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

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Authors
Smolders, K.
Verhoelst, T.
Neyskens, P.
Blommaert, J.A.D.L.
Decin, L.
Van Winckel, H.
Van Eck, S.
Sloan, G.C.
Cami, J.
Hony, S.
De Cat, P.
Menu, J.
Vos, J.
Discipline
Physical sciences
Subject
AGB stars
Circumstellar
Circumstellar matters
Column density
Dust emission
Emission bands
Emission features
Infrared emissions
Infrared spectrum
Infrared: star
Lower limits
S-process
Spatial extent
Spitzer
Stars:AGB and post AGB
Techniques: spectroscopic
TiO
Upper limits
Molecules
Stars
Audience
Scientific
Date
2012Metadata
Show full item recordDescription
We report on the discovery of an infrared emission band in the Spitzer spectrum of the S-type AGB star NP Aurigae that is caused by TiO molecules in the circumstellar environment. We modeled the observed emission to derive the temperature of the TiO molecules (≈600 K), an upper limit on the column density (≈1017.25 cm-2) and a lower limit on the spatial extent of the layer that contains these molecules. (≈4.6 R⋆). This is the first time that this TiO emission band is observed. A search for similar emission features in the sample of S-type stars yielded two additional candidates. However, owing to the additional dust emission, the identification is less stringent. By comparing the stellar characteristics of NP Aur to those of the other stars in our sample, we find that all stars with TiO emission show large-amplitude pulsations, s-process enrichment, and a low C/O ratio. These characteristics might be necessary requirements for a star to show TiO in emission, but they are not sufficient.
Citation
Smolders, K.; Verhoelst, T.; Neyskens, P.; Blommaert, J.A.D.L.; Decin, L.; Van Winckel, H.; Van Eck, S.; Sloan, G.C.; Cami, J.; Hony, S.; De Cat, P.; Menu, J.; Vos, J. (2012). Discovery of a TiO emission band in the infrared spectrum of the S star NP Aurigae. , Astronomy and Astrophysics, Vol. 543, L2, DOI: 10.1051/0004-6361/201219520.Identifiers
scopus: 2-s2.0-84862872573
Type
Article
Peer-Review
Yes
Language
eng