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Full-Text Articles in Astrophysics and Astronomy
Implications Of Gamma-Ray Transparency Constraints In Blazars: Minimum Distances And Gamma-Ray Collimation, P. A. Becker, Menas Kafatos
Implications Of Gamma-Ray Transparency Constraints In Blazars: Minimum Distances And Gamma-Ray Collimation, P. A. Becker, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
We develop a general expression for the γ-γ absorption coefficient, αγγ, for γ-rays propagating in an arbitrary direction at an arbitrary point in space above an X-ray-emitting accretion disk. The X-ray intensity is assumed to vary as a power law in energy and radius between the outer disk radius, R0 , and the inner radius, Rm., which is the radius of marginal stability for a Schwarzschild black hole. We use our result for αγγ to calculate the γ-γ optical depth, Tγγ, for γ-rays created at height z and propagating at angle Φ relative to the disk axis, and we show …
Multiwavelength Observations Of Markarian 421 During A Tev/X-Ray Flare, D. J. Macomb, C. W. Akerlof, H. D. Aller, M. F. Aller, D. L. Bertsch, Menas Kafatos
Multiwavelength Observations Of Markarian 421 During A Tev/X-Ray Flare, D. J. Macomb, C. W. Akerlof, H. D. Aller, M. F. Aller, D. L. Bertsch, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
A Te V flare from the BL Lac object Mrk 421 was detected in May of 1994 by the Whipple Observatory air Cherenkov experiment during which the flux above 250 GeV increased by nearly an order of magnitude over a 2-day period. Contemporaneous observations by ASCA showed the X-ray flux to be in a very high state. We present these results, combined with the first ever simultaneous or nearly simultaneous observations at Ge V gamma-ray, UV, IR, mm, and radio energies for this nearest BL Lac object. While the GeV gamma-ray flux increased slightly, there is little evidence for variability …
Ultraviolet Temporal Variability Of The Peculiar Star R Aquarii, S. R. Meier, Menas Kafatos
Ultraviolet Temporal Variability Of The Peculiar Star R Aquarii, S. R. Meier, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
This paper is a comprehensive study of all far-UV spectra obtained with the International Ultraviolet Explorer (IUE) satellite of the symbiotic star R Aquarii (R Aqr) covering a 13 yr period between 1979 and 1992. We have analyzed the ultraviolet emission for the compact H II region and the NE and SW extended "jetlike" filamentary structures. The results of our ultraviolet analysis indicate that the H II region and features A, B, and D of the NE jet are increasing in intensity, while the SW counterjet, feature A', has declined in intensity. We have found much stronger evidence that the …
Shock Study In Fully Relativistic Isothermal Flows. Ii, Ruixin Yang, Menas Kafatos
Shock Study In Fully Relativistic Isothermal Flows. Ii, Ruixin Yang, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
The isothermal shocks and their stabilities in fully relativistic accretion wedge flows onto black holes are studied. The jump condition across the shock is modified by the relativistic effects when the sound speed is comparable to the speed of light. With a new kind of instability analysis, it is found that only one of the two possible shocks is stable. The results are applied to the QPO behavior in galactic black hole candidates such as Cygnus X-1.
Osse Observations In Blazars, K. Mcnaron-Brown, W. N. Johnson, G. V. Jung, R. L. Kinzer, J. D. Kurfess, M. S. Strickman, C. D. Dermer, D. A. Grabelsky, W. R. Purcell, M. P. Ulmer, Menas Kafatos, P. A. Becker, R. Staubert, M. Maisack
Osse Observations In Blazars, K. Mcnaron-Brown, W. N. Johnson, G. V. Jung, R. L. Kinzer, J. D. Kurfess, M. S. Strickman, C. D. Dermer, D. A. Grabelsky, W. R. Purcell, M. P. Ulmer, Menas Kafatos, P. A. Becker, R. Staubert, M. Maisack
Mathematics, Physics, and Computer Science Faculty Articles and Research
Results are reported on observations obtained with the Oriented Scintillation Spectrometer Experiment (OSSE) instrument on the Compton Gamma Ray Observatory (CGRO) of 17 active galactic nuclei (AGNs) known to exhibit blazar properties at other wavelengths. These observations span the period from 1991 June through 1994 May. Of the 33 high-confidence EGRET detections of blazars during CGRO observing phases 1 and 2 (1991 May 16-1993 September 7), OSSE has observed eight and detected five, namely 3C 273, 3C 279, PKS 0528+134, CTA 102, and 3C 454.3. Additionally, OSSE has detected the BL Lac sources H1517+65.6 and PKS 2155-304, which were not …