OH 12.8-0.9: A New Water-Fountain Source

Boboltz, D. A.; Marvel, Kevin B.

doi:10.1086/431931

Cited by 37 publications

(65 citation statements)

References 10 publications

(21 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Such asymmetric outflows have already been reported for the CSE of evolved stars. For example, collimated H 2 O maser jets have been observed in a class of post-AGB objects, the so-called water-fountain sources (Imai et al 2002;Boboltz & Marvel 2005). Additionally, interferometric observations of the OH maser region of this class of objects have revealed aspherical morphologies with either equatorial or bi-conical distributions (Amiri et al 2011).…”

Section: Cse Morphology and Magnetic Fieldmentioning

confidence: 99%

VLBA SiO maser observations of the OH/IR star OH 44.8-2.3: magnetic field and morphology

Amiri

Vlemmings

Kemball

et al. 2012

A&A

View full text Add to dashboard Cite

Context. SiO maser emission occurs in the extended atmosphere of evolved stars and can be studied at high angular resolution. As compact, high-brightness components they can be used as important tracers of the dynamics at distances close to the central star. The masers also serve as probes of the evolutionary path from spherically symmetric AGB stars to aspherical PNe. Very long baseline interferometry (VLBI) observations of Mira variables indicate that SiO masers are significantly linearly polarized with linear polarization fractions up to 100%. However, no information is available at high angular resolution for SiO masers in higher mass loss OH/IR stars. Theory indicates a different SiO pumping mechanism in higher mass loss evolved stars. Aims. We extend the VLBI SiO maser studies to OH/IR stars. The observations enable us to understand the SiO pumping mechanisms in higher mass-loss evolved objects and to compare them with Mira variables. Additionally, polarimetric observations of SiO masers help us to understand the magnetic field strength and morphology and to distinguish between conflicting polarization theories. Methods. The 43 GHz SiO maser observations of the OH/IR star OH 44.8-2.3 were performed with the VLBA in full polarization spectral line mode. Auxiliary EVLA observations were performed to allow for the absolute calibration of the polarization angle. The Zeeman splitting was measured by cross correlating the right and left circular polarization spectra, as well as the S-curve fitting. Additionally, we analyzed the 1612 MHz OH maser observations of OH 44.8-2.3 from the VLA archive. Results. The SiO masers of OH 44.8-2.2 form a ring located at ∼5.4 AU around the star. The masers appear to be highly linearly polarized with fractional linear polarization up to 100%. The linear polarization vectors are consistent with a dipole field morphology in this star. We report a tentative detection of circular polarization of ∼0.7% for the brightest maser feature. The magnetic field measured for this feature corresponds to 1.5 ± 0.3 G. Additionally, the distribution of the 1612 MHz OH maser emission could indicate an elongated morphology. Conclusions. The SiO masers in OH 44.8-2.3 exhibit a ring morphology. Even though the central AGB star of OH 44.8-2.3 is expected to be larger than typical Mira variables, the SiO masers occur at a similar distance from the stellar photosphere as Mira variables. The SiO masers and the 1612 MHz OH maser emission suggest a mildly preferred direction of the outflow in the CSE of this star. Significant linear polarization is measured for the SiO region of this star, which could develop from either collisional or radiative pumping. In either case, the observed polarization is also consistent with magnetic field structures along the preferred outflow direction. This could reflect the possible role of the magnetic field in shaping the circumstellar environment of this object. Although we cannot firmly distinguish between the different polarization theories, the derived magnetic...

show abstract

Section: Cse Morphology and Magnetic Fieldmentioning

confidence: 99%

VLBA SiO maser observations of the OH/IR star OH 44.8-2.3: magnetic field and morphology

Amiri

Vlemmings

Kemball

et al. 2012

A&A

View full text Add to dashboard Cite

show abstract

“…We detected weak and relatively broad emission features in CO(2−1) and (3−2) lines covering the same velocity range as the maser peaks of H 2 O and OH, i.e. between −70 and −35 km s −1 (Boboltz & Marvel 2005). The detection is marginal, but the feature clearly appears above the 3σ noise level after smoothing the spectra to a resolution of 5-6 km s −1 , as can be seen in Fig.…”

Section: Co In Water-maser Starsmentioning

confidence: 65%

“…The velocity spread of their H 2 O spectra is very large, up to several 100 km s −1 , and frequently larger than that of their OH spectra. High-resolution interferometric observations have shown that their masers are in collimated jets with dynamical ages younger than 150 yr (Boboltz & Marvel 2005). Water-maser post-AGB stars and particularly water fountains A&A 542, A15 (2012) represent a very short evolutionary phase right after the end of the AGB; they therefore provide a unique opportunity for studying the physical conditions in the molecular envelopes as the shaping agent begins to act.…”

Section: Introductionmentioning

confidence: 99%

CO observations of water-maser post-asymptotic giant branch stars and detection of a high-velocity outflow in IRAS 15452–5459

Cerrigone

Menten

Kamiński

2012

A&A

View full text Add to dashboard Cite

Many aspects of the evolutionary phase in which asymptotic giant branch stars (AGB stars) are in transition to become planetary nebulae (PNe) remain poorly understood. An important question is how the circumstellar envelopes of AGB stars switch from spherical symmetry to the axially symmetric structures frequently observed in PNe. In many cases, there is clear evidence that the shaping of the circumstellar envelopes of PNe is linked to the formation of jets/collimated winds and their interaction with the remnant AGB envelope. Because of the short timescale of this evolutionary phase, objects are rare, but their identification provides valuable probes for testing evolutionary models. We observed (sub)millimeter CO rotational transitions with the APEX telescope in a small sample of stars hosting high-velocity OH and water masers. These targets are assumed to have recently left the AGB, as indicated by the presence of winds traced by masers with velocities larger than observed during that phase. We carried out observations of several CO lines, ranging from J = 2−1 up to J = 7−6. In IRAS 15452−5459, we detect a fast molecular outflow in the central region of the nebula and estimate a mass-loss rate between 1.2 × 10 −4 M yr −1 (assuming optically thin emission) and 4.9 × 10 −4 M yr −1 (optically thick emission). We model the SED of this target taking advantage of our continuum measurement at 345 GHz to constrain the emission at long wavelengths. For a distance of 2.5 kpc, we estimate a luminosity of 8000 L and a dust mass of ∼0.01 M . Through the flux in the [CII] line (158 μm), we calculate a total mass of about 12 M for the circumstellar envelope, but the line is likely affected by interstellar contamination.

show abstract

“…Vlemmings et al 2006;Boboltz & Marvel 2005). Thus the spherically symmetric CSE is modified, for example by carving out polar cavities.…”

Section: Description Of the Kinematical Reconstruction Proceduresmentioning

confidence: 99%

“…Interferometric observations of the H 2 O masers of other water-fountains (e.g. IRAS 16342-3814, IRAS 19134+2131, and OH 12.8-0.9) also revealed bipolar distributions (Morris et al 2003;Claussen et al 2004;Boboltz & Marvel 2005).…”

Section: Introductionmentioning

confidence: 99%

The kinematics and magnetic fields in water-fountain sources based on OH maser observations

Amiri

Vlemmings

Langevelde

2011

A&A

View full text Add to dashboard Cite

Context. water-fountain sources are a class of post-AGB objects that exhibit bipolar jet-like structures traced by H 2 O maser emission. The circumstellar envelopes of these objects show deviations from spherical symmetry. While the H 2 O masers originate in a collimated outflow in the polar region, the OH masers may be distributed in the equatorial region or a biconical outflow in the circumstellar shell. Magnetic fields could play an important role in collimating the jet and shaping the circumstellar envelope of these objects. Aims. The aim of this project is to understand the morphology of the OH masers in three water-fountain sources, for which we obtained high-resolution interferometric data. We compare the observational parameters of the spectral profile and spatial distribution with our models in order to constrain the morphology and velocity fields of the OH maser shell. We would also like to understand the role of the magnetic field in shaping the circumstellar envelope of these stars. Methods. We observed the OH masers of three water-fountain sources (OH 12.8-0.9, OH 37.1-0.8, and W43A) in full polarization spectral line mode using the UK Multi-Element Radio Linked Interferometer Network. Additionally, we performed reconstruction models of OH maser shells distributed uniformly in equatorial or biconical outflows and compared them with the OH maser observations.Results. The OH masers of W43A seem to be located in the equatorial region of the circumstellar shell, while for OH 12.8-0.9 the masers are likely distributed in a biconical outflow. We measured magnetic fields of ∼360 μG and ∼29 μG on average for OH 37.1-0.8 and OH 12.8-0.9, respectively. The measured field strengths show that a large-scale magnetic field is present in the circumstellar environment of these stars. Conclusions. Our observations show that the OH maser region of the three water-fountain sources studied in this work show signs of aspherical expansion. Reconstruction of the OH maser distribution of these objects show both biconical and equatorial distributions. Magnetic fields likely play an important role in shaping the OH maser region of water-fountain sources.

show abstract

OH 12.8-0.9: A New Water-Fountain Source

Cited by 37 publications

References 10 publications

VLBA SiO maser observations of the OH/IR star OH 44.8-2.3: magnetic field and morphology

VLBA SiO maser observations of the OH/IR star OH 44.8-2.3: magnetic field and morphology

CO observations of water-maser post-asymptotic giant branch stars and detection of a high-velocity outflow in IRAS 15452–5459

The kinematics and magnetic fields in water-fountain sources based on OH maser observations

Contact Info

Product

Resources

About