Issue |
A&A
Volume 458, Number 2, November I 2006
|
|
---|---|---|
Page(s) | 533 - 539 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20053982 | |
Published online | 12 September 2006 |
Near-IR variability properties of a selected sample of AGB stars
1
Observatorio Astronómico Nacional, Apartado 112, 28803 Alcalá de Henares, Spain e-mail: f.jimenez-esteban@oan.es
2
FRACTAL SLNE, Avda San Sebastián 5 3-D, 38003 Santa Cruz de Tenerife, Spain
3
Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
4
Research and Scientific Support Department of ESA, European Space Astronomy Centre, Villafranca del Castillo, Apartado de Correos 50727, 28080 Madrid, Spain
5
Instituto de Astrofísica de Canarias, Via Lactea s/n, 38200 La Laguna, Tenerife, Spain
6
Consejo Superior de Investigaciones Científicas, Spain
Received:
4
August
2005
Accepted:
8
June
2006
We present the results of a near-infrared monitoring programme of
a selected sample of stars, initially suspected to be Mira variables
and OH/IR stars, covering more than a decade of observations. The
objects monitored cover the typical range of IRAS colours shown by
O-rich stars on the asymptotic giant branch and show a surprisingly
large diversity of variability properties. Sixteen objects are
confirmed as large-amplitude variables. Periods between 360 and
1800d and typical amplitudes
1m
2m could be determined for nine of
them. In three light curves, we find a systematic decrease in the mean
brightness, and two light curves show pronounced asymmetry. One
source, IRAS 07222–2005, shows infrared colours typical of Mira
variables, but it pulsates with a much longer period
(≈1200d) than a normal Mira. Two objects are either close
to (IRAS 03293+6010) or probably in (IRAS 18299–1705) the post-AGB
phase. In IRAS 16029–3041 we found a systematic increase in the
colour of ≈1m, which we interpret as evidence of a recent
episode of enhanced mass loss. IRAS 18576+0341, a heavily obscured
luminous blue variable was also monitored. The star showed a continued
decrease in brightness over a period of 7 years (1995–2002).
Key words: stars: AGB and post-AGB / stars: late-type / stars: variables: general / infrared: stars
© ESO, 2006
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