On the excitation of CH microwave lines

Bujarrabal, V.; Salinas, F.; Gonzalo, Isabel

doi:10.1086/162507

Cited by 66 publications

(100 citation statements)

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“…Purely radiative pumps (e.g., Alcolea et al 1989;Bujarrabal 1994aBujarrabal , 1994b do not produce spatial coincidence of the v = 1 and v = 2 masers. On the other hand, collisional pumps lead to a large amount of overlap in the parameter space for these two transitions (e.g., Lockett & Elitzur 1992), in agreement with our Source I observations.…”

Section: Total Intensity Imagesmentioning

confidence: 94%

A FEATURE MOVIE OF SiO EMISSION 20-100 AU FROM THE MASSIVE YOUNG STELLAR OBJECT ORION SOURCE I

Matthews

Greenhill

Goddi

et al. 2009

ApJ

123

201

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We present multi-epoch Very Long Baseline Array imaging of the 28 SiO v = 1 and v = 2, J = 1-0 maser emission toward the massive young stellar object (YSO) Orion Source I. Both SiO transitions were observed simultaneously with an angular resolution of ∼0.5 mas (∼0.2 AU for d = 414 pc) and a spectral resolution of ∼0.2 km s −1 . Here we explore the global properties and kinematics of the emission through two 19-epoch animated movies spanning 21 months (from 2001 March 19 to 2002 December 10). These movies provide the most detailed view to date of the dynamics and temporal evolution of molecular material within ∼20-100 AU of a massive ( 8 M ) YSO. As in previous studies, we find that the bulk of the SiO masers surrounding Source I lie in an X-shaped locus; the emission in the south and east arms is predominantly blueshifted, and emission in the north and west is predominantly redshifted. In addition, bridges of intermediate-velocity emission are observed connecting the red and blue sides of the emission distribution. We have measured proper motions of over 1000 individual maser features and found that these motions are characterized by a combination of radially outward migrations along the four main maser-emitting arms and motions tangent to the intermediate-velocity bridges. We interpret the SiO masers as arising from a wide-angle bipolar wind emanating from a rotating, edge-on disk. The detection of maser features along extended, curved filaments suggests that magnetic fields may play a role in launching and/or shaping the wind. Our observations appear to support a picture in which stars with masses as high as at least 8 M form via disk-mediated accretion. However, we cannot yet rule out that the Source I disk may have been formed or altered following a recent close encounter.

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Section: Total Intensity Imagesmentioning

confidence: 94%

A FEATURE MOVIE OF SiO EMISSION 20-100 AU FROM THE MASSIVE YOUNG STELLAR OBJECT ORION SOURCE I

Matthews

Greenhill

Goddi

et al. 2009

ApJ

123

201

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“…Nyman et al (1993Nyman et al ( , 1986 found that the ratio of the 43 over 86 GHz (v = 1) SiO maser line flux is much higher for OH/IR stars, varying from 2 to 10 with increasing mass-loss rate, than for Mira stars (0.4) as found by Lane (1982). For typical 43 GHz maser line intensities measured for Galactic bulge OH/IR stars (Lindqvist et al 1991;Sjouwerman et al 2002a), and for the low 86 to 43 GHz line flux ratios generally seen towards OH/IR stars, such stars should be weak at 86 GHz and at the distance of the Galactic centre, while Mira stars should be stronger; -the SiO maser line flux correlates with the mIR continuum flux density (Alcolea et al 1989;Bujarrabal 1994;Bujarrabal et al 1987;Jiang 2002). Previous studies have shown that the 43 GHz (v = 1 and v = 2) line peak intensity correlates with the (∼7-12 µm) mIR continuum flux density (Bujarrabal 1994).…”

Section: Source Selectionmentioning

confidence: 99%

“…-SiO maser emission occurs more frequently towards M-type Mira stars than towards other AGB stars (Bujarrabal 1994;Habing 1996;Haikala et al 1994;Lewis 1990;Matsuura et al 2000); -86 GHz SiO maser emission is fainter towards OH/IR stars than towards Mira stars (Lewis 1990;Nyman et al 1993Nyman et al , 1986. Nyman et al (1993Nyman et al ( , 1986 found that the ratio of the 43 over 86 GHz (v = 1) SiO maser line flux is much higher for OH/IR stars, varying from 2 to 10 with increasing mass-loss rate, than for Mira stars (0.4) as found by Lane (1982).…”

Section: Source Selectionmentioning

confidence: 99%

“…Since the observations were taken at a random pulsation phase and since the SiO maser intensity is known to vary during the stellar phase by up to a factor ten (Bujarrabal 1994), this detection rate is a lower limit to the actual percentage of LPV sources characterized by 86 GHz SiO maser emission. Only 16% of those LPV stars have associated OH emission (Glass et al 2001), and among those within our defined colour-magnitude regions only 23%.…”

Section: Variabilitymentioning

confidence: 99%

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86 GHz SiO maser survey of late-type stars in the Inner Galaxy

Messineo¹,

Habing²,

Sjouwerman³

et al. 2002

A&A

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Abstract. We present 86 GHz (v = 1, J = 2 → 1) SiO maser line observations with the IRAM 30-m telescope of a sample of 441 late-type stars in the Inner Galaxy (−4 • < l < +30 • ). These stars were selected on the basis of their infrared magnitudes and colours from the ISOGAL and MSX catalogues. SiO maser emission was detected in 271 sources, and their line-of-sight velocities indicate that the stars are located in the Inner Galaxy. These new detections double the number of line-of-sight velocities available from previous SiO and OH maser observations in the area covered by our survey and are, together with other samples of e.g. OH/IR stars, useful for kinematic studies of the central parts of the Galaxy.

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“…Recent models of SiO masers, advocating pump mechanisms dominated by either collisional or radiative processes, suggest molecular hydrogen densities around 10 9 -10 10 cm Ϫ3 and temperatures ?1000 K for the masing region (Lockett & Elitzur 1992;Bujarrabal 1994). Alcolea & Menten (1993) performed numerical calculations which showed that inversion in the 96 GHz 4 40 3 5 33 and 233 GHz 5 50 3 6 43 2 ϭ H 2 O transitions can be achieved under similar conditions.…”

Section: No 2 1995 Discovery Of Strong Water Masers L69mentioning

confidence: 99%

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

Menten

1995

The Astrophysical Journal

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We report the astronomical discovery of the 1 10 3 1 01 rotational transition within the 2 ϭ 1 vibrationally excited state of water vapor (H 2 O). Using the 10.4 m telescope of the Caltech Submillimeter Observatory, we detect strong maser emission in this line, which has a frequency near 658 GHz, toward a diverse sample of oxygen-rich red giant and supergiant stars. In circumstellar envelopes these 658 GHz H 2 O masers appear to be as common as SiO masers and H 2 O masers in other transitions, while we fail to detect 658 GHz H 2 O emission toward the W49 N and W51 N star-forming regions. For all of the 11 stars detected, the luminosity in the 658 GHz H 2 O transition is comparable to or higher than the luminosity of any other known SiO or H 2 O maser line.

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On the excitation of CH microwave lines

Cited by 66 publications

References 0 publications

A FEATURE MOVIE OF SiO EMISSION 20-100 AU FROM THE MASSIVE YOUNG STELLAR OBJECT ORION SOURCE I

A FEATURE MOVIE OF SiO EMISSION 20-100 AU FROM THE MASSIVE YOUNG STELLAR OBJECT ORION SOURCE I

86 GHz SiO maser survey of late-type stars in the Inner Galaxy

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

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