Mapping the molecular emission of circumstellar envelopes with the Plateau de Bure interferometer

2008 ◽  
pp. 260-270
Author(s):  
M. Guélin
Keyword(s):  
Circumstellar Envelopes ◽  
Molecular Emission

scholarly journals Molecular Emissions from Circumstellar Envelopes in the Presence of a Binary Companion

2020 ◽  
Vol 31 ◽  
Author(s):  
Trung Van Dinh
Keyword(s):  
Angular Resolution ◽  
Line Emission ◽  
High Angular Resolution ◽  
Spiral Pattern ◽  
Circumstellar Envelopes ◽  
Hydrodynamic Simulations ◽  
Molecular Emission ◽  
Orbital Parameters ◽  
Physical Conditions ◽  
Spatial Kinematics

Following our previous work on the hydrodynamic simulations of the structure of circumstellar envelopes in the presence of a binary companion, in this paper we present the results of radiative transfer calculations for molecular emission line HC3N J=5 – 4 from these simulated circumstellar envelopes. We show that the molecular line emission traces closely the spiral pattern and the associated density enhancement induced by the presence of the binary companion. The molecular emission provides the spatial kinematics of the features within the envelope, which is valuable for estimating the orbital parameters of the binary system and for inferring the physical conditions of the gas within the envelope. We also show that the appearance of the molecular emission depends on the viewing angle resulting in a range of shapes from the spiral pattern to ring-like features, similar to that observed recently in a number of circumstellar envelopes at high angular resolution.

Deriving the Geometry of Be Star Circumstellar Envelopes from Continuum Spectropolarimetry. I. The Case of ζ Tauri

1997 ◽  
Vol 477 (2) ◽  
pp. 926-939 ◽  
Author(s):  
Kenneth Wood ◽  
K. S. Bjorkman ◽  
J. E. Bjorkman
Keyword(s):  
Circumstellar Envelopes ◽  
Be Star

scholarly journals The chemistry of cool circumstellar envelopes

1987 ◽  
Vol 122 ◽  
pp. 551-552
Author(s):  
L.A.M. Nejad ◽  
T. J. Millar
Keyword(s):  
Kinetic Model ◽  
Chemical Kinetic ◽  
Time Dependent ◽  
Circumstellar Envelopes ◽  
Chemical Kinetic Model ◽  
Ion Molecule Reactions ◽  
Cool Stars

We have developed a time-dependent chemical kinetic model to describe the chemistry in the circumstellar envelopes of cool stars, with particular reference to IRC + 10216. Our detailed calculations show that ion-molecule reactions are important in the formation of many of the species observed in IRC + 10216.

scholarly journals Activity of the first interstellar comet 2I/Borisov around perihelion: results from Indian observatories

2021 ◽  
Vol 502 (3) ◽  
pp. 3491-3499
Author(s):  
K Aravind ◽  
Shashikiran Ganesh ◽  
Kumar Venkataramani ◽  
Devendra Sahu ◽  
Dorje Angchuk ◽  
...  
Keyword(s):  
Solar System ◽  
Production Rate ◽  
Rate Ratio ◽  
Carbon Chain ◽  
Astronomical Observatory ◽  
Nucleus Size ◽  
Chain Molecules ◽  
Molecular Emission ◽  
Imaging And Spectroscopy ◽  
Gas Ratio

ABSTRACT Comet 2I/Borisov is the first true interstellar comet discovered. Here, we present results from observational programs at two Indian observatories, 2 m Himalayan Chandra Telescope at the Indian Astronomical Observatory, Hanle (HCT) and 1.2 m telescope at the Mount Abu Infrared Observatory (MIRO). Two epochs of imaging and spectroscopy were carried out at the HCT and three epochs of imaging at MIRO. We found CN to be the dominant molecular emission on both epochs, 2019 November 30 and December 22, at distances of rH = 2.013 and 2.031 au, respectively. The comet was inferred to be relatively depleted in Carbon bearing molecules on the basis of low C2 and C3 abundances. We find the production rate ratio, Q(C2)/Q(CN) = 0.54 ± 0.18, pre-perihelion and Q(C2)/Q(CN) = 0.34 ± 0.12 post-perihelion. This classifies the comet as being moderately depleted in carbon chain molecules. Using the results from spectroscopic observations, we believe the comet to have a chemically heterogeneous surface having variation in abundance of carbon chain molecules. From imaging observations, we infer a dust-to-gas ratio similar to carbon chain depleted comets of the Solar system. We also compute the nucleus size to be in the range 0.18 km ≤ r ≤ 3.1 km. Our observations show that 2I/Borisov’s behaviour is analogous to that of the Solar system comets.

Influence of an atomistic protrusion at the tip apex on enhancing molecular emission in tunnel junctions: A theoretical study

2021 ◽  
Vol 154 (21) ◽  
pp. 214706
Author(s):  
Jia-Zhe Zhu ◽  
Gong Chen ◽  
Talha Ijaz ◽  
Xiao-Guang Li ◽  
Zhen-Chao Dong
Keyword(s):  
Theoretical Study ◽  
Tunnel Junctions ◽  
Molecular Emission

scholarly journals Dust Production around Carbon-Rich Stars: The Role of Metallicity

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 233
Author(s):  
Ambra Nanni ◽  
Sergio Cristallo ◽  
Jacco Th. van Loon ◽  
Martin A. T. Groenewegen
Keyword(s):  
Wind Speed ◽  
Galactic Halo ◽  
Magellanic Clouds ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Circumstellar Envelopes ◽  
Chemical Enrichment ◽  
Wide Range ◽  
The Universe

Background: Most of the stars in the Universe will end their evolution by losing their envelope during the thermally pulsing asymptotic giant branch (TP-AGB) phase, enriching the interstellar medium of galaxies with heavy elements, partially condensed into dust grains formed in their extended circumstellar envelopes. Among these stars, carbon-rich TP-AGB stars (C-stars) are particularly relevant for the chemical enrichment of galaxies. We here investigated the role of the metallicity in the dust formation process from a theoretical viewpoint. Methods: We coupled an up-to-date description of dust growth and dust-driven wind, which included the time-averaged effect of shocks, with FRUITY stellar evolutionary tracks. We compared our predictions with observations of C-stars in our Galaxy, in the Magellanic Clouds (LMC and SMC) and in the Galactic Halo, characterised by metallicity between solar and 1/10 of solar. Results: Our models explained the variation of the gas and dust content around C-stars derived from the IRS Spitzer spectra. The wind speed of the C-stars at varying metallicity was well reproduced by our description. We predicted the wind speed at metallicity down to 1/10 of solar in a wide range of mass-loss rates.

scholarly journals Direct observation of long-lived cyanide anions in superexcited states

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Xiao-Fei Gao ◽  
Jing-Chen Xie ◽  
Hao Li ◽  
Xin Meng ◽  
Yong Wu ◽  
...  
Keyword(s):  
Direct Observation ◽  
Electron Attachment ◽  
Planetary Atmosphere ◽  
Interstellar Space ◽  
Dissociative Electron Attachment ◽  
Circumstellar Envelopes ◽  
Vibrational States ◽  
Cyanide Anion ◽  
Exceptional Stability ◽  
Electronic Ground

AbstractThe cyanide anion (CN−) has been identified in cometary coma, interstellar medium, planetary atmosphere and circumstellar envelopes, but its origin and abundance are still disputed. An isolated CN− is stabilized in the vibrational states up to ν = 17 of the electronic ground-state 1Σ+, but it is not thought to survive in the electronic or vibrational states above the electron autodetachment threshold, namely, in superexcited states. Here we report the direct observation of long-lived CN− yields of the dissociative electron attachment to cyanogen bromide (BrCN), and confirm that some of the CN− yields are distributed in the superexcited vibrational states ν ≥ 18 (1Σ+) or the superexcited electronic states 3Σ+ and 3Π. The triplet state can be accessed directly in the impulsive dissociation of BrCN− or by an intersystem transition from the superexcited vibrational states of CN−. The exceptional stability of CN− in the superexcited states profoundly influences its abundance and is potentially related to the production of other compounds in interstellar space.

Zooming into the complex dusty envelopes of C-rich AGB stars

2018 ◽  
Vol 14 (S343) ◽  
pp. 456-457
Author(s):  
Foteini Lykou ◽  
Josef Hron ◽  
Daniela Klotz
Keyword(s):  
Temperature Distribution ◽  
Near Infrared ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
Dust Formation ◽  
Agb Stars ◽  
Circumstellar Envelopes ◽  
Recent Advances ◽  
Multi Wavelength

AbstractRecent advances in high-angular resolution instruments (VLT and VLTI, ALMA) have enabled us to delve deep into the circumstellar envelopes of AGB stars from the optical to the sub-mm wavelengths, thus allowing us to study in detail the gas and dust formation zones (e.g., their geometry, chemistry and kinematics). This work focuses on four (4) C-rich AGB stars observed with a high-angular resolution technique in the near-infrared: a multi-wavelength tomographic study of the dusty layers of the circumstellar envelopes of these C-rich stars, i.e. the variations in the morphology and temperature distribution.

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