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Full-Text Articles in Physics

The Optical-Ultraviolet-Γ-Ray Spectrum Of 3c 279, Hagai Netzer, D. Kazanas, Beverley J. Wills, D. Wills, Han Mingsheng, M. S. Brotherton, J A. Baldwin, Gary J. Ferland, I. W. A. Browne Jul 1994

The Optical-Ultraviolet-Γ-Ray Spectrum Of 3c 279, Hagai Netzer, D. Kazanas, Beverley J. Wills, D. Wills, Han Mingsheng, M. S. Brotherton, J A. Baldwin, Gary J. Ferland, I. W. A. Browne

Physics and Astronomy Faculty Publications

We have obtained spectrosocpy of the violently variable quasar 3C 279, simultaneous with γ-ray observations, in 1992 April. Our combined optical (McDonald Observatory and Cerro Tololo InterAmerican Observatory (CTIO) and ultraviolet (HST) observations, made when the source was faint, show a very steep power-law continuum (Fν∝ν-1.95) and strong broad emission lines. This is the first time that the broad ultraviolet lines of this object have been measured, and we note several unusual properties of the spectrum. In particular, the profiles of C IV λ1549 and Mg II λ2798 are asymmetric, with very ...


A Protostellar Jet Model For The Water Masers In W49n, Mordecai-Mark Mac Low, Moshe Elitzur, James M. Stone, Arieh Königl Jun 1994

A Protostellar Jet Model For The Water Masers In W49n, Mordecai-Mark Mac Low, Moshe Elitzur, James M. Stone, Arieh Königl

Physics and Astronomy Faculty Publications

Observations by Gwinn, Moran, & Reid of the proper motions of water masers in W49N show that they have 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. We propose that these observations can be interpreted in terms of a shell of shocked molecular gas that is driven by the expanding cocoon of a high-velocity protostellar jet. We present three-dimensional numerical simulations in support of this interpretation and argue that this source provides a unique oppurtunity for a detailed study of jet-driven cocoons.


Hot Gas And The Origin Of The Nebular Continuum In Novae, Pedro Saizar, Gary J. Ferland Apr 1994

Hot Gas And The Origin Of The Nebular Continuum In Novae, Pedro Saizar, Gary J. Ferland

Physics and Astronomy Faculty Publications

A featureless blue continuum (with constant fν) is a defining feature of declining classical novae. The fact that fν is constant into the infrared, and the absence of a Balmer jump, suggests that this continuum originates in hot tenous gas. The electron temperature and density of the hot gas phase of classical nova QU Vul 1984 are estimated from ground-based optical and IUE ultraviolet observations. This region has a temperature of 105 - 106, and a density in the range of 2 x 104 to 3 x 105cm-3. In addition, a colder, denser ...


Nebular Properties And The Ionizing Radiation Field In The Galactic Center, Joseph C. Shields, Gary J. Ferland Apr 1994

Nebular Properties And The Ionizing Radiation Field In The Galactic Center, Joseph C. Shields, Gary J. Ferland

Physics and Astronomy Faculty Publications

Nebulosity in the central parsec of the Milky Way exhibits a low-ionization spectrum that has led previous analyses of this region to conclude that this material is photoionized by a relatively soft continuum. We have reanalyzed the infrared emission-line spectrum of te Galactic center in order to consider whether the data could actually be explained with photoionization by a relatively hard, yet dilute continuum, and additionally to constrain the properties of the reaiating plasma. We conclude that the composite infrared spectrum does not place strong restrictions on the nature of the ionizing continuum and that much of the ionized gas ...


On The Theory Of Astronomical Masers In Three Dimensions, Moshe Elitzur Feb 1994

On The Theory Of Astronomical Masers In Three Dimensions, Moshe Elitzur

Physics and Astronomy Faculty Publications

In the standard theory of three-dimensional astronomical masers, the radiation field is described as if the source were comprised of a collection of linear masers. To leading order, the standard theory is shown to provide the correct description of three-dimensional masers and its results remain intact, but only within a frequency core whose half-width is χsΔνD, where ΔνD is the Doppler width and χs is a dimensionless parameter. For any given geometry, χs is ~1θsat, where θsat is the beaming angle of a maser with that geometry that has just saturated ...