Science Sessions
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J.H.J. de Bruijne
ESA/RSSD/SRE-SA
Gaia is the next astrometry mission of the European Space Agency (ESA),
following up on the success of the Hipparcos mission. Gaia's primary
science goal is to unravel the kinematical, dynamical, and chemical
structure and evolution of the Milky Way. In addition, Gaia's data will
touch a wide variety of science topics, e.g., stellar physics,
solar-system bodies, fundamental physics, and exo-planets. With a launch
in the second half of 2013, the final catalogue is expected in 2021 -
the first intermediate data release is envisaged to take place some two
years after launch. Gaia will survey the entire sky and repeatedly
observe the brightest 1,000 million objects, down to 20th magnitude,
during its 5-year lifetime. Parallaxes will be measured with standard
errors less than 10 micro-arcsecond (μas) for stars brighter than 12th
magnitude, 25 μas for stars at 15th magnitude, and 300 μas at magnitude
20. The properties of the final astrometric catalogue depend, among
others, on the adopted scanning law and on the payload-operation and
on-ground calibration concepts, in particular the calibration of
radiation-induced systematic effects in the data. The importance of
these elements is highlighted. In addition, this presentation focuses on
expected correlations and systematic errors in the data and on the
expected astrometric performance of Gaia in high-density regions on the sky.
18+2 minutes
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Brian Mason
USNO
The resolution of binaries first detected astrometrically has a long
history. In the early 19th Century Friedrich Wilhelm Bessel found periodic
oscillations in the motions of Sirius and Procyon and reported them in a
letter to Humboldt in 1834. The large flux ratio and much smaller mass ratio
made these the easiest pairs to detect astrometrically. However, the large
magnitude difference made resolution difficult and it was not until Alvan
Clark and sons built two of their large refractors that this was
accomplished. Sirius B was seen by Alvan G. Clark at the end of January 1862
testing the Dearborn 18.5" instrument and Procyon B was first seen by John
Schaeberle in 1896 with the Lick 36" telescope. While
pairs of this extreme flux ratio will continue to be a problem for
resolution, the situation has improved markedly with smaller flux ratios
being detected astrometrically with improvements to accuracy and precision
of wide-angle astrometry. Also, new techniques and enhanced resolution
capability for narrow-angle astrometry has allowed these pairs to be more
easily resolved. The complimentary nature of these disparate techniques is
exemplified with the new relative solutions of the astrometric binaries
kappa For and HIP 42916 recently presented (Hartkopf et al. AJ 143, 42;
2012). A single resolution of a binary with an astrometric orbit allows for
the determination of the relative orbit by scaling the a_phot to a"
appropriately. If the Delta-m and parallax is known individual masses will
also be forthcoming. Solutions of binaries of these type are presented.
13+2 minutes
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Naoteru Gouda
National Astronomical Observatory of Japan
I will talk about the following present status of JASMINE
projects:
JASMINE is an abbreviation of Japan Astrometry Satellite Mission for Infrared
Exploration. Three satellites are planned as a series of JASMINE projects,
as a step-by-step approach, to overcome technical issues and promote
scientific results.
These are Nano-JASMINE, Small-JASMINE and (medium-sized) JASMINE.
Nano-JASMINE uses a very small nano-satellite and is scheduled to be
launched in November
2013 at the Alcantara space center in Brazil by a Cyclone-4 rocket
developed in Ukraine.
Nano-JASMINE will operate in zw-band (0.6---1.1 micron) to perform an all
sky survey with
an accuracy of 3 milli-arcseconds for position, parallaxes and proper
motions.
Moreover high-accuracy proper motions (0.1 milli-arcseconds/year) can be
obtained by
combining the Nano-JASMINE catalogue with the Hipparcos catalogue.
Small-JASMINE will observe towards a region around the Galactic center and
other small
regions, which include interesting scientific targets, with accuracies of 10
to 50 micro-
arcseconds in an infrared Hw-band (1.1---1.7 micron). The target launch date
is around
2017.
(Medium-sized) JASMINE is an extended mission of Small-JASMINE, which
will observe
towards almost the whole region of the Galactic bulge with accuracies of 10
micro-arcseconds in Kw-band (1.5---2.5 micron).
The target launch date is the first half of the 2020s.
18+2 minutes
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Youfen Wang
Shanghai Astronomical Observatory
We report the parallax and proper motions of five L
dwarfs obtained with observations from the robotic Liverpool Telescope.
These parallaxes represent new values and we use them to discuss the
physical properties of L dwarfs. Our derived proper motions are consistent
with the published values and have considerably smaller errors. The objects
appear to be normal L dwarfs, with space velocities that locate them in the
disk and with normal metal abundances according to spectroscopic and model
comparisons. For all five objects, we derive effective temperature,
luminosity, radius, gravity and mass from evolutional model. We have derived
the effective temperature combining observational optical and NIR spectra
with model synthetic spectra for three of our L dwarfs. We found the
degeneracy of temperature, gravity and metallicity in affecting the
absorption line strength through comparison among model spectra and among
observational spectra. Robotic Telescope provide us convenient in doing
parallax program which need a lot of repeated observations. Such robotic
telescopes are able enhance our efficiency in parallax programs, thus they
are continuously needed in future.
13+2 minutes
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Catia Cardoso, NPARSEC Collaboration
Osservatorio Astrofisico di Torino
We discuss the NPARSEC (NTT PARallaxes of Southern Extremely Cool
objects) program to determine parallaxes of ~80 objects covering the T
dwarf spectral range. The areas of research directly impacted by this
sample will be wide spread. On an individual object basis distances are
key for assignments of binarity, metallicity and gravity and more
generally the sample will provide key input for the substellar luminosity
and mass functions, the connection to exo-planetary models as well as
complex atmospheric processes such as non-equilibrium chemistry and
turbulent mixing. Eventually these objects will provide new insights into
the history of our galaxy, the kinematics of the solar neighborhood and
our understanding of differing formation scenarios from stars to brown
dwarfs to giant planets. In particular we will discuss the observational
and data reduction procedures adopted with a emphasis on the centroiding
which is fundamental to the final astrometric precision.
13+2 minutes
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W. F. van Altena, T. M. Girard, D. I. Casetti-Dinescu
and K. Vieira
Yale University & CIDA
The fourth installment of the Yale/San Juan Southern Proper Motion Catalog,
SPM4, contains absolute proper motions, celestial coordinates, and B, V
photometry for over 103 million stars and galaxies between the south
celestial pole and -20° declination. The catalog is roughly complete to
V =
17.5 and is based on photographic and CCD observations taken with the Yale
Southern Observatory's double astrograph at Cesco Observatory in El
Leoncito, Argentina. The proper-motion precision is 2-3 mas/yr for
well-measured stars; systematic uncertainties are on the order of 1 mas/yr.
In parallel with the SPM4 construction, and using the same SPM observations,
a more accurate catalog of proper motions was made over a 450 sq-deg
contiguous area that encloses both Magellanic Clouds. That catalog of 1.4
million objects was used to derive the mean absolute proper motions of the
LMC and the SMC and, importantly, to make the most precise determination to
date of the proper motion of the SMC relative to the LMC. The absolute
proper motions are consistent with the Clouds' orbits being marginally bound
to the Milky Way, albeit on an elongated orbit.
Combining UV, optical and IR photometry from existing large-area surveys
with SPM4 proper motions, we have identified young, OB-type candidates in an
extensive 8000 sq-deg region that includes the LMC/SMC, the Bridge, part of
the Magellanic Stream and the Leading Arm. Additionally, a proper-motion
analysis has been made of a radial-velocity selected sample of red giants
and supergiants in the LMC, shown by Olsen et al. (2011) to be a
kinematically and chemically distinct subgroup, most likely captured from
the SMC. These results help constrain the Cloud-Cloud interaction,
suggesting a near collision that took place 100 to 200 Myr ago.
Finally, SPM4 absolute proper motions have been cross-identified with radial
velocities from the second release of the Radial Velocity Experiment (RAVE)
and the resulting three-dimensional space motions of ~4400 red clump stars
used to derive the kinematical properties of the thick disk, including the
rotational velocity gradient, dispersions, and velocity-ellipsoid tilt angle.
13+2 minutes
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W. F. van Altena
Yale University
Astrometry for Astrophysics is intended to fill a serious gap in texts
available to introduce advanced undergraduates, beginning graduate students
and researchers in related fields to the science of Astrometry. This text
provides an introduction to the field with examples of current applications
to a variety of astronomical topics of current interest.
Astrometry for Astrophysics is intended for a one-semester introductory
course that will hopefully lead to further study by students or serve as a
primer on the field for researchers in related astronomical fields. To
accomplish the above goals, the book is divided into five parts. Part one
provides the impetus to study Astrometry by reviewing the opportunities and
challenges of micro-arcsecond positions, parallaxes and proper motions that
will be obtained by the new space astrometry missions as well as
ground-based telescopes that are now yielding milli-arcsecond data for
enormous numbers of objects. Part two includes introductions to the use of
vectors, the relativistic foundations of astrometry and the celestial
mechanics of n-body systems, as well as celestial coordinate systems and
positions. Part three introduces the deleterious effects of observing
through the atmosphere and methods developed to compensate or take advantage
of those effects by using techniques such as adaptive optics and
interferometric methods in the optical and radio parts of the spectrum.
Part four provides introductions to selected topics in optics and detectors
and then develops methods for analyzing the images formed by our telescopes
and the relations necessary to project complex focal plane geometries onto
the celestial sphere. Finally, Part five highlights applications of
astrometry to Galactic structure, binary stars, star clusters, Solar System
astrometry, extrasolar planets and cosmology. I hope that those chapters
will stimulate students and researchers to further explore our exciting
field.
Astrometry for Astrophysics consists of 28 chapters written by 28
specialists in the field from 15 different countries. The book is edited by
van Altena and will be published by Cambridge University Press in November
2012.
5 minutes
10 minute break
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Ralph Gaume
USNO
Current USNO Astrometry catalogs and products will be discussed,
including NOMAD and UCAC4. Prospects for future USNO astrometric
catalogs will be reviewed, including the status of on-going programs
such as URAT and UNAC, catalogs derived from large A-Omega programs,
and prospects for a future bright-star catalog from the JMAPS space
astrometry mission. The fundamental astrometric reference frame is
based on the radio interferometric positions of quasars. Prospects
for improvement of the fundamental astrometric reference frame will
be discussed.
13+2 minutes
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N.Zacharias,
C.Finch
USNO
Reduction details, properties and notes for users are
presented about the final USNO CCD Astrograph Catalog (UCAC)
release #4 which becomes public in June 2012. Accurate positions
(20 to 100 mas) of 113 million stars to R = 16 are given based on
over 200,000 CCD images taken by the 20cm astrograph at CTIO and
NOFS between 1998 and 2004.
Proper motions of most stars are based on SPM and NPM data with
average errors of about 4 to 7 mas/yr and smaller errors for
stars brighter than 13 utilizing many more catalogs.
UCAC4 includes 5-band photometry for about 50 million stars from
APASS and near IR photometry for over 100 million stars from 2MASS.
FK6, Hipparcos and Tycho2 data are used to supplement bright stars
in order to arrive at a complete all-sky catalog.
13+2 minutes
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N.Zacharias,
G.Bredthauer,
M.DiVittorio,
C.Finch,
F.Harris,
T.Rafferty,
G.Wieder
USNO
The USNO Robotic Astrometric Telescope (URAT) achieved first light
in 2011 at USNO in Washington DC and is now deployed at the Naval
Observatory Flagstaff Station (NOFS). The red-lens of the UCAC
program is again utilized for URAT, however, with a completely new
tube assembly, upgraded mount, new electronics and a new 4-shooter
camera containing 4 large CCDs (STA1600) each with 10,560 by 10,560
pixels of 9 micrometer size. A single exposure of URAT covers
28 square degrees of sky with a resolution of 0.9 arcsec/pixel.
The URAT all-sky survey will reach about magnitude 17.5 in a
bandpass between R and I with first data release expected by
end of 2013. Several built-in features allow URAT to observe
stars as bright as 1st magnitude. Multiple sky-overlaps taken over
more than 2 years per hemisphere allow determination of accurate
positions (10 mas level), proper motions, and parallaxes.
13+2 minutes
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James L. Hilton
USNO
Included in the UCAC observations made at Cerro Tololo Inter-American
Observatory (CTIO) are 5864 positions of asteroids. The number of
observations of individual asteroids varies from 49 observations of (2)
Pallas made over three oppositions to 556 asteroids with a single
observation each. Analysis of 47 observations of (692) Hippodamia and 10
observations of (755) Sulamitis each made over two oppositions suggest that
the accuracy of the these positions is approximately 50 mas in right
ascension and 80 mas in declination. The accuracy of the UCAC may be
somewhat better than this as the mean apparent diameters at opposition of
these two bodies are approximately 60 and 30 mas, respectively, and no
adjustments have been made for phase or possible albedo markings on the
surface. A preliminary analysis of 41 of the observations of Pallas (mean
apparent diameter 410 mas) are in good agreement with those of Hippodamia
and Sulamitis. However, the remaining eight observations show a systematic
offset in both right ascension and declination. These discrepant
observations may indicate an albedo marking on the surface rotating into
view.
13+2 minutes
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Erik Høg
Niels Bohr Institute, Copenhagen University
The approval in 1980 of the Hipparcos global astrometry mission
and the subsequent development gave rise to ideas and work towards a
Hipparcos follow-up mission which culminated with the approval of the ESA
cornerstone mission Gaia in the year 2000. Ideas for a successor for
global astrometry were studied in Russia (then USSR), and ideas for space
astrometry by interferometry were studied in the USA, both beginning in
the 1980s. The ESA community was however fully occupied with Hipparcos
and nobody there thought of a follow-up mission. That changed in 1990
when I visited Russia, became interested in the Russian ideas and began
discussions with Russian colleagues which led to the development in the
1990s, the main subject of the presentation.
13+2 minutes
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Erik Høg
Niels Bohr Institute, Copenhagen University
A modest astrometric experiment in Copenhagen in 1925 led to the Hipparcos
and Gaia space astrometry missions. - Astrophysicists need accurate
positions, distances and motions of stars in order to understand the
evolution of stars and the universe. Astrometry provides such information,
but this old branch of astronomy was facing extinction during much of the
20th century in the competition with astrophysics. The direction forward was
shown by observations at the Copenhagen Observatory in 1925 with a new
technique: photoelectric astrometry. Digital techniques were introduced in
photoelectric astrometry at the Hamburg Observatory in the 1960s by the
present author. This development paved the way for space technology as
pioneered in France and implemented in the European satellite Hipparcos
approved in 1980.
13+2 minutes