Einstein A-coefficients for vib-rotational transitions in
CO

Chandra, Suresh; Maheshwari, Vaibhav; Sharma, A. K.

doi:10.1051/aas:1996173

Cited by 60 publications

(63 citation statements)

References 12 publications

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“…Models were also considered that allowed the vibrational levels to fall out of thermal equilibrium while retaining thermal populations for the rotational levels. This is physically plausible, since pure rotational lifetimes are typically 10 4 -10 5 longer than their vibrational-rotational counterparts (Chandra, Maheshwari, & Sharma 1996). Under such conditions, the widths of the band heads are sensitive to the rotational temperature, while their relative intensities are determined primarily by the populations of the vibrational levels.…”

Section: Co Characteristicsmentioning

confidence: 98%

Near‐Infrared Spectrophotometry and the CO Emission in V2274 Cygni (Nova Cygni 2001 No. 1)

Rudy

Dimpfl

Lynch

et al. 2003

ApJ

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Infrared spectroscopy of V2274 Cygni (=Nova Cygni 2001 No. 1) is presented for two widely separated epochs, 17 and 370 days after discovery. In addition to the Paschen and Brackett series of H i, the early-time spectrum shows strong emission lines of C i and N i, fluorescently excited lines of O i, and emission from the first overtone of carbon monoxide. Because the initial data were probably acquired no more than 18 days after outburst, CO molecule formation occurred remarkably quickly in the dense, cool, carbon and oxygen rich ejecta. Rapid formation was also seen in NQ Vul, V842 Cen, and V705 Cas, three other novae in which first-overtone CO emission has been detected. Formation of the CO molecule may occur chemically in a process that requires H 2 as a precursor or directly through radiative association. The overtone emission of V2274 Cyg indicates a temperature of $2500 K. The vibrational levels show no obvious departures from thermal equilibrium, which may indicate high optical depths in the fundamental. A large 13 C/ 12 C ratio (0:83 AE 0:3) is also indicated by the observations, consistent with the fast CNO burning expected in novae explosions. By the time of the second epoch observations, the emission lines of the neutral C, N, and O had disappeared. He i 10830 was the dominant emission feature in the spectrum. In addition to the hydrogen lines, recombination features of He ii were also strong. The common nebular lines of [S iii] were seen but only two coronal line, [S viii] 9911 and [Si vi] 19645, were detected. The CO emission had disappeared, but a strong thermal dust component was present. The interstellar reddening for the system was found to be E(BÀV Þ ¼ 1:3. This extinction, together with the absolute magnitude derived from the rate of decline of the light curve, suggest a distance of $10.8 kpc. This places V2274 Cyg well out of the Galactic plane. The small number of novae with spectroscopic detections of carbon monoxide all have prominent C i lines, moderate speed classes and ejection velocities, exhibit marked dust formation events, and result from an explosion on a CO-type white dwarf. Based on these similarities, the spectrum of V2274 is proposed as a likely near-infrared spectral template for other novae that display carbon monoxide emission.

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Section: Co Characteristicsmentioning

confidence: 98%

Near‐Infrared Spectrophotometry and the CO Emission in V2274 Cygni (Nova Cygni 2001 No. 1)

Rudy

Dimpfl

Lynch

et al. 2003

ApJ

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“…B.2 and B.3). The transition frequencies, Einstein A coefficients, statistical weights, and energies of the upper levels are taken from Chandra et al (1996). We approximate the emitting region by a rectangle with the same width as the slit and length equal to the diameter of the emitting region of the CO (2 × 50 AU, Goto et al 2012): Ω = 0.…”

Section: Population Diagramsmentioning

confidence: 99%

CO ro-vibrational lines in HD 100546

Bertelsen

Kamp

Goto³

et al. 2014

A&A

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Aims. We have studied the emission of CO ro-vibrational lines in the disc around the Herbig Be star HD 100546 to determine physical properties, disc asymmetries, the CO excitation mechanism, and the spatial extent of the emission, with the final goal of using the CO ro-vibrational lines as a diagnostic to understand inner disc structure in the context of planet formation. Methods. High-spectral-resolution infrared spectra of CO ro-vibrational emission at eight different position angles were taken with the CRyogenic high-resolution InfraRed Echelle Spectrograph (CRIRES) at the Very Large Telescope (VLT). From these spectra flux tables, line profiles for individual CO ro-vibrational transitions, co-added line profiles, and population diagrams were produced. We have investigated variations in the line profile shapes and line strengths as a function of slit position angle. We used the thermochemical disc modelling code ProDiMo based on the chemistry, radiation field, and temperature structure of a previously published model for HD 100546. We calculated line fluxes and profiles for the whole set of observed CO ro-vibrational transitions using a large CO model molecule that includes the lowest two electronic states, each with 7 vibrational levels and within them 60 rotational levels. Comparing observations and the model, we investigated the possibility of disc asymmetries, the excitation mechanism (UV fluorescence), the geometry, and physical conditions of the inner disc. Results. The observed CO ro-vibrational lines are largely emitted from the inner rim of the outer disc at 10-13 AU. The line shapes are similar for all v levels and line fluxes from all vibrational levels vary only within one order of magnitude. All line profile asymmetries and variations can be explained with a symmetric disc model to which a slit correction and pointing offset is applied. Because the angular size of the CO emitting region (10-13 AU) and the slit width are comparable the line profiles are very sensitive to the placing of the slit. The model reproduces the line shapes and the fluxes of the v = 1-0 lines as well as the spatial extent of the CO rovibrational emission. It does not reproduce the observed band ratios of 0.5-0.2 with higher vibrational bands. We find that lower gas volume densities at the surface of the inner rim of the outer disc can make the fluorescence pumping more efficient and reproduce the observed band ratios.

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“…The optical depth is given by the absorption coefficient per CO molecule × the CO column density (i.e., N(r) because of the thin disc). Our model takes into account up to J = 100 rotational levels in local thermal equilibrium (LTE) for the two transitions, where the CO energy levels and the Einstein coefficients are taken from Farrenq et al (1991) and from Chandra et al (1996), respectively. The disc is split into radial and azimuthal cells.…”

Section: Co Bandhead Modellingmentioning

confidence: 99%

LBT/LUCIFER near-infrared spectroscopy of PV Cephei

Garatti

Lopez

Weigelt

et al. 2013

A&A

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Context. Young stellar objects (YSOs) occasionally experience enhanced accretion events, the nature of which is still poorly understood. The discovery of various embedded outbursting YSOs has recently questioned the classical definition of EXors and FUors. Aims. We present a detailed spectroscopic investigation of the young eruptive star PV Cep, to improve our understanding of its nature and characterise its circumstellar environment after its last outburst in 2004. Methods. The analysis of our medium-resolution spectroscopy in the near-infrared (NIR, 0.9-2.35 μm), collected in 2012 at the Large Binocular Telescope with the IR spectrograph LUCIFER, allows us to infer the main stellar parameters (visual extinction, accretion luminosity, mass accretion and ejection rates), and model the inner disc, jet, and wind. Results. The NIR spectrum displays several strong emission lines associated with accretion/ejection activity and circumstellar environment. Our analysis shows that the brightness of PV Cep is fading, as well as the mass accretion rate (2 × 10 −7 M yr −1 in 2012 vs. ∼5 × 10 −6 M yr −1 in 2004), which is more than one order of magnitude lower than in the outburst phase.Among the several emission lines, only the [Fe ii] intensity increased after the outburst. The observed [Fe ii] emission delineates blue-and red-shifted lobes, both with high-and low-velocity components, which trace an asymmetric jet and wind, respectively. The observed emission in the jet has a dynamical age of 7-8 years, indicating that it was produced during the last outburst. The visual extinction decreases moving from the red-shifted (A V (red) = 10.1 ± 0.7 mag) to the blue-shifted lobe (A V (blue) = 6.5 ± 0.4 mag). We measure an average electron temperature of 17 500 K and electron densities of 30 000 cm −3 and 15 000 cm −3 for the blue and the red lobe, respectively. The mass ejection rate in both lobes is ∼1.5 × 10 −7 M yr −1 , approximately matching the high accretion rate observed during and immediately after the outburst (Ṁ out /Ṁ acc ∼ 0.05-0.1). The observed jet/outflow asymmetries are consistent with an inhomogeneous medium. Our modelling of the CO emission hints at a small-scale gaseous disc ring, extending from ∼0.2-0.4 AU to ∼3 AU from the source, with an inner temperature of ∼3000 K. Our H i lines modelling indicates that most of the observed emission comes from an expanding disc wind at T e = 10 000 K. The line profiles are strongly affected by scattering, disc screening, and outflow self-absorption. Conclusions. According to the classical definition, PV Cep is not an EXor object, because it is more massive and younger than typical EXors. Nevertheless, its spectrum shows the signature of an "EXor-like" outburst, suggesting a common origin.

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Einstein A-coefficients for vib-rotational transitions in CO

Cited by 60 publications

References 12 publications

Near‐Infrared Spectrophotometry and the CO Emission in V2274 Cygni (Nova Cygni 2001 No. 1)

Near‐Infrared Spectrophotometry and the CO Emission in V2274 Cygni (Nova Cygni 2001 No. 1)

CO ro-vibrational lines in HD 100546

LBT/LUCIFER near-infrared spectroscopy of PV Cephei

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