Line profile variability in the spectra of Oef stars

Rauw, Grégor; Becker, M. De; Vreux, Jean-Marie

doi:10.1051/0004-6361:20021776

Cited by 22 publications

(33 citation statements)

References 26 publications

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“…The spectra have R ∼ 9000 and either cover the wavelength range 4100-4950 (see or 4450-4900 Å (see Mahy et al 2013). The data reduction procedure is described in Rauw et al (2003) and . Other reduced AURELIE data were retrieved from the Information Bulletin on Variable Stars (IBVS; De Becker et al 2008) 4 .…”

Section: Sample Observations and Data Reductionmentioning

confidence: 99%

Chemical abundances of fast-rotating massive stars

Cazorla

Morel

Nazé

et al. 2017

A&A

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Aims. Recent observations have challenged our understanding of rotational mixing in massive stars by revealing a population of fastrotating objects with apparently normal surface nitrogen abundances. However, several questions have arisen because of a number of issues, which have rendered a reinvestigation necessary; these issues include the presence of numerous upper limits for the nitrogen abundance, unknown multiplicity status, and a mix of stars with different physical properties, such as their mass and evolutionary state, which are known to control the amount of rotational mixing. Methods. We have carefully selected a large sample of bright, fast-rotating early-type stars of our Galaxy (40 objects with spectral types between B0.5 and O4). Their high-quality, high-resolution optical spectra were then analysed with the stellar atmosphere modelling codes DETAIL/SURFACE or CMFGEN, depending on the temperature of the target. Several internal and external checks were performed to validate our methods; notably, we compared our results with literature data for some well-known objects, studied the effect of gravity darkening, or confronted the results provided by the two codes for stars amenable to both analyses. Furthermore, we studied the radial velocities of the stars to assess their binarity.Results. This first part of our study presents our methods and provides the derived stellar parameters, He, CNO abundances, and the multiplicity status of every star of the sample. It is the first time that He and CNO abundances of such a large number of Galactic massive fast rotators are determined in a homogeneous way.

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Section: Sample Observations and Data Reductionmentioning

confidence: 99%

Chemical abundances of fast-rotating massive stars

Cazorla

Morel

Nazé

et al. 2017

A&A

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“…• 2522 has been suggested to explain variability on time-scales of hours (Rauw et al 2003), but the variability in BD +53…”

Section: Bd +53mentioning

confidence: 99%

Wind accretion in the massive X-ray binary 4U 2206+54: abnormally slow wind and a moderately eccentric orbit

Ribó

Negueruela

Blay³

et al. 2006

A&A

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Massive X-ray binaries are usually classified by the properties of the donor star in classical, supergiant and Be X-ray binaries, the main difference being the mass transfer mechanism between the two components. The massive X-ray binary 4U 2206+54 does not fit in any of these groups, and deserves a detailed study to understand how the transfer of matter and the accretion on to the compact object take place. To this end we study an IUE spectrum of the donor and obtain a wind terminal velocity (v ∞ ) of ∼350 km s −1 , which is abnormally slow for its spectral type. We also analyse here more than 9 years of available RXTE/ASM data. We study the long-term X-ray variability of the source and find it to be similar to that observed in the wind-fed supergiant system Vela X-1, reinforcing the idea that 4U 2206+54 is also a wind-fed system. We find a quasi-period decreasing from ∼270 to ∼130 d, noticed in previous works but never studied in detail. We discuss possible scenarios for its origin and conclude that long-term quasi-periodic variations in the mass-loss rate of the primary are probably driving such variability in the measured X-ray flux. We obtain an improved orbital period of P orb = 9.5591 ± 0.0007 d with maximum X-ray flux at MJD 51856.6 ± 0.1. Our study of the orbital X-ray variability in the context of wind accretion suggests a moderate eccentricity around 0.15 for this binary system. Moreover, the low value of v ∞ solves the long-standing problem of the relatively high X-ray luminosity for the unevolved nature of the donor, BD +53• 2790, which is probably an O9.5 V star. We note that changes in v ∞ and/or the mass-loss rate of the primary alone cannot explain the different patterns displayed by the orbital X-ray variability. We finally emphasize that 4U 2206+54, together with LS 5039, could be part of a new population of wind-fed HMXBs with main sequence donors, the natural progenitors of supergiant X-ray binaries.

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“…With this, we expected to be able to select some other early Be stars and also study the possible existence of objects with peculiar characteristics, perhaps resembling the Oef or Of?p stars (cf. Rauw et al 2003;Walborn et al 2003) at later spectral types or the peculiar O9 star BD +53 • 2790 (Negueruela & Reig 2001). All stars for which we could find in the literature an expla-nation for the "peculiarity", such as CNO anomalies, were excluded from the sample.…”

Section: Samplementioning

confidence: 99%

On the class of Oe stars'

2004

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Abstract. We present high-quality spectra of the majority of stars that have been classified as Oe and find that their published spectral types are generally too early, most likely due to infilling of He I lines. As a matter of fact, all stars classified as Oe actually fall inside the range O9-B0 with the important exception of HD 155806 (O7.5 III) and perhaps HD 39680 (difficult to classify, but likely O8.5 V). Observations of a sample of objects with published spectral types in the O9-B0 range previously classified as peculiar or emission-line stars fail to reveal any new Oe star with spectral type earlier than O9.5. Most objects classified as peculiar in "classical" literature show signs of binarity in our spectra, but no spectral anomalies. We conclude that there is likely a real decline in the fraction of Be stars for spectral types earlier than B0, not due to observational bias. The few Oe stars with spectral types earlier than O9.5 deserve detailed investigation in order to provide constraints on the physical reasons of the Be phenomenon.

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Line profile variability in the spectra of Oef stars

Cited by 22 publications

References 26 publications

Chemical abundances of fast-rotating massive stars

Chemical abundances of fast-rotating massive stars

Wind accretion in the massive X-ray binary 4U 2206+54: abnormally slow wind and a moderately eccentric orbit

On the class of Oe stars'

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