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Articles 1 - 7 of 7
Full-Text Articles in Astrophysics and Astronomy
Iue Observations Of Circumstellar Emission From The Late Type Variable R Aquarii (M7 + Pec), A. G. Michalitsianos, Menas Kafatos, R. W. Hobbs
Iue Observations Of Circumstellar Emission From The Late Type Variable R Aquarii (M7 + Pec), A. G. Michalitsianos, Menas Kafatos, R. W. Hobbs
Mathematics, Physics, and Computer Science Faculty Articles and Research
IUE observations of R Aquarii (M7 + pec) have been obtained in low dispersion in order to study its circumstellar emission. Strong permitted, semiforbidden, and forbidden emission lines are identified that are superposed on a bright ultraviolet continuum. From our analysis we deduce that the strong emission-line spectrum that involves C III], C IV, Si III], [0 II], and [0 III] probably arises from a dense compact nebula the size of which is comparable to the binary system of which R Aqr is the primary star. Low-excitation emission lines of Fe II, Mg II, 0 1, and Si II suggest …
150 Ghz Observations Of Three Radio Galaxies, Menas Kafatos, R. W. Hobbs, S. P. Maran, L. W. Brown
150 Ghz Observations Of Three Radio Galaxies, Menas Kafatos, R. W. Hobbs, S. P. Maran, L. W. Brown
Mathematics, Physics, and Computer Science Faculty Articles and Research
Radio galaxies were observed for the first time at 150 GHz. The central sources in Cyg A and 3C Ill were detected, as were the two radio lobes of Cyg A. No emission was found from the central source in 3C 236. Each of these three central sources has been previously discussed as the site of the energy supply for the associated distant components. The millimeter-wavelength emission from the central sources in Cyg A and 3C 111 is probably due in each case to a compact component that is optically thin to synchrotron radiation above about 35 GHz. These components …
Iue Observations Of Two Late Type Stars: R Aql And W Hya, Menas Kafatos, A. G. Michalitsianos, R. W. Hobbs
Iue Observations Of Two Late Type Stars: R Aql And W Hya, Menas Kafatos, A. G. Michalitsianos, R. W. Hobbs
Mathematics, Physics, and Computer Science Faculty Articles and Research
Ultraviolet spectra of two late type M stars R Aql and W Hya were obtained with the International Ultraviolet Explorer (IUE). Spectra were obtained of R Aql near maximum (cf>=0.21) and minimum (cf>=0.65) of the visible light curve. We find that the absolute flux intensity of the Mgn resonance doublet (2796 A, 2803 A) is essentially the same at these phases in the visible light curve. A nebular emission feature at 3133 A is detected at minimum light in R Aql that is possibly due to 0 III. Mg II emission is totally absent in W Hya, which …
Iue Observations Of Rw Hydrae (Gm2 + Pec), Menas Kafatos, A. G. Michalitsianos, R. W. Hobbs
Iue Observations Of Rw Hydrae (Gm2 + Pec), Menas Kafatos, A. G. Michalitsianos, R. W. Hobbs
Mathematics, Physics, and Computer Science Faculty Articles and Research
IUE observations of the late type star RW Hya (gM2 + pec) have been obtained. Analysis of the intense UV continuum observed between 1100 and 2000 A suggests that this object is a binary system in which the secondary is identified as the central star of a planetary nebula with Teff 105 K. The ultraviolet spectrum is characterized by semiforbidden and allowed transition lines, of which the C IV (1548 A, 1550 A) doublet is particularly strong. A general absence of strong forbidden line emission suggests that the compact nebula in which both primary and secondary stars are embedded has …
Iue Observations Of A Luminous M Supergiant That Exhibits Emission Continuum In The Far Ultraviolet, A. G. Michalitsianos, Menas Kafatos, R. W. Hobbs
Iue Observations Of A Luminous M Supergiant That Exhibits Emission Continuum In The Far Ultraviolet, A. G. Michalitsianos, Menas Kafatos, R. W. Hobbs
Mathematics, Physics, and Computer Science Faculty Articles and Research
IUE observations of the late-type M supergiant TV Gem (M1 lab) have been obtained that reveal strong UV continuum between 1200 and 3200 A. The continuum is essentially featureless with the exception of a number of broad absorption features in the short wavelength spectral range. UV emission from this star is unexpected because earlier ground-based observations give no indication of a possible association with an early companion or circumstellar ionized nebulosity. We find that a B9 or A1 III-IV type star approximately 2-3 magnitudes fainter than the M star could explain the level of UV continuum observed, but a fully …
The Evolution Of Supernova Remnants In Different Galactic Environments, And Its Effects On Supernova Statistics, Menas Kafatos, S. Sofia, C. Bruhweilier, T. R. Gull
The Evolution Of Supernova Remnants In Different Galactic Environments, And Its Effects On Supernova Statistics, Menas Kafatos, S. Sofia, C. Bruhweilier, T. R. Gull
Mathematics, Physics, and Computer Science Faculty Articles and Research
By examining the interaction between supernova (SN) ejecta and the various environments in which the explosive event might occur, we conclude that only a small fraction of the many SNs produce observable supernova remnants (SNRs). This fraction, which is found to depend weakly upon the lower mass limit of the SN progenitors, and more strongly on the specific characteristics of the associated interstellar medium, decreases from approximately 15% near the galactic center to 10% at R8a1 -10 kpc and drops nearly to zero for Rga~> 15 kpc. Generally, whether a SNR is detectable is determined by the density of the …
Gamma Rays From Penrose Powered Black Holes In Centaurus A, 3c 273, And Ngc 4151, Menas Kafatos
Gamma Rays From Penrose Powered Black Holes In Centaurus A, 3c 273, And Ngc 4151, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
Gamma-ray observations of active galaxies have important consequences for theories of the activity in their nuclei. The observations of Cen A, 3C 273, and NGC 4151 are examined under the assumption that Penrose collision processes in the ergospheres of massive black holes power their nuclei. The observed sharp break in the MeV region of the NGC 4151 spectrum cannot be due to the γ-γ pair production process. We attribute this break to the Penrose Compton scattering (PCS), in which γ-rays escape from the ergosphere as a result of Penrose processes involving electrons and lower energy X-ray photons in the ergosphere …