362 research outputs found
Detection and measurement of planetary systems with GAIA
We use detailed numerical simulations and the Andromedae,
planetary system as a template to evaluate the capability of the ESA
Cornerstone Mission GAIA in detecting and measuring multiple planets around
solar-type stars in the neighborhood of the Solar System. For the outer two
planets of the Andromedae, system, GAIA high-precision global
astrometric measurements would provide estimates of the full set of orbital
elements and masses accurate to better than 1--10%, and would be capable of
addressing the coplanarity issue by determining the true geometry of the system
with uncertainties of order of a few degrees. Finally, we discuss the
generalization to a variety of configurations of potential planetary systems in
the solar neighborhood for which GAIA could provide accurate measurements of
unique value for the science of extra-solar planets.Comment: 4 pages, 2 pictures, accepted for publication in A&A Letter
A test of Gaia Data Release 1 parallaxes: implications for the local distance scale
We present a comparison of Gaia Data Release 1 (DR1) parallaxes with
photometric parallaxes for a sample of 212 Galactic Cepheids at a median
distance of 2~kpc, and explore their implications on the distance scale and the
local value of the Hubble constant H_0. The Cepheid distances are estimated
from a recent calibration of the near-infrared Period-Luminosity P-L relation.
The comparison is carried out in parallax space, where the DR1 parallax errors,
with a median value of half the median parallax, are expected to be
well-behaved. With the exception of one outlier, the DR1 parallaxes are in
remarkably good global agreement with the predictions, and the published errors
may be conservatively overestimated by about 20%. The parallaxes of 9 Cepheids
brighter than G = 6 may be systematically underestimated, trigonometric
parallaxes measured with the HST FGS for three of these objects confirm this
trend. If interpreted as an independent calibration of the Cepheid luminosities
and assumed to be otherwise free of systematic uncertainties, DR1 parallaxes
would imply a decrease of 0.3% in the current estimate of the local Hubble
constant, well within their statistical uncertainty, and corresponding to a
value 2.5 sigma (3.5 sigma if the errors are scaled) higher than the value
inferred from Planck CMB data used in conjunction with Lambda-CDM. We also test
for a zeropoint error in Gaia parallaxes and find none to a precision of ~20
muas. We caution however that with this early release, the complete systematic
properties of the measurements may not be fully understood at the statistical
level of the Cepheid sample mean, a level an order of magnitude below the
individual uncertainties. The early results from DR1 demonstrate again the
enormous impact that the full mission will likely have on fundamental questions
in astrophysics and cosmology.Comment: A&A, submitted, 6 pages, 3 figure
Narrow-Angle Astrometry with the Space Interferometry Mission: The Search for Extra-Solar Planets. II. Detection and Characterization of Planetary Systems
(Abridged) The probability of detecting additional companions is essentially
unchanged with respect to the single-planet configurations, but after fitting
and subtraction of orbits with astrometric signal-to-noise ratio
the false detection rates can be enhanced by up to a
factor 2; the periodogram approach results in robust multiple-planet detection
for systems with periods shorter than the SIM mission length, even at low
values of , while the least squares technique combined with
Fourier series expansions is arguably preferable in the long-period regime. The
accuracy on multiple-planet orbit reconstruction and mass determination suffers
a typical degradation of 30-40% with respect to single-planet solutions; mass
and orbital inclination can be measured to better than 10% for periods as short
as 0.1 yr, and for as low as , while
is required in order to measure with similar
accuracy systems harboring objects with periods as long as three times the
mission duration. For systems with all components producing
or greater, quasi-coplanarity can be reliably
established with uncertainties of a few degrees, for periods in the range
yr; in systems where at least one component has
, coplanarity measurements are compromised, with typical
uncertainties on the mutual inclinations of order of . Our
findings are illustrative of the importance of the contribution SIM will make
to the fields of formation and evolution of planetary systems.Comment: 61 pages, 14 figures, 5 tables, to appear in the September 2003 Issue
of the Publications of the Astronomical Society of the Pacifi
Testing Planet Formation Models with Gaia as Astrometry
In this paper, we first summarize the results of a large-scale double-blind
tests campaign carried out for the realistic estimation of the Gaia potential
in detecting and measuring planetary systems. Then, we put the identified
capabilities in context by highlighting the unique contribution that the Gaia
exoplanet discoveries will be able to bring to the science of extrasolar
planets during the next decade.Comment: 4 pages, 1 figure. To appear in the proceedings of "IAU Symposium 248
- A Giant Step: from Milli- to Micro-arcsecond Astrometry", held in Shanghai,
China, 15-19 Oct. 200
A Gaia Data Release 3 View on the Tip of the Red Giant Branch Luminosity
The tip of the red giant branch (TRGB) is a standard candle that can be used
to help refine the determination of the Hubble constant. Data Release 3
(DR3) provides synthetic photometry constructed from low-resolution BP/RP
spectra for Milky Way field stars that can be used to directly calibrate the
luminosity of the TRGB in the Johnson-Cousins I band, where the TRGB is least
sensitive to metallicity. We calibrate the TRGB luminosity using a
two-dimensional maximum likelihood algorithm with field stars and
synthetic photometry and parallaxes. For a high-contrast and low-contrast break
(characterized by the values of the contrast parameter or the magnitude of
the break ), we find = and mag
respectively, or a midpoint of (sys)
(stat) mag. This measurement improves upon the TRGB measurement from Li
et al. (2022), as the higher precision photometry based on DR3 allows
us to constrain two additional free parameters of the luminosity function. We
also investigate the possibility of using DR3 synthetic photometry to
calibrate the TRGB luminosity with Centauri, but find evidence of
blending within the inner region for cluster member photometry that precludes
accurate calibration with DR3 photometry. We instead provide an updated
TRGB measurement of = mag in Centauri
using ground-based photometry from the most recent version of the database
described in Stetson et al. (2019), which gives =
(stat) 0.10 (sys) mag when tied to the EDR3 parallax
distance from the consensus of Vasiliev & Baumgardt (2021), Soltis et al.
(2021), and Ma\'{i}z Apell\'{a}niz et al. (2022a).Comment: 17 pages, 10 figures, 3 tables. Accepted by Ap
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