Transit Variations, is a Pair of Planets near the 2:1 Resonance
The Transit Timing Variations (TTVs) can be used as a diagnostic of
gravitational interactions between planets in a multi-planet system. Many
Kepler Objects of Interest (KOIs) exhibit significant TTVs, but KOI-142.01
stands out among them with an unrivaled, 12-hour TTV amplitude. Here we report
a thorough analysis of KOI-142.01's transits. We discover periodic Transit
Duration Variations (TDVs) of KOI-142.01 that are nearly in phase with the
observed TTVs. We show that KOI-142.01's TTVs and TDVs uniquely detect a
non-transiting companion with a mass 0.7 that of Jupiter (KOI-142c).
KOI-142.01's mass inferred from the transit variations is consistent with the
measured transit depth, suggesting a Neptune class planet (KOI-142b). The
orbital period ratio P_c/P_b=2.03 indicates that the two planets are just wide
of the 2:1 resonance. The present dynamics of this system, characterized here
in detail, can be used to test various formation theories that have been
proposed to explain the near-resonant pairs of exoplanets
Hermeneutics of New Testament eschatological texts*
No abstract available
The Hunt for Exomoons with Kepler (HEK): IV. A Search for Moons around Eight M-Dwarfs
With their smaller radii and high cosmic abundance, transiting planets around
cool stars hold a unique appeal. As part of our on-going project to measure the
occurrence rate of extrasolar moons, we here present results from a survey
focussing on eight Kepler planetary candidates associated with M-dwarfs. Using
photodynamical modeling and Bayesian multimodal nested sampling, we find no
compelling evidence for an exomoon in these eight systems. Upper limits on the
presence of such bodies probe down to in the best case. For
KOI-314, we are able to confirm the planetary nature of two out of the three
known transiting candidates using transit timing variations. Of particular
interest is KOI-314c, which is found to have a mass of
, making it the lowest mass transiting planet
discovered to date. With a radius of , this
Earth-mass world is likely enveloped by a significant gaseous envelope
comprising % of the planet by radius. We find evidence to
support the planetary nature of KOI-784 too via transit timing, but we advocate
further observations to verify the signals. In both systems, we infer that the
inner planet has a higher density than the outer world, which may be indicative
of photo-evaporation. These results highlight both the ability of Kepler to
search for sub-Earth mass moons and the exciting ancillary science which often
results from such efforts.Comment: 15 pages, 13 figures, 6 tables. Accepted in Ap
The Hunt for Exomoons with Kepler (HEK): II. Analysis of Seven Viable Satellite-Hosting Planet Candidates
From the list of 2321 transiting planet candidates announced by the Kepler
Mission, we select seven targets with favorable properties for the capacity to
dynamically maintain an exomoon and present a detectable signal. These seven
candidates were identified through our automatic target selection (TSA)
algorithm and target selection prioritization (TSP) filtering, whereby we
excluded systems exhibiting significant time-correlated noise and focussed on
those with a single transiting planet candidate of radius less than 6 Earth
radii. We find no compelling evidence for an exomoon around any of the seven
KOIs but constrain the satellite-to-planet mass ratios for each. For four of
the seven KOIs, we estimate a 95% upper quantile of M_S/M_P<0.04, which given
the radii of the candidates, likely probes down to sub-Earth masses. We also
derive precise transit times and durations for each candidate and find no
evidence for dynamical variations in any of the KOIs. With just a few systems
analyzed thus far in the in-going HEK project, projections on eta-moon would be
premature, but a high frequency of large moons around
Super-Earths/Mini-Neptunes would appear to be incommensurable with our results
so far.Comment: 32 pages, 11 figures, 23 tables, Accepted to Ap
The Hunt for Exomoons with Kepler (HEK): III. The First Search for an Exomoon around a Habitable-Zone Planet
Kepler-22b is the first transiting planet to have been detected in the
habitable-zone of its host star. At 2.4 Earth radii, Kepler-22b is too large to
be considered an Earth-analog, but should the planet host a moon large enough
to maintain an atmosphere, then the Kepler-22 system may yet possess a telluric
world. Aside from being within the habitable-zone, the target is attractive due
to the availability of previously measured precise radial velocities and low
intrinsic photometric noise, which has also enabled asteroseismology studies of
the star. For these reasons, Kepler-22b was selected as a target-of-opportunity
by the 'Hunt for Exomoons with Kepler' (HEK) project. In this work, we conduct
a photodynamical search for an exomoon around Kepler-22b leveraging the
transits, radial velocities and asteroseismology plus several new tools
developed by the HEK project to improve exomoon searches. We find no evidence
for an exomoon around the planet and exclude moons of mass >0.5 Earth masses to
95% confidence. By signal injection and blind retrieval, we demonstrate that an
Earth-like moon is easily detected for this planet even when the
time-correlated noise of the data set is taken into account. We provide updated
parameters for the planet Kepler-22b including a revised mass of <53 Earth
masses to 95% confidence and an eccentricity of 0.13(-0.13)(+0.36) by
exploiting Single-body Asterodensity Profiling (SAP). Finally, we show that
Kepler-22b has a >95% probability of being within the empirical habitable-zone
but a <5% probability of being within the conservative habitable-zone.Comment: 19 pages, 11 figures, 7 tables. Accepted in ApJ. Planet-moon transit
animations available at https://www.cfa.harvard.edu/~dkipping/kepler22.htm
The Hunt for Exomoons with Kepler (HEK): V. A Survey of 41 Planetary Candidates for Exomoons
We present a survey of 41 Kepler Objects of Interest (KOIs) for exomoons
using Bayesian photodynamics, more than tripling the number of KOIs surveyed
with this technique. We find no compelling evidence for exomoons although
thirteen KOIs yield spurious detections driven by instrumental artifacts,
stellar activity and/or perturbations from unseen bodies. Regarding the latter,
we find seven KOIs exhibiting >5 sigma evidence of transit timing variations,
including the 'mega-Earth' Kepler-10c, likely indicating an additional planet
in that system. We exploit the moderately large sample of 57 unique KOIs
surveyed to date to infer several useful statistics. For example, although
there is a diverse range in sensitivities, we find that we are sensitive to
Pluto-Charon mass-ratio systems for ~40% of KOIs studied and Earth-Moon
mass-ratios for 1 in 8 cases. In terms of absolute mass, our limits probe down
to 1.7 Ganymede masses, with a sensitivity to Earth-mass moons for 1 in 3 cases
studied and to the smallest moons capable of sustaining an Earth-like
atmosphere (0.3 Earth masses) for 1 in 4. Despite the lack of positive
detections to date, we caution against drawing conclusions yet, since our most
interesting objects remain under analysis. Finally, we point out that had we
searched for the photometric transit signals of exomoons alone, rather than
using photodynamics, we estimate that 1 in 4 KOIs would have erroneously been
concluded to harbor exomoons due to residual time correlated noise in the
Kepler data, posing a serious problem for alternative methods.Comment: 18 pages, 9 figures, 4 tables. Accepted in Ap
Experimental and theoretical lifetimes and transition probabilities in Sb I
We present experimental atomic lifetimes for 12 levels in Sb I, out of which
seven are reported for the first time. The levels belong to the 5p(P)6s
P, P and 5p(P)5d P, F and F terms. The
lifetimes were measured using time-resolved laser-induced fluorescence. In
addition, we report new calculations of transition probabilities in Sb I using
a Multiconfigurational Dirac-Hartree-Fock method. The physical model being
tested through comparisons between theoretical and experimental lifetimes for
5d and 6s levels. The lifetimes of the 5d F levels (19.5,
7.8 and 54 ns, respectively) depend strongly on the -value. This is
explained by different degrees of level mixing for the different levels in the
F term.Comment: 10 page
Filling in the Gaps in the 4.85 GHz Sky
We describe a 4.85 GHz survey of bright, flat-spectrum radio sources
conducted with the Effelsberg 100 m telescope in an attempt to improve the
completeness of existing surveys, such as CRATES. We report the results of
these observations and of follow-up 8.4 GHz observations with the VLA of a
subset of the sample. We comment on the connection to the WMAP point source
catalog and on the survey's effectiveness at supplementing the CRATES sky
coverage.Comment: 13 pages, 3 figures, 2 tables. Accepted for publication in the
Astronomical Journal. Tables available in electronic form:
http://astro.stanford.edu/gaps
Surface Modes on Bursting Neutron Stars and X-ray Burst Oscillations
Accreting neutron stars (NSs) often show coherent modulations during type I
X-ray bursts, called burst oscillations. We consider whether a nonradial mode
can serve as an explanation for burst oscillations from those NSs which are not
magnetic. We find that a surface wave in the shallow burning layer transitions
into a crustal interface wave as the envelope cools, a new and previously
uninvestigated phenomenon. The surface modulations decrease dramatically as the
mode switches, explaining why burst oscillations often disappear before burst
cooling ceases. When we include rotational modifications, we find mode
frequencies and drifts consistent with those observed. The large NS spin
() needed to make this match implies that accreting
NSs are spinning at frequencies above the burst
oscillation. Since the asymptotic frequency is set by the crustal interface
wave, the observed late time frequency drifts are a probe of the composition
and temperature of NS crusts. We compare our model with the observed drifts and
persistent luminosities of X-ray burst sources, and find that NSs with a higher
average accretion rate show smaller drifts, as we predict. Furthermore, the
drift sizes are consistent with crusts composed of iron-like nuclei, as
expected for the ashes of the He-rich bursts that are exhibited by these
objects.Comment: Submitted to Astrophysical Journal on February 7, 2005. 14 pages, 12
figures; some equation errors fixed and note added in proof include
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