2,216 research outputs found
Improving Transit Predictions of Known Exoplanets with TERMS
Transiting planet discoveries have largely been restricted to the
short-period or low-periastron distance regimes due to the bias inherent in the
geometric transit probability. Through the refinement of planetary orbital
parameters, and hence reducing the size of transit windows, long-period planets
become feasible targets for photometric follow-up. Here we describe the TERMS
project that is monitoring these host stars at predicted transit times.Comment: 3 pages, 2 figures, to be published in ASP Conf. Proceedings:
"Detection and dynamics of transiting exoplanets" 2010, OHP, France (eds.: F.
Bouchy, R.F. D{\i}az, C. Moutou
A Comparison of an Unhooded and Hooded Sprayer for Pesticide Drift Reduction
Management of drift from pesticide applications is important for human and environmental health concerns. It is also necessary to ensure adequate dosage of the pesticide meets the target species(s). A variety of factors can affect the drift potential of a pesticide application, including nozzle selection, solution chemistry, and application equipment. In the present study, a comparison of two ground sprayers, one with a hood and one without a hood, is made using three common ground nozzles in the US. The hooded sprayer reduced the drift potential of the pesticide application for all nozzles tested. In addition, higher spray coverage under the boom was measured when using the hooded sprayer. The results of this study indicate that incorporating a hood will lead to reduced drift potential from a pesticide application
The Lick-Carnegie Exoplanet Survey: A Saturn-Mass Planet in the Habitable Zone of the Nearby M4V Star HIP 57050
Precision radial velocities from Keck/HIRES reveal a Saturn-mass planet
orbiting the nearby M4V star HIP 57050. The planet has a minimum mass of 0.3
Jupiter-mass, an orbital period of 41.4 days, and an orbital eccentricity of
0.31. V-band photometry reveals a clear stellar rotation signature of the host
star with a period of 98 days, well separated from the period of the radial
velocity variations and reinforcing a Keplerian origin for the observed
velocity variations. The orbital period of this planet corresponds to an orbit
in the habitable zone of HIP 57050, with an expected planetary temperature of
approximately 230 K. The star has a metallicity of [Fe/H] = 0.32+/-0.06 dex, of
order twice solar and among the highest metallicity stars in the immediate
solar neighborhood. This newly discovered planet provides further support that
the well-known planet-metallicity correlation for F, G, and K stars also
extends down into the M-dwarf regime. The a priori geometric probability for
transits of this planet is only about 1%. However, the expected eclipse depth
is ~7%, considerably larger than that yet observed for any transiting planet.
Though long on the odds, such a transit is worth pursuing as it would allow for
high quality studies of the atmosphere via transmission spectroscopy with HST.
At the expected planetary effective temperature, the atmosphere may contain
water clouds.Comment: 20 pages, 5 figures, 3 tables, to appear in the May 20 issue of ApJ
Five Planets Orbiting 55 Cancri
We report 18 years of Doppler shift measurements of a nearby star, 55 Cancri,
that exhibit strong evidence for five orbiting planets. The four previously
reported planets are strongly confirmed here. A fifth planet is presented, with
an apparent orbital period of 260 days, placing it 0.78 AU from the star in the
large empty zone between two other planets. The velocity wobble amplitude of
4.9 \ms implies a minimum planet mass \msini = 45.7 \mearthe. The orbital
eccentricity is consistent with a circular orbit, but modest eccentricity
solutions give similar \chisq fits. All five planets reside in low eccentricity
orbits, four having eccentricities under 0.1. The outermost planet orbits 5.8
AU from the star and has a minimum mass, \msini = 3.8 \mjupe, making it more
massive than the inner four planets combined. Its orbital distance is the
largest for an exoplanet with a well defined orbit. The innermost planet has a
semi-major axis of only 0.038 AU and has a minimum mass, \msinie, of only 10.8
\mearthe, one of the lowest mass exoplanets known. The five known planets
within 6 AU define a {\em minimum mass protoplanetary nebula} to compare with
the classical minimum mass solar nebula. Numerical N-body simulations show this
system of five planets to be dynamically stable and show that the planets with
periods of 14.65 and 44.3 d are not in a mean-motion resonance. Millimagnitude
photometry during 11 years reveals no brightness variations at any of the
radial velocity periods, providing support for their interpretation as
planetary.Comment: accepted to Ap
Five New Extrasolar Planets
We report multiple Doppler measurements of five nearby FGK main-sequence stars and subgiants obtained during the past 4-6 yr at the Keck Observatory. These stars, namely, HD 183263, HD 117207, HD 188015, HD 45350, and HD 99492, all exhibit coherent variations in their Doppler shifts consistent with a planet in Keplerian motion. The five new planets occupy known realms of planetary parameter space, including a wide range of orbital eccentricities, e = 0-0.78, and semimajor axes, 0.1-3.8 AU, that provide further statistical information about the true distributions of various properties of planetary systems. One of the planets, HD 99492b, has a low minimum mass of 0.112M_(Jup) = 36M_(Earth). Four of the five planets orbit beyond 1 AU. We describe two quantitative tests of the false alarm probability for Keplerian interpretations of measured velocities. The more robust of these involves Monte Carlo realizations of scrambled velocities as a proxy for noise. Keplerian orbital fits to that "noise" yield the distribution of χ^2_v to compare with χ^2_v from the original (unscrambled) velocities. We establish a 1% false alarm probability as the criterion for candidate planets. All five of these planet-bearing stars are metal-rich, with [Fe/H] > +0.27, reinforcing the strong correlation between planet occurrence and metallicity. From the full sample of 1330 stars monitored at Keck, Lick, and the Anglo-Australian Telescope, the shortest orbital period for any planet is 2.64 days, showing that shorter periods occur less frequently than 0.1% in the solar neighborhood. Photometric observations were acquired for four of the five host stars with an automatic telescope at Fairborn Observatory. The lack of brightness variations in phase with the radial velocities supports planetary-reflex motion as the cause of the velocity variations. No transits were observed, but their occurrence is not ruled out by our observations
Five New Multicomponent Planetary Systems
We report Doppler measurements for six nearby G- and K-type main-sequence stars that show multiple low-mass companions, at least one of which has planetary mass. One system has three planets, the fourth triple-planet system known around a normal star, and another has an extremely low minimum mass of 18 M_⊕. HD 128311 (K0 V) has two planets (one previously known) with minimum masses (M sin i) of 2.18M_J and 3.21M_J and orbital periods of 1.26 and 2.54 yr, suggesting a possible 2 : 1 resonance. For HD 108874 (G5 V), the velocities reveal two planets (one previously known) having minimum masses and periods of (M sin i_b = 1.36M_J, P_b = 1.08 yr) and (M sin i_c = 1.02M_J, P_c = 4.4 yr). HD 50499 (G1 V) has a planet with P = 6.8 yr and M sin i = 1.7M_J, and the velocity residuals exhibit a trend of -4.8 m s^(-1) yr^(-1), indicating a more distant companion with P > 10 yr and minimum mass of 2M_J. HD 37124 (G4 IV-V) has three planets, one having M sin i = 0.61M_J and P = 154.5 days, as previously known. We find two plausible triple-planet models that fit the data, both having a second planet near P = 840 days, with the more likely model having its third planet in a 6 yr orbit and the other one in a 29 day orbit. For HD 190360, we confirm the planet having P = 7.9 yr and M sin i = 1.5M_J as found by the Geneva team, but we find a distinctly noncircular orbit with e = 0.36 ± 0.03, rendering this not an analog of Jupiter as had been reported. Our velocities also reveal a second planet with P = 17.1 days and M sin i = 18.1 M_⊕. HD 217107 (G8 IV) has a previously known "hot Jupiter" with M sin i = 1.4M_J and P = 7.13 days, and we confirm its high eccentricity, e = 0.13. The velocity residuals reveal an outer companion in an eccentric orbit, having minimum mass of M sin i > 2M_J, eccentricity e ~ 0.5, and a period P > 8 yr, implying a semimajor axis α > 4 AU and providing an opportunity for direct detection. We have obtained high-precision photometry of five of the six planetary host stars with three of the automated telescopes at Fairborn Observatory. We can rule out significant brightness variations in phase with the radial velocities in most cases, thus supporting planetary reflex motion as the cause of the velocity variations. Transits are ruled out to very shallow limits for HD 217107 and are also shown to be unlikely for the prospective inner planets of the HD 37124 and HD 108874 systems. HD 128311 is photometrically variable with an amplitude of 0.03 mag and a period of 11.53 days, which is much shorter than the orbital periods of its two planetary companions. This rotation period explains the origin of periodic velocity residuals to the two-planet model of this star. All of the planetary systems here would be further constrained with astrometry by the Space Interferometry Mission
Pennsylvania Folklife Vol. 42, No. 2
• Charles E. Starry, Adams County Chair Maker • Lewis Miller\u27s Chronicle of York: A Picture of Life in Early America • Family Anecdotes from a Georges Creek Home • The Pennsylvania-German Schrank • The Barns of Towamensing Township • A Review of Robert F. Ensminger\u27s The Pennsylvania Barnhttps://digitalcommons.ursinus.edu/pafolklifemag/1136/thumbnail.jp
A Planet at 5 AU Around 55 Cancri
We report precise Doppler shift measurements of 55 Cancri (G8V) obtained from
1989 to 2002 at Lick Observatory. The velocities reveal evidence for an outer
planetary companion to 55 Cancri orbiting at 5.5 AU. The velocities also
confirm a second, inner planet at 0.11 AU. The outer planet is the first
extrasolar planet found that orbits near or beyond the orbit of Jupiter. It was
drawn from a sample of ~50 stars observed with sufficient duration and quality
to detect a giant planet at 5 AU, implying that such planets are not rare. The
properties of this jupiter analog may be compared directly to those of the
Jovian planets in our Solar System. Its eccentricity is modest, e=0.16,
compared with e=0.05 for both Jupiter and Saturn. Its mass is at least 4.0
jupiter masses (M sin i). The two planets do not perturb each other
significantly. Moreover, a third planet of sub-Jupiter mass could easily
survive in between these two known planets. Indeed a third periodicity remains
in the velocity measurements with P = 44.3 d and a semi-amplitude of 13 m/s.
This periodicity is caused either by a third planet at a=0.24 AU or by
inhomogeneities on the stellar surface that rotates with period 42 d. The
planet interpretation is more likely, as the stellar surface is quiet,
exhibiting log(R'_{HK}) = -5.0 and brightness variations less than 1 millimag,
and any hypothetical surface inhomogeneity would have to persist in longitude
for 14 yr. Even with all three planets, an additional planet of
terrestrial--mass could orbit stably at ~1 AU. The star 55 Cancri is apparently
a normal, middle-aged main sequence star with a mass of 0.95 solar masses, rich
in heavy elements ([Fe/H] = +0.27). This high metallicity raises the issue of
the relationship between its age, rotation, and chromosphere.Comment: 47 pages, 4 tables, 12 figures, uses AASTE
The N2K Consortium. II. A Transiting Hot Saturn Around HD 149026 With a Large Dense Core
Doppler measurements from Subaru and Keck have revealed radial velocity
variations in the V=8.15, G0IV star HD 149026 consistent with a Saturn-Mass
planet in a 2.8766 day orbit. Photometric observations at Fairborn Observatory
have detected three complete transit events with depths of 0.003 mag at the
predicted times of conjunction. HD 149026 is now the second brightest star with
a transiting extrasolar planet. The mass of the star, based on interpolation of
stellar evolutionary models, is 1.3 +/- 0.1 solar masses; together with the
Doppler amplitude, K=43.3 m s^-1, we derive a planet mass Msin(i)=0.36 Mjup,
and orbital radius of 0.042 AU. HD 149026 is chromospherically inactive and
metal-rich with spectroscopically derived [Fe/H]=+0.36, Teff=6147 K, log g=4.26
and vsin(i)=6.0 km s^-1. Based on Teff and the stellar luminosity of 2.72 Lsun,
we derive a stellar radius of 1.45 Rsun. Modeling of the three photometric
transits provides an orbital inclination of 85.3 +/- 1.0 degrees and (including
the uncertainty in the stellar radius) a planet radius of 0.725 +/- 0.05 Rjup.
Models for this planet mass and radius suggest the presence of a ~67 Mearth
core composed of elements heavier than hydrogen and helium. This substantial
planet core would be difficult to construct by gravitational instability.Comment: 25 pages, 5 figures, accepted by the Astrophysical Journa
A Neptune-Mass Planet Orbiting the Nearby M Dwarf GJ 436
We report precise Doppler measurements of GJ 436 (M2.5V) obtained at Keck
Observatory. The velocities reveal a planetary companion with orbital period of
2.644 d, eccentricity of 0.12 (consistent with zero) and velocity
semi-amplitude of \ms. The minimum mass (\msini) for the planet is
0.067 \mjup = 1.2 M = 21 M, making it the lowest mass
exoplanet yet found around a main sequence star and the first candidate in the
Neptune mass domain. GJ 436 (Mass = 0.41 \msune) is only the second M dwarf
found to harbor a planet, joining the two--planet system around GJ 876. The low
mass of the planet raises questions about its constitution, with possible
compositions of primarily H and He gas, ice/rock, or rock--dominated. The
implied semi--major axis is = 0.028 AU = 14 stellar radii, raising issues
of planet formation, migration, and tidal coupling with the star. GJ 436 is
Gyr old, based on both kinematic and chromospheric diagnostics. The star
exhibits no photometric variability on the 2.644-day Doppler period to a
limiting amplitude of 0.0004 mag, supporting the planetary interpretation of
the Doppler periodicity. Photometric transits of the planet across the star are
ruled out for gas giant compositions and are also unlikely for solid
compositions. As the third closest known planetary system, GJ 436 warrants
follow--up observations by high resolution optical and I
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