Discovery of Strong Vibrationally Excited Water Masers at 658 GH[CLC]z[/CLC] toward Evolved Stars

Menten, K. M.

doi:10.1086/316776

Cited by 70 publications

(47 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We only detected vibrationally excited lines with Einstein-A coefficients higher than 10 −2 s −1 , except for the v 2 = 1 J K a ,K c = 1 1,0 -1 0,1 and 8 2,7 -7 3,4 lines at 658 and 968 GHz. The 658 GHz line is a maser (Menten & Young 1995), and shows the highest peak flux in our spectral survey. The profile of the 3 1,2 -3 0,3 line of the v 1,2 = 1,1 state is also suggestive of maser amplification.…”

Section: Carbon Monoxide (Co)mentioning

confidence: 77%

HIFISTARSHerschel/HIFI observations of VY Canis Majoris

Alcolea

Bujarrabal

Planesas

et al. 2013

A&A

View full text Add to dashboard Cite

Aims. The study of the molecular gas in the circumstellar envelopes of evolved stars is normally undertaken by observing lines of CO (and other species) in the millimetre-wave domain. In general, the excitation requirements of the observed lines are low at these wavelengths, and therefore these observations predominantly probe the cold outer envelope while studying the warm inner regions of the envelopes normally requires sub-millimetre (sub-mm) and far-infrared (FIR) observational data. Methods. To gain insight into the physical conditions and kinematics of the warm (100-1000 K) gas around the red hyper-giant VY CMa, we performed sensitive high spectral resolution observations of molecular lines in the sub-mm/FIR using the HIFI instrument of the Herschel Space Observatory. We observed CO, H 2 O, and other molecular species, sampling excitation energies from a few tens to a few thousand K. These observations are part of the Herschel guaranteed time key program HIFISTARS. Results. We detected the J = 6-5, J = 10-9, and J = 16-15 lines of 12 CO and 13 CO at ∼100, 300, and 750 K above the ground state (and the 13 CO J = 9-8 line). These lines are crucial for improving the modelling of the internal layers of the envelope around VY CMa. We also detected 27 lines of H 2 O and its isotopomers, and 96 lines of species such as NH 3 , SiO, SO, SO 2 HCN, OH and others, some of them originating from vibrationally excited levels. Three lines were not unambiguously assigned. Conclusions. Our observations confirm that VY CMa's envelope must consist of two or more detached components. The molecular excitation in the outer layers is significantly lower than in the inner ones, resulting in strong self-absorbed profiles in molecular lines that are optically thick in this outer envelope, for instance, low-lying lines of H 2 O. Except for the most abundant species, CO and H 2 O, most of the molecular emission detected at these sub-mm/FIR wavelengths arise from the central parts of the envelope. The spectrum of VY CMa is very prominent in vibrationally excited lines, which are caused by the strong IR pumping present in the central regions. Compared with envelopes of other massive evolved stars, VY CMa's emission is particularly strong in these vibrationally excited lines, as well as in the emission from less abundant species such as H 13 CN, SO, and NH 3 .

show abstract

Section: Carbon Monoxide (Co)mentioning

confidence: 77%

HIFISTARSHerschel/HIFI observations of VY Canis Majoris

Alcolea

Bujarrabal

Planesas

et al. 2013

A&A

View full text Add to dashboard Cite

show abstract

“…High frequency lines have also been detected from other RSGs, for example 321-and 325-GHz emission (Yates et al 1995), 658-GHz (Menten & Young 1995) from NML Cyg and VX Sgr, plus 183-GHz emission also from S Per and µ Cep (GonzalezAlfonso et al 1998).…”

Section: Water Masers In Red Supergiantsmentioning

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

“…[12][13][14] Finally, the vast majority of the over 100 molecular species which have been identified and studied in the interstellar medium have been observed by means of mm/sub mm ''radio'' astronomy. [15][16][17][18] …”

Section: A Applications and Impact Of Millimeter And Submillimeter Smentioning

confidence: 99%

A fast scan submillimeter spectroscopic technique

Petkie¹,

Goyette²,

Bettens³

et al. 1997

Review of Scientific Instruments

149

View full text Add to dashboard Cite

A new fast scan submillimeter spectroscopic technique ͑FASSST͒ has been developed which uses a voltage tunable backward wave oscillator ͑BWO͒ as a primary source of radiation, but which uses fast scan (ϳ10 5 Doppler limited resolution elements/s͒ and optical calibration methods rather than the more traditional phase or frequency lock techniques. Among its attributes are ͑1͒ absolute frequency calibration to ϳ1/10 of a Doppler limited gaseous absorption linewidth (Ͻ0.1 MHz, 0.000 003 cm Ϫ1 ), ͑2͒ high sensitivity, and ͑3͒ the ability to measure many thousands of lines/s. Key elements which make this system possible include the excellent short term spectral purity of the broadly (ϳ100 GHz) tunable BWO; a very low noise, rapidly scannable high voltage power supply; fast data acquisition; and software capable of automated calibration and spectral line measurement. In addition to the unique spectroscopic power of the FASSST system, its implementation is simple enough that it has the prospect of impacting a wide range of scientific problems.

show abstract

Discovery of Strong Vibrationally Excited Water Masers at 658 GH[CLC]z[/CLC] toward Evolved Stars

Cited by 70 publications

References 28 publications

HIFISTARSHerschel/HIFI observations of VY Canis Majoris

HIFISTARSHerschel/HIFI observations of VY Canis Majoris

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

A fast scan submillimeter spectroscopic technique

Contact Info

Product

Resources

About