Engineering topics

Elvis, M.

Publications and source records attributed to Elvis, M..

59 records · Page 4

NASA NTRS1979

X-ray studies of quasars with the Einstein Observatory

Results of an investigation of the X-ray properties of quasars conducted using the Einstein Observatory (HEAO 2) are reported. The positions, fluxes and luminosities of 35 known quasars were observed by the Einstein high-resolution imaging detector and the imaging proportional counter. Assuming optical redshifts as valid distance indicators, 0.5-4.5 keV X-ray luminosities ranging from 10 to the 43rd to 10 to the 47 ergs/sec are obtained, with evidence of very little cold gas absorption. Flux variability on a time scale of less than 10,000 sec is observed for the quasar OX 169, which implies a mass between 8 x 10 to the 5th and 2 x 10 to the 8th solar masses for the black hole assumed to be responsible for the emission. Preliminary results of the quasar survey also indicate that quasars contribute significantly to the diffuse X-ray background.

Tananbaum, H.↗

NASA NTRS1979

Discovery of an X-ray star association in VI Cygni /Cyg OB2/

A group of six X-ray sources located within 0.4 deg of Cygnus X-3 has been discovered with the Einstein Observatory. These sources have been positively identified and five of them correspond to stars in the heavily obscured OB association VI Cygni. The optical counterparts include four of the most luminous O stars within the field of view and a B5 supergiant. These sources are found to have typical X-ray luminosities of 5 x 10 to the 33rd ergs/s, with temperatures of 10 to the 6.8th K and hydrogen column densities of 10 to the 22nd/sq cm, and therefore comprise a new class of low-luminosity galactic X-ray sources associated with early-type stars.

Harnden, F. R., Jr.↗

NASA NTRS1976

Evidence for a 17-d periodicity from Cyg X-3

Data are presented from the Ariel-V All-Sky Monitor which indicate a 17-day periodicity of the X-ray spectra from Cyg X-3 (3U2030+40). The data are consistent with data from the Ariel V Sky Survey Experiment. Assuming that the high intensity state of Cyg X-3 is well fitted by a structureless black body (Serlemitsos et al., 1975), and that the 17-day maxima correspond to increased electron scattering in the source, it is suggested that the 17-day effect is analogous to the 35-day variation in Her X-1. The possible explanation of this phenomenon as a result of the 17-day orbital period of the binary system containing Cyg X-3 is severely constrained by the stability of the well-known 4.8-hour variation.

Holt, S. S.↗

NASA NTRS1976

Evidence for a 17d periodicity from Cyg X-3

Data which indicate a periodicity of 17d from Cyg X-3 are reviewed. The data are taken from the Ariel 5 satellite All-Sky Monitor and the Sky Survey Experiment.

Holt, S. S.↗

NASA NTRS1975

Evidence for a 17-day periodicity from Cyg-X-3

Data taken from the Ariel-5 All Sky Monitor and the Ariel-5 Sky Survey Experiment are analyzed. It is hypothesized that a periodicity of 17d is characteristic of CygX-3. Results of the analysis are given.

Holt, S. S.↗