Angular Sizes and Effective Temperatures of O-type Stars from Optical Interferometry with the CHARA Array

Gordon, Kathryn D.; Gies, Douglas R.; Schaefer, Gail H.; Huber, Daniel; Ireland, Michael; Hillier, D. J.

doi:10.3847/1538-4357/aaec04

Cited by 13 publications

(9 citation statements)

References 74 publications

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“…Distances are from Gaia Collaboration et al (2018). For HD36861, we adopted the distance from the mean Gaia DR2 parallaxes for the components C and D, as in Gordon et al (2018). Distance from van Leeuwen (2007) for HD 116852 is shown too.…”

Section: Ferosmentioning

confidence: 99%

“…For HD 36861 (λ Ori A), the distance from the GAIA DR2 parallaxes is 271 +47 −35 pc. As in Gordon et al (2018), we adopted the distance of 417 ± 10 pc from the mean of the parallaxes for components C and D, since the GAIA DR2 parallaxes for HD 36861 have large error bars. Furthermore, different methods in the literature provide a distance estimation for this star up to ∼ 400 pc (e.g., van Leeuwen 2007;Maíz Apellániz et al 2008;Mayne & Naylor 2008;Maíz Apellániz & Barbá 2018).…”

Section: Starmentioning

confidence: 99%

“…In this case, we use the extinction parameters from Maíz Apellániz & Barbá (2018) for this star (E(B− V) = 0.54 and R V =3.2), but they are very close to our adopted values. For HD 36861, we show four sets of SED models with different extinction parameters: our adopted values, derived from Wegner (2003), from Gordon et al (2018), and from Maíz Apellániz & Barbá (2018). In this case, our SED models encompass the observed one by just considering different values for E(B−V) and R V .…”

Section: Starmentioning

confidence: 99%

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Probing the weak wind phenomenon in Galactic O-type giants

Almeida

Marcolino

Bouret

et al. 2019

A&A

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Aims. Analyses of Galactic late O dwarfs (O8-O9.5V stars) raised the "weak wind problem": spectroscopic mass-loss rates (Ṁ) are up to two orders of magnitude lower than the theoretical values. We investigated the stellar and wind properties of Galactic late O giants (O8-O9.5III stars). These stars have luminosities log(L /L ) ∼ 5.2, which is the critical value (onset of weak winds) proposed in the literature. Methods. We performed a spectroscopic analysis of nine O8-O9.5III stars in the ultraviolet (UV) and optical regions using the model atmosphere code CMFGEN. Results. Stellar luminosities were adopted using calibrations from the literature. Overall, our model spectral energy distributions agree well with the observed ones considering parallaxes from the latest GAIA data release (DR2). The effective temperature derived from the UV region agrees well with the ones from the optical. As expected, the analysis of the Hertzsprung-Russell (HR) diagram shows that our sample is more evolved than late O dwarfs. From the UV region, we foundṀ ∼ 10 −8 − 10 −9 M yr -1 overall. This is lower by ∼ 0.9 − 2.3 dex than predicted values based on the (global) conservation of energy in the wind. The mass-loss rates predicted from first principles, based on the moving reversing layer theory, agree better with our findings, but it fails to match the spectroscopiċ M for the most luminous OB stars. The region of log(L /L ) ∼ 5.2 is critical for both sets of predictions in comparison with the spectroscopic mass-loss rates. CMFGEN models with the predictedṀ (the former one) fail to reproduce the UV wind lines for all the stars of our sample. We reproduce the observed Hα profiles of four objects with ourṀ derived from the UV. Hence, lowṀ values (weak winds) are favored to fit the observations (UV + optical), but discrepancies between the UV and Hα diagnostics remain for some objects. Conclusions. Our results indicate weak winds beyond the O8-9.5V class, since the region of log(L /L ) ∼ 5.2 is indeed critical to the weak wind phenomenon. Since O8-O9.5III stars are more evolved than O8-9.5V, evolutionary effects do not seem to play a role in the onset of the weak wind phenomenon. These findings support that theṀ (for low luminosity O stars) in use in the majority of modern stellar evolution codes must be severely overestimated up to the end of the H-burning phase. Further investigations must evaluate the consequences of weak winds in terms of physical parameters for massive stars (e.g., angular momentum and CNO surface abundances).

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Section: Ferosmentioning

confidence: 99%

Section: Starmentioning

confidence: 99%

Section: Starmentioning

confidence: 99%

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Probing the weak wind phenomenon in Galactic O-type giants

Almeida

Marcolino

Bouret

et al. 2019

A&A

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“…The situation concerning the early-type eclipsing binaries is more complex because the calibration of the SBCR requires high angular resolution measurements, and early-type stars are A&A 652, A26 (2021) particularly active (Martins et al 2015;Gordon et al 2018). Challouf et al (2014) improved, by a factor of 2, the precision on SBCR of early-type stars from about 15 to 7%, corresponding to the most accurate SBCR developed so far for early-type stars.…”

Section: Introductionmentioning

confidence: 99%

Progress on the calibration of surface brightness-color relations for early- and late-type stars

Salsi

Nardetto

Mourard

et al. 2021

A&A

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Context. Surface brightness-color relations (SBCRs) are widely used for estimating angular diameters and deriving stellar properties. They are critical to derive extragalactic distances of early-type and late-type eclipsing binaries or, potentially, for extracting planetary parameters of late-type stars hosting planets. Various SBCRs have been implemented so far, but strong discrepancies in terms of precision and accuracy still exist in the literature. Aims. We aim to develop a precise SBCR for early-type B and A stars using selection criteria, based on stellar characteristics, and combined with homogeneous interferometric angular diameter measurements. We also improve SBCRs for late-type stars, in particular in the Gaia photometric band. Methods. We observed 18 early-type stars with the VEGA interferometric instrument, installed on the CHARA array. We then applied additional criteria on the photometric measurements, together with stellar characteristics diagnostics in order to build the SBCRs. Results. We calibrated a SBCR for subgiant and dwarf early-type stars. The RMS of the relation is σFV0 = 0.0051 mag, leading to an average precision of 2.3% on the estimation of angular diameters, with 3.1% for V −K < −0.2 mag and 1.8% for V −K > −0.2 mag. We found that the conversion between Johnson-K and 2MASS-Ks photometries is a key issue for early-type stars. Following this result, we have revisited our previous SBCRs for late-type stars by calibrating them with either converted Johnson-K or 2MASS-Ks photometries. We also improve the calibration of these SBCRs based on the Gaia photometry. The expected precision on the angular diameter using our SBCRs for late-type stars ranges from 1.0 to 2.7%. Conclusions. By reaching a precision of 2.3% on the estimation of angular diameters for early-type stars, significant progress has been made to determine extragalactic distances, such as M31 and M33 galaxies, using early-type eclipsing binaries.

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“…By comparing the observed v sin(i) = 432 ± 16 km s −1 to the theoretical breakup rotation, Zehe et al (2018) constrained the inclination angle to i 56 degrees. Using optical interferometry, Gordon et al (2018) measured the centrifugal distortion of ζ Oph, finding a polar radius of 7.5 R and centrifugally increased equatorial radius of 9.1 R , corresponding to a v sin(i) = 348 km s −1 .…”

Section: A Prototypical Example Of An Accretor: ζ Ophiuchimentioning

confidence: 99%

Evolution of accretor stars in massive binaries: broader implications from modeling ζ Ophiuchi

Renzo¹,

Götberg²

2021

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Most massive stars are born in binaries close enough for mass transfer episodes. These modify the appearance, structure, and future evolution of both stars. We compute the evolution of a 100-day period binary consisting initially of a 25 M star and a 17 M star, which experiences stable mass transfer. We focus on the impact of mass accretion on the surface composition, internal rotation, and structure of the accretor. To anchor our models, we show that our accretor broadly reproduces the properties of ζ Ophiuchi, which has long been proposed to have accreted mass before being ejected as a runaway star when the companion exploded. We compare our accretor to models of single rotating stars and find that the later and stronger spin-up provided by mass accretion produces significant differences. Specifically, the core of the accretor retains higher spin at the end of the main sequence, and a convective layer develops that changes its density profile. Moreover, the surface of the accretor star is polluted by CNO-processed material donated by the companion. Our models show effects of mass accretion in binaries that are not captured in single rotating stellar models. This possibly impacts the further evolution (either in a binary or as single stars), the final collapse, and the resulting spin of the compact object.

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Angular Sizes and Effective Temperatures of O-type Stars from Optical Interferometry with the CHARA Array

Cited by 13 publications

References 74 publications

Probing the weak wind phenomenon in Galactic O-type giants

Probing the weak wind phenomenon in Galactic O-type giants

Progress on the calibration of surface brightness-color relations for early- and late-type stars

Evolution of accretor stars in massive binaries: broader implications from modeling ζ Ophiuchi

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