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Sample records for ghz methanol masers

  1. A New 95 GHz Methanol Maser Catalog. I. Data

    NASA Astrophysics Data System (ADS)

    Yang, Wenjin; Xu, Ye; Chen, Xi; Ellingsen, Simon P.; Lu, Dengrong; Ju, Binggang; Li, Yingjie

    2017-08-01

    The Purple Mountain Observatory 13.7 m radio telescope has been used to search for 95 GHz (80–71A+) class I methanol masers toward 1020 Bolocam Galactic Plane Survey (BGPS) sources, leading to 213 detections. We have compared the line width of the methanol and HCO+ thermal emission in all of the methanol detections, and on that basis, we find that 205 of the 213 detections are very likely to be masers. This corresponds to an overall detection rate of 95 GHz methanol masers toward our BGPS sample of 20%. Of the 205 detected masers, 144 (70%) are new discoveries. Combining our results with those of previous 95 GHz methanol maser searches, a total of 481 95 GHz methanol masers are now known. We have compiled a catalog listing the locations and properties of all known 95 GHz methanol masers.

  2. 37 GHz METHANOL MASERS : HORSEMEN OF THE APOCALYPSE FOR THE CLASS II METHANOL MASER PHASE?

    SciTech Connect

    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. A search for methanol masers at 44 GHz

    NASA Astrophysics Data System (ADS)

    Kalenskij, S. V.; Bachiller, R.; Berulis, I. I.; Val'tts, I. E.; Gomez-Gonzalez, J.; Martin-Pintado, J.; Rodriguez-Franco, A.; Slysh, V. I.

    1992-10-01

    Results of an extensive survey of young stellar objects in the methanol line 7(0) - 6(1)A(+) (44 GHz) are presented. Three new masers were detected towards cold IRAS sources in the dark clouds L 291 (GGD 27), L 379, and IC 1396 N. The new masers were also observed in 4(-1) - 3(0) E (36 GHz) and 1(0) - 0(0)A(+) (48 GHz) methanol transitions. A relationship between methanol masers and high-velocity flows with dense disks around central sources is proposed, and a possible correlation between maser emission and their intensity in the FIR is suggested.

  4. 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.

  5. 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.

  6. 6.7 GHz methanol maser variability in Cepheus A

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    6.7 GHz methanol maser emission from the well-studied star-forming region Cepheus A was monitored with the Torun 32 m radio telescope. We found synchronized and anticorrelated changes of the flux density of the two blueshifted and one redshifted maser features for ˜30 per cent of 1340 d of our observations. Two of those features exhibited high-amplitude flux density variations with periods of 84-87 d over the last 290 d interval of the monitoring. We also report on two flares of emission at two different redshifted velocities completely covered during the whole outburst. These flare events lasted 510-670 d and showed a very rapid linear rise and slow exponential decline, which may be caused by variability of the seed flux density. The flux density of the two strongest features dropped by a factor of 2-5 on a time-scale ˜22 yr, while other features have not changed significantly during this period, but showed strong variability on time-scales ≲ 5 yr.

  7. Class II 6.7 GHz Methanol Maser Association with Young Massive Cores Revealed by ALMA

    NASA Astrophysics Data System (ADS)

    Chibueze, James O.; Csengeri, Timea; Tatematsu, Ken’ichi; Hasegawa, Tetsuo; Iguchi, Satoru; Alhassan, Jibrin A.; Higuchi, Aya E.; Bontemps, Sylvain; Menten, Karl M.

    2017-02-01

    We explored the implication of the association (or lack of it) of 6.7 GHz class II methanol (CH3OH) masers with massive dense cores (MDCs) detected (within a sample of ATLASGAL selected infrared quiet massive clumps) at 0.9 mm with Atacama Large Millimeter/submillimeter array. We found 42 out of the 112 cores (37.5%) detected with the Atacama Compact Array (ACA) to be associated with 6.7 GHz CH3OH masers. The lowest mass core with CH3OH maser association is ∼ 12 {M}ȯ . The angular offsets of the ACA cores from the 6.7 GHz CH3OH maser peak positions range from 0.″17 to 4.″79, with a median value of 2.″19. We found a weak correlation between the 0.9 mm continuum (MDCs) peak fluxes and the peak fluxes of their associated methanol multibeam (MMB) 6.7 GHz CH3OH masers. About 90% of the cores associated with 6.7 GHz CH3OH masers have masses of >40 M ⊙. The CH3OH maser containing cores are candidates for embedded high-mass protostellar objects in their earliest evolutionary stages. With our ACA 0.9 continuum data compared with the MMB 6.7 GHz CH3OH maser survey, we have constrained the cores already housing massive protostars based on their association with the radiatively pumped 6.7 GHz CH3OH masers.

  8. Zeeman Effect observations toward 36 GHz methanol masers in the Galactic Center

    NASA Astrophysics Data System (ADS)

    Potvin, Justin A.; Momjian, Emmanuel; Pratim Sarma, Anuj

    2017-01-01

    We present observations of 36 GHz Class I methanol masers taken with the Karl G. Jansky Very Large Array (VLA) in the B configuration with the aim of detecting the Zeeman Effect. We targeted several 36 GHz Class I methanol masers associated with supernova remnants (SNRs) toward the Galactic Center. Each source was observed in dual circular polarizations for three hours. The observed spectral profiles of the masers are complex, with several components blended in velocity. In only one case was the Stokes V maser profile prominent enough to reveal a 2-sigma hint of a magnetic field of zBlos = 14.56 +/- 5.60 Hz; we have chosen to express our results in terms of zBlos since the Zeeman splitting factor (z) for 36 GHz methanol masers has not been measured. There are several hints that these spectra would reveal significant magnetic fields if they could be spatially and spectrally resolved.

  9. 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.

  10. A high-sensitivity 6.7 GHz methanol maser survey toward H2O sources

    NASA Astrophysics Data System (ADS)

    Xu, Y.; Li, J. J.; Hachisuka, K.; Pandian, J. D.; Menten, K. M.; Henkel, C.

    2008-07-01

    We present the results of a high sensitivity survey for 6.7 GHz methanol masers towards 22 GHz water masers using the 100 m Efflesberg telescope. A total of 89 sources were observed and 10 new methanol masers were detected. The new detections are relatively faint with peak flux densities of between 0.5 and 4.0 Jy. A nil detection rate from low-mass star forming regions enhances the conclusion that the masers are only associated with massive star formation. Even the faintest methanol maser in our survey, with a luminosity of 1.1 × 10-9 L_⊙, is associated with massive stars, as inferred from its infrared luminosity. Table 3 is only available in electronic form at http://www.aanda.org

  11. PHYSICAL CONDITIONS AROUND 6.7 GHz METHANOL MASERS. I. AMMONIA

    SciTech Connect

    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.

  12. A SEARCH FOR 95 GHz CLASS I METHANOL MASERS IN MOLECULAR OUTFLOWS

    SciTech Connect

    Gan, Cong-Gui; Chen, Xi; Shen, Zhi-Qiang; Xu, Ye; Ju, Bing-Gang

    2013-01-20

    We have observed a sample of 288 molecular outflow sources including 123 high-mass and 165 low-mass sources in order to search for class I methanol masers at the 95 GHz transition and to investigate the relationship between outflow characteristics and class I methanol maser emission with the Purple Mountain Observatory 13.7 m radio telescope. Our survey detected 62 sources with 95 GHz methanol masers above a 3{sigma} detection limit, which includes 47 high-mass sources and 15 low-mass sources. Therefore, the detection rate is 38% for high-mass outflow sources and 9% for low-mass outflow sources, suggesting that class I methanol masers are relatively easily excited in high-mass sources. There are 37 newly detected 95 GHz methanol masers (including 27 high-mass and 10 low-mass sources), 19 of which are newly identified (i.e., first identification) class I methanol masers (including 13 high-mass and 6 low-mass sources). A statistical analysis of the distributions of maser detections with the outflow parameters reveals that the maser detection efficiency increases with the outflow properties (e.g., mass, momentum, kinetic energy, mechanical luminosity of outflows, etc.). Systematic investigations of the relationships between the intrinsic luminosity of methanol masers and the outflow properties (including mass, momentum, kinetic energy, bolometric luminosity, and mass-loss rate of the central stellar sources) indicate a positive correlation. This further supports the theory that class I methanol masers are collisionally pumped and associated with shocks when outflows interact with the surrounding ambient medium.

  13. A 95 GHz CLASS I METHANOL MASER SURVEY TOWARD GLIMPSE EXTENDED GREEN OBJECTS (EGOs)

    SciTech Connect

    Chen Xi; Shen Zhiqiang; Gan Conggui; Ellingsen, Simon P.; Titmarsh, Anita

    2011-09-01

    We report the results of a systematic survey for 95 GHz class I methanol masers toward a new sample of 192 massive young stellar object candidates associated with ongoing outflows (known as extended green objects or EGOs) identified from the Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) survey. The observations were made with the Australia Telescope National Facility (ATNF) Mopra 22 m radio telescope and resulted in the detection of 105 new 95 GHz class I methanol masers. For 92 of the sources our observations provide the first identification of a class I maser transition associated with these objects (i.e., they are new class I methanol maser sources). Our survey proves that there is indeed a high detection rate (55%) of class I methanol masers toward EGOs. Comparison of the GLIMPSE point sources associated with EGOs with and without class I methanol maser detections shows that they have similar mid-IR colors, with the majority meeting the color selection criteria -0.6 < [5.8]-[8.0] < 1.4 and 0.5 < [3.6]-[4.5] < 4.0. Investigations of the Infrared Array Camera and Multiband Imaging Photometer for Spitzer 24 {mu}m colors and the associated millimeter dust clump properties (mass and density) of the EGOs for the sub-samples based on the class of methanol masers they are associated with suggest that the stellar mass range associated with class I methanol masers extends to lower masses than for class II methanol masers, or alternatively class I methanol masers may be associated with more than one evolutionary phase during the formation of a high-mass star.

  14. 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).

  15. A 6.7 GHz Methanol Maser Survey at High Galactic Latitudes

    NASA Astrophysics Data System (ADS)

    Yang, Kai; Chen, Xi; Shen, Zhi-Qiang; Li, Xiao-Qiong; Wang, Jun-Zhi; Jiang, Dong-Rong; Li, Juan; Dong, Jian; Wu, Ya-Jun; Qiao, Hai-Hua; Ren, Zhiyuan

    2017-09-01

    We performed a systematic 6.7 GHz Class II methanol maser survey using the Shanghai Tianma Radio Telescope toward targets selected from the all-sky Wide-Field Infrared Survey Explorer (WISE) point catalog. In this paper, we report the results from the survey of those at high Galactic latitudes, i.e., | b| > 2°. Of 1473 selected WISE point sources at high latitude, 17 point positions that were actually associated with 12 sources were detected with maser emission, reflecting the rarity (1%–2%) of methanol masers in the region away from the Galactic plane. Out of the 12 sources, 3 are detected for the first time. The spectral energy distribution at infrared bands shows that these new detected masers occur in the massive star-forming regions. Compared to previous detections, the methanol maser changes significantly in both spectral profiles and flux densities. The infrared WISE images show that almost all of these masers are located in the positions of the bright WISE point sources. Compared to the methanol masers at the Galactic plane, these high-latitude methanol masers provide good tracers for investigating the physics and kinematics around massive young stellar objects, because they are believed to be less affected by the surrounding cluster environment.

  16. 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.

  17. The Zeeman Effect in the 44 GHz Class I Methanol Maser Line toward DR21(OH)

    NASA Astrophysics Data System (ADS)

    Momjian, E.; Sarma, A. P.

    2017-01-01

    We report detection of the Zeeman effect in the 44 GHz Class I methanol maser line, toward the star-forming region DR21(OH). In a 219 Jy beam‑1 maser centered at an LSR velocity of 0.83 km s‑1, we find a 20-σ detection of zBlos = 53.5 ± 2.7 Hz. If 44 GHz methanol masers are excited at n ∼ 107–8 cm‑3, then the B versus n1/2 relation would imply, from comparison with Zeeman effect detections in the CN(1 ‑ 0) line toward DR21(OH), that magnetic fields traced by 44 GHz methanol masers in DR21(OH) should be ∼10 mG. Combined with our detected zBlos = 53.5 Hz, this would imply that the value of the 44 GHz methanol Zeeman splitting factor z is ∼5 Hz mG‑1. Such small values of z would not be a surprise, as the methanol molecule is non-paramagnetic, like H2O. Empirical attempts to determine z, as demonstrated, are important because there currently are no laboratory measurements or theoretically calculated values of z for the 44 GHz CH3OH transition. Data from observations of a larger number of sources are needed to make such empirical determinations robust.

  18. EXPANDED VERY LARGE ARRAY DETECTION OF 44.1 GHz CLASS I METHANOL MASERS IN SAGITTARIUS A

    SciTech Connect

    Pihlstroem, Y. M.; Sjouwerman, L. O.; Fish, V. L.

    2011-09-20

    We report on the detection of 44 GHz Class I methanol (CH{sub 3}OH) maser emission in the Sagittarius A (Sgr A) complex with the Expanded Very Large Array (EVLA). These EVLA observations show that the Sgr A complex harbors at least four different tracers of shocked regions in the radio regime. The 44 GHz masers correlate with the positions and velocities of previously detected 36 GHz CH{sub 3}OH masers, but less with 1720 MHz OH masers. Our detections agree with theoretical predictions that the densities and temperatures conducive for 1720 MHz OH masers may also produce 36 and 44 GHz CH{sub 3}OH maser emission. However, many 44 GHz masers do not overlap with 36 GHz methanol masers, suggesting that 44 GHz masers also arise in regions too hot and too dense for 36 GHz masers to form. This agrees with the non-detection of 1720 MHz OH masers in the same area, which are thought to be excited under even cooler and less dense conditions. We speculate that the geometry of the 36 GHz masers outlines the current location of a shock front.

  19. 44 GHz Class I Methanol (CH_3OH) Maser Survey in the Galactic Center

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    We report on a large 44 GHz (70-61 A +) methanol (CH3OH) maser survey of the Galactic Center. The Karl G. Jansky Very Large Array was used to search for CH3OH maser emission covering a large fraction of the region around Sgr A. In 25 pointings, over 300 CH3OH maser sources (>10σ) were detected. The majority of the maser sources have a single peak emission spectrum with line of sight velocities that range from about -13 to 72 km s-1. Most maser sources were found to have velocities around 35-55 km s-1, closely following velocities of neighboring interacting molecular clouds (MCs). The full width at half-maximum of each individual spectral feature is very narrow (˜0.85 km s-1 on average). In the north, where Sgr A East is known to be interacting with the 50 km s-1 MC, more than 100 44 GHz CH3OH masers were detected. In addition, three other distinct concentrations of masers were found, which appear to be located closer to the interior of the interacting MCs. It is possible that a subset of masers is associated with star formation, although conclusive evidence is lacking.

  20. 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.

  1. Techniques for Accurate Parallax Measurements for 6.7 GHz Methanol Masers

    NASA Astrophysics Data System (ADS)

    Reid, M. J.; Brunthaler, A.; Menten, K. M.; Sanna, A.; Xu, Y.; Li, J. J.; Wu, Y.; Hu, B.; Zheng, X. W.; Zhang, B.; Immer, K.; Rygl, K.; Moscadelli, L.; Sakai, N.; Bartkiewicz, A.; Choi, Y. K.

    2017-08-01

    The BeSSeL Survey is mapping the spiral structure of the Milky Way by measuring trigonometric parallaxes of hundreds of maser sources associated with high-mass star formation. While parallax techniques for water masers at high frequency (22 GHz) have been well documented, recent observations of methanol masers at lower frequency (6.7 GHz) have revealed astrometric issues associated with signal propagation through the ionosphere that could significantly limit parallax accuracy. These problems displayed as a “parallax gradient” on the sky when measured against different background quasars. We present an analysis method in which we generate position data relative to an “artificial quasar” at the target maser position at each epoch. Fitting parallax to these data can significantly mitigate the problems and improve parallax accuracy.

  2. Detection of 36 GHz Class I Methanol Maser Emission toward NGC 4945

    NASA Astrophysics Data System (ADS)

    McCarthy, Tiege P.; Ellingsen, Simon P.; Chen, Xi; Breen, Shari L.; Voronkov, Maxim A.; Qiao, Hai-hua

    2017-09-01

    We have searched for emission from the 36.2 GHz ({4}-1\\to {3}0{{E}}) methanol transition toward NGC 4945, using the Australia Telescope Compact Array. 36.2 GHz methanol emission was detected offset southeast from the Galactic nucleus. The methanol emission is narrow, with a line width <10 km s‑1 and a luminosity five orders of magnitude higher than Galactic class I masers from the same transition. These characteristics combined the with physical separation from the strong central thermal emission suggests that the methanol emission is a maser. This emission is a factor of ∼90 more luminous than the widespread emission detected from the Milky Way central molecular zone. This is the fourth detection of extragalactic class I emission and the third detection of extragalactic 36.2 GHz maser emission. These extragalactic class I methanol masers do not appear to be simply highly luminous variants of Galactic class I emission and instead appear to trace large-scale regions of low-velocity shocks in molecular gas, which may precede, or be associated with, the early stages of large-scale star formation.

  3. Studying Star Formation in the Central Molecular Zone using 22 GHz Water and 6.7 GHz Methanol Masers

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    The inner 400 pc of our Galaxy, or the so-called the central molecular zone (CMZ), has a unique environment with a large mass of dense, warm molecular gas. One of the premier questions is how star formation (SF) differs in this unique environment from elsewhere in the Galaxy. We intend to address this issue by identifying improved numbers and locations of early sites of SF. We have conducted high resolution surveys of the CMZ, looking for early SF indicators such as 22 GHz water and 6.7 GHz methanol masers. We present the initial water maser results from the SWAG survey and methanol results from the first full VLA survey of 6.7 GHz methanol masers in the CMZ. These surveys span beyond the inner 1.2ο x 0.5ο of the Galaxy, including Sgr B through Sgr C. The improved spatial and spectral resolutions (~26" and 2 km s-1) and sensitivity (RMS ~10 mJy beam-1) of our ATCA observations have allowed us to identify over 140 water maser candidates in the SWAG survey. This is a factor of 3 more than detected from prior surveys of the CMZ. The preliminary distribution of these candidates appears to be uniform along Galactic longitude. Should this distribution persist for water masers associated with star formation (as opposed to those produced by evolved stars), then this result would imply a more uniform distribution of recent SF activity in the CMZ. Prior works have shown that 2/3 of the molecular gas mass is located at positive Galactic longitudes, and young stellar objects (YSOs) identified by IR SEDs are located predominantly at negative Galactic longitudes. A combination of these results can provide insight on the evolution of SF within the CMZ. We are currently comparing the water maser positions to other catalogs (ex. OH/IR stars) in order to distinguish between the mechanisms producing these masers. We are also currently working on determining the distribution of 6.7 GHz methanol masers. These masers do not contain the same ambiguity as water masers as to their source

  4. Ammonia and CO Outflow around 6.7 GHz Methanol Masers

    NASA Astrophysics Data System (ADS)

    Li, F. C.; Xu, Y.; Wu, Y. W.; Yang, J.; Lu, D. R.; Menten, K. M.; Henkel, C.

    2016-10-01

    Single point observations are presented in NH3 (1, 1) and (2, 2) inversion transitions using the Effelsberg 100 m telescope for a sample of 100 6.7 GHz methanol masers and mapping observations in the 12CO and 13CO (1 - 0) transitions using the Purple Mountain Observatory Delingha 13.7 m telescope for 82 sample sources with detected ammonia. A further 62 sources were selected for either 12CO or 13CO line outflow identification, producing 45 outflow candidates, 29 using 12CO and 16 using 13CO data. Twenty-two of the outflow candidates were newly identified, and 23 had trigonometric parallax distances. Physical properties were derived from ammonia lines and CO outflow parameters were calculated. Histograms and statistical correlations for ammonia, CO outflow parameters, and 6.7 GHz methanol maser luminosities are also presented. No significant correlation was found between ammonia and maser luminosity. However, weak correlations were found between outflow properties and maser luminosities, which may indicate that outflows are physically associated with 6.7 GHz masers.

  5. 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.

  6. 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.

  7. VizieR Online Data Catalog: General Catalogue of 6.7GHz Methanol Masers (Pestalozzi+, 2005)

    NASA Astrophysics Data System (ADS)

    Pestalozzi, M. R.; Minier, V.

    2003-10-01

    The catalogue of the 6.7GHz methanol masers comprises all detected sources since the discovery of this intense radiation. For every source we report name, right ascension and declination in J2000, galactic coordinates, vlsr, velocity range, peak flux, galactocentric and heliocentric distances (near and far), IRAS and MSX associations if any, usual name, detected methanol masers at 12, 44, 85.5, 86.5, 95, 107, 108, 156GHz, reference of the 6.7GHz detection and reobservation. (2 data files).

  8. The protostellar mass limit for 6.7 GHz methanol masers. I. A low-mass YSO survey

    NASA Astrophysics Data System (ADS)

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

    2003-06-01

    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. The less massive objects in our sample do not exhibit any methanol maser stronger than 400 mJy (4sigma ). Based on the nil detection rate toward the low-mass YSOs we can place an upper limit of 3*E6 K on the brightness temperature of any methanol maser associated with class 0, I or II sources. These results support the hypothesis that no strong methanol masers are associated with low-mass star formation (la 3 Msun). Table \\ref{tab1} is only available in electronic form at http://www.edpsciences.org}

  9. 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.

  10. VizieR Online Data Catalog: 6.7GHz methanol maser emission survey (Szymczak+, 2000)

    NASA Astrophysics Data System (ADS)

    Szymczak, M.; Hrynek, G.; Kus, A. J.

    2000-03-01

    File table1 contains 182 methanol maser sources detected at 6.7GHz. The IRAS name, the start and end velocities of emission, the velocity of peak emission, the peak flux density, the integrated flux density, the epoch of observation and the discovery reference are given. The data were taken during 1999 using the 32m Torun radio telescope. The average sensitivity limit (3σ) was 1.7Jy and the velocity resolution was 0.044km/s. File table2 contains the sources not detected with the 32m Torun radio telescope at 6.7GHz. The IRAS name, the 1σ level, the epoch of observation and the IRAS name of possible contamination sources are given. The number of non-detections is 1217. (2 data files).

  11. The 6-GHz multibeam maser survey - II. Statistical analysis and Galactic distribution of 6668-MHz methanol masers

    NASA Astrophysics Data System (ADS)

    Green, J. A.; Breen, S. L.; Fuller, G. A.; McClure-Griffiths, N. M.; Ellingsen, S. P.; Voronkov, M. A.; Avison, A.; Brooks, K.; Burton, M. G.; Chrysostomou, A.; Cox, J.; Diamond, P. J.; Gray, M. D.; Hoare, M. G.; Masheder, M. R. W.; Pestalozzi, M.; Phillips, C.; Quinn, L. J.; Richards, A. M. S.; Thompson, M. A.; Walsh, A. J.; Ward-Thompson, D.; Wong-McSweeney, D.; Yates, J. A.

    2017-08-01

    The Methanol Multibeam survey has produced the largest and most complete census of methanol and excited-state hydroxyl masers in the Galaxy to date. Observing the entire Galactic plane visible from the Southern hemisphere for 6668-MHz methanol and 6030/6035-MHz hydroxyl masers, to an rms sensitivity of 0.015 Jy km s-1, the survey has detected a total of 972 methanol maser sources, implying a total Galactic population of ˜1290 sources with flux densities above the survey 3σ peak flux density limit of 0.51 Jy. We present here the statistical properties of the methanol detections of the survey, including distributions in flux density, variability and range of source velocities. The data suggest that the weaker masers exhibit greater variability. We also present an analysis of the Galactic distribution of 6668-MHz methanol masers. For the Galactic distribution, we present kinematic distance resolutions to an additional 202 sources to those published previously, and collate these with previous allocations, as well as exploring a recent Bayesian distance approach based on maser parallaxes to separately determine distances. We examine Galactic structure and determine the luminosity function of the Galactic population of methanol masers. We find that more luminous masers have an evenly distributed wide range of velocity widths compared with less luminous masers being dominated by narrow velocity ranges, with the implication that this may be tied to the evolution of the host protostar(s). We also see an indication that brighter sources are seen towards the arm origins.

  12. Probing the Evolution of Massive Young Stellar Objects using Weak Class II 6.7GHz Methanol Maser Emission

    NASA Astrophysics Data System (ADS)

    Ludwig, Bethany Ann; Cunningham, Nichol

    2017-01-01

    We present results from an investigation of class II 6.7GHz methanol masers towards four Massive Young Stellar Objects (MYSOs). The sources, selected from the Red MSX Source (RMS) Survey (Lumsden et al. 2013), were previously understood to be non-detections for class II methanol maser emission in the methanol multi-beam (MMB) Survey (Caswell et al. 2010.) Class II methanol masers are a well-known sign post of massive star forming regions and may be utilized to probe their relatively poorly understood formation. It is possible that these non-detections are simply weak masers that are potentially associated with a younger evolutionary phase of MYSOs as hypothesized by Olmi et al. (2014). The sources were chosen to sample various stages of evolution, having similar 21 to 8 micron flux ratios and bolometric luminosities as other MYSOs with previous class II methanol maser detections. We observed all 4 MYSOs with ATCA (~2" resolution) at 10 times deeper sensitivity than previously obtained with the MMB survey and have a spectral resolution of 0.087kms^-1 . The raw data is reduced using the program Miriad (Sault, R. J., et al., 1995) and deconvolutioned using the program CASA (McMullin, J. P., et al. 2007.) We determine one of the four observed MYSOs is harboring a weak class II methanol maser. We discuss the possibility of sensitivity limitations on the remaining sources as well as environmental and evolutionary differences between the sources.

  13. VLA Survey of Dense Gas in Extended Green Objects: Prevalence of 25 GHz Methanol Masers

    NASA Astrophysics Data System (ADS)

    Towner, A. P. M.; Brogan, C. L.; Hunter, T. R.; Cyganowski, C. J.; McGuire, B. A.; Indebetouw, R.; Friesen, R. K.; Chandler, C. J.

    2017-06-01

    We present ˜1″-4″ resolution Very Large Array (VLA) observations of four CH3OH {J}2{--}{J}1-E 25 GHz transitions (J = 3, 5, 8, 10) along with the 1.3 cm continuum toward 20 regions of active massive star formation containing Extended Green Objects (EGOs), 14 of which we have previously studied with the VLA in the Class I 44 GHz and Class II 6.7 GHz maser lines. Sixteen regions are detected in at least one 25 GHz line (J = 5), with 13 of 16 exhibiting maser emission. In total, we report 34 new sites of CH3OH maser emission and 10 new sites of thermal CH3OH emission, significantly increasing the number of 25 GHz Class I CH3OH masers observed at high angular resolution. We identify probable or likely maser counterparts at 44 GHz for all 15 of the 25 GHz masers for which we have complementary data, providing further evidence that these masers trace similar physical conditions despite uncorrelated flux densities. The sites of thermal and maser emission of CH3OH are both predominantly associated with the 4.5 μm emission from the EGO, and the presence of thermal CH3OH emission is accompanied by 1.3 cm continuum emission in 9 out of 10 cases. Of the 19 regions that exhibit 1.3 cm continuum emission, it is associated with the EGO in 16 cases (out of a total of 20 sites), 13 of which are new detections at 1.3 cm. Twelve of the 1.3 cm continuum sources are associated with 6.7 GHz maser emission and likely trace deeply embedded massive protostars.

  14. 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

  15. 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.

  16. European VLBI Network observations of 6.7 GHz methanol masers in clusters of massive young stellar objects

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    Context. Methanol masers at 6.7 GHz are associated with high-mass star-forming regions (HMSFRs) and often have mid-infrared (MIR) counterparts characterized by extended emission at 4.5 μm, which likely traces outflows from massive young stellar objects (MYSOs). Aims: Our objectives are to determine the milliarcsecond (mas) morphology of the maser emission and to examine if it comes from one or several candidate MIR counterparts in the clusters of MYSOs. Methods: The European VLBI Network (EVN) was used to image the 6.7 GHz maser line with ~2.´1 field of view toward 14 maser sites from the Torun catalog. Quasi-simultaneous observations were carried out with the Torun 32 m telescope. Results: We obtained maps with mas angular resolution that showed diversity of methanol emission morphology: a linear distribution (e.g., G37.753-00.189), a ring-like (G40.425+00.700), and a complex one (e.g., G45.467+00.053). The maser emission is usually associated with the strongest MIR counterpart in the clusters; no maser emission was detected from other MIR sources in the fields of view of 2.´1 in diameter. The maser source luminosity seems to correlate with the total luminosity of the central MYSO. Although the Very Long Baseline Interferometry (VLBI) technique resolves a significant part of the maser emission, the morphology is still well determined. This indicates that the majority of maser components have compact cores. Appendices are available in electronic form at http://www.aanda.org

  17. Simultaneous Observation of Water and Class I Methanol Masers toward Class II Methanol Maser Sources

    NASA Astrophysics Data System (ADS)

    Kang, Hyunwoo; Kim, Kee-Tae; Byun, Do-Young; Lee, Seokho; Park, Yong-Sun

    2015-11-01

    We present a simultaneous single-dish survey of 22 GHz water masers and 44 and 95 GHz class I methanol masers toward 77 6.7 GHz class II methanol maser sources, which were selected from the Arecibo methanol maser Galactic plane survey catalog. Water maser emission is detected in 39 (51%) sources, 15 of which are new detections. Methanol maser emission at 44 and 95 GHz is found in 25 (32%) and 19 (25%) sources, 21 and 13 of which, respectively, are newly detected. We find four high-velocity (>30 km s-1) water maser sources, including three dominant blue- or redshifted outflows. The 95 GHz masers always appear with 44 GHz maser emission. They are strongly correlated with 44 GHz masers in velocity, flux density, and luminosity, yet they are not correlated with either water or 6.7 GHz class II methanol masers. The average peak flux density ratio of 95 GHz masers to 44 GHz masers is close to unity, which is two times higher than previous estimates. The flux densities of class I methanol masers are more closely correlated with the associated Bolocam Galactic Plane Survey core mass than those of water masers or class II methanol masers. Using the large velocity gradient model and assuming unsaturated class I methanol maser emission, we derive the fractional abundance of methanol to be in the range 4.2 × 10-8-2.3 × 10-6, with a median value of 3.3 ± 2.7 × 10-7.

  18. A 95 GHz CLASS I METHANOL MASER SURVEY TOWARD A SAMPLE OF GLIMPSE POINT SOURCES ASSOCIATED WITH BGPS CLUMPS

    SciTech Connect

    Chen Xi; Gan Conggui; Shen Zhiqiang; An Tao; Ellingsen, Simon P.; He Jinhua

    2012-05-01

    We report a survey with the Purple Mountain Observatory 13.7 m radio telescope for class I methanol masers from the 95 GHz (8{sub 0}-7{sub 1} A{sup +}) transition. Two hundred and fourteen target sources were selected by combining information from both the Spitzer GLIMPSE and 1.1 mm Bolocam Galactic Plane Survey (BGPS) catalogs. The observed sources satisfy the GLIMPSE mid-IR criteria of [3.6]-[4.5] > 1.3, [3.6]-[5.8] > 2.5, [3.6]-[8.0] > 2.5 and 8.0 {mu}m mag less than 10; they also have an associated 1.1 mm BGPS source. Class I methanol maser emission was detected in 63 sources, corresponding to a detection rate of 29% for this survey. For the majority of detections (43), this is the first identification of class I methanol masers associated with these sources. We show that the intensity of the class I methanol maser emission is not closely related to mid-IR intensity or the colors of the GLIMPSE point sources; however, it is closely correlated with properties (mass and beam-averaged column density) of the BGPS sources. Comparison of measures of star formation activity for the BGPS sources with and without class I methanol masers indicates that the sources with class I methanol masers usually have higher column density and larger flux density than those without them. Our results predict that the criteria log (S{sub int}) {<=} -38.0 + 1.72log (N{sup beam}{sub H{sub 2}}) and log (N{sub H{sub 2}{sup beam}}){>=}22.1, which utilizes both the integrated flux density (S{sub int}) and beam-averaged column density (N{sub H{sub 2}{sup beam}}) of the BGPS sources, are very efficient for selecting sources likely to have an associated class I methanol maser. Our expectation is that searches using these criteria will detect 90% of the predicted number of class I methanol masers from the full BGPS catalog ({approx}1000), and that they will do so with a high detection efficiency ({approx}75%).

  19. Parallaxes of 6.7-GHz methanol masers towards the G 305.2 high-mass star formation region

    NASA Astrophysics Data System (ADS)

    Krishnan, V.; Ellingsen, S. P.; Reid, M. J.; Bignall, H. E.; McCallum, J.; Phillips, C. J.; Reynolds, C.; Stevens, J.

    2017-02-01

    We have made measurements to determine the parallax and proper motion of the three 6.7-GHz methanol masers G 305.200+0.019, G 305.202+0.208 and G 305.208+0.206. The combined parallax is found to be 0.25±0.05 mas, corresponding to a distance of 4.1^{+1.2}_{-0.7} kpc. This places the G 305.2 star formation region in the Carina-Sagittarius spiral arm. The inclusion of G 305.2 increases the Galactic azimuth range of the sources in this arm by 40° from Sato et al., allowing us to determine the pitch angle of this spiral with greater confidence to be ψ = 19.0° ± 2.6°. The first very long baseline interferometry spot maps of the 6.7-GHz methanol masers towards these sources show that they have simple linear and ring-like structures, consistent with emission expected from class II methanol masers in general.

  20. Measurement of the bipolar outflow motions of the 6.7 GHz Methanol Masers in G320.23-0.28

    NASA Astrophysics Data System (ADS)

    Sugiyama, Koichiro; Ellingsen, Simon; Fujisawa, Kenta; Bartkiewicz, Anna

    2010-10-01

    Internal proper-motion measurements of 6.7 GHz methanol masers can provide unique information about high-mass star-forming regions (HMSFRs). The source G320.23-0.28 is the best case where the methanol masers are parallel to a large-scale bi-lobed outflow traced by H_2, SiO, and EGO emissions in the east-west direction. Therefore, it appears that the G320.23-0.28 methanol maser spatially and physically trace the outflow ejected from a high-mass YSO in early evolutionary stage. We have accurately measured the spatial distribution of the G320.23-0.28 methanol maser using the LBA (Project: v292a), and that distribution exhibited a complex spatial distribution. By applying the bipolar outflow model of Moscadelli et al. (2000, 2005) to our observed distribution, we obtained maser-outflow axis and opening angles that were consistent with the large-scale outflow. We propose to carry out three-epoch observations of the 6.7 GHz methanol masers in G320.23-0.28 to measure their internal proper motions. This measurement will provide vital information about both the location of this maser with SFRs and studies of outflows at early evolutionary stages in HMSF.

  1. 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

    2016-10-01

    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.

  2. 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.

  3. THE FIRST VERY LONG BASELINE INTERFEROMETRY IMAGE OF A 44 GHz METHANOL MASER WITH THE KVN AND VERA ARRAY (KaVA)

    SciTech Connect

    Matsumoto, Naoko; Hirota, Tomoya; Honma, Mareki; Kameya, Osamu; Sunada, Kazuyoshi; Sugiyama, Koichiro; Motogi, Kazuhito; Kim, Kee-Tae; Kim, Mikyoung; Byun, Do-Young; Jung, Taehyun; Kim, Jongsoo; Lyo, A-Ran; Oh, Chungsik; Bae, Jaehan; Chung, Hyunsoo; Chung, Moon-Hee; Cho, Se-Hyung; Chibueze, James O.; Shino, Nagisa; and others

    2014-07-01

    We have carried out the first very long baseline interferometry (VLBI) imaging of a 44 GHz class I methanol maser (7{sub 0}-6{sub 1} A {sup +}) associated with a millimeter core MM2 in a massive star-forming region IRAS 18151–1208 with KaVA (KVN and VERA Array), which is a newly combined array of KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry). We have succeeded in imaging compact maser features with a synthesized beam size of 2.7 milliarcseconds × 1.5 milliarcseconds (mas). These features are detected at a limited number of baselines within the length of shorter than ≈ 650 km corresponding to 100 Mλ in the uv-coverage. The central velocity and the velocity width of the 44 GHz methanol maser are consistent with those of the quiescent gas rather than the outflow traced by the SiO thermal line. The minimum component size among the maser features is ∼5 mas × 2 mas, which corresponds to the linear size of ∼15 AU × 6 AU assuming a distance of 3 kpc. The brightness temperatures of these features range from ∼3.5 × 10{sup 8} to 1.0 × 10{sup 10} K, which are higher than the estimated lower limit from a previous Very Large Array observation with the highest spatial resolution of ∼50 mas. The 44 GHz class I methanol maser in IRAS 18151–1208 is found to be associated with the MM2 core, which is thought to be less evolved than another millimeter core MM1 associated with the 6.7 GHz class II methanol maser.

  4. Hub-filament System in IRAS 05480+2545: Young Stellar Cluster and 6.7 GHz Methanol Maser

    NASA Astrophysics Data System (ADS)

    Dewangan, L. K.; Ojha, D. K.; Baug, T.

    2017-07-01

    To probe the star formation (SF) process, we present a multi-wavelength study of IRAS 05480+2545 (hereafter I05480+2545). Analysis of Herschel data reveals a massive clump (M clump ˜ 1875 {M}⊙ ; peak N(H2) ˜ 4.8 × 1022 cm-2 A V ˜ 51 mag) containing the 6.7 GHz methanol maser and I05480+2545, which is also depicted in a temperature range of 18-26 K. Several noticeable parsec-scale filaments are detected in the Herschel 250 μm image and seem to be radially directed to the massive clump. It resembles more of a “hub-filament” system. Deeply embedded young stellar objects (YSOs) have been identified using the 1-5 μm photometric data, and a significant fraction of YSOs and their clustering are spatially found toward the massive clump, revealing the intense SF activities. An infrared counterpart (IRc) of the maser is investigated in the Spitzer 3.6-4.5 μm images. The IRc does not appear as a point-like source and is most likely associated with the molecular outflow. Based on the 1.4 GHz and Hα continuum images, the ionized emission is absent toward the IRc, indicating that the massive clump harbors an early phase of a massive protostar before the onset of an ultracompact H ii region. Together, the I05480+2545 is embedded in a very similar “hub-filament” system to those seen in the Rosette Molecular Cloud. The outcome of the present work indicates the role of filaments in the formation of the massive star-forming clump and cluster of YSOs, which might help channel material to the central hub configuration and the clump/core.

  5. The 6-GHz methanol multibeam maser catalogue - IV. Galactic longitudes 186°-330° including the Orion-Monoceros region

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

    We present the fourth portion of a Galactic plane survey of methanol masers at 6668 MHz, spanning the longitude range 186°-330°. We report 207 maser detections, 89 new to the survey. This completes the southern sky part of the methanol multibeam survey and includes a large proportion of new sources, 43 per cent. We also include results from blind observations of the Orion-Monoceros star-forming region, formally outside the latitude range of the methanol multibeam survey; only the four previously known methanol emitting sites were detected, of which we present new positions and spectra for masers at Orion A (south) and Orion B, obtained with the Multi-Element Radio Linked Interferometer Network (MERLIN) array.

  6. 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

  7. 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.

  8. 32-GHz Wideband Maser Amplifier

    NASA Technical Reports Server (NTRS)

    Shell, J. S.; Neff, D. E.

    1990-01-01

    High-gain, wideband, microwave amplifier based on ruby cooled by liquid helium. Features include low input equivalent noise temperature and 400-MHz bandwidth. Design basically extension of previous reflected-wave masers built for frequency range of 18 to 26 GHz. Maser amplifier includes eight stages connected in reflected-wave configuration. Particularly useful for detection of weak microwave signals in radio astronomy and communications.

  9. 32-GHz Wideband Maser Amplifier

    NASA Technical Reports Server (NTRS)

    Shell, J. S.; Neff, D. E.

    1990-01-01

    High-gain, wideband, microwave amplifier based on ruby cooled by liquid helium. Features include low input equivalent noise temperature and 400-MHz bandwidth. Design basically extension of previous reflected-wave masers built for frequency range of 18 to 26 GHz. Maser amplifier includes eight stages connected in reflected-wave configuration. Particularly useful for detection of weak microwave signals in radio astronomy and communications.

  10. 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.

  11. VizieR Online Data Catalog: Water maser survey of methanol maser sources (Szymczak+, 2005)

    NASA Astrophysics Data System (ADS)

    Szymczak, M.; Pillai, T.; Menten, K. M.

    2005-02-01

    High sensitivity observations of the 22GHz water maser emission have been carried out with the Effelsberg 100m radio telescope. The observed sample was 79 candidate high-mass protostellar objects from a flux-limited sample of 6.7GHz methanol sources (Szymczak et al., 2002A&A...392..277S). Water maser emission was found in 41 sources of which 28 were not previously catalogued. (3 data files).

  12. 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.

  13. The shortest periodic and flaring flux variability of a methanol maser emission at 6.7 GHz in G 014.23-00.50

    NASA Astrophysics Data System (ADS)

    Sugiyama, Koichiro; Nagase, Katsura; Yonekura, Yoshinori; Momose, Munetake; Yasui, Yasutaka; Saito, Yu; Motogi, Kazuhito; Honma, Mareki; Hachisuka, Kazuya; Matsumoto, Naoko; Uchiyama, Mizuho; Fujisawa, Kenta

    2017-08-01

    We detected flaring flux variability that regularly occurred with a period of 23.9 d on a 6.7 GHz methanol maser emission at Vlsr = 25.30 km s-1 in G 014.23-00.50 through highly frequent monitoring using the Hitachi 32 m radio telescope. Analyzing data from 2013 January 5 to 2016 January 21, the periodic variability has persisted in at least 47 cycles, corresponding to ∼1100 d. The period of 23.9 d is the shortest one observed in masers around high-mass young stellar objects so far. The flaring component normally falls below the detection limit (3 σ) of ∼0.9 Jy. In the flaring periods, the component rises above the detection limit with a ratio of the peak flux density more than 180 in comparison with the quiescent phase, showing intermittent periodic variability. The timescale of the flux rise was typically two days or shorter, and both symmetric and asymmetric profiles of flux variability were observed through intraday monitoring. These characteristics might be explained by a change in the flux of seed photons in a colliding-wind binary (CWB) system, or a variation of the dust temperature by the extra heating source of a shock formed by a CWB system within a gap region in a circumbinary disk, in which the orbital semi-major axes of the binary are 0.26-0.34 au.

  14. Observations of the Zeeman effect in Class I methanol masers

    NASA Astrophysics Data System (ADS)

    Pratim Sarma, Anuj; Momjian, Emmanuel

    2017-01-01

    We present observations of the Zeeman effect in Class I methanol maser sources toward high mass star forming regions. Toward DR21(OH), we have detected the Zeeman effect at 44 GHz in a 219 Jy/beam maser centered at an LSR velocity of 0.83 km/s, and we find $zB_\\text{los} = 53.5 \\pm 2.7$ Hz. If 44 GHz methanol masers are excited at $10^{7-8}$ cm$^{-3}$, then magnetic fields in DR21(OH) should be ~10 mG. Our detected $zB_\\text{los}$ would then imply that the Zeeman splitting factor for the 44 GHz methanol maser line should be ~5 Hz/mG. Such small values for z would not be surprising, since the methanol molecule is non-paramagnetic, like H2O. Since there are no direct measurements or calculations of the 44 GHz methanol maser Zeeman splitting factor to date, such empirical attempts could prove valuable in building a repository of measurements from which to gain an understanding of the magnitude of z.

  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. Development of 32-m Radio Telescopes for Monitoring Observations of Methanol Masers, H2O Masers, and Radio Continuum

    NASA Astrophysics Data System (ADS)

    Yonekura, Y.; Saito, Y.; Saito, T.; Mori, T.; Soon, K. L.; Momose, M.; Yokosawa, M.; Ogawa, H.; Fujisawa, K.; Sugiyama, K.; Motogi, K.; Takaba, H.; Sorai, K.; Nakai, N.; Kameno, S.; Kobayashi, H.; Kawaguchi, N.; Hachisuka, K.

    2013-10-01

    We report the renovation of two satellite-communication antennas, named Takahagi and Hitachi 32-m antennas, into cm-wave radio telescopes. Both antennas have been successfully renovated into radio telescopes until 2012. VLBI observations at 6.7, 8, and 22 GHz have been successful since 2010. We have started single-dish observations of methanol masers at 6.7 GHz and H2O masers at 22 GHz from 2013.

  17. ALMA Observations of the IRDC Clump G34.43+00.24 MM3: 278 GHz Class I Methanol Masers

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    We have observed a molecular clump (MM3) associated with the infrared dark cloud G34.43+00.24 in the CH3OH JK = 9-1-80 E, 50-40 E, and 5-1-4-1 E lines at sub-arcsecond resolution by using the Atacama Large Millimeter/submillimeter Array. By comparing the CH3OH JK = 9-1-80 E emission with the CH3OH 50-40 E and 5-1-4-1 E emission, we have found that the CH3OH JK = 9-1-80 E emission is masing. We have clearly shown that the CH3OH JK = 9-1-80 masers arise from the post shocked gas in the interacting regions between the outflows and ambient dense gas. Toward the strongest peak of the CH3OH maser emission, SiO J = 6-5 emission is very weak. This indicates that the CH3OH maser emission traces relatively old shocks or weak shocks.

  18. WATER AND METHANOL MASER ACTIVITIES IN THE NGC 2024 FIR 6 REGION

    SciTech Connect

    Choi, Minho; Kang, Miju; Byun, Do-Young; Lee, Jeong-Eun

    2012-11-10

    The NGC 2024 FIR 6 region was observed in the water maser line at 22 GHz and the methanol class I maser lines at 44, 95, and 133 GHz. The water maser spectra displayed several velocity components and month-scale time variabilities. Most of the velocity components may be associated with FIR 6n, while one component was associated with FIR 4. A typical lifetime of the water maser velocity components is about eight months. The components showed velocity fluctuations with a typical drift rate of about 0.01 km s{sup -1} day{sup -1}. The methanol class I masers were detected toward FIR 6. The methanol emission is confined within a narrow range around the systemic velocity of the FIR 6 cloud core. The methanol masers suggest the existence of shocks driven by either the expanding H II region of FIR 6c or the outflow of FIR 6n.

  19. VizieR Online Data Catalog: Ammonia and CO outflow around 6.7GHz methanol masers (Li+, 2016)

    NASA Astrophysics Data System (ADS)

    Li, F. C.; Xu, Y.; Wu, Y. W.; Yang, J.; Lu, D. R.; Menten, K. M.; Henkel, C.

    2017-04-01

    A sample of 100 sources with single point ammonia observations, with decl. and position accuracy better than 1'', was selected from Caswell 2009 (Cat. J/other/PASA/26.454) and Xu et al. (2009A&A...507.1117X). Table1 shows the chosen source maser properties. Single point observations of the sample in ammonia inversion transitions NH3(1,1) NH3(2,2) were performed during 2011 March and 2012 May using the Effelsberg 100m telescope. See Section 2.2 in the paper for further details about the ammonia observations. 12CO, 13CO, and C18OJ=1-0 data were obtained using the Purple Mountain Observatory (PMO) Delingha 13.7m millimeter telescope in 2014 May and June, and supplementary observations were performed in 2015 June. Please refer to Section 2.3 for additional details about the CO observations. (5 data files).

  20. 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).

  1. 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

  2. THE ENVIRONMENT OF THE STRONGEST GALACTIC METHANOL MASER

    SciTech Connect

    Sanna, A.; Menten, K. M.; Carrasco-González, C.; Brunthaler, A.; Reid, M. J.; Ellingsen, S. P.; Krishnan, V.; Moscadelli, L.; Cesaroni, R.

    2015-05-01

    The high-mass star-forming site G009.62+00.20 E hosts the 6.7 GHz methanol maser source with the greatest flux density in the Galaxy which has been flaring periodically over the last 10 yr. We performed high-resolution astrometric measurements of the CH{sub 3}OH, H{sub 2}O, and OH maser emission and 7 mm continuum in the region. The radio continuum emission was resolved in two sources separated by 1300 AU. The CH{sub 3}OH maser cloudlets are distributed along two north–south ridges of emission to the east and west of the strongest radio continuum component. This component likely pinpoints a massive young stellar object which heats up its dusty envelope, providing a constant IR pumping for the Class II CH{sub 3}OH maser transitions. We suggest that the periodic maser activity may be accounted for by an independent, pulsating, IR radiation field provided by a bloated protostar in the vicinity of the brightest masers. We also report the discovery of an elliptical distribution of CH{sub 3}OH maser emission in the region of periodic variability.

  3. The 6-GHz multibeam maser survey - I. Techniques

    NASA Astrophysics Data System (ADS)

    Green, J. A.; Caswell, J. L.; Fuller, G. A.; Avison, A.; Breen, S. L.; Brooks, K.; Burton, M. G.; Chrysostomou, A.; Cox, J.; Diamond, P. J.; Ellingsen, S. P.; Gray, M. D.; Hoare, M. G.; Masheder, M. R. W.; McClure-Griffiths, N. M.; Pestalozzi, M.; Phillips, C.; Quinn, L.; Thompson, M. A.; Voronkov, M. A.; Walsh, A.; Ward-Thompson, D.; Wong-McSweeney, D.; Yates, J. A.; Cohen, R. J.

    2009-01-01

    A new seven-beam 6-7GHz receiver has been built to survey the Galaxy and the Magellanic Clouds for newly forming high-mass stars that are pinpointed by strong methanol maser emission at 6668MHz. The receiver was jointly constructed by Jodrell Bank Observatory (JBO) and the Australia Telescope National Facility (ATNF) and allows simultaneous coverage at 6668 and 6035MHz. It was successfully commissioned at Parkes in 2006 January and is now being used to conduct the Parkes-Jodrell multibeam maser survey of the Milky Way. This will be the first systematic survey of the entire Galactic plane for masers of not only 6668-MHz methanol, but also 6035-MHz excited-state hydroxyl. The survey is two orders of magnitude faster than most previous systematic surveys and has an rms noise level of ~0.17Jy. This paper describes the observational strategy, techniques and reduction procedures of the Galactic and Magellanic Cloud surveys, together with deeper, pointed, follow-up observations and complementary observations with other instruments. It also includes an estimate of the survey detection efficiency. The 111d of observations with the Parkes telescope have so far yielded >800 methanol sources, of which ~350 are new discoveries. The whole project will provide the first comprehensive Galaxy-wide catalogue of 6668-MHz and 6035-MHz masers.

  4. REVISING THE KINEMATICS OF 12 GHz CH{sub 3}OH MASERS TOWARD W3(OH)

    SciTech Connect

    Moscadelli, L.; Xu, Y.; Chen, X.

    2010-06-20

    We derive accurate proper motions of the CH{sub 3}OH 12 GHz masers toward the W3(OH) ultra-compact (UC) H II region, employing seven epochs of VLBA observations spanning a time interval of about 10 yr. The achieved velocity accuracy is of the order of 0.1 km s{sup -1}, adequate to precisely measure the relative velocities of most of the 12 GHz masers in W3(OH), with amplitude varying in the range 0.3-3 km s{sup -1}. Toward W3(OH), the most intense 12 GHz masers concentrate in a small area toward the north (the northern clump) of the UC H II region. We have compared the proper motions of the CH{sub 3}OH 12 GHz masers with those (derived from literature data) of the OH 6035 MHz masers, emitting from the same region of the methanol masers. In the northern clump, the two maser emissions emerge from nearby (but likely distinct) cloudlets of masing gas with, in general, a rather smooth variation of line-of-sight and sky-projected velocities, which suggests some connection of the environments and kinematics traced by both maser types. The conical outflow model, previously proposed to account for the 12 GHz maser kinematics in the northern clump, does not reproduce the new, accurate measurements of 12 GHz maser proper motions and has to be rejected. We focus on the subset of 12 GHz masers of the northern clump belonging to the 'linear structure at P.A. = 130{sup 0}-140{sup 0}', whose regular variation of LSR velocities with position presents evidence for some ordered motion. We show that the three-dimensional velocities of this 'linear distribution' of 12 GHz masers can be well fitted considering a flat, rotating disk, seen almost edge-on.

  5. Linear Polarization of Class I Methanol Masers in Massive Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Kang, Ji-hyun; Byun, Do-Young; Kim, Kee-Tae; Kim, Jongsoo; Lyo, A.-Ran; Vlemmings, W. H. T.

    2016-12-01

    Class I methanol masers are found to be good tracers of the interaction between outflows from massive young stellar objects with their surrounding media. Although polarization observations of Class II methanol masers have been able to provide information about magnetic fields close to the central (proto)stars, polarization observations of Class I methanol masers are rare, especially at 44 and 95 GHz. We present the results of linear polarization observations of 39 Class I methanol maser sources at 44 and 95 GHz. These two lines are observed simultaneously with one of the 21 m Korean VLBI Network telescopes in single-dish mode. Approximately 60% of the observed sources have fractional polarizations of a few percent in at least one transition. This is the first reported detection of linear polarization of the 44 GHz methanol maser. The two maser transitions show similar polarization properties, indicating that they trace similar magnetic environments, although the fraction of the linear polarization is slightly higher at 95 GHz. We discuss the association between the directions of polarization angles and outflows. We also discuss some targets having different polarization properties at both lines, including DR21(OH) and G82.58+0.20, which show the 90° polarization angle flip at 44 GHz.

  6. 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.

  7. High Resolution Surveys of the Water and Methanol Star Formation Masers in the Central Molecular Zone

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

    We present some of the first high resolution fully interferometric surveys of 6.7 GHz methanol and 22 GHz water masers towards the Central Molecular Zone (CMZ). These masers are good signposts for early (<0.05 Myrs) star formation. Using the Jansky Very Large Array (VLA), we searched the inner 3 x 0.7 deg of the Galactic Center (GC) for methanol masers with resolutions of 0.9” (0.04 pc) and 0.4 km/s (8 kHz) and an average channel sensitivity of ~0.01 Jy/beam. With this high resolution and sensitivity, we have detected ~100 methanol masers, which is over a factor of two more than has previously been detected. We have also conducted two surveys of water masers in this region. As part of the Survey of Water and Ammonia in the Galactic Center (SWAG), the Australia Telescope Compact Array (ATCA) was used to survey a variety of molecular lines, including the 22 GHz water line. With the ATCA, we have detected over 200 water masers using resolutions of 26” (1 pc) and 2 km/s (60 kHz) and an average channel sensitivity of ~0.01 Jy/beam. Afterward, we conducted the first on-the-fly (OTF) VLA survey of water masers with improved resolutions of 0.7” (0.03 pc) and 0.4 km/s (26 kHz) and an average channel sensitivity of ~0.05 Jy/beam. Although the analysis of this OTF survey is not yet complete, we have already identified water masers that were not visible in the SWAG data.The improvement in the number of detected masers allows us to better analyze the distribution of these masers. We show that the SWAG water masers appear uniformly distributed along the Galactic plane, despite the asymmetry of the molecular gas distribution, where ~2/3 of the gas mass is located at positive Galactic longitudes. The methanol masers follow the molecular gas distribution, with a majority of the masers being found at positive longitudes. This could indicate a difference in the star forming history of these two parts of the CMZ and/or that the 22 GHz water masers are contaminated by water

  8. 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

  9. CANDIDATES FOR THE YOUNG STELLAR OUTFLOWS: WATER AND METHANOL MASERS FROM YOUNG STELLAR OBJECTS

    SciTech Connect

    Lim, Wanggi; Lyo, A-Ran; Kim, Kee-Tae; Byun, Do-Young

    2012-11-01

    We conducted simultaneous 22 GHz water maser and 44 GHz class I methanol maser surveys of newly identified 282 H{sub 2} emission features from the 2.122 {mu}m H{sub 2} narrowband image survey in the Galactic plane (UWISH2 project) using Korean VLBI Network 21 m radio telescopes. We detected 16 and 13 new water and methanol maser sources, respectively. This result indicates that at least {approx}5% of the H{sub 2} emission features originate from young stellar objects (YSOs) that are in the right physical condition to produce the water and methanol masers. The masers are closely related to the current outflow activities in the Galactic plane. The power sources of these 23 diffused/collimated H{sub 2} emission features (six sources are detected for both masers) are likely to be intermediate- to high-mass YSOs, based on a comparison with the maser luminosities of other well-studied YSOs. Both maser velocities are mostly close to their own systemic velocities within {approx}<5 km s{sup -1}, even though water masers generally show larger variabilities in the intensity, velocity, and shape than methanol masers. We also discovered three new water maser sources with high-velocity components: {approx}25 km s{sup -1} redshifted CMHO 019, {approx}50 km s{sup -1} blueshifted CMHO 132, and {approx}120 km s{sup -1} blueshifted CMHO 182. In particular, we propose that the dominant blueshifted water maser of CHMO 182 can be a unique laboratory for the study of the high-mass young stellar jet and its acceleration.

  10. On the Relationship of UC HII Regions and Class II Methanol Masers. I. Source Catalogs

    NASA Astrophysics Data System (ADS)

    Hu, B.; Menten, K. M.; Wu, Y.; Bartkiewicz, A.; Rygl, K.; Reid, M. J.; Urquhart, J. S.; Zheng, X.

    2016-12-01

    We conducted Very Large Array C-configuration observations to measure positions and luminosities of Galactic Class II 6.7 GHz methanol masers and their associated ultra-compact H ii regions. The spectral resolution was 3.90625 kHz and the continuum sensitivity reached 45 μJy beam-1. We mapped 372 methanol masers with peak flux densities of more than 2 Jy selected from the literature. Absolute positions have nominal uncertainties of 0.″3. In this first paper on the data analysis, we present three catalogs; the first gives information on the strongest feature of 367 methanol maser sources, and the second provides information on all detected maser spots. The third catalog presents derived data of the 127 radio continuum counterparts associated with maser sources. Our detection rate of radio continuum counterparts toward methanol masers is approximately one-third. Our catalogs list properties including distance, flux density, luminosity, and the distribution in the Galactic plane. We found no significant relationship between luminosities of masers and their associated radio continuum counterparts, however, the detection rate of radio continuum emission toward maser sources increases statistically with the maser luminosities.

  11. New OH Observations toward Northern Class I Methanol Masers

    NASA Astrophysics Data System (ADS)

    Val'tts, I. E.; Litovchenko, I. D.; Bayandina, O. S.; Alakoz, A. V.; Larionov, G. M.; Mukha, D. V.; Nabatov, A. S.; Konovalenko, A. A.; Zakharenko, V. V.; Alekseev, E. V.; Nikolaenko, V. S.; Kulishenko, V. F.; Odincov, S. A.

    2012-07-01

    Maser emission of OH(1720) is formed, according to modern concepts, under the influence of collisional pumping. Class I methanol masers (MMI) are also formed by a collisional mechanism of the inversion of the molecular levels. It is not excluded in this case that physical conditions in the condensations of the interstellar medium where masers are formed may be similar for MMI and OH(1720) masers, and they can associate with each other. To establish a possible association between these two kinds of masers, and obtain reliable statistical estimates, a survey of class I methanol masers at a frequency of 1720 MHz has been carried out.

  12. 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.

  13. VizieR Online Data Catalog: Ultra-compact HII regions & methanol masers. I. (Hu+, 2016)

    NASA Astrophysics Data System (ADS)

    Hu, B.; Menten, K. M.; Wu, Y.; Bartkiewicz, A.; Rygl, K.; Reid, M. J.; Urquhart, J. S.; Zheng, X.

    2017-03-01

    372 unique targets were selected from the following methanol maser surveys: the Methanol Multi-Beam catalog (MMB; Caswell & Breen 2010MNRAS.407.2599C; Green+ 2010-2012, VIII/96), the Arecibo Methanol Maser Galactic Plane Survey (AMGPS; Pandian+ 2011ApJ...730...55P), the Torun catalog of 6.7GHz methanol masers (Szymczak+ 2012, J/AN/333/634), and other individual observations of known 6.7GHz methanol masers or MSFRs (Caswell+ 1995MNRAS.272...96C; Walsh+ 1997, J/MNRAS/291/261; 1998, J/MNRAS/301/640; Xu+ 2008A&A...485..729X; Caswell 2009, J/other/PASA/26.454). The observations were conducted with the VLA in C-configuration using five sessions from 2012 February 28 to April 16. Spectral line data used 2048 channels across 8MHz, yielding a channel spacing of 3.90625kHz at the central frequency of 6.6685192GHz and a velocity resolution of 0.176km/s. The continuum observations employed two 1GHz sub-bands from 4.9840 to 6.0080GHz (the low band) and from 6.6245 to 7.6485GHz (the high band) and each sub-band was divided into 16 channels. (4 data files).

  14. Simulated Galactic methanol maser distribution to constrain Milky Way parameters

    NASA Astrophysics Data System (ADS)

    Quiroga-Nuñez, L. H.; van Langevelde, H. J.; Reid, M. J.; Green, J. A.

    2017-08-01

    Context. Using trigonometric parallaxes and proper motions of masers associated with massive young stars, the Bar and Spiral Structure Legacy (BeSSeL) survey has reported the most accurate values of the Galactic parameters so far. The determination of these parameters with high accuracy has a widespread impact on Galactic and extragalactic measurements. Aims: This research is aimed at establishing the confidence with which such parameters can be determined. This is relevant for the data published in the context of the BeSSeL survey collaboration, but also for future observations, in particular from the southern hemisphere. In addition, some astrophysical properties of the masers can be constrained, notably the luminosity function. Methods: We have simulated the population of maser-bearing young stars associated with Galactic spiral structure, generating several samples and comparing them with the observed samples used in the BeSSeL survey. Consequently, we checked the determination of Galactic parameters for observational biases introduced by the sample selection. Results: Galactic parameters obtained by the BeSSeL survey do not seem to be biased by the sample selection used. In fact, the published error estimates appear to be conservative for most of the parameters. We show that future BeSSeL data and future observations with southern arrays will improve the Galactic parameters estimates and smoothly reduce their mutual correlation. Moreover, by modeling future parallax data with larger distance values and, thus, greater relative uncertainties for a larger numbers of sources, we found that parallax-distance biasing is an important issue. Hence, using fractional parallax uncertainty in the weighting of the motion data is imperative. Finally, the luminosity function for 6.7 GHz methanol masers was determined, allowing us to estimate the number of Galactic methanol masers.

  15. 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.

  16. 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.

  17. A Catalog of Methanol Masers in Massive Star-forming Regions. III. The Molecular Outflow Sample

    NASA Astrophysics Data System (ADS)

    Gómez-Ruiz, A. I.; Kurtz, S. E.; Araya, E. D.; Hofner, P.; Loinard, L.

    2016-02-01

    We present an interferometric survey of the 44 GHz class I methanol maser transition toward a sample of 69 sources consisting of high-mass protostellar object (HMPO) candidates and ultracompact (UC) H ii regions. We found a 38% detection rate (16 of 42) in the HMPO candidates and a 54% detection rate (13 of 24) for the regions with ionized gas. This result indicates that class I methanol maser emission is more common toward the more evolved young stellar objects of our sample. Comparing with similar interferometric data sets, our observations show narrower linewidths, likely due to our higher spatial resolution. Based on a comparison between molecular outflow tracers and the maser positions, we find several cases where the masers appear to be located at the outflow interface with the surrounding core. Unlike previous surveys, we also find several cases where the masers appear to be located close to the base of the molecular outflow, although we cannot discard projection effects. This and other surveys of class I methanol masers not only suggest that these masers may trace shocks at different stages, but also that they may even trace shocks arising from a number of different phenomena occurring in star-forming regions: young/old outflows, cloud-cloud collisions, expanding H ii regions, among others.

  18. A CATALOG OF METHANOL MASERS IN MASSIVE STAR-FORMING REGIONS. III. THE MOLECULAR OUTFLOW SAMPLE

    SciTech Connect

    Gómez-Ruiz, A. I.; Kurtz, S. E.; Loinard, L.; Araya, E. D.; Hofner, P.

    2016-02-15

    We present an interferometric survey of the 44 GHz class I methanol maser transition toward a sample of 69 sources consisting of high-mass protostellar object (HMPO) candidates and ultracompact (UC) H ii regions. We found a 38% detection rate (16 of 42) in the HMPO candidates and a 54% detection rate (13 of 24) for the regions with ionized gas. This result indicates that class I methanol maser emission is more common toward the more evolved young stellar objects of our sample. Comparing with similar interferometric data sets, our observations show narrower linewidths, likely due to our higher spatial resolution. Based on a comparison between molecular outflow tracers and the maser positions, we find several cases where the masers appear to be located at the outflow interface with the surrounding core. Unlike previous surveys, we also find several cases where the masers appear to be located close to the base of the molecular outflow, although we cannot discard projection effects. This and other surveys of class I methanol masers not only suggest that these masers may trace shocks at different stages, but also that they may even trace shocks arising from a number of different phenomena occurring in star-forming regions: young/old outflows, cloud–cloud collisions, expanding H ii regions, among others.

  19. Insights into high mass star formation from methanol maser observations

    NASA Astrophysics Data System (ADS)

    Farmer, Hontas Freeman

    2013-06-01

    We present high angular resolution data on Class I and Class II methanol masers, together with other tracers of star formation like H2O masers, ultracompact (UC) ionized hydrogen (H II) regions, and 4.5 um infrared sources, taken from the literature. The aim is to study what these data tell us about the process of high mass star formation; in particular, whether disk-outflow systems are compatible with the morphology exhibited by Class I and Class II methanol masers. Stars form in the dense cores inside molecular clouds, and while the process of the formation of stars like our Sun is reasonably well understood, details of the formation of stars with masses eight times that of our Sun or greater, the so-called high mass stars, remain a mystery. Being compact and bright sources, masers provide an excellent way to observe high mass star forming regions. In particular, Class II methanol masers are found exclusively in high mass star forming regions. Based on the positions of the Class I and II methanol and H2O masers, UCHII regions and 4.5 um infrared sources, and the center velocities (vLSR) of the Class I methanol and H2O masers, compared to the vLSR of the Class II methanol masers, we propose three disk-outflow models that may be traced by methanol masers. In all three models, we have located the Class II methanol maser near the protostar, and the Class I methanol maser in the outflow, as is known from observations during the last twenty years. In our first model, the H2O masers trace the linear extent of the outflow. In our second model, the H2O masers are located in a circumstellar disk. In our third model, the H2O masers are located in one or more outflows near the terminating shock where the outflow impacts the ambient interstellar medium. Together, these models reiterate the utility of coordinated high angular resolution observations of high mass star forming regions in maser lines and associated star formation tracers.

  20. G23.657-0.127, what can we learn from a perfect methanol maser source?

    NASA Astrophysics Data System (ADS)

    Bartkiewicz, Anna; van Langevelde, Huib Jan; Szymczak, Marian; Brunthaler, Andreas

    2007-03-01

    In the course of following up compact methanol masers at 6.7 GHz which were found in the Torun blind survey (Szymczak et al. 2002), we discovered a ring structure in the source G23.657-00.127. This source provides interesting insights into whether methanol masers arise in rotating disks around massive stars, in their outflows, or behind shocks. By monitoring the 12.2 GHz masers, which fortunately follow the same structure, we hope to resolve the kinematics of the ring. Moreover, the symmetry of the source points to the existence of a central source. Early results on the nature of this source indicate the existence of a hyper compact H II region.

  1. 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.

  2. 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.

  3. Experimental evaluation of a ruby maser at 43 GHz

    NASA Astrophysics Data System (ADS)

    Moore, C. R.; Neff, D.

    1982-11-01

    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.

  4. The Revised Version of Class I Methanol Maser Catalog

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

    The revised version of the class I methanol maser catalog is presented. It contains 198 sources in total. New class I methanol masers detected in the direction of EGOs (38 sources) were added to the previous list containing ˜ 160 sources (the list have been published in the first version of this catalog - see reference in the text). Electronic version of the catalog has been generated in the form of html file - http://www.asc.rssi.ru/MMI. A statistical analysis was carried out within 2' around a maser position to find an identification of class I methanol masers with any objects typical for star-forming regions - UCHII regions, IRAS sources, dark clouds, bipolar outflows, CS lines as of dense gas tracer, and other masers (class II methanol masers, OH and H_2O). Class I methanol masers identification was made with short-wave infrared objects EGO (extended green objects), which are tracers of bipolar outflows in young stellar objects. It was shown that in the new version of catalog more than 50% of class I methanol masers are identified with bipolar outflow - given EGOs as bipolar outflows (compared with the result of 22% in the first version of the catalog that contains no information about EGO). This result is a strong evidence in favor of the fact that EGOs are indeed active bipolar outflows. At the same time it is important to note, that none of the bipolar outflow, already registered in the direction of class I methanol maser, did not coincide with EGO (with the exception of G45.47+0.07). The results are submitted in a form of a diagram.

  5. 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.

  6. Discovery Of 6.035 GHz OH Maser Flares In IRAS 18566+0408

    NASA Astrophysics Data System (ADS)

    Araya, Esteban; Marzouk, A. A. Al; Hofner, P.; Kurtz, S.; Linz, H.; Olmi, L.

    2011-05-01

    We report the discovery of 6.035 GHz hydroxyl (OH) maser flares toward the massive young stellar object IRAS 18566+0408, which is the only region known to show periodic formaldehyde (4.8 GHz H2CO) and methanol (6.7 GHz CH3OH) maser flares. The observations were conducted between October 2008 and January 2010 with the 305m Arecibo Telescope in Puerto Rico. We detected two flare events, one in March 2009 and the other in September to November 2009. The 6.035 GHz OH flares are not simultaneous with the H2CO flares; the peak of the OH flares appears to be delayed by 1 to 3 months with respect to the formaldehyde flares. On the other hand, the OH flares occurred simultaneously with CH3OH flares from maser components that have approximately the same LSR velocity as the OH. The correlated variability of OH and CH3OH masers in IRAS 18566+0408 supports a common excitation mechanism (IR pumping) as predicted by theory. EA acknowledges support from the WIU OSP. PH acknowledges partial support from NSF grant AST-0908901.

  7. VizieR Online Data Catalog: Class I methanol maser catalog (Bayandina+, 2012)

    NASA Astrophysics Data System (ADS)

    Bayandina, O. S.; Val'Tts, I. E.; Larionov, G. M.

    2012-11-01

    We have revised the Astro Space Center catalog of Class I methanol masers detected in starforming regions (MMI/SFR), mainly at 44GHz, and created a new electronic version of the catalog. Currently, the catalog contains 206 objects, selected from publications through 2011 inclusive. The data from the survey of Chen et al. (2011, Cat. J/ApJS/196/9), performed specifically for objects EGO, which form a new specific catalog, are not included. The MMI/SFR objects were identified with emission and absorption objects in the near IR, detected during the MSX and Spitzer space missions. Seventy-one percent of Class I methanol masers that emit at 44GHz and fall within the Galactic longitude range surveyed by Spitzer (GLIMPSE) are identified with Spitzer Dark Clouds (SDCs), and 42% with Extended Green Objects (EGOs). It is possible that Class I methanol masers arise in isolated, self-gravitating clumps, such as SDCs, at certain stages of their evolution. A sample of SDCs is proposed as a new target list for Class I methanol maser searches. A detailed statistical analysis was carried out, taking into account the characteristics of the regions of MMI/SFR formation presented in the catalog. (1 data file).

  8. 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

  9. Methanol masers probing the ordered magnetic field of W75N

    NASA Astrophysics Data System (ADS)

    Surcis, G.; Vlemmings, W. H. T.; Dodson, R.; van Langevelde, H. J.

    2009-11-01

    Context: The role of magnetic fields during the protostellar phase of high-mass star-formation is a debated topic. In particular, it is still unclear how magnetic fields influence the formation and dynamic of disks and outflows. Most current information on magnetic fields close to high-mass protostars comes from H2O and OH maser observations. Recently, the first 6.7 GHz methanol maser polarization observations were made, and they reveal strong and ordered magnetic fields. Aims: The morphology of the magnetic field during high-mass star-formation needs to be investigated on small scales, which can only be done using very long baseline interferometry observations. The massive star-forming region W75N contains three radio sources and associated masers, while a large-scale molecular bipolar outflow is also present. Polarization observations of the 6.7 GHz methanol masers at high angular resolution probe the strength and structure of the magnetic field and determine its relation to the outflow. Methods: Eight of the European VLBI network antennas were used to measure the linear polarization and Zeeman-splitting of the 6.7 GHz methanol masers in the star-forming region W75N. Results: We detected 10 methanol maser features, 4 of which were undetected in previous work. All arise near the source VLA 1 of W75N. The linear polarization of the masers reveals a tightly ordered magnetic field over more than 2000 AU around VLA 1 that is exactly aligned with the large-scale molecular outflow. This is consistent with the twisted magnetic field model proposed for explaining dust polarization observations. The Zeeman-splitting measured on 3 of the maser features indicates a dynamically important magnetic field in the maser region of the order of 50 mG. We suggest VLA 1 is the powering sources of the bipolar outflow. Member of the International Max Planck Research School (IMPRS) for Astronomy and Astrophysics at the Universities of Bonn and Cologne.

  10. Searching for Sites of Recent Star Formation Towards the Central Molecular Zone: Surveys of Water and Methanol Masers

    NASA Astrophysics Data System (ADS)

    Rickert, Matthew

    The Central Molecular Zone (CMZ) spans the inner 450 pc ( 3°) of our Galaxy. This region displays enhanced molecular emission and contains 5% of the entire Galaxy's gas mass. However, the number of detected star forming sites towards the CMZ is low for the amount of molecular gas that is present. We have conducted four sets of observations of this region in order to detect new sites of star formation. These observations can be broken into two types of surveys: blind (that span a wide region of the sky) and targeted (that point at specific sources). We use two telescopes (the Very Large Array and the Australia Telescope Compact Array) to observe two types of masers: the 6.7 GHz methanol maser and the 22 GHz water maser. Both are tracers of recent (<0.05 Myr) star formation. The 6.7 GHz methanol maser is a radiatively pumped maser that traces recent high mass star formation, while the 22 GHz water maser is collisionally pumped and can also be produced by evolved stars. Our only 6.7 GHz CH3OH maser survey used the Jansky Very Large Array (VLA) to conduct a blind survey of the inner 3° x 40' (450 pc x 100 pc) of the Galaxy. We detect 42 CH3OH masers towards 30 distinct locations. 16 of these masers are new detections. A majority of all the detected CH3OH masers are located towards positive Galactic longitudes, similar to how 2/3 of the molecular gas mass in the CMZ is also located at positive Galactic longitudes. The first of our 22 GHz observations used the VLA to target 22 GHz water masers that were previously detected with the Mopra telescope. We detect 293 water masers towards 31 distinct locations. This is a vast increase over the 37 water masers that had been detected by Mopra towards 29 distinct locations, demonstrating the benefit of observations with high spatial (<2") and spectral (< 1 km/s) resolutions for detecting masers. As part of the Search for Water and Ammonia in the Galactic Center (SWAG) collaboration, we then conducted a blind survey of the inner

  11. 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.

  12. 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.

  13. 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.

  14. Characterizing supernova remnant and molecular cloud interaction environments using Class I methanol (CH3OH) masers

    NASA Astrophysics Data System (ADS)

    McEwen, Bridget C.

    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, for example, star forming regions (SFRs), supernova remnants (SNRs), evolved stars, and outflows. In particular, collisionally excited 36 and 44 GHz methanol (CH3OH) and 1720 MHz hydroxl (OH) masers are found associated with gas shocked by the interaction between SNRs and neighboring molecular clouds (MCs). The overall goal of my thesis research is to combine modeling and observations to characterize the properties and formation of Class I CH3OH masers in these SNR/MC interaction regions. Developing a general model of the distribution of maser emission in these regions in all SNRs interacting with MCs will aid in the understanding of different processes that may be triggered through these interactions, namely induced star formation (SF) and cosmic ray (CR) acceleration. More accurate information on the density (and density gradients) in these turbulent regions could, for example, be used as inputs or constraints for models of galactic SNR CR acceleration and help explain if conditions are conducive for SF. In this thesis, I present results from calculations of the physical conditions necessary for the occurrence of collisionally pumped Class I 36, 44, 84, and 95 GHz CH3OH maser lines near SNRs, using an escape probability 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 10 4 < n 60 K, overlapping with masing conditions for 1720 MHz OH masers. In addition, 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

  15. 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.

  16. New detections of 321 GHz water masers toward late-type stars

    NASA Astrophysics Data System (ADS)

    Liljeström, Tarja; Winnberg, Anders; Booth, Roy

    The SEST telescope has been used for a submillimeter water maser survey toward late-type stars. Six new 321 GHz water masers were detected. These, as well as the earlier reported sources, VY CMa and o Cet, were also observed in the vibrationally excited water maser line at 96 GHz. However, only VY CMa and o Cet showed the 96 GHz emission. The line velocity of o Cet is blueshifted, suggesting that the hot water vapor at 96 GHz takes part in the pulsation-shock motion of the Mira variable.

  17. Annular-beam, 17 GHz free-electron maser experiment

    SciTech Connect

    Earley, L.M.; Carlsten, B.E.; Fazio, M.V.

    1997-06-01

    Experiments have been conducted on a 15-17 GHz free electron maser (FEM) for producing a 500 MW output pulse with a phase stability appropriate for linear collider applications. The electron beam source was a 1 {mu}s, 800 kV, 5 kA, 6-cm-dia annular electron beam machine called BANSHEE. The beam interacted with the TM{sub 02} and TM{sub 03} mode Raman FEM amplifier in a corrugated cylindrical waveguide where the beam runs close to the interaction device walls to reduce the power density in the fields. This greatly reduced the kinetic energy loss caused by the beam potential depression associated with the space charge which was a significant advantage in comparison with conventional solid beam microwave tubes at the same beam current. The experiment was operated in a single shot mode with a large number of diagnostics to measure power, frequency and energy.

  18. Methanol observation of IRAS 19312+1950: A possible new type of class I methanol maser

    NASA Astrophysics Data System (ADS)

    Nakashima, Jun-ichi; Sobolev, Andrej M.; Salii, Svetlana V.; Zhang, Yong; Yung, Bosco H. K.; Deguchi, Shuji

    2015-10-01

    We report the result of a systematic methanol observation toward IRAS 19312+1950. The properties of the SiO, H2O, and OH masers of this object are consistent with those of mass-losing evolved stars, but some other properties are difficult to explain in the standard scheme of stellar evolution in its late stage. Interestingly, a tentative detection of radio methanol lines was suggested toward this object by a previous observation. To date, there are no confirmed detections of methanol emission towards evolved stars, so investigation of this possible detection is important to better understand the circumstellar physical/chemical environment of IRAS 19312+1950. In this study, we systematically observed multiple methanol lines of IRAS 19312+1950 in the λ = 3 mm, 7 mm, and 13 mm bands, and detected six lines including four thermal lines and two class I maser lines. We derived basic physical parameters, including kinetic temperature and relative abundances, by fitting a radiative transfer model. According to the derived excitation temperature and line profiles, a spherically expanding outflow lying at the center of the nebulosity is excluded from the possibilities for methanol emission regions. The detection of class I methanol maser emission suggests that a shock region is involved in the system of IRAS 19312+1950. If the central star of IRAS 19312+1950 is an evolved star as suggested in the past, the class I maser detected in the present observation is the first case detected in an interaction region between an evolved star outflow and ambient molecular gas.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Identification of Class I Methanol Masers with Objects of Near and Mid-Infrared Bands and the Third Version of the Class I Methanol Maser (MMI) Catalog

    NASA Astrophysics Data System (ADS)

    Bayandina, Olga; Val'tts, Irina; Larionov, Grigorii

    2012-07-01

    An identification has been conducted of class I methanol masers with 1) short-wave infrared objects EGO (extended green objects) - tracer bipolar outflow of matter in young stellar objects, and 2) isolated pre-protostellar gas-dust cores of the interstellar medium which are observed in absorption in the mid-infrared in the Galactic plane. It is shown that more than 50% of class I methanol masers are identified with bipolar outflows, considering the EGO as bipolar outflows (as compared with the result of 22% in the first version of the MMI catalog that contains no information about EGO). 99 from 139 class I methanol masers (71%) are identified with SDC. Thus, it seems possible that the MMI can be formed in isolated self-gravitating condensations, which are the silhouette of dark clouds - IRDC and SDC.

  4. Discovery of four periodic methanol masers and updated light curve for a further one

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    We report the discovery of 6.7 GHz methanol maser periodic flares in four massive star-forming regions and the updated light curve for the known periodic source G22.357+0.066. The observations were carried out with the Torun 32-m radio telescope between 2009 June and 2014 April. Flux density variations with period of 120 to 245 d were detected for some or all spectral features. A variability pattern with a fast rise and relatively slow fall on time-scale of 30-60 d dominated. A reverse pattern was observed for some features of G22.357+0.066, while sinusoidal-like variations were detected in G25.411+0.105. A weak burst lasting ˜520 d with the velocity drift of 0.24 km s-1 yr-1 occurred in G22.357+0.066. For three sources for which high-resolution maps are available, we found that the features with periodic behaviour are separated by more than 500 au from those without any periodicity. This suggests that the maser flares are not triggered by large-scale homogeneous variations in either the background seed photon flux or the luminosity of the exciting source and a mechanism which is able to produce local changes in the pumping conditions is required.

  5. Class I methanol maser emission in infrared clouds and the third version of the Astro Space Center MMI/SFR catalog

    NASA Astrophysics Data System (ADS)

    Bayandina, O. S.; Val'tts, I. E.; Larionov, G. M.

    2012-07-01

    We have revised the Astro Space Center catalog of Class I methanol masers detected in star-forming regions (MMI/SFR), mainly at 44 GHz, and created a new electronic version of the catalog. Currently, the catalog contains 206 objects, selected from publications through 2011 inclusive. The data from the survey of Chen et al. (2011), performed specifically for objects EGO, which form a new specific catalog, are not included. The MMI/SFR objects were identified with emission and absorption objects in the near IR, detected during the MSX and Spitzer space missions. Seventy-one percent of Class I methanol masers that emit at 44 GHz and fall within the Galactic longitude range surveyed by Spitzer (GLIMPSE) are identified with Spitzer Dark Clouds (SDCs), and 42% with Extended Green Objects (EGOs). It is possible that Class I methanol masers arise in isolated, self-gravitating clumps, such as SDCs, at certain stages of their evolution. A sample of SDCs is proposed as a new target list for Class I methanol maser searches. A detailed statistical analysis was carried out, taking into account the characteristics of the regions of MMI/SFR formation presented in the catalog.

  6. 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.

  7. 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.

  8. GLOBAL VERY LONG BASELINE INTERFEROMETRY OBSERVATIONS OF THE 6.0 GHz HYDROXYL MASERS IN ONSALA 1

    SciTech Connect

    Fish, Vincent L.; Sjouwerman, Lorant O. E-mail: lsjouwer@nrao.ed

    2010-06-10

    We present global very long baseline interferometry observations of the first excited-state hydroxyl (OH) masers in the massive star-forming region Onsala 1 (ON 1). The 29 masers detected are nearly all from the 6035 MHz transition and nearly all are identifiable as Zeeman pair components. The 6030 and 6035 MHz masers are coincident with previously published positions of ground-state masers to within a few milliarcseconds, and the magnetic fields deduced from Zeeman splitting are comparable. The 6.0 GHz masers in ON 1 are always found in close spatial association with 1665 MHz OH masers, in contrast to the situation in the massive star-forming region W3(OH), suggesting that extreme high density OH maser sites (excited-state masers with no accompanying ground-state maser, as seen in W3(OH)) are absent from ON 1. The large magnetic field strength among the northern, blueshifted masers is confirmed. The northern masers may trace an outflow or be associated with an exciting source separate from the other masers, or the relative velocities of the northern and southern masers may be indicative of expansion and rotation. High angular resolution observations of nonmasing material will be required in order to understand the complex maser distribution in ON 1.

  9. A Sensitive Search for Predicted Methanol Maser Transitions with the Australia Telescope Compact Array

    NASA Astrophysics Data System (ADS)

    Chipman, A.; Ellingsen, S. P.; Sobolev, A. M.; Cragg, D. M.

    2016-11-01

    We have used the Australia Telescope Compact Array to search for a number of centimetre wavelength methanol transitions which are predicted to show weak maser emission towards star formation regions. Sensitive, high spatial, and spectral resolution observations towards four high-mass star formation regions which show emission in a large number of class II methanol maser transitions did not result in any detections. From these observations, we are able to place an upper limit of ≲ 1300 K on the brightness temperature of any emission from the 31A+-31A-, 17-2-18-3 E (vt = 1), 124-133 A-, 124-133 A+, and 41A+-41A- transitions of methanol in these sources on angular scales of 2 arcsec. This upper limit is consistent with current models for class II methanol masers in high-mass star formation regions and better constraints than those provided here will likely require observations with next-generation radio telescopes.

  10. 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.

  11. 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).

  12. Movie and Description of the 43-GHz SiO Masers in S Per

    NASA Astrophysics Data System (ADS)

    Ostrowski-Fukuda, T. A.; Stencel, R. E.; Kemball, A.; Harper, G.; Diamond, P. J.

    2002-12-01

    The Very Long Baseline Array (VLBA) has been used to monitor the 43 GHz SiO (v=1,J=1-0) maser emission in the red supergiant star, S Persei, monthly since 1999. SiO masers act as probes of the gas motions and magnetic fields of this star allowing us to investigate its extended atmosphere. Here we report the preliminary results of this on-going project. Many epochs of data have been reduced and pieced together in a time-lapse movie fashion, allowing us to follow the motions of the individual maser regions. The motion of twenty-three maser spots are followed through the selected epochs, revealing velocity and ring structure information. Proper motions are detected by using a pairwise separation test and the average expansion velocity will be discussed. Finally, the relation between the pulsational phase of the star and the SiO maser emission will be discussed. The results of this study provide the first SiO maser movie of a red supergiant star and allow us to make a comparison between S Per, and Mira-type red giant stars, such as TX Cam. This work is supported by the University of Denver's Menzel Scholarship Fund and in conjunction with the National Radio Astronomy Observatory, Socorro, NM.

  13. Survey of Water and Ammonia in Nearby Galaxies (SWAN): Resolved Ammonia Thermometry, and Water and Methanol Masers in the Nuclear Starburst of NGC 253

    NASA Astrophysics Data System (ADS)

    Gorski, Mark; Ott, Jürgen; Rand, Richard; Meier, David S.; Momjian, Emmanuel; Schinnerer, Eva

    2017-06-01

    We present Karl G. Jansky Very Large Array molecular line observations of the nearby starburst galaxy NGC 253, from SWAN, the Survey of Water and Ammonia in Nearby galaxies. SWAN is a molecular line survey at centimeter wavelengths designed to reveal the physical conditions of star-forming gas over a range of star-forming galaxies. NGC 253 has been observed in four 1 GHz bands from 21 to 36 GHz at 6″ ˜ 100 pc) spatial and 3.5 km s-1 spectral resolution. In total we detect 19 transitions from 7 molecular and atomic species. We have targeted the metastable inversion transitions of ammonia (NH3) from (1, 1) to (5, 5) and the (9, 9) line, the 22.2 GHz water (H2O) ({6}16{--}{5}23) maser, and the 36.1 GHz methanol (CH3OH) ({4}-1{--}{3}0) maser. Using NH3 as a thermometer, we present evidence for uniform heating over the central kpc of NGC 253. The molecular gas is best described by a two kinetic temperature model with a warm 130 K and a cooler 57 K component. A comparison of these observations with previous ALMA results suggests that the molecular gas is not heated in photon-dominated regions or shocks. It is possible that the gas is heated by turbulence or cosmic rays. In the galaxy center we find evidence for NH3(3, 3) masers. Furthermore, we present velocities and luminosities of three water maser features related to the nuclear starburst. We partially resolve CH3OH masers seen at the edges of the bright molecular emission, which coincides with expanding molecular superbubbles. This suggests that the masers are pumped by weak shocks in the bubble surfaces.

  14. Simultaneous 183 GHz H2O maser and SiO observations towards evolved stars using APEX SEPIA Band 5

    NASA Astrophysics Data System (ADS)

    Humphreys, E. M. L.; Immer, K.; Gray, M. D.; De Beck, E.; Vlemmings, W. H. T.; Baudry, A.; Richards, A. M. S.; Wittkowski, M.; Torstensson, K.; De Breuck, C.; Møller, P.; Etoka, S.; Olberg, M.

    2017-07-01

    Aims: The aim is to investigate the use of 183 GHz H2O masers for characterization of the physical conditions and mass loss process in the circumstellar envelopes of evolved stars. Methods: We used APEX SEPIA Band 5 (an ALMA Band 5 receiver on the APEX telescope) to observe the 183 GHz H2O line towards two red supergiant (RSG) and three asymptotic giant branch (AGB) stars. Simultaneously, we observed the J = 4-3 line for 28SiO v = 0, 1, 2 and 3, and for 29SiO v = 0 and 1. We compared the results with simulations and radiative transfer models for H2O and SiO, and examined data for the individual linear orthogonal polarizations. Results: We detected the 183 GHz H2O line towards all the stars with peak flux densities >100 Jy, including a new detection from VY CMa. Towards all five targets, the water line had indications of being caused by maser emission and had higher peak flux densities than for the SiO lines. The SiO lines appear to originate from both thermal and maser processes. Comparison with simulations and models indicate that 183 GHz maser emission is likely to extend to greater radii in the circumstellar envelopes than SiO maser emission and to similar or greater radii than water masers at 22, 321 and 325 GHz. We speculate that a prominent blue-shifted feature in the W Hya 183 GHz spectrum is amplifying the stellar continuum, and is located at a similar distance from the star as mainline OH maser emission. We note that the coupling of an SiO maser model to a hydrodynamical pulsating model of an AGB star yields qualitatively similar simulated results to the observations. From a comparison of the individual polarizations, we find that the SiO maser linear polarization fraction of several features exceeds the maximum fraction allowed under standard maser assumptions and requires strong anisotropic pumping of the maser transition and strongly saturated maser emission. The low polarization fraction of the H2O maser however, fits with the expectation for a non

  15. Polarisation observations of VY Canis Majoris H2O 532-441 620.701 GHz maser emission with HIFI

    NASA Astrophysics Data System (ADS)

    Harwit, M.; Houde, M.; Sonnentrucker, P.; Boogert, A. C. A.; Cernicharo, J.; De Beck, E.; Decin, L.; Henkel, C.; Higgins, R. D.; Jellema, W.; Kraus, A.; McCoey, C.; Melnick, G. J.; Menten, K. M.; Risacher, C.; Teyssier, D.; Vaillancourt, J. E.; Alcolea, J.; Bujarrabal, V.; Dominik, C.; Justtanont, K.; de Koter, A.; Marston, A. P.; Olofsson, H.; Planesas, P.; Schmidt, M.; Schöier, F. L.; Szczerba, R.; Waters, L. B. F. M.

    2010-10-01

    Context. Water vapour maser emission from evolved oxygen-rich stars remains poorly understood. Additional observations, including polarisation studies and simultaneous observation of different maser transitions may ultimately lead to greater insight. Aims: We have aimed to elucidate the nature and structure of the VY CMa water vapour masers in part by observationally testing a theoretical prediction of the relative strengths of the 620.701 GHz and the 22.235 GHz maser components of ortho H2O. Methods: In its high-resolution mode (HRS) the Herschel Heterodyne Instrument for the Far Infrared (HIFI) offers a frequency resolution of 0.125 MHz, corresponding to a line-of-sight velocity of 0.06 km s-1, which we employed to obtain the strength and linear polarisation of maser spikes in the spectrum of VY CMa at 620.701 GHz. Simultaneous ground based observations of the 22.235 GHz maser with the Max-Planck-Institut für Radioastronomie 100-m telescope at Effelsberg, provided a ratio of 620.701 GHz to 22.235 GHz emission. Results: We report the first astronomical detection to date of H2O maser emission at 620.701 GHz. In VY CMa both the 620.701 and the 22.235 GHz polarisation are weak. At 620.701 GHz the maser peaks are superposed on what appears to be a broad emission component, jointly ejected from the star. We observed the 620.701 GHz emission at two epochs 21 days apart, both to measure the potential direction of linearly polarised maser components and to obtain a measure of the longevity of these components. Although we do not detect significant polarisation levels in the core of the line, they rise up to approximately 6% in its wings. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendix (page 5) is only available in electronic form at http://www.aanda.org

  16. Observations of Non Typical Masers at the RT-22 Radio Telescope in 2004-2013

    NASA Astrophysics Data System (ADS)

    Shulga, V. M.; Antyufeyev, O. V.; Zubrin, S. Y.; Myshenko, V. V.; Piddyachiy, V. I.; Korolev, A. M.; Patoka, O. M.

    2017-06-01

    Purpose: Some peculiarities of emission of Class I methanol masers on the 80–71A+ transition at 95 GHz in sources closely associated with protostar-forming regions and in supernova remnants are studied. Here belongs the investigation of SiO (J=2–1) maser variability in R Cassiopeiae, too. Design/methodology/approach: Search for Class I methanol masers is based on the idea of coincidence of regions of their emission with sources of OH masing transition in the bottom level of energy at frequency of 1720 MHz (2Π3/2 J=3/2 F=2–1). Findings: Two methanol masers on transition 80–71A+ (95 GHz) in the supernova remnants IC 443 and Kes 79 are detected. Variabilities of SiO maser emission on transition J=2–1 in R Cassiopeiae are shown for the first time. Conclusions: Variability of methanol and SiO masers is their general feature. On the example of three objects, the possibility of using the 1720 MHz OH maser as an indicator in the search for Class I methanol masers is shown. Especially it is important in the study of methanol maser emission in supernova remnants that has been proved to be true by detection of methanol masers on transition 80–71A+ (95 GHz) in IC 443 and Kes 79. Features of spectra variability of emission in R Cassiopeiae testify to formation and disappearance of SiO (J=2–1) masers.

  17. 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.

  18. 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%).

  19. VLA survey of 22 GHz H2O masers toward ten silicate carbon stars

    NASA Astrophysics Data System (ADS)

    Ohnaka, K.; Boboltz, D. A.; Mulitz-Schimel, G.; Izumiura, H.; Wittkowski, M.

    2013-11-01

    Context. Despite their carbon-rich photospheres, silicate carbon stars show evidence of oxygen-rich circumstellar material, which is thought to exist in disks. Silicate carbon stars represent interesting cases that allow us to study the possible effects of binarity on stellar evolution and mass loss accompanied by the formation of disks. Aims: We present a small survey of 22 GHz H2O masers toward ten silicate carbon stars with much better sensitivity than is the case for previous observations. Methods: We observed our sample with the Karl G. Jansky Very Large Array (VLA) using the most expanded configuration (A-configuration) with a maximum baseline of 36 km. For some of our program stars with noisy Infrared Astronomical Satellite (IRAS) Low Resolution Spectra (LRS), we present new mid-IR spectra obtained with the Very Large Telescope Interferometer and the Spitzer Space Telescope. Results: We detected H2O masers toward five out of ten silicate carbon stars (EU And, V778 Cyg, IRAS 06017+1011, V1415 Cyg, and NC83 = V1945 Cyg), with NC83 being a new detection. No H2O masers were detected toward BM Gem, IRAS 07221-0431, IRAS 08002-3803, IRAS 18006-3213, and HD 189605. The velocity separation between the most blue- and red-shifted maser features is 10-14 km s-1. If we assume that the masers originate in circum-companion disks, the measured velocity separations translate into a lower limit of the rotational velocity of 5-7 km s-1, and the upper limit of the radius of the maser emitting region is estimated to be 10-68 AU for a companion mass of 0.5-1.7 M⊙. The new mid-IR spectra of NC83, IRAS 06017+1011, and HD 189605 confirm the 10 μm silicate emission. The latter two stars show a bump at ~11.5 μm, which is presumably due to SiC originating in the ongoing mass loss from the carbon-rich primary star, not due to crystalline silicate. We also report on the detection of the UV flux at 2271 Å toward HD 189605. Based on MIDI observations made with the Very Large

  20. 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

  1. 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.

  2. 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.

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

    NASA Technical Reports Server (NTRS)

    Trowbridge, D. L.; Loreman, J. R.; Brunzie, T. J.; Jenkins, B.

    1988-01-01

    An 8.4 GHz front-end system consisting of a feedhorn, a waveguide feed assembly, dual masers, and downconverters is being 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 on the Parkes antenna for the Giotto project. It was also used on a time-sharing basis by the DSN as part of the Parkes-Canberra Telemetry Array to enhance the data return from Voyager 2 at Uranus. At the conclusion of these projects in 1986, the front-end system was dismantled, packed, and shipped to Europe. Part of the system was then shipped to JPL on loan for reimplementation at Parkes for the Voyager Neptune encounter. The system is being redesigned and refurbished for operation at Parkes. Tasks include new microwave front-end control cabinets, a closed-cycle refrigeration data acquisition system, a new noise-adding radiometer system, a front-end controller assembly, and refurbishment of the dual 8.4 GHz traveling-wave masers (TWMs) and waveguide feed system.

  4. 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}.

  5. VizieR Online Data Catalog: 22-GHz water maser clouds (Richards+, 2012)

    NASA Astrophysics Data System (ADS)

    Richards, A. M. S.; Etoka, S.; Gray, M. D.; Lekht, E. E.; Mendoza-Torres, J. E.; Murakawa, K.; Rudnitskij, G.; Yates, J. A.

    2012-07-01

    Measurements of 22-GHz water maser clouds, made with the MERLIN radio interferometer. Obects presented (number of epochs): S Per (2); U Ori (4); U Her (3); IK Tau (3); RT Vir (7); W Hya (4). Results for VX Sgr were presented in Murakawa et al, 2003, Cat. J/MNRAS/344/1. The position and other properties of each patch of maser emission in each channel were measured by fitting 2D Gaussian components. The components form features corresponding to spatially distinct clouds and the properties of each cloud was calculated as described in the paper. For each cloud, we give the mean Vlsr, the total velocity extent DV, the full width half maximum DV1/2, the offsets of the cloud centroid from the assumed stellar position x, y and a (=sqrt(x2+y2), the feature largest angular size l and the peak flux density I. All velocities, angular distances and flux densities are in km/s, mas and Jy, respectively. (2 data files).

  6. 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.

  7. OH 1720-MHz lines as tracers of bipolar outflows in the vicinity of Class I methanol masers

    NASA Astrophysics Data System (ADS)

    Litovchenko, I. D.; Bayandina, O. S.; Alakoz, A. V.; Val'tss, I. E.; Larionov, G. M.; Mukha, D. V.; Nabatov, A. S.; Konovalenko, A. A.; Zakharenko, V. V.; Alekseev, E. V.; Nikolaenko, V. S.; Kulishenko, V. F.; Odintsov, S. A.

    2012-07-01

    A sample of Class I methanol masers (MMI) has been surveyed at 1720 MHz to search for possible associations between MMI and 1720-MHz OH masers, which should be formed by the same collisional pumping mechanism. If the model for methanol masers is correct, the sample should contain a statistically significant number of 1720-MHz OH masers at the positions of MMI. The observations were conducted on the 70-meter radio telescope of the National Academy of Sciences of Ukraine (NASU). The results show that ˜50% of 72 MMI are associated with OH emission at 1720 MHz. In many sources, strong absorption lines are also observed. In most cases, the OH (1720) lines are narrow (linewidths of <2 km/s) suggesting they may be maser lines. The OH column densities obtained from Gaussian fitting of these narrow OH lines are, on average, 1.5 × 1017 cm-2. TheH2 density in the emitting medium reaches 107 cm-3 if the region of the OH (1720) emission has been subject to interaction with a bipolar-outflow front. This is sufficient to excite MMI, and the presence of narrow, possibly masing OH (1720) lines at the MMI velocities indicates the likely presence of shocks from bipolar outflows in the vicinity of the maser condensations, supporting models in which these molecules are collisionally pumped.

  8. Mid-infrared observations of methanol maser sites and ultracompact H ii regions: signposts of high-mass star formation

    NASA Astrophysics Data System (ADS)

    Walsh, A. J.; Bertoldi, F.; Burton, M. G.; Nikola, T.

    2001-09-01

    N-band (10.5μm) and/or Q-band (20.0μm) images taken with MANIAC on the ESO/MPI 2.2-m telescope are presented for 31 methanol maser sites and 19 ultracompact (UC) Hii regions. Most of the maser sites and UC Hii regions are coincident with mid-infrared (MIR) sources to within the positional uncertainties of ~3arcsec, consistent with the maser emission being powered by the MIR source. The IRAS source positions, however, do not always coincide with the MIR sources. Based on an average infrared spectral energy distribution, we deduce that the MIR objects are luminous enough that they should also produce a strong ionizing radiation. Some sources are consistent with stars of later spectral type, but not all can be. A number of maser sites show no detectable radio continuum emission associated with MIR emission, despite a powering source luminous enough potentially to produce an UC Hii region. Since no signs of an UC Hii region are detected here, these maser sites might be produced during a very early stage of stellar evolution. We present objects that show evidence of outflow activity stemming from a maser site, exhibiting CO and/or CS line profiles indicative of outflows coincident with the MIR source. These cases are promising examples of maser sites signposting the earliest stages of high-mass star formation.

  9. 183 GHz H{sub 2}O MASER EMISSION AROUND THE LOW-MASS PROTOSTAR SERPENS SMM1

    SciTech Connect

    Van Kempen, T. A.; Wilner, D.; Gurwell, M.

    2009-11-20

    We report the first interferometric detection of 183 GHz water emission in the low-mass protostar Serpens SMM1 using the Submillimeter Array with a resolution of 3'' and rms of approx7 Jy in a 3 km s{sup -1} bin. Due to the small size and high brightness of more than 240 Jy beam{sup -1}, it appears to be maser emission. In total, three maser spots were detected out to approx700 AU from the central protostar, lying along the redshifted outflow axis, outside the circumstellar disk but within the envelope region as evidenced by the continuum measurements. Two of the maser spots appear to be blueshifted by about 1-2 km s{sup -1}. No extended or compact thermal emission from a passively heated protostellar envelope was detected with a limit of 7 Jy (16 K), in agreement with recent modeling efforts. We propose that the maser spots originate within the cavity walls due to the interaction of the outflow jet with the surrounding protostellar envelope. Hydrodynamical models predict that such regions can be dense and warm enough to invert the 183 GHz water transition.

  10. Reappearance of 22 GHz water maser in proto-planetary nebula OH17.7-2.0.

    NASA Astrophysics Data System (ADS)

    Wolak, P.; Szymczak, M.; Bartkiewicz, A.; Pazderski, E.; Kus, A. J.; Kepa, A.; Katarzynski, K.; Borkowski, K. M.; Feiler, R.; Mazurek, J.; Szymanski, W.; Filarecki, J.; Krol, J.

    2013-07-01

    We observed OH17.7-2.0 (also known as: IRAS18276-1431, V445 Sct), a young proto-planetary nebula (Sanchez Contreras et al., 2007, ApJ, 656, 1150; Bains et al., 2003, MNRAS, 338, 287), in the 22 GHz water maser line using a new K-band receiver at the Torun 32m radio telescope. The system equivalent flux density was about 480 Jy and spectral resolution was 0.03 km/s.

  11. A CATALOG OF CH{sub 3}OH 7{sub 0}-6{sub 1} A {sup +} MASER SOURCES IN MASSIVE STAR-FORMING REGIONS. II. MASERS IN NGC 6334F, G8.67-0.36, AND M17

    SciTech Connect

    Gomez, Laura; Luis, Leticia; Hernandez-Curiel, Idalia; Kurtz, Stan E.; Hofner, Peter; Araya, Esteban D.

    2010-12-15

    We present Very Large Array (VLA) observations of the 7{sub 0}-6{sub 1} A {sup +} methanol maser transition at 44 GHz toward NGC 6334F, G8.67-0.36, and M17. These arcsecond resolution observations complete a previous, larger VLA survey of this maser transition in high-mass, star-forming regions reported by Kurtz et al. We confirm the presence of 44 GHz methanol maser emission in all 3 sources, detecting 8 distinct maser components in NGC 6334F, 12 components in G8.67-0.36, and 1 in M17.

  12. 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.

  13. 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.

  14. 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.

  15. Future Observations of Cosmic Masers

    NASA Astrophysics Data System (ADS)

    Slysh, V.

    size to 1.9 mas [4]. In W3(OH) the same spectral resolution will smear 12 GHz methanol maser spot images to the size from 0.15 to 2 mas [5]. Similar gradient may be present in OH and H2O masers. It is interesting that the position-velocity gradient of the same magnitude is required by OH maser pump models in order to provide non-local overlap of far-infrared rotational lines [6]. VLBI observations with high spectral resolution like those described in [5] show that when the spectral resolution is sufficient to avoid bandwidth smearing the maser spots remain unresolved. Therefore more angular resolution is needed in order to image maser spots. For the masers the only way to increase angular resolution is to increase the baseline, up to the space baselines. The imaging of the maser spots is one of the goals of the space-ground interferometer RADIOASTRON.

  16. The structure of methanol radio sources in star-forming regions from observations at 44 and 95 GHz

    NASA Astrophysics Data System (ADS)

    Kalenskij, S. V.

    1995-08-01

    A simple analytical model for excitation of methanol is developed. It is shown that Class I methanol sources may occur near the boundaries of dense gas-dust clouds. Masres at the transition 8(0)-7(1)A(+) of comparable intensity with masers at the transition 7(0)-6(1)A(+) are possible only when the kinetic temperature is no less than 30 K. Cavities formed by high-velocity streams facilitate the occurrence of masers; it is possible that this is one of the reasons for the link between methanol masers and high-velocity flows of material. It is possible that the radiation field close to young stars 'moves aside' Class I masers to some distance from the stars.

  17. Polarisation observations of H2O JK-1 K1 = 532 - 441 620.701 GHz maser emission with Herschel/HIFI in Orion KL

    NASA Astrophysics Data System (ADS)

    Jones, S. C.; Houde, M.; Harwit, M.; Kidger, M.; Kraus, A.; MCoey, C.; Marston, A.; Melnick, G.; Menten, K. M.; Morris, P.; Teyssier, D.; Tolls, V.

    2014-07-01

    Context. The high intensities and narrow bandwidths exhibited by some astronomical masers make them ideal tools for studying star-forming giant molecular clouds. The water maser transition JK-1K1 = 532-441 at 620.701 GHz can only be observed from above Earth's strongly absorbing atmosphere; its emission has recently been detected from space. Aims: We sought to further characterize the star-forming environment of Orion KL by investigating the linear polarisation of a source emitting a narrow 620.701 GHz maser feature with the heterodyne spectrometer HIFI on board the Herschel Space Observatory. Methods: High-resolution spectral datasets were collected over a thirteen month period beginning in 2011 March, to establish not only the linear polarisation but also the temporal variability of the source. Results: Within a 3σ uncertainty, no polarisation was detected to an upper limit of approximately 2%. These results are compared with coeval linear polarisation measurements of the 22.235 GHz JK-1K1 = 616 - 523 maser line from the Effelsberg 100-m radio telescope, typically a much stronger maser transition. Although strongly polarised emission is observed for one component of the 22.235 GHz maser at 7.2 km s-1, a weaker component at the same velocity as the 620.701 GHz maser at 11.7 km s-1 is much less polarised. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with significant participation from NASA.Appendices are available in electronic form at http://www.aanda.org

  18. Extended CH3OH maser flare excited by a bursting massive YSO

    NASA Astrophysics Data System (ADS)

    Moscadelli, L.; Sanna, A.; Goddi, C.; Walmsley, M. C.; Cesaroni, R.; Caratti o Garatti, A.; Stecklum, B.; Menten, K. M.; Kraus, A.

    2017-04-01

    Aims: Recently, substantial flaring in the 6.7 GHz methanol maser line has been observed toward the high-mass young stellar object (YSO) S255 NIRS 3, where an accretion burst was also detected in the IR. Our goal is to study the change in the properties of the 6.7 GHz masers between the pre- and outburst phases, and investigate the connection between the maser and the accretion burst. Methods: With the Karl G. Jansky Very Large Array (JVLA) and the European VLBI Network (EVN), we performed observations of the 6.7 GHz masers (covering a range in angular resolution from a few milliarcseconds to ≈1'') during the burst phase and compared these observations with pre-burst measurements at similar spatial scales. Results: The accretion burst and the subsequent increase in IR luminosity are very likely the origin of the 6.7 GHz maser flare. Since most maser centers operate in the unsaturated regime, a change by a relatively small factor (≈5) in the flux of pumping photons has produced an exponential growth in the maser intensity. The main pre-burst maser cluster is no longer detected during the burst. Compared to the pre-burst phase, flaring 6.7 GHz masers emit across a different VLSR range that is more strongly redshifted, and the emission extends over a larger area at larger separation from the high-mass YSO. In particular, the outburst peak emission originates from a remarkably extended (0.̋2-0.̋3) maser plateau at a radial distance of 500-1000 AU from the source. Conclusions: Both the maser flare and the extraordinarily large extent of the maser structure can be a natural consequence of the burst in the accretion luminosity of the high-mass YSO. Our results strongly support models that predict IR radiative pumping for the 6.7 GHz CH3OH masers.

  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. 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.

  1. The Design of a 100 GHz CARM (Cyclotron Auto-Resonance Maser) Oscillator Experiment

    DTIC Science & Technology

    1988-09-14

    2364. (Radio Engng. Electron. Phys., 21, 78-73). 5) Ginzburg , N. S., Zarnitsyna, I. G., and Nusinovich, G. S., 1981, Theory of relativistic cyclotron...An efficient Doppler-shifted electron-cyclotron maser oscillator. Int J. Electron., 53, 555-57 1. 7) Bratman, V. L., Ginzburg , N. S., Nusinovich, G...1386-1389. (Sov. Tech. Phys. Lett., 8, 596-597). 12) Botvinnik, I. E., Bratman, V. L., Volkov, A. B., Ginzburg , N. S, Denisov, G. G., Kol’chugin, B

  2. 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.

  3. Resolved Ammonia Thermometry, Water and Methanol Masers from the “Survey of Water and Ammonia in Nearby Galaxies (SWAN)”

    NASA Astrophysics Data System (ADS)

    Gorski, Mark; Ott, Juergen; Rand, Richard J.; Meier, David S.; Momjian, Emmanuel; Walter, Fabian; Schinnerer, Eva

    2017-01-01

    We present Karl G Jansky Very Large Array (VLA) molecular line observations of the nearby star forming galaxies NGC 253 and IC 342. These galaxies are close enough to be resolved with a few tens of pc resolution with the VLA. At this resolution we are well matched to the physical scales of Giant Molecular Clouds (GMCs) and therefore sensitive to the dominant processes therein. We have selected metastable inversion transitions of NH3 from (1,1) to (5,5) and the (9,9), the 22.2 GHz H2O (616-523) maser, and the 36.1 GHz CH3OH (414-303) maser. We use the metastable NH3 transitions to calculate rotation temperatures of the gas, and apply LVG models to estimate kinetic temperatures. Our selected masers are collisionally pumped and reveal the locations of shocked material. We find that the molecular gas is well described by cool 57K and warm 130K components, and there is no significant temperature variation over the central kpc. The result suggests that neither PDRs nor superbubbles significantly heat the molecular gas, but superbubbles likely increase the bulk motion of GMCs. We also report the discovery of H2O masers associated with the large-scale biconical outflow for the first time, indicating the presence of shocked dense gas. Finally, we find CH3OH masers, indicative of weak shocks, coincident with superbubble walls.

  4. Terahertz water masers

    NASA Astrophysics Data System (ADS)

    Neufeld, David

    Using the GREAT instrument, we will observe terahertz water masers toward seven oxygen-rich evolved stars with circumstellar envelopes that emit maser radiation in the 22 and 321 GHz water transitions: o Cet, U Ori, R Leo, R Crt, RS Vir, S CrB and R Cas. Our primary target will be the 8(27)-7(34) line of water vapor at 1296.411 GHz, a transition that our models predicted would be a strong maser - a prediction recently confirmed by our Cycle 4 observations of W Hya and U Her. This transition, which was not accessible with Herschel/HIFI, has a significantly higher frequency than any water maser transition observed to date. In combination with ground-based maser observations at lower frequencies, the proposed observations will provide new constraints on the conditions of gas temperature, gas density, and IR radiation field within the maser-emitting region, providing important information about the maser pumping mechanism.

  5. 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.

  6. 6.7 GHz maser astrometry with the Australian long baseline array

    NASA Astrophysics Data System (ADS)

    Krishnan, Vasaant

    2016-01-01

    Astrometry is the science of measuring the positions of astronomical objects in the sky, and as such forms a practical bedrock for astrophysics in general. This is because it is only when a source's position is unambiguously known, can it be observed while it transits across the sky or be detected at different wavelengths. One of the first discoveries as a result of astrometry was in differentiating between the planets in our Solar System and the stars in the Milky Way. Early astronomers would have noted the arcminute/day rate of proper motion of the nearby planets with respect to the distant celestial objects fixed in the sky with the passage of time. With the advancement of telescopes the arcsecond/year proper motions for the fastest moving nearby stars was resolved as well. In comparing comets or asteroid size objects of a few kilometres, to galaxies spanning hundreds of thousands of light-years, it becomes apparent that the absolute size of astronomical objects extends across dimensions spanning many orders of magnitude. Despite this, the distances to these objects render many of them regardless of size to be minuscule pinpoints, when viewed from the Earth. The accuracy with which an object's position can be known is governed by the diffraction limit θd ≈ λ/D of the observing system and improvements in astrometric resolution have led to astronomical discoveries including Earth's precession, stellar aberration, atmospheric refraction, particle jets from black holes, the rate of expansion of planetary nebulae, detailed structure of circumstellar disks and out outflows from protostars, high-energy jets from quasars and the orbits of exoplanets around distant stars. The focus of this thesis is on the impact of accurate astrometry to measure trigonometric stellar parallaxes (from now on parallax) towards masers in high-mass star formation regions (HMSFRs) in the Milky Way galaxy using the Australian Long Baseline Array (LBA).

  7. MeerKAT and its potential for Cosmic MASER Research

    NASA Astrophysics Data System (ADS)

    Booth, Roy; Goedhart, Sharmila; Jonas, Justin

    2012-07-01

    The MeerKAT radio telescope array is the South African precursor instrument for the proposed Square Kilometer Array's mid-band frequency range. It will be the most sensitive centimetre-wavelength telescope in the southern hemisphere until the SKA is built. It will cover a broad range of astronomical science from the evolution of galaxies to tests of Einstein's theory of General Relativity, using Pulsars. The chosen frequency bands will enable sensitive southern Galactic maser surveys in the main lines of hydroxyl, 12 GHz methanol and perhaps 14.5 GHz formaldehyde lines as well as searches for redshifted water masers from red-shifts greater than about 0.5. Proposals for Large Surveys using MeerKAT were solicited in late 2009 and resulted in some 20 proposals from teams comprising 500 scientists, world-wide. The successful proposals relevant to maser research will be discussed below.

  8. 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).

  9. Massive star-formation in G24.78+0.08 explored through VLBI maser observations

    NASA Astrophysics Data System (ADS)

    Moscadelli, L.; Goddi, C.; Cesaroni, R.; Beltrán, M. T.; Furuya, R. S.

    2007-09-01

    Context: Previous interferometric observations have demonstrated that, across a distance of a few 0.1 pc, the high-mass star forming region (SFR) G24.78+0.08 contains at least four distinct centers of massive star formation, possibly in different evolutionary stages. Aims: This study aims to provide a detailed picture of the physical environment and the gas kinematics in a cluster of high-mass YSOs. Methods: Using EVN (single epoch) and VLBA (four epochs) phase-referenced observations, we have derived the absolute positions and velocities for 6.7 GHz methanol and 22.2 GHz water masers, respectively. Using the BIMA and VLA interferometers, positions and line of sight velocities of 95 GHz and 44 GHz methanol masers, are also obtained. The derived interferometric and VLBI maser maps are compared with previous sub-arcsecond maps of the G24.78+0.08 region, observed in thermal continuum and molecular line tracers. Results: In the hot molecular cores G24 A1 and G24 A2, 6.7 GHz methanol and 22.2 GHz water masers are emerging at similar positions and line of sight velocities, which suggests that in both cores a same YSO is responsible for the excitation of the two types of maser emission. At the center of the G24 A1 core, water masers distribute along an arc at the border of a hyper-compact HII region (of size ≈1000 AU) and expand away from the center of the HII region with high velocities (≈40 km s-1). We think that such a fast expansion is driven by a strong stellar wind emitted by the star exciting the hyper-compact HII region. This outflowing motion might dominate the gas kinematics of G24 A1 also at larger (≈0.1 pc) scale, where a well defined velocity gradient in the CH3CN line and 6.7 GHz masers is observed. Alternatively, water masers might mark the border of the dynamical interaction between the evolving star and harboring core, and the gas surrounding the hyper-compact HII region, not yet affected by the expansion of the ionized gas, might be still rotating

  10. ON THE METHANOL MASERS IN G9.62+0.20E AND G188.95+0.89

    SciTech Connect

    Van der Walt, D. J.

    2011-05-15

    A comparison between the observed light curves of periodic masers in G9.62+0.20E and G188.95+0.89 and the results of a simple colliding-wind binary model is made to establish whether the flaring and other time-dependent behavior of the masers in these two star-forming regions can be ascribed to changes in the environment of the masers or in the continuum emission from parts of the background H II region. It is found that the light curves of widely different shape and amplitude in these two objects can be explained within the framework of a periodic pulse of ionizing radiation that raises the electron density in a volume of partially ionized gas against which the masers are projected. It is also shown that the decay of the 11.405 km s{sup -1} maser in G188.95+0.89 can be explained very well in terms of the recombination of the ionized gas against which the maser is projected, while it would require very special conditions to explain it in terms of changes in the environment of the maser. We conclude that for G9.62+0.20E and G188.95+0.89 the observed changes in the masers are most likely due to changes in the background free-free emission which is amplified by the masers.

  11. Applied research using a 30 GHz free-electron maser: Experimental study of interacton of high-power pulsed radiation with metals

    NASA Astrophysics Data System (ADS)

    Baev, V. G.; Vdovin, V. A.; Vikharev, A. A.; Ginzburg, N. S.; Golubev, I. I.; Golubykh, S. M.; Zaitsev, N. I.; Kaminsky, A. K.; Kovalev, Yu. A.; Kozlov, A. P.; Kratko, A. F.; Kryachko, I. A.; Kuzikov, S. V.; Lesnikovich, A. I.; Milevich, I. A.; Perel'shtein, E. A.; Peskov, N. Yu.; Petelin, M. I.; Sedykh, S. N.; Tyutyunnikov, S. I.; Fedotova, Yu. A.

    2012-01-01

    We describe a facility for testing the properties of different objects affected by a sequence of highpower pulses of the microwave electromagnetic field. The facility performance is implemented due to the power level and stability of the single-mode generation of a free electron maser with an output frequency of 30 GHz, which have been achieved at the Joint Institute for Nuclear Research and the Institute of Applied Physics of the Russian Academy of Sciences. This paper describes the experiments on studying of the thermal fatigue of the copper surface in a test cavity, which models the thermal regime of the accelerating structure of the CLIC project (CERN), as well as the experiments on irradiation of biological tissues, metal films, and nanoclusters.

  12. The Complete, Temperature Resolved Spectrum of Methanol Between 214 and 265 GHZ

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    We have studied methanol, one of the so-called 'astronomical weeds', in the 215--265 GHz band. We have gathered a set of intensity calibrated, complete, experimental, and temperature resolved spectra from across the temperature range of 240--389 K. A number of low lying transitions, including the ν_t = 3, have not been produced by available catalogs. Using our previously reported method of analysis we were able generate a line list that contains lower state energies and linestrengths, for all of the observed lines in the band. This line list includes those lines which have no quantum mechanical assignment. In addition to this line list we provide a point by point method capable of generating the complete spectrum at an arbitrary temperature. The sensitivity of the point by point analysis is such that we are able to identify lines which would not have manifest in a single scan across the band. The consequence has been to reveal not only a number of new methanol lines, but also trace amounts of contaminants. We show how the intensities from the contaminants can be removed with indiscernible impact on the signal from methanol. To do this we use the point by point results from our previous studies of these contaminants. The efficacy of this process serves as strong proof of concept for usage of our point by point results on the problem of the weeds. The success of this approach for dealing with the weeds has also previously been reported. S. Fortman et al. 2014 ApJ 782 75 S. Fortman et al. 2012 J. Mol. Spectrosc. 782, 75

  13. Maser observation in VY CMa with VERA

    NASA Astrophysics Data System (ADS)

    Choi, Yoon Kyung

    We present the results of multi-epoch VERA (VLBI Exploration of Radio Astrometry) observations of H2O masers at 22 GHz and ^28SiO masers at 43 GHz in the supergiant VY Canis Majoris (hereafter, VY CMa). We estimate the inner motion of H2O masers over 6 months and that of SiO masers over 1 month. Using the inner motion, we calculated the statistical parallax of VY CMa. The size of the emitting region for ^28SiO masers is R_SiO ~1.81-2.89 R_* and it is consistent with the previous study.

  14. The Complete, Temperature Resolved Experimental Spectrum of Methanol Between 560 and 654 GHZ

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

    The complete spectrum of methanol (CH_3OH) in the 560.4-654.0 GHz spectral region has been characterized over a range of astrophysically significant temperatures, 248-397 K. Analysis of experimental spectra recorded with absolute intensity calibration over a slow temperature ramp provides a means for the simulation of the spectrum as a function of temperature without a complete quantum mechanical (QM) model. These results include contributions from v_t = 3 and other higher states that are difficult to model via QM techniques. They also contain contributions from the ^{13}C isotopologue in natural abundance. These results are used to both provide catalogs in the usual line frequency, linestrength, and lower state energy format and in a frequency point-by-point format that is particularly well suited for the characterization of blended lines. In contrast to our earlier work on the semi-rigid species ethyl cyanide and vinyl cyanide, significant intensity difference between these experimental values and those calculated by QM methods were found for some of the lines. Analysis of these differences points to the difficulty of the calculation of dipole matrix elements in the context of the internal rotation of the methanol molecule. We will compare our experimental intensities with the most recent QM model, as well as an earlier QM model that includes the variation of the dipole moment function with the torsional angle. S. M. Fortman, I. R. Medvedev, C. F. Neese, and F. C. De Lucia, Astrophys. J. 737, 20/1-6 (2011). L.-H. Xu, et al. J. Mol. Spectrosc. 251, 305-313 (2008). M. A. Mekhtiev, P. D. Godfrey, and J. T. Hougen, J. Mol. Spectrosc. 194, 171-178 (1999).

  15. Astronomical masers

    NASA Technical Reports Server (NTRS)

    Elitzur, Moshe

    1992-01-01

    Recent research related to astronomical masers is reviewed. First, attention is given to phenomenology, including observations and modeling of galactic and extragalactic maser sources. The discussion then focuses on the developments concerning the physical properties of maser radiation. Finally, the use of masers as general tools for the study of astronomical environments where the radiation is produced and where it propagates, is discussed.

  16. Molecular maser flares in the high-mass star-forming region IRAS18566+0408

    NASA Astrophysics Data System (ADS)

    Halbe, Daniel M.

    We report results of a long-termmonitoring study of 6cmformaldehyde (H 2CO), 6.035GHz hydroxyl (OH), and 6.7GHz methanol (CH3OH) masers in the young high-mass protostellar object IRAS18566+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 together with data from the literature, we present H2CO flux density measurements from 2002 to 2014, CH3OH data from 2006 to 2013, and discuss OH observations obtained between 2008 and 2012. Our extended monitoring observations of the H2CO maser agree with the quasi-periodic flare phenomenon and exponential decrease in quiescent and flare flux densities proposed by Araya and collaborators in 2010. We also confirm the occurrence of 6.035GHz OH flares and a time delay with respect to the H2CO flares. An analysis between the variability behavior of different CH3OH maser components and the H2CO maser suggests that multiple variability mechanisms are responsible for CH3OH flux density changes.

  17. A Large-scale Spectroscopic Survey of Methanol and OH Line Emission from the Galactic Center: Observations and Data

    NASA Astrophysics Data System (ADS)

    Cotton, W. D.; Yusef-Zadeh, F.

    2016-11-01

    Class I methanol masers are collisionally pumped and are generally correlated with outflows in star-forming sites in the Galaxy. Using the Very Large Array in its A-array configuration, we present a spectral line survey to identify methanol J={4}-1\\to {3}0E emission at 36.169 GHz. Over 900 pointings were used to cover a region 66‧ × 13‧ along the inner Galactic plane. A shallow survey of OH at 1612, 1665, 1667, and 1720 MHz was also carried out over the area covered by our methanol survey. We provide a catalog of 2240 methanol masers with narrow line-widths of ˜1 km s-1, spatial resolutions of ˜ 0\\buildrel{\\prime\\prime}\\over{.} 14× 0\\buildrel{\\prime\\prime}\\over{.} 05, and rms noises ˜20 mJy beam-1 per channel. Lower limits on the brightness temperature range from 27,000 to 10,000,000 K, showing that the emission is of non-thermal origin. We also provide a list of 23 OH (1612), 14 OH (1665), 5 OH (1667), and 5 OH (1720 MHz) masers. The origin of such a large number of methanol masers is not clear. Many methanol masers appear to be associated with infrared dark clouds, though it appears unlikely that the entire population of these masers traces the early phase of star formation in the Galactic center.

  18. Interpretation of the newly discovered submillimeter water maser

    NASA Technical Reports Server (NTRS)

    Neufeld, David A.; Melnick, Gary J.

    1990-01-01

    The 10(29)-9(36)321 GHz water maser discovered recently by Menten et al. (1990) may be pumped collisionally under a wide range of physical conditions. This range of conditions is similar but not identical to that required to excite the well-studied 22 GHz water maser. The ratio of the observed 22 GHz and 321 GHz intersteller maser luminosities can be explained by collisional excitation within the same warm, dense gas. Collisional pumping in a circumstellar envelope can account for the observed 321 GHz maser emission in the supergiant star VY CMa.

  19. Class I Methanol Emission Around DR 21 (OH)

    NASA Astrophysics Data System (ADS)

    Polushkin, S. V.; Val'Tts, I. E.

    2010-06-01

    Results of new observations of the vicinity of DR 21 (OH) conducted on the 20-m Onsala radio telescope are presented. The goal was to search for associations between molecular hydrogen emission tracing shock waves and class I methanol maser emission. Observations at 44 and 36 GHz have shown that an extensive region of faint methanol maser emission elongated North-South is probably present in the vicinity of DR 21(OH). The linear size of this structure may be a factor of ten larger than the central region in DR 21(OH) that emits at 44 GHz. Three maser emission peaks are clearly visible in the northern (DR 21N), central (DR 21(OH)), and southern (vicinity of DR 21 West) parts of this structure. Many other structures are also embedded in this region, including the protostellar disk ERO 3 previously detected at 6.7 GHz. Maser components of these objects are formed with velocities from -5 to-2 km/s, with a velocity gradient from -5 in the North to -2 km/s in the South. The spatial resolution of the map is not high enough to distinguish fine structures at 44 GHz associated with spots and jets emitting in molecular hydrogen.

  20. VizieR Online Data Catalog: CH3OH and H2O Galactic center masers (Ch

    NASA Astrophysics Data System (ADS)

    Chambers, E. T.; Yusef-Zadeh, F.; Ott, J.

    2014-05-01

    The 6.7GHz CH3OH masers we use in our analysis were identified b (Caswell et al., 2010MNRAS.404.1029C, Cat. VIII/96) as part of the Parkes Methanol Multibeam Survey. Initial detections of the 6.7GHz CH3OH masers were made with the Parkes Observatory, and subsequent follow-up observations with the Australia Telescope Compact Array to pinpoint the maser locations to 0.4" accuracy. We observed the Galactic center region with the CSIRO/CASS Mopra telescope in the period 2006 Sep. 13 to 2006 Oct. 15 and 2007 July 24 to September 17. Data were taken in the on-the-fly mode, dumping data every 2s with the then newly installed 12mm receiver, dual polarization. To identify enhanced 4.5μm sources, we use data obtained with the Spitzer Space Telescope using the Infrared Array Camera (IRAC) (5 data files).

  1. 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.

  2. VizieR Online Data Catalog: Torun methanol source catalogue (Szymczak+, 2012)

    NASA Astrophysics Data System (ADS)

    Szymczak, M.; Wolak, P.; Bartkiewicz, A.; Borkowski, K. M.

    2012-08-01

    Table contains 284 methanol masers at 6.7GHz. For every source the following information is given: name (based on the galactic coordinates), other name, right ascension and declination in J2000, velocity range, peak flux density, integrated flux density, reference of the 6.7GHz detection, reference of coordinates and notes on multiple sources and/or possible confusion effect. The spectrum of each source is given. (5 data files).

  3. H2CO Observations Towards CH3OH Maser Sources

    NASA Astrophysics Data System (ADS)

    Okoh, Daniel; Esimbek, Jarken; Zhou, JianJun; Tang, Xindi; Chukwude, Augustine; Urama, Johnson; Okeke, Pius

    2013-03-01

    Formaldehyde (H2CO) is an accurate probe of physical conditions in dense and low-temperature molecular clouds towards massive star formation regions, while 6.7 GHz methanol (CH3OH) masers provide ideal sites to probe the earliest stages of massive stellar formation. We present preliminary results of our investigation into the possible relationship between formaldehyde and methanol astrophysical masers with the view to expanding knowledge on massive star formation processes. Observations are done using the Nanshan 25m radio telescope of the Xinjiang Astronomical Observatories, Urumqi, China. 127 Methanol sources (from the work of Green et al. 2010, Xu et al. 2003, Pestalozzi et al. 2005, and Xu et al. 2009) have been observed so far for 4.8 GHz formaldehyde absorption lines, and H2CO signals have been detected in 86 of them, 31 of which are newly discovered. We obtained good correlation (0.85 correlation coefficient) between the velocities of the sources, and a poor correlation (-0.03 correlation coefficient) between their intensities, an indication that signals from the two lines originate from about the same region, but that the excitation mechanisms that drive them are likely different.

  4. 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.

  5. Explaining recurring maser flares in the ISM through large-scale entangled quantum mechanical states

    PubMed Central

    Rajabi, Fereshteh; Houde, Martin

    2017-01-01

    We apply Dicke’s theory of superradiance (introduced in 1954) to the 6.7-GHz methanol and 22-GHz water spectral lines, often detected in molecular clouds as signposts for the early stages of the star formation process. We suggest that superradiance, characterized by burst-like features taking place over a wide range of time scales, may provide a natural explanation for the recent observations of periodic and seemingly alternating methanol and water maser flares in G107.298+5.639. Although these observations would be very difficult to explain within the context of maser theory, we show that these flares may result from simultaneously initiated 6.7-GHz methanol and 22-GHz water superradiant bursts operating on different time scales, thus providing a natural mechanism for their observed durations and time ordering. The evidence of superradiance in this source further suggests the existence of entangled quantum mechanical states, involving a very large number of molecules, over distances of up to a few kilometers in the interstellar medium. PMID:28378015

  6. Explaining recurring maser flares in the ISM through large-scale entangled quantum mechanical states.

    PubMed

    Rajabi, Fereshteh; Houde, Martin

    2017-03-01

    We apply Dicke's theory of superradiance (introduced in 1954) to the 6.7-GHz methanol and 22-GHz water spectral lines, often detected in molecular clouds as signposts for the early stages of the star formation process. We suggest that superradiance, characterized by burst-like features taking place over a wide range of time scales, may provide a natural explanation for the recent observations of periodic and seemingly alternating methanol and water maser flares in G107.298+5.639. Although these observations would be very difficult to explain within the context of maser theory, we show that these flares may result from simultaneously initiated 6.7-GHz methanol and 22-GHz water superradiant bursts operating on different time scales, thus providing a natural mechanism for their observed durations and time ordering. The evidence of superradiance in this source further suggests the existence of entangled quantum mechanical states, involving a very large number of molecules, over distances of up to a few kilometers in the interstellar medium.

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

    NASA Technical Reports Server (NTRS)

    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.

  8. ATCA OBSERVATIONS OF SiO MASERS IN THE GALACTIC CENTER

    SciTech Connect

    Li Juan; An Tao; Shen Zhiqiang; Miyazaki, Atsushi E-mail: antao@shao.ac.c E-mail: amiya@miz.nao.ac.j

    2010-09-01

    We present the Australia Telescope Compact Array observations of the SiO masers in the Galactic center (GC) in transitions of v = 1, J = 2-1 at 86 GHz and v = 1, J = 1-0 at 43 GHz. Two 86 GHz SiO masers were detected within the central parsec, and they are associated with IRS 10EE and IRS 15NE, respectively. We detected eighteen 43 GHz SiO masers within a projected separation of {approx_lt}2 pc from Sagittarius A*, among which seven masers are newly discovered from our observations. This raises the total number of 43 GHz SiO masers within the central 4 pc of the GC region to 22. Simultaneous observations at 86 and 43 GHz showed that the intensity of 43 GHz SiO maser is {approx}3 times higher than that of 86 GHz maser in IRS 10EE (an OH/IR star), while the integrated flux of the SiO maser emission at 43 GHz is comparable with that at 86 GHz in IRS 15NE (an ordinary Mira variable). These results are consistent with previous observations of massive late-type stars in the Galaxy in which the 86 GHz SiO maser is in general weaker than the 43 GHz SiO maser in OH/IR stars, while the two transitions are comparably strong in Mira stars.

  9. 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)

  10. Development of a High-Power Wideband Amplifier on the Basis of a Free-Electron Maser Having an Operating Frequency Near 30 GHz: Modeling and Results of the Initial Experiments

    NASA Astrophysics Data System (ADS)

    Bandurkin, I. V.; Donets, D. E.; Kaminsky, A. K.; Kuzikov, S. V.; Perel'shteyn, E. A.; Peskov, N. Yu.; Savilov, A. V.; Sedykh, S. N.

    2017-01-01

    We develop a high-power wideband amplifier based on a free-electron maser for particle acceleration, which will be operated in the 30 GHz frequency band, on the basis of the LIU-3000 linear induction accelerator forming an electron beam with an electron energy of 0.8 MeV, a current of 250 A, and a pulse duration of 200 ns. As the operating regime, we chose the regime of grazing of dispersion curves, since, according to the modeling performed, it allows one to ensure an instantaneous amplification band of about 5-7% in an undulator with regular winding for an output radiation power at a level of 20 MW and a gain of 30-35 dB. The results of the first experiments studying this FEM-based scheme are presented, in which the specified power level is achieved in the range around 30 GHz, and fast tuning of ±0.5 GHz in the band of variations in the frequency of the master magnetron is demonstrated. Modeling shows that the use of the non-resonance trapping/braking regime, which is realized in an undulator with profiled parameters, allows one to expect an increase in the radiation power of up to 35-40 MW with simultaneous widening of the amplification band up to 30% under the conditions of the LIU-3000 experiments.

  11. 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.

  12. Methanol

    Integrated Risk Information System (IRIS)

    Methanol ; CASRN 67 - 56 - 1 Human health assessment information on a chemical substance is included in IRIS only after a comprehensive review of toxicity data by U.S . EPA health scientists from several program offices , regional offices , and the Office of Research and Development . Sections I ( H

  13. 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.

  14. 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.

  15. 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.

  16. Water Maser Emission and the Visual Light Curve of R Draconis

    NASA Astrophysics Data System (ADS)

    Osmer, Samantha J.; Benson, Priscilla J.; Little-Marenin, Irene R.

    1991-10-01

    The water maser emmision of R Draconis was observed at 22 GHz at the Haystack Observatory approximately once each month from November 1988 to July 1990. There is a correlation between the variations of the maser emission and the AAVSO light curve; the peak of the maser activity follows the light activity by about 0.2 period.

  17. Hydrogen maser frequency standard

    NASA Technical Reports Server (NTRS)

    Vessot, R. F. C.

    1980-01-01

    The fundamental theoretical limitations of the maser, systematic processes that cause instability, and some aspects of recently designed masers are described. A design for field use that has evolved from the development of the space borne maser is presented. The performance of this type of maser is close to theoretical limits imposed by thermal noise. Further developments of smaller masers for space and terrestrial use and recent work on masers operating at low temperatures is also discussed.

  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. 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.

  20. Pumping Mechanisms for SiO Masers around VX Sgr

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

    VX Sgr, a semi-regular variable, is a red giant star with intense SiO maser emission at 43 GHz. The pumping mechanism of the circumstellar SiO masers has been controversial for decades since its discovery. In order to pursue this long-standing problem further, we have carried out simultaneous VLBA observations of two 7 mm SiO masers at five epochs in about two years. We present relatively aligned υ = 1 and υ = 2, J = 1-0 SiO maser maps and discuss the dominant pumping mechanism, which may be epoch dependent or a combination of both mechanisms.

  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. Detectability of Circumstellar SiO Maser Emission on VSOP-2 Baselines

    NASA Astrophysics Data System (ADS)

    Colomer, F.; Bujarrabal, V.; Ruiz, R. S.; Dodson, R.; Alcolea, J.; Desmurs, J.-F.

    2009-08-01

    We have studied compact circumstellar SiO maser emission at 86 GHz with the Global Millimeter VLBI Array (GMVA), which provides the same spatial resolution as the VSOP-2 to ground baselines at 43 GHz. We present preliminary maps of the emission, estimate the flux and size of the maser spots, and discuss their detectability on baselines from VSOP-2 to ground telescopes.

  3. Spectral line profiles and luminosities of astrophysical water masers

    NASA Technical Reports Server (NTRS)

    Nedoluha, Gerald E.; Watson, William D.

    1991-01-01

    The spectral line narrowing and rebroadening that occurs for astrophysical masers as a function of the emergent radiative flux is calculated for the prominent, 22 GHz masing transition of water. The increased line breadths due to hyperfine structure lead to reliable, essentially model-independent upper limits to the emergent flux that tend to be lower than other estimates for these masers. For many 22 GHz masers, including the outbursts in W49 and Orion, the observed line breadths are less than 0.9 km/s. For these, the upper limit to the emergent maser flux is 10 to the 10th K-sr when expressed in terms of the brightness temperature and the solid angle for beaming. It is concluded that the extreme brightness of the interstellar water masers is due to a high degree of beaming and not to more effective pumping.

  4. Multiple Methanol Transitions Detected in W51-E2 from the Arecibo Galactic Chemistry Survey

    NASA Astrophysics Data System (ADS)

    Minchin, Robert F.; Harrington, Kevin; Ghosh, Tapasi; Salter, Christopher J.; Araya, Esteban; Arce, Hector G.; Lebron Santos, Mayra E.; De Vries, Christopher H.

    2015-01-01

    Two major components of the star-forming region W51 have been observed with the Arecibo 305-m telescope as a part of the Arecibo Galactic Chemistry Survey. Located at a distance of ~6 kpc towards the Sagittarius Arm, W51 is one of the most luminous and massive (upper 5-10% by mass and upper 1% by size of all Giant Molecular Clouds in our Galaxy; Carpenter & Sanders, 1998). The infrared source, IRS1, was observed over 1.1 - 10 GHz from 2010 through 2012, and the angularly nearby compact component, E2, over 4.3 - 4.9 GHz and 8.0 - 10.2 GHz in 2014. Methanol (CH3OH) transitions at 8.34-GHz (4(1,3)-4(1,4)-+), 9.94-GHz (9(-1,9)-8(-2,7)), 9.98-GHz (4(3,2)-5(2,3)++), and 10.06-GHz (4(3,1)-5(2,4)--) were detected towards W51-E2 for the first time, some showing a mixture of emission and absorption. The peak emission ratios for the 9.94- to 9.98-GHz, and the 9.94- to 10.06-GHz transitions are consistent with the predictions of Slysh, Kalenskii & Val'tts (1993). All three 6-cm wavelength hydroxyl (OH) transitions were also detected, with the 4.66-GHz satellite line masing strongly. In IRS1, the intense methanol maser at 6.67 GHz (Araya et al. 2013) was observed to have a flux density of > 200 Jy, with the 4.66-GHz OH maser having an intensity of ~1 Jy. In IRS1, we also detected the methanol 9.94-GHz transition featuring emission with multiple components. Additionally, a total of over 60 H, 30 He, and 8 C radio recombination lines (RRLs) were identified in E2 over the two frequency ranges observed. This includes the highest frequency spectral line yet detected at Arecibo, namely the He(86)α RRL at 10.17 GHz. Over 120 H, 70 He, and 40 C recombination lines were identified in IRS1 over the frequency range of 4 - 10 GHz.

  5. Proton maser

    NASA Astrophysics Data System (ADS)

    Ensley, D. L.

    1988-01-01

    New calculations are reported which confirm the ability of an a priori random, initial-phase proton beam to drive a simple, single-stage microwave cavity maser or transit-time oscillator (TTO) to saturation conversion efficiencies of about 11 percent. The required initial TE(011) mode field can be provided from beam ramp-up bandwidth of excitation to a low level from an external source. A saturation field of 45 tesla and output power of 0.2 TW are calculated using an electron insulation field of 10 tesla and a 3 MeV, 400 Ka/sq cm beam. Results are compared to those for an electron beam of the same energy and geometry, and it is shown that proton beams potentially can provide a three order of magnitude increase in overall microwave power production density over that obtainable from electron beam TTOs.

  6. NEW MASER EMISSION FROM NONMETASTABLE AMMONIA IN NGC 7538

    SciTech Connect

    Hoffman, Ian M.; Kim, Stella Seojin

    2011-09-20

    We present the first interferometric observations at 18.5 GHz of IRS 1 in NGC 7538. These observations include images of the nonmetastable {sup 14}NH{sub 3} (9, 6) masers with a synthesized beam of 2 arcsec and images of the continuum emission with a synthesized beam of 150 mas. Of the maser emission, the previously known feature near v {sub LSR} = -60 km s{sup -1} is spectrally resolved into at least two components and we observe several new maser emission features near v {sub LSR} = -57 km s{sup -1}. The new maser emission near -57 km s{sup -1} lies 250 {+-} 90 mas northwest of the maser emission near -60 km s{sup -1}. All of the masers are angularly unresolved indicating brightness temperatures T{sub B} > 2000 K. We are also able to conclusively associate the ammonia masers with the position of IRS 1. The excitation of these rare ammonia masers is discussed in the context of the rich maser environment of IRS 1.

  7. Correlation of SiO maser flux with stellar flux

    SciTech Connect

    Cahn, J.H.

    1981-12-01

    A survey of available SiO maser observations of the 43.122-GHz, v = 1, J = 1..-->..0 transition has been made in order to further investigate the question of a correlation of maser flux with bolometric flux. This correlation has been shown to exist both for data which have been phase shifted to mean maximum and for those which have not.

  8. Origin of Observed Periodic Components in Astrophysical Masers' Spectra

    NASA Astrophysics Data System (ADS)

    Siparov, S.; Samodurov, V.; Laptev, G.

    2017-01-01

    Further analysis of data previously obtained during the monitoring observations of 49 astrophysical water (22 GHz) masers shows that in some cases the intensity of an individual component of the maser spectrum changes periodically, on timescales of tens of minutes. It is argued that this variation cannot be the effect of instrumental errors, weather conditions or interstellar medium instabilities, because only a single feature of the maser spectrum fluctuates but not the whole spectrum. The suggested interpretation of this effect is based on the optic-metrical parametric resonance produced by gravitational radiation emitted by short-period binary stars, with the examples of such binaries sufficing the conditions given.

  9. Discovery of four water masers in the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Breen, S. L.; Lovell, J. E. J.; Ellingsen, S. P.; Horiuchi, S.; Beasley, A. J.; Marvel, K.

    2013-06-01

    We report the detection of four water masers within the Small Magellanic Cloud (SMC): two discovered with the 70-m Tidbinbilla radio telescope, and two discovered with the Australia Telescope Compact Array (ATCA). Precise positions of all four masers have been derived from ATCA observations, and the characteristics of each water maser have been monitored over a period of several years. Sensitive observations towards two previously detected water masers reported in the literature failed to detect any emission. The detected water masers show evidence of higher levels of temporal variability than equivalent Galactic sources, and one of the features associated with NGC 346 IR1 shows an acceleration of 9.6 km s-1 yr-1 over a 31 d period. Sensitive targeted observations for methanol and OH masers failed to detect any accompanying emission - in the case of methanol perhaps highlighting an under abundance in the SMC, consistent with expectations due to lower metallicity. The water masers are both bright and compact making them excellent targets for Very Long Baseline Interferometry (VLBI) observations, which can potentially measure the proper motion of the SMC (˜1-2 mas yr-1) with temporal baselines of ˜12 months. Such observations would utilize sources associated with only the current epoch of star formation and hence have several advantages over alternative methods.

  10. OPTICAL PROPERTIES OF HOST GALAXIES OF EXTRAGALACTIC NUCLEAR WATER MASERS

    SciTech Connect

    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 ({lambda} = 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 (M{sub B} ), larger velocity dispersion ({sigma}), and higher [O III] {lambda}5007 luminosity, with [O III] {lambda}5007 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] {lambda}5007 flux when available. This prioritization would improve maser detection efficiency, from an overall {approx}3% without pre-selection to {approx}16% for the strongest intrinsic [O III] {lambda}5007 emitters, by a factor of {approx}5.

  11. 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.

  12. 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.

  13. Maser Source-Finding Methods in HOPS

    NASA Astrophysics Data System (ADS)

    Walsh, A. J.; Purcell, C.; Longmore, S.; Jordan, C. H.; Lowe, V.

    2012-12-01

    The H2O Southern Galactic Plane Survey (HOPS) has observed 100 deg2 of the Galactic plane, using the Mopra radio telescope to search for emission from multiple spectral lines in the 12-mm band (19.5-27.5GHz). Perhaps the most important of these spectral lines is the 22.2-GHz water-maser transition. We describe the methods used to identify water-maser candidates and subsequent confirmation of the sources. Our methods involve a simple determination of likely candidates by searching peak emission maps, utilising the intrinsic nature of water-maser emission, spatially unresolved and spectrally narrow-lined. We estimate completeness limits and compare our method with results from the DUCHAMP source finder. We find that the two methods perform similarly. We conclude that the similarity in performance is due to the intrinsic limitation of the noise characteristics of the data. The advantages of our method are that it is slightly more efficient in eliminating spurious detections and is simple to implement. The disadvantage is that it is a manual method of finding sources and so is not practical on datasets much larger than HOPS, or for datasets with extended emission that needs to be characterised. We outline a two-stage method for the most efficient means of finding masers, using DUCHAMP.

  14. Theory of astronomical masers

    NASA Astrophysics Data System (ADS)

    Kylafis, Nikolaos D.

    The theory of astronomical masers is reviewed. As with laboratory masers, masing occurs when a transition between two energy levels of a molecule exhibits inverted populations. In order to present the basic concepts about masers, an idealized two-level system is used. The exact energy level structure is taken into account later on when the pumping of specific molecules is discussed. Unlike laboratory masers, where the radiation must be bounced between two mirrors to accumulate gain, the propagation of radiation in astronomical masers is a lot simpler. This is because astronomical masers are single-pass and broadband. Thus, the main theoretical effort has concentrated on inventing efficient mechanisms that produce population inversion. Specific pumping mechanisms for the three molecules (H2O, SiO and OH) that exhibit strong masing are presented and their ability to explain the observations is discussed.

  15. Polarized maser growth

    SciTech Connect

    Melrose, D.B.; Judge, A.C.

    2004-11-01

    A polarized maser is assumed to operate in an anisotropic medium with natural modes polarized differently to the maser. It is shown that when the spatial growth rate and the generalized Faraday rotation rate are comparable, the polarization of the growing radiation is different from those of the maser and medium. In particular, for a lineary polarized maser operating in a medium with linearly polarized natural modes, the growing radiation is partially circularly polarized. This provides a previously unrecognized source of circular polarization that may be relevant to pulsar radio emission.

  16. Integral Cavity Hydrogen Maser

    DTIC Science & Technology

    1986-12-01

    development on a new microwave cavity for the NASA Research (NR) hydrogen maser for the NASA Crustal Dynamics Program. Also included with the results will be...bulb and all the cavity components bonded together, was developed. The "integral cavity" was installed in the NR maser. This NASA Research Experimental

  17. S Persei: Optical and water maser variability - 1984 to 1990

    NASA Technical Reports Server (NTRS)

    Little-Marenin, I. R.; Benson, P. J.; Mcconahay, M. M.; Cadmus, R. R., Jr.; Stencel, R. E.; Eriksson, K.

    1991-01-01

    The M supergiant S Persei was monitored since 1984 optically and since 1987 for water maser emission at 22 GHz. The dozen H2O maser features show complex variations in intensity with many of the features varying independently of one another. Some of the water maser features brightened dramatically at the time of the bright optical maximum observed in 1988 August and again 10 weeks later. It is possible the increase in water maser intensity is related to the ejection of a dust shell near the time of the preceding optical minimum. The intensity variations of the maser spectrum as being produced by an asymmetric distribution of maser spots are interpreted. A double shell of maser spots may be present on the near side of the shell, but appears to be lacking or be occulted on the far side. No chromospheric activity was detected about 10 weeks after optical maximum. A well developed shock is seen in a near-infrared spectrum obtained in 1988 October.

  18. S Persei: Optical and water maser variability - 1984 to 1990

    NASA Technical Reports Server (NTRS)

    Little-Marenin, I. R.; Benson, P. J.; Mcconahay, M. M.; Cadmus, R. R., Jr.; Stencel, R. E.; Eriksson, K.

    1991-01-01

    The M supergiant S Persei was monitored since 1984 optically and since 1987 for water maser emission at 22 GHz. The dozen H2O maser features show complex variations in intensity with many of the features varying independently of one another. Some of the water maser features brightened dramatically at the time of the bright optical maximum observed in 1988 August and again 10 weeks later. It is possible the increase in water maser intensity is related to the ejection of a dust shell near the time of the preceding optical minimum. The intensity variations of the maser spectrum as being produced by an asymmetric distribution of maser spots are interpreted. A double shell of maser spots may be present on the near side of the shell, but appears to be lacking or be occulted on the far side. No chromospheric activity was detected about 10 weeks after optical maximum. A well developed shock is seen in a near-infrared spectrum obtained in 1988 October.

  19. Mapping the surprisingly high-velocity submm H2O masers of water-fountain nebulae

    NASA Astrophysics Data System (ADS)

    Franco, Ramiro; Chapman, Jessica; Vlemmings, Wouter; Tafoya, Daniel; Chavarria, Luis; Perez-Sanchez, Andres

    2014-04-01

    Understanding the outflows and their formation for water-fountain nebulae is crucial for understanding the formation of bipolar planetary nebulae. Our first discovery of submillimeter water masers towards a number of water-fountains has created an exciting new opportunity to study these important sources. We intend to image the water masers towards three sources recently detected in the submillimeter water masers transition simultaneously at 22 GHz with ATCA and at 321 GHz with ALMA. These observations will allow us to determine the physical conditions of the gas in the fast jets responsible for shaping their circumstellar environment.

  20. DIRECT DIAGNOSTICS OF FORMING MASSIVE STARS: STELLAR PULSATION AND PERIODIC VARIABILITY OF MASER SOURCES

    SciTech Connect

    Inayoshi, Kohei; Tanaka, Kei E. I.; Sugiyama, Koichiro; Hosokawa, Takashi; Motogi, Kazuhito E-mail: koichiro@yamaguchi-u.ac.jp

    2013-06-01

    The 6.7 GHz methanol maser emission, a tracer of forming massive stars, sometimes shows enigmatic periodic flux variations over several 10-100 days. In this Letter, we propose that these periodic variations could be explained by the pulsation of massive protostars growing under rapid mass accretion with rates of M-dot{sub *}{approx}>10{sup -3} M{sub Sun} yr{sup -1}. Our stellar evolution calculations predict that the massive protostars have very large radii exceeding 100 R{sub Sun} at maximum, and here we study the pulsational stability of such bloated protostars by way of the linear stability analysis. We show that the protostar becomes pulsationally unstable with various periods of several 10-100 days depending on different accretion rates. With the fact that the stellar luminosity when the star is pulsationally unstable also depends on the accretion rate, we derive the period-luminosity relation log (L/ L{sub Sun }) = 4.62 + 0.98log (P/100 days), which is testable with future observations. Our models further show that the radius and mass of the pulsating massive protostar should also depend on the period. It would be possible to infer such protostellar properties and the accretion rate with the observed period. Measuring the maser periods enables a direct diagnosis of the structure of accreting massive protostars, which are deeply embedded in dense gas and are inaccessible with other observations.

  1. UNUSUAL SHOCK-EXCITED OH MASER EMISSION IN A YOUNG PLANETARY NEBULA

    SciTech Connect

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

    2016-01-20

    We report on OH maser emission toward G336.644−0.695 (IRAS 16333−4807), which is a H{sub 2}O 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 H{sub 2}O masers, whereas the 1720 MHz masers show a variable spectrum, with several components spread over a higher velocity range (up to 36 km s{sup −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.

  2. Water Masers in AGN Accretion Disks

    NASA Astrophysics Data System (ADS)

    Braatz, J. A.; Reid, M. J.; Greenhill, L. J.; Kuo, C.-Y.; Condon, J. J.; Lo, K.-Y.; Henkel, C.

    2009-08-01

    Water vapor masers at 22 GHz have been detected in over 100 galaxies, most of them AGNs. High resolution VLBI observations of these masers provide the only opportunity for direct imaging of sub-parsec structure in AGN accretion disks. The key science goals associated with such observations are concentrated in two areas. First, observations of nearby, bright sources, exemplified by NGC 4258, enable unique investigations of accretion disk geometry, substructure, thickness, and rotation properties. Second, when combined with spectral line monitoring, VLBI imaging and subsequent disk modeling enables the estimation of a distance to the host galaxy independent of standard candle arguments. In this contribution we present VLBI observations of two maser disk systems in galaxies well into the Hubble flow, UGC 3789 and NGC 6323. A long term goal in these studies is to measure the Hubble constant with high precision and, as a complement to CMB observations, constrain several key cosmological parameters, including the equation of state for dark energy. Observations with VSOP-2 at 22 GHz will have the resolution critical for mapping substructure in these accretion disks and will contribute to reducing systematic errors in the measurement of distances to galaxies.

  3. 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.

  4. Water Masers in the Early (z > 2) Universe

    NASA Astrophysics Data System (ADS)

    Huynh, Minh; Norris, Ray; Emonts, Bjorn; Seymour, Nick

    2013-04-01

    We propose to use the ATCA to search for and measure the 22 GHz (rest-frame) water maser emission in the early (z > 2) universe. Powerful water masers are found in warm dense molecular clouds closely associated with supermassive black holes at the centres of active galaxies. Locally, water maser emission is mostly found in type-2 AGN (AGN viewed edge-on) because of the large column densities of molecular gas along the line of sight in the torus, confirming the unified model of AGN. However, galaxies at redshifts z > 2 might be quite different from those found locally, not least because of more frequent mergers in the past. Finding masers at high redshift will therefore provide a unique probe of the inner physics of very powerful AGN in the early universe. We will target two extremely IR-luminous AGN at z > 2. A search for masers at z > 2 is only feasible on the ATCA because of the improvement in sensitivity expected from the new 4cm receivers and the wide bandwidth of CABB. Detecting high redshift water masers would be an exciting demonstration of the new science enabled by the ATCA upgrades.

  5. Relaxation of molecular velocities and spectral line profiles of astrophysical masers

    NASA Technical Reports Server (NTRS)

    Anderson, Nels; Watson, William D.

    1993-01-01

    The rates at which the velocities of water molecules relax to a Maxwellian distribution are calculated under conditions that are representative of those in astrophysical water masers. Populations are calculated as a function of velocity for the lowest 40 rotational energy levels of ortho-water in order to make a detailed determination of the velocity relaxation rate. Relaxation rates for the 22 GHz maser at H2 densities of 10 exp 9/cu cm are 2.0/s and 5.1/s for temperatures of 400 K and 1000 K, respectively. Under these and other conditions, as well as for other maser transitions, the relaxation rate far exceeds the loss rate - usually by more than a factor of 10. Thus maser lines can remain narrow up to intensities that are at least a factor of 10 greater than the saturation intensity, and to path lengths that are at least a factor of 10 greater than the path length at which saturation occurs. Relaxation is dominated by the effects of trapped infrared radiation, though elastic and inelastic collisions are also included in the calculations. These relaxation rates, together with the observed line breadths of the 22 GHz masers, provide limits on maser luminosities which indicate that the brightest 22 GHz masers are highly beamed, with solid angles smaller than 10 exp -5 to 10 exp -4 Sr.

  6. Excited-State OH Masers and Supernova Remnants

    NASA Astrophysics Data System (ADS)

    Pihlström, Ylva M.; Fish, Vincent L.; Sjouwerman, Loránt O.; Zschaechner, Laura K.; Lockett, Philip B.; Elitzur, Moshe

    2008-03-01

    The collisionally pumped, ground-state 1720 MHz maser line of OH is widely recognized as a tracer for shocked regions and observed in star-forming regions and supernova remnants. Whereas some lines of excited states of OH have been detected and studied in star-forming regions, the subject of excited-state OH in supernova remnants—where high collision rates are to be expected—is only recently being addressed. Modeling of collisional excitation of OH demonstrates that 1720, 4765, and 6049 MHz masers can occur under similar conditions in regions of shocked gas. In particular, the 6049 and 4765 MHz masers become more significant at increased OH column densities where the 1720 MHz masers begin to be quenched. In supernova remnants, the detection of excited-state OH line maser emission could therefore serve as a probe of regions of higher column densities. Using the Very Large Array, we searched for excited-state OH in the 4.7, 7.8, 8.2, and 23.8 GHz lines in four well-studied supernova remnants with strong 1720 MHz maser emission (Sgr A East, W28, W44 and IC 443). No detections were made, at typical detection limits of around 10 mJy beam-1. The search for the 6 GHz lines were done using Effelsberg since the VLA receivers did not cover those frequencies, and are reported on in an accompanying letter (Fish and coworkers). We also cross-correlated the positions of known supernova remnants with the positions of 1612 MHz maser emission obtained from blind surveys. No probable associations were found, perhaps except in the Sgr A East region. The lack of detections of excited-state OH indicates that the OH column densities suffice for 1720 MHz inversion but not for inversion of excited-state transitions, consistent with the expected results for C-type shocks.

  7. Evolved star water maser cloud size determined by star size

    NASA Astrophysics Data System (ADS)

    Richards, A. M. S.; Etoka, S.; Gray, M. D.; Lekht, E. E.; Mendoza-Torres, J. E.; Murakawa, K.; Rudnitskij, G.; Yates, J. A.

    2012-10-01

    Context. Cool, evolved stars undergo copious mass loss but the detailed mechanisms and the form in which the matter is returned to the ISM are still under debate. Aims: We investigated the structure and evolution of the wind at 5 to 50 stellar radii from asymptotic giant branch and red supergiant stars. Methods: 22-GHz water masers around seven evolved stars were imaged using MERLIN, at sub-AU resolution. Each source was observed at between 2 and 7 epochs, covering several stellar periods. We compared our results with long-term single dish monitoring provided by the Pushchino radio telescope. Results: The 22-GHz emission is located in approximately spherical, thick, unevenly filled shells. The outflow velocity increases twofold or more between the inner and outer shell limits. Water maser clumps could be matched at successive epochs separated by less than two years for AGB stars, or at least 5 years for RSG. This is much shorter than the decades taken for the wind to cross the maser shell, and comparison with spectral monitoring shows that some features fade and reappear. In five sources, most of the matched maser features brighten or dim in concert from one epoch to the next. A number of individual maser features show idiosyncratic behaviour, including one cloud in W Hya caught in the act of passing in front of a background cloud leading to 50-fold, transient amplification. The masing clouds are one or two orders of magnitude denser than the wind average and contain a substantial fraction of the mass loss in this region, with a filling factor <1%. The RSG clouds are about ten times bigger than those round the AGB stars. Conclusions: Proper motions are dominated by expansion, with no systematic rotation. The maser clouds presumably survive for decades (the shell crossing time) but the masers are not always beamed in our direction. Only radiative effects can explain changes in flux density throughout the maser shells on short timescales. The size of the clouds is

  8. Axial Symmetry and Rotation in the SiO Maser Shell of IK Tauri

    NASA Astrophysics Data System (ADS)

    Boboltz, D. A.; Diamond, P. J.

    2005-06-01

    We observed v=1, J=1-0 43 GHz SiO maser emission toward the Mira variable IK Tauri (IK Tau) using the Very Long Baseline Array (VLBA). The images resulting from these observations show that SiO masers form a highly elliptical ring of emission approximately 58×32 mas with an axial ratio of 1.8:1. The major axis of this elliptical distribution is oriented at a position angle of ~59°. The line-of-sight velocity structure of the SiO masers has an apparent axis of symmetry consistent with the elongation axis of the maser distribution. Relative to the assumed stellar velocity of 35 km s-1, the blue- and redshifted masers were found to lie to the northwest and southeast of this symmetry axis, respectively. This velocity structure suggests a northwest-southeast (NW-SE) rotation of the SiO maser shell with an equatorial velocity, which we determine to be ~3.6 km s-1. Such a NW-SE rotation is in agreement with a circumstellar envelope geometry invoked to explain previous H2O and OH maser observations. In this geometry, H2O and OH masers are preferentially created in a region of enhanced density along the NE-SW equator orthogonal to the rotation/polar axis suggested by the SiO maser velocities.

  9. 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.

  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. Extragalactic Water Maser Observations with VSOP-2

    NASA Astrophysics Data System (ADS)

    Hagiwara, Y.; VSOP-2 Science Working Group

    2009-08-01

    Space-VLBI is known to achieve greatly increased angular resolution compared with ground-based VLBI observations. VSOP-2 will offer 75 μarcsec angular resolution at 22 GHz. With this improved angular resolution, VSOP-2 observations of H_2O megamaser will refine the measurements of proper motions, accelerations, distances to galaxies, and other physical parameters of galactic nuclei. In this presentation, the prospects of VSOP-2 observations of extragalactic H_2O maser with strong emphasis on H_2O megamaser are presented.

  12. 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.

  13. SOFIA/GREAT Discovery of Terahertz Water Masers

    NASA Astrophysics Data System (ADS)

    Neufeld, David A.; Melnick, Gary J.; Kaufman, Michael J.; Wiesemeyer, Helmut; Güsten, Rolf; Kraus, Alex; Menten, Karl M.; Ricken, Oliver; Faure, Alexandre

    2017-07-01

    We report the discovery of water maser emission at frequencies above 1 THz. Using the GREAT instrument on SOFIA, we have detected emission in the 1.296411 THz {8}27-{7}34 transition of water toward three oxygen-rich evolved stars: W Hya, U Her, and VY CMa. An upper limit on the 1.296 THz line flux was obtained toward R Aql. Near-simultaneous observations of the 22.23508 GHz {6}16-{5}23 water maser transition were carried out toward all four sources using the Effelsberg 100 m telescope. The measured line fluxes imply 22 GHz/1.296 THz photon luminosity ratios of 0.012, 0.12, and 0.83, respectively, for W Hya, U Her, and VY CMa, values that confirm the 22 GHz maser transition to be unsaturated in W Hya and U Her. We also detected the 1.884888 THz {8}45-{7}52 transition toward W Hya and VY CMa, and the 1.278266 THz {7}43-{6}52 transition toward VY CMa. Like the 22 GHz maser transition, all three of the THz emission lines detected here originate from the ortho-H2O spin isomer. Based upon a model for the circumstellar envelope of W Hya, we estimate that stimulated emission is responsible for ∼85% of the observed 1.296 THz line emission, and thus that this transition may be properly described as a terahertz-frequency maser. In the case of the 1.885 THz transition, by contrast, our W Hya model indicates that the observed emission is dominated by spontaneous radiative decay, even though a population inversion exists. GREAT is a development by the MPI für Radioastronomie and the KOSMA/Universität zu Köln, in cooperation with the MPI für Sonnensystemforschung and the DLR Institut für Planetenforschung.

  14. VizieR Online Data Catalog: Water masers in M31. II. Multiwavelength data (Amiri+, 2016)

    NASA Astrophysics Data System (ADS)

    Amiri, N.; Darling, J.

    2016-09-01

    In this paper, we present a comparative multiwavelength analysis of 22GHz water-maser-emitting and non-maser-emitting 24um luminous star-forming regions in M31. We use WISE, Spitzer, and Herschel infrared continuum maps, maps of derived quantities such as star formation and dust temperature, and archival catalogs to examine the differences between maser-emitting and non-maser-emitting regions, to examine correlations between observable quantities among each population, and to constrain the parameter space most likely to produce detectable water masers. Throughout the manuscript, we assume a distance to M31 of 780kpc when calculating luminosities from continuum or line flux measurements. (2 data files).

  15. HIGH-RESOLUTION IMAGING OF WATER MASER EMISSION IN THE ACTIVE GALAXIES NGC 6240 AND M51

    SciTech Connect

    Hagiwara, Yoshiaki; Edwards, Philip G. E-mail: Philip.Edwards@csiro.au

    2015-12-20

    We present the results of observations of 22 GHz H{sub 2}O maser emission in NGC 6240 and M51 made with the Karl G. Jansky Very Large Array. Two major H{sub 2}O maser features and several minor features are detected toward the southern nucleus of NGC 6240. These features are redshifted by about 300 km s{sup −1} from the galaxy’s systemic velocity and remain unresolved at the synthesized beam size. A combination of our two-epoch observations and published data reveals an apparent correlation between the strength of the maser and the 22 GHz radio continuum emission, implying that the maser excitation relates to the activity of an active galactic nucleus in the southern nucleus rather than star-forming activity. The star-forming galaxy M51 hosts H{sub 2}O maser emission in the center of the galaxy; however, the origin of the maser has been an open question. We report the first detection of 22 GHz nuclear radio continuum emission in M51. The continuum emission is co-located with the maser position, which indicates that the maser arises from nuclear active galactic nucleus-activity and not from star-forming activity in the galaxy.

  16. 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.

  17. Maser and laser engineering

    SciTech Connect

    Ishii, T.K.

    1980-01-01

    This book is intended to be a textbook for an upper division one-semester electrical engineering course. Students are expected to have had some undegraduate course work in modern physics and in electromagnetic field theory. General aspects regarding devices based on quantum electronics are considered along with gas masers, solid masers, gas lasers, solid lasers, semiconductor lasers, liquid lasers, modulation techniques for lasers, and opto-electrical demodulators and energy convertors. Attention is given to quantum electric harmonic generators, Raman lasers, optical parametric interactions, holograms, optical terms, crystallographic terms, band theory, Schroedinger formulation and Dirac formation, and the quantum number of electrons in a hydrogen atom.

  18. Recirculating cryogenic hydrogen maser

    SciTech Connect

    Huerlimann, M.D.; Hardy, W.N.; Berlinsky, A.J.; Cline, R.W.

    1986-08-01

    We report on the design and initial testing of a new type of hydrogen maser, operated at dilution refrigerator temperatures, in which H atoms circulate back and forth between a microwave-pumped state selector and the maser cavity. Other novel design features include liquid-/sup 4/He-coated walls, He-cooled electronics, and the use of microscopic magnetic particles to relax the two lowest hyperfine levels in the state selector. Stabilities at least as good as that of a Rb clock and a high-stability quartz oscillator are observed for measuring times between 1 and 300 s.

  19. 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.

  20. 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.

  1. VizieR Online Data Catalog: OH maser emission from star forming regions (Szymczak+, 2004)

    NASA Astrophysics Data System (ADS)

    Szymczak, M.; Gerard, E.

    2003-11-01

    High sensitivity observations of all four transitions of the ground state at 18cm of OH in both senses of circular polarization have been carried out with the Nancay radio telescope. The sample was a set of 100 star forming regions detected in a recent unbiased survey of 6668MHz methanol masers (Szymczak et al., 2002A&A...392..277S). OH maser emission was found in 55 objects of which 31 were not previously catalogued. (4 data files).

  2. Masers and VSOP-2

    NASA Astrophysics Data System (ADS)

    Elitzur, M.

    2009-08-01

    Maser studies where VSOP-2 can make its strongest impact involve proper motion measurements. In this talk I review outstanding issues in topics ranging from star forming regions to active galactic nuclei in which VSOP-2 proper motion measurements offer the promise of seminal contributions.

  3. A Statistical Investigation of the Connection between X-ray and Water Maser Emission in Galaxy Centers

    NASA Astrophysics Data System (ADS)

    Nutter, Andrew; Constantin, A.

    2014-01-01

    Previous studies reveal a potential intimate connection between maser emission and X-ray obscuring columns in galaxy centers, with higher obscuration for more pronounced water maser activity. The number statistics involved in these investigations remain small, however. Currently, there are 151 confirmed maser detections and over 3300 surveyed non-maser galaxies. A careful crossmatch with public data from five X-ray telescope survey catalogs (the 2XMMi-DR3 from the XMM-Newton telescope, the Chandra Source Catalog, the ROSAT All-Sky Survey bright and faint source catalogs, the Swift Burst Alert Telescope 70 month survey, and the Integral IBIS 7-year All-Sky Survey) reveals X-ray information for 103 detected maser galaxies and ~650 non-detections, offering a clear statistical advantage over previous work. We are thus able to conduct a statistical comparison of the X-ray properties of the largest sample of X-ray active galaxies surveyed for water vapor emission at 22 GHz. We find that the X-ray detection rate of masers is on average 3.5 times greater than that of non-masers, with the rates increasing in harder X-ray bands. The X-ray apparent brightness of maser and non-maser detections are similar at soft X-rays, but the maser galaxies are increasingly brighter than the non-masers in the harder bands. The X-ray luminosities calculated without correction for intrinsic absorption are lower for maser galaxies, which supports previous results showing generally higher neutral hydrogen column densities (NH) in these sources. We statistically test the potential evidence for greater obscuration in increasingly more luminous maser galaxies via monte carlo simulations of various NH distributions that are motivated by previous studies, and explore the possible physical connections that could govern them.

  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. Light-weight hydrogen maser

    NASA Astrophysics Data System (ADS)

    Peters, H. E.

    1985-12-01

    Based upon a new approach to cavity resonator and atom storage assembly design, experimental work was undertaken to develop a much smaller and lighter hydrogen maser frequency standard. An operational prototype maser of light-weight and small size resulted, but the new cavity and bulb design did not result in improved stability. Upon knowledge gained in this program further work funded by other government agencies has resulted in successful hydrogen maser oscillators having unprecedent frequency stability.

  6. Physical Characteristics of Astronomical Masers

    SciTech Connect

    Elitzur, M.

    1982-10-01

    The radio line emission of interstellar molecules routinely shows deviations from thermal equilibrium which culminate with strong maser radiation in some sources. Like its laboratory counterpart, the maser radiation is amplified through the effect of induced processes in a region where a population inversion exists and displays many of the basic features of laboratory lasers. This review is intended to explain the basic theory of astronomical masers and to survey the theoretical models which were developed for specific sources.

  7. Natural lasers and masers in the solar system

    NASA Technical Reports Server (NTRS)

    Mumma, Michael J.

    1993-01-01

    Population inversions have been found in the atmospheres of planets and comets, and amplification has been inferred for several cases. In this paper, I review the molecular systems that exhibit lasing and masing action, review the properties of atmospheres that permit these natural lasers and masers to exist, and give examples of their use as probes of remote regions. One potential future application is the possible communication over interstellar distances at GHz rates.

  8. 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.

  9. 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.

  10. Very Large Array Detection of the 36 GHz Zeeman Effect in DR21W Revisited

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

    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-1/z) is instrumental in nature and thus incorrect. With the improved performance of the array, we now deduce a 3σ limit of -4.7 to +0.4 mG (1.7 Hz mG-1/z) for the line-of-sight component of the magnetic field strength in DR21W.

  11. FAST Maser Surveys

    NASA Astrophysics Data System (ADS)

    Zhang, J. S.

    2014-09-01

    FAST, the Five-hundred meter Aperture Spherical radio Telescope, will become the largest operating single-dish telescope in the coming years. It has many advantages: much better sensitivity for its largest collecting area; large sky coverage due to its innovative design of the active primary surface; extremely radio quiet from its unique location, etc. In this work, I will highlight the future capabilities of FAST to discover and observe both galactic and extragalactic masers.

  12. 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.

  13. High-resolution VLBA Observations of Three 7 mm SiO Masers toward VX Sgr at Five Epochs

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

    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→0 (v = 1, 2) 28SiO 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→0 (v = 0) 29SiO line emission is also detected, but is too weak to produce any VLBI map.

  14. A search for gravitationally lensed water masers in dusty quasars and star-forming galaxies

    NASA Astrophysics Data System (ADS)

    McKean, J. P.; Impellizzeri, C. M. V.; Roy, A. L.; Castangia, P.; Samuel, F.; Brunthaler, A.; Henkel, C.; Wucknitz, O.

    2011-02-01

    Luminous extragalactic water masers are known to be associated with active galactic nuclei and have provided accurate estimates for the mass of the central supermassive black hole and the size and structure of the circumnuclear accretion disc in nearby galaxies. To find water maser systems at much higher redshifts, we have begun a survey of known gravitationally lensed quasars and star-forming galaxies. In this paper, we present a search for 22 GHz (rest-frame) water masers towards five dusty, gravitationally lensed quasars and star-forming galaxies at redshifts between 2.3 and 2.9 with the Effelsberg radio telescope and the Expanded Very Large Array (EVLA). Our observations do not find any new definite examples of high-redshift water maser galaxies, suggesting that large reservoirs of dust and gas are not a sufficient condition for powerful water maser emission. However, we do find the tentative detection of a water maser system in the active galaxy IRAS 10214+4724 at redshift 2.285. Our survey has now doubled the number of gravitationally lensed galaxies and quasars that have been searched for high-redshift water maser emission. We also present an updated analysis of the high-redshift water maser luminosity function that is based on the results presented here and from the only cosmologically distant (z > 1) water maser galaxy found thus far, MG J0414+0534 at redshift 2.64. By comparing with the water maser luminosity function locally and at moderate redshifts, we find that there must be some evolution in the luminosity function of water maser galaxies at high redshifts. By assuming a moderate evolution [(1 +z)4] in the water maser luminosity function, we find that blind surveys for water maser galaxies are only worthwhile with extremely high sensitivity like that of the planned Square Kilometre Array (Phase 2), which is scheduled to be completed by 2020. However, instruments like the EVLA and MeerKAT will be capable of detecting water maser systems similar to the

  15. DISCOVERY OF NUCLEAR WATER MASER EMISSION IN CENTAURUS A

    SciTech Connect

    Ott, Juergen; Meier, David S.; Walter, Fabian; Mao, Minnie Y. E-mail: dmeier@nmt.edu E-mail: mmao@nrao.edu; and others

    2013-07-10

    We report the detection of a 22 GHz water maser line in the nearest (D {approx} 3.8 Mpc) radio galaxy Centaurus A (Cen A) using the Australia Telescope Compact Array (ATCA). The line is centered at a velocity of {approx}960 km s{sup -1}, which is redshifted by about 415 km s{sup -1} from the systemic velocity. Such an offset, as well as the width of {approx}120 km s{sup -1}, could be consistent with either a nuclear maser arising from an accretion disk of the central supermassive black hole (SMBH), or with a jet maser that is emitted from the material that is shocked near the base of the jet in Cen A. The best spatial resolution of our ATCA data constrains the origin of the maser feature within <3 pc of the SMBH. The maser exhibits an isotropic luminosity of {approx}1 L{sub Sun }, which classifies it as a kilomaser, and appears to be variable on timescales of months. A kilomaser can also be emitted by shocked gas in star-forming regions. Given the small projected distance from the core, the large offset from systemic velocity, and the smoothness of the line feature, we conclude that a jet maser line emitted by shocked gas around the base of the active galactic nucleus is the most likely explanation. For this scenario we can infer a minimum density of the radio jet of {approx}> 10 cm{sup -3}, which indicates substantial mass entrainment of surrounding gas into the propagating jet material.

  16. 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.

  17. 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.

  18. VizieR Online Data Catalog: H2O maser emission from irregular variables (Szymczak+ 1997)

    NASA Astrophysics Data System (ADS)

    Szymczak, M.; Engels, D.

    1997-05-01

    We have performed a search for the 22 GHz water maser line among 72 optically identified irregular and semiregular red variables. New detections were made of five stars, while only four of nine objects previously known as maser sources were redetected. The probability for the detection of H2O maser emission increases with V light amplitude, and with H-K and K-[12] colours just as in regular Mira and semiregular variables of SRa- and SRb-types. The detection rate of water masers is about 25% for nearby Lb objects (D<400pc) in the sample, comparable to that observed in the SRa and SRb stars. No masers were detected in objects with mass loss rates <=4x10-8M⊙/yr. Maser luminosities are 1041-1043photons/s similar to that of the bluest Miras and typical SRa and SRb stars showing water maser emission. A comparison of our data on irregular stars with those previously obtained on SRa and SRb variables suggests that most radio and infrared properties are indistinguishable among both classes of objects. (1 data file).

  19. A Search for H2O Maser Emission from Wide-Angle Outflows in Nearby AGN

    NASA Astrophysics Data System (ADS)

    Wilson, Emily; Braatz, James A.; Pesce, Dom; Megamaser Cosmology Project

    2017-01-01

    As part of large surveys for 22 GHz water maser emission in external galaxies, the Green Bank Telescope has made over 4000 distinct observations resulting in nondetections. Most of these observations are 10-minute integrations toward nearby active galaxies, often as part of the Megamaser Cosmology Project. We have grouped the observed galaxies according their nuclear activity type and made stacked averages of the nondetections, searching for low-level, ubiquitous maser emission. Such emission might be expected, for example, if there is faint maser emission from a wide-angle outflow component in the nuclei of AGNs. We detected no maser emission in our stacked averages of Seyfert 1s and Seyfert 2s, or in the sum of all nondetections. We explore the significance of this result in the context of clumpy outflow models.

  20. 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.

  1. 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.

  2. 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.

  3. Ultra-stable performance of the superconducting cavity maser

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    Recent measurements on the superconducting cavity maser (SCM) oscillator show frequency stability of parts in 10 exp 15 for times from 1 to 1000 sec. Phase noise of approximately -80 dB/f-cubed was also measured. This short- and mid-term performance is believed to be better than that of any known microwave oscillator. In particular, stability at a measuring time of 1 sec is 10 times better than that of a hydrogen maser, and phase noise at 8 GHz is more than 20 dB below that of the best multiplied quartz crystal oscillators. Substantial technical improvements have been made to eliminate frequency instability due to operational parameters. They are temperature, pump frequency, pump power, pump frequency polarization, temperature gradient, coupling strength, and output VSWR. Either the parameter was stabilized or the coefficient which couples the parameter to the operating frequency was minimized. A frequency pulling coil has been implemented and tested to enable the SCM to be slaved to a hydrogen maser with a time constant of approximately 50 sec. This combination would allow the excellent long term performance of the hydrogen maser to be improved by the newly available short term performance of the SCM.

  4. Ultra-stable performance of the superconducting cavity maser

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    Recent measurements on the superconducting cavity maser (SCM) oscillator show frequency stability of parts in 10 exp 15 for times from 1 to 1000 sec. Phase noise of approximately -80 dB/f-cubed was also measured. This short- and mid-term performance is believed to be better than that of any known microwave oscillator. In particular, stability at a measuring time of 1 sec is 10 times better than that of a hydrogen maser, and phase noise at 8 GHz is more than 20 dB below that of the best multiplied quartz crystal oscillators. Substantial technical improvements have been made to eliminate frequency instability due to operational parameters. They are temperature, pump frequency, pump power, pump frequency polarization, temperature gradient, coupling strength, and output VSWR. Either the parameter was stabilized or the coefficient which couples the parameter to the operating frequency was minimized. A frequency pulling coil has been implemented and tested to enable the SCM to be slaved to a hydrogen maser with a time constant of approximately 50 sec. This combination would allow the excellent long term performance of the hydrogen maser to be improved by the newly available short term performance of the SCM.

  5. Dust Grains and the Luminosity of Circumnuclear Water Masers in Active Galaxies

    NASA Technical Reports Server (NTRS)

    Collison, Alan J.; Watson, William D.

    1995-01-01

    In previous calculations for the luminosities of 22 GHz water masers, the pumping is reduced and ultimately quenched with increasing depth into the gas because of trapping of the infrared (approximately equals 30-150 micrometers), spectral line radiation of the water molecule. When the absorption (and reemission) of infrared radiation by dust grains is included, we demonstrate that the pumping is no longer quenched but remains constant with increasing optical depth. A temperature difference between the grains and the gas is required. Such conditions are expected to occur, for example, in the circumnuclear masing environments created by X-rays in active galaxies. Here, the calculated 22 GHz maser luminosities are increased by more than an order of magnitude. Application to the well-studied, circumnuclear masing disk in the galaxy NGC 4258 yields a maser luminosity near that inferred from observations if the observed X-ray flux is assumed to be incident onto only the inner surface of the disk.

  6. The Protocluster G18.67+0.03: A Test Case for Class I CH3OH Masers as Evolutionary Indicators for Massive Star Formation

    NASA Astrophysics Data System (ADS)

    Cyganowski, C. J.; Brogan, C. L.; Hunter, T. R.; Zhang, Q.; 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 CH3OH 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 13CO(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 CH3OH 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 13CO 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.

  7. 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).

  8. Surface-state hydrogen maser

    SciTech Connect

    Maan, A.C.; Verhaar, B.J.; Stoof, H.T.C. ); Silvera, I.F. )

    1993-11-01

    We describe a hydrogen maser operating at very low temperatures in which most of the hydrogen atoms are condensed on a superfluid helium surface in long-lived states. This proposed maser can be used to obtain information on the properties of the hydrogen--liquid-helium-surface system. In addition, it promises to be an interesting system from the point of view of nonlinear dynamics. It is found that the surface recombination to molecular hydrogen, which might be considered as undesirable, is actually necessary to achieve the masing conditions. We develop the maser equations and consider a number of realistic conditions for operation.

  9. 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.

  10. VizieR Online Data Catalog: Semiregular variables H2O maser (Szymczak+, 1995)

    NASA Astrophysics Data System (ADS)

    Szymczak, M.; Engels, D.

    1994-10-01

    107 semiregular variables of spectral type M have been observed in the H2O 6(16)-5(23) line at 22.235GHz with the 100m Effelsberg radio telescope and maser emission has been detected in 23 objects, of which 10 are new detections. (4 data files).

  11. Monitoring Observatinos of H2O and SiO Masers Toward Post-AGB Stars

    NASA Astrophysics Data System (ADS)

    Kim, Jaeheon; Cho, Se-Hyung; Yoon, Dong-Hwan

    2016-12-01

    We present the results of simultaneous monitoring observations of H_2O 6_{1,6}-5_{2,3} (22 GHz) and SiO J=1-0, 2-1, 3-2 maser lines (43, 86, 129 GHz) toward five post-AGB (candidate) stars, using the 21-m single-dish telescopes of the Korean VLBI Network. Depending on the target objects, 7 - 11 epochs of data were obtained. We detected both H_2O and SiO maser lines from four sources: OH16.1-0.3, OH38.10-0.13, OH65.5+1.3, and IRAS 19312+1950. We could not detect H_2O maser emission toward OH13.1+5.1 between the late OH/IR and post-AGB stage. The detected H_2O masers show typical double-peaked line profiles. The SiO masers from four sources, except IRAS 19312+1950, show the peaks around the stellar velocity as a single peak, whereas the SiO masers from IRAS 19312+1950 occur above the red peak of the H_2O maser. We analyzed the properties of detected maser lines, and investigated their evolutionary state through comparison with the full widths at zero power. The distribution of observed target sources was also investigated in the IRAS two-color diagram in relation with the evolutionary stage of post-AGB stars. From our analyses, the evolutionary sequence of observed sources is suggested as OH65.5+1.3 → OH13.1+5.1 → OH16.1-0.3 → OH38.10-0.13, except for IRAS 19312+1950. In addition, OH13.1+5.1 from which the H_2O maser has not been detected is suggested to be on the gateway toward the post-AGB stage. With respect to the enigmatic object, IRAS 19312+1950, we could not clearly figure out its nature. To properly explain the unusual phenomena of SiO and H_2O masers, it is essential to establish the relative locations and spatial distributions of two masers using VLBI technique. We also include the 1.2 - 160 μm spectral energy distribution using photometric data from the following surveys: 2MASS, WISE, MSX, IRAS, and AKARI (IRC and FIS). In addition, from the IRAS LRS spectra, we found that the depth of silicate absorption features shows significant variations

  12. 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.

  13. Location of H2O maser in the double-nuclei system of NGC 6240

    NASA Astrophysics Data System (ADS)

    Hagiwara, Y.; Diamond, P. J.; Miyoshi, M.

    2003-03-01

    We performed VLA observations of the 22 GHz H2O; maser emission in the merging galaxy NGC 6240, which hosts the well-known double active nuclei. In a previous paper, we reported on the first solid detection of the H2O; maser emission in 2001. After two abortive attempts due to the weakness and probable variability of the emission, the maser was detected with the VLA in June 2002. The emission is unresolved at ~ 0.3 arcsec and coincides with the southern 22 GHz continuum peak to ~ 0.007 arcsec ( ~ 3 pc: D = 97 Mpc). The detection of the maser in the southern nucleus indicates that nuclear activity of the galaxy, which is significant in X-ray and far-infrared (FIR) bands, lies mainly in the southern nucleus, and the nucleus without a high brightness peak could be explained by thick dust emitting FIR radiation. We favour the idea that the maser in NGC 6240 is associated with the AGN-activity.

  14. Nanosecond time-resolved characterization of a pentacene-based room-temperature MASER

    PubMed Central

    Salvadori, Enrico; Breeze, Jonathan D.; Tan, Ke-Jie; Sathian, Juna; Richards, Benjamin; Fung, Mei Wai; Wolfowicz, Gary; Oxborrow, Mark; Alford, Neil McN.; Kay, Christopher W. M.

    2017-01-01

    The performance of a room temperature, zero-field MASER operating at 1.45 GHz has been examined. Nanosecond laser pulses, which are essentially instantaneous on the timescale of the spin dynamics, allow the visible-to-microwave conversion efficiency and temporal response of the MASER to be measured as a function of excitation energy. It is observed that the timing and amplitude of the MASER output pulse are correlated with the laser excitation energy: at higher laser energy, the microwave pulses have larger amplitude and appear after shorter delay than those recorded at lower laser energy. Seeding experiments demonstrate that the output variation may be stabilized by an external source and establish the minimum seeding power required. The dynamics of the MASER emission may be modeled by a pair of first order, non-linear differential equations, derived from the Lotka-Volterra model (Predator-Prey), where by the microwave mode of the resonator is the predator and the spin polarization in the triplet state of pentacene is the prey. Simulations allowed the Einstein coefficient of stimulated emission, the spin-lattice relaxation and the number of triplets contributing to the MASER emission to be estimated. These are essential parameters for the rational improvement of a MASER based on a spin-polarized triplet molecule. PMID:28169331

  15. Nanosecond time-resolved characterization of a pentacene-based room-temperature MASER.

    PubMed

    Salvadori, Enrico; Breeze, Jonathan D; Tan, Ke-Jie; Sathian, Juna; Richards, Benjamin; Fung, Mei Wai; Wolfowicz, Gary; Oxborrow, Mark; Alford, Neil McN; Kay, Christopher W M

    2017-02-07

    The performance of a room temperature, zero-field MASER operating at 1.45 GHz has been examined. Nanosecond laser pulses, which are essentially instantaneous on the timescale of the spin dynamics, allow the visible-to-microwave conversion efficiency and temporal response of the MASER to be measured as a function of excitation energy. It is observed that the timing and amplitude of the MASER output pulse are correlated with the laser excitation energy: at higher laser energy, the microwave pulses have larger amplitude and appear after shorter delay than those recorded at lower laser energy. Seeding experiments demonstrate that the output variation may be stabilized by an external source and establish the minimum seeding power required. The dynamics of the MASER emission may be modeled by a pair of first order, non-linear differential equations, derived from the Lotka-Volterra model (Predator-Prey), where by the microwave mode of the resonator is the predator and the spin polarization in the triplet state of pentacene is the prey. Simulations allowed the Einstein coefficient of stimulated emission, the spin-lattice relaxation and the number of triplets contributing to the MASER emission to be estimated. These are essential parameters for the rational improvement of a MASER based on a spin-polarized triplet molecule.

  16. Nanosecond time-resolved characterization of a pentacene-based room-temperature MASER

    NASA Astrophysics Data System (ADS)

    Salvadori, Enrico; Breeze, Jonathan D.; Tan, Ke-Jie; Sathian, Juna; Richards, Benjamin; Fung, Mei Wai; Wolfowicz, Gary; Oxborrow, Mark; Alford, Neil Mcn.; Kay, Christopher W. M.

    2017-02-01

    The performance of a room temperature, zero-field MASER operating at 1.45 GHz has been examined. Nanosecond laser pulses, which are essentially instantaneous on the timescale of the spin dynamics, allow the visible-to-microwave conversion efficiency and temporal response of the MASER to be measured as a function of excitation energy. It is observed that the timing and amplitude of the MASER output pulse are correlated with the laser excitation energy: at higher laser energy, the microwave pulses have larger amplitude and appear after shorter delay than those recorded at lower laser energy. Seeding experiments demonstrate that the output variation may be stabilized by an external source and establish the minimum seeding power required. The dynamics of the MASER emission may be modeled by a pair of first order, non-linear differential equations, derived from the Lotka-Volterra model (Predator-Prey), where by the microwave mode of the resonator is the predator and the spin polarization in the triplet state of pentacene is the prey. Simulations allowed the Einstein coefficient of stimulated emission, the spin-lattice relaxation and the number of triplets contributing to the MASER emission to be estimated. These are essential parameters for the rational improvement of a MASER based on a spin-polarized triplet molecule.

  17. Excited-state hydroxyl maser polarimetry: who ate all the πs?

    NASA Astrophysics Data System (ADS)

    Green, J. A.; Caswell, J. L.; McClure-Griffiths, N. M.

    2015-07-01

    We present polarimetric maser observations with the Australia Telescope Compact Array of excited-state hydroxyl (OH) masers. We observed 30 fields of OH masers in full Stokes polarization with the Compact Array Broadband Backend at both the 6030 and 6035 MHz excited-state OH transitions, and the 6668 MHz methanol maser transition, detecting 70 sites of maser emission. Amongst the OH we found 112 Zeeman pairs, of which 18 exhibited candidate π components. This is the largest single full polarimetric study of multiple sites of star formation for these frequencies, and the rate of 16 per cent π components clearly indicates that the π component exists, and is comparable to the percentage recently found for ground-state transitions. This significant percentage of π components, with consistent proportions at both ground- and excited-state transitions, argues against Faraday rotation suppressing the π component emission. Our simultaneous observations of methanol found the expected low level of polarization, with no circular detected, and linear only found at the ≤10 per cent level for the brightest sources.

  18. 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.

  19. 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).

  20. 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.

  1. 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.

  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. Intermittent maser flare around the high-mass young stellar object G353.273+0.641

    NASA Astrophysics Data System (ADS)

    Motogi, Kazuhito; Sorai, Kazuo; Fujisawa, Kenta; Sugiyama, Koichiro; Honma, Mareki

    2012-07-01

    The water maser site associated with G353.273+0.641 is classified as a dominant blueshifted H2O maser, which shows an extremely wide velocity range (+/- 100 km s-1) with almost all flux concentrated in the highly blueshifted emission. The previous study has proposed that this peculiar H2O maser site is excited by a pole-on jet from high mass protostellar object. We report on the monitoring of 22-GHz H2O maser emission from G353.273+0.641 with the VLBI Exploration of Radio Astrometry (VERA) and the Tomakamai 11-m radio telescope. Our VLBI imaging has shown that all maser features are distributed within a very small area of 200 × 200 au2, in spite of the wide velocity range (> 100 km s-1). The light curve obtained by weekly single-dish monitoring shows notably intermittent variation. We have detected three maser flares during three years. Frequent VLBI monitoring has revealed that these flare activities have been accompanied by a significant change of the maser alignments. We have also detected synchronized linear acceleration (-5 km s-1yr-1) of two isolated velocity components, suggesting a lower-limit momentum rate of 10-3 M⊙ km s-1yr-1 for the maser acceleration. All our results support the previously proposed pole-on jet scenario, and finally, a radio jet itself has been detected in our follow-up ATCA observation. If highly intermittent maser flares directly reflect episodic jet-launchings, G353.273+0.641 and similar dominant blueshifted water maser sources can be suitable targets for a time-resolved study of high mass protostellar jet.

  4. Merging Maser and Cesium Clocks in Timescales

    DTIC Science & Technology

    2011-10-01

    OCT 2011 2. REPORT TYPE 3. DATES COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE Merging Maser And Cesium Clocks In Timescales 5a...Prescribed by ANSI Std Z39-18 Merging Maser and Cesium Clocks In Timescales Demetrios...recent maser data relatively higher than older maser data. A Kalman Filter could assign different phase, frequency, and frequency drift process

  5. OH Observations in the Direction of H2O Masers in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Gardner, F. F.; Whiteoak, J. B.

    1985-07-01

    1.6-GHz OH observations have been made towards five LMC H II regions that have been associated with H2O maser emission. Circularly polarized maser emission was observed in two cases, 0510-689 and 0540-696B, but not towards 0540-697A (N159), where emission had been previously reported. Weak OH absorption was detected for two regions (0539-691 and 0540-697A) and possibly a third (0540-696). The optical depths are low (around 0.01), providing additional evidence that molecular densities in the LMC are signficantly lower than in our Galaxy.

  6. Radiative transfer in astronomical masers. III - Filamentary masers

    NASA Technical Reports Server (NTRS)

    Elitzur, Moshe; Mckee, Christopher F.; Hollenbach, David J.

    1991-01-01

    The complete solution of a filamentary maser is presented. An integral equation and an iterative procedure are developed to calculate and solve the contribution of rays emanating from the filament sidewall. The solution provides complete expressions for the distributions of intensity and flux across the source as functions of position and direction with regard to the axis. The results are used to find the number distribution of brightness temperature in a large sample of randomly oriented filaments with an arbitrary distribution of lengths. The effects of external radiation on the maser structure and intensity are studied. It is proposed that the two giant bursts of H2O maser emission observed in W49 and Orion resulted from the interaction or two interacting filaments and a foreground slab amplifying a background filament.

  7. Radiative transfer in astronomical masers. III - Filamentary masers

    NASA Technical Reports Server (NTRS)

    Elitzur, Moshe; Mckee, Christopher F.; Hollenbach, David J.

    1991-01-01

    The complete solution of a filamentary maser is presented. An integral equation and an iterative procedure are developed to calculate and solve the contribution of rays emanating from the filament sidewall. The solution provides complete expressions for the distributions of intensity and flux across the source as functions of position and direction with regard to the axis. The results are used to find the number distribution of brightness temperature in a large sample of randomly oriented filaments with an arbitrary distribution of lengths. The effects of external radiation on the maser structure and intensity are studied. It is proposed that the two giant bursts of H2O maser emission observed in W49 and Orion resulted from the interaction or two interacting filaments and a foreground slab amplifying a background filament.

  8. A transportable hydrogen maser for Australia Telescope.

    NASA Astrophysics Data System (ADS)

    He, J. W.; Lin, C. F.; Zhai, Z. C.; Wilson, W. E.; Fagg, H.

    To equip the Chinese VLBI network, a transportable compact active hydrogen maser has been developed at Shanghai Observatory (SO) since 1985. So far five such masers have come into use for VLBI radioastronomy and some military. These hydrogen masers are all compact, relatively light, rugged and easily transportable. In Nov. 1993, one of these masers was transported to Australia Telescope National Facility (ATNF) to determine its performance as a stable oscillator for VLBI. This paper describes the design and construction of the hydrogen maser and presents the results tested at Parkes Observatory of ATNF.

  9. Water masers in dusty environments

    NASA Astrophysics Data System (ADS)

    Babkovskaia, N.; Poutanen, J.

    2004-04-01

    We study in detail a pumping mechanism for the λ=1.35 cm maser transition 616 -> 523 in ortho-H2O based on the difference between gas and dust temperatures. The upper maser level is populated radiatively through 414 -> 505 and 505 -> 616 transitions. The heat sink is realized by absorbing the 45 μm photons, corresponding to the 523 -> 414 transition, by cold dust. We compute the inversion of maser level populations in the optically thick medium as a function of the hydrogen concentration, the water-to-dust mass ratio, and the difference between the gas and the dust temperatures. The main results of the numerical simulations are interpreted in terms of a simplified four-level model. We show that the maser strength depends mostly on the product of hydrogen concentration and the dust-to-water mass ratio but not on the size distribution of the dust particles or their type. We also suggest approximate formulae that describe accurately the inversion and can be used for fast calculations of the maser luminosity. Depending on the gas temperature, the maximum maser luminosity is reached when the water concentration NH_2O approx 106-107 cm-3 times the dust-to-hydrogen mass ratio, and the inversion completely disappears at densities just an order of magnitude larger. For a dust temperature of 130 K, the 616 -> 523 transition becomes inverted already at a temperature difference of Δ T˜ 1 K, while other possible masing transitions require a larger Δ T⪆ 30 K. We identify the region of the parameter space where other ortho- and para-water masing transitions can appear.

  10. MAGMO: Mapping the Galactic Magnetic field through OH masers

    NASA Astrophysics Data System (ADS)

    Green, James A.; McClure-Griffiths, Naomi M.; Caswell, James L.; Robishaw, Tim; Harvey-Smith, Lisa; Mao, Sui Ann

    2015-03-01

    We are undertaking a project (MAGMO) to examine large-scale magnetic fields pervading regions of high-mass star formation. The project will test if the orientations of weak large-scale magnetic fields can be maintained in the contraction (and field amplification) to the high densities encountered in high-mass star forming regions. This will be achieved through correlating targeted observations of ground-state hydroxyl (OH) maser emission towards hundreds of sites of high-mass star formation spread throughout the spiral arms of the Milky Way. Through the Zeeman splitting of the OH maser emission these observations will determine the strength and orientation of the in-situ magnetic field. The completion of the southern hemisphere Methanol Multibeam survey has provided an abundance of targets for ground-state OH maser observations, approximately 1000 sites of high-mass star formation. With this sample, much larger and more homogeneous than previously available, we will have the statistics necessary to outweigh random fluctuations and observe an underlying Galactic magnetic field if it exists. We presented details of the overall progress of the project illustrated by the results of a pilot sample of sources towards the Carina-Sagittarius spiral arm tangent, where a coherent field is implied.

  11. 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.

  12. An Analysis of NTSC's Timekeeping Hydrogen Masers

    NASA Astrophysics Data System (ADS)

    Hui-jie, Song; Shao-wu, Dong; Zheng-ming, Wang; Li-li, Qu; Yue-juan, Jing; Wei, Li

    2016-10-01

    In this article, the hydrogen masers in the NTSC (National Time Service Center) timekeeping laboratory are tested. In order to avoid the impact of larger noise of caesium atomic clocks, TA(k) or UTC(k) is not used as reference, instead, the four hydrogen masers are mutually referred and tested. The frequency stability of hydrogen masers is analyzed using the four-cornered hat method, and the Allan standard deviations of each single hydrogen maser in different sample times are estimated. Then, according to the characteristics of hydrogen masers, by removing the trend term, excluding outliers, and smoothing the data with a mathematical method to separate the Gaussian noises of hydrogen masers, and finally by through the Kolmogorov-Smirnov test, the Gaussian noise of each hydrogen maser is estimated.

  13. 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.

  14. A Circumstellar H2O Maser Associated With the Galactic Circumnuclear Molecular Disk?

    NASA Technical Reports Server (NTRS)

    Levine, Deborah A.

    1995-01-01

    In the course of conducting a survey of 22-GHzH2O masers in the inner galaxy, we discovered a maser source in Sgr A West. It is located 30'N and 35'E of Sgr A*, near the edge of the Eastern arm of the radio mini-spiral, which presumably coincides with the inside edge of the circumnuclear disk. Furthermore, the radial velocity of the maser is remarkably similar to that expected for gas in the circumnuclear disk at this location. We have also found a luminous, reddened star having a bolometric magnitude and IR spectrum characteristic of an M supergiant at this location. The extinction is consistent with a location in the inner galaxy, near or possibly within the circumnuclear disk. If this star is associated with the circumnuclear disk, it will have implications for star formation in the unusual galactic center environment.

  15. Measuring the Distance of VX Sagittarii with SiO Maser Proper Motions

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Shen, Zhi-Qiang; Xu, Ye

    2007-08-01

    We report on 43 GHz v=1, J=1--0 SiO maser proper motions in the circumstellar envelope of the M-type semi-regular variable star VX Sgr, observed by Very Long Baseline Array (VLBA) at 3 epochs during 1999 April--May. Applying the statistical parallax analysis to these proper motions, we estimated a distance of VX Sgr of 1.57±0.27 kpc, which is consistent with that based on the proper motions of H2O masers, or on the assumption that VX Sgr belongs to the Sgr OB1 association. At this distance, VX Sgr can be classified as a red supergiant. Comparing the statistical parallax method with those of model fitting and annual parallax, we think that the statistical parallax method may be a good way of estimating SiO maser distances at present.

  16. A Circumstellar H2O Maser Associated With the Galactic Circumnuclear Molecular Disk?

    NASA Technical Reports Server (NTRS)

    Levine, Deborah A.

    1995-01-01

    In the course of conducting a survey of 22-GHzH2O masers in the inner galaxy, we discovered a maser source in Sgr A West. It is located 30'N and 35'E of Sgr A*, near the edge of the Eastern arm of the radio mini-spiral, which presumably coincides with the inside edge of the circumnuclear disk. Furthermore, the radial velocity of the maser is remarkably similar to that expected for gas in the circumnuclear disk at this location. We have also found a luminous, reddened star having a bolometric magnitude and IR spectrum characteristic of an M supergiant at this location. The extinction is consistent with a location in the inner galaxy, near or possibly within the circumnuclear disk. If this star is associated with the circumnuclear disk, it will have implications for star formation in the unusual galactic center environment.

  17. FORMALDEHYDE MASERS: EXCLUSIVE TRACERS OF HIGH-MASS STAR FORMATION

    SciTech Connect

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

    2015-11-15

    The detection of four formaldehyde (H{sub 2}CO) 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 H{sub 2}CO masers are an exclusive tracer of young high-mass stellar objects. We report the first survey specifically focused on the search for 6 cm H{sub 2}CO 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 H{sub 2}CO emission in our sample of non HMSFRs. To check for the association between high-mass star formation and H{sub 2}CO 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 CH{sub 3}OH masers. We detected a new 6 cm H{sub 2}CO emission line in G32.74−0.07. This work provides further evidence that supports an exclusive association between H{sub 2}CO masers and young regions of high-mass star formation. Furthermore, we detected H{sub 2}CO 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), CH{sub 3}OH (5005 MHz), and CH{sub 2}NH (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.

  18. 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.

  19. 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.

  20. TWO EPOCHS OF VERY LARGE ARRAY OBSERVATIONS OF WATER MASER EMISSION IN THE ACTIVE GALAXY NGC 6240

    SciTech Connect

    Hagiwara, Yoshiaki

    2010-12-15

    Studies of 22 GHz H{sub 2}O maser emission from the merging galaxy NGC 6240 with double nuclei are presented. Two epochs of Very Large Array (VLA) observations in the A-configuration in spectral-line mode were carried out at 0.1 arcsec resolution by covering the redshifted velocity range of {approx}300 km s{sup -1} with respect to the systemic velocity of the galaxy. The purpose of these new observations is twofold: to detect an H{sub 2}O maser that an earlier VLA observation pinpointed in the southern nucleus in the northern nucleus as well to clarify the kinematics of the double nuclei, and to understand the origin of the maser in the galaxy. In the second epoch, one velocity feature peaking at V{sub LSR} = 7491.1 km s{sup -1}, redshifted by {approx}200 km s{sup -1} relative to the systemic velocity, was detected only toward the southern nucleus. The detection of an H{sub 2}O maser feature at or near this velocity had never been reported in earlier observations. However, including the known velocity features at redshifted velocities, no other velocity features were observed toward either nuclei throughout these epochs. The maser remains unresolved at an angular resolution of {approx}0.''1, corresponding to a linear size of less than about 45 pc. The two epochs of VLA observations show that the maser intensity is variable on timescales of at least three months, while the correlation between the maser intensity and the radio continuum intensity is not certain from our data. It is plausible that the maser in NGC 6240 is associated with the activity of an active galactic nucleus in the southern nucleus. Alternatively, the maser can be explained by star-forming activity at the site of massive star formation in the galaxy.

  1. Cyclotron resonance maser experiment in a nondispersive waveguide

    SciTech Connect

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

    1996-06-01

    A cyclotron-resonance maser (CRM) oscillator experiment in which a spiraling electron beam interacts with a transverse electromagnetic wave in a nondispersive waveguide is presented. The experiment employs a low-energy low-current electron beam in a two-wire (Lecher type) waveguide. The microwave output frequency is tuned in this experiment by the axial magnetic field in the range 3.5--6.0 GHz. A second harmonic emission is observed at {approximately}7 GHz. CRM theory shows that in a free-space TEM-mode interaction, the gain might be canceled due to the equal and opposite effects of the axial (Weibel) and the azimuthal bunching mechanisms. This balance is violated in the large transverse velocity regime (V{sub {perpendicular}} {much_gt} V{sub z}) in which the experiment operates. The tunability measurements of the CRM oscillator experiment in the nondispersive waveguide are discussed in view of the CRM theory.

  2. MASERS (CHAPTERS I THRU III),

    DTIC Science & Technology

    This work was provided in order to illustrate the possibility of creation of a maser by use of inversional transitions in a beam of heavy ammonia ND3...radiation of such a generator at frequency of 1656.18 Mc. (line J = 6, K = 6 of inversional spectrum of ND3) constitutes a magnitude of the order of

  3. Different type of maser star

    SciTech Connect

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

    1982-03-01

    A systematic survey of short-period, semiregular variable stars has been made resulting in the detection of six new water masers. Of the 14 short-period maser stars now known, nine are classified as SRb variables. All are very late spectral type SRb's typically M7, while the overwhelming majority of normal SRb stars is M4 to M6. Their (2.2 ..mu..)--(11 ..mu..) colar indices are among the lowest of any known maser stars. They are presumably less dusty as well. Four of the SRb stars and two of the remainder do not obey the correlation between period and velocity spread of the emission features that is found for the Mira and long-period, semiregular variables. Finally, high galactic latitudes dominate; 13 of the 14 are in excess of 13/sup 0/, and nine of these are greater than 25/sup 0/. These facts suggest that the short-period semiregular variables: particularly the SRb stars: may be a very different type of maser star than the Mira and long-period semiregular variables.

  4. Ammonia masers in the interstellar medium

    NASA Astrophysics Data System (ADS)

    Wilson, T. L.; Schilke, P.

    Since 1986, 10 ammonia masers have been found. Most of these are found in the sources W51D, W51e1/e2, NGC7538, DR21, and W33. Among them are a few masers or maser candidates, arising from metastable inversion lines. There are many more masers arising from nonmetastable inversion lines. The most outstanding is intense maser emission from the (J,K) = (9,6) inversion line. Only in W51D are any masering nonmetastable transitions of para-NH3 to be found. Since the masering levels are more than 500 K above ground state, there are a large number of levels populated, and the excitation scheme must be complex. It is likely that there is no unique excitation scheme for all types of ammonia masers. Although there have been a few attempts to model the ammonia maser excitation, including excitation involving vibrationally excited levels, the quest for an all-encompassing ammonia maser excitation model is still going on.

  5. Room-temperature solid-state maser.

    PubMed

    Oxborrow, Mark; Breeze, Jonathan D; Alford, Neil M

    2012-08-16

    The invention of the laser has resulted in many innovations, and the device has become ubiquitous. However, the maser, which amplifies microwave radiation rather than visible light, has not had as large an impact, despite being instrumental in the laser's birth. The maser's relative obscurity has mainly been due to the inconvenience of the operating conditions needed for its various realizations: atomic and free-electron masers require vacuum chambers and pumping; and solid-state masers, although they excel as low-noise amplifiers and are occasionally incorporated in ultrastable oscillators, typically require cryogenic refrigeration. Most realizations of masers also require strong magnets, magnetic shielding or both. Overcoming these various obstacles would pave the way for improvements such as more-sensitive chemical assays, more-precise determinations of biomolecular structure and function, and more-accurate medical diagnostics (including tomography) based on enhanced magnetic resonance spectrometers incorporating maser amplifiers and oscillators. Here we report the experimental demonstration of a solid-state maser operating at room temperature in pulsed mode. It works on a laboratory bench, in air, in the terrestrial magnetic field and amplifies at around 1.45 gigahertz. In contrast to the cryogenic ruby maser, in our maser the gain medium is an organic mixed molecular crystal, p-terphenyl doped with pentacene, the latter being photo-excited by yellow light. The maser's pumping mechanism exploits spin-selective molecular intersystem crossing into pentacene's triplet ground state. When configured as an oscillator, the solid-state maser's measured output power of around -10 decibel milliwatts is approximately 100 million times greater than that of an atomic hydrogen maser, which oscillates at a similar frequency (about 1.42 gigahertz). By exploiting the high levels of spin polarization readily generated by intersystem crossing in photo-excited pentacene and other

  6. 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.

  7. Temperature-Control Apparatus For Hydrogen Maser

    NASA Technical Reports Server (NTRS)

    Vessot, R. F. C.; Mattison, E. M.

    1994-01-01

    Thermal-control apparatus maintains hydrogen maser at nearly constant temperature during long-term operational test. Designed to maintain, in small cylindrical vacuum tank containing maser, nearly isothermal condition when test conducted in air. Provides approximation of more nearly isothermal condition expected to be maintained in intended application, in which maser operated in vacuum environment and losses of heat reduced further by multilayer reflective insulation.

  8. 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.

  9. Design of a tunable 4-MW Free Electron Maser for heating fusion plasmas

    SciTech Connect

    Caplan, M.; Kamin, G.; Shang, C.C.; Lindquist, W.

    1993-09-01

    There is an ongoing program at the FOM institute, The Netherlands, to develop a 1-MW, long-pulse, 200-Ghz Free Electron Maser (FEM) using a DC accelerator system with depressed collector. We present an extrapolation of this design to more than 4MW of output microwave power in order to reduce the cost per kW and increase the power per module in a plasma heating system.

  10. SiO Maser Emission in Miras

    DTIC Science & Technology

    2008-09-01

    Mon. Not. R. Astron. Soc. 394, 51–66 (2009) doi:10.1111/j.1365-2966.2008.14237.x SiO maser emission in Miras M. D. Gray,1 M. Wittkowski,2 M. Scholz...October 27; in original form 2008 September 1 ABSTRACT We describe a combined dynamic atmosphere and maser propagation model of SiO maser emission in...brightest at an optical phase of 0.1–0.25, which is consistent with observed phase lags. Dust can have both mild and profound effects on the maser emission

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Hydrogen maser oscillation at 10 K

    NASA Technical Reports Server (NTRS)

    Crampton, S. B.; Jones, K. M.; Souza, S. P.

    1984-01-01

    A low temperature atomic hydrogen maser was developed using frozen atomic neon as the storage surface. The maser has been operated in the pulsed mode at temperatures from 6 K to 11 K and as a self-excited oscillator from 9 K to 10.5 K.

  17. First experiences with the H-maser EFOS 1

    NASA Technical Reports Server (NTRS)

    Schlueter, W.; Nottarp, K.; Feil, D.; Busca, G.

    1983-01-01

    The results are given on the performance measurements, on the dependence on external temperature, and on external magnetic field of a hydrogen maser. It is compared with another hydrogen maser. Details of the transportation and installation of the maser are given. The hydrogen maser frequency is compared with cesium oscillators to derive long-term behavior.

  18. Low-noise receivers: Microwave maser development

    NASA Technical Reports Server (NTRS)

    Quinn, R.; Wiebe, E. R.

    1977-01-01

    An S-Band traveling-wave maser with a 2260- to 2400-MHz tuning capability has been built and installed on the 26-m antenna. The traveling-wave maser closed cycle refrigerator package was assembled within a limited time schedule and at low cost to meet the requirements of the very long baseline interferometry validation task. The maser uses a superconducting magnet with a field staggering coil for gain/bandwidth adjustment. The maser pump source is a Gunn effect oscillator with the capability of continuous tuning throughout the entire maser tuning range. The package was assembled from surplus components that have been used previously in the Deep Space Network in a variety of applications.

  19. A kind of small hydrogen maser for time-keeping

    NASA Technical Reports Server (NTRS)

    Zhai, Z. C.; Lin, C. F.; He, J. W.; Huang, H. X.; Lu, J. F.

    1992-01-01

    A kind of small hydrogen maser standard for timekeeping is being developed at Shanghai Observatory. The maser employs a cylindrical capacitively loaded cavity construction, resulting in significant size and weight reduction compared to a traditional hydrogen maser. The Q of the compact cavity is electronically enhanced by a suitable positive feedback into the cavity to enable sustained maser oscillation. The long-term stability of the maser is improved by a cavity frequency stabilization servo-system. The design and development of the maser, as well as photographs of the new maser system during the construction phase are described.

  20. 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 (VLBI Exploration of Radio Astrometry) multi-epoch VLBI (very long baseline interferometry) 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 time-scales of ˜1000 yr.

  1. 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.

  2. ON THE NUCLEAR OBSCURATION OF H{sub 2}O MASER GALAXIES

    SciTech Connect

    Zhang, J. S.; Guo, Q.; Wang, H. G.; Fan, J. H.; Henkel, C.

    2010-01-10

    To shed light onto the circumnuclear environment of 22 GHz ({lambda} {approx} 1.3 cm) H{sub 2}O maser galaxies, we have analyzed some of their multiwavelength properties, including the far-infrared luminosity (FIR), the luminosity of the [O{sub III}]{lambda}5007 emission line, the nuclear X-ray luminosity, and the equivalent width (EW) of the neutral iron K{alpha} emission line (EW (K{sub {alpha}})). Our statistical analysis includes a total of 85 sources, most of them harboring an active galactic nucleus (AGN). There are strong anticorrelations between EW (K{sub {alpha}}) and two 'optical thickness parameters', i.e., the ratios of the X-ray luminosity versus the presumably more isotropically radiated [O{sub III}] and FIR luminosities. Based on these anticorrelations, a set of quantitative criteria, EW (K{sub {alpha}})>300 eV, L{sub 2-10keV}<2L{sub [O{sub III}]}, and L{sub FIR}>600 L{sub 2-10{sub keV}} can be established for Compton-thick nuclear regions. Eighteen H{sub 2}O maser galaxies belong to this category. There are no obvious correlations between the EW (K{sub a}lpha), the [O{sub III}] luminosity, and the isotropic H{sub 2}O maser luminosity. When comparing samples of Seyfert 2s with and without detected H{sub 2}O maser lines, there seem to exist differences in EW (K{sub {alpha}}) and the fraction of Compton-thick nuclei. This should be studied further. For AGN masers alone, there is no obvious correlation between FIR and H{sub 2}O maser luminosities. However, including masers associated with star-forming regions, a linear correlation is revealed. Overall, the extragalactic FIR-H{sub 2}O data agree with the corresponding relation for Galactic maser sources, extrapolated by several orders of magnitude to higher luminosities.

  3. The Circumstellar Environment of Evolved Stars as Revealed by Studies of Circumstellar Water Masers

    NASA Astrophysics Data System (ADS)

    Marvel, K.

    1997-11-01

    This dissertation presents the results of a multi-epoch very long baseline interferometric (VLBI) study of water masers located in the extended atmospheres of seven evolved stars. The research was performed using the Very Long Baseline Array and Very Large Array of the National Radio Astronomy Observatory. Water masers are found to exist in the atmospheres of evolved, oxygen-rich stars where a population inversion of the rotational transition at 22 GHz can be maintained by collisional pumping. The masers are identified as individual pockets or filaments of gas, which have good velocity coherence and may be imaged using radio interferometry. Stellar winds are initiated in these sources by dust formation and acceleration of the gas through momentum coupling. The typical wind speeds in the region of the water masers are 10 to 20 \\kms. The water masers in several evolved stars (VY CMa, VX Sgr, S Per, U Her, IK Tau, RX Boo and NML Cyg) have been observed at three epochs and exhibit proper motions consistent with the assumed source distances and the measured outflow velocity in the water maser region. Estimates of the distance to the sources using statistical approximation are in agreement with the currently accepted distances to the stars. The following stars had reliable distances determined using proper motion data: S Per (2.3 +/- 0.5 kpc), VY CMa (1.4 +/- 0.2 kpc), VX Sgr (1.4 +/- 0.3 kpc). An upper limit for the distance of NML Cyg was obtained ( 3.5 kpc). The remaining stars had too few maser detections (RX BOO, IK Tau) or were not strong enough at all epochs (U Her) to self-calibrate using the VLBA. A detailed kinematic model was used to describe the flow motions of the gas in the maser region. The regions are found to be complex and not well modeled by uniform radial outflow, radial outflow with rotation, or radial outflow with acceleration. The reasons for this are explored and include the probable presence of anisotropic velocity fields induced through non

  4. VizieR Online Data Catalog: 22GHz observations of VX Sgr (Murakawa+, 2003)

    NASA Astrophysics Data System (ADS)

    Murakawa, K.; Yates, J. A.; Richards, A. M. S.; Cohen, R. J.

    2012-07-01

    The 22-GHz H2O maser emission from VX Sgr was observed on 1994 26 and 1999 January 16 for 5 and 7hr, respectively, in both left and right circular polarization, using 5 antennas of MERLIN. (3 data files).

  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. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Operational parameters for the superconducting cavity maser

    NASA Astrophysics Data System (ADS)

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

    1989-05-01

    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. 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.

  13. Water Masers Outburst in the Massive Stellar Cluster W49A

    NASA Astrophysics Data System (ADS)

    Kramer, Busaba H.; Menten, Karl M.; Kamiński, Tomasz; Zhang, Bo; Patel, Nimesh A.; Kraus, Alex

    2017-03-01

    We report a multi-wavelength study of a recent major flare (~ 80,000 Jy at V LSR ~ -98.1 km s-1) of the 22-GHz water maser in W49A. In February 2014, we started monthly monitoring with the Effelsberg 100-m radio telescope. In May 2014, we carried out the nearly simultaneous observations of the 22-GHz transition with selected submillimeter water transitions using the IRAM 30-m telescope (at 183 GHz) and the Atacama Pathfinder Experiment (APEX) 12-m telescope (from 321 to 475 GHz). We have also performed interferometric observations using the NRAO Very Long Baseline Array (VLBA) at 22 GHz and the Submillimeter Array (SMA) at 321 and 325 GHz. One remarkable result is the detection of very high velocity emission features in several transitions. Our data also represent its first detection of the 475-GHz water transition in a star-forming region. Studying these multiple masing transitions in conjunction with theoretical modeling of their excitation not only places strong constraints on the physical conditions of the masing gas but also allows us to study their association with the embedded massive stellar cluster in W49A.

  14. 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.

  15. 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.

  16. Resonant isolator for maser amplifier

    NASA Technical Reports Server (NTRS)

    Clauss, R. C.; Quinn, R. B. (Inventor)

    1983-01-01

    An isolator is described for use in a low noise maser amplifier, which provides low loss across a wide bandwidth and which can be constructed at moderate cost. The isolator includes a train of garnet or ferrite elements extending along the length of a microwave channel parallel to the slow wave structure, with the elements being of staggered height, so that the thin elements which are resonant to the microwaves are separated by much thicker elements. The thick garnet or ferrite elements reduce the magnetic flux passing through the thin elements to permit altering of the shape of the thin elements so as to facilitate their fabrication and to provide better isolation with reduced loss, by increasing the thickness of the thin elements and decreasing their length and width.

  17. External bulb variable volume maser

    NASA Technical Reports Server (NTRS)

    Reinhardt, V. S.; Cervenka, P. O. (Inventor)

    1978-01-01

    A maser functioning as a frequency standard stable to one part in 10 to the 14th power includes a variable volume, constant surface area storage bulb having a fixed volume portion located in a resonant cavity from which the frequency standard is derived. A variable volume portion of the bulb, exterior to the resonant cavity, has a maximum volume on the same order of magnitude as the fixed volume bulb portion. The cavity has a length to radius ratio of at least 3:1 so that the operation is attained without the need for a feedback loop. A baffle plate, between the fixed and variable volume bulb portions, includes apertures for enabling hydrogen atoms to pass between the two bulb portions and is an electromagnetic shield that prevents coupling of the electromagnetic field of the cavity into the variable volume bulb portion.

  18. EVOLUTION OF THE WATER MASER EXPANDING SHELL IN W75N VLA 2

    SciTech Connect

    Kim, Jeong-Sook; Kim, Sang Joon; Kim, Soon-Wook; Kurayama, Tomoharu; Honma, Mareki; Sasao, Tesuo; Surcis, Gabriele; Canto, Jorge; Torrelles, Jose M. E-mail: skim@kasi.re.kr

    2013-04-10

    We present Very Long Baseline Interferometry (VLBI) observations of 22 GHz H{sub 2}O masers in the high-mass star-forming region of W75N, carried out with VLBI Exploration of Radio Astrometry (VERA) for three epochs in 2007 with an angular resolution of {approx}1 mas. We detected H{sub 2}O maser emission toward the radio jet in VLA 1 and the expanding shell-like structure in VLA 2. The spatial distribution of the H{sub 2}O masers detected with VERA and measured proper motions around VLA 1 and VLA 2 are similar to those found with previous VLBI observations in epochs 1999 and 2005, with the masers in VLA 1 mainly distributed along a linear structure parallel to the radio jet and, on the other hand, forming a shell-like structure around VLA 2. We have made elliptical fits to the VLA 2 H{sub 2}O maser shell-like structure observed in the different epochs (1999, 2005, and 2007), and found that the shell is still expanding eight years after its discovery. From the difference in the size of the semi-major axes of the fitted ellipses in epochs 1999 ({approx_equal}71 {+-} 1 mas), 2005 ({approx_equal}97 {+-} 3 mas), and 2007 ({approx_equal}111 {+-} 1 mas), we estimate an average expanding velocity of {approx}5 mas yr{sup -1}, similar to the proper motions measured in the individual H{sub 2}O maser features. A kinematic age of {approx}20 yr is derived for this structure. In addition, our VERA observations indicate an increase in the ellipticity of the expanding shell around VLA 2 from epochs 1999 to 2007. In fact, the elliptical fit of the VERA data shows a ratio of the minor and major axes of {approx}0.6, in contrast with an almost circular shape for the shell detected in 1999 and 2005 (b/a {approx} 0.9). This suggests that we are probably observing the formation of a jet-driven H{sub 2}O maser structure in VLA2, evolving from a non-collimated pulsed-outflow event during the first stages of evolution of a massive young stellar object (YSO). This may support predictions made

  19. 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.

  20. 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.

  1. Extrapolation of the FOM 1MW free electron maser to a multi-megawatt millimeter microwave source

    SciTech Connect

    Caplan, M.; Valentini, M.; Verhoeven, A.; Urbanus, W.; Tulupov, A.

    1996-12-01

    A Free Electron Maser is now under test at the FOM Institute (Rijnhuizen) Netherlands with the goal of producing 1 MW long pulse to CW microwave output in the range 130 GHz to 250 GHz with wall plug efficiencies of 60%. An extrapolated version of this device is proposed, which would produce microwave power levels of up to 5 MW CW. This would allow for practical applications in such diverse areas as space power beaming, heating of fusion plasmas and hearing of high Mach number wind tunnels.

  2. Radio continuum of galaxies with H2O megamaser disks: 33 GHz VLA data

    NASA Astrophysics Data System (ADS)

    Kamali, F.; Henkel, C.; Brunthaler, A.; Impellizzeri, C. M. V.; Menten, K. M.; Braatz, J. A.; Greene, J. E.; Reid, M. J.; Condon, J. J.; Lo, K. Y.; Kuo, C. Y.; Litzinger, E.; Kadler, M.

    2017-09-01

    Context. Galaxies with H2O megamaser disks are active galaxies in whose edge-on accretion disks 22 GHz H2O maser emission has been detected. Because their geometry is known, they provide a unique view into the properties of active galactic nuclei. Aims: The goal of this work is to investigate the nuclear environment of galaxies with H2O maser disks and to relate the maser and host galaxy properties to those of the radio continuum emission of the galaxy. Methods: The 33 GHz (9 mm) radio continuum properties of 24 galaxies with reported 22 GHz H2O maser emission from their disks are studied in the context of the multiwavelength view of these sources. The 29-37 GHz Ka-band observations are made with the Karl Jansky Very Large Array in B, CnB, or BnA configurations, achieving a resolution of 0.2-0.5 arcsec. Hard X-ray data from the Swift/BAT survey and 22 μm infrared data from WISE, 22 GHz H2O maser data and 1.4 GHz data from NVSS and FIRST surveys are also included in the analysis. Results: Eighty-seven percent (21 out of 24) galaxies in our sample show 33 GHz radio continuum emission at levels of 4.5-240σ. Five sources show extended emission (deconvolved source size larger than 2.5 times the major axis of the beam), including one source with two main components and one with three main components. The remaining detected 16 sources (and also some of the above-mentioned targets) exhibit compact cores within the sensitivity limits. Little evidence is found for extended jets (>300 pc) in most sources. Either they do not exist, or our chosen frequency of 33 GHz is too high for a detection of these supposedly steep spectrum features. In NGC 4388, we find an extended jet-like feature that appears to be oriented perpendicular to the H2O megamaser disk. NGC 2273 is another candidate whose radio continuum source might be elongated perpendicular to the maser disk. Smaller 100-300 pc sized jets might also be present, as is suggested by the beam-deconvolved morphology of our

  3. Outward Motions of SiO Masers around VX Sgr

    NASA Astrophysics Data System (ADS)

    Su, J. B.; Shen, Z.-Q.; Chen, X.; Jiang, D. R.

    2014-09-01

    We report the proper motions of SiO maser features around VX Sgr from the two-epoch VLBA observations (2006 December 15 and 2007 August 19). The majority of maser feature activities show a trend of outward motions. It is consistent with our previous finding that the outflow may play an important role for SiO maser pumping.

  4. VizieR Online Data Catalog: 86 and 43GHz observations of NRAO 150 (Agudo+, 2007)

    NASA Astrophysics Data System (ADS)

    Agudo, I.; Bach, U.; Krichbaum, T. P.; Marscher, A. P.; Gonidakis, I.; Diamond, P. J.; Perucho, M.; Alef, W.; Graham, D. A.; Witzel, A.; Zensus, J. A.; Bremer, M.; Acosta-Pulido, J. A.; Barrena, R.

    2008-01-01

    The data set presented here consists of 5 VLBI images at 86GHz taken with the Global mm VLBI Array (GMVA, and its predecessor, the CMVA) covering the time range from October 2001 to April 2004, and 34 Very Long Baseline Array (VLBA) images taken at 43GHz from June 1997 to February 2007. Among these 34 images, 20 obtained from June 1997 to May 2002 were taken as calibration measurements of the SiO maser monitoring program of TX Cam. A new 8.4GHz VLBA image obtained in June 2002 is also presented here. (3 data files).

  5. The magnetic field of IRAS 16293-2422 as traced by shock-induced H2O masers

    NASA Astrophysics Data System (ADS)

    Alves, F. O.; Vlemmings, W. H. T.; Girart, J. M.; Torrelles, J. M.

    2012-06-01

    Context. Shock-induced H2O masers are important magnetic field tracers of very high density gas. Water masers are found in both high- and low-mass star-forming regions, and are a powerful tool for comparing magnetic field morphologies in both mass regimes. Aims: We present one of the first magnetic field determinations for the low-mass protostellar core IRAS 16293-2422 at volume densities as high as 108-10 cm-3. Our goal is to determine wether the collapsing regime of this source is controlled by magnetic fields or other factors such as turbulence. Methods: We used the Very Large Array (VLA) to carry out spectropolarimetric observations of the 22 GHz Zeeman emission from H2O masers. From the Stokes V line profile, we are then able to estimate the magnetic field strength in the dense regions around the protostar. Results: A blend of at least three maser features can be inferred from our relatively high spatial resolution data set (~0.1''), which is reproduced as a clear non-Gaussian line profile. The emission is very stable in terms of polarization fraction and position angle across the channels. The maser spots are aligned with some components of the complex outflow configuration of IRAS 16293-2422, and are excited in zones of compressed gas produced by shocks. The post-shock particle density is in the range of 1-3 × 109 cm-3, consistent with typical water-maser pumping densities. Zeeman emission is produced by a very strong line-of-sight magnetic field (B ~ 113 mG). Conclusions: The magnetic field pressure derived from our data is comparable to the ram pressure of the outflow dynamics. This indicates that the magnetic field is energetically important to the dynamical evolution of IRAS 16293-2422.

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

    NASA Astrophysics Data System (ADS)

    Tokumaru, Munetoshi; Yamauchi, Yohei; Kondo, Tetsuro

    2001-03-01

    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 (Rs) 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.

  7. 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.

  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 (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.

  9. 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.

  10. Flexible bulb large storage box hydrogen maser

    NASA Technical Reports Server (NTRS)

    Reinhardt, V.

    1973-01-01

    The principal limitation on the accuracy of the hydrogen maser as a primary frequency standard has been the irreproducibility of the frequency shift caused by collisions of the radiating atoms with the walls of the vessel containing them. The flexible bulb-large storage box hydrogen maser allows correction for this wall shift within a single device, sidestepping the reproducibility problem, and reducing the frequency error from the wall shift to the level imposed by the device's stability. The principles of the device are discussed including the flexible bulb technique and the complications caused by a multiple region storage bulb. The stability of the device is discussed including a comparison with an ordinary hydrogen maser. Data is presented from a working flexible bulb-large storage box hydrogen maser demonstrating the feasibility of the device and showing some of its operating characteristics. The flexibility of the device is demonstrated by showing how the device's added degrees of freedom allow measurement of parameters unmeasurable in an ordinary hydrogen maser.

  11. Cryogenic masers. [frequency stability and design parameters

    NASA Technical Reports Server (NTRS)

    Berlinsky, A. J.; Hardy, W. N.

    1982-01-01

    Various factors affecting the frequency stability of hydrogen masers are described and related to maser design parameters. The long-term frequency stability of a hydrogen maser is limited by the mechanical stability of the cavity, and the magnitudes of the wall relaxation, spin exchange, and recombination rates which affect the Q of the line. Magnetic resonance studies of hydrogen atoms at temperatures below 1 K and in containers coated with liquid helium films demonstrated that cryogenic masers may allow substantial improvements in all of these parameters. In particular the thermal expansion coefficients of most materials are negligible at 1 K. Spin exchange broadening is three orders of magnitude smaller at 1 K than at room temperature, and the recombination and wall relaxation rates are negligible at 0.52 K where the frequency shift due to the 4 He-coated walls of the container has a broad minimum as a function of temperature. Other advantages of the helium-cooled maser result from the high purity, homogeneity, and resilence of helium-film-coated walls and the natural compatibility of the apparatus with helium-cooled amplifiers.

  12. Quantum-Chemical Calculations Revealing the Effects of Magnetic Fields on Methanol

    NASA Astrophysics Data System (ADS)

    Lankhaar, Boy; van der Avoird, Ad; Vlemmings, Wouter H. T.; Groenenboom, Gerrit; van Langevelde, Huib Jan; Surcis, Gabriele

    2017-06-01

    Maser observations of both linear and circular emission have provided unique information on the magnetic field in the densest regions of star forming regions. While linear polarization observations provide morphological constraints, the magnetic field strength determination is done by comparing the Zeeman-induced velocity shifts between left- and right-circularly polarized emission of molecular maser species. Soon, full-polarization observations with be possible with ALMA, making magnetic field measurements with unprecedented spatial resolution possible. In particular, methanol is of special interest as it is the most abundant maser species and its different transitions probe unique areas of high-mass proto-stellar disks and outflows. However, its exact Zeeman-parameters are unknown. Experimental efforts to determine the Zeeman-parameters have failed. Here we present quantum chemical calculations to the Zeeman-parameters of methanol, along with calculations to the hyperfine structure, which are also necessary to interpret the Zeeman effect in methanol. We present the proper treatment of the torsional motion in computing hyperfine and Zeeman effects. Our results on the hyperfine structure show good agreement with recent experimental data. We find that the Zeeman-effect in methanol is non-linear and comment on its applicability in astronomical magnetic field studies. We give an outlook on rigorously treating non-linear Zeeman effects in radiative transfer modeling of maser-species interacting with a magnetic field.

  13. 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.

  14. Molecular masers as tracers of early stellar evolution

    NASA Astrophysics Data System (ADS)

    Strel'Nitskii, V. S.

    The discovery, observation, and interpretation of molecular masers in regions of active star formation are discussed. OH masers noted in these regions are the product of the disintegration of dense molecular envelopes surrounding compact H-II regions of young OB stars, and they typically have densities of about 10 to the 6th/cu cm and temperatures of about 100 K. H2O masers are connected with still earlier stages of stellar evolution, and are located closer to their parent stars than the OH sources. Strong CH3OH 2.5-cm masers are closely associated with OH masers.

  15. ALMA sub-mm maser and dust distribution of VY Canis Majoris

    NASA Astrophysics Data System (ADS)

    Richards, A. M. S.; Impellizzeri, C. M. V.; Humphreys, E. M.; Vlahakis, C.; Vlemmings, W.; Baudry, A.; De Beck, E.; Decin, L.; Etoka, S.; Gray, M. D.; Harper, G. M.; Hunter, T. R.; Kervella, P.; Kerschbaum, F.; McDonald, I.; Melnick, G.; Muller, S.; Neufeld, D.; O'Gorman, E.; Parfenov, S. Yu.; Peck, A. B.; Shinnaga, H.; Sobolev, A. M.; Testi, L.; Uscanga, L.; Wootten, A.; Yates, J. A.; Zijlstra, A.

    2014-12-01

    Aims: Cool, evolved stars have copious, enriched winds. Observations have so far not fully constrained models for the shaping and acceleration of these winds. We need to understand the dynamics better, from the pulsating stellar surface to ~10 stellar radii, where radiation pressure on dust is fully effective. Asymmetric nebulae around some red supergiants imply the action of additional forces. Methods: We retrieved ALMA Science Verification data providing images of sub-mm line and continuum emission from VY CMa. This enables us to locate water masers with milli-arcsec accuracy and to resolve the dusty continuum. Results: The 658, 321, and 325 GHz masers lie in irregular, thick shells at increasing distances from the centre of expansion. For the first time this is confirmed as the stellar position, coinciding with a compact peak offset to the NW of the brightest continuum emission. The maser shells overlap but avoid each other on scales of up to 10 au. Their distribution is broadly consistent with excitation models but the conditions and kinematics are complicated by wind collisions, clumping, and asymmetries. Appendices are available in electronic form at http://www.aanda.org

  16. Observations of water maser sources at Arcetri

    NASA Astrophysics Data System (ADS)

    Comoretto, Giovanni; Valdettaro, Riccardo; Palla, Francesco; Brand, Jan; Cesaroni, Riccardo; Felli, Marcello; Natale, Enzo; Palagi, Francesco; Panella, Dario; Tofani, Gianni

    We present the current activity of the Arcetri group in the field of water masers. This is mainly represented by observations with the Medicina radiotelescope, whose main outcome has been the compilation of the Arcetri Catalog and the study of time variability of selected sources. The Arcetri Catalog update reports the results of the observations carried out from January 1993 to April 2000 on a sample of 300 sources. The global properties of the complete Arcetri Catalog (including Comoretto et al. 1990, and Brand et al. 1994) are discussed. Of the 1013 sources, 937 have an IRAS counterpart within 1 arcmin from the nominal position of the maser. We establish a classification scheme based on the IRAS flux densities which allows to distinguish between water masers associated with star forming regions and late-type stars. The time variability study shows a large variety of behaviors. Generally more luminous sources present less variable emission and spectral components over a wider velocity range.

  17. Stability limit of the cryogenic hydrogen maser

    SciTech Connect

    Maan, A.C.; Stoof, H.T.C.; Verhaar, B.J. ); Mandel, P. )

    1990-05-28

    It is pointed out that the usual oscillation condition of the H maser is only a necessary condition for steady operation. Reducing the coupled field-matter dynamics to the complex Lorenz equations we derive a second requirement which together with the first forms a set of necessary and sufficient conditions for the steady operation to be stable. The instability of the steady state predicted by the equations should be easily accessible experimentally for the cryogenic H maser. It will be characterized by a pulsed output power which, depending on the detuning, is either periodic or chaotic.

  18. 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.

  19. VLA positions and distributions of H2O masers associated with 15 Mira and semiregular variables

    NASA Astrophysics Data System (ADS)

    Bowers, P. F.; Johnston, K. J.

    1994-05-01

    Results of VLA observations of 22 GHz H2O masers associated with 15 Mira and semiregular variables are reported. The combination of angular resolution (approximately equals 70 mas), spectral resolution (0.3 km/sec), rms sensitivity (+/- 35 mJy/beam), and hour-angle coverage is the best yet obtained for H2O masers from a significant sample of stars. Comparison of accurate optical positions of the stars with estimates from the masers yields total differences typically less than or equal to 0 sec .15-an improvement over previous comparisons by a factor of about 2. There are indications of some combination of nonuniformities in the density distribution, deviations from sphericity, and anisotropies in the velocity field, but it is difficult to disentangle the effects of these phenomena and achieve unique interpretation. A plausible model is clumps or filaments distributed at radii which vary with direction from the star. From the angular distributions and velocity ranges, there is good evidence that at least some parcels of gas are accelerated to the terminal outflow velocity at rho greater than or equal to 20 AU and that there is a component of outflow at rho approximately equals 10 to 15 AU; some gas probably is fully accelerated at radii less than 10 AU. To illustrate the problems of interpretation, the well-known case of VX Sgr is reexamined. The data do not support a simple model of increasing outflow velocity with increasing maser shell radius. It is proposed that the outflow is weakly bipolar.

  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. 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.

  2. Performance Of Superconducting-Cavity Maser

    NASA Technical Reports Server (NTRS)

    Dick, G. John; Wang, Rabi T.

    1991-01-01

    Report describes experiments on operation of superconducting-cavity maser - all-cryogenic oscillator. Operates with degree of stability, at short measuring times, superior to that achievable by any other means. All components designed for cryogenic operation and stabilizing cavity very rigid, consisting of sapphire filling coated with lead.

  3. W43A: a Maverick Maser Source

    NASA Astrophysics Data System (ADS)

    Diamond, P. J.; Nyman, L. Å.

    The authors report on some preliminary results from a multi-epoch monitoring project of the OH and H2O masers in the source W43A. Their results suggest that W43A is a very young stellar object which has just entered a strong stellar wind stage.

  4. 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

  5. Report on the Special Hydrogen Maser Workshop

    NASA Technical Reports Server (NTRS)

    Morris, Derek

    1990-01-01

    This workshop was held as a discussion forum for hydrogen maser problems, particularly for those related to wall shift and wall relaxation effects. Brief summaries of the presentations made by the speakers together with some of the discussion that followed are given. These summaries were derived from tape recordings of the session and from notes.

  6. A different type of maser star

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    A systematic survey of short-period, semiregular variable stars has been made resulting in the detection of six new water masers. Of the 14 short-period maser stars now known, nine are classified as SRb variables. All are very late spectral type SRb's, typically M7, while the overwhelming majority of normal SRb stars is M4 to M6. Their 2.2-11 micron color indices are among the lowest of any known maser stars. They are presumably less dusty as well. Four of the SRb stars and two of the remainder do not obey the correlation between period and velocity spread of the emission features that is found for the Mira and long-period, semiregular variables. Finally, high galactic latitudes dominate; 13 of the 14 are in excess of 13 deg, and nine of these are greater than 25 deg. These facts suggest that the short-period semiregular variables - particularly in SRb stars - may be a very different type of maser star than the Mira and long-period semiregular variables.

  7. MICROWAVE AND OPTICAL MASERS FOR MM WAVES

    DTIC Science & Technology

    associated cryogenic equipment. Preliminary study of the lattice absorption spectrum of CaWO4, CaMoO4 and PbMoO4 is presented. A possible 5 micron optical maser transition in the CaWO4:Nd(3) system is evaluated.

  8. Report on the Special Hydrogen Maser Workshop

    NASA Astrophysics Data System (ADS)

    Morris, Derek

    1990-05-01

    This workshop was held as a discussion forum for hydrogen maser problems, particularly for those related to wall shift and wall relaxation effects. Brief summaries of the presentations made by the speakers together with some of the discussion that followed are given. These summaries were derived from tape recordings of the session and from notes.

  9. ABUNDANT CH{sub 3}OH MASERS BUT NO NEW EVIDENCE FOR STAR FORMATION IN GCM0.253+0.016

    SciTech Connect

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

    2015-05-20

    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{sup −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 NH{sub 3}–(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6), (7, 7), and (9, 9), as well as the HC{sub 3}N (3–2) and (4–3) lines, and CH{sub 3}OH 4{sub −1}–3{sub 0}, the latter of which is known to be a collisionally excited maser. We identify 148 CH{sub 3}OH 4{sub −1}–3{sub 0} (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 H{sub 2}O maser.

  10. 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.

  11. 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).

  12. Broadband terahertz-power extracting by using electron cyclotron maser.

    PubMed

    Pan, Shi; Du, Chao-Hai; Qi, Xiang-Bo; Liu, Pu-Kun

    2017-08-04

    Terahertz applications urgently require high performance and room temperature terahertz sources. The gyrotron based on the principle of electron cyclotron maser is able to generate watt-to-megawatt level terahertz radiation, and becomes an exceptional role in the frontiers of energy, security and biomedicine. However, in normal conditions, a terahertz gyrotron could generate terahertz radiation with high efficiency on a single frequency or with low efficiency in a relatively narrow tuning band. Here a frequency tuning scheme for the terahertz gyrotron utilizing sequentially switching among several whispering-gallery modes is proposed to reach high performance with broadband, coherence and high power simultaneously. Such mode-switching gyrotron has the potential of generating broadband radiation with 100-GHz-level bandwidth. Even wider bandwidth is limited by the frequency-dependent effective electrical length of the cavity. Preliminary investigation applies a pre-bunched circuit to the single-mode wide-band tuning. Then, more broadband sweeping is produced by mode switching in great-range magnetic tuning. The effect of mode competition, as well as critical engineering techniques on frequency tuning is discussed to confirm the feasibility for the case close to reality. This multi-mode-switching scheme could make gyrotron a promising device towards bridging the so-called terahertz gap.

  13. 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

  14. [Weak coherent radiation of OH and ortho- H2O space masers as a carrier in biocommunication: the ortho/para-conversion of H2O spin isomers?].

    PubMed

    Pershin, S M

    2010-01-01

    A conception of biocommunication based on the principle of radiophysics stating that the carrier modulation takes place at the resonance frequency in the transmission-receiver system has been substantiated and proved. The coherent radiation of space OH-masers (1.6-1.7 GHz) and ortho-H2O-maser (22.3 GHz) is proposed as a source of the carrier frequency. The narrow lines of rotational transition of H2O and OH molecules in liquid water were proposed to be considered as an analog of selective resonances of transmitter and receiver in radiocommunication. The possibility of the ortho-para conversion of H2O spin isomers, induced by weak electromagnetic fields, is discussed.

  15. Ground-state OH maser distributions in the Galactic Centre region

    NASA Astrophysics Data System (ADS)

    Qiao, Hai-Hua; Walsh, Andrew J.; Shen, Zhi-Qiang; Dawson, Joanne R.

    2017-01-01

    Ground-state OH masers identified in the Southern Parkes Large-Area Survey in Hydroxyl were observed with the Australia Telescope Compact Array to obtain positions with high accuracy (~1 arcsec). We classified these OH masers into evolved star OH maser sites, star formation OH maser sites, supernova remnant OH maser sites, planetary nebula OH maser sites and unknown maser sites using their accurate positions. Evolved star and star formation OH maser sites in the Galactic Centre region (between Galactic longitudes of -5° to +5° and Galactic latitudes of -2° and +2°) were studied in detail to understand their distributions.

  16. Atomic Velocity Distributions Out of Hydrogen Maser Dissociators

    DTIC Science & Technology

    1990-02-15

    REPORT SSD-TR-90-02 10 Atomic Velocity Distributions Out of Hydrogen 0’) Maser Dissociators B. JADUSZLIWER and Y. C. CHAN Chemistry and Physics...Maser Dissociators 12 PERSONAL AUTHOP4S) Jaduszliwer, B.; and Chan, Y. C. 13a. TYPE OF REPORT 13b. TIME COVERED 14. DATE OF REPORT (ba, AMa, Day) 15...number) FIELD GROUP SUB-GROUP _...Atomic clocks Hydrogen maser; Hydrogen dissociator ; Velocity distributions. K .-K / - 19. ABSTRACT (Contum on reverse

  17. Atomic Velocity Distributions Out of Hydrogen Maser Dissociators

    DTIC Science & Technology

    1989-11-01

    ATOMIC VELOCITY DISTRIBUTIONS OUT OF HYDROGEN MASER DISSOCIATORS Bernardo Jaduszliwer and Yat C. Chan Chemistry and Physics Laboratory The... dissociators , of the type used in hydrogen masers. This work was moti- vated by lang-term reliability issues related to the possible usc of masers as...hydrogen budgct will depend not only on the dissoci - ation efficiency, but also the vclocity distribution of the hydrogen atorrls leaving the

  18. Radiative Instabilities in Three-Dimensional Astrophysical Masers

    NASA Technical Reports Server (NTRS)

    Scappaticci, Gerardo A.; Watson, William D.

    1995-01-01

    Inherent instabilities in the radiative transfer for astrophysical masers have been recognized and calculated in the linear maser idealization in our previous investigations. The same instabilities are now shown to occur in the more realistic, three-dimensional geometries. Fluctuations in the emergent flux result and may be related to the observed fluctuations in the radiative flux from the 1665 MHz OH masers that have been reported to occur on timescales as short as 1000 s. The time-dependent differential equations of radiative transfer are solved numerically for three-dimensional astrophysical masers. Computations are performed for spherical and elongated (rectangular parallelepiped) geometries.

  19. Survey of Outer Galaxy Molecular Lines Associated with Water Masers

    NASA Astrophysics Data System (ADS)

    Mochizuki, N.; Hachisuka, K.; Umemoto, T.

    2009-08-01

    H_2O masers in Young stellar objects (YSOs) in our Galaxy are one of the targets of the VSOP-2 science. The advantage of VSOP-2 observation is the highest angular resolution which can detect a proper motion of H_2O masers for distant objects over short time intervals. To find candidate sources, we observed H2O maser sources in the outer Galaxy using the VLA, and we surveyed the molecular lines toward these sources to understand the environment of YSOs. Higher H2 column densities of YSOs were found for objects with active H2O masers.

  20. 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.

  1. 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

  2. VizieR Online Data Catalog: Water masers in M31. I. Recombination lines (Darling+, 2016)

    NASA Astrophysics Data System (ADS)

    Darling, J.; Gerard, B.; Amiri, N.; Lawrence, K.

    2016-09-01

    We constructed a catalog of 506 unresolved 24um sources from the Spitzer 24um map of M31 (Gordon et al. 2006ApJ...638L..87G); see Figure 1. Darling (2011ApJ...732L...2D) observed 206 24um sources in M31 using the Green Bank Telescope (GBT) in 2010 October through December. The 616-523 22.23508GHz ortho-water maser line observations were reported in Darling (2011ApJ...732L...2D), but simultaneous observations of the para-ammonia (NH3) rotational ground-state inversion transitions in the metastable states (J,K)=(1,1) and (2,2) at 23.6945 and 23.72263GHz, respectively, and the hydrogen recombination line H66α at 22.36417GHz were not. We subsequently observed all four of these lines toward an additional 300 24um sources in 2011 October through 2012 January. The resolution of the 24um Spitzer image is 6" (Gordon et al. 2006ApJ...638L..87G), so the unresolved IR sources remained within the 33" GBT beam even during the largest pointing drifts. The 33" beam (FWHM) at 22GHz spans 125pc in M31. (1 data file).

  3. Synchrotron masers and fast radio bursts

    NASA Astrophysics Data System (ADS)

    Ghisellini, G.

    2017-02-01

    Fast radio bursts, with a typical duration of 1 ms and 1 Jy flux density at gigahertz frequencies, have brightness temperatures exceeding 1033 K, requiring a coherent emission process. This can be achieved by bunching particles in volumes smaller than the typical wavelength, but this may be challenging. Maser emission is a possibility. Under certain conditions, the synchrotron-stimulated emission process can be more important than true absorption, and a synchrotron maser can be created. This occurs when the emitting electrons have a very narrow distribution of pitch angles and energies. This process overcomes the difficulties of having extremely dense bunches of particles and relaxes the light-crossing time limits, since there is no simple relation between the actual size of the source and the observed variability time-scale.

  4. Maser Astrometry with VERA and VSOP-2

    NASA Astrophysics Data System (ADS)

    Honma, M.; Bushimata, T.; Choi, Y. K.; Hirota, T.; Imai, H.; Iwadate, K.; Jike, T.; Kameno, S.; Kameya, O.; Kamohara, R.; Kawaguchi, N.; Kijima, M.; Kim, M.; Kobayashi, H.; Kuji, S.; Kurayama, T.; Manabe, S.; Matsui, M.; Matsumoto, N.; Miyaji, T.; Nagayama, T.; Nakagawa, A.; Nakamura, K.; Oh, C. S.; Omodaka, T.; Oyama, T.; Sakai, S.; Sato, K.; Sato, M.; Sasao, T.; Shibata, K. M.; Tamura, Y.; Yamashita, K.

    2009-08-01

    We present recent results of maser astrometry obtained with VERA (VLBI Exploration of Radio Astrometry), which is a Japanese VLBI array dedicated to phase-referencing astrometry to explore the 3-D structure of the Milky Way Galaxy. Since 2004 we have been conducting regular monitoring of maser sources with VERA, and we have already detected parallaxes for several sources, ranging from a few 100 pc to 5 kpc. These results include measurements for Galactic star-forming regions such as ORI-KL, S269, NGC 281 as well as those for late type stars such as VY CMa. We also discuss the VERA---VSOP-2 connection in the near future, and propose astrometric observations with VSOP-2.

  5. OH maser proper motions in Cepheus A

    NASA Astrophysics Data System (ADS)

    Migenes, V.; Cohen, R. J.; Brebner, G. C.

    1992-02-01

    MERLIN measurements made between 1982 and 1989 reveal proper motions of OH masers in the source Cepheus A. The proper motions are typically a few milliarcsec per year, and are mainly directed away from the central H II regions. Statistical analysis of the data suggests an expansion time-scale of some 300 yr. The distance of the source implied by the proper motions is 320+140/-80 pc, assuming that the expansion is isotropic. The proper motions can be reconciled with the larger distance of 730 pc which is generally accepted, provided that the masers are moving at large angles to the line of sight. The expansion time-scale agrees with that of the magnetic field decay recently reported by Cohen, et al. (1990).

  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. 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.

  8. MASER OBSERVATIONS OF WESTERLUND 1 AND COMPREHENSIVE CONSIDERATIONS ON MASER PROPERTIES OF RED SUPERGIANTS ASSOCIATED WITH MASSIVE CLUSTERS

    SciTech Connect

    Fok, Thomas K. T.; Nakashima, Jun-ichi; Yung, Bosco H. K.; Hsia, Chih-Hao; Deguchi, Shuji

    2012-11-20

    We report the results of Australia Telescope Compact Array observations of the Westerlund 1 (Wd1) region in the SiO v = 1, J = 1-0, and H{sub 2}O 6{sub 16}-5{sub 23} maser lines, and we also report the analysis of maser properties of red supergiants (RSGs) associated with six massive clusters including Wd1. The primary purpose of this research is to explore possibilities of using maser emission for investigating the nature of massive clusters and associated RSGs. The SiO v = 1, J = 1-0, and H{sub 2}O 6{sub 16}-5{sub 23} maser lines are detected toward two of four known RSGs in Wd1. The large velocity ranges of maser emission are consistent with the RSG status. RSGs with maser emission tend to exhibit redder log (F {sub 21}/F {sub 12}) and [K-12.13] colors compared to RSGs with no maser emission. The mass-loss rates derived from dust radiative transfer modeling suggest that RSGs with maser emission tend to exhibit larger mass-loss rates compared to RSGs with no maser emission. In an extended sample of 57 RSGs in six massive clusters, detections in the SiO line tend to homogeneously distribute in absolute luminosity L, whereas those in the H{sub 2}O line tend to distribute in a region with large L values.

  9. Maser Observations of Westerlund 1 and Comprehensive Considerations on Maser Properties of Red Supergiants Associated with Massive Clusters

    NASA Astrophysics Data System (ADS)

    Fok, Thomas K. T.; Nakashima, Jun-ichi; Yung, Bosco H. K.; Hsia, Chih-Hao; Deguchi, Shuji

    2012-11-01

    We report the results of Australia Telescope Compact Array observations of the Westerlund 1 (Wd1) region in the SiO v = 1, J = 1-0, and H2O 616-523 maser lines, and we also report the analysis of maser properties of red supergiants (RSGs) associated with six massive clusters including Wd1. The primary purpose of this research is to explore possibilities of using maser emission for investigating the nature of massive clusters and associated RSGs. The SiO v = 1, J = 1-0, and H2O 616-523 maser lines are detected toward two of four known RSGs in Wd1. The large velocity ranges of maser emission are consistent with the RSG status. RSGs with maser emission tend to exhibit redder log (F 21/F 12) and [K-12.13] colors compared to RSGs with no maser emission. The mass-loss rates derived from dust radiative transfer modeling suggest that RSGs with maser emission tend to exhibit larger mass-loss rates compared to RSGs with no maser emission. In an extended sample of 57 RSGs in six massive clusters, detections in the SiO line tend to homogeneously distribute in absolute luminosity L, whereas those in the H2O line tend to distribute in a region with large L values.

  10. 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.

  11. 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.

  12. Hydrogen masers with cavity frequency switching servos

    NASA Technical Reports Server (NTRS)

    Peters, Harry E.; Owings, H. B.; Koppang, Paul A.

    1990-01-01

    The stability of the free-running hydrogen maser is limited by pulling of the unperturbed hydrogen transition frequency due to instability of the cavity resonance frequency. While automatic spin-exchange tuning is in principle the more basic and accurate method, the required beam intensity switching and the long servo time constant result in reduced stability for measuring intervals up to 10(exp 6) seconds. More importantly, the spin-exchange tuning method requires a second stable frequency source as a reference, ideally a second hydrogen maser, to get the best results. The cavity frequency switching servo, on the other hand, has very little effect on the maser short term stability, and is fast enough to correct for cavity drift while maintaining the cavity at the spin-exchange tuned offset required to minimize instability due to beam intensity fluctuations. Not only does the cavity frequency switching servo not require a second stable frequency source, but the frequency reference is the atomic hydrogen radiated beam signal, so that no extra RF connections need be made to the cavity, and externally generated signals that would perturb the hydrogen atom need not be transmitted through the cavity. The operation of the cavity frequency switching stabilization method is discussed and the transient response of the servo and certain other aspects of the technique that have potential for achieving improved basic accuracy are illustrated.

  13. 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.

  14. Method for making methanol

    DOEpatents

    Mednick, R. Lawrence; Blum, David B.

    1986-01-01

    Methanol is made in a liquid-phase methanol reactor by entraining a methanol-forming catalyst in an inert liquid and contacting said entrained catalyst with a synthesis gas comprising hydrogen and carbon monoxide.

  15. Method for making methanol

    DOEpatents

    Mednick, R. Lawrence; Blum, David B.

    1987-01-01

    Methanol is made in a liquid-phase methanol reactor by entraining a methanol-forming catalyst in an inert liquid and contacting said entrained catalyst with a synthesis gas comprising hydrogen and carbon monoxide.

  16. Intermittent maser flare around the high-mass young stellar object G353.273+0.641 - I. Data and overview

    NASA Astrophysics Data System (ADS)

    Motogi, K.; Sorai, K.; Honma, M.; Minamidani, T.; Takekoshi, T.; Akiyama, K.; Tateuchi, K.; Hosaka, K.; Ohishi, Y.; Watanabe, Y.; Habe, A.; Kobayashi, H.

    2011-10-01

    We have performed very long baseline interferometry (VLBI) and single-dish monitoring of 22-GHz H2O maser emission from the high-mass young stellar object G353.273+0.641 with the VLBI Exploration of Radio Astrometry (VERA) and the Tomakamai 11-m radio telescope. Two maser flares have been detected, separated by almost two years. Frequent VLBI monitoring has revealed that the flare activity has been accompanied by structural change of the prominent shock front traced by H2O maser alignments. We have detected only blueshifted emission and all maser features have been distributed within a very small area of 200 × 200 au2, in spite of a wide velocity range (>100 km s-1). The light curve shows notably intermittent variation and suggests that the H2O masers in G353.273+0.641 are excited by an episodic radio jet. The time-scale of ˜2 yr and characteristic velocity of ˜500 km s-1 also support this interpretation. Two isolated velocity components, C50 (-53 ± 7 km s-1) and C70 (-73 ± 7 km s-1), have shown synchronized linear acceleration of the flux-weighted ? values (˜ -5 km s-1 yr-1) during the flare phase. This can be converted to the lower-limit momentum rate of 1.1 × 10-3 M⊙ km s-1 yr-1. The maser properties are quite similar to those of IRAS 20126+4104 especially. This corroborates the previous suggestion that G353.273+0.641 is a candidate high-mass protostellar object. The possible pole-on geometry of the disc-jet system may be suitable for direct imaging of the accretion disc in this case.

  17. Accurate OH Maser Positions from the SPLASH Pilot Region

    NASA Astrophysics Data System (ADS)

    Qiao, Hai-Hua; Walsh, Andrew J.; Green, James A.; Breen, Shari L.; Dawson, J. R.; Ellingsen, Simon P.; Gómez, José F.; Jordan, Christopher H.; Shen, Zhi-Qiang; Lowe, Vicki; Jones, Paul A.

    2016-12-01

    We report on high spatial resolution observations, using the Australia Telescope Compact Array (ATCA), of ground-state OH masers. These observations were carried out toward 196 pointing centers previously identified in the Southern Parkes Large-Area Survey in Hydroxyl (SPLASH) pilot region, between Galactic longitudes of 334° and 344° and Galactic latitudes of ‑2° and +2°. Supplementing our data with data from the MAGMO (Mapping the Galactic Magnetic field through OH masers) survey, we find maser emission toward 175 of the 196 target fields. We conclude that about half of the 21 nondetections were due to intrinsic variability. Due to the superior sensitivity of the followup ATCA observations, and the ability to resolve nearby sources into separate sites, we have identified 215 OH maser sites toward the 175 fields with detections. Among these 215 OH maser sites, 111 are new detections. After comparing the positions of these 215 maser sites to the literature, we identify 122 (57%) sites associated with evolved stars (one of which is a planetary nebula), 64 (30%) with star formation, two sites with supernova remnants, and 27 (13%) of unknown origin. The infrared colors of evolved star sites with symmetric maser profiles tend to be redder than those of evolved star sites with asymmetric maser profiles, which may indicate that symmetric sources are generally at an earlier evolutionary stage.

  18. Coating a Hydrogen-Maser Chamber With CF4

    NASA Technical Reports Server (NTRS)

    Vessot, Robert F. C.; Mattison, Edward

    1987-01-01

    Coating of carbon tetrafluoride formed on interior surface of atomic-hydrogen maser by allowing gas to freeze on surface. New coating enables maser to oscillate down to 26 K; most effective previous coating, fluorinated ethylene/polypropylene (FEP) copolymer allowed oscillation down to about 50 K.

  19. SIMULTANEOUS OBSERVATIONS OF SiO AND H{sub 2}O MASERS TOWARD KNOWN STELLAR SiO MASER SOURCES

    SciTech Connect

    Cho, Se-Hyung; Kim, Jaeheon E-mail: jhkim@kasi.re.kr

    2012-11-01

    We carried out simultaneous observations of four maser lines, SiO v = 1, 2, {sup 29}SiO v = 0, J = 1-0, and H{sub 2}O 6{sub 16}-5{sub 23}, toward 83 known SiO maser sources without H{sub 2}O maser detections using the Korean VLBI Network single dish telescopes. Both SiO and H{sub 2}O masers were detected from 14 sources, resulting in a detection rate of 16.9%. H{sub 2}O maser emission without SiO maser emission was detected from one source. Therefore, H{sub 2}O maser emission was newly detected from 15 sources. SiO maser emission without H{sub 2}O detection was detected from 55 sources, which gives a total SiO maser detection rate of 83.1% when including sources that have both SiO and H{sub 2}O maser emission detected. SiO v = 2 maser emission was detected from nine sources without v = 1 maser detection. The SiO v = 2 maser sources without the v = 1 maser detections need to be investigated, with a large number of v = 2 only maser sources related to the development of dust shells and their evolutionary sequence from asymptotic giant branch (AGB) to post-AGB stars. The average values of the peak and integrated antenna temperature ratios of H{sub 2}O to SiO masers are 0.44 and 0.28 in the 14 sources that have both SiO and H{sub 2}O detections. Observational characteristics of several individual sources are noted and the dependence of the different maser intensity ratios on the stellar phase is discussed. In addition, the observational results of SiO and H{sub 2}O masers are discussed in IRAS two-color diagrams.

  20. 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

  1. Rapid time variations and radiative instabilities of astrophysical masers

    NASA Technical Reports Server (NTRS)

    Scappaticci, Gerardo A.; Watson, William D.

    1992-01-01

    The time-varying intensities are obtained for astrophysical masers that are radiatively unstable. Numerical integrations of the time-dependent, nonlinear equations of radiative transfer are performed with the usual approximation of a linear maser. At long times after changes in the physical conditions, the intensity of maser radiation reaches an asymptotic behavior and oscillates permanently in these idealized calculations with a period that is related to the length of the maser divided by the speed of light. The intensity varies by more than a factor of 10. These intensities depend upon the same four parameters as we originally found to determine the regime for radiative instabilities based on a stability analysis of the steady state. A detailed comparison is made between the predictions of the stability analysis and the time variations of the intensities. Calculations are performed for interacting pairs as well as isolated, individual masers.

  2. Shock-excited NH3 (3, 3) masers in the NGC 6334 star-forming region

    NASA Technical Reports Server (NTRS)

    Kraemer, Kathleen E.; Jackson, James M.

    1995-01-01

    We report the discovery of four NH3 (3, 3) masers in the NGC 6334 star formation region. The masers are found in two of the seven far-infrared continuum sources where high-mass star formation is taking place in this molecular cloud. These masers occur at the ends of high-velocity molecular outflows; no maser emission was found near regions without high-velocity outflows. The NH3 masers are not associated with any other type of maser. These results confirm that the NH3 (3, 3) masers are caused by shocks and probably mark the location where the molecular outflow jet impinges upon the ambient medium.

  3. Shock-excited NH3 (3, 3) masers in the NGC 6334 star-forming region

    NASA Technical Reports Server (NTRS)

    Kraemer, Kathleen E.; Jackson, James M.

    1995-01-01

    We report the discovery of four NH3 (3, 3) masers in the NGC 6334 star formation region. The masers are found in two of the seven far-infrared continuum sources where high-mass star formation is taking place in this molecular cloud. These masers occur at the ends of high-velocity molecular outflows; no maser emission was found near regions without high-velocity outflows. The NH3 masers are not associated with any other type of maser. These results confirm that the NH3 (3, 3) masers are caused by shocks and probably mark the location where the molecular outflow jet impinges upon the ambient medium.

  4. Methanol as A Tracer of Fundamental Constants

    NASA Astrophysics Data System (ADS)

    Levshakov, S. A.; Kozlov, M. G.; Reimers, D.

    2011-09-01

    The methanol molecule CH3OH has a complex microwave spectrum with a large number of very strong lines. This spectrum includes purely rotational transitions as well as transitions with contributions of the internal degree of freedom associated with the hindered rotation of the OH group. The latter takes place due to the tunneling of hydrogen through the potential barriers between three equivalent potential minima. Such transitions are highly sensitive to changes in the electron-to-proton mass ratio, μ = m e/m p, and have different responses to μ-variations. The highest sensitivity is found for the mixed rotation-tunneling transitions at low frequencies. Observing methanol lines provides more stringent limits on the hypothetical variation of μ than ammonia observation with the same velocity resolution. We show that the best-quality radio astronomical data on methanol maser lines constrain the variability of μ in the Milky Way at the level of |Δμ/μ| < 28 × 10-9 (1σ) which is in line with the previously obtained ammonia result, |Δμ/μ| < 29 × 10-9 (1σ). This estimate can be further improved if the rest frequencies of the CH3OH microwave lines will be measured more accurately.

  5. New Approaches in SiO Maser Shell Tomography Analysis

    NASA Astrophysics Data System (ADS)

    Phillips, R. B.; Boboltz, D. A.; Winter, L. A.; Straughn, A. H.

    2003-12-01

    Silicon Monoxide (SiO) masers form at a few stellar radii in the extended atmospheres of evolved stars, the innermost of the commonly seen stellar maser species. As compact, high brightness-temperature regions that lie inside the dust forming radius, SiO masers as imaged by mm-wavelength Very Long Baseline Interferometry (mm-VLBI) have frequently been cited as probes of physical conditions at the photosphere-wind boundary. Current SiO maser studies exploit the remarkable resolution of mm-VLBI and the responsiveness and fast duty cycles of the Very Long Baseline Array (VLBA) to make images in multiple transitions of SiO. Yet VLBI leaves the observer with a disjointed set of images, with the different excitation transitions generally not registered, even within the same epoch. We have explored and applied a variety of techniques intended for unbiased extraction of physical data from SiO maser images, and explain for two red giant case studies how simple mathematical approaches can register transitions and epochs and extract apparent maser proper motions from VLBA data. In the case of Mira (o Ceti), we fit proper motions and attempt to register the sparse shells of v=1 and v=2 7mm masers. For R Cas, we register the two bright 7mm maser shells plus the v=1 3mm maser shell, and make the case for the passage of a pulsation shock re-invigorating the 3mm masers. This research was part of the Research Experiences for Undergraduates (REU) Program at Haystack, with additional development carried out under Haystack's mission in mm-VLBI techniques. The REU program and mm-VLBI at Haystack are sponsored by the National Science Foundation.

  6. Detection of the First beta-LINE Hydrogen Maser in MWC 349

    NASA Astrophysics Data System (ADS)

    Smith, H. A.; Strelnitski, V. S.; Thum, C.; Matthews, H. E.

    1993-12-01

    We report the discovery of the first recombination beta-line of hydrogen, H32beta, in MWC 349, using the JCMT. MWC 349, an early type emission line star, is believed to be surrounded by an edge-on Keplerian disk, where numerous, previously observed masing alpha-lines are generated. The double-peaked profile of H32beta, with a deep central dip (quite similar to the profiles of the masing alpha-lines) can not be interpreted except in terms of exponential maser amplification in the disk. With its high frequency (367 GHz), this line should come from a deeper part of the disk than the corresponding alpha-lines which are more heavily extinguished by the free-free absorption. This discovery opens new possibilities for probing the kinematical and physical properties of the disk by comparing the observed parameters of the line with our numerical models of maser amplification in a Keplerian disk (e.g., Ponomarev, Smith, and Strelnitski, ApJ. April 1994). This investigation has been supported in part by the Smithsonian Institution Scientific Studies Program.

  7. New Maser Emission from Nonmetastable Ammonia in NGC 7538. IV. Coincident Masers in Adjacent States of Para-ammonia

    NASA Astrophysics Data System (ADS)

    Hoffman, Ian M.; Joyce, Spenser A.

    2014-02-01

    We present the first detection of para-ammonia masers in NGC 7538: multiple epochs of observation of the 14NH3 (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/kB ~ 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 15NH3 (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.

  8. 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.

  9. The turbulent bremsstrahlung (plasma-maser) effect

    SciTech Connect

    Vladimirov, S. V.

    2011-01-04

    Because of nonlinear interaction between particles and waves, energy conversion between waves of large frequency difference can occur without particle population inversion or resonant wave-wave interaction. The effect involves the nonresonant interaction of the plasma particles with a pair of plasma modes of large frequency difference, and wave energy is converted into particle energy. This effect can appear in laboratory as well as astrophysical plasmas and is important in determining the transport properties of weakly turbulent plasmas. Here, the most important aspects of the plasma-maser theory is discussed.

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

    NASA Astrophysics Data System (ADS)

    Tokumaru, Munetoshi; Yamauchi, Yohei; Kondo, Tetsuro

    2001-03-01

    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.

  11. 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.

  12. 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.

  13. Evidence from masers for a rapidly rotating disk at the nucleus of NGC 4258

    NASA Technical Reports Server (NTRS)

    Watson, William D.; Wallin, Bradley K.

    1994-01-01

    We demonstrate how maser emission from a rapidly rotating, thin Keplerian disk viewed edge-on can reproduce the general features of the observed 22 GHz radiation from the nucleus of NGC 4258, including the high-velocity satellites that are Doppler shifted by nearly +/- 1000 km/s from the central emission. Newly reported data about variations in time and space for the Doppler shifts of the central emission features fit especially well into a disk interpretation. We point out that their ratio gives a velocity of 700 km/s for the rotation at the outer edge of the masing ring -- a value that is essentially the same as the rotational velocity inferred from the Doppler shifts of the high-velocity satellites. The radius of the masing ring is 0.1 pc and the central mass at the nucleus of NGC 4258 about which the disk rotates is then 10(exp 7) solar mass.

  14. Free-electron maser with high-selectivity Bragg resonator using coupled propagating and trapped modes

    NASA Astrophysics Data System (ADS)

    Ginzburg, N. S.; Golubev, I. I.; Golubykh, S. M.; Zaslavskii, V. Yu.; Zotova, I. V.; Kaminsky, A. K.; Kozlov, A. P.; Malkin, A. M.; Peskov, N. Yu.; Perel'Shteĭn, É. A.; Sedykh, S. N.; Sergeev, A. S.

    2010-10-01

    A free-electron maser (FEM) with a double-mirror resonator involving a new modification of Bragg structures operating on coupled propagating and quasi-cutoff (trapped) modes has been studied. The presence of trapped waves in the feedback chain improves the selectivity of Bragg resonators and ensures stable single-mode generation regime at a considerable superdimensionality of the interaction space. The possibility of using the new feedback mechanism has been confirmed by experiments with a 30-GHz FEM pumped by the electron beam of LIU-3000 (JINR) linear induction accelerator, in which narrow-band generation was obtained at a power of ˜10 MW and a frequency close to the cutoff frequency of the trapped mode excited in the input Bragg reflector.

  15. Demonstrating gain in a dielectric Cherenkov maser with a rod slow-wave system

    NASA Astrophysics Data System (ADS)

    Avgustinovich, V. A.; Artemenko, S. N.; Mashchenko, A. I.; Shlapakovskii, A. S.; Yushkov, Yu. G.

    2010-03-01

    We report the first results of experiments that demonstrate the amplification of megawatt nanosecond microwave pulses in a Cherenkov maser with a dielectric rod and moderately relativistic annular electric beam generated in a compact linear induction accelerator module. The input signal was generated by a resonant microwave compressor operating in a 3-cm wavelength range. A maximum gain of ˜12.5 dB and a maximum output power of ˜16 MW for a pulse duration of ˜4 ns at a frequency of 9.388 GHz were obtained with a quartz rod. The dependence of the gain on the compressor power was determined for various values of the accelerating voltage and beam current.

  16. MM-wave cyclotron auto-resonance maser for plasma heating

    NASA Astrophysics Data System (ADS)

    Ceccuzzi, S.; Dattoli, G.; Di Palma, E.; Doria, A.; Gallerano, G. P.; Giovenale, E.; Mirizzi, F.; Spassovsky, I.; Ravera, G. L.; Surrenti, V.; Tuccillo, A. A.

    2014-02-01

    Heating and Current Drive systems are of outstanding relevance in fusion plasmas, magnetically confined in tokamak devices, as they provide the tools to reach, sustain and control burning conditions. Heating systems based on the electron cyclotron resonance (ECRH) have been extensively exploited on past and present machines DEMO, and the future reactor will require high frequencies. Therefore, high power (≥1MW) RF sources with output frequency in the 200 - 300 GHz range would be necessary. A promising source is the so called Cyclotron Auto-Resonance Maser (CARM). Preliminary results of the conceptual design of a CARM device for plasma heating, carried out at ENEA-Frascati will be presented together with the planned R&D development.

  17. A reflected-wave ruby maser with K-band tuning range and large instantaneous bandwidth

    NASA Technical Reports Server (NTRS)

    Moore, C. R.; Clauss, R. C.

    1979-01-01

    A novel maser concept is outlined and a unique design described which permits wide bandwidth and waveguide tuning range by employing four stages cascaded via cryogenically cooled circulators. Theoretical considerations for gain, bandwidth, gain ripple, and noise temperature are included. Operated on a closed-cycle helium refrigerator with a superconducting persistence-mode magnet, the four-stage amplifier is tunable from 18.3 to 26.6 GHz with 30 dB of net gain and achieves 240 MHz of 3-dB bandwidth near the center of this band. The measured noise temperature is 13 + or - 2 K referred to the room-temperature input flange. Applications are foreseen utilizing cooled parametric downconverters and upconverters with this amplifier at IF to extend the low-noise performance up to millimeter frequencies and down to L-band for radio astronomy and planetary spacecraft communications.

  18. MM-wave cyclotron auto-resonance maser for plasma heating

    SciTech Connect

    Ceccuzzi, S.; Ravera, G. L.; Tuccillo, A. A.; Dattoli, G.; Di Palma, E.; Doria, A.; Gallerano, G. P.; Giovenale, E.; Spassovsky, I.; Surrenti, V.; Mirizzi, F.

    2014-02-12

    Heating and Current Drive systems are of outstanding relevance in fusion plasmas, magnetically confined in tokamak devices, as they provide the tools to reach, sustain and control burning conditions. Heating systems based on the electron cyclotron resonance (ECRH) have been extensively exploited on past and present machines DEMO, and the future reactor will require high frequencies. Therefore, high power (≥1MW) RF sources with output frequency in the 200 - 300 GHz range would be necessary. A promising source is the so called Cyclotron Auto-Resonance Maser (CARM). Preliminary results of the conceptual design of a CARM device for plasma heating, carried out at ENEA-Frascati will be presented together with the planned R and D development.

  19. High-power, high-frequency, annular-beam free-electron maser

    SciTech Connect

    Fazio, M.V.; Carlsten, B.E.; Earley, L.M.; Fortgang, C.M.; Haynes, W.B.; Haddock, P.C.

    1998-11-01

    The authors have developed a 15--17 GHz free electron maser (FEM) capable of producing high power pulses with a phase stability appropriate for linear collider applications. The electron beam source is a 1 {micro}s, 800 kV, 5 kA, 6-cm-dia annular electron beam machine called BANSHEE. The beam interacts with the TM{sub 02} mode Raman FEM amplifier in a corrugated cylindrical waveguide where the beam runs close to the interaction device walls to reduce the power density in the fields. They studied the phase stability by analyzing the dispersion relation for an axial FEL, in which the rf field was transversely wiggled and the electron trajectories were purely longitudinal. Detailed particle-in-cell simulations demonstrated the transverse wiggling of the rf mode and the axial FEL interaction and explicit calculations of the growing root of the dispersion relation are included to verify the phase stability.

  20. Instabilities and the transport of polarized astrophysical maser radiation

    NASA Technical Reports Server (NTRS)

    Wallin, Bradley K.; Watson, William D.

    1995-01-01

    Time-dependent, radiative instabilities in the creation and transport of polarized astrophysical maser radiation in the presence of a magnetic field are calculated. The instabilities are similar to and occur under the same conditions as those found previously by Scappaticci & Watson for unpolarized maser radiation. The common limits in which the Zeeman splitting is much greater than, and much less than, the spectral line breadths are both considered in the current investigation. The resulting fluctuations in the emergent radiation are potentially relevant for the OH 1665 MHz masers which have been reported to fluctuate on timescales of 1000 s and which tend to be polarized. Instabilities occur and alter the transport of maser radiation only under a quite limited range of conditions. In particular, we find here that the instabilities do not occur for conditions that are appropriate for astrophysical masers with small Zeeman splittings such as the SiO and H2O masers. The time-independent, numerical solutions to the GKK equations of radiative transfer that have been obtained in previous investigations are thus essentially always valid except within a narrow range of conditions relevant for the OH masers.

  1. Radiative instabilities and 1000 second fluctuations in astrophysical masers

    NASA Technical Reports Server (NTRS)

    Scappaticci, Gerardo A.; Watson, William D.

    1992-01-01

    A stability analysis for small (linear) perturbations is presented for the radiation in astrophysical masers treated in the usual, linear maser approximation. Instabilities that oscillate with a period of about L/c, where L is the length of the maser are found. They occur (1) when the maser is partly but not heavily saturated, (2) when the decay rate Gamma for the molecular states is near c/L, and (3) when the product of the brightness temperature T sub 0 of the incident radiation and the angle for the beaming is less than a critical value that depends upon the particular masing transition. A fourth parameter, the fractional inversion in the pumping multiplied by (T sub 0/frequency), determines the importance of spontaneous emission which can eliminate the instabilities. These instabilities are a likely cause for the fluctuations in the radiation from the 18 cm OH masers that have been reported to occur on time scales as short as 1000 s. The calculations are applicable to other types of astrophysical masers as well, and suggest that spontaneous emission will prevent similar instabilities in the H2O and SiO masers.

  2. New Observations Deepen Mystery Surrounding Water Masers in Elliptical Galaxy

    NASA Astrophysics Data System (ADS)

    New observations with the National Science Foundation's Very Long Baseline Array (VLBA) radio telescope have deepened the mystery surrounding water molecules in a galaxy 65 million light- years away. The water molecules are acting as natural masers -- amplifiers of microwave radio emissions -- and these cosmic masers within the galaxy NGC 1052 are raising difficult questions for astronomers trying to explain them. Results of the new observations, which pinpoint the location of water masers in NGC 1052, were announced today at the American Astronomical Society meeting in Toronto, Ontario. The researchers are: Jim Braatz of Harvard University in Cambridge, Massachusetts, Mark Claussen and Phil Diamond of the National Radio Astronomy Observatory in Socorro, New Mexico, Andrew Wilson of the University of Maryland in College Park, Maryland, and Christian Henkel of the Max Planck Institute fur Radioastronomie in Bonn, Germany. Water masers have been detected in several other galaxies. However, most galaxies containing water "megamasers" such as those in NGC 1052 are spiral galaxies. NGC 1052 is one of only two elliptical galaxies in which water megamasers have been detected. Because ellipticals tend to have much less gas and dust than spirals, the existence of the water masers in NGC 1052 is surprising by itself, though that galaxy does have more gas and dust than the typical elliptical. Located in the constellation Cetus, NGC 1052 also has an active nucleus, believed to be powered by the gravitational energy of a supermassive black hole at its core. The new VLBA observations produced an additional mystery. In other galaxies with water megamasers, the masers are believed to lie within a disk of molecules orbiting the galaxy's central black hole. This is the case, for example, in the now-famous galaxy NGC 4258, where the movement of the orbiting disk can be traced by measuring both the Doppler shift of radio emission from the masers and by tracking the motion of

  3. Research on the Frequency Steering Strategy of a Hydrogen Maser

    NASA Astrophysics Data System (ADS)

    Yin, Dong-shan; Zhao, Shu-hong; Gao, Yu-ping

    2017-07-01

    In the master clock system, the local standard time UTC(k) with a better short-term stability will be generated, if the hydrogen maser is set as a frequency source of the master clock. But the hydrogen maser always exhibits an apparent frequency drift, thus its long-term stability gets poor with the time, therefore the stability and accuracy of UTC(k) become worse. To solve this problem, the performance of hydrogen maser is compared with cesium clocks, and the time scale algorithm is modified when the hydrogen maser is involved, a new steering strategy is proposed when a hydrogen maser is used as the frequency source of the master clock. An experimental system is set up with the programs compiled, and finally the new steering strategy is testified with the laboratory data. The results show that when the hydrogen maser is involved in the atomic time scale calculation, the short-term frequency stability of the reference time scale will be improved. Meanwhile, the local time UTC(k) has a better short-term frequency stability when the frequency source of the master clock uses a hydrogen maser instead of a cesium clock.

  4. Research on the Steering Strategy for Hydrogen Maser

    NASA Astrophysics Data System (ADS)

    Yin, D. S.; Zhao, S. H.; Gao, Y. P.

    2016-07-01

    In the master clock system, the local standard time UTC(k) with a better short-term stability will be generated, if the hydrogen maser is set as a frequency source of the master clock. But the hydrogen maser always exhibits an apparent frequency drift, thus its long-term stability gets poor with time, therefore the stability and accuracy of UTC(k) become worse. To solve this problem, we compare the performance of hydrogen maser with cesium clocks, and modify the time scale algorithm when the hydrogen maser is involved, we also propose a new steering strategy when hydrogen maser is used as the frequency source of master clock. We set up an experiment system and write programs, and finally the new steering strategy is testified with the laboratory data. Results show that when the hydrogen maser is involved in the atomic time scale calculation, the short-term frequency stability of reference time scale will be improved. Meanwhile, the local time UTC(k) has a better short-term frequency stability when the frequency source of the master clock uses hydrogen maser instead of cesium clock.

  5. WATER MASERS ASSOCIATED WITH STAR FORMATION IN THE ANTENNAE GALAXIES

    SciTech Connect

    Brogan, Crystal; Johnson, Kelsey; Darling, Jeremy

    2010-06-10

    We present Very Large Array (VLA) observations with 80 mas resolution ({approx}9 pc) of the recently discovered Galactic-analog (GA)-H{sub 2}O masers in the Antennae interacting galaxies (NGC 4038/NGC 4039; Arp244). Three regions of water maser emission are detected: two in the 'interaction region' (IAR) and the third {approx}5.''6 ({approx_gt}600 pc) west of the NGC 4039 nucleus. The isotropic H{sub 2}O maser luminosities range from 1.3 to 7.7 L{sub sun}. All three maser regions are mostly obscured in the optical/near-infrared continuum, and are coincident with massive CO-identified molecular clouds. The H{sub 2}O maser velocities are in excellent agreement with those of the molecular gas. We also present archival VLA 3.6 cm data with {approx}0.''28 ({approx}30 pc) and {approx}0.''8 ({approx}90 pc) resolution toward the maser locations. All three maser regions are coincident with compact 3.6 cm radio continuum emission, and two are dominated by thermal ionized gas, suggesting the presence of natal super star clusters containing the equivalent of a few thousand O stars. We also present detailed comparisons between the radio data and existing Hubble Space Telescope Advanced Camera for Surveys (optical) and NICMOS (near-IR) data and find that both maser regions in the IAR are also associated with Pa{alpha} emission and neither source is detected shortward of 2 {mu}m. These results highlight the potential of using GA-H{sub 2}O masers to pinpoint sites of young super star cluster formation with exquisite angular resolution.

  6. 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.

  7. In orbit demonstration of a H-maser clock system

    NASA Technical Reports Server (NTRS)

    Busca, Giovanni; Bernier, Laurent-Guy; Starker, Siegfried K.; Feltham, S.

    1992-01-01

    The ESA/NASA technology demonstration flight of a pair of hydrogen masers on the EURECA 3 mission is planned for 1998. The ESA part of the experiment will have a maser built by Neuchatel Observatory and a microwave time and frequency transfer system derived from the existing Precise Range and Range Rate Equipment (PRARE) system. The NASA part of the experiment will have a maser built by the Smithsonian Astrophysical Observatory and a laser time transfer system. The technology demonstration experiment is described with its expected outcomes and applications.

  8. In orbit demonstration of a H-maser clock system

    NASA Astrophysics Data System (ADS)

    Busca, Giovanni; Bernier, Laurent-Guy; Starker, Siegfried K.; Feltham, S.

    1992-07-01

    The ESA/NASA technology demonstration flight of a pair of hydrogen masers on the EURECA 3 mission is planned for 1998. The ESA part of the experiment will have a maser built by Neuchatel Observatory and a microwave time and frequency transfer system derived from the existing Precise Range and Range Rate Equipment (PRARE) system. The NASA part of the experiment will have a maser built by the Smithsonian Astrophysical Observatory and a laser time transfer system. The technology demonstration experiment is described with its expected outcomes and applications.

  9. The electron-cyclotron maser for astrophysical application

    NASA Astrophysics Data System (ADS)

    Treumann, Rudolf A.

    2006-08-01

    The electron-cyclotron maser is a process that generates coherent radiation from plasma. In the last two decades, it has gained increasing attention as a dominant mechanism of producing high-power radiation in natural high-temperature magnetized plasmas. Originally proposed as a somewhat exotic idea and subsequently applied to include non-relativistic plasmas, the electron-cyclotron maser was considered as an alternative to turbulent though coherent wave-wave interaction which results in radio emission. However, when it was recognized that weak relativistic corrections had to be taken into account in the radiation process, the importance of the electron-cyclotron maser rose to the recognition it deserves. Here we review the theory and application of the electron-cyclotron maser to the directly accessible plasmas in our immediate terrestrial and planetary environments. In situ access to the radiating plasmas has turned out to be crucial in identifying the conditions under which the electron-cyclotron maser mechanism is working. Under extreme astrophysical conditions, radiation from plasmas may provide a major energy loss; however, for generating the powerful radiation in which the electron-cyclotron maser mechanism is capable, the plasma must be in a state where release of susceptible amounts of energy in the form of radiation is favorable. Such conditions are realized when the plasma is unable to digest the available free energy that is imposed from outside and stored in its particle distribution. The lack of dissipative processes is a common property of collisionless plasmas. When, in addition, the plasma density becomes so low that the amount of free energy per particle is large, direct emission becomes favorable. This can be expressed as negative absorption of the plasma which, like in conventional masers, leads to coherent emission even though no quantum correlations are involved. The physical basis of this formal analogy between a quantum maser and the

  10. Mega-masers, Dark Energy and the Hubble Constant

    SciTech Connect

    Lo, Fred K. Y.

    2007-10-15

    Powerful water maser emission (water mega-masers) can be found in accretion disks in the nuclei of some galaxies. Besides providing a measure of the mass at the nucleus, such mega-masers can be used to determine the distance to the host galaxy, based on a kinematic model. We will explain the importance of determining the Hubble Constant to high accuracy for constraining the equation of state of Dark Energy and describe the Mega-maser Cosmology Project that has the goal of determining the Hubble Constant to better than 3%. Time permitting, we will also present the scientific capabilities of the current and future NRAO facilities: ALMA, EVLA, VLBA and GBT, for addressing key astrophysical problems

  11. Spectra of circularly polarized radiation from astrophysical OH masers

    NASA Technical Reports Server (NTRS)

    Nedoluha, Gerald E.; Watson, William D.

    1990-01-01

    A striking feature of astrophysical masers is the tendency for either one or the other of the circular polarizations to dominate in the radiation from the strong, widely observed masing transitions of OH at 18 cm. Spectral line profiles are calculated for polarized maser radiation due to the combined effects of a velocity gradient and, as is indicated for these transitions, a Zeeman splitting that is at least comparable with the thermal contributions to the breadths of the spectral lines. The resulting spectral features are similar in appearance, including the presence of large net circular polarization and narrow line breadths, to the commonly observed spectra of OH masers in molecular clouds. The calculations presented here are performed as a function of frequency without making the approximations of a large velocity gradient. Rapid cross relaxation, which has been advocated by others for the OH masers, is assumed.

  12. Spectra of circularly polarized radiation from astrophysical OH masers

    NASA Technical Reports Server (NTRS)

    Nedoluha, Gerald E.; Watson, William D.

    1990-01-01

    A striking feature of astrophysical masers is the tendency for either one or the other of the circular polarizations to dominate in the radiation from the strong, widely observed masing transitions of OH at 18 cm. Spectral line profiles are calculated for polarized maser radiation due to the combined effects of a velocity gradient and, as is indicated for these transitions, a Zeeman splitting that is at least comparable with the thermal contributions to the breadths of the spectral lines. The resulting spectral features are similar in appearance, including the presence of large net circular polarization and narrow line breadths, to the commonly observed spectra of OH masers in molecular clouds. The calculations presented here are performed as a function of frequency without making the approximations of a large velocity gradient. Rapid cross relaxation, which has been advocated by others for the OH masers, is assumed.

  13. Planar H2O masers in star-forming regions

    NASA Technical Reports Server (NTRS)

    Elitzur, Moshe; Hollenbach, David J.; Mckee, Christopher F.

    1992-01-01

    The paper examines the planar geometry of shocked material, which is the key property in enabling the high brightness temperatures of H2O masers in star-forming regions. The brightness temperature, beaming angle, and the maser spot size are determined for thin, saturated planar masers under the assumption that the velocity change across the maser due to ordered motions is small compared with the thermal or microturbulent line width. For a given set of physical parameters, the brightness temperature is essentially fully determined by the length of the velocity-coherent region in the shocked plane along the line of sight. Effective aspect ratios (about 5-50) are found that are in agreement with values previously inferred from observed brightness temperatures.

  14. Atomic hydrogen maser active oscillator cavity and bulb design optimization

    NASA Technical Reports Server (NTRS)

    Peters, H. E.; Washburn, P. J.

    1984-01-01

    The performance characteristics and reliability of the active oscillator atomic hydrogen maser depend upon oscillation parameters which characterize the interaction region of the maser, the resonant cavity and atom storage bulb assembly. With particular attention to use of the cavity frequency switching servo (1) to reduce cavity pulling, it is important to maintain high oscillation level, high atomic beam flux utilization efficiency, small spin exchange parameter and high cavity quality factor. It is also desirable to have a small and rigid cavity and bulb structure and to minimize the cavity temperature sensitivity. Curves for a novel hydrogen maser cavity configuration which is partially loaded with a quartz dielectric cylinder and show the relationships between cavity length, cavity diameter, bulb size, dielectric thickness, cavity quality factor, filling factor and cavity frequency temperature coefficient are presented. The results are discussed in terms of improvement in maser performance resulting from particular design choices.

  15. Mega-masers, Dark Energy and the Hubble Constant

    SciTech Connect

    Lo, Fred K.Y.

    2007-10-15

    Powerful water maser emission (water mega-masers) can be found in accretion disks in the nuclei of some galaxies. Besides providing a measure of the mass at the nucleus, such mega-masers can be used to determine the distance to the host galaxy, based on a kinematic model. We will explain the importance of determining the Hubble Constant to high accuracy for constraining the equation of state of Dark Energy and describe the Mega-maser Cosmology Project that has the goal of determining the Hubble Constant to better than 3%. Time permitting, we will also present the scientific capabilities of the current and future NRAO facilities: ALMA, EVLA, VLBA and GBT, for addressing key astrophysical problems

  16. Planar H2O masers in star-forming regions

    NASA Technical Reports Server (NTRS)

    Elitzur, Moshe; Hollenbach, David J.; Mckee, Christopher F.

    1992-01-01

    The paper examines the planar geometry of shocked material, which is the key property in enabling the high brightness temperatures of H2O masers in star-forming regions. The brightness temperature, beaming angle, and the maser spot size are determined for thin, saturated planar masers under the assumption that the velocity change across the maser due to ordered motions is small compared with the thermal or microturbulent line width. For a given set of physical parameters, the brightness temperature is essentially fully determined by the length of the velocity-coherent region in the shocked plane along the line of sight. Effective aspect ratios (about 5-50) are found that are in agreement with values previously inferred from observed brightness temperatures.

  17. Timescale algorithms combining cesium clocks and hydrogen masers

    NASA Technical Reports Server (NTRS)

    Breakiron, Lee A.

    1992-01-01

    The United States Naval Observatory (USNO) atomic timescale, formerly based on an ensemble of cesium clocks, is now produced by an ensemble of cesium clocks and hydrogen masers. In order to optimize stability and reliability, equal clock weighting has been replaced by a procedure reflecting the relative, time-varying noise characteristics of the two different types of clocks. Correlation of frequency drift is required, and residual drift is avoided by the eventual complete deweighting of the masers.

  18. On the line Q degradation in hydrogen masers

    NASA Technical Reports Server (NTRS)

    Bernier, L. G.; Busca, Giovanni; Schweda, Hartmut S.

    1990-01-01

    In hydrogen masers, the atomic resonance quality factor is largely determined by the properties of the Teflon coating on the quartz storage bulb. Normally a good Teflon coating will last many years. On the other hand, there may be a relatively fast degradation of the quality factor if the Teflon coating is bad. A series of observations and measurements performed on an hydrogen maser that had successively a bad and a good Teflon coating are discussed.

  19. The Discovery of New Ammonia Masers in the Galactic Center

    NASA Astrophysics Data System (ADS)

    Teachey, Alex; Mills, Elisabeth A.; Meier, David S.; Ott, Juergen; Butterfield, Natalie; Lang, Cornelia C.; Morris, Mark

    2015-01-01

    The ammonia molecule has long been recognized as a reliable gauge of cloud temperatures. Certain ammonia transitions are known to have a potential for masing, but to date only a handful of these masers have been identified. In this work we have examined several Galactic Center clouds using K-band data from the Very Large Array in DnC configuration (resolution ~3" / 0.1 pc) to identify new ammonia masers in the (3,3) metastable line. At present we have found four compact (< 3'') regions -- two in G0.253+0.016 (The Brick) and two near Sagittarius A -- that we can report with high confidence as newly-discovered ammonia (3,3) masers. A total of 16 additional regions are identified as likely maser candidates requiring additional analysis. Our findings suggest that the maser mechanism will preferentially amplify the main ammonia emission line over its hyperfine satellite lines, resulting in artificially low opacities measured from the ratio of these lines. This property can have the effect of partially hiding the signature of the (3,3) maser in opacity-corrected Boltzmann plots. In the highest confidence regions we measure main-to-hyperfine ratios significantly in excess of the maximum theoretical ratio for an optically-thin line, yielding negative opacities, consistent with our hypothesis of main line maser amplification. These results will be of value not only in future ammonia maser searches but also for the reliability of the ammonia molecule as a temperature tracer, and for the determination of ammonia ortho-to-para ratios.

  20. Graphene based GHz detectors

    NASA Astrophysics Data System (ADS)

    Boyd, Anthony K.; El Fatimy, Abdel; Barbara, Paola; Nath, Anindya; Campbell, Paul M.; Myers-Ward, Rachael; Daniels, Kevin; Gaskill, D. Kurt

    Graphene demonstrates great promise as a detector over a wide spectral range especially in the GHz range. This is because absorption is enhanced due to the Drude contribution. In the GHz range there are viable detection mechanisms for graphene devices. With this in mind, two types of GHz detectors are fabricated on epitaxial graphene using a lift off resist-based clean lithography process to produce low contact resistance. Both device types use asymmetry for detection, consistent with recent thoughts of the photothermoelectric effect (PTE) mechanism. The first is an antenna coupled device. It utilizes two dissimilar contact metals and the work function difference produces the asymmetry. The other device is a field effect transistor constructed with an asymmetric top gate that creates a PN junction and facilitates tuning the photovoltaic response. The response of both device types, tested from 100GHz to 170GHz, are reported. This work was sponsored by the U.S. Office of Naval Research (Award Number N000141310865).

  1. Proposal for a room-temperature diamond maser

    PubMed Central

    Jin, Liang; Pfender, Matthias; Aslam, Nabeel; Neumann, Philipp; Yang, Sen; Wrachtrup, Jörg; Liu, Ren-Bao

    2015-01-01

    The application of masers is limited by its demanding working conditions (high vacuum or low temperature). A room-temperature solid-state maser is highly desirable, but the lifetimes of emitters (electron spins) in solids at room temperature are usually too short (∼ns) for population inversion. Masing from pentacene spins in p-terphenyl crystals, which have a long spin lifetime (∼0.1 ms), has been demonstrated. This maser, however, operates only in the pulsed mode. Here we propose a room-temperature maser based on nitrogen-vacancy centres in diamond, which features the longest known solid-state spin lifetime (∼5 ms) at room temperature, high optical pumping efficiency (∼106 s−1) and material stability. Our numerical simulation demonstrates that a maser with a coherence time of approximately minutes is feasible under readily accessible conditions (cavity Q-factor ∼5 × 104, diamond size ∼3 × 3 × 0.5 mm3 and pump power <10 W). A room-temperature diamond maser may facilitate a broad range of microwave technologies. PMID:26394758

  2. Proposal for a room-temperature diamond maser.

    PubMed

    Jin, Liang; Pfender, Matthias; Aslam, Nabeel; Neumann, Philipp; Yang, Sen; Wrachtrup, Jörg; Liu, Ren-Bao

    2015-09-23

    The application of masers is limited by its demanding working conditions (high vacuum or low temperature). A room-temperature solid-state maser is highly desirable, but the lifetimes of emitters (electron spins) in solids at room temperature are usually too short (∼ns) for population inversion. Masing from pentacene spins in p-terphenyl crystals, which have a long spin lifetime (∼0.1 ms), has been demonstrated. This maser, however, operates only in the pulsed mode. Here we propose a room-temperature maser based on nitrogen-vacancy centres in diamond, which features the longest known solid-state spin lifetime (∼5 ms) at room temperature, high optical pumping efficiency (∼10(6) s(-1)) and material stability. Our numerical simulation demonstrates that a maser with a coherence time of approximately minutes is feasible under readily accessible conditions (cavity Q-factor ∼5 × 10(4), diamond size ∼3 × 3 × 0.5 mm(3) and pump power <10 W). A room-temperature diamond maser may facilitate a broad range of microwave technologies.

  3. A model for extremely powerful extragalactic water masers

    SciTech Connect

    Wu, Ying-Cheng; Alcock, C.

    1988-08-01

    The reasons for the differences between extremely powerful extragalatic water masers (EPEWMs) and strong Galactic H/sub 2/O masers are discussed. This model quite successfully explains many important characteristics of EPEWMs; the rapid time variations, the broad range and random velocity distribution, the extremely high luminosities, the various heights or widths of features in spectra, the strong infrared radiation from the galaxies, how an active nucleus contributes to an EPEWM, how some parts of EPEWMs producing strong features are pumped, why this pump mechanism can work, and why EPEWMs are different from strong Galactic H/sub 2/O masers. Recent observations of extragalactic water masers which have extremely high luminosities raise the possibility that the stimulated emission rate in the maser emission line in these regions is much higher than in Galactic masers. It is possible that the local stimulated emission rate exceeds the local bandwidth for the radiation. In this case the standard expression relating the photon emission rate to the profile averaged mean intensity does not apply. A new expression for the photon emission rate is derived.

  4. Molecular catastrophes and circumstellar SiO masers

    NASA Technical Reports Server (NTRS)

    Stencel, Robert E.

    1993-01-01

    Understanding the complex SiO maser regions of highly evolved stars can be improved through multiwavelength studies of 'premaser' stars, such as M0-M4 giants and semiregular variables, which can be placed on normal H-R diagrams unlike most of the OH-IR stars. I argue that SiO masers are a key part of the transformation of hot stellar plasma into cold circumstellar silicate dust, in the outflows from evolved, oxygen rich stars. Evidence for this statement rests on the following: (1) red giant mass loss originates in a stochastic, amsotropic manner; (2) SiO maser maps of Miras and red supergiants show numerous maser spots within a few stellar radii; (3) molecules and dust naturally form in a cooling outflow; (4) the IRAS Low Resolution Spectrometer provided evidence for diverse and variable 10 micron silicate features in Miras, and these shapes correlate well with the proposed maser chronology, suggesting a formation and annealing sequence. The theory for the occurrence of SiO masers involving thermal instability, related 'new' physics, recent calculations and a prediction are discussed.

  5. Cyclotron maser using the anomalous Doppler effect

    NASA Astrophysics Data System (ADS)

    Didenko, A. N.; Borisov, A. R.; Fomenko, G. P.; Shlapakovskii, A. S.; Shtein, Iu. G.

    1983-11-01

    The operation of an anomalous-Doppler-effect cyclotron-resonance maser using a waveguide partially filled with dielectric as the slow-wave system is reported. The device investigated is similar to that of Didenko et al. (1983) and comprises a 300-mm-long 50-mm-o.d. 30-mm-i.d. waveguide with fabric-laminate dielectric, located 150 mm from the cathode in a 500-mm-long region of uniform 0-20-kG magnetic field, and a coaxial magnetic-insulation gun producing a 13-mm-i.d. 25-mm-o.d. hollow electron beam. Radiation at 12 + or - 1 mm wavelength and optimum power 20 MW is observed using hot-carrier detectors, with a clear peak in the power-versus-magnetic-field curve at about 6.4 kG.

  6. Maser cavity servo-tuning system

    NASA Technical Reports Server (NTRS)

    Sydnor, R. L. (Inventor)

    1985-01-01

    Two collocated, weakly coupled probes, one loop and one dipole, detect the magnetic and electric fields inside a maser cavity. Signals from the probes are compared in phase, and the signal output from the phase detector is applied to a varactor, the reactance of which is coupled into the cavity by a microwave coupler. Alternatively, the varactor may be placed inside the cavity. Any deviation of phase from 90 deg as detected by the phase detector will then produce an error signal that will change the reactance coupled into the resonant cavity to change its reactance, and thus correct its resonance frequency. An alternative to using two probes is to use a single disk probe oriented to detect both the magnetic and electric fields, and thus provide the error signal directly.

  7. Nonlinear theory of a plasma Cherenkov maser

    SciTech Connect

    Choi, J.S.; Heo, E.G.; Choi, D.I.

    1995-12-31

    The nonlinear saturation state in a plasma Cherenkov maser (PCM) propagating the intense relativistic electron beam through a circular waveguide partially filled with a dense annular plasma, is analyzed from the nonlinear formulation based on the cold fluid-Maxwell equations. We obtain the nonlinear efficiency and the final operation frequency under consideration of the effects of the beam current, the beam energy and the slow wave structure. We show that the saturation mechanism of a PCM instablity is a close correspondence in that of the relativistic two stream instability by the coherent trapping of electrons in a single most-ustable wave. And the optimal conditions in PCM operation are also obtained from performing our nonliear analysis together with computer simulations.

  8. Ultra-Stable Superconducting-Maser Oscillator

    NASA Technical Reports Server (NTRS)

    Strayer, Donald M.; Dick, G. John

    1989-01-01

    Unprecedented stability of frequency in superconducting, triple-cavity ruby maser oscillator achieved by incorporation of amplitude-control subsystem. New design enhances ultra-stable measurements of time by reducing fluctuations to 2 X 10 to negative 19th power routinely, and to as little as 10 to negative 20th power in exceptional cases. Currents induced in superconducting pickup coil by changes in magnetic field in ruby. Currents from coil fed to superconducting quantum-interference device (SQUID) magnetometer, output used to generate control signal for electronically variable attenuator. Attenuator varies pump-signal amplitude in response to magnetic-field fluctuations in ruby. Very high feedback-loop gain used for sensitivity of control and adequate compensation of fluctuations.

  9. Discovering metal-poor circumstellar OH masers

    NASA Astrophysics Data System (ADS)

    Goldman, Steve; Green, James; van Loon, Jacco; Wood, Peter; Imai, Hiroshi; Groenewegen, Martin; Nanni, Ambra

    2014-10-01

    OH masers are excellent signposts for a variety of phenomenon including winds of highly-evolved stars (1612 MHz). Using the superior angular resolution and sensitivity of the ATCA, high spectral resolution of the CABB backend, and close proximity to the LMC (with half solar metallicity), this observation will allow us to extend an important relation involving the evolution of red giants and supergiants in a lower metallicity (van Loon, 2012). With even fewer detections with clear double-peaked profiles, indicating an expansion velocity of the circumstellar envelope, successful observation is vital for the advancement of our stellar mass-loss models. By refining the metallicity dependence of the mass-loss of highly-evolved red giants and supergiants in their superwind phase, we can better understand the evolution of these stars and their feedback within galaxies.

  10. SIMULTANEOUS OBSERVATIONS OF SiO AND H{sub 2}O MASERS TOWARD KNOWN STELLAR SiO AND H{sub 2}O MASER SOURCES. I

    SciTech Connect

    Kim, Jaeheon; Cho, Se-Hyung; Oh, Chung Sik; Byun, Do-Young E-mail: cho@kasi.re.k E-mail: bdy@kasi.re.k

    2010-05-15

    We present the results of simultaneous observations of both SiO and H{sub 2}O masers toward 166 known SiO and H{sub 2}O maser sources using the Korean VLBI Network Yonsei 21 m radio telescope during 2009 June. Both SiO and H{sub 2}O maser emission were detected from 112 sources giving a detection rate of 67% at one epoch observation. SiO-only maser emission was detected from 42 sources, while H{sub 2}O-only maser emission was detected from four sources. Most of the SiO masers appear around the stellar velocity, while H{sub 2}O masers show different characteristics compared with SiO masers. There are more than 20 sources that show a one-way peak or double peaks with respect to the stellar velocity and SiO maser peak velocity. The H{sub 2}O maser peak and integrated intensity ratios with respect to those of SiO (v = 1) show increasingly larger values from Mira variables, to OH/IR stars, to semi-regular variables. In addition, the IRAS two-color diagram of SiO and H{sub 2}O maser observational results is discussed.

  11. A New Cryogenically Cooled 8.4 GHZ Traveling Wave Maser For The Deep Space Network

    NASA Technical Reports Server (NTRS)

    Kovatch, Jason J.; Trowbridge, David L.

    1993-01-01

    This design has recently been adapted for operation in a 1.6K liquid helium bath with a cryogenic feed system on a 34 meter beam waveguide antenna and has achieved an input noise temperature of 1.7 K at the feedhorn aperture.

  12. Experimental Observations of Microwave Emission from a 35 GHz Cyclotron Autoresonant Maser

    DTIC Science & Technology

    1990-07-27

    beam to corkscrew about the axis with a specific amount of perpendicular velocity. Having received sufficient perpendicular velocity, the beam .xits the...power input to the crystal is shown in figure 2-13 and is treated as linear on the log - log scale. The calibration equation corresponding to the...power values rise linearly (on the log ordinate) to some point of saturation and then begin an oscillatory motion, consistent with numer- ical simulation

  13. Microwave Spectrum of the Ethanol-Methanol Dimer

    NASA Astrophysics Data System (ADS)

    Finneran, Ian A.; Carroll, Brandon; Mead, Griffin; Blake, Geoffrey

    2016-06-01

    The hydrogen bond donor/acceptor competition in mixed alcohol clusters remains a fundamental question in physical chemistry. Previous theoretical work on the prototype ethanol-methanol dimer has been inconclusive in predicting the energetically preferred structure. Here, we report the microwave spectrum of the ethanol-methanol dimer between 8-18 GHz, using a chirped pulse Fourier transform microwave spectrometer. With the aid of ab initio calculations, 36 transitions have been fit and assigned to a t-ethanol-acceptor, methanol-donor structure in an argon-backed expansion. In a helium-backed expansion, a second excited conformer has been observed, and tentatively assigned to a g-ethanol-acceptor, methanol-donor structure. No ethanol-donor, methanol-acceptor structures have been found, suggesting such structures are energetically disfavored.

  14. Detection of a weak maser emission pedestal associated with the SiO maser. [in variable late stars

    NASA Technical Reports Server (NTRS)

    Snyder, L. E.; Dickinson, D. F.; Brown, L. W.; Buhl, D.

    1978-01-01

    Results are reported for high-spectral-resolution observations of the v = 1, J = 1-0 SiO maser sources at 43,122.027 MHz (6.95 mm wavelength) associated with the variable stars Omega Cet, NML Tau, VY CMa, R Leo, W Hya, VX Sgr, NML Cyg, and R Cas. A weak underlying maser emission pedestal is clearly observed in the spectra of all but NML Cyg and R Cas. The data indicate that the underlying pedestal of SiO emission appears to originate in a shell-like region around the star, has a thermal appearance even though it must be due to weak maser emission, and appears to be part of the spectral signature of SiO maser emission from late-type stars. It is found that the center velocities of the pedestals may be used to determine stellar radial velocities. Observations of large-scale time variations in the intensity of the Ori A SiO maser and the detection of weak maser pedestals associated with each of the two strong emission-feature groups in Orion are also discussed. It is suggested that the Orion molecular cloud might contain two late-type long-period variable stars that may be semiregular variables.

  15. Torsion-rotation intensities in methanol

    NASA Astrophysics Data System (ADS)

    Pearson, John

    Methanol exists in numerous kinds of astronomical objects featuring a wide range of local conditions. The light nature of the molecule coupled with the internal rotation of the methyl group with respect to the hydroxyl group results in a rich, strong spectrum that spans the entire far-infrared region. As a result, any modest size observational window will have a number of strong methanol transitions. This has made it the gas of choice for testing THz receivers and to extract the local physical conditions from observations covering small frequency windows. The latter has caused methanol to be dubbed the Swiss army knife of astrophysics. Methanol has been increasingly used in this capacity and will be used even more for subsequent investigations into the Herschel archive, and with SOFIA and ALMA. Interpreting physical conditions on the basis of a few methanol lines requires that the molecular data, line positions, intensities, and collision rates, be complete, consistent and accurate to a much higher level than previously required for astrophysics. The need for highly reliable data is even more critical for modeling the two classes of widespread maser action and many examples of optical pumping through the torsional bands. Observation of the torsional bands in the infrared will be a unique opportunity to directly connect JWST observations with those of Herschel, SOFIA, and ALMA. The theory for the intensities of torsion-rotation transitions in a molecule featuring a single internally rotating methyl group is well developed after 70 years of research. However, other than a recent very preliminary and not completely satisfactory investigation of a few CH3OH torsional bands, this theory has never been experimentally tested for any C3V internal rotor. More alarming is a set of recent intensity calibrated microwave measurements that showed deviations relative to calculations of up to 50% in some ground state rotational transitions commonly used by astronomers to extract

  16. Supernova remnant masers: Shock interactions with molecular clouds

    NASA Astrophysics Data System (ADS)

    Hewitt, John William

    Maser emission from the 1720-MHz transition of hydroxyl(OH) has identified shock interactions in 10% of all supernova remnants(SNRs). Such maser-emitting SNRs are also bright in molecular line emission. Though somewhat rare, SNRs interacting with dense molecular clouds are an important class in which to study cosmic ray acceleration, SNR evolution, and effects on the energetics and chemistry of the interstellar medium. To study molecular shocks via a multiwavelength approach, the VLA, GBT, Spitzer Space Telescope have been used in the following ways: (i) With the GBT widespread OH(1720 MHz) emission and absorption in other OH lines is observed across the interaction site. Observations of all four ground-state transitions at 1720, 1667/5 and 1612 MHz allows us to model OH excitation, yielding the temperature, density and OH abundance in the post-shock gas. Maser emission is found to have a higher flux density with the GBT than with high-resolution VLA observations for 10 of 15 observed remnants, suggesting maser emission is present on large spatial scales. (ii) Sensitive VLA observations of select SNRs (W44, IC 443, Kes 69, 3C 391, G357.7+0.3) reveal the nature of enhanced 1720 MHz emission. Numerous weak compact masers as well as diffuse extended emission are detected tracing the shock-front. Zeeman splitting of masers permits the post-shock magnetic field strength and the line of sight field direction to be directly measured. (iii) Rotational lines of molecular hydrogen are detected at the position of several masers with Spitzer IRS spectroscopy between 5 and 35 mm. Excitation of the hydrogen lines requires the passage of a C-type shock through dense molecular gas, in agreement with the conditions derived from OH excitation. The presence of bright ionic lines requires multiple shocks present at the interaction site. (iv) A new survey for SNR-masers has identified four new interacting SNRs within 10 degrees of the Galactic Center. Maser-emitting SNRs are found to

  17. Detection of the torsionally excited state of methanol in Orion A

    NASA Technical Reports Server (NTRS)

    Lovas, F. J.; Suenram, R. D.; Snyder, L. E.; Hollis, J. M.; Lees, R. M.

    1982-01-01

    Torsionally excited methanol has been detected in Orion A, where three emission lines observed in the region of 93-100 GHz coincide with laboratory measurements of three methanol transitions. Torsionally excited methanol may therefore be used as a novel temperature probe, since this state lies near 200 per cm above the ground state, or about 290 K. No emission was detected from the transition arising from levels near 300 per cm, or approximately 430 K above the ground state.

  18. Preliminary results from a 7 station VLBI survey of OH masers in the galactic plane

    SciTech Connect

    Diamond, P.J.; Martinson, A.; Dennison, B.; Booth, R.S.; Winnberg, A.

    1988-11-01

    An initial analysis of a large VLBI survey of OH masers in the Galactic Plane reveals a correlation of maser component angular size with source distance. This correlation is presumably due to the effect of an intervening scattering medium.

  19. Ground-Based Investigations with the Cryogenic Hydrogen Maser

    NASA Technical Reports Server (NTRS)

    Walsworth, Ronald L.; Mattison, Edward; Vessot, Robert F. C.

    2003-01-01

    The cryogenic hydrogen maser (CHM) developed at the Smithsonian Astrophysical Observatory (SAO) was designed to be functionally similar to SAO room temperature hydrogen masers with appropriate modifications made for operation at cryogenic temperatures. A schematic of the SAO CHM is shown in Figure 1, and a description of this device and its operation follows. A beam of molecular hydrogen is dissociated into atoms at room temperature. The resultant beam of atomic hydrogen is then cooled, magnetically state selected, and focused into a quartz storage bulb centered inside of a microwave cavity resonant with the hydrogen hyperfine transition at 1420 MHz. The quartz storage bulb is coated with a superfluid He-4 film, and both the bulb and cavity are maintained near 0.5 K. The maser signal is coupled out inductively and carried to room temperature via semi-rigid coaxial cable. After passing through a room temperature isolator and preamp, the maser signal is detected with a low-noise heterodyne receiver as used in the room temperature SAO hydrogen masers. The maser temperature is lowered to 0.5 K using a recirculating He-3 refrigerator. This refrigerator consists of several cooling stages: a liquid nitrogen stage at 77 K, a liquid 4He bath at 4.2 K, a pumped He-4 pot at approximately 1.7 K, and the pumped, recirculating He-3 stage at 0.5 K. The atomic hydrogen beam, state selector, storage bulb and cavity are all connected inside a single, maser vacuum chamber (MVC). This space is pumped out from below by a turbo pump. Above the MVC, an inlet to the space allows for the input of flowing superfluid 4He film. External to the MVC is a second, outer vacuum chamber (OVC), maintained for operation of the cryostat and also pumped by a turbo pump. Inside the OVC, there is radiation shielding at 77 K and 1.7 K.

  20. Ground-Based Investigations with the Cryogenic Hydrogen Maser

    NASA Technical Reports Server (NTRS)

    Walsworth, Ronald L.; Mattison, Edward; Vessot, Robert F. C.

    2003-01-01

    The cryogenic hydrogen maser (CHM) developed at the Smithsonian Astrophysical Observatory (SAO) was designed to be functionally similar to SAO room temperature hydrogen masers with appropriate modifications made for operation at cryogenic temperatures. A schematic of the SAO CHM is shown in Figure 1, and a description of this device and its operation follows. A beam of molecular hydrogen is dissociated into atoms at room temperature. The resultant beam of atomic hydrogen is then cooled, magnetically state selected, and focused into a quartz storage bulb centered inside of a microwave cavity resonant with the hydrogen hyperfine transition at 1420 MHz. The quartz storage bulb is coated with a superfluid He-4 film, and both the bulb and cavity are maintained near 0.5 K. The maser signal is coupled out inductively and carried to room temperature via semi-rigid coaxial cable. After passing through a room temperature isolator and preamp, the maser signal is detected with a low-noise heterodyne receiver as used in the room temperature SAO hydrogen masers. The maser temperature is lowered to 0.5 K using a recirculating He-3 refrigerator. This refrigerator consists of several cooling stages: a liquid nitrogen stage at 77 K, a liquid 4He bath at 4.2 K, a pumped He-4 pot at approximately 1.7 K, and the pumped, recirculating He-3 stage at 0.5 K. The atomic hydrogen beam, state selector, storage bulb and cavity are all connected inside a single, maser vacuum chamber (MVC). This space is pumped out from below by a turbo pump. Above the MVC, an inlet to the space allows for the input of flowing superfluid 4He film. External to the MVC is a second, outer vacuum chamber (OVC), maintained for operation of the cryostat and also pumped by a turbo pump. Inside the OVC, there is radiation shielding at 77 K and 1.7 K.

  1. Nuclear Spin Maser at Highly Stabilized Low Magnetic Field and Search for Atomic EDM

    SciTech Connect

    Yoshimi, A.; Asahi, K.; Inoue, T.; Uchida, M.; Hatakeyama, N.; Tsuchiya, M.; Kagami, S.

    2009-08-04

    A nuclear spin maser is operated at a low static field through an active feedback scheme based on an optical nuclear spin detection and succeeding spin control by a transverse field application. The frequency stability of this optical-coupling spin maser is improved by installation of a low-noise current source for a solenoid magnet producing a static magnetic field in the maser operation. Experimental devices for application of the maser to EDM experiment are being developed.

  2. How to Detect Inclined Water Maser Disks (and Possibly Measure Black Hole Masses)

    NASA Astrophysics Data System (ADS)

    Darling, Jeremy

    2017-03-01

    We describe a method for identifying inclined water maser disks orbiting massive black holes and for potentially using them to measure black hole masses. Owing to the geometry of maser amplification pathways, the minority of water maser disks are observable: only those viewed nearly edge-on have been identified, suggesting that an order of magnitude additional maser disks exist. We suggest that inward-propagating masers are gravitationally deflected by the central black hole, thereby scattering water maser emission out of the disk plane and enabling detection. The signature of an inclined water maser disk would be narrow masers near the systemic velocity that appear to emit from the black hole position, as identified by the radio continuum core. To explore this possibility, we present high-resolution (0.″07-0.″17) Very Large Array line and continuum observations of 13 galaxies with narrow water maser emission and show that three are good inclined-disk candidates (five remain ambiguous). For the best case, CGCG 120-039, we show that the maser and continuum emission are coincident to within 3.5 ± 1.4 pc (6.7 ± 2.7 mas). Subsequent very long baseline interferometric maps can confirm candidate inclined disks and have the potential to show maser rings or arcs that provide a direct measurement of black hole mass, although the mass precision will rely on knowledge of the size of the maser disk.

  3. Simultaneous VLBA polarimetric observations of the v = {1,2} J = 1-0 and v = 1, J = 2-1 SiO maser emission towards VY CMa II: component-level polarization analysis

    NASA Astrophysics Data System (ADS)

    Richter, L.; Kemball, A.; Jonas, J.

    2016-09-01

    This paper presents a component-level comparison of the polarized v = 1 J = 1-0, v = 2 J = 1-0 and v = 1 J = 2-1 SiO maser emission towards the supergiant star VY CMa at milliarcsecond-scale, as observed using the Very Long Baseline Array at λ = 7 and 3 mm. An earlier paper considered overall maser morphology and constraints on SiO maser excitation and pumping derived from these data. The goal of the current paper is to use the measured polarization properties of individual co-spatial components detected across multiple transitions to provide constraints on several competing theories for the transport of polarized maser emission. This approach minimizes the significant effects of spatial blending. We present several diagnostic tests designed to distinguish key features of competing theoretical models for maser polarization. The number of coincident features is limited by sensitivity however, particularly in the v = 1 J = 2-1 transition at 86 GHz, and deeper observations are needed. Preliminary conclusions based on the current data provide some support for: (i) spin-independent solutions for linear polarization; (ii) the influence of geometry on the distribution of fractional linear polarization with intensity; and, (iii) π/2 rotations in linear polarization position angle arising from transitions across the Van Vleck angle (sin 2θ = 2/3) between the maser line of sight and magnetic field. There is weaker evidence for several enumerated non-Zeeman explanations for circular polarization. The expected 2:1 ratio in circular polarization between J = 1-0 and J = 2-1 predicted by standard Zeeman theory cannot unfortunately be tested conclusively due to insufficient coincident components.

  4. SIMULTANEOUS OBSERVATIONS OF SiO AND H{sub 2}O MASERS TOWARD KNOWN STELLAR H{sub 2}O MASER SOURCES

    SciTech Connect

    Kim, Jaeheon; Cho, Se-Hyung; Kim, Sang Joon E-mail: cho@kasi.re.kr

    2013-01-01

    We present the results of simultaneous observations of SiO v = 1, 2, {sup 29}SiO v = 0, J = 1-0, and H{sub 2}O 6{sub 16}-5{sub 23} maser lines toward 152 known stellar H{sub 2}O maser sources using the Yonsei 21 m radio telescope of the Korean VLBI Network from 2009 June to 2011 January. Both SiO and H{sub 2}O masers were detected from 62 sources with a detection rate of 40.8%. The SiO-only maser emission without H{sub 2}O maser detection was detected from 27 sources, while the H{sub 2}O-only maser without SiO maser detection was detected from 22 sources. Therefore, the overall SiO maser emission was detected from 89 sources, resulting in a detection rate of 58.6%. We have identified 70 new detections of the SiO maser emission. For both H{sub 2}O and SiO maser detected sources, the peak and integrated antenna temperatures of SiO masers are stronger than those of H{sub 2}O masers in both Mira variables and OH/IR stars and the relative intensity ratios of H{sub 2}O to SiO masers in OH/IR stars are larger than those in Mira variables. In addition, distributions of 152 observed sources were investigated in the IRAS two-color diagram.

  5. Development of the maser-caviton ball lightning theory

    NASA Astrophysics Data System (ADS)

    Handel, Peter H.; Leitner, Jean-Francois

    1994-05-01

    The maser-caviton ball lightning theory is briefly described, is compared with the available observations of ball lightning, and is further developed on the basis of the rate equations governing the evolution of the photon number in a single-mode maser. The focus of this paper is on the explosive growth of the photon number at the premature demise of a large atmospheric maser. Ball lightning is a localized high-field soliton forming a cavity surrounded by plasma in this theory. The source of VHF energy is a large atmospheric maser occupying a volume of serveral cubic miles for the case of open air ball lightning, and occupying the volume of the room in electrically shielded confined ball lightning cases. The main, well-known features of ball lightning, including its appearance right after a strong electric field pulse usually caused by lightning, its passage through closed windows and other dielectrics, its always harmless existence in electrically shielded (e.g., metallic) enclosures, without the possibility of electrostatic-explosive demise, its total absence in the vicinity of high peaks or lightning observation stations, as well as the character of its positioning and motion with respect to conducting bodies, and its apparent lack of buoyancy in the air can all be explained consistently only with the help of this theory as far as we can see. The explosive demise of open air ball lightning is described here in terms of maser spiking phonomena with the help of elementary equations.

  6. SiO isotopic maser emission from VY Canis Majoris

    SciTech Connect

    Deguchi, S.; Good, J.; Fan, Y.; Mao, X.; Wang, D.; Ukita, N.

    1983-01-15

    We have detected strong maser emission from VY CMa in the /sup 29/SiO J = 2--1, v = 0 transition. The intensity of the /sup 29/SiO emission is about twice that of the ground-state /sup 28/SiO maser emission which we have also measured. We also looked for /sup 30/SiO emission, but none was detected. Both the /sup 28/SiO and /sup 29/SiO emission profiles have been measured on occasions separated by as much as 3 months, and no variability has been detected in the detailed structure of the lines above the level of the noise. The radial velocities of the masers in VY CMa are close to the central star velocity as derived from the OH 1612 MHz double-peaked maser emission and the broad /sup 28/SiO weak emission. One possible explanation for this is that the maser emission comes from a rotating disk around the central star.

  7. Pilot Search for 54-MHz Maser Emission from Interstellar Hydroxyl Using LOFAR

    NASA Astrophysics Data System (ADS)

    Hoffman, Ian M.; Heald, G.; Oonk, R.; McKean, J.; Mol, J.; Hessels, J.; Toribio, C.; LOFAR Collaboration

    2014-01-01

    We present the results of the most sensitive search to date for the two 54-MHz spectral lines of the hydroxyl (OH) molecule. These are the preliminary results of a larger, planned observational campaign. The splitting of the rotational ground state of the hydroxyl molecule gives rise to the four familiar 1.7-GHz transitions by which OH is known in the interstellar medium. There are also two magnetic-dipole transitions among these states at frequencies of 53.2 MHz and 55.1 MHz. These 54-MHz transitions have never been detected astronomically. Because of the relative weakness of the magnetic-dipole emission process, it is expected that only maser emission will generate a detectable 54-MHz signal. Two previous searches have been conducted by other authors with other instruments toward Galactic sources of known 1720-MHz OH maser emission: three sources were searched at 55.1 MHz and two other sources were searched at 53.2 MHz, resulting in upper limits of approximately 30 Jy for spectral channels of 2 km/s in width. In preparation for our future observational campaign that will apply the unprecedented sensitivity of LOFAR to the search for 54-MHz OH emission, we conducted a pilot project using six hours of Commissioning Time. These observations employed 21 48-element stations and produced a spectral resolution of approximately 0.5 km/s for both the 53.2- and 55.1-MHz lines. This spectral resolution is a considerable improvement over previous searches since it is suitable both for resolving the characteristically narrow width of maser lines and for identifying radiofrequency interference. In our pilot observations, no emission was detected at either frequency with an upper limit of approximately 3 Jy. We observed the Galactic sources W75N and W3(OH), neither of which have been searched previously at either frequency. We discuss the astrophysical implications of these sensitive non-detections. LOFAR, the Low Frequency Array designed and constructed by ASTRON, has

  8. Nonlinear analysis of the Cerenkov maser

    SciTech Connect

    Freund, H.P.; Ganguly, A.K. )

    1990-10-01

    The nonlinear evolution of the Cerenkov maser amplifier is investigated numerically for a configuration that consists of an energetic electron beam propagating through a dielectric-lined cylindrical waveguide. An axial guide magnetic field is included in the formulation in order to improve beam confinement. A set of coupled nonlinear differential equations is derived in three dimensions that governs the evolution of both the electromagnetic field and the trajectories of an ensemble of electrons. The system is assumed to be azimuthally symmetric, and the electromagnetic field is represented as a superposition of the TM{sub 0{ital n}} modes of the vacuum waveguide. The initial conditions are chosen to model the simultaneous injection of either a solid or annular electron beam, and an electromagnetic wave of arbitrary input power. Thermal effects are treated under the assumption that the beam is {ital initially} monoenergetic but exhibits a pitch angle spread; however, the subsequent evolution of the beam is treated in a self-consistent manner. This class of distribution is appropriate to the treatment of diode-produced beams and describes a beam with an initial axial energy spread. This is the crucial determinant in the efficiency, since saturation occurs by means of an axial bunching mechanism that results in the phase trapping of the beam. The specific parameters used in the numerical analysis correspond to experiments conducted at Dartmouth College (J. Appl. Phys. {bold 58}, 627 (1985)), and good agreement is found between theory and experiment.

  9. Amplification of OAM radiation by astrophysical masers

    NASA Astrophysics Data System (ADS)

    Gray, M. D.; Pisano, G.; Maccalli, S.; Schemmel, P.

    2014-12-01

    We extend the theory of astrophysical maser propagation through a medium with a Zeeman-split molecular response to the case of a non-uniform magnetic field, and allow a component of the electric field of the radiation in the direction of propagation: a characteristic of radiation with orbital angular momentum. A classical reduction of the governing equations leads to a set of nine differential equations for the evolution of intensity-like parameters for each Fourier component of the radiation. Four of these parameters correspond to the standard Stokes parameters, whilst the other five represent the z-component of the electric field, and its coupling to the conventional components in the x-y-plane. A restricted analytical solution of the governing equations demonstrates a non-trivial coupling of the Stokes parameters to those representing orbital angular momentum: the z-component of the electric field can grow from a background in which only Stokes-I is non-zero. A numerical solution of the governing equations reveals radiation patterns with a radial and angular structure for the case of an ideal quadrupole magnetic field perpendicular to the propagation direction. In this ideal case, generation of radiation orbital angular momentum, like polarization, can approach 100 per cent.

  10. Cyclotron autoresonance maser in the millimeter region

    NASA Astrophysics Data System (ADS)

    Nikolov, N. A.; Spasovski, I. P.; Kostov, K. G.; Velichkov, J. N.; Spasov, V. A.

    1990-06-01

    This paper investigates the optimal experimental conditions for a cyclotron autoresonance maser (CARM) regime realized by a nonadiabatic magnetic beam pumping in the millimeter wavelength region. In the experiment, a Blumline-type accelerator with a voltage up to 650 kV and maximal current up to 10 kA is used to generate a hollow beam with a pulse duration of 30 ns. The electron beam, emitted from a graphite cathode with a 10-mm diameter, propagates in a cylindrical drift tube of 56 mm diam and a length of 500 mm. The external magnetic field B, provided by a solenoidal magnet, is homogeneous along the drift tube up to a distance of 300 mm from the cathode. The experiment demonstrated the generation of microwave radiation in the time interval from 0.0016 to 0.0023 sec after the switch-on of the external magnetic field. Two maxima of the output microwave power (8 and 10 MW) at a wavelength of 5 and 5.5 mm, respectively, were observed.

  11. The Methanol Economy Project

    SciTech Connect

    Olah, George; Prakash, G. K.

    2014-02-01

    The Methanol Economy Project is based on the concept of replacing fossil fuels with methanol generated either from renewable resources or abundant natural (shale) gas. The full methanol cycle was investigated in this project, from production of methanol through bromination of methane, bireforming of methane to syngas, CO2 capture using supported amines, co-electrolysis of CO2 and water to formate and syngas, decomposition of formate to CO2 and H2, and use of formic acid in a direct formic acid fuel cell. Each of these projects achieved milestones and provided new insights into their respective fields.

  12. A correlational analysis of the effects of changing environmental conditions on the NR atomic hydrogen maser

    NASA Technical Reports Server (NTRS)

    Dragonette, Richard A.; Suter, Joseph J.

    1992-01-01

    An extensive statistical analysis has been undertaken to determine if a correlation exists between changes in an NR atomic hydrogen maser's frequency offset and changes in environmental conditions. Correlation analyses have been performed comparing barometric pressure, humidity, and temperature with maser frequency offset as a function of time for periods ranging from 5.5 to 17 days. Semipartial correlation coefficients as large as -0.9 have been found between barometric pressure and maser frequency offset. Correlation between maser frequency offset and humidity was small compared to barometric pressure and unpredictable. Analysis of temperature data indicates that in the most current design, temperature does not significantly affect maser frequency offset.

  13. NASA hydrogen maser accuracy and stability in relation to world standards

    NASA Technical Reports Server (NTRS)

    Peters, H. E.; Percival, D. B.

    1973-01-01

    Frequency comparisons were made among five NASA hydrogen masers in 1969 and again in 1972 to a precision of one part in 10 to the 13th power. Frequency comparisons were also made between these masers and the cesium-beam ensembles of several international standards laboratories. The hydrogen maser frequency stabilities as related to IAT were comparable to the frequency stabilities of individual time scales with respect to IAT. The relative frequency variations among the NASA masers, measured after the three-year interval, were 2 + or - 2 parts in 10 to the 13th power. Thus time scales based on hydrogen masers would have excellent long-term stability and uniformity.

  14. A correlational analysis of the effects of changing environmental conditions on the NR atomic hydrogen maser

    NASA Technical Reports Server (NTRS)

    Dragonette, Richard A.; Suter, Joseph J.

    1992-01-01

    An extensive statistical analysis has been undertaken to determine if a correlation exists between changes in an NR atomic hydrogen maser's frequency offset and changes in environmental conditions. Correlation analyses have been performed comparing barometric pressure, humidity, and temperature with maser frequency offset as a function of time for periods ranging from 5.5 to 17 days. Semipartial correlation coefficients as large as -0.9 have been found between barometric pressure and maser frequency offset. Correlation between maser frequency offset and humidity was small compared to barometric pressure and unpredictable. Analysis of temperature data indicates that in the most current design, temperature does not significantly affect maser frequency offset.

  15. Physics of systematic frequency variations in hydrogen masers

    NASA Technical Reports Server (NTRS)

    Mattison, Edward M.

    1990-01-01

    The frequency stability of hydrogen masers for intervals longer that 10(exp 4) seconds is limited at present by systematic processes. Researchers discuss the physics of frequency-determining mechanisms internal to the maser that are susceptible to systematic variations, and the connections between these internal mechanisms and external environmental factors. Based upon estimates of the magnitudes of systematic effects, they find that the primary internal mechanisms currently limiting long-term maser frequency stability are cavity pulling, at the level parts in 10(exp 15) per day, and wall shift variations, at the level of parts in 10(exp 16) to parts in 10(exp 15) per day. They discuss strategies for reducing systematic frequency variations.

  16. Physics of systematic frequency variations in hydrogen masers

    NASA Technical Reports Server (NTRS)

    Mattison, Edward M.

    1992-01-01

    The frequency stability of hydrogen masers for intervals longer than 10 exp 4 s is currently limited by systematic processes. The physics of frequency-determining mechanisms internal to the maser that are susceptible to systematic variations, and the connections between these internal mechanisms and external environmental factors are discussed. From estimates of the magnitudes of systematic effects, it is found that the primary internal mechanisms limiting long-term maser frequency stability are cavity pulling, at the level of parts in 1015 per day, and wall shift variations, at the level of parts in 10 exp 16 to parts in 10 exp 15 per day. Strategies for reducing systematic frequency variations are discussed.

  17. Physics of systematic frequency variations in hydrogen masers

    NASA Technical Reports Server (NTRS)

    Mattison, Edward M.

    1992-01-01

    The frequency stability of hydrogen masers for intervals longer than 10 exp 4 s is currently limited by systematic processes. The physics of frequency-determining mechanisms internal to the maser that are susceptible to systematic variations, and the connections between these internal mechanisms and external environmental factors are discussed. From estimates of the magnitudes of systematic effects, it is found that the primary internal mechanisms limiting long-term maser frequency stability are cavity pulling, at the level of parts in 1015 per day, and wall shift variations, at the level of parts in 10 exp 16 to parts in 10 exp 15 per day. Strategies for reducing systematic frequency variations are discussed.

  18. Water masers in W49N - The youngest stellar jet?

    NASA Technical Reports Server (NTRS)

    Mac Low, MORDECAI-M.; Elitzur, Moshe

    1992-01-01

    Observations by Gwinn et al. (1992) of the proper motions of water masers in W49N show that they have an elongated distribution expanding from a common center. Features with high space velocity only occur far from the center, while low-velocity features occur at all distances. It is proposed that water masers in star-forming regions occur in expanding shells swept up by high-velocity winds from young, massive stars during the early phases of the expansion. In W49N, confinement of the bubble by a density distribution with an axial cavity can explain both the velocity field and the shape of the maser distribution. A fully dynamical calculation of the expanding bubble is presented which provides a satisfactory fit for the observations and suggests that this system is only about 250 yr old. Thus these observations may show the very first stages of the formation of a jet from a young stellar object.

  19. The distribution of maser emission in OH/IR stars

    NASA Technical Reports Server (NTRS)

    Welty, Alan D.; Fix, John D.; Mutel, Robert L.

    1987-01-01

    The 1612 MHz OH emission from five OH/IR stars has been mapped at three epochs over a 2.5 yr period of time. Although the stars were observed at very different phases in the radio light curve of each, there were no remarkable changes in the appearance of the maps. This probably implies that the properties of the masers do not range widely throughout a maser shell. The maps have been used to produce star-centered surface maps of the distribution of maser emission from each star. The surface maps generally are sparsely filled with OH emission and are dominated by relatively few (about 10) major clumps of emission. The presence of large regions of low intensity in the surface maps suggests that the number of individual emitting elements is relatively small or that there are a larger number of elements which are distributed in the shell in a distinctly nonrandom manner.

  20. Non-Zeeman circular polarization of molecular maser spectral lines

    SciTech Connect

    Houde, Martin

    2014-11-01

    We apply the anisotropic resonant scattering model developed to explain the presence of non-Zeeman circular polarization signals recently detected in the {sup 12}CO (J = 2 → 1) and (J = 1 → 0) transitions in molecular clouds to Stokes V spectra of SiO v = 1 and v = 2, (J = 1 → 0) masers commonly observed in evolved stars. It is found that the observed antisymmetric 'S'- and symmetric '∪'- or '∩'-shaped spectral profiles naturally arise when the maser radiation scatters off populations of foreground molecules located outside the velocity range covered by the background maser radiation. Using typical values for the relevant physical parameters, it is estimated that magnetic field strengths on the order of a few times 15 mG are sufficient to explain the observational results found in the literature.

  1. Runaway electrons in a tokamak: A free-electron maser

    SciTech Connect

    Kurzan, B.; Steuer, K.

    1997-04-01

    In ohmic divertor plasma discharges of the ASDEX upgrade tokamak containing a small population of runaway electrons, fluctuating emission in the microwave region with a very narrow bandwidth is observed. The radiation can be explained by relativistic runaway electrons, which are captured in a ripple resonance of the tokamak and are thus made monoenergetic enough that they can undergo the collective instability of a free-electron maser. From the frequency of the maser, the energy of the runaway electrons, and from the linewidth and energy per radiation pulse, the particle density of the runaway electrons is determined locally. Observing this maser radiation is thus a different diagnostic for runaway electrons in tokamaks. {copyright} {ital 1997} {ital The American Physical Society}

  2. Binary systems: implications for outflows & periodicities relevant to masers

    NASA Astrophysics Data System (ADS)

    Singh, Nishant K.; Deshpande, Avinash A.

    2012-07-01

    Bipolar molecular outflows have been observed and studied extensively in the past, but some recent observations of periodic variations in maser intensity pose new challenges. Even quasi-periodic maser flares have been observed and reported in the literature. Motivated by these data, we have tried to study situations in binary systems with specific attention to the two observed features, i.e., the bipolar flows and the variabilities in the maser intensity. We have studied the evolution of spherically symmetric wind from one of the bodies in the binary system, in the plane of the binary. Our approach includes the analytical study of rotating flows with numerical computation of streamlines of fluid particles using PLUTO code. We present the results of our findings assuming simple configurations, and discuss the implications.

  3. Binary systems: implications for outflows and periodicities relevant to masers

    NASA Astrophysics Data System (ADS)

    Singh, Nishant K.; Deshpande, Avinash A.

    Bipolar molecular outflows have been observed and studied extensively in the past, but some recent observations of periodic variations in maser intensity pose new challenges. Even quasi-periodic maser flares have been observed and reported in the literature. Motivated by these data, we have tried to study situations in binary systems with specific attention to the two observed features, i.e., the bipolar flows and the variabilities in the maser intensity. We have studied the evolution of spherically symmetric wind from one of the bodies in the binary system, in the plane of the binary. Our approach includes the analytical study of rotating flows with numerical computation of streamlines of fluid particles using PLUTO code. We present the results of our findings assuming simple configurations, and discuss the implications.

  4. Physics of systematic frequency variations in hydrogen masers

    NASA Technical Reports Server (NTRS)

    Mattison, Edward M.

    1990-01-01

    The frequency stability of hydrogen masers for intervals longer that 10(exp 4) seconds is limited at present by systematic processes. Researchers discuss the physics of frequency-determining mechanisms internal to the maser that are susceptible to systematic variations, and the connections between these internal mechanisms and external environmental factors. Based upon estimates of the magnitudes of systematic effects, they find that the primary internal mechanisms currently limiting long-term maser frequency stability are cavity pulling, at the level parts in 10(exp 15) per day, and wall shift variations, at the level of parts in 10(exp 16) to parts in 10(exp 15) per day. They discuss strategies for reducing systematic frequency variations.

  5. Proper Motions of Water Masers in Circumstellar Shells

    NASA Astrophysics Data System (ADS)

    Marvel, K. B.; Diamond, P. J.; Kemball, A. J.

    We present proper motion measurements of circumstellar water masers obtained with the VLBA. The objects observed include S Persei, VX Sagittarii, U Herculis, VY Canis Majoris, NML Cygni, IK Tauri and RX Bootis. Results of the observations and modeling indicate that the water masers exist in a kinematically complex region of the circumstellar envelope, which is not well fit by the standard model of a uniformly expanding spherical wind. Attempts at fitting an ellipsoidal geometric distribution with a variety of kinematic models are presented. Estimates for the distances of the stars are also discussed. A change in position of the maser spots as a function of velocity has been measured. This effect may be used to place limits on accelerations in the masing gas.

  6. Water masers in W49N - The youngest stellar jet?

    NASA Technical Reports Server (NTRS)

    Mac Low, MORDECAI-M.; Elitzur, Moshe

    1992-01-01

    Observations by Gwinn et al. (1992) of the proper motions of water masers in W49N show that they have an elongated distribution expanding from a common center. Features with high space velocity only occur far from the center, while low-velocity features occur at all distances. It is proposed that water masers in star-forming regions occur in expanding shells swept up by high-velocity winds from young, massive stars during the early phases of the expansion. In W49N, confinement of the bubble by a density distribution with an axial cavity can explain both the velocity field and the shape of the maser distribution. A fully dynamical calculation of the expanding bubble is presented which provides a satisfactory fit for the observations and suggests that this system is only about 250 yr old. Thus these observations may show the very first stages of the formation of a jet from a young stellar object.

  7. SIMULTANEOUS OBSERVATIONS OF SiO AND H{sub 2}O MASERS TOWARD SYMBIOTIC STARS

    SciTech Connect

    Cho, Se-Hyung; Kim, Jaeheon E-mail: jhkim@kasi.re.k

    2010-08-10

    We present the results of simultaneous observations of SiO v = 1, 2, J = 1-0, {sup 29}SiO v = 0, J = 1-0, and H{sub 2}O 6{sub 16}-5{sub 23} maser lines performed with the KVN Yonsei 21 m radio telescope from 2009 November to 2010 January. We searched for these masers in 47 symbiotic stars and detected maser emission from 21 stars, giving the first time detection from 19 stars. Both SiO and H{sub 2}O masers were detected from seven stars of which six were D-type symbiotic stars and one was an S-type star, WRAY 15-1470. In the SiO maser emission, the {sup 28}SiO v = 1 maser was detected from 10 stars, while the v = 2 maser was detected from 15 stars. In particular, the {sup 28}SiO v = 2 maser emission without the v = 1 maser detection was detected from nine stars with a detection rate of 60%, which is much higher than that of isolated Miras/red giants. The {sup 29}SiO v = 0 maser emission was also detected from two stars, H 2-38 and BF Cyg, together with the {sup 28}SiO v = 2 maser. We conclude that these different observational results between isolated Miras/red giants and symbiotic stars may be related with the presence of hot companions in a symbiotic binary system.

  8. Where do the Nuclear H2O masers in Centaurus A Originate?

    NASA Astrophysics Data System (ADS)

    Ott, Juergen; Henkel, Christian; Edwards, Philip; Meier, David; Brunthaler, Andreas; Mao, Minnie; Peck, Alison; Brisken, Walter; Mueller, Cornelia; Impellizzeri, Caterina M. V.; McCoy, Mark

    2013-10-01

    We have recently detected nuclear water maser emission in the closest radio galaxy, Centaurus A, using the ATCA (Ott et al. 2013). Even with a maximum baseline of 6 km, the ATCA lacks the spatial resolution required to pin down the exact location of the maser spots and hence unambiguously determine the origin of the maser emission. The spectral properties suggest a jet maser scenario, a maser that is pumped by the jet colliding with an ambient molecular cloud. However, we cannot exclude a disk maser, ie. a maser excited in the accretion disk of Centaurus A's central supermassive black hole (SMBH). Here we propose to use the LBA to spatially resolve the location of the water maser emission in Centaurus A. For a jet maser we will be able to determine the distance from the SMBH, whether it is located at the receding or approaching jet, and measure any positional offset between the maser and the jet. For a disk maser, we will be able to derive a disk model and thus the mass of the SMBH, as well as a geometric distance to the merely 3.8 Mpc distant Cen A. This would contribute to the calibration of the cosmological distance ladder.

  9. X-Band Ultra-Low Noise Maser Amplifier Performance

    NASA Technical Reports Server (NTRS)

    Glass, G.; Johnson, D.; Ortiz, G.

    1993-01-01

    Noise temperature measurements of an 8440 MHz ultra-low noise maser amplifier (ULNA) have been performed at sub-atmospheric, liquid helium temperatures. The traveling wave maser operated while immersed in a liquid helium bath. The lowest input noise temperature measured was 1.23 plus or minus 0.16 K at a physical temperature of 1.60 kelvin. At this physical temperature the observed gain per unit length of ruby was 4.6 dB/cm, and the amplifier had a 3 dB-bandwidth of 76 MHz.

  10. X-band ultralow-noise maser amplifier performance

    NASA Technical Reports Server (NTRS)

    Glass, G. W.; Ortiz, G. G.; Johnson, D. L.

    1994-01-01

    Noise temperature measurements of an 8440-MHz ultralow noise maser amplifier (ULNA) have been performed at subatmospheric, liquid-helium temperatures. The traveling-wave maser was operated while immersed in a liquid helium bath. The lowest input noise temperature measured was 1.43 +/- 0.16 K at a physical temperature of 1.60 K. At this physical temperature, the observed gain per centimeter of ruby was 4.9 dB/cm. The amplifier had a 3-dB bandwidth of 76 MHz.

  11. N-bursty emission from Uranus: A cyclotron maser source?

    NASA Technical Reports Server (NTRS)

    Curran, D. B.; Menietti, J. D.

    1993-01-01

    Ray tracing studies of RX-mode emission from the north polar regions of Uranus indicate that the n-bursty radio emission may have a source along field lines with footprints near the northern magnetic pole (perhaps in the cusp), but not necessarily associated with regions of strong UV emission. This is in contrast with similar studies for the Uranus nightside smooth radio emission, which are believed to be due to the cyclotron maser instability. Source regions can be found for both hollow and filled emission cones and for frequencies well above the local gyrofreuquency implying that mechanisms other than the cyclotron maser mechanism may be operating.

  12. Cryogenic H maser in a strong B field

    SciTech Connect

    Maan, A.C.; Stoof, H.T.C.; Verhaar, B.J. )

    1990-03-01

    We study the spin-exchange frequency shift of the cryogenic hydrogen maser for {ital B}{ne}0. A general expression is derived in terms of populations of ground-state hyperfine levels. The coefficients in this expression are calculated in the degenerate-internal-states approximation, as well as to first order in the hyperfine plus Zeeman splitting. Numerical results are compared with rigorous coupled-channel calculations. Some implications are pointed out for the frequency stability of the H maser in a magnetic field.

  13. Magnetic shielding and vacuum test for passive hydrogen masers

    NASA Technical Reports Server (NTRS)

    Gubser, D. U.; Wolf, S. A.; Jacoby, A. B.; Jones, L. D.

    1982-01-01

    Vibration tests on high permeability magnetic shields used in the SAO-NRL Advanced Development Model (ADM) hydrogen maser were made. Magnetic shielding factors were measured before and after vibration. Preliminary results indicate considerable (25%) degradation. Test results on the NRL designed vacuum pumping station for the ADM hydrogen maser are also discussed. This system employs sintered zirconium carbon getter pumps to pump hydrogen plus small ion pumps to pump the inert gases. In situ activation tests and pumping characteristics indicate that the system can meet design specifications.

  14. Atomic hydrogen maser measurements with wall surfaces of carbon tetrafluoride

    NASA Technical Reports Server (NTRS)

    Vessot, R. F. C.; Mattison, E. M.; Imbier, E. A.; Zhai, Z. C.

    1984-01-01

    The principal objectives of the Smithsonian Astrophysical Observatory cold maser research programs are given. This work is aimed principally at understanding more about the interaction of hydrogen atoms with wall coatings of fluorinated ethylene propylene (Dupont Teflon FEP-120 co-polymer) and of carbon tetrafluoride (CE4). The principal measured quantity in these experiments is the wall shift of the maser's output frequency. The wall shift per atomic collision was calculated from the measured wall frequency shift. This assumes that the wall surface area is smooth on a molecular scale.

  15. Dielectric-loaded waveguide circulator for cryogenically cooled and cascaded maser waveguide structures

    NASA Technical Reports Server (NTRS)

    Clauss, R. C.; Quinn, R. B. (Inventor)

    1980-01-01

    A dielectrically loaded four port waveguide circulator is used with a reflected wave maser connected to a second port between first and third ports to form one of a plurality of cascaded maser waveguide structures. The fourth port is connected to a waveguide loaded with microwave energy absorbing material. The third (output signal) port of one maser waveguide structure is connected by a waveguide loaded with dielectric material to the first (input) port of an adjacent maser waveguide structure, and the second port is connected to a reflected wave maser by a matching transformer which passes the signal to be amplified into and out of the reflected wavemaser and blocks pumping energy in the reflected wave maser from entering the circulator. A number of cascaded maser waveguide structures are thus housed in a relatively small volume of conductive material placed within a cryogenically cooled magnet assembly.

  16. NEW MASER EMISSION FROM NONMETASTABLE AMMONIA IN NGC 7538. II. GREEN BANK TELESCOPE OBSERVATIONS INCLUDING WATER MASERS

    SciTech Connect

    Hoffman, Ian M.; Seojin Kim, Stella

    2011-12-15

    We present new maser emission from {sup 14}NH{sub 3} (9,6) in NGC 7538. Our observations include the known spectral features near v{sub LSR} = -60 km s{sup -1} and -57 km s{sup -1} and several more features extending to -46 km s{sup -1}. In three epochs of observation spanning two months we do not detect any variability in the ammonia masers, in contrast to the >10-fold variability observed in other {sup 14}NH{sub 3} (9,6) masers in the Galaxy over comparable timescales. We also present observations of water masers in all three epochs for which emission is observed over the velocity range -105 km s{sup -1} < v{sub LSR} < -4 km s{sup -1}, including the highest velocity water emission yet observed from NGC 7538. Of the remarkable number of maser species in IRS 1, H{sub 2}O and, now, {sup 14}NH{sub 3} are the only masers known to exhibit emission outside of the velocity range -62 km s{sup -1} < v{sub LSR} < -51 km s{sup -1}. However, we find no significant intensity or velocity correlations between the water emission and ammonia emission. We also present a non-detection in the most sensitive search to date toward any source for emission from the CC{sup 32}S and CC{sup 34}S molecules, indicating an age greater than Almost-Equal-To 10{sup 4} yr for IRS 1-3. We discuss these findings in the context of embedded stellar cores and recent models of the region.

  17. Methanol partial oxidation reformer

    DOEpatents

    Ahmed, Shabbir; Kumar, Romesh; Krumpelt, Michael

    1999-01-01

    A partial oxidation reformer comprising a longitudinally extending chamber having a methanol, water and an air inlet and an outlet. An igniter mechanism is near the inlets for igniting a mixture of methanol and air, while a partial oxidation catalyst in the chamber is spaced from the inlets and converts methanol and oxygen to carbon dioxide and hydrogen. Controlling the oxygen to methanol mole ratio provides continuous slightly exothermic partial oxidation reactions of methanol and air producing hydrogen gas. The liquid is preferably injected in droplets having diameters less than 100 micrometers. The reformer is useful in a propulsion system for a vehicle which supplies a hydrogen-containing gas to the negative electrode of a fuel cell.

  18. Methanol partial oxidation reformer

    DOEpatents

    Ahmed, S.; Kumar, R.; Krumpelt, M.

    1999-08-17

    A partial oxidation reformer is described comprising a longitudinally extending chamber having a methanol, water and an air inlet and an outlet. An igniter mechanism is near the inlets for igniting a mixture of methanol and air, while a partial oxidation catalyst in the chamber is spaced from the inlets and converts methanol and oxygen to carbon dioxide and hydrogen. Controlling the oxygen to methanol mole ratio provides continuous slightly exothermic partial oxidation reactions of methanol and air producing hydrogen gas. The liquid is preferably injected in droplets having diameters less than 100 micrometers. The reformer is useful in a propulsion system for a vehicle which supplies a hydrogen-containing gas to the negative electrode of a fuel cell. 7 figs.

  19. Methanol partial oxidation reformer

    DOEpatents

    Ahmed, S.; Kumar, R.; Krumpelt, M.

    1999-08-24

    A partial oxidation reformer is described comprising a longitudinally extending chamber having a methanol, water and an air inlet and an outlet. An igniter mechanism is near the inlets for igniting a mixture of methanol and air, while a partial oxidation catalyst in the chamber is spaced from the inlets and converts methanol and oxygen to carbon dioxide and hydrogen. Controlling the oxygen to methanol mole ratio provides continuous slightly exothermic partial oxidation reactions of methanol and air producing hydrogen gas. The liquid is preferably injected in droplets having diameters less than 100 micrometers. The reformer is useful in a propulsion system for a vehicle which supplies a hydrogen-containing gas to the negative electrode of a fuel cell. 7 figs.

  20. Methanol partial oxidation reformer

    DOEpatents

    Ahmed, Shabbir; Kumar, Romesh; Krumpelt, Michael

    2001-01-01

    A partial oxidation reformer comprising a longitudinally extending chamber having a methanol, water and an air inlet and an outlet. An igniter mechanism is near the inlets for igniting a mixture of methanol and air, while a partial oxidation catalyst in the chamber is spaced from the inlets and converts methanol and oxygen to carbon dioxide and hydrogen. Controlling the oxygen to methanol mole ratio provides continuous slightly exothermic partial oxidation reactions of methanol and air producing hydrogen gas. The liquid is preferably injected in droplets having diameters less than 100 micrometers. The reformer is useful in a propulsion system for a vehicle which supplies a hydrogen-containing gas to the negative electrode of a fuel cell.

  1. Methanol partial oxidation reformer

    DOEpatents

    Ahmed, Shabbir; Kumar, Romesh; Krumpelt, Michael

    1999-01-01

    A partial oxidation reformer comprising a longitudinally extending chamber having a methanol, water and an air inlet and an outlet. An igniter mechanism is near the inlets for igniting a mixture of methanol and air, while a partial oxidation catalyst in the chamber is spaced from the inlets and converts methanol and oxygen to carbon dioxide and hydrogen. Controlling the oxygen to methanol mole ratio provides continuous slightly exothermic partial oxidation reactions of methanol and air producing hydrogen gas. The liquid is preferably injected in droplets having diameters less than 100 micrometers. The reformer is useful in a propulsion system for a vehicle which supplies a hydrogen-containing gas to the negative electrode of a fuel cell.

  2. Dual frequency 230/690 GHz interferometry and phase transfer at the Submillimeter Array

    NASA Astrophysics Data System (ADS)

    Hunter, T. R.; Zhao, J. H.; Liu, S.-Y.; Su, Y.-N.

    2006-01-01

    The Submillimeter Array (SMA) is an eight-element radio interferometer located on Mauna Kea and designed to operate in the major atmospheric windows from 180 to 900 GHz with 2 GHz IF bandwidth in each sideband. With baseline lengths up to 500m, atmospheric instabilities can limit the phase coherence of the array, especially in the higher frequency bands. For this reason, the array was designed to support simultaneous operation of a low frequency receiver (< 350 GHz) with a high frequency receiver (> 330 GHz). The overlap region of 330-350 GHz was chosen to facilitate dual polarization measurements in the frequency range most likely to offer the highest sensitivity to dust continuum emission. At present, the array is equipped with SIS receivers covering the frequency ranges 176-250 GHz, 260-350 GHz, and 600-700 GHz. Single frequency operation has been routine in the lower two frequency bands for the past two years. In February 2005, with the completion of the IF hardware, dual receiver operation became possible. Since then we have made a number of Galactic and extragalactic astronomical observations in dual-band mode. Facing a severe lack of gain calibrators at high frequency, we have primarily used minor planets (Ceres, Io, Callisto) or 658 GHz water masers. However, the minor planets are resolved in our extended configurations, and new calibration techniques are needed. We have begun to explore the option of using the 230 GHz receiver as a phase reference to enable improved interferometry in the 650 GHz band. We will present the current antenna and receiver performance, and our initial attempts at phase transfer. New functions have been added to the Miriad and MIR/IDL data analysis software packages for fitting and applying antenna-based phase transfer coefficients. During some of the observing sessions, good phase correlations are seen, and the phase transfer method has been demonstrated to recover images of a point source, albeit at a somewhat reduced signal

  3. Observation of harmonic gyro-backward-wave oscillation in a 100 GHz CARM oscillator experiment

    NASA Astrophysics Data System (ADS)

    McCowan, Robert B.; Sullivan, Carol A.; Gold, Steven H.; Fliflet, Arne W.

    1991-02-01

    A cyclotron autoresonance maser (CARM) oscillator experiment is reported, using a 600 keV, 200 A electron beam, and a whispering gallery-mode rippled-wall Bragg cavity. This device was designed to produce tens of megawatts of radiation at 100 GHz from a CARM interaction, but instead has produced only moderate powers (tens of kWs) in fundamental gyrotron modes near 35 GHz, in third-harmonic-gyro-BWO modes, and possible third-harmonic gyrotron modes at frequencies near the expected CARM frequency, with no discernable CARM radiation. The lack of observable CARM radiation is attributed to excessive ripple on the voltage waveform and to mode competition. Calculations of the spectrum and growth rate of the backward-wave oscillations are consistent with the experimental observation.

  4. Cyclotron Maser Emission - Stars, Planets and Laboratory

    NASA Astrophysics Data System (ADS)

    Vorgul, Irena

    2010-11-01

    X-ray and radio observations of active stars over many years have shown that they frequently generate X-ray bursts that are quickly followed by radio bursts. In many cases the radio bursts are highly polarised. More recently, the star CU Virginis has been found to exhibit pulsar-like behaviour. In both these situations we believe that the radio emission can be best explained by a cyclotron maser type instability initiated by electron beams funnelling down converging magnetic field configurations typical of a dipole magnetic topology. Just such a geometry also exists in the Earth's auroral zone and so our model can explain the Earth's auroral kilometric radiation (AKR). Via a similar process, all the gas giant/magnetised planets in the solar system also emit radio emission. We have established a laboratory-based facility that has verified many of the details of our original theoretical description. The experiment has demonstrated, for example, that an electron beam entering a strongly converging magnetic field geometry does indeed produce a ``horse-shoe'' (or crescent-shaped) distribution in velocity space. It is the generation of this horse-shoe distribution, also observed in the Earth's auroral zone, which is vital for our theoretical model. It leads to a population inversion in the perpendicular velocity distribution and generation of electromagnetic waves close to the cyclotron frequency. We will discuss recent developments in the theory and simulation of the instability and relate these to the laboratory, space and astrophysical observations. The research was supported by UK Engineering and Physical Sciences Research Council. The input of R.A. Cairns, R. Bingham, B.J. Kellett and the experimental and computer modelling team at Strathclyde University, Glasgow is gratefully acknowledged.

  5. A 90-GHz Photoinjector

    SciTech Connect

    Palmer, D.T.; Hogan, M.J.; Ferrario, M.; Serafini, L.; /Frascati /INFN, Milan

    2005-09-12

    Photocathode rf guns depend on mode locked laser systems to produce an electron beam at a given phase of the rf. In general, the laser pulse is less than {sigma}{sub z} = 10{sup o} of rf phase in length and the required stability is on the order of {Delta}{phi} = 1{sup o}. At 90 GHz (W-band), these requirements correspond to {sigma}{sub z} = 333 fsec and {Delta}{phi} = 33 fsec. Laser system with pulse lengths in the fsec regime are commercially available, the timing stability is a major concern. We propose a multi-cell W-band photoinjector that does not require a mode locked laser system. Thereby eliminating the stability requirements at W-band. The laser pulse is allowed to be many rf periods long. In principle, the photoinjector can now be considered as a thermionic rf gun. Instead of using an alpha magnet to compress the electron bunch, which would have a detrimental effect on the transverse phase space quality due to longitudinal phase space mixing, we propose to use long pulse laser system and a pair of undulators to produce a low emittance, high current, ultra-short electron bunch for beam dynamics experiments in the 90 GHz regime.

  6. Runaway electrons in a Tokamak: A free-electron maser

    SciTech Connect

    Kurzan, B.; Steuer, K.; Suttrop, W.

    1997-01-01

    In Ohmic divertor plasma discharges of the ASDEX Upgrade tokamak a small population of runaway electrons is purposely generated at the beginning of the discharge. About 1.5 s after the runaways` generation fluctuating emission in the microwave region with a very narrow bandwidth is observed. The radiation can be explained by relativistic runaway electrons forming a free-electron maser in the tokamak: The dynamics of the runaways is simulated by taking into account the acceleration in the electric field, collisions with the plasma particles, synchrotron radiation losses and the resonances between the gyromotion and harmonics of the magnetic ripple field. According to this the runaways reach a final energy determined by the ripple resonance mechanism and are monoenergetic enough to form a cyclotron autoresonance maser. The guiding of the radiation along the bent path of the runaways is accomplished by nearly resonant runaways around the amplifying runaways. The emission frequency depends on the final energy of the runaways and the observed bandwidth via the maser`s gain on their particle density. Analyzing the emitted fluctuating emission is thus a potentially new diagnostic for runaways. {copyright} {ital 1997 American Institute of Physics.}

  7. Study of Improvement of Hydrogen Maser Frequency Standard

    NASA Technical Reports Server (NTRS)

    Crampton, S. B.

    1977-01-01

    The research work dealt primarily with reducing the atom leakage rate using as storage surfaces the FEP Teflon surfaces conventionally used in contemporary hydrogen maser frequency standards. Some work was also done on a possible alternative to the conventional surfaces, but the results here and elsewhere suggest that the alternative surface is not promising enough to warrant much further work.

  8. A shock origin for interstellar H2O masers

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    We present a comprehensive model for the powerful H2O masers observed in starforming regions. In this model the masers occur behind dissociative shocks propagating in dense regions. This paper focuses on high-velocity dissociative shocks in which the heat of H2 reformation on dust grains maintains a large column of 300 - 400 K gas, where the chemistry drives a considerable fraction of the oxygen not in CO to form H2O. The H2O column densities, the hydrogen densities, and the warm temperatures produced by these shocks are sufficiently high to enable powerful maser action, where the maser is excited by thermal collisions with H atoms and H2 molecules. A critical ingredient in determining the shock structure is the magnetic pressure, and the fields required by our models are in agreement with recent observations. The observed brightness temperatures are the result of coherent velocity regions which have dimensions in the shock plane that are five to 50 times the postshock thickness.

  9. Improved masers for X-band and Ku band

    NASA Technical Reports Server (NTRS)

    Clauss, R. C.; Quinn, R. B.

    1973-01-01

    Slow-wave structure of traveling-wave maser utilizes comb system which is comprised of ruby on one side and alumina on other; alumina also supports isolator material. Radiation at pump frequency is coupled to ruby through shaped alumina strips. Contact between ruby bars and comb completes conductance path for heat transfer.

  10. A beam-maser instability: Direct amplification of radiation

    NASA Astrophysics Data System (ADS)

    Chen, Y. P.; Zhou, G. C.; Yoon, Peter H.; Wu, C. S.

    2002-06-01

    The cyclotron maser instability has been applied in the past to laboratory microwave generation devices, and radiation from planetary magnetospheres, such as Earth's kilometric radiation and Jovian decametric radiation. Recently, the same concept was put forth to explain solar coronal radio bursts. In particular, it was suggested that the ordinary (O) mode propagating in antiparallel direction with respect to the electron beam may be important. For this reason, this article revisits the maser instability theory with a particular emphasis on understanding the key difference between forward- and backward-propagating O-mode masers. It is found that the O-mode maser instability is excited over a significant range of wave phase angle which corresponds to the backward propagation. Of the various physical parameters the average beam speed and the ratio of plasma-to-gyro-frequencies, ωp/Ω, play important roles. Past discussions have emphasized the role of ωp/Ω. The present analysis also includes the effects of average beam speed on the instability. It is shown that there is a critical beam speed for the instability onset, beyond which the growth rate is quasi-independent of the beam speed. Such a finding has not been reported in the literature before.

  11. A shock origin for interstellar H2O masers

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    We present a comprehensive model for the powerful H2O masers observed in starforming regions. In this model the masers occur behind dissociative shocks propagating in dense regions. This paper focuses on high-velocity dissociative shocks in which the heat of H2 reformation on dust grains maintains a large column of 300 - 400 K gas, where the chemistry drives a considerable fraction of the oxygen not in CO to form H2O. The H2O column densities, the hydrogen densities, and the warm temperatures produced by these shocks are sufficiently high to enable powerful maser action, where the maser is excited by thermal collisions with H atoms and H2 molecules. A critical ingredient in determining the shock structure is the magnetic pressure, and the fields required by our models are in agreement with recent observations. The observed brightness temperatures are the result of coherent velocity regions which have dimensions in the shock plane that are five to 50 times the postshock thickness.

  12. Dietary methanol and autism.

    PubMed

    Walton, Ralph G; Monte, Woodrow C

    2015-10-01

    The authors sought to establish whether maternal dietary methanol during pregnancy was a factor in the etiology of autism spectrum disorders. A seven item questionnaire was given to women who had given birth to at least one child after 1984. The subjects were solicited from a large primary care practice and several internet sites and separated into two groups - mothers who had given birth to a child with autism and those who had not. Average weekly methanol consumption was calculated based on questionnaire responses. 550 questionnaires were completed by women who gave birth to a non-autistic child. On average these women consumed 66.71mg. of methanol weekly. 161 questionnaires were completed by women who had given birth to an autistic child. The average estimated weekly methanol consumption for this group was 142.31mg. Based on the results of the Wilcoxon rank sum-test, we see a significant difference between the reported methanol consumption rates of the two groups. This study suggests that women who have given birth to an autistic child are likely to have had higher intake of dietary sources of methanol than women who have not. Further investigation of a possible link of dietary methanol to autism is clearly warranted.

  13. SiO and CH3OH mega-masers in NGC 1068

    PubMed Central

    Wang, Junzhi; Zhang, Jiangshui; Gao, Yu; Zhang, Zhi-Yu; Li, Di; Fang, Min; Shi, Yong

    2014-01-01

    Maser is an acronym for microwave amplification by stimulated emission of radiation; in astronomy mega-masers are masers in galaxies that are ≥106 times more luminous than typical galactic maser sources. Observational studies of mega-masers can help us to understand their origins and characteristics. More importantly, mega-masers can be used as diagnostic tracers to probe the physical properties of their parent galaxies. Since the late 1970s, only three types of molecules have been found to form mega-masers: H2O, OH and H2CO. Here we report the detection of both SiO and CH3OH mega-masers near the centre of Seyfert 2 galaxy NGC 1068 at millimetre wavelengths, obtained using the IRAM 30-m telescope. We argue that the SiO mega-maser originated from the nuclear disk and the CH3OH mega-maser originated from shock fronts. High-resolution observations in the future will enable us to investigate AGN feedback and determine the masses of central supermassive black holes in such galaxies. PMID:25386834

  14. SiO and CH3OH mega-masers in NGC 1068.

    PubMed

    Wang, Junzhi; Zhang, Jiangshui; Gao, Yu; Zhang, Zhi-Yu; Li, Di; Fang, Min; Shi, Yong

    2014-11-11

    Maser is an acronym for microwave amplification by stimulated emission of radiation; in astronomy mega-masers are masers in galaxies that are ≥ 10(6) times more luminous than typical galactic maser sources. Observational studies of mega-masers can help us to understand their origins and characteristics. More importantly, mega-masers can be used as diagnostic tracers to probe the physical properties of their parent galaxies. Since the late 1970s, only three types of molecules have been found to form mega-masers: H2O, OH and H2CO. Here we report the detection of both SiO and CH3OH mega-masers near the centre of Seyfert 2 galaxy NGC 1068 at millimetre wavelengths, obtained using the IRAM 30-m telescope. We argue that the SiO mega-maser originated from the nuclear disk and the CH3OH mega-maser originated from shock fronts. High-resolution observations in the future will enable us to investigate AGN feedback and determine the masses of central supermassive black holes in such galaxies.

  15. Thousands of Stellar SiO masers in the Galactic center: The Bulge Asymmetries and Dynamic Evolution (BAaDE) survey

    NASA Astrophysics Data System (ADS)

    Sjouwerman, Loránt O.; Pihlström, Ylva M.; Rich, R. Michael; Morris, Mark R.; Claussen, Mark J.

    2017-01-01

    A radio survey of red giant SiO sources in the inner Galaxy and bulge is not hindered by extinction. Accurate stellar velocities (<1 km/s) are obtained with minimal observing time (<1 min) per source. Detecting over 20,000 SiO maser sources yields data comparable to optical surveys with the additional strength of a much more thorough coverage of the highly obscured inner Galaxy. Modeling of such a large sample would reveal dynamical structures and minority populations; the velocity structure can be compared to kinematic structures seen in molecular gas, complex orbit structure in the bar, or stellar streams resulting from recently infallen systems. Our Bulge Asymmetries and Dynamic Evolution (BAaDE) survey yields bright SiO masers suitable for follow-up Galactic orbit and parallax determination using VLBI. Here we outline our early VLA observations at 43 GHz in the northern bulge and Galactic plane (0GHz in the southern bulge (250

  16. An H2O Maser survey towards BGPS sources in the Outer Galaxy

    NASA Astrophysics Data System (ADS)

    Xi, Hong-Wei; Zhou, Jian-Jun; Esimbek, Jarken; Wu, Gang; He, Yu-Xin; Ji, Wei-Guang; Tang, Xiao-Ke; Yuan, Ye

    2016-06-01

    We performed an H2O maser survey towards 274 Bolocam Galactic Plane Survey (BGPS) sources with 85° < l < 193° using the Nanshan 25 m radio telescope. We detected 25 H2O masers, and five of them are new detections. The detection rate of H2O masers in our sample is 9% which is very low. The detection rate of H2O masers increases as the 1.1 mm flux density of BGPS sources increases, and both the peak flux density and luminosity of H2O masers increase as the sources evolve. The detection rate of H2O masers toward BGPS sources without HCO+ emission is low. The BGPS sources associated with both H2O and CH3OH masers seem to be more compact than those only associated with H2O masers. This indicates that the sources with both masers may be in a relatively later evolutionary stage. The strongest H2O maser source G133.715+01.217, also well known as W3 IRS 5 which has a flux density of 2.9×103 Jy, was detected at eight different nearby positions. By measuring the correlation between the flux densities of these H2O masers and their angular distance from the true source location, we get the influence radius r = \\frac{1}{{0.8}}log ≤ft({\\frac{{F_0}}{{3\\text{rms}}}}\\right). For our observations, strong sources can be detected anywhere within this radius. It is helpful to determine whether or not a weak maser nearby the strong maser is a true detection.

  17. A Water Maser and NH3 Survey of GLIMPSE Extended Green Objects

    NASA Astrophysics Data System (ADS)

    Cyganowski, C. J.; Koda, J.; Rosolowsky, E.; Towers, S.; Donovan Meyer, J.; Egusa, F.; Momose, R.; Robitaille, T. P.

    2013-02-01

    We present the results of a Nobeyama 45 m H2O maser and NH3 survey of all 94 northern GLIMPSE extended green objects (EGOs), a sample of massive young stellar objects (MYSOs) identified based on their extended 4.5 μm emission. We observed the NH3(1,1), (2,2), and (3,3) inversion lines, and detected emission toward 97%, 63%, and 46% of our sample, respectively (median rms ~ 50 mK). The H2O maser detection rate is 68% (median rms ~ 0.11 Jy). The derived H2O maser and clump-scale gas properties are consistent with the identification of EGOs as young MYSOs. To explore the degree of variation among EGOs, we analyze subsamples defined based on mid-infrared (MIR) properties or maser associations. H2O masers and warm dense gas, as indicated by emission in the higher-excitation NH3 transitions, are most frequently detected toward EGOs also associated with both Class I and II CH3OH masers. Ninety-five percent (81%) of such EGOs are detected in H2O (NH3(3,3)), compared to only 33% (7%) of EGOs without either CH3OH maser type. As populations, EGOs associated with Class I and/or II CH3OH masers have significantly higher NH3 line widths, column densities, and kinetic temperatures than EGOs undetected in CH3OH maser surveys. However, we find no evidence for statistically significant differences in H2O maser properties (such as maser luminosity) among any EGO subsamples. Combining our data with the 1.1 mm continuum Bolocam Galactic Plane Survey, we find no correlation between isotropic H2O maser luminosity and clump number density. H2O maser luminosity is weakly correlated with clump (gas) temperature and clump mass.

  18. An SIS Waveguide heterodyne Reciever for 600 GHz - 635 GHz

    NASA Technical Reports Server (NTRS)

    Salez, Morvan; Febvre, Pascal; McGrath, William R.; Bumble, Bruce; LeDuc, Henry G.

    1994-01-01

    A waveguide SIS heterodyne receiver using a Nb/A10xNb junction has been built for astronomical observations of molecular tranitions in the frequency range 600GHz - 635GHZ, and has been successfully used at the Caltech Submillimeter Observatory (CSO).

  19. 180-GHz Interferometric Imager

    NASA Technical Reports Server (NTRS)

    Kangaslahti, Pekka P.; Lim, Boon H.; O'Dwyer, Ian J.; Soria, Mary M.; Owen, Heather R.; Gaier, Todd C.; Lambrigtsen, Bjorn, H.; Tanner, Alan B.; Ruf, Christopher

    2011-01-01

    A 180-GHz interferometric imager uses compact receiver modules, combined high- and low-gain antennas, and ASIC (application specific integrated circuit) correlator technology, enabling continuous, all-weather observations of water vapor with 25-km resolution and 0.3-K noise in 15 minutes of observation for numerical weather forecasting and tropical storm prediction. The GeoSTAR-II prototype instrument is broken down into four major subsystems: the compact, low-noise receivers; sub-array modules; IF signal distribution; and the digitizer/correlator. Instead of the single row of antennas adopted in GeoSTAR, this version has four rows of antennas on a coarser grid. This dramatically improves the sensitivity in the desired field of view. The GeoSTAR-II instrument is a 48-element, synthetic, thinned aperture radiometer operating at 165-183 GHz. The instrument has compact receivers integrated into tiles of 16 elements in a 4x4 arrangement. These tiles become the building block of larger arrays. The tiles contain signal distribution for bias controls, IF signal, and local oscillator signals. The IF signals are digitized and correlated using an ASIC correlator to minimize power consumption. Previous synthetic aperture imagers have used comparatively large multichip modules, whereas this approach uses chip-scale modules mounted on circuit boards, which are in turn mounted on the distribution manifolds. This minimizes the number of connectors and reduces system mass. The use of ASIC technology in the digitizers and correlators leads to a power reduction close to an order of magnitude.

  20. Methanol Cannon Demonstrations Revisited.

    ERIC Educational Resources Information Center

    Dolson, David A.; And Others

    1995-01-01

    Describes two variations on the traditional methanol cannon demonstration. The first variation is a chain reaction using real metal chains. The second example involves using easily available components to produce sequential explosions that can be musical in nature. (AIM)