SIMBAD references

Twenty-five low-redshift quasars have been monitored for several decades at five near- and midinfrared wavelengths to detect rapid variations that would indicate that a nonthermal component was present in the ``10 µm bump.'' Such variability has apparently been detected in several radio-loud quasars and in the radio-quiet quasar PG 1535+547. In addition, the structure function of PG 1226+023 shows that an apparently periodic component is present in its near-infrared emission.