Is Fermi 1544-0649 a misaligned blazar? discovering the jet structure with VLBI

TL;DR

This study investigates Fermi J1544-0649, a transient GeV source, revealing jet structures via VLBI and supporting its classification as a misaligned blazar with low gamma-ray activity and potential neutrino associations.

Contribution

The paper provides the first VLBI-based jet structure analysis of Fermi J1544-0649, supporting its classification as a misaligned blazar with detailed jet component measurements.

Findings

Discovered four jet components with VLBI data.

Estimated a viewing angle between 3.7° and 7.4°.

Detected a 3.1σ neutrino excess associated with the source.

Abstract

Fermi J1544-0649 is a transient GeV source first detected during its GeV flares in 2017. Multi-wavelength observations during the flaring time demonstrate variability and spectral energy distribution(SED) that are typical of a blazar. Other than the flare time, Fermi J1544-0649 is quiet in the GeV band and looks rather like a quiet galaxy (2MASX J15441967-0649156) for a decade. Together with the broad absorption lines feature we further explore the "misaligned blazar scenario". We analyzed the Very Long Baseline Array (VLBA) and East Asian VLBI Network (EAVN) data from 2018 to 2020 and discovered the four jet components from Fermi J1544-0649. We found a viewing angle around 3.7{\deg} to 7.4{\deg}. The lower limit of the viewing angle indicates a blazar with an extremely low duty cycle of the gamma-ray emission, the upper limit of it supports the "misaligned blazar scenario". Follow-up multi-wavelength observations after 2018 show Fermi J1544-0649 remains quiet in GeV, X-ray, and optical bands. Multi-messenger search of neutrinos is also performed, and an excess of 3.1 {\sigma} significance is found for this source.