scholarly journals Observing the linked depletion of dust and CO gas at 0.1–10 au in disks of intermediate-mass stars

2018 ◽  
Vol 609 ◽  
pp. L2 ◽  
Author(s):  
A. Banzatti ◽  
A. Garufi ◽  
M. Kama ◽  
M. Benisty ◽  
S. Brittain ◽  
...  
Keyword(s):  
Near Infrared ◽  
Intermediate Mass ◽  
Gas Emission ◽  
Infrared Excess ◽  
Intermediate Mass Stars ◽  
Refractory Elements ◽  
Definition Of ◽  
Disk Region ◽  
Co Emission ◽  
Co Gas

We report on the discovery of correlations between dust and CO gas tracers of the 0.1–10 au region in planet-forming disks around young intermediate-mass stars. The abundance of refractory elements on stellar photospheres decreases as the location of hot CO gas emission recedes to larger disk radii, and as the near-infrared excess emission from hot dust in the inner disk decreases. The linked behavior between these observables demonstrates that the recession of infrared CO emission to larger disk radii traces an inner disk region where dust is being depleted. We also find that Herbig disk cavities have either low (~5–10%) or high (~20–35%) near-infrared excess, a dichotomy that has not been captured by the classic definition of “pre-transitional” disks.

scholarly journals Near–Infrared Imaging of Proto-Planetary Nebulae

1993 ◽  
Vol 155 ◽  
pp. 340-340 ◽  
Author(s):  
R.E.S. Clegg ◽  
N. A. Walton ◽  
M.J. Barlow
Keyword(s):  
Molecular Hydrogen ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Planetary Nebulae ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Preliminary Results ◽  
Near Ir ◽  
Intermediate Mass Stars ◽  
Hydrogen Lines

It is not really known how low and intermediate mass stars eject mass to form PNs. We present preliminary results from a programme of near–IR imaging, in which we study a sequence of objects, from extreme AGB stars through proto–planetaries to young, compact PNs. We aim to study the sequence of morphologies, to see where the onset of bipolar shaping occurs, and to use the IR molecular hydrogen lines to map neutral regions around ionized nebulae.

scholarly journals Rapid CO gas dispersal from NO Lup’s class III circumstellar disc

2020 ◽  
Author(s):  
J B Lovell ◽  
G M Kennedy ◽  
S Marino ◽  
M C Wyatt ◽  
M Ansdell ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Spectral Type ◽  
Circumstellar Dust ◽  
Class Iii ◽  
Gas Emission ◽  
Central Mass ◽  
Spatially Resolved ◽  
Break Up ◽  
Co Emission ◽  
Co Gas

Abstract We observed the K7 class III star NO Lup in an ALMA survey of the 1-3 Myr Lupus association and detected circumstellar dust and CO gas. Here we show that the J = 3-2 CO emission is both spectrally and spatially resolved, with a broad velocity width ∼19 km s−1 for its resolved size ∼1″ (∼130 au). We model the gas emission as a Keplerian disc, finding consistency, but only with a central mass of ∼11M⊙, which is implausible given its spectral type and X-Shooter spectrum. A good fit to the data can also be found by modelling the CO emission as outflowing gas with a radial velocity ∼22 km s−1. We interpret NO Lup’s CO emission as the first imaged class III circumstellar disc with outflowing gas. We conclude that the CO is continually replenished, but cannot say if this is from the break-up of icy planetesimals or from the last remnants of the protoplanetary disc. We suggest further work to explore the origin of this CO, and its higher than expected velocity in comparison to photoevaporative models.

scholarly journals Six intermediate-mass stars with far-infrared excess: a search for evolutionary connections

1999 ◽  
Vol 302 (3) ◽  
pp. 612-624 ◽  
Author(s):  
A. S. Miroshnichenko ◽  
C. L. Mulliss ◽  
K. S. Bjorkman ◽  
N. D. Morrison ◽  
K. S. Kuratov ◽  
...  
Keyword(s):  
Far Infrared ◽  
Intermediate Mass ◽  
Infrared Excess ◽  
Intermediate Mass Stars

scholarly journals AGB Winds with Gas-Dust Drift in Stellar Evolution Codes

Universe ◽  
2021 ◽  
Vol 7 (5) ◽  
pp. 113
Author(s):  
Lars Mattsson ◽  
Christer Sandin
Keyword(s):  
Stellar Evolution ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Carbon Star ◽  
Intermediate Mass ◽  
Future Directions ◽  
Physical Description ◽  
Intermediate Mass Stars ◽  
Dust Component ◽  
Improved Model

A significant fraction of new metals produced in stars enter the interstellar medium in the form of dust grains. Including dust and wind formation in stellar evolution models of late-stage low- and intermediate-mass stars provides a way to quantify their contribution to the cosmic dust component. In doing so, a correct physical description of dust formation is of course required, but also a reliable prescription for the mass-loss rate. Here, we present an improved model of dust-driven winds to be used in stellar evolution codes and insights from recent detailed numerical simulations of carbon-star winds including drift (decoupling of dust and gas). We also discuss future directions for further improvement.

scholarly journals IPHAS A-type Stars with Mid-IR Excesses in Spitzer Surveys

2009 ◽  
Vol 5 (H15) ◽  
pp. 815-815
Author(s):  
Antonio S. Hales ◽  
Michael J. Barlow ◽  
Janet E. Drew ◽  
Yvonne C. Unruh ◽  
Robert Greimel ◽  
...  
Keyword(s):  
Cross Correlation ◽  
Main Sequence ◽  
Terrestrial Planet ◽  
Circumstellar Disks ◽  
Main Sequence Stars ◽  
Intermediate Mass ◽  
Mid Infrared ◽  
Isaac Newton ◽  
Intermediate Mass Stars ◽  
Dust Disks

AbstractThe Isaac Newton Photometric H-Alpha Survey (IPHAS) provides (r′-Hα)-(r′-i′) colors, which can be used to select AV0-5 Main Sequence star candidates (age~20-200 Myr). By combining a sample of 23050 IPHAS-selected A-type stars with 2MASS, GLIMPSE and MIPSGAL photometry we searched for mid-infrared excesses attributable to dusty circumstellar disks. Positional cross-correlation yielded a sample of 2692 A-type stars, of which 0.6% were found to have 8-μm excesses above the expected photospheric values. The low fraction of main sequence stars with mid-IR excesses found in this work indicates that dust disks in the terrestrial planet zone of Main Sequence intermediate mass stars are rare. Dissipation mechanisms such as photo-evaporation, grain growth, collisional grinding or planet formation could possibly explain the depletion of dust detected in the inner regions of these disks.

An IRTF-iSHELL Survey of 4.52–5.25 μm CO Spectra in Protoplanetary Disks of Intermediate-mass Stars: Preliminary Sample and Analysis

2021 ◽  
Vol 5 (4) ◽  
pp. 80
Author(s):  
Kirsten M. Abernathy ◽  
Andrea Banzatti ◽  
Stanley Jensen ◽  
Sean Brittain ◽  
Adwin Boogert ◽  
...  
Keyword(s):  
Protoplanetary Disks ◽  
Intermediate Mass ◽  
Intermediate Mass Stars

Co Emission Modeling in a Heavy Duty Annular Combustor Operating with Natural Gas

2021 ◽  
Author(s):  
Roberto Meloni ◽  
Stefano Gori ◽  
Antonio Andreini ◽  
Pier Carlo Nassini
Keyword(s):  
Turbulent Flame ◽  
Flame Temperature ◽  
Production Region ◽  
Turbulent Flame Speed ◽  
Eddy Simulation ◽  
Extinction Limit ◽  
Flamelet Generated Manifold ◽  
Annular Combustor ◽  
Definition Of ◽  
Co Emission

Abstract The present paper summarizes the development of a Large-Eddy Simulation (LES) based approach for the prediction of CO emission in an industrial gas turbine combustor. Since the operating point of the modern combustors is really close to the extinction limit, the availability of a tool able to detect the onset of high-CO production can be useful for the proper definition of the combustion chamber air split or to introduce design improvements for the premixer itself. The accurate prediction of CO cannot rely on the flamelet assumption, representing the fundament of the modern combustion models. Consequently, in this work, the Extended Turbulent Flame Speed Closure (ETFSC) of the standard Flamelet Generated Manifold (FGM) model is employed to consider the effect of the heat loss and the strain rate on the flame brush. Moreover, a customized CO-Damköhler number is introduced to de-couple the in-flame CO production region from the post-flame contribution where the oxidation takes place. A fully premixed burner working at representative values of pressure and flame temperature of an annular combustor is selected for the validation phase of the process. The comparison against the experimental data shows that the process is not only able to capture the trend but also to predict CO in a quantitative manner. In particular, the interaction between the flame and the air fluxes at some critical sections of the combustor, leading the CO emission from the equilibrium value to the super-equilibrium, has been correctly reproduced.

scholarly journals Revised SED of the triple protostellar system VLA 1623−2417

2018 ◽  
Vol 615 ◽  
pp. L14 ◽  
Author(s):  
N. M. Murillo ◽  
D. Harsono ◽  
M. McClure ◽  
S.-P. Lai ◽  
M. R. Hogerheijde
Keyword(s):  
Energy Distribution ◽  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Gas Emission ◽  
Circumstellar Gas ◽  
Infrared Wavelengths ◽  
Previous Assumption

Context. VLA 1623−2417 is a triple protostellar system deeply embedded in Ophiuchus A. Sources A and B have a separation of 1.1″, making their study difficult beyond the submillimeter regime. Lack of circumstellar gas emission suggested that VLA 1623−2417 B has a very cold envelope and is much younger than source A, which is generally considered the prototypical Class 0 source. Aims. We explore the consequences of new ALMA Band 9 data on the spectral energy distribution (SED) of VLA 1623−2417 and their inferred nature. Methods. We constructed and analyzed the SED of each component in VLA 1623−2417 using dust continuum observations spanning from centimeter to near-infrared wavelengths. Results. The ALMA Band 9 data presented in this work show that the SED of VLA 1623−2417 B does not peak at 850 µm as previously expected, but instead presents the same shape as VLA 1623−2417 A at wavelengths shorter than 450 µm. Conclusions. The results presented in this work indicate that the previous assumption that the flux in Herschel and Spitzer observations is solely dominated by VLA 1623−2417 A is not valid, and instead, VLA 1623−2417 B most likely contributes a significant portion of the flux at λ < 450 µm. These results, however, do not explain the lack of circumstellar gas emission and puzzling nature of VLA 1623−2417 B.

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