Issue |
Astron. Astrophys. Suppl. Ser.
Volume 139, Number 3, November I 1999
|
|
---|---|---|
Page(s) | 461 - 482 | |
DOI | https://doi.org/10.1051/aas:1999112 | |
Published online | 15 November 1999 |
Six years of short-spaced monitoring of the
and
,
28SiO maser emission in evolved stars
1
Observatorio Astronómico Nacional (OAN), Apartado 1143, E-28800 Alcalá de Henares, Spain
2
DEMIRM/Observatoire de Paris-Meudon, 61 avenue de l'Observatoire, 75014 Paris, France
3
NASA-Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, U.S.A.
4
Departamento de Matemática Aplicada II (Biomatemática), Sección Departamental de Óptica, Escuela Universitaria de Óptica, Universidad Complutense de Madrid, Av. Arcos de Jalón s/n, E-28037 Madrid, Spain
5
Departamento de Física, Universidad de Alcalá de Henares, Campus Universitario, E-28871 Alcalá de Henares, Spain
Send offprint request to: J. Alcolea e-mail: j.alcolea@oan.es
Received:
26
January
1999
Accepted:
28
June
1999
We present the results from a monitoring of the and
,
28SiO maser emission in 21 objects, covering all types of known
SiO maser emitters: 13 Mira variables, 2 long period semi regu lars (SRGs),
3 variable super giants (SGs), 2 OH/IR stars, and one young stellar object.
This study has been carried out with the 13.7 meter radiotelescope of the
Centro Astronómico de Yebes (Guadalajara, Spain), from July 1984 to May
1990, and represents the longest and most tightly sampled monitoring
of SiO masers ever published.
Our data show that for Mira-type (i.e. regular) variables, the SiO and
optical light curves agree in period, and that the maxima of the SiO
emission lag the optical ones by about 0.1-0.2 periods. Since a similar
lag characterizes the near infrared (NIR) emission variability
from these stars, we conclude that for regular variables SiO and NIR
vary in phase. This result was confirmed in three objects for which NIR
variability curves are available. For SRGs and SGs, we found a less
systematic behavior, but when the SiO emission is periodic, its variability
curve agrees with the optical one, also showing a lag between maximum epochs
similar to that of Mira-type stars. The data clearly reveal other interesting
details on the SiO maser variability, such as the strong intensity
differences between different maxima and changes in the velocity distribution
of the emission. Finally, the SiO masers associated to the young stellar
object Orion IRc2 showed a double peaked spectrum with low amplitude,
aperiodic variations.
Key words: masers / stars: AGB / circumstellar matter / stars: late-type / stars: variables / radio-lines: stars
© European Southern Observatory (ESO), 1999