47 research outputs found
Orbit Determination of Close Binary Systems using Lucky Imaging
We present relative positions of visual binaries observed during 2009 with
the FastCam "lucky-imaging" camera at the 1.5-m Carlos Sanchez Telescope (TCS)
at the Observatorio del Teide. We obtained 424 CCD observations (averaged in
198 mean relative positions) of 157 binaries with angular separations in the
range 0.14-15.40", with a median separation of 0.51". For a given system, each
CCD image represents the sum of the best 10-25% images from 1000-5000
short-exposure frames. Derived internal errors were 7 mas in r and 1.2^{\circ}
(9 mas) in q. When comparing to systems with very well-known orbits, we find
that the rms deviation in r residuals is 23 mas, while the rms deviation in q
residuals is 0.73 deg/r. We confirmed 18 Hipparcos binaries and we report new
companions to BVD 36 A and J 621 B. For binaries with preliminary orbital
parameters, the relative radial velocity was estimated as well. We also present
four new revised orbits computed for LDS 873, BU 627 A-BC, BU 628 and HO 197
AB. This work is the first results on visual binaries using the FastCam
lucky-imaging camera.Comment: 23 pages, 10 figures, 14 tables, accepted August 18th, 2011, to be
published in MNRA
The High Angular Resolution Multiplicity of Massive Stars
We present the results of a speckle interferometric survey of Galactic
massive stars that complements and expands upon a similar survey made over a
decade ago. The speckle observations were made with the KPNO and CTIO 4 m
telescopes and USNO speckle camera, and they are sensitive to the detection of
binaries in the angular separation regime between 0.03" and 5" with relatively
bright companions (Delta V < 3). We report on the discovery of companions to 14
OB stars. In total we resolved companions of 41 of 385 O-stars (11%), 4 of 37
Wolf-Rayet stars (11%), and 89 of 139 B-stars (64%; an enriched visual binary
sample that we selected for future orbital determinations). We made a
statistical analysis of the binary frequency among the subsample that are
listed in the Galactic O Star Catalog by compiling published data on other
visual companions detected through adaptive optics studies and/or noted in the
Washington Double Star Catalog and by collecting published information on
radial velocities and spectroscopic binaries. We find that the binary frequency
is much higher among O-stars in clusters and associations compared to the
numbers for field and runaway O-stars, consistent with predictions for the
ejection processes for runaway stars. We present a first orbit for the O-star
Delta Orionis, a linear solution of the close, apparently optical, companion of
the O-star Iota Orionis, and an improved orbit of the Be star Delta Scorpii.
Finally, we list astrometric data for another 249 resolved and 221 unresolved
targets that are lower mass stars that we observed for various other science
programs.Comment: 76 pages, 6 figures, 11 table
A catalog of visual double and multiple stars with eclipsing components
A new catalog of visual double systems containing eclipsing binaries as one
component is presented. The main purpose of this catalog is to compile a
complete list of all known multiples of this variety, both for current analysis
and to highlight those in need of additional observations. All available
photometric and astrometric data were analyzed, resulting in new orbits for
eight systems and new times of minimum light for a number of the eclipsing
binaries. Some of the systems in the catalog have acceptable solutions for
their visual orbits, although in most cases their orbital periods are too long
for simultaneous analysis. Also included, however, are a number of systems
which currently lack an orbital solution but which may be suitable for
simultaneous analysis in the future.Comment: 15 pages, 8 figures, 4 tables, published in A
Accretion of chemically fractionated material on a wide binary with a blue straggler
The components of the wide binary HIP64030=HD 113984 show a large (about 0.25
dex) iron content difference (Desidera et al.~2006 A&A 454, 581). The positions
of the components on the color magnitude diagram suggest that the primary is a
blue straggler. We studied the abundance difference of several elements besides
iron, and we searched for stellar and substellar companions around the
components to unveil the origin of the observed iron difference. A line-by-line
differential abundance analysis for several elements was performed, while
suitable spectral synthesis was performed for C, N, and Li. High precision
radial velocities obtained with the iodine cell were combined with available
literature data. The analysis of additional elements shows that the abundance
difference for the elements studied increases with increasing condensation
temperature, suggesting that accretion of chemically fractionated material
might have occurred in the system. Alteration of C and N likely due to CNO
processing is also observed. We also show that the primary is a spectroscopic
binary with a period of 445 days and moderate eccentricity. The minimum mass of
the companion is 0.17 Msun. Two scenarios were explored to explain the observed
abundance pattern. In the first, all abundance anomalies arise on the blue
straggler. If this is the case, the dust-gas separation may have been occurred
in a circumbinary disk around the blue straggler and its expected white dwarf
companion, as observed in several RV Tauri and post AGB binaries. In the second
scenario, accretion of dust-rich material occurred on the secondary. This would
also explain the anomalous carbon isotopic ratio of the secondary. Such a
scenario requires that a substantial amount of mass lost by the central binary
has been accreted by the wide component
Orbits for five southern visual binaries
First orbits have been calculated for the visual binaries WDS 00090–5400,
01061–4643, 05248–5219 and 08447–5443 (Alzner & Argyle [CITE]; Argyle & Alzner
[CITE]). The current period for the orbit of (Wierzbinski
[CITE]) is too short to represent recent observations. The period has been lengthened
to 450 years (Alzner & Argyle [CITE]). For 00090–5400 the period is 221 years with
a moderate eccentricity; 01061–4643 is currently near periastron but is underobserved;
05248–5219 has passed periastron but there have been no observations since 1993.
The visual component of WDS 08447–5443 (= δ Vel), which is not the
same as the eclipsing component recently discovered by Otero ([CITE]),
has an unexpectedly short period