59,994 research outputs found
Observation of double star by long-baseline interferometry
This paper serves as a reference on how to estimate the parameters of binary
stars and how to combine multiple techniques, namely astrometry, interferometry
and radial velocities.Comment: F. Millour, A. Chiavassa, L. Bigot, O. Chesneau, A. Meilland \& P.
Stee. What can the highest angular resolution bring to stellar astrophysics?,
69-70, EDP sciences, 2015, EAS publication series, 978-2-7598-1833-4.
\<10.1051/eas/1569020\>.
\<http://www.eas-journal.org/articles/eas/abs/2014/04/contents/contents.html\&g
Initial Scientific Results from Phase-Referenced Astrometry of Sub-Arcsecond Binaries
The Palomar Testbed Interferometer has observed several binary star systems
whose separations fall between the interferometric coherence length (a few
hundredths of an arcsecond) and the typical atmospheric seeing limit of one
arcsecond. Using phase-referencing techniques we measure the relative
separations of the systems to precisions of a few tens of micro-arcseconds. We
present the first scientific results of these observations, including the
astrometric detection of the faint third stellar component of the kappa Pegasi
system.Comment: 8 pages, 5 figures. To appear in SPIE conference proceedings volume
5491, "New Frontiers in Stellar Interferometery
Sub-Hz line width diode lasers by stabilization to vibrationally and thermally compensated ULE Fabry-Perot cavities
We achieved a 0.5 Hz optical beat note line width with ~ 0.1 Hz/s frequency
drift at 972 nm between two external cavity diode lasers independently
stabilized to two vertically mounted Fabry-Perot (FP) reference cavities.
Vertical FP reference cavities are suspended in mid-plane such that the
influence of vertical vibrations to the mirror separation is significantly
suppressed. This makes the setup virtually immune for vertical vibrations that
are more difficult to isolate than the horizontal vibrations. To compensate for
thermal drifts the FP spacers are made from Ultra-Low-Expansion (ULE) glass
which possesses a zero linear expansion coefficient. A new design using Peltier
elements in vacuum allows operation at an optimal temperature where the
quadratic temperature expansion of the ULE could be eliminated as well. The
measured linear drift of such ULE FP cavity of 63 mHz/s was due to material
aging and the residual frequency fluctuations were less than 40 Hz during 16
hours of measurement. Some part of the temperature-caused drift is attributed
to the thermal expansion of the mirror coatings. High-frequency thermal
fluctuations that cause vibrations of the mirror surfaces limit the stability
of a well designed reference cavity. By comparing two similar laser systems we
obtain an Allan instability of 2*10-15 between 0.1 and 10 s averaging time,
which is close to the theoretical thermal noise limit.Comment: submitted to Applied Physics
Polarized Redundant-Baseline Calibration for 21 cm Cosmology Without Adding Spectral Structure
21 cm cosmology is a promising new probe of the evolution of visible matter
in our universe, especially during the poorly-constrained Cosmic Dawn and Epoch
of Reionization. However, in order to separate the 21 cm signal from bright
astrophysical foregrounds, we need an exquisite understanding of our telescopes
so as to avoid adding spectral structure to spectrally-smooth foregrounds. One
powerful calibration method relies on repeated simultaneous measurements of the
same interferometric baseline to solve for the sky signal and for instrumental
parameters simultaneously. However, certain degrees of freedom are not
constrained by asserting internal consistency between redundant measurements.
In this paper, we review the origin of these "degeneracies" of
redundant-baseline calibration and demonstrate how they can source unwanted
spectral structure in our measurement and show how to eliminate that
additional, artificial structure. We also generalize redundant calibration to
dual-polarization instruments, derive the degeneracy structure, and explore the
unique challenges to calibration and preserving spectral smoothness presented
by a polarized measurement.Comment: 12 pages, 3 figures, updated to match the published MNRAS versio
Ultra-compact branchless plasmonic interferometers
Miniaturization of functional optical devices and circuits is a key
prerequisite for a myriad of applications ranging from biosensing to quantum
information processing. This development has considerably been spurred by rapid
developments within plasmonics exploiting its unprecedented ability to squeeze
light into subwavelength scale. In this study, we investigate on-chip plasmonic
systems allowing for synchronous excitation of multiple inputs and examine the
interference between two adjacent excited channels. We present a branchless
interferometer consisting of two parallel plasmonic waveguides that can be
either selectively or coherently excited via ultra-compact antenna couplers.
The total coupling efficiency is quantitatively characterized in a systematic
manner and shown to exceed 15% for small waveguide separations, with the power
distribution between the two waveguides being efficiently and dynamically
shaped by adjusting the incident beam position. The presented design principle
can readily be extended to other configurations, giving new perspectives for
highly dense integrated plasmonic circuitry, optoelectronic devices, and
sensing applications.Comment: 15 pages, 6 figure
Differential Astrometry of Sub-arcsecond Scale Binaries at the Palomar Testbed Interferometer
We have used the Palomar Testbed Interferometer to perform very high
precision differential astrometry on the 0.25 arcsecond separation binary star
HD 171779. In 70 minutes of observation we achieve a measurement uncertainty of
approximately 9 micro-arcseconds in one axis, consistent with theoretical
expectations. Night-to-night repeatability over four nights is at the level of
16 micro-arcseconds. This method of very-narrow-angle astrometry may be
extremely useful for searching for planets with masses as small as 0.5 Jupiter
Masses around a previously neglected class of stars -- so-called ``speckle
binaries.'' It will also provide measurements of stellar parameters such as
masses and distances, useful for constraining stellar models at the 10^-3
level.Comment: 19 pages including 6 figures. Submitted to ApJ. Typos corrected,
several parts reworded for clarificatio
Binary and Millisecond Pulsars at the New Millennium
We review the properties and applications of binary and millisecond pulsars.
Our knowledge of these exciting objects has greatly increased in recent years,
mainly due to successful surveys which have brought the known pulsar population
to over 1300. There are now 56 binary and millisecond pulsars in the Galactic
disk and a further 47 in globular clusters. This review is concerned primarily
with the results and spin-offs from these surveys which are of particular
interest to the relativity community.Comment: 59 pages, 26 figures, 5 tables. Accepted for publication in Living
Reviews in Relativity (http://www.livingreviews.org
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