NICER / ISS Science Nugget
for October 22, 2020
BL Lacertae (BL Lac) is a blazar approximately 900 million light-years from Earth. A blazar is a type of Active Galactic Nucleus (AGN), a supermassive black hole found near the center of a galaxy, viewed from the Earth nearly along the axis of one of the black hole's relativisitic jets. Blazars exhibit extremely rapid variations in flux as measured from our perspective.
On October 10th, 2020, NICER received a Target of Opportunity (TOO) request to observe BL Lac in coordination with NASA's NuSTAR (hard X-ray) and Fermi (gamma-ray) observatories. NICER regularly receives TOO requests through its publicly available online form; the Fermi Observatory had recently observed a historically high gamma-ray intensity from BL Lac, which triggered this TOO request.
NICER observed BL Lac for nearly 15 ksec on October 11-12, 2020 (see figure). The TOO requester, Dr. F. D'Ammando, is analyzing the NICER and NuSTAR data jointly to characterize the "inverse Compton peak" in the X-ray spectrum. This will provide insight into the environment of the relativistic jet in BL Lac. Initial results were reported by F. D'Ammando in Astronomer's Telegram #14096.
Figure: The measured NICER light curve of BL Lac showing X-ray intensity from varying by roughly a factor of two over the observation.