A Dramatic (and Invisible!) flare in NRAO 530 3 mm λ VLBI Observations

Extract

3 mm λ VLBI observations of the extremely flat spectrum QSO NRAO 530 at the peak of its brightest recorded flare show a resolved core only slightly changed from its pre-outburst state. Observations with Haystack, Kitt Peak and Owens Valley observatories in April 1994, prior to the onset of the flare found a single component with T_b = 8 × 10¹⁰ K. One year later, within one week of the peak of flare at 3 mm λ, observations with Haystack, Kitt Peak and Hat Creek observatories revealed a component comparable in size and flux density with T_b = 7 × 10¹⁰ K. Table 1 details the source models for the two experiments.