Science.gov

Sample records for ghz methanol masers

  1. 25 GHz methanol masers in regions of massive star formation

    NASA Astrophysics Data System (ADS)

    Britton, Tui R.; Voronkov, Maxim A.

    2012-07-01

    The bright 25 GHz series of methanol masers is formed in highly energetic regions of massive star formation and provides a natural signpost of shocked gas surrounding newly forming stars. A systematic survey for the 25 GHz masers has only recently been carried out. We present the preliminary results from the interferometric follow up of 51 masers at 25 GHz in the southern sky.

  2. 37 GHz Methanol Masers : Horsemen of the Apocalypse for the Class II Methanol Maser Phase?

    NASA Astrophysics Data System (ADS)

    Ellingsen, S. P.; Breen, S. L.; Sobolev, A. M.; Voronkov, M. A.; Caswell, J. L.; Lo, N.

    2011-12-01

    We report the results of a search for class II methanol masers at 37.7, 38.3, and 38.5 GHz toward a sample of 70 high-mass star formation regions. We primarily searched toward regions known to show emission either from the 107 GHz class II methanol maser transition, or from the 6.035 GHz excited OH transition. We detected maser emission from 13 sources in the 37.7 GHz transition, eight of these being new detections. We detected maser emission from three sources in the 38 GHz transitions, one of which is a new detection. We find that 37.7 GHz methanol masers are only associated with the most luminous 6.7 and 12.2 GHz methanol maser sources, which in turn are hypothesized to be the oldest class II methanol sources. We suggest that the 37.7 GHz methanol masers are associated with a brief evolutionary phase (of 1000-4000 years) prior to the cessation of class II methanol maser activity in the associated high-mass star formation region.

  3. STATISTICAL PROPERTIES OF 12.2 GHz METHANOL MASERS ASSOCIATED WITH A COMPLETE SAMPLE OF 6.7 GHz METHANOL MASERS

    SciTech Connect

    Breen, S. L.; Caswell, J. L.; Green, J. A.; Voronkov, M. A.; Ellingsen, S. P.; Fuller, G. A.; Quinn, L. J.; Avison, A.

    2011-06-01

    We present definitive detection statistics for 12.2 GHz methanol masers toward a complete sample of 6.7 GHz methanol masers detected in the Methanol Multibeam survey south of declination -20{sup 0}. In total, we detect 250 12.2 GHz methanol masers toward 580 6.7 GHz methanol masers. This equates to a detection rate of 43.1%, which is lower than that of previous significant searches of comparable sensitivity. Both the velocity ranges and the flux densities of the target 6.7 GHz sources surpass that of their 12.2 GHz companion in almost all cases. Eighty percent of the detected 12.2 GHz methanol maser peaks are coincident in velocity with the 6.7 GHz maser peak. Our data support an evolutionary scenario whereby the 12.2 GHz sources are associated with a somewhat later evolutionary stage than the 6.7 GHz sources devoid of this transition. Furthermore, we find that the 6.7 GHz and 12.2 GHz methanol sources increase in luminosity as they evolve. In addition to this, evidence for an increase in velocity range with evolution is presented. This implies that it is not only the luminosity but also the volume of gas conducive to the different maser transitions that increases as the sources evolve. Comparison with GLIMPSE mid-infrared sources has revealed a coincidence rate between the locations of the 6.7 GHz methanol masers and GLIMPSE point sources similar to that achieved in previous studies. Overall, the properties of the GLIMPSE sources with and without 12.2 GHz counterparts are similar. There is a higher 12.2 GHz detection rate toward those 6.7 GHz methanol masers that are coincident with extended green objects.

  4. A survey of 44-GHz Class I methanol masers toward High Mass Protostellar Objects

    NASA Astrophysics Data System (ADS)

    Berenice Rodríguez Garza, Carolina; Kurtz, Stan

    2016-01-01

    We present preliminary results of 44-GHz Class I methanol maser observations made with the Very Large Array toward a sample of 55 High Mass Protostellar Objects. We found a 44% detection rate of methanol maser emission. We present a statistical description of our results, along with a comparison of the location of the 44-GHz masers with respect to shocked gas, traced by Extended Green Objects seen in the Spitzer/IRAC bands.

  5. Resolving distance ambiguities towards 6.7 GHz methanol masers

    NASA Astrophysics Data System (ADS)

    Pandian, J. D.; Momjian, E.; Goldsmith, P. F.

    2008-07-01

    Context: Distances to most star forming regions are determined using kinematics, through the assumption that the observed radial velocity arises from the motion of the source with respect to the Sun resulting from the differential rotation of Galaxy. The primary challenge associated with the application of this technique in the inner Galaxy is the kinematic distance ambiguity. Aims: In this work, we aim to resolve the kinematic distance ambiguity towards a sample of 6.7 GHz methanol masers, which are signposts of the early stages of massive star formation. Methods: We measured 21 cm H I absorption spectra using the Very Large Array in C and CnB configurations. A comparison of the maximum velocity of H I absorption with the source velocity and tangent point velocity was used to resolve the kinematic distance ambiguity. Results: We resolved the distance ambiguity towards 41 sources. Distance determinations that are in conflict with previous measurements are discussed. The NE2001 spiral arm model is broadly consistent with the locations of the star forming complexes. We find that the use of vertical scale height arguments to resolve the distance ambiguity can lead to erroneous classifications for a significant fraction of sources.

  6. 6.7 GHz methanol masers: Properties, Associations and Tracers of Galactic Structure

    NASA Astrophysics Data System (ADS)

    Pandian, Jagadheep D.

    2007-01-01

    The 6.7 GHz transition of methanol is the strongest of methanol masers, and is the second strongest maser transition ever observed in the Milky Way. There is st rong theoretical and observational evidence that the masers trace an early phase of massive star formation. The lack of association of these masers with other astronomical objects such as low-mass young stellar objects (YSOs) and late type stars, and their high brightness temperatures makes them excellent tools to detect and study massive star formation across our Galaxy. The preponderance of massive stars along the spiral arms of galaxies also imply the potential utility of these methanol masers to study the spiral structure of our Galaxy. In this dissertation, we present a study of 6.7 GHz methanol masers and their properties based on the Arecibo Methanol Maser Galactic Plane Survey (AMGPS), a sensitive blind survey carried out with the Arecibo radio telescope. To carry out this study, we built a receiver for Arecibo that could process signals between 6 and 8 GHz. The high sensitivity of the cooled receiver and the large collecting area of Arecibo made AMGPS the most sensitive blind survey to date for 6.7 GHz methanol masers, and resulted in the detection of 86 methanol masers, 48 of which are new detections. The distribution of methanol masers as a function of Galactic latitude and the statistics of their multi-wavelength counterparts show our data to be consistent with the hypothesis of 6.7 GHz methanol masers being associated with massive YSOs. Using the detection statistics of AMGPS, we estimate the minimum number of methanol masers in the Galaxy to be 1125. The l-v diagram of the AMGPS sample shows the tangent point of the Carina-Sagittarius spiral arm to be around 49.6°, and suggests occurrence of massive star formation along the extension of the Crux-Scutum arm. A Gaussian component analysis of methanol masers shows the mean line-width to be 0.38 km s^{-1} which is more a factor of two larger than

  7. The Rare 23.1 GHz Methanol Masers in NGC 7538 IRS 1

    NASA Astrophysics Data System (ADS)

    Galván-Madrid, Roberto; Montes, Gabriela; Ramírez, Edgar A.; Kurtz, Stan; Araya, Esteban; Hofner, Peter

    2010-04-01

    We present high angular resolution (θ_syn ≲ 0.2") observations of the 23.1 GHz methanol (CH3OH) transition toward the massive star-forming region NGC 7538 IRS 1. The two velocity components previously reported by Wilson et al. are resolved into distinct spatial features with brightness temperatures (TB ) greater than 104 K, proving their maser nature. Thus, NGC 7538 IRS 1 is the third region confirmed to show methanol maser emission at this frequency. The brighter 23.1 GHz spot coincides in position with a rare formaldehyde (H2CO) maser, and marginally with a 22.2 GHz water (H2O) maser, for which we report archival observations. The weaker CH3OH spot coincides with an H2O maser. The ratio of TB for the 23.1 GHz masers to that of the well-known 12.2 GHz CH3OH masers in this region roughly agrees with model predictions. However, the 23.1 GHz spots are offset in position from the CH3OH masers at other frequencies. This is difficult to interpret in terms of models that assume that all the masers arise from the same clumps, but it may result from turbulent conditions within the gas or rapid variations in the background radiation field.

  8. The Medicina survey of methanol masers at 6.7 GHz

    NASA Astrophysics Data System (ADS)

    Slysh, V. I.; Val'tts, I. E.; Kalenskii, S. V.; Voronkov, M. A.; Palagi, F.; Tofani, G.; Catarzi, M.

    1999-01-01

    A survey of Class II methanol masers at 6.7 GHz was made in the Northern hemisphere with the 32-m Medicina radio telescope. 42 objects were detected, 20 of them are new detections at 6.7 GHz. Our results show that the detection rate of 6.7 GHz masers toward the inner part of the Galaxy is higher than in other directions. It is confirmed that most of the methanol masers are associated with faint compact HII regions. The 6.7 GHz methanol masers show large velocity dispersion and large velocity offset from the velocity of parent molecular clouds. Table 2 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

  9. Class I Methanol Maser Observations at 44 GHz in the Direction of some SNRs and SFRs.

    NASA Astrophysics Data System (ADS)

    Larionov, G. M.; Litovchenko, I. D.; Val'tts, I. E., Alakoz, A. V.

    2011-05-01

    The results of searching for class I methanol maser emission in the interstellar medium are presented. Observations at Onsala 20-m radio telescope at 44 GHz in methanol transition 7_0-6_1A has been conducted in the direction of different types of objects of the northern hemisphere: in a little-studied region of maser emission G27.4-0.2, in some supernova remnants, in high mass protostars regions, in the dust rings around HII regions and in protostellar candidates associated with powerful bipolar outflows. In the source G27.4-0.2, which is identified with two SNR well known G27.4 +0.0 (Kes73) and possible G27.3-0.2 - class I methanol maser emission was detected at the frequency of 44 GHz. In the vicinity of the maser a map of size (27 'x 27') has been obtained. It was shown that emission at 44 GHz is formed only within the previously known maser region at 95 GHz. In four supernova remnants class I methanol maser emission was not detected at the coordinates of satellite OH (1720) maser emission. In the direction of high mass star-forming regions 9 new class I methanol masers were detected at 44 GHz. These 9 new masers are from areas characterized by high density and lack of continuum radio emission. This fact indicates the absence of ultra-compact HII regions, hence the young age of star forming regions, which have not yet formed protostar to ensure the ionization of the environment. This conclusion confirms the hypothesis of a purely collisional pumping of class I methanol masers.

  10. Physical Conditions around 6.7 GHz Methanol Masers. I. Ammonia

    NASA Astrophysics Data System (ADS)

    Pandian, J. D.; Wyrowski, F.; Menten, K. M.

    2012-07-01

    Methanol masers at 6.7 GHz are known to be tracers of high-mass star formation in our Galaxy. In this paper, we study the large-scale physical conditions in the star-forming clumps/cores associated with 6.7 GHz methanol masers using observations of the (1, 1), (2, 2), and (3, 3) inversion transitions of ammonia with the Effelsberg telescope. The gas kinetic temperature is found to be higher than in infrared dark clouds, highlighting the relatively evolved nature of the maser sources. Other than a weak correlation between maser luminosity and the ammonia line width, we do not find any differences between low- and high-luminosity methanol masers.

  11. A survey of 12.2 GHz methanol masers and their polarization properties

    NASA Astrophysics Data System (ADS)

    Koo, Bon-Chul; Williams, David R. D.; Heiles, Carl; Backer, Donald C.

    1988-03-01

    Methanol emission at 12.1786 GHz, 2 - 3(-1)E, has been searched for toward 78 nonstellar H2O masers and 33 type I OH/IR stars. Eleven new methanol sources were found in nonstellar water masers, whereas no sources were found in stellar masers. Most of the new sources show narrow lines with velocity widths smaller than 1 km/s and are considered to be masers. Tentative evidence is presented that the methanol masers are not all associated with H2O and OH masers. Polarization properties have also been observed for five strong sources including Cepheus A and G188.94 + 0.89, which were detected in this survey. Three sources, G188.94 + 0.89, Cepheus A, and NGC 7538, are completely unpolarized, and the other two sources show a small amount of linear polarization: a few percent for W3(OH) and 10 + or - 3 percent for NGC 6334.

  12. AMMONIA AND CO OBSERVATIONS TOWARD LOW-LUMINOSITY 6.7 GHz METHANOL MASERS

    SciTech Connect

    Wu, Y. W.; Xu, Y.; Yang, J.; Zhang, S. B.; Pandian, J. D.; Henkel, C.; Menten, K. M.

    2010-09-01

    To investigate whether distinctions exist between low- and high-luminosity Class II 6.7 GHz methanol masers, we have undertaken multi-line mapping observations of various molecular lines, including the NH{sub 3} (1,1), (2,2), (3,3), (4,4), and {sup 12}CO (1-0) transitions, toward a sample of nine low-luminosity 6.7 GHz masers and {sup 12}CO (1-0) observations toward a sample of eight high-luminosity 6.7 GHz masers, for which we already had NH{sub 3} spectral line data. Emission in the NH{sub 3} (1,1), (2,2), and (3,3) transitions was detected in eight out of nine low-luminosity maser sources, in which 14 cores were identified. We derive densities, column densities, temperatures, core sizes, and masses of both low- and high-luminosity maser regions. A comparative analysis of the physical quantities reveals marked distinctions between the low-luminosity and high-luminosity groups: in general, cores associated with high-luminosity 6.7 GHz masers are larger and more massive than those traced by low-luminosity 6.7 GHz masers; regions traced by the high-luminosity masers have larger column densities but lower densities than those of the low-luminosity maser regions. Further, strong correlations between 6.7 GHz maser luminosity and NH{sub 3} (1,1) and (2,2) line widths are found, indicating that internal motions in high-luminosity maser regions are more energetic than those in low-luminosity maser regions. A {sup 12}CO (1-0) outflow analysis also shows distinctions in that outflows associated with high-luminosity masers have wider line wings and larger sizes than those associated with low-luminosity masers.

  13. VizieR Online Data Catalog: 95GHz class I methanol maser survey (Chen+, 2012)

    NASA Astrophysics Data System (ADS)

    Chen, X.; Ellingsen, S. P.; He, J.-H.; Xu, Y.; Gan, C.-G.; Shen, Z.-Q.; An, T.; Sun, Y.; Ju, B.-G.

    2012-07-01

    We used the released catalogs from the GLIMPSE survey (version 2.0; Cat. II/293) and the BGPS (version 1.0.1; Cat. J/ApJS/188/123) to construct a target sample for our class I methanol maser search. The observations of the 80-71A+ (95.1964630GHz) class I methanol maser transition were made using the PMO 13.7m telescope in Delingha, China during 2011 March-April. (4 data files).

  14. 12.2-GHz methanol maser MMB follow-up catalogue - IV. Longitude range 20°-60°

    NASA Astrophysics Data System (ADS)

    Breen, S. L.; Ellingsen, S. P.; Caswell, J. L.; Green, J. A.; Voronkov, M. A.; Avison, A.; Fuller, G. A.; Quinn, L. J.

    2016-07-01

    This is the fourth and final instalment of a series of catalogues presenting 12.2-GHz methanol maser observations made towards each of the 6.7-GHz methanol masers detected in the Methanol Multibeam (MMB) survey. This final portion of the survey covers the 20°-60° longitude range, increasing the 12.2-GHz follow-up range to the full MMB coverage of 186° ≥ l ≤ 60° and |b| ≤ 2°. Towards a total of 260 6.7-GHz MMB methanol masers (we were unable to observe five of the MMB sources in this longitude range) we detect 116 12.2-GHz masers counterparts, 64 of which were discovered in this survey. Including data from the literature, we find that there are 12.2-GHz methanol masers towards 47.1 per cent of the 6.7-GHz methanol masers in this portion of the Galaxy. Across the entire MMB survey range, we find a detection rate of 45.3 per cent. We find that the detection rate of 12.2-GHz methanol masers as a function of Galactic longitude is not uniform and there is an excess of masers with broad velocity ranges at longitudes near 30° and 330°. Comparing the occurrence of 12.2-GHz methanol masers with MMB-targeted CO observations has shown that those outflows associated with a 12.2-GHz source have a larger average dynamical time-scale than those associated with only 6.7-GHz methanol masers, supporting the notion that the 12.2-GHz masers are associated with a later phase of high-mass star formation.

  15. The almost ubiquitous association of 6.7-GHz methanol masers with dust

    NASA Astrophysics Data System (ADS)

    Urquhart, J. S.; Moore, T. J. T.; Menten, K. M.; König, C.; Wyrowski, F.; Thompson, M. A.; Csengeri, T.; Leurini, S.; Eden, D. J.

    2015-02-01

    We report the results of 870-μm continuum observations, using the Large APEX Bolometer Camera, towards 77 class-II, 6.7-GHz methanol masers identified by the Methanol MultiBeam (MMB) survey to map the thermal emission from cool dust towards these objects. These data complement a study of 630 methanol masers associated with compact dense clumps identified from the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) survey. Compact dust emission is detected towards 70 sources, which implies a dust-association rate of 99 per cent for the full MMB catalogue. Evaluation of the derived dust and maser properties leads us to conclude that the combined sample represents a single population tracing the same phenomenon. We find median clump masses of a few 103 M⊙ and that all but a handful of sources satisfy the mass-size criterion required for massive star formation. This study provides the strongest evidence of the almost ubiquitous association of methanol masers with massive, star-forming clumps. The fraction of methanol-maser associated clumps is a factor of ˜2 lower in the outer Galaxy than the inner Galaxy, possibly a result of the lower metallicity environment of the former. We find no difference in the clump-mass and maser-luminosity distributions of the inner and outer Galaxy. The maser-pumping and clump formation mechanisms are therefore likely to be relatively invariant to Galactic location. Finally, we use the ratio of maser luminosity and clump mass to investigate the hypothesis that the maser luminosity is a good indicator of the evolutionary stage of the embedded source, however, we find no evidence to support this.

  16. DETECTION OF 36 GHz CLASS I METHANOL MASER EMISSION TOWARD NGC 253

    SciTech Connect

    Ellingsen, Simon P.; Chen, Xi; Qiao, Hai-Hua; Baan, Willem; An, Tao; Li, Juan; Breen, Shari L.

    2014-08-01

    We have used the Australia Telescope Compact Array to search for emission from the 4{sub –1} → 3{sub 0} E transition of methanol (36.2 GHz) toward the center of the nearby starburst galaxy NGC 253. Two regions of emission were detected, offset from the nucleus along the same position angle as the inner spiral arms. The emission is largely unresolved on a scale of 5'', has a FWHM line width of <30 km s{sup –1}, and an isotropic luminosity orders of a magnitude larger than that observed in any Galactic star formation region. These characteristics suggest that the 36.2 GHz methanol emission is most likely a maser, although observations with higher angular and spectral resolution are required to confirm this. If it is a maser, this represents the first detection of a class I methanol maser outside the Milky Way. The 36.2 GHz methanol emission in NGC 253 has more than an order of magnitude higher isotropic luminosity than the widespread emission recently detected toward the center of the Milky Way. If emission from this transition scales with the nuclear star formation rate, then it may be detectable in the central regions of many starburst galaxies. Detection of methanol emission in ultra-luminous infrared galaxies would open up a new tool for testing for variations in fundamental constants (particularly the proton-to-electron mass ratio) on cosmological scales.

  17. The 44 GHz methanol masers - Results of an extensive survey in the 7(0)-6(1)A(+) line

    NASA Astrophysics Data System (ADS)

    Bachiller, R.; Gomez-Gonzalez, J.; Barcia, A.; Menten, K. M.

    1990-12-01

    A search for emission in the 44-GHz 7(0)-6(1)A(+) transition of CH3OH toward 124 known water masers associated with star-formation regions and evolved stars was conducted. Emission was detected toward 16 sources. In most sources maser action was observed, indicated by narrow intense spectral features. The methanol maser velocities were similar to the systemic velocities of the regions in question and showed no high-velocity features. Several new maser components were found in regions containing previously known methanol masers.

  18. The VLBI Monitoring Project for 6.7 GHz Methanol Masers Using the Jvn/eavn

    NASA Astrophysics Data System (ADS)

    Sugiyama, Koichiro; Fujisawa, Kenta; Hachisuka, Kazuya; Yonekura, Yoshinori; Motogi, Kazuhito; Sawada-Satoh, Satoko; Matsumoto, Naoko; Saito, Yu; Hirano, Daiki; Hayashi, Kyonosuke; Shen, Zhiqiang; Honma, Mareki; Hirota, Tomoya; Murata, Yasuhiro; Doi, Akihiro; Niinuma, Kotaro; Dodson, Richard; Rioja, Maria; Ellingsen, Simon; Chen, Xi; Kim, Kee-Tae; Ogawa, Hideo

    2015-09-01

    We have initiated a Very Long Baseline Interferometer (VLBI) monitoring project of 36 methanol maser sources at 6.7 GHz using the Japanese VLBI Network (JVN) and East-Asian VLBI Network (EAVN), starting in August 2010. The purpose of this project is to systematically reveal 3-dimensional (3-D) kinematics of rotating disks around forming high-mass protostars. As an initial result, we present proper motion detections for two methanol maser sources showing an elliptical spatial morphology, G 002.53+00.19 and G 006.79-00.25, which could be the best candidates associated with the disk. The detected proper motions indicate a simple rotation in G 002.53+00.19 and rotation with expansion in G 006.79-00.25, respectively, on the basis of disk model fits with rotating and expanding components. The expanding motions might be caused by the magnetic-centrifugal wind on the disk.

  19. MAJOR STRUCTURES OF THE INNER GALAXY DELINEATED BY 6.7 GHz METHANOL MASERS

    SciTech Connect

    Green, J. A.; Caswell, J. L.; McClure-Griffiths, N. M.; Breen, S. L.; Voronkov, M. A.; Avison, A.; Fuller, G. A.; Gray, M. D.; Burton, M. G.; Ellingsen, S. P.; Pestalozzi, M.

    2011-05-20

    We explore the longitude-velocity distribution of 6.7 GHz methanol masers in the context of the inner structure of our Galaxy. We analyze the correlation in velocities within this distribution and identify density enhancements indicating large-scale regions of enhanced star formation. These are interpreted as the starting points of the spiral arms and the interaction of the Galactic bar with the 3 kpc arms. The methanol masers support the presence of a long thin bar with a 45{sup 0} orientation. Signatures of the full 3 kpc arm structure are seen, including a prominent tangent at approximately -22{sup 0} Galactic longitude. We compare this distribution with existing models of the gas dynamics of our Galaxy. The 3 kpc arm structure appears likely to correspond to the radius of corotation resonance of the bar, with the bar on its inner surface and the starting points of the spiral arms on its outer surface.

  20. New periodic 6.7 GHz class II methanol maser associated with G358.460-0.391

    NASA Astrophysics Data System (ADS)

    Maswanganye, J. P.; Gaylard, M. J.; Goedhart, S.; Walt, D. J. van der; Booth, R. S.

    2015-01-01

    Eight new class II methanol masers selected from the 6.7 GHz Methanol Multibeam survey catalogues I and II were monitored at 6.7 GHz with the 26 m Hartebeesthoek Radio Astronomy Observatory radio telescope for three years and seven months, from 2011 February to 2014 September. The sources were also observed at 12.2 GHz and two were sufficiently bright to permit monitoring. One of the eight sources, namely G358.460-0.391, was found to show periodic variations at 6.7 GHz. The period was determined and tested for significance using the Lomb-Scargle, epoch-folding and Jurkevich methods, and by fitting a simple analytic function. The best estimate for the period of the 6.7 GHz class II methanol maser line associated with G358.460-0.391 is 220.0 ± 0.2 d.

  1. Detection of the Zeeman Effect in the 36 GHz Class I Methanol Maser Line with the EVLA

    NASA Astrophysics Data System (ADS)

    Momjian, Emmanuel; Sarma, A. P.

    2010-01-01

    We report the first detection of the Zeeman effect in the 36 GHz Class I methanol maser line. The observations were carried out with 13 antennas of the Expanded Very Large Array (EVLA) equipped with the new 27-40 GHz (Ka-Band) receivers, and targeted the high-mass star-forming region M8E. The detected line of sight magnetic field values are -31.3 ± 3.5 mG and 20.2 ± 3.5 mG to the northwest and southeast of the maser line peak, respectively. These magnetic field values have been derived using a Zeeman splitting factor based on laboratory measurements of the 25 GHz methanol line, since no measurements exist for the 36 GHz line. The change in sign of the magnetic field, as revealed in our observations, is over a size scale of 1300 AU in the source M8E (assuming a distance of 1.5 kpc). This may indicate that the masers are tracing two regions with different magnetic fields, or that the same field curves across the regions where the masers are being excited. The detected fields are not significantly different from the magnetic fields detected in the 6.7 GHz Class II methanol maser line, indicating that these masers may trace the large scale magnetic field, or that the magnetic field remains unchanged during the early evolution of star forming regions. Given what is known about the densities at which 36 GHz methanol masers are excited, we find that the magnetic field is dynamically significant in this star forming region. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

  2. VizieR Online Data Catalog: 6.7GHz methanol masers survey of low-mass YSO (Minier+, 2003)

    NASA Astrophysics Data System (ADS)

    Minier, V.; Ellingsen, S. P.; Norris, R. P.; Booth, R. S.

    2003-07-01

    We report the results of a search for 6.7-GHz methanol masers toward low-mass young stellar objects (YSOs) and (pre)protostellar condensations with the Australia Telescope Compact Array (ATCA). Our sample consisted of 13 class 0 protostars and 44 class I YSOs as well as 66 (pre)protostellar condensations. A single detection was obtained toward NGC 2024: FIR4 in the Orion B region. This is the first detection of a 6.7-GHz methanol maser in Orion. The nature of FIR4 has been a subject of debate with some evidence suggesting that it is a very cold high-mass (pre)protostellar condensation and others arguing that it is a low-mass YSO. The discovery of a methanol maser associated with this source is inconsistent with both of these hypotheses and we suggest that FIR4 probably harbours an intermediate- or high-mass YSO. (1 data file).

  3. European VLBI Network imaging of 6.7 GHz methanol masers

    NASA Astrophysics Data System (ADS)

    Bartkiewicz, A.; Szymczak, M.; van Langevelde, H. J.

    2016-03-01

    Context. Methanol masers at 6.7 GHz are well known tracers of high-mass star-forming regions. However, their origin is still not clearly understood. Aims: We aimed to determine the morphology and velocity structure for a large sample of the maser emission with generally lower peak flux densities than those in previous surveys. Methods: Using the European VLBI Network (EVN) we imaged the remaining sources from a sample of sources that were selected from the unbiased survey using the Torun 32 m dish. In this paper we report the results for 17 targets. Together they form a database of a total of 63 source images with high sensitivity (3σrms = 15-30 mJy beam-1), milliarcsecond angular resolution (6-10 mas) and very good spectral resolution (0.09 km s-1 or 0.18 km s-1) for detailed studies. Results: We studied in detail the properties of the maser clouds and calculated the mean and median values of the projected size (17.4 ± 1.2 au and 5.5 au, respectively) as well as the FWHM of the line (0.373 ± 0.011 km s-1 and 0.315 km s-1 for the mean and median values, respectively), testing whether it was consistent with Gaussian profile. We also found maser clouds with velocity gradients (71%) that ranged from 0.005 km s-1 au-1 to 0.210 km s-1 au-1. We tested the kinematic models to explain the observed structures of the 6.7 GHz emission. There were targets where the morphology supported the scenario of a rotating and expanding disk or a bipolar outflow. Comparing the interferometric and single-dish spectra we found that, typically, 50-70% of the flux was missing. This phenomena is not strongly related to the distance of the source. Conclusions: The EVN imaging reveals that in the complete sample of 63 sources the ring-like morphology appeared in 17% of sources, arcs were seen in a further 8%, and the structures were complex in 46% cases. The ultra-compact (UC) H II regions coincide in position in the sky for 13% of the sources. They are related both to extremely high and low

  4. DISCOVERY OF THE ZEEMAN EFFECT IN THE 44 GHz CLASS I METHANOL (CH{sub 3}OH) MASER LINE

    SciTech Connect

    Sarma, A. P.; Momjian, E.

    2011-03-20

    We report the discovery of the Zeeman effect in the 44 GHz Class I methanol (CH{sub 3}OH) maser line. The observations were carried out with 22 antennas of the Expanded Very Large Array toward a star-forming region in OMC-2. Based on our adopted Zeeman splitting factor of z = 1.0 Hz mG{sup -1}, we detect a line-of-sight magnetic field of 18.4 {+-} 1.1 mG toward this source. Since such 44 GHz CH{sub 3}OH masers arise from shocks in the outflows of star-forming regions, we can relate our measurement of the post-shock magnetic field to field strengths indicated by species tracing pre-shock regions, and thus characterize the large-scale magnetic field. Moreover, since Class I masers trace regions more remote from the star-forming core than Class II masers, and possibly earlier phases, magnetic fields detected in 6.7 GHz Class II and 36 and 44 GHz Class I methanol maser lines together offer the potential of providing a more complete picture of the magnetic field. This motivates further observations at high angular resolution to find the positional relationships between Class I and Class II masers, and masers at various frequencies within each category. In particular, CH{sub 3}OH masers are widespread in high- as well as intermediate-mass star-forming regions, and our discovery provides a new method of studying the magnetic field in such regions, by observing small physical scales that are not accessible by any other lines.

  5. A new probe of magnetic fields during high-mass star formation. Zeeman splitting of 6.7 GHz methanol masers

    NASA Astrophysics Data System (ADS)

    Vlemmings, W. H. T.

    2008-06-01

    Context: The role of magnetic fields during high-mass star formation is a matter of fierce debate, yet only a few direct probes of magnetic field strengths are available. Aims: The magnetic field is detected in a number of massive star-forming regions through polarization observations of 6.7 GHz methanol masers. Although these masers are the most abundant of the maser species occurring during high-mass star formation, most magnetic field measurements in the high-density gas currently come from OH and H2O maser observations. Methods: The 100-m Effelsberg telescope was used to measure the Zeeman splitting of 6.7 GHz methanol masers for the first time. The observations were performed on a sample of 24 bright northern maser sources. Results: Significant Zeeman splitting is detected in 17 of the sources with an average magnitude of 0.56 m s-1. Using the current best estimate of the 6.7 GHz methanol maser Zeeman splitting coefficient and a geometrical correction, this corresponds to an absolute magnetic field strength of 23 mG in the methanol maser region. Conclusions: The magnetic field is dynamically important in the dense maser regions. No clear relation is found with the available OH maser magnetic field measurements. The general sense of direction of the magnetic field is consistent with other Galactic magnetic field measurements, although a few of the masers display a change of direction between different maser features. Due to the abundance of methanol masers, measuring their Zeeman splitting provides the opportunity to construct a comprehensive sample of magnetic fields in high-mass star-forming regions. Figures 6-8 are only available in electronic form at http://www.aanda.org

  6. Observations of 6.7 GHz methanol masers with East-Asian VLBI Network. II. Internal proper motion measurement in G006.79-00.25

    NASA Astrophysics Data System (ADS)

    Sugiyama, Koichiro; Fujisawa, Kenta; Hachisuka, Kazuya; Yonekura, Yoshinori; Motogi, Kazuhito; Sawada-Satoh, Satoko; Matsumoto, Naoko; Hirano, Daiki; Hayashi, Kyonosuke; Kobayashi, Hideyuki; Kawaguchi, Noriyuki; Shibata, Katsunori M.; Honma, Mareki; Hirota, Tomoya; Murata, Yasuhiro; Doi, Akihiro; Ogawa, Hideo; Kimura, Kimihiro; Niinuma, Kotaro; Chen, Xi; Xia, Bo; Li, Bin; Sorai, Kazuo; Momose, Munetake; Saito, Yu; Takaba, Hiroshi; Omodaka, Toshihiro; Kim, Kee-Tae; Shen, Zhiqiang

    2015-10-01

    We detected internal proper motions of the methanol maser features at 6.7 GHz in a high-mass star-forming region G006.79-00.25 with the East-Asian VLBI Network. The spatial distribution of the maser features shows an elliptical morphology. The internal proper motions of 17 methanol maser features relative to the barycenter of the features were measured. The amplitude of the internal motions ranged from 1.30 to 10.25 km s-1. Most of the internal proper motions of the maser features seem to point counterclockwise along the elliptical morphology of the maser features. We applied the disk model, which includes both rotating and expanding components, to the observed positions, l.o.s. velocities, and proper motions. The derived rotation, expansion, and systemic velocities are +3^{+2}_{-2}, +6^{+2}_{-2}, and +21^{+2}_{-2}km s-1, respectively, at the radius of 1260 au on the disk with a position angle of the semi-major axis of - 140° and an inclination of 60°. The derived rotating motion suggests that the methanol maser emissions showing the elliptical spatial morphology possibly trace the rotating disk. The derived expanding motion might be caused by the magnetic-centrifugal wind on the disk, which was estimated on the basis of the typical magnetic field strength at emitting zones of a methanol maser.

  7. COMPARISON OF TWO EPOCHS OF THE ZEEMAN EFFECT IN THE 44 GHz CLASS I METHANOL (CH{sub 3}OH) MASER LINE IN OMC-2

    SciTech Connect

    Momjian, E.; Sarma, A. P. E-mail: asarma@depaul.edu

    2012-12-01

    We present a second epoch of observations of the 44 GHz Class I methanol maser line toward the star-forming region Orion Molecular Cloud 2. The observations were carried out with the Very Large Array, and constitute one of the first successful Zeeman effect detections with the new Wide-band Digital Architecture correlator. Comparing to the result of our earlier epoch of data for this region, we find that the intensity of the maser increased by 50%, but the magnetic field value has stayed the same, within the errors. This suggests that the methanol maser may be tracing the large-scale magnetic field that is not affected by the bulk gas motions or turbulence on smaller scales that is causing the change in maser intensity.

  8. Observations of 6.7 GHz methanol masers with East-Asian VLBI Network. I. VLBI images of the first epoch of observations

    NASA Astrophysics Data System (ADS)

    Fujisawa, Kenta; Sugiyama, Koichiro; Motogi, Kazuhito; Hachisuka, Kazuya; Yonekura, Yoshinori; Sawada-Satoh, Satoko; Matsumoto, Naoko; Sorai, Kazuo; Momose, Munetake; Saito, Yu; Takaba, Hiroshi; Ogawa, Hideo; Kimura, Kimihiro; Niinuma, Kotaro; Hirano, Daiki; Omodaka, Toshihiro; Kobayashi, Hideyuki; Kawaguchi, Noriyuki; Shibata, Katsunori M.; Honma, Mareki; Hirota, Tomoya; Murata, Yasuhiro; Doi, Akihiro; Mochizuki, Nanako; Shen, Zhiqiang; Chen, Xi; Xia, Bo; Li, Bin; Kim, Kee-Tae

    2014-04-01

    Very-long-baseline interferometry (VLBI) monitoring of the 6.7 GHz methanol maser allows us to measure the internal proper motion of maser spots and therefore study the gas motion around high-mass young stellar objects. To this end, we have begun monitoring observations with the East-Asian VLBI Network. In this paper we present the results of the first epoch observation for 36 sources, including 35 VLBI images of the methanol maser. Since two independent sources were found in three images, images of 38 sources were obtained. In 34 sources, 10 or more spots were detected. The observed spatial scale of the maser distribution was from 9 to 4900 astronomical units, and the following morphological categories were observed: elliptical, arched, linear, paired, and complex. The position of the maser spot was determined with an accuracy of approximately 0.1 mas, which is sufficiently high to measure the internal proper motion from two years of monitoring observations. The VLBI observation, however, detected only approximately 20% of all maser emissions, suggesting that the remaining 80% of the total flux was spread into an undetectable extended distribution. Therefore, in addition to high-resolution observations, it is important to observe the whole structure of the maser emission including extended low-brightness structures, in order to reveal the associated site of the maser and gas motion.

  9. Unveiling the gas kinematics at 10 AU scales in high-mass star-forming regions. Milliarcsecond structure of 6.7 GHz methanol masers

    NASA Astrophysics Data System (ADS)

    Moscadelli, L.; Sanna, A.; Goddi, C.

    2011-12-01

    Context. High-mass stars play a prominent role in Galactic evolution, but their formation mechanism is still poorly understood. This lack of knowledge reflects the observational limitations of present instruments, whose angular resolution (at the typical distances of massive protostars) precludes probing circumstellar gas on scales of 1-100 AU, relevant for a detailed investigation of accretion structures and launch/collimation mechanims of outflows in high-mass star formation. Aims: This work presents a study of the milliarcsecond structure of the 6.7 GHz methanol masers at high-velocity resolution (0.09 km s-1) in four high-mass star-forming regions: G16.59-0.05, G23.01-0.41, IRAS 20126 + 4104, and AFGL 5142. Methods: We studied these sources by means of multi-epoch VLBI observations in the 22 GHz water and 6.7 GHz methanol masers, to determine the 3-D gas kinematics within a few thousand AU from the (proto)star. Our results demonstrate the ability of maser emission to trace kinematic structures close to the (proto)star, revealing the presence of fast wide-angle and/or collimated outflows (traced by the H2O masers), and of rotation and infall (indicated by the CH3OH masers). The present work exploits the 6.7 GHz maser data collected so far to investigate the milliarcsecond structure of this maser emission at high-velocity resolution. Results: Most of the detected 6.7 GHz maser features present an ordered (linear, or arc-like) distribution of maser spots on the plane of the sky, together with a regular variation in the spot LSR velocity (VLSR) with position. Typical values for the amplitude of the VLSR gradients (defined in terms of the derivative of the spot VLSR with position) are found to be 0.1-0.2 km s-1 mas-1. In each of the four target sources, the orientation and the amplitude of most of the feature VLSR gradients remain remarkably stable in time, on timescales of (at least) several years. We also find that the data are consistent with having the VLSR

  10. Class i Methanol Maser Conditions Near SNRS

    NASA Astrophysics Data System (ADS)

    McEwen, Bridget C.; Pihlström, Ylva M.; Sjouwerman, Loránt O.

    2015-06-01

    We present results from calculations of the physical conditions necessary for the occurrence of 36.169 (4-1-30 E), 44.070 (70-61 A^+), 84.521 (5-1-40 E), and 95.169 (80-71 A^+) GHz methanol (CH_3OH) maser emission lines near supernova remnants (SNRs), using the MOLPOP-CEP program. The calculations show that given a sufficient methanol abundance, methanol maser emission arises over a wide range of densities and temperatures, with optimal conditions at n˜ 10^4-10^6 cm-3 and T>60 K. The 36~GHz and 44~GHz transitions display more significant maser optical depths compared to the 84~GHz and 95~GHz transitions over the majority of physical conditions. It is also shown that line ratios are an important and applicable probe of the gas conditions. The line ratio changes are largely a result of the E-type transitions becoming quenched faster at increasing densities. The modeling results will be discussed using recent observations of CH_3OH masers near the SNRs G1.4-0.1, W28, and Sgr A East and used as a diagnostic tool to estimate densities and temperatures of the regions in which the CH_3OH masers are observed.

  11. Physical characteristics of bright Class I methanol masers

    NASA Astrophysics Data System (ADS)

    Leurini, S.; Menten, K. M.; Walmsley, C. M.

    2016-07-01

    Context. Class I methanol masers are thought to be tracers of interstellar shock waves. However, they have received relatively little attention mostly as a consequence of their low luminosities compared to other maser transitions. This situation has changed recently and Class I methanol masers are now routinely used as signposts of outflow activity especially in high extinction regions. The recent detection of polarisation in Class I lines now makes it possible to obtain direct observational information about magnetic fields in interstellar shocks. Aims: We make use of newly calculated collisional rate coefficients for methanol to investigate the excitation of Class I methanol masers and to reconcile the observed Class I methanol maser properties with model results. Methods: We performed large velocity gradient calculations with a plane-parallel slab geometry appropriate for shocks to compute the pump and loss rates which regulate the interactions of the different maser systems with the maser reservoir. We study the dependence of the pump rate coefficient, the maser loss rate, and the inversion efficiency of the pumping scheme of several Class I masers on the physics of the emitting gas. Results: We predict inversion in all transitions where maser emission is observed. Bright Class I methanol masers are mainly high-temperature (>100 K) high-density (n(H2) ~ 107-108 cm-3) structures with methanol maser emission measures, ξ, corresponding to high methanol abundances close to the limits set by collisional quenching. Our model predictions reproduce reasonably well most of the observed properties of Class I methanol masers. Class I masers in the 25 GHz series are the most sensitive to the density of the medium and mase at higher densities than other lines. Moreover, even at high density and high methanol abundances, their luminosity is predicted to be lower than that of the 44 GHz and 36 GHz masers. Our model predictions also reflect the observational result that the

  12. VizieR Online Data Catalog: 6.7-GHz methanol masers-dust associations (Urquhart+, 2015)

    NASA Astrophysics Data System (ADS)

    Urquhart, J. S.; Moore, T. J. T.; Menten, K. M.; Konig, C.; Wyrowski, F.; Thompson, M. A.; Csengeri, T.; Leurini, S.; Eden, D. J.

    2015-06-01

    To complement the sample of inner Galaxy methanol-maser associated clumps identified in Paper I (Urquhart et al., 2013MNRAS.431.1752U, Cat. J/MNRAS/431/1752), we have made submillimetre-continuum observations towards 77 MMB sources that either lie outside the region covered by the ATLASGAL survey (i.e. 180°1.5°) or were not found to be associated with an ATLASGAL source. (3 data files).

  13. A search for water masers associated with class II methanol masers - II. Longitude range 341° to 6°

    NASA Astrophysics Data System (ADS)

    Titmarsh, A. M.; Ellingsen, S. P.; Breen, S. L.; Caswell, J. L.; Voronkov, M. A.

    2016-06-01

    This is the second paper in a series of catalogues of 22-GHz water maser observations towards the 6.7-GHz methanol masers from the Methanol Multibeam (MMB) survey. In this paper, we present our water maser observations made with the Australia Telescope Compact Array towards the masers from the MMB survey between l = 341° through the Galactic Centre to l = 6°. Of the 204 6.7-GHz methanol masers in this longitude range, we found 101 to have associated water maser emission (˜50 per cent). We found no difference in the 6.7-GHz methanol maser luminosities of those with and without water masers. In sources where both maser species are observed, the luminosities of the methanol and water masers are weakly correlated. Studying the mid-infrared colours from GLIMPSE (Galactic Legacy Infrared Midplane Survey Extraordinaire), we found no differences between the colours of those sources associated with both methanol and water masers and those associated with just methanol. Comparing the column density and dust mass calculated from the 870-μm thermal dust emission observed by ATLASGAL (APEX Telescope Large Area Survey of the GALaxy), we found no differences between those sources associated with both water and methanol masers and those with methanol only. Since water masers are collisionally pumped and often show emission further away from their accompanying young stellar object (YSO) than the radiatively pumped 6.7-GHz methanol masers, it is likely that water masers are not as tightly correlated to the evolution of the parent YSO and so do not trace such a well-defined evolutionary state as 6.7-GHz methanol masers.

  14. Unbiased water and methanol maser surveys of NGC 1333

    SciTech Connect

    Lyo, A-Ran; Kim, Jongsoo; Byun, Do-Young; Lee, Ho-Gyu

    2014-11-01

    We present the results of unbiased 22 GHz H{sub 2}O water and 44 GHz class I CH{sub 3}OH methanol maser surveys in the central 7' × 10' area of NGC 1333 and two additional mapping observations of a 22 GHz water maser in a ∼3' × 3' area of the IRAS4A region. In the 22 GHz water maser survey of NGC 1333 with a sensitivity of σ ∼ 0.3 Jy, we confirmed the detection of masers toward H{sub 2}O(B) in the region of HH 7-11 and IRAS4B. We also detected new water masers located ∼20'' away in the western direction of IRAS4B or ∼25'' away in the southern direction of IRAS4A. We could not, however, find young stellar objects or molecular outflows associated with them. They showed two different velocity components of ∼0 and ∼16 km s{sup –1}, which are blue- and redshifted relative to the adopted systemic velocity of ∼7 km s{sup –1} for NGC 1333. They also showed time variabilities in both intensity and velocity from multi-epoch observations and an anti-correlation between the intensities of the blue- and redshifted velocity components. We suggest that the unidentified power source of these masers might be found in the earliest evolutionary stage of star formation, before the onset of molecular outflows. Finding this kind of water maser is only possible through an unbiased blind survey. In the 44 GHz methanol maser survey with a sensitivity of σ ∼ 0.5 Jy, we confirmed masers toward IRAS4A2 and the eastern shock region of IRAS2A. Both sources are also detected in 95 and 132 GHz methanol maser lines. In addition, we had new detections of methanol masers at 95 and 132 GHz toward IRAS4B. In terms of the isotropic luminosity, we detected methanol maser sources brighter than ∼5 × 10{sup 25} erg s{sup –1} from our unbiased survey.

  15. Detection of class I methanol (CH{sub 3}OH) maser candidates in supernova remnants

    SciTech Connect

    Pihlström, Y. M.; Mesler, R. A.; McEwen, B. C.; Sjouwerman, L. O.; Frail, D. A.; Claussen, M. J.

    2014-04-01

    We have used the Karl G. Jansky Very Large Array to search for 36 GHz and 44 GHz methanol (CH{sub 3}OH) lines in a sample of 21 Galactic supernova remnants (SNRs). Mainly the regions of the SNRs with 1720 MHz OH masers were observed. Despite the limited spatial extent covered in our search, methanol masers were detected in both G1.4–0.1 and W28. Additional masers were found in Sgr A East. More than 40 masers were found in G1.4–0.1, which we deduce are due to interactions between the SNR and at least two separate molecular clouds. The six masers in W28 are associated with the molecular cloud that is also associated with the OH maser excitation. We discuss the possibility that the methanol maser may be more numerous in SNRs than the OH maser, but harder to detect due to observational constraints.

  16. Interstellar A-type methanol masers

    NASA Astrophysics Data System (ADS)

    Zeng, Q.; Lou, G. F.

    1990-02-01

    The formation conditions for A-type methanol masers are discussed. The correlation between A-type masers and external radiation fields is determined, with emphasis on the energy levels of A-type methanol and brightness temperature. Radiative transfer equations and statistical equilibrium are solved using a large velocity gradient model and the escape probability model. It is demonstrated that the 9(2)-10(1)A+ emission in W3(OH) and 7(0)-6(1)A in SgrB2 are masers, as discovered previously. The formation of the first type of masers requires pumping from an external radiation field, while the second type might be excited in the absence of an external radiation field. It is also pointed out that according to calculations there are A-type maser series similar to E-type methanol maser series of J2-J1E.

  17. On the classification and list of transitions of methanol masers

    NASA Astrophysics Data System (ADS)

    Sobolev, A. M.

    A classification of methanol masers according to the type of maser sources is suggested. The list of candidates to be methanol masering transitions is compiled on the basis of general regularities analysis combined with results of statistical equilibrium calculations.

  18. VizieR Online Data Catalog: 6.7GHz methanol maser polarization in SFR (Surcis+, 2015)

    NASA Astrophysics Data System (ADS)

    Surcis, G.; Vlemmings, W. H. T.; van Langevelde, H. J.; Hutawarakorn Kramer, B.; Bartkiewicz, A.; Blasi, M. G.

    2015-09-01

    The first seven massive SFRs were observed at 6.7GHz in full polarization spectral mode with eight of the EVN antennas (Effelsberg, Jodrell, Onsala, Medicina, Noto, Torun, Westerbork, and Yebes-40m) between November 2012 and June 2013, for a total observation time of 49h. The bandwidth was 2MHz, providing a velocity range of ~100km/s. (8 data files).

  19. A CO observation of the Galactic methanol masers

    NASA Astrophysics Data System (ADS)

    Ren, Zhiyuan; Wu, Yuefang; Liu, Tie; Li, Lixin; Li, Di; Ju, Binggang

    2014-07-01

    Context. We investigated the molecular gas associated with 6.7 GHz methanol masers throughout the Galaxy using a J = 1-0 transition of the CO isotopologues. Aims: The methanol maser at 6.7 GHz is an ideal tracer for young high-mass star-forming cores. Based on molecular line emissions in the maser sources throughout the Galaxy, we can estimate their physical parameters and, thereby, investigate the forming conditions of the high-mass stars. Methods: Using the 13.7-m telescope at the Purple Mountain Observatory (PMO), we have obtained 12CO and 13CO (1-0) lines for 160 methanol masers sources from the first to the third Galactic quadrants. We made efforts to resolve the distance ambiguity by careful comparison with the radio continuum and HI 21 cm observations. We examined the statistical properties in three aspects: first, the variation throughout the Galaxy; second, the correlation between the different parameters; third, the difference between the maser sources and the infrared dark clouds. In addition, we have also carried out 13CO mapping for 33 sources in our sample. Results: First, the maser sources show increased 13CO line widths toward the Galactic center, suggesting that the molecular gas are more turbulent toward the Galactic center. This trend can be noticeably traced by the 13C line width. In comparison, the Galactic variation for the H2 column density and the 12CO excitation temperature are less significant. Second, the 12CO excitation temperature shows a noticeable correlation with the H2 column density. A possible explanation consistent with the collapse model is that the higher surface-density gas is more efficient to the stellar heating and/or has a higher formation rate of high-mass stars. Third, comparing the infrared dark clouds, the maser sources on average have significantly lower H2 column densities, moderately higher temperatures, and similar line widths. Fourth, In the mapped regions around 33 masers, 51 13CO cores have been revealed. Among

  20. Discovery of periodic class II methanol masers associated with G339.986-0.425 region

    NASA Astrophysics Data System (ADS)

    Maswanganye, J. P.; van der Walt, D. J.; Goedhart, S.; Gaylard, M. J.

    2016-03-01

    10 new class II methanol masers from the 6.7-GHz Methanol Multibeam survey catalogues III and IV were selected for a monitoring programme at both 6.7 and 12.2 GHz with the 26-m Hartebeesthoek Radio Astronomy Observatory radio telescope for 2 yr and 9 months, from 2012 August to 2015 May. In the sample, only masers associated with G339.986-0.425 were found to show periodic variability at both 6.7 and 12.2 GHz. The existence of periodic variation was tested with four independent methods. The analytical method gave the best estimation of the period, which was 246 ± 1 d. The time series of G339.986-0.425 show strong correlations across velocity channels and between the 6.7- and 12.2-GHz masers. The time delay was also measured across channels and shows structure across the spectrum which is continuous between different maser components.

  1. Traveling-Wave Maser for 32 GHz

    NASA Technical Reports Server (NTRS)

    Shell, James; Clauss, Robert

    2009-01-01

    The figure depicts a traveling-wave ruby maser that has been designed (though not yet implemented in hardware) to serve as a low-noise amplifier for reception of weak radio signals in the frequency band of 31.8 to 32.3 GHz. The design offers significant improvements over previous designs of 32-GHz traveling-wave masers. In addition, relative to prior designs of 32-GHz amplifiers based on high-electron-mobility transistors, this design affords higher immunity to radio-frequency interference and lower equivalent input noise temperature. In addition to the basic frequency-band and low-noise requirements, the initial design problem included a requirement for capability of operation in a closed-cycle helium refrigerator at a temperature .4 K and a requirement that the design be mechanically simplified, relative to prior designs, in order to minimize the cost of fabrication and assembly. Previous attempts to build 32- GHz traveling-wave masers involved the use of metallic slow-wave structures comprising coupled transverse electromagnetic (TEM)-mode resonators that were subject to very tight tolerances and, hence, were expensive to fabricate and assemble. Impedance matching for coupling signals into and out of these earlier masers was very difficult. A key feature of the design is a slow-wave structure, the metallic portions of which would be mechanically relatively simple in that, unlike in prior slow-wave structures, there would be no internal metal steps, irises, or posts. The metallic portions of the slow-wave structure would consist only of two rectangular metal waveguide arms. The arms would contain sections filled with the active material (ruby) alternating with evanescent-wave sections. This structure would be transparent in both the signal-frequency band (the aforementioned range of 31.8 to 32.3 GHz) and the pump-frequency band (65.75 to 66.75 GHz), and would impose large slowing factors in both frequency bands. Resonant ferrite isolators would be placed in the

  2. Widespread strong methanol masers near H II regions

    NASA Astrophysics Data System (ADS)

    Norris, R. P.; Caswell, J. L.; Gardner, F. F.; Wellington, K. J.

    1987-10-01

    A strong (up to 1000 Jy) methanol maser transition has recently been discovered by Batrla et al. (1987). Here a search of southern sources for masers in this transition is reported, with the aim of establishing how common the masers are, where they might be found, and the extent to which their observation might be hindered by interference. Methanol masers were found in 25 of the 106 star-formation regions searched, predominantly those with associated OH masers. A number of other types of object were searched, including OH/IR stars and OH/H2O megamaser galaxies, but no methanol masers were detected in any of these.

  3. DISCOVERY OF 6.035 GHz HYDROXYL MASER FLARES IN IRAS 18566+0408

    SciTech Connect

    Al-Marzouk, A. A.; Araya, E. D.; Hofner, P.; Kurtz, S.; Linz, H.; Olmi, L.

    2012-05-10

    We report the discovery of 6.035 GHz hydroxyl (OH) maser flares toward the massive star-forming region IRAS 18566+0408 (G37.55+0.20), which is the only region known to show periodic formaldehyde (4.8 GHz H{sub 2}CO) and methanol (6.7 GHz CH{sub 3}OH) maser flares. The observations were conducted between 2008 October and 2010 January with the 305 m Arecibo Telescope in Puerto Rico. We detected two flare events, one in 2009 March and one in 2009 September to November. The OH maser flares are not simultaneous with the H{sub 2}CO flares, but may be correlated with CH{sub 3}OH flares from a component at corresponding velocities. A possible correlated variability of OH and CH{sub 3}OH masers in IRAS 18566+0408 is consistent with a common excitation mechanism (IR pumping) as predicted by theory.

  4. The Arecibo Methanol Maser Galactic Plane Survey. II. Statistical and Multiwavelength Counterpart Analysis

    NASA Astrophysics Data System (ADS)

    Pandian, Jagadheep D.; Goldsmith, Paul F.

    2007-11-01

    We present an analysis of the properties of the 6.7 GHz methanol maser sample detected in the Arecibo Methanol Maser Galactic Plane Survey. The distribution of the masers in the Galaxy, and statistics of their multiwavelength counterparts is consistent with the hypothesis of 6.7 GHz maser emission being associated with massive young stellar objects. Using the detection statistics of our survey, we estimate the minimum number of methanol masers in the Galaxy to be 1275. The l-v diagram of the sample shows the tangent point of the Carina-Sagittarius spiral arm to be around 49.6°, and suggests the occurrence of massive star formation along the extension of the Crux-Scutum arm. A Gaussian component analysis of the maser spectra shows the mean line width to be 0.38 km s-1, which is more than a factor of 2 larger than what has been reported in the literature. We also find no evidence that faint methanol masers have different properties than their bright counterparts.

  5. Detection of a series of methanol maser lines at 1.9 millimeter wavelength

    NASA Astrophysics Data System (ADS)

    Slysh, V. I.; Kalenskii, S. V.; Val'tts, I. E.

    1995-04-01

    The series of methanol J0-J-1 E lines at 157 GHz has been detected in known methanol line sources together with the 21-30 A+ line of A-type methanol. In W3(OH), 345.01+1.79, W48, and Cep A the Jo-J-1 lines are intense and narrow and are believed to be maser lines. The radial velocities and profiles are similar to those of other class II methanol lines in these sources. The intensity of the lines increases with rotational number J, in contrast to thermal methanol features which were detected in the same sources at slightly different radial velocities. It is suggested that the new maser line sources are the class II methanol masers but are excited with higher radiation temperature than the lower frequency class II masers at 6.7 and 12.2 GHz. The masers may be related to molecular outflows or cometary bow shocks of ultracompact H II regions as is evidenced by their velocity shift relative to the parent molecular clouds.

  6. The Onsala blind survey of the galactic plane: new methanol masers in the northern hemisphere.

    NASA Astrophysics Data System (ADS)

    Pestalozzi, Michele R.; Minier, Vincent; Booth, Roy; Conway, John

    We are conducting a blind survey of the galatic plane, searching for the powerful 6.7 GHz maser emission of methanol. The purpose is to cover a region of sky across the galatic plane (+/- 0.5o in galactic latitude) from 35o to 220o in galactic longitude. Since late 1998 we have surveyed about 35 deg2, and have made 15 detections. Some masers have already been detected during other surveys and allowed us to test our system sensitivity. We can nevertheless count 3 detections apparently missed by previous pointed surveys, allowing us to make some conclusions about the selection criteria used in those observations. Our unbiased survey should be regarded as complementary to the work carried out towards the galactic center from Australia and Tasmania. Methanol masers are detected in regions with typical signposts of massive star formation, such as H2O and OH masers, and some of them are detected towards IRAS sources satisfying the Wood & Churchwell criteria for UCHII regions. It is nevertheless not possible to uniquely associate methanol masers with IRAS UCHII regions, which lead us to suppose that the maser activity can appear at a very early stage in the formation of a star. The reason for conducting a blind survey is to find a correlation between methanol masers and other properties related to star formation. What is more, by increasing the number of detected methanol masers we can produce better statistics, and also increase the sample of objects studied in more detail using VLBI. We also perform follow up observations of the detections, searching for other typical signposts of star formation as well as other methanol masing transitions and thermal emission of both methanol and larger, more complex molecules using the Onsala 20m millimeter telescope. We present here the state of the art after almost two years of observations presenting the new detections and the preliminary statistics.

  7. DISCOVERY OF THE FIRST METHANOL (CH{sub 3}OH) MASER IN THE ANDROMEDA GALAXY (M31)

    SciTech Connect

    Sjouwerman, Lorant O.; Murray, Claire E.; Pihlstroem, Ylva M.; Fish, Vincent L.; Araya, Esteban D.

    2010-12-01

    We present the first detection of a 6.7 GHz Class II methanol (CH{sub 3}OH) maser in the Andromeda galaxy (M31). The CH{sub 3}OH maser was found in a VLA survey during the fall of 2009. We have confirmed the methanol maser with the new EVLA, in operation since 2010 March, but were unsuccessful in detecting a water maser at this location. A direct application for this methanol maser is the determination of the proper motion of M31, such as was previously obtained with water masers in M33 and IC10. Unraveling the three-dimensional velocity of M31 would solve for the biggest unknown in the modeling of the dynamics and evolution of the Local Group of galaxies.

  8. Class I Methanol (CH3OH) Maser Conditions near Supernova Remnants

    NASA Astrophysics Data System (ADS)

    McEwen, Bridget C.; Pihlström, Ylva M.; Sjouwerman, Loránt O.

    2014-10-01

    We present results from calculations of the physical conditions necessary for the occurrence of 36.169 (4-1-30 E), 44.070 (70-61 A +), 84.521 (5-1-40 E), and 95.169 (80-71 A +) GHz methanol (CH3OH) maser emission lines near supernova remnants (SNRs), using the MOLPOP-CEP program. The calculations show that given a sufficient methanol abundance, methanol maser emission arises over a wide range of densities and temperatures, with optimal conditions at n ~ 104-106 cm-3 and T > 60 K. The 36 GHz and 44 GHz transitions display more significant maser optical depths compared to the 84 GHz and 95 GHz transitions over the majority of physical conditions. It is also shown that line ratios are an important and applicable probe of the gas conditions. The line ratio changes are largely a result of the E-type transitions becoming quenched faster at increasing densities. The modeling results are discussed using recent observations of CH3OH and hydroxyl (OH) masers near the SNRs G1.4-0.1, W28, and Sgr A East.

  9. Class I methanol (CH{sub 3}OH) maser conditions near supernova remnants

    SciTech Connect

    McEwen, Bridget C.; Pihlström, Ylva M.; Sjouwerman, Loránt O.

    2014-10-01

    We present results from calculations of the physical conditions necessary for the occurrence of 36.169 (4{sub –1}-3{sub 0} E), 44.070 (7{sub 0}-6{sub 1} A {sup +}), 84.521 (5{sub –1}-4{sub 0} E), and 95.169 (8{sub 0}-7{sub 1} A {sup +}) GHz methanol (CH{sub 3}OH) maser emission lines near supernova remnants (SNRs), using the MOLPOP-CEP program. The calculations show that given a sufficient methanol abundance, methanol maser emission arises over a wide range of densities and temperatures, with optimal conditions at n ∼ 10{sup 4}-10{sup 6} cm{sup –3} and T > 60 K. The 36 GHz and 44 GHz transitions display more significant maser optical depths compared to the 84 GHz and 95 GHz transitions over the majority of physical conditions. It is also shown that line ratios are an important and applicable probe of the gas conditions. The line ratio changes are largely a result of the E-type transitions becoming quenched faster at increasing densities. The modeling results are discussed using recent observations of CH{sub 3}OH and hydroxyl (OH) masers near the SNRs G1.4–0.1, W28, and Sgr A East.

  10. Class I methanol masers in low-mass star-forming regions

    NASA Astrophysics Data System (ADS)

    Kalenskii, S. V.; Kurtz, S.; Bergman, P.

    2013-02-01

    Results of observations of Class I methanol masers in regions of low-mass star formation (MMIL) are summarized and analyzed. Four masers were detected at 44, 84, and 95 GHz towards "chemically active" bipolar outflows in the low-mass star-forming regions NGC1333 I4A, NGC 1333 I2A, HH 25, and L1157. Another maser was found at 36 GHz towards a similar outflow in NGC 2023. Thus, all the detected MMILs are associated with chemically active outflows. The brightness temperatures of the strongest 44-GHz maser spots in NGC 1333 I4A, HH 25, and L1157 exceed 2000 K, whereas the brightness temperature in NGC 1333 I2A is only 176 K, although a rotational-diagram analysis shows that this last source is also amaser. The flux densities of the newly detectedmasers are no higher than 18 Jy, and are much lower than those of strong masers in regions of high-mass star formation (MMIH). The MMIL luminosities match the maser luminosity-protostar luminosity relation established earlier for MMIHs. No MMIL variability was detected in 2004-2011. The radial velocities of the newly detected masers are close to the systemic velocities of the associated regions, except for NGC 2023, where the maser radial velocity is lower than the systemic velocity by approximately 3.5 km/s. Thus, the main MMILproperties are similar to those of MMIHs. MMILs are likely to be an extension of the MMIH population toward lower luminosities of both the masers and the associated young stellar objects. The results of VLA observations of MMILs can be explained using a turbulent-cloud model, which predicts that compact maser spots can arise in extended sources because the coherence lengths along some directions randomly appear to be longer than the mean coherence length in a turbulent velocity field. However, one must assume that the column density of methanol towardM1, the strongest maser in L1157, is appreciably higher than the mean column density of the clump B0a where the maser arises. The shape of the maser lines

  11. ALMA OBSERVATIONS OF THE IRDC CLUMP G34.43+00.24 MM3: 278 GHz CLASS I METHANOL MASERS

    SciTech Connect

    Yanagida, Takahiro; Sakai, Takeshi; Hirota, Tomoya; Sanhueza, Patricio; Sakai, Nami; Yamamoto, Satoshi; Foster, Jonathan B.; Jackson, James M.; Furuya, Kenji; Aikawa, Yuri

    2014-10-10

    We have observed a molecular clump (MM3) associated with the infrared dark cloud G34.43+00.24 in the CH{sub 3}OH J{sub K}  = 9{sub –1}-8{sub 0} E, 5{sub 0}-4{sub 0} E, and 5{sub –1}-4{sub –1} E lines at sub-arcsecond resolution by using the Atacama Large Millimeter/submillimeter Array. By comparing the CH{sub 3}OH J{sub K}  = 9{sub –1}-8{sub 0} E emission with the CH{sub 3}OH 5{sub 0}-4{sub 0} E and 5{sub –1}-4{sub –1} E emission, we have found that the CH{sub 3}OH J{sub K}  = 9{sub –1}-8{sub 0} E emission is masing. We have clearly shown that the CH{sub 3}OH J{sub K}  = 9{sub –1}-8{sub 0} masers arise from the post shocked gas in the interacting regions between the outflows and ambient dense gas. Toward the strongest peak of the CH{sub 3}OH maser emission, SiO J = 6-5 emission is very weak. This indicates that the CH{sub 3}OH maser emission traces relatively old shocks or weak shocks.

  12. Experimental evaluation of a ruby maser at 43 GHz

    NASA Technical Reports Server (NTRS)

    Moore, C. R.; Neff, D.

    1982-01-01

    Inversion ratio measurements were conducted at several frequencies between 27 and 43 GHz for a pink ruby material (0.05% Cr/3+/ in Al2O3) at the push-pull pump angle of 54.7 degrees in order to determine the upper frequency limit where pink ruby could be expected to operate as a practical maser amplifier. Based on these measurements, a single-stage maser was developed which yielded 8 + or - 1 dB net gain and a 3 dB bandwidth of 180 MHz at a center frequency of 42.5 GHz. It is concluded that a multistage reflected wave maser could achieve bandwidths exceeding 1 GHz with 30 dB net gain at center frequencies near 40 GHz.

  13. Theoretical comparison of maser materials for a 32-GHz maser amplifier

    NASA Technical Reports Server (NTRS)

    Lyons, James R.

    1988-01-01

    The computational results of a comparison of maser materials for a 32 GHz maser amplifier are presented. The search for a better maser material is prompted by the relatively large amount of pump power required to sustain a population inversion in ruby at frequencies on the order of 30 GHz and above. The general requirements of a maser material and the specific problems with ruby are outlined. The spin Hamiltonian is used to calculate energy levels and transition probabilities for ruby and twelve other materials. A table is compiled of several attractive operating points for each of the materials analyzed. All the materials analyzed possess operating points that could be superior to ruby. To complete the evaluation of the materials, measurements of inversion ratio and pump power requirements must be made in the future.

  14. Finding Short-Term Variability in Methanol Masers

    NASA Astrophysics Data System (ADS)

    Bonin, Samuel; Barott, W. C.; Catanach, T.

    2012-05-01

    The Allen Telescope Array (ATA) performed 53 observations of 6.7 GHz methanol masers between July 2010 and January 2011 in an effort to identify short-timescale variability. With the notable exception of Weisberg et al. (2005), few analyses have been performed analyzing variability in masers on timescales of minutes or less. This work is aimed both at providing additional data (including refined positions) on the catalog of observed sources as well as identifying the prevalence and cause of short-term phenomena. Observations utilized both the ATA correlator (for mapping) and beamformer (for recording voltage time series). A combination of Fast-Fourier Transforms and Continuous Wavelet Transforms are applied to channelized power series waterfalls) in this investigation. Wavelet analysis can be thought of as a generalization of Fourier analysis that allows us to examine non-stationary characteristics of the spectra. The survey included both short (10 minute), long (60 minute), and follow-up observations on candidate targets. Analysis so far has identified three variable sources out of 43 distinct objects that were observed. These objects exhibit significant variation on the order of several minutes, are consistent in follow-up observations, and we have ruled out instrumental variation. Future and ongoing work includes identifying the source of this variation as intrinsic to the source or a property of the ISM. Shorter time-scales will be investigated using a combination of techniques, including total power variation, pulse searching (in an attempt to find pulsars), and phase-shift demodulation techniques. The case for SETI analysis of these data is given, for example, by Cordes (1993), who suggested that extraterrestrial intelligences could use masers to amplify interstellar signals.This project was funded by the National Science Foundation Grant AST0852095. [1] Weisberg J. M. et al. (2005) Science, 309, 5731. [2] Cordes J. M. (1993) Astron. Soc. Pacific Conf. Series

  15. Detection of a new type of methanol maser

    NASA Astrophysics Data System (ADS)

    Wilson, T. L.; Walmsley, C. M.; Jewell, P. R.; Snyder, L. E.

    1984-05-01

    The discovery of emission and absorption at 23121 MHz, attributed to the 92 - 101 A+ transition of methanol (CH3OH) is reported. The emission lines are from W3(OH), Orion-KL, and NGC 7538-IRS1; absorption was found toward the compact H II region in W31. Negative results for a number of other regions are given. The emission from W3(OH) is caused by maser amplification of the background continuum source. Maser amplification probably also explains the observed emission from NGC 7538-IRS1. The 92 - 101 A+ maser emission is the first detected from the A symmetry state of methanol and the first methanol maser found outside of Orion-KL.

  16. Characterizing Supernova Remnant and Molecular Cloud Interaction Sites Using Methanol (CH3OH) Masers

    NASA Astrophysics Data System (ADS)

    McEwen, Bridget; Pihlstrom, Ylva; Sjouwerman, Lorant

    2016-01-01

    Astronomical masers are useful probes of the physical conditions of the gas in which they are formed. Masers form under specific physical conditions and therefore, can be used to trace distinct environments. In particular, collisionally excited 36 and 44 GHz methanol (CH3OH) and 1720 MHz hydroxl (OH) masers are found associated with shocked gas produced by the interaction between supernova remnants (SNRs) and molecular clouds (MCs). The overall goal of my thesis research is to combine modeling and observations to characterize the properties and formation of CH3OH masers in these SNR/MC interaction regions. More accurate information of the density (and density gradients) could, for example, be used as inputs or constraints for models of SNR cosmic ray acceleration. In this talk, I will present results from calculations of the physical conditions necessary for the occurence of 36.169, 44.070, 84.521, and 95.169 GHz CH3OH maser lines near SNRs, using a coupled radiative transfer and level population code. The modeling shows that given a sufficient CH3OH abundance, CH3OH maser emission arises over a wide range of densities and temperatures, with optimal conditions at n ~ 104 to 106 cm-3 and T > 60 K, overlapping with masing conditions for OH masers. Furthermore, the 36 and 44 GHz transitions display more significant maser optical depths compared to the 84 and 95 GHz transitions over the majority of the physical conditions. The line intensity ratios between multiple transitions significantly change with altering physical conditions and can be used to constrain the physical parameters of the gas where CH3OH masers are detected. I use the modeling results as a diagnostic tool to interpret the observational results of a sample of SNRs with previous and recent CH3OH maser detections (G1.4-0.1, W28, Sgr A East, G5.7-0.0, W44 and W51C). I will also discuss the close spatial and kinematic correlation of CH3OH masers and ammonia (NH3 (3,3)) emission peaks, which is a reliable

  17. THE ARECIBO METHANOL MASER GALACTIC PLANE SURVEY. III. DISTANCES AND LUMINOSITIES

    SciTech Connect

    Pandian, J. D.; Menten, K. M.; Goldsmith, P. F. E-mail: kmenten@mpifr-bonn.mpg.d

    2009-12-01

    We derive kinematic distances to the 86 6.7 GHz methanol masers discovered in the Arecibo Methanol Maser Galactic Plane Survey. The systemic velocities of the sources were derived from {sup 13}CO (J = 2-1), CS (J = 5-4), and NH{sub 3} observations made with the ARO Submillimeter Telescope, the APEX telescope, and the Effelsberg 100 m telescope, respectively. Kinematic distance ambiguities were resolved using H I self-absorption with H I data from the VLA Galactic Plane Survey. We observe roughly three times as many sources at the far distance compared to the near distance. The vertical distribution of the sources has a scale height of approx 30 pc, and is much lower than that of the Galactic thin disk. We use the distances derived in this work to determine the luminosity function of 6.7 GHz maser emission. The luminosity function has a peak at approximately 10{sup -6} L{sub sun}. Assuming that this luminosity function applies, the methanol maser population in the Large Magellanic Cloud and M33 is at least 4 and 14 times smaller, respectively, than in our Galaxy.

  18. Targeted VLA Observations of 22 GHz Water Masers Towards the Galactic Center

    NASA Astrophysics Data System (ADS)

    Rickert, Matthew; Ott, Juergen; Yusef-Zadeh, Farhad; Meier, David S.

    2015-01-01

    The Central Molecular Zone (CMZ) has a unique environment with a large amount (5 x107 M⊙) of dense (104 cm-3) warm (75-200 K) molecular gas. To probe sites of ongoing star formation in this region, we carried out follow-up VLA observations targeting 22 GHz water masers detected by a recent Mopra survey of the inner 3° x 1° of the Galactic Center (Chambers et al. 2014, A&A 563, A68). We present preliminary results of these measurements with higher angular resolution (2" x 0.9"), spectral resolution (0.2 km s-1), and sensitivity (40 mJy beam-1) and a velocity coverage of -200 to 250 km s-1. A total of 32 maser positions are detected. Several sources display complex spectra with a number of new velocity components. From the 32 maser positions, over 200 spectral features have been identified, indicating clusters of masers. The complex spectra are indicative of young (< 105 years) star forming regions, with some of the components likely being produced from outflows. The brightest component is over 500 Jy beam-1 towards the HII region G359.14+0.03 with a vLSR of -9 km s-1. The most prominent location of water masers is the star forming region Sgr B2, where over 80 spectral components are identified from 9 different positions with peak flux densities ranging from 0.8 to 142 Jy beam-1. Three of these positions contain enhanced 4.5 μm green extended sources, indicating these masers are likely associated with outflows. Sgr C contains 3 separate maser positions with a total of 4 spectral components ranging from -70 to -66 km s-1 and peak flux densities of 4 to 15 Jy beam-1. One of these positions is also associated with a green source. We will compare the water maser positions with positions of radiatively pumped 6.7 GHz methanol masers and other green (3-8 μm) sources. This comparison will be used to verify that star formation is the underlying source of these masers and to identify masers associated with outlfows.

  19. Discovery of periodic and alternating flares of the methanol and water masers in G107.298+5.639

    NASA Astrophysics Data System (ADS)

    Szymczak, M.; Olech, M.; Wolak, P.; Bartkiewicz, A.; Gawroński, M.

    2016-06-01

    Methanol and water vapour masers are signposts of early stages of high-mass star formation but it is generally thought that due to different excitation processes they probe distinct parts of stellar environments. Here we present observations of the intermediate-mass young stellar object G107.298+5.639, revealing for the first time that 34.4 d flares of the 6.7 GHz methanol maser emission alternate with flares of individual features of the 22 GHz water maser. High angular resolution data reveal that a few components of both maser species showing periodic behaviour coincide in position and velocity and all the periodic water maser components appear in the methanol maser region of size of 360 au. The maser flares could be caused by variations in the infrared radiation field induced by cyclic accretion instabilities in a circumstellar or protobinary disc. The observations do not support either the stellar pulsations or the seed photon flux variations as the underlying mechanisms of the periodicity in the source.

  20. Massive Molecular Outflows Toward Methanol Masers: by Eye and Machine Learning

    NASA Astrophysics Data System (ADS)

    de Villiers, Helena

    2013-07-01

    The best known evolutionary state of massive stars is that of the UC HII region, occurring a few 10^5 years after the initial formation of a massive YSO. Currently objects in the "hot core" phase, occurring prior to the UC HII region, are studied with great interest. Because the YSO is still supposed to be accreting at this stage, one would expect outflows from the central object to develop during this phase, entraining surrounding cold molecular gas in their wake. During this time, 6.7 GHz (Class II) methanol masers will also turn on. They are uniquely associated with massive YSO's, thus serve as a useful signpost. We searched for molecular outflows with the JCMT and HARP focal plane array in a sample of targets toward 6.7 GHz methanol maser coordinates within 20 < Glon < 34. We found 58 CO clumps but only 47 of them were closely associated with the methanol masers. Their spectra were analyzed for broadened line wings, which were found to be present in 46 of the spectra, indicating either bi- or mono-polar outflows. This is a 98% detection frequency. The velocity ranges of these spectrum wings were used to create two dimensional blue and red maps. The out flows' physical parameters were calculated and compared with literature. We created a catalog of kinematic distances and properties of all the 13CO outflows associated with Class II methanol masers, as well as their associated H_2 core and virial masses as derived from the C18O data. In the the light of our results we emphasize the need for an automated detection process, especially with the increasing number of wide-area surveys. We are currently exploring the use of machine learning algorithms (specifically Support Vector Machines) in the detection of high velocity structures in p-p-v cubes.

  1. Instrumental and Observational Studies in Radio Astronomy, Low Noise Amplifier Design and Methanol Maser Research

    NASA Astrophysics Data System (ADS)

    Minier, V.

    1998-10-01

    ``Radio astronomy is the study of the universe by observing electromagnetic radiation after it has been amplified. The use of amplifiers that preserve the oscillatory character of radiation - the phase information - is the mark of Radio astronomy.'' Thus, the development of low noise amplifiers for microwave and millimeter wavelengths is a major part of Radio astronomy as important as the observations themselves. This technical report involves those two aspects of Radio astronomy, the observational and technical aspects. In the first part, observations of methanol masers in massive star forming regions using Very Long Baseline Interferometry (VLBI) are presented. The second part concerns the realization of low noise amplifiers using in a radio camera. Recent observations have confirmed that the methanol masers are powerful tools for probing the regions of massive star formation. The methanol masers fall in two distinct classes related to their location in the star forming regions. Class I methanol masers are observed offset far away from the UC HII region emission peak. They are certainly collisionally pumped and may occur in the interface between high velocity gas outflows and the ambient molecular material. Class II methanol masers coincide with the UC HII region emission. They may be radiatively pumped by FIR radiation from the dust grains and reside either in spherical layers surrounding the UC HII regions or in circumstellar discs. The maser spots are usually compact (~1-10 AU) and lie in region of physical conditions n(H)~104-108 cm-3 and T=100-1000 K. CH3OH may be produced by hydrogenation of CO on the surface of the icy mantles of the dust grains . The methanol is then injected in the molecular gas by evaporation of the ice (n(H)=106 cm-3, T=100-300 K). In this report we present VLBI observations of 6.7 and 12.2 GHz methanol masers in the star forming regions NGC7538, W75N and S252. Our results show the existence of two groups of masers in NGC7538. The

  2. A 32-GHz reflected-wave maser amplifier with wide instantaneous bandwidth

    NASA Technical Reports Server (NTRS)

    Shell, J.; Neff, D.

    1988-01-01

    An eight stage, 32 GHz reflected wave ruby maser was built. The maser operates in a 3 watt closed cycle refrigerator at 4.5 K and is capable of 21 dB of net gain with an instantaneous bandwidth of 400 MHz. The input noise temperature referred to the room temperature flange is approximately 21 K.

  3. Periodic methanol masers in G9.62+0.20E

    NASA Astrophysics Data System (ADS)

    van der Walt, D. J.; Maswanganye, J. P.; Etoka, S.; Goedhart, S.; van den Heever, S. P.

    2016-04-01

    A number of mechanisms for understanding the periodic class II methanol masers associated with some high-mass star forming regions have been proposed in the past. Two recent proposals by Parfenov & Sobolev (2014, MNRAS, 444, 620) and Sanna et al. (2015, ApJ, 804, L2) have been presented in order to explain the periodic masers in sources with light curves similar to the methanol masers in G9.62+0.20E. We evaluate to what extent the proposals and models presented by these authors can explain the light curve of the methanol masers in G9.62+0.20E. It is argued that neither of the proposed mechanisms can reproduce the light curves of the methanol masers in G9.62+0.20E.

  4. Dual-polarization 8.45 GHz traveling-wave maser

    NASA Technical Reports Server (NTRS)

    Quinn, R. B.

    1987-01-01

    An 8.5 GHz dual-channel, dual-polarization traveling-wave maser (TWM) amplifier was installed in the XKR solar system radar cone at DSS 14. The TWM is based on the Blk IIA 8.45 GHz maser structure, with two of the four maser stages being used for each channel, and each maser half then followed by a high-performance GaAs FET amplifier to achieve the desired net gain. A shortened low-noise input waveguide and an orthogonal-mode junction which is cooled to 4.5 K feeds each amplifier chain. The rotation of an external polarizer permits the polarization of each channel to be defined as either linear or circular. A circular waveguide switch was also developed to provide for noise calibration and to protect the maser from incident transmitter power.

  5. Extragalactic Sub-millimeter H2O Maser - Detection of a 321 GHz Water Maser in Circinus Galaxy

    NASA Astrophysics Data System (ADS)

    Hagiwara, Y.; Horiuchi, S.; Doi, A.; Miyoshi, M.

    2015-12-01

    We present the first detection of the extragalactic 321 GHz H2O emission towards the Circinus Galaxy, the nearby Type2 Seyfert galaxy. It is likely that the detected emission is a maser because of the narrow line shape, the compact emission (< 0.66″) and the high energy level of the transition. High velocity emission, red-shifted up to 635 km/s, was tentatively detected. The maser location of about 0.02 pc from the center of the galaxy is estimated by adopting the Kepler rotating disk model. This could be the molecular material observed closest to the central engine.

  6. Classification and list of transitions of, and observation prospects for, extragalactic methanol masers

    NASA Astrophysics Data System (ADS)

    Sobolev, A. M.

    1993-08-01

    A new classification of methanol masers based on different types of maser sources is proposed. A division into two broad classes, with the designations of the generally accepted classification taken into account, is suggested. Class I consists of GMCs and their large-scale fragments and clumps comprising GCM hot cores. Class II contains sources connected with the boundaries of compact HII regions. Results of statistical equilibrium calculations for methanol masers as well as regularities of torsional pumping of Class II masers are considered. It is shown that the most promising observations, from the standpoint of the search for extragalactic methanol masers, are those of starburst galaxies in the 4(-1)-3(0)E and 5(-1)-4(0)E lines.

  7. Methanol masers and millimetre lines : a common origin in protostellar envelopes

    NASA Astrophysics Data System (ADS)

    Torstensson, Karl Johan Erik

    2011-12-01

    In this thesis we study the earliest stages of high-mass star formation. Class II methanol masers are only associated with massive star formation and are a unique probe of these environments. Through observations we have studied where and when the methanol maser emission occur in relation to the protostar. We have found that for a fair fraction of the sources the methanol masers appear on size scales of ca. 1000 AU, in the equatorial region of the massive protostar. It appears that infall, rather than rotation, is the dominant motion. We propose that the maser emission occur close to or in a shock interface, possibly related to the accretion flow of the more extended gas in the protostellar envelope onto an accretion disk. The morphology and kinematics of the thermal methanol gas support the hypothesis that the maser region is also the region where the methanol molecules are released from the icy mantles of the du st grains. We have also estimated the temperature and column density of the methanol gas in the outflows and find evidence for radiative excitation of the methanol gas at the location of the maser emission.

  8. Detection of 183 GHz water vapor maser emission from interstellar and circumstellar sources

    NASA Astrophysics Data System (ADS)

    Cernicharo, J.; Thum, C.; Hein, H.; John, D.; Garcia, P.; Mattioco, F.

    1990-05-01

    The IRAM 30-m telescope was used to observe the emission of the 183 GHz 3(13)-2(20) rotational transition of water from a selected sample of giant molecular clouds, low mass star forming regions and evolved stars. The zenith atmospheric transmission was 25-30 percent during the observations. The water emission shows strong and narrow masing lines (flux = about 1000-15000 Jy) toward the hot molecular clouds with strong 22 GHz water masers. Broad line emission, perhaps of thermal origin, is found in the sources associated with molecular outflows. Double peaked profiles, corresponding to masing lines (flux = about 100-600 Jy), are observed toward the evolved stars. Finally, 183 GHz maser emission is also observed in the more quiescent clouds, but at velocities different from those of the associated 22 GHz masers.

  9. 22 GHz H2O maser survey towards 221 BGPS sources

    NASA Astrophysics Data System (ADS)

    Xi, Hongwei; Zhou, Jianjun; Esimbek, Jarken; Wu, Gang; He, Yuxin; Ji, Weiguang; Tang, Xiaoke

    2015-11-01

    We performed a 22 GHz H2O maser survey towards 221 Bolocam Galactic Plane Survey (BGPS) sources. We detected 107 H2O masers, of which 12 are new. The detection rate is 48.4 per cent for our sample. We obtained the positions of five new H2O masers via On The Fly (OTF) observations. The detection rate of H2O masers is correlated with continuum emission fluxes of BGPS sources at far-infrared, sub-millimetre and millimetre wavelengths. We employed the classification of Dunham et al. to classify the evolutionary stage of BGPS sources into Group 0, 1, 2, and 3. The detection rate and velocity range of H2O masers increases as the BGPS sources evolve from Group 1 to Group 3. The BGPS sources associated with both H2O and CH3OH masers are more compact than that associated with either only H2O or only CH3OH masers. This indicates that the sources associated with both H2O and CH3OH masers are in relative later evolutionary stage. The detection rate of H2O masers towards BGPS sources displaying evidence of the collapse phenomenon is 62.1 per cent, which suggests that most BGPS sources showing indications of collapse phenomena contain ongoing active star formation activities.

  10. 22 GHz Water Maser Survey of the Xinjiang Astronomical Observatory

    NASA Astrophysics Data System (ADS)

    Zhou, Jian-jun; Esimbek, Jarken; Wu, Gang

    2012-07-01

    Water masers are good tracers of high-mass star-forming regions. Water maser VLBI observations provide a good probe for studying high-mass star formation and galactic structure. We plan to make a blind survey toward the northern Galactic plane in future years using the 25 m radio telescope of the Xinjiang Astronomical Observatory. We will select some water maser sources discovered in the survey and perform high resolution observations to study the gas kinematics close to high-mass protostars.

  11. TESTING THE HYPOTHESIS THAT METHANOL MASER RINGS TRACE CIRCUMSTELLAR DISKS: HIGH-RESOLUTION NEAR-INFRARED AND MID-INFRARED IMAGING

    SciTech Connect

    De Buizer, James M.; Bartkiewicz, Anna; Szymczak, Marian

    2012-08-01

    Milliarcsecond very long baseline interferometry maps of regions containing 6.7 GHz methanol maser emission have lead to the recent discovery of ring-like distributions of maser spots and the plausible hypothesis that they may be tracing circumstellar disks around forming high-mass stars. We aimed to test this hypothesis by imaging these regions in the near- and mid-infrared at high spatial resolution and compare the observed emission to the expected infrared morphologies as inferred from the geometries of the maser rings. In the near-infrared we used the Gemini North adaptive optics system of ALTAIR/NIRI, while in the mid-infrared we used the combination of the Gemini South instrument T-ReCS and super-resolution techniques. Resultant images had a resolution of {approx}150 mas in both the near-infrared and mid-infrared. We discuss the expected distribution of circumstellar material around young and massive accreting (proto)stars and what infrared emission geometries would be expected for the different maser ring orientations under the assumption that the masers are coming from within circumstellar disks. Based upon the observed infrared emission geometries for the four targets in our sample and the results of spectral energy distribution modeling of the massive young stellar objects associated with the maser rings, we do not find compelling evidence in support of the hypothesis that methanol masers rings reside in circumstellar disks.

  12. A Search for Submillimeter H2O Masers in Active Galaxies: The Detection of 321 GHZ H2O Maser Emission in NGC 4945

    NASA Astrophysics Data System (ADS)

    Hagiwara, Yoshiaki; Horiuchi, Shinji; Doi, Akihiro; Miyoshi, Makoto; Edwards, Philip G.

    2016-08-01

    We present further results of a search for extragalactic submillimeter H2O masers using the Atacama Large Millimeter/submillimeter Array (ALMA). The detection of a 321 GHz H2O maser in the nearby type 2 Seyfert galaxy, the Circinus galaxy, has previously been reported, and here the spectral analysis of four other galaxies is described. We have discovered H2O maser emission at 321 GHz toward the center of NGC 4945, a nearby type 2 Seyfert. The maser emission shows Doppler-shifted velocity features with velocity ranges similar to those of the previously reported 22 GHz H2O masers however, the non-contemporaneous observations also show differences in velocity offsets. The subparsec-scale distribution of the 22 GHz H2O masers revealed by earlier very long baseline interferometry observations suggests that the submillimeter masers could arise in an edge-on rotating disk. The maser features remain unresolved by the synthesized beam of ∼0.″54 (∼30 pc) and are located toward the 321 GHz continuum peak within errors. A marginally detected (3σ) high-velocity feature is redshifted by 579 km {{{s}}}-1 with respect to the systemic velocity of the galaxy. Assuming that this feature is real and arises from a Keplerian rotating disk in this galaxy, it is located at a radius of ∼0.020 pc (∼1.5 × 105 Schwarzschild radii), which would enable molecular material closer to the central engine to be probed than the 22 GHz H2O masers. This detection confirms that submillimeter H2O masers are a potential tracer of the circumnuclear regions of active galaxies, which will benefit from higher angular resolution studies with ALMA.

  13. A Search for Submillimeter H2O Masers in Active Galaxies: The Detection of 321 GHZ H2O Maser Emission in NGC 4945

    NASA Astrophysics Data System (ADS)

    Hagiwara, Yoshiaki; Horiuchi, Shinji; Doi, Akihiro; Miyoshi, Makoto; Edwards, Philip G.

    2016-08-01

    We present further results of a search for extragalactic submillimeter H2O masers using the Atacama Large Millimeter/submillimeter Array (ALMA). The detection of a 321 GHz H2O maser in the nearby type 2 Seyfert galaxy, the Circinus galaxy, has previously been reported, and here the spectral analysis of four other galaxies is described. We have discovered H2O maser emission at 321 GHz toward the center of NGC 4945, a nearby type 2 Seyfert. The maser emission shows Doppler-shifted velocity features with velocity ranges similar to those of the previously reported 22 GHz H2O masers however, the non-contemporaneous observations also show differences in velocity offsets. The subparsec-scale distribution of the 22 GHz H2O masers revealed by earlier very long baseline interferometry observations suggests that the submillimeter masers could arise in an edge-on rotating disk. The maser features remain unresolved by the synthesized beam of ˜0.″54 (˜30 pc) and are located toward the 321 GHz continuum peak within errors. A marginally detected (3σ) high-velocity feature is redshifted by 579 km {{{s}}}-1 with respect to the systemic velocity of the galaxy. Assuming that this feature is real and arises from a Keplerian rotating disk in this galaxy, it is located at a radius of ˜0.020 pc (˜1.5 × 105 Schwarzschild radii), which would enable molecular material closer to the central engine to be probed than the 22 GHz H2O masers. This detection confirms that submillimeter H2O masers are a potential tracer of the circumnuclear regions of active galaxies, which will benefit from higher angular resolution studies with ALMA.

  14. THE FIRST DETECTION OF THE 232 GHz VIBRATIONALLY EXCITED H{sub 2}O MASER IN ORION KL WITH ALMA

    SciTech Connect

    Hirota, Tomoya; Kim, Mi Kyoung; Honma, Mareki

    2012-09-20

    We investigated the ALMA science verification data of Orion KL and found a spectral signature of the vibrationally excited H{sub 2}O maser line at 232.68670 GHz ({nu}{sub 2} = 1, 5{sub 5,0}-6{sub 4,3}). This line has been detected previously in circumstellar envelopes of late-type stars but not in young stellar objects such as Orion KL. Thus, this is the first detection of the 232 GHz vibrationally excited H{sub 2}O maser in star-forming regions. The distribution of the 232 GHz maser is concentrated at the position of the radio Source I, which is remarkably different from other molecular lines. The spectrum shows a double-peak structure at the peak velocities of -2.1 and 13.3 km s{sup -1}. It appears to be consistent with the 22 GHz H{sub 2}O masers and 43 GHz SiO masers observed around Source I. Thus, the 232 GHz H{sub 2}O maser around Source I would be excited by the internal heating by an embedded protostar, being associated with either the root of the outflows/jets or the circumstellar disk around Source I, as traced by the 22 GHz H{sub 2}O masers or 43 GHz SiO masers, respectively.

  15. ALMA Observation of the 658 GHz Vibrationally Excited H2O Maser in Orion KL Source I

    NASA Astrophysics Data System (ADS)

    Hirota, Tomoya; Kim, Mi Kyoung; Honma, Mareki

    2016-02-01

    We present an observational study of the vibrationally excited H2O line at 658 GHz ({ν }2 = 1, {1}{1,0}-1{}{0,1}) toward Orion KL using the Atacama Large Millimeter/Submillimeter Array (ALMA). This line is clearly detected at the position of the massive protostar candidate, Source I. The spatial structure is compact, with a size of about 100 AU, and is elongated along the northeast-southwest low-velocity (18 km -1) bipolar outflow traced by 22 GHz H2O masers, SiO masers, and thermal SiO lines. A velocity gradient can be seen perpendicular to the bipolar outflow. The overall spatial and velocity structure seems to be analogous to that of the 321 GHz H2O maser line previously detected with ALMA and vibrationally excited SiO maser emission. The brightness temperature of the 658 GHz H2O line is estimated to be higher than 2 × 104 K, implying that it is emitted via maser action. Our results suggest that the 658 GHz H2O maser line is emitted from the base of the outflow from a rotating and expanding accretion disk as observed for the SiO masers and the 321 GHz H2O maser. We also search for two other H2O lines at 646 GHz (9{}{7,3}-8{}{8,0} and {9}{7,2}-8{}{8,1}), but they are not detected in Orion KL.

  16. The 8.4-GHz low-noise maser pump source assembly

    NASA Technical Reports Server (NTRS)

    Cardenas, R.

    1987-01-01

    Improved pump source assemblies and new 8.4-GHz low noise traveling-wave masers (TWMs) were installed at the same time at Deep Space Stations 14 and 43 as part of the Mark IVA DSCC Antenna Microwave Subsystems upgrade. The pump source assemblies are part of the new 8.4-GHz TWMs, which are identified as Block IIA Low-Noise TWMs. Improved reliability of the pump source assemblies was required to meet stress analysis criteria.

  17. Excited-state hydroxyl maser catalogue from the methanol multibeam survey - I. Positions and variability

    NASA Astrophysics Data System (ADS)

    Avison, A.; Quinn, L. J.; Fuller, G. A.; Caswell, J. L.; Green, J. A.; Breen, S. L.; Ellingsen, S. P.; Gray, M. D.; Pestalozzi, M.; Thompson, M. A.; Voronkov, M. A.

    2016-09-01

    We present the results of the first complete unbaised survey of the Galactic plane for 6035-MHz excited-state hydroxyl (ex-OH) masers undertaken as part of the methanol multibeam (MMB) survey. These observations cover the Galactic longitude ranges 186° < l < 60° including the Galactic Centre. We report the detection of 127 ex-OH masers within the survey region, 47 being new sources. The positions of new detections were determined from interferometric observations with the Australia Telescope Compact Array. We discuss the association of 6035-MHz masers in our survey with the 6668-MHz masers from the MMB Survey, finding 37 likely CH3OH-ex-OH maser pairs with physical separations of ≤0.03 pc and 55 pairings separated by ≤0.1 pc. Using these we calculate for the first time an ex-OH maser lifetime of between 3.3 × 103 and 8.3 × 103 yr. We also discuss the variability of the 6035-MHz masers and detection rates of counterpart 6030-MHz ex-OH masers (28 per cent of our sample having detection at both frequencies).

  18. The masers of E-type methanol in Orion KL and SGR B2

    NASA Astrophysics Data System (ADS)

    Zeng, Q.; Lou, G. F.; Li, S. Z.

    1987-04-01

    Using a simplified model, the statistical equilibrium and radiative transfer equations of E-type-CH3OH are solved for Orion KL and Sgr B2. According to the authors' calculation results and the observation data taken by Matsakis et al. (1980) and Morimoto et al. (1985), the physical conditions of both sources are estimated. In the J2 - J1 E methanol maser region of Orion KL, the density, kinetic temperature, dust temperature, and the fractional abundance are 0.8 - 2×106cm-3, ⪉150, 30 - 90K, 0.8 - 8×10-6, respectively. In the 4-1 - 30 E and 5-1 - 40 E methanol maser region of Sgr B2 the corresponding physical conditions are 104cm3, 45, 23K, and 7×10-7, respectively.

  19. Search for the 22 GHz water maser emission in selected comets

    NASA Astrophysics Data System (ADS)

    Cosmovici, C. B.; Pluchino, S.; Montebugnoli, S.; Pogrebenko, S.

    2014-06-01

    Following the first evidence of planetary water maser emission induced by the collision of comet Shoemaker/Levy with Jupiter and the puzzling detection of the 22 GHz water emission line in Comet Hyakutake we started in the period 2002-2008 systematic observations of selected comets at 22 GHz (1.35 cm) with the aim of clarifying the unusual behavior of the maser line in the cometary “scenario”. Using a fast multichannel spectrometer coupled to the 32 m dish of the Medicina (Bologna, Italy) Radio Telescope we investigated 6 bright or sungrazing comets down to a heliocentric distance of 0.11 AU: 96P/Machholz, 153P/ Ikeya-Zhang, C/2002 V1 (NEAT), C/2002 X5 (Kudo-Fujikawa), C/2002 T7 (Linear), and 73P/Schwassmann-Wachmann 3. All of them, similarly to Comet Hyakutake, demonstrate spectral features that, if real and due to the 1.35 cm water vapor transition, are strongly (up to tens of km/s) shifted relative to the radial velocity of the nucleus and, at least sometimes, seem to be present as two separate peaks. If our interpretation of these spectral peaks is correct, there must be some mechanism of acceleration of neutral water molecules up to the velocities of ions. We discuss here the results achieved and the possible explanation of the chemo-physical constraints. First possible detection of the water maser emission line at 22 GHz in sun-grazing comets Observed puzzling acceleration of neutral water molecules at ion velocities and split of the line in two components. Evidence of plasma-grain interaction in sun-grazing comets. Possible new detections in six peculiar comets.

  20. Angular wander measurements of maser clusters

    NASA Astrophysics Data System (ADS)

    Mutel, Robert L.

    Angular wander measurements of the relative positions of closely spaced maser features provides a powerful probe of interstellar turbulence associated with regions of star formation. Differential angular wander is easily measured in a maser complex and can strongly distinguish between shallow and steep power-law turbulence. The best candidates for such measurements appear to be the 6 and 12 GHz type II methanol masers.

  1. A 250-GHz CARM (Cyclotron Auto Resonance Maser) oscillator experiment driven by an induction linac

    SciTech Connect

    Caplan, M.; Kulke, B.; Bubp, D.G. ); McDermott, D.; Luhmann, N. )

    1990-09-14

    A 250-GHz Cyclotron Auto Resonance Maser (CARM) oscillator has been designed and constructed and will be tested using a 1-kA, 2-MeV electron beam produced by the induction linac at the Accelerator Research Center (ARC) facility of Lawrence Livermore National Laboratory (LLNL). The oscillator circuit was made to operate in the TE{sub 11} mode at ten times cutoff using waveguide Bragg reflectors to create an external cavity Q of 8000. Theory predicts cavity fill times of less than 30 ns (pulse length) and efficiencies approaching 20% is sufficiently low transverse electron velocity spreads are maintained (2%).

  2. Design of an induction linac driven CARM (Cyclotron Auto Resonance Maser) oscillator at 250 GHz

    SciTech Connect

    Caplan, M.; Kulke, B.

    1990-01-24

    We present the design of a 250 GHz, 400 MW Cyclotron Auto Resonance Maser (CARM) oscillator driven by a 1 KA, 2 MeV electron beam produced by the induction linac at the ARC facility of LLNL. The oscillator circuit is designed as a feedback amplifier operating in the TE{sub 11} mode at ten times cutoff terminated at each end with Bragg reflectors. Theory and cold test results are in good agreement for a manufactured Bragg reflector using 50 {mu}m corrugations to ensure mode purity. The CARM is to be operational by February 1990. 3 figs., 2 tabs.

  3. The 22 GHz Water Maser Line: A New Diagnostic Tool for Extrasolar Planet Search

    NASA Astrophysics Data System (ADS)

    Cosmovici, Cristiano; Pogrebenko, Sergej; Montebugnoli, Stelio; Maccaferri, Giuseppe

    The impact of 21 nuclei of Comet Shoemaker-Levy with the atmosphere of Jupiter in July 1994, permitted the detection of the 22 GHz water MASER line for the first time in the Solar System. This emission line was originated by a water cloud released from cometary ices after the explosion of the nuclei in the upper atmosphere. Our measurements have shown that, under particular physical conditions, water MASER emission can be observed from planetary atmospheres. Thus water (and probably other molecules like SiO) MASER emission can be used as a powerful diagnostic tool for planetary search outside the Solar System, since comets are able to deliver huge amounts of water into planetary atmospheres, increasing the probability of life development. We therefore started a search program with the 32m dish of the Medicina Radiotelescope using a 132,000 multichannel spectrometer in order to cover Doppler shifts due to planetary rotation. In this paper we will illustrate the feasibility, the technique used, and the first selected targets for the search within 50 ly.

  4. The discovery of a new masering transition of interstellar methanol

    NASA Astrophysics Data System (ADS)

    Wilson, T. L.; Walmsley, C. M.; Menten, K. M.; Hermsen, W.

    1985-06-01

    A spectral line of strength ≡50 Jy has been detected towards the compact H II region W3(OH). From the agreement with the laboratory line frequency, the authors identify this line with the Jk = 21-30 transition of E-type methanol. If, as with the 92-101 A+ line, the emission region is less than 1arcsec in diameter, the line brightness temperature is >1.5×105K. The phenomenon appears to be relatively unusual however since a short survey of galactic sources in the 21-30 E line revealed no other sources of this kind.

  5. An 8.4-GHz dual-maser front-end system for Parkes reimplementation

    NASA Astrophysics Data System (ADS)

    Trowbridge, D. L.; Loreman, J. R.; Brunzie, T. J.; Quinn, R.

    1990-02-01

    An 8.4-GHz front-end system consisting of a feedhorn, a waveguide feed assembly, dual masers, and downconverters was reimplemented at Parkes as part of the Parkes Canberra Telemetry Array for the Voyager Neptune encounter. The front-end system was originally assembled by the European Space Agency and installed on the Parkes antenna for the Giotto project. It was also used on a time-sharing basis by the Deep Space Network as part of the Parkes Canberra Telemetry Array to enhance the data return from the Voyager Uranus encounter. At the conclusion of these projects in 1986, part of the system was then shipped to JPL on loan for reimplementation at Parkes for the Voyager Neptune encounter. New design and implementation required to make the system operable at Parkes included new microwave front-end control cabinets, closed-cycle refrigeration monitor system, noise-adding radiometer system, front-end controller assembly, X81 local oscillator multiplier, and refurbishment of the original dual 8.4-GHz traveling-wave masers and waveguide feed system. The front-end system met all requirements during the encounter and was disassembled in October 1989 and returned to JPL.

  6. An 8.4-GHz dual-maser front-end system for Parkes reimplementation

    NASA Technical Reports Server (NTRS)

    Trowbridge, D. L.; Loreman, J. R.; Brunzie, T. J.; Quinn, R.

    1990-01-01

    An 8.4-GHz front-end system consisting of a feedhorn, a waveguide feed assembly, dual masers, and downconverters was reimplemented at Parkes as part of the Parkes Canberra Telemetry Array for the Voyager Neptune encounter. The front-end system was originally assembled by the European Space Agency and installed on the Parkes antenna for the Giotto project. It was also used on a time-sharing basis by the Deep Space Network as part of the Parkes Canberra Telemetry Array to enhance the data return from the Voyager Uranus encounter. At the conclusion of these projects in 1986, part of the system was then shipped to JPL on loan for reimplementation at Parkes for the Voyager Neptune encounter. New design and implementation required to make the system operable at Parkes included new microwave front-end control cabinets, closed-cycle refrigeration monitor system, noise-adding radiometer system, front-end controller assembly, X81 local oscillator multiplier, and refurbishment of the original dual 8.4-GHz traveling-wave masers and waveguide feed system. The front-end system met all requirements during the encounter and was disassembled in October 1989 and returned to JPL.

  7. 22 GHz water maser search in 37 nearby galaxies. Four new water megamasers in Seyfert 2 and OH maser/absorber galaxies

    NASA Astrophysics Data System (ADS)

    Wagner, J.

    2013-12-01

    Aims: We report four new 22 GHz H2O water masers found in a Green Bank Telescope search toward 37 nearby objects. Our goal was to find new maser galaxies, active galactic nucleus (AGN) disk masers, and objects where hydroxyl and water maser species coexist. Methods: We observed 37 sources within 250 Mpc that were selected by high X-ray luminosity (LX > 1040 W) and high absorbing column density (NH ≳ 1022 cm-2). Sources included dual or triple AGN and interacting systems. We also searched objects detected in hydroxyl (OH). A catalog of 4038 known H2O (non)detections was assembled to avoid unnecessary reobservations. The final selection consisted of 16 new sources, 13 nondetections to follow up with a factor 10 higher sensitivity, 10 OH masers and 1 deep OH absorber, of which 37 were observed. Results: Water megamasers were detected towards the Sy 2 galaxy 2MFGC 13581, towards the 6 GHz OH absorber NGC 4261 and towards the two 1.6 GHz OH maser sources IRAS 17526+3253 and IRAS 20550+1656. We set upper limits on 33 nondetections. The detection rate was 25% in OH galaxies and 11% overall. The mean sensitivity was 4 mJy over 24.4 kHz (0.31 km s-1) or between 0.1 L⊙ and 1.0 L⊙ rms for the distances covered by the source sample. Combined with other searches, a total of 95 objects have now been searched for both OH and H2O masers. Conclusions: The maser features in 2MFGC 13581 are typical of a sub-parsec accretion disk, whereas NGC 4261 likely has jet masers in a masing torus. The NGC 4261 galaxy (3C 270; dusty torus, twin jet) and its masers appear similar to NGC 1052, where continuum seed emission by a twin jet supports masers in the torus. Imaging with very long baseline interferometry is required to determine the masing regions in NGC 4261 and 2MFGC 13581. IRAS 17526+3253 has narrow 350 L⊙ systemic masers, and the tentative 5σ detection in IRAS 20550+1656 (II Zw 96) strongly resembles massive star formation kilomasers in NGC 2146. The latter two detections

  8. Observacoes do Cometa de Halley no Continuo de 22 GHz E 44 GHz, E NA Raia Maser de Vapor de H20 EM 22.2 GHz

    NASA Astrophysics Data System (ADS)

    Abraham, Z.; Scalise, E., Jr.; Botti, L. C. L.; Cancoro, A. C. O.; Monteiro Do Vale, J. L.; del Ciampo, L. F.; Tateyama, C. E.; Vilas Boas, J. W. S.; Homor, J. L.; Kaufmann, P.

    1987-05-01

    0 cometa de Halley foi observado no contínuo nas frequencias de 22 GHz e 44 GHz no Observatório de Itapetinga, Brasil, no período Fevereiro-Abril de 1986. 0 cometa foi detetado em ambas frequẽncias, apresentando variabilidade corn escalas de tempo de horas. Cálculos teóricos mostram que a radicão não pode ser devida a transicões livre-livre na região ionizada resultante da interacão do cometa corn 0 vento solar. A emissão seria então devida à radiacão térmica dos gráos da coma do cometa, cuja densidade também foi variável em intervalo de horas. Não foi detetada emissão maser de H2O maior que 4 Jy.

  9. A MULTI-EPOCH, SIMULTANEOUS WATER AND METHANOL MASER SURVEY TOWARD INTERMEDIATE-MASS YOUNG STELLAR OBJECTS

    SciTech Connect

    Bae, Jae-Han; Kim, Kee-Tae; Youn, So-Young; Kim, Won-Ju; Byun, Do-Young; Kang, Hyunwoo; Oh, Chung Sik E-mail: whorujh@kasi.re.kr

    2011-10-01

    We report a multi-epoch, simultaneous 22 GHz H{sub 2}O and 44 GHz Class I CH{sub 3}OH maser line survey toward 180 intermediate-mass young stellar objects, including 14 Class 0 and 19 Class I objects, and 147 Herbig Ae/Be stars. We detected H{sub 2}O and CH{sub 3}OH maser emission toward 16 (9%) and 10 (6%) sources with one new H{sub 2}O and six new CH{sub 3}OH maser sources. The detection rates of both masers rapidly decrease as the central (proto)stars evolve, which is contrary to the trends in high-mass star-forming regions. This suggests that the excitations of the two masers are closely related to the evolutionary stage of the central (proto)stars and the circumstellar environments. H{sub 2}O maser velocities deviate on average 9 km s{sup -1} from the ambient gas velocities whereas CH{sub 3}OH maser velocities match quite well with the ambient gas velocities. For both maser emissions, large velocity differences (|v{sub H{sub 2}O} - v{sub sys}| > 10kms{sup -1} and |v{sub CH3OH} - v{sub sys}| > 1kms{sup -1}) are mostly confined to Class 0 objects. The formation and disappearance of H{sub 2}O masers is frequent and their integrated intensities change by up to two orders of magnitude. In contrast, CH{sub 3}OH maser lines usually show no significant change in intensity, shape, or velocity. This is consistent with the previous suggestion that H{sub 2}O maser emission originates from the base of an outflow while 44 GHz Class I CH{sub 3}OH maser emission arises from the interaction region of the outflow with the ambient gas. The isotropic maser luminosities are well correlated with the bolometric luminosities of the central objects. The fitted relations are L{sub H2O}= 1.71x10{sup -9}(L{sub bol}){sup 0.97} and L{sub CH3OH}= 1.71x10{sup -10}(L{sub bol}){sup 1.22}.

  10. Research on Haystack radiometer, 20-24 GHz maser, and radio astronomy programs

    NASA Technical Reports Server (NTRS)

    1973-01-01

    During the first half of 1973, the Haystack antenna was utilized 76% of the time. Of this useful time, 72% was devoted to radio astronomy observing, 5% was spent on radar-related research and 23% went into maintenance and system improvements. Twenty-eight new radio astronomy programs were accepted, eight of which were completed during the period. One new radar program, topographic observations of Mars, was started in June and will be completed early in 1974. Fourteen programs continued from the previous period were also defined as complete. As of 1 July, 28 ratio observing programs were in a continuing status on the Haystack books. Four radar projects were also continuing. The 20-24 GHz maser development described in the preceding report progressed very well during an on-antenna test phase which began early in the year, but which terminated unfortunately in June with the complete loss of gain in the maser. Investigation of this problem is in progress. During this on-antenna test phase, the most sensitive water vapor observing capability which has yet become available was demonstrated.

  11. The detection of the 4(-1)-3(0) E transition of methanol at 36.2 GHz toward hot H II regions

    NASA Astrophysics Data System (ADS)

    Haschick, Aubrey D.; Baan, Willem A.

    1989-04-01

    Using Haystack Observatory at 36.169240 GHz, the 4(-1)-3(0) E transition of methanol toward 26 H II regions has been detected. The strong emission lines have narrow velocity components, thus exhibiting some of the characteristics of maser emission, as well as broader features which are assumed to be thermal in origin. The methanol emission preferably occurs in molecular clouds associated with hot H II regions and has not been detected in cold dark cloud regions or late-type stellar sources. The characteristics of the emission are discussed.

  12. Experimental and theoretical studies of a 35 GHz cyclotron autoresonance maser amplifier

    SciTech Connect

    DiRienzo, A.C.; Bekefi, G.; Chen, C.; Wurtele, J.S. )

    1991-07-01

    Experimental and theoretical studies of a cyclotron autoresonance maser (CARM) amplifier are reported. The measurements are carried out at a frequency of 35 GHz using a mildly relativistic electron beam (1.5 MeV, 130 A, 30 nsec) generated by a field emission electron gun followed by an emittance selector that removes the outer, hot electrons. Perpendicular energy is imparted to the electrons by means of a short bifilar helical wiggler. The entire system is immersed in a uniform axial magnetic field of 6--8 kG. With an input power of 17 kW at 35 GHz from a magnetron driver, the saturated power output is 12 MW in the lowest TE{sub 11} mode of a circular waveguide, corresponding to an electronic efficiency of 6.3%. The accompanying linear growth rate is 50 dB/m. When the system operates in the superradiant mode (in the absence of the magnetron driver) excitation of multiple waveguide modes is observed. A three-dimensional simulation code that has been developed to investigate the self-consistent interaction of the copropagating electromagnetic waveguide mode and the relativistic electron beam is in good agreement with the experimental observations.

  13. Radio Search for Extrasolar Cometary Impacts at 22 GHz (Water Maser Emission)

    NASA Astrophysics Data System (ADS)

    Cosmovici, C. B.; Pogrebenko, S.; Montebugnoli, S.; Maccaferri, G.

    2000-01-01

    The impact of 21 fragments of Comet Shoemaker-Levy 9 with the jovian atmosphere in July 1994 gave astronomers for the first time the opportunity to study the chemistry and physics of a planet during a catastrophic impact. A great amount of scientific data could be achieved by using space- and ground-based facilities and one of the most important results was the delivery of water and new molecules into the atmosphere of Jupiter. These observations could support the theory that, between 4 and 4.5 billion of years ago, the necessary water and organics were delivered to Earth by showers of comets, thus permitting the development of life. As comets are universal objects and the organics contained in their nuclei are originated in interstellar clouds responsible for stellar and planetary origins, we may assume that comets are delivering the 'bricks' of life, containing the same biochemical information, everywhere in the galaxy. By using a 132,000 channel spectrometer coupled to the 32 m dish of the Medicine radiotelescope (Bologna,Italy), we were able during the impact of the cometary nuclei with the upper atmosphere of Jupiter not only to detect water at 22 GHz, but to observe for the first time in the solar system a water MASER emission induced by a catastrophic impact. This emission line was originated by a water cloud released from cometary ices after the explosion of the nuclei in the upper atmosphere of Jupiter. Thus water MASER emission can be used as a powerful diagnostic tool for planetary search outside the solar system, as comets are able to deliver huge amounts of water (about 50 billion tons per comet) in planetary atmospheres rising the probability of life development. We started therefore a search program at Medicina using the same multichannel spectrometer in order to cover the Doppler shifts due to planetary rotation. The most suitable candidates for such a search, within 50 light years, are stellar systems like Epsilon Eridani and Beta Pictoris where

  14. Modeling and spatial structure of interstellar masers

    NASA Astrophysics Data System (ADS)

    Voronkov, Maxim A.

    2002-09-01

    This thesis presents a study of masers on the methanol, hydroxyl, and water vapor molecules seen in star-forming regions. A modeling of such masers is a complex numerical task where the radiation transfer equation is coupled with the system describing the balance of the level populations. The general method to solve such non-LTE multiline problem is a Monte Carlo method, the algorithm of which was described by Bernes (1979). The latter algorithm appears to account for the radiation field incorrectly. A modification of the Monte-Carlo method which is based on the averaging of formal solutions of the radiation transfer equation is proposed. This method was tested on two models of E-methanol masers in the limiting cases of the hot gas and the hot external radiation, which are probably corresponded to Class I and Class II methanol masers. Another model of the Class II methanol masers developed by Sobolev and Deguchi (1994) involve the pumping through two first torsionally excited states of the methanol molecule. Among other transitions the model predicts a weak maser at 44.9 GHz. The search for this transition towards brightest Class II methanol maser sources was undertaken to confirm the model. The line was detected in W3(OH) and probably NGC 6334F. The arguments in favor of weak masing in W3(OH) is given. The observational studies of interstellar masers are mainly devoted to the interferometric (VLBI) experiments. In this thesis the first space-VLBI observations of OH maser (1665/1667 MHz) were reported. The study with high angular resolution allows us to put a constraint on the interstellar scattering in the direction of the maser OH34.26+0.15. It appears to be about one order of magnitude lower than that obtained using the pulsar data. This fact gives rise to an idea that there is large scale variations in the spatial distribution of the scattering material. In this thesis the detailed study of the star-forming region GL2789 was performed. Using the Medicina 32-m

  15. HERSCHEL /HIFI OBSERVATIONS OF A NEW INTERSTELLAR WATER MASER: THE 5{sub 32}-4{sub 41} TRANSITION AT 620.701 GHz

    SciTech Connect

    Neufeld, David A.; Wu, Yuanwei; Kraus, Alex; Menten, Karl M.; Tolls, Volker; Melnick, Gary J.; Nagy, Zsofia

    2013-05-20

    Using the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared, we have performed mapping observations of the 620.701 GHz 5{sub 32}-4{sub 41} transition of ortho-H{sub 2}O within a {approx}1.'5 Multiplication-Sign 1.'5 region encompassing the Kleinmann-Low nebula in Orion (Orion-KL), and pointed observations of that transition toward the Orion South condensation and the W49N region of high-mass star formation. Using the Effelsberg 100 m radio telescope, we obtained ancillary observations of the 22.23508 GHz 6{sub 16}-5{sub 23} water maser transition; in the case of Orion-KL, the 621 GHz and 22 GHz observations were carried out within 10 days of each other. The 621 GHz water line emission shows clear evidence for strong maser amplification in all three sources, exhibiting narrow ({approx}1 km s{sup -1} FWHM) emission features that are coincident (kinematically and/or spatially) with observed 22 GHz features. Moreover, in the case of W49N-for which observations were available at three epochs spanning a 2 yr period-the spectra exhibited variability. The observed 621 GHz/22 GHz line ratios are consistent with a maser pumping model in which the population inversions arise from the combined effects of collisional excitation and spontaneous radiative decay, and the inferred physical conditions can plausibly arise in gas heated by either dissociative or non-dissociative shocks. The collisional excitation model also predicts that the 22 GHz population inversion will be quenched at higher densities than that of the 621 GHz transition, providing a natural explanation for the observational fact that 22 GHz maser emission appears to be a necessary but insufficient condition for 621 GHz maser emission.

  16. DETECTION OF THE ZEEMAN EFFECT IN THE 36 GHz CLASS I CH{sub 3}OH MASER LINE WITH THE EVLA

    SciTech Connect

    Sarma, A. P.; Momjian, E.

    2009-11-10

    We report the first detection of the Zeeman effect in the 36 GHz Class I CH{sub 3}OH maser line. The observations were carried out with 13 antennas of the EVLA toward the high mass star-forming region M8E. Based on our adopted Zeeman splitting factor of z = 1.7 Hz mG{sup -1}, we detect a line-of-sight magnetic field of -31.3 +- 3.5 mG and 20.2 +- 3.5 mG to the northwest and southeast of the maser line peak, respectively. This change in sign over a 1300 AU size scale may indicate that the masers are tracing two regions with different fields, or that the same field curves across the regions where the masers are being excited. The detected fields are not significantly different from the magnetic fields detected in the 6.7 GHz Class II CH{sub 3}OH maser line, indicating that CH{sub 3}OH masers may trace the large-scale magnetic field, or that the magnetic field remains unchanged during the early evolution of star-forming regions. Given what is known about the densities at which 36 GHz CH{sub 3}OH masers are excited, we find that the magnetic field is dynamically significant in the star-forming region.

  17. G 10.472+0.027: AN EXTREME WATER MASER OUTFLOW ASSOCIATED WITH A MASSIVE PROTOSTELLAR CLUSTER

    SciTech Connect

    Titmarsh, A. M.; Ellingsen, S. P.; Breen, S. L.; Caswell, J. L.; Voronkov, M. A.

    2013-09-20

    An Australia Telescope Compact Array search for 22 GHz water masers toward 6.7 GHz class II methanol masers detected in the Methanol Multibeam survey has resulted in the detection of extremely high-velocity emission from one of the sources. The water maser emission associated with this young stellar object covers a velocity span of nearly 300 km s{sup –1}. The highest velocity water maser emission is redshifted from the systemic velocity by 250 km s{sup –1}, which is a new record for high-mass star formation regions. The maser is associated with a very young late O, or early B star, which may still be actively accreting matter (and driving the extreme outflow). If that is the case, future observations of the kinematics of this water maser will provide a unique probe of accretion processes in the highest mass young stellar objects and test models of water maser formation.

  18. Excitation of the 51 - 60 A+ Methanol Transition

    NASA Astrophysics Data System (ADS)

    Kuiper, T. B. H.; Goldsmith, P.; de Gregorio Monsalvo, I.; Kalensky, S.; Peng, R.; Slysh, V.

    2009-01-01

    We are conducting an investigation of the excitation of the 6.7 GHz methanol maser line to determine the physical conditions that produce the inversion in this strongest of methanol masers. We have observed the ΔJ = -1, ΔK = 0 transitions at 290.1, 287.7 and 239.7 GHz, which connect to the levels of the maser line, towards a sample of strong Class II masers. The observations of the 51-41 A+ line at 239.7 GHz and 60-50 A+ line at 290.1 GHz make it possible to determine the relative populations (excitation temperature) of the 6.7 GHz maser levels. The derived excitation temperatures for the maser line, averaged over the 30" CSO beam, are in most cases positive. The lack of inversion suggests that the beam averages over regions with quasi-thermal and maser emission and that the regions which are inverted are much smaller than the CSO beam. A map of the W51 region in thermal methanol lines shows that the strongest masers occur at or near the peak of thermal methanol emission which indicates a correlation between methanol column density and maser intensity. We plan also to map the Orion OMC-1 region, where the mm emission is intense but the 6.7 GHz emission fairly weak and, interestingly, extended. The DR21 region also has mm emission strong enough to be mapped in reasonable time. Our colleague and friend Slava Slysh passed away in September. We miss his inspiring insights and dedicate this work to his memory. The work by TBHK and PFG was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to the National Aeronautics and Space Administration.

  19. Astrophysical masers; Proceedings of the Conference, Arlington, VA, Mar. 9-11, 1992

    NASA Technical Reports Server (NTRS)

    Clegg, Andrew W. (Editor); Nedoluha, Gerald E. (Editor)

    1993-01-01

    Various papers on astrophysical masers are presented. The general topics addressed include: theory, maser surveys, extragalactic masers, masers in star-forming regions (general), OH masers in star-forming regions, water masers in star-forming regions, methanol masers in star-forming regions, proper motions, scattering, variability, circumstellar masers (general), circumstellar OH masers, circumstellar water masers, circumstellar SiO masers, and solar system masers.

  20. Astrometrically registered simultaneous observations of the 22 GHz H{sub 2}O and 43 GHz SiO masers toward R Leonis Minoris using KVN and source/frequency phase referencing

    SciTech Connect

    Dodson, Richard; Rioja, María J.; Jung, Tae-Hyun; Sohn, Bong-Won; Byun, Do-Young; Cho, Se-Hyung; Lee, Sang-Sung; Kim, Jongsoo; Kim, Kee-Tae; Oh, Chung-Sik; Han, Seog-Tae; Je, Do-Heung; Chung, Moon-Hee; Wi, Seog-Oh; Kang, Jiman; Lee, Jung-Won; Chung, Hyunsoo; Kim, Hyo-Ryoung; Kim, Hyun-Goo; Lee, Chang-Hoon; and others

    2014-11-01

    Oxygen-rich asymptotic giant branch (AGB) stars can be intense emitters of SiO (v = 1 and 2, J = 1 → 0) and H{sub 2}O maser lines at 43 and 22 GHz, respectively. Very long baseline interferometry (VLBI) observations of the maser emission provide a unique tool to probe the innermost layers of the circumstellar envelopes in AGB stars. Nevertheless, the difficulties in achieving astrometrically aligned H{sub 2}O and v = 1 and v = 2 SiO maser maps have traditionally limited the physical constraints that can be placed on the SiO maser pumping mechanism. We present phase-referenced simultaneous spectral-line VLBI images for the SiO v = 1 and v = 2, J = 1 → 0, and H{sub 2}O maser emission around the AGB star R LMi, obtained from the Korean VLBI Network (KVN). The simultaneous multi-channel receivers of the KVN offer great possibilities for astrometry in the frequency domain. With this facility, we have produced images with bona fide absolute astrometric registration between high-frequency maser transitions of different species to provide the positions of the H{sub 2}O maser emission and the center of the SiO maser emission, hence reducing the uncertainty in the proper motions for R LMi by an order of magnitude over that from Hipparcos. This is the first successful demonstration of source frequency phase referencing for millimeter VLBI spectral-line observations and also where the ratio between the frequencies is not an integer.

  1. The Methanol Multibeam Survey

    NASA Astrophysics Data System (ADS)

    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.

    2007-03-01

    A 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.

  2. VizieR Online Data Catalog: Methanol maser associated outflows (de Villiers+, 2014)

    NASA Astrophysics Data System (ADS)

    de Villiers, H. M.; Chrysostomou, A.; Thompson, M. A.; Ellingsen, S. P.; Urquhart, J. S.; Breen, S. L.; Burton, M. G.; Csengeri, T.; Ward-Thompson, D.

    2015-04-01

    The targets were observed with the JCMT, on the summit of Mauna Kea, Hawaii on seven nights between 2007 May 17 and 2008 July 22. Targets were mapped in the 13CO and C18O (J=3-2) transitions (330.6 and 329.3GHz), using the 16-receptor HARP. (5 data files).

  3. Accurate maser positions for MALT-45

    NASA Astrophysics Data System (ADS)

    Jordan, Christopher; Bains, Indra; Voronkov, Maxim; Lo, Nadia; Jones, Paul; Muller, Erik; Cunningham, Maria; Burton, Michael; Brooks, Kate; Green, James; Fuller, Gary; Barnes, Peter; Ellingsen, Simon; Urquhart, James; Morgan, Larry; Rowell, Gavin; Walsh, Andrew; Loenen, Edo; Baan, Willem; Hill, Tracey; Purcell, Cormac; Breen, Shari; Peretto, Nicolas; Jackson, James; Lowe, Vicki; Longmore, Steven

    2013-10-01

    MALT-45 is an untargeted survey, mapping the Galactic plane in CS (1-0), Class I methanol masers, SiO masers and thermal emission, and high frequency continuum emission. After obtaining images from the survey, a number of masers were detected, but without accurate positions. This project seeks to resolve each maser and its environment, with the ultimate goal of placing the Class I methanol maser into a timeline of high mass star formation.

  4. The MMB Survey: Variable sources and the weakest masers

    NASA Astrophysics Data System (ADS)

    Ellingsen, Simon; Caswell, James; Voronkov, Maxim; Green, James; Fuller, Gary; Breen, Shari; Quinn, Lyshia

    2010-04-01

    The Methanol MultiBeam (MMB) survey has completed its survey of the southern Galactic plane for the 6,7 GHz class II methanol maser using the 7 beam receiver on Parkes. The first catalogue paper has been submitted. So far the MMB has detected over 800 massive star forming regions throughout our Galaxy. In this proposal we request time to obtain high quality spectra of a sample of highly variable weak masers which may represent a hither-to unknown population. In addition we will obtain final spectra of a sample of faint masers from deep piggyback pulsar observations and northernly sources whose positions have only recently been measured using the VLA and MERLIN.

  5. The distribution of the 6(2)-6(1) and 5(2)-5(1) E-type methanol masers in OMC-1

    NASA Astrophysics Data System (ADS)

    Johnston, K. J.; Gaume, R.; Stolovy, S.; Wilson, T. L.; Walmsley, C. M.; Menten, K. M.

    1992-01-01

    Results are presented of mapping of the 6(2)-6(1) and 5(2)-5(1) E transition of CH3OH toward the Orion-KL region with an angular resolution of 3 arcsec and a frequency resolution of 12 kHz (0.15 km/s). They are shown to lie over an area of approximately 40 arcsec, as previously shown by Matsakis et al. (1980). A detailed comparison exhibits a qualitative agreement of the intensities and sizes with the previous map. In 11 of 14 cases, the positions, flux densities, and radial velocities of the 6(2)-6(1) E and 5(2)-5(1) E maser components agree. Although individual maser emission regions are unresolved in the present 3-arcsec beam, the variation of position with velocity within what is thought to be a single feature implies clustering of masers on scales of less than 3 arcsec. The most intense feature has a brightness temperature in excess of 100,000 K. The best agreement is within the map of the 8(0)-7(1) A transition of methanol.

  6. VLBI study of maser kinematics in high-mass star-forming regions. I. G16.59-0.05

    NASA Astrophysics Data System (ADS)

    Sanna, A.; Moscadelli, L.; Cesaroni, R.; Tarchi, A.; Furuya, R. S.; Goddi, C.

    2010-07-01

    Aims: To study the high-mass star-forming process, we started a large project to unveil the gas kinematics close to young stellar objects (YSOs) through the Very Long Baseline Interferometry (VLBI) of maser associations. By comparing the high spatial resolution maser data that traces the inner kinematics of the (proto)stellar cocoon with interferometric thermal data that traces the large-scale environment of the hot molecular core (HMC) harboring the (proto)stars, we can investigate the nature and identify the sources of large-scale motions. The present paper focuses on the high-mass star-forming region G16.59-0.05. Methods: Using the VLBA and the EVN arrays, we conducted phase-referenced observations of the three most powerful maser species in G16.59-0.05: H2O at 22.2 GHz (4 epochs), CH3OH at 6.7 GHz (3 epochs), and OH at 1.665 GHz (1 epoch). In addition, we performed high-resolution (≥0.1 arcsec), high-sensitivity (< 0.1 mJy) VLA observations of the radio continuum emission from the star-forming region at 1.3 and 3.6 cm. Results: This is the first work to report accurate measurements of the relative proper motions of the 6.7 GHz CH3OH masers. The different spatial and 3-D velocity distributions clearly indicate that the 22 GHz water and 6.7 GHz methanol masers trace different kinematic environments. The bipolar distribution of 6.7 GHz maser line-of-sight velocities and the regular pattern of observed proper motions suggest that these masers are tracing rotation around a central mass of about 35 M⊙. The flattened spatial distribution of the 6.7 GHz masers, oriented NW-SE, suggests that they can originate in a disk/toroid rotating around the massive YSO that drives the 12CO (2-1) outflow, oriented NE-SW, observed on an arcsec scale. The extended, radio continuum source observed close to the 6.7 GHz masers could be excited by a wide-angle wind emitted from the YSO associated with the methanol masers, and such a wind has proven to be energetic enough to drive the

  7. New detections of HC5N towards hot cores associated with 6.7 GHz methanol masers

    NASA Astrophysics Data System (ADS)

    Green, C.-E.; Green, J. A.; Burton, M. G.; Horiuchi, S.; Tothill, N. F. H.; Walsh, A. J.; Purcell, C. R.; Lovell, J. E. J.; Millar, T. J.

    2014-09-01

    We present new detections of cyanodiacetylene (HC5N) towards hot molecular cores, observed with the Tidbinbilla 34 m radio telescope (DSS-34). In a sample of 79 hot molecular cores, HC5N was detected towards 35. These results are counter to the expectation that long chain cyanopolyynes, such as HC5N, are not typically found in hot molecular cores, unlike their shorter chain counterpart HC3N. However, it is consistent with recent models which suggest HC5N may exist for a limited period during the evolution of hot molecular cores.

  8. DETECTION OF A METHANOL MEGAMASER IN A MAJOR-MERGER GALAXY

    SciTech Connect

    Chen, Xi; Baan, Willem A.; Qiao, Hai-Hua; Li, Juan; An, Tao; Ellingsen, Simon P.; Breen, Shari L.

    2015-02-10

    We have detected emission from both the 4{sub −1}→3{sub 0} E (36.2 GHz) class I and 7{sub −2}→8{sub −1} E (37.7 GHz) class II methanol transitions toward the center of the closest ultra-luminous infrared galaxy Arp 220. The emission in both methanol transitions shows narrow spectral features and has luminosities approximately 8 orders of magnitude stronger than those observed from typical class I methanol masers observed in Galactic star formation regions. The emission is also orders of magnitude stronger than the expected intensity of thermal emission from these transitions and based on these findings we suggest that the emission from the two transitions are masers. These observations provide the first detection of a methanol megamaser in the 36.2 and 37.7 GHz transitions and represent only the second detection of a methanol megamaser, following the recent report of an 84 GHz methanol megamaser in NGC 1068. We find that the methanol megamasers are significantly offset from the nuclear region and arise toward regions where there is Hα emission, suggesting that they are associated with starburst activity. The high degree of correlation between the spatial distribution of the 36.2 GHz methanol and X-ray plume emission suggests that the production of strong extragalactic class I methanol masers is related to galactic-outflow-driven shocks and perhaps cosmic rays. In contrast to OH and H{sub 2}O megamasers which originate close to the nucleus, methanol megamasers provide a new probe of feedback (e.g., outflows) processes on larger scales and of star formation beyond the circumnuclear starburst regions of active galaxies.

  9. The complete, temperature resolved experimental spectrum of methanol (CH{sub 3}OH) between 560 and 654 GHz

    SciTech Connect

    Fortman, Sarah M.; Neese, Christopher F.; De Lucia, Frank C.

    2014-02-20

    The complete spectrum of methanol (CH{sub 3}OH) has been characterized over a range of astrophysically significant temperatures in the 560.4-654.0 GHz spectral region. Absolute intensity calibration and analysis of 166 experimental spectra recorded over a slow 248-398 K temperature ramp provide a means for the simulation of the complete spectrum of methanol as a function of temperature. These results include contributions from v{sub t} = 3 and other higher states that are difficult to model via quantum mechanical (QM) techniques. They also contain contributions from the {sup 13}C isotopologue in terrestrial abundance. In contrast to our earlier work on semi-rigid species, such as ethyl cyanide and vinyl cyanide, significant intensity differences between these experimental values and those calculated by QM methods were found for many of the lines. Analysis of these differences shows the difficulty of the calculation of dipole matrix elements in the context of the internal rotation of the methanol molecule. These results are used to both provide catalogs in the usual line frequency, linestrength, and lower state energy format, as well as in a frequency point-by-point catalog that is particularly well suited for the characterization of blended lines.

  10. Precise laboratory measurements of methanol rotational transition frequencies in the 5 to 13 GHz region

    NASA Astrophysics Data System (ADS)

    Breckenridge, S. M.; Kukolich, S. G.

    1995-01-01

    Rotational transitions for CH3OH were measured in the 5-13 GHz range with a precision and accuracy of a few kilohertz or less using a Flygare-Balle type pulsed-beam Fourier transform microwave spectrometer. The accurate center frequencies measured should be useful in determining accurate Doppler shifts and making positive molecule identification in radio astronomy.

  11. Long-Term Monitoring of Molecular Masers in IRAS 18566+0408

    NASA Astrophysics Data System (ADS)

    Halbe, Daniel Michael; Araya, Esteban; Hofner, Peter; Linz, Hendrik; Olmi, Luca; Kurtz, Stan

    2016-01-01

    We report results of a long-term monitoring study of 6 cm formaldehyde (H2CO),6.035 GHz hydroxyl (OH), and 6.7 GHz methanol (CH3OH) masers in the young high-mass protostellar object IRAS 18566+0408 (G37.55+0.20). This is the only high-mass star forming region where correlated variability of three different maser species has been reported. The observations were conducted with the 305m Arecibo Radio Telescope and the Very Large Array. Together with data from the literature, we present H2CO flux density measurements from 2002 to 2014, CH3OH data from 2006 to 2015, and OH observations from 2008 to 2015. Our extended monitoring observations of the H2CO maser agree with quasi-periodic variability and exponential flux density decrease during the quiescent and flare states as proposed by Araya and collaborators in 2010. We also confirm the occurrence of 6.035 GHz OH flares and a time delay with respect to the H2CO flares (first reported by Al-Marzouk and collaborators in 2012). An analysis of the variability behavior of different CH3OH velocity components and the H2CO maser suggests that multiple variability mechanisms may be responsible for the CH3OH flux density changes.

  12. Cosmic Masers

    ERIC Educational Resources Information Center

    Dickinson, Dale F.

    1978-01-01

    Intense radiation at microwave frequencies is emitted by certain nebular regions and stellar atmospheres. It is generated by maser action, which does for microwaves what laser action does for light. Describes in detail the types of masers and their action. (Author/MA)

  13. Methanol

    Integrated Risk Information System (IRIS)

    Methanol ; CASRN 67 - 56 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effects )

  14. I-VLBI of molecular masers

    NASA Astrophysics Data System (ADS)

    Moscadelli, L.; Porceddu, I.

    Intense maser emissions of several molecular species (OH, CH3OH, H2O, SiO) are widely observed toward both star-formation regions and late-type stars. VLBI observations of molecular masers offer an unique opportunity to study the kinematics of the circumstellar gas in both the earliest and latest evolution phases of a star. The forthcoming Sardinia Radio Telescope (SRT) together with the other two Italian antennae of Medicina and Noto, will in the near future constitute a three-element VLBI array of sufficiently high sensitivity and angular resolution to allow one to map the strongest maser lines of CH3OH (at 6.7 GHz), H2O (at 22.2 GHz) and SiO (at 43 GHz). The Italian VLBI network (I-VLBI) can be competitive in the observation of molecular masers provided that time flexibility and frequency agility will be granted.

  15. Maser maps and magnetic field of OH 337.705-0.053

    NASA Astrophysics Data System (ADS)

    Caswell, J. L.; Kramer, B. Hutawarakorn; Reynolds, J. E.

    2011-08-01

    New high resolution studies of the Galactic maser site 337.705-0.053 reveal its magnetic field and velocity morphology. The long baseline array of the Australia Telescope National Facility provided simultaneous observations of both the 1665- and 1667-MHz OH transitions which yielded a sequence of maps at velocity spacing 0.09 km s-1, in both senses of circular polarization, with tenth-arcsec spatial resolution. 38 small diameter maser spots were detected, spread over an ellipse with largest dimension of 1.5 arcsec. Pairs of spots with the same position, but with right and left circular polarization at different frequency, reveal Zeeman splitting. Five pairs at 1665 MHz and four at 1667 MHz are seen; at one position, pairs at both transitions indicate a comparable magnetic field and similar (central) velocity. All estimates of magnetic field are in the same sense, with a median value of -2.5 mG (pointing towards the earth), confirming an interpretation from single-dish observations. The morphology and kinematics have been compared with that of maser emission from the excited state of OH at 6035 MHz, with methanol at 6668 MHz and 12 GHz, and with water at 22 GHz. All species are intermingled, and associated with an ultracompact H II region. The site most likely lies near the tangent point of the Galactic 3-kpc ring, at a distance of 7.9 kpc. The maser spot distribution over 1.5 arcsec then corresponds to a diameter of 60 mpc, amongst the largest known, and likely to be approaching the end of the maser emitting phase. 337.705-0.053 adds to the maser sites studied in sufficient detail to explore ordered patterns in the global Galactic magnetic field.

  16. FIRST INTERSTELLAR HCO{sup +} MASER

    SciTech Connect

    Hakobian, Nicholas S.; Crutcher, Richard M. E-mail: crutcher@illinois.edu

    2012-10-10

    A previously unseen maser in the J = 1-0 transition of HCO{sup +} has been detected by the Combined Array for Millimeter-wave Astronomy (CARMA). A subarcsecond map was produced of the 2 arcmin{sup 2} region around DR21(OH), which has had previous detections of OH and methanol masers. This new object has remained undetected until now due to its extremely compact size. The object has a brightness temperature of >2500 K and an FWHM linewidth of 0.497 km s{sup -1}, both of which suggest non-thermal line emission consistent with an unsaturated maser. This object coincides in position and velocity with the methanol maser named DR21(OH)-1 by Plambeck and Menten. No compact HCO{sup +} emission was present in the CARMA data toward the other methanol masers described in that Letter. These new results support the theory introduced in Plambeck and Menten that these masers likely arise from strong outflows interacting with low mass, high density pockets of molecular gas. This is further supported by recent observations of a CO outflow by Zapata et al. that traces the outflow edges and confirms that the maser position lies along the edge of the outflow where interaction with molecular tracers can occur.

  17. Excitation of millimeter and submillimeter water masers

    NASA Technical Reports Server (NTRS)

    Neufeld, David A.; Melnick, Gary J.

    1991-01-01

    The excitation of maser emission in millimeter and submillimeter transitions of interstellar and circumstellar water is considered. An escape probability method is used to determine the equilibrium populations in 349 rotational states of both ortho- and para-water under varying conditions of gas temperature, density, water abundance, and radiation field. It is shown that, under those conditions believed to prevail around late-type stars and within star-forming regions, strong millimeter and submillimeter water maser emission can be generated by collisional excitations by H2. Several maser transitions can have strengths close to that of the 22 GHz line. The water maser line which can be observed from mountaintop facilities and those which will require air- or space-borne platforms are indicated. The exact portion of parameter space in which each maser transition exhibits peak emission is shown.

  18. The complete, temperature resolved experimental spectrum of methanol (CH{sub 3}OH) between 214.6 and 265.4 GHz

    SciTech Connect

    McMillan, James P.; Fortman, Sarah M.; Neese, Christopher F.; De Lucia, Frank C.

    2014-11-01

    The spectrum of methanol (CH{sub 3}OH) has been characterized between 214.6 and 265.4 GHz for astrophysically significant temperatures. Four hundred and eighty-six spectra with absolute intensity calibration recorded between 240 and 389 K provided a means for the calculation of the complete experimental spectrum (CES) of methanol as a function of temperature. The CES includes contributions from v{sub t} = 3 and other higher states that are difficult to model quantum mechanically (QM). It also includes the spectrum of the {sup 13}C isotopologue in terrestrial abundance. In general the QM models provide frequencies that are within 1 MHz of their experimental values, but there are several outliers that differ by tens of MHz. As in our recent work on methanol in the 560-654 GHz region, significant intensity differences between our experimental intensities and cataloged values were found. In this work these differences are explored in the context of several QM analyses. The experimental results presented here are analyzed to provide a frequency point-by-point catalog that is well suited for the simulation of crowded and overlapped spectra. Additionally, a catalog in the usual line frequency, line strength, and lower state energy format is provided.

  19. Simultaneous Observatinos of H2O and SiO Masers Toward Known Extragalactic Water Maser Sources

    NASA Astrophysics Data System (ADS)

    Cho, Se-Hyung; Yoon, Dong-Hwan; Kim, Jaeheon; Byun, Do-Young; Wagner, Jan

    2015-12-01

    We observe ten known 22 GHz H_{2}O maser galaxies during February 19-22, 2011 using the 21 m Tamna telescope of the Korean VLBI Network and a new wide-band digital spectrometer. Simultaneously we searched for 43 GHz SiO v = 1, 2, J = 1-0 maser emission. We detect H_{2}O maser emission towards five sources (M 33, NGC 1052, NGC 1068, NGC 4258, M 82), with non-detections towards the remaining sources (UGC 3193, UGC 3789, Antennae H_{2}O-West, M 51, NGC 6323) likely due to sensitivity. Our 22 GHz spectra are consistent with earlier findings. Our simultaneous 43 GHz SiO maser search produced non-detections, yielding - for the first time - upper limits on the 43 GHz SiO maser emission in these sources at a 3 σ sensitivity level of 0.018 K-0.033 K (0.24 Jy-0.44 Jy) in a 1.75 km s^{-1} velocity resolution. Our findings suggest that any 43 GHz SiO masers in these sources (some having starburst-associated H_{2}O kilomasers) must be faint compared to the 22 GHz H_{2}O maser emission.

  20. The detection of extragalactic methanol

    NASA Astrophysics Data System (ADS)

    Henkel, C.; Jacq, T.; Mauersberger, R.; Menten, K. M.; Steppe, H.

    1987-12-01

    The detection of emission in the 96 GHz 2(kappa)-1(kappa) lines of methanol is reported toward the central regions of NGC253 and IC342. A possible detection is also obtained toward NGC6946, while no emission is seen toward M82. (CH3OH)/(H2) abundance ratios appear to be consistent with those determined for galactic sources. The strength of the CH3OH emission, however, is not found to be correlated with infrared or CO luminosities. Toward NGC253, two distinct clouds are identified. One of these appears to be directly associated with the nucleus and remains spatially unresolved. The recently detected H2O maser at 100-150 km/s does not originate from this centrally located cloud.

  1. Water masers in the Saturnian system

    NASA Astrophysics Data System (ADS)

    Pogrebenko, S. V.; Gurvits, L. I.; Elitzur, M.; Cosmovici, C. B.; Avruch, I. M.; Montebugnoli, S.; Salerno, E.; Pluchino, S.; Maccaferri, G.; Mujunen, A.; Ritakari, J.; Wagner, J.; Molera, G.; Uunila, M.

    2009-02-01

    Context: The presence of water has long been seen as a key condition for life in planetary environments. The Cassini spacecraft discovered water vapour in the Saturnian system by detecting absorption of UV emission from a background star. Investigating other possible manifestations of water is essential, one of which, provided physical conditions are suitable, is maser emission. Aims: We report detection of water maser emission at 22 GHz associated with several Kronian satellites using Earth-based radio telescopes. Methods: We searched for water maser emission in the Saturnian system in an observing campaign using the Metsähovi and Medicina radio telescopes. Spectral data were Doppler-corrected over orbital phase for the Saturnian satellites, yielding detections of water maser emission associated with the moons Hyperion, Titan, Enceladus, and Atlas. Results: The detection of Saturnian water molecules by remote astronomical observation can be combined with in situ spacecraft measurements to harmonise the physical model of the Saturnian system.

  2. Detection of water masers toward young stellar objects in the Large Magellanic Cloud

    SciTech Connect

    Johanson, A. K.; Migenes, V.; Breen, S. L.

    2014-02-01

    We present results from a search for water maser emission toward N4A, N190, and N206, three regions of massive star formation in the Large Magellanic Cloud (LMC). Four water masers were detected; two toward N4A, and two toward N190. In the latter region, no previously known maser emission has been reported. Future studies of maser proper motion to determine the galactic dynamics of the LMC will benefit from the independent data points the new masers in N190 provide. Two of these masers are associated with previously identified massive young stellar objects (YSOs), which strongly supports the authenticity of the classification. We argue that the other two masers identify previously unknown YSOs. No masers were detected toward N206, but it does host a newly discovered 22 GHz continuum source, also associated with a massive YSO. We suggest that future surveys for water maser emission in the LMC be targeted toward the more luminous, massive YSOs.

  3. Masers in GLIMPSE Extended Green Objects (EGOs)

    NASA Astrophysics Data System (ADS)

    Cyganowski, Claudia J.; Brogan, Crystal L.; Hunter, Todd R.; Churchwell, Ed; Koda, Jin; Rosolowsky, Erik; Towers, Sarah; Whitney, Barb; Zhang, Qizhou

    2012-07-01

    Large-scale Spitzer surveys of the Galactic plane have yielded a new diagnostic for massive young stellar objects (MYSOs) that are actively accreting and driving outflows: extended emission in the IRAC 4.5 μm band, believed to trace shocked molecular gas. Maser studies of these extended 4.5 μm sources (called EGOs, Extended Green Objects, for the common coding of 3-color IRAC images) have been and remain crucial for understanding the nature of EGOs. High detection rates in VLA CH3OH maser surveys provided the first proof that EGOs were indeed MYSOs driving outflows; our recent Nobeyama 45-m survey of northern EGOs shows that the majority are associated with H2O masers. Maser studies of EGOs also provide important constraints for the longstanding goal of a maser evolutionary sequence for MYSOs, particularly in combination with high resolution (sub)mm data. New SMA results show that Class I methanol masers can be excited by both young (hot core) and evolved (ultracompact HII region) sources within the same massive star-forming region.

  4. Water Masers in W49N

    NASA Astrophysics Data System (ADS)

    Kramer, Busaba; Menten, Karl M.; Kaminski, Tomasz; Zhang, Bo; Patel, Nimesh; Kraus, Alex

    2015-08-01

    Water masers have long been known to be one of the best signposts of active star formation and regions of extremely dense gas (>108 cm-3) and therefore tracing high-velocity outflows and shock fronts. W49N is one of the richest and most luminous water maser in our Galaxy. The variability of water masers in W49N has been studied since its discovery, showing short and long time scale variations. Short-time scale monitoring often shows dramatic variations in flux density, line width and line center velocity. However, the models accounted for such variations are still under debate. We report the study of the recent major outburst of the 22-GHz water maser in W49N in 2014. We carried out the simultaneous observations of several water transitions both at millimeter and submillimeter wavelengths with the Effelsberg 100-m radio telescope, the IRAM 30-m telescope, and the APEX 12-m submillimeter telescope. We have also performed interferometric observations of the 22-GHz transition using the NRAO Very Long Baseline Array (VLBA) and of the 321- and 325-GHz transitions using the Submillimeter Array (SMA). Studying these multiple masing transitions in conjunction with theoretical modeling of their excitation places strong constraints on the physical conditions of the masing gas and also allows us to probe the embedded environment.

  5. Accurate positions of H2 O masers in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Lazendic, J. S.; Whiteoak, J. B.; Klamer, I.; Harbison, P. D.; Kuiper, T. B. H.

    2002-04-01

    Positions with subarcsecond accuracy have been measured for seven 22-GHz H2 O masers associated with Hii regions in the Large Magellanic Cloud (LMC); two of the masers are new detections. Initial position measurements were obtained with the 70-m antenna of the Canberra NASA Deep Space Network during a period of more than two years in which the antenna was used to monitor the maser emission. The positions were further improved using 22-GHz observations involving three antennas of the Australia Telescope Compact Array. The positions have been compared with those of 1.6-GHz continuum emission and other LMC masers (of OH and CH3 OH). The H2 O maser positions range from within 1arcsec (270mpc) of the centre of a compact Hii component to beyond the boundary of significant continuum emission. Three of the four masers located near continuum peaks are close to OH masers. In two cases the positional agreement is better than 0.2arcsec (53mpc) in the third case the agreement is worse (0.9arcsec) but the positions of the individual H2 O features appear to be spread over more than 1arcsec. The velocities of the OH masers are within the spread of the H2 O velocities. The three H2 O masers offset from continuum centres are located 3-7arcsec from optical or infrared phenomena probably associated with very early stages of star formation; no other molecular masers are known in these directions.

  6. A receiver design for the superconducting cavity-maser oscillator

    NASA Technical Reports Server (NTRS)

    Wang, R. T.; Dick, G. J.

    1991-01-01

    A new frequency standard was demonstrated with the aid of a double phase locked loop (PLL) receiver. A superconducting cavity maser oscillator (SCMO) and a hydrogen maser are combined to show the medium term performance of the hydrogen maser together with improved short term performance made possible by the SCMO. The receiver, which generates a 100 MHz signal with reduced noise, is phase locked to (and may be used in place of) the 100 MHz hydrogen maser output. The maser signal, 2.69xxx-GHz SCMO output, and a 100 MHz quartz crystal oscillator are optimally combined by the receiver. A measured two source fractional frequency stability of 2 x 10(exp -14) was obtained for a measuring time of r = 1 sec, and 1 x 10(exp -15) at r = 1,000 sec. The 1 sec value is approx. 10 times lower than that for hydrogen masers, while the 1,000 sec value is identical to hydrogen maser performance. The design is based on phase noise models for the hydrogen maser, the SCMO, and quartz crystal oscillators for offset frequencies down to 1 x 10(exp -6) Hz.

  7. Optical Properties of Host Galaxies of Extragalactic Nuclear Water Masers

    NASA Astrophysics Data System (ADS)

    Zhu, Guangtun; Zaw, Ingyin; Blanton, Michael R.; Greenhill, Lincoln J.

    2011-12-01

    We study the optical properties of the host galaxies of nuclear 22 GHz (λ = 1.35 cm) water masers. To do so, we cross-match the galaxy sample surveyed for water maser emission (123 detections and 3806 non-detections) with the Sloan Digital Sky Survey (SDSS) low-redshift galaxy sample (z < 0.05). Out of 1636 galaxies with SDSS photometry, we identify 48 detections; out of the 1063 galaxies that also have SDSS spectroscopy, we identify 33 detections. We find that maser detection rate is higher at higher optical luminosity (MB ), larger velocity dispersion (σ), and higher [O III] λ5007 luminosity, with [O III] λ5007 being the dominant factor. These detection rates are essentially the result of the correlations of isotropic maser luminosity with all three of these variables. These correlations are natural if maser strength increases with central black hole mass and the level of active galactic nucleus (AGN) activity. We also find that the detection rate is higher in galaxies with higher extinction. Based on these results, we propose that maser surveys seeking to efficiently find masers should rank AGN targets by extinction-corrected [O III] λ5007 flux when available. This prioritization would improve maser detection efficiency, from an overall ~3% without pre-selection to ~16% for the strongest intrinsic [O III] λ5007 emitters, by a factor of ~5.

  8. Unusual Shock-excited OH Maser Emission in a Young Planetary Nebula

    NASA Astrophysics Data System (ADS)

    Qiao, Hai-Hua; Walsh, Andrew J.; Gómez, José F.; Imai, Hiroshi; Green, James A.; Dawson, Joanne R.; Shen, Zhi-Qiang; Ellingsen, Simon P.; Breen, Shari L.; Jones, Paul A.; Gibson, Steven J.; Cunningham, Maria R.

    2016-01-01

    We report on OH maser emission toward G336.644-0.695 (IRAS 16333-4807), which is a H2O maser-emitting Planetary Nebula (PN). We have detected 1612, 1667, and 1720 MHz OH masers at two epochs using the Australia Telescope Compact Array, hereby confirming it as the seventh known case of an OH-maser-emitting PN. This is only the second known PN showing 1720 MHz OH masers after K 3-35 and the only evolved stellar object with 1720 MHz OH masers as the strongest transition. This PN is one of a group of very young PNe. The 1612 MHz and 1667 MHz masers are at a similar velocity to the 22 GHz H2O masers, whereas the 1720 MHz masers show a variable spectrum, with several components spread over a higher velocity range (up to 36 km s-1). We also detect Zeeman splitting in the 1720 MHz transition at two epochs (with field strengths of ˜2 to ˜10 mG), which suggests the OH emission at 1720 MHz is formed in a magnetized environment. These 1720 MHz OH masers may trace short-lived equatorial ejections during the formation of the PN.

  9. SUBMILLIMETER H{sub 2}O MASER IN CIRCINUS GALAXY-A NEW PROBE FOR THE CIRCUMNUCLEAR REGION OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Hagiwara, Yoshiaki; Miyoshi, Makoto; Doi, Akihiro; Horiuchi, Shinji

    2013-05-10

    We present the first detection of extragalactic submillimeter H{sub 2}O maser in the 321 GHz transition toward the center of Circinus galaxy, the nearby Type 2 Seyfert using the Atacama Large Millimeter/Submillimeter Array. We find that Doppler features of the detected 321 GHz H{sub 2}O maser straddle the systemic velocity of the galaxy as seen in the spectrum of the known 22 GHz H{sub 2}O maser in the galaxy. By comparing the velocities of the maser features in both transitions, it can be deduced that the 321 GHz maser occurs in a region similar to that of the 22 GHz maser, where the sub-parsec-scale distribution of the 22 GHz maser was revealed by earlier very long baseline interferometry observations. The detected maser features remain unresolved at the synthesized beam of {approx}0.''66 ({approx}15 pc) and coincide with the 321 GHz continuum peak within small uncertainties. We also present a tentative detection of the highest velocity feature (redshifts up to {approx}635 km s{sup -1}) in the galaxy. If this high-velocity feature arises from a Keplerian rotating disk well established in this galaxy, it is located at a radius of {approx}0.018 pc ({approx}1.2 Multiplication-Sign 10{sup 5} Schwarzschild radii), which might probe molecular material closest to the central engine.

  10. Hydrogen-Maser/Ruby-Maser/Quartz-Crystal Oscillator

    NASA Technical Reports Server (NTRS)

    Wang, Rabi T.; Dick, G. John

    1994-01-01

    Highly stable oscillator suitable for use as 100-MHz frequency standard consists of 100-MHz hydrogen maser combined with double-phase-locked-loop receiver. Generates 100-MHz signal with reduced noise. Contains 100-MHz voltage-controlled quartz-crystal oscillator (VCO) locked in phase to superconducting-cavity maser oscillator (SCMO). SCMO, locks in phase to hydrogen maser, phase-locking receiver and its SCMO/ VCO combination to hydrogen maser. Aspects of SCMO described in previous reports, including "Performance of Superconducting-Cavity Maser" (NPO-18175), NASA Tech Briefs, Vol. 15, No. 6. Performances of component oscillators complement each other.

  11. Block 2A traveling-wave maser

    NASA Technical Reports Server (NTRS)

    Trowbridge, D. L.

    1986-01-01

    Two 8.4GHz low-noise traveling-wave masers (TWMS) with effective input noise temperatures of 3.6 to 3.9 K and bandwidth in excess of 100 MHz have been supplied to the Deep Space Network. These TWMs are used on the 64-meter antennas at Deep Space Stations 14 and 43 to meet the requirements of the Voyager Uranus encounter. The TWMs have improved isolator assemblies and new interstage matching configurations to reduce gain/bandwidth ripple. They are equipped with followup Field Effect Transistor Amplifiers as part of the design to meet the 100-MHz bandwidth requirements of very long baseline interferometry.

  12. Water Maser Emission Around Low/Intermediate Mass Evolved Stars

    NASA Astrophysics Data System (ADS)

    Leal-Ferreira, M. L.; Vlemmings, W. H. T.; Diamond, P. J.; Kemball, A.; Amiri, N.; Desmurs, J.-F.

    2012-07-01

    We present results of Very Long Baseline Array (VLBA) polarimetric 22 GHz H2O maser observations of a number of low/intermediate mass evolved stars. We observed 3 Miras (Ap Lyn, IK Tau and IRC+60370), 1 semi-regular variable (RT Vir) and 1 pPN (OH231.8+4.2). Circular polarization is detected in the H2O maser region of OH231.8+4.2 and we infer a magnetic field of |B||| = ~45 mG. This implies an extrapolated magnetic field of ~2.5 G on the surface of the central star. The preliminary results on RT Vir and IRC+60370 also indicate the first detection of weak H2O maser linear polarization.

  13. INTERSTELLAR H{sub 2}O MASERS FROM J SHOCKS

    SciTech Connect

    Hollenbach, David; Elitzur, Moshe; McKee, Christopher F.

    2013-08-10

    We present a model in which the 22 GHz H{sub 2}O masers observed in star-forming regions occur behind shocks propagating in dense regions (preshock density n{sub 0} {approx} 10{sup 6}-10{sup 8} cm{sup -3}). We focus on high-velocity (v{sub s} {approx}> 30 km s{sup -1}) dissociative J shocks in which the heat of H{sub 2} re-formation maintains a large column of {approx}300-400 K gas; at these temperatures the chemistry drives a considerable fraction of the oxygen not in CO to form H{sub 2}O. The H{sub 2}O column densities, the hydrogen densities, and the warm temperatures produced by these shocks are sufficiently high to enable powerful maser action. The observed brightness temperatures (generally {approx} 10{sup 11}-10{sup 14} K) are the result of coherent velocity regions that have dimensions in the shock plane that are 10-100 times the shock thickness of {approx}10{sup 13} cm. The masers are therefore beamed toward the observer, who typically views the shock ''edge-on'', or perpendicular to the shock velocity; the brightest masers are then observed with the lowest line-of-sight velocities with respect to the ambient gas. We present numerical and analytic studies of the dependence of the maser inversion, the resultant brightness temperature, the maser spot size and shape, the isotropic luminosity, and the maser region magnetic field on the shock parameters and the coherence path length; the overall result is that in galactic H{sub 2}O 22 GHz masers, these observed parameters can be produced in J shocks with n{sub 0} {approx} 10{sup 6}-10{sup 8} cm{sup -3} and v{sub s} {approx} 30-200 km s{sup -1}. A number of key observables such as maser shape, brightness temperature, and global isotropic luminosity depend only on the particle flux into the shock, j = n{sub 0} v{sub s} , rather than on n{sub 0} and v{sub s} separately.

  14. SiO and H2O maser emission in OH/IR objects and late-type variable stars

    NASA Technical Reports Server (NTRS)

    Nyman, L.-A.; Johansson, L. E. B.; Booth, R. S.

    1986-01-01

    A four-year search for 86-GHz SiO and H2O maser emission towards about 20 unidentified OH/IR objects and about 35 optically identified variable stars has yielded information on the temporal variations of many of these sources. The SiO maser emission is noted to behave differently in OH/IR objects as compared with Mira variables. An attempt is made to explain the appearance of strong masers in both vibrational states solely at the 43 GHz transition, under the assumption that an intrinsically weak pump mechanism generates weak (v=1, J=2-1) emission.

  15. Maser pulse emission mechanisms

    NASA Astrophysics Data System (ADS)

    Melrose, D. B.

    Polar cap models of coherent radio emission mechanisms in pulsars are reviewed, noting deficiencies present in models with curvature emission due to bunches and the possibilities of descriptions based on maser processes. The lack of a no-velocity dispersion theory of bunching radiation is noted to make assumptions based on uniform particle velocities questionable. Streaming instability-produced bunching is also subject to inaccuracy when the bunching occurs at distances of over one stellar radius, or when the growth velocity is insufficient. Conditions are defined for successful bunching through particle trapping by waves, and it is mentioned that models with this mechanism offer predictions which do not match data from observations. Similar objections are found with self-bunching, plasma emission, and klystron mechanisms. Maser-emission models are concluded to avoid the problems associated with differences between observed and predicted dispersion delays found in other types of models.

  16. Maser science at Tidbinbilla

    NASA Astrophysics Data System (ADS)

    Horiuchi, Shinji; Lovell, Jim

    2007-03-01

    The 70 m antenna at Canberra Deep Space Communication Complex (Tidbinbilla) is the largest and most sensitive dish in the southern hemisphere, working at 1, 3, 13 and 18 cm, and as such is in high demand from astronomers both in Australia and overseas. In this paper we present the current status of the single dish spectroscopy system and highlight some recent results in maser science.

  17. H2O maser survey of IRAS sources at high galactic latitude

    NASA Astrophysics Data System (ADS)

    Caselli, P.; Codella, C.; Palumbo, G. G. C.; Pareschi, G.

    A high galactic latitude sample of 175 IRAS sources located within the core of molecular clouds has been searched for H2O maser emission with the Medicina 32 m dish operated at 22 GHz. Seventeen percent of the sample previously searched by other authors contained only four detections. The search did not produce any new water maser emitter, while the previously known maser were seen again. The low value of 2 percent overall detection rate can be explained in terms of Galactic distribution of massive cores.

  18. H2O masers from low and intermediate luminosity young stellar objects: H2O masers and YSOs

    NASA Astrophysics Data System (ADS)

    Persi, P.; Palagi, F.; Felli, M.

    1994-11-01

    We have used the Medicina 32-m radiotelescope to search for H2O 22.2 GHz maser emission from a sample of 68 red peculiar nebulosities associated with low luminosity (LIR less than 103 solar luminosity)) and intermediate luminosity (LIR approximately 104 solar luminosity) Young Stellar Objects (YSOs). H2O maser emission was detected in 9 sources, with a new detection in IRAS 18265+0028. Comparison with other samples indicates that YSOs have a higher probability of hosting an H2O maser, when they are associated with red peculiar nebulosities. Seven of the detected sources are associated with molecular outflows, which confirms that these two phenomena are strictly correlated. The maser sources associated with the Class I YSOs (IRAS 03225+3034, and IRAS 03245+3002, in the dark clouds L1448 and L1455 respectively) appear overluminous with respect to their IR luminosity. The maser emission shows a remarkable variability on time scales of months and years, which tends to be larger for lower luminosity sources. This is indicative of unsaturated emission in low luminosity sources.

  19. Submillimeter Array Imaging of the Maser Emission from the H30α Radio Recombination Line in MWC 349A

    NASA Astrophysics Data System (ADS)

    Weintroub, Jonathan; Moran, James M.; Wilner, David J.; Young, Ken; Rao, Ramprasad; Shinnaga, Hiroko

    2008-04-01

    We used the Submillimeter Array to map the angular distribution of the H30α recombination line (231.9 GHz) in the circumstellar region of the peculiar star MWC 349A. The resolution was 1.2'', but because of high signal-to-noise ratio we measured the positions of all maser components to accuracies better than 0.01'', at a velocity resolution of 1 km s-1. The two strongest maser components (called high-velocity components) at velocities near -14 and 32 km s-1 are separated by 0.048'' +/- 0.001'' (60 AU) along a position angle of 102° +/- 1°. The distribution of maser emission at velocities between and beyond these two strongest components were also provided. The continuum emission lies at the center of the maser distribution to within 10 mas. The masers appear to trace a nearly edge-on rotating disk structure, reminiscent of the water masers in Keplerian rotation in the nuclear accretion disk of the galaxy NGC 4258. However, the maser components in MWC 349A do not follow a simple Keplerian kinematic prescription with v ~ r-1/2, but have a larger power-law index. We explore the possibility that the high-velocity masers trace spiral density or shock waves. We also emphasize caution in the interpretation of relative centroid maser positions where the maser is not clearly resolved in position or velocity, and we present simulations that illustrate the range of applicability of the centroiding method.

  20. Free electron maser experiments in the low-frequency limit

    SciTech Connect

    Drori, R.; Jerby, E.; Shahadi, A.

    1995-12-31

    Table-top free-electron maser (FEM) experiments operating in the low-frequency (< 1 GHz) low-energy ({approximately} 1 keV) limit are reported. These FEM devices employ parallel-stripline non-dispersive waveguides (which support TEM-modes), and planar folded-foil wigglers. Thermionic cathodes and carbon-fiber cold-cathodes are used in these experiments. Results of oscillator and amplifier experiments are presented and compared with theory.

  1. VERY LARGE ARRAY DETECTION OF THE 36 GHz ZEEMAN EFFECT IN DR21W REVISITED

    SciTech Connect

    Momjian, Emmanuel; Sjouwerman, Lorant O.; Fish, Vincent L.

    2012-09-20

    We report on the observation of the 36 GHz methanol maser line in the star-forming region DR21W to accurately measure the Zeeman effect. The Zeeman signature reported by Fish et al. became suspicious after an instrumental effect was discovered in the early days of the commissioning of the Very Large Array Wide-band Digital Architecture correlator. We conclude that the previously reported magnetic field strength of 58 mG (1.7 Hz mG{sup -1}/z) is instrumental in nature and thus incorrect. With the improved performance of the array, we now deduce a 3{sigma} limit of -4.7 to +0.4 mG (1.7 Hz mG{sup -1}/z) for the line-of-sight component of the magnetic field strength in DR21W.

  2. Passive maser development at NRL

    NASA Technical Reports Server (NTRS)

    White, J. D.; Frank, A.; Folen, V.

    1981-01-01

    The application of passive hydrogen masers to satellites was investigated. The NRL maser is of compact design suitable for the space environment. It is based on a dielectrically loaded sapphire cavity and uses a computer optimized set of four shields. The servo design is a phase sensitive method which directly measures the phase dispersion of the interrogating signal as it passes through the cavity.

  3. Exploring the engines of molecular outflows. Radio continuum and H_2_O maser observations.

    NASA Astrophysics Data System (ADS)

    Tofani, G.; Felli, M.; Taylor, G. B.; Hunter, T. R.

    1995-09-01

    We present A-configuration VLA observations of the 22GHz H_2_O maser line and 8.4GHz continuum emission of 22 selected CO bipolar outflows associated with water masers. These observations allow us to study the region within 10^4^AU of the engine powering the outflow. The positions of the maser spots are compared with those of ultra-compact (UC) continuum sources found in our observations, with IRAS data and with data from the literature on the molecular outflows. Weak unresolved continuum sources are found in several cases associated with the maser. Most probably they represent the ionized envelope surrounding the young stellar object (YSO) which powers the maser and the outflow. These weak radio continuum sources are not necessarily associated with the IRAS sources, which are more representative of the global emission from the star forming region. A comparison of the velocity pattern of the CO outflow with those of the maser spots detected with the VLA is also made. Asymmetries in the H_2_O velocities are found on opposite sides of the YSO, suggesting that the outflow acceleration begins from the YSO itself. In a few cases we find evidence for two outflows in different evolutionary stages. The H_2_O masers in these sources are always found at the centre of the younger outflow. The degree of variability of each maser is derived from single dish observations obtained with the Medicina radiotelescope before and after the VLA observations. Velocity drifts of some features are interpreted as acceleration of the maser.

  4. A multiple system of high-mass YSOs surrounded by disks in NGC 7538 IRS1 . Gas dynamics on scales of 10-700 AU from CH3OH maser and NH3 thermal lines

    NASA Astrophysics Data System (ADS)

    Moscadelli, L.; Goddi, C.

    2014-06-01

    Context. It has been claimed that NGC 7538 IRS1 is a high-mass young stellar object (YSO) with 30 M⊙, surrounded by a rotating Keplerian disk, probed by a linear distribution of methanol masers. The YSO is also powering a strong compact Hii region or ionized wind, and is driving at least one molecular outflow. The axis orientations of the different structures (ionized gas, outflow, and disk) are, however, misaligned, which has led to the different competing models proposed to explain individual structures. Aims: We investigate the 3D kinematics and dynamics of circumstellar gas with very high linear resolution, from tens to 1500 AU, with the ultimate goal of building a comprehensive dynamical model for what is considered the best high-mass accretion disk candidate around an O-type young star in the northern hemisphere. Methods: We used high-angular resolution observations of 6.7 GHz CH3OH masers with the EVN, NH3 inversion lines with the JVLA B-Array, and radio continuum with the VLA A-Array. In particular, we employed four different observing epochs of EVN data at 6.7 GHz, spanning almost eight years, which enabled us to measure line-of-sight (l.o.s.) accelerations and proper motions of CH3OH masers, besides l.o.s. velocities and positions (as done in previous works). In addition, we imaged highly excited NH3 inversion lines, from (6,6) to (13,13), which enabled us to probe the hottest molecular gas very close to the exciting source(s). Results: We confirm previous results that five 6.7 GHz maser clusters (labeled from "A" to "E") are distributed over a region extended N-S across ≈1500 AU, and are associated with three components of the radio continuum emission. We propose that these maser clusters identify three individual high-mass YSOs in NGC 7538 IRS1, named IRS1a (associated with clusters "B" and "C"), IRS1b (associated with cluster "A"), and IRS1c (associated with cluster "E"). We find that the 6.7 GHz masers distribute along a line, with a regular

  5. Formaldehyde Masers: Exclusive Tracers of High-mass Star Formation

    NASA Astrophysics Data System (ADS)

    Araya, E. D.; Olmi, L.; Morales Ortiz, J.; Brown, J. E.; Hofner, P.; Kurtz, S.; Linz, H.; Creech-Eakman, M. J.

    2015-11-01

    The detection of four formaldehyde (H2CO) maser regions toward young high-mass stellar objects in the last decade, in addition to the three previously known regions, calls for an investigation of whether H2CO masers are an exclusive tracer of young high-mass stellar objects. We report the first survey specifically focused on the search for 6 cm H2CO masers toward non high-mass star-forming regions (non HMSFRs). The observations were conducted with the 305 m Arecibo Telescope toward 25 low-mass star-forming regions, 15 planetary nebulae and post-AGB stars, and 31 late-type stars. We detected no H2CO emission in our sample of non HMSFRs. To check for the association between high-mass star formation and H2CO masers, we also conducted a survey toward 22 high-mass star-forming regions from a Hi-GAL (Herschel infrared Galactic Plane Survey) sample known to harbor 6.7 GHz CH3OH masers. We detected a new 6 cm H2CO emission line in G32.74-0.07. This work provides further evidence that supports an exclusive association between H2CO masers and young regions of high-mass star formation. Furthermore, we detected H2CO absorption toward all Hi-GAL sources, and toward 24 low-mass star-forming regions. We also conducted a simultaneous survey for OH (4660, 4750, 4765 MHz), H110α (4874 MHz), HCOOH (4916 MHz), CH3OH (5005 MHz), and CH2NH (5289 MHz) toward 68 of the sources in our sample of non HMSFRs. With the exception of the detection of a 4765 MHz OH line toward a pre-planetary nebula (IRAS 04395+3601), we detected no other spectral line to an upper limit of 15 mJy for most sources.

  6. W-band free-electron masers

    SciTech Connect

    Freund, H. P.; Jackson, R. H.; Danly, B. G.; Levush, B.

    1999-05-07

    Theoretical analyses of high power W-band (i.e., {approx_equal}94 GHz) free-electron maser amplifiers are presented for a helical wiggler/cylindrical waveguide configuration using the three-dimensional slow-time-scale ARACHNE simulation code [9]. The geometry treated by ARACHNE is that of an electron beam propagating through the cylindrical waveguide subject to a helical wiggler and an axial guide magnetic field. Two configurations are discussed. The first is the case of a reversed-guide field geometry where the guide field is oriented antiparallel to the helicity of the wiggler field. Using a 330 kV/20 A electron beam, efficiencies of the order of 7% are calculated with a bandwidth (FWHM) of 5 GHz. The second example employs a strong guide field of 20 kG oriented parallel to the helicity of the wiggler. Here, efficiencies of greater than 8% are possible with a FWHM bandwidth of 4.5 GHz using a 300 kV/20 A electron beam. A normalized emittance of 95 mm-mrad is assumed in both cases, and no beam losses are observed for either case. Both cases assume interaction with the fundamental TE{sub 11} mode, which has acceptably low losses in the W-band.

  7. Water maser emission in the Saturnian system

    NASA Astrophysics Data System (ADS)

    Horiuchi, Shinji; Cimo, Giuseppe; Gurvits, Leonid; Pogrebenko, Sergei; Molera Calves, Guifré

    2010-10-01

    Prompted by the recent discovery of a water vapour plume of Enceladus by the Cassini spacecraft, our team started an observational programme to search for possible 22 GHz water vapour maser emission associated with different objects in the Kronian system. The observations have been conducted so far with the 32 m Medicina radio telescope (INAF-IRA, Italy) and the 14 m Metsahovi radio telescope (Aalto University, MRO, Finland). During the 2006-2008 campaigns, more than 300 hours of data have been analysed, and initial results including maser detections up to 7.0 sigma level have been presented. The detections attracted considerable interest and attempts to confirm them and investigate the phenomenon in depth. No confirmations have been published so far. In order to provide critical verification of these detections and study the details of masing conditions efficiently, we request a total of 20 hours on the Tidbinbilla 70 m telescope (DSS43) to observe Saturn and its moons during several, non-consecutive days. Due to natural changes of the planetary target positions, targets' coordinates will be provided after the antenna time is allocated.

  8. HIGH-RESOLUTION VLBA OBSERVATIONS OF THREE 7 mm SiO MASERS TOWARD VX Sgr AT FIVE EPOCHS

    SciTech Connect

    Su, J. B.; Shen, Z.-Q.; Chen, X.; Jiang, D. R.; Yi Jiyune; Yun, Y. J.

    2012-07-20

    VX Sgr is a red supergiant at an adopted distance of 1.6 kpc with intense 43 GHz SiO maser emission. In this paper, we present the high-resolution very long baseline interferometry (VLBI) observations of SiO masers toward VX Sgr at five epochs. We used the Very Long Baseline Array to map the J = 1{yields}0 (v = 1, 2) {sup 28}SiO masers and confirmed a ring-like structure. In the first two epochs, the v = 1 masers form a ring, but v = 2 maser spots residing only in the southern and northern regions do not form a complete ring. In the third epoch, the two masers are distributed in a ring structure and the v = 2 masers are a bit closer to the central star. In the last two epochs, many new maser spots appear and overlap each other. These overlapping maser spots can be related to the shock waves and reflect the collisional pumping. We compare the observations with the pumping models and speculate that the real pumping mechanism may be complex in VX Sgr and vary with time. The J = 1{yields}0 (v = 0) {sup 29}SiO line emission is also detected, but is too weak to produce any VLBI map.

  9. New H2O masers in Seyfert and FIR bright galaxies. III. The southern sample

    NASA Astrophysics Data System (ADS)

    Surcis, G.; Tarchi, A.; Henkel, C.; Ott, J.; Lovell, J.; Castangia, P.

    2009-08-01

    Context: A relationship between the water maser detection rate and far infrared (FIR) flux densities was established as a result of two 22 GHz maser surveys in a complete sample of galaxies ({Dec>-30°) with {100 μ m} flux densities of >50 Jy and >30 Jy. Aims: We attempted to discover new maser sources and investigate the galaxies hosting the maser spots by extending previous surveys to southern galaxies with particular emphasis on the study of their nuclear regions. Methods: A sample of 12 galaxies with {Dec<-30° and S100 μ m>50 Jy was observed with the 70-m telescope of the Canberra deep space communication complex (CDSCC) at Tidbinbilla (Australia) in a search for water maser emission. The average 3σ noise level of the survey was 15 mJy for a {0.42 km s-1} channel, corresponding to a detection threshold of ˜ 0.1 L⊙ for the isotropic maser luminosity at a distance of 25 Mpc. Results: Two new detections are reported: a kilomaser with an isotropic luminosity L{H2O}˜5 L⊙ in NGC 3620 and a maser with about twice this luminosity in the merger system NGC 3256. The detections have been followed-up by continuum and spectral line interferometric observations with the Australia Telescope Compact Array (ATCA). In NGC 3256, a fraction (about a third) of the maser emission originates in two hot spots associated with star formation activity, which are offset from the galactic nuclei of the system. The remaining emission may originate in weaker centres of maser activity distributed over the central 50''. For NGC 3620, the water maser is coincident with the nuclear region of the galaxy. Our continuum observations indicate that the nature of the nuclear emission is probably linked to particularly intense star formation. Including the historical detection in NGC 4945, the water maser detection rate in the southern sample is 15% (3/20), consistent with the northern sample. The high rate of maser detections in the complete all-sky FIR sample (23%, 15/65) confirms the

  10. Water vapour masers in long-period variable stars. I. RX Bootis and SV Pegasi

    NASA Astrophysics Data System (ADS)

    Winnberg, A.; Engels, D.; Brand, J.; Baldacci, L.; Walmsley, C. M.

    2008-05-01

    Context: Water vapour maser emission from late-type stars characterises them as asymptotic-giant-branch stars with oxygen-rich chemistry that are losing mass at a substantial rate. Further conclusions on the properties of the stars, however, are hampered by the strong variability of the emission. Aims: We wish to understand the reasons for the strong variability of H2O masers in circumstellar shells of late-type stars. In this paper we study RX Bootis and SV Pegasi as representatives of semiregular variable stars (SRVs). Methods: We monitored RX Boo and SV Peg in the 22-GHz maser line of water vapour with single-dish telescopes. The monitoring period covered two decades for RX Boo (1987-2007) and 12 years for SV Peg (1990-1995, 2000-2007). In addition, maps were obtained of RX Boo with the Very Large Array over several years. Results: We find that most of the emission in the circumstellar shell of RX Boo is located in an incomplete ring with an inner radius of 91 mas (15 AU). A velocity gradient is found in a NW-SE direction. The maser region can be modelled as a shell with a thickness of 22 AU, which is only partially filled. The gas crossing time is 16.5 years. The ring-like structure and the velocity gradient remained stable for at least 11 years, while the maser line profiles varied strongly. This suggests that the spatial asymmetry is not accidental, so that either the mass loss process or the maser excitation conditions in RX Boo are not spherically symmetric. The strong variability of the maser spectral features is mainly due to incoherent intensity fluctuations of maser emission spots, which have lifetimes of the order of 1 year. We found no correlation between the optical and the maser variability in either star. The variability properties of the SV Peg masers do not differ substantially from those of RX Boo. There were fewer spectral features present, and the range of variations was narrower. The maser was active on the >10-Jy level only 1990-1992 and

  11. Water maser emission from X-ray-heated circumnuclear gas in active galaxies

    NASA Technical Reports Server (NTRS)

    Neufeld, David A.; Maloney, Philip R.; Conger, Sarah

    1994-01-01

    We have modeled the physical and chemical conditions present within dense circumnuclear gas that is irradiated by X-rays from an active galactic nucleus. Over a wide range of X-ray fluxes and gas pressures, the effects of X-ray heating give rise to a molecular layer at temperatures of 400-1000 K within which the water abundance is large. The physical conditions within this molecular layer naturally give rise to collisionally pumped maser emission in the 6(sub 16) - 5(sub 23) 22 GHz transition of ortho-water, with predicted maser luminosities of 10(exp 2 +/- 0.5) solar luminosity per sq. pc of illuminated area. Given plausible assumptions about the geometry of the source and about the degree to which the maser emission is anisotropic, such surface luminosities are sufficient to explain the large apparent luminosities observed in water maser sources that are associated with active galactic nuclei.

  12. The centimeter transitions of E-type methanol

    NASA Astrophysics Data System (ADS)

    Menten, K. M.; Walmsley, C. M.; Henkel, C.; Wilson, T. L.

    1986-03-01

    The authors have used the 100-m telescope at a frequency of 25 GHz to observe the 22→21, 32→31, 42→41, 52→51, 62→61, and 92→91 transitions of E-type methanol towards a selection of galactic molecular-line sources. They have found several sources of strong narrow line emission in these transitions which are believed to be masers similar to those known in the Orion-KL region. The authors also observe absorption in these lines towards W3(OH) and NGC 7538 showing that the transitions are not necessarily inverted under interstellar conditions. Finally, most strong molecular line sources show emission in these transitions with a profile similar to that known from observations of other molecules. The rotation temperatures estimated for such emission features range between 20 and 100K. The authors conclude that they are observing hot (100K) compact (1017cm) clumps immersed in the general molecular cloud material, which is preferentially sampled, for example, in surveys of the J = 2→1 methanol transitions.

  13. A study of the region of massive star formation L379IRS1 in radio lines of methanol and other molecules

    NASA Astrophysics Data System (ADS)

    Kalenskii, S. V.; Shchurov, M. A.

    2016-04-01

    The results of spectral observations of the region of massive star formation L379IRS1 (IRAS18265-1517) are presented. The observations were carried out with the 30-m Pico Veleta radio telescope (Spain) at seven frequencies in the 1-mm, 2-mm, and 3-mm wavelength bands. Lines of 24 molecules were detected, from simple diatomic or triatomic species to complex eight- or nine-atom compounds such as CH3OCHO or CH3OCH3. Rotation diagrams constructed from methanol andmethyl cyanide lines were used to determine the temperature of the quiescent gas in this region, which is about 40-50 K. In addition to this warm gas, there is a hot component that is revealed through high-energy lines of methanol and methyl cyanide, molecular lines arising in hot regions, and the presence of H2O masers and Class II methanol masers at 6.7 GHz, which are also related to hot gas. One of the hot regions is probably a compact hot core, which is located near the southern submillimeter peak and is related to a group of methanol masers at 6.7 GHz. High-excitation lines at other positions may be associated with other hot cores or hot post-shock gas in the lobes of bipolar outflows. The rotation diagrams can be use to determine the column densities and abundances of methanol (10-9) and methyl cyanide (about 10-11) in the quiescent gas. The column densities of A- and E-methanol in L379IRS1 are essentually the same. The column densities of other observedmolecules were calculated assuming that the ratios of the molecular level abundances correspond to a temperature of 40 K. The molecular composition of the quiescent gas is close to that in another region of massive star formation, DR21(OH). The only appreciable difference is that the column density of SO2 in L379IRS1 is at least a factor of 20 lower than the value in DR21(OH). The SO2/CS and SO2/OCS abundance ratios, which can be used as chemical clocks, are lower in L379IRS1 than in DR21(OH), suggesting that L379IRS1 is probably younger than DR21(OH).

  14. Evaluation of modern hydrogen masers

    NASA Technical Reports Server (NTRS)

    Kirk, A.; Kuhnle, P.; Sydnor, R. L.

    1983-01-01

    The masers were tested for environmental sensitivities (magnetic field, temperature, barometric pressure) and long-term aging. Allan variance runs of 72 days were made in order to attain averaging times from several seconds to 1 million seconds. Auto- and cross-correlation techniques were used to determine the effects of uncontrolled parameters such as humidity. Three-cornered-hat and other data reduction techniques were used to determine the characteristics of the individual masers.

  15. A dual-cavity ruby maser for the Ka-band link experiment

    NASA Technical Reports Server (NTRS)

    Shell, J.; Quinn, R. B.

    1994-01-01

    A 33.68-GHz dual-cavity ruby maser was built to support the Ka-Band Link Experiment (KABLE) conducted with the Mars Observer spacecraft. It has 25 dB of net gain and a 3-dB bandwidth of 85 MHz. Its noise temperature in reference to the cooled feedhorn aperture is 5 K.

  16. Class I methanol megamasers: a potential probe of starburst activity and feedback in active galaxies

    NASA Astrophysics Data System (ADS)

    Chen, X.; Ellingsen, S. P.; Zhang, J.-S.; Wang, J.-Z.; Shen, Z.-Q.; Wu, Q.-W.; Wu, Z.-Z.

    2016-06-01

    Previous observations have shown that the distribution of 36.2-GHz class I methanol megamaser (MM) emission in Arp 220 is highly correlated with the diffuse X-rays. On this basis it was suggested that methanol MM may be produced either by the effects of galactic-outflow-driven shocks and/or cosmic rays. Here we report the results of a single-dish survey undertaken with the Greenbank Telescope (GBT) to improve our understanding of the pumping conditions of extragalactic class I methanol masers and their relationship to starburst and feedback processes within the host galaxies, towards a sample which includes 16 galaxies which show both extended soft X-ray emission, and either OH or H2O MM emission. Large baseline ripples in the GBT spectra limited our results to tentative detections towards 11 of the target galaxies. Analysis of these tentative detections shows that there are significant correlations between the methanol intensity and the host-galaxy infrared, radio and OH MM emission, but no correlation with the X-ray and H2O MM emission. Some sources show methanol emission significantly offset from the systemic velocity of the galaxy (by up to 1000 km s-1) and we propose that these are associated with galactic-scale outflows from active galactic nuclei (AGNs) feedback. The combined observational properties suggest that class I methanol MMs are related to significant starburst and molecular outflow activity and hence may provide a potential probe of AGN feedback and starburst processes in the host galaxies.

  17. WIDESPREAD METHANOL EMISSION FROM THE GALACTIC CENTER: THE ROLE OF COSMIC RAYS

    SciTech Connect

    Yusef-Zadeh, F.; Royster, M.; Cotton, W.; Viti, S.; Wardle, M.

    2013-02-20

    We report the discovery of a widespread population of collisionally excited methanol J = 4{sub -1} to 3{sub 0} E sources at 36.2 GHz from the inner 66' Multiplication-Sign 18' (160 Multiplication-Sign 43 pc) of the Galactic center. This spectral feature was imaged with a spectral resolution of 16.6 km s{sup -1} taken from 41 channels of a Very Large Array continuum survey of the Galactic center region. The revelation of 356 methanol sources, most of which are maser candidates, suggests a large abundance of methanol in the gas phase in the Galactic center region. There is also spatial and kinematic correlation between SiO (2-1) and CH{sub 3}OH emission from four Galactic center clouds: the +50 and +20 km s{sup -1} clouds and G0.13-0.13 and G0.25 + 0.01. The enhanced abundance of methanol is accounted for in terms of induced photodesorption by cosmic rays as they travel through a molecular core, collide, dissociate, ionize, and excite Lyman Werner transitions of H{sub 2}. A time-dependent chemical model in which cosmic rays drive the chemistry of the gas predicts CH{sub 3}OH abundance of 10{sup -8} to 10{sup -7} on a chemical timescale of 5 Multiplication-Sign 10{sup 4} to 5 Multiplication-Sign 10{sup 5} years. The average methanol abundance produced by the release of methanol from grain surfaces is consistent with the available data.

  18. Computational and Observational Studies of Interstellar Thioformaldehyde Masers

    NASA Astrophysics Data System (ADS)

    Simpson, Lisa; Hoffman, I. M.

    2013-06-01

    Interstellar spectroscopy of thioformaldehyde (H2CS) holds considerable promise because of the close relationship between the H2CS molecule and the well-studied formaldehyde (H2CO) molecule. In particular, the well-known J(Ka,Kc) = 1(1,0) to 1(1,1) transition of H2CO at 6 cm (4.8 GHz) has an analogous H2CS transition at 1046 MHz. However, the 1046-MHz line of H2CS has never been detected astronomically. We present here a summary of: (1) a computational investigation of H2CS level populations related to known H2CO 6-cm masers, and (2) an observational campaign of four isotopologues of H2CS. Maser emission from H2CO has been observed at 6 cm for which Boland and de Jong (1981) have developed a pump model. We have extended this model to H2CS and we present preliminary calculations for a 1046-MHz maser. We intend to develop a quantitative tool for interpreting H2CS observations toward Galactic and extragalactic locations of H2CO maser emission by constructing a radiative-transfer maser model for H2CS. Thioformaldehyde has been detected in a few Galactic sources via J>1 transitions. However, interpretation of these results has two outstanding problems: the H2CS/H2CO abundances do not agree with known sulfur-to-oxygen ratios nor do the J>1 populations have the expected Boltzmann relationship to the J=1 states. A detection of the 1046-MHz transition of H2CS with J=1 would alleviate many of the ambiguities in the interpretation of existing observational results. We describe our forthcoming experiment to search in a Galactic star-forming region for thermal and nonthermal emission and absorption from four thioformaldehyde isotopologues: H2(12C)(32S), H2(13C)(32S), H2(12C)(34S), and D2(12C)(32S). Taken together, both parts of this research effort will provide valuable and novel constraints on H2CS and H2CO. New observations of H2CS isotopologues will yield new measurements of deuterium-to-hydrogen and sulfur-to-oxygen ratios in star-forming environments. Also, the application

  19. A commercial hydrogen maser: Progress report

    NASA Technical Reports Server (NTRS)

    Dials, M. A.; Wert, L.

    1983-01-01

    The design of the new small passive hydrogen maser prototype and some anticipated design changes between the version reported and the commercial versions are discussed. Specifications of the commercial hydrogen maser and performance data of the prototype are given.

  20. A Survey for Water Maser Emission toward Planetary Nebulae: New Detection in IRAS 17347-3139

    NASA Astrophysics Data System (ADS)

    de Gregorio-Monsalvo, Itziar; Gómez, Yolanda; Anglada, Guillem; Cesaroni, Riccardo; Miranda, Luis F.; Gómez, José F.; Torrelles, José M.

    2004-02-01

    We report on a water maser survey toward a sample of 27 planetary nebulae (PNe) using the Robledo de Chavela and Medicina single-dish antennas, as well as the Very Large Array (VLA). Two detections have been obtained: the already known water maser emission in K3-35, and a new cluster of masers in IRAS 17347-3139. This low rate of detections is compatible with the short lifetime of water molecules in PNe (~100 yr). The water maser cluster at IRAS 17347-3139 are distributed on a ellipse of size ~=0.2"×0.1", spatially associated with compact 1.3 cm continuum emission (simultaneously observed with the VLA). From archive VLA continuum data at 4.9, 8.4, and 14.9 GHz, a spectral index α=0.76+/-0.03 (Sν~να) is derived for this radio source, which is consistent with either a partially optically thick ionized region or an ionized wind. However, the latter scenario can be ruled out by mass-loss considerations, thus indicating that this source is probably a young PN. The spatial distribution and the radial velocities of the water masers are suggestive of a rotating and expanding maser ring, tracing the innermost regions of a torus formed at the end of the asymptotic giant branch phase. Given that the 1.3 cm continuum emission peak is located near one of the tips of the major axis of the ellipse of masers, we speculate on a possible binary nature of IRAS 17347-3139, where the radio continuum emission could belong to one of the components and the water masers would be associated with a companion.

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

    NASA Astrophysics Data System (ADS)

    Gray, M. D.; Baudry, A.; Richards, A. M. S.; Humphreys, E. M. L.; Sobolev, A. M.; Yates, J. A.

    2016-02-01

    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 H2O, 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. 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 multitransition water maser observations to constrain physical conditions down to the size of individual masing clouds (size of a few astronomical units).

  2. Detection of 183 GHz H2O megamaser emission towards NGC 4945

    NASA Astrophysics Data System (ADS)

    Humphreys, E. M. L.; Vlemmings, W. H. T.; Impellizzeri, C. M. V.; Galametz, M.; Olberg, M.; Conway, J. E.; Belitsky, V.; De Breuck, C.

    2016-08-01

    Aims: The aim of this work is to search Seyfert 2 galaxy NGC 4945, a well-known 22 GHz water megamaser galaxy, for H2O (mega)maser emission at 183 GHz. Methods: We used APEX SEPIA Band 5 (an ALMA Band 5 receiver on the APEX telescope) to perform the observations. Results: We detected 183 GHz H2O maser emission towards NGC 4945 with a peak flux density of ~3 Jy near the galactic systemic velocity. The emission spans a velocity range of several hundred km s-1. We estimate an isotropic luminosity of >1000 L⊙, classifying the emission as a megamaser. A comparison of the 183 GHz spectrum with that observed at 22 GHz suggests that 183 GHz emission also arises from the active galactic nucleus (AGN) central engine. If the 183 GHz emission originates from the circumnuclear disk, then we estimate that a redshifted feature at 1084 km s-1 in the spectrum should arise from a distance of 0.022 pc from the supermassive black hole (1.6 × 105 Schwarzschild radii), i.e. closer than the water maser emission previously detected at 22 GHz. This is only the second time 183 GHz maser emission has been detected towards an AGN central engine (the other galaxy being NGC 3079). It is also the strongest extragalactic millimetre/submillimetre water maser detected to date. Conclusions: Strong millimetre 183 GHz H2O maser emission has now been shown to occur in an external galaxy. For NGC 4945, we believe that the maser emission arises, or is dominated by, emission from the AGN central engine. Emission at higher velocity, i.e. for a Keplerian disk closer to the black hole, has been detected at 183 GHz compared with that for the 22 GHz megamaser. This indicates that millimetre/submillimetre H2O masers can indeed be useful for tracing out more of AGN central engine structures and dynamics than previously probed. Future observations using ALMA Band 5 should unequivocally determine the origin of the emission in this and other galaxies.

  3. Analysis of NTSC's Timekeeping Hydrogen Masers

    NASA Astrophysics Data System (ADS)

    Song, H. J.; Dong, S. W.; Wang, Z. M.; Qu, L. L.; Jing, Y. J.; Li, W.

    2015-11-01

    In this article, the hydrogen masers were tested in NTSC (National Time Service Center) keeping time laboratory. In order to avoid the impact of larger noise of caesium atomic clocks, TA(k) or UTC(k) was not used as reference, and four hydrogen masers were mutually referred and tested. The frequency stabilities of hydrogen masers were analyzed by using four-cornered hat method, and the Allan standard deviation of single hydrogen maser was estimated in different sampling time. Then according to the characteristics of hydrogen masers, by removing the trend term, excluding outliers, and smoothing data with mathematical methods to separate the Gaussian noise of hydrogen masers, and finally through the normal Kolmogorov-Smirnov test, a single hydrogen maser's Gaussian noise has been estimated.

  4. Characteristics of advanced hydrogen maser frequency standards

    NASA Technical Reports Server (NTRS)

    Peters, H. E.

    1973-01-01

    In house research and development at Goddard Space Flight Center to provide advanced frequency and time standards for the most demanding applications is concentrated primarily in field operable atomic hydrogen masers. Some of the most important goals for the new maser designs have been improved long and short term stability, elimination of the need for auto tuning, increased maser oscillation level, improved hydrogen economy, increased operational life, minimization of operator control or monitoring, improvement in magnetic isolation or sensitivity, and reduction in size and weight. New design concepts which have been incorporated in these masers to achieve these goals are described. The basic maser assemblies and control systems have recently been completed; the masers are oscillating; and operational testing has begun. Data illustrating the improvements in maser performance was available and presented.

  5. A search for water maser emission toward obscured post-AGB star and planetary nebula candidates

    NASA Astrophysics Data System (ADS)

    Gómez, J. F.; Rizzo, J. R.; Suárez, O.; Palau, A.; Miranda, L. F.; Guerrero, M. A.; Ramos-Larios, G.; Torrelles, J. M.

    2015-06-01

    Context. Water maser emission at 22 GHz is a useful probe for studying the transition between the nearly spherical mass loss in the asymptotic giant branch (AGB) to a collimated one in the post-AGB phase. In their turn, collimated jets in the post-AGB phase could determine the shape of planetary nebulae once photoionization starts. Aims: We intend to find new cases of post-AGB stars and planetary nebulae (PNe) with water maser emission, including some especially interesting and rare types: water fountains (evolved objects with high velocity collimated jets traced by water masers) or water-maser-emitting PNe. Since previous studies have shown a higher detection rate of water maser emission in evolved objects that are optically obscured, we selected a sample that contains a significant fraction of post-AGB and young PN candidate sources showing signs of strong obscuration. Methods: We searched for water maser emission in 133 evolved objects using the radio telescopes in Robledo de Chavela, Parkes, and Green Bank. Results: We detected water maser emission in 15 sources of our sample, of which seven are reported here for the first time (IRAS 13483-5905, IRAS 14249-5310, IRAS 15408-5413, IRAS 17021-3109, IRAS 17348-2906, IRAS 17393-2727, and IRAS 18361-1203). We identified three water fountain candidates: IRAS 17291-2147, with a total velocity spread of ≃96 km s-1 in its water maser components and two sources (IRAS 17021-3109 and IRAS 17348-2906) that show water maser emission whose velocity lies outside the velocity range covered by OH masers. We have also identified IRAS 17393-2727 as a possible new water-maser-emitting PN. Conclusions: The detection rate is higher in obscured objects (14%) than in those with optical counterparts (7%), which is consistent with previous results. Water maser emission seems to be common in objects that are bipolar in the near-IR (43% detection rate in such sources). The water maser spectra of water fountain candidates like IRAS 17291

  6. Cyclotron-resonance maser in a magnetic mirror.

    PubMed

    Caspi, R; Jerby, E

    1999-08-01

    A cyclotron-resonance maser (CRM) experiment is performed in a high-gradient magnetic field using a low-energy electron beam ( approximately 10 keV/1 A). The magnetic field exceeds 1.63 T, which corresponds to a 45-GHz cyclotron frequency. The CRM radiation output is observed in much lower frequencies, between 6.6 and 20 GHz only. This discrepancy is explained by the finite penetration depth of the electrons into the growing magnetic field, as in a magnetic mirror. The electrons emit radiation at the local cyclotron frequency in their reflection point from that magnetic mirror; hence, the radiation frequency depends mostly on the initial electron energy. A conceptual reflex gyrotron scheme is proposed in this paper, as a CRM analogue for the known reflex klystron. PMID:11970042

  7. A CLASS I AND CLASS II CH{sub 3}OH MASER SURVEY OF EGOs FROM THE GLIMPSE SURVEY

    SciTech Connect

    Cyganowski, C. J.; Churchwell, E.; Brogan, C. L.; Hunter, T. R.

    2009-09-10

    We present the results of a high angular resolution Very Large Array (VLA) Class I 44 GHz and Class II 6.7 GHz CH{sub 3}OH maser survey of a sample of {approx}20 massive young stellar object (MYSO) outflow candidates selected on the basis of extended 4.5 {mu}m emission in Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire images. These 4.5 {mu}m selected candidates are referred to as extended green objects (EGOs), for the common coding of this band as green in three-color Infrared Array Camera images. The detection rate of 6.7 GHz Class II CH{sub 3}OH masers, which are associated exclusively with massive YSOs, toward EGOs is {approx}>64%-nearly double the detection rate of surveys using other MYSO selection criteria. The detection rate of Class I 44 GHz CH{sub 3}OH masers, which trace molecular outflows, is {approx}89% toward EGOs associated with 6.7 GHz CH{sub 3}OH masers. The two types of CH{sub 3}OH masers exhibit different spatial distributions: 6.7 GHz masers are centrally concentrated and usually coincide with 24 {mu}m emission, while 44 GHz masers are widely distributed and generally trace diffuse 4.5 {mu}m features. We also present results of a complementary James Clerk Maxwell Telescope (JCMT) single-pointing molecular line survey of EGOs in the outflow tracers HCO{sup +}(3-2) and SiO(5-4). The HCO{sup +} line profiles and high SiO detection rate (90%) are indicative of the presence of active outflows. No 44 GHz continuum emission is detected at the 5 mJy beam{sup -1} (5{sigma}) level toward 95% of EGOs surveyed, excluding bright ultracompact H II regions as powering sources for the 4.5 {mu}m outflows. The results of our surveys constitute strong evidence that EGOs are young, massive YSOs, with active outflows, presumably powered by ongoing accretion.

  8. QUASI-PERIODIC FORMALDEHYDE MASER FLARES IN THE MASSIVE PROTOSTELLAR OBJECT IRAS 18566+0408

    SciTech Connect

    Araya, E. D.; Hofner, P.; Goss, W. M.; Kurtz, S.; Richards, A. M. S.; Linz, H.; Olmi, L.; Sewilo, M.

    2010-07-10

    We report results of an extensive observational campaign of the 6 cm formaldehyde maser in the young massive stellar object IRAS 18566+0408 (G37.55+0.20) conducted from 2002 to 2009. Using the Arecibo Telescope, the Very Large Array, and the Green Bank Telescope, we discovered quasi-periodic formaldehyde flares (P {approx} 237 days). Based on Arecibo observations, we also discovered correlated variability between formaldehyde (H{sub 2}CO) and methanol (CH{sub 3}OH) masers. The H{sub 2}CO and CH{sub 3}OH masers are not spatially coincident, as demonstrated by different line velocities and high angular resolution MERLIN observations. The flares could be caused by variations in the infrared radiation field, possibly modulated by periodic accretion onto a young binary system.

  9. Accurate water maser positions from HOPS

    NASA Astrophysics Data System (ADS)

    Walsh, Andrew J.; Purcell, Cormac R.; Longmore, Steven N.; Breen, Shari L.; Green, James A.; Harvey-Smith, Lisa; Jordan, Christopher H.; Macpherson, Christopher

    2014-08-01

    We report on high spatial resolution water maser observations, using the Australia Telescope Compact Array, towards water maser sites previously identified in the H2O southern Galactic Plane Survey (HOPS). Of the 540 masers identified in the single-dish observations of Walsh et al., we detect emission in all but 31 fields. We report on 2790 spectral features (maser spots), with brightnesses ranging from 0.06 to 576 Jy and with velocities ranging from -238.5 to +300.5 km s-1. These spectral features are grouped into 631 maser sites. We have compared the positions of these sites to the literature to associate the sites with astrophysical objects. We identify 433 (69 per cent) with star formation, 121 (19 per cent) with evolved stars and 77 (12 per cent) as unknown. We find that maser sites associated with evolved stars tend to have more maser spots and have smaller angular sizes than those associated with star formation. We present evidence that maser sites associated with evolved stars show an increased likelihood of having a velocity range between 15 and 35 km s-1 compared to other maser sites. Of the 31 non-detections, we conclude they were not detected due to intrinsic variability and confirm previous results showing that such variable masers tend to be weaker and have simpler spectra with fewer peaks.

  10. Water masers in the Kronian system

    NASA Astrophysics Data System (ADS)

    Pogrebenko, Sergei V.; Gurvits, Leonid I.; Elitzur, Moshe; Cosmovici, Cristiano B.; Avruch, Ian M.; Pluchino, Salvatore; Montebugnoli, Stelio; Salerno, Emma; Maccaferri, Giuseppe; Mujunen, Ari; Ritakari, Jouko; Molera, Guifre; Wagner, Jan; Uunila, Minttu; Cimo, Giuseppe; Schilliro, Francesco; Bartolini, Marco

    The presence of water has been considered for a long time as a key condition for life in planetary environments. The Cassini mission discovered water vapour in the Kronian system by detecting absorption of UV emission from a background star (Hansen et al. 2006). Prompted by this discovery, we started an observational campaign for search of another manifestation of the water vapour in the Kronian system, its maser emission at the frequency of 22 GHz (1.35 cm wavelength). Observations with the 32 m Medicina radio telescope (INAF-IRA, Italy) started in 2006 using Mk5A data recording and the JIVE-Huygens software correlator. Later on, an on-line spectrometer was used at Medicina. The 14 m Metsähovi radio telescope (TKK-MRO, Finland) joined the observational campaign in 2008 using a locally developed data capture unit and software spectrometer. More than 300 hours of observations were collected in 2006-2008 campaign with the two radio telescopes. The data were analysed at JIVE using the Doppler tracking technique to compensate the observed spectra for the radial Doppler shift for various bodies in the Kronian system (Pogrebenko et al. 2009). Here we report the observational results for Hyperion, Titan, Enceladus and Atlas, and their physical interpretation. Encouraged by these results we started a campaign of follow up observations including other radio telescopes.

  11. Pumping the stellar hydroxyl maser

    NASA Technical Reports Server (NTRS)

    Dickinson, Dale F.

    1987-01-01

    IRAS far-IR flux data for 163 OH maser stars were analyzed to quantify the contributions 35 and 53 microns inversions make to pumping of the hydroxyl maser. The 35 microns transition is from the 3,3 ground state to the 1,5 rotationally excited level and subsequent decay; the 53 microns transition is a change from the ground state to the 1,3 excited level and relaxation. The stars examined included Mira, short period semi-regular and long-period semi-regular variables. Both transition lines had rough parity in contributing to the approximately 8 percent pumping efficiency at 1612 MHz. However, the individual contributions of the lines could not be determined for the stellar population studied.

  12. Water Masers Embedded in Ultracompact HII Regions in the W75N Cloud Core

    NASA Astrophysics Data System (ADS)

    Hunter, T. R.; Taylor, G. B.; Phillips, T. G.; Felli, M.; Tofani, G.

    1993-05-01

    We present high-resolution radio continuum, H2O maser emission, and molecular line maps of the W75N star-forming region. In addition, we present results from a six-year monitoring campaign of the H2O maser emission from W75N with the 32-m Medicina telescope. Since H2O masers are usually found to be displaced from compact continuum sources in star-forming regions, it has been conjectured that the masers trace young stellar objects at an earlier stage of evolution, perhaps related to energetic molecular outflows. Using the VLA in A-configuration, we find that the 22 GHz H2O maser spots in W75N spatially coincide with weak ultracompact (<1'') radio continuum sources located in the dense molecular cloud core. The masers and continuum sources extend a few arc seconds along a roughly N-S line, a feature also evident as an elongation in the peak of the CS J=7->6 map taken at the CSO. This structure suggests a nearly edge-on, warm, dense disk surrounding the central ionizing source. Past VLBI observations of OH emission have shown a ridge of maser spots along the continuum emission feature, possibly evidence for a shock front in the proposed disk. As a tracer of outflowing molecular gas, we present a map of the CO J=3->2 line wings at 20'' resolution, also from the CSO. Due to foreground contamination of the blue wing, only a monopolar red wing is observed on this scale. We believe W75N to be an important source for further study as it may help unify the various evolutionary features of massive star formation.

  13. The z distribution of hydrogen clouds and masers with kinematic distances

    NASA Astrophysics Data System (ADS)

    Bobylev, V. V.; Bajkova, A. T.

    2016-03-01

    Data on HII regions, molecular clouds, and methanol masers have been used to estimate the Sun's distance from the symmetry plane z ⊙ and the vertical disk scale height h. Kinematic distance estimates are available for all objects in these samples. The Local-arm (Orion-arm) objects are shown to affect noticeably the pattern of the z distribution. The deviations from the distribution symmetry are particularly pronounced for the sample of masers with measured trigonometric parallaxes, where the fraction of Local-arm masers is large. The situation with the sample of HII regions in the solar neighborhood is similar. We have concluded that it is better to exclude the Local arm from consideration. Based on the model of a self-gravitating isothermal disk, we have obtained the following estimates from objects located in the inner region of the Galaxy ( R ≤ R 0): z ⊙ = -5.7 ± 0.5 pc and h 2 = 24.1 ± 0.9 pc from the sample of 639 methanol masers, z ⊙ = -7.6±0.4 pc and h 2 = 28.6±0.5 pc from 878HII regions, z ⊙ = -10.1 ± 0.5 pc and h 2 = 28.2 ± 0.6 pc from 538 giant molecular clouds.

  14. Design and analysis of optically pumped submillimeter waveguide maser amplifiers and oscillators

    NASA Technical Reports Server (NTRS)

    Galantowicz, T. A.

    1975-01-01

    The design and experimental measurements are described of an optically pumped far-infrared (FIR) waveguide maser; preliminary measurements on a FIR waveguide amplifier are presented. The FIR maser was found to operate satisfactorily in a chopped CW mode using either methanol (CH3OH) or acetonitrile (CH3CN) as the active molecule. Two other gases, difluoroethane and difluoroethylene, produced an unstable output with high threshold and low output power when operated in the chopped CW mode. Experimental measurements include FIR output versus cavity length, output beam pattern, output power versus pressure, and input power. The FIR output was the input to an amplifier which was constructed similar to the oscillator. An increase of 10% in output power was noted on the 118.8 microns line of methanol.

  15. Water Masers in the Andromeda Galaxy. II. Where Do Masers Arise?

    NASA Astrophysics Data System (ADS)

    Amiri, Nikta; Darling, Jeremy

    2016-08-01

    We present a comparative multiwavelength analysis of water-maser-emitting regions and non-maser-emitting luminous 24 μm star-forming regions in the Andromeda Galaxy (M31) to identify the sites most likely to produce luminous water masers useful for astrometry and proper motion studies. Included in the analysis are Spitzer 24 μm photometry, Herschel 70 and 160 μm photometry, Hα emission, dust temperature, and star-formation rate. We find significant differences between the maser-emitting and non-maser-emitting regions: water-maser-emitting regions tend to be more infrared-luminous and show higher star-formation rates. The five water masers in M31 are consistent with being analogs of water masers in Galactic star-forming regions and represent the high-luminosity tail of a larger (and as yet undetected) population. Most regions likely to produce water masers bright enough for proper motion measurements using current facilities have already been surveyed, but we suggest three ways to detect additional water masers in M31: (1) reobserve the most luminous mid- or far-infrared sources with higher sensitivity than was used in the Green Bank Telescope survey; (2) observe early-stage star-forming regions selected by millimeter continuum that have not already been selected by their 24 μm emission, and (3) reobserve the most luminous mid- or far-infrared sources and rely on maser variability for new detections.

  16. Water maser variability over 20 years in a large sample of star-forming regions: the complete database

    NASA Astrophysics Data System (ADS)

    Felli, M.; Brand, J.; Cesaroni, R.; Codella, C.; Comoretto, G.; Di Franco, S.; Massi, F.; Moscadelli, L.; Nesti, R.; Olmi, L.; Palagi, F.; Panella, D.; Valdettaro, R.

    2007-12-01

    Context: Water vapor emission at 22 GHz from masers associated with star-forming regions is highly variable. Aims: We present a database of up to 20 years of monitoring of a sample of 43 masers within star-forming regions. The sample covers a large range of luminosities of the associated IRAS source and is representative of the entire population of H2O masers of this type. The database forms a good starting point for any further study of H2O maser variability. Methods: The observations were obtained with the Medicina 32-m radiotelescope, at a rate of 4-5 observations per year. Results: To provide a database that can be easily accessed through the web, we give for each source: plots of the calibrated spectra, the velocity-time-flux density plot, the light curve of the integrated flux, the lower and upper envelopes of the maser emission, the mean spectrum, and the rate of the maser occurrence as a function of velocity. Figures for just one source are given in the text for representative purposes. Figures for all the sources are given in electronic form the appendix. A discussion of the main properties of the H2O variability in our sample will be presented in a forthcoming paper. Based on observations with the Medicina radiotelescope operated by INAF - Istituto di Radioastronomia.

  17. The Arcetri 40-50 GHz receiver for the Medicina Radiotelescope.

    NASA Astrophysics Data System (ADS)

    Tofani, G.; Catarzi, M.; Natale, V.

    Numerous spectral lines of relevant astronomical importance are available in the wavelength range between 20 and 70 GHz. In this band transitions of several molecules like SiO, CS, HNCO, CH3OH, H2CO plays a central role in the different phases of the interstellar medium. In order to extend the observations with the Medicina Radiotelescope of Galactic masers, a cooled receiver operating in the range 40-50 GHz has been built for continuum and line observations. The system has been tested at the Cassegrain focus of the Medicina Radiotelescope on continuum and SiO maser sources.

  18. A search for 183-GHz emission from water in late-type stars

    NASA Technical Reports Server (NTRS)

    Kuiper, T. B. H.; Swanson, P. N.; Dickinson, D. F.; Kuiper, E. N. R.; Zimmerman, P.

    1984-01-01

    A search was made for 183 GHz line emission from water vapor in the direction of twelve Mira and two semiregular variables. Upper limits to the emission are in the range of 2000 to 5000 Jy. It is estimated that thermal emission from the inner regions of late type stellar envelopes will be on the order of ten Jy. Maser emission, according to one model, would be an order of magnitude stronger. From the limited set sampled, the possibility of very strong maser emission at 183 GHz cannot yet be ruled out.

  19. A search for 183 GHz emission from water in late-type stars

    NASA Technical Reports Server (NTRS)

    Kuiper, T. B. H.; Swanson, P. N.; Rodriguez Kuiper, E. N.; Zimmermann, P.; Dickinson, D. F.

    1984-01-01

    A search was made for 183 GHz line emission from water vapor in the direction of twelve Mira and two semiregular variables. Upper limits to the emission are in the range of 2000 to 5000 Jy. It is estimated that thermal emission from the inner regions of late type stellar envelopes will be on the order of ten Jy. Maser emission, according to one model, would be an order of magnitude stronger. From the limited set sampled, the possibility of very strong maser emission at 183 GHz cannot yet be ruled out.

  20. The Zeeman effect in astrophysical water masers and the observation of strong magnetic fields in regions of star formation

    NASA Technical Reports Server (NTRS)

    Nedoluha, Gerald E.; Watson, William D.

    1992-01-01

    The present study solves the transfer equations for the polarized radiation of astrophysical 22-GHz water masers in the presence of a magnetic field which causes a Zeeman splitting that is much smaller than the spectral line breadth. The emphasis is placed on the relationship between the recently detected circular polarization in this maser radiation and the strength of the magnetic field. When the observed spectral line breadth is smaller than about 0.8 km/s (FWHM), it is calculated that the uncertainty is less than a factor of about 2. The accuracy is improved significantly when the angle between the line of sight and the direction of the magnetic field does not exceed about 45 deg. Uncertainty in the strength of the magnetic field due to lack of knowledge about which hyperfine transition is the source of the 22-GHz masers is removed. The 22-GHz maser feature is found to be the result of a merger of the three strongest hyperfine components.

  1. THE PROTOCLUSTER G18.67+0.03: A TEST CASE FOR CLASS I CH{sub 3}OH MASERS AS EVOLUTIONARY INDICATORS FOR MASSIVE STAR FORMATION

    SciTech Connect

    Cyganowski, C. J.; Zhang, Q.; Brogan, C. L.; Hunter, T. R.; Friesen, R. K.; Indebetouw, R.; Chandler, C. J.

    2012-12-01

    We present high angular resolution Submillimeter Array and Karl G. Jansky Very Large Array observations of the massive protocluster G18.67+0.03. Previously targeted in maser surveys of GLIMPSE Extended Green Objects (EGOs), this cluster contains three Class I CH{sub 3}OH maser sources, providing a unique opportunity to test the proposed role of Class I masers as evolutionary indicators for massive star formation. The millimeter observations reveal bipolar molecular outflows, traced by {sup 13}CO(2-1) emission, associated with all three Class I maser sources. Two of these sources (including the EGO) are also associated with 6.7 GHz Class II CH{sub 3}OH masers; the Class II masers are coincident with millimeter continuum cores that exhibit hot core line emission and drive active outflows, as indicated by the detection of SiO(5-4). In these cases, the Class I masers are coincident with outflow lobes, and appear as clear cases of excitation by active outflows. In contrast, the third Class I source is associated with an ultracompact (UC) H II region, and not with Class II masers. The lack of SiO emission suggests that the {sup 13}CO outflow is a relic, consistent with its longer dynamical timescale. Our data show that massive young stellar objects (MYSOs) associated only with Class I masers are not necessarily young and provide the first unambiguous evidence that Class I masers may be excited by both young (hot core) and older (UC H II) MYSOs within the same protocluster.

  2. Self-consistent simulation of cyclotron autoresonance maser amplifiers

    SciTech Connect

    Pendergast, K.D.; Danly, B.G.; Temkin, R.J.; Wurtele, J.S.

    1988-04-01

    A self-consistent, one-dimensional model of the cyclotron autoresonance maser (CARM) amplifier is developed, and numerical simulations based on this model are described. Detailed studies of the CARM gain and efficiency for a wide range of initial energy and velocity spreads are presented. The interaction efficiency is found to be substantially increased when the axial magnetic field is tapered. For example, efficiencies of greater than 41 percent are obtained for a 140-GHz CARM amplifier with a tapered axial magnetic field and a 700-kV 4.5-A electron beam with parallel velocity spreads of less than 1 percent. A discussion of the nonlinear bandwidth and interaction sensitivity to axial field inhomogeneities is presented.

  3. New OH masers at 13 441 MHz

    NASA Astrophysics Data System (ADS)

    Caswell, J. L.

    2004-07-01

    The Parkes radio telescope has been used to study maser emission from the 13441-MHz transition of highly excited OH. The targets were 56 catalogued sites of 6035-MHz maser emission. Eight 13441-MHz maser sites were detected, six of them new and two that had previously been reported. This more than doubles the number now known to 11. At every 13441-MHz maser site, spectral features occur as right- and left-hand circularly polarized matched pairs, with small, but mostly significant, frequency separation. This is attributed to the Zeeman effect in magnetic fields of a few mG. Some of the 13441-MHz maser sites show features at several different velocities. All of the 13441-MHz maser features have 6035-MHz counterparts that closely correspond in velocity. At three sites, features of 13441-MHz emission rival the intensities of their 6035-MHz counterparts; at the other sites, features are weaker than at 6035 MHz by factors of between 3 and 50. Upper limits at some sites searched can be set more than 2 orders of magnitude weaker than 6035-MHz emission. The detection statistics provide unique opportunities to test recent advances in maser modelling. A search for the 13434-MHz transition towards the same 56 targets yielded no detections.

  4. Hydrogen maser development at Laval University

    NASA Technical Reports Server (NTRS)

    Vanier, J.; Racine, G.; Kunski, R.; Picard, M.

    1981-01-01

    The physical construction of two hydrogen masers is described and results of measurements made on one of the masers are given. These include: cavity Q, thermal time constant, line Q, signal power output, magnetic shielding factor. Preliminary results indicate that the frequency stability will be mainly affected by the thermal of the cavity. The magnetic field and the barometric fluctuations should not affect the maser at the stability level above a few parts in 10 to the 15th power, which is the goal for averaging times of several hours.

  5. Frequency stability of maser oscillators operated with cavity Q. [hydrogen and rubidium masers

    NASA Technical Reports Server (NTRS)

    Tetu, M.; Tremblay, P.; Lesage, P.; Petit, P.; Audoin, C.

    1982-01-01

    The short term frequency stability of masers equipped with an external feedback loop to increase the cavity quality factor was studied. The frequency stability of a hydrogen and a rubidium maser were measured and compared with theoretical evaluation. It is shown that the frequency stability passes through an optimum when the cavity Q is varied. Long term fluctuations are discussed and the optimum mid term frequency stability achievably by small size active and passive H-masers is considered.

  6. WATER MASER SURVEY ON AKARI AND IRAS SOURCES: A SEARCH FOR ''LOW-VELOCITY'' WATER FOUNTAINS

    SciTech Connect

    Yung, Bosco H. K.; Nakashima, Jun-ichi; Kwok, Sun; Imai, Hiroshi; Deguchi, Shuji; Henkel, Christian

    2013-05-20

    We present the results of a 22 GHz H{sub 2}O maser survey toward a new sample of asymptotic giant branch (AGB) and post-AGB star candidates. Most of the objects are selected for the first time based on the AKARI data, which have high flux sensitivity in the mid-infrared ranges. We aim at finding H{sub 2}O maser sources in the transient phase between the AGB and post-AGB stages of evolution, where the envelopes start to develop large deviations from spherical symmetry. The observations were carried out with the Effelsberg 100 m radio telescope. Among 204 observed objects, 63 detections (36 new) were obtained. We found four objects that may be ''water fountain'' sources (IRAS 15193+3132, IRAS 18056-1514, OH 16.3-3.0, and IRAS 18455+0448). They possess an H{sub 2}O maser velocity coverage much smaller than those in other known water fountains. However, the coverage is still larger than that of the 1612 MHz OH maser. It implies that there is an outflow with a higher velocity than the envelope expansion velocity (typically {<=}25 km s{sup -1}), meeting the criterion of the water fountain class. We suggest that these candidates are possibly oxygen-rich late AGB or early post-AGB stars in a stage of evolution immediately after the spherically symmetric AGB mass loss has ceased.

  7. A 20-year H2O maser monitoring program with the Medicina 32-m telescope

    NASA Astrophysics Data System (ADS)

    Brand, J.; Felli, M.; Cesaroni, R.; Codella, C.; Comoretto, G.; Di Franco, S.; Massi, F.; Moscadelli, L.; Nesti, R.; Olmi, L.; Palagi, F.; Palla, F.; Panella, D.; Valdettaro, R.

    2007-03-01

    The Arcetri/Bologna H2O maser group has been monitoring the 1.3-cm water maser emission from a sample of 43 star-forming regions (SFRs) and 22 late-type stars for about 20 years at a sampling rate of 4-5 observations each year, using the 32-m Medicina Radio Telescope (HPBW 1.‧9 at 22 GHz). For the late-type stars we observe representative samples of OH/IR-stars, Mira's, semi-regular variables, and supergiants. The SFR-sample spans a large interval in FIR luminosity of the associated Young Stellar Object (YSO), from 20 L to 1.5 × 106 L, and offers a unique data base for the study of the long-term (years) variability of the maser emission in regions of star formation. This presentation concerns only the masers in SFRs. The information obtained from single-dish monitoring is complementary to what is extracted from higher-resolution (VLA and VLBI) observations, and can better explore the velocity domain and the long-term variability therein. We characterize the variability of the sources in various ways and we study how it depends on the luminosity and other properties of the associated YSO and its environment.

  8. H2O masers in a jet-driven bowshock: Episodic ejection from a massive young stellar object

    NASA Astrophysics Data System (ADS)

    Burns, R. A.; Handa, T.; Nagayama, T.; Sunada, K.; Omodaka, T.

    2016-04-01

    We report the results of VERA multi-epoch VLBI 22 GHz water maser observations of S255IR-SMA1, a massive young stellar object located in the S255 star forming region. By annual parallax the source distance was measured as D = 1.78^{+0.12}_{-0.11} kpc and the source systemic motion was (μαcos δ, μδ) = (-0.13 ± 0.20, -0.06 ± 0.27) mas yr-1. Masers appear to trace a U-shaped bow shock whose morphology and proper motions are well reproduced by a jet-driven outflow model with a jet radius of about 6 AU. The maser data, in the context of other works in the literature, reveal ejections from S255IR-SMA1 to be episodic, operating on timescales of ˜1000 years.

  9. H2O masers in a jet-driven bow shock: episodic ejection from a massive young stellar object

    NASA Astrophysics Data System (ADS)

    Burns, R. A.; Handa, T.; Nagayama, T.; Sunada, K.; Omodaka, T.

    2016-07-01

    We report the results of VERA multi-epoch VLBI 22 GHz water maser observations of S255IR-SMA1, a massive young stellar object located in the S255 star forming region. By annual parallax the source distance was measured as D = 1.78 +-0.12 kpc and the source systemic motion was (u alpha cos d, u d) = (-0.13 +- 0.20, -0.06 +- 0.27) mas yr-1. Masers appear to trace a U-shaped bow shock whose morphology and proper motions are well reproduced by a jet-driven outflow model with a jet radius of about 6 AU. The maser data, in the context of other works in the literature, reveal ejections from S255IR-SMA1 to be episodic, operating on timescales of ~1000 years.

  10. Cosmic masers: yesterday, today, and tomorrow.

    NASA Astrophysics Data System (ADS)

    Strel'Nitskij, V. S.

    This article is not a systematic review of the problem of cosmic masers. Its first section (Yesterday) is a memory about Pikel'ner and Shklovsky on the background of the problem which occurred to the author with these two contributing people. In the section Today a series of current problems is briefly considered connected with cosmic masers. In the section Tomorrow some directions of future research are noted.

  11. Operational parameters for the superconducting cavity maser

    NASA Technical Reports Server (NTRS)

    Wang, R. T.; Dick, G. J.; Strayer, D. M.

    1989-01-01

    Tests of the superconducting cavity maser (SCM) ultra-stable frequency source have been made for the first time using a hydrogen maser for a frequency reference. In addition to characterizing the frequency stability, the sensitivity of the output frequency to several crucial parameters was determined for various operating conditions. Based on this determination, the refrigeration and thermal control systems of the SCM were modified. Subsequent tests showed substantially improved performance, especially at the longest averaging times.

  12. Photoinjector-driven chirped-pulsed free electron maser

    NASA Astrophysics Data System (ADS)

    Lesage, G. P.; Hartemann, F. V.; Feng, H. X. C.; Fochs, S. N.; Heritage, J. P.; Luhmann, N. C., Jr.; Perry, M. D.; Westenskow, G. A.

    1995-03-01

    An ultra-short pulse, millimeter-wave free electron maser experiment is currently underway at UC Davis and Lawrence Livermore National Laboratory. A 8.5 kG, 30 mm period helical wiggler is used to transversally accelerate a train of one hundred 5 MeV, 0.25 nC, 1 ps duration micro bunches synchronously energized by a 20 MW, X-band photocathode RF linac. The photocathode is irradiated by a burst-mode, UV laser system which produces up to 100 pulses at 207 nm, with an energy of 10 mJ/pulse, and a pulse duration of 200 fs, at a repetition rate of 2.142 GHz. This system includes a 400 fs jitter synchronously modelocked AlGaAs semiconductor laser oscillator which is amplified by an eight-pass Ti:Al2O3 chirped pulse laser amplifier. The output of this amplifier is subsequently frequency quadrupled into the UV. Because the electron micro bunches are shorter than the radiation wavelength, the system coherently synchrotron radiates and behaves essentially as a prebunched FEM. In addition, by operating in a waveguide structure at grazing, where the bunch axial velocity in the wiggler matches the group velocity of the electromagnetic waves, one obtains output radiation pulses which are extremely short, and have greatly enhanced peak power. The device operates in the TE(sub 12) mode of a cylindrical waveguide, and will produce up to 2 MW of coherent synchrotron radiation power at 140 GHz, in a 15 ps FWHM pulse. The -3 dB instantaneous interaction bandwidth extends from 125 GHz to 225 GHz. The output pulse is chirped over the full interaction bandwidth. One of the major potential applications of such a device is an ultra-wideband millimeter-wave radar.

  13. Hydrogen masers and cesium fountains at NRC

    NASA Technical Reports Server (NTRS)

    Boulanger, J.-S.; Morris, D.; Douglas, R. J.; Gagne, M.-C.

    1994-01-01

    The NRC masers H-3 and H-4 have been operating since June 1993 with cavity servo control. These low-flux active H masers are showing stabilities of about 10(exp -15) from 1 hour to several days. Stability results are presented, and the current and planned uses of the masers are discussed. A cesium fountain primary frequency standard project has been started at NRC. Trapping and launching experiments with the goal of 7 m/s launches are beginning. We discuss our plans for a local oscillator and servo that exploit the pulsed aspect of cesium fountain standards, and meet the challenge of 10(exp -14) tau(exp -1/2) stability without requiring masers. At best, we expect to run this frequency standard initially for periods of hours each working day rather than continuously for years, and so frequency transfer to outside laboratories has been carefully considered. We conclude that masers (or other even better secondary clocks) are required to exploit this potential accuracy of the cesium fountain. We present and discuss our conclusion that it is feasible to transfer frequency in this way with a transfer-induced uncertainty of less than 10(exp -15), even in the presence of maser frequency drift and random walk noise.

  14. Performance of Soviet and US hydrogen masers

    NASA Technical Reports Server (NTRS)

    Uljanov, Adolph A.; Demidov, Nikolai A.; Mattison, Edward M.; Vessot, Robert F. C.; Allan, David W.; Winkler, Gernot M. R.

    1990-01-01

    The frequencies of Soviet- and U.S.-built hydrogen masers located at the Smithsonian Astrophysical Observatory and at the United States Naval Observatory (USNO) were compared with each other and, via Global Positioning System (GPS) common-view measurements, with three primary frequency-reference scales. The best masers were found to have fractional frequency stabilities as low as 6 times 10(exp -16) for averaging times of approximately 10(exp 4) s. Members of the USNO maser ensemble provided frequency prediction better than 1 times 10(exp 14) for periods up to a few weeks. The frequency residuals of these masers, after removal of frequency drift and rate of change of drift, had stabilities of a few parts in 10(exp -15), with serveral masers achieving residual stabilities well below 1 times 10(exp -15) for intervals from 10(exp 5)s to 2 times 10(exp 6)s. The fractional frequency drifts of the 13 masers studied, relative to the primary reference standards, ranged from -0.2 times 10(exp -15)/day to +9.6 times 10(exp -15)/day.

  15. Abundant CH3OH Masers but no New Evidence for Star Formation in GCM0.253+0.016

    NASA Astrophysics Data System (ADS)

    Mills, E. A. C.; Butterfield, N.; Ludovici, D. A.; Lang, C. C.; Ott, J.; Morris, M. R.; Schmitz, S.

    2015-05-01

    We present new observations of the quiescent giant molecular cloud GCM0.253+0.016 in the Galactic center, using the upgraded Karl G. Jansky Very Large Array. Observations were made at wavelengths near 1 cm, at the K (24-26 GHz) and Ka (27 and 36 GHz) bands, with velocity resolutions of 1-3 km s-1 and spatial resolutions of ˜0.1 pc, at the assumed 8.4 kpc distance of this cloud. The continuum observations of this cloud are the most sensitive yet made, and reveal previously undetected emission which we attribute primarily to free-free emission from external ionization of the cloud. In addition to the sensitive continuum map, we produce maps of 12 molecular lines: 8 transitions of NH3-(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6), (7, 7), and (9, 9), as well as the HC3N (3-2) and (4-3) lines, and CH3OH 4-1-30, the latter of which is known to be a collisionally excited maser. We identify 148 CH3OH 4-1-30 (36.2 GHz) sources, of which 68 have brightness temperatures in excess of the highest temperature measured for this cloud (400 K) and can be confirmed to be masers. The majority of these masers are concentrated in the southernmost part of the cloud. We find that neither these masers nor the continuum emission in this cloud provide strong evidence for ongoing star formation in excess of that previously inferred by the presence of an H2O maser.

  16. Intensity-dependent circular polarization and circumstellar magnetic fields from the observation of SiO masers

    NASA Technical Reports Server (NTRS)

    Nedoluha, Gerald E.; Watson, William D.

    1994-01-01

    A new aspect of the propagation of astrophysical maser radiation in the presence of a magnetic field is described in which circular polarization is created. The resulting antisymmetric spectral line profile for this circular polarization resembles that produced by the ordinary Zeeman effect when the Zeeman splittings are much less than the spectral line breadth. It is caused by the change, with increasing maser intensity, in the axis of symmetry for the molecular quantum states from a direction that is parallel to the magnetic field to a direction that is parallel to the direction of propagation. When the maser is radiatively saturated, and the rate for stimulated emission is within an order of magnitude of the Zeeman splitting in frequency units, this 'intensity-dependent circular polarization' is greater than that due to the ordinary Zeeman effect by factors as large as 1000. The circular polarization that is observed in the spectra of circumstellar SiO (J = 1-0) masers associated with late-type giants and supergiants may then be caused by magnetic fields as weak as about 10 mG. With the standard Zeeman interpretation of the observations, magnetic fields of 10-100 G are indicated. The lower fields are similar to the limits obtained from the observation of the 22 GHz water masers which are typically somewhat further from the central star. The observed tendency for the fractional linear polarization of SiO masers to increase with increasing angular momentum of the molecular state is shown to be a likely result of anisotropic pumping. Errors are identified that invalidate a recent conflicting claim in the literature about the basic theory of maser polarization in the regime that is relevant here.

  17. A search for H2O maser emission in the Serpens region

    NASA Astrophysics Data System (ADS)

    Palla, F.; Giovanardi, C.

    1989-10-01

    This paper presents the results of repeated H2O maser line observations (22.2 GHz) in the Serpens region obtained with the 32-m parabola of the Medicina Station over a period of 16 months. Several positions coincident with pre-main-sequence objects and far-infrared sources were observed, with no positive detection at an average rms = 1.5 Jy. In addition, three regions were mapped: the cloud molecular core, the Ser/G3-G6 complex, and the strong IRAS source 18278+O111. Only within the core, and only in one out of six observing runs, a feature of 48 Jy was observed. This line coincides in position and velocity with one of the two masers reported by Blair et al. (1975), but never detected since then.

  18. Water masers associated with compact molecular clouds and ultracompact H II regions - The extended sample

    NASA Astrophysics Data System (ADS)

    Cesaroni, R.; Comoretto, G.; Felli, M.; Palla, F.; Brand, J.; Caselli, P.

    We present the results of a survey of water maser emission at 22.2 GHz towards a selected sample of IRAS-PSC sources which are believed to be associated with very young massive stars. The sample consists of 591 sources. The observations have been carried out using the Medicina 32-m radiotelescope, operated by the Istituto di Radioastronomia - C.N.R., Bologna. Whereas previous searches for maser emission have been directed towards known H II regions, the aim of the present survey is to identify new sources in an even earlier evolutionary phase, corresponding to the development of an ultracompact H II region. It is shown that our sample contains a significant number of sources that could be considered good candidates of massive protostellar cores still in the main accretion phase.

  19. Discovery of a young stellar object near the water masers in W3(OH)

    NASA Astrophysics Data System (ADS)

    Turner, J. L.; Welch, W. J.

    1984-12-01

    A high-resolution (1.2 arcsec) aperture synthesis map of the ultracompact H II region W3(OH) in the 88.6 GHz transition of HCN is presented. The map is based on observations carried out with the Hat Creek millimeter interferometer. An HCN emission feature was detected near the position of the H20 masers, approximately 7 arcsec west of the continuum source. The velocity of the HCN emission indicates a physical association with the masers. The luminosity and high brightness temperature of the emission, and the broad HCN line width indicate the presence of an obscured young star within the clump. An optical depth of more than 50 at 10 microns toward the source was calculated, corresponding to a visual extinction of greater than 900 mag. Due to the high mid-infrared extinction, it is suggested that the star may only be studied by high resolution molecular line observations.

  20. Time variation of the H2O and SiO masers in late-type stars

    NASA Astrophysics Data System (ADS)

    Gomez Balboa, A. M.; Lepine, J. R. D.

    1986-04-01

    The results of six years of monitoring of the 22-GHz H2O maser, and less extensive monitoring of the 43-GHz SiO line, of ten late-type variables (o Cet, R Dor, L2 Pup, VY CMa, R Crt, W Hya, U Her, AH Sco, VX Sgr, R Aql) are presented. The observations were made with the 13.2 m Itapetinga Radiotelescope, Brazil. The variability curves are compared with visual curves from the Association Francaise des Observateurs d'Etoiles Variables. Aperiodic variability of the H2O maser, spanning several cycles of the stellar pulsation (R Crt), or superperiodic behavior with periods equal to multiples of the fundamental period (R Aql, W Hya) have been noted. These results can be understood in terms of the models of Wood (1979) and Willson and Hill (1979) for shock wave propagation into the envelopes.

  1. First high power experiments with the Dutch free electron maser

    NASA Astrophysics Data System (ADS)

    Verhoeven, A. G. A.; Bongers, W. A.; Bratman, V. L.; Caplan, M.; Denisov, G. G.; van Dijk, G.; van der Geer, C. A. J.; Manintveld, P.; Poelman, A. J.; Pluygers, J.; Shmelyov, M. Yu.; Smeets, P. H. M.; Sterk, A. B.; Urbanus, W. H.

    1998-05-01

    A free electron maser (FEM) has been built as a mm-wave source for applications on future fusion research devices such as ITER, the international tokamak experimental reactor [M. A. Makowski, F. Elio, and D. Loeser, April 97, Proc. 10th Workshop on ECE and ECRH, EC10, 549-559. World Scientific (1998)]. A unique feature of the Dutch fusion-FEM is the possibility to tune the frequency over the entire range from 130 to 260 GHz at an output power exceeding 1 MW. In the first phase of the project, a so-called inverse setup is used. The electron gun is mounted inside the high-voltage terminal. The entire beam line was tested successfully with extremely low loss current, lower than 0.05%. This included the accelerating structure up to 2 MV level and the transport through the undulator. First generation of mm-waves was achieved in October 1997. With an electron beam current around 8 A and an accelerator voltage of 1.76 MV the mm-wave pulse starts after 3 μs and lasts for 3 μs, reaching a maximum saturated peak power level of more than 500 kW at a frequency of 200 GHz. Output power, start-up time, and frequency correspond well with simulation results.

  2. Hydrogen Maser Clock (HMC) Experiment

    NASA Technical Reports Server (NTRS)

    Vessot, Robert F. C.; Mattison, Edward M.

    1997-01-01

    The Hydrogen Maser Clock (HMC) project was originally conceived to fly on a reflight of the European Space Agency (ESA) free flying platform, the European Recoverable Carrier (EURECA) that had been launched into space and recovered by NASA's Space Transportation System (STS). A Phase B study for operation of HMC as one of the twelve EURECA payload components was begun in July 1991, and completed a year later. Phase C/D of HMC began in August 1992 and continued into early 1995. At that time ESA decided not to refly EURECA, leaving HMC without access to space. Approximately 80% of the flight support electronics are presently operating the HMC's physics package in a vacuum tank at the Smithsonian Astrophysical Observatory, and are now considered to be well-tested flight electronics. The package will continue to be operated until the end of 1997 or until a flight opportunity becomes avaiable. Appendices: letters and trip report; proceedings of the symposium on frequency standards and metrology; milli-celsius-stability thermal control for an orbiting frequency standard.

  3. Theory of relativistic cyclotron masers

    NASA Astrophysics Data System (ADS)

    Nusinovich, G. S.; Latham, P. E.; Dumbrajs, O.

    1995-07-01

    In this paper we have made an attempt to review the present status of the theory of cyclotron masers with relativistic electron beams. After discussing the basic features of electron-cyclotron radiation under conditions of normal and anomalous Doppler frequency shifts, we consider particle deceleration by a constant amplitude electromagnetic wave in a constant magnetic field using the formalism developed earlier for cyclotron autoresonance acceleration of electrons. An optimal cyclotron resonance mismatch was found that corresponds to the possibility of complete deceleration of relativistic electrons. Then, interaction of relativistic electrons with resonator fields is considered and the efficiency increase due to electron prebunching is demonstrated in a simple model. Since an efficient interaction of relativistic electrons with the large amplitude electromagnetic field of a resonator occurs at a short distance, where electrons make a small number of electron orbits, the issue of the simultaneous interaction of electrons with the field at several cyclotron harmonics is discussed. Finally, we consider deceleration of a prebunched electron beam by a traveling electromagnetic wave in a tapered magnetic field. This simple modeling is illustrated with a number of simulations of relativistic gyroklystrons and gyrotwistrons (gyrodevices in which the bunching cavity of the gyroklystron is combined with the output waveguide of the gyro-traveling-wave-tube).

  4. Ammonia Masers in W51: Interferometric Studies

    NASA Astrophysics Data System (ADS)

    Wilson, Thomas L.; Clarke, T. E.; Boboltz, D. A.; Henkel, C.; Mauersberger, R.; Wootten, H. A.; Broullet, N.; Baudry, A.; Despois, D.

    2014-01-01

    The galactic continuum sources W51D and W51e1e2 have been long recognized as remarkable centers of ammonia maser phenomena in the centimeter wavelength range. Henkel et al. (2013 A&A 549, A90) have measured 19 masers, of which 13 are newly found for W51-IRS2, otherwise known as W51D. These arise from inversion-rotation transitions. The single dish data were taken with the Effelsberg 100-m radio telescope of the MPIfR with an angular resolution of 43 arc seconds. The conclusion that these lines were caused by maser action is based on: (1) time variability, and (2) narrow linewidths. In addition, some lines showed systematic velocity variations. High brightness temperatures and compact sizes are needed to conclusively prove maser action. We have measured a sub-set of these ammonia lines with the C array of the Jansky-Very Large Array of the National Radio Astronomy Observatory in June 2013 with an angular resolution of better than 1 arc second. Source sizes, positions, excitation models and reasons why W51 shows such a plethora of masers will be presented.

  5. Exploration of Solar Wind Acceleration Region Using Interplanetary Scintillation of Water Vapor Maser Source and Quasars

    NASA Technical Reports Server (NTRS)

    Tokumaru, Munetoshi; Yamauchi, Yohei; Kondo, Tetsuro

    2001-01-01

    Single-station observations of interplanetary scintillation (IPS) at three microwave frequencies; 2 GHz, 8 GHz and 22 GHz have been carried out between 1989 and 1998 using a large (34 m farad) radio telescope at the Kashima Space Research Center of the Communications Research Laboratory. The aim of these observations is to explore the near-sun solar wind, which is the key region for the study of the solar wind acceleration mechanism. Strong quasars; 3C279 and 3C273B were used for Kashima IPS observations at 2 GHz and 8 GHz, and a water vapor maser source, IRC20431 was used for the IPS observations at 22 GHz. Solar wind velocities derived from Kashima IPS data suggest that the solar wind acceleration takes place at radial distances between 10 and 30 solar radii (R(sub s)) from the sun. Properties of the turbulence spectrum (e.g. anisotropy, spectral index, inner scale) inferred from Kashima data are found to change systematically in the solar wind acceleration region. While the solar wind in the maximum phase appears to be dominated by the slow wind, fast and rarefied winds associated with coronal holes are found to develop significantly at high latitudes as the solar activity declines. Nevertheless, Kashima data suggests that the location of the acceleration region is stable throughout the solar cycle.

  6. A hydrogen maser with cavity auto-tuner for timekeeping

    NASA Technical Reports Server (NTRS)

    Lin, C. F.; He, J. W.; Zhai, Z. C.

    1992-01-01

    A hydrogen maser frequency standard for timekeeping was worked on at the Shanghai Observatory. The maser employs a fast cavity auto-tuner, which can detect and compensate the frequency drift of the high-Q resonant cavity with a short time constant by means of a signal injection method, so that the long term frequency stability of the maser standard is greatly improved. The cavity auto-tuning system and some maser data obtained from the atomic time comparison are described.

  7. Search for Cyclotron-maser Radio Emission from Extrasolar Planets

    NASA Astrophysics Data System (ADS)

    Dulk, G. A.; Leblanc, Y.; Bastian, T. S.

    1997-07-01

    There is reason to believe that extrasolar planets and/or brown dwarfs of mass about 1 to 50 M_J have magnetic fields, that they emit extremely intense cyclotron-maser radiation at metric wavelengths, and that this radiation may be detectable with sensitive radio telescopes like the VLA. The radiation is emitted at the electron cyclotron frequency, and has been detected from Earth, Jupiter, Saturn, Uranus and Neptune, from the Sun, from flare stars, and close binaries. The frequency range of cyclotron maser radiation is fixed by the magnetic field strength on the object. To be detected at, say 0.33 GHz, the required field strength is 118 G, which is intermediate between the 14 G field of Jupiter and the ~ 1000 G field of stellar active regions. An estimation of the flux density of the expected radiation can be made from an interpolation between Jupiter's radio emission (10(10) mJy at 5 AU) and that of nearby red dwarf stars ( ~ 100 mJy at 3 pc). Thus the flux from a planet or brown dwarf 3 to 30 times massive than Jupiter is plausibly 1 to 10 mJy, easily detectable with the VLA. If emission is detected, several important parameters about the planet can be deduced: the strength of its magnetic field, the period of its rotation, and the possible existence of a moon such as Jupiter's Io. Possible means of distinguishing stellar maser emissions from those of planets include: 1) Temporal variations and spectra differ from stars to planets. 2) The polarization is likely to be 100% circular or elliptical for planets, but not for stars. We have searched for exoplanet radio emission with 60 hours of observations with the VLA during November 1996. The observed stars with giant planets or brown dwarfs included 51 Peg, 70 Vir, 47 UMa, 55 CnC, Tau Boo, Gl 229, and HD 114762. We will present the method of observation, the limitations due to confusion and background noise, and the results.

  8. A small, passively operated hydrogen maser

    NASA Technical Reports Server (NTRS)

    Howe, D. A.; Walls, F. L.; Bell, H. E.; Hellwig, H.

    1979-01-01

    The paper describes a compact passive hydrogen maser with unique features including a reduction in size. It uses a passive operation mode, permitting the use of a small microwave TE(011) cavity dielectrically loaded by a low loss alumina. The Teflon coated quartz bulb common in other masers has been replaced by a Teflon coating on the inside wall of the cavity producing a simpler designed and a more rugged H-maser package. The cavity and the attached endcaps comprise the vacuum envelope, allowing the use of a single vacuum system. The dimensional stability of the ceramic cavity under barometric changes is sufficiently within the range of the electronic cavity servo so that a second vacuum system is not required. For temperature control, a single oven is located in the magnetic shield nest.

  9. Dynamic nuclear polarization with a cyclotron resonance maser at 5 T

    NASA Astrophysics Data System (ADS)

    Becerra, Lino R.; Gerfen, Gary J.; Temkin, Richard J.; Singel, David J.; Griffin, Robert G.

    1993-11-01

    DNP (dynamic nuclear polarization) experiments at 5 T are reported, in which a cycoltron resonance maser (gyrotron) is utilized as a 20 W, 140 GHz microwave source to perform the polarization. MAS (magic angle spinning) NMR spectroscopy with DNP has been performed on samples of polystyrene doped with the free radical BDPA (α,γ-bisdiphenylene-β-phenylallyl) at room temperature. Maximal DNP enhancements of ~10 for 1H and ~40 for 13C are observed and are considerably larger than expected. The DNP and spin relaxation mechanisms that lead to these enhancements at 5 T are discussed.

  10. First operation of a dielectric-loaded double-stripline free-electron maser experiment

    SciTech Connect

    Einat, M.; Jerby, E.; Shahadi, A.

    1995-12-31

    A tabletop free-electron maser (FEM) experiment based on a dielectric-loaded double-stripline waveguide is presented. It employs a low-energy (8 keV, 0.5 A) electron beam and a folded-foil wiggler ({lambda}w = 2 cm). Metal striplines protects the dielectric slabs from the electron beam and support quasi-TEM modes in the waveguide. Radiation output is observed at f = 3.5 GHz, in agreement with the dielectric-loaded FEM tuning relation.

  11. VizieR Online Data Catalog: VLBA SiO maser maps of the star OH 44.8-2.3 (Amiri+, 2012)

    NASA Astrophysics Data System (ADS)

    Amiri, N.; Vlemmings, W. H. T.; Kemball, A. J.; van Langevelde, H. J.

    2012-02-01

    The 43GHz SiO maser observations of the OH/IR star OH 44.8-2.3 were performed with the VLBA in full polarization spectral line mode. Auxiliary EVLA observations were performed to allow for the absolute calibration of the polarization angle. The Zeeman splitting was measured by cross correlating the right and left circular polarization spectra, as well as the S-curve fitting. Additionally, we analyzed the 1612MHz OH maser observations of OH 44.8-2.3 from the VLA archive. (3 data files).

  12. Far infrared maser communications technology

    NASA Technical Reports Server (NTRS)

    Claspy, P. C.; Pao, Y. H.

    1975-01-01

    An optically pumped FIR laser was constructed and tested. Optimum operating conditions were determined with CH3OH as the lasing medium. The laser was found to operate equally well with flowing gas or in a sealed off configuration. The FIR cavity stability and pump laser stability were found to have significant problems. The absorption coefficient per unit pressure of 1-1 difluoroethylene at the P(22) and P(24) lines of the 10.4 micron CO2 band was measured. The FIR line pumped by P(22) occurs at approximately 890 microns, which may be in an atmospheric transmission window. It was found that significant Stark tuning of absorption lines of methanol and 1-1 difluoroethylene can be accomplished, even at the usual 100 to 300 mTorr operating pressures of FIR lasers. This means that the use of Stark tuning may enable more effective use of pump laser output.

  13. Characteristics of advanced hydrogen maser frequency standards

    NASA Technical Reports Server (NTRS)

    Peters, H. E.

    1973-01-01

    Measurements with several operational atomic hydrogen maser standards have been made which illustrate the fundamental characteristics of the maser as well as the analysability of the corrections which are made to relate the oscillation frequency to the free, unperturbed, hydrogen standard transition frequency. Sources of the most important perturbations, and the magnitude of the associated errors, are discussed. A variable volume storage bulb hydrogen maser is also illustrated which can provide on the order of 2 parts in 10 to the 14th power or better accuracy in evaluating the wall shift. Since the other basic error sources combined contribute no more than approximately 1 part in 10 to the 14th power uncertainty, the variable volume storage bulb hydrogen maser will have net intrinsic accuracy capability of the order of 2 parts in 10 to the 14th power or better. This is an order of magnitude less error than anticipated with cesium standards and is comparable to the basic limit expected for a free atom hydrogen beam resonance standard.

  14. A database of circumstellar OH masers

    NASA Astrophysics Data System (ADS)

    Engels, D.; Bunzel, F.

    2015-10-01

    We present a new database of circumstellar OH masers at 1612, 1665, and 1667 MHz in the Milky Way galaxy. The database (version 2.4) contains 13 655 observations and 2341 different stars detected in at least one transition. Detections at 1612 MHz are considered to be complete until the end of 2014 as long as they were published in refereed papers. Detections of the main lines (1665 and 1667 MHz) and non-detections in all transitions are included only if published after 1983. The database contains flux densities and velocities of the two strongest maser peaks, the expansion velocity of the shell, and the radial velocity of the star. Links are provided for about 100 stars (<5% of all stars with OH masers) to interferometric observations and monitoring programs of the maser emission published since their beginnings in the 1970s. Access to the database is possible over the Web (http://www.hs.uni-hamburg.de/maserdb), allowing cone searches for individual sources and lists of sources. A general search is possible in selected regions of the sky and by defining ranges of flux densities and/or velocities. Alternative ways to access the data are via the German Virtual Observatory and the CDS. The data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/582/A68

  15. A catalog of nonstellar water maser sources

    NASA Technical Reports Server (NTRS)

    Dinger, A. S. C.; Dickinson, D. F.

    1980-01-01

    A list of 195 nonstellar galactic sources of water maser emission has been compiled. This list is not a comprehensive catalog of all the available information; it is intended to be used as an index. As such, it contains only coordinates, velocities, and selected references. The extragalatic sources are listed in a separate table.

  16. Reflected-wave maser. [low noise amplifier

    NASA Technical Reports Server (NTRS)

    Clauss, R. C. (Inventor)

    1976-01-01

    A number of traveling-wave, slow-wave maser structures, containing active maser material but absent the typical ferrite isolators, are immersed in a nonuniform magnetic field. The microwave signal to be amplified is inserted at a circulator which directs the signal to a slow-wave structure. The signal travels through the slow-wave structure, being amplified according to the distance traveled. The end of the slow-wave structure farthest from the circulator is arranged to be a point of maximum reflection of the signal traveling through the slow-wave structure. As a consequence, the signal to be amplified traverses the slow-wave structure again, in the opposite direction (towards the circulator) experiencing amplification equivalent to that achieved by a conventional traveling-wave maser having twice the length. The circulator directs the amplified signal to following like stages of amplification. Isolators are used in between stages to prevent signals from traveling in the wrong direction, between the stages. Reduced signal loss is experienced at each stage. The high gain produced by each slow-wave structure is reduced to a moderate value by use of a nonuniform magnetic field which also broadens the line width of the maser material. The resulting bandwidth can be exceptionally wide. Cascaded stages provide high gain, exceptionally wide bandwith and very low noise temperature.

  17. VLBA SiO maser observations of the OH/IR star OH 44.8-2.3: magnetic field and morphology

    NASA Astrophysics Data System (ADS)

    Amiri, N.; Vlemmings, W. H. T.; Kemball, A. J.; van Langevelde, H. J.

    2012-02-01

    Context. SiO maser emission occurs in the extended atmosphere of evolved stars and can be studied at high angular resolution. As compact, high-brightness components they can be used as important tracers of the dynamics at distances close to the central star. The masers also serve as probes of the evolutionary path from spherically symmetric AGB stars to aspherical PNe. Very long baseline interferometry (VLBI) observations of Mira variables indicate that SiO masers are significantly linearly polarized with linear polarization fractions up to 100%. However, no information is available at high angular resolution for SiO masers in higher mass loss OH/IR stars. Theory indicates a different SiO pumping mechanism in higher mass loss evolved stars. Aims: We extend the VLBI SiO maser studies to OH/IR stars. The observations enable us to understand the SiO pumping mechanisms in higher mass-loss evolved objects and to compare them with Mira variables. Additionally, polarimetric observations of SiO masers help us to understand the magnetic field strength and morphology and to distinguish between conflicting polarization theories. Methods: The 43 GHz SiO maser observations of the OH/IR star OH 44.8-2.3 were performed with the VLBA in full polarization spectral line mode. Auxiliary EVLA observations were performed to allow for the absolute calibration of the polarization angle. The Zeeman splitting was measured by cross correlating the right and left circular polarization spectra, as well as the S-curve fitting. Additionally, we analyzed the 1612 MHz OH maser observations of OH 44.8-2.3 from the VLA archive. Results: The SiO masers of OH 44.8-2.2 form a ring located at ~5.4 AU around the star. The masers appear to be highly linearly polarized with fractional linear polarization up to 100%. The linear polarization vectors are consistent with a dipole field morphology in this star. We report a tentative detection of circular polarization of ~0.7% for the brightest maser feature

  18. An Alfven wave maser in the laboratory

    SciTech Connect

    Maggs, J.E.; Morales, G.J.; Carter, T.A.

    2005-01-01

    A frequency selective Alfven wave resonator results from the application of a locally nonuniform magnetic field to a plasma source region between the cathode and anode in a large laboratory device. When a threshold in the plasma discharge current is exceeded, selective amplification produces a highly coherent ({delta}{omega}/{omega}<5x10{sup -3}), large amplitude shear Alfven wave that propagates out of the resonator, through a semitransparent mesh anode, into the adjacent plasma column where the magnetic field is uniform. This phenomenon is similar to that encountered in the operation of masers/lasers at microwave and optical frequencies. The current threshold for maser action is found to depend upon the confinement magnetic field strength B{sub 0}. Its scaling is consistent with the condition for matching the drift speed of the bulk plasma electrons with the phase velocity of the mode in the resonator. The largest spontaneously amplified signals are obtained at low B{sub 0} and large plasma currents. The magnetic fluctuations {delta}B associated with the Alfven maser can be as large as {delta}B/B{sub 0}{approx_equal}1.5% and are observed to affect the plasma current. Steady-state behavior leading to coherent signals lasting until the discharge is terminated can be achieved when the growth conditions are well-above threshold. The maser is observed to evolve in time from an initial m=0 mode to an m=1 mode structure in the transition to the late steady state. The laboratory phenomenon reported is analogous to the Alfven wave maser proposed to exist in naturally occurring, near-earth plasmas.

  19. Water masers embedded in ultracompact H II regions: The W 75N cloud core

    NASA Astrophysics Data System (ADS)

    Hunter, T. R.; Taylor, G. B.; Felli, M.; Tofani, G.

    1994-04-01

    We present radio observations of the W 75N star forming region consisting of:(1) high-resolution Very Large Array (VLA) radio continuum and H2O maser maps, (2) CSO molecular maps in the CS and CO lines, (3) results from a six-year monitoring campaign of the H2O maser emission with the 32-m Medicina telescope. Using the VLA in A-configuration, we find that the 22 GHz H2O maser spots in W 75N spatially coincide with very weak, small diameter (less than 1 sec) radio continuum sources at the center of the dense molecular cloud core. The very high optical obscuration (Ar greater than or equal 90 mag), the high total luminosity of the source and the high electron density suggest that in W 75N we are witnessing the first appearance of an ultracompact H II region (UCH II) produced by an early type star still deeply embedded in the progenitor molecular cloud. The H2O maser - UCH II association may last only for the short time (approximately 103 y) needed by the H II to expand out to the distance where masers are formed. Both the H2O and OH masers as well as the continuum sources extend a few seconds of arc along a roughly N-S line, matching the extension of the core evident in the CS J = 7 goes to 6 map and nearly perpendicular to the axis of the molecular outflow. As traced by the CO J = 3 goes to 2 transition, the origin of the outflow lies at the position of the UCH IIs, suggesting that they are associated with the powering source. The H2O spectrum extends over approximately 30 km/s, with many distinct velocity components, part of which can be unambiguously identified with individual spatial components of the VLA H2O map. The variability of the H2O emission of each velocity component is very high, with time scales of the order of a few years and dynamic range almost up to two orders of magnitude. For the bluest velocity component, well isolated in the velocity and space domains, there is evidence of a continuous velocity drift of approximately 4 km/s over 2 years. The

  20. CARM and harmonic gyro-amplifier experiments at 17 GHz

    SciTech Connect

    Menninger, W.L.; Danly, B.G.; Alberti, S.; Chen, C.; Rullier, J.L.; Temkin, R.J.; Giguet, E. |

    1993-11-01

    Cyclotron resonance maser amplifiers are possible sources for applications such as electron cyclotron resonance heating of fusion plasmas and driving high-gradient rf linear accelerators. For accelerator drivers, amplifiers or phase locked-oscillators are required. A 17 GHz cyclotron autoresonance maser (CARM) amplifier experiment and a 17 GHz third harmonic gyro-amplifier experiment are presently underway at the MIT Plasma Fusion Center. Using the SRL/MIT SNOMAD II introduction accelerator to provide a 380 kV, 180 A, 30 ns flat top electron beam, the gyro-amplifier experiment has produced 5 MW of rf power with over 50 dB of gain at 17 GHz. The gyro-amplifier operates in the TE{sub 31} mode using a third harmonic interaction. Because of its high power output, the gyro-amplifier will be used as the rf source for a photocathode rf electron gun experiment also taking place at MIT. Preliminary gyro-amplifier results are presented, including measurement of rf power, gain versus interaction length, and the far-field pattern. A CARM experiment designed to operate in the TE{sub 11} mode is also discussed.

  1. Iras-Selected Galactic Star-Forming Regions - Part One - New 6/16-5/23 Water Maser Detections in Molecular Cores North of DEC +15DEG

    NASA Astrophysics Data System (ADS)

    Palumbo, G. G. C.; Scappini, F.; Pareschi, G.; Codella, C.; Caselli, P.; Attolini, M. R.

    1994-01-01

    The results are presented of a survey, performed with the Medicina 32-m parabolic reflector, of a sample of IRAS-selected sources associated with molecular clouds for water masers at 22 GHz (616 → 523). The final aim is to study the occurrence of maser emission from star-forming regions in the very early stages of evolution. The whole sample consists of 1409 IRAS sources selected by applying Emerson's colour criteria. In the present paper, results are given for sources with declinations greater than +15°, belonging to two subsamples that satisfy more restrictive colour criteria which should identify ultracompact H II regions (subsample A, 288 sources) and H II regions (subsample B, 133 sources). The main result of the present study is that 59 IRAS sources in the samples are water maser emitters, 11 of which are new detections from the present survey.

  2. Rubidium 87 gas cell studies, phase 2. [design and characteristics of rubidium maser

    NASA Technical Reports Server (NTRS)

    Vanier, J.

    1974-01-01

    The design, development, and characteristics of a rubidium 87 maser are discussed. The design of a receiver capable of locking a crystal oscillator to the maser signal is reported. The subjects considered are: (1) maser construction, (2) maser control electronics, (3) the characteristics of the receiver, and (4) results of experimental maser tests.

  3. A gravitationally lensed water maser in the early Universe.

    PubMed

    Impellizzeri, C M Violette; McKean, John P; Castangia, Paola; Roy, Alan L; Henkel, Christian; Brunthaler, Andreas; Wucknitz, Olaf

    2008-12-18

    Water masers are found in dense molecular clouds closely associated with supermassive black holes at the centres of active galaxies. On the basis of the understanding of the local water-maser luminosity function, it was expected that masers at intermediate and high redshifts would be extremely rare. However, galaxies at redshifts z > 2 might be quite different from those found locally, not least because of more frequent mergers and interaction events. Here we use gravitational lensing to search for masers at higher redshifts than would otherwise be possible, and find a water maser at redshift 2.64 in the dust- and gas-rich, gravitationally lensed type-1 quasar MG J0414+0534 (refs 6-13). The isotropic luminosity is 10,000 (, solar luminosity), which is twice that of the most powerful local water maser and half that of the most distant maser previously known. Using the locally determined luminosity function, the probability of finding a maser this luminous associated with any single active galaxy is 10(-6). The fact that we see such a maser in the first galaxy we observe must mean that the volume densities and luminosities of masers are higher at redshift 2.64. PMID:19092930

  4. H2O maser emission in circumstellar envelopes around AGB stars: Physical conditions in gas-dust clouds

    NASA Astrophysics Data System (ADS)

    Nesterenok, A. V.

    2013-10-01

    The pumping of 22.2-GHz H2O masers in the circumstellar envelopes of asymptotic giant branch stars has been simulated numerically. The physical parameters adopted in the calculations correspond to those of the circumstellar envelope around IK Tau. The one-dimensional plane-parallel structure of the gas-dust cloud is considered. The statistical equilibrium equations for the H2O level populations and the thermal balance equations for the gas-dust cloud are solved self-consistently. The calculations take into account 410 rotational levels belonging to the five lowest vibrational levels of H2O. The stellar radiation field is shown to play an important role in the thermal balance of the gas-dust cloud due to the absorption of emission in rotational-vibrational H2O lines. The dependence of the gain in the 22.2-GHz maser line on the gas density and H2O number density in the gas-dust cloud is investigated. Gas densities close to the mean density of the stellar wind, 107-108 cm-3, and a high relative H2O abundance, more than 10-4, have been found to be the most likely physical conditions in maser sources.

  5. Water Masers Associated with IRAS 4A

    NASA Astrophysics Data System (ADS)

    Marvel, K. B.; Claussen, M.; Wootten, A.; Wilking, B.

    2000-05-01

    Observations of water masers near Young Stellar Objects (YSOs) are capable of revealing gas kinematics within a few AU of stars undergoing formation. Low mass YSOs are especially interesting as they are analogues of our own Sun. Several sources have been mapped in recent years and have shown proper motions indicative of bipolar outflowing material. Velocities are typically about 75 km/s and are clearly bipolar. Occasionally, bowshock structures have been observed (Imai et al. 1999, Claussen et al. 1999), showing the interaction between the jet and the ambient medium and perhaps indicating that the bipolar outflow occurs episodically. I present images and proper motions for the water masers associated with IRAS 4A. They are consistent with other sources of this class.

  6. Magnetic refrigeration for maser amplifier cooling

    NASA Technical Reports Server (NTRS)

    Johnson, D. L.

    1982-01-01

    The development of a multifrequency upconverter-maser system for the DSN has created the need to develop a closed-cycle refrigerator (CCR) capable of providing more than 3 watts of refrigeration capability at 4.5 K. In addition, operating concerns such as the high cost of electrical power consumption and the loss of maser operation due to CCR failures require that improvements be made to increase the efficiency and reliability of the CCR. One refrigeration method considered is the replacement of the Joule-Thomson expansion circuit with a magnetic refrigeration. Magnetic refrigerators can provide potentially reliable and highly efficient refrigeration at a variety of temperature ranges and cooling power. The concept of magnetic refrigeration is summarized and a literature review of existing magnetic refrigerator designs which have been built and tested and that may also be considered as possibilities as a 4 K to 15 K magnetic refrigeration stage for the DSN closed-cycle refrigerator is provided.

  7. Astrophysical Masers and their Environments (IAU S242)

    NASA Astrophysics Data System (ADS)

    Chapman, Jessica M.; Baan, Willem A.

    2008-02-01

    Preface; Conference prelims; Tribute to Raymond James Cohen J. M. Chapman and W. A. Baan; History P. Edwards; Session 1. Maser theory Anne Green; Session 2. Polarization and magnetic fields Athol Kemball; Session 3. Masers and star formation Mark Wardle; Session 4. Galactic maser surveys Philip Diamond and Hiroshi Imai; Session 5. Stellar masers, circumstellar winds and supernova remnants Hiroshi Imai, Crystal Brogan and Miller Goss; Session 6. Galactic structure and the Galactic Centre Luis Rodriguez; Session 7. Masers in AGN environments Moshe Elitzur; Session 8. Megamaser and starburst activity Lincoln Greenhill; Session 9. Diagnostics and interpretation in extragalactic environments Colin Lonsdale; Session 10. New millimeter and sub-millimeter masers Indra Bains; Session 11. Future facilities and conference summary Elizabeth Humphreys and Karl Menten; Author index.

  8. Astrophysical Masers and their Environments (IAU S242)

    NASA Astrophysics Data System (ADS)

    Chapman, Jessica M.; Baan, Willem A.

    2007-03-01

    Preface; Conference prelims; Tribute to Raymond James Cohen J. M. Chapman and W. A. Baan; History P. Edwards; Session 1. Maser theory Anne Green; Session 2. Polarization and magnetic fields Athol Kemball; Session 3. Masers and star formation Mark Wardle; Session 4. Galactic maser surveys Philip Diamond and Hiroshi Imai; Session 5. Stellar masers, circumstellar winds and supernova remnants Hiroshi Imai, Crystal Brogan and Miller Goss; Session 6. Galactic structure and the Galactic Centre Luis Rodriguez; Session 7. Masers in AGN environments Moshe Elitzur; Session 8. Megamaser and starburst activity Lincoln Greenhill; Session 9. Diagnostics and interpretation in extragalactic environments Colin Lonsdale; Session 10. New millimeter and sub-millimeter masers Indra Bains; Session 11. Future facilities and conference summary Elizabeth Humphreys and Karl Menten; Author index.

  9. Enhanced magnetic Purcell effect in room-temperature masers

    PubMed Central

    Breeze, Jonathan; Tan, Ke-Jie; Richards, Benjamin; Sathian, Juna; Oxborrow, Mark; Alford, Neil McN

    2015-01-01

    Recently, the world’s first room-temperature maser was demonstrated. The maser consisted of a sapphire ring housing a crystal of pentacene-doped p-terphenyl, pumped by a pulsed rhodamine-dye laser. Stimulated emission of microwaves was aided by the high quality factor and small magnetic mode volume of the maser cavity yet the peak optical pumping power was 1.4 kW. Here we report dramatic miniaturization and 2 orders of magnitude reduction in optical pumping power for a room-temperature maser by coupling a strontium titanate resonator with the spin-polarized population inversion provided by triplet states in an optically excited pentacene-doped p-terphenyl crystal. We observe maser emission in a thimble-sized resonator using a xenon flash lamp as an optical pump source with peak optical power of 70 W. This is a significant step towards the goal of continuous maser operation. PMID:25698634

  10. Enhanced magnetic Purcell effect in room-temperature masers.

    PubMed

    Breeze, Jonathan; Tan, Ke-Jie; Richards, Benjamin; Sathian, Juna; Oxborrow, Mark; Alford, Neil McN

    2015-01-01

    Recently, the world's first room-temperature maser was demonstrated. The maser consisted of a sapphire ring housing a crystal of pentacene-doped p-terphenyl, pumped by a pulsed rhodamine-dye laser. Stimulated emission of microwaves was aided by the high quality factor and small magnetic mode volume of the maser cavity yet the peak optical pumping power was 1.4 kW. Here we report dramatic miniaturization and 2 orders of magnitude reduction in optical pumping power for a room-temperature maser by coupling a strontium titanate resonator with the spin-polarized population inversion provided by triplet states in an optically excited pentacene-doped p-terphenyl crystal. We observe maser emission in a thimble-sized resonator using a xenon flash lamp as an optical pump source with peak optical power of 70 W. This is a significant step towards the goal of continuous maser operation. PMID:25698634

  11. Maser and infrared studies of oxygen-rich late/post-asymptotic giant branch stars and water fountains: development of a new identification method

    SciTech Connect

    Yung, Bosco H. K.; Nakashima, Jun-ichi; Henkel, Christian

    2014-10-10

    We explored an efficient method to identify evolved stars with oxygen-rich envelopes in the late asymptotic giant branch (AGB) or post-AGB phase of stellar evolution, which include a rare class of objects—the 'water fountains (WF)'. Our method considers the OH and H{sub 2}O maser spectra, the near-infrared Q-parameters (these are color indices accounting for the effect of extinction), and far-infrared AKARI colors. Here we first present the results of a new survey on OH and H{sub 2}O masers. There were 108 color-selected objects: 53 of them were observed in the three OH maser lines (1612, 1665, and 1667 MHz), with 24 detections (16 new for 1612 MHz); and 106 of them were observed in the H{sub 2}O maser line (22 GHz), with 24 detections (12 new). We identify a new potential WF source, IRAS 19356+0754, with large velocity coverages of both OH and H{sub 2}O maser emission. In addition, several objects with high-velocity OH maser emission are reported for the first time. The Q-parameters as well as the infrared [09]–[18] and [18]–[65] AKARI colors of the surveyed objects are then calculated. We suggest that these infrared properties are effective in isolating aspherical from spherical objects, but the morphology may not necessarily be related to the evolutionary status. Nonetheless, by considering altogether the maser and infrared properties, the efficiency of identifying oxygen-rich late/post-AGB stars could be improved.

  12. The superconducting cavity stability ruby maser oscillator

    NASA Technical Reports Server (NTRS)

    Dick, G. J.; Strayer, D. M.

    1985-01-01

    Analysis of an application of the rudy maser to a superconducting Cavity Stabilized oscillator shows many attractive features. These derive from the mechancial stability inherent in an all-cryogenic design and from the properties of the ruby maser itself. A multiple-cavity design has been developed to allow physical separation of the high-Q superconducting cavity and the ruby element with its requried applied magnetic field. Mode selection is accomplished in this design by tuning the ruby by means of the applied field. We conclude that such an oscillator would perform well, even with cavity Q's as low as 10 to the 8th power allowing the use of a superconductor-on-sapphire resonator with its greater rigidity and lower thermal expansion. A first test of the Superconducting Cavity Stabilized Maser Oscillator (SCSMO) confirms the efficacy of the multiple-cavity design and the applicability of the ruby maser. Frequency variation less than 4x10 to the minus 11th power was measured in the stabilized mode and is attributed to the reference oscillator and to instabilities in the pump source. Variation of 10 to the minus 10th power was observed in the low-Q unstabilized mode, again attributable to pump fluctuations. Even so, direct scaling to a Q of 10 the 9th power predicts a stability better than 10 to the minus 15th power. Together with results showing the lowest losses to date in sapphire at microwave frequencies, and preliminary experiments on superconductor-on-sapphire resonators, frequency stability, levels as low as 10 to the minus 17th power are indicated.

  13. A superconducting hydrogen maser resonator made from electrophoretic YBa sub 2 Cu sub 3 O sub 7 minus. delta

    SciTech Connect

    Opie, D.; Schone, H. . Dept. of Physics); Hein, M.; Muller, G.; Piel, H.; Wehler, D. ); Folen, V.; Wolf, S. )

    1991-03-01

    This paper reports on a compact loop-gap hydrogen maser resonator constructed by electrophoretic deposition of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (YBCO) onto silver. The resonator is tuned to operate at the hyperfine transition frequency of hydrogen (1.42 GHz). This device is considered to be the first step towards a superconducting cavity for a compact hydrogen maser to be used in the Global Positioning System (GPS). The required miniaturization of the resonator reduces its Q value. This effect can be compensated for by the low surface resistance of YBCO at 77 K. Large and curved polycrystalline YBCO layers can be obtained by the electrophoretic deposition technique. In this contribution we report on the construction and the test of High Temperature Superconductor Space Experiment (HTSSE).

  14. New interstellar masers in nonmetastable ammonia

    NASA Technical Reports Server (NTRS)

    Madden, S. C.; Irvine, W. M.; Matthews, H. E.; Brown, R. D.; Godfrey, P. D.

    1986-01-01

    The first astronomical detections of several ammonia inversion transitions involving nonmetastable levels with energies as high as 1090 K above the ground state are reported. The (J, K) = (9, 6) inversion transition shows maser-like emission in the directions of W51, NGC 7538, W49, and DR 21(OH). The NH3 (6, 3) line exhibits similar characteristics in W51 but is seen in absorption in NGC 7538. These are the first definite detections of ammonia masers in space. The intensities and narrow line widths (0.5-1.5 km/s) for the emission features are in contrast to the previously detected broad, weak, nonmetastable lines attributed to thermal emission in these sources. Temporal variability appears to be evident in the (9, 6) emission in W49 over a 4 month period. The highly excited (J, K) = (9, 6) and (6, 3) ammonia lines are found in regions containig compact H II regions and strongly infrared sources with associated H2O and OH masers; i.e., in regions of active star formation.

  15. Evidence for cyclotron maser emission from the sun and stars

    NASA Technical Reports Server (NTRS)

    Dulk, G. A.; Winglee, R. M.

    1987-01-01

    Recent observational and theoretical work on cyclotron maser instability is reviewed, with emphasis on the similarities between microwave spike bursts from the sun and bursts from stars and planets. Results on particle-in-cell simulations are discussed, and it is suggested that such studies may provide further information on the amount and efficiency of energy transfer by the maser radiation. Observational tests of the cyclotron maser theory are considered, in addition to the role of the cyclotron maser as an energy transport mechanism in solar flares.

  16. New auto-tuning technique for the hydrogen maser

    NASA Technical Reports Server (NTRS)

    Sydnor, R. L.; Maleki, L.

    1983-01-01

    Auto-tuning of the maser cavity compensates for cavity pulling effect, and other sources of contribution to the long term frequency drift. Schemes previously proposed for the maser cavity auto-tuning can have adverse effects on the performance of the maser. A new scheme is proposed based on the phase relationship between the electric and the magnetic fields inside the cavity. This technique has the desired feature of auto-tuning the cavity with a very high sensitivity and without disturbing the maser performance. Some approaches for the implementation of this scheme and possible areas of difficulty are examined.

  17. Short-term frequency stability of the Rb-87 maser.

    NASA Technical Reports Server (NTRS)

    Tetu, M.; Busca, G.; Vanier, J.

    1973-01-01

    Measurements of the short-term stability of the Rb-87 maser as a function of the maser power output and the receiver cutoff frequency are reported. The experimental data are compared to theoretical results obtained from an approximate theory. In this theory the transfer function of the maser for thermal noise is derived, and the spectral density of the phase fluctuations is calculated. An analytical expression for the 'Allan variance' is also given. A comparison of the stability of the Rb-87 maser with existing frequency standards shows its superiority for averaging times less than 1 sec.

  18. Water Masers in the Andromeda Galaxy. I. A Survey for Water Masers, Ammonia, and Hydrogen Recombination Lines

    NASA Astrophysics Data System (ADS)

    Darling, Jeremy; Gerard, Benjamin; Amiri, Nikta; Lawrence, Kelsey

    2016-07-01

    We report the results of a Green Bank Telescope survey for water masers, ammonia (1, 1) and (2, 2), and the H66α recombination line toward 506 luminous compact 24 μm emitting regions in the Andromeda Galaxy (M31). We include the 206 sources observed in the Darling water maser survey for completeness. The survey was sensitive enough to detect any maser useful for ˜10 μas yr‑1 astrometry. No new water masers, ammonia lines, or H66α recombination lines were detected individually or in spectral stacks reaching rms noise levels of ˜3 mJy and ˜0.2 mJy, respectively, in 3.1–3.3 km s‑1 channels. The lack of detections in individual spectra and in the spectral stacks is consistent with Galactic extrapolations. Contrary to previous assertions, there do not seem to be any additional bright water masers to be found in M31. The strong variability of water masers may enable new maser detections in the future, but variability may also limit the astrometric utility of known (or future) masers because flaring masers must also fade.

  19. Water Masers in the Andromeda Galaxy. I. A Survey for Water Masers, Ammonia, and Hydrogen Recombination Lines

    NASA Astrophysics Data System (ADS)

    Darling, Jeremy; Gerard, Benjamin; Amiri, Nikta; Lawrence, Kelsey

    2016-07-01

    We report the results of a Green Bank Telescope survey for water masers, ammonia (1, 1) and (2, 2), and the H66α recombination line toward 506 luminous compact 24 μm emitting regions in the Andromeda Galaxy (M31). We include the 206 sources observed in the Darling water maser survey for completeness. The survey was sensitive enough to detect any maser useful for ∼10 μas yr‑1 astrometry. No new water masers, ammonia lines, or H66α recombination lines were detected individually or in spectral stacks reaching rms noise levels of ∼3 mJy and ∼0.2 mJy, respectively, in 3.1–3.3 km s‑1 channels. The lack of detections in individual spectra and in the spectral stacks is consistent with Galactic extrapolations. Contrary to previous assertions, there do not seem to be any additional bright water masers to be found in M31. The strong variability of water masers may enable new maser detections in the future, but variability may also limit the astrometric utility of known (or future) masers because flaring masers must also fade.

  20. First evidence of planetary water maser emission induced by the comet/Jupiter catastrophic impact

    NASA Astrophysics Data System (ADS)

    Cosmovici, Cristiano B.; Montebugnoli, Stelio; Orfei, Alessandro; Pogrebenko, Sergej; Colom, Pierre

    1996-08-01

    The comet Shoemaker-Levy 9/Jupiter event gave a unique opportunity to study the consequences of a catastrophic impact in a planetary atmosphere and the subsequent changes in the chemistry and in the excitation conditions of atomic and molecular species. In particular previous attempts to detect molecular radio lines from the Jupiter atmosphere gave negative results. By using a new fast multichannel spectrometer (up to 128,000 channels), coupled with the 32 m dish of the Medicina Radiotelescope, three molecular lines observable in the available region of our system were searched for: water at 22.235 GHz, formaldehyde at 4.830 GHz and ammonia at 23.694 GHz. The detection of the 616→5 23 rotational transition of the 1.35 cm water line from blob E on July 19, 1994, 2 days after impact is reported. A possible detection of water emission from blobs A and C on the same day may be given only with a 3-sigma level. Emission from blob E was probably detected also on August 3 and September 9, i.e. up to 54 days after impact. The very narrow line width (40 kHz) and the high brightness temperature (20,000 K) of the water emission detected cannot be explained in terms of usual thermal emission when taking into account thermal and/or collisional broadening. In this paper it is shown that only a MASER effect could explain the observed values. This would be the first detection of a water MASER in the Solar System and the first evidence of masing effects induced by catastrophic impacts.

  1. Towards detecting methanol emission in low-mass protoplanetary discs with ALMA: the role of non-LTE excitation

    NASA Astrophysics Data System (ADS)

    Parfenov, S. Yu.; Semenov, D. A.; Sobolev, A. M.; Gray, M. D.

    2016-08-01

    The understanding of organic content of protoplanetary discs is one of the main goals of the planet formation studies. As an attempt to guide the observational searches for weak lines of complex species in discs, we modelled the (sub)millimetre spectrum of gaseous methanol (CH3OH), one of the simplest organic molecules, in the representative T Tauri system. We used 1+1D disc physical model coupled to the gas-grain ALCHEMIC chemical model with and without 2D-turbulent mixing. The computed CH3OH abundances along with the CH3OH scheme of energy levels of ground and excited torsional states were used to produce model spectra obtained with the non-local thermodynamic equilibrium (non-LTE) 3D line radiative transfer code LIME. We found that the modelled non-LTE intensities of the CH3OH lines can be lower by factor of >10-100 than those calculated under assumption of LTE. Though population inversion occurs in the model calculations for many (sub)millimetre transitions, it does not lead to the strong maser amplification and noticeably high line intensities. We identify the strongest CH3OH (sub)millimetre lines that could be searched for with the Atacama Large Millimeter Array (ALMA) in nearby discs. The two best candidates are the CH3OH 50 - 40A+ (241.791 GHz) and 5-1 - 4-1E (241.767 GHz) lines, which could possibly be detected with the ˜5σ signal-to-noise ratio after ˜3 h of integration with the full ALMA array.

  2. Water masers in Compton-thick AGN. I. Detailed study of the new water megamaser in IRAS 15480-0344

    NASA Astrophysics Data System (ADS)

    Castangia, P.; Tarchi, A.; Caccianiga, A.; Severgnini, P.; Della Ceca, R.

    2016-02-01

    Context. A relationship between the water maser detection rate and large nuclear column densities in AGN has often been cited in the literature. Indeed, detailed studies of luminous water masers, typically associated with the nuclear activity, allow us to investigate the innermost regions of AGN, with an impact on the still debated Unified Model for this class of objects. Aims: We have recently entertained a search for maser emission in a well-defined sample of Compton-thick AGN aimed at investigating, on firm statistical bases, the aforementioned relationship. While the survey is still ongoing, and is the subject of a forthcoming publication, a new luminous water maser has been detected in the lenticular (field) S0 galaxy IRAS 15480-0344, whose origin, associated with an accretion disc or a nuclear outflow/jet, needs to be assessed. Methods: Multi-epoch single-dish observations and VLBI measurements were performed to investigate the distribution, spatial extension, and variability of the maser emission in order to infer the main characteristics of the water megamaser. Results: The new detection in IRAS 15480-0344 is reported: a megamaser with a total single-dish isotropic luminosity of ~200 L⊙ and a profile composed of two main features, a broad line with a full width to half maximum (FWHM) linewidth of ~90 km s-1 and a narrow (FWHM< 1 km s-1) one. We performed a follow-up to the detection with the Very Long Baseline Array (VLBA) and confidently detected only the narrow component, which is coincident with the nuclear radio continuum emission detected with the Very Large Array at 8.4 GHz. A weak narrow feature has also been detected in the velocity range of the broad feature and is located 15 pc to the north-west with respect to the stronger component. Neither maser spot is associated with the compact radio continuum sources derived from the same VLBA dataset. Conclusions: The different line profiles and the spatial separation between the two features in the

  3. Thermal short improves sensitivity of cryogenically cooled maser

    NASA Technical Reports Server (NTRS)

    Clauss, R. C.

    1968-01-01

    In-line, quarter-wave thermal short cools the center conductor of the signal-input coaxial transmission line to a cryogenically cooled traveling wave maser. It reduces both the thermal noise contribution of the coaxial line and the heat leak through the center conductor to the maser at 4.4 degrees K.

  4. The polarized water maser source in orion

    NASA Astrophysics Data System (ADS)

    Abraham, Zulema; Vilas Boas, J. W. S.

    We report the time behaviour of the highly polarized 8 km s-1 water maser source in the Orion nebula. During the last few years the flux density was low and it presented three small outbursts. In each case, although the total intensity was of the same order of magnitude, the degree of polarization and polarization angle were different, as well as their variation across the line profile. In November of 1991, twelve years after its first detection, the source disappeared or became too weak to be detected.

  5. Measurement of the Fundamental Thermal Noise Limit in a Cryogenic Sapphire Frequency Standard Using Bimodal Maser Oscillations

    SciTech Connect

    Benmessai, Karim; Kersale, Yann; Giordano, Vincent; Creedon, Daniel Lloyd; Tobar, Michael Edmund; Bourgeois, Pierre-Yves

    2008-06-13

    We report observations of the Schawlow-Townes noise limit in a cryogenic sapphire secondary frequency standard. The effect causes a fundamental limit to the frequency stability, and was measured through the novel excitation of a bimodal maser oscillation of a Whispering Gallery doublet at 12.04 GHz. The beat frequency of 10 kHz between the oscillations enabled a sensitive probe for this measurement of fractional frequency instability of 10{sup -14}{tau}{sup -1/2} with only 0.5 pW of output power.

  6. Outflow structure within 1000 au of high-mass YSOs. I. First results from a combined study of maser and radio continuum emission

    NASA Astrophysics Data System (ADS)

    Moscadelli, L.; Sánchez-Monge, Á.; Goddi, C.; Li, J. J.; Sanna, A.; Cesaroni, R.; Pestalozzi, M.; Molinari, S.; Reid, M. J.

    2016-01-01

    Context. In high-mass (≥7 M⊙) star formation (SF) studies, high-angular resolution is crucial for resolving individual protostellar outflows (and possibly accretion disks) from the complex contribution of nearby (high- and low-mass) young stellar objects (YSO). Previous interferometric studies have focused mainly on single objects. Aims: A sensitive survey at high angular resolution is required to investigate outflow processes in a statistically significant sample of high-mass YSOs and on spatial scales relevant to testing theories. Methods: We selected a sample of 40 high-mass YSOs from water masers observed within the BeSSeL Survey. We investigated the 3D velocity and spatial structures of the molecular component of massive outflows at milli-arcsecond angular resolution using multi-epoch Very Long Baseline Array (VLBA) observations of 22 GHz water masers. We also characterize the ionized component of the flows using deep images of the radio continuum emission with resolutions of ~0."2, at 6, 13, and 22 GHz with the Jansky Very Large Array (JVLA). Results: We report the first results obtained for a subset of 11 objects from the sample. The water maser measurements provide us with a very accurate description of the molecular gas kinematics. This in turn enables us to estimate the momentum rate of individual outflows, varying in the range 10-3-100M⊙ yr-1 km s-1, among the highest values reported in the literature. In all the observed objects, the continuum emission at 13 and 22 GHz has a compact structure, with its position coincident with that of the water masers. The 6 GHz continuum consists of either compact components (mostly well aligned with the 13 and/or 22 GHz sources) or extended emission (either highly elongated or approximately spherical), which can be offset by up to a few arcseconds from the water masers. The unresolved continuum emission associated with the water masers likely points to the YSO location. The comparison of the radio continuum

  7. Loss cone-driven cyclotron maser instability

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Yun; Yi, Sibaek; Lim, Dayeh; Kim, Hee-Eun; Seough, Jungjoon; Yoon, Peter H.

    2013-11-01

    The weakly (or mildly) relativistic cyclotron maser instability has been successfully applied to explain the Earth's auroral kilometric radiation and other radio sources in nature and laboratory. Among the most important physical parameters that determine the instability criteria is the ratio of plasma-to-electron cyclotron frequencies, ωp/Ω. It is therefore instructive to consider how the normalized maximum growth rate, γmax/Ω, varies as a function of ωp/Ω. Although many authors have already discussed this problem, in order to complete the analysis, one must also understand how the radiation emission angle corresponding to the maximum growth, θmax, scales with ωp/Ω, since the propagation angle determines the radiation beaming pattern. Also, the behavior of the frequency corresponding to the maximum growth rate at each harmonic, (ωmax-sΩ)/Ω, where s=1,2,3,ċ , as a function of ωp/Ωis of importance for a complete understanding of the maser excitation. The present paper computes these additional quantities for the first time, making use of a model loss cone electron distribution function.

  8. Exploration of Solar Wind Acceleration Region Using Interplanetary Scintillation of Water Vapor Maser Source and Quasars

    NASA Technical Reports Server (NTRS)

    Tokumaru, Munetoshi; Yamauchi, Yohei; Kondo, Tetsuro

    2001-01-01

    Single-station observations of interplanetary scintillation UPS) at three microwave frequencies 2, 8, and 22GHz, were carried out between 1989 and 1998 using a large (34-micro farad) radio telescope at the Kashima Space Research Center of the Communications Research Laboratory. The aim of these observations was to explore the near-sun solar wind, which is the key region for the study of the solar wind acceleration mechanism. Strong quasars, 3C279 and 3C273B, were used for the Kashima IPS observations at 2 and 8GHz, and a water-vapor maser source, IRC20431, was used for the IPS observations at 22GHz. Solar wind speeds derived from Kashima IPS data suggest that the solar wind acceleration takes place at radial distances between 10 and 30 solar radii (Rs) from the sun. The properties of the turbulence spectrum (e.g. anisotropy, spectral index, inner scale) inferred from the Kashima data were found to change systematically in the solar wind acceleration region. While the solar wind in the maximum phase appears to be dominated by the slow wind, fast and rarefied winds associated with the coronal holes were found to develop significantly at high latitudes as the solar activity declined. Nevertheless, the Kashima data suggests that the location of the acceleration region is stable throughout the solar cycle.

  9. Simulation of high power broadband cyclotron autoresonance maser amplifier and electron beam experiments

    NASA Astrophysics Data System (ADS)

    Speirs, D. C.; Phelps, A. D. R.; Konoplev, I. V.; Cross, A. W.; He, W.

    2004-04-01

    The design, simulation, and preliminary experimental implementation of an efficient, broadband cyclotron autoresonance maser (CARM) amplifier operating over the 9-13 GHz frequency band is presented. The amplifier is based on a high current accelerator capable of generating a ˜35 A pencil electron beam at an accelerating voltage of ˜450 kV. A full three-dimensional numerical model of the CARM amplifier has been constructed within the particle-in-cell code KARAT taking into account electron beam parameters derived from simulation and experiment. An electron beam current of 32A at an accelerating voltage of 400 kV was measured. Numerical simulations demonstrate the possibility of obtaining 37 dB gain and an interaction efficiency of 17%. In addition a viable amplification bandwidth of 9-13 GHz is apparent, with a minimum gain and efficiency of 25 dB and 10%, respectively, at the boundaries of the amplification band. The peak modeled efficiency and gain (17%, 37 dB) were obtained at a frequency of 12 GHz. Computational simulations have also revealed correlation between the instantaneous amplification bandwidth and the spectral width of cyclotron superradiant emission within the system.

  10. New maser emission from nonmetastable ammonia in NGC 7538. IV. Coincident masers in adjacent states of para-ammonia

    SciTech Connect

    Hoffman, Ian M.; Joyce, Spenser A.

    2014-02-20

    We present the first detection of para-ammonia masers in NGC 7538: multiple epochs of observation of the {sup 14}NH{sub 3} (J, K) = (10, 8) and (9,8) lines. We detect both thermal absorption and nonthermal emission in the (10,8) and (9,8) transitions and the absence of a maser in the (11,8) transition. The (9,8) maser is observed to increase in intensity by 40% over six months. Using interferometric observations with a synthesized beam of 0.''25, we find that the (10,8) and (9,8) masers originate at the same sky position near IRS 1. With strong evidence that the (10,8) and (9,8) masers arise in the same volume, we discuss the application of pumping models for the simultaneous excitation of nonmetastable (J > K) para-ammonia states having the same value of K and consecutive values of J. We also present detections of thermal absorption in rotational states ranging in energy from E/k{sub B} ∼ 200 K to 2000 K, and several non-detections in higher-energy states. In particular, we describe the populations in eight adjacent rotational states with K = 6, including two maser transitions, along with the implications for ortho-ammonia pumping models. An existing torus model for molecular gas in the environment of IRS 1 has been applied to the masers; a variety of maser species are shown to agree with the model. Historical and new interferometric observations of {sup 15}NH{sub 3} (3,3) masers in the region indicate a precession of the rotating torus at a rate comparable to continuum-emission-based models of the region. We discuss the general necessity of interferometric observations for diagnosing the excitation state of the masers and for determining the geometry of the molecular environment.