Binary System HD Research Articles

Stellar Companions to Stars with Planets

A combination of high-resolution and wide-field imaging reveals two binary stars and one triple star system among the sample of the first 11 stars with planets detected by radial velocity variations. High-resolution speckle or adaptive optics (AO) data probe subarcsecond scales down to the diffraction limit of the Keck 10 m or the Lick 3 m, and direct images or AO images are sensitive to a wider field, extending to 10'' or 38'', depending on the camera. One of the binary system—HD 114762—was not previously known to be a spatially resolved multiple system; additional data taken with the combination of Keck adaptive optics and NIRSPEC are used to characterize the new companion. The second binary system—τ Boo—was a known multiple with two conflicting orbital solutions; the current data will help constrain the discrepant estimates of periastron time and separation. Another target—16 Cyg B—was a known common proper motion binary, but the current data resolve a new third component, close to the wide companion 16 Cyg A. Both the HD 114762 and 16 Cyg B systems harbor planets in eccentric orbits, while the τ Boo binary contains an extremely close planet in a tidally circularized orbit. Although the sample is currently small, the proportion of binary systems is comparable to that measured in the field over a similar separation range. Incorporating the null result from another companion search project lowers the overall fraction of planets in binary systems, but the detections in our survey reveal that planets can form in binaries separated by less than 50 AU.

Testing Models of Stellar Evolution for Metal-poor Stars: An Interferometric-spectroscopic Orbit for the Binary HD 195987

We report spectroscopic and interferometric observations of the moderately metal-poor double-lined binary system HD 195987, with an orbital period of 57.3 days. By combining our radial-velocity and visibility measurements, we determine the orbital elements and derive absolute masses for the components of MA = 0.844 ± 0.018 M⊙ and MB = 0.6650 ± 0.0079 M⊙, with relative errors of 2% and 1%, respectively. We also determine the orbital parallax, πorb = 46.08 ± 0.27 mas, corresponding to a distance of 21.70 ± 0.13 pc. The parallax and the measured brightness difference between the stars in V, H, and K yield the component absolute magnitudes in those bands. We also estimate the effective temperatures of the stars as T = 5200 ± 100 K and T = 4200 ± 200 K. Together with detailed chemical abundance analyses from the literature giving [Fe/H] ≈ -0.5 (corrected for binarity) and [α/Fe] = +0.36, we use these physical properties to test current models of stellar evolution for metal-poor stars. Among the four that we considered, we find that no single model fits all observed properties at the measured composition, although we identify the assumptions in each one that account for the discrepancy, and we conclude that a model with the proper combination of assumptions should be able to reproduce all the radiative properties. The indications from the isochrone fits and the pattern of enhancement of the metals in HD 195987 are consistent with this being a thick disk object, with an age of 10–12 Gyr.

Discovery of an Extremely Red Object in the Field of HD 155826

We have discovered an extremely red object, LSF 1, located 7'' southwest (P.A. 217°) of the bright spectroscopic binary system HD 155826. Originally reported by IRAS as one source detected at 12-60 μm, and found as a single 6-25 μm source of similar flux in the Midcourse Space Experiment Galactic plane survey, two bright point sources were found in arcsecond resolution infrared images obtained with the MIRLIN camera at the Infrared Telescope Facility and confirmed by the Long Wavelength Spectrometer camera on Keck I. While HD 155826 itself was easily detected in all the broadband and narrowband filters from 0.9 to 12 μm that we used, the new counterpart, LSF 1, is only visible at 10 μm. In Gunn z, J, H, and K', the upper limit to the new object's magnitude is ~14. The detection of the new bright IR source explains the confusing [K]-[N] IRAS colors that originally implied that HD 155826 was a possible Vega-like system. The anomalous long-wavelength emission is found to arise entirely from the new source. Without mid-IR extension or excess long-wavelength emission, HD 155826 should no longer be classified as a Vega-like system. We suspect LSF 1 to be either a highly reddened carbon star or a Class II YSO, with no association with the high proper motion HD 155826 system.

Calculation of the masses of the binary star HD 93205 by application of the theory of apsidal motion

ABSTRA C T We present a method to calculate masses for components of both eclipsing and non-eclipsing binary systems as long as their apsidal motion rates are available. The method is based on the fact that the equation that gives the rate of apsidal motion is a supplementary equation that allows the computation of the masses of the components, if their radii and the internal structure constants can be obtained from theoretical models. For this reason the use of this equation makes the method presented here model dependent. We apply this method to calculate the mass of the components of the non-eclipsing massive binary system HD 93205OO3 Va O8 VU, which is suspected to be a very young system. To this end, we have computed a grid of evolutionary models covering the mass range of interest, and taking the mass of the primary (M1) as the only independent variable, we solve the equation of apsidal motion for M1 as a function of the age of the system. The mass of the primary that we find ranges from M1a 60 ^ 19 M( for zero-age main-sequence models, which sets an upper limit for M1 ,d own toM1a 40 ^ 9M ( for an age of 2 Myr. Accordingly, the upper limit derived for the mass of the secondaryOM2a QM1U M2a 25 M( is in very good agreement with the masses derived for other O8 V stars occurring in eclipsing binaries.

First orbital elements for theλ Bootis spectroscopic binary systems HD 84948 and HD 171948

We present high-resolution spectroscopic observations of the two Bootis type spectroscopic binary systems HD 84948 and HD 171948. Both systems consist of two true Bootis stars, as has already been proven by a detailed abundance analysis taking into account the binary nature. Nevertheless, we have obtained non- LTE abundances for carbon and oxygen in order to investigate those important elements. The abundances t excellently into the typical pattern for this group, leaving no doubt that all four components are true Bootis stars. With the help of the derived orbital elements it is possible to establish the ages of the two systems. For the rst time we can estimate the evolutionary status of Galactic eld Bootis stars. The origin of those nonmagnetic, metal-weak, Population I, late B- to early F-type stars is still controversial. The two widely discussed theories explaining the Bootis phenomenon (diusion together with either accretion of circumstellar matter or mass- loss) predict signicantly dierent evolutionary stages for this group of objects (close to either the Zero-Age Main Sequence or Terminal-Age Main Sequence). It is already known that very young members of the group exist in the Orion OBI association and probably in NGC 2264. Hipparcos data established six further Galactic eld Bootis stars which are close to the Zero-Age Main Sequence, whereas the evolutionary status for the other objects remained undetermined. The Hipparcos data reveal that the Galactic space motions of both the systems that we discuss here are typical of those of Population I objects. The photometric data from the Hipparcos mission conrm the pulsation previously discovered for HD 84948 with a period of about 110 min and a V -amplitude of about 14 mmag. For HD 84948, we estimate from the mass ratio an age of about 1 Gyr, ruling out a possible Pre-Main-Sequence status. HD 171948 has an age of about 0.01 to 0.1 Gyr which is close to the Zero-Age Main Sequence. We therefore conclude that the Bootis phenomenon can be found continuously from very early stages to the Terminal-Age Main Sequence, suggesting that dierent mechanisms might work at dierent stages of stellar evolution producing the same abundance pattern.

HD 152248: Evidence for a colliding wind interaction

We present the results of a four year spectroscopic campaign on the early-type binary system HD 152248. Our analysis yields a new classication as O7.5III(f) + O7III(f), in contradiction with previous classications of the components as supergiants. We derive improved orbital elements and the corresponding masses (M1 =2 9:6M and M2 =2 9:9M) are somewhat larger than previously reported in the literature, although they are still signicantly lower than the ones expected from evolutionary tracks. Both components of the system are close to lling their Roche lobe at periastron passage. We also investigate the equivalent width variations of the lines of the two components and we discuss their relation to the Struve-Sahade eect. Finally, we show that the line prole variability of the He ii 4686 and H lines is consistent with a strong wind interaction between the two stars, quite as predicted by current colliding wind models.

The strange case of the massive binary HD 149404

We report the analysis of an extensive set of high-resolution spectroscopic observations of the massive binary system HD 149404. We compare different techniques to measure the radial velocities of the heavily blended absorption lines and we derive a new orbital solution. The absorption lines display strong variability that slightly affects the orbital solution and the determination of the spectral types of the components of the binary. We find that the primary is probably of spectral type O7.5 I(f), while the secondary is most likely an ON9.7 I supergiant. The secondary seems to be the most evolved component of the system and its current evolutionary status could best be explained if the system has undergone a Roche lobe overflow episode during the past. The secondary could actually still be rather close to filling its critical volume and this could lead to an enhanced mass loss of the secondary. The spectrum of HD 149404 displays many emission lines some of which show phase-locked line profile variations. In particular, the H α line displays a double-peaked morphology at orbital phases near conjunction. We investigate the radial velocity behaviour of the emission lines and we find that some of them must be formed in an interaction region. We propose a simple model where some of the optical emission lines arise in a heavily bended shock region.

The probable role of cloudy wind structure in the X-ray emission of the binary HD 193793

A model with interacting two-phase winds, each consisting of rarified gas and dense, compact clouds, is proposed to explain the weakness of the variability of the X-ray emission of the binary system HD 193793. The flowing together of the rarified components, collisions of clouds, and the motion of the clouds in the rarified component of the other wind are considered. Computations of the interactions of the rarified components were carried out using the method of Cherny $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l}$$ for standard, two-dimensional, gas-dynamical problems, taking into account differences in the ion and electron temperatures. Due to the adiabatic expansion of the rarifield gas behind the shock front, the X-ray luminosity decreases at 1/r, where r is the distance between the stars in the system. The gas in the dense clouds radiates, leading, on the contrary, to a gradual growth in their luminosity in the transition from periastron to apoastron, approximately proportional to r 1/3. The joint action of these two factors could give rise to the observed nearly constant luminosity of the system at 2–5 and 2–6 keV. The contribution of the clouds exceeds that of the rarified component by a substantial factor.

Evidence of Interstellar N[CLC]a[/CLC] [CSC]i[/CSC] Structure at Scales Down to 15 AU in Low-Density Gas

We present high-resolution Hubble Space Telescope/Space Telescope Imaging Spectrograph and multiepoch KPNO coudé feed observations of multiple interstellar lines toward the binary system HD 32039/40. Comparisons of the Na I profiles observed over a period of 4.25 yr reveal significant temporal variation in the Na I column in at least one component, implying that there is structure at scales on the order of the proper motion (~15-21 AU). Large differences are also observed among multiple components in the profiles of the neutral species between the binary sight lines (5060 AU separation). In addition, significant differences in the S II profile are seen between the stars—the first optical/UV detection of small-scale variations in a dominant ion. Measurements of the C I fine-structure excitation in the variable components suggest that the densities in these components are ~20-200 cm-3, significantly lower than the densities inferred in past H I 21 cm and Na I studies.

Hubble Space TelescopeObservations of the Luminous Blue Variable/W‐R Eclipsing Binary System HD 5980

We report the results of Hubble Space Telescope STIS observations of the intriguing luminous blue variable/Wolf-Rayet binary system HD 5980 in the Small Magellanic Cloud. Although its spectral char- acteristics (WN6) are currently very similar to those observed in 1995 in the FUV, some of the line —uxes continue with the increasing trend observed since the 1980s. The erupting star still dominates the emission-line spectrum, and a radial velocity curve from UV lines is derived, supporting previous esti- mates of its mass (50 A rough estimate of 2 ) 10~4 yr~1 for the current mass-loss rate of this M _ ). M _ star is derived. The only spectral lines attributable to the close companion are the very extended P Cygni absorption components of the strong UV lines, present only during the eclipse of the eruptor, implying that the wind-wind collision shock cone winds tightly around this companion. A third stellar component contributing to the spectrum is detected through the presence of stationary photospheric absorption lines in the UV spectrum. This object contributes D30% to the UV continuum luminosity. A new set of ISM absorption components at (680 km s~1 has appeared as a result of the shock interface between the slow wind (D400 km s~1) that emerged during the 1994 eruption and the subsequently emerging fast wind (D2000 km s~1) phases. Subject headings: binaries: generalstars: evolutionstars: individual (HD 5980) ¨ stars: variables: otherstars: winds, out—owsstars: Wolf-Rayet

Correction to a Paper on HD 207739

Ten years ago there appeared in these Publications a paper entitled ““ Orbital Elements and Optical Spectroscopy of the Enigmatic cF]B Binary System HD 207739 II (Griffin et al. 1990). In that paper its authors gave as comprehensive a description as they were able of that unusual binary system, which is strongly interacting despite having a period as long as 140 days. Soon after the paper was published, the authors received a letter fromDr. Johannes Andersen suggesting that a) the small but deÐnite orbital eccentricity (7 times its standard error) found for the system did not necessarily imply a noncircular orbit for the center of mass of the cF component to which the radial velocity observations referred, but might be due to the e†ects of tidal deformation, reNection, etc., as had actually been proved to be the case with RX Cas (Andersen, Pavlovski, & Piirola 1989) ; b) the discussion that purported to show from the relationship between v sin i andK that the F star is far from Ðlling its Roche lobe was mistaken ; and c) the product of v sin i and P gives a minimum value for the radius of the F star, from which estimates of the luminosity and hence distance, etc., could follow.

Non-spherical Outflows in Massive Binary Systems: Circumbinary Disks?

AbstractThe trajectories of wind particles emitted from the surface of a massive star in a close binary system are analyzed. Within a radius 1000 times the separation of the two stars, a significant fraction of the particle trajectories are found to cross the orbital plane, leading to the formation of a large-scale, outflowing circumbinary disk-like structure. The shocks which arise due to the collision of particles which are within crossing streamlines are expected to produce selected regions within the wind, particularly in the orbital plane, in which a higher degree of ionization prevails than in the wind in general. X-ray emission might also be expected from these regions. Such a model is suggested to be applicable to the erupting WR/LBV binary system HD 5980 and other binary LBV systems, during phases when wind velocities are slow.

Discrepancies between observational and theoretical parameters for three O-type binaries

Here we present fundamental parameters (masses, spectral classifications, rotational velocities) obtained from a combination of spectroscopic and photometric orbital solutions for the O-type binary systems HD 152248, HD 149404, and HD 135240. We also present estimated masses derived from theoretical single star evolutionary tracks for these same stars. In all cases the evolutionary masses are larger than those derived from observations.

Spatially resolved optical spectroscopy of the Herbig Ae/Vega-like binary star HD 35187

We report on observations of the young binary system HD 35187 (SAO 77144). For the first time, we have obtained spatially resolved optical spectra of the individual stars. Analysis of their effective temperatures indicates that the stars have spectral types of A2 (HD 35187B) and A7 (HD 35187A). Analysis of the Hγ Balmer line indicates a luminosity class V for both stars. At the time of these observations, net Hα emission was present only towards HD 35187B. However, there is evidence that the photospheric Hα line in HD 35187A has been ‘filled in’ relative to its expected strength in an A7 star, so this star may also be associated with some process leading to Hα emission. Moreover, both stars exhibit absorption in the He iλ5876 line well in excess of that expected for their spectral types. Comparison with earlier observations reveals that both the Hα and He i lines are variable, so both stars are ‘active’ in some sense. We suggest that the variable He i absorption detected towards both stars is a result of chromospheric activity, and is not necessarily related to the circumstellar environment. We find tentative evidence for a narrow Ca K circumstellar absorption line and excess redshifted absorption of the Na D line profiles in the spectrum of HD 35187B, both of which are absent in the spectrum of HD 35187A. The heliocentric radial velocity of the presumed circumstellar Ca K line (+54.5 km s−1) is similar to that of redshifted circumstellar absorption lines previously identified in IUE spectra of this star, and the velocity range of the Na D absorption precisely matches that of the UV circumstellar components. Moreover, by placing the stars on the HR diagram (with the aid of the reliable Hipparcos distances) we find evidence that HD 35187B is dimmed by about 0.4 mag of grey circumstellar extinction. The detection of net Hα emission, circumstellar absorption lines, and significant circumstellar extinction for HD 35187B suggests that it has far more mass in its circumstellar environment than its companion, and that the observed IR excess of this system originates from a disc surrounding HD 35187B alone.

Mass‐Loss Rate and He/H Abundance of the Erupting Component in the Small Magellanic Cloud System HD 5980

The binary Wolf-Rayet system HD 5980 in the Small Magellanic Cloud underwent a major luminous blue variable-type eruptive event in 1994. It is the first such recorded event in which the apparent precursor transits from WNE to WNL spectral types prior to the eruption. In this paper we analyze the spectrum of the system obtained when the outburst was declining (1994 December), but the dominant spectrum was that of the eruptor. From non-LTE analysis we obtain =10−3 M☉ yr-1, N[He]/N[H] = 0.43 (by number; Y = 0.63 by mass), v∞ = 600 km s-1, T* = 35,500 K, and Leruptor = 3 × 106L☉. A comparison of the He/H abundance derived here and an estimate obtained from published data of 20 yr ago leads us to conclude that the member of the binary system that underwent the eruption is the star formerly classified as an O7 supergiant. The considerable amount of He in this star indicates that it is in transition to becoming an H-poor W-R. By comparing the stellar parameters with single-star evolutionary tracks, we derive that the progenitor was more massive than 120 M☉, and that its current mass is close to 80 M☉.

A COLLIDING-WIND MODEL FOR THE WOLF-RAYET SYSTEM HD 152270

ABSTRACT New orbital elements for the binary system HD 152270 (WC7 + O6) are derived from high resolution observations and literature data, obtained between 1944 to 1989. Variations in position and structure of the peak profile, overlying the flat-topped C 3 569.59 nm line, are used to derive a colliding wind model (cone model) for the system. The model is used to construct synthetic line profiles which are compared with the observed profiles.

Sudden Luminous Blue Variable--Like Behavior of the Wolf-Rayet Binary System HD 5980 in the Small Magellanic Cloud

view Abstract Citations (62) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Sudden Luminous Blue Variable--Like Behavior of the Wolf-Rayet Binary System HD 5980 in the Small Magellanic Cloud Barba, Rodolfo H. ; Niemela, Virpi S. ; Baume, Gustavo ; Vazquez, R. A. Abstract We report a sudden outburst-like behavior of the WR binary system HD 5980 in the SMC, as disclosed by spectroscopic and photometric observations performed in 1994 October and November. Our spectra show that the WR type spectrum of HD 5980 has changed drastically, now exhibiting a luminous blue variable (LBV) type spectrum with strong emission of H I and He I with P Cyg profiles and weaker emissions of N II, Si II, Si III, and Fe III. The previously dominant He II 4686 ÅA emission has remarkably weakened and other WR type emission lines have disappeared. Our photometry of HD 5980 reveals a visual brightening of 2.3 mag. The behavior shown by HD 5980, i.e., the transformation of a WNE star in a sort of LBV star, is unprecedented. Publication: The Astrophysical Journal Pub Date: June 1995 DOI: 10.1086/187921 Bibcode: 1995ApJ...446L..23B Keywords: STARS: BINARIES: CLOSE; STARS: INDIVIDUAL HENRY DRAPER NUMBER: HD 60435; STARS: VARIABLES: OTHER LUMINOUS BLUE VARIABLES; STARS: WOLF-RAYET full text sources ADS | data products SIMBAD (8) NED (1)

A CCD spectroscopic orbit and line-variability near periastron for HD 193793

Since 1987 we have been observing long-period WR binaries about once every two months with the 1.6m telescope at Observatoire du mont Mégantic. The spectra cover the range λλ ∼ 4000—6000Â with 2-pixel resolution (∼2.5Â) and S/N ∼ 500 in the strongest line-peaks. We present a new orbit obtained from several lines in the WC7 and the O4—5 components of the binary system HD 193793 (WR140) and discuss emission-line variability especially in the 2—3 month interval around periastron.

Spectroscopy and orbit determination of the chromospherically active double-lined binary system HD 163621 = V835 Herculis

HD 163621 is a double-lined spectroscopic binary in a circular orbit whose period is 3.3 days. Spectral classification of the components has proved difficult, but current results of K0 V and late K V are reasonably consistent with our best model of the system, which has spectral types of G8V and K7V. The object shows photometric variability and chromospheric activity and is therefore a member of the BY Draconis class of variables. The minimum masses are quite small, 0.10 and 0.07 M⊙ for the primary and secondary, respectively, suggesting an orbital inclination of about 30°. The system is synchronously rotating. Its distance is estimated to be 31 pc, which makes it an excellent candidate for a trigonometric parallax determination.

1988–1991 photometry of the chromospherically active double-lined binary system HD 163621 = V835 Herculis

Photometry inV andB with a 16inch automatic telescope from 1988 to 1991 confirms the synchronous rotation suspected earlier and reveals variability up to 0M.10 in theB bandpass at one epoch. Five spots formed with lifetimes ranging from 0.15 to 0.77 years. As with other rapid rotators, the differential rotation coefficient (k = 0.03) is significantly smaller than that of the Sun (k = 0.19).