Discovery of a TiO emission band in the infrared spectrum of the S star NP Aurigae

Smolders, K.; Verhoelst, Tijl; Neyskens, P.; Blommaert, J. A. D. L.; Decin, L.; Winckel, H. Van; Eck, S. Van; Sloan, G. C.; Cami, J.; Hony, S.; Cat, P. De; Menu, J.; Vos, J.

doi:10.1051/0004-6361/201219520

Cited by 10 publications

(14 citation statements)

References 26 publications

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“…Although emission bands of TiO are rarely observed, they are present in VY CMa, and very rich TiO emission is seen in the spectra of U Equ and V4332 Sgr (Barnbaum et al 1996;Kamiński et al 2010 (Zickgraf et al 1989) and a few protostars (Hillenbrand et al 2012), including some that are known to be explosive objects. Recently, an emission feature of TiO was discovered in the IR (around 10 μm) in four S-type Mira variables that are large-amplitude pulsators (Smolders et al 2012). A common property of these objects (including VY CMa) is the relatively violent environment in which the TiO emission is observed.…”

Section: Ti Oxides and The Formation Of Inorganic Dustmentioning

confidence: 99%

Pure rotational spectra of TiO and TiO₂in VY Canis Majoris

Kamiński

Gottlieb

Menten

et al. 2013

A&A

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We report the first detection of pure rotational transitions of TiO and TiO 2 at (sub-)millimeter wavelengths towards the red supergiant VY CMa. A rotational temperature, T rot , of about 250 K was derived for TiO 2 . Although T rot was not well constrained for TiO, it is likely somewhat higher than that of TiO 2 . The detection of the Ti oxides confirms that they are formed in the circumstellar envelopes of cool oxygen-rich stars and may be the "seeds" of inorganic-dust formation, but alternative explanations for our observation of TiO and TiO 2 in the cooler regions of the envelope cannot be ruled out at this time. The observations suggest that a significant fraction of the oxides is not converted to dust, but instead remains in the gas phase throughout the outflow.

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Section: Ti Oxides and The Formation Of Inorganic Dustmentioning

confidence: 99%

Pure rotational spectra of TiO and TiO₂in VY Canis Majoris

Kamiński

Gottlieb

Menten

et al. 2013

A&A

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“…Observations of TiO emission in the 10 micron spectral region from circumstellar environments around AGB stars will be more sensitive (by one order of magnitude 6 ), and with higher spatial resolution than those of Spitzer. Detection of a better upper limit by the James Webb Space Telescope (JWST) of TiO 2 and other titanium oxides not seen by Spitzer (Smolders et al 2012) will allow testing of the chemical calculations presented here. The detection of TiO and TiO 2 in the cooler region of late-type stars implies that other small transition metal-bearing molecules such as VO, might be found with sensitive interferometers in the submillimeter wave band (Kamiński et al 2013).…”

Section: Conclusion and Prospectsmentioning

confidence: 97%

“…Using Spitzer infrared data, Smolders et al (2012) derived a TiO column density of ∼10 17.25 cm −2 in the circumstellar environment of the S star NP Aurigae at temperatures higher than 1900 K. Kamiński et al (2013) of TiO and TiO 2 at submillimeter wavelengths in the stellar environment of VY Canis Majoris, with column densities of ∼10 14 cm −2 for both species, but for T = 1000 ± 870 K. On the other hand, our calculations predict TiO abundances of ∼1.0 × 10 −8 and ∼1.0 × 10 −11 for, respectively, T ∼ 1800 K and T ∼ 1600 K at P ∼ 10 −4 bar (typical gas pressure in circumstellar environments) in the C/O = 0.5 case (see Fig. 2).…”

Section: Comparison With Observationsmentioning

confidence: 99%

“…Since then, these molecules have been detected in various astrophysical environments; TiO and TiO 2 have been observed at sub-millimeter wavelengths in the circumstellar envelope of VY Canis Majoris (Kamiński et al 2013). Moreover, TiO and VO have been identified around protostars in optical emission bands (Hillenbrand et al 2012) and also in the infrared emission spectrum of S-type star atmospheres (Smolders et al 2012). Recently, TiO and VO have been proposed as the cause of the thermal inversions observed in several highly irradiated hot-Jupiters (Hubeny et al 2003;Fortney et al 2008) in which the determination of the C/O ratio is possible (Madhusudhan 2012).…”

Section: Introductionmentioning

confidence: 99%

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Influence of the C/O ratio on titanium and vanadium oxides in protoplanetary disks

Ali-Dib

Mousis

Pekmezci

et al. 2013

A&A

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Context. The observation of carbon-rich disks have motivated several studies questioning the influence of the C/O ratio on their gas phase composition in order to establish the connection between the metallicity of hot-Jupiters and that of their parent stars. Aims. We propose a method that allows the characterization of the adopted C/O ratio in protoplanetary disks independently from the determination of the host star composition. Titanium and vanadium chemistries are investigated because they are strong optical absorbers and also because their oxides are known to be sensitive to the C/O ratio in some exoplanet atmospheres. Methods. We use a commercial package based on the Gibbs energy minimization technique to compute the titanium and vanadium equilibrium chemistries in protoplanetary disks for C/O ratios ranging from 0.05 to 10. Our calculations are performed for pressures in the 10 −6 -10 −2 bar domain, and for temperatures ranging from 50 K to 2000 K. Results. We find that the vanadium nitride/vanadium oxide and titanium hydride/titanium oxide gas phase ratios strongly depend on the C/O ratio in the hot parts of disks (T ≥ 1000 K). Our calculations suggest that, in these regions, these ratios can be used as tracers of the C/O value in protoplanetary disks.

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“…[29][30][31] Because of the relatively high cosmic abundances of these monoxides, some of them can even be considered as indicators of certain star types. [29][30][31] Because of the relatively high cosmic abundances of these monoxides, some of them can even be considered as indicators of certain star types.…”

Section: Introductionmentioning

confidence: 99%

Decomposition pathways of formamide in the presence of vanadium and titanium monoxides

Nguyen

2015

Phys. Chem. Chem. Phys.

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Thermally feasible decomposition pathways of formamide (FM) in the presence of vanadium VO(X(4)Σ(-)) and titanium TiO(X(3)Δ) monoxides are determined using density functional theory (BP86 functional) and coupled-cluster theory (CCSD(T)) computations with large basis sets. These diatomic metal oxides have been shown to be present in the prebiotic conditions. The dehydration, decarbonylation and dehydrogenation reactions of the molecular and dissociative complexes of FM and MO (M = V, Ti) turn out to be more favourable than those of the ground state isolated FM. The effect of addition of one or two water molecules on energy barriers is also probed for these reaction pathways. In some cases, a combined catalytic effect when adding water is observed. This enhanced catalytic effect was not observed in previously reported cases of FM transformation, for example, when adding water molecules into the mineral-catalyzed isomerizations of FM. The dehydration process of MO-FM complexes without the presence of water is found to be more feasible than the decarbonylation and dehydrogenation. The overall energy barrier for the non-water VO-FM dehydration is ∼3 kcal mol(-1) lower than the reference energy of the separated systems, whereas those of the two latter reactions are higher than the reference. Although the TiO-FM dehydration has a larger overall barrier of 14 kcal mol(-1) as compared to the VO-FM counterpart, the two other decomposition pathways still have much higher energy barriers. Direct formation of urea and H2CO from a FM dimer and indirect formation of urea from FM via the intermediate HNCO are also established. Urea formation in an indirect pathway is preferred. These low-energy-barrier pathways leading to the formation of important prebiotic molecules suggest that metal monoxides MO could play an important catalytic role in the prebiotic reactions of FM.

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Discovery of a TiO emission band in the infrared spectrum of the S star NP Aurigae

Cited by 10 publications

References 26 publications

Pure rotational spectra of TiO and TiO₂in VY Canis Majoris

Pure rotational spectra of TiO and TiO₂in VY Canis Majoris

Influence of the C/O ratio on titanium and vanadium oxides in protoplanetary disks

Decomposition pathways of formamide in the presence of vanadium and titanium monoxides

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Discovery of a TiO emission band in the infrared spectrum of the S star NP Aurigae

Cited by 10 publications

References 26 publications

Pure rotational spectra of TiO and TiO2in VY Canis Majoris

Pure rotational spectra of TiO and TiO2in VY Canis Majoris

Influence of the C/O ratio on titanium and vanadium oxides in protoplanetary disks

Decomposition pathways of formamide in the presence of vanadium and titanium monoxides

Contact Info

Product

Resources

About

Pure rotational spectra of TiO and TiO₂in VY Canis Majoris

Pure rotational spectra of TiO and TiO₂in VY Canis Majoris