scholarly journals 86-GHz SiO masers in Galactic centre OH/IR stars

2020 ◽  
Vol 72 (4) ◽  
Author(s):  
Maria Messineo ◽  
Lorant O Sjouwerman ◽  
Harm J Habing ◽  
Alain Omont
Keyword(s):  
Detection Rate ◽  
Space Experiment ◽  
Galactic Centre ◽  
Maser Emission ◽  
Circumstellar Material ◽  
Spectral Peaks ◽  
Ir Stars ◽  
Molecular Transition

Abstract We present results on a search for 86.243-GHz SiO (J = 2→1, $v$ = 1) maser emission toward 67 OH/IR stars located near the Galactic centre. We detected 32 spectral peaks, of which 28 correspond to SiO maser lines arising from the envelopes of these OH/IR stars. In OH/IR stars, we obtained an SiO maser detection rate of about $40\%$. We serendipitously detected two other lines from OH/IR stars at ≈86.18 GHz, which could be due to a CCS-molecule transition at 86.181 GHz or probably to an highly excited OH molecular transition at 86.178 GHz. The detection rate of 86-GHz maser emission is found to be about $60\%$ for sources with the Midcourse Space Experiment (MSX) A − E < 2.5 mag; but it drops to $25\%$ for the reddest OH/IR stars with MSX A − E > 2.5 mag. This supports the hypothesis by Messineo (2002, A&A, 393, 115) that the SiO masers are primarily found in relatively thinner circumstellar material.

scholarly journals The Presence of Water Masers in Color-Selected IRAS Sources

1989 ◽  
Vol 131 ◽  
pp. 450-450
Author(s):  
B. M. Lewis ◽  
D. Engels
Keyword(s):  
Point Source ◽  
Detection Rate ◽  
Type Ii ◽  
Maser Emission ◽  
Companion Star ◽  
Alternative Scenario ◽  
Ir Stars ◽  
Circumstellar Shell ◽  
Water Masers ◽  
Water Maser

Eder, Lewis, and Terzian (1987) examined ∼ 400 sources from the IRAS Point Source Catalogue with colors appropriate to OH/IR stars, for the presence of 1612 MHz emission. We examined a proportion of these objects at Effelsberg for the presence of water-maser emission. In sources with |bII| > 10° which are therefore relatively local, we find a 68% detection rate for water-masers among objects associated with 1612 MHz masers, as opposed to a 17% detection rate among sources with similar colors but without 1612 MHz emission. Those conditions in a circumstellar shell that favor the presence of water-masers also favor the presence of a 1612 MHz maser. These results are consistent with most Type II masers being associated with water-masers. Since Cooke and Elitzur (1985) show that water-masers are collisionally excited, this result excludes stirring of the envelope by a companion star with an associated loss of velocity coherence, as the primary cause for the existence of the color-analogue sources without 1612 MHz masers. We discuss an alternative scenario.

scholarly journals Millimetre wavelength methanol masers survey towards massive star forming regions

2007 ◽  
Vol 3 (S242) ◽  
pp. 234-235
Author(s):  
T. Umemoto ◽  
N. Mochizuki ◽  
K. M. Shibata ◽  
D.-G. Roh ◽  
H.-S. Chung
Keyword(s):  
Detection Rate ◽  
Massive Star ◽  
Molecular Line ◽  
Maser Emission ◽  
Star Forming ◽  
Methanol Maser ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Methanol Masers ◽  
Maser Sources

AbstractWe present the results of a mm wavelength methanol maser survey towards massive star forming regions. We have carried out Class II methanol maser observations at 86.6 GHz, 86.9 GHz and 107.0 GHz, simultaneously, using the Nobeyama 45 m telescope. We selected 108 6.7 GHz methanol maser sources with declinations above −25 degrees and fluxes above 20 Jy. The detection limit of maser observations was ~3 Jy. Of the 93 sources surveyed so far, we detected methanol emission in 25 sources (27%) and “maser” emission in nine sources (10%), of which thre “maser” sources are new detections. The detection rate for maser emission is about half that of a survey of the southern sky (Caswell et al. 2000). There is a correlation between the maser flux of 107 GHz and 6.7 GHz/12 GHz emission, but no correlation with the “thermal” (non maser) emission. From results of other molecular line observations, we found that the sources with methanol emission show higher gas temperatures and twice the detection rate of SiO emission. This may suggest that dust evaporation and destruction by shock are responsible for the high abundance of methanol molecules, one of the required physical conditions for maser emission.

A new jet/outflow maser in the nucleus of the Compton-thick AGN IRAS 15480-0344

2017 ◽  
Vol 13 (S336) ◽  
pp. 129-132
Author(s):  
Paola Castangia ◽  
Andrea Tarchi ◽  
Alessandro Caccianiga ◽  
Paola Severgnini ◽  
Gabriele Surcis ◽  
...  
Keyword(s):  
Detection Rate ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Maser Emission ◽  
X Ray ◽  
Vlbi Observations ◽  
S0 Galaxies ◽  
Water Maser

AbstractInvestigations of H2O maser galaxies at X-ray energies reveal that most harbor highly absorbed AGN. Possible correlations between the intrinsic X-ray luminosity and the properties of water maser emission have been suggested. With the aim of looking into these correlations on a more solid statistical basis, we have search for maser emission in a well-defined sample of Compton-thick AGN. Here we report the results of the survey, which yielded a surprisingly high maser detection rate, with a particular focus on the newly discovered luminous water maser in the lenticular (field) S0 galaxy IRAS 15480-0344. Recently, VLBI observations have been obtained to image the line and continuum emission in the nucleus of this galaxy. The radio continuum emission at VLBI scales is resolved into two compact components that are interpreted as jet knots. Based on the single-dish profile, the variability of the maser emission, and the position of the maser spots with respect to these continuum sources, we favor of a jet/outflow origin for the maser emission, consistent with similar cases found in other radio-quiet AGN. This scenario is consistent with the hypothesis of the presence of strong nuclear winds recently invoked to explain the main characteristics of field S0 galaxies.

The Mass Distribution in the Galactic Centre Estimated from OH/IR stars

1989 ◽  
pp. 503-508 ◽  
Author(s):  
M. Lindqvist ◽  
A. Winnberg ◽  
H. J. Habing ◽  
H. E. Matthews ◽  
F. M. Olnon
Keyword(s):  
Mass Distribution ◽  
Galactic Centre ◽  
Ir Stars

scholarly journals Mainline and water maser observations of OH/IR stars in the Arecibo sky

1997 ◽  
Vol 180 ◽  
pp. 356-356
Author(s):  
B. M. Lewis
Keyword(s):  
Detection Rate ◽  
Planetary Nebulae ◽  
Complete Sample ◽  
Detection Rates ◽  
Ir Stars ◽  
Circumstellar Shells ◽  
Water Masers ◽  
The Many ◽  
Water Maser

A complete sample of color selected IRAS sources with S(25) ≥ 2 Jy in the Arecibo sky and(0° ≤ δ ≤ 37°) was examined previously for 1612 MHz masers. The resulting set of OH/IR stars has now been searched for mainline OH masers at Arecibo (Lewis 1997) and for 22 GHz water masers at Effelsberg (Engels & Lewis 1996). The high overall detection rate of 61.6% for the mainlines and 54.8% for water is partly a result of deployed sensitivity, and partly due to the many blue objects in the sample. But the detectability of both masers improves when S(25)> 20 Jy, as the accompanying tables show. Still the bluest objects exhibit higher (usually ≥80%) detection rates, while there is a clear decrease in detections from redder shells: this decrease begins circa (25–12) μm=–0.55 for mainline masers, and abruptly circa (25–12) μm = −0.35 for water. These trends adhere to the descriptive sequence of the chronological scenario for masers in circumstellar shells, though a few proto planetary nebulae and very red OH/IR stars have water masers and a few mainline masers are detected in shells with (25-12) μm ≥ −0.2.

scholarly journals OH masers in envelopes of late type stars

1987 ◽  
Vol 122 ◽  
pp. 243-244
Author(s):  
A.M. Le Squeren ◽  
P. Sivagnanam ◽  
F. Tran Minh ◽  
M. Dennefeld ◽  
F. Foy
Keyword(s):  
Radio Telescope ◽  
Detection Rate ◽  
Point Sources ◽  
Spectral Classification ◽  
Late Type ◽  
Maser Emission ◽  
Galactic Longitude

Two studies of OH maser emission in envelopes of late type stars -miras (3) and OH/IR objects- have been performed with the Nancay radio-telescope. Mainly, the OH miras are found with thicker dust envelopes than the non OH ones. A sample of unidentified IRAS point sources selected on their colors has been observed. We have detected 46 new OH sources. The OH detection rate is a function of the galactic longitude and of the IRAS spectral classification.

scholarly journals The Galactic Distribution of OH/IR Stars

1977 ◽  
Vol 42 ◽  
pp. 399-433
Author(s):  
H.J. Habing
Keyword(s):  
Present Status ◽  
Line Emission ◽  
Microwave Line ◽  
Late Type ◽  
Maser Emission ◽  
Long Period ◽  
Ir Stars ◽  
Long Period Variables ◽  
Recent Compilation ◽  
Galactic Distribution

In 1967 Wilson and Barrett (1968, 1970) discovered that some long period variables, very red and apparently very late type stars, emit OH microwave line emission that is especially strong in the 1612 MHz line at 18 cm. At present some 65 such OH-emitting stars have been identified - for a recent compilation see Bowers and Kerr (1977, M giants) and Baudry et al. (1977, M supergiants). Several stars show maser emission in H2O and SiO as well. At this colloquium Winnberg will review the present status of our knowledge of these stars.

OH/IR stars and the Galactic Centre distance

1993 ◽  
pp. 345-348 ◽  
Author(s):  
Jessica M. Chapman ◽  
N. E. B. Killeen ◽  
P. te Lintel Hekkert ◽  
J. L. Caswell ◽  
J. Harnett
Keyword(s):  
Galactic Centre ◽  
Ir Stars

scholarly journals Dynamics of OH/IR Stars in the Inner Galactic Bulge

1993 ◽  
Vol 153 ◽  
pp. 341-342
Author(s):  
Anders Winnberg ◽  
Michael Lindqvist ◽  
Harm J. Habing
Keyword(s):  
Mass Distribution ◽  
Gravitational Potential ◽  
Progress Report ◽  
Dynamical Model ◽  
Galactic Centre ◽  
Galactic Bulge ◽  
Ir Stars

Using the VLA at 1612 MHz Lindqvist et al. (1992a) have found 134 OH/IR stars close to the Galactic Centre (GC). These stars plus 15 from Habing et al. (1983) have been used as probes of the gravitational potential to derive the mass distribution in the inner galactic bulge between ≈ 5 to ≈ 100 pc from the GC (Lindqvist et al., 1992b). In this paper we present a progress report of a dynamical model which we have applied to the data.

scholarly journals A Southern Survey of OH Masers at 1612 MHz

1981 ◽  
Vol 34 (3) ◽  
pp. 333 ◽  
Author(s):  
JL Caswell ◽  
RF Haynes ◽  
WM Goss ◽  
U Mebold
Keyword(s):  
Galactic Plane ◽  
Galactic Centre ◽  
Emission Sources ◽  
Classification Schemes ◽  
Mira Variables ◽  
Population Type ◽  
Ir Stars ◽  
Kinematic Properties ◽  
Line Type

A search for OH at 1612 MHz has been made along the galactic plane from longitude 3400 to the galactic centre, yielding 78 emission sources (mostly new discoveries); a further 5 sources have been found in a less sensitive survey between longitudes 2700 and 3260 Of these 83 sources 55 are masers of the variety showing two intensity peaks spaced in velocity-a characteristic of OH/IR stars. The velocity and spatial distributions of these new OHjIR stars (which are not as yet identified in the optical or infrared) are discussed, with special reference to their kinematic properties and population type; it is still not clear whether they are predominantly late-type giants (Mira variables) or supergiants. The other 28 OH sources detected include 11 of the type lIe variety (extended OH clouds exhibiting 1612 MHz emission with accompanying 1720 MHz absorption) and 4 with accompanying main-line (type 1)OH masers; the remaining 13 sources do not readily fit within existing classification schemes and are discussed individually

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