James Terrell

Quasi-Stellar Objects: Possible Local Origin

Many difficulties face the conventional interpretation of the red shift of quasars as a Hubble shift, with associated immense distances. These objects are not of galactic size or nature, and are not associated with galaxies or clusters of galaxies. The continuing energy source for such enormous powers for a period of 106 to 107 years has not been clearly revealed. The absence of the expected absorption for the Lyman-α spectral line of hydrogen is a new difficulty. Because of the relativistic limit on the diameter which can produce rapid fluctuations of light output, there may not be enough surface to radiate the required light.A similar and perhaps more serious difficulty exists for the fluctuating radio output. Calculations given here for synchrotron radiation self-absorption lead to a reasonably accurate formula for the angular diameter of a radio source. For the quasar 3C 273B these relations indicate a conflict with the usually assumed distance. However, the discrepancy may be explained in terms of strong variation of radio diameter with frequency. For CTA 102 the conflict is more serious, and could be explained —for cosmological distance—only by rejecting the data of Sholomitskii. These difficulties are removed by the hypothesis that the observed quasars were ejected from a gravitational collapse at the center of our own galaxy, which may have occurred roughly 5 million years ago. The resultant distances, of the order of a million lightyears, reduce the energy problem by a factor of 106 or 107. On this basis the optical diameter would be less than a light-hour, about the size of the earths orbit. A rotating mass of a few thousand solar masses with this diameter would account for the unusual line width, could easily produce the required radiated energy, and could readily account for observed short fluctuation periods and variations in spectrum. It is suggested that the radio output may be produced by high-speed passage of the quasar through intergalactic gas. This would probably correspond to a radio size of a few light-years or less, in agreement with the fluctuations. Since the radio power would be considerably less than that of radio galaxies, it is suggested that radio galaxies may have ejected groups of quasars. This would explain the peculiarly distant locations of the radio sources for many such galaxies. The objections to this model that have been raised are apparently not fatal. In particular, the receding hydrogen cloud discovered by Koehler to be in the line of sight to 3C 273 is more plausibly interpreted as having been ejected from our own galaxy, in the manner observed for other galaxies, than as being associated with the Virgo cluster of galaxies. The latter interpretation, which would place 3C 273 further away, is in conflict with Lyman-α absorption data for 3C 9 and other quasars. Thus the local model seems to give a reasonable explanation not only of quasars but also of radio galaxies, bothv of which seem largely to defy explanation on other grounds. Whether or not this model is valid, it is clear that an understanding of quasars will radically change our understanding of the universe.

DMSP 14 Observations of GRB011121 and the Giant SGR1900+14 Flare of 98/08/27

The bright gamma‐ray burst GRB011121 was observed by DMSP 13 and DMSP 14 at a time resolution of 2s. Event data also obtained by DMSP 14 covered 13.1s of the burst at a time resolution of 12.8ms, and an energy range of 53–3000 keV. Fourier analysis gives evidence, at 95% confidence, of a 1.7s oscillation in the event data. DMSP 14 data for the giant 98/08/27 flare of SGR 1900+14 are also presented, giving high‐time‐resolution data, not previously available, on the initial outburst.

Gamma-ray burst observations from the UCB/LASL experiment of ISEE-3

Since the discovery of the intense bursts of γ rays by Klebesadel et al.1 in 1973, little progress has been made in the identification of the sources of the bursts. The initial observations provided directions to several sources with sufficient accuracy to establish the approximate isotropic distribution of the sources2, but not to provide a basis for association with any known objects, γ-ray burst astronomy entered a new phase in 1976 with the launch of Helios 2 and Solrad 11 containing the first experiments designed expressly for that purpose3,4. It then became possible to derive several error boxes that were very narrow in one dimension3,5. Using these data it was determined that the bursts are not associated with any type of object that has previously been recognized as a high energy astrophysical source—for example, X-ray sources. In 1978 a true interplanetary network of burst detectors was established with the launch of instruments on Pioneer Venus Orbiter6, ISEE 37–9 and Venera 11 and 1210,11. With baseline separations that can exceed 1 AU, this network provides a basis for the location of the γ burst sources with an accuracy sufficient for optical identifications. We briefly describe here one of these instruments, a joint Berkeley/Los Alamos experiment on the ISEE 3 spacecraft, and present some initial results from that experiment. These results are currently being combined with those from the other experiments to obtain accurate burst locations to be reported elsewhere.

Ten years of vela x‐ray observations

The Vela spacecraft, particularly Vela 5B, produced all‐sky X‐ray data of unprecedented length and completeness. Recent re‐analysis has put the data in the form of 10‐day skymaps covering a 7‐year period, which have led to the discovery or confirmation of a number of long‐term periodicities, and have made possible a time‐lapse movie of the X‐ray sky.