We confirmed the binary nature of the Be star 7 Vul, derived a more accurate spectroscopic orbit with an orbital period of 69
.
d
4212±0
.
d
0034, and improved the knowledge of the basic physical ...elements of the system. Analyzing available photometry and the strength of the H
α
emission, we also document the long-term spectral variations of the Be primary. In addition, we confirmed rapid light changes with a period of 0
.
d
5592, which is comparable to the expected rotational period of the Be primary, but note that its amplitude and possibly its period vary with time. We were able to disentangle only the He
I
6678 Å line of the secondary, which could support our tentative conclusion that the secondary appears to be a hot subdwarf. A search for this object in high-dispersion far-UV spectra could provide confirmation. Probable masses of the binary components are (6 ± 1)
⊙
N
and (0.6 ± 0.1)
⊙
N
. If the presence of a hot subdwarf is firmly confirmed, 7 Vul might be identified as a rare object with a B4-B5 primary; all Be + hot subdwarf systems found so far contain B0-B3 primaries.
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The complex binary system
β
Lyr A has an extensive observational dataset: light curves (from far UV to far IR), interferometric squared visibility, closure phase, triple product measurements, ...spectral-energy distribution, high-resolution spectroscopy, differential visibility amplitude, and also a differential phase. In particular, we used spectra from the Ondřejov 2m telescope from 2013 to 2015 to measure the emission in H
α
, He
I
, Si
II
, Ne
I
, or C
II
lines, and differential interferometry by CHARA/VEGA from the 2013 campaign to measure wavelength-dependent sizes across H
α
and He
I
6678. This allowed us to constrain not only optically thick objects (primary, secondary, accretion disc), but also optically thin objects (disc atmosphere, jets, shell). We extended our modelling tool, Pyshellspec (based on Shellspec; a 1D local thermodynamical equilibrium radiative transfer code), to include all new observables, to compute differential visibilities/phases, to perform a Doppler tomography, and to determine a joint
χ
2
metric. After an optimisation of 38 free parameters, we derived a robust model of the
β
Lyr A system. According to the model, the emission is formed in an extended atmosphere of the disc, two perpendicular jets expanding at ∼700 km s
−1
, and a symmetric shell with the radius ∼70
R
⊙
. The spectroscopy indicates a low abundance of carbon, 10
−2
of the solar value. We also quantified systematic differences between datasets, and we discuss here alternative models with higher resolutions, additional asymmetries, or He-rich abundances.
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δ
Orionis is the closest massive multiple stellar system and one of the brightest members of the Orion OB association. The primary (Aa1) is a unique evolved O star. In this work, we applied a ...two-step disentangling method to a series of spectra in the blue region (430–450 nm), and we detected spectral lines of the secondary (Aa2). For the first time, we were able to constrain the orbit of the tertiary (Ab) – to 55 450 d or 152 yr – using variable
γ
velocities and new speckle interferometric measurements, which have been published in the Washington Double Star Catalogue. In addition, the
Gaia
DR3 parallax of the faint component (Ca+Cb) constrains the distance of the system to (381 ± 8) pc, which is just in the centre of the Orion OB1b association, at (382 ± 1) pc. Consequently, we found that the component masses according to the three-body model are 17.8, 8.5, and 8.7
M
⊙
, for Aa1, Aa2, and Ab, respectively, with the uncertainties of the order of 1
M
⊙
. We used new photometry from the BRITE satellites together with astrometry, radial velocities, eclipse timings, eclipse duration, spectral line profiles, and spectral energy distribution to refine radiative properties. The components, classified as O9.5 II + B2 V + B0 IV, have radii of 13.1, 4.1, and 12.0
R
⊙
, which means that
δ
Ori A is a pre-mass-transfer object. The frequency of 0.478 cycles per day, known from the Fourier analysis of the residual light curve and X-ray observations, was identified as the rotation frequency of the tertiary.
δ
Ori could be related to other bright stars in Orion, in particular,
ζ
Ori, which has a similar architecture, or
ε
Ori, which is a single supergiant, and possibly a post-mass-transfer object.
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The hot nine-component system HD 93206, which contains a gravitationally bounded eclipsing Ac1+Ac2 binary (P = 5.9987 d) and a spectroscopic Aa1+Aa2 (P = 20.734 d) binary can provide important ...insights into the origin and evolution of massive stars. Using archival and new spectra, and a rich collection of ground-based and space photometric observations, we carried out a detailed study of this object. We provide a much improved description of both short orbits and a good estimate of the mutual period of both binaries of about 14 500 d (i.e. 40 years). For the first time, we detected weak lines of the fainter component of the 6.0 d eclipsing binary in the optical region of the spectrum, measured their radial velocities, and derived a mass ratio of MAc2/MAc1 = 1.29, which is the opposite of what was estimated from the International Ultraviolet explorer (IUE) spectra. We confirm that the eclipsing subsystem Ac is semi-detached and is therefore in a phase of large-scale mass transfer between its components. The Roche-lobe filling and spectroscopically brighter component Ac1 is the less massive of the two and is eclipsed in the secondary minimum. We show that the bulk of the Hα emission, so far believed to be associated with the eclipsing system, moves with the primary O9.7 I component Aa1 of the 20.73 d spectroscopic binary. However, the weak emission in the higher Balmer lines seems to be associated with the accretion disc around component Ac2. We demonstrate that accurate masses and other basic physical properties including the distance of this unique system can be obtained but require a more sophisticated modelling. A first step in this direction is presented in the accompanying Paper II (Brož et al.).
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Abstract
Bright Be star
β
CMi has been identified as a nonradial pulsator on the basis of space photometry with the
Microvariability and Oscillations of Stars
(
MOST
) satellite and also as a ...single-line spectroscopic binary with a period of 170.ͩ4. The purpose of this study is to re-examine both these findings using numerous electronic spectra from the Dominion Astrophysical Observatory, Ondřejov Observatory, Universitätssterwarte Bochum, archival electronic spectra from several observatories, as well as the original
MOST
satellite photometry. We measured the radial velocity of the outer wings of the double H
α
emission in all spectra at our disposal, and were not able to confirm significant radial-velocity changes. We also discuss the problems related to the detection of very small radial-velocity changes and conclude that while it is still possible that the star is a spectroscopic binary, there is currently no convincing proof of it from the radial-velocity measurements. Wavelet analysis of the
MOST
photometry shows that there is only one persistent (and perhaps slightly variable) periodicity of 0.ͩ617 of the light variations, with a double-wave light curve; all other short periods having only transient character. Our suggestion that this dominant period is the star’s rotational period agrees with the estimated stellar radius, projected rotational velocity, and with the orbital inclination derived by two teams of investigators. New spectral observations obtained in the whole-night series would be needed to find out whether some possibly real, very small radial-velocity changes cannot, in fact, be due to rapid line-profile changes.
Analyses of 13 FEROS spectra from the ESO archive and 617 V-band photometric observations from the ASAS3 database allowed us to demonstrate that HD 165246 is a double-lined spectroscopic binary. As ...an earlier finding revealed, HD 165246 is also an eclipsing system. We were able to derive consistent orbital and light-curve solutions and all basic physical properties of the system. The period of this O8 V + B7 V binary is 4\hbox{$\fd$}.d592706 and the semiamplitudes of the radial-velocity curves are K1 = 55.5 km s-1 and K2 = 321 km s-1. As the mass ratio is small (0.173), the secondary lines cannot be seen directly in the spectra; however the application of spectral disentangling allowed us to detect weak Balmer and He i lines of the secondary component. The primary component rotates with a high projected velocity of v sin i = 243 km s-1. A combined radial-velocity and light-curve solution led to the component masses and radii expected for the young stars of the given spectral types. Due to the high rotation velocity, the primary component might display changes in surface abundances of some elements. However, we did not find any significant differences with respect to the abundances of slowly rotating stars.
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We present the latest results of a long-term observational project aimed at observing, collecting from the literature, and homogenising the light, colour, and spectral variations of the well-known ...emission-line Be star V923 Aql. Our analysis of these parameters confirms that all of the observables exhibit cyclic changes with variable cycle length between about 1800 and 3000 days, so far documented for seven consecutive cycles. We show that these variations can be qualitatively understood within the framework of the model of one-armed oscillation of the circumstellar disk, with a wave of increased density and prograde revolution in space. We confirm the binary nature of the object with a 214.716 day period and estimate the probable system properties. We also confirm the presence of rapid light, and likely also spectral changes. However, we cannot provide any firm conclusions regarding their nature. A quantitative modelling study of long-term changes is planned as a follow-up to this work.
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Properties and nature of Be stars Koubský, P.; Harmanec, P.; Brož, M. ...
Astronomy & astrophysics,
09/2019, Volume:
629
Journal Article
Peer reviewed
Open access
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 ...not easy, however, due to the presence of circumstellar matter. Here, we report the first detailed investigation of a new representative of this class of binaries, HD 81357, based on the analysis of spectra and photometry from several observatories. HD 81357 was found to be a double-lined spectroscopic binary and an ellipsoidal variable seen under an intermediate orbital inclination of ∼(63 ± 5)°, having an orbital period of 33.d . d $ {{\overset{\text{ d}}{.}}} $ 77445(41) and a circular orbit. From an automated comparison of the observed and synthetic spectra, we estimate the component’s effective temperatures to be 12930(540) K and 4260(24) K. The combined light-curve and orbital solutions, also constrained by a very accurate Gaia Data Release 2 parallax, give the following values of the basic physical properties: masses 3.36 ± 0.15 and 0.34 ± 0.04M⊙N 0.34 ± 0.04 M ⊙ N $ 0.34\pm0.04\,{\mathcal{M}^\mathrm{N}_\odot} $ , radii 3.9 ± 0.2 and 13.97 ± 0.05R⊙N 13.97 ± 0.05 R ⊙ N $ 13.97\pm0.05\,{\mathcal{R}^\mathrm{N}_\odot} $ , and a mass ratio 10.0 ± 0.5. Evolutionary modelling of the system including the phase of mass transfer between the components indicated that HD 81357 is a system observed in the final slow phase of the mass exchange after the mass-ratio reversal. Contrary to what has been seen for similar binaries like AU Mon, no cyclic light variations were found on a time scale an order of magnitude longer than the orbital period.
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In a recent excellent study by Southworth and Clausen, refined orbital elements and basic physical properties of DW Carinae were derived. A suggestion was made that this binary is a Be-star system ...since a double, Hα emission line was observed. I argue that the observed Hα emission is nebular emission from the Carina nebula and that neither of the binary components of DW Carinae is a Be star.
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Accurate photometric CoRoT space observations of a secondary seismological target, HD 174884, led to the discovery that this star is an astrophysically important double-lined eclipsing spectroscopic ...binary in an eccentric orbit ($e\sim0.3$), unusual for its short 3$\fd$65705 orbital period. The high eccentricity, coupled with the orientation of the binary orbit in space, explains the very unusual observed light curve with strongly unequal primary and secondary eclipses having the depth ratio of 1-to-100 in the CoRoT “seismo” passband. Without the high accuracy of the CoRoT photometry, the secondary eclipse, 1.5 mmag deep, would have gone unnoticed. A spectroscopic follow-up program provided 45 high dispersion spectra. The analysis of the CoRoT light curve was performed with an adapted version of PHOEBE that supports CoRoT passbands. The final solution was obtained by a simultaneous fitting of the light and the radial velocity curves. Individual star spectra were obtained by spectrum disentangling. The uncertainties of the fit were achieved by bootstrap resampling and the solution uniqueness was tested by heuristic scanning. The results provide a consistent picture of the system composed of two late B stars. The Fourier analysis of the light curve fit residuals yields two components, with orbital frequency multiples and an amplitude of ~0.1 mmag, which are tentatively interpreted as tidally induced pulsations. An extensive comparison with theoretical models is carried out by means of the Levenberg-Marquardt minimization technique, and the discrepancy between the models and the derived parameters is discussed. The best fitting models yield a young system age of 125 million years which is consistent with the eccentric orbit and synchronous component rotation at periastron.
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