Identifications of Five INTEGRAL Sources via Optical Spectroscopy

TL;DR

This study uses optical spectroscopy combined with X-ray data to identify and classify five previously unknown INTEGRAL sources, revealing their nature as active galactic nuclei, cataclysmic variables, and high mass X-ray binaries.

Contribution

It provides new optical identifications and classifications for five INTEGRAL sources, enhancing understanding of their nature and properties.

Findings

IGR J16426+6536 is a Seyfert 1.5 galaxy at z=0.323.

IGR J22292+6647 is a Seyfert 1 galaxy at z=0.113.

IGR J18308-1232 is a confirmed cataclysmic variable.

Abstract

The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) is discovering hundreds of new hard X-ray sources, many of which remain unidentified. We report on optical spectroscopy of five such sources for which X-ray observations at lower energies (~0.5-10 keV) and higher angular resolutions than INTEGRAL have allowed for unique optical counterparts to be located. We find that IGR J16426+6536 and IGR J22292+6647 are Type 1 Seyfert active galactic nuclei (with IGR J16426+6536 further classified as a Seyfert 1.5) which have redshifts of z=0.323 and z=0.113, respectively. IGR J18308-1232 is identified as a cataclysmic variable (CV), and we confirm a previous identification of IGR J19267+1325 as a magnetic CV. IGR J18214-1318 is identified as an obscured high mass X-ray binary (HMXB), which are systems thought to have a compact object embedded in the stellar wind of a massive star. We combine Chandra fluxes with distances based on the optical observations to calculate X-ray luminosities of the HMXB and CVs, finding L_(0.3-10 keV)=5e36 erg s^-1 for IGR J18214-1318, L_(0.3-10 keV)=1.3e32 erg s^-1 for IGR J18308-1232, and L_(0.3-10 keV)=6.7e32 erg s^-1 for IGR J19267+1325.