A study of the spectrum of HD 108, an unusual Of star

Underhill, Anne B.

doi:10.1086/173610

Cited by 22 publications

(47 citation statements)

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“…Some interstellar features can also be seen in Fig. 1 (Morgan et al 1955), O7 If (Conti & Alschuler 1971), O6:f?pe (Walborn 1972) and finally O7 IIIfpe (Underhill 1994).…”

Section: The Spectrum Of Hd 108mentioning

confidence: 81%

“…5. Underhill (1994) also mentionned that the RV s of the absorption and emission lines show different behaviours. But in our data, He ii absorptions and He ii, O ii, Si iv and N iii emissions display quite similar behaviours (as can be seen in Fig.…”

Section: Long-term Behaviourmentioning

confidence: 99%

“…She suggested instead that HD 108 was a single star surrounded by a disc and displaying jets that were almost perpendicular to the line of sight. According to Underhill (1994), this particular geometry accounts for the peculiar line profile morphology and could explain the spectral variations seen in HD 108. Using V -band polarimetric observations, Fox & Hines (1998) did not find any evidence of a binary nature of HD 108, but their results did not allow them to choose between largescale jets or small-scale blobs as the structures triggering the variability.…”

Section: Introductionmentioning

confidence: 97%

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What is the real nature of HD 108?

Nazé

Vreux

Rauw

2001

A&A

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Abstract. Since the beginning of the past century, the nature of HD 108 has been a subject of intense debate. One after another, astronomers explored its variability and attributed it either to binarity, or to changes in the stellar wind of a single star. In this article, we analyse a 30 year campaign of spectroscopic observations of this star with special emphasis on the last 15 years during which photographic plates have been replaced by CCD detectors. Our investigation of the radial velocities of HD 108 yields no significant short-or long-term period and does not confirm the published periodicities either. Though the radial velocity of HD 108 appears clearly variable, the variations cannot be explained by the orbital motion in a spectroscopic binary. However, our data reveal spectacular changes in the H i Balmer lines and some He i profiles over the years. These lines continuously evolved from P Cygni profiles to "pure" absorption lines. A similar behaviour has already been observed in the past, suggesting that these changes are recurrent. HD 108 seems to share several characteristics of Oe stars and we discuss different hypotheses for the origin of the observed long-term variations. As we are now in a transition period, a continuous monitoring of HD 108 should be considered for the next few years.

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“…Some interstellar features can also be seen in Fig. 1 (Morgan et al 1955), O7 If (Conti & Alschuler 1971), O6:f?pe (Walborn 1972) and finally O7 IIIfpe (Underhill 1994).…”

Section: The Spectrum Of Hd 108mentioning

confidence: 81%

Section: Long-term Behaviourmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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What is the real nature of HD 108?

Nazé

Vreux

Rauw

2001

A&A

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“…For the computation of the radial velocities, we adopted the rest wavelengths from Conti et al (1977), for the lines with a rest wavelength shorter than 5000 Å, and Underhill (1994), for the other ones.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Evidence for a physically bound third component in HD 150136

Mahy

Gosset

Sana

et al. 2012

A&A

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Context. HD 150136 is one of the nearest systems harbouring an O3 star. Although this system was considered for a long time as a binary, more recent investigations have suggested the possible existence of a third component. Aims. We present a detailed analysis of HD 150136 to test its triple nature. In addition, we investigate the physical properties of the individual components of this system. Methods. We analysed high-resolution, high signal-to-noise data collected through multi-epoch runs spread over ten years. We applied a disentangling program to refine the radial velocities and to obtain the individual spectra of each star. With the radial velocities, we computed the orbital solution of the inner system, and we describe the main properties of the orbit of the outer star such as the preliminary mass ratio, the eccentricity, and the orbital-period range. With the individual spectra, we determined the stellar parameters of each star by means of the CMFGEN atmosphere code. Results. We offer clear evidence that HD 150136 is a triple system composed of an O3V((f * ))-3.5V((f + )), an O5.5-6V((f)), and an O6.5-7V((f)) star. The three stars are between 0-3 Myr old. We derive dynamical masses of about 64, 40, and 35 M for the primary, the secondary and the third components by assuming an inclination of 49 • (sin 3 i = 0.43). It currently corresponds to one of the most massive systems in our galaxy. The third star moves with a period in the range of 2950 to 5500 d on an outer orbit with an eccentricity of at least 0.3. However, because of the long orbital period, our dataset is not sufficient to constrain the orbital solution of the tertiary component with high accuracy. Conclusions. We confirm there is a tertiary star in the spectrum of HD 150136 and show that it is physically bound to the inner binary system. This discovery makes HD 150136 the first confirmed triple system with an O3 primary star.

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“…These effective wavelengths are from Conti et al (1977) below 5000Å, and from Underhill (1994) above. As our spectra taken with different instruments cover different wavelength ranges, the number of RV points associated with the different lines is variable.…”

Section: Rv Measurementsmentioning

confidence: 99%

HD 152248: Evidence for a colliding wind interaction

Sana

Rauw

Gosset

2001

A&A

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Abstract. We present the results of a four year spectroscopic campaign on the early-type binary system HD 152248. Our analysis yields a new classification as O7.5III(f) + O7III(f), in contradiction with previous classifications of the components as supergiants. We derive improved orbital elements and the corresponding masses (M1 = 29.6 M and M2 = 29.9 M ) are somewhat larger than previously reported in the literature, although they are still significantly lower than the ones expected from evolutionary tracks. Both components of the system are close to filling 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 effect. Finally, we show that the line profile variability of the He ii λ4686 and H α lines is consistent with a strong wind interaction between the two stars, quite as predicted by current colliding wind models.

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A study of the spectrum of HD 108, an unusual Of star

Cited by 22 publications

References 0 publications

What is the real nature of HD 108?

What is the real nature of HD 108?

Evidence for a physically bound third component in HD 150136

HD 152248: Evidence for a colliding wind interaction

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