explanation blue bibcodes open ADS page with paths to full text
Author name code: vantveer
ADS astronomy entries on 2022-09-14
author:van 't Veer, Frans
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Title: Short-period RS CVn and W UMa binaries: how are they related?
Authors: van't Veer, F.
1999TJPh...23..313V Altcode:
Two groups of late-type very close main sequence binaries, the
so-called short period RS CVn and W UMa systems, are important for
the understanding of the structure and evolutionary consequences of
angular momentum loss (AML) resulting from magnetic stellar winds of
fast rotating solar type stars. The components of RS CVn stars are close
to their Roche lobes, but still detached, whereas W UMa binaries are
contact systems; both are rotating fast. One of the crucial problems
is trying to answer the question if there is a dynamical relation
between the two types of binaries in the sense that, as a consequence
of the AML, the orbit of the detached sytems will shrink, so that both
components come in contact and produce a W UMa type binary. The author
discusses the relation between wind and starspots and the dependance of
AML on the latitude of these spots. No obvious conclusion is possible
concerning the shrinking of the orbit of RS CVn binaries. He shows
that other possibilities for orbits of detached systems with magnetic
activity also exist.
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Title: Christiaan Huygens: des lunettes de plus en plus longues.
Authors: van't Veer, F.
1998LAstr.112..110V Altcode:
No abstract at ADS
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Title: Late-Type Close Binaries and Single Stars
Authors: van't Veer, Frans
1997ASPC..130...57V Altcode: 1997rdbs.conf...57V
No abstract at ADS
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Title: The properties of W Ursae Majoris contact binaries: new
results and old problems.
Authors: Maceroni, C.; van't Veer, F.
1996A&A...311..523M Altcode:
The physical properties of W UMa binary systems are revisited on the
basis of the observational data published in the last decade and of
the recent theoretical studies on angular-momentum-loss-driven secular
evolution. The absolute elements (masses, radii, luminosities) are
derived by an inference method and a calibration based on the available
high quality spectroscopic orbits. The derived age (8Gy) agrees with
the estimate of Guinan and Bradstreet from space motions. The analysis
of the resulting physical parameters shows little correlation between
the standard classification in A and W subtype (first proposed by
Binnendijk (1970) and only related to the light curve morphology)
and the evolutionary status and origin of the systems. Most A-subtype
systems seem to have no evolutionary link with W-subtype ones. The
relation between total mass and mass ratio for the "bona fide" sample
also suggests that mass loss from the system may play an important role.
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Title: VizieR Online Data Catalog: Photometry of W UMa (Maceroni+,
1996)
Authors: Maceroni, C.; van't Veer, F.
1996yCat..33110523M Altcode:
The physical properties of W UMa binary systems are revisited on the
basis of the observational data published in the last decade and of
the recent theoretical studies on angular-momentum-loss-driven secular
evolution. The absolute elements (masses, radii, luminosities) are
derived by an inference method and a calibration based on the available
high quality spectroscopic orbits. The derived age (8Gy) agrees with
the estimate of Guinan and Bradstreet from space motions. The analysis
of the resulting physical parameters shows little correlation between
the standard classification in A and W subtype (first proposed by
Binnendijk (1970) and only related to the light curve morphology)
and the evolutionary status and origin of the systems. Most A-subtype
systems seem to have no evolutionary link with W-subtype ones. The
relation between total mass and mass ratio for the "bona fide" sample
also suggests that mass loss from the system may play an important
role. (1 data file).
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Title: The Lifetime of Late Type Contact Binaries
Authors: van't Veer, F.
1996ASPC...90..280V Altcode: 1996oedb.conf..280V
No abstract at ADS
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Title: Si proche et encore si secret.
Authors: van't Veer, F.
1995LAstr.109..156V Altcode:
This article mentions some problems concerning the Sun.
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Title: Detection of a photometric period in the non-eclipsing binary
HR 8800. Towards a better description of the system.
Authors: Sareyan, J. P.; Chauville, J.; van't Veer, F.; Alvarez, M.;
Gonzalez-Bedolla, S.; Valera, F.
1994A&A...291..815S Altcode:
High precision photometry has allowed light variations to be
detected in the spectroscopic binary HR 8800, with the same well
known orbital period. It is shown that the phase and light variation
range are coherent with a reflexion of the primary's light on the
secondary. Although at the very limit of detection, an overmodulation
of the visible light curve could be due to the variable geometric
appearance of the secondary.
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Title: Period variations of the late type contact binaries YY ERI
and AE Phe: how to use light curves outside minimum.
Authors: Maceroni, C.; van't Veer, F.
1994A&A...289..871M Altcode:
We present and compare minimum times, computed for light curves of
the W Uma type binaries YY Eri and AE Phe. Two different methods are
used: the Leiden method formulated by Kwee & van Woerden and the
light curve synthesis method developed by Wilson & Devinney. It is
shown that the latter gives more and better information, and is even
capable to extract the times of conjunction. Its application requires a
complete analysis of the parameters of the system, including the surface
inhomogeneities. The observations are available in electronic form.
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Title: Surface imaging of late-type contact binaries I: AE Phoenicis
and YY Eridani
Authors: Maceroni, C.; Vilhu, O.; van't Veer, F.; van Hamme, W.
1994A&A...288..529M Altcode:
This paper presents the results of the first application of Doppler
Imaging to solar-type contact binaries. Our aim was to examine
whether this technique can help discriminate between various types
of surface inhomogeneities (dark vs. bright star-spots) which are
produced by different physical processes and which affect not only
the surface brightness distribution but also the system's secular
evolution. Simultaneous high dispersion spectroscopy and photometry for
the systems AE Phe and YY Eri were obtained at ESO using the Coude
Auxiliary Telescope (CAT) and the 50 cm telescope. The observed
light-curves were solved by means of the latest version of the
Wilson-Devinney program. Doppler maps were constructed taking into
account the effects of fast rotation and proximity of the system's
components. Doppler maps reveal the presence of dark spots on both
systems. For AE Phe, this result is in agreement with the light-curve
solution. Indirect evidence of enhanced chromospheric emission is
also found. This emission appears to be more intense on the primary
components.
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Title: VizieR Online Data Catalog: YY Eri & AE Phe (Maceroni+,
1994)
Authors: Maceroni, C.; van't Veer, F.
1994yCat..32890871M Altcode:
Not Available (2 data files).
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Title: Global evolution of contact binaries.
Authors: vant'veer, F.
1994MmSAI..65..105V Altcode:
No abstract at ADS
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Title: The uniqueness of photometric solutions for spotted W Ursae
Majoris binaries
Authors: Maceroni, C.; van't Veer, F.
1993A&A...277..515M Altcode:
The perturbations frequently affecting the W UMa binaries light curves
are usually explained in terms of bright/dark spots appearing on
the surface of the components. The localization of these perturbed
regions is usually obtained from the study of the light curves in
different colors and by means of the so-called light curve synthesis
method. The problem of this type of analysis is: i) how far we can
trust the solutions and feel confident in their uniqueness, in order
to better judge the increasing number of "spotted" solutions appearing
in the literature, ii) in which degree the other system parameters
(different from those of the spots) are affected by the incorrect
determination of the spots. To answer these questions we solved a
certain number of artificially constructed "spotted" light curves,
corresponding to particularly critical spot configurations. The
results clearly show that spot determination by photometry alone is
unreliable. Moreover, in some cases, incorrect values may be derived
for the system parameters as well.
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Title: How to Study the Approach of Late-type Very Close Binary
Components?
Authors: van't Veer, F.
1993ASPC...38..229V Altcode: 1993nfbs.proc..229V
No abstract at ADS
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Title: The essential contribution of double star study to
astrophysical understanding.
Authors: van't Veer, F.
1992ctap.conf..756V Altcode:
Binary stars are at the origin of our fundamental knowledge of
stellar masses and dimensions. In a short historical review of the
development of double star research, the work of Barbier and Chalonge
on the eclipsing spectroscopic binary Algol, and an estimation of the
percentage of binary or multiple stars is given. For the discussion
that follows the historical overview a distinction is made between
close, wide and very wide binaries. Each of these types has its own
particular interest for the study of stellar evolution and the angular
momentum organization of our galaxy. In the last section it is tried
to present a short evaluation of some future developments that are
expected from the study of the different types of binary systems,
and the observational methods used for this study.
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Title: The Synchronization of Binary Components from the Motion
of Starspots
Authors: van't Veer, Frans; Maceroni, Carla
1992LNP...397...85V Altcode: 1992sils.conf...85V
No abstract at ADS
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Title: Statistics of Magnetic Cycles in Late-type Single and Close
Binary Stars
Authors: Maceroni, C.; Bianchini, A.; Rodonó, M.; van't Veer, F.;
Vio, R.
1992LNP...397..303M Altcode: 1992sils.conf..303M
No abstract at ADS
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Title: The dynamical and physical evolution of close solar type
binaries as a consequence of angular momentum loss.
Authors: van't Veer, F.
1992saee.conf....1V Altcode:
Angular momentum loss is the driving force for the dynamical evolution
of close tidally interacting binaries with solar type components. A
description of the different stages of this evolution is given,
and the variation with time of the binary orbit is formulated. The
final single star stage of these binaries is also described and a
first tentative is made to distinguish between ordinary single stars
and coalesced binaries, with particular attention to differences of
the chemical composition of their atmospheres. A short review of the
possible presence of disks of circumstellar material around very close
angular momentum losing binaries is presented.
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Title: The dynamical evolution of G-type main sequence binaries.
Authors: van't Veer, F.; Maceroni, C.
1992btsf.work..237V Altcode: 1992bats.proc..237V
The authors will speak about the dynamical evolution of AMLOSC
binaries. AMLOSC binaries are defined as angular momentum losing
binaries with orbit-spin coupling. They limit theirselves to the
main-sequence group. The AML is produced by stellar winds trapped
by magnetic fields. The OSC may have different origins. The authors
mainly consider the mechanism of turbulent friction in the convective
zone without neglecting however alternative solutions. The components
of AMLOSC binaries continuously approach each other until contact is
reached. The dynamical evolution of the rotation of the components
and the of the orbital revolutuion is given. The comparison between
observations and theory is discussed.
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Title: Surface imaging of W Ursae Majoris contact binaries.
Authors: Maceroni, C.; van't Veer, F.; Vilhu, O.
1991Msngr..66...47M Altcode:
Results of simultaneous spectroscopic and photometric
observations of two southern W UMa systems, AE Phe and YY Eri,
are described. Photometric observations were performed using a CAT
telescope, equipped with a CES spectrograph, a short camera, and CCD,
and an ESO 50-cm telescope. The high-precision spectroscopy was based
on the Doppler imaging method. It is concluded that both systems
show asymmetric perturbations of the light curves. The most evident
feature of this effect is that the maximum following primary minimum
(max I) is brighter than the maximum II. There was similarity between
photometric and spectroscopic maps, especially in reference to the
spot location and temperature distribution.
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Title: The period variations of W Ursae Majoris binaries and their
relation to magnetic activity.
Authors: van't Veer, F.
1991A&A...250...84V Altcode:
The influence of magnetic activity on the period variations of very
close late-type main sequence binaries is studied for W UMa-type
contact systems. In particular, the hypothesis connecting changes
of the inertial and quadrupole moment of the components with period
variations is critically studied and rejected.
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Title: The galactic cluster NGC 188 : W Ursae Majoris contact binaries
as a clueto two separate bursts of star formation.
Authors: Maceroni, C.; van't Veer, F.
1991A&A...248..430M Altcode:
The problem of the unique richness in W UMa binaries of the galactic
cluster NGC 188 is revisited, applying recent results on the dynamical
evolution of close binaries (van't Veer and Maceroni, 1988, 1989;
Maceroni and van't Veer, 1991). It is shown how the presence of seven
contact binaries and the alleged absence of less close ones finds a
straightforward explanation in terms of a scenario developed from the
properties of field solar type close binaries. The present model of
NGC 188 requires: (1) that the dynamical evolution of late-type MS
or solar-type close binaries is governed by the loss and transfer of
angular momentum, (2) that a second burst of star formation has taken
place about 2.5 Gyr ago. This second burst can also explain some other
characteristics of this peculiar cluster, for instance, the presence
of several blue stragglers, which may be the results of the delayed
star formation.
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Title: The evolution and synchronization of angular-momentum-losing
G-type main sequence binaries
Authors: Maceroni, C.; van't Veer, F.
1991A&A...246...91M Altcode:
A new law for rapid rotators is presented. This law is definitely
different from the exponential expressions derived for slow rotators
from cluster members of known age. From a comparison between the
computed and observed synchronization of some well studied binary
systems, the amount of AM transferred from the orbit to the components
is discussed. There is strong evidence that this transfer is greater
than predicted by current theories of tidal interaction.
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Title: The Angular Momentum Evolution of Young and Old Binary
Components
Authors: van't-Veer, F.; Maceroni, C.
1991ASIC..340..167V Altcode: 1991amey.conf..167V
No abstract at ADS
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Title: Magnetic cycles in solar-type single and close binary stars.
Authors: Maceroni, C.; Bianchini, A.; Rodono, M.; van't Veer, F.;
Vio, R.
1990A&A...237..395M Altcode:
A statistical analysis of magnetic cycle periods from different samples
of single and close binary stars is presented. All samples, analyzed by
modern statistical methods, show the same cycle period distribution
at a high confidence level. The total distribution is compatible
with a unimodal function with a peak at about 6 yr. Secondary peaks,
typical of some samples, might be due to statistical fluctuations. A
correlation is also found between spectral type and cycle period, but
apparently no relation exists between the cycle period distribution
and the rotational velocity of the stars.
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Title: A spotted component in the very close late-type binary system
VZ Piscium.
Authors: Maceroni, C.; van Hamme, W.; van't Veer, F.
1990A&A...234..177M Altcode:
The light curve solution of the WUMa B-type binary VZ Psc has been
redetermined. A model with two dark spots on the surface of one of
the components was used. The presence of these spots is suggested by
the variability of the light curve. The new solution yields absolute
dimensions which are in better agreement with the late spectral type
of the two stars. This removes some of the problems with previously
published solutions. The problem of the uniqueness of solutions with
spots is briefly discussed.
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Title: The Evolution of the Period and Synchronization for Close
G-Type MS Binaries
Authors: vant-Veer, F.; Maceroni, C.
1990ASIC..319..321V Altcode: 1990acb..proc..321V
No abstract at ADS
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Title: The A-Type W-Ursae System Aw-Ursae
Authors: Heintze, J. R. W.; Int-Zand, J. J. M.; vant-Veer, F.
1990ASIC..319..331H Altcode: 1990acb..proc..331H
No abstract at ADS
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Title: Do Thermally Decoupled Late Type Contact Binaries Really Exist
Authors: Maceroni, C.; vant-Veer, F.
1990ASIC..319..309M Altcode: 1990acb..proc..309M
No abstract at ADS
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Title: The angular momentum loss for late-type stars.
Authors: van't Veer, F.; Maceroni, C.
1989A&A...220..128V Altcode:
A previously derived power law for the angular momentum loss (AML)
of rapidly rotating tidally coupled binary components is used to
determine the time scales of binary evolution involving AML. The AML
of binary components with spin periods of less than 4 d is shown to be
at least 10 times greater than that expected from the extrapolation of
the rules that can be found for slow rotators, a result which explains
the relatively short approach time (7.5 x 10 to the 8th yr) obtained
for the components of tidally coupled late-type binaries. This result
is also consistent with the relatively short duration of the contact
phase of W UMa binaries (shorter than 1.5 x 10 to the 8th yr) and the
rapid spin-down of very young late type MS stars.
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Title: Book-Review - the Analysis of Starlight - One Hundred and
Fifty Years of Astronomical Spectroscopy
Authors: Hearnshaw, J. B.; van t-Veer, F.
1989SSRv...49..444H Altcode:
No abstract at ADS
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Title: Les binaires de type Algol.
Authors: Heintze, Hans; van't Veer, Frans
1988LAstr.102..528H Altcode:
Various scenarios for the ejection of matter by the primary component
of Algol binaries are possible, depending on the masses of the two
component and on their distance from each other. Algol-type binaries
are characterized by irregularly variable periods. IUE observations
reveal that certain Algols have elevated Al III, Fe III, Si IV, C IV,
and N V ionization levels.
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Title: Etoiles multiples et hiérarchie.
Authors: van't Veer, F.; Durand, P.
1988LAstr.102..506V Altcode:
No abstract at ADS
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Title: Les binaires les plus serrées: W Ursae Majoris.
Authors: Maceroni, Carla; van't Veer, Frans
1988LAstr.102..533M Altcode:
The properties of the components of W UMa binaries are reviewed, and
explanations for their nonperiodic variations are proposed. These
binaries are characterized by equatorial velocities for the two
components of not less than 200 km/s, heterogeneous temperature
distributions, and variable perturbations including starspots and
local reheating in the region of contact. A scenario is proposed in
which losses in angular momentum due to the stellar wind eventually
place the two stars in contact, following which the secondary component
becomes increasingly smaller until the binary becomes a single star.
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Title: The angular momentum loss of rapidly rotating late-type main
sequence binaries
Authors: van't Veer, F.; Maceroni, C.
1988A&A...199..183V Altcode:
Magnetic activity generated in the convective zone is at the origin of
angular momentum loss of late type stars, and is generally accepted as
the explanation for the decay of rotation observed in these stars. The
angular momentum loss can be expressed as a power law of the angular
velocity whose validity is established for equatorial velocities up
to 40 km/s. Synchronized late-type binaries losing angular momentum
will evolve toward smaller orbits and, hence, toward increasing angular
velocities of the components, by virtue of the coupling between spin and
orbital momentum. This effect is used to explain the bimodal character
of the period distribution of close G type binaries. It is also possible
to derive a new power law for the loss of angular momentum of these very
rapidly rotating (up to 200 km/s) tidally coupled binary components.
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Title: How to correct for selection effects the period distribution
of eclipsing binaries.
Authors: Maceroni, C.; van't Veer, F.
1988dcev.conf...11M Altcode:
No abstract at ADS
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Title: Stream models and period variations for contact binaries.
Authors: van't Veer, F.
1988covp.conf...23V Altcode:
The author gives a short discussion of the influence of fixed ideas
haunting the physical models of contact binaries. Some new suggestions
concerning the nature of W UMa type binaries are made.
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Title: Observation et compréhension des étoiles doubles
serrées. Histoire et avenir.
Authors: van't Veer, F.
1988LAstr.102..451V Altcode:
No abstract at ADS
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Title: Bibliography and program notes on close binaries,
No. 46. Material published by September 15, 1987 (in part, by December
15, 1987).
Authors: Cester, B.; Mauder, H.; Olowin, R.; Papoušek, J.; Sarma,
M. B. K.; Scarfe, C. D.; Schulberg, A.; Sistero, R. F.; van't Veer,
F.; Vetešník, M.; Yamasaki, A.; Herczeg, T. J.
1988bpnc...46.....C Altcode:
No abstract at ADS
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Title: Bibliography and program notes on close binaries,
No. 45. Literature surveyed: September 15, 1986 - March 15, 1987.
Authors: Herczeg, T. J.; Cester, B.; Demircan, O.; Mauder, H.; Olowin,
R.; Papousek, J.; Sarma, M. B. K.; Scarfe, C. D.; Schulberg, A.;
Sistero, R. F.; van't Veer, F.; Vetesnik, M.; Yamasaki, A.
1987bpnc...45.....H Altcode:
No abstract at ADS
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Title: Period variations of binary systems as a possible source of
information about motions in the stellar core
Authors: vant Veer, F.
1986A&A...156..181V Altcode:
The author discusses the size of the period variations currently
observed for the W UMa and RS CVn type eclipsing binaries. From a
theoretical discussion, taking into account the different modes of
mass loss and angular momentum loss, he concludes that it is impossible
to believe these mechanisms responsible for all the period variations
observed. On the basis of recent results of solar research he proposes
an alternative mechanism using matter flows in the radiative core of
these synchronously rotating binary components.
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Title: Bibliography and program notes on close binaries,
No. 43. (Material published by March 15, 1986).
Authors: Herczeg, T. J.; Cester, B.; Mauder, H.; Olowin, R.; Papousek,
J.; Sarma, M. B. K.; Scarfe, C. D.; Schulberg, A.; Sistero, R. F.;
van't Veer, F.; Vetesnik, M.; Yamasaki, A.
1986bpnc...43.....H Altcode:
No abstract at ADS
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Title: High Resolution Problems in Astrometry and Spectroscopy of
Binaries and Their Significance for the Progress of Stellar Physics
Authors: van t Veer, F.
1985Ap&SS.110...65V Altcode:
Two centuries were necessary for binaries to become, after having
been unknown and ignored, one of the outstanding subjects of stellar
research. This remarkable evolution has resulted now in the reversed
situation with the painful question, at least for some of us: do
single stars really exist? It is recognized by everybody, that many
essential properties of stars can only be obtained from observations of
close and wide binaries. It is the aim of this contribution to see how
binaries can help us to better understand binaries and single stars,
even if the existence of the latter is not yet definitely confirmed.
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Title: Friedrich Wilhelm Bessel. Un astronome destiné au commerce
(1784 - 1846).
Authors: van't Veer, F.
1985LAstr..99...83V Altcode:
No abstract at ADS
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Title: Bibliography and program notes on close binaries,
No. 41. (Material received by September 15, 1984).
Authors: Herczeg, T. J.; Abhyankar, K. D.; Cester, B.; Hall, D. S.;
Kitamura, M.; Scarfe, C. D.; Schulberg, A.; Sisteró, R. F.; van't
Veer, F.; Vetešnik, M.
1985bpnc...41.....H Altcode:
No abstract at ADS
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Title: Bibliography and program notes on close binaries,
No. 42. (Material received by March 15, 1985).
Authors: Herczeg, T. J.; Abhyankar, K. D.; Cester, B.; Hall, D. S.;
Kitamura, M.; Mauder, H.; Papousek, J.; Scarfe, C. D.; Schulberg,
A.; Sisteró, R. F.; van't Veer, F.; Vetesnik, M.
1985bpnc...42.....H Altcode:
No abstract at ADS
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Title: Young stars in the old galactic cluster NGC 188 ?
Authors: vant Veer, F.
1984A&A...139..477V Altcode:
The author first briefly discusses the age of the oldest known galactic
cluster, according to recently published determinations. The now
definitely established membership of four W UMa type contact binaries
in this cluster is difficult to understand if the age of these stars
is that of the cluster. It appears therefore that these binaries are
much younger and that several episodes of star formation took place
in NGC 188. This conclusion is reached after a new study of the mean
density of the four contact binaries and a critical discussion of the
chemical composition and the mixing length parameter.
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Title: The Magnetic Activity of Rapidly Rotating Solar Type Dwarfs
Authors: vant-Veer, F.
1984apoa.conf..146V Altcode:
For slowly rotating stars of solar type the magnetic activity rapidly
increases with the rotational velocity of the star. The author deduces
from a study of binary frequencies that the activity level of fast
rotating solar-type stars is nearly independent of rotation.
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Title: Bibliography and program notes on close binaries, No. 40,
(Material received by March 15, 1984).
Authors: Herczeg, T. J.; Abhyankar, K. D.; Cester, B.; Hall, D. S.;
Kitamura, M.; Mauder, H.; Scarfe, C. D.; Schulberg, A.; Sisteró,
R. F.; van't Veer, F.; Vetešnik, M.
1984bpnc...40.....H Altcode:
No abstract at ADS
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Title: Bibliography and program notes on close binaries,
No. 38. (Material received by March 15, 1983).
Authors: Herczeg, T. J.; Abhyankar, K. D.; Cester, B.; Hall, D. S.;
Kitamura, M.; Mauder, H.; Scarfe, C. D.; Schulberg, A.; Sisteró,
R. F.; van't Veer, F.; Vetešnik, M.
1983bpnc...38.....H Altcode:
No abstract at ADS
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Title: Why do the Simple Stars Exist
Authors: vant-Veer, F.
1983bist.conf..145V Altcode:
The author explains single stars as the evolutionary product of double
stars and not as the consequence of direct formation in an interstellar
cloud. Tidal coupling combined with intense magnetic fields and strong
stellar winds is the necessary and sufficient condition for binaries
to become single stars.
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Title: A 2.2 Micrometer Light Curve of the Eclipsing Binary VW Cephei
Authors: Lunel, M.; Garnier, R.; Bergeat, J.; van't Veer, F.
1982IBVS.2176....1L Altcode:
No abstract at ADS
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Title: Evolutionary possibilities and impossibilities for solar type
contact binaries in NGC 188
Authors: van t Veer, F.
1982ASSL...98..279V Altcode: 1982IAUCo..69..279V; 1982bmst.proc..279V
Evidence for the occurrence of several epochs of star formation in
the old galactic cluster NGC 188 is discussed, along with possible
relationships between the 4 contact binaries in that cluster. The
contact binaries are all W UMa systems, which comprise 25-30% of all
known late contact type binaries. It is noted that the age of NGC 188
has been calculated to be greater than the normal lifespan of W UMa
binaries. Light curve amplitudes are constructed to place the 4 contact
binaries in group I. It is argued that the stars must have formed after
the cluster, approximately several hundred million years ago. The common
orientations of all 4 binaries between 90-75 deg is cited as evidence
for preferred orbital orientations of binary stars in certain groups.
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Title: The initial mass ratio of solar type contact binaries
Authors: van t Veer, F.
1981A&A....98..213V Altcode:
The initial mass ratio distribution function, which gives the normalized
number of binary objects formed at a given mass ratio, is computed
for solar-type contact binaries (W UMa stars). The initial function is
derived from the present mass ratio distribution function by integrating
backwards in time based on a mass ratio evolution function describing
the variation of the mass ratio with time since the coming into contact
of the components, which is determined by the rate of angular momentum
loss which is in turn determined by the total mass and mass ratio of
the system. All contact binaries produced are found to exhibit initial
mass ratios greater than 0.8, indicating that the components had nearly
equal masses. Implications of the results for RS CVn stars are noted.
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Title: Infrared Light Curves of the Contact Binary 44-IOTA-BOOTIS
Authors: Bergeat, J.; vant-Veer, F.; Lunel, M.; Garnier, R.; Sibille,
F.; Roux, S.
1981A&AS...43..257B Altcode:
No abstract at ADS
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Title: Infrared light curves of the contact binary 44 i Boo.
Authors: Bergeat, J.; vant-Veer, F.; Lunel, M.; Garnier, R.; Sibille,
F.; Roux, S.
1981A&A....94..350B Altcode:
Accurate infrared light curves (λ=2.25μm) are given for the W
UMa type system 44 ι Bootis, three of which were secured within a
single night. The coverage of a period of the variable is made as
complete as possible with typically more than one hundred individual
observations. This program was initiated in an attempt to determine
the source for perturbations of the visible light curves of ι
Bootis published by many authors. It fell short of its aim since
the binary proved to be in a low activity phase of its history at
the time of the observations (1978 March).' Maxima are very nearly
equal and asymmetries of minima are shown to be at a very low level
where they merge in with noise and uncertainties on the atmospheric
correction. On the other hand, Fourier cosine terms which are predicted
by the standard model for close or contact binary, are detected up to
the eighth overtone. The photometric solution of the system is studied
through new multicolour photometric observations (visual binary ADS
9494 whose component A cannot be separated for the moment). We adopt
the spectral energy distribution of a F<SUB>8</SUB>V star for ι Boo
A together with that of a G<SUB>2</SUB>III star for ι Boo (B+ C) and
ΔV= 0.4 mag for the yellow magnitude difference between A and B + C,
which gives the better fit to the observations. Luminosities and radii
of the eclipsing system components are however class V data and they
are strong arguments against the adoption of a K<SUB>2</SUB>V spectral
energy distribution. Expansion of a common low pressure atmosphere
through the inner lagrangian surface is tentatively suggested as a
possible explanation of the luminosity class discrepancy. A forthcoming
paper will be devoted to the determinations of the elements of 44 ι
Bootis (W UMa system) by the method of light curve synthesis.
---------------------------------------------------------
Title: Nauwe dubbelsterren en planetenstelsels.
Authors: van't Veer, F.
1981Zenit...8..403V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the origin and decay of contact binaries.
Authors: van't Veer, F.
1981fsa..symp...89V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar type contact binaries - The initial mass ratio
distribution function
Authors: van t Veer, F.
1980IAUS...88..517V Altcode:
The distribution function of contact binaries at the beginning of
their existence, designated the initial mass ratio function (IMRF), is
investigated using data for the actual mass ratio function (AMRF) and
the dynamical evolution of solar type contact binaries. In addition, a
function which defines the relation between the mass ratio and time for
an arbitrary contact binary, called the mass ratio evolution function
(MREF), is introduced and employed in the IMRF analysis. It is shown
that the majority of newly formed binaries have high mass ratios with
at least 50% of them having a mass ratio value higher than 0.8, and
that most possess nearly equal components at the moment of formation.
---------------------------------------------------------
Title: Reply to the note of Rucinski on the existence of W UMa-type
systems in the cluster Cr 359.
Authors: van't Veer, F.
1980AcA....30..381V Altcode:
Rucinski's note is a logical reaction on my somewhat speculative and
controversial paper (van't Veer 1975) concerning the age of the W
Ursae Majoris stars. I already agreed therein that my arguments were
not strong enough to convince everybody, and I am glad to see that
a new point of view is given on the evolutionary status of contact
binaries. However I must immediately say that Rucinski's arguments do
not make me abandon my conclusions and a rediscussion of the problem
now, 5 years later, makes me still believe my original conception. There
are 4 important questions and I should like to comment upon in order:
(1) - Is Cr 359 really a young physical association? (2) - If so,
are the observed W UMa binaries members of this association? (3) -
If not can we explain them from the generally adopted estimates of
their space density? (4) - What are the implications of the answer
on the preceding questions, on our understanding of the evolutionary
history of W UMa stars?
---------------------------------------------------------
Title: The angular momentum controlled evolution of solar type
contact binaries.
Authors: vant Veer, F.
1979A&A....80..287V Altcode:
The paper deals with the dynamical evolution of contact binaries of
solar spectral type. An attempt is made to give an evolutionary model
which takes into account the recent observational results especially
concerning period changes, mass ratios, and contact parameters on
one hand, and precise computations of the geometrical model and the
different contributions to the angular momentum on the other hand. The
proposed model is based on the dynamical evolution caused by stellar
winds with emphasis placed on the coupling of axial rotation and orbital
motion of components. The lifetime of the contact binaries related to
the amount of angular momentum loss is analyzed.
---------------------------------------------------------
Title: The mass ratio function of W UMa type binaries.
Authors: van't Veer, F.
1978A&A....70...91V Altcode:
Summary. Mass ratios for W UMa type binaries may be determined
from radial velocity curves or photometric light curves. The
frequency distribution of these mass ratios (mass ratio function)
is one of the crucial tests for evolutionary studies of contact
binaries. Observational selection effects play an important role in
the determination of the mass ratio function. In the present paper
an attempt is made to list these selection effects and to correct
them. The resulting mass ratio function is given in Figure 2. Key ords:
contact binaries - W UMa type stars - mass ratio
---------------------------------------------------------
Title: Perte de masse des étoiles binaires serrées.
Authors: van't Veer, F.
1977pdm..book.....V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Young W UMa Binaries and the Interaction with Their Environment
Authors: van't Veer, F.
1977ivsw.conf..388V Altcode: 1977IAUCo..42..388V
No abstract at ADS
---------------------------------------------------------
Title: The Evolution of Contact Binaries
Authors: van't Veer, F.
1976IAUS...73..343V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The age of the W Ursae Majoris stars.
Authors: vant Veer, F.
1975A&A....44..437V Altcode:
Consequences are discussed for the hypothesis that more than 50% of
contact binaries are formed by a fission process of the Jeans-Roxburgh
type. Some arguments are presented which support the hypothesis of
the fission process from W UMa stars which are members of galactic
clusters. The problem of alignment of the axes of rotation in young
galactic clusters is examined, and the detectability of W UMa stars
is discussed. It is concluded that stars of young clusters generally
have a preferential orientation of their rotation axes, which need
not coincide with the general orientation of the galactic disk.
---------------------------------------------------------
Title: The Frequency of Contact Binaries and Its Consequence on
Their Evolution
Authors: van't Veer, F.
1975A&A....40..167V Altcode:
Summary. I. We try to estimate the number of contact binaries (CB)
limited to a certain apparent magnitude. The number of CB's must be
deduced from the number of observed W UMa type eclipsing binaries
(EW). In this deduction two selection effects are involved. It is
difficult to detect EW's with: I) a low inclination angle and hence
a weak amplitude Arn= mmax - mmin, or 2) a weak apparent magnitude
mmax. We corrected the first effect, by calculating the distribution
N(A m) we would observe if the effect was absent and by comparing
it to the really observed distribution (Table 1). The second effect
was corrected by comparing the increase with mmax of the number of
observed EW's with the theoretically expected increase corrected for
interstellar absorption (Table 2). We conclude that 1/500th of the
counted stars is a CB. II. In order to find the percentage of CB's among
the dwarf stars of different spectral type, we used the EW's which are
classified spectroscopically, and extrapolated this distribution for
the whole sample of CB's (Table 3). For the spectral and luminosity
distribution of the totality of counted stars use was made of the
numerous publications on stellar statistics. Tables 4 and 5 summarize
the deduced spectral and dwarf star distribution for stars until I 3
, taking into account the spatial distribution of the CB's. III. The
third paragraph contains a discussion on the precision which can be
obtained by using the above mentioned procedure. We further deduce
that I to 2 % of the G dwarfs is suspected to be CB. For the F dwarfs
the percentages are a little lower 0.5 to 1.5. We finally explain
the reason why these percentages are significantly higher than those
found by others, and emphasize the fact that the percentage would be
even higher if we limited our statistics to the F 8 to G 2 dwarfs,
because of their outstanding preponderance among EW's. IV. The main
sequence lifetime of a F 8-G 2 star is about 5 10 years. The lifetime
of a CB is more difficult to estimate, but from observational and
theoretical considerations one can conclude that it must probably be
relatively short, of the order of years. If this conclusion is correct,
we find that (almost) all solar type dwarfs must be CB's during about
1/100th of their lifetime. After a short review of the current theories
concerning the formation of CB's we adopt the fission theory as having
the best chance. The end of binary life is more difficult to imagine
physically and clear ideas on this ultimate process are fully lacking in
the literature. V We found it tempting to postulate that the secundary
component is transformed in a protoplanetary cloud having the primary
star as central condensation. The next step could be the formation
of the planets and satellites out of this orbiting material. We are
not yet fully convinced that this evolutionary way is the right one,
but we propose it as a hypothesis which can, at the same time, suggest
the existence of the solar planetary system. VI. In this last section
we briefly discuss the following points: 1) A distinction must be
made between early and late type CB's. It is probable that these two
classes do not follow the same evolution and do not have the same life
time. 2) If our conclusions are true the CB's must be young stars and
so the study of their presence in galactic clusters is important. 3)
Our knowledge on the angular momentum of the splitting protostars,
the CB's and the solar system does not contradict the suggested
evolution. Key words: contact binaries stellar statistics stellar
evolution planetary systems
---------------------------------------------------------
Title: The eclipsing contact binary VW Cephei.
Authors: van't Veer, F.
1973A&A....26..357V Altcode:
Summary. This study of the eclipsing contact binary VW Cep is mainly
based on the observational material collected by Kwee (1966a, b),
during the years 1957-1959. New minimum times are calculated according
to different polynomial solutions for primary and secondary minima. The
so-called Kwee-effect is interpreted as the consequence of gas flows
from regions in the neighbourhood of the first lagrangian point to
the outer envelope of the system. The long term period variation is
briefly discussed. Key words: eclipsing binaries - contact binaries -
period changes of double stars - gasstreams
---------------------------------------------------------
Title: A statistical method for the determination of the rate of
changes of period for eclipsing binaries.
Authors: van't Veer, F.
1972A&A....20..131V Altcode:
Summary. A statistical treatment for the quantitative analysis of
period changes AP for eclipsing binaries is given. The method can be
applied to a series of measurements of minima times. It allows one to
determine the rate of period change AP/At and also gives a test of the
reality of sudden period changes of contact binaries. The method can
only be applied to the best observed stars. Examples are given for SW
Lac and 44i Boo. Key words: eclipsing binaries - contact binaries -
period changes of double stars
---------------------------------------------------------
Title: Mass flow and period changes of contact binaries.
Authors: van't Veer, F.
1972A&A....19..337V Altcode:
Period changes of eclipsing contact binaries are interpreted as the
consequence of mass flows from the flrst and second lagrangian points
L1 and L2. The measured values of the rate of period change dP/dt
are related to the rate of mass outflow dm/dt. A distinction is made
between binaries with a well developed common envelope and binaries for
which such an envelope is supposed to be absent or is at least still
capable of absorbing large quantities of stellar matter. The following
possibilities of material flow are studied separately: 1.From L1 to
the envelope, 2.fro n L1 or L2 to outer space, 3.from one component
to the other. Formulae are given for the rate of increase or decrease
of the orbital radius and the period as a function of the rate of mass
transport and the mass ratio of the components in a certain number of
idealized cases. The stellar orbits are supposed to be circular and the
angnlar momentum due to the (synchronized) stellar rotation is taken
into account. A short discussion of some evolutionary aspects is also
given. Key words: contact binaries - change of period of double stars -
mass ejection
---------------------------------------------------------
Title: Sudden changes in the period of the eclipsing contact binary
44i Bootis.
Authors: Bergeat, J.; Lunel, M.; Sibille, F.; van't Veer, F.
1972A&A....17..215B Altcode:
From photeelectric observations of 44 i Boo obtained during the years
1969-1971, we made 23 determinations of the times of conjunction from
the observed minima. A critical analysis of the data combined with
those published by other observers permitted us to conclude that this
eclipsing system suffers periodic changes of the Period. The general
aspect of the light curve confirms the existence of active and quiet
periods. The interval between sudden period changes is of the order
of 10 years. Key words: photometry - eclipsing binaries - contact
binaries - period changes - mass ejection
---------------------------------------------------------
Title: The spectral type of the brightest component of the triple
system 44 i Bootis.
Authors: van't Veer, F.
1971A&A....11..197V Altcode:
The spectral type of the slowly revolving brightest component of the
triple system 44 i Boo was studied using spectra taken at the Dominion
Astrophysical Observatory Victoria in 1922. At that time the separation
between the brightest component and the two others (which form an
eclipsing contact binary) was sufficiently large, so that separate
spectra could be taken. This study confirms the hypothesis suggested
by a photometric study in eight colours of the eclipsing system in a
previous paper (Kurpinska and van `t Veer, 1970) according to which
the spectral type of the third and brightest component is earlier (F5V)
than previously supposed (G1V). One can conclude that the conspicuous
reddening of 44 i Boo during the maxima is not an intrinsic phenomenon
of the eclipsing system but merely due to the presence of the third
component. Key words: eclipsing binaries - spectral classffication -
triple systems
---------------------------------------------------------
Title: Eight-colour photometric study of the eclipsing binary
44i Bootis.
Authors: Kurpinska, M.; van't Veer, F.
1970A&A.....4..253K Altcode:
Eight-colour photometric observations of the eclipsing system 44 i
Bootis have been analysed. This well known triple system is composed
of an eclipsing contact binary p and a brighter third companion o'. In
the integrated light of the system cc + p the observations reveal
a remarkable behaviour of the colour-differences between the maxima
and the minima. Th the range 4000-3500 both minima are redder than the
maximum; in the visual wavelength region ( 6000-4000) however we find a
reddened maximum (Fig. 4 and 5). For the other known eclipsing contact
binaries showing colour-differences between the maxima and minima
one always finds on the contrary the nnnimum to be redder (up till A
m =0,05) than the maximum in the visible colour- range. Th order to
explain this phenomenon as due to the presence of the third companion
we computed the colour- variation theoretically for a certain number
of combinations of the initial data. Concerning these initial data
we have to estimate the individual spectral types Sp and Sp and the
intrinsic colour-variation of the binary i. e. the colour-variation
we should observe if the third companion were not present. The mean
spectral type Sp of the system is generally given as G 2, so that we
can use the combinations G 1- G 3, G 0- G 4 and so on. The intrinsic
colour-variation between maximum and minimum light of the binary,
deduced from other systems of the same type (Table 4), should be
about 0m.02. The basic photometric equations in our computations
are given by the formulae 1-5. When we also take into account the
difference of the Balmer discontinuity of the two spectra Sp and Sp,t
it is possible indeed to adjust the different parameters in such a way
that the observed colour-variation is fully explained in the limit of
observational errors, the most probable solution being Sp = F 9, Sp =
G 4 and an intrinsic reddening less than 0 .01. We can also admit a
more pronounced reddening of 0 .02, but in that case the corresponding
spectral types would be Sp = F 7 and Sp = G 5 which seems a little
excessive. Th every case the strange colour behaviour of 44 i Boo during
the minima can be explained by the presence of a third companion when
the Balmer jump is taken into account and it does not seem necessary to
invoke a special physical constitution of the system. From the exact
determination of the times of minima we could confirm that the period
of the binary has remained unchanged during the last 6 years. The
secondary maximum shows a displacement in phase of A = 0.014 + 0.003
in comparison with the primary minimum. Key words: eclipsing binary -
light-curve - period - colour-variation - colour-gradient
---------------------------------------------------------
Title: Modèles empiriques d'atmosphères stellaires. I. Introduction
et première application
Authors: van't Veer, F.
1966AnAp...29....7V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Modèles empiriques d'atmosphères stellaires. III. Comparaison
des différents modèles pour les taches solaires
Authors: van't Veer, F.
1966AnAp...29..223V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: L'automatisation de la classification spectrale
tri-dimensionnelle de Paris
Authors: van't Veer, F.
1966AnAp...29..293V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Modèles empiriques d'atmosphères stellaires. II. Étude
statistique, modèle d'une tache solaire
Authors: van't Veer, F.
1966AnAp...29..119V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Les taches solaires
Authors: van't Veer, F.
1965LAstr..79..265V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: La pression gazeuse dans les taches solaires
Authors: van't Veer, F.
1965AnAp...28.1026V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectroscopic observations of sunspots
Authors: van't Veer, F.
1964susp.conf..150V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Un nouveau modèle des taches solaires
Authors: van't Veer, F.
1963AnAp...26..185V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Die Bestimmung des Gasdrucks in Sonnenflecken aus
Flügelstärken von Fraunhoferlinien II. Mit 5 Textabbildungen
Authors: van't Veer, F.
1962ZA.....55..208V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Remarques et critiques sur l'interpretation des courbes de
lumiere des etoiles a eclipse du type W UMa.
Authors: van't Veer, F.
1962JO.....45....7V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Remarques et critiques sur l'interprétation des courbes de
lumière des étoiles variables à éclipses du type W Ursae Majoris
Authors: van't Veer, F.
1962JO.....45....6V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Die Bestimmung des Gasdrucks in Sonnenflecken aus
Flügelstärken von Fraunhoferlinien
Authors: van't Veer, Frans
1961VeGoe...7..345V Altcode:
The wings of five selected strong and medium strong Fraunhofer lines are
studied in the umbra of sunspots and in the undisturbed photosphere at
the same distance from the limb. It appears to be possible to interpret
the ratio c/c* of the strengths of the wings in photosphere an sunspot
as a measure for the ratio of the gas pressure if the temperature
model is known. For the two spots studied in this paper we obtained
coherent results from the five Magnesium- and Iron lines. On the basis
of a constand difference ΔΘ = 0,26α pressure model is derived from
a sunspot with a standard area of 80.10&sup-6; hemispheres. The
model is given in table 6. For equal optical depths the gas pressure
in the sunspot is somewhat lower than in the photosphere while the
transparency is greater and decreasing less rapidly with increasing
depth. A discussion of the influence of the magnetic field in the
spots is given. The effect of scattered light of the photosphere on
the strength of the wings has been estimated.
---------------------------------------------------------
Title: Die Bestimmung des Gasdrucks in Sonnenflecken aus
Flügelstärken von Fraunhoferlinien. Mit 3 Textabbildungen
Authors: van't Veer, Frans
1961ZA.....52..165V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: L'assombrissement centre-bord des etoiles.
Authors: van't Veer, F.
1960acbe.book.....V Altcode: 1960QB4.U8l14p3....
No abstract at ADS
---------------------------------------------------------
Title: Book Reviews: Discussion of Short-lived Solar Radio Transients
Authors: de Jager, C.; van't Veer, F.
1959IrAJ....5..158D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A discussion of short-lived solar radio transients at 200 Mc/s
Authors: de Jager, Cornelis; van't Veer, F.
1958dsls.book.....D Altcode: 1958QB4.U8l14p1....
No abstract at ADS
---------------------------------------------------------
Title: A discussion of short-lived solar radio transients at 200 Mc/s
Authors: de Jager, C.; van't Veer, F.
1958VKAWA..21....1D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Some properties of solar radio-transients on fast 200
Mc./s. records
Authors: de Jager, C.; van't Veer, F.
1957IAUS....4..366D Altcode:
No abstract at ADS
