scholarly journals Water Fountains in Pre-Planetary Nebulae: The Case of IRAS16342–3814

2012 ◽  
Vol 8 (S287) ◽  
pp. 225-229 ◽  
Author(s):  
Mark Claussen ◽  
Raghvendra Sahai ◽  
Mark Morris ◽  
Hannah Rogers
Keyword(s):  
General Structure ◽  
Planetary Nebulae ◽  
Large Array ◽  
Very Large Array ◽  
Long Baseline ◽  
Stellar Velocity ◽  
Water Masers ◽  
Very Long Baseline Array ◽  
Water Maser

AbstractWe present a brief review of Very Long Baseline Array (VLBA) observations of water masers in the so-called water fountain pre-planetary nebulae, and report on new VLBA and Very Large Array (VLA) data for the water masers in the prototypical water fountain source IRAS16342–3814, taken approximately monthly in 2008–2009. A new and very strong water maser is found at an LSR velocity of −3 km s−1, which is offset from the central (likely stellar) velocity. The new VLBA observations still show a similar general structure as was observed in 2002, but there are details which are difficult to explain.

scholarly journals Imaging the water masers toward the H2O-PN IRAS 18061–2505

2012 ◽  
Vol 8 (S287) ◽  
pp. 258-259
Author(s):  
Yolanda Gómez ◽  
Daniel Tafoya ◽  
Olga Suárez ◽  
Jose F. Gómez ◽  
Luis F. Miranda ◽  
...  
Keyword(s):  
Planetary Nebulae ◽  
Central Star ◽  
Large Array ◽  
Maser Emission ◽  
Very Large Array ◽  
Kinematical Model ◽  
Water Masers ◽  
Central Stars ◽  
Water Maser

AbstractIt has been suggested that the presence of disks or tori around the central stars of pre Planetary Nebulae and Planetary Nebulae is related to the collimation of the jet that are frequently observed in these sources. These disks or tori can be traced by the maser emission of some molecules such as water. In this work we present Very Large Array (VLA) observations of the water maser emission at 22 GHz toward the PN IRAS 18061–2505, for which the masers appear located on one side of the central star. For comparison with the observations, we present a simple kinematical model of a disk rotating and expanding around the central star. The model matches qualitatively the observations. However, since the masers appear only on one side of the disk, these results are not conclusive.

scholarly journals A Review of Astrophysical Jets

2014 ◽  
Vol 1 (1) ◽  
pp. 259-264 ◽  
Author(s):  
James H. Beall
Keyword(s):  
International Cooperation ◽  
Gamma Ray ◽  
Theoretical Models ◽  
Large Array ◽  
Astrophysical Jets ◽  
Very Large Array ◽  
Anisotropic Models ◽  
Long Baseline ◽  
Computational Resources ◽  
Very Long Baseline Array

Astrophysical jets are ubiquitous: this simple statement has become a commonplace over the last three decades and more as a result of observing campaigns using detectors sensitive from radio to gamma-ray energies. During this epoch, theoretical models of these sources have become more complex, moving from assumptions of isotropy that made analytic calculations possible, to fully anisotropic models of emission from the jets and their interactions with the interstellar and intra-cluster medium. Such calculations are only possible because we have extensive computational resources. In addition, the degree of international cooperation required for observing campaigns of these sorts is remarkable, since the instruments include among others the Very Large Array (VLA), the Very Long Baseline Array (VLBA), and entire constellations of satellite instruments, often working in concert. In this paper, I discuss some relevant observations from these eorts and the theoretical interpretations they have occasioned.

scholarly journals The Formaldehyde Masers in Sgr B2: Very Long Baseline Array and Very Large Array Observations

2007 ◽  
Vol 654 (2) ◽  
pp. 971-977 ◽  
Author(s):  
Ian M. Hoffman ◽  
W. M. Goss ◽  
Patrick Palmer
Keyword(s):  
Large Array ◽  
Very Large Array ◽  
Long Baseline ◽  
Very Long Baseline Array

scholarly journals Submillimeter Array observations of 321 GHz water maser emission in Cepheus A

2007 ◽  
Vol 3 (S242) ◽  
pp. 489-493
Author(s):  
Nimesh A. Patel ◽  
Salvador Curiel ◽  
Qizhou Zhang ◽  
T. K. Sridharan ◽  
Paul T. P. Ho ◽  
...  
Keyword(s):  
High Mass ◽  
Mass Star ◽  
Large Array ◽  
Maser Emission ◽  
Very Large Array ◽  
Star Forming ◽  
Water Masers ◽  
Cepheus A ◽  
First Time ◽  
Water Maser

AbstractUsing the Submillimeter Array (SMA) we have imaged for the first time the 321.226 GHz, 1029 − 936 ortho-H2O maser emission. This is also the first detection of this line in the Cepheus A high-mass star-forming region. The 22.235 GHz, 616 – 523 water masers were also observed with the Very Large Array 43 days following the SMA observations. Three of the nine detected submillimeter maser spots are associated with the centimeter masers spatially as well as kinematically, while there are 36 22 GHz maser spots without corresponding submillimeter masers. In the HW2 source, both the 321 GHz and 22 GHz masers occur within the region of ~1″ which includes the disk-jet system, but the position angles of the roughly linear structures traced by the masers indicate that the 321 GHz masers are along the jet while the 22 GHz masers are perpendicular to it. We interpret the submillimeter masers in Cepheus A to be tracing significantly hotter regions (600~2000 K) than the centimeter masers.

scholarly journals VLBA Imaging of UX Ari

1998 ◽  
Vol 164 ◽  
pp. 321-322
Author(s):  
A. J. Beasley ◽  
T.S. Bastian
Keyword(s):  
Large Array ◽  
Extended Source ◽  
Very Large Array ◽  
Long Baseline ◽  
Radio Imaging ◽  
Multi Wavelength ◽  
Very Long Baseline Array

AbstractWe have used the Very Long Baseline Array (VLBA) and the Very Large Array (VLA) to perform multi-wavelength radio imaging of the RS CVn active binary UX Arietis during the period November 16–21 1995. A series of strong flaring events exhibiting optically-thick spectra peaking above 100 GHz and extended source structures consistent with inter-binary emission were detected.

scholarly journals Water masers in Compton-thick AGN

2019 ◽  
Vol 629 ◽  
pp. A25 ◽  
Author(s):  
P. Castangia ◽  
G. Surcis ◽  
A. Tarchi ◽  
A. Caccianiga ◽  
P. Severgnini ◽  
...  
Keyword(s):  
Radio Continuum ◽  
Continuum Emission ◽  
Maser Emission ◽  
Long Baseline ◽  
Imaginary Line ◽  
Ngc 1068 ◽  
Water Masers ◽  
Very Long Baseline Array ◽  
Green Bank Telescope ◽  
Water Maser

Aims. Investigations of H2O maser galaxies at X-ray energies reveal that most active galactic nuclei (AGN) associated with water masers are characterized by high levels of absorption. With the aim of finding new maser sources for possible interferometric follow-ups, we have searched for water maser emission in a well-defined sample of heavily absorbed AGN (NH >  1023 cm−2), including Compton-thick (CT) sources. Methods. Previous surveys already searched for 22 GHz water maser emission in all the galaxies in this sample. With the goal of providing a detection or a stringent upper limit on the H2O luminosity, we reobserved some of the non-detected sources with the Green Bank Telescope. A new luminous H2O maser (LH2O ∼ 200 L⊙) was detected in the mid-IR-bright Seyfert 2 galaxy IRAS 15480−0344 and then followed-up with the Very Long Baseline Array. In order to shed light on the origin of the maser (jet, outflow, or disk), we recently observed the radio continuum emission in IRAS 15480-0344 with the European VLBI network (EVN) at 1.7 and 5.0 GHz. Results. With the newly discovered megamaser in IRAS 15480−0344 revealing a narrow (∼0.6 km s−1) and a broad (∼90 km s−1) component, the maser detection rate of the CT AGN sample is 50% (18/36), which is one of the highest ever found in maser surveys. The EVN maps show two bright sources (labeled SW and NE) in the nuclear region of IRAS 15480−0344, which we interpret as jet knots tracing regions where the radio plasma impacts dense molecular clouds. The narrow maser feature is approximately at the center of the imaginary line connecting the two continuum sources, likely pinpointing the core, and might be associated with the accretion disk or a nuclear outflow. The location of the broad maser feature, instead, coincides with source NE, suggesting that the maser emission might be produced by a jet-cloud interaction, as it was proposed for NGC 1068 and Mrk 348.

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