# The nature of fifty Palermo Swift-BAT hard X-ray objects through optical spectroscopy

## TL;DR

This study used optical spectroscopy to identify the nature of 50 hard X-ray sources from the Swift-BAT catalog, revealing mostly active galactic nuclei and some galactic objects, with new redshift measurements provided.

## Contribution

First comprehensive optical spectroscopic classification of 50 unidentified Swift-BAT hard X-ray sources, including new redshift data and detailed source types.

## Key findings

- 45 sources are active galactic nuclei, including 27 type 1 and 18 type 2.
- 30 new redshift measurements, with 13 confirmations and 2 refined values.
- 5 galactic sources, including cataclysmic variables and X-ray binaries.

## Abstract

We present the nature of 50 hard X-ray emitting objects unveiled through an optical spectroscopy campaign performed at seven telescopes in the northern and southern hemispheres. These objects were detected with Swift-BAT and listed as of unidentified nature in the 54-month Palermo BAT catalogue. In detail, 45 sources in our sample are identified as active galactic nuclei of which, 27 are classified as type 1 (with broad and narrow emission lines) and 18 are classified as type 2 (with only narrow emission lines). Among the broad-line emission objects, one is a type 1 high-redshift quasi-stellar object, and among the narrow-line emission objects, one is a starburst galaxy, one is a X-ray bright optically normal galaxy, and one is a low ionization nuclear emission line region. We report 30 new redshift measurements, 13 confirmations and 2 more accurate redshift values. The remaining five objects are galactic sources: three are Cataclismic Variables, one is a X-ray Binary probably with a low mass secondary star, and one is an active star.