4,281 research outputs found
Deriving Iodine-free spectra for high-resolution echelle spectrographs
We describe a new method to derive clean, iodine-free spectra directly from
observations acquired using high-resolution echelle spectrographs equipped with
iodine cells. The main motivation to obtain iodine-free spectra is to use
portions of the spectrum that are superimposed with the dense forest of iodine
absorption lines, in order to retrieve lines that can be used to monitor the
magnetic activity of the star, helping to validate candidate planets. In short,
we provide a straight-forward methodology to clean the spectra by using the
forward model used to derive radial velocities, the Line Spread Function
information plus the stellar spectrum without iodine to reconstruct and
subtract the iodine spectrum from the observations. We show our results using
observations of the star Ceti acquired with the PFS, HIRES and UCLES
spectrographs, reaching an iodine-free spectrum correction at the 1% RMS
level. We additionally discuss the limitations and further applications of the
method.Comment: 15 pages, 7 figures. Accepted for publication in A
Limits to Transits of the Neptune-mass planet orbiting Gl 581
We have monitored the Neptune-mass exoplanet-hosting M-dwarf Gl 581 with the
1m Swope Telescope at Las Campanas Observatory over two predicted transit
epochs. A neutral density filter centered at 550nm was used during the first
epoch, yielding 6.33 hours of continuous light curve coverage with an average
photometric precision of 1.6 mmags and a cadence of 2.85 min. The second epoch
was monitored in B-band over 5.85 hours, with an average photometric precision
of 1.2 mmags and 4.28 min cadence. No transits are apparent on either night,
indicating that the orbital inclination is less than 88.1 deg for all planets
with radius larger than 0.38 R_Nep = 1.48 R_Earth. Because planets of most
reasonable interior composition have radii larger than 1.55 R_Earth we place an
inclination limit for the system of 88.1 deg. The corresponding minimum mass of
Gl 581b remains 0.97 M_Nep = 16.6 M_Earth.Comment: 7 pages, 2 figures, 1 table, to appear in PAS
Detection of the nearest Jupiter analog in radial velocity and astrometry data
© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.The presence of Jupiter is crucial to the architecture of the Solar System and models underline this to be a generic feature of planetary systems. We find the detection of the difference between the position and motion recorded by the contemporary astrometric satellite Gaia and its precursor Hipparcos can be used to discover Jupiter-like planets. We illustrate how observations of the nearby star Indi A giving astrometric and radial velocity data can be used to independently find the orbit of its suspected companion. The radial velocity and astrometric data provide complementary detections which allow for a much stronger solution than either technique would provide individually. We quantify Indi A b as the closest Jupiter-like exoplanet with a mass of 3 on a slightly eccentric orbit with an orbital period of 45 yr. While other long-period exoplanets have been discovered, Indi A b provides a well constrained mass and along with the well-studied brown dwarf binary in orbit around Indi A means that the system provides a benchmark case for our understanding of the formation of gas giant planets and brown dwarfs.Peer reviewe
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
Numerical approximation of statistical solutions of scalar conservation laws
We propose efficient numerical algorithms for approximating statistical
solutions of scalar conservation laws. The proposed algorithms combine finite
volume spatio-temporal approximations with Monte Carlo and multi-level Monte
Carlo discretizations of the probability space. Both sets of methods are proved
to converge to the entropy statistical solution. We also prove that there is a
considerable gain in efficiency resulting from the multi-level Monte Carlo
method over the standard Monte Carlo method. Numerical experiments illustrating
the ability of both methods to accurately compute multi-point statistical
quantities of interest are also presented
Sub-Saturn Planet Candidates to HD 16141 and HD 46375
Precision Doppler measurements from the Keck/HIRES spectrometer reveal
periodic Keplerian velocity variations in the stars HD 16141 and HD 46375. HD
16141 (G5 IV) has a period of 75.8 d and a velocity amplitude of 11 m/s,
yielding a companion having Msini = 0.22 Mjup and a semimajor axis, a = 0.35
AU. HD 46375 (K1 IV/V) has a period of 3.024 d and a velocity amplitude of 35
m/s, yielding a companion with Msini=0.25 Mjup, a semimajor axis of a = 0.041
AU, and an eccentricity of 0.04 (consistent with zero). These companions
contribute to the rising planet mass function toward lower masses.Comment: 4 Figure
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