A new HCN maser in IRAS 15082−4808

Smith, C. L.; Zijlstra, A. A.; Fuller, G. A.

doi:10.1093/mnras/stu309

Cited by 7 publications

(13 citation statements)

References 38 publications

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“…The most unusual detection made is that of the vibrational (v2=2) HCN maser emission at 89.087 GHz. Only ten of these masers, including this detection, have been found to date (Smith et al 2014;Lucas et al 1986;Guilloteau et al 1987;Lucas et al 1988;Lucas & Cernicharo 1989). An in-depth study of this maser can be found in Smith et al (2014) and the maser line is shown in Fig.…”

Section: Iras 15082-4808mentioning

confidence: 71%

“…This line, as shown in Smith et al (2014), can be well modelled by a blend of the three hyperfine components, each having a Gaussian velocity distribution. The hyperfine structure lines in C4H are blended, with their relative intensities impossible to determine from the observed blended transition.…”

Section: Iras 15194-5115mentioning

confidence: 90%

“…HCN displays a Gaussian line shape, implying it does not originate from a region of constant velocity expansion. This line, as shown in Smith et al (2014), can be well modelled by a blend of the three hyperfine components, each having a Gaussian velocity distribution.…”

Section: Moleculementioning

confidence: 90%

“…A polynomial baseline was fitted to the averaged spectrum and subtracted to remove any remaining baseline rippling. The full spectra from all sources can be found in Appendix A of Smith (2014) 4 . The lines were identified using the NIST databases (Lovas 1992;Markwick-Kemper et al 2006).…”

Section: Data Reduction and Line Identificationmentioning

confidence: 99%

“…For this work, the relative intensities of the lines have been taken as the relative intrinsic line strengths, taken from the JPL or CDMS databases and normalised (Pickett et al 1998;Müller et al 2005). These parameters can also be found in Appendix B of Smith (2014) 5 . It is important to note that there is a distinct difference between the upper level, u, which is the unsplit upper energy level, and that of the individual hyperfine transitions, i.…”

Section: Hyperfine Structure: Separablementioning

confidence: 99%

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A molecular line survey of a sample of AGB stars and planetary nebulae

Smith

Zijlstra

Fuller

2015

Mon. Not. R. Astron. Soc.

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A millimeter molecular line survey of three carbon-rich AGB stars and two oxygenrich planetary nebulae has been carried out over the frequency range 80.5-115.5 GHz. Sixty eight different transitions were detected in the data from 27 different molecular species. The hyperfine structure of C 2 H and C 13 CH has been fitted to constrain the optical depth of their transitions. All other transitions have been constrained on the basis of their line profile shapes. Rotation temperatures and column densities have been calculated for all possible species, with adaptations to the methods applied in order to account for the hyperfine structure of various transitions. From the column densities, carbon, silicon and sulphur isotopic ratios have been determined. The results corroborate IRAS 15194-5115 as a J-type star, whilst excluding IRAS 15082-4808 and IRAS 07454-7112 as such.

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Section: Iras 15082-4808mentioning

confidence: 71%

Section: Iras 15194-5115mentioning

confidence: 90%

Section: Moleculementioning

confidence: 90%

Section: Data Reduction and Line Identificationmentioning

confidence: 99%

Section: Hyperfine Structure: Separablementioning

confidence: 99%

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A molecular line survey of a sample of AGB stars and planetary nebulae

Smith

Zijlstra

Fuller

2015

Mon. Not. R. Astron. Soc.

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Widespread HCN maser emission in carbon-rich evolved stars

Menten

Wyrowski

Keller

et al. 2018

A&A

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Context. HCN is a major constituent of the circumstellar envelopes of carbon-rich evolved stars, and rotational lines from within its vibrationally excited states probe parts of these regions closest to the stellar surface. A number of such lines are known to show maser action. Historically, in one of them, the 177 GHz J = 2 → 1 line in the l-doubled bending mode has been found to show relatively strong maser action, with results only published for a single object, the archetypical high-mass loss asymptotic giant branch (AGB) star IRC+10216. Aims. To examine how common 177 GHz HCN maser emission is, we conducted an exploratory survey for this line toward a select sample of carbon-rich asymptotic giant branch stars that are observable from the southern hemisphere. Methods. We used the Atacama Pathfinder Experiment 12 meter submillimeter Telescope (APEX) equipped with a new receiver to simultaneously observe three J = 2 → 1 HCN rotational transitions, the (0, 1 1c , 0) and (0, 1 1 d , 0) l-doublet components, and the line from the (0, 0, 0) ground state.Results. The (0, 1 1c , 0) maser line is detected toward 11 of 13 observed sources, which all show emission in the (0, 0, 0) transition. In most of the sources, the peak intensity of the (0, 1 1c , 0) line rivals that of the (0, 0, 0) line; in two sources, it is even stronger. Except for the object with the highest mass-loss rate, IRC+10216, the (0, 1 1c , 0) line covers a smaller velocity range than the (0, 0, 0) line. The (0, 1 1 d , 0) line, which is detected in four of the sources, is much weaker than the other two lines and covers a velocity range that is smaller yet, again except for IRC+10216. Compared to its first detection in 1989, the profile of the (0, 1 1c , 0) line observed toward IRC+10216 looks very different, and we also appear to see variability in the (0, 0, 0) line profile (at a much lower degree). Our limited information on temporal variability, taken together with results for another HCN maser line from the literature, disfavors a strong correlation of maser and stellar continuum flux. Conclusions. Maser emission in the 177 GHz J = 2 → 1 (0, 1 1c , 0) transition of HCN appears to be common in carbon-rich AGB stars. Like for other vibrationally excited HCN lines, our observations indicate that the origin of these lines is in the acceleration zone of the stellar outflow in which dust is forming. For all the stars toward which we detect the maser line, the number of photons available at 7 and 14 µm, corresponding to transitions to vibrationally excited states possibly involved in its pumping, is found to be far greater than that of the maser photons, which makes radiative pumping feasible. Other findings point to a collisional pumping scheme, however.

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Vibrationally excited HCN transitions in circumstellar envelopes of carbon-rich AGB stars

Jeste

Gong

Wong

et al. 2022

A&A

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Context. The most abundant molecule after H 2 and CO in the circumstellar envelopes (CSEs) of carbon-rich asymptotic giant branch (AGB) stars is HCN. Its rotational lines within vibrationally excited states are exceptional tracers of the innermost region of carbonrich CSEs. Aims. We aim to constrain the physical conditions of CSEs of carbon-rich stars using thermal lines of the HCN molecule. Additionally, we also search for new HCN masers and probe the temporal variations for HCN masers, which should shed light on their pumping mechanisms. Methods. We observed 16 carbon-rich AGB stars in various HCN rotational transitions, within the ground and 12 vibrationally excited states, with the Atacama Pathfinder EXperiment (APEX) 12-metre sub-millimetre telescope. Results. We detect 68 vibrationally excited HCN lines from 13 carbon-rich stars, including 39 thermal transitions and 29 maser lines, suggesting that vibrationally excited HCN lines are ubiquitous in carbon-rich stars. Population diagrams constructed for two objects from the sample, for thermal transitions from different vibrationally excited states, give excitation temperatures around 800-−900 K, confirming that they arise from the hot innermost regions of CSEs (i.e. r <20R * ). Among the detected masers, 23 are newly detected, and the results expand the total number of known HCN masers lines towards carbon-rich stars by 47%. In particular, the J = 2-1 (0, 3 1e , 0), J = 3-2 (0, 2, 0), and J = 4-3 (0, 1 1 f , 0) masers are detected in an astronomical source for the first time. Our observations confirm temporal variations of the 2-1 (0, 1 1e , 0) maser on a timescale of a few years. Our analysis of the data suggests that all detected HCN masers are unsaturated. A gas kinetic temperature of ≳700 K and an H 2 number density of >10 8 cm −3 are required to excite the HCN masers. In some ways, HCN masers in carbon-rich stars might be regarded as an analogy of SiO masers in oxygen-rich stars.

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A new HCN maser in IRAS 15082−4808

Cited by 7 publications

References 38 publications

A molecular line survey of a sample of AGB stars and planetary nebulae

A molecular line survey of a sample of AGB stars and planetary nebulae

Widespread HCN maser emission in carbon-rich evolved stars

Vibrationally excited HCN transitions in circumstellar envelopes of carbon-rich AGB stars

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