Blazars
Blazars are objects with relativistic jets aligned with our line of sight, producing very luminous, highly variable and polarized emission. The spectral energy distributions are dominated by two components, one at lower energies (radio-optical-UV), and one at higher energies (X-ray/gamma-ray). The lower energy component is generally agreed to be due to synchrotron radiation from relativistic electrons accelerated at shocks in the jet, but the source of the high energy radiation is still disputed, with a wildly different theoretical models able to fit single-epoch observations. I am performing multi-wavelength observations of blazars in order to better constrain these models for high energy emission from blazar jets.
Credit: W. Steffen and Cosmovision
Access the data for the first year of SMARTS observations of the Fermi/LAT monitored blazars here.
News: The blazar 3C 454.3 has undergone several extraordinary flares in gamma rays as well as in optical wavelengths. In the beginning of December 2009, it was the brightest persistent source in the gamma-ray sky, outshining the Vela pulsar. Our Astronomer's Telegram reporting the corresponding optical and infrared flare was mentioned in an article on 3C 454.3 at the online magazine Universe Today .
Recoiling black holes
Numerical simulations of binary black holes through coalescence and merger have shown that the product of such a merger may gain a kick of several thousand kilometers per second. This velocity is mall compared to the high speeds of the black holes just before they collide, but it is comparable to the escape velocity of a typical galaxy. If two galaxies, each hosting a supermassive black hole, merge under the right conditions, it is possible that such kicked black holes may be detected. In particular, if the kicked black hole carries bound material with it, it may shine as a quasar and be detectable with current observations. I am currently combing astronomical data sets, searching for runaway black holes. A confirmed detection would be a very exciting confirmation of General Relativity in strong field regimes.
Credit: Tim Jones/McDonald Observatory
Read all about it! Those with a subscription to Stardate Magazine can check out an article for a lay audience written with my colleague Greg Shields of the University of Texas on our hunt for recoiling black holes.
Press coverage: It was a pretty interesting, and somewhat unexpected, result that we found no convincing kick candidates in a search of the Sloan Digital Sky Survey. Here is a press release put out by the McDonald Observatory of the University of Texas at Austin about our work. Coinciding with the Summer 2007 meeting of the AAS, this negative result was covered by Nature, New Scientist, Astronomy, and MSNBC.