High spectral resolution spectroscopy of the SiO fundamental lines in red giants and red supergiants with VLT/VISIR

Ohnaka, K.

doi:10.1051/0004-6361/201321581

Cited by 16 publications

(12 citation statements)

References 74 publications

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“…This is expected because the isotopic ratio of 28 Si/ 29 Si in oxygen-rich giants is 13 (e.g. Tsuji et al 1994;Decin et al 2010;Ohnaka 2014). The 29 SiO emission within ∼0 .…”

Section: Imagesmentioning

confidence: 91%

Resolving the extended atmosphere and the inner wind of Mira (oCeti) with long ALMA baselines

Wong

Kamiński

Menten

et al. 2016

A&A

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Context. High angular resolution (sub)millimetre observations of asymptotic giant branch (AGB) stars, now possible with the Atacama Large Millimeter/submillimeter Array (ALMA), allow direct imaging of these objects' photospheres. The physical properties of the molecular material around these regions, which until now has only been studied by imaging of maser emission and spatially unresolved absorption spectroscopy, can be probed with radiative transfer modelling and compared to hydrodynamical model predictions. The prototypical Mira variable, o Cet (Mira), was observed as a Science Verification target in the 2014 ALMA Long Baseline Campaign, offering the first opportunity to study these physical conditions in detail. Aims. With the longest baseline of 15 km, ALMA produces clearly resolved images of the continuum and molecular line emission/absorption at an angular resolution of ∼30 mas at 220 GHz. Models are constructed for Mira's extended atmosphere to investigate the physics and molecular abundances therein. Methods. We imaged the data of 28 SiO = 0, 2 J = 5−4 and H 2 O v 2 = 1 J Ka,Kc = 5 5,0 −6 4,3 transitions and extracted spectra from various lines of sight towards Mira's extended atmosphere. In the course of imaging the emission/absorption, we encountered ambiguities in the resulting images and spectra that appear to be related to the performance of the CLEAN algorithm when applied to a combination of extended emission, and compact emission and absorption. We addressed these issues by a series of tests and simulations. We derived the gas density, kinetic temperature, molecular abundance, and outflow/infall velocities in Mira's extended atmosphere by modelling the SiO and H 2 O lines. Results. We resolve Mira's millimetre continuum emission and our data are consistent with a radio photosphere with a brightness temperature of 2611 ± 51 K. In agreement with recent results obtained with the Very Large Array, we do not confirm the existence of a compact region (<5 mas) of enhanced brightness. Our modelling shows that SiO gas starts to deplete beyond 4 R and at a kinetic temperature of 600 K. The inner dust shells are probably composed of grain types other than pure silicates. During this ALMA observation, Mira's atmosphere generally exhibited infall motion with a shock front of velocity 12 km s −1 outside the radio photosphere. Despite the chaotic nature of Mira's atmosphere, the structures predicted by the hydrodynamical model, codex, can reproduce the observed spectra in astonishing detail, while some other models fail when confronted with the new data. Conclusions. For the first time, millimetre-wavelength molecular absorption against the stellar continuum has been clearly imaged. Combined with radiative transfer modelling, the ALMA data successfully demonstrates the ability to reveal the physical conditions of the extended atmospheres and inner winds of AGB stars in unprecedented detail. Long-term monitoring of oxygen-rich evolved stars will be the key to understanding the unsolved problem of dust ...

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“…This is expected because the isotopic ratio of 28 Si/ 29 Si in oxygen-rich giants is 13 (e.g. Tsuji et al 1994;Decin et al 2010;Ohnaka 2014). The 29 SiO emission within ∼0 .…”

Section: Imagesmentioning

confidence: 91%

Resolving the extended atmosphere and the inner wind of Mira (oCeti) with long ALMA baselines

Wong

Kamiński

Menten

et al. 2016

A&A

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“…The MOLspheric temperature-density distribution shows a slight decrease in temperature and NCO from T mol R mol,0 R = 960K to T mol R mol,end R = 958K and from NCO R mol,0 R = 10 21.5 mol/cm −2 to NCO R mol,end R = 10 21.1 mol/cm −2 respectively. We adjusted / = 24.7 ± 0.4mas to obtain the best fit between the model and the visibilities in the continuum, and according to Ohnaka (2014, and references therein) we fixed v micro,mol = vmicro = 2km.s −1 in order to obtain the best agreement between the width of modeled molecular lines and the observations. The bottom portion of Fig.…”

Section: γ Crumentioning

confidence: 99%

“…We adjusted / = 37mas to obtain the best fit between the model and the observed visibilities in the continuum, and according to (Ohnaka 2014, and references therein) we fixed v micro,mol = vmicro = 5km.s −1 in order to get the best agreement between the width of modeled molecular lines and the observations. The bottom portion of Fig.…”

Section: α Scomentioning

confidence: 99%

A CO-multilayer outer atmosphere for eight evolved stars revealed with VLTI/AMBER

Hadjara

Cruzalèbes

Nitschelm

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We determine the physical parameters of the outer atmosphere of a sample of eight evolved stars, including the Red SuperGiant α Sco, the Red Giant Branch stars α Boo and γ Cru, the K giant λ Vel, the normal M-giants BK Vir and SW Vir, and the Mira star W Hya (in two different luminosity phases) by spatially resolving the stars in the individual carbon monoxide (CO) first overtone lines. We used the AM-BER (Astronomical Multi-BEam combineR) instrument at the Very Large Telescope Interferometer (VLTI), in high-resolution mode (λ/∆λ ≈ 12000) between 2.28 and 2.31 µm in K-band. The maximal angular resolution is 10 mas, obtained by triplets telescope configuration, with baselines from 7 to 48 m. By using a numerical model of a molecular atmosphere in spherical shells (MOLsphere), named PAMPERO (for Physical Approach of Molecular Photospheric Ejection at high-angular-Resolution for evOlved-stars) we add multiple extended CO layers above the photospheric MARCS model at an adequate spatial resolution. We use the differential visibilities and the spectrum to estimate the size (R) of the CO MOLsphere, its column density (N CO ) and temperature (T mol ) distributions along the stellar radius. The combining of the χ2 minimization and a fine grid approach for uncertainty analysis leads to reasonable N CO and T mol distributions along the stellar radius of the MOLsphere.

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“…Knowing the mass of the central star in L 2 Pup is essential to constrain its age and evolutionary state. Indirect estimates vary considerably in the literature: from 0.5 ± 0.2 M by Ohnaka (2014), 0.7 M by Lykou et al (2015a), and 1.7 M by Dumm & Schild (1998) to 2 M by Kervella et al (2014). With the goal of precisely determining the mass of the AGB star, we obtained very high angular resolution observations in ALMA's band 7 (330−360 GHz), covering several molecular lines and the continuum (Sect.…”

Section: Introductionmentioning

confidence: 99%

ALMA observations of the nearby AGB star L₂ Puppis

Kervella

Homan

Richards

et al. 2016

A&A

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Six billion years from now, while evolving on the asymptotic giant branch (AGB), the Sun will metamorphose from a red giant into a beautiful planetary nebula. This spectacular evolution will impact the solar system planets, but observational confirmations of the predictions of evolution models are still elusive as no planet orbiting an AGB star has yet been discovered. The nearby AGB red giant L 2 Puppis (d = 64 pc) is surrounded by an almost edge-on circumstellar dust disk. We report new observations with ALMA at very high angular resolution (18 × 15 mas) in band 7 (ν ≈ 350 GHz) that allow us to resolve the velocity profile of the molecular disk. We establish that the gas velocity profile is Keplerian within the central cavity of the dust disk, allowing us to derive the mass of the central star L 2 Pup A, m A = 0.659 ± 0.011 ± 0.041 M (±6.6%). From evolutionary models, we determine that L 2 Pup A had a near-solar main-sequence mass, and is therefore a close analog of the future Sun in 5 to 6 Gyr. The continuum map reveals a secondary source (B) at a radius of 2 AU contributing f B / f A = 1.3 ± 0.1% of the flux of the AGB star. L 2 Pup B is also detected in CO emission lines at a radial velocity of v B = 12.2 ± 1.0 km s −1 . The close coincidence of the center of rotation of the gaseous disk with the position of the continuum emission from the AGB star allows us to constrain the mass of the companion to m B = 12 ± 16 M Jup . L 2 Pup B is most likely a planet or low-mass brown dwarf with an orbital period of about five years. Its continuum brightness and molecular emission suggest that it may be surrounded by an extended molecular atmosphere or an accretion disk. L 2 Pup therefore emerges as a promising vantage point on the distant future of our solar system.

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High spectral resolution spectroscopy of the SiO fundamental lines in red giants and red supergiants with VLT/VISIR

Cited by 16 publications

References 74 publications

Resolving the extended atmosphere and the inner wind of Mira (oCeti) with long ALMA baselines

Resolving the extended atmosphere and the inner wind of Mira (oCeti) with long ALMA baselines

A CO-multilayer outer atmosphere for eight evolved stars revealed with VLTI/AMBER

ALMA observations of the nearby AGB star L₂ Puppis

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High spectral resolution spectroscopy of the SiO fundamental lines in red giants and red supergiants with VLT/VISIR

Cited by 16 publications

References 74 publications

Resolving the extended atmosphere and the inner wind of Mira (oCeti) with long ALMA baselines

Resolving the extended atmosphere and the inner wind of Mira (oCeti) with long ALMA baselines

A CO-multilayer outer atmosphere for eight evolved stars revealed with VLTI/AMBER

ALMA observations of the nearby AGB star L2 Puppis

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ALMA observations of the nearby AGB star L₂ Puppis