On the identification of the Fermi/LAT source 0FGL J2001.0+4352 with a BL Lac

TL;DR

This paper reports the identification of a gamma-ray source as a high-frequency peaked BL Lac object through multiwavelength observations and classification, confirming its nature as a blazar with specific spectral and variability characteristics.

Contribution

The study provides the first optical classification of 0FGL J2001.0+4352 as a BL Lac object using archival and follow-up data, linking gamma-ray emission to a specific blazar type.

Findings

The source is a bright, variable X-ray emitter with a steep spectrum.

It coincides with a radio bright, flat spectrum object.

Optical spectroscopy confirms it as a BL Lac object.

Abstract

We report on the identification of the gamma-ray source 0FGL J20001.0+4352 listed in the Fermi bright source catalogue. This object, which has an observed 1-100 GeV flux of (7.8 +/- 1.2) x 10^{-9} ph cm^{-2} s^{-1} and is located close to the Galactic plane, is not associated with any previously known high energy source. We use archival XMM-Newton and Swift/XRT data to localise with arcsec accuracy the X-ray counterpart of this GeV emitter and to characterise its X-ray properties: the source is bright (the 0.2-12 keV flux is 1.9 x 10^{-12} erg cm^{-2} s^{-1}), variable (by a factor of ~2) and with a steep power law spectrum (Gamma = 2.7). It coincides with a radio bright (~200 mJy at 8.4 GHz) and flat spectrum object (MG4 J200112+4352 in NED). Broad-band optical photometry of this source suggests variability also in this waveband, while a spectroscopic follow-up observation provides the first source classification as a BL Lac object. The source SED, as well as the overall characteristics and optical classification, point to a high frequency peaked blazar identification for 0FGL J2001.0+4352.