27 research outputs found
The orbital elements and physical properties of the eclipsing binary BD+36 3317, a probable member of Lyr cluster
Context. The fact that eclipsing binaries belong to a stellar group is
useful, because the former can be used to estimate distance and additional
properties of the latter, and vice versa. Aims. Our goal is to analyse new
spectroscopic observations of BD along with the photometric
observations from the literature and, for the first time, to derive all basic
physical properties of this binary. We aim to find out whether the binary is
indeed a member of the Lyr open cluster. Methods. The spectra were
reduced using the IRAF program and the radial velocities were measured with the
program SPEFO. The line spectra of both components were disentangled with the
program KOREL and compared to a grid of synthetic spectra. The final combined
radial-velocity and photometric solution was obtained with the program PHOEBE.
Results. We obtained the following physical elements of BD: , , , , ,
. We derived the effective temperatures
K, K. Both components
are located close to ZAMS in the Hertzsprung-Russell (HR) diagram and their
masses and radii are consistent with the predictions of stellar evolutionary
models. Our results imply the average distance to the system d = pc.
We re-investigated the membership of BD in the Lyr
cluster and confirmed it. The distance to BD, given above,
therefore represents an accurate estimate of the true distance for Lyr
cluster. Conclusions. The reality of the Lyr cluster and the cluster
membership of BD have been reinforced.Comment: 10 pages, 7 figures. Accepted for publication in A&
HD 152246 - a new high-mass triple system and its basic properties
Analyses of multi-epoch, high-resolution (R ~ 50.000) optical spectra of the
O-type star HD 152246 (O9 IV according to the most recent classification),
complemented by a limited number of earlier published radial velocities, led to
the finding that the object is a hierarchical triple system, where a close
inner pair (Ba-Bb) with a slightly eccentric orbit (e = 0.11) and a period of
6.0049 days revolves in a 470-day highly eccentric orbit (e = 0.865) with
another massive and brighter component A. The mass ratio of the inner system
must be low since we were unable to find any traces of the secondary spectrum.
The mass ratio A/(Ba+Bb) is 0.89. The outer system has recently been resolved
using long-baseline interferometry on three occasions. The interferometry
confirms the spectroscopic results and specifies elements of the system. Our
orbital solutions, including the combined radial-velocity and interferometric
solution indicate an orbital inclination of the outer orbit of 112{\deg} and
stellar masses of 20.4 and 22.8 solar masses. We also disentangled the spectra
of components A and Ba and compare them to synthetic spectra from two
independent programmes, TLUSTY and FASTWIND. In either case, the fit was not
satisfactory and we postpone a better determination of the system properties
for a future study, after obtaining observations during the periastron passage
of the outer orbit (the nearest chance being March 2015). For the moment, we
can only conclude that component A is an O9 IV star with v*sin(i) = 210 +\- 10
km/s and effective temperature of 33000 +\- 500 K, while component Ba is an O9
V object with v*sin(i) = 65 +/- 3 km/s and T_eff = 33600 +\- 600 K.Comment: 9 pages, 6 figures, accepted for publication in Astronomy and
Astrophysic
Improved model of the triple system V746 Cas that has a bipolar magnetic field associated with the tertiary
V746 Cas is known to be a triple system composed of a close binary with an
alternatively reported period of either 25.4d or 27.8d and a third component in
a 62000d orbit. The object was also reported to exhibit multiperiodic light
variations with periods from 0.83d to 2.50d, on the basis of which it was
classified as a slowly pulsating B star. Interest in further investigation of
this system was raised by the detection of a variable magnetic field. Analysing
spectra from four instruments, earlier published radial velocities, and several
sets of photometric observations, we arrived at the following conclusions: (1)
The optical spectrum is dominated by the lines of the B-type primary
(Teff1~16500(100) K), contributing 70% of the light in the optical region, and
a slightly cooler B tertiary (Teff3~13620(150) K). The lines of the low-mass
secondary are below our detection threshold; we estimate that it could be a
normal A or F star. (2) We resolved the ambiguity in the value of the inner
binary period and arrived at a linear ephemeris of T_super.conj.=HJD
2443838.78(81)+25.41569(42)xE. (3) The intensity of the magnetic field
undergoes a~sinusoidal variation in phase with one of the known photometric
periods, namely 2.503867(19)d, which we identify with the rotational period of
the tertiary. (4) The second photometric 1.0649524(40)d period is identified
with the rotational period of the B-type primary, but this interpretation is
much less certain and needs further verification. (5) If our interpretation of
photometric periods is confirmed, the classification of the object as a slowly
pulsating B star should be revised. (6) Applying an N-body model to different
types of available observational data, we constrain the orbital inclination of
the inner orbit to ~60 deg to 85 deg even in the absence of eclipses, and
estimate the probable properties of the triple system and its components.Comment: Accepted for publication in Astronomy and Astrophysic
Revised physical elements of the astrophysically important O9.5+O9.5V eclipsing binary system Y Cyg
Thanks to its long and rich observational history and rapid apsidal motion,
the massive eclipsing binary Y Cyg represents one of the cornestones to
critical tests of stellar evolution theory for massive stars. Yet, the
determination of the basic physical properties is less accurate than it could
be given the existing number of spectral and photometric observations. Our goal
is to analyze all these data simultaneously with the new dedicated series of
our own spectral and photometric observations from observatories widely
separated in longitude. We obtained new series of UBV observations at three
observatories separated in local time to obtain complete light curves of Y Cyg
for its orbital period close to 3 days. This new photometry was reduced and
carefully transformed to the standard UBV system using the HEC22 program. We
also obtained new series of red spectra secured at two observatories and
re-analyzed earlier obtained blue electronic spectra. Our analyses provide the
most accurate so far published value of the apsidal period of 47.805 +/- 0.030
yrs and the following physical elements: M1=17.72+/-0.35$ Msun, M2=17.73+/-0.30
Msun, R1=5.785+/-0.091 Rsun, and R2=5.816+/-0.063 Rsun. The disentangling thus
resulted in the masses, which are somewhat higher than all previous
determinations and virtually the same for both stars, while the light curve
implies a slighly higher radius and luminosity for star 2. The above empirical
values imply the logarithm of the internal structure constant log k2 = -1.937.
A comparison with Claret's stellar interior models implies an age close to 2
millions yrs for both stars. The claimed accuracy of modern element
determination of 1-2 per cent seems still a bit too optimistic and obtaining
new high-dispersion and high-resolution spectra is desirable.Comment: 13 pages; accepted for publication in Astronomy and Astrophysic
Properties and nature of Be stars 30. Reliable physical properties of a semi-detached B9.5e+G8III binary BR CMi = HD 61273 compared to those of other well studied semi-detached emission-line binaries
Reliable determination of the basic physical properties of hot emission-line
binaries with Roche-lobe filling secondaries is important for developing the
theory of mass exchange in binaries. It is a very hard task, however, which is
complicated by the presence of circumstellar matter in these systems. So far,
only a small number of systems with accurate values of component masses, radii,
and other properties are known. Here, we report the first detailed study of a
new representative of this class of binaries, BR CMi, based on the analysis of
radial velocities and multichannel photometry from several observatories, and
compare its physical properties with those for other well-studied systems. BR
CMi is an ellipsoidal variable seen under an intermediate orbital inclination
of ~51 degrees, and it has an orbital period of 12.919059(15) d and a circular
orbit. We used the disentangled component spectra to estimate the effective
temperatures 9500(200) K and 4655(50) K by comparing them with model spectra.
They correspond to spectral types B9.5e and G8III. We also used the
disentangled spectra of both binary components as templates for the 2-D
cross-correlation to obtain accurate RVs and a reliable orbital solution. Some
evidence of a secular period increase at a rate of 1.1+/-0.5 s per year was
found. This, together with a very low mass ratio of 0.06 and a normal mass and
radius of the mass gaining component, indicates that BR CMi is in a slow phase
of the mass exchange after the mass-ratio reversal. It thus belongs to a still
poorly populated subgroup of Be stars for which the origin of Balmer emission
lines is safely explained as a consequence of mass transfer between the binary
components.Comment: 17 pages, 5 figures, accepted for publication in Astronomy and
Astrophysics. appears in Astronomy and Astrophysics 201
Properties and nature of Be stars: 29. Orbital and long-term spectral variations of \gamma\ Cassiopei\ae
A detailed analysis of more than 800 electronic high-resolution spectra of
gamma Cas, which were obtained during a time interval of over 6000 days (16.84
yrs) at several observatories, documents the smooth variations in the density
and/or extend of its circumstellar envelope. We found a clear anticorrelation
between the peak intensity and FWHM of the H alpha emission, which seems to
agree with recent models of such emission lines. The main result of this study
is a confirmation of the binary nature of the object, determination of a
reliable linear ephemeris T_{min.RV} = HJD (2452081.90.6) +
(203.520.08)*E, and a rather definitive set of orbital elements. We
clearly demonstrated that the orbit is circular within the limits of accuracy
of our measurements and has a semi-amplitude of radial-velocity curve of
4.300.09 (km/s). No trace of the low-mass secondary was found. The time
distribution of our spectra does not allow a reliable investigation of rapid
spectral variations, which are undoubtedly present in the spectra. We postpone
this investigation for a future study, based on series of dedicated whole-night
spectral observations
Properties and nature of Be stars: 27. Orbital and recent long-term variations of the Pleiades Be star Pleione = BU Tauri
Radial-velocity variations of the H-alpha emission measured on the steep
wings of the H-alpha line, prewhitened for the long-time changes, vary
periodically with a period of (218.025 +/- 0.022)d, confirming the suspected
binary nature of the bright Be star Pleione, a member of the Pleiades cluster.
The orbit seems to have a high eccentricity over 0.7, but we also briefly
discuss the possibility that the true orbit is circular and that the
eccentricity is spurious owing to the phase-dependent effects of the
circumstellar matter. The projected angular separation of the spectroscopic
orbit is large enough to allow the detection of the binary with large optical
interferometers, provided the magnitude difference primary - secondary is not
too large. Since our data cover the onset of a new shell phase up to
development of a metallic shell spectrum, we also briefly discuss the recent
long-term changes. We confirm the formation of a new envelope, coexisting with
the previous one, at the onset of the new shell phase. We find that the full
width at half maximum of the H-alpha profile has been decreasing with time for
both envelopes. In this connection, we briefly discuss Hirata's hypothesis of
precessing gaseous disk and possible alternative scenarios of the observed
long-term changes
Yet Another Spectro-Interferometric Study of The Gas Distribution in The Enigmatic Semi-Detached Binary
The majority of close binaries undergo episodes of mass transfer between their components, which completely change their further evolution. Simulations and observations agree that the mass transfer has two phases: i) short and rapid one, and ii) long and slow one. The bulk of the mass is likely exchanged during the rapid phase, but due to its shortness, systems undergoing this phase are rare, but they hold the key to understanding of the process. One system that is either undergoing the rapid mass transfer phase or is in a transient phase between the two phases is β Lyrae. Our goal is to map the distribution of circumstellar gas in the system. To achieve it, a series of spectro-interferometric observations acquired with the optical instrument VEGA/CHARA are investigated. Here we present our tools and preliminary results of our analysis
Unique sextuple system: 65 Ursae Majoris
Context. The study of stellar multiple systems provides us with important information about the stellar formation processes and can help us to estimate the multiplicity fraction in the Galaxy. 65 UMa belongs to a rather small group of stellar systems of higher multiplicity, whose inner and outer orbits are well-known. This allows us to study the long-term stability and evolution of the orbits in these systems.
Aims. We obtained new photometric and spectroscopic data that when combined with interferometric data enables us to analyze the system 65 UMa and determine its basic physical properties.
Methods. We perform a combined analysis of the light and radial velocity curves, as well as the period variation by studying the times of the minima and the interferometric orbit. A disentangling technique is used to perform the spectra decomposition. This combined approach allows us to study the long-term period changes in the system for the first time, identifying the period variation due to the motion on the visual orbit, in addition to some short-term modulation.
Results. We find that the system contains one more component, hence we tread it as a sextuple hierarchical system. The most inner pair of components consists of an eclipsing binary orbiting around a barycenter on a circular orbit, both components being almost identical of spectral type about A7. This pair orbits on an eccentric orbit around a barycenter, and the third component orbits with a period of about 640 days. This motion is reflected in the period variation in the minima times of the eclipsing pair, as well as in the radial velocities of the primary, secondary, and tertiary components. Moreover, this system orbits around a barycenter with the distant component resolved interferometrically, whose period is of about 118 years. Two more distant components (4′′ and 63′′) are also probably gravitationally bound to the system. The nodal period of the eclipsing-pair orbit is on the order of only a few centuries, which makes this system even more interesting for a future prospective detection of changing the depths of minima.
Conclusions. We identify a unique solution of the system 65 UMa, decomposing the individual components and even shifting the system to higher multiplicity. The study of this kind of multiple can help us to understand the origin of stellar systems. Besides 65 UMa, only another 11 sextuple systems have been studied