1,405 research outputs found
Transits and starspots in the WASP-19 planetary system
We have developed a new model for analysing light curves of planetary
transits when there are starspots on the stellar disc. Because the parameter
space contains a profusion of local minima we developed a new optimisation
algorithm which combines the global minimisation power of a genetic algorithm
and the Bayesian statistical analysis of the Markov chain. With these tools we
modelled three transit light curves of WASP-19. Two light curves were obtained
on consecutive nights and contain anomalies which we confirm as being due to
the same spot. Using these data we measure the star's rotation period and
velocity to be d and \kms, respectively, at a
latitude of 65. We find that the sky-projected angle between the
stellar spin axis and the planetary orbital axis is , indicating axial alignment. Our results are consistent with and
more precise than published spectroscopic measurements of the
Rossiter-McLaughlin effect.Comment: 9 pages, 6 figures, 5 table
High-precision photometry by telescope defocussing. III. The transiting planetary system WASP-2
We present high-precision photometry of three transits of the extrasolar
planetary system WASP-2, obtained by defocussing the telescope, and achieving
point-to-point scatters of between 0.42 and 0.73 mmag. These data are modelled
using the JKTEBOP code, and taking into account the light from the
recently-discovered faint star close to the system. The physical properties of
the WASP-2 system are derived using tabulated predictions from five different
sets of stellar evolutionary models, allowing both statistical and systematic
errorbars to be specified. We find the mass and radius of the planet to be M_b
= 0.847 +/- 0.038 +/- 0.024 Mjup and R_b = 1.044 +/- 0.029 +/- 0.015 Rjup. It
has a low equilibrium temperature of 1280 +/- 21 K, in agreement with a recent
finding that it does not have an atmospheric temperature inversion. The first
of our transit datasets has a scatter of only 0.42 mmag with respect to the
best-fitting light curve model, which to our knowledge is a record for
ground-based observations of a transiting extrasolar planet.Comment: Accepted for publication in MNRAS. 9 pages, 3 figures, 10 table
Letter from E. C. Southworth to Governor E. Ransom
A letter of E. C. Southworth to Governor E. Ransom. The writer says that believing thus Mr. Littlejohn bill for appropriation of Land for the benefit of the Holland Colony will receive that attention at the hands of the Legislature which we in this part of the state think it merits and thus a commissioner will be appointed to cary [sic] out the design of the law. I would respectfully solicit the appointment to that office if it can be done consistiently [sic] with your feelings and with a view to the public good,...https://digitalcommons.hope.edu/vrp_1840s/1185/thumbnail.jp
Analysis of reduced film cooling effects on the performance, ignition, and thermal characteristics of the Marquardt Apollo SM-LM RCS engine
IBM 360/40 computer programs on preigniter rocket engine hydraulics and steady state performance of Apollo SM-LM RCS engin
Analysis of new high-precision transit light curves of WASP-10 b: starspot occultations, small planetary radius, and high metallicity
The WASP-10 planetary system is intriguing because different values of radius
have been reported for its transiting exoplanet. The host star exhibits
activity in terms of photometric variability, which is caused by the rotational
modulation of the spots. Moreover, a periodic modulation has been discovered in
transit timing of WASP-10 b, which could be a sign of an additional body
perturbing the orbital motion of the transiting planet. We attempt to refine
the physical parameters of the system, in particular the planetary radius,
which is crucial for studying the internal structure of the transiting planet.
We also determine new mid-transit times to confirm or refute observed anomalies
in transit timing. We acquired high-precision light curves for four transits of
WASP-10 b in 2010. Assuming various limb-darkening laws, we generated best-fit
models and redetermined parameters of the system. The prayer-bead method and
Monte Carlo simulations were used to derive error estimates. Three transit
light curves exhibit signatures of the occultations of dark spots by the planet
during its passage across the stellar disk. The influence of stellar activity
on transit depth is taken into account while determining system parameters. The
radius of WASP-10 b is found to be no greater than 1.03 Jupiter radii, a value
significantly smaller than most previous studies indicate. We calculate
interior structure models of the planet, assuming a two-layer structure with
one homogeneous envelope atop a rock core. The high value of the WASP-10 b's
mean density allows one to consider the planet's internal structure including
270 to 450 Earth masses of heavy elements. Our new mid-transit times confirm
that transit timing cannot be explained by a constant period if all literature
data points are considered. They are consistent with the ephemeris assuming a
periodic variation of transit timing...Comment: Accepted for publication in A&
Recurring sets of recurring starspots on exoplanet-host Qatar-2
We announce the detection of recurring sets of recurring starspot occultation events in the short-cadence K2 light curve of Qatar-2, a K dwarf star transited every 1.34 d by a hot Jupiter. In total, we detect 34 individual starspot occultation events, caused by five different starspots, occulted in up to five consecutive transits or after a full stellar rotation. The longest recurring set of recurring starspot occultations spans over three stellar rotations, setting a lower limit for the longest starspot lifetime of 58 d. Starspot analysis provided a robust stellar rotational period measurement of 18.0 ± 0.2 d and indicates that the system is aligned, having a skyprojected obliquity of 0◦ ± 8◦. A pronounced rotational modulation in the light curve has a period of 18.2 ± 1.6 d, in agreement with the rotational period derived from the starspot occultations. We tentatively detect an ellipsoidal modulation in the phase curve, with a semiamplitude of 18 ppm, but cannot exclude the possibility that this is the result of red noise or imperfect removal of the rotational modulation. We detect no transit-timing and transitduration variations with upper limits of 15 s and 1 min, respectively. We also reject any additional transiting planets with transit depths above 280 ppm in the orbital period region 0.5–30 d
WASP-33: The first delta Scuti exoplanet host star
We report the discovery of photometric oscillations in the host star of the
exoplanet WASP-33 b (HD 15082). The data were obtained in the R band in both
transit and out-of-transit phases from the 0.3-m telescope and the Montcabrer
Observatory and the 0.8-m telescope at the Montsec Astronomical Observatory.
Proper fitting and subsequent removal of the transit signal reveals stellar
photometric variations with a semi-amplitude of about 1 mmag. The detailed
analysis of the periodogram yields a structure of significant signals around a
frequency of 21 cyc per day, which is typical of delta Scuti-type variable
stars. An accurate study of the power spectrum reveals a possible
commensurability with the planet orbital motion with a factor of 26, but this
remains to be confirmed with additional time-series data that will permit the
identification of the significant frequencies. These findings make WASP-33 the
first transiting exoplanet host star with delta Sct variability and a very
interesting candidate to search for star-planet interactions.Comment: 5 pages, 6 figures. Revised version accepted for publication in A&A
Letter
Orbital periods of cataclysmic variables identified by the SDSS. IX. NTT photometry of eight eclipsing and three magnetic systems
We report the discovery of eclipses and the first orbital period measurements
for four cataclysmic variables, plus the first orbital period measurements for
one known eclipsing and two magnetic systems. SDSS J093537.46+161950.8 exhibits
1-mag deep eclipses with a period of 92.245 min. SDSS J105754.25+275947.5 has
short and deep eclipses and an orbital period of 90.44 min. Its light curve has
no trace of a bright spot and its spectrum is dominated by the white dwarf
component, suggesting a low mass accretion rate and a very low-mass and cool
secondary star. CSS J132536+210037 shows 1-mag deep eclipses each separated by
89.821 min. SDSS J075653.11+085831.8 shows 2-mag deep eclipses on a period of
197.154 min. CSS J112634-100210 is an eclipsing dwarf nova identified in the
Catalina Real Time Transit Survey, for which we measure a period of 111.523
min. SDSS J092122.84+203857.1 is a magnetic system with an orbital period of
84.240 min; its light curve is a textbook example of cyclotron beaming. A
period of 158.72 min is found for the faint magnetic system SDSS
J132411.57+032050.4, whose orbital light variations are reminiscent of AM Her.
Improved orbital period measurements are also given for three known SDSS
cataclysmic variables. We investigate the orbital period distribution and
fraction of eclipsing systems within the SDSS sample and for all cataclysmic
variables with a known orbital period, with the finding that the fraction of
known CVs which are eclipsing is not strongly dependent on the orbital period.Comment: Accepted for publication in A&A. 12 pages, 16 figures, 5 tables. The
data are available on request and will be lodged with the CD
- …