Perspectives of a visible instrument on the VLTI

Millour, F.; Mourard, D.; Woillez, J.; Bério, Philippe; Chiavassa, A.; Creevey, O.; Lagadec, E.; Martinod, Marc-Antoine; Meilland, A.; Nardetto, N.; Perraut, K.; Stee, Philippe

doi:10.1007/s10686-018-9615-0

Cited by 4 publications

(6 citation statements)

References 27 publications

(28 reference statements)

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“…Despite being a decommissioned instrument, by the end of 2017, a large number of observations performed with AMBER are still used in very recent works about circumstellar environments (e.g., Koutoulaki et al 2018;Adam & Ohnaka 2019;Ohnaka et al 2019;Hadjara et al 2019), and it yielded the largest number of articles among the VLTI instruments to date. the interesting science cases pointed out by Millour et al (2018) for a future visible spectro-interferometric instrument on VLTI.…”

Section: Vlti/ambermentioning

confidence: 95%

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: Vlti/ambermentioning

confidence: 95%

Probing the weak wind phenomenon in Galactic O-type giants

Almeida

Marcolino

Bouret

et al. 2019

A&A

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“…Ertel et al [3], and Hönig et al [4] as well as the science cases of the 2nd gen VLTI GRAVITY 1 and MATISSE 2 instruments with full imaging capability now online, highlight possible future directions of these key fields of modern long baseline interferometry. While as discussed in these articles, increasing the angular resolution and imaging capabilities by longer baselines and additional telescopes allow to study new aspects, Millour et al [5], and the community effort behind describe how doing interferometry in the visible (<0.9 μm) will unlock new areas of research thanks to the combination of higher angular resolution and different wavelengths, making new classes of (bluer) stars and eventually AGN accessible to interferometers.…”

Section: Modern Science Cases Of Optical-infrared Interferometrymentioning

confidence: 99%

“…4 In Defrère et al [7] on Hi-5, such a focused instrument concept is presented, which could be realized as a visitor-instrument, similar to the successful PIONIER. 5 This high-dynamic range imager for the thermal infrared relies on a combination of new integrated optics technology which is currently developed for thermal infrared wavelengths [8], and statistically robust data processing techniques, emphasizing the importance of technological progress.…”

Section: Before 2025: Parallel To the Construction Vlt 3rd Generationmentioning

confidence: 99%

“…Given the likely focus of the PFI on longer wavelengths, exploiting visible interferometry at the VLTI will allow for a complementary scientific use. Millour et al [5] discuss opto-mechanical upgrades of the current VLTI infrastructure that would be needed to control the wavelengths leading to a 2-3 times higher angular resolution, as a prerequisite for visible-wavelength interferometry. Important technological pathfinding is currently done at the CHARA facility.…”

Section: -2035: Towards a New Facilitymentioning

confidence: 99%

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Future of optical-infrared interferometry in Europe

Pott

Surdej

2018

Exp Astron

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“…to explore interferometry at visible wavelengths -in R-band or I-band -to spatially resolve fundamental stellar physics (e.g. IVis proposal 16,17 ).…”

Section: Introductionmentioning

confidence: 99%

Dimensioning adaptive optics for future VLTI projects

Patru

Millour

Lai

et al. 2020

Adaptive Optics Systems VII

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Perspectives of a visible instrument on the VLTI

Cited by 4 publications

References 27 publications

Probing the weak wind phenomenon in Galactic O-type giants

Probing the weak wind phenomenon in Galactic O-type giants

Future of optical-infrared interferometry in Europe

Dimensioning adaptive optics for future VLTI projects

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