Engineering topics

Cook, M. C.

Publications and source records attributed to Cook, M. C..

3 records

NASA NTRS1985

High-speed photometry of Z Chamaeleontis covering the 1983 March normal outburst

High-speed photometry over a three-week period covering the Mar. 13, 1983 normal outburst of Z Cha is presented. Multicolor observations revealed significant reddening during eclipse in both the quiescent and outburst states. Quiescent primary eclipse timings remained consistent with an increasing orbital period. Hotspot eclipse timings revealed that the accretion disk had physically expanded in radius after the outburst. The duration of the eclipse during outburst, however, limited the optical emission to a region bounded by the radius of the preoutburst accretion disk. In the final stages of decline this emission region had shrunk in size by a factor of approximately 4. The postoutburst observations showed the hotspot eclipse to be less stable in structure compared to before the outburst.

Cook, M. C.↗

NASA NTRS1985

High-speed photometry of the eclipsing dwarf nova OY Carinae

High-speed photometry of the eclipsing dwarf nova OY Car in the quiescent state is presented. OY Car becomes highly reddened during eclipse, with minimum flux colours inconsistent with optically thick emission in the U and B bandpasses. Mass ratios in the range 6.5 to 12 are required to reconcile the eclipse structure with theoretical gas stream trajectories. Primary eclipse timings reveal a significant decrease in the orbital period and the duration of primary eclipse indicates the presence of a luminous ring about the white dwarf. The hotspot eclipse reveals a hotspot which is elongated along the rim of the accretion disc, with optical emission being non-uniformly distributed along the rim. The location of the hotspot in the accretion disc implies a disc radius larger than that of an inviscid disc, with variation in the position of the hotspot being consistent with a fixed stream trajectory.

Cook, M. C.↗

NASA NTRS1983

Synchronization of magnetic stars in binary systems

Asynchronous rotation of magnetic stars in close binary systems drives substantial field-aligned electrical currents between the magnetic star and its companion. The resulting magnetohydrodynamic torque is able to account for the heretofore unexplained synchronous rotation of the strongly magnetic degenerate dwarf component in systems like AM Her, VV Pup, AN UMa, and EF Eri as well as the magnetic A type component in systems like HD 98088 and 41 Tauri. The electric fields produced by even a small asynchronism are large and may accelerate some electrons to high energies, producing radio emission. The total energy dissipation rate in systems with degenerate dwarf spin periods as short as 1 minute may reach 10 to the 33rd ergs/s. Total luminosities of this order may be a characteristic feature of such systems.

Lamb, F. K.↗