Issue |
A&A
Volume 412, Number 2, December III 2003
|
|
---|---|---|
Page(s) | 405 - 416 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20031271 | |
Published online | 28 November 2003 |
Polarimetry of evolved stars*,**
III. RV Tau and R CrB stars
1
Central Astronomical Observatory of the Russian Academy of Sciences at Pulkovo, 196140 Saint-Petersburg, Russia
2
Isaac Newton Institute of Chile, St.-Petersburg Branch, Russia
3
Astrophysics Group, School of Chemistry & Physics, Keele University, Keele, Staffordshire, ST5 5BG, UK
4
NASA Goddard Space Flight Center, Code 681, Greenbelt, MD20771, USA
5
Joint Astronomy Centre, 660 N. A'ohoku Place, University Park, Hilo, HI96720, USA
Corresponding author: R. V. Yudin, ruslan61@gao.spb.ru
Received:
25
February
2002
Accepted:
5
August
2003
We present broadband optical polarimetry, and broadband
optical and infrared photometry, of eight RV Tau-type and five
R CrB-type stars; much of the photometry and polarimetry was
obtained simultaneously. For nine of the objects polarimetric data
is reported for the first time. We have estimated and subtracted
the interstellar component of polarization, allowing us to
determine the level of intrinsic polarization. In some cases this
is 1%–2% even when the star is in a bright photometric
state. We consider this to be evidence for the presence of
permanent clumpy non-spherical dust shells around the RV Tau and R CrB-type stars we observed. Our polarimetric and photometric data
lead us to conclude that, for most of our programme stars, neutral
extinction must be significant in their circumstellar envelopes.
Apart from the brightness variations due to pulsations and changes
in the effective temperature of stars, there is clear evidence of
wavelength-independent flux variations – with amplitude from
to
– implying the presence of large
(
m) dust particles. Rapid (~2 hours)
evolution of the infrared flux distribution at the level of ~
in the JHKL bands was detected in the RV Tau star R Sct.
Key words: polarization / stars: circumstellar matter / stars: variable: general
© ESO, 2003
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