Volume 9, Issue 3
September 1988, pages 127-183
pp 127-136 September 1988
Photoelectric radial-velocity measurements show that HD 106947 is a double-lined spectroscopic binary. The components have spectral types of about F6 V and G5 V and are in a 59-day orbit of moderate eccentricity. The system is a member of the Coma Cluster.
pp 137-154 September 1988
Solar Active Region NOAA 2372 was observed extensively by the Solar Maximum Mission (SMM) satellite and several ground-based observatories during 1980 April 4–13 in the Solar Maximum Year. After its birth around April 4, it underwent a rapid growth and produced a reported 84 flares in the course of its disc passage. In this paper, we have studied photospheric and chromospheric observations of this active region together with Marshall Space Flight Center magnetograms and X-ray data from HXIS aboard the SMM satellite. In particular, we discuss the relationship of the flare-productivity with sunspot proper motions and emergence of new regions of magnetic flux in the active region from its birth to its disappearance at the W-limb.
pp 155-160 September 1988
Cygnus X-3, an X-ray binary with an orbital period 4.8 hr was seen to be emitting γ-rays with the same period at TeV energies by several groups. In addition the Durham group (Chadwicket al. 1985) published their observations on the existence of a pulsar in the Cyg X-3 system, emitting TeV γ-rays with a periodicity of approximately 12.6 ms. We observed this object during 1986 October-November and did not detect any pulsed emission of TeV γ-rays in the range of periods from 12.5850 to 12.5967 ms.
pp 161-172 September 1988
Two Wolf-Rayet members of the cluster NGC 6231 are studied spectrophotometrically. HD 151932, a suspected variable, shows variations in the emission line flux as well as continuum magnitude measurements. An attempt is made to understand this variation as due to the asymmetric atmospheric structure. The other, HD 152270, a (WC7 + O) binary, shows variation of emission line flux for C III and C IV lines only. This variation is studied as a possible phenomenon of atmospheric eclipses.
pp 173-183 September 1988
A comparison is made between a hot-spot model and a recently proposed oblate spheroid model (Böhm-Vitense & Van Dyk 1987) to explain the spectroscopic and photometric variations of α2 CVn. It is found that the spot model gives a better fit to the spectroscopic and photometric variations. The spot model requires five high temperature circular patches over the surface of the star. The positions of these patches agree well with those derived spectroscopically by Pyper (1969).
Volume 40 | Issue 2
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