WATER MASER SURVEY ON<i>AKARI</i>AND<i>IRAS</i>SOURCES: A SEARCH FOR “LOW-VELOCITY” WATER FOUNTAINS

Yung, Bosco H. K.; Nakashima, Jun-ichi; Imai, Hiroshi; Deguchi, Shuji; Henkel, C.; Kwok, Sun

doi:10.1088/0004-637x/769/1/20

Cited by 22 publications

(39 citation statements)

References 74 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The absence of the extreme components before 2010 (Paper I) should indicate the absence of the gas corresponding to these maser components at that time. Yung et al (2013) found new velocity components in 2011 around VLSR ∼ −90 and 230 km s −1 . However, the absence of information of their locations makes it difficult for us to suggest that they were also associated with the same gas clumps as those hosting our discovered maser components.…”

Section: Discussionmentioning

confidence: 83%

“…Before 2010, the H2O masers in I18286 covered a velocity range of −60 ≤ VLSR ≤ 180 km s −1 with respect to the local standard of rest (LSR). Yung et al (2013) found new velocity components in 2011 around VLSR ∼ −90 and 230 km s −1 . This paper focuses on even newer, faster velocity components (surpassing the previously detected velocity range), found with our monitoring in FLASHING.…”

Section: Introductionmentioning

confidence: 83%

See 1 more Smart Citation

FLASHING: New high-velocity H2O masers in IRAS 18286−0959

Imai

Uno

Maeyama

et al. 2020

Publications of the Astronomical Society of Japan

Self Cite

View full text Add to dashboard Cite

We discovered new high-velocity components of H2O maser emission in one of the “water fountain” sources, IRAS 18286−0959, which has been monitored using the Nobeyama 45 m telescope in the FLASHING (Finest Legacy Acquisitions of SiO- and H2O-maser Ignitions by Nobeyama Generation) project since 2018 December. The maser spectra show new components with extremely high expansion velocities (>200 km s−1 projected in the line of sight), some of which are located symmetrically in the spectrum with respect to the systemic velocity. They were also mapped with KaVA (KVN and VERA Combined Array) in 2019 March. We located some of these maser components closer to the central stellar system than other high-velocity components (50–200 km s−1) that have been confirmed to be associated with the known bipolar outflow. The new components would have flashed in the fast collimated jet at a speed of over 300 km s−1 (soon) after 2011 when they had not been detected. The fastest of the new components seem to indicate rapid deceleration in these spectra; however, our present monitoring is still too sparse to unambiguously confirm it (up to 50 km s−1 yr−1) and too short to reveal their terminal expansion velocity, which will be equal to the expansion velocity that has been observed ($v$exp ∼ 120 km s−1). Future occurrences of such extreme-velocity components may provide a good opportunity to investigate possible recurrent outflow ignitions. Thus, the sculpture of the parental envelope will be traced by the dense gas that is entrained by the fast jet and exhibits spectacular distributions of the relatively stable maser features.

show abstract

Section: Discussionmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 83%

FLASHING: New high-velocity H2O masers in IRAS 18286−0959

Imai

Uno

Maeyama

et al. 2020

Publications of the Astronomical Society of Japan

Self Cite

View full text Add to dashboard Cite

show abstract

“…One month later in April 2011, the most blue-shifted feature halved in flux density while the red-shifted component became stronger by a factor of a few. A further Effelsberg epoch was taken by Yung et al (2013) in December 2011, which again showed two strong features at ∼19 and ∼46 km s −1 and a weak third feature even more blue-shifted at ∼11 km s −1 . Our JVLA observations from June 2013 show the now persisting red-shifted feature and show again an even more complex blue-shifted set of maser features between ∼13−27 km s −1 .…”

Section: Maser Variabilitymentioning

confidence: 97%

From the ashes: JVLA observations of water fountain nebula candidates show the rebirth of IRAS 18455+0448

Vlemmings

Amiri

Langevelde

et al. 2014

A&A

View full text Add to dashboard Cite

Context. The class of water fountain nebulae is thought to represent the stage of the earliest onset of collimated bipolar outflows during the post-asymptotic giant branch phase. They thus play a crucial role in the study of the formation of bipolar planetary nebulae (PNe). To date, 14 water fountain nebulae have been identified. The identification of more sources in this unique stage of stellar evolution will enable us to study the origin of bipolar PNe morphologies in more detail. Aims. Water fountain candidates can be identified based on the often double peaked 22 GHz H 2 O maser spectrum with a large separation between the maser peaks (often >100 km s −1 ). However, even a fast bipolar outflow will only have a moderate velocity extent in its maser spectrum when located close to the plane of the sky. In this project we aim to enhance the water fountain sample by identifying objects whose jets are aligned close to the plane of the sky. Methods. We present the results of seven sources observed with the Jansky Very Large Array (JVLA) that were identified as water fountain candidates in an Effelsberg 100 m telescope survey of 74 AGB and early post-AGB stars. Results. We find that our sample of water fountain candidates displays strong variability in their 22 GHz H 2 O maser spectra. The JVLA observations show an extended bipolar H 2 O maser outflow for one source, the OH/IR star IRAS 18455+0448. This source was previously classified as a dying OH/IR star based on the exponential decrease of its 1612 MHz OH maser and the lack of H 2 O masers. We therefore also re-observed the 1612, 1665, and 1667 MHz OH masers. We confirm that the 1612 MHz masers have not reappeared and find that the1665/1667 MHz masers have decreased in strength by several orders of magnitude during the last decade. The JVLA observations also reveal a striking asymmetry in the red-shifted maser emission of IRAS 19422+3506. Conclusions. The OH/IR star IRAS 18455+0448 is confirmed to be a new addition to the class of water fountain nebulae. Its kinematic age is ∼70 yr, but could be lower, depending on the distance and inclination. Previous observations indicate, with significant uncertainty, that IRAS 18455+0448 has a surprisingly low mass compared to available estimates for other water fountain nebulae. The available historical OH maser observations make IRAS 18455+0448 unique for the study of water fountain nebulae and the launch of post-AGB bipolar outflows. The other candidate sources appear high mass-loss OH/IR stars with partly radially beamed H 2 O masers.

show abstract

“…Selective surveys of water masers in high-mass young stellar objects (HMYSOs) (Urquhart et al 2009(Urquhart et al , 2011 typically observe towards sources that satisfy certain infra-red colour criteria based, for example, on the Red MSX Source survey, or 4.5 µm emission detected by the GLIMPSE instrument aboard the Spitzer satellite (Yung et al 2013). Unlike 6.7-GHz methanol masers that are believed to be associated only with the formation of high-mass stars (Xu et al 2008), 22-GHz water masers are also associated with low-mass protostellar objects, and surveys of objects of this type include work by Furuya et al (2001) and Furuya et al (2003) (respective errata in Furuya et al (2007b,a)) that showed that water masers are associated primarily with low-mass protostars of class 0 c 2002 RAS with some in class 1.…”

Section: Introductionmentioning

confidence: 99%

The physics of water masers observable with ALMA and SOFIA: model predictions for evolved stars

Gray

Baudry

Richards

et al. 2015

Mon. Not. R. Astron. Soc.

View full text Add to dashboard Cite

We present the results of models that were designed to study all possible water maser transitions in the frequency range 0-1.91 THz, with particular emphasis on maser transitions that may be generated in evolved-star envelopes and observed with the ALMA and SOFIA telescopes. We used tens of thousands of radiative transfer models of both spin species of H 2 O, spanning a considerable parameter space in number density, kinetic temperature and dust temperature. Results, in the form of maser optical depths, have been summarized in a master table, Table 6. Maser transitions identified in these models were grouped according to loci of inverted regions in the density/kinetic temperature plane, a property clearly related to the dominant mode of pumping. A more detailed study of the effect of dust temperature on maser optical depth enabled us to divide the maser transitions into three groups: those with both collisional and radiative pumping schemes (22,96,209,321,325,395,941 and 1486 GHz), a much larger set that are predominantly radiatively pumped, and another large group with a predominantly collisional pump. The effect of accelerative and decelerative velocity shifts of up to 5 km s −1 was found to be generally modest, with the primary effect of reducing computed maser optical depths. More subtle asymmetric effects, dependent on line overlap, include maximum gains offset from zero shift by >1 km s −1 , but these effects were predominantly found under conditions of weak amplification. These models will allow astronomers to use multi-transition water maser observations to constrain physical conditions down to the size of individual masing clouds (size of a few astronomical units).

show abstract

WATER MASER SURVEY ONAKARIANDIRASSOURCES: A SEARCH FOR “LOW-VELOCITY” WATER FOUNTAINS

Cited by 22 publications

References 74 publications

FLASHING: New high-velocity H2O masers in IRAS 18286−0959

FLASHING: New high-velocity H2O masers in IRAS 18286−0959

From the ashes: JVLA observations of water fountain nebula candidates show the rebirth of IRAS 18455+0448

The physics of water masers observable with ALMA and SOFIA: model predictions for evolved stars

Contact Info

Product

Resources

About