60 research outputs found
A consideration of the use of optical fibers to remotely couple photometers to telescopes
The possible use of optical fibers to remotely couple photometers to telescopes is considered. Such an application offers the apparent prospect of enhancing photometric stability as a consequence of the benefits of remote operation and decreased sensitivity to image details. A properly designed fiber optic coupler will probably show no significant changes in optical transmisssion due to normal variations in the fiber configuration. It may be more difficult to eliminate configuration-dependent effects on the pupil of the transmitted beam, and thus achieve photometric stability to guiding and seeing errors. In addition, there is some evidence for significant changes in the optical throughputs of fibers over the temperature range normally encountered in astronomical observatories
Spectral Mapping Reconstruction of Extended Sources
Three dimensional spectroscopy of extended sources is typically performed
with dedicated integral field spectrographs. We describe a method of
reconstructing full spectral cubes, with two spatial and one spectral
dimension, from rastered spectral mapping observations employing a single slit
in a traditional slit spectrograph. When the background and image
characteristics are stable, as is often achieved in space, the use of
traditional long slits for integral field spectroscopy can substantially reduce
instrument complexity over dedicated integral field designs, without loss of
mapping efficiency -- particularly compelling when a long slit mode for single
unresolved source followup is separately required. We detail a custom
flux-conserving cube reconstruction algorithm, discuss issues of extended
source flux calibration, and describe CUBISM, a tool which implements these
methods for spectral maps obtained with ther Spitzer Space Telescope's Infrared
Spectrograph.Comment: 11 pages, 8 figures, accepted by PAS
SB9: The Ninth Catalogue of Spectroscopic Binary Orbits
The Ninth Catalogue of Spectroscopic Binary Orbits
(http://sb9.astro.ulb.ac.be) continues the series of compilations of
spectroscopic orbits carried out over the past 35 years by Batten and
collaborators. As of 2004 May 1st, the new Catalogue holds orbits for 2,386
systems. Some essential differences between this catalogue and its predecessors
are outlined and three straightforward applications are presented: (1)
Completeness assessment: period distribution of SB1s and SB2s; (2) Shortest
periods across the H-R diagram; (3) Period-eccentricity relation.Comment: Accepte for publication in A&A, 6 pages, 6 figure
The CORALIE survey for southern extra-solar planets VIII. The very low-mass companions of HD141937, HD162020, HD168443, HD202206: brown dwarfs or superplanets?
Doppler CORALIE measurements of the solar-type stars HD141937, HD162020,
HD168443 and HD202206 show Keplerian radial-velocity variations revealing the
presence of 4 new companions with minimum masses close to the
planet/brown-dwarf transition, namely with m_2sin(i) = 9.7, 14.4, 16.9, and
17.5 M_Jup, respectively. The orbits present fairly large eccentricities
(0.22<e<0.43). Except for HD162020, the parent stars are metal rich compared to
the Sun, as are most of the detected extra-solar planet hosts. Considerations
of tidal dissipation in the short-period HD162020 system points towards a
brown-dwarf nature for the low-mass companion. HD168443 is a multiple system
with two low-mass companions being either brown dwarfs or formed simultaneously
in the protoplanetary disks as superplanets. For HD202206, the radial
velocities show an additional drift revealing a further outer companion, the
nature of which is still unknown. Finally, the stellar-host and orbital
properties of massive planets are examined in comparison to lighter exoplanets.
Observed trends include the need of metal-rich stars to form massive exoplanets
and the lack of short periods for massive planets. If confirmed with improved
statistics, these features may provide constraints for the migration scenario.Comment: 14 pages including figures, accepted for publication in A&
HD 80606 b, a planet on an extremely elongated orbit
We report the detection of a planetary companion orbiting the solar-type star
HD 80606, the brighter component of a wide binary with a projected separation
of about 2000 AU. Using high-signal spectroscopic observations of the two
components of the visual binary, we show that they are nearly identical. The
planet has an orbital period of 111.8 days and a minimum mass of 3.9 M_Jup.
With e=0.927, this planet has the highest orbital eccentricity among the
extrasolar planets detected so far. We finally list several processes this
extreme eccentricity could result from.Comment: 4 pages, 1 figure included, submitted to A&A, final versio
Reprocessing the Hipparcos Intermediate Astrometric Data of spectroscopic binaries: II. Systems with a giant component
By reanalyzing the Hipparcos Intermediate Astrometric Data of a large sample
of spectroscopic binaries containing a giant, we obtain a sample of 29 systems
fulfilling a carefully derived set of constraints and hence for which we can
derive an accurate orbital solution. Of these, one is a double-lined
spectroscopic binary and six were not listed in the DMSA/O section of the
catalogue. Using our solutions, we derive the masses of the components in these
systems and statistically analyze them. We also briefly discuss each system
individually.Comment: 15 pages, 25 figures, Accepted in A&
The CORALIE survey for southern extrasolar planets V: 3 new extrasolar planets
We report the detection of 3 new planetary companions orbiting the solar-type
stars GJ 3021, HD 52265 and HD 169830 using radial-velocity measurements taken
with the CORALIE echelle spectrograph. All these planetary companions have
longer orbital periods than the 51 Peg-like objects. The orbits are fairly
eccentric. The minimum masses of these planets range from 1 to 3.3 M_Jup. The
stars have spectral types from F8V to G6V. They are metal-rich. We also present
our radial-velocity measurements for three solar-type stars known to host
planetary companions iota Hor (HD 17051), HD 210277 and HD 217107.Comment: 14 pages, 5 figures (included), A&A in press, a1sini unit corrected
in table 6, Fig.3 correcte
New neighbours. III. 21 new companions to nearby dwarfs, discovered with adaptive optics
We present some results of a CFHT adaptive optics search for companions to
nearby dwarfs. We identify 21 new components in solar neighbourhood systems, of
which 13 were found while surveying a volume-limited sample of M dwarfs within
12pc. We are obtaining complete observations for this subsample, to derive
unbiased multiplicity statistics for the very-low-mass disk population.
Additionally, we resolve for the first time 6 known spectroscopic or
astrometric binaries, for a total of 27 newly resolved companions. A fair
fraction of the new binaries has favourable parameters for accurate mass
determinations. The newly resolved companion of Gl120.1C had an apparent
spectroscopic minimum mass in the brown-dwarf range (Duquennoy & Mayor 1991)
and it contributed to the statistical evidence that a few percent of solar type
stars might have close-in brown-dwarf companions. We find that Gl~120.1C
actually is an unrecognised double-lined spectroscopic pair. Its
radial-velocity amplitude had therefore been strongly underestimated by
Duquennoy & Mayor, and it does not truly belong to their sample of single-lined
systems with minimum spectroscopic mass below the substellar limit. We also
present the first direct detection of Gl~494B, an astrometric brown-dwarf
candidate. Its luminosity does straddle the substellar limit, and it is a brown
dwarf if its age is less than 300Myr. A few more years of observations will
ascertain its mass and status from first principles.Comment: Accepted by Astronomy & Astrophysic
- …