Observation of the BL Lac objects 1ES 1215+303 and 1ES 1218+304 with the MAGIC telescopes

TL;DR

This study reports the first detection of VHE gamma-ray emission from 1ES 1215+303 and provides a detailed spectrum of 1ES 1218+304, using MAGIC telescopes and multi-wavelength data to analyze their flaring activity and emission characteristics.

Contribution

First detection of VHE gamma-ray emission from 1ES 1215+303 and high-precision spectral measurement of 1ES 1218+304 with MAGIC telescopes.

Findings

1ES 1215+303 was detected at VHE during a high optical state.

1ES 1215+303 showed flaring activity in VHE gamma-rays in 2011.

Spectrum of 1ES 1218+304 was measured with higher accuracy.

Abstract

The two BL Lac objects 1ES 1215+303 and 1ES 1218+304, separated by 0.8 deg, were observed with the MAGIC telescopes in 2010 and 2011. The 20 hours of data registered in January 2011 resulted in the first detection at Very High Energy (>100 GeV) of 1ES 1215+303 (also known as ON-325). This observation was triggered by a high optical state of the source reported by the Tuorla blazar monitoring program. Comparison with the 25 hours of data carried out from January to May 2010 suggests that 1ES 1215+303 was flaring also in VHE gamma-rays in 2011. In addition, the Swift ToO observations in X-rays showed that the flux was almost doubled respect to previous observations (December 2009). Instead, 1ES 1218+304 is a well known VHE gamma-ray emitter lying in the same field of view, which was then simultaneously observed with the MAGIC telescopes. The overall observation time of nearly 45 hours has permitted to measure the spectrum of this source with a much higher precision than previously reported by MAGIC. Here, we present the results of the MAGIC and the multi-wavelength observations of these two VHE gamma-ray emitting AGNs.