Submillimeter‐Wave Measurements and Analysis of the Ground and ν
                    <sub>2</sub>
                     = 1 States of Water

Chen, Pin; Pearson, John C.; Pickett, Herbert M.; Matsuura, Shuji; Blake, Geoffrey A.

doi:10.1086/313377

Cited by 40 publications

(32 citation statements)

References 47 publications

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“…Ground-state water maser lines observed with APEX. Chen et al (2000). The difference between their values and the ones used by us is typically of order 20 kHz, corresponding to less than 0.02 km s −1 , which is smaller than the uncertainties in our velocity determinations.…”

Section: Introductionmentioning

confidence: 46%

A multi-transition submillimeter water maser study of evolved stars. Detection of a new line near 475 GHz

Menten

Lundgren²,

Беллоче

et al. 2007

A&A

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Context. Maser emission from the H 2 O molecule probes the warm, inner circumstellar envelopes of oxygen-rich red giant and supergiant stars. Multi-maser transition studies can be used to put constraints on the density and temperature of the emission regions. Aims. A number of known H 2 O maser lines were observed toward the long period variables R Leo and W Hya and the red supergiant VY CMa. A search for a new, not yet detected line near 475 GHz was conducted toward these stars. Methods. The Atacama Pathfinder Experiment telescope was used for a multi-transition observational study of submillimeter H 2 O lines.Results. The 5 33 -4 40 transition near 475 GHz was clearly detected toward VY CMa and W Hya. Many other H 2 O lines were detected toward all three target stars. Relative line intensity ratios and velocity widths were found to vary significantly from star to star. Conclusions. Maser action is observed in all but one line for which it was theoretically predicted. In contrast, one of the strongest maser lines, in R Leo by far the strongest, the 437 GHz 7 53 -6 60 transition, is not predicted to be inverted. Some other qualitative predictions of the model calculations are at variance with our observations. Plausible reasons for this are discussed. Based on our findings for W Hya and VY CMa, we find evidence that the H 2 O masers in the AGB star W Hya arise from the regular circumstellar outflow, while shock excitation in a high velocity flow seems to be required to excite masers far from the red supergiant VY CMa.

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Section: Introductionmentioning

confidence: 46%

A multi-transition submillimeter water maser study of evolved stars. Detection of a new line near 475 GHz

Menten

Lundgren²,

Беллоче

et al. 2007

A&A

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“…In the following subsections, these parameters are discussed in detail. Water vapour rotational resonances in the T-ray regime have been extensively measured and analysed via either conventional Fourier transform infrared spectroscopy (Kauppinen et al 1978;Messer et al 1983), THz-TDS (van Exter et al 1989Cheville & Grischkowsky 1999) or other techniques Matsushima et al 1995;Chen et al 2000)-the extensive study is probably due to the abundance of water vapour, which involves many physical processes in nature. Subsequently, the computer-accessible spectroscopic parameters of water vapour, including the line position, line strengths and linewidth, are available from many research groups.…”

Section: Model Of Water Vapour Absorption and Dispersionmentioning

confidence: 99%

Numerical removal of water vapour effects from terahertz time-domain spectroscopy measurements

Withayachumnankul

Fischer²,

Mickan³

et al. 2008

Proc. R. Soc. A.

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The use of T-rays, or terahertz radiation, to identify substances by their spectroscopic fingerprints is a rapidly moving field. The dominant approach is presently terahertz timedomain spectroscopy. However, a key problem is that ambient water vapour is ubiquitous and the consequent water absorption distorts the T-ray pulses. Water molecules in the gas phase selectively absorb incident T-rays at discrete frequencies corresponding to their molecular rotational transitions. When T-rays propagate through an atmosphere, this results in prominent resonances spread over the T-ray spectrum; furthermore, in the time domain, fluctuations after the main pulse are observed in the T-ray signal. These effects are generally undesired, since they may mask critical spectroscopic data. So, ambient water vapour is commonly removed from the T-ray path by using a closed chamber during the measurement. Yet, in some applications, a closed chamber is not always feasible. This situation, therefore, motivates the need for an optional alternative method for reducing these unwanted artefacts. This paper represents a study on a computational means that is a step towards addressing the problem arising from water vapour absorption over a moderate propagation distance. Initially, the complex frequency response of water vapour is modelled from a spectroscopic catalogue. Using a deconvolution technique, together with fine tuning of the strength of each resonance, parts of the water vapour response are removed from a measured T-ray signal, with minimal signal distortion, thus providing experimental validation of the technique.

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“…The spw centered at 658.2 GHz included the 2 n = 1, 1 1,0 -1 0,1 line of H 2 O at a rest frequency of 658.006550 GHz (Chen et al 2000). We also observed other H 2 O lines at 645.766010 GHz (9 7,3 -8 8,0 ) and 645.950620 GHz (9 7,2 -8 8,1 ) in the vibrationally ground state, with a lower state energy of E l = 2574 K (Chen et al 2000), which were in another spw centered at 646.8 GHz. However, we could not detect these two lines with an rms noise level (1σ) of ∼1 Jy beam.…”

Section: Observationsmentioning

confidence: 99%

ALMA OBSERVATION OF THE 658 GHz VIBRATIONALLY EXCITED H₂O MASER IN ORION KL SOURCE I

Hirota

Kim

Honma

2016

ApJ

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We present an observational study of the vibrationally excited H 2 O line at 658 GHz ( 2 n = 1, 1 1,0 -1 0,1 ) toward Orion KL using the Atacama Large Millimeter/Submillimeter Array (ALMA). This line is clearly detected at the position of the massive protostar candidate, SourceI. The spatial structure is compact, with a size of about 100 AU, and is elongated along the northeast-southwest low-velocity (18 km −1 ) bipolar outflow traced by 22 GHz H 2 O masers, SiO masers, and thermal SiO lines. A velocity gradient can be seen perpendicular to the bipolar outflow. The overall spatial and velocity structure seems to be analogous to that of the 321 GHz H 2 O maser line previously detected with ALMA and vibrationally excited SiO maser emission. The brightness temperature of the 658 GHz H 2 O line is estimated to be higher than 2×10 4 K, implying that it is emitted via maser action. Our results suggest that the 658 GHz H 2 O maser line is emitted from the base of the outflow from a rotating and expanding accretion disk as observed for the SiO masers and the 321 GHz H 2 O maser. We also search for two other H 2 O lines at 646 GHz (9 7,3 -8 8,0 and 9 7,2 -8 8,1 ), but they are not detected in Orion KL.

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Submillimeter‐Wave Measurements and Analysis of the Ground and ν ₂ = 1 States of Water

Cited by 40 publications

References 47 publications

A multi-transition submillimeter water maser study of evolved stars. Detection of a new line near 475 GHz

A multi-transition submillimeter water maser study of evolved stars. Detection of a new line near 475 GHz

Numerical removal of water vapour effects from terahertz time-domain spectroscopy measurements

ALMA OBSERVATION OF THE 658 GHz VIBRATIONALLY EXCITED H₂O MASER IN ORION KL SOURCE I

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Submillimeter‐Wave Measurements and Analysis of the Ground and ν 2 = 1 States of Water

Cited by 40 publications

References 47 publications

A multi-transition submillimeter water maser study of evolved stars. Detection of a new line near 475 GHz

A multi-transition submillimeter water maser study of evolved stars. Detection of a new line near 475 GHz

Numerical removal of water vapour effects from terahertz time-domain spectroscopy measurements

ALMA OBSERVATION OF THE 658 GHz VIBRATIONALLY EXCITED H2O MASER IN ORION KL SOURCE I

Contact Info

Product

Resources

About

Submillimeter‐Wave Measurements and Analysis of the Ground and ν ₂ = 1 States of Water

ALMA OBSERVATION OF THE 658 GHz VIBRATIONALLY EXCITED H₂O MASER IN ORION KL SOURCE I