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Verfasser Titel Jahr
zeige Details Hawkins, M. R. S. Gravitational microlensing, quasar variability and missing matter
in: Nature . - London [u.a.] : Nature Publising Group, ISSN 1476-4687, Vol. 366, No. 6452 (1993), p. 242-245
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1993
QUASARS have long been known to vary in magnitude1,and it now appears that all quasars are to some extentvariable2. In a few extreme cases, quasar luminosities havevaried over several magnitudes on a timescale of months; this behaviour isnormally accompanied by other phenomena (such as radio emission or enhancedpolarization) indicative of processes intrinsic to the quasars. Long-termluminosity variations, while less dramatic, are much more common, but theirorigin remains poorly understood. Here I investigate this longer-term behaviourfor a sample of approximately 300 quasars at redshifts ranging from 1 to 3,whose optical magnitudes have been measured periodically for 17 years. I showthat there is a positive correlation between the timescale of variability andthe average luminosity, but little evidence for an increase in timescale due toredshift (and hence time dilation). These findings are inconsistent with anyknown variability mechanism intrinsic to quasars, but can be explained bygravitational lensing of the quasar images by compact substellar objects alongthe lines of sight. If this interpretation is correct, the population oflensing objects must have a density of at least 0.1 of the criticalcosmological density.
beteiligte Personen: Hawkins, M. R. S.
Format: Elektronisch
Erschienen: 1993.
Serie: Nature Archives 1869 - 2007 [Dig. Serial]
Schlagwörter:
URL: http://dx.doi.org/10.1038/366242a0

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