Scientific and Technical Aerospace Reports Volume 38 July 28, 2000

20000064089 Smithsonian Astrophysical Observatory, Cambridge, MA USA
X-ray Variability in M87
Harris, D. E., Smithsonian Astrophysical Observatory, USA; Biretta, J. A., Space Telescope Science Inst., USA; Junor, W., New
Mexico Univ., USA; Monthly Notices of the Royal Astronomical Society; 1997; Volume 284, pp. L21-L27; In English
Contract(s)/Grant(s): NAS5-30934; NAG5-2957; Copyright; Avail: Issuing Activity
We present evidence for X-ray variability from the core and from knot A in the M87 jet based on data from two observations
with the Einstein Observatory High Resolution Imager (HRI) and three observations with the ROSAT HRI. The core intensity
showed a 16 per cent increase in 17 months (1979-80); a 12 per cent increase in the 3 years 1992 to 1995; and a 17 per cent drop
in the last half of 1995. The intensity of knot A appears to have decreased by 16 per cent between 1992 June and 1995 December.
Although the core variability is consistent with general expectations for AGN, the changes in knot A provide constraints on the
X-ray emission process and geometry. Thus we predict that the X-ray morphology of knot A will differ significantly from the radio
and optical structure.
Author
X Rays; Variability; Elliptical Galaxies; Morphology
20000064097 NASA Marshall Space Flight Center, Huntsville, AL USA
Optical Variability of Blazars
Ghosh, K. K., NASA Marshall Space Flight Center, USA; Ramsey, B. D., NASA Marshall Space Flight Center, USA; Sadun, A.
C., Colorado Univ., USA; Soundararajaperumal, S., National Academy of Sciences - National Research Council, USA; Astrophysical
Journal Supplement Series; March 2000; Volume 127, No. 1, pp. 11-26; In English; Copyright; Avail: Issuing Activity
In this paper we show the results of our monitoring the flux variability of 15 blazars, within the redshift range of 0.07 - 2.06,
all with a visual magnitude range between 14 and 20 mag. Because blazars have displayed variability on diverse timescales, we
have chosen to study them over both short and long timescales, ranging from minutes to years. These blazars were observed on
58 nights between 1995 March and 1998 June. Individual sources are discussed in detail. For example, one of our sources, Mrk
501, showed microvariability of as much as 0.13 mag change within 12 minutes. The usual parameters for size, mass, and luminosity
are calculated. Relativistic beaming is implied by the data. We also searched for correlations between amplitude of variability,
redshift, and luminosity. We found few, if any, such correlations. Discussion and conclusions are given for these and other results
as implied by the data.
Author
Blazars; Variability; Optical Control; Time Dependence; Computation
20000065637 NASA Marshall Space Flight Center, Huntsville, AL USA
The Intensity Distribution of Faint Gamma-Ray Bursts Detected with BATSE
Kommers, Jefferson M., Massachusetts Inst. of Tech., USA; Lewin, Walter H. G., Massachusetts Inst. of Tech., USA; Kouveliotou,
Chryssa, Universities Space Research Association, USA; VanParadijs, Jan, Alabama Univ., USA; Pendleton, Geoffrey N.,
Alabama Univ., USA; Meegan, Charles A., NASA Marshall Space Flight Center, USA; Fishman, Gerald J., NASA Marshall
Space Flight Center, USA; Astrophysical Journal; Apr. 20, 2000; Volume 533, pp. 696-709; In English
Contract(s)/Grant(s): NGT8-52816; NAG5-3804; NAG5-32490; NAG5-4799; NAG5-2755; NAG5-3674; Copyright; Avail: Issuing
Activity
We have recently completed a search of 6 years of archival BATSE data for gamma-ray bursts (GRBS) that were too faint
to activate the real-time burst detection system running on board the spacecraft. These ”nontriggered” bursts can be combined
with the ”triggered” bursts detected on board to produce a GRB intensity distribution that reaches peak fluxes a factor of approximately
2 lower than could be studied previously. The value of the