High Velocity Precessing Jets From the Water Fountain Iras 18286–0959 Revealed by Very Long Baseline Array Observations

Yung, Bosco H. K.; Nakashima, Jun-ichi; Imai, Hiroshi; Deguchi, Shuji; Diamond, P. J.; Kwok, Sun

doi:10.1088/0004-637x/741/2/94

Cited by 34 publications

(48 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This source exhibits a very rich 22 GHz water maser spectrum with emission spread over a velocity range 200 km s −1 and distributed in a double-helix pattern (Deguchi et al 2007;Yung et al 2011). The 321 GHz water emission also extends over a wide velocity range from ∼−50 km s −1 to ∼200 km s −1 , similar to the range of the 22 GHz masers.…”

Section: Iras 18286−0959mentioning

confidence: 89%

“…As mentioned above, for this temperature the luminosity ratio L p (22 GHz)/L p (321 GHz) is expected to be 5. Comparing the intensities of the 22 GHz masers (see Deacon et al 2007;Walsh et al 2009;Pérez-Sánchez et al 2011;Yung et al 2011) and the 321 GHz masers of IRAS 18043−2116 and IRAS 18286−0959, it can be seen that the luminosity ratio is close to unity. This implies a kinetic temperature T k > 1000 K for the gas (Neufeld & Melnick 1990;Yates et al 1997).…”

Section: The Origin Of the 321 Ghz Water Masersmentioning

confidence: 94%

See 1 more Smart Citation

Submillimeter H₂O masers in water-fountain nebulae

Tafoya¹,

Franco-Hernández²,

Vlemmings³

et al. 2014

A&A

View full text Add to dashboard Cite

We report the first detection of submillimeter water maser emission toward water-fountain nebulae, which are post-AGB stars that exhibit high-velocity water masers. Using APEX we found emission in the ortho-H 2 O (10 29 → 9 36 ) transition at 321.226 GHz toward three sources: IRAS 15445−5449, IRAS 18043−2116, and IRAS 18286−0959. Similar to the 22 GHz masers, the submillimeter water masers are expanding with higher velocity than do OH masers, suggesting that these masers also originate in fast bipolar outflows. In IRAS 18043−2116 and IRAS 18286−0959, which figure among the sources with the fastest water masers, the velocity range of the 321 GHz masers coincides with the range of the 22 GHz masers, indicating that they probably coexist. Toward IRAS 15445−5449, the submillimeter masers appear in a different velocity range, indicating that they trace different regions. The intensity of the submillimeter masers is comparable to the 22 GHz masers, implying that the kinetic temperature of the region where the masers originate should be T k > 1000 K. We propose that the passage of two shocks through the same gas can create the conditions for explaining the strong high-velocity 321 GHz masers coexisting with the 22 GHz masers in the same region.

show abstract

Section: Iras 18286−0959mentioning

confidence: 89%

Section: The Origin Of the 321 Ghz Water Masersmentioning

confidence: 94%

Submillimeter H₂O masers in water-fountain nebulae

Tafoya¹,

Franco-Hernández²,

Vlemmings³

et al. 2014

A&A

View full text Add to dashboard Cite

show abstract

“…Results from interferometric observations towards the circumstellar envelopes (CSE) of WFs indicate that, in most cases, the spatial distribution of the detected H 2 O maser components (projected on the plane of the sky) can be correlated with large-scale bipolar structures (e.g. Sahai et al 2005b;Vlemmings et al 2006;Gómez et al 2011;Lagadec et al 2011;Yung et al 2011). …”

Section: Introductionmentioning

confidence: 99%

Deep into the Water Fountains

Pérez-Sánchez

Tafoya

López

et al. 2017

A&A

View full text Add to dashboard Cite

Context. The formation of large-scale (hundreds to few thousands of AU) bipolar structures in the circumstellar envelopes (CSEs) of post-Asymptotic Giant Branch (post-AGB) stars is poorly understood. The shape of these structures, traced by emission from fast molecular outflows, suggests that the dynamics at the innermost regions of these CSEs does not depend only on the energy of the radiation field of the central star. Aims. Multi-frequency observations towards a group of post-AGB sources known as Water Fountain nebulae can help to constrain the nature of the mechanism responsible for the launching and collimation of the fast molecular outlflows traced by high-velocity features of H 2 O maser emission. Methods. Deep into the Water Fountains is an observational project based on the results of programs carried out with three telescope facilities: The Karl G. Jansky Very Large Array (JVLA), The Australia Telescope Compact Array (ATCA), and the Very Large Telescope (SINFONI-VLT). Results. Here we report the results of the observations towards the WF nebula IRAS 18043−2116: Detection of radio continuum emission in the frequency range 1.5 GHz -8.0 GHz; H 2 O maser spectral features and radio continuum emission detected at 22 GHz, and H 2 ro-vibrational emission lines detected at the near infrared. Conclusions. The high-velocity H 2 O maser spectral features, and the shock-excited H 2 emission detected could be produced in molecular layers which are swept up as a consequence of the propagation of a jet-driven wind. Using the derived H 2 column density, we estimated a molecular mass-loss rate of the order of 10 −9 M yr −1 . On the other hand, if the radio continuum flux detected is generated as a consequence of the propagation of a thermal radio jet, the mass-loss rate associated to the outflowing ionized material is of the order of 10 −5 M yr −1 . The presence of a rotating disk could be a plausible explanation for the mass-loss rates estimated.

show abstract

“…In IRAS 18286-0959, the water masers are tracing a double-helix structure (Yung et al 2011). In all cases, these recent ejections represent one of the earliest known manifestations of collimated mass-loss in evolved stars.…”

Section: Introductionmentioning

confidence: 99%

Sensitive CO and¹³CO survey of water fountain stars

Rizzo¹,

Gómez²,

Miranda³

et al. 2013

A&A

View full text Add to dashboard Cite

Context. Water fountain stars represent a stage between the asymptotic giant branch (AGB) and planetary nebulae phases, when the mass loss changes from spherical to bipolar. These types of evolved objects are characterized by high-velocity jets in the 22 GHz water maser emission. Aims. The objective of this work is to detect and study in detail the circumstellar gas in which the bipolar outflows are emerging. The detection and study of thermal lines may help in understanding the nature and physics of the envelopes in which the jets are developing. Methods. We surveyed the CO and 13 CO line emission towards a sample of ten water fountain stars through observing the J = 1 → 0 and 2 → 1 lines of CO and 13 CO, using the 30 m IRAM radio-telescope at Pico Veleta. All the water fountains visible from the observatory were surveyed. Results. Most of the line emission arises from foreground or background Galactic clouds, and we had to thoroughly analyse the spectra to unveil the velocity components related to the stars. In two sources, IRAS 18460-0151 and IRAS 18596+0315, we identified wide velocity components with a width of 35−40 km s −1 that are centred at the stellar velocities. These wide components can be associated with the former AGB envelope of the progenitor star. A third case, IRAS 18286-0959, is reported as tentative; in this case a pair of narrow velocity components, symmetrically located with respect to the stellar velocity, have been discovered. We also modelled the line emission using an LVG code and derived some global physical parameters, which allowed us to discuss the possible origin of this gas in relation to the known bipolar outflows. For IRAS 18460-0151 and IRAS 18596+0315, we derived molecular masses close to 0.2 M , mean densities of 10 4 cm −3 , and mass-loss rates of 10 −4 M yr −1 . The kinetic temperatures are rather low, between 10 and 50 K in both cases, which suggests that the CO emission is arising from the outer and cooler regions of the envelopes. No fitting was possible for IRAS 18286-0959, because line contamination can not be discarded in this case. Conclusions. The molecular masses, mean densities, and mass-loss rates estimated for the circumstellar material associated with IRAS 18460-0151 and IRAS 18596+0315 confirm that these sources are at the end of the AGB or the beginning of the post-AGB evolutionary stages. The computed mass-loss rates are among the highest ones possible according to current evolutionary models, which leads us to propose that the progenitors of these water fountains had masses in the range from 4 to 8 M . We speculate that CO emission is detected in water fountains as a result of a CO abundance enhancement caused by current episodes of low-collimation mass-loss.

show abstract

High Velocity Precessing Jets From the Water Fountain Iras 18286–0959 Revealed by Very Long Baseline Array Observations

Cited by 34 publications

References 31 publications

Submillimeter H₂O masers in water-fountain nebulae

Submillimeter H₂O masers in water-fountain nebulae

Deep into the Water Fountains

Sensitive CO and¹³CO survey of water fountain stars

Contact Info

Product

Resources

About

High Velocity Precessing Jets From the Water Fountain Iras 18286–0959 Revealed by Very Long Baseline Array Observations

Cited by 34 publications

References 31 publications

Submillimeter H2O masers in water-fountain nebulae

Submillimeter H2O masers in water-fountain nebulae

Deep into the Water Fountains

Sensitive CO and13CO survey of water fountain stars

Contact Info

Product

Resources

About

Submillimeter H₂O masers in water-fountain nebulae

Submillimeter H₂O masers in water-fountain nebulae

Sensitive CO and¹³CO survey of water fountain stars