Browsing by Subject "infrared: stars"

Now showing 1 - 3 of 3
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    Open Access
    On the nature of the cool component of MWC 560
    (2007) Gromadzki, M; Mikołajewska, J; Whitelock, P A; Marang, F
    Context.MWC 560 (V694 Mon) is one of the most enigmatic symbiotic system with a very active accretion-powered hot component. Such activity can be supported only by a luminous asymptotic giant branch star, i.e. a Mira or SR variable, with a high mass-loss rate. It is also a very unusual jet source because the jet axis lies practically parallel to the line of sight. Aims. The aims of our study are the determination of the evolutionary status of the cool component of MWC 560. Methods. Our methods involve analysis of near-IR JHKL and optical light curves. Results. The cool component of MWC 560 pulsates with a period of ∼340 days, and it is probably a red SR variable on the thermally pulsing AGB. The high mass-loss rate expected for such a star is sufficient to power the observed activity of the hot companion.
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    Open Access
    The Spitzer spectroscopic survey of S-type stars
    (2012) Smolders, K; Neyskens, P; Blommaert, J A D L; Hony, S; Van Winckel, H; Decin, L; Van Eck, S; Sloan, G C; Cami, J; Uttenthaler, S; Degroote, P; Barry, D; Feast, M; Groenewegen, M A T; Matsuura, M; Menzies, J; Sahai, R; van Loon, J Th; Zijlstra, A A; Acke, B; Bloemen, S; Cox, N; de Cat, P; Desmet, M; Exter, K; Ladjal, D; Østensen, R; Saesen, S; van Wyk, F; Verhoelst, T; Zima, W
    Context. S-type AGB stars are thought to be in the transitional phase between M-type and C-type AGB stars. Because the composition of the circumstellar environment reflects the photospheric abundances, one may expect a strong influence of the stellar C/O ratio on the molecular chemistry and the mineralogy of the circumstellar dust.
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    Open Access
    The VMC survey: I. strategy and first data
    (2011) Cioni, M- R L; Clementini, G; Girardi, L; Guandalini, R; Gullieuszik, M; Miszalski, B; Moretti, M-I; Ripepi, V; Rubele, S; Bagheri, G; Bekki, K; Cross, N; de Blok, W J G; de Grijs, R; Emerson, J P; Evans, C J; Gibson, B; Gonzales-Solares, E; Groenewegen, M A T; Irwin, M; Ivanov, V D; Lewis, J; Marconi, M; Marquette, J-B; Mastropietro, C; Moore, B; Napiwotzki, R; Naylor, T; Oliveira, J M; Read, M; Sutorius, E; van Loon, J Th
    Context. The new VISual and Infrared Telescope for Astronomy (VISTA) has started operations. Over its first five years it will be collecting data for six public surveys, one of which is the near-infrared YJK(s) VISTA survey of the Magellanic Clouds system (VMC). This survey comprises the Large Magellanic Cloud (LMC), the Small Magellanic Cloud, the Magellanic Bridge connecting the two galaxies and two fields in the Magellanic Stream. Aims. This paper provides an overview of the VMC survey strategy and presents first science results. The main goals of the VMC survey are the determination of the spatially-resolved star-formation history and the three-dimensional structure of the Magellanic system. The VMC survey is therefore designed to reach stars as faint as the oldest main sequence turn-off point and to constrain the mean magnitude of pulsating variables such as RR Lyrae stars and Cepheids. This paper focuses on observations of VMC fields in the LMC obtained between November 2009 and March 2010. These observations correspond to a completeness of 7% of the planned LMC fields. Methods. The VMC data are comprised of multi-epoch observations which are executed following specific time constraints. The data were reduced using the VISTA Data Flow System pipeline with source catalogues, including astrometric and photometric corrections, produced and made available via the VISTA Science Archive. The VMC data will be released to the astronomical community following the European Southern Observatorys Public Survey policy. The analysis of the data shows that the sensitivity in each wave band agrees with expectations. Uncertainties and completeness of the data are also derived. Results. The first science results, aimed at assessing the scientific quality of the VMC data, include an overview of the distribution of stars in colour-magnitude and colour-colour diagrams, the detection of planetary nebulae and stellar clusters, and the K-s band light-curves of variable stars. Conclusions. The VMC survey represents a tremendous improvement, in spatial resolution and sensitivity, on previous panoramic observations of the Magellanic system in the near-infrared, providing a powerful complement to deep observations at other wavelengths.