Contemporary optical spectral classification of the OB stars - A digital atlas

Walborn, N. R.; Fitzpatrick, E. L.

doi:10.1086/132646

Cited by 443 publications

(606 citation statements)

References 1 publication

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“…For O stars, the He i λ4471/He ii λ4541 ratio and the He i λ4388 × He ii λ4686 product were also used in accordance with the prescription by Mathys (1988Mathys ( , 1989. Finally, we refined the spectral classification by comparing with the digital spectral atlas of Walborn & Fitzpatrick (1990), observing the specific characteristics of each spectral subtype individually described by these authors. To classify late B or cooler stars, we relied solely on the average spectral type characteristics presented by Jaschek & Jaschek (1990).…”

Section: Spectral Classificationmentioning

confidence: 99%

Spectral classification and distance determination of stars in nine southern Galactic $\ion{H}{ii}$ regions

Pinheiro

Copetti

Oliveira

2010

A&A

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Aims. We attempt to identify the ionising stars and to determine the photometric distances of nine southern Galactic H ii regions.Methods. We carried out optical spectroscopy and UBV photometry of the stellar content of these objects. The distance of individual stars were obtained by spectroscopic parallax. To avoid using a fixed value for the total-to-selective extinction ratio R V , the reddening A V was determined directly by the colour-difference approach by comparing our V apparent magnitudes and the JHK magnitudes from the 2MASS survey with the intrinsic colour indices. Results. As types O or B, we classified 24 of the 31 stars for which optical spectra were obtained. In particular, we identified two new O stars, one in RCW 98 and the other in RCW 99. The values of reddening obtained correspond to a mean R V = 3.44, which is about 10% higher than the value found for field stars. For three of the H ii regions studied (Bran 186, NGC 2626, and RCW 32), the distance estimates (with errors from 25% to 50%) were based on the data obtained for only one star. For the other six objects (NGC 3503, NGC 6334, RCW 55, RCW 87, RCW 98, and RCW 99), we obtained more precise photometric distances (with a mean error of ≈18%) calculated to be the median of the parallax distances obtained for two to six different stars in each nebulae. The parallax distances of individual stars belonging to a given nebula were similar to each other, with internal errors smaller than 5%, as a consequence of the method used to derive the reddening correction A V . The distance of 1.23 ± 0.30 kpc obtained for RCW 87 disagrees with the value of 7.6 kpc previously found. Conclusions. The dispersion in individual distance estimates for stars in a given nebula can be significantly reduced by calculating the reddening A V from a comparison between the V and the 2MASS JHK magnitudes instead of using A V = R V E(B − V) with a fixed value for R V . Therefore, more precise distances can be calculated with our proposed method.

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Section: Spectral Classificationmentioning

confidence: 99%

Spectral classification and distance determination of stars in nine southern Galactic $\ion{H}{ii}$ regions

Pinheiro

Copetti

Oliveira

2010

A&A

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“…5 ; Table 2), our spectra conÐrm the B0 type, based on a comparison of the blue spectrum with the atlas of Walborn & Fitzpatrick (1990). We attempt to better constrain the luminosity class based on the strength of the Hc absorption line, for which a calibration with the absolute magnitude has been derived by Millward & Walker (1985 Luminosity classes of early-B stars can also be estimated from the ratio of Si III j5740 and He I j5876.…”

Section: Observationsmentioning

confidence: 99%

Spatially Resolved STIS Spectra of WR + OB Binaries with Colliding Winds

Lépine

Wallace

Shara

et al. 2001

The Astronomical Journal

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We present spatially resolved spectra of the visual WR ] OB massive binaries WR 86, WR 146, and WR 147, obtained with the Space Telescope Imaging Spectrograph on board the Hubble Space T elescope. The systems are classiÐed as follows : WR 86 \ WC 7 ] B0 III, WR 146 \ WC 6 ] O8 IÈIIf, WR 147 \ WN 8 ] O5È7 IÈII(f ). Both WR 146 and WR 147 are known to have strong nonthermal radio emission arising in a wind-wind collision shock zone between the WR and OB components. We Ðnd that the spectra of their O companions show Ha proÐles in emission, indicative of large mass-loss rates and consistent with the colliding-wind model. Our spectra indicate that the B component in WR 86 has a low mass-loss rate, which possibly explains the fact that WR 86, despite being a long-period WR ] OB binary, was not found to be a strong nonthermal radio emitter. Because of the small massloss rate of the B-star component in WR 86, the wind collision region must be closer to the B star and smaller in e †ective area, hence generating smaller amounts of nonthermal radio emission. Absolute magnitudes for all the stars are estimated based on the spectral types of the components (based on the tables by Schmidt-Kaler for OB stars and van der Hucht for WR stars) and compared with actual, observed magnitude di †erences. While the derived luminosities for the WC 7 and B0 III stars in WR 86 are consistent with the observed magnitude di †erence, we Ðnd a discrepancy of at least 1.5 mag between the observed luminosities of the components in each of WR 146 and WR 147 and the absolute magnitudes expected from their spectral types. In both cases, it looks as though either the WR components are about 2 mag too bright for their spectral types or that the O components are about 2 mag too faint. We discuss possible explanations for this apparent discrepancy.

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“…We plot the wavelength range between 4300 Å and 4710 Å, where the main lines used to define the spectral type (SpT) in mid-O stars are found (see e.g. Walborn & Fitzpatrick 1990). The first spectrum from the bottom (#13) is probably similar to the one analysed by Walborn (1982).…”

Section: Observationsmentioning

confidence: 96%

The massive multiple system HD 64315

Lorenzo

Negueruela

Vilardell

et al. 2017

A&A

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Context. The O6 Vn star HD 64315 is believed to belong to the star-forming region known as NGC 2467, but previous distance estimates do not support this association. Moreover, it has been identified as a spectroscopic binary, but existing data support contradictory values for its orbital period. Aims. We explore the multiple nature of this star with the aim of determining its distance, and understanding its connection to NGC 2467. Methods. A total of 52 high-resolution spectra have been gathered over a decade. We use their analysis, in combination with the photometric data from All Sky Automated Survey and Hipparcos catalogues, to conclude that HD 64315 is composed of at least two spectroscopic binaries, one of which is an eclipsing binary. We have developed our own program to fit four components to the combined line shapes. Once the four radial velocities were derived, we obtained a model to fit the radial-velocity curves using the Spectroscopic Binary Orbit Program (SBOP). We then implemented the radial velocities of the eclipsing binary and the light curves in the Wilson-Devinney code iteratively to derive stellar parameters for its components. We were also able to analyse the non-eclipsing binary, and to derive minimum masses for its components which dominate the system flux. Results. HD 64315 contains two binary systems, one of which is an eclipsing binary. The two binaries are separated by ∼ 0.09 arcsec (or ∼ 500 AU) if the most likely distance to the system, ∼ 5 kpc, is considered. The presence of fainter companions is not excluded by current observations. The non-eclipsing binary (HD 64315 AaAb) has a period of 2.70962901 ± 0.00000021 d. Its components are hotter than those of the eclipsing binary, and dominate the appearance of the system. The eclipsing binary (HD 64315 BaBb) has a shorter period of 1.0189569 ± 0.0000008 d. We derive masses of 14.6 ± 2.3 M ⊙ for both components of the BaBb system. They are almost identical; both stars are overfilling their respective Roche lobes, and share a common envelope in an overcontact configuration. The non-eclipsing binary is a detached system composed of two stars with spectral types around O6 V with minimum masses of 10.8 M ⊙ and 10.2 M ⊙ , and likely masses ≈ 30 M ⊙ . Conclusions. HD 64315 provides a cautionary tale about high-mass star isolation and multiplicity. Its total mass is likely above 90 M ⊙ , but it seems to have formed without an accompanying cluster. It contains one the most massive overcontact binaries known, a likely merger progenitor in a very wide multiple system.

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Contemporary optical spectral classification of the OB stars - A digital atlas

Cited by 443 publications

References 1 publication

Spectral classification and distance determination of stars in nine southern Galactic $\ion{H}{ii}$ regions

Spectral classification and distance determination of stars in nine southern Galactic $\ion{H}{ii}$ regions

Spatially Resolved STIS Spectra of WR + OB Binaries with Colliding Winds

The massive multiple system HD 64315

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