Yale University | 2015 Jan 22
[img3="This artist's rending shows "before" and "after" images of a changing look quasar. (Illustration by Michael S. Helfenbein)"]http://news.yale.edu/sites/default/file ... -holes.jpg[/img3]Yale University astronomers have identified the first “changing look” quasar, a gleaming object in deep space that appears to have its own dimmer switch.
The discovery may offer a glimpse into the life story of the universe’s great beacons.
Quasars are massive, luminous objects that draw their energy from black holes. Until now, scientists have been unable to study both the bright and dim phases of a quasar in a single source.
As described in an upcoming edition of The Astrophysical Journal, Yale-led researchers spotted a quasar that had dimmed by a factor of six or seven, compared with observations from a few years earlier. ...
Even more significant for astronomers was the weakening of the quasar’s broad emission lines. Visible on the optical spectrum, these broad emission lines are signatures of gas that is too distant to be consumed by a black hole, yet close enough to be “excited” by energy from material that does fall into a black hole.
The change in the emission lines is what told researchers that the black hole had essentially gone on a diet, and was giving off less energy as a result. That’s when the “changing look” quasar hit its dimmer switch, and most of its broad emission lines disappeared. ...
The findings may prove invaluable on several fronts. First, they provide direct information about the intermittent nature of quasar activity; even more intriguingly, they hint at the sporadic activity of black holes. ...
The Discovery of the First "Changing Look" Quasar: New Insights into the Physics & Phenomenology of AGN - Stephanie M. LaMassa et al
- arXiv.org > astro-ph > arXiv:1412.2136 > 05 Dec 2014 (v1), 20 Jan 2015 (v3)