Masaharu Matsuoka

Simultaneous Multifrequency Observations of the BL Lacertae Object Markarian 421

Simultaneous multifrequency observations of the BL Lac object Mrk 421 covering radio through X-ray wavelengths were performed on two occasions separated by 5 weeks in January and March 1984, and each observation was coordinated for about 1 week. Composite multifrequency spectra of the central nonthermal component were obtained at the two epochs after subtracting the optical and infrared light of the underlying galaxy. The spectra show the gradual steepening toward high frequency; the power law indices are about 0.1, about 0.6, and about 1.0 for radio, infrared-optical, and UV bands, respectively. The UV and optical-infrared fluxes decreased by about 20 percent in 5 weeks, while the radio flux remained stable. The X-ray flux decreased by a factor of about 2, and the change was more pronounced at hard X-rays, which suggest that X-ray emission possibly consists of two components. The degree of polarization at the optical band varied on the time scale of a few days, while the position angle remained unchanged. Physical parameters of Mrk 421 are discussed in terms of the synchrotron self-Compton model. 55 references.

Delays of Optical Bursts in Simultaneous Optical and X-Ray Observations of MXB 1636-53

Observations of simultaneous optical and X-ray bursts from 4U/MXB 1636-53 were made using the Hakucho burst monitor system and optical telescopes at the European Southern Observatory during 1979 and 1980. The six best cases among the 10 coinciding observations are analyzed in terms of a model in which the optical emission is the result of reprocessing of X-rays (through blackbody heating). From this analysis, the temperature (spatially averaged) and size of a reprocessor, and the smearing and delay of the optical bursts are obtained. For the maximum temperatures of the optical reprocessor, the values differ from burst to burst, ranging from about 3 x 10 to the 4th to about 10 to the 5th K. The present analysis suggests that the size of the reprocessor varies by a factor of a few. For the smearing of the optical bursts an upper limit of a few seconds is derived. The most important result of this analysis is that the delay times are not the same for all bursts. The possible constraints which these results put on a low-mass binary model of this burst source are discussed.