292 research outputs found
VARTOOLS: A Program for Analyzing Astronomical Time-Series Data
This paper describes the VARTOOLS program, which is an open-source
command-line utility, written in C, for analyzing astronomical time-series
data, especially light curves. The program provides a general-purpose set of
tools for processing light curves including signal identification, filtering,
light curve manipulation, time conversions, and modeling and simulating light
curves. Some of the routines implemented include the Generalized Lomb-Scargle
periodogram, the Box-Least Squares transit search routine, the Analysis of
Variance periodogram, the Discrete Fourier Transform including the CLEAN
algorithm, the Weighted Wavelet Z-Transform, light curve arithmetic, linear and
non-linear optimization of analytic functions including support for Markov
Chain Monte Carlo analyses with non-trivial covariances, characterizing and/or
simulating time-correlated noise, and the TFA and SYSREM filtering algorithms,
among others. A mechanism is also provided for incorporating a user's own
compiled processing routines into the program. VARTOOLS is designed especially
for batch processing of light curves, including built-in support for parallel
processing, making it useful for large time-domain surveys such as searches for
transiting planets. Several examples are provided to illustrate the use of the
program.Comment: 83 pages, 5 figures, accepted for publication in Astronomy and
Computing, code available at
http://www.astro.princeton.edu/~jhartman/vartools.htm
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
On the Rotation Period of (90377) Sedna
We present precise, ~1%, r-band relative photometry of the unusual solar
system object (90377) Sedna. Our data consist of 143 data points taken over
eight nights in October 2004 and January 2005. The RMS variability over the
longest contiguous stretch of five nights of data spanning nine days is only
1.3%. This subset of data alone constrain the amplitude of any long-period
variations with period P to be A<1% (P/20 days)^2. Over the course of any given
5-hour segment, the data exhibits significant linear trends not seen in a
comparison star of similar magnitude, and in a few cases these segments show
clear evidence for curvature at the level of a few millimagnitudes per hour^2.
These properties imply that the rotation period of Sedna is O(10 hours), cannot
be 10 days, unless the intrinsic light curve has
significant and comparable power on multiple timescales, which is unlikely. A
sinusoidal fit yields a period of P=(10.273 +/- 0.002) hours and semi-amplitude
of A=(1.1 +/- 0.1)%. There are additional acceptable fits with flanking periods
separated by ~3 minutes, as well as another class of fits with P ~ 18 hours,
although these later fits appear less viable based on visual inspection. Our
results indicate that the period of Sedna is likely consistent with typical
rotation periods of solar system objects, thus obviating the need for a massive
companion to slow its rotation.Comment: 7 pages, 4 figures, 2.5 tables. Final ApJL version, minor changes.
Full light curve data in tex
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
On the hierarchical triple nature of the former red nova precursor candidate KIC 9832227
We revisit the issue of period variation of the recently claimed red nova
precursor candidate KIC 9832227. By using the data gathered during the main
mission of the Kepler satellite, those collected by ground-based wide-field
surveys and other monitoring programs (such as ASAS-SN), we find that the
currently available timing data strongly support a model consisting of the
known W UMa binary and a distant low-mass companion with an orbital period of
~13.5 years. The period of the W UMa component exhibits a linear period
decrease with a pace of (1.10+/-0.05)x10^{-6} days per year, within the range
of many other similar systems. This rate of decrease is several orders of
magnitude lower than that of V1309 Sco, the first (and so far the only)
well-established binary precursor of a nova observed a few years before the
outburst. The high-fidelity fit of the timing data and the conformity of the
derived minimum mass of (0.38+/-0.02) Msun of the outer companion from these
data with the limit posed by the spectroscopic non-detection of this component,
are in agreement with the suggested hierarchical nature of this system.Comment: Submitted to A&A; 11 pages, ~0.6 Mb, after the first favorable
referee repor
HAT-P-68b: A TRANSITING HOT JUPITER AROUND A K5 DWARF STAR
We report the discovery by the ground-based HATNet survey of the transiting exoplanet HAT-P-68b, which has a mass of 0.724 ± 0.043 M_Jupiter , and radius of 1.072 ± 0.012 R_Jupiter. The planet is in a circular P = 2.2984 day orbit around a moderately bright V = 13.937 ± 0.030 magnitude K dwarf star of mass 0.673 M_Sun , and radius 0.6726 ± 0.0069 R_Sun . The planetary nature of this system is confirmed through follow-up transit photometry obtained with the FLWO 1.2 m telescope, high-precision RVs measured using Keck-I/HIRES, FLWO 1.5 m/TRES, and OHP 1.9 m/Sophie, and high-spatial-resolution speckle imaging from WIYN 3.5 m/DSSI. HAT-P-68 is at an ecliptic latitude of +3degrees and outside the field of view of both the NASA TESS primary mission and the K2 mission. The large transit depth of 0.036 mag (r-band) makes HAT-P-68b a promising target for atmospheric characterization via transmission spectroscopy
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