Results 121 to 130 of about 154 (145)
Some of the next articles are maybe not open access.
Masers in the Interstellar Medium
1987The basic concepts that govern the production and propagation of maser radiation in interstellar space are introduced and discussed. Specific interstellar masers, in particular those in star forming regions, are described in some detail.
openaire +1 more source
Maser Action in Interstellar OH
Publications of the Astronomical Society of Australia, 1968Since 1965 we have been unravelling the curious properties of the intense 18 cm emission lines observed from OH molecules. We are still without a quantitative theory of the emission that might tie the threads together and provide guidelines for the observational work.
openaire +1 more source
A shock origin for interstellar H2O masers
1993We 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 (preshock density n o ≈ 106 – 108 cm−3). This paper focuses on high-velocity (ν s ≳ 30 km/s) dissociative shocks in which the heat of H2 reformation on dust grains maintains
David Hollenbach +2 more
openaire +1 more source
Radiative stability of interstellar masers ? A variational technique
Astrophysics and Space Science, 1982A variational technique has been developed to study the stability of the radiation field in a cylindrical homogeneous interstellar maser with steady state pumping. A dynamical potential has been constructed, the extremal of which gives the radiative transfer equations and rate equations.
openaire +1 more source
Magnetic fields in interstellar water masers
2008We report the first detection of Zeeman splitting in the (616−523) rotational transition of interstellar H2O masers. The measurements of Stokes parameter V and I spectra (circular polarization) have been performed at the MPIfR 100-m telescope. Depending on the hyperfine transition that is actually masing, we derive typical magnetic field strengths of B‖
D. Fiebig, R. Güsten
openaire +1 more source
Interstellar scattering of maser radiation
1993Interstellax scattering of pulsars, extragalactic sources, and galactic masers is used to discuss the overall galactic distribution of scattering material and the implied angular scattering vs galactic coordinates. I discuss the prospects for observing diffractive and refractive scintillations of maser signals.
openaire +1 more source
Maser action without inversion in interstellar space
Optics Communications, 1998Abstract It is recognized that interstellar 6.7 and 12.2 GHz methanol masers toward Class II sources are associated with each other and coexist toward ultracompact HII regions. Therefore we suggest a new excitation mechanism – methanol masers without population inversion.
Hanping Liu, Jin Sun
openaire +1 more source
Interstellar Masers and Star Formation in the Galaxy
1988Interstellar molecular lines have produced spectacular examples of non-equilibrium excitation, culminating in strong maser action of OH,SiO,H2O and CH3OH. Within the past 10 years it was recognized that maser emission is associated with star formation.
openaire +1 more source
A monitoring program of interstellar OH and H2O masers
1993We obtained spectra of a set of interstellar-OH and H2O masers at intervals of a few days to about a week throughout a period of about 5 months. The purpose was to determine whether interstellar scintillation and scattering processes contribute to maser variability.
John H. Simonetti +4 more
openaire +1 more source
Angular structure and motions of interstellar masers
2008A brief historical account is given of the discovery of OH emission and the experiments that led to the identification of the radiation mechanism as maser amplification. An outline is presented of the progress by the MIT, CfA and Jodrell Bank groups in mapping the prototypical maser, W3(OH).
openaire +1 more source