Magic constraints on Gamma-ray emission from Cygnus X-3

TL;DR

This study used MAGIC telescopes to search for very high energy gamma-ray emission from Cygnus X-3, setting the most stringent upper limits so far and providing insights into the emission region within the jets.

Contribution

The paper presents the deepest upper limits on VHE gamma-ray emission from Cygnus X-3, constraining models of jet emission and absorption.

Findings

No VHE gamma-ray signal detected from Cygnus X-3.

Set an upper limit of 2.2 x 10^-12 photons cm^-2 s^-1 for energies above 250 GeV.

Results suggest VHE emission likely originates from the innermost jet regions.

Abstract

Cygnus X-3 is a microquasar consisting of an accreting compact object orbiting around a Wolf-Rayet star. It has been detected at radio frequencies and up to high-energy gamma rays (above 100 MeV). However, many models also predict a very high energy (VHE) emission (above hundreds of GeV) when the source displays relativistic persistent jets or transient ejections. Therefore, detecting such emission would improve the understanding of the jet physics. The imaging atmospheric Cherenkov telescope MAGIC observed Cygnus X-3 for about 70 hours between 2006 March and 2009 August in different X-ray/radio spectral states and also during a period of enhanced gamma-ray emission. MAGIC found no evidence for a VHE signal from the direction of the microquasar. An upper limit to the integral flux for energies higher than 250 GeV has been set to 2.2 x 10-12 photons cm-2 s-1 (95% confidence level). This is the best limit so far to the VHE emission from this source. The non-detection of a VHE signal during the period of activity in the high-energy band sheds light on the location of the possible VHE radiation favoring the emission from the innermost region of the jets, where absorption is significant. The current and future generations of Cherenkov telescopes may detect a signal under precise spectral conditions.