2,302 research outputs found
Improved Orbital Parameters and Transit Monitoring for HD 156846b
HD 156846b is a Jovian planet in a highly eccentric orbit (e = 0.85) with a
period of 359.55 days. The pericenter passage at a distance of 0.16 AU is
nearly aligned to our line of sight, offering an enhanced transit probability
of 5.4% and a potentially rich probe of the dynamics of a cool planetary
atmosphere impulsively heated during close approach to a bright star (V = 6.5).
We present new radial velocity (RV) and photometric measurements of this star
as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS). The
RV measurements from Keck-HIRES reduce the predicted transit time uncertainty
to 20 minutes, an order of magnitude improvement over the ephemeris from the
discovery paper. We photometrically monitored a predicted transit window under
relatively poor photometric conditions, from which our non-detection does not
rule out a transiting geometry. We also present photometry that demonstrates
stability at the millimag level over its rotational timescale.Comment: 7 pages, 4 figures, accepted for publication in Ap
The Grand Tour of the Ruby-East Humboldt Metamorphic Core Complex, Northeastern Nevada: Part 1-Introduction & Road Log
The purpose of this geological excursion is to provide an overview of the multiphase developmental history of the Ruby Mountains and East Humboldt Range, northeastern Nevada. Although these mountain ranges are commonly cited as a classic example of a Cordilleran metamorphic core complex developed through large-magnitude, mid-Tertiary crustal extension, a preceding polyphase Mesozoic contractional history is also well preserved in the ranges. An early phase of this history involved Late Jurassic two-mica granitic magmatism, high-temperature but relatively low-pressure metamorphism, and polyphase deformation in the central Ruby Mountains. In the northern Ruby Mountains and East Humboldt Range, a Late Cretaceous history of crustal shortening, metamorphism, and magmatism is manifested by fold-nappes (involving Archean basement rocks in the northern East Humboldt Range), widespread migmatization, injection of monzogranitic and leucogranitic magmas, all coupled with sillimanite-grade metamorphism.
Following Late Cretaceous contraction, a protracted extensional deformation partially overprinted these areas during the Cenozoic. This extensional history may have begun as early as the Late Cretaceous or as late as the mid-Eocene. Late Eocene and Oligocene magmatism occurred at various levels in the crust yielding mafic to felsic orthogneisses in the deep crust, a composite granitic pluton in the upper crust, and volcanic rocks at the surface. Movement along a west-rooted, extensional shear zone in the Oligocene and early Miocene led to core-complex exhumation. The shear zone produced mylonitic rocks about 1 km thick at deep crustal levels, and an overprint of brittle detachment faulting at shallower levels as unroofing proceeded.
Megabreccias and other synextensional sedimentary deposits are locally preserved in a tilted, upper Eocene through Miocene stratigraphic sequence. Neogene magmatism included the emplacement of basalt dikes and eruption of rhyolitic rocks. Subsequent Basin and Range normal faulting, as young as Holocene, records continued tectonic extension
Alternative Fourier Expansions for Inverse Square Law Forces
Few-body problems involving Coulomb or gravitational interactions between
pairs of particles, whether in classical or quantum physics, are generally
handled through a standard multipole expansion of the two-body potentials. We
discuss an alternative based on a compact, cylindrical Green's function
expansion that should have wide applicability throughout physics. Two-electron
"direct" and "exchange" integrals in many-electron quantum systems are
evaluated to illustrate the procedure which is more compact than the standard
one using Wigner coefficients and Slater integrals.Comment: 10 pages, latex/Revtex4, 1 figure
Characterizing the Cool KOIs II. The M Dwarf KOI-254 and its Hot Jupiter
We report the confirmation and characterization of a transiting gas giant
planet orbiting the M dwarf KOI-254 every 2.455239 days, which was originally
discovered by the Kepler mission. We use radial velocity measurements, adaptive
optics imaging and near infrared spectroscopy to confirm the planetary nature
of the transit events. KOI-254b is the first hot Jupiter discovered around an
M-type dwarf star. We also present a new model-independent method of using
broadband photometry to estimate the mass and metallicity of an M dwarf without
relying on a direct distance measurement. Included in this methodology is a new
photometric metallicity calibration based on J-K colors. We use this technique
to measure the physical properties of KOI-254 and its planet. We measure a
planet mass of Mp = 0.505 Mjup, radius Rp = 0.96 Rjup and semimajor axis a =
0.03 AU, based on our measured stellar mass Mstar = 0.59 Msun and radius Rstar
= 0.55 Rsun. We also find that the host star is metal-rich, which is consistent
with the sample of M-type stars known to harbor giant planets.Comment: AJ accepted (in press
Refined stellar, orbital and planetary parameters of the eccentric HAT-P-2 planetary system
We present refined parameters for the extrasolar planetary system HAT-P-2
(also known as HD 147506), based on new radial velocity and photometric data.
HAT-P-2b is a transiting extrasolar planet that exhibits an eccentric orbit. We
present a detailed analysis of the planetary and stellar parameters, yielding
consistent results for the mass and radius of the star, better constraints on
the orbital eccentricity, and refined planetary parameters. The improved
parameters for the host star are M_star = 1.36 +/- 0.04 M_sun and R_star = 1.64
+/- 0.08 R_sun, while the planet has a mass of M_p = 9.09 +/- 0.24 M_Jup and
radius of R_p = 1.16 +/- 0.08 R_Jup. The refined transit epoch and period for
the planet are E = 2,454,387.49375 +/- 0.00074 (BJD) and P = 5.6334729 +/-
0.0000061 (days), and the orbital eccentricity and argument of periastron are e
= 0.5171 +/- 0.0033 and omega = 185.22 +/- 0.95 degrees. These orbital elements
allow us to predict the timings of secondary eclipses with a reasonable
accuracy of ~15 minutes. We also discuss the effects of this significant
eccentricity including the characterization of the asymmetry in the transit
light curve. Simple formulae are presented for the above, and these, in turn,
can be used to constrain the orbital eccentricity using purely photometric
data. These will be particularly useful for very high precision, space-borne
observations of transiting planets.Comment: Revised version, accepted for publication in MNRAS, 11 pages, 6
figure
Obliquities of Hot Jupiter host stars: Evidence for tidal interactions and primordial misalignments
We provide evidence that the obliquities of stars with close-in giant planets
were initially nearly random, and that the low obliquities that are often
observed are a consequence of star-planet tidal interactions. The evidence is
based on 14 new measurements of the Rossiter-McLaughlin effect (for the systems
HAT-P-6, HAT-P-7, HAT-P-16, HAT-P-24, HAT-P-32, HAT-P-34, WASP-12, WASP-16,
WASP-18, WASP-19, WASP-26, WASP-31, Gl 436, and Kepler-8), as well as a
critical review of previous observations. The low-obliquity (well-aligned)
systems are those for which the expected tidal timescale is short, and likewise
the high-obliquity (misaligned and retrograde) systems are those for which the
expected timescale is long. At face value, this finding indicates that the
origin of hot Jupiters involves dynamical interactions like planet-planet
interactions or the Kozai effect that tilt their orbits, rather than
inspiraling due to interaction with a protoplanetary disk. We discuss the
status of this hypothesis and the observations that are needed for a more
definitive conclusion.Comment: Accepted for publication in ApJ; typos corrected, 2 broken references
fixed, 26 pages, 25 figure
Precise Doppler Monitoring of Barnard's Star
We present 248 precise Doppler measurements of Barnard's Star (Gl 699), the
second nearest star system to Earth, obtained from Lick and Keck Observatories
during 25 years between 1987 and 2012. The early precision was 20 \ms{} but was
2 \ms{} during the last 8 years, constituting the most extensive and sensitive
search for Doppler signatures of planets around this stellar neighbor. We
carefully analyze the 136 Keck radial velocities spanning 8 years by first
applying a periodogram analysis to search for nearly circular orbits. We find
no significant periodic Doppler signals with amplitudes above 2 \ms{},
setting firm upper limits on the minimum mass (\msini) of any planets with
orbital periods from 0.1 to 1000 days. Using a Monte Carlo analysis for
circular orbits, we determine that planetary companions to Barnard's Star with
masses above 2 \mearth{} and periods below 10 days would have been detected.
Planets with periods up to 2 years and masses above 10 \mearth{} (0.03 \mjup)
are also ruled out. A similar analysis allowing for eccentric orbits yields
comparable mass limits. The habitable zone of Barnard's Star appears to be
devoid of roughly Earth-mass planets or larger, save for face-on orbits.
Previous claims of planets around the star by van de Kamp are strongly refuted.
The radial velocity of Barnard's Star increases with time at
\msy{}, consistent with the predicted geometrical effect, secular acceleration,
that exchanges transverse for radial components of velocity.Comment: 21 pages & 11 figures; accepted to ApJ for publication; revision
comments: the conclusions and results remain unchanged, removed the last
paragraph in section 4.2, a few minor changes to the text, replaced figure 7
with figures 7 and 8, corrected typos in the rv data tables (tables 2 and 3,
data downloadable from ApJ
Rotation of planet-harbouring stars
The rotation rate of a star has important implications for the detectability,
characterisation and stability of any planets that may be orbiting it. This
chapter gives a brief overview of stellar rotation before describing the
methods used to measure the rotation periods of planet host stars, the factors
affecting the evolution of a star's rotation rate, stellar age estimates based
on rotation, and an overview of the observed trends in the rotation properties
of stars with planets.Comment: 16 pages, 4 figures: Invited review to appear in 'Handbook of
Exoplanets', Springer Reference Works, edited by Hans J. Deeg and Juan
Antonio Belmont
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