Temperatures and Radii of O Stars

Underhill, Anne B.; Divan, L.; Doazan, V.; Prevot-Burnichon, M. L.

doi:10.1007/978-94-009-9452-2_16

Cited by 36 publications

(44 citation statements)

References 4 publications

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“…The β parameters used are from the Hauck & Mermilliod (1975) compilation and the log g(β, T eff ) relations used are from Castelli & Kurucz (2006). An extensive use of the BFM was made by Underhill et al (1979), where unfortunately Eqs. (1) and (2) were iterated only twice, which left the derived effective temperatures strongly correlated with their initial approximate values.…”

Section: The Bolometric-flux Methods (Bfm)mentioning

confidence: 99%

“…2) The temperature is determined from integration of fluxes over a large interval of wavelengths, as was done by Code et al (1976); Underhill et al (1979); Malagnini et al (1986). 3) The temperature is obtained by means of the BFM by Remie & Lamers (1981).…”

Section: Effective Temperaturesmentioning

confidence: 99%

“…As regards B supergiants, Code et al (1976) and Underhill et al (1979) derived effective temperatures based on spectrophotometric observations in the far-UV, visible and near-IR spectral regions. Later, effective temperature determinations for these stars were made using the silicon lines in the optical spectral region, either by fitting the line profiles or by measuring their equivalent widths (Becker & Butler 1990;McErlean et al 1999;Trundle et al 2004).…”

Section: Introductionmentioning

confidence: 99%

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Fundamental parameters of B supergiants from the BCD system

Zorec¹,

Cidale

Arias

et al. 2009

A&A

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Context. Effective temperatures of early-type supergiants are important to test stellar atmosphere-and internal structure-models of massive and intermediate mass objects at different evolutionary phases. However, these T eff values are more or less discrepant depending on the method used to determine them. Aims. We aim to obtain a new calibration of the T eff parameter for early-type supergiants as a function of observational quantities that are: a) highly sensitive to the ionization balance in the photosphere and its gas pressure; b) independent of the interstellar extinction; c) as much as possible model-independent. Methods. The observational quantities that best address our aims are the (λ 1 , D) parameters of the BCD spectrophotometric system. They describe the energy distribution around the Balmer discontinuity, which is highly sensitive to T eff and log g. We perform a calibration of the (λ 1 , D) parameters into T eff using effective temperatures derived with the bolometric-flux method for 217 program stars, whose individual uncertainties are on average |ΔT eff |/T f eff = 0.05. Results. We obtain a new and homogeneous calibration of the BCD (λ 1 , D) parameters for OB supergiants and revisit the current calibration of the (λ 1 , D) zone occupied by dwarfs and giants. The final comparison of calculated with obtained T eff values in the (λ 1 , D) calibration show that the latter have total uncertainties, which on average are T eff /T f eff ±0.05 for all spectral types and luminosity classes. Conclusions. The effective temperatures of OB supergiants derived in this work agree on average within some 2000 K with other determinations found in the literature, except those issued from wind-free non-LTE plane-parallel models of stellar atmospheres, which produce effective temperatures that can be overestimated by up to more than 5000 K near T eff = 25 000 K. Since the stellar spectra needed to obtain the (λ 1 , D) parameters are of low resolution, a calibration based on the BCD system is useful to study stars and stellar systems like open clusters, associations or stars in galaxies observed with multi-object spectrographs and/or spectro-imaging devices.

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Section: The Bolometric-flux Methods (Bfm)mentioning

confidence: 99%

Section: Effective Temperaturesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fundamental parameters of B supergiants from the BCD system

Zorec¹,

Cidale

Arias

et al. 2009

A&A

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“…The source ψ Per (HD 22192, HR 1087) is classified as a B4IIIe Underhill et al (1979) with a diameter of 4.7 ± 0.3 R Bohm-Vitense (1989). It was listed by Campbell (1895) among stars with Hα line emission.…”

Section: ψ Permentioning

confidence: 99%

Kinematics and geometrical study of the Be stars 48 Persei andψPersei with the VEGA/CHARA interferometer

Delaa

Stee

Meilland

et al. 2011

A&A

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Context. Five different physical processes might be responsible for the formation of decretion disks around Be stars: fast rotation of the star, stellar pulsations, binarity, stellar winds, and magnetic fields. Our observations indicate that fast rotation seems to produce a disk in Keplerian rotation, at least in the specific case of the two stars observed. We do not know if this observational result is a generality or not. Aims. We measure the size, orientation, shape, and kinematics of the disks around 2 Be stars, namely 48 Per and ψ Per. Methods. We used the VEGA/CHARA interferometer with a spectral resolution of 5000 to obtain spectrally dispersed visibility modulus and phases within the Hα emission line. Results. We were able to estimate the disk extension in the continuum and in the Hα line, as well as flattening, for both stars. Both stars rotate at nearly a critical rotation, but while the disk of 48 Per seems to be in Keplerian rotation, our preliminary data suggest that the disk of ψ Per is possibly faster than Keplerian, similarly to what has been found for κ CMa with observations carried out in the near-IR. However, more data is needed to confirm the fast rotation of the disk. Conclusions. Assuming a simple uniform disk model for the stellar photosphere in the continuum and a Gaussian brightness distribution in the line emission region, we obtain a ratio of the disk diameter over the photospheric diameter of 8 for 48 Per and 11 for and ψ Per. We also found that the major axis of 48 Per is parallel to the polarization angle and not perpendicular to it as previously observed for many Be stars, including ψ Per. This might be due to the optical thickness of the disk, which is also responsible for the incoherent scattering of a non negligible part of the Hα line emission. To our knowledge, this is the first time that this effect has been measured in a Be star.

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“…Using the results of Underhill et al (1979), we can also infer a radius R * 10R , although values for the same spectral types determined by Popper (1980) are lower by ∼30%.…”

Section: Photometrymentioning

confidence: 86%

Optical Counterpart of the X-ray Transient RX J0117·6–7330: Spectroscopy and Photometry

Soria

1999

Publ. – Astron. Soc. Aust

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Abstract:We conducted spectroscopic and photometric observations of the optical companion of the X-ray transient RX J0117 · 6−7330 in the Small Magellanic Cloud, during a quiescent state. The primary star is identified as a B0 · 5 IIIe with a mass M * = (18 ± 2)M and bolometric magnitude M bol = −7 · 4 ± 0 · 2. The main spectral features are strong Hα emission, Hβ and Hγ emission cores with absorption wings, and narrow He I and O II absorption lines. Equivalent widths and full widths at half maximum of the main lines are listed. The average systemic velocity over our observing run is v r = (184 ± 4) km s −1 ; measurements over a longer period of time are needed to determine the binary period and the K velocity of the primary. We determine a projected rotational velocity v sin i = (145 ± 10) km s −1 for the Be star; if we assume a true rotational velocity at the equator v = (400 ± 50) km s −1 , we deduce that the inclination angle of the system is i = (21 ± 3) deg.

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Temperatures and Radii of O Stars

Cited by 36 publications

References 4 publications

Fundamental parameters of B supergiants from the BCD system

Fundamental parameters of B supergiants from the BCD system

Kinematics and geometrical study of the Be stars 48 Persei andψPersei with the VEGA/CHARA interferometer

Optical Counterpart of the X-ray Transient RX J0117·6–7330: Spectroscopy and Photometry

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