|
IRAS 18596+0315 (OH 37.12 -0.85,
OH 37.1 -0.8, PN PM 1-275) -- a likely
water fountain star
 | Simultaneous NIR and OH maser observations were done to a sample of
OH/IR stars in Galactic center
or near tangential point. A distance of
8 kpc was derived by treating IRAS 18596+0315 as a star at the tangential of the galactic disk. A
OH maser velocity separation dV(OH) = 13.25 km/s was derived.
NIR observations didn't detected IRAS 18596+0315. (from Baud et al., 1985ApJ...292..628B) |
| VLA and Heystack Observatory single dish observations of OH and H2O masers in IRAS
18596+0315 showed a larger expansion H2O maser velocity than OH
maser, indicating a possible water fountain star.
(from Gomez et al., 1994RMxAA..28...97G)
(figure: left -- LVA spectra of OH and H2O masers during 1991-1992 (Y:
Jy); right
-- detection of H2O masers on 1990, Jan. 14, with the short horizontal line
showing the velocity range of OH maser peaks.)
  |
| VLBA observation of OH 1612 MHz masers towards
IRAS 18596+0315 revealed a bipolar distribution of maser spots (blue and red groups separated by
~0.15"), indicating bipolar outflow. (from Gomez & Rodriguez,
2000ASPC..199...75G)
(figure: left -- OH maser spectrum; right -- spatial
distribution of OH maser spots.)
 |
| Monitoring of the 22GHz H2O masers in 4 non-variable OH/IR stars showed stable gross spetral structure with varying
features. Life time of individual maser features is 1-3
yrs. These behaviors are quite different from ordinary OH/IR stars, which
allows identification of PPNs by maser observations. The H2O masers of two sources,
IRAS 18135-1456 (OH
15.7+0.8) and IRAS 18276-1431 (OH 17.7-2.0), continued to weaken and disappeared in the end. The H2O masers of the other two sources,
IRAS18139-1816 (OH
12.8-0.9) and IRAS 18596+0315 (OH 37.1-0.8), showed acceleration of outflow velocity (with current l.o.s. Vexp = 28 and 28.5 km/s
respectively). (from Engels, 2002A&A...388..252E)
(figure: OH maser spectral variation
for IRAS18596+0315)
 |
| The 22 GHz H2O maser is searched for 85 post-AGB
candidates using the Tidbinbilla 70m radio telescope between 2003 April to
2004 April. There are 21 detections. Also
present Mopra observations of 86 GHz SiO masers
to a sub-sample. Five stars were found to show high velocity H2O maser lines
and are water fountain star candidates, including IRAS
18596+0315 (their source name: v270). (from Deacon et al., 2007ApJ...658.1096D)
(figure: H2O maser and OH 1612 GHz maser
spectra of IRAS 18596+0315 (Y: Jy, X: km/s). Note that the H2O velocity is higher than that
of OH masers.)
 |
|
ynao.ac.cn
[back
to my Home]
