174 research outputs found
Interferometry, spectroscopy and astrometry of the bright eclipsing system Delta Velorum
The bright southern star Delta Vel is a multiple system comprising at least
three stars. Its brightest component, Delta Vel A, was identified in 2000 as
one of the brightest eclipsing system in the sky. Its eclipses are easily
observable with the unaided eye, a remarkable property shared only by Algol,
Beta Aur, Alpha CrB and Psi Cen. We determined dynamical masses from a
combination of spectroscopy, high-precision astrometry of the orbits of Aab-B
and Aa-Ab using adaptive optics (VLT/NACO) and optical interferometry
(VLTI/AMBER). The main eclipsing component is a pair of A-type stars in rapid
rotation. We modeled the photometric and radial velocity measurements of the
eclipsing pair Aa-Ab using a self consistent method based on physical
parameters (mass, radius, luminosity, rotational velocity). From this modeling,
we derive the fundamental parameters of the eclipsing stars with a typical
accuracy of 1%. We find that they have similar masses, respectively 2.43 +/-
0.02 and 2.27 +/- 0.02 Msun. The physical parameters of the tertiary component
(Delta Vel B) are also derived, although to a lower accuracy, as well as the
parallax of the system, 39.8 +/- 0.4 mas. This value is in satisfactory
agreement (-1.2 sigma) with the Hipparcos parallax of the system (pi_Hip =40.5
+/- 0.4 mas).Comment: 4 pages, 5 figures, in GREAT-ESF Workshop 'Orbital Couples: "Pas de
Deux" in the Solar System and the Milky Way', Paris, IMCCE proceedings, in
pres
Search for the wide-orbit massive companion of XO-7b in the follow-up radial-velocity and transit-timing data: no significant clues
XO-7b is a hot Jupiter transiting a mag G0V-type star. The
planetary system is interesting because the linear slope in the discovery
radial-velocity (RV) data indicated a wide-orbit massive companion. In 2020 we
started an RV campaign for the system with the main scientific goal to
follow-up this linear slope, and to put constraints on the orbital period of
the companion. Furthermore, we aimed at refining the system parameters and we
wanted to probe transit timing variations (TTVs) of XO-7b in order to search
for long-term dynamical signs of the companion of XO-7b in the
observed-minus-calculated (O-C) data of mid-transit times. Apart from the
discovery RVs, we obtained and analyzed 20 follow-up RV observations and TESS
photometric data. The previously observed significant linear RV slope was not
confirmed with the follow-up RV data, where we detected only a marginal linear
slope with the opposite trend. If the announced companion really exists, the
most convincing explanation is that both RV datasets were collected near its
quadrature position. Based on the RVs we estimated the minimum orbital period,
which is d, and the 'minimum'
minimum mass of the companion, which is . We did not find significant evidence of the companion of
XO-7b in the O-C dataset of mid-transit times. We can again conclude that if
the announced companion really exists, this is in agreement with previous
results that distant companions of exoplanets are only known by RV solutions.Comment: Accepted for publication in MNRA
VW LMi: tightest quadruple system known. Light-time effect and possible secular changes of orbits
Tightest known quadruple systems VW LMi consists of contact eclipsing binary
with P_12 = 0.477551 days and detached binary with P_34 = 7.93063 days
revolving in rather tight, 355.0-days orbit. This paper presents new
photometric and spectroscopic observations yielding 69 times of minima and 36
disentangled radial velocities for the component stars. All available radial
velocities and minima times are combined to better characterize the orbits and
to derive absolute parameters of components. The total mass of the quadruple
system was estimated at 4.56 M_sun. The detached, non-eclipsing binary with
orbital period P = 7.93 days is found to show apsidal motion with U
approximately 80 years. Precession period in this binary, caused by the
gravitational perturbation of the contact binary, is estimated to be about 120
years. The wide mutual orbit and orbit of the non-eclipsing pair are found to
be close to coplanarity, preventing any changes of the inclination angle of the
non-eclipsing orbit and excluding occurrence of the second system of eclipses
in future. Possibilities of astrometric solution and direct resolving of the
wide, mutual orbit are discussed. Nearby star, HD95606, was found to form loose
binary with quadruple system VW LMi.Comment: 4 figures. accepted to MNRAS on July 31, 200
Contact binaries with additional components. III. The adaptive optics detections
We present results of the CFHT adaptive optics search for companions of a
homogeneous group of contact binary stars, as a contribution to our attempts to
prove a hypothesis that these binaries require a third star to become so close
as observed. In addition to companions directly discovered at separations of
>=1", we introduced a new method of AO image analysis utilizing distortions of
the AO diffraction ring pattern at separations of 0.07"-1". Very close
companions, with separations in the latter range were discovered in systems HV
Aqr, OO Aql, CK Boo, XY Leo, BE Scl, and RZ Tau. More distant companions were
detected in V402 Aur, AO Cam, V2082 Cyg. Our results provide a contribution to
the mounting evidence that the presence of close companions is a very common
phenomenon for very close binaries with orbital periods <1 day.Comment: Full Figs.4 and 5 are in
http://www.astro.utoronto.ca/~rucinski/Triples3
Transient jets in the symbiotic prototype Z Andromedae
We present development of the collimated bipolar jets from the symbiotic
prototype Z And that appeared and disappeared during its 2006 outburst. In 2006
July Z And reached its historical maximum at U ~ 8.0. During this period, rapid
photometric variations with Dm ~ 0.06 mag on the timescale of hours developed.
Simultaneously, high-velocity satellite components appeared on both sides of
the H-alpha and H-beta emission line profiles. They were launched
asymmetrically with the red/blue velocity ratio of 1.2 - 1.3. From about
mid-August they became symmetric. Their spectral properties indicated ejection
of bipolar jets collimated within an average opening angle of 6.1 degrees. We
estimated average outflow rate via jets to dM(jet)/dt ~
2xE10-6(R(jet)/1AU)**(1/2) M(Sun)/year, during their August - September
maximum, which corresponds to the emitting mass in jets, M(jet, emitting) ~
6xE-10(Rjet)/1AU)^{3/2} M(Sun). During their lifetime, the jets released the
total mass of M(jet, total) approx 7.4x1E-7 M(Sun). Evolution in the rapid
photometric variability and asymmetric ejection of jets around the optical
maximum can be explained by a disruption of the inner parts of the disk caused
by radiation-induced warping of the disk.Comment: 31 pages, 9 figures, 2 tables, accepted for Ap
Physical Parameters of Some Close Binaries: ET Boo, V1123 Tau, V1191 Cyg, V1073 Cyg and V357 Peg
With the aim of providing new and up-to-date absolute parameters of some
close binary systems, new BVR CCD photometry was carried out at the Ankara
University Observatory (AUG) for five eclipsing binaries, ET Boo, V1123 Tau,
V1191 Cyg, V1073 Cyg and V357 Peg between April, 2007 and October, 2008. In
this paper, we present the orbital solutions for these systems obtained by
simultaneous light and radial velocity curve analyses. Extensive orbital
solution and absolute parameters for ET Boo system were given for the first
time through this study. According to the analyses, ET Boo is a detached binary
while the parameters of four remaining systems are consistent with the nature
of contact binaries. The evolutionary status of the components of these systems
are also discussed by referring to their absolute parameters found in this
study.Comment: this accepted paper will be published in New Astronom
A Catalog of 1022 Bright Contact Binary Stars
In this work we describe a large new sample of contact binary stars extracted
in a uniform manner from sky patrol data taken by the ROTSE-I telescope.
Extensive ROTSE-I light curve data is combined with J, H, and K band
near-infrared data taken from the Two Micron All-Sky Survey (2MASS) to add
color information. Contact binaries candidates are selected using the observed
period-color relation. Candidates are confirmed by visual examination of the
light curves. To enhance the utility of this catalog, we derive a new J-H
period-color-luminosity relation and use this to estimate distances for the
entire catalog. From these distance estimates we derive an estimated contact
binary space density of (1.7 +/- 0.6) x 10^-5 pcs^-3.Comment: 26 pages, 12 figures, accepted for publication in A
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