bluuebunny/crossref_metadata_2025_split huggingface dataset:
Water masers within the G 333.2–0.6 giant molecular cloud
Authors: Breen S. L. , Ellingsen S. P. , Johnston-Hollitt M. , Wotherspoon S. , Bains I. , Burton M. G. , Cunningham M. , Lo N. , Senkbeil C. E. , Wong T. 
Published: January 2008

AbstractWe report the results of a blind search for 22 GHz water masers in two regions, covering approximately half a square degree, within the G 333.2–0.6 giant molecular cloud. The complete search of the two regions was carried out with the 26 m Mount Pleasant radio telescope and resulted in the detection of nine water masers, five of which are new detections. Australia Telescope Compact Array (ATCA) observations of these detections have allowed us to obtain positions with arcsecond accuracy, allowing meaningful comparison with infrared and molecular data for the region. We find that for the regions surveyed there are more water masers than either 6.7 GHz methanol, or main-line OH masers. The water masers are concentrated towards the central axis of the star formation region, in contrast to the 6.7 GHz methanol masers which tend to be located near the periphery. The colours of the GLIMPSE point sources associated with the water masers are slightly less red than those associated with methanol masers. Statistical investigation of the properties of the 13CO and 1.2 mm dust clumps with and without associated water masers shows that the water masers are associated with the more massive, denser and brighter 13CO and 1.2 mm dust clumps. We present statistical models that can predict those 13CO and 1.2 mm dust clumps likely to have associated water masers.
Tick tock – the 12.2 GHz methanol masers in G9.62+0.20
Authors: Gaylard Michael J. , Goedhart Sharmila 
Published: January 2008

AbstractThe bright interstellar methanol masers at 12.2 GHz and 6.7 GHz were discovered in 1987 and 1991 respectively. It was soon established that many were quite variable. Goedhart Gaylard & van der Walt (2003) reported that one source, G9.62+0.20E, exhibited flares at 12.2 and 6.7 GHz that appeared to be periodic, repeating every 246 days. Since then, monitoring of this and other possibly periodic sources has continued with the 26-m Hartebeesthoek telescope. We discuss here the full 12.2 GHz time series data of G9.62+0.20 through 2006. The data quality has been much improved by telescope upgrades. Flares in the main maser peak continue, the repetition rate remains close to that originally determined.
Discovery of polarized 6.7-GHz methanol masers in DR21/W75
Authors: Harvey-Smith L. , Soria-Ruiz R. , Duarte-Cabral A. , Cohen R. J. 
Published: January 2008

AbstractWe present the first images of 6.7 GHz methanol masers in the DR21 star-forming complex. We have discovered two sites of Class II methanol maser emission; in DR21(OH) and DR21(OH)N. The emission comprises clusters of linearly extended masers which have velocity gradients along their length. There are four maser spots in DR21(OH)N, some of which show a small fraction of linear polarization. The twelve masers in DR21(OH) lie in a linear arrangement stretching approximately 0.7 arcseconds and show no significant linear polarization. We were not able to detect any circular polarization in the masers.
Astrometry of H2O maser sources in nearby molecular clouds with VERA
Authors: Hirota Tomoya , Bushimata Takeshi , Choi Yoon Kyung , Honma Mareki , Imai Hiroshi , Iwadate Kenzaburo , Jike Takaaki , Kameno Seiji , Kameya Osamu , Kamohara Ryuichi , Kan-ya Yukitoshi , Kawaguchi Noriyuki , Kijima Masachika , Kim Mi Kyoung , Kobayashi Hideyuki , Kuji Seisuke , Kurayama Tomoharu , Manabe Seiji , Maruyama Kenta , Matsui Makoto , Matsumoto Naoko , Miyaji Takeshi , Nagayama Takumi , Nakagawa Akiharu , Nakamura Kayoko , Oh Chung Sik , Omodaka Toshihiro , Oyama Tomoaki , Sakai Satoshi , Sasao Tetsuo , Sato Katsuhisa , Sato Mayumi , Shibata Katsunori M. , Shintani Motonobu , Tamura Yoshiaki , Tsushima Miyuki , Yamashita Kazuyoshi 
Published: January 2008

AbstractWe have carried out multi-epoch VLBI observations of the H2O maser sources associated with young stellar objects (YSOs) in nearby molecular clouds with VERA (VLBI Exploration of Radio Astrometry), which is a newly constructed VLBI network in Japan (Kobayashiet al. 2003). The main goal of our study is to measure the absolute proper motions and distances to nearby molecular clouds within 1 kpc from the Sun, to reveal their 3-dimensional structures and dynamical properties. Using the VERA dual-beam receiving system (Honmaet al. 2003), we have carried out phase-referencing VLBI observations and measured annual parallaxes and absolute proper motions of the H2O maser features with respect to the extragalactic radio sources. We have successfully detected the annual parallax of one of the H2O maser features in Orion KL to be 2.29±0.10 mas, corresponding to the distance of 437±19 pc from the Sun (Hirotaet al. 2007). In addition, the annual parallax of SVS13 in NGC 1333 is also determined to be4.10±0.17 mas, corresponding to the distance of 244±10 pc from the Sun, although the life time of the maser features are only 6 months. The absolute proper motions of the H2O maser features associated with Orion KL and NGC 1333 are derived, possibly indicating the outflow motions from the YSOs as well as the systemic motions of the powering sources.
The 44 GHz methanol maser line in massive star forming regions
Authors: Hofner P. , Jordan E. , Araya E. , Kurtz S. 
Published: January 2008

AbstractWe present the results of recent surveys in the 44GHz methanol maser line toward regions of massive star formation using the Haystack 37m telescope and the VLA. We discuss a possible shock origin of this maser line and present evidence for variability from multi-epoch observations of selected sources.
A precise distance to IRAS 00420+5530 via H2O maser parallax with the VLBA
Authors: Moellenbrock G. A. , Claussen M. J. , Goss W. M. 
Published: January 2008

AbstractWe have used the VLBA to measure the annual parallax of the H2O masers in the star-forming region IRAS 00420+5530 (l=122.0°, b= -7.1°). This measurement yields a direct distance estimate of 2.17±0.05kpc, which disagrees substantially with most other published estimates (a range from 1.7 to 7.7kpc). This distance is consistent with recent parallax-based distances reported for W3(OH) (Xu et al. 2006, Hachisuka et al. 2006), lending additional support to the conclusion that the Perseus Spiral Arm of the Milky Way is a factor of at least two closer than kinematic distance estimates imply at galactic longitude ~130 degrees.
Absolute proper motions of water masers in NGC 281 measured with VERA
Authors: Sato Mayumi , Hirota Tomoya , Honma Mareki , Kobayashi Hideyuki ,   VERA Project Team
Published: January 2008

AbstractWe report on absolute proper-motion measurements of H2O maser features in the NGC 281 West molecular cloud, located ~320 pc above the Galactic plane and associated with an HI loop extending from the Galactic plane. We conducted six-epoch phase-referencing observations of the maser source with VERA (VLBI Exploration of Radio Astrometry) over six months since May 2006. The H2O maser features are found to be systematically moving toward the southwest and further away from the Galactic plane with a vertical velocity of ~20–30 km s−1 at its estimated distance of 2.2–3.5 kpc. Our new results provide the most direct evidence that the gas in the NGC 281 region was blown out from the Galactic plane, most likely in a superbubble driven by multiple or sequential supernova explosions in the Galactic plane.
Japanese VLBI network observations of 6.7-GHz methanol masers II. Results
Authors: Sugiyama Koichiro , Fujisawa Kenta , Honma Mareki , Doi Akihiro , Mochizuki Nanako , Murata Yasuhiro , Isono Yasuko 
Published: January 2008

AbstractWe are using a Japanese VLBI network (JVN) for VLBI observations of 6.7-GHz methanol masers associated with massive star-forming regions. Here we present results for Cepheus A (Cep A) from observations taken on September 9, 2006. The distribution of the maser spots indicates either a spherical bubble or a disk having an inclination of several tens degree. We construct a disk model with an inclination of ~70° and a radius of ~700 AU. From a luminosity of 1.7 × 104L⊙for a source observed in this region, the excitation of the maser is probably radiative.
Where methanol masers spring
Authors: Torstensson Karl J. E. , van Langevelde Huib Jan , Bourke Stephen 
Published: January 2008

AbstractWe are carrying out a program to observe the 6.7 GHz methanol maser emission in high-mass star-forming regions using large FOV (~2'), astrometric, VLBI data. Here we report on the first results of the inner few arc seconds in Cepheus A East. We find a maser filament extending over ~1.7” (1200 AU), straddling the waist of Cep A HW2. The region in which the CH3OH masers are found contains several YSO's and it is not clear whether the CH3OH masers are associated with several different objects or rather the larger scale surrounding environment.
Water maser and radio continuum emission towards IRAS 23139+5939
Authors: Trinidad M. A. , Curiel S. , Torrelles J. M. , Rodríguez L. F. , Migenes V. , Patel N. 
Published: January 2008

AbstractWe present simultaneous observations of continuum (3.5 and 1.3cm) and water maser line emission (1.3cm) carried out with the VLA-A toward the high-mass object IRAS 23139+5939. We detected two radio continuum sources at 3.5cm separated by 0”5 (~2400 AU), I23139 and I23139S. Based on the observed continuum flux density and the spectral index, we suggest that I23139 is a thermal radio jet associated with a high-mass YSO. On the other hand, based on the spatio-kinematical distribution of the water masers, together with the continuum emission information, we speculate that I23139S is also a jet source powering some of the masers detected in the region.
Imaging of selected sources from the Methanol Multibeam Survey
Authors: Wong-McSweeney D. , Fuller G. A. , Etoka S. 
Published: January 2008

AbstractHigh angular resolution observations are essential for understanding the nature of maser emission and the sources which excite it. Here we present preliminary results from MERLIN observations of three methanol masers from the Toruń survey. These MERLIN observations are being analysed as part of the interferometric component of the Methanol Multibeam (MMB) Survey which is surveying the Galactic plane at |b|≤2° for 6.67 GHz methanol maser sources.
The Arecibo Methanol Maser Galactic Plane Survey
Authors: Pandian Jagadheep D. , Goldsmith Paul. F. , Deshpande Avinash A. 
Published: January 2008

AbstractThe Arecibo Methanol Maser Galactic Plane Survey (AMGPS) is a blind survey for 6.7 GHz methanol masers in a section of the Galactic plane visible from the Arecibo radio telescope. The survey for these signposts of massive star formation is complete at a flux density level of 0.27 Jy making it the most sensitive blind survey for methanol masers carried out to date, and resulted in the detection of 86 methanol masers, 48 of which are new discoveries. The properties of methanol masers discovered in the survey are consistent with their being associated with early phases of massive star formation. The data also show the tangent point of the Carina-Sagittarius spiral arm to be around a Galactic longitude of 49.6°.
The Methanol Multibeam Survey
Authors: Green James A. , Cohen R. J. , Caswell J. L. , Fuller G. A. , Brooks K. , Burton M. G. , Chrysostomou A. , Diamond P. J. , Ellingsen S. P. , Gray M. D. , Hoare M. G. , Masheder M. R. W. , McClure-Griffiths N. , Pestalozzi M. , Phillips C. , Quinn L. , Thompson M. A. , Voronkov M. , Walsh A. , Ward-Thompson D. , Wong-McSweeney D. , Yates J. A. , Cox J. 
Published: January 2008

AbstractA new 7-beam methanol multibeam receiver is being used to survey the Galaxy for newly forming massive stars, that are pinpointed by strong methanol maser emission at 6.668 GHz. The receiver, jointly constructed by Jodrell Bank Observatory (JBO) and the Australia Telescope National Facility (ATNF), was successfully commissioned at Parkes in January 2006. The Parkes-Jodrell survey of the Milky Way for methanol masers is two orders of magnitude faster than previous systematic surveys using 30-m class dishes, and is the first systematic survey of the entire Galactic plane. The first 53 days of observations with the Parkes telescope have yielded 518 methanol sources, of which 218 are new discoveries. We present the survey methodology as well as preliminary results and analysis.
The 3D morphology of the ejecta surrounding VY Canis Majoris
Authors: Jones Terry Jay , Humphreys Roberta M. , Helton L. Andrew 
Published: January 2008

AbstractWe use second epoch images taken with WFPC2 on the HST and imaging polarimetry taken with the HST/ACS/HRC to explore the three dimensional structure of the circumstellar dust distribution around the red supergiant VY Canis Majoris. Transverse motions, combined with radial velocities, provide a picture of the kinematics of the ejecta, including the total space motions. The fractional polarization and photometric colors provide an independent method of locating the physical position of the dust along the line-of-sight. Most of the individual arc-like features and clumps seen in the intensity image are also features in the fractional polarization map, and must be distinct geometric objects. The location of these features in the ejecta of VY CMa using kinematics and polarimetry agree well with each other, and strongly suggest they are the result of relatively massive ejections, probably associated with magnetic fields.
Variability of masers in circumstellar shells on timescales of decades
Authors: Engels D. , Winnberg A. , Brand J. , Jiménez-Esteban F. 
Published: January 2008

AbstractBased on a 15–20 year long monitoring program of H2O masers and new observations of OH masers discovered 35 years ago, we studied the variability of maser emission in AGB stars over timescales of decades. The H2O maser features in the semi-regular variable stars RX Boo and SV Peg, and of the Mira stars U Her and R Cas, showed strong fluctuations superposed in case of the Mira stars on regular variations due to the pulsation of the stars. The spatial distribution of the emission regions in RX Boo and U Her showed deviations from spherical symmetry, which remained unchanged over >10 years. We conclude that the spatial asymmetry is determined by the underlying asymmetry of the mass loss process. There is no evidence that mass loss rates or the wind geometry in these stars have varied over the last 20 years. In 2005 we re-detected at 1612 MHz the 114 OH/IR stars discovered before 1978, implying an OH maser lifetime of >2800 years (1σ).
Infrared OH absorption lines in 1612 MHz OH maser sources
Authors: He J. H. , Chen P. S. , Szczerba R. , Sobolev A. M. 
Published: January 2008

AbstractISO mid-infrared absorption data helps to distinguish between radiative and collisional pumping mechanisms in 1612 MHz OH masers in various environments. Archive data of OH absorption at 34.6 and 53.3μm shows different behavior and different pumping rates for different types of maser sources.
Maser emission towards the young planetary nebula IRAS 17347-3139
Authors: Tafoya D. , Gómez Y. , Gómez J. F. , de Gregorio-Monsalvo I. , Uscanga L. , Anglada G. , Torelles J. M. 
Published: January 2008

AbstractWe have re-analyzed observations of the water maser emission in IRAS 17347-3139 carried out previously and compared them with new higher angular resolution and more sensitive radio-continuum observations to explain the shift between the position of the peak of the radio-continuum with respect to the center of the ring-like distribution. From our analysis, we found that the water maser emission is not distributed in a closed ring-like structure, but in what appears to be a segment of an ellipse centered in the position of the peak of the radio-continuum. These results can explain the shift between the radio-continuum and the water maser emission. We also present interferometric observations of the OH maser emission towards IRAS 17347-3139 from which we have found that the OH maser emission detected previously is not associated with this source. Furthermore, since our observations are more sensitive, we have detected for the first time weak OH maser emission associated with IRAS 17347-3139.
VLBA H2O and SiO maser observations in the pPN OH 231.8+4.2
Authors: Desmurs J.-F. , Contreras C. Sánchez , Bujarrabal V. , Alcolea J. , Colomer F. 
Published: January 2008

AbstractWe report high-resolution observations of H2O, 61,6−52,3 and 28SiO v=2, J=1-0 maser emissions obtained with the Very Long Baseline Array in the bipolar pre-planetary nebulae OH 231.8+4.2 (see Desmurs et al., 2007). A phase referencing technique was used to recover the absolute position of both emissions. We detected two groups of water vapour emission oriented nearly north-south. SiO masers are tentatively found to be placed between the two H2O maser emitting regions.
A collimated jet and an infalling-rotating disk in G192 traced by H2O maser emission
Authors: Imai Hiroshi , Omodaka Toshihiro , Hirota Tomoya , Umemoto Tomofumi , Sorai Kazuo , Kondo Tetsuro ,   the VERA collaboration
Published: January 2008

AbstractWe present H2O masers associated with the massive-star forming region G192 observed with the Japan VLBI network since the year 2005, The spatio-kinematical structure of the maser feature clusters has well persisted since previous observations, in which the masers are associated with two young stellar objects (YSOs) separated by ~1200 AU and expected to be associated with a highly-collimated bipolar jet and an infalling-rotating disk in the northern and southern YSOs, respectively. We estimated a jet speed of ~100 km s−1 and re-estimated a dynamical age of the whole jet to be 5.6×104 years. The spatial distribution of maser Doppler velocities found during the previous and present observations, relative proper motions of H2O maser features in the southern cluster found in the present observations, a relative bulk motion between the two maser clusters are well explained by a model of an infalling-rotating disk with a radius of ~1000 AU and a central stellar mass of ~8 M⊙.
Improving the parallaxes of OH bearing Miras
Authors: Vlemmings W. H. T. , van Langevelde H. J. 
Published: January 2008

AbstractWe have carried out observations with the Very Long Baseline Array (VLBA) to measure the parallaxes of Mira variables and are able to improve the distance estimates significantly for a fraction of our sample (U Her, S CrB and RR Aql). This is predominantly because we have enhanced our technique by making use of nearby, in-beam calibrators. Additionally, the observing conditions have improved during the current solar minimum. The distances of these stars are of fundamental importance for studying the physical properties of Asymptotic Giant Branch (AGB) stars with high mass loss.
Discrete survey of 5-cm OH emission from planetary and proto-planetary nebulae
Authors: Desmurs J.-F. , Baudry A. , Sivagnanam P. , Henkel C. , Richards A. M. S. 
Published: January 2008

AbstractWe have undertaken a comprehensive search for the first excited state of OH emission (J=5/2, 2Π3/2) in Planetary and Proto- Planetary Nebulae. With the Effelsberg telescope, we confirm the detection of Vy 2–2 and we present one new detection in the pPN K3−35. This detection has been confirmed by subsequent observations made at 6035 MHz with the MERLIN interferometer. This is the first detection of 6 GHz OH maser emission from a post-AGB star.
Measurements of annual parallaxes and proper motions of the red supergiant S Per
Authors: Asaki Yoshiharu , Deguchi Shuji , Imai Hirishi , Hachisuka Kazuya , Miyoshi Makoto , Honma Mareki 
Published: January 2008

AbstractVLBI phase-referencing monitoring of water vapor masers around the red supergiant, S Per, was conducted over four years. We successfully obtained proper motions and an annual parallax of the masers and determined the distance to S Per of 2.51±0.09 kpc. The proper motion of the star itself was inferred from the maser proper motions, and it was −0.38 and −1.54 mas/yr for right ascension and declination, respectively. Assuming the distance from the sun to the Galactic center, R0, of 8.5 kpc and the rotation velocity around the sun, Θ0, of 220 km/s, the Galactic rotation velocity around S Per is 200 km/s.
Positional coincidence between an H2O maser and a plasma torus in NGC 1052
Authors: Sawada-Satoh S. , Kameno S. , Nakamura K. , Namikawa D. , Shibata K. M. , Inoue M. 
Published: January 2008

AbstractWe present VLBA observation towards the nucleus of a nearby radio galaxy NGC 1052. In NGC 1052, two-sided jet structure and a dense plasma circumnuclear torus with a radius of 0.7 pc have been found around the central mass. It emits a H2O megamaser, which is redshifted with respect to the systemic velocity of the galaxy (1491 kms−1) with a large velocity width of 100 kms−1 (FWHM). The maser gas is found at the inner jet components of both the approaching and receding jets. The maser gas is positionally coincident with a plasma torus. The maser gas in NGC 1052 could be explained as a circumnuclear torus or disk, as found for the nucleus of NGC 4258.
The nuclear environment of the water megamaser radiogalaxy 3C 403
Authors: Tarchi Andrea , Brunthaler A. , Henkel C. , Menten K. M. , Braatz J. A. , Weiss A. 
Published: January 2008

AbstractSo far, few direct sub-arcsecond resolution studies exist of the dense material that, according to the standard unified scheme, should obscure the central engines of radio galaxies. In the following, observations are presented that highlight the nuclear environment of the prototypical X-shaped FR II galaxy 3C 403. To date, it is the only powerful radio galaxy known to host a water megamaser.
OH emission and absorption associated with supernovae in Arp 220
Authors: Lonsdale Colin J. , de Kleer Katherine R. , Diamond Philip J. , Thrall Hannah , Lonsdale Carol J. , Smith Harding E. 
Published: January 2008

AbstractWe present parsec-resolution spectral-line VLBI data for two epochs separated by 15 months as a precise new probe of the innermost regions of the nearby Ultraluminous Infrared Galaxy (ULIRG) Arp 220. This galaxy hosts a powerful starburst, with an associated supernova (SN) rate of order 4/yr. An extensive population of compact continuum sources interpreted as radio supernovae (RSNe) and young supernova remnants (SNR) has been imaged. We show here that many of the supernova-related radio continuum point sources exhibit clear evidence of OH absorption or maser emission in the intervening gas, and as such provide us with a sampling of conditions along very narrow and specific lines of sight through the nuclear environment. The OH gas along these lines of sight exhibits velocity dispersions of up to several tens of km/sec, and that in some cases, multiple distinct concentrations of masing gas at different radial velocities can be discerned. There is evidence for variability in the OH properties on ~1yr timescales. Our results are discussed in the context of the overall OH megamaser properties of Arp 220.
Arp 220 – IC 4553/4: understanding the system and diagnosing the ISM
Authors: Baan W. A. 
Published: January 2008

AbstractArp 220 is a nearby system in final stages of galaxy merger with powerful ongoing star-formation at and surrounding the two nuclei. Arp 220 was detected in HI absorption and OH Megamaser emission and later recognized as the nearest ultra-luminous infrared galaxy also showing powerful molecular and X-ray emissions. In this paper we review the available radio and mm-wave observational data of Arp 220 in order to obtain an integrated picture of the dense interstellar medium that forms the location of the powerful star-formation at the two nuclei.