High temporal resolution monitoring of a distant active galaxy

Recently, a comprehensive high temporal resolution optical survey of BL Lacertae (BL Lac) – a distant active galaxy – was conducted by a group of 86 scientists from 13 countries. One of the astronomers contributing to this project is Mike Joner, BYU Research professor in physics and astronomy.

Artistic representation of the BL Lac jet with a spiraling magnetic field. Image credit: Iris Nieh.

At BYU West Mountain Observatory, Dr. Joner and BYU undergraduate student Gilvan Apolonio obtained more than 200 observations of the galaxy using the 0.9m Reflecting Telescope. Their measurements were combined with observations made by other researchers around the world in an association called Whole Earth Blazar Telescope (WEBT). In a time of high variability, the WEBT network allows continuous monitoring of objects from various locations.

Astronomers have found incredibly rapid brightness oscillations in the central jet of the BL Lac galaxy, with the WEBT observations noted in the summer of 2020. The researchers attribute these cycles of brightness change to twists in the jet’s magnetic field. . Naturea scientific journal, recently published this study.

BYU’s West Mountain Observatory was one of 37 ground-based telescopes around the world monitoring optical variations in BL Lac, an active galaxy classified as a blazar that lies about 1 billion light-years away.

Joner and Apolonio replaced each other working on various groups of nights at the observatory throughout the summer and spring of 2020, a task that was very arduous at the height of the pandemic. This unusual schedule of duties was essential because observations were required every clear night and no other qualified student observers remained in the Provo area.

A survey of high-rate optical observations was essential to understanding the high-energy observations of the Fermi Gamma-Ray Space Telescope.

You need to combine data from high-energy space observatories with ground-based optical surveillance data. Billion-dollar space telescopes that are used on projects like this often have to compare results with optical observations on the ground. Correlating what was seen in the high-energy observations with the light curves on the ground helped confirm the rapid periodic oscillations that were seen in the high-energy data from space..

Mike Joner, Research Professor, Physics and Astronomy, Brigham Young University

Although he is a recognized specialist in astrophysical research, Joner says he is always surprised at the level of detail that researchers capture through such observations. He is also grateful for the opportunity to explore the wide spectrum of the cosmos with his students at BYU.

On a galactic scale, the central jet of a blazar is quite small. It’s amazing to be able to see the variations of the jet so clearly. The variability of the jet is easily visible even when combined with the light from hundreds of billions of stars in the host galaxy. It should be noted that in the age of giant telescopes and space research, it is still necessary to rely on modestly sized and well-equipped facilities like the ones we have at BYU to explore the unknown reaches of the planet. ‘Universe..

Mike Joner, Research Professor, Physics and Astronomy, Brigham Young University

Melissa Hallum, a Boston University PhD student, BYU graduate and former student of Dr. Joner, was also a co-author on the study.

Journal reference

Jorstad, SG, et al. (2022) Fast quasi-periodic oscillations in the relativistic jet of BL Lacertae. Nature. doi.org/10.1038/s41586-022-05038-9.

Source: https://byu.edu