Satio Hayakawa

The submillimeter spectrum of the cosmic background radiation

The diffuse brightness of the sky has been measured in six submillimeter passbands, using a rocket-borne, liquid helium-cooled, absolute radiometer. The flux measured at 1160 microns is in good agreement with the average of longer wavelength measurements of the temperature of the cosmic background radiation. The fluxes measured at 709 microns and 481 microns show a rapid decrease toward shorter wavelength, but correspond to significantly higher temperatures. No local source of this excess flux has been identified. The spectrum of the excess significantly constrains cosmological models. Data at 262, 137, and 102 microns are consistent with emission from interstellar dust. 22 references.

Spectra and pulse period of the binary X-ray pulsar 4U 1538-52

The 530 s binary X-ray pulsar 4U 1538-52 was observed from the X-ray astronomy satellite Tenma in 1983 June-July. An improved orbital ephemeris was derived. Also, high-quality X-ray spectra were obtained by taking into account the contribution of the Galactic ridge emission. It was found that the iron K-line emission from this source is weak, contrary to previous reports. The observed pulsation period, about 529.8 s, is about 0.4 s longer than that measured in 1976-1977, implying an average spin-down rate of 3.8 x 10 to the -9th s/s. In addition, there is some evidence for a much larger rate of instantaneous period increase. These results suggest that 4U 1538-52 is a wind-fed pulsar, and its pulsation period changes in a random-walk manner in response to fluctuations in the external torque. This is very similar to the case of Vela X-1. 46 references.

ORIGIN OF COSMIC RAYS

Opinions of different investigators om the origin of cosmic rays are summarized. Papers containing information on the following subjects are reviewed: isotopic abundance of He in primary cosmic rays; electrons and galactic radio emission; heavy nuclei at high energies; supernova explosion; equipartition of energy into three modes (the turbulent motion, the magnetic field, and the cosmic rays); preferential acceleration of heavy nuclei; range of metagalactic cosmic rays; relation of cosmic rays to the galactic structure. (A.G.W.)

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.

Roughness Measurement of X-Ray Mirror Surfaces

In order to fabricate an X-ray mirror telescope, we investigated the roughness of mirror surfaces using X-ray scattering. With Al-K (8.34A) X-rays we measured the scattering profiles of plate glass. The spectral structure of surface roughness was revealed by the angular distribution of the X-ray scattering. The power spectral density functions of the surface-height distribution for these materials (except for a gold evapolated surface) were represented by the power-law spectra with power indices ranging from -1 to -2. The rms heights were derived to be 1.8-8.3A for a wavelength range as expected from the power-law spectrum. The results obtained with this method were found to be consistent with those with an ordinary optical profilometer.

Diffuse component of the cosmic far UV radiation and interstellar dust grains

The diffuse far UV radiation (λλ 1350–1480 Å) observed in the sky region oflII≈180°, 0°≤bII≲40° is analyzed in connection with the distributions of stars and dust grains as well as with optical properties of grains. Its intensity (starlight+scattered light) is about 6×10−7 erg cm−2 sec−1 sr−1 Å−1 in the direction ofbII≈0° andlII≈180°. The latitude dependence of the intensity is in approximate agreement with the plane parallel slab model of the galaxy with a reasonable set of parameters. The interstellar scattering gives an albedo close to unity and forward phase function of about 0.6, which are not inconsistent with the model of interstellar grains of Wickramasinghe. The upper limit of the extragalactic UV is 2×10−8 erg cm−2 sec−1 sr−1 Å−1 in the same region of wave-length.

Dust grain origin of cosmic-ray air showers

It is suggested that cosmic rays of energies as high as 1020 eV consist of dust grains of relativistic energies. Such dust grains as typical in interstellar space are accelerated first by a strong radiation pressure of luminous, compact galaxies and then by magnetic processes. A grain with the mass of about 10−16 g and the Lorentz factor of about 103 attains an energy as large as 1020 eV and produces a huge extensive air shower. Such grains survive against the collisions with cosmic microwave photons. This would remove the serious difficulty, if both the cosmic microwave radiation and the huge extensive air showers, which were regarded as due to protons of energies greater than 1019 eV, existed in spite of that the protons should strongly attenuate by the collisions with the radiation.

X-rays from accreting neutron stars

Abstract The paper gives an overall picture of accreting neutron stars as obtained from X-ray observations. Theories of X-ray binaries, accreting processes, and X-ray emission mechanisms are reviewed to give qualitative understanding of physics relevant to X-rays from accreting neutron stars. Some quantitative results under simplified conditions are given for the application to the interpretation of observational results. Recent results obtained by Japanese X-ray astronomy satellites HAKUCHO and TENMA are presented in comparison with theoretical models.

Elastic and Inelastic Collisions of 55 MeV Proton with 4He

Elastic and inelastic collisions induced by 55 MeV protons with 4 He nuclei were investigated by use of the Δ E - E counter detecting protons and deuterons, and the solid counter detecting recoil 4 He and 3 He nuclei. The differential cross sections at 15°–160° were measured for the elastic scattering and for the inelastic process 4 He( p ; d ) 3 He, as shown in Fig. 6. The total cross section for the latter is 40 mb. The total cross section for all inelastic events were estimated from the continuum portion in the energy spectra of protons as 50–80 mb. The existence of an excited state in 4 He at the excitation of about 22 MeV was indicated by searching an anomalous peak in the energy spectra of protons.

Rocket-borne submillimeter radiometer.

We report the performance of a rocket-borne absolute radiometer which was designed to measure the diffuse brightness of the sky in six passbands between 100 microm and 1 mm. The radiometer consisted of a horn antenna and a photometer, both of which were cooled to 1.2 K by liquid (4)He. The performance of the instrument was satisfactory, but no astrophysical data were obtained during the flight because a lid covering the horn antenna failed to pen. Another flight of a similar apparatus is planned for 1986.