960 research outputs found
Alien Registration- Bedell, Caroline L. (Houlton, Aroostook County)
https://digitalmaine.com/alien_docs/35958/thumbnail.jp
Spectroscopic binaries in the Solar Twin Planet Search program: from substellar-mass to M dwarf companions
Previous studies on the rotation of Sun-like stars revealed that the
rotational rates of young stars converge towards a well-defined evolution that
follows a power-law decay. It seems, however, that some binary stars do not
obey this relation, often by displaying enhanced rotational rates and activity.
In the Solar Twin Planet Search program we observed several solar twin
binaries, and found a multiplicity fraction of in the whole
sample; moreover, at least three of these binaries (HIP 19911, HIP 67620 and
HIP 103983) clearly exhibit the aforementioned anomalies. We investigated the
configuration of the binaries in the program, and discovered new companions for
HIP 6407, HIP 54582, HIP 62039 and HIP 30037, of which the latter is orbited by
a M brown dwarf in a 1-month long orbit. We report the orbital
parameters of the systems with well-sampled orbits and, in addition, the lower
limits of parameters for the companions that only display a curvature in their
radial velocities. For the linear trend binaries, we report an estimate of the
masses of their companions when their observed separation is available, and a
minimum mass otherwise. We conclude that solar twin binaries with low-mass
stellar companions at moderate orbital periods do not display signs of a
distinct rotational evolution when compared to single stars. We confirm that
the three peculiar stars are double-lined binaries, and that their companions
are polluting their spectra, which explains the observed anomalies.Comment: 13 pages, 7 figures, accepted for publication in MNRA
The Solar Twin Planet Search II. A Jupiter twin around a solar twin
Through our HARPS radial velocity survey for planets around solar twin stars,
we have identified a promising Jupiter twin candidate around the star HIP11915.
We characterize this Keplerian signal and investigate its potential origins in
stellar activity. Our analysis indicates that HIP11915 hosts a Jupiter-mass
planet with a 3800-day orbital period and low eccentricity. Although we cannot
definitively rule out an activity cycle interpretation, we find that a planet
interpretation is more likely based on a joint analysis of RV and activity
index data. The challenges of long-period radial velocity signals addressed in
this paper are critical for the ongoing discovery of Jupiter-like exoplanets.
If planetary in nature, the signal investigated here represents a very close
analog to the solar system in terms of both Sun-like host star and Jupiter-like
planet.Comment: 8 pages, 5 figures; A&A accepted; typos corrected in this versio
Physical properties of ferromagnetic-superconducting coexistent system
We studied the nuclear relaxation rate 1/T1 of a
ferromagnetic-superconducting system from the mean field model proposed in
Ref.14. This model predicts the existence of a set of gapless excitations in
the energy spectrum which will affect the properties studied here, such as the
density of states and, hence, 1/T1. The study of the temperature variation of
1/T1(for T<Tc) shows that the usual Hebel-Slichter peak exists, but will be
reduced because of the dominant role of the gapless fermions and the background
magnetic behavior. We have also presented the temperature dependence of
ultrasonic attenuation and the frequency dependence of electromagnetic
absorption within this model. We are successful in explaining certain
experimental results.Comment: 10 Pages, 9 figute
Orally Active MMP-1 Sparing α-tetrahydropyranyl and α-piperidinyl Sulfone Matrix Metalloproteinase (MMP) Inhibitors with Efficacy in Cancer, Arthritis, and Cardiovascular Disease
α-Sulfone-α-piperidine and α-tetrahydropyranyl hydroxamates were explored that are potent inhibitors of MMP’s-2, -9, and -13 that spare MMP-1, with oral efficacy in inhibiting tumor growth in mice and left-ventricular hypertrophy in rats and in the bovine cartilage degradation ex vivo explant system. α-Piperidine 19v (SC-78080/SD-2590) was selected for development toward the initial indication of cancer, while α-piperidine and α-tetrahydropyranyl hydroxamates 19w (SC-77964) and 9i (SC-77774), respectively, were identified as backup compounds
eleanor: An open-source tool for extracting light curves from the TESS Full-Frame Images
During its two year prime mission the Transiting Exoplanet Survey Satellite
(TESS) will perform a time-series photometric survey covering over 80% of the
sky. This survey comprises observations of 26 24 x 96 degree sectors that are
each monitored continuously for approximately 27 days. The main goal of TESS is
to find transiting planets around 200,000 pre-selected stars for which fixed
aperture photometry is recorded every two minutes. However, TESS is also
recording and delivering Full-Frame Images (FFIs) of each detector at a 30
minute cadence. We have created an open-source tool, eleanor, to produce light
curves for objects in the TESS FFIs. Here, we describe the methods used in
eleanor to produce light curves that are optimized for planet searches. The
tool performs background subtraction, aperture and PSF photometry,
decorrelation of instrument systematics, and cotrending using principal
component analysis. We recover known transiting exoplanets in the FFIs to
validate the pipeline and perform a limited search for new planet candidates in
Sector 1. Our tests indicate that eleanor produces light curves with
significantly less scatter than other tools that have been used in the
literature. Cadence-stacked images, and raw and detrended eleanor light curves
for each analyzed star will be hosted on MAST, with planet candidates on
ExoFOP-TESS as Community TESS Objects of Interest (CTOIs). This work confirms
the promise that the TESS FFIs will enable the detection of thousands of new
exoplanets and a broad range of time domain astrophysics.Comment: 21 pages, 13 figures, 2 tables, Accepted to PAS
The temporal evolution of neutron-capture elements in the Galactic discs
Important insights into the formation and evolution of the Galactic disc(s)
are contained in the chemical compositions of stars. We analysed
high-resolution and high signal to noise HARPS spectra of 79 solar twin stars
in order to obtain precise determinations of their atmospheric parameters, ages
(0.4 Gyr) and chemical abundances (0.01~dex) of 12
neutron-capture elements (Sr, Y, Zr, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, and Dy).
This valuable dataset allows us to study the [X/Fe]-age relations over a time
interval of 10 Gyr and among stars belonging to the thin and thick discs.
These relations show that i) the -process has been the main channel of
nucleosynthesis of -capture elements during the evolution of the thin disc;
ii) the thick disc is rich in -process elements which suggests that its
formation has been rapid and intensive. %; iii) a chemical continuity between
the thin and thick discs is evident in the abundances of Ba. In addition, the
heavy (Ba, La, Ce) and light (Sr, Y, Zr) -process elements revealed details
on the dependence between the yields of AGB stars and the stellar mass or
metallicity. Finally, we confirmed that both [Y/Mg] and [Y/Al] ratios can be
employed as stellar clocks, allowing ages of solar twin stars to be estimated
with an average precision of 0.5~Gyr
Robustness of a local Fermi Liquid against Ferromagnetism and Phase Separation
We study the properties of Fermi Liquids with the microscopic constraint of a
local self-energy. In this case the forward scattering sum-rule imposes strong
limitations on the Fermi-Liquid parameters, which rule out any Pomeranchek
instabilities. For both attractive and repulsive interactions, ferromagnetism
and phase separation are suppressed. Superconductivity is possible in an s-wave
channel only. We also study the approach to the metal-insulator transition, and
find a Wilson ratio approaching 2. This ratio and other properties of
Sr_{1-x}La_xTiO_3 are all consistent with the local Fermi Liquid scenario.Comment: 4 pages (twocolumn format), can compile with or without epsf.sty
latex style file -- Postscript files: fig1.ps and fig2.p
Constraining the evolution of stellar rotation using solar twins
The stellar Rotation Age relation is commonly considered as a useful
tool to derive reliable ages for Sun-like stars. However, in the light of
\kepler\ data, the presence of apparently old and fast rotators that do not
obey the usual gyrochronology relations led to the hypothesis of weakened
magnetic breaking in some stars. In this letter, we constrain the solar
rotation evolutionary track using solar twins. Predicted rotational periods as
a function of mass, age, [Fe/H] and given critical Rossby number () were estimated for the entire rotational sample. Our analysis favors
the smooth rotational evolution scenario and suggests that, if the magnetic
weakened breaking scenario takes place at all, it should arise after or ages 5.3 Gyr (at 95 confidence level).Comment: 5 pages, 3 figures, accepted for publication in MNRA
- …