scholarly journals The loss of large amplitude pulsations at the end of AGB evolution

2018 ◽  
Vol 14 (S343) ◽  
pp. 389-390
Author(s):  
D. Engels ◽  
S. Etoka ◽  
E. Gérard
Keyword(s):  
Radio Telescope ◽  
Large Amplitude ◽  
Galactic Disk ◽  
Monitoring Program ◽  
Maser Emission ◽  
Ir Stars

AbstractSince 2013, we are performing with the Nancay Radio Telescope (NRT) a monitoring program of > 100 Galactic disk OH/IR stars, having bright 1612-MHz OH maser emission. The variations of the maser emission are used to probe the underlying stellar variability. We wish to understand how the large-amplitude variations are lost during the AGB – post-AGB transition. The fading out of pulsations with steadily declining amplitudes seems to be a viable process.

OH masers as probes: How does the variability fade away during the AGB - post-AGB transition?

2017 ◽  
Vol 13 (S336) ◽  
pp. 389-390 ◽  
Author(s):  
D. Engels ◽  
S. Etoka ◽  
M. West ◽  
E. Gérard
Keyword(s):  
Radio Telescope ◽  
Large Amplitude ◽  
Small Amplitude ◽  
Galactic Center ◽  
Galactic Disk ◽  
Monitoring Program ◽  
Maser Emission ◽  
Center Region ◽  
Ir Stars ◽  
Current Program

AbstractWe are currently performing a monitoring program of the 1612 MHz OH maser emission of several dozen Galactic disk OH/IR stars with the Nancay Radio Telescope (NRT). They are complemented by several OH/IR stars toward the Galactic center, which were monitored with the Hartebeesthoek radio telescope. We use the maser variations to probe the underlying stellar variability. As early monitoring programs already have shown, some stars are large amplitude variables with periods up to 7 years, others show small or even no amplitude variations. This dichotomy in the variability behaviour is assumed to mark the border between the AGB and the post-AGB stages. With the current program, we wish to find objects in transition and to describe their variability properties. We consider the fading out of pulsations with steadily declining amplitudes as a viable process. Promising candidates in the disk are the small-amplitude variables OH 138.0+7.2 and OH 51.8−0.2. ’Non-variable’ OH/IR stars in the Galactic center region may be as frequent as in the disk.

scholarly journals Detection of OH Maser Emission at 1667 MHz from IC 4997

1989 ◽  
Vol 131 ◽  
pp. 209-209 ◽  
Author(s):  
S. Tamura ◽  
I. Kazes
Keyword(s):  
Radio Telescope ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Optical Emission ◽  
Emission Lines ◽  
Satellite Line ◽  
Maser Emission ◽  
Large Radio Telescope ◽  
Ir Stars

We report the first detection of OH emission at 1667 MHz from a planetary nebula, IC 4997 (Figure 1). OH emission in satellite line of 1612 MHz was detected already from planetary nebulae not only Vy 2-2 (Davis and Seaquist 1979), but also two IRAS objects which were distinguished from OH/IR stars as planetary nebulae (Pottasch et al 1987). OH observations of IC 4997 have been carried out with the large radio telescope at Nançay, France. Highly resolved optical emission lines were obtained at the Okayama Astrophysical Observatory, Japan.

scholarly journals Masers as probes of proto-planetary discs

2004 ◽  
Vol 202 ◽  
pp. 362-364
Author(s):  
A.M.S. Richards ◽  
R. J. Cohen ◽  
M. Crocker ◽  
E. E. Lekht ◽  
V. Samodourov ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Radio Telescope ◽  
Keplerian Orbit ◽  
Proper Motions ◽  
Central Mass ◽  
Maser Emission ◽  
Star Forming ◽  
Star Forming Regions ◽  
Velocity Variations ◽  
Water Maser

Water maser emission from star forming regions has been monitored for several decades using the Puschino radio telescope, showing radial velocity variations consistent with material in Keplerian orbit around protostars. MERLIN and the EVN are now being used to image the 22 GHz emission on au scales and measure proper motions. This will distinguish discs from outflows, and provide an estimate of the central mass and possibly orbiting condensations.

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.

Sardinia Radio Telescope (SRT) observations of Local Group dwarf galaxies

2017 ◽  
Vol 13 (S336) ◽  
pp. 109-112
Author(s):  
A. Tarchi ◽  
P. Castangia ◽  
G. Surcis ◽  
A. Brunthaler ◽  
K. M. Menten ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Radio Continuum ◽  
Maser Emission ◽  
Star Forming ◽  
Star Forming Regions ◽  
First Results ◽  
Ngc 6822 ◽  
Almost All

AbstractThe dwarf galaxies in the Local Group (LG) reveal a surprising amount of spatial structuring. In particular, almost all non-satellite dwarfs belong to one of two planes that show a very pronounced symmetry. In order to determine if these structures in the LG are dynamically stable or, alternatively, if they only represent transient alignments, proper motion measurements of these galaxies are required. A viable method to derive proper motions is offered by VLBI studies of 22-GHz water (and 6.7-GHz methanol) maser lines in star-forming regions.In 2016, in the framework of the Early Science Program of the Sardinia Radio Telescope (SRT), we have conducted an extensive observational campaign to map the entire optical body of all the LG dwarf galaxies that belong to the two planes, at C and K band, in a search for methanol and water maser emission.Here, we outline the project and present its first results on 3 targets, NGC 6822, IC 1613, and WLM. While no luminous maser emission has been detected in these galaxies, a number of interesting weaker detections has been obtained, associated with particularly active star forming regions. In addition, we have produced deep radio continuum maps for these galaxies, aimed at investigating their star forming activity and providing an improved assessment of star formation rates in these galaxies.

scholarly journals Monitoring of extragalactic water masers with the MPIfR 100-m telescope

2002 ◽  
Vol 206 ◽  
pp. 392-395
Author(s):  
Yoshiaki Hagiwara ◽  
Christian Henkel ◽  
William A. Sherwood
Keyword(s):  
Radio Telescope ◽  
Radio Galaxy ◽  
Maser Emission ◽  
Monitoring Period ◽  
Water Masers ◽  
Water Maser

We present single-dish monitoring of the 22 GHz water maser lines from the Seyfert 2 galaxies NGC 3079, M51(NGC 5194), NGC 5793, and the radio galaxy NGC 315 with the Effelsberg 100-m radio telescope. During the monitoring period of 1995 − 2001, the H2O masers flared in M51 and NGC 5793, while maser emission from NGC 315 was not detected in 1996 and 2000. During 2000, we discovered new red-shifted velocity features in NGC 3079 and blue-shifted features in M51. These velocity components are crucial to model the distribution of maser emission in each galaxy.

Detection of OH Maser Emission from Cornet Giacobini-Zinner

1985 ◽  
Vol 6 (2) ◽  
pp. 180-181 ◽  
Author(s):  
R. P. Norris ◽  
J. R. Forster ◽  
R. A. Duncan
Keyword(s):  
Production Rate ◽  
Radio Telescope ◽  
Ground State ◽  
Maser Emission ◽  
Upper Limit ◽  
Maser Radiation ◽  
Comet Halley

AbstractWe have detected OH maser radiation from the comet Giacobini-Zinner using the Parkes radio telescope. The emission was detected in two transitions of the ground state of OH, at an intensity consistent with the predicted OH molecular production rate. We also searched unsuccessfully for OH emission from comet Halley, from which we are able to place a significant upper limit on the intensity of OH emission.

scholarly journals Timing of PSR J2055+3829, an eclipsing black widow pulsar discovered with the Nançay Radio Telescope

2019 ◽  
Vol 629 ◽  
pp. A92 ◽  
Author(s):  
L. Guillemot ◽  
F. Octau ◽  
I. Cognard ◽  
G. Desvignes ◽  
P. C. C. Freire ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Globular Clusters ◽  
Gamma Ray ◽  
Radio Signal ◽  
Galactic Disk ◽  
Mass Function ◽  
Large Area ◽  
Black Widow ◽  
Low Mass ◽  
Mass Functions

We report on the timing observations of the millisecond pulsar PSR J2055+3829 originally discovered as part of the SPAN512 survey conducted with the Nançay Radio Telescope. The pulsar has a rotational period of 2.089 ms and is in a tight 3.1 h orbit around a very low mass (0.023 ≤ mc ≲ 0.053 M⊙, 90% c.l.) companion. Our 1.4 GHz observations reveal the presence of eclipses of the radio signal of the pulsar, caused by the outflow of material from the companion, for a few minutes around superior conjunction of the pulsar. The very low companion mass, the observation of radio eclipses, and the detection of time variations of the orbital period establish PSR J2055+3829 as a “black widow” (BW) pulsar. Inspection of the radio signal from the pulsar during ingress and egress phases shows that the eclipses in PSR J2055+3829 are asymmetric and variable, as is commonly observed in other similar systems. More generally, the orbital properties of the new pulsar are found to be very similar to those of other known eclipsing BW pulsars. No gamma-ray source has been detected at the location of the pulsar in recent Fermi-LAT source catalogs. We used the timing ephemeris to search ten years of Fermi Large Area Telescope (LAT) data for gamma-ray pulsations, but were unable to detect any. This non-detection could be a consequence of the large distance of the pulsar compared to those of known gamma-ray millisecond pulsars outside of globular clusters. We finally compared the mass functions of eclipsing and non-eclipsing BW pulsars and confirmed previous findings that eclipsing BWs have higher mass functions than their non-eclipsing counterparts. Larger inclinations could explain the higher mass functions of eclipsing BWs. On the other hand, the mass function distributions of Galactic disk and globular cluster BWs appear to be consistent, suggesting, despite the very different environments, the existence of common mechanisms taking place in the last stages of evolution of BWs.

scholarly journals OH masers in oxygen-rich late-type stars

2002 ◽  
Vol 206 ◽  
pp. 319-322
Author(s):  
Sandra Etoka ◽  
A.M. Le Squeren
Keyword(s):  
Mass Loss ◽  
Radio Telescope ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Monitoring Programme ◽  
Late Type ◽  
Wide Range ◽  
Ir Stars ◽  
Circumstellar Shell

We present here some noteworthy results of two related studies on oxygen-rich late type stars. The aim of this work was to study the OH circumstellar shell properties in terms of evolution. These studies are based on an OH monitoring programme carried out with the Nançay Radio Telescope. The first study concerns seven Miras distributed along the colour-colour diagram. They were observed at two or three different epochs covering one to seven cycles over a period from 1980 to 1995 at 1612, 1667 and 1665 MHz in both circular polarizations. The second study concerns thirty objects covering a wide range of mass loss rate from Miras to OH/IR stars. They were observed in 1994 at 1665 & 1667 MHz in both circular polarizations.

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