Fermi Gamma-ray Space Telescope

A decade of observations of the TeV blazar 1ES 1215+303 with Fermi-LAT & VERITAS: Using LAT's unique capabilities to explore the physics of blazar jets.

Janeth Valverde
(Janeth Valverde & Deirdre Horan on behalf of the Fermi-LAT Collaboration; Qi Feng & Olivier Hervet on behalf of the VERITAS Collaboration; and multi-wavelength partners.)


We present an unprecedented monitoring campaign on the TeV blazar 1ES 1215+303. Anchored by GeV data from Fermi's Large Area Telescope (LAT) and TeV data from the Very Energetic Radiation Imaging Telescope Array System (VERITAS), we study its emission over a ten-year period using previously unpublished data from ten different instruments. The Fermi-LAT dataset is the richest of our sample comprising a 3-day binned light curve between 2008 and 2017, enabled by the LAT’s unique capabilities. This high-resolution light curve has allowed us to study the gamma-ray emission from this object in great detail and our results indicate evidence for a flux rising trend, log-normally distributed fluxes and episodic flaring both at GeV and at TeV energies. We perform time-resolved modelling of this object's broadband emission concluding that the individual flares observed have different characteristics and therefore different origins. Radio data allows us to identify at least three knots that have remained stationary over the course of the observations indicating a likely high degree of collimation in the jet. VLBI measurements at 43 GHz allow us to produce the highest-resolution radio image of this object to date. We use this decade-long rich data set to explore the physics of high energy emission in this object.